WorldWideScience

Sample records for altitude polar orbiting

  1. Medical Implications of Space Radiation Exposure Due to Low-Altitude Polar Orbits.

    Science.gov (United States)

    Chancellor, Jeffery C; Auñon-Chancellor, Serena M; Charles, John

    2018-01-01

    Space radiation research has progressed rapidly in recent years, but there remain large uncertainties in predicting and extrapolating biological responses to humans. Exposure to cosmic radiation and solar particle events (SPEs) may pose a critical health risk to future spaceflight crews and can have a serious impact on all biomedical aspects of space exploration. The relatively minimal shielding of the cancelled 1960s Manned Orbiting Laboratory (MOL) program's space vehicle and the high inclination polar orbits would have left the crew susceptible to high exposures of cosmic radiation and high dose-rate SPEs that are mostly unpredictable in frequency and intensity. In this study, we have modeled the nominal and off-nominal radiation environment that a MOL-like spacecraft vehicle would be exposed to during a 30-d mission using high performance, multicore computers. Projected doses from a historically large SPE (e.g., the August 1972 solar event) have been analyzed in the context of the MOL orbit profile, providing an opportunity to study its impact to crew health and subsequent contingencies. It is reasonable to presume that future commercial, government, and military spaceflight missions in low-Earth orbit (LEO) will have vehicles with similar shielding and orbital profiles. Studying the impact of cosmic radiation to the mission's operational integrity and the health of MOL crewmembers provides an excellent surrogate and case-study for future commercial and military spaceflight missions.Chancellor JC, Auñon-Chancellor SM, Charles J. Medical implications of space radiation exposure due to low-altitude polar orbits. Aerosp Med Hum Perform. 2018; 89(1):3-8.

  2. Investigating the auroral electrojets with low altitude polar orbiting satellites

    DEFF Research Database (Denmark)

    Moretto, T.; Olsen, Nils; Ritter, P.

    2002-01-01

    Three geomagnetic satellite missions currently provide high precision magnetic field measurements from low altitude polar orbiting spacecraft. We demonstrate how these data can be used to determine the intensity and location of the horizontal currents that flow in the ionosphere, predominantly...... to another event for which the combined measurements of the three satellites provide a comprehensive view of the current systems. The analysis hereof reveals some surprising results concerning the connection between solar wind driver and the resulting ionospheric currents. Specifically, preconditioning.......8-0.9) is observed between the amplitudes of the derived currents and the commonly used auroral electro-jet indices based on magnetic measurements at ground. This points to the potential of defining an auroral activity index based on the satellite observations, which could be useful for space weather monitoring...

  3. Stable low-altitude orbits around Ganymede considering a disturbing body in a circular orbit

    Science.gov (United States)

    Cardoso dos Santos, J.; Carvalho, J. P. S.; Vilhena de Moraes, R.

    2014-10-01

    Some missions are being planned to visit Ganymede like the Europa Jupiter System Mission that is a cooperation between NASA and ESA to insert the spacecraft JGO (Jupiter Ganymede Orbiter) into Ganymedes orbit. This comprehension of the dynamics of these orbits around this planetary satellite is essential for the success of this type of mission. Thus, this work aims to perform a search for low-altitude orbits around Ganymede. An emphasis is given in polar orbits and it can be useful in the planning of space missions to be conducted around, with respect to the stability of orbits of artificial satellites. The study considers orbits of artificial satellites around Ganymede under the influence of the third-body (Jupiter's gravitational attraction) and the polygenic perturbations like those due to non-uniform distribution of mass (J_2 and J_3) of the main body. A simplified dynamic model for these perturbations is used. The Lagrange planetary equations are used to describe the orbital motion of the artificial satellite. The equations of motion are developed in closed form to avoid expansions in eccentricity and inclination. The results show the argument of pericenter circulating. However, low-altitude (100 and 150 km) polar orbits are stable. Another orbital elements behaved variating with small amplitudes. Thus, such orbits are convenient to be applied to future space missions to Ganymede. Acknowledgments: FAPESP (processes n° 2011/05671-5, 2012/12539-9 and 2012/21023-6).

  4. Investigating the auroral electrojets with low altitude polar orbiting satellites

    Directory of Open Access Journals (Sweden)

    T. Moretto

    2002-07-01

    Full Text Available Three geomagnetic satellite missions currently provide high precision magnetic field measurements from low altitude polar orbiting spacecraft. We demonstrate how these data can be used to determine the intensity and location of the horizontal currents that flow in the ionosphere, predominantly in the auroral electrojets. First, we examine the results during a recent geomagnetic storm. The currents derived from two satellites at different altitudes are in very good agreement, which verifies good stability of the method. Further, a very high degree of correlation (correlation coefficients of 0.8–0.9 is observed between the amplitudes of the derived currents and the commonly used auroral electrojet indices based on magnetic measurements at ground. This points to the potential of defining an auroral activity index based on the satellite observations, which could be useful for space weather monitoring. A specific advantage of the satellite observations over the ground-based magnetic measurements is their coverage of the Southern Hemisphere, as well as the Northern. We utilize this in an investigation of the ionospheric currents observed in both polar regions during a period of unusually steady interplanetary magnetic field with a large negative Y-component. A pronounced asymmetry is found between the currents in the two hemispheres, which indicates real inter-hemispheric differences beyond the mirror-asymmetry between hemispheres that earlier studies have revealed. The method is also applied to another event for which the combined measurements of the three satellites provide a comprehensive view of the current systems. The analysis hereof reveals some surprising results concerning the connection between solar wind driver and the resulting ionospheric currents. Specifically, preconditioning of the magnetosphere (history of the interplanetary magnetic field is seen to play an important role, and in the winther hemisphere, it seems to be harder to

  5. Space environment monitoring by low-altitude operational satellites

    International Nuclear Information System (INIS)

    Kroehl, H.W.

    1982-01-01

    The primary task of the Defense Meteorological Satellite Program (DMSP) is the acquisition of meteorological data in the visual and infrared spectral regions. The Air Weather Service operates two satellites in low-altitude, sun-synchronous, polar orbits at 850 km altitude, 98.7 deg inclination, 101.5 minute period and dawn-dusk or noon-midnight equatorial crossing times. Special DMSP sensors of interest to the space science community are the precipitating electron spectrometer, the terrestrial noise receiver, and the topside ionosphere plasma monitor. Data from low-altitude, meteorological satellites can be used to build empirical models of precipitating electron characteristics of the auroral zone and polar cap. The Tiros-NOAA satellite program complements the DMSP program. The orbital elements are the same as DMSP's, except for the times of equatorial crossing, and the tilt of the orbital plane. The Tiros-NOAA program meets the civilian community's needs for meteorological data as the DMSP program does for the military

  6. NOAA Polar-orbiting Operational Environmental Satellites (POES) Radiometer Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Polar-orbiting Operational Environmental Satellite (POES) series offers the advantage of daily global coverage, by making nearly polar orbits 14 times per day...

  7. Identifications of the polar cap boundary and the auroral belt in the high-altitude magnetosphere: a model for field-aligned currents

    International Nuclear Information System (INIS)

    Sugiura, M.

    1975-01-01

    By means of the Ogo 5 Goddard Space Flight Center fluxgate magnetometer data the polar cap boundary is identified in the high-altitude magnetosphere by a sudden transition from a dipolar field to a more taillike configuration. It is inferred that there exists a field-aligned-current layer at the polar cap boundary. In the night side magnetosphere the polar cap boundary is identified as the high-latitude boundary of the plasma sheet. The field-aligned current flows downward to the ionosphere on the morning side of the magnetosphere and upward from the ionosphere on the afternoon side. The basic pattern of the magnetic field variations observed during the satellite's traversal of the auroral belt is presented. Currents flow in opposite directions in the two field-aligned-current layers. The current directions in these layers as observed by Ogo 5 in the high-altitude magnetosphere are the same as those observed at low altitudes by the polar-orbiting Triad satellite (Armstrong and Zmuda, 1973). The magnetic field in the region where the lower-latitude field-aligned-current layer is situated is essentially meridional. A model is presented in which two field-aligned-current systems, one at the polar cap boundary and the other on the low-latitude part of the auroral belt, are main []y connected by ionospheric currents flowing across the auroral belt. The existence of field-aligned currents deduced from the Ogo 5 observations is a permanent feature of the magnetosphere. Intensifications of the field-aligned currents and occurrences of multiple pairs of field-aligned-current layers characterize the disturbed conditions of these regions

  8. Magnetic-field fluctuations from 0 to 26 Hz observed from a polar-orbiting satellite

    International Nuclear Information System (INIS)

    Erlandson, R.E.; Zanetti, L.J.; Potemra, T.A.

    1989-01-01

    The polar orbit of the Viking satellite provides a unique opportunity to obtain observations of magnetic fluctuations at mid-altitudes on the dayside of the magnetosphere and in the polar-cusp region. One type of magnetic-field fluctuation, observed in the dayside magnetosphere, was Pc 1 waves. Pc 1 waves are in the electromagnetic ion-cyclotron mode and are generated by anisotropies in energetic ion distributions. The waves are thought to be generated near the equator and to propagate large distances along magnetic-field lines. Most observations of Pc 1 waves have been obtained near the equator using geosynchronous satellites and on the surface of the earth. The Viking observations provide an opportunity to observe Pc 1 waves at mid-latitudes above the ionosphere and to determine the spectral structure and polarization of the waves. ULF/ELF broadband noise represents a second type of magnetic fluctuation acquired by Viking. This type of magnetic fluctuation was observed at high latitudes near the polar cusp and may be useful in the identification of polar-cusp boundaries. Thirdly, electromagnetic ion-cyclotron waves have also been observed in the polar-cusp region. These waves occur only during an unusually high level of magnetic activity and appear to be generated locally

  9. Relativity mission with two counter-orbiting polar satellites

    International Nuclear Information System (INIS)

    Van Patten, R.A.; Everitt, C.W.F.

    1975-01-01

    In 1918, J. Lense and H. Thirring calculated that a moon in orbit around a massive rotating planet would experience a nodal dragging effect due to general relativity. An experiment to measure this effect with two counter-orbiting drag-free satellites in polar earth orbit is described. For a 2 1 / 2 year experiment, the measurement accuracy should approach 1 percent. In addition to precision tracking data from existing ground stations, satellite-to-satellite Doppler ranging data are taken at points of passing near the poles. New geophysical information on both earth harmonics and tidal effects is inherent in the polar ranging data. (auth)

  10. Interrogation of orbital structure by elliptically polarized intense femtosecond laser pulses

    International Nuclear Information System (INIS)

    Abu-samha, M.; Madsen, L. B.

    2011-01-01

    We solve the three-dimensional time-dependent Schroedinger equation and present investigations of the imprint of the orbital angular node in photoelectron momentum distributions of an aligned atomic p-type orbital following ionization by an intense elliptically polarized laser pulse of femtosecond duration. We investigate the role of light ellipticity and the alignment angle of the major polarization axis of the external field relative to the probed orbital by studying radial and angular momentum distributions, the latter at a fixed narrow interval of final momenta close to the peak of the photoelectron momentum distribution. In general only the angular distributions carry a clear signature of the orbital symmetry. Our study shows that circular polarization gives the most clear imprints of orbital nodes. These findings are insensitive to pulse duration.

  11. Orbit Correction for the Newly Developed Polarization-Switching Undulator

    Science.gov (United States)

    Obina, Takashi; Honda, Tohru; Shioya, Tatsuro; Kobayashi, Yukinori; Tsuchiya, Kimichika; Yamamoto, Shigeru

    2007-01-01

    A new scheme of undulator magnet arrangements has been proposed and developed as a polarization-switching radiation source, and its test-stand was installed in the 2.5-GeV Photon Factory storage ring (PF ring) in order to investigate the effects on the beam orbit. The closed orbit distortion (COD) over 200 μm was produced in a vertical direction when we switched the polarization of the radiation from the test-stand. In a horizontal direction, the COD was less than 50μm. The results agreed well with the predictions from the magnetic-field measurement on the bench. In order to suppress the CODs and realize a stable operation of the ring with the polarization-switching, we developed an orbit correction system which consists of an encoder to detect motion of magnets, a pair of beam position monitors (BPMs), signal processing parts, and a pair of steering magnets. We succeeded in suppressing the CODs to the level below 3μm using the system even when we switch the polarization at a maximum frequency of 0.8 Hz.

  12. Localized electron density enhancements in the high-altitude polar ionosphere and their relationships with storm-enhanced density (SED plumes and polar tongues of ionization (TOI

    Directory of Open Access Journals (Sweden)

    Y. Kitanoya

    2011-02-01

    Full Text Available Events of localized electron density increase in the high-altitude (>3000 km polar ionosphere are occasionally identified by the thermal plasma instruments on the Akebono satellite. In this paper, we investigate the vertical density structure in one of such events in detail using simultaneous observations by the Akebono and DMSP F15 satellites, the SuperDARN radars, and a network of ground Global Positioning System (GPS receivers, and the statistical characteristics of a large number (>10 000 of such events using Akebono data over half of an 11-year solar cycle. At Akebono altitude, the parallel drift velocity is remarkably low and the O+ ion composition ratio remarkably high, inside the high plasma-density regions at high altitude. Detailed comparisons between Akebono, DMSP ion velocity and density, and GPS total electron content (TEC data suggest that the localized plasma density increase observed at high altitude on Akebono was likely connected with the polar tongue of ionization (TOI and/or storm enhanced density (SED plume observed in the F-region ionosphere. Together with the SuperDARN plasma convection map these data suggest that the TOI/SED plume penetrated into the polar cap due to anti-sunward convection and the plume existed in the same convection channel as the dense plasma at high altitude; in other words, the two were probably connected to each other by the convecting magnetic field lines. The observed features are consistent with the observed high-density plasma being transported from the mid-latitude ionosphere or plasmasphere and unlikely a part of the polar wind population.

  13. Chorus observations by the Polar spacecraft near the mid-altitude cusp

    Czech Academy of Sciences Publication Activity Database

    Menietti, J. D.; Santolík, Ondřej; Abaci, P. C.

    2009-01-01

    Roč. 57, č. 12 (2009), s. 1412-1418 ISSN 0032-0633 R&D Projects: GA AV ČR IAA301120601 Grant - others:NSF(US) ATM-04-43531; NASA (US) NNG05GM52G.; GA MŠk(CZ) ME 842 Institutional research plan: CEZ:AV0Z30420517 Keywords : chorus * mid-altitude cusp * Polar spacecraft Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.067, year: 2009

  14. The radiation protection problems of high altitude and space flight

    International Nuclear Information System (INIS)

    Fry, R.J.M.

    1993-01-01

    This paper considers the radiation environment in aircraft at high altitudes and spacecraft in low earth orbit and in deep space and the factors that influence the dose equivalents. Altitude, latitude and solar cycle are the major influences for flights below the radiation belts. In deep space, solar cycle and the occurrence of solar particle events are the factors of influence. The major radiation effects of concern are cancer and infertility in males. In high altitude aircraft the radiation consists mainly of protons and neutrons, with neutrons contributing about half the equivalent dose. The average dose rate at altitudes of transcontinental flights that approach the polar regions are greater by a factor of about 2.5 than on routes at low latitudes. Current estimates of does to air crews suggest they are well within the ICRP (1990) recommended dose limits for radiation workers

  15. Lesions to polar/orbital prefrontal cortex selectively impair reasoning about emotional material.

    Science.gov (United States)

    Goel, Vinod; Lam, Elaine; Smith, Kathleen W; Goel, Amit; Raymont, Vanessa; Krueger, Frank; Grafman, Jordan

    2017-05-01

    While it is widely accepted that lesions to orbital prefrontal cortex lead to emotion related disruptions and poor decision-making, there is very little patient data on this issue involving actual logical reasoning tasks. We tested patients with circumscribed, focal lesions largely confined to polar/orbital prefrontal cortex (BA 10 & 11) (N=17) on logical reasoning tasks involving neutral and emotional content, and compared their performance to that of an age and education-matched normal control group (N=22) and a posterior lesion control group (N=24). Our results revealed a significant group by content interaction driven by a selective impairment in the polar/orbital prefrontal cortex group compared to healthy normal controls and to the parietal patient group, in the emotional content reasoning trials. Subsequent analyses of congruent and incongruent reasoning trials indicated that this impairment was driven by the poor performance of patients with polar/orbital lesions in the incongruent trials. We conclude that the polar/orbital prefrontal cortex plays a critical role in filtering emotionally charged content from the material before it is passed on to the reasoning system in lateral/dorsal regions of prefrontal cortex. Where unfiltered content is passed to the reasoning engine, either as a result of pathology (as in the case of our patients) or as a result of individual differences, reasoning performance suffers. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Circular-Polarization-Selective Transmission Induced by Spin-Orbit Coupling in a Helical Tape Waveguide

    Science.gov (United States)

    Liu, Yahong; Guo, Qinghua; Liu, Hongchao; Liu, Congcong; Song, Kun; Yang, Biao; Hou, Quanwen; Zhao, Xiaopeng; Zhang, Shuang; Navarro-Cía, Miguel

    2018-05-01

    Spin-orbit coupling of light, describing the interaction between the polarization (spin) and spatial degrees of freedom (orbit) of light, plays an important role in subwavelength scale systems and leads to many interesting phenomena, such as the spin Hall effect of light. Here, based on the spin-orbit coupling, we design and fabricate a helical tape waveguide (HTW), which can realize a circular-polarization-selective process. When the incident circularly polarized wave is of the same handedness as the helix of the HTW, a nearly complete transmission is observed; in contrast, a counterrotating circular polarization of incident wave results in a much lower transmission or is even totally blocked by the HTW. Indeed, both simulations and experiments reveal that the blocked component of power leaks through the helical aperture of the HTW and forms a conical beam analogous to helical Cherenkov radiation due to the conversion from the spin angular momentum to the orbital angular momentum. Our HTW structure demonstrates its potential as a polarization selector in a broadband frequency range.

  17. Current-induced spin polarization in a spin-polarized two-dimensional electron gas with spin-orbit coupling

    International Nuclear Information System (INIS)

    Wang, C.M.; Pang, M.Q.; Liu, S.Y.; Lei, X.L.

    2010-01-01

    The current-induced spin polarization (CISP) is investigated in a combined Rashba-Dresselhaus spin-orbit-coupled two-dimensional electron gas, subjected to a homogeneous out-of-plane magnetization. It is found that, in addition to the usual collision-related in-plane parts of CISP, there are two impurity-density-free contributions, arising from intrinsic and disorder-mediated mechanisms. The intrinsic parts of spin polarization are related to the Berry curvature, analogous with the anomalous and spin Hall effects. For short-range collision, the disorder-mediated spin polarizations completely cancel the intrinsic ones and the total in-plane components of CISP equal those for systems without magnetization. However, for remote disorders, this cancellation does not occur and the total in-plane components of CISP strongly depend on the spin-orbit interaction coefficients and magnetization for both pure Rashba and combined Rashba-Dresselhaus models.

  18. Ionic Potential and Band Narrowing as a Source of Orbital Polarization in Nickelate/Insulator Superlattices

    Science.gov (United States)

    Georgescu, Alexandru B.; Disa, Ankit S.; Kumah, Divine P.; Ismail-Beigi, Sohrab; Walker, Frederick J.; Ahn, Charles H.

    Nickelate interfaces display complex, interacting electronic properties such as thickness dependent metal-insulator transitions. One large body of effort involving nickelates has aimed to split the energies of the Ni 3d orbitals (orbital polarization) to make the resulting band structure resemble that of cuprate superconductors. The most commonly studied interfacial system involves superlattices of alternating nickelate and insulating perovksite-structure layers; the resulting orbital polarization at the nickelate-insulator interface is understood as being due to confinement or structural symmetry breaking. By using first principles theory on the NdNiO3/NdAlO3 superlattice, we show that another important source of orbital polarization stems from electrostatic effects: the more ionic nature of the cations in the insulator (when compared to the nickelate) can shift the relative orbital energies of the Ni. We use density functional theory (DFT) and add electronic correlations via slave-bosons to describe the effect of correlation-induced band narrowing on the orbital polarization. Work supported by NSF Grant MRSEC DMR-1119826.

  19. Interrogation of orbital structure by elliptically polarized intense femtosecond laser pulses

    DEFF Research Database (Denmark)

    Abu-Samha, Mahmoud; Madsen, Lars Bojer

    2011-01-01

    We solve the three-dimensional time-dependent Schrödinger equation and present investigations of the imprint of the orbital angular node in photoelectron momentum distributions of an aligned atomic p-type orbital following ionization by an intense elliptically polarized laser pulse of femtosecond...

  20. Monitoring Mars LOD Variations from a High Altitude Circular Equatorial Orbit: Theory and Simulation

    Science.gov (United States)

    Barriot, J.; Dehant, V.; Duron, J.

    2003-12-01

    We compute the perturbations of a high altitude circular equatorial orbit of a martian probe under the influence of an annual variation of the martian lenght of day. For this purpose, we use the first order perturbations of the newtonian equations of motion, where the small parameter is given from the hourglass model of Chao and Rubincam, which allow a simple computation of CO2 exchanges during the martian year. We are able to demonstrate that the perturbations contains two components: the first one is a sine/cosine modulation at the orbit frequency, the second one is composed of terms of the form exp(t)*sin(t), so the orbit may not stable in the long term (several martian years), with perturbations growing exponentially. We give the full theory and numbers.

  1. High Altitude Launch for a Practical SSTO

    Science.gov (United States)

    Landis, Geoffrey A.; Denis, Vincent

    2003-01-01

    Existing engineering materials allow the constuction of towers to heights of many kilometers. Orbital launch from a high altitude has significant advantages over sea-level launch due to the reduced atmospheric pressure, resulting in lower atmospheric drag on the vehicle and allowing higher rocket engine performance. High-altitude launch sites are particularly advantageous for single-stage to orbit (SSTO) vehicles, where the payload is typically 2% of the initial launch mass. An earlier paper enumerated some of the advantages of high altitude launch of SSTO vehicles. In this paper, we calculate launch trajectories for a candidate SSTO vehicle, and calculate the advantage of launch at launch altitudes 5 to 25 kilometer altitudes above sea level. The performance increase can be directly translated into increased payload capability to orbit, ranging from 5 to 20% increase in the mass to orbit. For a candidate vehicle with an initial payload fraction of 2% of gross lift-off weight, this corresponds to 31% increase in payload (for 5-km launch altitude) to 122% additional payload (for 25-km launch altitude).

  2. Prototype detector development for measurement of high altitude Martian dust using a future orbiter platform

    Science.gov (United States)

    Pabari, Jayesh; Patel, Darshil; Chokhawala, Vimmi; Bogavelly, Anvesh

    2016-07-01

    Dust devils mostly occur during the mid of Southern hemisphere summer on Mars and play a key role in the background dust opacity. Due to continuous bombardment of micrometeorites, secondary ejecta come out from the Moons of the Mars and can easily escape. This phenomenon can contribute dust around the Moons and therefore, also around the Mars. Similar to the Moons of the Earth, the surfaces of the Martian Moons get charged and cause the dust levitation to occur, adding to the possible dust source. Also, interplanetary dust particles may be able to reach the Mars and contribute further. It is hypothesized that the high altitude Martian dust could be in the form of a ring or tori around the Mars. However, no such rings have been detected to the present day. Typically, width and height of the dust torus is ~5 Mars radii wide (~16950 km) in both the planes as reported in the literature. Recently, very high altitude dust at about 1000 km has been found by MAVEN mission and it is expected that the dust may be concentrated at about 150 to 500 km. However, a langmuir probe cannot explain the source of such dust particles. It is a puzzling question to the space scientist how dust has reached to such high altitudes. A dedicated dust instrument on future Mars orbiter may be helpful to address such issues. To study origin, abundance, distribution and seasonal variation of Martian dust, a Mars Orbit Dust Experiment (MODEX) is proposed. In order to measure the Martian dust from a future orbiter, design of a prototype of an impact ionization dust detector has been initiated at PRL. This paper presents developmental aspects of the prototype dust detector and initial results. The further work is underway.

  3. Altitude Registration of Limb-Scattered Radiation

    Science.gov (United States)

    Moy, Leslie; Bhartia, Pawan K.; Jaross, Glen; Loughman, Robert; Kramarova, Natalya; Chen, Zhong; Taha, Ghassan; Chen, Grace; Xu, Philippe

    2017-01-01

    One of the largest constraints to the retrieval of accurate ozone profiles from UV backscatter limb sounding sensors is altitude registration. Two methods, the Rayleigh scattering attitude sensing (RSAS) and absolute radiance residual method (ARRM), are able to determine altitude registration to the accuracy necessary for long-term ozone monitoring. The methods compare model calculations of radiances to measured radiances and are independent of onboard tracking devices. RSAS determines absolute altitude errors, but, because the method is susceptible to aerosol interference, it is limited to latitudes and time periods with minimal aerosol contamination. ARRM, a new technique introduced in this paper, can be applied across all seasons and altitudes. However, it is only appropriate for relative altitude error estimates. The application of RSAS to Limb Profiler (LP) measurements from the Ozone Mapping and Profiler Suite (OMPS) on board the Suomi NPP (SNPP) satellite indicates tangent height (TH) errors greater than 1 km with an absolute accuracy of +/-200 m. Results using ARRM indicate a approx. 300 to 400m intra-orbital TH change varying seasonally +/-100 m, likely due to either errors in the spacecraft pointing or in the geopotential height (GPH) data that we use in our analysis. ARRM shows a change of approx. 200m over 5 years with a relative accuracy (a long-term accuracy) of 100m outside the polar regions.

  4. Spin-polarized spin-orbit-split quantum-well states in a metal film

    Energy Technology Data Exchange (ETDEWEB)

    Varykhalov, Andrei; Sanchez-Barriga, Jaime; Gudat, Wolfgang; Eberhardt, Wolfgang; Rader, Oliver [BESSY Berlin (Germany); Shikin, Alexander M. [St. Petersburg State University (Russian Federation)

    2008-07-01

    Elements with high atomic number Z lead to a large spin-orbit coupling. Such materials can be used to create spin-polarized electronic states without the presence of a ferromagnet or an external magnetic field if the solid exhibits an inversion asymmetry. We create large spin-orbit splittings using a tungsten crystal as substrate and break the structural inversion symmetry through deposition of a gold quantum film. Using spin- and angle-resolved photoelectron spectroscopy, it is demonstrated that quantum-well states forming in the gold film are spin-orbit split and spin polarized up to a thickness of at least 10 atomic layers. This is a considerable progress as compared to the current literature which reports spin-orbit split states at metal surfaces which are either pure or covered by at most a monoatomic layer of adsorbates.

  5. Earth's external magnetic fields at low orbital altitudes

    Science.gov (United States)

    Klumpar, D. M.

    1990-01-01

    Under our Jun. 1987 proposal, Magnetic Signatures of Near-Earth Distributed Currents, we proposed to render operational a modeling procedure that had been previously developed to compute the magnetic effects of distributed currents flowing in the magnetosphere-ionosphere system. After adaptation of the software to our computing environment we would apply the model to low altitude satellite orbits and would utilize the MAGSAT data suite to guide the analysis. During the first year, basic computer codes to run model systems of Birkeland and ionospheric currents and several graphical output routines were made operational on a VAX 780 in our research facility. Software performance was evaluated using an input matchstick ionospheric current array, field aligned currents were calculated and magnetic perturbations along hypothetical satellite orbits were calculated. The basic operation of the model was verified. Software routines to analyze and display MAGSAT satellite data in terms of deviations with respect to the earth's internal field were also made operational during the first year effort. The complete set of MAGSAT data to be used for evaluation of the models was received at the end of the first year. A detailed annual report in May 1989 described these first year activities completely. That first annual report is included by reference in this final report. This document summarizes our additional activities during the second year of effort and describes the modeling software, its operation, and includes as an attachment the deliverable computer software specified under the contract.

  6. Suomi National Polar-Orbiting Partnership Visible Infrared Imaging Radiometer Suite Polarization Sensitivity Analysis

    Science.gov (United States)

    Sun, Junqiang; Xiong, Xiaoxiong; Waluschka, Eugene; Wang, Menghua

    2016-01-01

    The Visible Infrared Imaging Radiometer Suite (VIIRS) is one of five instruments onboard the Suomi National Polar-Orbiting Partnership (SNPP) satellite that launched from Vandenberg Air Force Base, California, on October 28, 2011. It is a whiskbroom radiometer that provides +/-56.28deg scans of the Earth view. It has 22 bands, among which 14 are reflective solar bands (RSBs). The RSBs cover a wavelength range from 410 to 2250 nm. The RSBs of a remote sensor are usually sensitive to the polarization of incident light. For VIIRS, it is specified that the polarization factor should be smaller than 3% for 410 and 862 nm bands and 2.5% for other RSBs for the scan angle within +/-45deg. Several polarization sensitivity tests were performed prelaunch for SNPP VIIRS. The first few tests either had large uncertainty or were less reliable, while the last one was believed to provide the more accurate information about the polarization property of the instrument. In this paper, the measured data in the last polarization sensitivity test are analyzed, and the polarization factors and phase angles are derived from the measurements for all the RSBs. The derived polarization factors and phase angles are band, detector, and scan angle dependent. For near-infrared bands, they also depend on the half-angle mirror side. Nevertheless, the derived polarization factors are all within the specification, although the strong detector dependence of the polarization parameters was not expected. Compared to the Moderate Resolution Imaging Spectroradiometer on both Aqua and Terra satellites, the polarization effect on VIIRS RSB is much smaller.

  7. Electrical polarization and orbital magnetization: the modern theories

    International Nuclear Information System (INIS)

    Resta, Raffaele

    2010-01-01

    Macroscopic polarization P and magnetization M are the most fundamental concepts in any phenomenological description of condensed media. They are intensive vector quantities that intuitively carry the meaning of dipole per unit volume. But for many years both P and the orbital term in M evaded even a precise microscopic definition, and severely challenged quantum-mechanical calculations. If one reasons in terms of a finite sample, the electric (magnetic) dipole is affected in an extensive way by charges (currents) at the sample boundary, due to the presence of the unbounded position operator in the dipole definitions. Therefore P and the orbital term in M-phenomenologically known as bulk properties-apparently behave as surface properties; only spin magnetization is problemless. The field has undergone a genuine revolution since the early 1990s. Contrary to a widespread incorrect belief, P has nothing to do with the periodic charge distribution of the polarized crystal: the former is essentially a property of the phase of the electronic wavefunction, while the latter is a property of its modulus. Analogously, the orbital term in M has nothing to do with the periodic current distribution in the magnetized crystal. The modern theory of polarization, based on a Berry phase, started in the early 1990s and is now implemented in most first-principle electronic structure codes. The analogous theory for orbital magnetization started in 2005 and is partly work in progress. In the electrical case, calculations have concerned various phenomena (ferroelectricity, piezoelectricity, and lattice dynamics) in several materials, and are in spectacular agreement with experiments; they have provided thorough understanding of the behaviour of ferroelectric and piezoelectric materials. In the magnetic case the very first calculations are appearing at the time of writing (2010). Here I review both theories on a uniform ground in a density functional theory (DFT) framework, pointing out

  8. Spin-orbit-induced spin splittings in polar transition metal dichalcogenide monolayers

    KAUST Repository

    Cheng, Yingchun

    2013-06-01

    The Rashba effect in quasi two-dimensional materials, such as noble metal surfaces and semiconductor heterostructures, has been investigated extensively, while interest in real two-dimensional systems has just emerged with the discovery of graphene. We present ab initio electronic structure, phonon, and molecular-dynamics calculations to study the structural stability and spin-orbit-induced spin splitting in the transition metal dichalcogenide monolayers MXY (M = Mo, W and X, Y = S, Se, Te). In contrast to the non-polar systems with X = Y, in the polar systems with X ≠ Y the Rashba splitting at the Γ-point for the uppermost valence band is caused by the broken mirror symmetry. An enhancement of the splitting can be achieved by increasing the spin-orbit coupling and/or the potential gradient. © Copyright EPLA, 2013.

  9. Spin-orbit controlled capacitance of a polar heterostructure

    Energy Technology Data Exchange (ETDEWEB)

    Steffen, Kevin; Kopp, Thilo [Center for Electronic Correlations and Magnetism, EP VI, Institute of Physics, University of Augsburg, 86135 Augsburg (Germany); Loder, Florian [Center for Electronic Correlations and Magnetism, EP VI and TP III, Institute of Physics, University of Augsburg, 86135 Augsburg (Germany)

    2015-07-01

    Oxide heterostructures with polar films display special electronic properties, such as the electronic reconstruction at their internal interfaces with the formation of two-dimensional metallic states. Moreover, the electrical field from the polar layers is inversion-symmetry breaking and may generate a strong Rashba spin-orbit coupling (RSOC) in the interfacial electronic system. We investigate the capacitance of a heterostructure in which a strong RSOC at a metallic interface is controlled by the electric field of a surface electrode. Such a structure is for example given by a LaAlO{sub 3} film on a SrTiO{sub 3} substrate which is gated by a top electrode. We find that due to a strong RSOC the capacitance can be larger than the classical geometric value.

  10. Development of an Architecture of Sun-Synchronous Orbital Slots to Minimize Conjunctions

    Science.gov (United States)

    Weeden, B.

    Sun-synchronous orbit (SSO) satellites serve many important functions, primarily in the areas of Earth reconnaissance and weather. The orbital parameters of altitude, inclination and right ascension which allow for the unique utility of Sun-sync orbit limit these satellites to a very specific region of space. The popularity of these satellite missions combined with the use of similar engineering solutions has resulted in the majority of current Sun-sync satellites within this region having very similar inclinations and altitudes while also spaced around the Equator in right ascension, creating the opportunity for conjunctions at the polar crossing points and a serious safety issue that could endanger long-term sustainability of SSO. This paper outlines the development of a new architecture of SSO zoning to create specific slots separating SSO satellites in altitude, right ascension and time at all orbital intersections while minimizing the limitations on utility. A methodical approach for the development of the system is presented along with the work-to-date and a software tool for calculating repeating ground track orbits. The slot system is intended to allow for continued utility of and safe operation within SSO while greatly decreasing the chance of collisions at orbital intersections. This architecture is put forward as one possible element of a new Space Traffic Management (STM) system with the overall goal of maintaining the safe and continued used of space by all actors.

  11. Spin-orbit torque induced magnetic vortex polarity reversal utilizing spin-Hall effect

    Science.gov (United States)

    Li, Cheng; Cai, Li; Liu, Baojun; Yang, Xiaokuo; Cui, Huanqing; Wang, Sen; Wei, Bo

    2018-05-01

    We propose an effective magnetic vortex polarity reversal scheme that makes use of spin-orbit torque introduced by spin-Hall effect in heavy-metal/ferromagnet multilayers structure, which can result in subnanosecond polarity reversal without endangering the structural stability. Micromagnetic simulations are performed to investigate the spin-Hall effect driven dynamics evolution of magnetic vortex. The mechanism of magnetic vortex polarity reversal is uncovered by a quantitative analysis of exchange energy density, magnetostatic energy density, and their total energy density. The simulation results indicate that the magnetic vortex polarity is reversed through the nucleation-annihilation process of topological vortex-antivortex pair. This scheme is an attractive option for ultra-fast magnetic vortex polarity reversal, which can be used as the guidelines for the choice of polarity reversal scheme in vortex-based random access memory.

  12. Monte Carlo simulations of the secondary neutron ambient and effective dose equivalent rates from surface to suborbital altitudes and low Earth orbit.

    Science.gov (United States)

    El-Jaby, Samy; Richardson, Richard B

    2015-07-01

    Occupational exposures from ionizing radiation are currently regulated for airline travel (Earth orbit (∼300-400 km). Aircrew typically receive between 1 and 6 mSv of occupational dose annually, while aboard the International Space Station, the area radiation dose equivalent measured over just 168 days was 106 mSv at solar minimum conditions. It is anticipated that space tourism vehicles will reach suborbital altitudes of approximately 100 km and, therefore, the annual occupational dose to flight crew during repeated transits is expected to fall somewhere between those observed for aircrew and astronauts. Unfortunately, measurements of the radiation environment at the high altitudes reached by suborbital vehicles are sparse, and modelling efforts have been similarly limited. In this paper, preliminary MCNPX radiation transport code simulations are developed of the secondary neutron flux profile in air from surface altitudes up to low Earth orbit at solar minimum conditions and excluding the effects of spacecraft shielding. These secondary neutrons are produced by galactic cosmic radiation interacting with Earth's atmosphere and are among the sources of radiation that can pose a health risk. Associated estimates of the operational neutron ambient dose equivalent, used for radiation protection purposes, and the neutron effective dose equivalent that is typically used for estimates of stochastic health risks, are provided in air. Simulations show that the neutron radiation dose rates received at suborbital altitudes are comparable to those experienced by aircrew flying at 7 to 14 km. We also show that the total neutron dose rate tails off beyond the Pfotzer maximum on ascension from surface up to low Earth orbit. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

  13. Effect of Rashba and Dresselhaus Spin-Orbit Couplings on Electron Spin Polarization in a Hybrid Magnetic-Electric Barrier Nanostructure

    Science.gov (United States)

    Yang, Shi-Peng; Lu, Mao-Wang; Huang, Xin-Hong; Tang, Qiang; Zhou, Yong-Long

    2017-04-01

    A theoretical study has been carried out on the spin-dependent electron transport in a hybrid magnetic-electric barrier nanostructure with both Rashba and Dresselhaus spin-orbit couplings, which can be experimentally realized by depositing a ferromagnetic strip and a Schottky metal strip on top of a semiconductor heterostructure. The spin-orbit coupling-dependent transmission coefficient, conductance, and spin polarization are calculated by solving the Schrödinger equation exactly with the help of the transfer-matrix method. We find that both the magnitude and sign of the electron spin polarization vary strongly with the spin-orbit coupling strength. Thus, the degree of electron spin polarization can be manipulated by properly adjusting the spin-orbit coupling strength, and such a nanosystem can be employed as a controllable spin filter for spintronics applications.

  14. Signatures of the high-altitude polar cusp and dayside auroral regions as seen by the Viking electric field experiment

    International Nuclear Information System (INIS)

    Marklund, G.T.; Blomberg, L.G.; Faelthammar, C.G.; Erlandson, R.E.; Potemra, T.A.

    1990-01-01

    Electric field and satellite potential observations along 42 Viking orbits in the high-altitude (2R E ) polar cusp and dayside auroral region have been examined. Within the cusp the plasma density usually reaches a maximum, and it is typically very homogeneous, in contrast to the irregular and lower density in the cleft and dayside auroral regions. The maxima in the plasma density are sometimes anticorrelated with the magnetic field strength, indicating a diamagnetic effect. The entire cusp and dayside auroral regions are characterized by irregular and burstlike electric fields, comprising field reversals on various scales (up to 3 min or 500 km), the larger scales, however, being rare in the cusp. Another common feature in these regions is the high correlation between mutually orthogonal components of the electric and magnetic fields, both for large-scale variations across spatial structures and for wave and pulsations in the ULF frequency range. The electric field signatures in the cusp (in the 1100-1300 MLT sector) are, however, characteristically different from the cleft and oval field signatures in that the electric field is usually less intense and less structured and not correlated with the substorm activity level

  15. Cassini ISS Observation of Saturn from Grand Finale Orbits

    Science.gov (United States)

    Blalock, J. J.; Sayanagi, K. M.; Ingersoll, A. P.; Dyudina, U.; Ewald, S. P.; McCabe, R. M.; Garland, J.; Gunnarson, J.; Gallego, A.

    2017-12-01

    We present images captured during Cassini's Grand Finale orbits, and their preliminary analyses. During the final 22 orbits of the mission, the spacecraft is in orbits that have 6.5 day period at an inclination of 62 degrees, apoapsis altitude of about 1,272,000 km, and periapsis altitudes of about 2,500 km. Images captured during periapsis passes show Saturn's atmosphere at unprecedented spatial resolution. We present preliminary analyses of these images, including the final images captured before the end of the mission when the spacecraft enters Saturn's atmosphere on September 15th, 2017. Prominent features captured during the final orbits include the north polar vortex and other vortices as well as very detailed views of the "popcorn clouds" that reside between the Hexagon and the north pole. In the cloud field between zonal jets, clouds either resemble linear streaks suggestive of cirrus-like clouds or round shapes suggestive of vortices or cumulus anvil. The presence of linear streaks that follow lines of constant latitudes suggests that meridional mixing is inhibited at those latitudes. The size of vortices may reflect latitudinal variation in the atmospheric deformation radius. We also compare the new images to those captured earlier in the Cassini mission to characterize the temporal evolution such as changes in the zonal jet speeds, and prevalence and colors of vortices. A particular focus of our interest is the long-term change in the color of the hexagon, the evolution of the wind speeds in the jetstream that blows eastward at the boundary of the hexagon, and the morphology of the north polar vortex. Our work has been supported by NASA PATM NNX14AK07G, NSF AAG 1212216, and NASA NESSF NNX15AQ70H.

  16. Detecting a Subsurface Ocean From Periodic Orbits at Enceladus

    Science.gov (United States)

    Casotto, S.; Padovan, S.; Russell, R. P.; Lara, M.

    2008-12-01

    Enceladus is a small icy satellite of Saturn which has been observed by the Cassini orbiter to eject plumes mainly consisting of water vapor from the "tiger stripes" located near its South pole. While tidal heating has been ruled out as an inadequate energy source to drive these eruptions, tidally induced shear stress both along and across the stripes appears to be sufficiently powerful. The internal constitution of Enceladus that fits this model is likely to entail a thin crust and a subcrustal water layer above an undifferentiated interior. Apart from the lack of a core/mantle boundary, the situation is similar to the current hypothetical models of Europa's interior. The determination of the existence of a subsurface fluid layer can therefore be pursued with similar methods, including the study of the gravitational perturbations of tidal origin on an Enceladus orbiter, and the use of altimeter measurements to the tidally deformed surface. The dynamical environment of an Enceladus orbiter is made very unstable by the overwhelming presence of nearby Saturn. The Enceladus sphere of influence is roughly twice its radius. This makes it considerably more difficult to orbit than Europa, whose sphere of influence is ~six times its radius. While low-altitude, near-polar Enceladus orbits suffer extreme instability, recent works have extended the inclination envelope for long-term stable orbits at Enceladus. Several independent methods suggest that ~65 degrees inclination is the maximum attainable for stable, perturbed Keplerian motion. These orbits are non-circular and exist with altitude variations from ~200 to ~300 km. We propose a nominal reference orbit that enjoys long term stability and is favorable for long-term mapping and other scientific experiments. A brief excursion to a lower altitude, slightly higher inclined, yet highly unstable orbit is proposed to improve gravity signatures and enable high resolution, nadir-pointing experiments on the geysers emanating

  17. Modification of the method of polarized orbitals for electron--alkali-metal scattering: Application to e-Li

    International Nuclear Information System (INIS)

    Bhatia, A.K.; Temkin, A.; Silver, A.; Sullivan, E.C.

    1978-01-01

    The method of polarized orbitals is modified to treat low-energy scattering of electrons from highly polarizable systems, specifically alkali-metal atoms. The modification is carried out in the particular context of the e-Li system, but the procedure is general; it consists of modifying the polarized orbital, so that when used in the otherwise orthodox form of the method, it gives (i) the correct electron affinity of the negative ion (in this case Li - ), (ii) the proper (i.e., Levinson-Swan) number of nodes of the associated zero-energy scattering orbital, and (iii) the correct polarizability. A procedure is devised whereby the scattering length can be calculated from the (known) electron affinity without solving the bound-state equation. Using this procedure we adduce a 1 S scattering length of 8.69a 0 . (The 3 S scattering length is -9.22a 0 .) The above modifications can also be carried out in the (lesser) exchange adiabatic approximation. However, they lead to qualitatively incorrect 3 S phase shifts. The modified polarized-orbital phase shifts are qualitatively similar to close-coupling and elaborate variational calculations. Quantitative differences from the latter calculations, however, remain; they are manifested most noticeably in the very-low-energy total and differential spin-flip cross sections

  18. The Study of a Super Low Altitude Satellite

    Science.gov (United States)

    Noda, Atsushi; Homma, Masanori; Utashima, Masayoshi

    This paper reports the result of a study for super low altitude satellite. The altitude of this satellite's orbit is lower than ever. The altitude of a conventional earth observing satellite is generally around from 600km to 900km. The lowest altitude of earth observing satellite launched in Japan was 350km; the Tropical Rainfall Measuring Mission (TRMM). By comparison, the satellite reported in this paper is much lower than that and it is planned to orbit below 200km. Furthermore, the duration of the flight planned is more than two years. Any satellite in the world has not achieved to keep such a low altitude that long term. The satellite in such a low orbit drops quickly because of the strong air drag. Our satellite will cancel the air drag effect by ion engine thrust. To realize this idea, a drag-free system will be applied. This usually leads a complicated and expensive satellite system. We, however, succeeded in finding a robust control law for a simple system even under the unpredictable change of air drag. When the altitude of the satellite is lowered successfully, the spatial resolution of an optical sensor can be highly improved. If a SAR is equipped with the satellite, it enables the drastic reduction of electric power consumption and the fabulous spatial resolution improvement at the same time.

  19. Spin polarization of tunneling current in barriers with spin-orbit coupling

    International Nuclear Information System (INIS)

    Fujita, T; Jalil, M B A; Tan, S G

    2008-01-01

    We present a general method for evaluating the maximum transmitted spin polarization and optimal spin axis for an arbitrary spin-orbit coupling (SOC) barrier system, in which the spins lie in the azimuthal plane and finite spin polarization is achieved by wavevector filtering of electrons. Besides momentum filtering, another prerequisite for finite spin polarization is asymmetric occupation or transmission probabilities of the eigenstates of the SOC Hamiltonian. This is achieved most efficiently by resonant tunneling through multiple SOC barriers. We apply our analysis to common SOC mechanisms in semiconductors: pure bulk Dresselhaus SOC, heterostructures with mixed Dresselhaus and Rashba SOC and strain-induced SOC. In particular, we find that the interplay between Dresselhaus and Rashba SOC effects can yield several advantageous features for spin filter and spin injector functions, such as increased robustness to wavevector spread of electrons

  20. Spin polarization of tunneling current in barriers with spin-orbit coupling.

    Science.gov (United States)

    Fujita, T; Jalil, M B A; Tan, S G

    2008-03-19

    We present a general method for evaluating the maximum transmitted spin polarization and optimal spin axis for an arbitrary spin-orbit coupling (SOC) barrier system, in which the spins lie in the azimuthal plane and finite spin polarization is achieved by wavevector filtering of electrons. Besides momentum filtering, another prerequisite for finite spin polarization is asymmetric occupation or transmission probabilities of the eigenstates of the SOC Hamiltonian. This is achieved most efficiently by resonant tunneling through multiple SOC barriers. We apply our analysis to common SOC mechanisms in semiconductors: pure bulk Dresselhaus SOC, heterostructures with mixed Dresselhaus and Rashba SOC and strain-induced SOC. In particular, we find that the interplay between Dresselhaus and Rashba SOC effects can yield several advantageous features for spin filter and spin injector functions, such as increased robustness to wavevector spread of electrons.

  1. Spatial analysis of galactic cosmic ray particles in low earth orbit/near equator orbit using SPENVIS

    International Nuclear Information System (INIS)

    Suparta, W; Zulkeple, S K

    2014-01-01

    The space environment has grown intensively harmful to spacecraft and astronauts. Galactic cosmic rays (GCRs) are one of the radiation sources that composed of high energetic particles originated from space and capable of damaging electronic systems through single event upset (SEU) process. In this paper, we analyzed GCR fluxes at different altitudes by using Space Environment Information System (SPENVIS) software and the results are compared to determine their intensities with respect to distance in the Earth's orbit. The altitudes are set at low earth orbit (400 km and 685 km), medium earth orbit (19,100 km and 20,200 km) and high earth orbit (35,793 km and 1,000,000 km). Then, within Low Earth Orbit (LEO) near the equator (NEqO), we used altitude of 685 km to compare GCRs with the intensities of solar particles and trapped particles in the radiation belt to determine the significance of GCRs in the orbit itself.

  2. National Polar-orbiting Operational Environmental Satellite System (NPOESS) Design and Architecture

    Science.gov (United States)

    Hinnant, F.

    2008-12-01

    The National Oceanic and Atmospheric Administration (NOAA), Department of Defense (DoD), and National Aeronautics and Space Administration (NASA) are jointly acquiring the next-generation weather and environmental satellite system - the National Polar-orbiting Operational Environmental Satellite System (NPOESS). NPOESS will replace the current Polar-orbiting Operational Environmental Satellites (POES) managed by NOAA and the Defense Meteorological Satellite Program (DMSP) managed by the DoD and will provide continuity for the NASA Earth Observing System (EOS) with the launch of the NPOESS Preparatory Project (NPP). This poster will provide an overview of the NPOESS architecture, which includes four segments. The space segment includes satellites in two orbits that carry a suite of sensors to collect meteorological, oceanographic, climatological, and solar-geophysical observations of the Earth, atmosphere, and near-Earth space environment. The NPOESS design allows centralized mission management and delivers high quality environmental products to military, civil and scientific users through a Command, Control, and Communication Segment (C3S). The data processing for NPOESS is accomplished through an Interface Data Processing Segment (IDPS)/Field Terminal Segment (FTS) that processes NPOESS satellite data to provide environmental data products to NOAA and DoD processing centers operated by the United States government as well as to remote terminal users. The Launch Support Segment completes the four segments that make up NPOESS that will enhance the connectivity between research and operations and provide critical operational and scientific environmental measurements to military, civil, and scientific users until 2026.

  3. Polarized atomic orbitals for linear scaling methods

    Science.gov (United States)

    Berghold, Gerd; Parrinello, Michele; Hutter, Jürg

    2002-02-01

    We present a modified version of the polarized atomic orbital (PAO) method [M. S. Lee and M. Head-Gordon, J. Chem. Phys. 107, 9085 (1997)] to construct minimal basis sets optimized in the molecular environment. The minimal basis set derives its flexibility from the fact that it is formed as a linear combination of a larger set of atomic orbitals. This approach significantly reduces the number of independent variables to be determined during a calculation, while retaining most of the essential chemistry resulting from the admixture of higher angular momentum functions. Furthermore, we combine the PAO method with linear scaling algorithms. We use the Chebyshev polynomial expansion method, the conjugate gradient density matrix search, and the canonical purification of the density matrix. The combined scheme overcomes one of the major drawbacks of standard approaches for large nonorthogonal basis sets, namely numerical instabilities resulting from ill-conditioned overlap matrices. We find that the condition number of the PAO overlap matrix is independent from the condition number of the underlying extended basis set, and consequently no numerical instabilities are encountered. Various applications are shown to confirm this conclusion and to compare the performance of the PAO method with extended basis-set calculations.

  4. A planet in a polar orbit of 1.4 solar-mass star

    Directory of Open Access Journals (Sweden)

    Guenther E.W.

    2015-01-01

    Full Text Available Although more than a thousand transiting extrasolar planets have been discovered, only very few of them orbit stars that are more massive than the Sun. The discovery of such planets is interesting, because they have formed in disks that are more massive but had a shorter life time than those of solar-like stars. Studies of planets more massive than the Sun thus tell us how the properties of the proto-planetary disks effect the formation of planets. Another aspect that makes these planets interesting is that they have kept their original orbital inclinations. By studying them we can thus find out whether the orbital axes planets are initially aligned to the stars rotational axes, or not. Here we report on the discovery of a planet of a 1.4 solar-mass star with a period of 5.6 days in a polar orbit made by CoRoT. This new planet thus is one of the few known close-in planets orbiting a star that is substantially more massive than the Sun.

  5. Spin-orbit-coupled Bose-Einstein condensates of rotating polar molecules

    Science.gov (United States)

    Deng, Y.; You, L.; Yi, S.

    2018-05-01

    An experimental proposal for realizing spin-orbit (SO) coupling of pseudospin 1 in the ground manifold 1Σ (υ =0 ) of (bosonic) bialkali polar molecules is presented. The three spin components are composed of the ground rotational state and two substates from the first excited rotational level. Using hyperfine resolved Raman processes through two select excited states resonantly coupled by a microwave, an effective coupling between the spin tensor and linear momentum is realized. The properties of Bose-Einstein condensates for such SO-coupled molecules exhibiting dipolar interactions are further explored. In addition to the SO-coupling-induced stripe structures, the singly and doubly quantized vortex phases are found to appear, implicating exciting opportunities for exploring novel quantum physics using SO-coupled rotating polar molecules with dipolar interactions.

  6. Airborne Laser Polarization Sensor

    Science.gov (United States)

    Kalshoven, James, Jr.; Dabney, Philip

    1991-01-01

    Instrument measures polarization characteristics of Earth at three wavelengths. Airborne Laser Polarization Sensor (ALPS) measures optical polarization characteristics of land surface. Designed to be flown at altitudes of approximately 300 m to minimize any polarizing or depolarizing effects of intervening atmosphere and to look along nadir to minimize any effects depending on look angle. Data from measurements used in conjunction with data from ground surveys and aircraft-mounted video recorders to refine mathematical models used in interpretation of higher-altitude polarimetric measurements of reflected sunlight.

  7. Influence of the Choice of Lunar Gravity Model on Orbit Determination for Lunar Orbiters

    Directory of Open Access Journals (Sweden)

    Young-Rok Kim

    2018-01-01

    Full Text Available We examine the influence of the lunar gravity model on the orbit determination (OD of a lunar orbiter operating in a 100 km high, lunar polar orbit. Doppler and sequential range measurements by three Deep Space Network antennas and one Korea Deep Space Antenna were used. For measurement simulation and OD analysis, STK11 and ODTK6 were utilized. GLGM2, LP100K, LP150Q, GRAIL420A, and GRAIL660B were used for investigation of lunar gravity model selection effect. OD results were assessed by position and velocity uncertainties with error covariance and an external orbit comparison using simulated true orbit. The effect of the lunar gravity models on the long-term OD, degree and order level, measurement-acquisition condition, and lunar altitude was investigated. For efficiency verification, computational times for the five lunar gravity models were compared. Results showed that significant improvements to OD accuracy are observed by applying a GRAIL-based model; however, applying a full order and degree gravity modeling is not always the best strategy, owing to the computational burden. Consequently, we consider that OD using GRAIL660B with 70 × 70 degree and order is the most efficient strategy for mission preanalysis. This study provides useful guideline for KPLO OD analysis during nominal mission operation.

  8. Design and "As Flown" Radiation Environments for Materials in Low Earth Orbit

    Science.gov (United States)

    Minow, Joseph; McWilliams, Brett; Altstatt, Richard; Koontz, Steven

    2006-01-01

    the ISS flight trajectory including variations in altitude due to decay of the vehicle orbit and periodic reboosts to higher altitudes. In addition, an estimate of the AE-8 model to predict low Earth orbit electron flux (because the radiation dose for thin materials is dominated by the electron component of the radiation environment) is presented based on comparisons of the AE-8 model to measurements of electron integral flux at approximately 850 km from the Medium Energy Proton and Electron Detector on board the NOAA Polar Operational Environmental Satellite.

  9. Joint Polar Satellite System: the United States New Generation Civilian Polar Orbiting Environmental Satellite System

    Science.gov (United States)

    Mandt, G.

    2017-12-01

    The Joint Polar Satellite System (JPSS) is the Nation's advanced series of polar-orbiting environmental satellites. JPSS represents significant technological and scientific advancements in observations used for severe weather prediction and environmental monitoring. The Suomi National Polar-orbiting Partnership (S-NPP) is providing state-of-the art atmospheric, oceanographic, and environmental data, as the first of the JPSS satellites while the second in the series, J-1, is scheduled to launch in October 2017. The JPSS baseline consists of a suite of four instruments: an advanced microwave and infrared sounders which are critical for weather forecasting; a leading-edge visible and infrared imager critical to data sparse areas such as Alaska and needed for environmental assessments such as snow/ice cover, droughts, volcanic ash, forest fires and surface temperature; and an ozone sensor primarily used for global monitoring of ozone and input to weather and climate models. The same suite of instruments that are on JPSS-1 will be on JPSS-2, 3 and 4. The JPSS-2 instruments are well into their assembly and test phases and are scheduled to be completed in 2018. The JPSS-2 spacecraft critical design review (CDR) is scheduled for 2Q 2018 with the launch in 2021. The sensors for the JPSS-3 and 4 spacecraft have been approved to enter into their acquisition phases. JPSS partnership with the US National Aeronautics and Space Agency (NASA) continues to provide a strong foundation for the program's success. JPSS also continues to maintain its important international relationships with European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) and the Japan Aerospace Exploration Agency (JAXA). JPSS works closely with its user community through the Proving Ground and Risk Reduction (PGRR) Program to identify opportunities to maximize the operational application of current JPSS capabilities. The PGRR Program also helps identify and evaluate the use of JPSS

  10. Orbital Dynamics of Low-Earth Orbit Laser-Propelled Space Vehicles

    International Nuclear Information System (INIS)

    Yamakawa, Hiroshi; Funaki, Ikkoh; Komurasaki, Kimiya

    2008-01-01

    Trajectories applicable to laser-propelled space vehicles with a laser station in low-Earth orbit are investigated. Laser vehicles are initially located in the vicinity of the Earth-orbiting laser station in low-earth orbit at an altitude of several hundreds kilometers, and are accelerated by laser beaming from the laser station. The laser-propelled vehicles start from low-earth orbit and finally escape from the Earth gravity well, enabling interplanetary trajectories and planetary exploration

  11. Statistics of a parallel Poynting vector in the auroral zone as a function of altitude using Polar EFI and MFE data and Astrid-2 EMMA data

    Directory of Open Access Journals (Sweden)

    P. Janhunen

    2005-07-01

    Full Text Available We study the wave-related (AC and static (DC parallel Poynting vector (Poynting energy flux as a function of altitude in auroral field lines using Polar EFI and MFE data. The study is statistical and contains 5 years of data in the altitude range 5000–30000 km. We verify the low altitude part of the results by comparison with earlier Astrid-2 EMMA Poynting vector statistics at 1000 km altitude. The EMMA data are also used to statistically compensate the Polar results for the missing zonal electric field component. We compare the Poynting vector with previous statistical DMSP satellite data concerning the electron precipitation power. We find that the AC Poynting vector (Alfvén-wave related Poynting vector is statistically not sufficient to power auroral electron precipitation, although it may, for Kp>2, power 25–50% of it. The statistical AC Poynting vector also has a stepwise transition at R=4 RE, so that its amplitude increases with increasing altitude. We suggest that this corresponds to Alfvén waves being in Landau resonance with electrons, so that wave-induced electron acceleration takes place at this altitude range, which was earlier named the Alfvén Resonosphere (ARS. The DC Poynting vector is ~3 times larger than electron precipitation and corresponds mainly to ionospheric Joule heating. In the morning sector (02:00–06:00 MLT we find that the DC Poynting vector has a nontrivial altitude profile such that it decreases by a factor of ~2 when moving upward from 3 to 4 RE radial distance. In other nightside MLT sectors the altitude profile is more uniform. The morning sector nontrivial altitude profile may be due to divergence of the perpendicular Poynting vector field at R=3–4 RE.

    Keywords. Magnetospheric physics (Auroral phenomena; Magnetosphere-ionosphere interactions – Space plasma physics (Wave-particle interactions

  12. Statistics of a parallel Poynting vector in the auroral zone as a function of altitude using Polar EFI and MFE data and Astrid-2 EMMA data

    Directory of Open Access Journals (Sweden)

    P. Janhunen

    2005-07-01

    Full Text Available We study the wave-related (AC and static (DC parallel Poynting vector (Poynting energy flux as a function of altitude in auroral field lines using Polar EFI and MFE data. The study is statistical and contains 5 years of data in the altitude range 5000–30000 km. We verify the low altitude part of the results by comparison with earlier Astrid-2 EMMA Poynting vector statistics at 1000 km altitude. The EMMA data are also used to statistically compensate the Polar results for the missing zonal electric field component. We compare the Poynting vector with previous statistical DMSP satellite data concerning the electron precipitation power. We find that the AC Poynting vector (Alfvén-wave related Poynting vector is statistically not sufficient to power auroral electron precipitation, although it may, for Kp>2, power 25–50% of it. The statistical AC Poynting vector also has a stepwise transition at R=4 RE, so that its amplitude increases with increasing altitude. We suggest that this corresponds to Alfvén waves being in Landau resonance with electrons, so that wave-induced electron acceleration takes place at this altitude range, which was earlier named the Alfvén Resonosphere (ARS. The DC Poynting vector is ~3 times larger than electron precipitation and corresponds mainly to ionospheric Joule heating. In the morning sector (02:00–06:00 MLT we find that the DC Poynting vector has a nontrivial altitude profile such that it decreases by a factor of ~2 when moving upward from 3 to 4 RE radial distance. In other nightside MLT sectors the altitude profile is more uniform. The morning sector nontrivial altitude profile may be due to divergence of the perpendicular Poynting vector field at R=3–4 RE. Keywords. Magnetospheric physics (Auroral phenomena; Magnetosphere-ionosphere interactions – Space plasma physics (Wave-particle interactions

  13. Local time asymmetry of Pc 4--5 pulsations and associated particle modulations at synchronous orbit

    International Nuclear Information System (INIS)

    Kokubun, S.; Erickson, K.N.; Fritz, T.A.; McPherron, R.L.

    1989-01-01

    Magnetic field and particle flux observations on board ATS 6 at synchronous altitude are used to examine the dawn-dusk asymmetry of characteristics of Pc 4--5 waves and associated particle flux modulation. Most waves at synchronous orbit having ground correlations are polarized in the azimuthal direction (A class) and are usually detected in the dawn sector. Waves with a radially oriented polarization ellipse (R-class) are almost never observed near the subsatellite point on the ground, except for the regular pulsations known as giant pulsation Pg, observed in the early morning. R class Pc 4 waves occur at all local times and have an occurrence peak in the afternoon

  14. The National Polar-orbiting Operational Environmental Satellite System

    Science.gov (United States)

    Bloom, H.

    The tri-agency Integrated Program Office (IPO) is responsible for managing the development of the National Polar-orbiting Operational Environmental Satellite System (NPOESS). NPOESS will replace the current military and civilian operational polar-orbiting ``weather'' satellites. The Northrop Grumman Space Technology - Raytheon team was competitively selected in 2002 as the Acquisition and Operations contractor team to develop, integrate, deploy, and operate NPOESS satellites to meet the tri-agency user requirements for NPOESS over the 10-year (2009-2018) operational life of the program. Beginning in 2009, NPOESS spacecraft will be launched into three orbital planes to provide significantly improved operational capabilities and benefits to satisfy critical civil and national security requirements for space-based, remotely sensed environmental data. With the development of NPOESS, we are evolving operational ``weather'' satellites into integrated environmental observing systems by expanding our capabilities to observe, assess, and predict the total Earth system - atmosphere, ocean, land, and the space environment. In recent years, the operational weather forecasting and climate science communities have levied more rigorous requirements on space-based observations of the Earth's system that have significantly increased demands on performance of the instruments, spacecraft, and ground systems required to deliver NPOESS data, products, and information to end users. The ``end-to-end'' system consists of: the spacecraft; instruments and sensors on the spacecraft; launch support capabilities; the command, control, communications, and data routing infrastructure; and data processing hardware and software. NPOESS will observe significantly more phenomena simultaneously from space than its operational predecessors. NPOESS is expected to deliver large volumes of more accurate measurements at higher spatial (horizontal and vertical) and temporal resolution at much higher data

  15. KEPLER-63b: A GIANT PLANET IN A POLAR ORBIT AROUND A YOUNG SUN-LIKE STAR

    International Nuclear Information System (INIS)

    Sanchis-Ojeda, Roberto; Winn, Joshua N.; Albrecht, Simon; Marcy, Geoffrey W.; Isaacson, Howard; Howard, Andrew W.; Johnson, John Asher; Torres, Guillermo; Carter, Joshua A.; Dawson, Rebekah I.; Geary, John C.; Campante, Tiago L.; Chaplin, William J.; Davies, Guy R.; Lund, Mikkel N.; Buchhave, Lars A.; Everett, Mark E.; Fischer, Debra A.; Gilliland, Ronald L.; Horch, Elliott P.

    2013-01-01

    We present the discovery and characterization of a giant planet orbiting the young Sun-like star Kepler-63 (KOI-63, m Kp = 11.6, T eff = 5576 K, M * = 0.98 M ☉ ). The planet transits every 9.43 days, with apparent depth variations and brightening anomalies caused by large starspots. The planet's radius is 6.1 ± 0.2 R ⊕ , based on the transit light curve and the estimated stellar parameters. The planet's mass could not be measured with the existing radial-velocity data, due to the high level of stellar activity, but if we assume a circular orbit, then we can place a rough upper bound of 120 M ⊕ (3σ). The host star has a high obliquity (ψ = 104°), based on the Rossiter-McLaughlin effect and an analysis of starspot-crossing events. This result is valuable because almost all previous obliquity measurements are for stars with more massive planets and shorter-period orbits. In addition, the polar orbit of the planet combined with an analysis of spot-crossing events reveals a large and persistent polar starspot. Such spots have previously been inferred using Doppler tomography, and predicted in simulations of magnetic activity of young Sun-like stars

  16. KEPLER-63b: A GIANT PLANET IN A POLAR ORBIT AROUND A YOUNG SUN-LIKE STAR

    Energy Technology Data Exchange (ETDEWEB)

    Sanchis-Ojeda, Roberto; Winn, Joshua N.; Albrecht, Simon [Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Marcy, Geoffrey W.; Isaacson, Howard [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Howard, Andrew W. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Johnson, John Asher [Department of Astronomy, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Torres, Guillermo; Carter, Joshua A.; Dawson, Rebekah I.; Geary, John C. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Campante, Tiago L.; Chaplin, William J.; Davies, Guy R. [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Lund, Mikkel N. [Stellar Astrophysics Centre (SAC), Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Buchhave, Lars A. [Niels Bohr Institute, University of Copenhagen, Juliane Maries vej 30, DK-2100 Copenhagen (Denmark); Everett, Mark E. [National Optical Astronomy Observatory, 950 N. Cherry Ave, Tucson, AZ 85719 (United States); Fischer, Debra A. [Astronomy Department, Yale University, New Haven, CT (United States); Gilliland, Ronald L. [Center for Exoplanets and Habitable Worlds, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Horch, Elliott P. [Southern Connecticut State University, New Haven, CT 06515 (United States); and others

    2013-09-20

    We present the discovery and characterization of a giant planet orbiting the young Sun-like star Kepler-63 (KOI-63, m{sub Kp} = 11.6, T{sub eff} = 5576 K, M{sub *} = 0.98 M{sub ☉}). The planet transits every 9.43 days, with apparent depth variations and brightening anomalies caused by large starspots. The planet's radius is 6.1 ± 0.2 R{sub ⊕}, based on the transit light curve and the estimated stellar parameters. The planet's mass could not be measured with the existing radial-velocity data, due to the high level of stellar activity, but if we assume a circular orbit, then we can place a rough upper bound of 120 M{sub ⊕} (3σ). The host star has a high obliquity (ψ = 104°), based on the Rossiter-McLaughlin effect and an analysis of starspot-crossing events. This result is valuable because almost all previous obliquity measurements are for stars with more massive planets and shorter-period orbits. In addition, the polar orbit of the planet combined with an analysis of spot-crossing events reveals a large and persistent polar starspot. Such spots have previously been inferred using Doppler tomography, and predicted in simulations of magnetic activity of young Sun-like stars.

  17. High-resolution Ceres Low Altitude Mapping Orbit Atlas derived from Dawn Framing Camera images

    Science.gov (United States)

    Roatsch, Th.; Kersten, E.; Matz, K.-D.; Preusker, F.; Scholten, F.; Jaumann, R.; Raymond, C. A.; Russell, C. T.

    2017-06-01

    The Dawn spacecraft Framing Camera (FC) acquired over 31,300 clear filter images of Ceres with a resolution of about 35 m/pxl during the eleven cycles in the Low Altitude Mapping Orbit (LAMO) phase between December 16 2015 and August 8 2016. We ortho-rectified the images from the first four cycles and produced a global, high-resolution, uncontrolled photomosaic of Ceres. This global mosaic is the basis for a high-resolution Ceres atlas that consists of 62 tiles mapped at a scale of 1:250,000. The nomenclature used in this atlas was proposed by the Dawn team and was approved by the International Astronomical Union (IAU). The full atlas is available to the public through the Dawn Geographical Information System (GIS) web page [http://dawngis.dlr.de/atlas] and will become available through the NASA Planetary Data System (PDS) (http://pdssbn.astro.umd.edu/).

  18. Four Years on Orbit at the Moon with LOLA

    Science.gov (United States)

    Smith, D. E.; Zuber, M. T.; Neumann, G. A.; Mazarico, E.; Torrence, M. H.; Lemoine, F. G.

    2013-12-01

    After four years of near-continuous operation at the Moon, the Lunar Orbiter Laser Altimeter (LOLA) continues to collect altimetry, surface roughness, slope and normal reflectance data. Although the instrument is beginning to show the effects of tens of thousands of thermal cycles and the natural process of the aging of the laser transmitters, LOLA continues to acquire data on the sunlit portion of every orbit on all 5 laser beams when below 100-km altitude. LOLA has acquired over 6x10^9 altimeter measurements, all geodetically controlled to the center-of-mass of the Moon with a radial precision of around 10 cm and an accuracy of about 1 meter. The position of the measurements on the lunar surface is primarily limited by the knowledge of the position of the spacecraft in orbit; in the last year the LRO orbit accuracy has improved significantly as a result of the availability of an accurate gravity model of the Moon from the GRAIL Discovery mission. Our present estimate of positional accuracy is less than 10 m rms but is only achievable with a GRAIL gravity model to at least degree and order 600 because of the perturbing gravitational effect of the Moon's surface features. Significant improvements in the global shape and topography have assisted the Lunar Reconnaissance Orbiter Camera (LROC) stereo mapping program, and the identification of potential lunar landing sites for ESA and Russia, particularly in the high-latitude polar regions where 5- and 10-meter average horizontal resolution has been obtained. LOLA's detailed mapping of the polar regions has improved the delineation of permanently-shadowed areas and assisted in the understanding of the LEND neutron data and its relationship to surface slopes. Recently, a global, calibrated LOLA normal albedo dataset at 1064 nm has been developed and is being combined with analysis and modeling by the Diviner team for the identification of the coldest locations in the polar regions.

  19. Fuel Optimization for Low Earth Orbit Maintenance

    Directory of Open Access Journals (Sweden)

    Yong Jae Park

    2008-06-01

    Full Text Available The resolution of Earth images taken from a satellite has close relation with satellite's altitude. If a satellite has lower altitude, it gets a picture having better resolution. However the satellite will be exposed to heavier air drag and will spend more fuel to maintain its altitude for a desired mission. Therefore, in this study, the required fuel to maintain very low earth orbit(LEO with severe air drag is analyzed using optimization method such as collocation method. The required fuel to maintain the low altitude has significantly increased as the mission altitude is lowered and the solar activity is maximized. This study also shows that the fuel reduced by increasing the period of the satellite maneuver is very small, and that slightly increasing the satellite's mission altitude is much effective in reducing the amount of fuel to maintain its altitude. The calculated fuel to maintain very low earth orbit in this study would give useful information in planning the budget of fuel and cost for LEO satellites.

  20. The Gravity Field of Mercury After the Messenger Low-Altitude Campaign

    Science.gov (United States)

    Mazarico, Erwan; Genova, Antonio; Goossens, Sander; Lemoine, Frank G.; Smith, David E.; Zuber, Maria T.; Neumann, Gary A.; Solomon, Sean C.

    2015-01-01

    The final year of the MESSENGER mission was designed to take advantage of the remaining propellant onboard to provide a series of lowaltitude observation campaigns and acquire novel scientific data about the innermost planet. The lower periapsis altitude greatly enhances the sensitivity to the short-wavelength gravity field, but only when the spacecraft is in view of Earth. After more than 3 years in orbit around Mercury, the MESSENGER spacecraft was tracked for the first time below 200-km altitude on 5 May 2014 by the NASA Deep Space Network (DSN). Between August and October, periapsis passages down to 25-km altitude were routinely tracked. These periods considerably improved the quality of the data coverage. Before the end of its mission, MESSENGER will fly at very low altitudes for extended periods of time. Given the orbital geometry, however the periapses will not be visible from Earth and so no new tracking data will be available for altitudes lower than 75 km. Nevertheless, the continuous tracking of MESSENGER in the northern hemisphere will help improve the uniformity of the spatial coverage at altitudes lower than 150 km, which will further improve the overall quality of the Mercury gravity field.

  1. Space station orbit maintenance

    Science.gov (United States)

    Kaplan, D. I.; Jones, R. M.

    1983-01-01

    The orbit maintenance problem is examined for two low-earth-orbiting space station concepts - the large, manned Space Operations Center (SOC) and the smaller, unmanned Science and Applications Space Platform (SASP). Atmospheric drag forces are calculated, and circular orbit altitudes are selected to assure a 90 day decay period in the event of catastrophic propulsion system failure. Several thrusting strategies for orbit maintenance are discussed. Various chemical and electric propulsion systems for orbit maintenance are compared on the basis of propellant resupply requirements, power requirements, Shuttle launch costs, and technology readiness.

  2. Stability of orbits around planetary satellites considering a disturbing body in an elliptical orbit: Applications to Europa and Ganymede

    Science.gov (United States)

    Cardoso dos Santos, Josué; Carvalho, Jean Paulo; Vilhena de Moraes, Rodolpho

    Europa and Ganymede are two of the four Jupiter’s moons which compose the Galilean satellite. These ones are planetary satellites of greater interest at the present moment among the scientific community. There are some missions being planned to visit them and and the Jovian system. One of them is the cooperation between NASA and ESA for the Europa Jupiter System Mission (EJSM). In this mission are planned the insertion of the spacecrafts JEO (Jupiter Europa Orbiter) and JGO (Jupiter Ganymede Orbiter) into Europa and Ganymede’s orbit. Thus, there is a great necessity for having a better comprehension of the dynamics of the orbits around this planetary satellite. This comprehension is essential for the success of this type of mission. In this context, this work aims to perform a search for low-altitude orbits around these planetary satellites. An emphasis is given in polar orbits. These orbits can be useful in the planning of aerospace activities to be conducted around this planetary satellite, with respect to the stability of orbits of artificial satellites. The study considers orbits of an artificial satellite around Europa and Ganymede under the influence of the third-body perturbation (the gravitational attraction of Jupiter) and the polygenic perturbations. These last ones occur due to forces such as the non-uniform distribution of mass (J2 and J3) of the main (central) body. A simplified dynamic model for polygenic perturbations is used. A new model for the third-body disturbance is presented considering it in an elliptical orbit. The Lagrange planetary equations, which compose a system of nonlinear differential equations, are used to describe the orbital motion of the artificial satellite around Ganymede. The equations showed here are developed in closed form to avoid expansions in inclination and eccentricity.

  3. Environmental Satellites. Polar-orbiting Satellite Acquisition Faces Delays; Decisions Needed on Whether and How to Ensure Climate Data Continuity

    National Research Council Canada - National Science Library

    2008-01-01

    The National Polar-orbiting Operational Environmental Satellite System (NPOESS) is a triagency acquisition managed by the Department of Commerce's National Oceanic and Atmospheric Administration (NOAA...

  4. Environmental Satellites: Polar-orbiting Satellite Acquisition Faces Delays; Decisions Needed on Whether and How to Ensure Climate Data Continuity

    National Research Council Canada - National Science Library

    2008-01-01

    The National Polar-orbiting Operational Environmental Satellite System (NPOESS) is a triagency acquisition managed by the Department of Commerce s National Oceanic and Atmospheric Administration (NOAA...

  5. Ejectile polarization and nuclear orbitals

    International Nuclear Information System (INIS)

    Ohnishi, A.; Maruyama, T.; Horiuchi, H.

    1992-01-01

    Ejectile polarization phenomena are studied by the use of 'Quantum Molecular Dynamics plus external mean field' model. It is shown that the far-side contribution increases as the incident energy increases or the target charge decreases. The incident energy and the target dependence of ejectile polarization data is reproduced qualitatively. The near- and far-side contributions themselves are calculated to be almost monotone functions of ejectile momentum as is predicted in a simple projectile fragmentation scheme without the assumption that the linear and angular momentum transfers are negligible, and their statistical average results in various shapes in ejectile polarization

  6. A novel orbiter mission concept for venus with the EnVision proposal

    Science.gov (United States)

    de Oliveira, Marta R. R.; Gil, Paulo J. S.; Ghail, Richard

    2018-07-01

    In space exploration, planetary orbiter missions are essential to gain insight into planets as a whole, and to help uncover unanswered scientific questions. In particular, the planets closest to the Earth have been a privileged target of the world's leading space agencies. EnVision is a mission proposal designed for Venus and competing for ESA's next launch opportunity with the objective of studying Earth's closest neighbor. The main goal is to study geological and atmospheric processes, namely surface processes, interior dynamics and atmosphere, to determine the reasons behind Venus and Earth's radically different evolution despite the planets' similarities. To achieve these goals, the operational orbit selection is a fundamental element of the mission design process. The design of an orbit around Venus faces specific challenges, such as the impossibility of choosing Sun-synchronous orbits. In this paper, an innovative genetic algorithm optimization was applied to select the optimal orbit based on the parameters with more influence in the mission planning, in particular the mission duration and the coverage of sites of interest on the Venusian surface. The solution obtained is a near-polar circular orbit with an altitude of 259 km that enables the coverage of all priority targets almost two times faster than with the parameters considered before this study.

  7. Solar Illumination Control of the Polar Wind

    Science.gov (United States)

    Maes, L.; Maggiolo, R.; De Keyser, J.; André, M.; Eriksson, A. I.; Haaland, S.; Li, K.; Poedts, S.

    2017-11-01

    Polar wind outflow is an important process through which the ionosphere supplies plasma to the magnetosphere. The main source of energy driving the polar wind is solar illumination of the ionosphere. As a result, many studies have found a relation between polar wind flux densities and solar EUV intensity, but less is known about their relation to the solar zenith angle at the ionospheric origin, certainly at higher altitudes. The low energy of the outflowing particles and spacecraft charging means it is very difficult to measure the polar wind at high altitudes. We take advantage of an alternative method that allows estimations of the polar wind flux densities far in the lobes. We analyze measurements made by the Cluster spacecraft at altitudes from 4 up to 20 RE. We observe a strong dependence on the solar zenith angle in the ion flux density and see that both the ion velocity and density exhibit a solar zenith angle dependence as well. We also find a seasonal variation of the flux density.

  8. Low altitude observations of the energetic electrons in the outer radiation belt during isolated substorms

    International Nuclear Information System (INIS)

    Varga, L.; Venkatesan, D.; Johns Hopkins Univ., Laurel, MD; Meng, C.I.

    1985-01-01

    The low energy (1-20 keV) detector registering particles onboard the polar-orbiting low altitude (approx. 850 km) DMSP-F2 and -F3 satellites also records high energy electrons penetrating the detector walls. Thus the dynamics of this electron population at L=3.5 can be studied during isolated periods of magnetospheric substorms identified by the indices of auroral electrojet (AE), geomagnetic (Ksub(p)) and ring current (Dsub(st)). Temporal changes in the electron flux during the substorms are observed to be an additional contribution riding over the top of the pre-storm (or geomagnetically quiet-time) electron population; the duration of the interval of intensity variations is observed to be about the same as that of the enhancement of the AE index. This indicates the temporal response of the outer radiation belt to the substorm activity, since the observation was made in the ''horns'' of the outer radiation belt. The observed enhanced radiation at low altitude may associate with the instantaneous increase and/or dumping of the outer radiation belt energetic electrons during each isolated substorm activity. (author)

  9. Energy spectrum, the spin polarization, and the optical selection rules of the Kronig-Penney superlattice model with spin-orbit coupling

    Science.gov (United States)

    Li, Rui

    2018-02-01

    The Kronig-Penney model, an exactly solvable one-dimensional model of crystal in solid physics, shows how the allowed and forbidden bands are formed in solids. In this paper, we study this model in the presence of both strong spin-orbit coupling and the Zeeman field. We analytically obtain four transcendental equations that represent an implicit relation between the energy and the Bloch wave vector. Solving these four transcendental equations, we obtain the spin-orbital bands exactly. In addition to the usual band gap opened at the boundary of the Brillouin zone, a much larger spin-orbital band gap is also opened at some special sites inside the Brillouin zone. The x component of the spin-polarization vector is an even function of the Bloch wave vector, while the z component of the spin-polarization vector is an odd function of the Bloch wave vector. At the band edges, the optical transition rates between adjacent bands are nonzero.

  10. Perfect tuning of spin-polarization in a ring-shaped multiple-quantum-dot nanostructure in the presence of Rashba spin–orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Eslami, L., E-mail: Leslami@iust.ac.ir; Chaghari, Z.; Faizabadi, E.

    2013-09-02

    Spin-dependent electronic transport through an open multiple-quantum-dot ring threaded by a magnetic flux is theoretically investigated by using the single particle Green's function method. By introducing local Rashba spin–orbit interaction on an individual quantum dot and local magnetic moments on two of other quantum dots, we calculate the spin-polarization in the output lead. We find the spin-polarization can be tuned by manipulating magnetic moments, adjusting magnetic flux and setting the Rashba spin–orbit strength. It is also shown the system can operate as an efficient spin-inverter when the structure is adjusted properly. The analysis can be utilized in designing optimized nanodevices.

  11. The case for a modern multiwavelength, polarization-sensitive LIDAR in orbit around Mars

    International Nuclear Information System (INIS)

    Brown, Adrian J.; Michaels, Timothy I.; Byrne, Shane; Sun, Wenbo; Titus, Timothy N.; Colaprete, Anthony; Wolff, Michael J.; Videen, Gorden; Grund, Christian J.

    2015-01-01

    We present the scientific case to build a multiple-wavelength, active, near-infrared (NIR) instrument to measure the reflected intensity and polarization characteristics of backscattered radiation from planetary surfaces and atmospheres. We focus on the ability of such an instrument to enhance, potentially revolutionize, our understanding of climate, volatiles and astrobiological potential of modern-day Mars. Such an instrument will address the following three major science themes, which we address in this paper: Science Theme 1. Surface. This would include global, night and day mapping of H 2 O and CO 2 surface ice properties. Science Theme 2. Ice Clouds. This would including unambiguous discrimination and seasonal mapping of CO 2 and H 2 O ice clouds. Science Theme 3. Dust Aerosols. This theme would include multiwavelength polarization measurements to infer dust grain shapes and size distributions. - Highlights: • We present the scientific rationale for a multi-wavelength, polarization sensitive lidar to be placed in orbit around Mars. • Scientific questions focus on the Martian climate and modern-day interactions between surface, ice clouds and dust aerosols. • What we would learn about volatile transport and deposition has implications for past, present and future life on Mars

  12. Tunable ferroelectric polarization and its interplay with spin-orbit coupling in tin iodide perovskites

    Science.gov (United States)

    Stroppa, Alessandro; di Sante, Domenico; Barone, Paolo; Bokdam, Menno; Kresse, Georg; Franchini, Cesare; Whangbo, Myung-Hwan; Picozzi, Silvia

    2014-12-01

    Ferroelectricity is a potentially crucial issue in halide perovskites, breakthrough materials in photovoltaic research. Using density functional theory simulations and symmetry analysis, we show that the lead-free perovskite iodide (FA)SnI3, containing the planar formamidinium cation FA, (NH2CHNH2)+, is ferroelectric. In fact, the perpendicular arrangement of FA planes, leading to a ‘weak’ polarization, is energetically more stable than parallel arrangements of FA planes, being either antiferroelectric or ‘strong’ ferroelectric. Moreover, we show that the ‘weak’ and ‘strong’ ferroelectric states with the polar axis along different crystallographic directions are energetically competing. Therefore, at least at low temperatures, an electric field could stabilize different states with the polarization rotated by π/4, resulting in a highly tunable ferroelectricity appealing for multistate logic. Intriguingly, the relatively strong spin-orbit coupling in noncentrosymmetric (FA)SnI3 gives rise to a co-existence of Rashba and Dresselhaus effects and to a spin texture that can be induced, tuned and switched by an electric field controlling the ferroelectric state.

  13. Proton isotropy boundaries as measured on mid- and low-altitude satellites

    Directory of Open Access Journals (Sweden)

    N. Yu. Ganushkina

    2005-07-01

    Full Text Available Polar CAMMICE MICS proton pitch angle distributions with energies of 31-80 keV were analyzed to determine the locations where anisotropic pitch angle distributions (perpendicular flux dominating change to isotropic distributions. We compared the positions of these mid-altitude isotropic distribution boundaries (IDB for different activity conditions with low-altitude isotropic boundaries (IB observed by NOAA 12. Although the obtained statistical properties of IDBs were quite similar to those of IBs, a small difference in latitudes, most pronounced on the nightside and dayside, was found. We selected several events during which simultaneous observations in the same local time sector were available from Polar at mid-altitudes, and NOAA or DMSP at low-altitudes. Magnetic field mapping using the Tsyganenko T01 model with the observed solar wind input parameters showed that the low- and mid-altitude isotropization boundaries were closely located, which leads us to suggest that the Polar IDB and low-altitude IBs are related. Furthermore, we introduced a procedure to control the difference between the observed and model magnetic field to reduce the large scatter in the mapping. We showed that the isotropic distribution boundary (IDB lies in the region where Rc/ρ~6, that is at the boundary of the region where the non-adiabatic pitch angle scattering is strong enough. We therefore conclude that the scattering in the large field line curvature regions in the nightside current sheet is the main mechanism producing isotropization for the main portion of proton population in the tail current sheet. This mechanism controls the observed positions of both IB and IDB boundaries. Thus, this tail region can be probed, in its turn, with observations of these isotropy boundaries. Keywords. Magnetospheric physics (Energetic particles, Precipitating; Magnetospheric configuration and dynamics; Magnetotail

  14. Proton isotropy boundaries as measured on mid- and low-altitude satellites

    Directory of Open Access Journals (Sweden)

    N. Yu. Ganushkina

    2005-07-01

    Full Text Available Polar CAMMICE MICS proton pitch angle distributions with energies of 31-80 keV were analyzed to determine the locations where anisotropic pitch angle distributions (perpendicular flux dominating change to isotropic distributions. We compared the positions of these mid-altitude isotropic distribution boundaries (IDB for different activity conditions with low-altitude isotropic boundaries (IB observed by NOAA 12. Although the obtained statistical properties of IDBs were quite similar to those of IBs, a small difference in latitudes, most pronounced on the nightside and dayside, was found. We selected several events during which simultaneous observations in the same local time sector were available from Polar at mid-altitudes, and NOAA or DMSP at low-altitudes. Magnetic field mapping using the Tsyganenko T01 model with the observed solar wind input parameters showed that the low- and mid-altitude isotropization boundaries were closely located, which leads us to suggest that the Polar IDB and low-altitude IBs are related. Furthermore, we introduced a procedure to control the difference between the observed and model magnetic field to reduce the large scatter in the mapping. We showed that the isotropic distribution boundary (IDB lies in the region where Rc/ρ~6, that is at the boundary of the region where the non-adiabatic pitch angle scattering is strong enough. We therefore conclude that the scattering in the large field line curvature regions in the nightside current sheet is the main mechanism producing isotropization for the main portion of proton population in the tail current sheet. This mechanism controls the observed positions of both IB and IDB boundaries. Thus, this tail region can be probed, in its turn, with observations of these isotropy boundaries.

    Keywords. Magnetospheric physics (Energetic particles, Precipitating; Magnetospheric configuration and dynamics; Magnetotail

  15. The Mars Reconnaissance Orbiter Mission: 10 Years of Exploration from Mars Orbit

    Science.gov (United States)

    Johnston, M. Daniel; Zurek, Richard W.

    2016-01-01

    The Mars Reconnaissance Orbiter ( MRO ) entered Mars orbit on March 10, 2006. After five months of aerobraking, a series of propulsive maneuvers were used to establish the desired low -altitude science orbit. The spacecraft has been on station in its 255 x 320 k m, sun -synchronous (approximately 3 am -pm ), primary science orbit since September 2006 performing both scientific and Mars programmatic support functions. This paper will provide a summary of the major achievements of the mission to date and the major flight activities planned for the remainder of its third Extended Mission (EM3). Some of the major flight challenges the flight team has faced are also discussed.

  16. Image Positioning Accuracy Analysis for Super Low Altitude Remote Sensing Satellites

    Directory of Open Access Journals (Sweden)

    Ming Xu

    2012-10-01

    Full Text Available Super low altitude remote sensing satellites maintain lower flight altitudes by means of ion propulsion in order to improve image resolution and positioning accuracy. The use of engineering data in design for achieving image positioning accuracy is discussed in this paper based on the principles of the photogrammetry theory. The exact line-of-sight rebuilding of each detection element and this direction precisely intersecting with the Earth's elliptical when the camera on the satellite is imaging are both ensured by the combined design of key parameters. These parameters include: orbit determination accuracy, attitude determination accuracy, camera exposure time, accurately synchronizing the reception of ephemeris with attitude data, geometric calibration and precise orbit verification. Precise simulation calculations show that image positioning accuracy of super low altitude remote sensing satellites is not obviously improved. The attitude determination error of a satellite still restricts its positioning accuracy.

  17. The effects of Rashba spin-orbit coupling on spin-polarized transport in hexagonal graphene nano-rings and flakes

    Science.gov (United States)

    Laghaei, M.; Heidari Semiromi, E.

    2018-03-01

    Quantum transport properties and spin polarization in hexagonal graphene nanostructures with zigzag edges and different sizes were investigated in the presence of Rashba spin-orbit interaction (RSOI). The nanostructure was considered as a channel to which two semi-infinite armchair graphene nanoribbons were coupled as input and output leads. Spin transmission and spin polarization in x, y, and z directions were calculated through applying Landauer-Buttiker formalism with tight binding model and the Green's function to the system. In these quantum structures it is shown that changing the size of system, induce and control the spin polarized currents. In short, these graphene systems are typical candidates for electrical spintronic devices as spin filtering.

  18. A Wide Field Auroral Imager (WFAI for low Earth orbit missions

    Directory of Open Access Journals (Sweden)

    N. P. Bannister

    2007-03-01

    Full Text Available A comprehensive understanding of the solar wind interaction with Earth's coupled magnetosphere-ionosphere system requires an ability to observe the charged particle environment and auroral activity from the same platform, generating particle and photon image data which are matched in time and location. While unambiguous identification of the particles giving rise to the aurora requires a Low Earth Orbit satellite, obtaining adequate spatial coverage of aurorae with the relatively limited field of view of current space bourne auroral imaging systems requires much higher orbits. A goal for future satellite missions, therefore, is the development of compact, wide field-of-view optics permitting high spatial and temporal resolution ultraviolet imaging of the aurora from small spacecraft in low polar orbit. Microchannel plate optics offer a method of achieving the required performance. We describe a new, compact instrument design which can observe a wide field-of-view with the required spatial resolution. We report the focusing of 121.6 nm radiation using a spherically-slumped, square-pore microchannel plate with a focal length of 32 mm and an F number of 0.7. Measurements are compared with detailed ray-trace simulations of imaging performance. The angular resolution is 2.7±0.2° for the prototype, corresponding to a footprint ~33 km in diameter for an aurora altitude of 110 km and a spacecraft altitude of 800 km. In preliminary analysis, a more recent optic has demonstrated a full width at half maximum of 5.0±0.3 arcminutes, corresponding to a footprint of ~1 km from the same spacecraft altitude. We further report the imaging properties of a convex microchannel plate detector with planar resistive anode readout; this detector, whose active surface has a radius of curvature of only 100 mm, is shown to meet the spatial resolution and sensitivity requirements of the new wide field auroral imager (WFAI.

  19. Dresselhaus spin-orbit coupling induced spin-polarization and resonance-split in n-well semiconductor superlattices

    International Nuclear Information System (INIS)

    Ye Chengzhi; Xue Rui; Nie, Y.-H.; Liang, J.-Q.

    2009-01-01

    Using the transfer matrix method, we investigate the electron transmission over multiple-well semiconductor superlattices with Dresselhaus spin-orbit coupling in the potential-well regions. The superlattice structure enhances the effect of spin polarization in the transmission spectrum. The minibands of multiple-well superlattices for electrons with different spin can be completely separated at the low incident energy, leading to the 100% spin polarization in a broad energy windows, which may be an effective scheme for realizing spin filtering. Moreover, for the transmission over n-quantum-well, it is observed that the resonance peaks in the minibands split into n-folds or (n-1)-folds depending on the well-width and barrier-thickness, which is different from the case of tunneling through n-barrier structure

  20. Limitations of Electromagnetic Ion Cyclotron Wave Observations in Low Earth Orbit

    Directory of Open Access Journals (Sweden)

    Junga Hwang

    2018-03-01

    Full Text Available Pc1 pulsations are geomagnetic fluctuations in the frequency range of 0.2 to 5 Hz. There have been several observations of Pc1 pulsations in low earth orbit by MAGSAT, DE-2, Viking, Freja, CHAMP, and SWARM satellites. However, there has been a clear limitation in resolving the spatial and temporal variations of the pulsation by using a single-point observation by a single satellite. To overcome such limitations of previous observations, a new space mission was recently initiated, using the concept of multi-satellites, named the Small scale magNetospheric and Ionospheric Plasma Experiments (SNIPE. The SNIPE mission consists of four nanosatellites (~10 kg, which will be launched into a polar orbit at an altitude of 600 km (TBD in 2020. Four satellites will be deployed in orbit, and the distances between each satellite will be controlled from 10 to 1,000 km by a high-end formation-flying algorithm. One of the possible science targets of the SNIPE mission is observing electromagnetic ion cyclotron (EMIC waves. In this paper, we report on examples of observations, showing the limitations of previous EMIC observations in low earth orbit, and suggest possibilities to overcome those limitations through a new mission.

  1. Modeling the Exo-Brake and the Development of Strategies for De-Orbit Drag Modulation

    Science.gov (United States)

    Murbach, M. S.; Papadopoulos, P.; Glass, C.; Dwyer-Cianciolo, A.; Powell, R. W.; Dutta, S.; Guarneros-Luna, A.; Tanner, F. A.; Dono, A.

    2016-01-01

    The Exo-Brake is a simple, non-propulsive means of de-orbiting small payloads from orbital platforms such as the International Space Station (ISS). Two de-orbiting experiments with fixed surface area Exo-Brakes have been successfully conducted in the last two years on the TechEdSat-3 and -4 nano-satellite missions. The development of the free molecular flow aerodynamic data-base is presented in terms of angle of attack, projected front surface area variation, and altitude. Altitudes are considered ranging from the 400km ISS jettison altitude to 90km. Trajectory tools are then used to predict de-orbit/entry corridors with the inclusion of the key atmospheric and geomagnetic uncertainties. Control system strategies are discussed which will be applied to the next two planned TechEdSat-5 and -6 nano-satellite missions - thus increasing the targeting accuracy at the Von Karman altitude through the proposed drag modulation technique.

  2. POLARIZED BEAMS: 2 - Partial Siberian Snake rescues polarized protons at Brookhaven

    International Nuclear Information System (INIS)

    Huang, Haixin

    1994-01-01

    To boost the level of beam polarization (spin orientation), a partial 'Siberian Snake' was recently used to overcome imperfection depolarizing resonances in the Brookhaven Alternating Gradient Synchrotron (AGS). This 9-degree spin rotator recently permitted acceleration with no noticeable polarization loss. The intrinsic AGS depolarizing resonances (which degrade the polarization content) had been eliminated by betatron tune jumps, but the imperfection resonances were compensated by means of harmonic orbit corrections. However, at high energies these orbit corrections are difficult and tedious and a Siberian Snake became an attractive alternative

  3. Observations of upflowing ionospheric ions in the mid-altitude cusp/cleft region with the Viking satellite

    International Nuclear Information System (INIS)

    Thelin, B.; Aparicio, B.; Lundin, R.

    1990-01-01

    Measurements of positive ions (0.1-10 keV) from the polar-orbiting Viking satellite have been obtained in the cusp/cleft region and have been tabulated in MLT versus invariant latitude plots to get a synoptic picture of the occurrence of upgoing auroral positive ions. A distinction was made between ion distributions with peak fluxes along B (ion beam) and those exhibiting flux maxima that are not field-aligned (conics). Both beams and conics are shown to be common auroral phenomena, whose frequencies of occurrence in MLT, invariant latitude, and altitude were studied. During the period of study (March-June 1986) the ion beams were more frequenty (about a factor of 2) in the dusk sector than in the dawn sector. This effect seemed to increase with magnetic activity but was mostly unchanged with the sign of the interplanetary magnetic field B y component. An investigation was also made of the invariant latitude dependence for beams and conics, where the dawn sector beams have a tendency to be lcoated toward higher invariant latitudes for both positive and negative B y components. The ion beams were observed primarily above 5,000 km with a frequency of occurrence increasing with altitude up to the satellite apogee at about 13,500 km. The ion conics were observed from above 7,000 km to be steadily increasing in altitude

  4. A multi-satellite study of accelerated ionospheric ion beams above the polar cap

    Directory of Open Access Journals (Sweden)

    R. Maggiolo

    2006-07-01

    Full Text Available This paper presents a study of nearly field-aligned outflowing ion beams observed on the Cluster satellites over the polar cap. Data are taken at geocentric radial distances of the order of 5–9 RE. The distinction is made between ion beams originating from the polar cusp/cleft and beams accelerated almost along the magnetic field line passing by the spacecraft. Polar cusp beams are characterized by nearly field-aligned proton and oxygen ions with an energy ratio EO+ / EH+, of the order of 3 to 4, due to the ion energy repartition inside the source and to the latitudinal extension of the source. Rapid variations in the outflowing ion energy are linked with pulses/modifications of the convection electric field. Cluster data allow one to show that these perturbations of the convection velocity and the associated ion structures propagate at the convection velocity. In contrast, polar cap local ion beams are characterized by field-aligned proton and oxygen ions with similar energies. These beams show the typical inverted V structures usually observed in the auroral zone and are associated with a quasi-static converging electric field indicative of a field-aligned electric field. The field-aligned potential drop fits well the ion energy profile. The simultaneous observation of precipitating electrons and upflowing ions of similar energies at the Cluster orbit indicates that the spacecraft are crossing the mid-altitude part of the acceleration region. In the polar cap, the parallel electric field can thus extend to altitudes higher than 5 Earth radii. A detailed analysis of the distribution functions shows that the ions are heated during their parallel acceleration and that energy is exchanged between H+ and O+. Furthermore, intense electrostatic waves are observed simultaneously. These observations could be due to an ion-ion two-stream instability.

  5. Altitude Compensating Nozzle

    Science.gov (United States)

    Ruf, Joseph H.; Jones, Daniel

    2015-01-01

    The dual-bell nozzle (fig. 1) is an altitude-compensating nozzle that has an inner contour consisting of two overlapped bells. At low altitudes, the dual-bell nozzle operates in mode 1, only utilizing the smaller, first bell of the nozzle. In mode 1, the nozzle flow separates from the wall at the inflection point between the two bell contours. As the vehicle reaches higher altitudes, the dual-bell nozzle flow transitions to mode 2, to flow full into the second, larger bell. This dual-mode operation allows near optimal expansion at two altitudes, enabling a higher mission average specific impulse (Isp) relative to that of a conventional, single-bell nozzle. Dual-bell nozzles have been studied analytically and subscale nozzle tests have been completed.1 This higher mission averaged Isp can provide up to a 5% increase2 in payload to orbit for existing launch vehicles. The next important step for the dual-bell nozzle is to confirm its potential in a relevant flight environment. Toward this end, NASA Marshall Space Flight Center (MSFC) and Armstrong Flight Research Center (AFRC) have been working to develop a subscale, hot-fire, dual-bell nozzle test article for flight testing on AFRC's F15-D flight test bed (figs. 2 and 3). Flight test data demonstrating a dual-bell ability to control the mode transition and result in a sufficient increase in a rocket's mission averaged Isp should help convince the launch service providers that the dual-bell nozzle would provide a return on the required investment to bring a dual-bell into flight operation. The Game Changing Department provided 0.2 FTE to ER42 for this effort in 2014.

  6. High degree gravitational sensitivity from Mars orbiters for the GMM-1 gravity model

    Science.gov (United States)

    Lerch, F. J.; Smith, D. E.; Chan, J. C.; Patel, G. B.; Chinn, D. S.

    1994-01-01

    Orbital sensitivity of the gravity field for high degree terms (greater than 30) is analyzed on satellites employed in a Goddard Mars Model GMM-1, complete in spherical harmonics through degree and order 50. The model is obtained from S-band Doppler data on Mariner 9 (M9), Viking Orbiter 1 (VO1), and Viking Orbiter 2 (VO2) spacecraft, which were tracked by the NASA Deep Space Network on seven different highly eccentric orbits. The main sensitivity of the high degree terms is obtained from the VO1 and VO2 low orbits (300 km periapsis altitude), where significant spectral sensitivity is seen for all degrees out through degree 50. The velocity perturbations show a dominant effect at periapsis and significant effects out beyond the semi-latus rectum covering over 180 degrees of the orbital groundtrack for the low altitude orbits. Because of the wideband of periapsis motion covering nearly 180 degrees in w and +39 degrees in latitude coverage, the VO1 300 km periapsis altitude orbit with inclination of 39 degrees gave the dominant sensitivity in the GMM-1 solution for the high degree terms. Although the VO2 low periapsis orbit has a smaller band of periapsis mapping coverage, it strongly complements the VO1 orbit sensitivity for the GMM-1 solution with Doppler tracking coverage over a different inclination of 80 degrees.

  7. ULF Narrowband Emissions Analysis in the Terrestrial Polar Cusps

    Science.gov (United States)

    Grison, B.; Pisa, D.

    2013-05-01

    Polar cusps are known to be a key region for transfer of mass and momentum between the adjacent magnetosheath and the magnetosphere. The 4 spacecraft of the Cluster ESA mission crossed the polar cusps in their most distant part to the Earth in the early years of the mission (2000-2004) because of their highly eccentric orbit. The ULF wave activity in the cusp region has been linked with the magnetosheath plasma penetration since HEOS observations (D'Angelo et al., 1974). Wave and particle interaction play an important role in this colisionless plasma. The observed wave activity certainly results from both distant and local generation mechanisms. From Cluster case studies we propose to focus on one aspect for each of this place of generation. Concerning the distant generation, the possibility of a wave generation at the magnetopause itself is investigated. For this purpose we compare the propagation of the emissions on each side of the magnetopasue, i.e. in the cusp and in the magnetosheath. Concerning the local generation, the presence of locally generated waves above the local proton gyrofrequency that display a left hand polarization has been reported in Polar and Cluster studies (Le et al., 2001; Nykyri et al., 2003 ). The Doppler shift was not large enough to explain the observed frequency. We propose here to combine various techniques (k-filtering analysis, WHAMP simulations) to achieve a precise wave vector estimation and to explain these observations. References: D'Angelo, N., A. Bahnsen, and H. Rosenbauer (1974), Wave and particle measurements at the polar cusp, J. Geophys. Res., 79( 22), 3129-3134, doi:10.1029/JA079i022p03129. Le, G., X. Blanco-Cano, C. T. Russell, X.-W. Zhou, F. Mozer, K. J. Trattner, S. A. Fuselier, and B. J. Anderson (2001), Electromagnetic ion cyclotron waves in the high-altitude cusp: Polar observations, J. Geophys. Res., 106(A9), 19067-19079, doi:10.1029/2000JA900163. Nykyri, K., P. J. Cargill, E. A. Lucek, T. S. Horbury, A. Balogh

  8. Polar-Orbiting Satellite (POES) Images

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Visible and Infrared satellite imagery taken from camera systems or radiometer instruments on satellites in orbit around the poles. Satellite campaigns include...

  9. Useful lower limits to polarization contributions to intermolecular interactions using a minimal basis of localized orthogonal orbitals: theory and analysis of the water dimer.

    Science.gov (United States)

    Azar, R Julian; Horn, Paul Richard; Sundstrom, Eric Jon; Head-Gordon, Martin

    2013-02-28

    The problem of describing the energy-lowering associated with polarization of interacting molecules is considered in the overlapping regime for self-consistent field wavefunctions. The existing approach of solving for absolutely localized molecular orbital (ALMO) coefficients that are block-diagonal in the fragments is shown based on formal grounds and practical calculations to often overestimate the strength of polarization effects. A new approach using a minimal basis of polarized orthogonal local MOs (polMOs) is developed as an alternative. The polMO basis is minimal in the sense that one polarization function is provided for each unpolarized orbital that is occupied; such an approach is exact in second-order perturbation theory. Based on formal grounds and practical calculations, the polMO approach is shown to underestimate the strength of polarization effects. In contrast to the ALMO method, however, the polMO approach yields results that are very stable to improvements in the underlying AO basis expansion. Combining the ALMO and polMO approaches allows an estimate of the range of energy-lowering due to polarization. Extensive numerical calculations on the water dimer using a large range of basis sets with Hartree-Fock theory and a variety of different density functionals illustrate the key considerations. Results are also presented for the polarization-dominated Na(+)CH4 complex. Implications for energy decomposition analysis of intermolecular interactions are discussed.

  10. Spin-orbit beams for optical chirality measurement

    Science.gov (United States)

    Samlan, C. T.; Suna, Rashmi Ranjan; Naik, Dinesh N.; Viswanathan, Nirmal K.

    2018-01-01

    Accurate measurement of chirality is essential for the advancement of natural and pharmaceutical sciences. We report here a method to measure chirality using non-separable states of light with geometric phase-gradient in the circular polarization basis, which we refer to as spin-orbit beams. A modified polarization Sagnac interferometer is used to generate spin-orbit beams wherein the spin and orbital angular momentum of the input Gaussian beam are coupled. The out-of-phase interference between counter-propagating Gaussian beams with orthogonal spin states and lateral-shear or/and linear-phase difference between them results in spin-orbit beams with linear and azimuthal phase gradient. The spin-orbit beams interact efficiently with the chiral medium, inducing a measurable change in the center-of-mass of the beam, using the polarization rotation angle and hence the chirality of the medium are accurately calculated. Tunable dynamic range of measurement and flexibility to introduce large values of orbital angular momentum for the spin-orbit beam, to improve the measurement sensitivity, highlight the techniques' versatility.

  11. Cosmic microwave background science at commercial airline altitudes

    Science.gov (United States)

    Feeney, Stephen M.; Gudmundsson, Jon E.; Peiris, Hiranya V.; Verde, Licia; Errard, Josquin

    2017-07-01

    Obtaining high-sensitivity measurements of degree-scale cosmic microwave background (CMB) polarization is the most direct path to detecting primordial gravitational waves. Robustly recovering any primordial signal from the dominant foreground emission will require high-fidelity observations at multiple frequencies, with excellent control of systematics. We explore the potential for a new platform for CMB observations, the Airlander 10 hybrid air vehicle, to perform this task. We show that the Airlander 10 platform, operating at commercial airline altitudes, is well suited to mapping frequencies above 220 GHz, which are critical for cleaning CMB maps of dust emission. Optimizing the distribution of detectors across frequencies, we forecast the ability of Airlander 10 to clean foregrounds of varying complexity as a function of altitude, demonstrating its complementarity with both existing (Planck) and ongoing (C-BASS) foreground observations. This novel platform could play a key role in defining our ultimate view of the polarized microwave sky.

  12. Spatiotemporal polarization gradients in phase-bearing light

    International Nuclear Information System (INIS)

    Lembessis, V. E.; Babiker, M.

    2010-01-01

    It is shown how the interference of two circularly polarized laser beams endowed with orbital angular momentum can give rise to spatial and temporal polarization gradients, displaying axial as well as angular symmetry properties. Illustrations are given with reference to circularly polarized Laguerre-Gaussian beams as typical light beams carrying orbital angular momentum.

  13. GPS Low Cross-polarization Antenna Array for Orbit Determination beyond Geostationary Earth Orbits

    Data.gov (United States)

    National Aeronautics and Space Administration — This work will expand on the recent successes of Navigator on MMS, opening new and unforeseen possibilities for the use of GPS for very high-altitude applications up...

  14. Orbital parameters of extrasolar planets derived from polarimetry

    Science.gov (United States)

    Fluri, D. M.; Berdyugina, S. V.

    2010-03-01

    Context. Polarimetry of extrasolar planets becomes a new tool for their investigation, which requires the development of diagnostic techniques and parameter case studies. Aims: Our goal is to develop a theoretical model which can be applied to interpret polarimetric observations of extrasolar planets. Here we present a theoretical parameter study that shows the influence of the various involved parameters on the polarization curves. Furthermore, we investigate the robustness of the fitting procedure. We focus on the diagnostics of orbital parameters and the estimation of the scattering radius of the planet. Methods: We employ the physics of Rayleigh scattering to obtain polarization curves of an unresolved extrasolar planet. Calculations are made for two cases: (i) assuming an angular distribution for the intensity of the scattered light as from a Lambert sphere and for polarization as from a Rayleigh-type scatterer; and (ii) assuming that both the intensity and polarization of the scattered light are distributed according to the Rayleigh law. We show that the difference between these two cases is negligible for the shapes of the polarization curves. In addition, we take the size of the host star into account, which is relevant for hot Jupiters orbiting giant stars. Results: We discuss the influence of the inclination of the planetary orbit, the position angle of the ascending node, and the eccentricity on the linearly polarized light curves both in Stokes Q/I and U/I. We also analyze errors that arise from the assumption of a point-like star in numerical modeling of polarization as compared to consistent calculations accounting for the finite size of the host star. We find that errors due to the point-like star approximation are reduced with the size of the orbit, but still amount to about 5% for known hot Jupiters. Recovering orbital parameters from simulated data is shown to be very robust even for very noisy data because the polarization curves react

  15. Earth Orbiting Support Systems for commercial low Earth orbit data relay: Assessing architectures through tradespace exploration

    Science.gov (United States)

    Palermo, Gianluca; Golkar, Alessandro; Gaudenzi, Paolo

    2015-06-01

    As small satellites and Sun Synchronous Earth Observation systems are assuming an increased role in nowadays space activities, including commercial investments, it is of interest to assess how infrastructures could be developed to support the development of such systems and other spacecraft that could benefit from having a data relay service in Low Earth Orbit (LEO), as opposed to traditional Geostationary relays. This paper presents a tradespace exploration study of the architecture of such LEO commercial satellite data relay systems, here defined as Earth Orbiting Support Systems (EOSS). The paper proposes a methodology to formulate architectural decisions for EOSS constellations, and enumerate the corresponding tradespace of feasible architectures. Evaluation metrics are proposed to measure benefits and costs of architectures; lastly, a multicriteria Pareto criterion is used to downselect optimal architectures for subsequent analysis. The methodology is applied to two case studies for a set of 30 and 100 customer-spacecraft respectively, representing potential markets for LEO services in Exploration, Earth Observation, Science, and CubeSats. Pareto analysis shows how increased performance of the constellation is always achieved by an increased node size, as measured by the gain of the communications antenna mounted on EOSS spacecraft. On the other hand, nonlinear trends in optimal orbital altitude, number of satellites per plane, and number of orbital planes, are found in both cases. An upward trend in individual node memory capacity is found, although never exceeding 256 Gbits of onboard memory for both cases that have been considered, assuming the availability of a polar ground station for EOSS data downlink. System architects can use the proposed methodology to identify optimal EOSS constellations for a given service pricing strategy and customer target, thus identifying alternatives for selection by decision makers.

  16. Project Freebird: An orbital transfer vehicle

    Science.gov (United States)

    Aneses, Carlos A.; Blanchette, Ryan L.; Brann, David M.; Campos, Mario J.; Cohen, Lisa E.; Corcoran, Daniel J., III; Cox, James F.; Curtis, Trevor J.; Douglass, Deborah A.; Downard, Catherine L.

    1994-08-01

    Freebird is a space-based orbital transfer vehicle designed to repair and deorbit orbital assets. Freebird is based at International Space Station Alpha (ISSA) at an inclination of 51.6 deg and is capable of three types of missions: crewed and teleoperated LEO missions, and extended robotic missions. In a crewed local configuration, the vehicle can visit inclinations between 30.8 deg and 72.4 deg at altitudes close to 390 km. Adding extra fuel tanks extends this range of inclination up to 84.9 deg and down to 18.3 deg. Furthermore, removing the crew module, using the vehicle in a teleoperated manner, and operating with extra fuel tanks allows missions to polar and geosynchronous orbits. To allow for mission flexibility, the vehicle was designed in a semimodular configuration. The major system components include a crew module, a 'smart box' (which contains command, communications, guidance, and navigation equipment), a propulsion pack, extra fuel tanks, and a vehicle storage facility (VSF) for storage purposes. To minimize risk as well as development time and cost, the vehicle was designed using only proven technology or technology which is expected to be flight-qualified in time for the intended launch date of 2002. And, because Freebird carries crew and operates near the space station, it must meet or exceed the NASA reliability standard of 0.994, as well as other standard requirements for such vehicles. The Freebird program was conceived and designed as a way to provide important and currently unavailable satellite repair and replacement services of a value equal to or exceeding operational costs.

  17. Use of Advanced Solar Cells for Commercial Communication Satellites

    Science.gov (United States)

    Bailey, Sheila G.; Landis, Geoffrey A.

    1995-01-01

    The current generation of communications satellites are located primarily in geosynchronous Earth orbit (GEO). Over the next decade, however, a new generation of communications satellites will be built and launched, designed to provide a world-wide interconnection of portable telephones. For this mission, the satellites must be positioned in lower polar and near-polar orbits. To provide complete coverage, large numbers of satellites will be required. Because the required number of satellites decreases as the orbital altitude is increased, fewer satellites would be required if the orbit chosen were raised from low to intermediate orbit. However, in intermediate orbits, satellites encounter significant radiation due to trapped electrons and protons. Radiation tolerant solar cells may be necessary to make such satellites feasible. We analyze the amount of radiation encountered in low and intermediate polar orbits at altitudes of interest to next-generation communication satellites, calculate the expected degradation for silicon, GaAs, and InP solar cells, and show that the lifetimes can be significantly increased by use of advanced solar cells.

  18. Conductance and spin polarization for a quantum wire with the competition of Rashba and Dresselhaus spin-orbit coupling

    International Nuclear Information System (INIS)

    Fu Xi; Chen Zeshun; Zhong Feng; Zhou Guanghui

    2010-01-01

    We investigate theoretically the spin transport of a quantum wire (QW) with weak Rashba and Dresselhaus spin-orbit coupling (SOC) nonadiabatically connected to two normal leads. Using scattering matrix method and Landauer-Buettiker formula within effective free-electron approximation, we have calculated spin-dependent conductances G ↑ and G ↓ , total conductance G and spin polarization P z for a hard-wall potential confined QW. It is demonstrated that, the SOCs induce the splitting of G ↑ and G ↓ and form spin polarization P z . Moreover, the conductances present quantized plateaus, the plateaus and P z show oscillation structures near the subband edges. Furthermore, with the increase of QW width a strong spin polarization (P z ∼1) gradually becomes weak, which can be used to realize a spin filter. When the two SOCs coexist, the total conductance presents an isotropy transport due to the Rashba and Dresselhaus Hamiltonians being fixed, and the alteration of two SOCs strength ratio changes the sign of spin polarization. This may provide a way of realizing the expression of unit information by tuning gate voltage.

  19. Operational factors affecting microgravity levels in orbit

    Science.gov (United States)

    Olsen, R. E.; Mockovciak, J., Jr.

    1980-01-01

    Microgravity levels desired for proposed materials processing payloads are fundamental considerations in the design of future space platforms. Disturbance sources, such as aerodynamic drag, attitude control torques, crew motion and orbital dynamics, influence the microgravity levels attainable in orbit. The nature of these effects are assessed relative to platform design parameters such as orbital altitude and configuration geometry, and examples are presented for a representative spacecraft configuration. The possible applications of control techniques to provide extremely low acceleration levels are also discussed.

  20. Exploring the Limits of High Altitude GPS for Future Lunar Missions

    Science.gov (United States)

    Ashman, Benjamin W.; Parker, Joel J. K.; Bauer, Frank H.; Esswein, Michael

    2018-01-01

    An increasing number of spacecraft are relying on the Global Positioning System (GPS) for navigation at altitudes near or above the GPS constellation itself - the region known as the Space Service Volume (SSV). While the formal definition of the SSV ends at geostationary altitude, the practical limit of high-altitude space usage is not known, and recent missions have demonstrated that signal availability is sufficient for operational navigation at altitudes halfway to the moon. This paper presents simulation results based on a high-fidelity model of the GPS constellation, calibrated and validated through comparisons of simulated GPS signal availability and strength with flight data from recent high-altitude missions including the Geostationary Operational Environmental Satellite 16 (GOES-16) and the Magnetospheric Multiscale (MMS) mission. This improved model is applied to the transfer to a lunar near-rectilinear halo orbit (NRHO) of the class being considered for the international Deep Space Gateway concept. The number of GPS signals visible and their received signal strengths are presented as a function of receiver altitude in order to explore the practical upper limit of high-altitude space usage of GPS.

  1. Characterization of cosmic rays and direction dependence in the Polar Region up to 88 km altitude

    Directory of Open Access Journals (Sweden)

    Zábori Balázs

    2016-01-01

    Full Text Available Aims: The sounding rocket experiment REM-RED was developed to operate on board the REXUS-17 rocket in order to measure the intensity of cosmic rays. The experiment was launched from the ESRANGE Space Center (68 °N, 21 °E on the 17th of March 2015 at the beginning of the most intense geomagnetic storm within the preceding 10 years. The experiment provided the opportunity to measure the intensity of cosmic rays in the Polar Region up to an altitude of 88 km above sea level. Methods: The experiment employed Geiger-Müller (GM counters oriented with their axes perpendicular to each other in order to measure the cosmic ray intensity during the flight of the rocket. This measurement setup allowed performing direction-sensitive measurements as well. During the ascent phase the rocket was spinning and hence stabilized along its longitudinal axis looking close to the zenith direction. This phase of the flight was used for studying the direction dependence of the charged particle component of the cosmic rays. Results: In comparison with earlier, similar rocket experiments performed with GM tubes at lower geomagnetic latitudes, significantly higher cosmic radiation flux was measured above 50 km. A non-isotropic behavior was found below 50 km and described in detail for the first time in the Polar Region. This behavior is in good agreement with the results of the TECHDOSE experiment that used the same type of GM tubes on board the BEXUS-14 stratospheric balloon.

  2. O+ trough zones in the polar cap ionosphere-magnetosphere coupling region

    Science.gov (United States)

    Horwitz, James; Zeng, Wen; Jaafari, Fajer

    Regions of low-density troughs in O+ have been observed at 1 RE altitude in the polar cap ionosphere-magnetosphere region by the Thermal Ion Dynamics Experiment(TIDE) on the POLAR spacecraft. In this presentation, the UT Arlington Dynamic Fluid-Kinetic (DyFK) code is employed to investigate the formation of such O+ density troughs. We utilize convection paths of flux tubes in the high-latitude region as prescribed by an empirical convection model with solar wind inputs to track the evolution of ionospheric plasma transport and in particular O+ densities along these tubes with time/space. The flux tubes are subjected to auroral processes of precipitation and wave-driven ion heating when they pass through the auroral oval, which tends to elevate the plasma densities in these tubes. When the F-regions of such tubes traverse locations where the F-region is in darkness, recombination there causes the higher-altitude regions to drain and the densities to decline throughout. Owing to the varying effects of these processes, significant and low trough-like densities at higher altitudes developed along these flux tubes. The modeled densities near 6000 km altitudes will be compared with multiple POLAR passes featuring POLAR/TIDE-measured O+ densities for inside and outside of such trough regions.

  3. Polar observations of electron density distribution in the Earth’s magnetosphere. 2. Density profiles

    Directory of Open Access Journals (Sweden)

    H. Laakso

    2002-11-01

    Full Text Available Using spacecraft potential measurements of the Polar electric field experiment, we investigate electron density variations of key plasma regions within the magnetosphere, including the polar cap, cusp, trough, plasmapause, and auroral zone. The statistical results were presented in the first part of this study, and the present paper reports detailed structures revealed by individual satellite passes. The high-altitude (> 3 RE polar cap is generally one of the most tenuous regions in the magnetosphere, but surprisingly, the polar cap boundary does not appear as a steep density decline. At low altitudes (1 RE in summer, the polar densities are very high, several 100 cm-3 , and interestingly, the density peaks at the central polar cap. On the noonside of the polar cap, the cusp appears as a dense, 1–3° wide region. A typical cusp density above 4 RE distance is between several 10 cm-3 and a few 100 cm-3 . On some occasions the cusp is crossed multiple times in a single pass, simultaneously with the occurrence of IMF excursions, as the cusp can instantly shift its position under varying solar wind conditions, similar to the magnetopause. On the nightside, the auroral zone is not always detected as a simple density cavity. Cavities are observed but their locations, strengths, and sizes vary. Also, the electric field perturbations do not necessarily overlap with the cavities: there are cavities with no field disturbances, as well as electric field disturbances observed with no clear cavitation. In the inner magnetosphere, the density distributions clearly show that the plasmapause and trough densities are well correlated with geomagnetic activity. Data from individual orbits near noon and midnight demonstrate that at the beginning of geomagnetic disturbances, the retreat speed of the plasmapause can be one L-shell per hour, while during quiet intervals the plasmapause can expand anti-earthward at the same speed. For the trough region, it is found

  4. Mid-Latitude versus Polar-Latitude Transitional Impact Craters: Geometric Properties from Mars Orbiter Laser Altimeter (MOLA) Observations and Viking Images

    Science.gov (United States)

    Matias, A.; Garvin, J. B.; Sakimoto, S. E. H.

    1998-01-01

    One intriguing aspect of martian impact crater morphology is the change of crater cavity and ejecta characteristics from the mid-latitudes to the polar regions. This is thought to reflect differences in target properties such as an increasing presence of ice in the polar regions. Previous image-based efforts concerning martian crater morphology has documented some aspects of this, but has been hampered by the lack of adequate topography data. Recent Mars Orbiter Laser Altimeter (MOLA) topographic profiles provide a quantitative perspective for interpreting the detailed morphologies of martian crater cavities and ejecta morphology. This study is a preliminary effort to quantify the latitude-dependent differences in morphology with the goal of identifying target-dependent and crater modification effects from the combined of images and MOLA topography. We combine the available MOLA profiles and the corresponding Viking Mars Digital Image Mosaics (MDIMS), and high resolution Viking Orbiter images to focus on two transitional craters; one on the mid-latitudes, and one in the North Polar region. One MOLA pass (MGS Orbit 34) traverses the center of a 15.9 km diameter fresh complex crater located at 12.8degN 83.8degE on the Hesperian ridge plains unit (Hvr). Viking images, as well as MOLA data, show that this crater has well developed wall terraces and a central peak with 429 m of relative relief. Three MOLA passes have been acquired for a second impact crater, which is located at 69.5degN 41degE on the Vastitas Borealis Formation. This fresh rampart crater lacks terraces and central peak structures and it has a depth af 579 m. Correlation between images and MOLA topographic profiles allows us to construct basic facies maps of the craters. Eight main units were identified, four of which are common on both craters.

  5. Detecting Canopy Water Status Using Shortwave Infrared Reflectance Data From Polar Orbiting and Geostationary Platforms

    DEFF Research Database (Denmark)

    Fensholt, Rasmus; Huber Gharib, Silvia; Proud, Simon Richard

    2010-01-01

    -based canopy water status detection from geostationary Meteosat Second Generation (MSG) Spinning Enhanced Visible and Infrared Imager (SEVIRI) data as compared to polar orbiting environmental satellite (POES)-based moderate resolution imaging spectroradiometer (MODIS) data. The EO-based SWIR water stress index...... (SIWSI) is evaluated against in situ measured canopy water content indicators at a semi-arid grassland savanna site in Senegal 2008. Daily SIWSI from both MODIS and SEVIRI data show an overall inverse relation to Normalized Difference Vegetation Index (NDVI) throughout the growing season. SIWSI...... for SWIR-based canopy water status and stress monitoring in a semi-arid environment....

  6. A multi-satellite study of accelerated ionospheric ion beams above the polar cap

    Directory of Open Access Journals (Sweden)

    R. Maggiolo

    2006-07-01

    Full Text Available This paper presents a study of nearly field-aligned outflowing ion beams observed on the Cluster satellites over the polar cap. Data are taken at geocentric radial distances of the order of 5–9 RE. The distinction is made between ion beams originating from the polar cusp/cleft and beams accelerated almost along the magnetic field line passing by the spacecraft. Polar cusp beams are characterized by nearly field-aligned proton and oxygen ions with an energy ratio EO+ / EH+, of the order of 3 to 4, due to the ion energy repartition inside the source and to the latitudinal extension of the source. Rapid variations in the outflowing ion energy are linked with pulses/modifications of the convection electric field. Cluster data allow one to show that these perturbations of the convection velocity and the associated ion structures propagate at the convection velocity.

    In contrast, polar cap local ion beams are characterized by field-aligned proton and oxygen ions with similar energies. These beams show the typical inverted V structures usually observed in the auroral zone and are associated with a quasi-static converging electric field indicative of a field-aligned electric field. The field-aligned potential drop fits well the ion energy profile. The simultaneous observation of precipitating electrons and upflowing ions of similar energies at the Cluster orbit indicates that the spacecraft are crossing the mid-altitude part of the acceleration region. In the polar cap, the parallel electric field can thus extend to altitudes higher than 5 Earth radii. A detailed analysis of the distribution functions shows that the ions are heated during their parallel acceleration and that energy is exchanged between H+ and O+. Furthermore, intense electrostatic waves are observed simultaneously. These observations could be due to an ion-ion two-stream instability.

  7. Optically induced rotation of Rayleigh particles by vortex beams with different states of polarization

    International Nuclear Information System (INIS)

    Li, Manman; Yan, Shaohui; Yao, Baoli; Liang, Yansheng; Lei, Ming; Yang, Yanlong

    2016-01-01

    Optical vortex beams carry optical orbital angular momentum (OAM) and can induce an orbital motion of trapped particles in optical trapping. We show that the state of polarization (SOP) of vortex beams will affect the details of this optically induced orbital motion to some extent. Numerical results demonstrate that focusing the vortex beams with circular, radial or azimuthal polarizations can induce a uniform orbital motion on a trapped Rayleigh particle, while in the focal field of the vortex beam with linear polarization the particle experiences a non-uniform orbital motion. Among the formers, the vortex beam with circular polarization induces a maximum optical torque on the particle. Furthermore, by varying the topological charge of the vortex beams, the vortex beam with circular polarization gives rise to an optimum torque superior to those given by the other three vortex beams. These facts suggest that the circularly polarized vortex beam is more suitable for rotating particles. - Highlights: • States of polarization of vortex beams affect the optically induced orbital motion of particles. • The dependences of the force and orbital torque on the topological charge, the size and the absorptivity of particles were calculated. • Focused vortex beams with circular, radial or azimuthal polarizations induce a uniform orbital motion on particles. • Particles experience a non-uniform orbital motion in the focused linearly polarized vortex beam. • The circularly polarized vortex beam is a superior candidate for rotating particles.

  8. Spin tune dependence on closed orbit in RHIC

    International Nuclear Information System (INIS)

    Ptitsyn, V.; Bai, M.; Roser, T.

    2010-01-01

    Polarized proton beams are accelerated in RHIC to 250 GeV energy with the help of Siberian Snakes. The pair of Siberian Snakes in each RHIC ring holds the design spin tune at 1/2 to avoid polarization loss during acceleration. However, in the presence of closed orbit errors, the actual spin tune can be shifted away from the exact 1/2 value. It leads to a corresponding shift of locations of higher-order ('snake') resonances and limits the available betatron tune space. The largest closed orbit effect on the spin tune comes from the horizontal orbit angle between the two snakes. During RHIC Run in 2009 dedicated measurements with polarized proton beams were taken to verify the dependence of the spin tune on the local orbits at the Snakes. The experimental results are presented along with the comparison with analytical predictions.

  9. Chaos and its control in the pitch motion of an asymmetric magnetic spacecraft in polar elliptic orbit

    Energy Technology Data Exchange (ETDEWEB)

    Inarrea, Manuel [Universidad de La Rioja, Area de Fisica Aplicada, 26006 Logrono (Spain)], E-mail: manuel.inarrea@unirioja.es

    2009-05-30

    We study the pitch attitude dynamics of an asymmetric magnetic spacecraft in a polar almost circular orbit under the influence of a gravity gradient torque. The spacecraft is perturbed by the small eccentricity of the elliptic orbit and by a small magnetic torque generated by the interaction between the Earth's magnetic field and the magnetic moment of the spacecraft. Under both perturbations, we show that the pitch motion exhibits heteroclinic chaotic behavior by means of the Melnikov method. Numerical methods applied to simulations of the pitch motion also confirm the chaotic character of the spacecraft attitude dynamics. Finally, a linear time-delay feedback method for controlling chaos is applied to the governing equations of the spacecraft pitch motion in order to remove the chaotic character of initially irregular attitude motions and transform them into periodic ones.

  10. Chaos and its control in the pitch motion of an asymmetric magnetic spacecraft in polar elliptic orbit

    International Nuclear Information System (INIS)

    Inarrea, Manuel

    2009-01-01

    We study the pitch attitude dynamics of an asymmetric magnetic spacecraft in a polar almost circular orbit under the influence of a gravity gradient torque. The spacecraft is perturbed by the small eccentricity of the elliptic orbit and by a small magnetic torque generated by the interaction between the Earth's magnetic field and the magnetic moment of the spacecraft. Under both perturbations, we show that the pitch motion exhibits heteroclinic chaotic behavior by means of the Melnikov method. Numerical methods applied to simulations of the pitch motion also confirm the chaotic character of the spacecraft attitude dynamics. Finally, a linear time-delay feedback method for controlling chaos is applied to the governing equations of the spacecraft pitch motion in order to remove the chaotic character of initially irregular attitude motions and transform them into periodic ones.

  11. Densities inferred from ESA's Venus Express aerobraking campaign at 130 km altitude

    Science.gov (United States)

    Bruinsma, Sean; Marty, Jean-Charles; Svedhem, Håkan; Williams, Adam; Mueller-Wodarg, Ingo

    2015-04-01

    In June-July 2014, ESA performed a planned aerobraking campaign with Venus Express to measure neutral densities above 130 km in Venus' atmosphere by means of the engineering accelerometers. To that purpose, the orbit perigee was lowered to approximately 130 km in order to enhance the atmospheric drag effect to the highest tolerable levels for the spacecraft; the accelerometer resolution and precision were not sufficient at higher altitudes. This campaign was requested as part of the Venus Express Atmospheric Drag Experiment (VExADE). A total of 18 orbits (i.e. days) were processed using the attitude quaternions to correctly orient the spacecraft bus and solar arrays in inertial space, which is necessary to accurately compute the exposed surface in the ram direction. The accelerometer data provide good measurements approximately from 130-140 km altitude; the length of the profiles is about 85 seconds, and they are on the early morning side (LST=4.5) at high northern latitude (70°N-82°N). The densities are a factor 2-3 larger than Hedin's VTS-3 thermosphere model, which is consistent with earlier results obtained via classical precise orbit determination at higher altitudes. Wavelike structures with amplitudes of 20% and more are detected, with wavelengths of about 100-500 km. We cannot entirely rule out that these waves are caused by the spacecraft or due to some unknown instrumental effect, but we estimate this probability to be very low.

  12. Reduced oxygen at high altitude limits maximum size.

    Science.gov (United States)

    Peck, L S; Chapelle, G

    2003-11-07

    The trend towards large size in marine animals with latitude, and the existence of giant marine species in polar regions have long been recognized, but remained enigmatic until a recent study showed it to be an effect of increased oxygen availability in sea water of a low temperature. The effect was apparent in data from 12 sites worldwide because of variations in water oxygen content controlled by differences in temperature and salinity. Another major physical factor affecting oxygen content in aquatic environments is reduced pressure at high altitude. Suitable data from high-altitude sites are very scarce. However, an exceptionally rich crustacean collection, which remains largely undescribed, was obtained by the British 1937 expedition from Lake Titicaca on the border between Peru and Bolivia in the Andes at an altitude of 3809 m. We show that in Lake Titicaca the maximum length of amphipods is 2-4 times smaller than other low-salinity sites (Caspian Sea and Lake Baikal).

  13. Mapping the space radiation environment in LEO orbit by the SATRAM Timepix payload on board the Proba-V satellite

    Energy Technology Data Exchange (ETDEWEB)

    Granja, Carlos, E-mail: carlos.granja@utef.cvut.cz; Polansky, Stepan

    2016-07-07

    Detailed spatial- and time-correlated maps of the space radiation environment in Low Earth Orbit (LEO) are produced by the spacecraft payload SATRAM operating in open space on board the Proba-V satellite from the European Space Agency (ESA). Equipped with the hybrid semiconductor pixel detector Timepix, the compact radiation monitor payload provides the composition and spectral characterization of the mixed radiation field with quantum-counting and imaging dosimetry sensitivity, energetic charged particle tracking, directionality and energy loss response in wide dynamic range in terms of particle types, dose rates and particle fluxes. With a polar orbit (sun synchronous, 98° inclination) at the altitude of 820 km the payload samples the space radiation field at LEO covering basically the whole planet. First results of long-period data evaluation in the form of time-and spatially-correlated maps of total dose rate (all particles) are given.

  14. Differential roles of polar orbital prefrontal cortex and parietal lobes in logical reasoning with neutral and negative emotional content.

    Science.gov (United States)

    Eimontaite, Iveta; Goel, Vinod; Raymont, Vanessa; Krueger, Frank; Schindler, Igor; Grafman, Jordan

    2018-05-14

    To answer the question of how brain pathology affects reasoning about negative emotional content, we administered a disjunctive logical reasoning task involving arguments with neutral content (e.g. Either there are tigers or women in NYC, but not both; There are no tigers in NYC; There are women in NYC) and emotionally laden content (e.g. Either there are pedophiles or politicians in Texas, but not both; There are politicians in Texas; There are no pedophiles in Texas) to 92 neurological patients with focal lesions to various parts of the brain. A Voxel Lesion Symptom Mapping (VLSM) analysis identified 16 patients, all with lesions to the orbital polar prefrontal cortex (BA 10 & 11), as being selectively impaired in the emotional reasoning condition. Another 17 patients, all with lesions to the parietal cortex, were identified as being impaired in the neutral content condition. The reasoning scores of these two patient groups, along with 23 matched normal controls, underwent additional analysis to explore the effect of belief bias. This analysis revealed that the differences identified above were largely driven by trials where there was an incongruency between the believability of the conclusion and the validity of the argument (i.e. valid argument /false conclusion or invalid argument /true conclusion). Patients with lesions to polar orbital prefrontal cortex underperformed in incongruent emotional content trials and over performed in incongruent neutral content trials (compared to both normal controls and patients with parietal lobe lesions). Patients with lesions to parietal lobes underperformed normal controls (at a trend level) in neutral trials where there was a congruency between the believability of the conclusion and the validity of the argument (i.e. valid argument/true conclusion or invalid argument/false conclusion). We conclude that lesions to the polar orbital prefrontal cortex (i) prevent these patients from enjoying any emotionally induced cognitive

  15. Prospective Ukrainian lunar orbiter mission

    Science.gov (United States)

    Shkuratov, Y.; Litvinenko, L.; Shulga, V.; Yatskiv, Y.; Kislyuk, V.

    Ukraine has launch vehicles that are able to deliver about 300 kg to the lunar orbit. Future Ukrainian lunar program may propose a polar orbiter. This orbiter should fill principal information gaps in our knowledge about the Moon after Clementine and Lunar Prospector missions and the future missions, like Smart-1, Lunar-A, and Selene. We consider that this can be provided by radar studies of the Moon with supporting optical polarimetric observations from lunar polar orbit. These experiments allow one to better understand global structure of the lunar surface in a wide range of scales, from microns to kilometers. We propose three instruments for the prospective lunar orbiter. They are: a synthetic aperture imaging radar (SAR), ground-penetrating radar (GPR), and imaging polarimeter (IP). The main purpose of SAR is to study with high resolution (50 m) the permanently shadowed sites in the lunar polar regions. These sites are cold traps for volatiles, and have a potential of resource utilization. Possible presence of water ice in the regolith in the sites makes them interesting for permanent manned bases on the Moon. Radar imaging and mapping of other interesting regions could be also planned. Multi-frequencies multi-polarization soun d ing of the lunar surface with GPR can provide information about internal structure of the lunar surface from meters to several hundred meters deep. GPR can be used for measuring the megaregolith layer properties, detection of cryptomaria, and studies of internal structure of the largest craters. IP will be a CCD camera with an additional suite of polarizers. Modest spatial resolution (100 m) should provide a total coverage or a large portion of the lunar surface in oblique viewing basically at large phase angles. Polarization degree at large (>90°) phase angles bears information about characteristic size of the regolith particles. Additional radiophysical experiments are considered with the use of the SAR system, e.g., bistatic radar

  16. Global pictures of the ozone field from high altitudes from DE-I

    Science.gov (United States)

    Keating, G. M.; Frank, L.; Craven, J.; Shapiro, M.; Young, D.; Bhartia, P.

    1982-01-01

    Detailed synoptic views of the column ozone field can be obtained by the Spin-Scan Ozone Imager (SOI) (Keating et al., 1981) aboard the Dynamics Explorer I satellite. The eccentric polar orbit with an apogee altitude of 23,000 km allows high resolution global-scale images to be obtained within 12 minutes, and allows regions to be viewed for long periods of time. At perigee, a pixel size of nadir measurements of 3 km is possible, and measurements are determined using the backscattered ultraviolet technique. A wavelength measurement of 317.5 nm is used as there are limitations in filter locations and it allows comparison with Nimbus 7 SBUV/TOMS data. Consideration of the reflectivities of this data aids in checking the SOI data reduction algorithm. SOI data show short-term (less than one day) variations in the observed ozone field, and a negative correlation (greater than 0.9) between ozone and tropopause heights. It is expected, due to this correlation, that SOI data will aid in understanding the time evolution of dynamics near the tropopause.

  17. Gamma rays in L-B coordinates at CORONAS-I altitude

    Directory of Open Access Journals (Sweden)

    I. N. Myagkova

    2005-09-01

    Full Text Available We present here observations of gamma rays in the energy range between 3.0 and 8.3 MeV gathered by the SONG instrument aboard low-altitude polar-orbiting satellite CORONAS-I throughout the period March-June 1994. We concentrate on the emissions related to the trapped particles and organize CORONAS-I measurements in the magnetic L–B coordinate system. The spatial distribution of the average gamma-ray counts reveals that the most intense fluxes were observed under the inner radiation belt, at L<2, and that they are exclusively confined into the region of stably trapped particles, where daughter gamma rays could result from the interactions within the spacecraft and instrumental matter. In the outer radiation zone (L~4, the enhanced gamma radiation, also detected outside the stably trapping region, shows pronounced longitudinal variations. The observed eastward increase in the gamma-ray count rate suggests quasi-traped energetic (megavolt electrons as a source of the gamma rays both in the upper atmosphere and in the satellite matter, most likely, through the bremsstrahlung process in the studied energy domain. Keywords. Magnetospheric physics (Energetic particles, precipitating; Energetic particles, trapped; Magnetosphereionosphere interactions

  18. Burn Delay Analysis of the Lunar Orbit Insertion for Korea Pathfinder Lunar Orbiter

    Science.gov (United States)

    Bae, Jonghee; Song, Young-Joo; Kim, Young-Rok; Kim, Bangyeop

    2017-12-01

    The first Korea lunar orbiter, Korea Pathfinder Lunar Orbiter (KPLO), has been in development since 2016. After launch, the KPLO will execute several maneuvers to enter into the lunar mission orbit, and will then perform lunar science missions for one year. Among these maneuvers, the lunar orbit insertion (LOI) is the most critical maneuver because the KPLO will experience an extreme velocity change in the presence of the Moon’s gravitational pull. However, the lunar orbiter may have a delayed LOI burn during operation due to hardware limitations and telemetry delays. This delayed burn could occur in different captured lunar orbits; in the worst case, the KPLO could fly away from the Moon. Therefore, in this study, the burn delay for the first LOI maneuver is analyzed to successfully enter the desired lunar orbit. Numerical simulations are performed to evaluate the difference between the desired and delayed lunar orbits due to a burn delay in the LOI maneuver. Based on this analysis, critical factors in the LOI maneuver, the periselene altitude and orbit period, are significantly changed and an additional delta-V in the second LOI maneuver is required as the delay burn interval increases to 10 min from the planned maneuver epoch.

  19. The Suomi National Polar-Orbiting Partnership (SNPP): Continuing NASA Research and Applications

    Science.gov (United States)

    Butler, James; Gleason, James; Jedlovec, Gary; Coronado, Patrick

    2015-01-01

    The Suomi National Polar-orbiting Partnership (SNPP) satellite was successfully launched into a polar orbit on October 28, 2011 carrying 5 remote sensing instruments designed to provide data to improve weather forecasts and to increase understanding of long-term climate change. SNPP provides operational continuity of satellite-based observations for NOAA's Polar-orbiting Operational Environmental Satellites (POES) and continues the long-term record of climate quality observations established by NASA's Earth Observing System (EOS) satellites. In the 2003 to 2011 pre-launch timeframe, NASA's SNPP Science Team assessed the adequacy of the operational Raw Data Records (RDRs), Sensor Data Records (SDRs), and Environmental Data Records (EDRs) from the SNPP instruments for use in NASA Earth Science research, examined the operational algorithms used to produce those data records, and proposed a path forward for the production of climate quality products from SNPP. In order to perform these tasks, a distributed data system, the NASA Science Data Segment (SDS), ingested RDRs, SDRs, and EDRs from the NOAA Archive and Distribution and Interface Data Processing Segments, ADS and IDPS, respectively. The SDS also obtained operational algorithms for evaluation purposes from the NOAA Government Resource for Algorithm Verification, Independent Testing and Evaluation (GRAVITE). Within the NASA SDS, five Product Evaluation and Test Elements (PEATEs) received, ingested, and stored data and performed NASA's data processing, evaluation, and analysis activities. The distributed nature of this data distribution system was established by physically housing each PEATE within one of five Climate Analysis Research Systems (CARS) located at either at a NASA or a university institution. The CARS were organized around 5 key EDRs directly in support of the following NASA Earth Science focus areas: atmospheric sounding, ocean, land, ozone, and atmospheric composition products. The PEATES provided

  20. Climatic changes on orbital and sub-orbital time scale recorded by the Guliya ice core in Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    姚檀栋; 徐柏青; 蒲健辰

    2001-01-01

    Based on ice core records in the Tibetan Plateau and Greenland, the features and possible causes of climatic changes on orbital and sub-orbital time scale were discussed. Orbital time scale climatic change recorded in ice core from the Tibetan Plateau is typically ahead of that from polar regions, which indicates that climatic change in the Tibetan Plateau might be earlier than polar regions. The solar radiation change is a major factor that dominates the climatic change on orbital time scale. However, climatic events on sub-orbital time scale occurred later in the Tibetan Plateau than in the Arctic Region, indicating a different mechanism. For example, the Younger Dryas and Heinrich events took place earlier in Greenland ice core record than in Guliya ice core record. It is reasonable to propose the hypothesis that these climatic events were affected possibly by the Laurentide Ice Sheet. Therefore, ice sheet is critically important to climatic change on sub-orbital time scale in some ice ages.

  1. Characterizing Longitude-Dependent Orbital Debris Congestion in the Geosynchronous Orbit Regime

    Science.gov (United States)

    Anderson, Paul V.

    The geosynchronous orbit (GEO) is a unique commodity of the satellite industry that is becoming increasingly contaminated with orbital debris, but is heavily populated with high-value assets from the civil, commercial, and defense sectors. The GEO arena is home to hundreds of communications, data transmission, and intelligence satellites collectively insured for an estimated 18.3 billion USD. As the lack of natural cleansing mechanisms at the GEO altitude renders the lifetimes of GEO debris essentially infinite, conjunction and risk assessment must be performed to safeguard operational assets from debris collisions. In this thesis, longitude-dependent debris congestion is characterized by predicting the number of near-miss events per day for every longitude slot at GEO, using custom debris propagation tools and a torus intersection metric. Near-miss events with the present-day debris population are assigned risk levels based on GEO-relative position and speed, and this risk information is used to prioritize the population for debris removal target selection. Long-term projections of debris growth under nominal launch traffic, mitigation practices, and fragmentation events are also discussed, and latitudinal synchronization of the GEO debris population is explained via node variations arising from luni-solar gravity. In addition to characterizing localized debris congestion in the GEO ring, this thesis further investigates the conjunction risk to operational satellites or debris removal systems applying low-thrust propulsion to raise orbit altitude at end-of-life to a super-synchronous disposal orbit. Conjunction risks as a function of thrust level, miss distance, longitude, and semi-major axis are evaluated, and a guidance method for evading conjuncting debris with continuous thrust by means of a thrust heading change via single-shooting is developed.

  2. Estimation of land-atmosphere energy transfer over the Tibetan Plateau by a combination use of geostationary and polar-orbiting satellite data

    Science.gov (United States)

    Zhong, L.; Ma, Y.

    2017-12-01

    Land-atmosphere energy transfer is of great importance in land-atmosphere interactions and atmospheric boundary layer processes over the Tibetan Plateau (TP). The energy fluxes have high temporal variability, especially in their diurnal cycle, which cannot be acquired by polar-orbiting satellites alone because of their low temporal resolution. Therefore, it's of great practical significance to retrieve land surface heat fluxes by a combination use of geostationary and polar orbiting satellites. In this study, a time series of the hourly LST was estimated from thermal infrared data acquired by the Chinese geostationary satellite FengYun 2C (FY-2C) over the TP. The split window algorithm (SWA) was optimized using a regression method based on the observations from the Enhanced Observing Period (CEOP) of the Asia-Australia Monsoon Project (CAMP) on the Tibetan Plateau (CAMP/Tibet) and Tibetan observation and research platform (TORP), the land surface emissivity (LSE) from the Moderate Resolution Imaging Spectroradiometer (MODIS), and the water vapor content from the National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) project. The 10-day composite hourly LST data were generated via the maximum value composite (MVC) method to reduce the cloud effects. The derived LST was validated by the field observations of CAMP/Tibet and TORP. The results show that the retrieved LST and in situ data have a very good correlation (with root mean square error (RMSE), mean bias (MB), mean absolute error (MAE) and correlation coefficient (R) values of 1.99 K, 0.83 K, 1.71 K, and 0.991, respectively). Together with other characteristic parameters derived from polar-orbiting satellites and meteorological forcing data, the energy balance budgets have been retrieved finally. The validation results showed there was a good consistency between estimation results and in-situ measurements over the TP, which prove the robustness of the proposed estimation

  3. Influence of atmospheric turbulence on the quantum polarization state

    Science.gov (United States)

    Yang, Ru; Xue, Yang; Li, Yunxia; Shi, Lei; Zhu, Yu; Zhu, Qiuli

    2018-03-01

    In order to study the influence of atmospheric turbulence on the polarization state of the free space quantum communication, the relationship between the refractive index and altitude, the refractive index structure constant and the turbulence dimension is deduced based on two different atmospheric refractive index structural constants models. The turbulence intensity factor κ is introduced and the equation of the variation of the quantum polarization degree with turbulence intensity is established. Through the simulation of the turbulent refractive index and the performance of four different polarization states in the low altitude turbulence environment, the results show that the atmospheric turbulence in the near ground will affect the fluctuation of the degree of polarization, and the degree of polarization varies linearly with the change of turbulence intensity. In the case of polarization |H>, the range of polarization |H> varies from 0 to 0.14 with the change of turbulence intensity. The influence of atmospheric turbulence on four different polarization states is different, and the degree of |H> and |V> depolarization is greater in the daytime and back. The depolarization degree of |-> at night is greater. The relationship between the degree of polarization and the change of turbulence intensity is analyzed by mathematical modeling, which is helpful to select the reasonable experimental scheme and compensate the change of polarization state in the aviation quantum Secure communication channel.

  4. Characteristics of high altitude oxygen ion energization and outflow as observed by Cluster: a statistical study

    Energy Technology Data Exchange (ETDEWEB)

    Nilsson, H.; Waara, M.; Arvelius, S.; Yamauchi, M.; Lundin, R. [Inst. of Space Physics, Kiruna (Sweden); Marghitu, O. [Max-Planck-Inst. fuer Extraterrestriche Physik, Garching (Germany); Inst. for Space Sciences, Bucharest (Romania); Bouhram, M. [Max-Planck-Inst. fuer Extraterrestriche Physik, Garching (Germany); CETP-CNRS, Saint-Maur (France); Hobara, Y. [Inst. of Space Physics, Kiruna (Sweden); Univ. of Sheffield, Sheffield (United Kingdom); Reme, H.; Sauvaud, J.A.; Dandouras, I. [Centre d' Etude Spatiale des Rayonnements, Toulouse (France); Balogh, A. [Imperial Coll. of Science, Technology and Medicine, London (United Kingdom); Kistler, L.M. [Univ. of New Hampshire, Durham (United States); Klecker, B. [Max-Planck-Inst. fuer Extraterrestriche Physik, Garching (Germany); Carlson, C.W. [Space Science Lab., Univ. of California, Berkeley (United States); Bavassano-Cattaneo, M.B. [Ist. di Fisica dello Spazio Interplanetario, Roma (Italy); Korth, A. [Max-Planck-Inst. fuer Sonnensystemforschung, Katlenburg-Lindau (Germany)

    2006-07-01

    The results of a statistical study of oxygen ion outflow using cluster data obtained at high altitude above the polar cap is reported. Moment data for both hydrogen ions (H{sup +}) and oxygen ions (O{sup +}) from 3 years (2001-2003) of spring orbits (January to May) have been used. The altitudes covered were mainly in the range 5-12 R{sub E} geocentric distance. It was found that O{sup +} is significantly transversely energized at high altitudes, indicated both by high perpendicular temperatures for low magnetic field values as well as by a tendency towards higher perpendicular than parallel temperature distributions for the highest observed temperatures. The O{sup +} parallel bulk velocity increases with altitude in particular for the lowest observed altitude intervals. O{sup +} parallel bulk velocities in excess of 60 km s{sup -1} were found mainly at higher altitudes corresponding to magnetic field strengths of less than 100 nT. For the highest observed parallel bulk velocities of O{sup +} the thermal velocity exceeds the bulk velocity, indicating that the beam-like character of the distribution is lost. The parallel bulk velocity of the H{sup +} and O{sup +} was found to typically be close to the same throughout the observation interval when the H{sup +} bulk velocity was calculated for all pitch-angles. When the H{sup +} bulk velocity was calculated for upward moving particles only the H{sup +} parallel bulk velocity was typically higher than that of O{sup +}. The parallel bulk velocity is close to the same for a wide range of relative abundance of the two ion species, including when the O{sup +} ions dominates. The thermal velocity of O{sup +} was always well below that of H{sup +}. Thus perpendicular energization that is more effective for O{sup +} takes place, but this is not enough to explain the close to similar parallel velocities. Further parallel acceleration must occur. The results presented constrain the models of perpendicular heating and parallel

  5. Characteristics of high altitude oxygen ion energization and outflow as observed by Cluster: a statistical study

    Directory of Open Access Journals (Sweden)

    H. Nilsson

    2006-05-01

    Full Text Available The results of a statistical study of oxygen ion outflow using Cluster data obtained at high altitude above the polar cap is reported. Moment data for both hydrogen ions (H+ and oxygen ions (O+ from 3 years (2001-2003 of spring orbits (January to May have been used. The altitudes covered were mainly in the range 5–12 RE geocentric distance. It was found that O+ is significantly transversely energized at high altitudes, indicated both by high perpendicular temperatures for low magnetic field values as well as by a tendency towards higher perpendicular than parallel temperature distributions for the highest observed temperatures. The O+ parallel bulk velocity increases with altitude in particular for the lowest observed altitude intervals. O+ parallel bulk velocities in excess of 60 km s-1 were found mainly at higher altitudes corresponding to magnetic field strengths of less than 100 nT. For the highest observed parallel bulk velocities of O+ the thermal velocity exceeds the bulk velocity, indicating that the beam-like character of the distribution is lost. The parallel bulk velocity of the H+ and O+ was found to typically be close to the same throughout the observation interval when the H+ bulk velocity was calculated for all pitch-angles. When the H+ bulk velocity was calculated for upward moving particles only the H+ parallel bulk velocity was typically higher than that of O+. The parallel bulk velocity is close to the same for a wide range of relative abundance of the two ion species, including when the O+ ions dominates. The thermal velocity of O+ was always well below that of H+. Thus perpendicular energization that is more effective for O+ takes place, but this is not enough to explain the close to similar parallel velocities. Further parallel acceleration must occur. The results presented constrain the models of perpendicular heating and parallel acceleration. In particular centrifugal acceleration of the outflowing ions, which may

  6. Drag Coefficient Estimation in Orbit Determination

    Science.gov (United States)

    McLaughlin, Craig A.; Manee, Steve; Lichtenberg, Travis

    2011-07-01

    Drag modeling is the greatest uncertainty in the dynamics of low Earth satellite orbits where ballistic coefficient and density errors dominate drag errors. This paper examines fitted drag coefficients found as part of a precision orbit determination process for Stella, Starlette, and the GEOSAT Follow-On satellites from 2000 to 2005. The drag coefficients for the spherical Stella and Starlette satellites are assumed to be highly correlated with density model error. The results using MSIS-86, NRLMSISE-00, and NRLMSISE-00 with dynamic calibration of the atmosphere (DCA) density corrections are compared. The DCA corrections were formulated for altitudes of 200-600 km and are found to be inappropriate when applied at 800 km. The yearly mean fitted drag coefficients are calculated for each satellite for each year studied. The yearly mean drag coefficients are higher for Starlette than Stella, where Starlette is at a higher altitude. The yearly mean fitted drag coefficients for all three satellites decrease as solar activity decreases after solar maximum.

  7. Dimensional crossover of effective orbital dynamics in polar distorted He 3 -A : Transitions to antispacetime

    Science.gov (United States)

    Nissinen, J.; Volovik, G. E.

    2018-01-01

    Topologically protected superfluid phases of He 3 allow one to simulate many important aspects of relativistic quantum field theories and quantum gravity in condensed matter. Here we discuss a topological Lifshitz transition of the effective quantum vacuum in which the determinant of the tetrad field changes sign through a crossing to a vacuum state with a degenerate fermionic metric. Such a transition is realized in polar distorted superfluid He 3 -A in terms of the effective tetrad fields emerging in the vicinity of the superfluid gap nodes: the tetrads of the Weyl points in the chiral A-phase of He 3 and the degenerate tetrad in the vicinity of a Dirac nodal line in the polar phase of He 3 . The continuous phase transition from the A -phase to the polar phase, i.e., the transition from the Weyl nodes to the Dirac nodal line and back, allows one to follow the behavior of the fermionic and bosonic effective actions when the sign of the tetrad determinant changes, and the effective chiral spacetime transforms to antichiral "anti-spacetime." This condensed matter realization demonstrates that while the original fermionic action is analytic across the transition, the effective action for the orbital degrees of freedom (pseudo-EM) fields and gravity have nonanalytic behavior. In particular, the action for the pseudo-EM field in the vacuum with Weyl fermions (A-phase) contains the modulus of the tetrad determinant. In the vacuum with the degenerate metric (polar phase) the nodal line is effectively a family of 2 +1 d Dirac fermion patches, which leads to a non-analytic (B2-E2)3/4 QED action in the vicinity of the Dirac line.

  8. The Carter constant for inclined orbits about a massive Kerr black hole: I. Circular orbits

    Energy Technology Data Exchange (ETDEWEB)

    Komorowski, P G; Valluri, S R; Houde, M, E-mail: pkomorow@uwo.c, E-mail: valluri@uwo.c, E-mail: mhoude2@uwo.c [Department of Physics and Astronomy, University of Western Ontario, London, Ontario (Canada)

    2010-11-21

    In an extreme binary black hole system, an orbit will increase its angle of inclination ({iota}) as it evolves in Kerr spacetime. We focus our attention on the behaviour of the Carter constant (Q) for near-polar orbits, and develop an analysis that is independent of and complements radiation-reaction models. For a Schwarzschild black hole, the polar orbits represent the abutment between the prograde and retrograde orbits at which Q is at its maximum value for given values of the latus rectum ({tilde l}) and the eccentricity (e). The introduction of spin ({tilde S}={vert_bar}J{vert_bar}/M{sup 2}) to the massive black hole causes this boundary, or abutment, to be moved towards greater orbital inclination; thus, it no longer cleanly separates prograde and retrograde orbits. To characterize the abutment of a Kerr black hole (KBH), we first investigated the last stable orbit (LSO) of a test-particle about a KBH, and then extended this work to general orbits. To develop a better understanding of the evolution of Q we developed analytical formulae for Q in terms of {tilde l}, e and {tilde S} to describe elliptical orbits at the abutment, polar orbits and LSOs. By knowing the analytical form of {partial_derivative}Q/{partial_derivative}{tilde l} at the abutment, we were able to test a 2PN flux equation for Q. We also used these formulae to numerically calculate the {partial_derivative}{iota}/{partial_derivative}{tilde l} of hypothetical circular orbits that evolve along the abutment. From these values we have determined that {partial_derivative}{iota}/{partial_derivative}{tilde l} = -(122.7{tilde S} - 36{tilde S}{sup 3}){tilde l}{sup -11/2} - (63/2 {tilde S} + 35/4 {tilde S}{sup 3}){tilde l}{sup -9/2} - 15/2 {tilde S}{tilde l}{sup -7/2} - 9/2 {tilde S}{tilde l}{sup -5/2}. By taking the limit of this equation for {tilde l} {yields} {infinity}, and comparing it with the published result for the weak-field radiation reaction, we found the upper limit on

  9. Exploration for fossil and nuclear fuels from orbital altitudes

    Science.gov (United States)

    Short, N. M.

    1977-01-01

    The paper discusses the application of remotely sensed data from orbital satellites to the exploration for fossil and nuclear fuels. Geological applications of Landsat data are described including map editing, lithologic identification, structural geology, and mineral exploration. Specific results in fuel exploration are reviewed and a series of related Landsat images is included.

  10. Optic neuropathy following an altitude exposure.

    Science.gov (United States)

    Steigleman, Allan; Butler, Frank; Chhoeu, Austin; O'Malley, Timothy; Bower, Eric; Giebner, Stephen

    2003-09-01

    This case report describes a 20-yr-old man who presented with retro-orbital pain and blurred vision in his left eye 3 wk after an altitude exposure in a hypobaric chamber. He was found to have significant deficits in color vision and visual fields consistent with an optic neuropathy in his left eye. The patient was diagnosed with decompression sickness and treated with hyperbaric oxygen with a U.S. Navy Treatment Table VI. All signs and symptoms resolved with a single hyperbaric oxygen treatment but recurred. A head MRI revealed a left frontoethmoid sinus opacity. A concomitant sinusitis was diagnosed. The patient had full resolution of symptoms after a total of four hyperbaric oxygen treatments and antibiotic therapy at 6-wk follow-up. Although a para-infectious etiology for this patient's optic neuropathy cannot be excluded, his history of altitude exposure and significant, rapid response to hyperbaric oxygen treatment strongly implies decompression sickness in this case.

  11. Juno/JEDI observations of 0.01 to >10 MeV energetic ions in the Jovian auroral regions: Anticipating a source for polar X-ray emission

    Science.gov (United States)

    Haggerty, D. K.; Mauk, B. H.; Paranicas, C. P.; Clark, G.; Kollmann, P.; Rymer, A. M.; Bolton, S. J.; Connerney, J. E. P.; Levin, S. M.

    2017-07-01

    After a successful orbit insertion, the Juno spacecraft completed its first 53.5 day orbit and entered a very low altitude perijove with the full scientific payload operational for the first time on 27 August 2016. The Jupiter Energetic particle Detector Instrument measured ions and electrons over the auroral regions and through closest approach, with ions measured from 0.01 to >10 MeV, depending on species. This report focuses on the composition of the energetic ions observed during the first perijove of the Juno mission. Of particular interest are the ions that precipitate from the magnetosphere onto the polar atmosphere and ions that are accelerated locally by Jupiter's powerful auroral processes. We report preliminary findings on the spatial variations, species, including energy and pitch angle distributions throughout the prime science region during the first orbit of the Juno mission. The prime motivation for this work was to examine the heavy ions that are thought to be responsible for the observed polar X-rays. Jupiter Energetic particle Detector Instrument (JEDI) did observe precipitating heavy ions with energies >10 MeV, but for this perijove the intensities were far below those needed to account for previously observed polar X-ray emissions. During this survey we also found an unusual signal of ions between oxygen and sulfur. We include here a report on what appears to be a transitory observation of magnesium, or possibly sodium, at MeV energies through closest approach.

  12. Long-period polar rain variations, solar wind and hemispherically symmetric polar rain

    International Nuclear Information System (INIS)

    Makita, K.; Meng, C.

    1987-01-01

    On the basic of electron data obtained by the Defense Meteorological Satellite Program (DMSP) F2 satellite the long-period variations of the polar rain flux are examined for four consecutive solar rotations. It is clearly demonstrated that the asymmetric enhancement of the polar rain flux is strongly controlled by the sector structure of the interplanetary magnetic field (IMF). However, the orbit-to-orbit and day-to-day variations of the polar rain flux are detected even during a very stable sector period, and the polar rain flux does not have any clear relationship to the magnitude of the IMF B/sub x/ or B/sub y/. Thus the polarity of B/sub x/ controls only the accessibility of a polar region. It is also noticed that the intensity of polar rain fluxes does not show any relationship to the density of the solar wind, suggesting that the origin of the polar rain electrons is different from the commonly observed part of the solar wind electron distribution function. In addition to the asymmetric polar rain distribution, increasing polar rain fluxes of similar high intensity are sometimes detected over both polar caps. An examination of more than 1 year's data from the DMSP F2 and F4 satellites shows that simultaneous intense uniform precipitations (>10 7 electrons/cm 2 s sr) over both polar caps are not coincidental; it also shows that the spectra are similar. The occurrence of hemispherically symmetric events is not common. They generally are observed after an IMF sector transition period, during unstable periods in the sector structure, and while the solar wind density is high. copyright American Geophysical Union 1987

  13. Source of spin polarized electrons

    International Nuclear Information System (INIS)

    Pierce, D.T.; Meier, F.A.; Siegmann, H.C.

    1976-01-01

    A method is described of producing intense beams of polarized free electrons in which a semiconductor with a spin orbit split valence band and negative electron affinity is used as a photocathode and irradiated with circularly polarized light

  14. Bulk electron spin polarization generated by the spin Hall current

    OpenAIRE

    Korenev, V. L.

    2005-01-01

    It is shown that the spin Hall current generates a non-equilibrium spin polarization in the interior of crystals with reduced symmetry in a way that is drastically different from the previously well-known equilibrium polarization during the spin relaxation process. The steady state spin polarization value does not depend on the strength of spin-orbit interaction offering possibility to generate relatively high spin polarization even in the case of weak spin-orbit coupling.

  15. Bulk electron spin polarization generated by the spin Hall current

    Science.gov (United States)

    Korenev, V. L.

    2006-07-01

    It is shown that the spin Hall current generates a nonequilibrium spin polarization in the interior of crystals with reduced symmetry in a way that is drastically different from the previously well-known “equilibrium” polarization during the spin relaxation process. The steady state spin polarization value does not depend on the strength of spin-orbit interaction offering possibility to generate relatively high spin polarization even in the case of weak spin-orbit coupling.

  16. Mapping magnetized geologic structures from space: The effect of orbital and body parameters

    Science.gov (United States)

    Schnetzler, C. C.; Taylor, P. T.; Langel, R. A.

    1984-01-01

    When comparing previous satellite magnetometer missions (such as MAGSAT) with proposed new programs (for example, Geopotential Research Mission, GRM) it is important to quantify the difference in scientific information obtained. The ability to resolve separate magnetic blocks (simulating geological units) is used as a parameter for evaluating the expected geologic information from each mission. The effect of satellite orbital altitude on the ability to resolve two magnetic blocks with varying separations is evaluated and quantified. A systematic, nonlinear, relationship exists between resolution and distance between magnetic blocks as a function of orbital altitude. The proposed GRM would provide an order-of-magnitude greater anomaly resolution than the earlier MAGSAT mission for widely separated bodies. The resolution achieved at any particular altitude varies depending on the location of the bodies and orientation.

  17. Polarization effects in hadron fragmentation

    International Nuclear Information System (INIS)

    Lednicky, R.

    1984-01-01

    Hadron polarization (spin alignment) and polarization asymmetry are discussed in terms of the quark recombination model with the spin-orbit interaction taken into account. It is shown that predictions of this model are at least in qualitative agreement with experimental data. Various polarization mechanisms in terms of this model and the possibility of their checking are also discussed

  18. Peripheral orbit model

    CERN Document Server

    Hara, Yasuo

    1975-01-01

    Peripheral orbit model, in which an incoming hadron is assumed to revolve in a peripheral orbit around a target hadron, is discussed. The non-diffractive parts of two-body reaction amplitudes of hadrons are expressed in terms of the radius, width an absorptivity of the orbit. The radius of the orbit is about 1 fm and the width of the orbit is determined by the range of the interaction between the hadrons. The model reproduces all available experimental data on differential cross-sections and polarizations of $K^{-}p\\to K^{-}p$ and $\\bar K^{\\circ}n$ reactions for all angles successfully. This contribution is not included in the proceedings since it will appear in Progress of Theoretical Physics Vol. 51 (1974) No 2. Any person interested in the subject may apply for reprints to the author.

  19. Solar Array Disturbances to Spacecraft Pointing During the Lunar Reconnaissance Orbiter (LRO) Mission

    Science.gov (United States)

    Calhoun, Philip

    2010-01-01

    The Lunar Reconnaissance Orbiter (LRO), the first spacecraft to support NASA s return to the Moon, launched on June 18, 2009 from the Cape Canaveral Air Force Station aboard an Atlas V launch vehicle. It was initially inserted into a direct trans-lunar trajectory to the Moon. After a five day transit to the Moon, LRO was inserted into the Lunar orbit and successfully lowered to a low altitude elliptical polar orbit for spacecraft commissioning. Successful commissioning was completed in October 2009 when LRO was placed in its near circular mission orbit with an approximate altitude of 50km. LRO will spend at least one year orbiting the Moon, collecting lunar environment science and mapping data, utilizing a suite of seven instruments to enable future human exploration. The objective is to provide key science data necessary to facilitate human return to the Moon as well as identification of opportunities for future science missions. LRO's instrument suite will provide the high resolution imaging data with sub-meter accuracy, highly accurate lunar cartographic maps, mineralogy mapping, amongst other science data of interest. LRO employs a 3-axis stabilized attitude control system (ACS) whose primary control mode, the "Observing Mode", provides Lunar nadir, off-nadir, and inertial fine pointing for the science data collection and instrument calibration. This controller combines the capability of fine pointing with on-demand large angle full-sky attitude reorientation. It provides simplicity of spacecraft operation as well as additional flexibility for science data collection. A conventional suite of ACS components is employed in the Observing Mode to meet the pointing and control objectives. Actuation is provided by a set of four reaction wheels developed in-house at NASA Goddard Space Flight Center (GSFC). Attitude feedback is provided by a six state Kalman filter which utilizes two SELEX Galileo Star Trackers for attitude updates, and a single Honeywell Miniature

  20. First ever in situ observations of Venus' polar upper atmosphere density using the tracking data of the Venus Express Atmospheric Drag Experiment (VExADE)

    Science.gov (United States)

    Rosenblatt, P.; Bruinsma, S. L.; Müller-Wodarg, I. C. F.; Häusler, B.; Svedhem, H.; Marty, J. C.

    2012-02-01

    On its highly elliptical 24 h orbit around Venus, the Venus Express (VEX) spacecraft briefly reaches a periapsis altitude of nominally 250 km. Recently, however, dedicated and intense radio tracking campaigns have taken place in August 2008, October 2009, February and April 2010, for which the periapsis altitude was lowered to the 186-176 km altitude range in order to be able to probe the upper atmosphere of Venus above the North Pole for the first time ever in situ. As the spacecraft experiences atmospheric drag, its trajectory is measurably perturbed during the periapsis pass, allowing us to infer total atmospheric mass density at the periapsis altitude. A Precise Orbit Determination (POD) of the VEX motion is performed through an iterative least-squares fitting process to the Doppler tracking data, acquired by the VEX radioscience experiment (VeRa). The drag acceleration is modelled using an initial atmospheric density model (VTS3 model, Hedin, A.E., Niemann, H.B., Kasprzak, W.T., Seiff, A. [1983]. J. Geophys. Res. 88, 73-83). A scale factor of the drag acceleration is estimated for each periapsis pass, which scales Hedin's density model in order to best fit the radio tracking data. Reliable density scale factors have been obtained for 10 passes mainly from the second (October 2009) and third (April 2010) VExADE campaigns, which indicate a lower density by a factor of about 1.8 than Hedin's model predicts. These first ever in situ polar density measurements at solar minimum have allowed us to construct a diffusive equilibrium density model for Venus' thermosphere, constrained in the lower thermosphere primarily by SPICAV-SOIR measurements and above 175 km by the VExADE drag measurements (Müller-Wodarg et al., in preparation). The preliminary results of the VExADE campaigns show that it is possible to obtain with the POD technique reliable estimates of Venus' upper atmosphere densities at an altitude of around 175 km. Future VExADE campaigns will benefit from

  1. Satellite orbits in Levi-Civita space

    Science.gov (United States)

    Humi, Mayer

    2018-03-01

    In this paper we consider satellite orbits in central force field with quadratic drag using two formalisms. The first using polar coordinates in which the satellite angular momentum plays a dominant role. The second is in Levi-Civita coordinates in which the energy plays a central role. We then merge these two formalisms by introducing polar coordinates in Levi-Civita space and derive a new equation for satellite orbits which unifies these two paradigms. In this equation energy and angular momentum appear on equal footing and thus characterize the orbit by its two invariants. Using this formalism we show that equatorial orbits around oblate spheroids can be expressed analytically in terms of Elliptic functions. In the second part of the paper we derive in Levi-Civita coordinates a linearized equation for the relative motion of two spacecrafts whose trajectories are in the same plane. We carry out also a numerical verification of these equations.

  2. Linear Magnetoelectric Effect by Orbital Magnetism

    NARCIS (Netherlands)

    Scaramucci, A.; Bousquet, E.; Fechner, M.; Mostovoy, M.; Spaldin, N. A.

    2012-01-01

    We use symmetry analysis and first-principles calculations to show that the linear magnetoelectric effect can originate from the response of orbital magnetic moments to the polar distortions induced by an applied electric field. Using LiFePO4 as a model compound we show that spin-orbit coupling

  3. Explicit polarization (X-Pol) potential using ab initio molecular orbital theory and density functional theory.

    Science.gov (United States)

    Song, Lingchun; Han, Jaebeom; Lin, Yen-lin; Xie, Wangshen; Gao, Jiali

    2009-10-29

    The explicit polarization (X-Pol) method has been examined using ab initio molecular orbital theory and density functional theory. The X-Pol potential was designed to provide a novel theoretical framework for developing next-generation force fields for biomolecular simulations. Importantly, the X-Pol potential is a general method, which can be employed with any level of electronic structure theory. The present study illustrates the implementation of the X-Pol method using ab initio Hartree-Fock theory and hybrid density functional theory. The computational results are illustrated by considering a set of bimolecular complexes of small organic molecules and ions with water. The computed interaction energies and hydrogen bond geometries are in good accord with CCSD(T) calculations and B3LYP/aug-cc-pVDZ optimizations.

  4. The status of polarization studies at HERA

    International Nuclear Information System (INIS)

    Boege, M.

    1993-01-01

    In August 1992 a vertical electron beam polarization of nearly 60% at 26.7 GeV (spin tune=60.5) was obtained at HERA. This was achieved by optimizing the energy and orbit tunes and by applying harmonic corrections to the closed orbit. The polarization level was reproducible from fill to fill and the calibration of the Compton polarimeter was confirmed by measuring the polarization build up curve. The polarization measurements were made with currents of one to two milliamps. Much higher currents are expected for the 1993 luminosity run (∼ 30 mA were obtained in May 1993). The high polarization level was reproduced at high current. Further polarization studies in parallel with e-p operation are planned. In 1993/94 a pair of spin rotators will be installed in the East straight section so that longitudinal polarization is available at the East interaction point. Simulations with the spin tracking program SITROS are in qualitative agreement with the measurements. Calculations with SITROS show that longitudinal polarizations of up to 50% could then still be achieved

  5. Globally Polarized Quark-gluon Plasma in Non-central A+ACollisions

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Zuo-tang; Wang, Xin-Nian

    2004-10-01

    Produced partons have large local relative orbital angular momentum along the direction opposite to the reaction plane in the early stage of non-central heavy-ion collisions. Parton scattering is shown to polarize quarks along the same direction due to spin-orbital coupling.Such global quark polarization will lead to many observable consequences,such as left-right asymmetry of hadron spectra, global transverse polarization of thermal photons, dileptons and hadrons. Hadrons from the decay of polarized resonances will have azimuthal asymmetry similar to the elliptic flow. Global hyperon polarization is predicted with indifferent hadronization scenarios and can be easily tested.

  6. Polarized proton beam for eRHIC

    Energy Technology Data Exchange (ETDEWEB)

    Huang, H. [Brookhaven National Lab. (BNL), Upton, NY (United States); Meot, F. [Brookhaven National Lab. (BNL), Upton, NY (United States); Ptitsyn, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Roser, T. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-05-03

    RHIC has provided polarized proton collisions from 31 GeV to 255 GeV in the past decade. To preserve polarization through numerous depolarizing resonances through the whole accelerator chain, harmonic orbit correction, partial snakes, horizontal tune jump system and full snakes have been used. In addition, close attentions have been paid to betatron tune control, orbit control and beam line alignment. The polarization of 60% at 255 GeV has been delivered to experiments with 1.8×1011 bunch intensity. For the eRHIC era, the beam brightness has to be maintained to reach the desired luminosity. Since we only have one hadron ring in the eRHIC era, existing spin rotator and snakes can be converted to six snake configuration for one hadron ring. With properly arranged six snakes, the polarization can be maintained at 70% at 250 GeV. This paper summarizes the effort and plan to reach high polarization with small emittance for eRHIC.

  7. Spin-polarization and spin-flip in a triple-quantum-dot ring by using tunable lateral bias voltage and Rashba spin-orbit interaction

    Energy Technology Data Exchange (ETDEWEB)

    Molavi, Mohamad, E-mail: Mo_molavi@yahoo.com [Faculty of Physics, Kharazmi University, Tehran (Iran, Islamic Republic of); Faizabadi, Edris, E-mail: Edris@iust.ac.ir [School of Physics, Iran University of Science and Technology, 16846 Tehran (Iran, Islamic Republic of)

    2017-04-15

    By using the Green's function formalism, we investigate the effects of single particle energy levels of a quantum dot on the spin-dependent transmission properties through a triple-quantum-dot ring structure. In this structure, one of the quantum dots has been regarded to be non-magnetic and the Rashba spin-orbit interaction is imposed locally on this dot while the two others can be magnetic. The on-site energy of dots, manipulates the interference of the electron spinors that are transmitted to output leads. Our results show that the effects of magnetic dots on spin-dependent transmission properties are the same as the difference of on-site energies of the various dots, which is applicable by a controllable lateral bias voltage externally. Besides, by tuning the parameters such as Rashba spin-orbit interaction, and on-site energy of dots and magnetic flux inside the ring, the structure can be indicated the spin-flip effect and behave as a full spin polarizer or splitter. - Highlights: • The effects of magnetic dots on spin-dependent transmission properties are the same as the difference of on-site energies of the various dots. • In the situation that the QDs have non-zero on-site energies, the system can demonstrate the full spin-polarization. • By tuning the Rashba spin-orbit strength and magnetic flux encountered by the ring the system operates as a Stern-Gerlach apparatus.

  8. Platelet injectors for Space Shuttle orbit maneuvering engine

    Science.gov (United States)

    Kahl, R. C.; Labotz, R. J.; Bassham, L. B.

    1974-01-01

    The Space Shuttle Orbit Maneuvering Subsystem Rocket Engine employs a platelet element injector concept. This injector has demonstrated 316-sec vacuum specific impulse performance under simulated altitude conditions when tested with a milled slot/electroformed nickel close-out regenerative chamber and a full 71 area ratio nozzle. To date, over 300 altitude engine tests and 300 stability bomb tests have demonstrated stable, erosion free operation with this concept to test durations of 150 seconds. The injector and chamber also meet the reusable requirements of the shuttle with a cycle life capability in excess of 1000 cycles. An extensive altitude restart program has also demonstrated OMS-engine operation over large variations in the burn and coast times with helium saturated propellants.

  9. Eddy intrusion of hot plasma into the polar cap and formation of polar-cap arcs

    International Nuclear Information System (INIS)

    Chiu, Y.T.; Gorney, D.J.

    1983-01-01

    We present plasma and electric field data obtained by the S3-3 satellite over the polar caps. We demonstrate that: (1) plasma signatures in the polar cap arc formation region near 5000 km altitude show clear intrusions of plasma sheet (approx.keV) and magneto sheath (approx.100 eV) plasma into a background of low-energy polar cap plasma; (2) the combined plasma and electric field signatures (electron inverted-V, ion beam and delxE<0) are exactly the same as in the evening discrete arc. We interpret this equivalence of polar cap and evening discrete arc signatures as indication that their formation processes are identical. The spatial structures of polar cap electric fields and the associated plasma signatures are consistent with the hypothesis that plasma intrusion into the polar cap takes the form of multiple cellular eddies. This hypothesis provides a unifying view of arc formation and arc configurations

  10. Electromagnetic Ion Cyclotron Waves in the High Altitude Cusp: Polar Observations

    Science.gov (United States)

    Le, Guan; Blanco-Cano, X.; Russell, C. T.; Zhou, X.-W.; Mozer, F.; Trattner, K. J.; Fuselier, S. A.; Anderson, B. J.; Vondrak, Richard R. (Technical Monitor)

    2001-01-01

    High-resolution magnetic field data from the Polar Magnetic Field Experiment (MFE) show that narrow band waves at frequencies approximately 0.2 to 3 Hz are a permanent feature in the vicinity of the polar cusp. The waves have been found in the magnetosphere adjacent to the cusp (both poleward and equatorward of the cusp) and in the cusp itself. The occurrence of waves is coincident with depression of magnetic field strength associated with enhanced plasma density, indicating the entry of magnetosheath plasma into the cusp region. The wave frequencies are generally scaled by the local proton cyclotron frequency, and vary between 0.2 and 1.7 times local proton cyclotron frequency. This suggests that the waves are generated in the cusp region by the precipitating magnetosheath plasma. The properties of the waves are highly variable. The waves exhibit both lefthanded and right-handed polarization in the spacecraft frame. The propagation angles vary from nearly parallel to nearly perpendicular to the magnetic field. We find no correlation among wave frequency, propagation angle and polarization. Combined magnetic field and electric field data for the waves indicate that the energy flux of the waves is guided by the background magnetic field and points downward toward the ionosphere.

  11. Electromagnetic Ion Cyclotron Waves in the High-Altitude Cusp: Polar Observations

    Science.gov (United States)

    Le, G.; Blanco-Cano, X.; Russell, C. T.; Zhou, X.-W.; Mozer, F.; Trattner, K. J.; Fuselier, S. A.; Anderson, B. J.

    2005-01-01

    High-resolution magnetic field data from the Polar Magnetic Field Experiment (MFE) show that narrow-band waves at frequencies approx. 0.2-3 Hz are a permanent feature in the vicinity of the polar cusp. The waves have been found in the magnetosphere adjacent to the cusp (both poleward and equatorward of the cusp) and in the cusp itself. The occurrence of waves is coincident with depression of magnetic field strength associated with enhanced plasma density, indicating the entry of magnetosheath plasma into the cusp region. The wave frequencies are generally scaled by the local proton cyclotron frequency and vary between 0.2 and 1.7 times local proton cyclotron frequency. This suggests that the waves are generated in the cusp region by the precipitating magnetosheath plasma. The properties of the waves are highly variable. The waves exhibit both left-handed and right-handed polarization in the spacecraft frame. The propagation angles vary from nearly parallel to nearly perpendicular to the magnetic field. We find no correlation among wave frequency, propagation angle, and polarization. Combined magnetic field and electric field data for the waves indicate that the energy flux of the waves is guided by the background magnetic field and points downward toward the ionosphere.

  12. Early Assessment of VIIRS On-Orbit Calibration and Support Activities

    Science.gov (United States)

    Xiong, Xiaoxiong; Chiang, Kwofu; McIntire, Jeffrey; Oudrari, Hassan; Wu, Aisheng; Schwaller, Mathew; Butler, James

    2012-01-01

    The Suomi National Polar-orbiting Partnership (S-NPP) satellite, formally the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP), provides a bridge between current and future low-Earth orbiting weather and environmental observation satellite systems. The NASA s NPP VIIRS Characterization Support Team (VCST) is designed to assess the long term geometric and radiometric performance of the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument onboard the S-NPP spacecraft and to support NPP Science Team Principal Investigators (PI) for their independent evaluation of VIIRS Environmental Data Records (EDRs). This paper provides an overview of Suomi NPP VIIRS on-orbit calibration activities and examples of sensor initial on-orbit performance. It focuses on the radiometric calibration support activities and capabilities provided by the NASA VCST.

  13. Characteristics of high altitude oxygen ion energization and outflow as observed by Cluster: a statistical study

    Directory of Open Access Journals (Sweden)

    H. Nilsson

    2006-05-01

    Full Text Available The results of a statistical study of oxygen ion outflow using Cluster data obtained at high altitude above the polar cap is reported. Moment data for both hydrogen ions (H+ and oxygen ions (O+ from 3 years (2001-2003 of spring orbits (January to May have been used. The altitudes covered were mainly in the range 5–12 RE geocentric distance. It was found that O+ is significantly transversely energized at high altitudes, indicated both by high perpendicular temperatures for low magnetic field values as well as by a tendency towards higher perpendicular than parallel temperature distributions for the highest observed temperatures. The O+ parallel bulk velocity increases with altitude in particular for the lowest observed altitude intervals. O+ parallel bulk velocities in excess of 60 km s-1 were found mainly at higher altitudes corresponding to magnetic field strengths of less than 100 nT. For the highest observed parallel bulk velocities of O+ the thermal velocity exceeds the bulk velocity, indicating that the beam-like character of the distribution is lost. The parallel bulk velocity of the H+ and O+ was found to typically be close to the same throughout the observation interval when the H+ bulk velocity was calculated for all pitch-angles. When the H+ bulk velocity was calculated for upward moving particles only the H+ parallel bulk velocity was typically higher than that of O+. The parallel bulk velocity is close to the same for a wide range of relative abundance of the two ion species, including when the O+ ions dominates. The thermal velocity of O+ was always well below that of H+. Thus perpendicular energization that is more effective for O+ takes place, but this is not enough to explain the close to similar parallel velocities. Further

  14. Spin Polarization Oscillations without Spin Precession: Spin-Orbit Entangled Resonances in Quasi-One-Dimensional Spin Transport

    Directory of Open Access Journals (Sweden)

    D. H. Berman

    2014-03-01

    Full Text Available Resonant behavior involving spin-orbit entangled states occurs for spin transport along a narrow channel defined in a two-dimensional electron gas, including an apparent rapid relaxation of the spin polarization for special values of the channel width and applied magnetic field (so-called ballistic spin resonance. A fully quantum-mechanical theory for transport using multiple subbands of the one-dimensional system provides the dependence of the spin density on the applied magnetic field and channel width and position along the channel. We show how the spatially nonoscillating part of the spin density vanishes when the Zeeman energy matches the subband energy splittings. The resonance phenomenon persists in the presence of disorder.

  15. Spin polarization, orbital occupation and band gap opening in vanadium dioxide: The effect of screened Hartree-Fock exchange

    KAUST Repository

    Wang, Hao

    2014-07-01

    The metal-insulator transition of VO2 so far has evaded an accurate description by density functional theory. The screened hybrid functional of Heyd, Scuseria and Ernzerhof leads to reasonable solutions for both the low-temperature monoclinic and high-temperature rutile phases only if spin polarization is excluded from the calculations. We explore whether a satisfactory agreement with experiment can be achieved by tuning the fraction of Hartree Fock exchange (α) in the density functional. It is found that two branches of locally stable solutions exist for the rutile phase for 12.5%≤α≤20%. One is metallic and has the correct stability as compared to the monoclinic phase, the other is insulating with lower energy than the metallic branch. We discuss these observations based on the V 3d orbital occupations and conclude that α=10% is the best possible choice for spin-polarized VO2 calculations. © 2014 Elsevier B.V. All rights reserved.

  16. Quantifying the importance of orbital over spin correlations in delta-Pu within density-functional theory

    International Nuclear Information System (INIS)

    Soderlind, P

    2008-01-01

    The electronic structure of plutonium is studied within the density-functional theory (DFT) model. Key features of the electronic structure are correctly modeled and bonding, total energy, and electron density of states are all consistent with measure data, although the prediction of magnetism is not consistent with many observations. Here we analyze the contributions to the electronic structure arising from spin polarization, orbital polarization, and spin-orbit interaction. These effects give rise to spin and orbital moments that are of nearly equal magnitude, but anti-parallel, suggesting a magnetic-moment cancellation with a zero total moment. Quantifying the spin versus orbital effects on the bonding, total energy, and electron spectra it becomes clear that the spin polarization is much less important than the orbital correlations. Consequently, a restricted DFT approach with a non-spin polarized electronic structure can produce reasonable equation-of-state and electron spectra for (delta)-Pu when the orbital effects are accounted for. Hence, we present two non-magnetic models. One in which the spin moment is canceled by the orbital moment and another in which the spin moment (and therefore the orbital moment) is restricted to zero

  17. Auroral and magnetic variations in the polar cusp and cleft. Signatures of magnetopause boundary layer dynamics

    International Nuclear Information System (INIS)

    Sandholt, P.E.; Egeland, A.

    1987-10-01

    By combining continous ground-based observations of polar cleft/cusp auroras and local magnetic variations with electromagnetic parameters obtained from satellites in polar orbit (low-altitude cleft/cusp) and in the magnetosheath/interplanetary space, different electrodynamic processes in the polar cleft/cusp have been investigated. One of the more controversial questions in this field is related to the observed shifts in latitude of cleft/cusp auroras and the relationships with the interplanetary magnetic field (IMF) orientation, local magnetic disturbances (DP2 and DPY modes) and magnetospheric substorms. A new approach which may contribute to clarifying these complicated relationships, simultaneous groundbased observations of the midday and evening-midnight sectors of the auroral oval, is illustrated. A related topic is the spatial relationship between the cleft/cusp auroras and the ionospheric convection currents. A characteristic feature of the polar cusp and cleft regions during negative IMF B z is repeated occurrence of certain short-lived auroral structures moving in accordance with the local convection pattern. Satellite measurements of particle precipitation, magnetic field and ion drift components permit detailed investigations of the electrodynamics of these cusp/cleft structures. Information on electric field components, Birkeland currents, Poynting flux, height-integrated Pedersen conductivity and Joule heat dissipation rate has been derived. These observations are discussed in relation to existing models of temporal plasma injections from the magnetosheath

  18. Cygnus X-1: Discovery of variable circular polarization

    International Nuclear Information System (INIS)

    Michalsky, J.J.; Swedlund, J.B.; Stokes, R.A.

    1975-01-01

    HDE 226868, the optical counterpart of Cyg X-1, has been observed for circular polarization during 1974. Observations in five colors suggest that circular polarization results from an interstellar effect. Measurements of the blue polarization reveal circular polarization variations synchronous with the 5)./sub /6 orbital period. The circular polarization variation appears to be similar to the blue intensity variation

  19. Sunlight effects on the 3D polar current system determined from low Earth orbit measurements

    DEFF Research Database (Denmark)

    Laundal, Karl M.; Finlay, Chris; Olsen, Nils

    2016-01-01

    Interaction between the solar wind and the Earth’s magnetosphere is associated with large-scale currents in the ionosphere at polar latitudes that flow along magnetic field lines (Birkeland currents) and horizontally. These current systems are tightly linked, but their global behaviors are rarely...... analyzed together. In this paper, we present estimates of the average global Birkeland currents and horizontal ionospheric currents from the same set of magnetic field measurements. The magnetic field measurements, from the low Earth orbiting Swarm and CHAMP satellites, are used to co-estimate poloidal...... and toroidal parts of the magnetic disturbance field, represented in magnetic apex coordinates. The use of apex coordinates reduces effects of longitudinal and hemispheric variations in the Earth’s main field. We present global currents from both hemispheres during different sunlight conditions. The results...

  20. Spin-Orbit Coupling for Photons and Polaritons in Microstructures

    Directory of Open Access Journals (Sweden)

    V. G. Sala

    2015-03-01

    Full Text Available We use coupled micropillars etched out of a semiconductor microcavity to engineer a spin-orbit Hamiltonian for photons and polaritons in a microstructure. The coupling between the spin and orbital momentum arises from the polarization-dependent confinement and tunneling of photons between adjacent micropillars arranged in the form of a hexagonal photonic molecule. It results in polariton eigenstates with distinct polarization patterns, which are revealed in photoluminescence experiments in the regime of polariton condensation. Thanks to the strong polariton nonlinearities, our system provides a photonic workbench for the quantum simulation of the interplay between interactions and spin-orbit effects, particularly when extended to two-dimensional lattices.

  1. Catalystlike effect of orbital angular momentum on the conversion of transverse to three-dimensional spin states within tightly focused radially polarized beams

    Science.gov (United States)

    Han, Lei; Liu, Sheng; Li, Peng; Zhang, Yi; Cheng, Huachao; Zhao, Jianlin

    2018-05-01

    We report on the catalystlike effect of orbital angular momentum (OAM) on local spin-state conversion within the tightly focused radially polarized beams associated with optical spin-orbit interaction. It is theoretically demonstrated that the incident OAM can lead to a conversion of purely transverse spin state to a three-dimensional spin state on the focal plane. This conversion can be conveniently manipulated by altering the sign and value of the OAM. By comparing the total OAM and spin angular momentum (SAM) on the incident plane to those on the focal plane, it is indicated that the incident OAM have no participation in the angular momentum intertransfer, and just play a role as a catalyst of local SAM conversion. Such an effect of OAM sheds new light on the optical spin-orbit interaction in tight-focusing processes. The resultant three-dimensional spin states may provide more degrees of freedom in optical manipulation and spin-dependent directive coupling.

  2. Solar Cell Short Circuit Current Errors and Uncertainties During High Altitude Calibrations

    Science.gov (United States)

    Snyder, David D.

    2012-01-01

    High altitude balloon based facilities can make solar cell calibration measurements above 99.5% of the atmosphere to use for adjusting laboratory solar simulators. While close to on-orbit illumination, the small attenuation to the spectra may result in under measurements of solar cell parameters. Variations of stratospheric weather, may produce flight-to-flight measurement variations. To support the NSCAP effort, this work quantifies some of the effects on solar cell short circuit current (Isc) measurements on triple junction sub-cells. This work looks at several types of high altitude methods, direct high altitude meas urements near 120 kft, and lower stratospheric Langley plots from aircraft. It also looks at Langley extrapolation from altitudes above most of the ozone, for potential small balloon payloads. A convolution of the sub-cell spectral response with the standard solar spectrum modified by several absorption processes is used to determine the relative change from AMO, lscllsc(AMO). Rayleigh scattering, molecular scatterin g from uniformly mixed gases, Ozone, and water vapor, are included in this analysis. A range of atmosph eric pressures are examined, from 0. 05 to 0.25 Atm to cover the range of atmospheric altitudes where solar cell calibrations a reperformed. Generally these errors and uncertainties are less than 0.2%

  3. [Physiological aspects of altitude training and the use of altitude simulators].

    Science.gov (United States)

    Ranković, Goran; Radovanović, Dragan

    2005-01-01

    Altitude training in various forms is widely practiced by athletes and coaches in an attempt to improve sea level endurance. Training at high altitude may improve performance at sea level through altitude acclimatisation, which improves oxygen transport and/or utilisation, or through hypoxia, which intensifies the training stimulus. This basic physiological aspect allows three training modalities: live high and train high (classic high-altitude training), live low and train high (training through hypoxia), and live high and train low (the new trend). In an effort to reduce the financial and logistical challenges of travelling to high-altitude training sites, scientists and manufactures have developed artificial high-altitude environments, which simulate the hypoxic conditions of moderate altitude (2000-3000 meters). Endurance athletes from many sports have recently started using nitrogen environments, or hypoxic rooms and tents as part of their altitude training programmes. The results of controlled studies on these modalities of high-altitude training, their practical approach, and ethics are summarised.

  4. Physiological aspects of altitude training and the use of altitude simulators

    Directory of Open Access Journals (Sweden)

    Ranković Goran

    2005-01-01

    Full Text Available Altitude training in various forms is widely practiced by athletes and coaches in an attempt to improve sea level endurance. Training at high altitude may improve performance at sea level through altitude acclimatization, which improves oxygen transport and/or utilization, or through hypoxia, which intensifies the training stimulus. This basic physiological aspect allows three training modalities: live high and train high (classic high-altitude training, live low and train high (training through hypoxia, and live high and train low (the new trend. In an effort to reduce the financial and logistical challenges of traveling to high-altitude training sites, scientists and manufactures have developed artificial high-altitude environments, which simulate the hypoxic conditions of moderate altitude (2000-3000 meters. Endurance athletes from many sports have recently started using nitrogen environments, or hypoxic rooms and tents as part of their altitude training programmes. The results of controlled studies on these modalities of high-altitude training, their practical approach, and ethics are summarized.

  5. Magnus Effect on a Spinning Satellite in Low Earth Orbit

    Science.gov (United States)

    Ramjatan, Sahadeo; Fitz-Coy, Norman; Yew, Alvin Garwai

    2016-01-01

    A spinning body in a flow field generates an aerodynamic lift or Magnus effect that displaces the body in a direction normal to the freestream flow. Earth orbiting satellites with substantial body rotation in appreciable atmospheric densities may generate a Magnus force to perturb orbital dynamics. We investigate the feasibility of using this effect for spacecraft at a perigee of 80km using the Systems Tool Kit (STK). Results show that for a satellite of reasonable properties, the Magnus effect doubles the amount of time in orbit. Orbital decay was greatly mitigated for satellites spinning at 10000 and 15000RPM. This study demonstrates that the Magnus effect has the potential to sustain a spacecraft's orbit at a low perigee altitude and could also serve as an orbital maneuver capability.

  6. Lidar Orbital Angular Momentum Sensor

    Data.gov (United States)

    National Aeronautics and Space Administration — The recognition in recent decades that electromagnetic fields have angular momentum (AM) in the form of not only polarization (or spin AM) but also orbital (OAM) has...

  7. Ellipsometry with randomly varying polarization states

    NARCIS (Netherlands)

    Liu, F.; Lee, C. J.; Chen, J. Q.; E. Louis,; van der Slot, P. J. M.; Boller, K. J.; F. Bijkerk,

    2012-01-01

    We show that, under the right conditions, one can make highly accurate polarization-based measurements without knowing the absolute polarization state of the probing light field. It is shown that light, passed through a randomly varying birefringent material has a well-defined orbit on the Poincar

  8. Constellations of Next Generation Gravity Missions: Simulations regarding optimal orbits and mitigation of aliasing errors

    Science.gov (United States)

    Hauk, M.; Pail, R.; Gruber, T.; Purkhauser, A.

    2017-12-01

    The CHAMP and GRACE missions have demonstrated the tremendous potential for observing mass changes in the Earth system from space. In order to fulfil future user needs a monitoring of mass distribution and mass transport with higher spatial and temporal resolution is required. This can be achieved by a Bender-type Next Generation Gravity Mission (NGGM) consisting of a constellation of satellite pairs flying in (near-)polar and inclined orbits, respectively. For these satellite pairs the observation concept of the GRACE Follow-on mission with a laser-based low-low satellite-to-satellite tracking (ll-SST) system and more precise accelerometers and state-of-the-art star trackers is adopted. By choosing optimal orbit constellations for these satellite pairs high frequency mass variations will be observable and temporal aliasing errors from under-sampling will not be the limiting factor anymore. As part of the European Space Agency (ESA) study "ADDCON" (ADDitional CONstellation and Scientific Analysis Studies of the Next Generation Gravity Mission) a variety of mission design parameters for such constellations are investigated by full numerical simulations. These simulations aim at investigating the impact of several orbit design choices and at the mitigation of aliasing errors in the gravity field retrieval by co-parametrization for various constellations of Bender-type NGGMs. Choices for orbit design parameters such as altitude profiles during mission lifetime, length of retrieval period, value of sub-cycles and choice of prograde versus retrograde orbits are investigated as well. Results of these simulations are presented and optimal constellations for NGGM's are identified. Finally, a short outlook towards new geophysical applications like a near real time service for hydrology is given.

  9. SEE in-flight measurement on the MIR orbital station

    International Nuclear Information System (INIS)

    Falguere, D.; Duzellier, S.; Ecoffet, R.

    1994-01-01

    SEE spaceflight measurements are presented on HM65756 SRAM from Matra-MHS, Seeq 28C256 and Motorola MC68020 microprocessor (bulk version) in the MIR station orbit (350 km altitude, 51.6 degree inclination). Accelerator testing (heavy ion and proton) of flight spares permits the prediction of the event rates using standard model such as CREME and SPACERAD as well as characterizations of the flight components allowing the comparison of in-orbit observations. Event rate prediction and ground-testing data are compared

  10. A statistical study of high-altitude electric fields measured on the Viking satellite

    International Nuclear Information System (INIS)

    Lindqvist, P.A.; Marklund, G.T.

    1990-01-01

    Characteristics of high-altitude data from the Viking electric field instrument are presented in a statistical study based on 109 Viking orbits. The study is focused in particular on the signatures of and relationships between various parameters measured by the electric field instrument, such as the parallel and transverse (to B) components of the electric field instrument, such as electric field variability. A major goal of the Viking mission was to investigate the occurrence and properties of parallel electric fields and their role in the auroral acceleration process. The results in this paper on the altitude distribution of the electric field variability confirm earlier findings on the distribution of small-scale electric fields and indicate the presence of parallel fields up to about 11,000 km altitude. The directly measured parallel electric field is also investigated in some detail. It is in general directed upward with an average value of 1 mV/m, but depends on, for example, altitude and plasma density. Possible sources of error in the measurement of the parallel field are also considered and accounted for

  11. Direct measurement of discrete valley and orbital quantum numbers in bilayer graphene.

    Science.gov (United States)

    Hunt, B M; Li, J I A; Zibrov, A A; Wang, L; Taniguchi, T; Watanabe, K; Hone, J; Dean, C R; Zaletel, M; Ashoori, R C; Young, A F

    2017-10-16

    The high magnetic field electronic structure of bilayer graphene is enhanced by the spin, valley isospin, and an accidental orbital degeneracy, leading to a complex phase diagram of broken symmetry states. Here, we present a technique for measuring the layer-resolved charge density, from which we directly determine the valley and orbital polarization within the zero energy Landau level. Layer polarization evolves in discrete steps across 32 electric field-tuned phase transitions between states of different valley, spin, and orbital order, including previously unobserved orbitally polarized states stabilized by skew interlayer hopping. We fit our data to a model that captures both single-particle and interaction-induced anisotropies, providing a complete picture of this correlated electron system. The resulting roadmap to symmetry breaking paves the way for deterministic engineering of fractional quantum Hall states, while our layer-resolved technique is readily extendable to other two-dimensional materials where layer polarization maps to the valley or spin quantum numbers.The phase diagram of bilayer graphene at high magnetic fields has been an outstanding question, with orders possibly between multiple internal quantum degrees of freedom. Here, Hunt et al. report the measurement of the valley and orbital order, allowing them to directly reconstruct the phase diagram.

  12. Polarization transfer from polarized nuclear spin to μ- spin in muonic atom

    International Nuclear Information System (INIS)

    Kuno, Yoshitaka; Nagamine, Kanetada; Yamazaki, Toshimitsu.

    1987-02-01

    A theoretical study of polarization transfer from an initially-polarized nuclear spin to a μ - spin in a muonic atom is given. The switching of the hyperfine interaction at excited muonic states as well as at the ground 1s state is taken into account. The upper state of hyperfine doublet at the muonic 1s state is considered to proceed down to the lower state. It is found that as the hyperfine interaction becomes effective at higher excited muonic orbitals, a less extent of polarization is transferred from the nuclear spin to the μ - spin. The theoretical values obtained are compared with the recent experiment of μ - repolarization in a polarized 209 Bi target. (author)

  13. Statistics of high-altitude and high-latitude O+ ion outflows observed by Cluster/CIS

    Directory of Open Access Journals (Sweden)

    A. Korth

    2005-07-01

    Full Text Available The persistent outflows of O+ ions observed by the Cluster CIS/CODIF instrument were studied statistically in the high-altitude (from 3 up to 11 RE and high-latitude (from 70 to ~90 deg invariant latitude, ILAT polar region. The principal results are: (1 Outflowing O+ ions with more than 1keV are observed above 10 RE geocentric distance and above 85deg ILAT location; (2 at 6-8 RE geocentric distance, the latitudinal distribution of O+ ion outflow is consistent with velocity filter dispersion from a source equatorward and below the spacecraft (e.g. the cusp/cleft; (3 however, at 8-12 RE geocentric distance the distribution of O+ outflows cannot be explained by velocity filter only. The results suggest that additional energization or acceleration processes for outflowing O+ ions occur at high altitudes and high latitudes in the dayside polar region. Keywords. Magnetospheric physics (Magnetospheric configuration and dynamics, Solar wind-magnetosphere interactions

  14. Sentinel-5: the new generation European operational atmospheric chemistry mission in polar orbit

    Science.gov (United States)

    Pérez Albiñana, Abelardo; Erdmann, Matthias; Wright, Norrie; Martin, Didier; Melf, Markus; Bartsch, Peter; Seefelder, Wolfgang

    2017-08-01

    Sentinel-5 is an Earth Observation instrument to be flown on the Metop Second Generation (Metop-SG) satellites with the fundamental objective of monitoring atmospheric composition from polar orbit. The Sentinel-5 instrument consists of five spectrometers to measure the solar spectral radiance backscattered by the earth atmosphere in five bands within the UV (270nm) to SWIR (2385nm) spectral range. Data provided by Sentinel-5 will allow obtaining the distribution of important atmospheric constituents such as ozone, on a global daily basis and at a finer spatial resolution than its precursor instruments on the first generation of Metop satellites. The launch of the first Metop-SG satellite is foreseen for 2021. The Sentinel-5 instrument is being developed by Airbus DS under contract to the European Space Agency. The Sentinel-5 mission is part of the Space Component of the Copernicus programme, a joint initiative by ESA, EUMETSAT and the European Commission. The Preliminary Design Review (PDR) for the Sentinel-5 development was successfully completed in 2015. This paper provides a description of the Sentinel-5 instrument design and data calibration.

  15. Polarization measurement and vertical aperture optimization for obtaining circularly polarized bend-magnet radiation

    Energy Technology Data Exchange (ETDEWEB)

    Kortright, J.B.; Rice, M.; Hussain, Z. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    Growing interest in utilizing circular polarization prompted the design of bend-magnet beamline 9.3.2 at the Advanced Light Source, covering the 30-1500 eV spectral region, to include vertical aperturing capabilities for optimizing the collection of circular polarization above and below the orbit plane. After commissioning and early use of the beamline, a multilayer polarimeter was used to characterize the polarization state of the beam as a function of vertical aperture position. This report partially summarizes the polarimetry measurements and compares results with theoretical calculations intended to simulate experimental conditions.

  16. The Eccentric Behavior of Nearly Frozen Orbits

    Science.gov (United States)

    Sweetser, Theodore H.; Vincent, Mark A.

    2013-01-01

    Frozen orbits are orbits which have only short-period changes in their mean eccentricity and argument of periapse, so that they basically keep a fixed orientation within their plane of motion. Nearly frozen orbits are those whose eccentricity and argument of periapse have values close to those of a frozen orbit. We call them "nearly" frozen because their eccentricity vector (a vector whose polar coordinates are eccentricity and argument of periapse) will stay within a bounded distance from the frozen orbit eccentricity vector, circulating around it over time. For highly inclined orbits around the Earth, this distance is effectively constant over time. Furthermore, frozen orbit eccentricity values are low enough that these orbits are essentially eccentric (i.e., off center) circles, so that nearly frozen orbits around Earth are bounded above and below by frozen orbits.

  17. HIGH-ALTITUDE ILLNESS

    Directory of Open Access Journals (Sweden)

    Dwitya Elvira

    2015-05-01

    Full Text Available AbstrakHigh-altitude illness (HAI merupakan sekumpulan gejala paru dan otak yang terjadi pada orang yang baru pertama kali mendaki ke ketinggian. HAI terdiri dari acute mountain sickness (AMS, high-altitude cerebral edema (HACE dan high-altitude pulmonary edema (HAPE. Tujuan tinjauan pustaka ini adalah agar dokter dan wisatawan memahami risiko, tanda, gejala, dan pengobatan high-altitude illness. Perhatian banyak diberikan terhadap penyakit ini seiring dengan meningkatnya popularitas olahraga ekstrim (mendaki gunung tinggi, ski dan snowboarding dan adanya kemudahan serta ketersediaan perjalanan sehingga jutaan orang dapat terpapar bahaya HAI. Di Pherice, Nepal (ketinggian 4343 m, 43% pendaki mengalami gejala AMS. Pada studi yang dilakukan pada tempat wisata di resort ski Colorado, Honigman menggambarkan kejadian AMS 22% pada ketinggian 1850 m sampai 2750 m, sementara Dean menunjukkan 42% memiliki gejala pada ketinggian 3000 m. Aklimatisasi merupakan salah satu tindakan pencegahan yang dapat dilakukan sebelum pendakian, selain beberapa pengobatan seperti asetazolamid, dexamethasone, phosopodiestrase inhibitor, dan ginko biloba.Kata kunci: high-altitude illness, acute mountain sickness, edema cerebral, pulmonary edema AbstractHigh-altitude illness (HAI is symptoms of lung and brain that occurs in people who first climb to altitude. HAI includes acute mountain sickness (AMS, high-altitude cerebral edema (HACE and high altitude pulmonary edema (HAPE. The objective of this review was to understand the risks, signs, symptoms, and treatment of high-altitude illness. The attention was given to this disease due to the rising popularity of extreme sports (high mountain climbing, skiing and snowboarding and the ease and availability of the current travelling, almost each year, millions of people could be exposed to the danger of HAI. In Pherice, Nepal (altitude 4343 m, 43% of climbers have symptoms of AMS. Furthermore, in a study conducted at sites in

  18. Three-dimensional thermal structure of the South Polar Vortex of Venus

    Science.gov (United States)

    Hueso, Ricardo; Garate-Lopez, Itziar; Garcia-Muñoz, Antonio; Sánchez-Lavega, Agustín

    2014-11-01

    We have analyzed thermal infrared images provided by the VIRTIS-M instrument aboard Venus Express (VEX) to obtain high resolution thermal maps of the Venus south polar region between 55 and 85 km altitudes. The maps investigate three different dynamical configurations of the polar vortex including its classical dipolar shape, a regularly oval shape and a transition shape between the different configurations of the vortex. We apply the atmospheric model described by García Muñoz et al. (2013) and a variant of the retrieval algorithm detailed in Grassi et al. (2008) to obtain maps of temperature over the Venus south polar region in the quoted altitude range. These maps are discussed in terms of cloud motions and relative vorticity distribution obtained previously (Garate-Lopez et al. 2013). Temperature maps retrieved at 55 - 63 km show the same structures that are observed in the ~5 µm radiance images. This altitude range coincides with the optimal expected values of the cloud top altitude at polar latitudes and magnitudes derived from the analysis of ~5 µm images are measured at this altitude range. We also study the imprint of the vortex on the thermal field above the cloud level which extends up to 80 km. From the temperature maps, we also study the vertical stability of different atmospheric layers. The cold collar is clearly the most statically stable structure at polar latitudes, while the vortex and subpolar latitudes show lower stability values. Furthermore, the hot filaments present within the vortex at 55-63 km exhibit lower values of static stability than their immediate surroundings.ReferencesGarate-Lopez et al. Nat. Geosci. 6, 254-257 (2013).García Muñoz et al. Planet. Space Sci. 81, 65-73 (2013).Grassi, D. et al. J. Geophys. Res. 113, 1-12 (2008).AcknowledgementsWe thank ESA for supporting Venus Express, ASI, CNES and the other national space agencies supporting VIRTIS on VEX and their principal investigators G. Piccioni and P. Drossart. This work

  19. A Dual Polarization, Active, Microstrip Antenna for an Orbital Imaging Radar System Operating at L-Band

    Science.gov (United States)

    Kelly, Kenneth C.; Huang, John

    2000-01-01

    A highly successful Earth orbiting synthetic antenna aperture radar (SAR) system, known as the SIR-C mission, was carried into orbit in 1994 on a U.S. Shuttle (Space Transportation System) mission. The radar system was mounted in the cargo bay with no need to fold, or in any other way reduce the size of the antennas for launch. Weight and size were not limited for the L-Band, C-Band, and X-Band radar systems of the SIR-C radar imaging mission; the set of antennas weighed 10,500 kg, the L-Band antenna having the major share of the weight. This paper treats designing an L-Band antenna functionally similar to that used for SIR-C, but at a fraction of the cost and at a weight in the order of 250 kg. Further, the antenna must be folded to fit into the small payload shroud of low cost booster rocket systems. Over 31 square meters of antenna area is required. This low weight, foldable, electronic scanning antenna is for the proposed LightSAR radar system which is to be placed in Earth orbit on a small, dedicated space craft at the lowest possible cost for an efficient L- Band radar imaging system. This LightSAR spacecraft radar is to be continuously available for at least five operational years, and have the ability to map or repeat-map any area on earth within a few days of any request. A microstrip patch array, with microstrip transmission lines heavily employed in the aperture and in the corporate feed network, was chosen as the low cost approach for this active dual-polarization, 80 MHz (6.4%) bandwidth antenna design.

  20. The structure of high altitude O+ energization and outflow: a case study

    Directory of Open Access Journals (Sweden)

    H. Nilsson

    2004-07-01

    Full Text Available Multi-spacecraft observations from the CIS ion spectrometers on board the Cluster spacecraft have been used to study the structure of high-altitude oxygen ion energization and outflow. A case study taken from 12 April 2004 is discussed in more detail. In this case the spacecraft crossed the polar cap, mantle and high-altitude cusp region at altitudes between 4RE and 8RE and 2 of the spacecraft provided data. The oxygen ions were seen as a beam with narrow energy distribution, and increasing field-aligned velocity and temperature at higher altitude further in the upstream flow direction. The peak O+ energy was typically just above the highest energy of observed protons. The observed energies reached the upper limit of the CIS ion spectrometer, i.e. 38keV. Moment data from the spacecraft have been cross-correlated to determine cross-correlation coefficients, as well as the phase delay between the spacecraft. Structures in ion density, temperature and field-aligned flow appear to drift with the observed field-perpendicular drift. This, together with a velocity dispersion analysis, indicates that much of the structure can be explained by transverse heating well below the spacecraft. However, temperature isotropy and the particle flux as a function of field-aligned velocity are inconsistent with a single altitude Maxwellian source. Heating over extended altitude intervals, possibly all the way up to the observation point, seem consistent with the observations.

  1. Valley polarization in magnetically doped single-layer transition-metal dichalcogenides

    KAUST Repository

    Cheng, Yingchun

    2014-04-28

    We demonstrate that valley polarization can be induced and controlled in semiconducting single-layer transition-metal dichalcogenides by magnetic doping, which is important for spintronics, valleytronics, and photonics devices. As an example, we investigate Mn-doped MoS2 by first-principles calculations. We study how the valley polarization depends on the strength of the spin orbit coupling and the exchange interaction and discuss how it can be controlled by magnetic doping. Valley polarization by magnetic doping is also expected for other honeycomb materials with strong spin orbit coupling and the absence of inversion symmetry.

  2. Resonant Orbital Dynamics in LEO Region: Space Debris in Focus

    Directory of Open Access Journals (Sweden)

    J. C. Sampaio

    2014-01-01

    Full Text Available The increasing number of objects orbiting the earth justifies the great attention and interest in the observation, spacecraft protection, and collision avoidance. These studies involve different disturbances and resonances in the orbital motions of these objects distributed by the distinct altitudes. In this work, objects in resonant orbital motions are studied in low earth orbits. Using the two-line elements (TLE of the NORAD, resonant angles and resonant periods associated with real motions are described, providing more accurate information to develop an analytical model that describes a certain resonance. The time behaviors of the semimajor axis, eccentricity, and inclination of some space debris are studied. Possible irregular motions are observed by the frequency analysis and by the presence of different resonant angles describing the orbital dynamics of these objects.

  3. Assessing Sahelian vegetation and stress from seasonal time series of polar orbiting and geostationary satellite imagery

    DEFF Research Database (Denmark)

    Olsen, Jørgen Lundegaard

    that short term variations in anomalies from seasonally detrended time series of indices could carry information on vegetation stress was examined and confirmed. However, it was not found sufficiently robust on pixel level to be implemented for monitoring vegetation water stress on a per-pixel basis...... provide good sensitivity to canopy water content, which can make vegetation stress detection possible. Furthermore, the high frequency observations in the optical spectrum now available from geostationary instruments have the potential for detection of changes in vegetation related surface properties...... on short timescales, which are challenging from polar orbiting instruments. Geostationary NDVI and the NIR and SWIR based Shortwave Infrared Water Stress Index (SIWSI) indices are compared with extensive field data from the Dahra site, supplemented by data from the Agoufou and Demokeya sites. The indices...

  4. Polar Stratigraphy

    Science.gov (United States)

    1999-01-01

    These three images were taken on three different orbits over the north polar cap in April 1999. Each shows a different part of the same ice-free trough. The left and right images are separated by a distance of more than 100 kilometers (62 miles). Note the similar layers in each image.

  5. FLUKA Calculation of the Neutron Albedo Encountered at Low Earth Orbits

    CERN Document Server

    Claret, Arnaud; Combier, Natacha; Ferrari, Alfredo; Laurent, Philippe

    2014-01-01

    This paper presents Monte-Carlo simulations based on the Fluka code aiming to calculate the contribution of the neutron albedo at a given date and altitude above the Earth chosen by the user. The main input parameters of our model are the solar modulation affecting the spectra of cosmic rays, and the date of the Earth’s geomagnetic fi eld. The results consist in a two-parameter distribution, the neutron energy and the angle to the tangent plane of the sphere containing the orbi t of interest, and are provided by geographical position above the E arth at the chosen altitude. This model can be used to predict the te mporal variation of the neutron fl ux encountered along the orbit, and thus constrain the determination of the instrumental backg round noise of space experiments in low earth orbit.

  6. Application of circular polarized synchrotron radiation

    International Nuclear Information System (INIS)

    Miyahara, Tsuneaki; Kawata, Hiroshi

    1988-03-01

    The idea of using the polarizing property of light for physical experiment by controlling it variously has been known from old time, and the Faraday effect and the research by polarizing microscopy are its examples. The light emitted from the electron orbit of an accelerator has the different polarizing characteristics from those of the light of a laboratory light source, and as far as observing it within the electron orbit plane, it becomes linearly polarized light. By utilizing this property well, research is carried out at present in synchrotron experimental facilities. Recently, the technology related to the insert type light cources using permanent magnets has advanced remarkably, and circular polarized light has become to be producible. If the light like this can be obtained with the energy not only in far ultraviolet region but also to x-ray region at high luminance, new possibility should open. At the stage that the design of an insert type light source was finished, and its manufacture was started, the research on the method of evaluating the degree of circular polarization and the research on the utilization of circular polarized synchrotron radiation are earnestly carried out. In this report, the results of researches presented at the study meeting are summarized. Moreover, the design and manufacture of the beam lines for exclusive use will be carried out. (Kako, I.)

  7. Application of Semi-analytical Satellite Theory orbit propagator to orbit determination for space object catalog maintenance

    Science.gov (United States)

    Setty, Srinivas J.; Cefola, Paul J.; Montenbruck, Oliver; Fiedler, Hauke

    2016-05-01

    Catalog maintenance for Space Situational Awareness (SSA) demands an accurate and computationally lean orbit propagation and orbit determination technique to cope with the ever increasing number of observed space objects. As an alternative to established numerical and analytical methods, we investigate the accuracy and computational load of the Draper Semi-analytical Satellite Theory (DSST). The standalone version of the DSST was enhanced with additional perturbation models to improve its recovery of short periodic motion. The accuracy of DSST is, for the first time, compared to a numerical propagator with fidelity force models for a comprehensive grid of low, medium, and high altitude orbits with varying eccentricity and different inclinations. Furthermore, the run-time of both propagators is compared as a function of propagation arc, output step size and gravity field order to assess its performance for a full range of relevant use cases. For use in orbit determination, a robust performance of DSST is demonstrated even in the case of sparse observations, which is most sensitive to mismodeled short periodic perturbations. Overall, DSST is shown to exhibit adequate accuracy at favorable computational speed for the full set of orbits that need to be considered in space surveillance. Along with the inherent benefits of a semi-analytical orbit representation, DSST provides an attractive alternative to the more common numerical orbit propagation techniques.

  8. Mars orbiter redirected in bid to find Beagle

    CERN Multimedia

    2003-01-01

    "Mission controllers in Darmstadt, Germany, have successfully redirected Europe's Mars Express orbiter into a polar orbit, putting it on course for a last-ditch attempt to contact Beagle 2, the lander that has been missing since Christmas day when it should have touched down on the red planet" (1/2 page).

  9. Characteristics of anomalous Hall effect in spin-polarized two-dimensional electron gases in the presence of both intrinsic, extrinsic, and external electric-field induced spin—orbit couplings

    International Nuclear Information System (INIS)

    Liu Song; Yan Yu-Zhen; Hu Liang-Bin

    2012-01-01

    The various competing contributions to the anomalous Hall effect in spin-polarized two-dimensional electron gases in the presence of both intrinsic, extrinsic and external electric-field induced spin—orbit coupling were investigated theoretically. Based on a unified semiclassical theoretical approach, it is shown that the total anomalous Hall conductivity can be expressed as the sum of three distinct contributions in the presence of these competing spin—orbit interactions, namely an intrinsic contribution determined by the Berry curvature in the momentum space, an extrinsic contribution determined by the modified Bloch band group velocity and an extrinsic contribution determined by spin—orbit-dependent impurity scattering. The characteristics of these competing contributions are discussed in detail in the paper. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  10. Optimizing the degree of polarization in PETRA

    International Nuclear Information System (INIS)

    Bremer, H.D.; Kewisch, J.; Lewin, H.C.; Mais, H.; Rossmanith, R.; Schmidt, R.; Barber, D.P.

    1982-05-01

    A method is described for compensating the depolarizing effects caused by vertical orbit distortions. The technique has been successfully applied during measurements of beam polarization at PETRA and reproducible polarizations of 70 to 80% have been obtained both in single beam and colliding beam operation. (orig.)

  11. Classical altitude training.

    Science.gov (United States)

    Friedmann-Bette, B

    2008-08-01

    For more than 40 years, the effects of classical altitude training on sea-level performance have been the subject of many scientific investigations in individual endurance sports. To our knowledge, no studies have been performed in team sports like football. Two well-controlled studies showed that living and training at an altitude of >or=1800-2700 m for 3-4 weeks is superior to equivalent training at sea level in well-trained athletes. Most of the controlled studies with elite athletes did not reveal such an effect. However, the results of some uncontrolled studies indicate that sea-level performance might be enhanced after altitude training also in elite athletes. Whether hypoxia provides an additional stimulus for muscular adaptation, when training is performed with equal intensity compared with sea-level training is not known. There is some evidence for an augmentation of total hemoglobin mass after classical altitude training with duration >or=3 weeks at an altitude >or=2000 m due to altitude acclimatization. Considerable individual variation is observed in the erythropoietic response to hypoxia and in the hypoxia-induced reduction of aerobic performance capacity during training at altitude, both of which are thought to contribute to inter-individual variation in the improvement of sea-level performance after altitude training.

  12. PALOMA: A Magnetic CV between Polars and Intermediate Polars

    Science.gov (United States)

    Joshi, Arti; Pandey, J. C.; Singh, K. P.; Agrawal, P. C.

    2016-10-01

    We present analyses of archival X-ray data obtained from the XMM-Newton satellite and optical photometric data obtained from 1 m class telescopes of ARIES, Nainital of a magnetic cataclysmic variable (MCV) Paloma. Two persistent periods at 156 ± 1 minutes and 130 ± 1 minutes are present in the X-ray data, which we interpret as the orbital and spin periods, respectively. These periods are similar to those obtained from the previous as well as new optical photometric observations. The soft-X-ray excess seen in the X-ray spectrum of Paloma and the averaged X-ray spectra are well fitted by two-temperature plasma models with temperatures of {0.10}-0.01+0.02 and {13.0}-0.5+0.5 keV with an Fe Kα line and an absorbing column density of 4.6 × 1022 cm-2. This material partially covers 60 ± 2% of the X-ray source. We also present the orbital and spin-phase-resolved spectroscopy of Paloma in the 0.3{--}10.0 {keV} energy band and find that the X-ray spectral parameters show orbital and spin-phase dependencies. New results obtained from optical and X-ray studies of Paloma indicate that it belongs to a class of a few magnetic CVs that seem to have the characteristics of both the polars and the intermediate polars.

  13. Polarization Smoothing Generalized MUSIC Algorithm with Polarization Sensitive Array for Low Angle Estimation.

    Science.gov (United States)

    Tan, Jun; Nie, Zaiping

    2018-05-12

    Direction of Arrival (DOA) estimation of low-altitude targets is difficult due to the multipath coherent interference from the ground reflection image of the targets, especially for very high frequency (VHF) radars, which have antennae that are severely restricted in terms of aperture and height. The polarization smoothing generalized multiple signal classification (MUSIC) algorithm, which combines polarization smoothing and generalized MUSIC algorithm for polarization sensitive arrays (PSAs), was proposed to solve this problem in this paper. Firstly, the polarization smoothing pre-processing was exploited to eliminate the coherence between the direct and the specular signals. Secondly, we constructed the generalized MUSIC algorithm for low angle estimation. Finally, based on the geometry information of the symmetry multipath model, the proposed algorithm was introduced to convert the two-dimensional searching into one-dimensional searching, thus reducing the computational burden. Numerical results were provided to verify the effectiveness of the proposed method, showing that the proposed algorithm has significantly improved angle estimation performance in the low-angle area compared with the available methods, especially when the grazing angle is near zero.

  14. The effects of Dresselhaus and Rashba spin-orbit interactions on the electron tunneling in a non-magnetic heterostructure

    International Nuclear Information System (INIS)

    Lu Jianduo; Li Jianwen

    2010-01-01

    We theoretically investigate the electron transport properties in a non-magnetic heterostructure with both Dresselhaus and Rashba spin-orbit interactions. The detailed-numerical results show that (1) the large spin polarization can be achieved due to Dresselhaus and Rashba spin-orbit couplings induced splitting of the resonant level, although the magnetic field is zero in such a structure, (2) the Rashba spin-orbit coupling plays a greater role on the spin polarization than the Dresselhaus spin-orbit interaction does, and (3) the transmission probability and the spin polarization both periodically change with the increase of the well width.

  15. Lunar Reconnaissance Orbiter Camera (LROC) instrument overview

    Science.gov (United States)

    Robinson, M.S.; Brylow, S.M.; Tschimmel, M.; Humm, D.; Lawrence, S.J.; Thomas, P.C.; Denevi, B.W.; Bowman-Cisneros, E.; Zerr, J.; Ravine, M.A.; Caplinger, M.A.; Ghaemi, F.T.; Schaffner, J.A.; Malin, M.C.; Mahanti, P.; Bartels, A.; Anderson, J.; Tran, T.N.; Eliason, E.M.; McEwen, A.S.; Turtle, E.; Jolliff, B.L.; Hiesinger, H.

    2010-01-01

    The Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) and Narrow Angle Cameras (NACs) are on the NASA Lunar Reconnaissance Orbiter (LRO). The WAC is a 7-color push-frame camera (100 and 400 m/pixel visible and UV, respectively), while the two NACs are monochrome narrow-angle linescan imagers (0.5 m/pixel). The primary mission of LRO is to obtain measurements of the Moon that will enable future lunar human exploration. The overarching goals of the LROC investigation include landing site identification and certification, mapping of permanently polar shadowed and sunlit regions, meter-scale mapping of polar regions, global multispectral imaging, a global morphology base map, characterization of regolith properties, and determination of current impact hazards.

  16. METRIC: A Dedicated Earth-Orbiting Spacecraft for Investigating Gravitational Physics and the Space Environment

    Directory of Open Access Journals (Sweden)

    Roberto Peron

    2017-07-01

    Full Text Available A dedicated mission in low Earth orbit is proposed to test predictions of gravitational interaction theories and to directly measure the atmospheric density in a relevant altitude range, as well as to provide a metrological platform able to tie different space geodesy techniques. The concept foresees a small spacecraft to be placed in a dawn-dusk eccentric orbit between 450 and 1200 km of altitude. The spacecraft will be tracked from the ground with high precision, and a three-axis accelerometer package on-board will measure the non-gravitational accelerations acting on its surface. Estimates of parameters related to fundamental physics and geophysics should be obtained by a precise orbit determination, while the accelerometer data will be instrumental in constraining the atmospheric density. Along with the mission scientific objectives, a conceptual configuration is described together with an analysis of the dynamical environment experienced by the spacecraft and the accelerometer.

  17. Discovery of highly spin-polarized conducting surface states in the strong spin-orbit coupling semiconductor Sb2Se3

    Science.gov (United States)

    Das, Shekhar; Sirohi, Anshu; Kumar Gupta, Gaurav; Kamboj, Suman; Vasdev, Aastha; Gayen, Sirshendu; Guptasarma, Prasenjit; Das, Tanmoy; Sheet, Goutam

    2018-06-01

    Majority of the A2B3 -type chalcogenide systems with strong spin-orbit coupling (SOC), such as Bi2Se3,Bi2Te3 , and Sb2Te3 , etc., are topological insulators. One important exception is Sb2Se3 where a topological nontrivial phase was argued to be possible under ambient conditions, but such a phase could be detected to exist only under pressure. In this paper, we show that Sb2Se3 like Bi2Se3 displays a generation of highly spin-polarized current under mesoscopic superconducting point contacts as measured by point-contact Andreev reflection spectroscopy. In addition, we observe a large negative and anisotropic magnetoresistance of the mesoscopic metallic point contacts formed on Sb2Se3 . Our band-structure calculations confirm the trivial nature of Sb2Se3 crystals and reveal two trivial surface states one of which shows large spin splitting due to Rashba-type SOC. The observed high spin polarization and related phenomena in Sb2Se3 can be attributed to this spin splitting.

  18. Physiological aspects of altitude training and the use of altitude simulators

    OpenAIRE

    Ranković Goran; Radovanović Dragan

    2005-01-01

    Altitude training in various forms is widely practiced by athletes and coaches in an attempt to improve sea level endurance. Training at high altitude may improve performance at sea level through altitude acclimatization, which improves oxygen transport and/or utilization, or through hypoxia, which intensifies the training stimulus. This basic physiological aspect allows three training modalities: live high and train high (classic high-altitude training), live low and train high (training thr...

  19. The Delta low-inclination satellite concept, an opportunity to enhance the science return of the Swarm mission

    DEFF Research Database (Denmark)

    Hulot, Gauthier; Leger, Jean-Michel; Olsen, Nils

    ESA’s Swarm mission aims at studying all sources of Earth’s magnetic field. It consists of two satellites (Alpha and Charlie), which fly side-by-side on near polar orbits at an altitude of slightly less than 500 km, and of a third satellite (Bravo) on a similar but slightly more polar and higher ...

  20. Polarization-dependent pump-probe studies in atomic fine-structure levels: towards the production of spin-polarized electrons

    International Nuclear Information System (INIS)

    Sokell, E.; Zamith, S.; Bouchene, M.A.; Girard, B.

    2000-01-01

    The precession of orbital and spin angular momentum vectors has been observed in a pump-probe study of the 4P fine-structure states of atomic potassium. A femtosecond pump pulse prepared a coherent superposition of the two fine-structure components. A time-delayed probe pulse then ionized the system after it had been allowed to evolve freely. Oscillations recorded in the ion signal reflect the evolution of the orientation of the orbital and spin angular momentum due to spin-orbit coupling. This interpretation gives physical insight into the cause of the half-period phase shift observed when the relative polarizations of the laser pulses were changed from parallel to perpendicular. Finally, it is shown that these changes in the orientation of the spin momentum vector of the system can be utilized to produce highly spin-polarized free electrons on the femtosecond scale. (author)

  1. Athletes at High Altitude.

    Science.gov (United States)

    Khodaee, Morteza; Grothe, Heather L; Seyfert, Jonathan H; VanBaak, Karin

    2016-01-01

    Athletes at different skill levels perform strenuous physical activity at high altitude for a variety of reasons. Multiple team and endurance events are held at high altitude and may place athletes at increased risk for developing acute high altitude illness (AHAI). Training at high altitude has been a routine part of preparation for some of the high level athletes for a long time. There is a general belief that altitude training improves athletic performance for competitive and recreational athletes. A review of relevant publications between 1980 and 2015 was completed using PubMed and Google Scholar. Clinical review. Level 3. AHAI is a relatively uncommon and potentially serious condition among travelers to altitudes above 2500 m. The broad term AHAI includes several syndromes such as acute mountain sickness (AMS), high altitude pulmonary edema (HAPE), and high altitude cerebral edema (HACE). Athletes may be at higher risk for developing AHAI due to faster ascent and more vigorous exertion compared with nonathletes. Evidence regarding the effects of altitude training on athletic performance is weak. The natural live high, train low altitude training strategy may provide the best protocol for enhancing endurance performance in elite and subelite athletes. High altitude sports are generally safe for recreational athletes, but they should be aware of their individual risks. Individualized and appropriate acclimatization is an essential component of injury and illness prevention.

  2. A Dynamical Systems Approach to the Design of the Science Orbit Around Europa

    Science.gov (United States)

    Gomez, Gerard; Lara, Martin; Russell, Ryan P.

    2006-01-01

    The science orbit for a future mission to Europa requires low eccentricity, low altitude, and high inclination. However, high inclination orbits around planetary satellites are unstable due to third-body perturbations. Without control, the orbiter impacts Europa after few weeks. To minimize control, a tour over the stable-unstable, averaged manifolds of unstable frozen orbits has been suggested. We proceed with the unaveraged equations and study the manifolds of unstable orbits that are periodic in a rotating frame attached to Europa. Massive numerical computation helps in understanding the unstable dynamics close to Europa, and, thus, in selecting long lifetime high inclination orbits. A final test of a selected set of initial conditions on a high fidelity, ephemeris model, validate the results.

  3. Polarized beams in high energy storage rings

    Energy Technology Data Exchange (ETDEWEB)

    Montague, B W [European Organization for Nuclear Research, Geneva (Switzerland)

    1984-11-01

    In recent years there has been a considerable advance in understanding the spin motion of particles in storage rings and accelerators. The survey presented here outlines the early historical development in this field, describes the basic ideas governing the kinetics of polarized particles in electromagnetic fields and shows how these have evolved into the current description of polarized beam behaviour. Orbital motion of particles influences their spin precession, and depolarization of a beam can result from excitation of spin resonances by orbit errors and oscillations. Electrons and positrons are additionally influenced by the quantized character of synchrotron radiation, which not only provides a polarizing mechanism but also enhances depolarizing effects. Progress in the theoretical formulation of these phenomena has clarified the details of the physical processes and suggested improved methods of compensating spin resonances. Full use of polarized beams for high-energy physics with storage rings requires spin rotators to produce longitudinal polarization in the interaction regions. Variants of these schemes, dubbed Siberian snakes, provide a curious precession topology which can substantially reduce depolarization in the high-energy range. Efficient polarimetry is an essential requirement for implementing polarized beams, whose utility for physics can be enhanced by various methods of spin manipulation.

  4. Electron spin polarization in high-energy storage rings

    International Nuclear Information System (INIS)

    Mane, S.R.

    1987-01-01

    In a high energy storage ring, a single photon emission has relatively little effect on the orbital motion, but it can produce a relatively large change in the electron spin state. Hence the unperturbed orbital motion can be satisfactorily described using classical mechanics, but the spin must be treated quantum mechanically. The electron motion is therefore treated semi-classically in this thesis. It is explained how to diagonalize the unperturbed Hamiltonian to the leading order in Planck's constant. The effects of perturbations are then included, and the relevant time-scales and ensemble averages are elucidated. The Derbenev-Kondratenko formula for the equilibrium degree of polarization is rederived. Mathematical details of the rederivation are given. Since the original authors used a different formalism, a proof is offered of the equivalence between their method and the one used in this thesis. An algorithm is also presented to evaluate the equilibrium polarization. It has a number of new features, which enable the polarization to be calculated to a higher degree of approximation than has hitherto been possible. This facilitates the calculation of so-called spin resonances, which are points at which the polarization almost vanishes. A computer program has been written to implement the above algorithm, in the approximation of linear orbital dynamics, and sample results are presented

  5. Reaching High Altitudes on Mars with an Inflatable Hypersonic Drag Balloon (Ballute)

    CERN Document Server

    Griebel, Hannes

    2010-01-01

    The concept of probing the atmosphere of planet Mars by means of a hypersonic drag balloon, a device known as a “ballute”, is a novel approach to planetary science. In this concept, the probe deploys an inflatable drag body out in space and may then enter the atmosphere either once or several times until it slowly descends towards the ground, taking continuous atmospheric and other readings across a large altitude and ground range. Hannes Griebel discusses the theory behind such a mission along with experience gained during its practical implementation, such as mission design, manufacturing, packing and deployment techniques as well as ground and flight tests. The author also studies other ballute applications, specifically emergency low Earth orbit recovery and delivering payloads to high altitude landing sites on Mars.

  6. Global communication using a constellation of low earth meridian orbits

    Science.gov (United States)

    Oli, P. V. S.; Nagarajan, N.; Rayan, H. R.

    1993-07-01

    The concept of 'meridian orbits' is briefly reviewed. It is shown that, if a satellite in the meridian orbit makes an odd number of revolutions per day, then the satellite passes over the same set of meridians twice a day. Satellites in such orbits pass over the same portion of the sky twice a day and every day. This enables a user to adopt a programmed mode of tracking, thereby avoiding a computational facility for orbit prediction, look angle generation, and auto tracking. A constellation of 38 or more satellites placed in a 1200 km altitude circular orbit is favorable for global communications due to various factors. It is shown that appropriate phasing in right ascension of the ascending node and mean anomaly results in a constellation, wherein each satellite appears over the user's horizon one satellite after another. Visibility and coverage plots are provided to verify the continuous coverage.

  7. Spin-polarized gapped Dirac spectrum of unsupported silicene

    Energy Technology Data Exchange (ETDEWEB)

    Podsiadły-Paszkowska, A., E-mail: agata.podsiadly@gmail.com; Krawiec, M., E-mail: mariusz.krawiec@umcs.pl

    2016-06-15

    Highlights: • Effects of spin–orbit interaction and atomic reconstruction of silicene on its electronic properties have been studied. • Spin-polarized gapped Dirac spectrum has been revealed. • Two different AFM phases have been obtained. - Abstract: We study effects of the spin–orbit interaction and the atomic reconstruction of silicene on its electronic spectrum. As an example we consider unsupported silicene pulled off from Pb(111) substrate. Using first principles density functional theory we show that the inversion symmetry broken arrangement of atoms and the spin–orbit interaction generate a spin-polarized electronic spectrum with an energy gap in the Dirac cone. These findings are particularly interesting in view of the quantum anomalous and quantum valley Hall effects and should be observable in weakly interacting silicene-substrate systems.

  8. Local-time survey of plasma at low altitudes over the auroral zones.

    Science.gov (United States)

    Frank, L. A.; Ackerson, K. L.

    1972-01-01

    Local-time survey of the low-energy proton and electron intensities precipitated into the earth's atmosphere over the auroral zones during periods of magnetic quiescence. This survey was constructed by selecting a typical individual satellite crossing of this region in each of eight local-time sectors from a large library of similar observations with the polar-orbiting satellite Injun 5. The trapping boundary for more-energetic electron intensities, E greater than 45 keV, was found to be a 'natural coordinate' for delineating the boundary between the two major types of lower-energy, 50 less than or equal to E less than or equal to 15,000 eV, electron precipitation commonly observed over the auroral zones at low altitudes. Poleward of this trapping boundary inverted 'V' electron precipitation bands are observed in all local-time sectors. These inverted 'V' electron bands in the evening and midnight sectors are typically more energetic and have greater latitudinal widths than their counterparts in the noon and morning sectors. In general, the main contributors to the electron energy influx into the earth's atmosphere over the auroral zones are the electron inverted 'V' precipitation poleward of the trapping boundary in late evening, the plasma-sheet electron intensities equatorward of this boundary in early morning, and both of these precipitation events near local midnight.

  9. Instrumentation with polarized neutrons

    International Nuclear Information System (INIS)

    Boeni, P.; Muenzer, W.; Ostermann, A.

    2009-01-01

    Neutron scattering with polarization analysis is an indispensable tool for the investigation of novel materials exhibiting electronic, magnetic, and orbital degrees of freedom. In addition, polarized neutrons are necessary for neutron spin precession techniques that path the way to obtain extremely high resolution in space and time. Last but not least, polarized neutrons are being used for fundamental studies as well as very recently for neutron imaging. Many years ago, neutron beam lines were simply adapted for polarized beam applications by adding polarizing elements leading usually to unacceptable losses in neutron intensity. Recently, an increasing number of beam lines are designed such that an optimum use of polarized neutrons is facilitated. In addition, marked progress has been obtained in the technology of 3 He polarizers and the reflectivity of large-m supermirrors. Therefore, if properly designed, only factors of approximately 2-3 in neutron intensity are lost. It is shown that S-benders provide neutron beams with an almost wavelength independent polarization. Using twin cavities, polarized beams with a homogeneous phase space and P>0.99 can be produced without significantly sacrificing intensity. It is argued that elliptic guides, which are coated with large m polarizing supermirrors, provide the highest flux.

  10. Mercury's Seasonal Sodium Exosphere: MESSENGER Orbital Observations

    Science.gov (United States)

    Cassidy, Timothy A.; Merkel, Aimee W.; Burger, Matthew H.; Killen, Rosemary M.; McClintock, William E.; Vervack, Ronald J., Jr.; Sarantos, Menelaos

    2014-01-01

    The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) Ultraviolet and Visible Spectrometer (UVVS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft now orbiting Mercury provides the first close-up look at the planet's sodium exosphere. UVVS has observed the exosphere from orbit almost daily for over 10 Mercury years. In this paper we describe and analyze a subset of these data: altitude profiles taken above the low-latitude dayside and south pole. The observations show spatial and temporal variations, but there are no obvious year-to-year variations in most of the observations. We do not see the episodic variability reported by some ground-based observers. We used these altitude profiles to make estimates of sodium density and temperature. The bulk of the exosphere, at about 1200 K, is much warmer than Mercury's surface. This value is consistent with some ground-based measurements and suggests that photon-stimulated desorption is the primary ejection process. We also observe a tenuous energetic component but do not see evidence of the predicted thermalized (or partially thermalized) sodium near Mercury's surface temperature. Overall we do not see the variable mixture of temperatures predicted by most Monte Carlo models of the exosphere.

  11. Polar cap ion beams during periods of northward IMF: Cluster statistical results

    Directory of Open Access Journals (Sweden)

    R. Maggiolo

    2011-05-01

    Full Text Available Above the polar caps and during prolonged periods of northward IMF, the Cluster satellites detect upward accelerated ion beams with energies up to a few keV. They are associated with converging electric field structures indicating that the acceleration is caused by a quasi-static field-aligned electric field that can extend to altitudes higher than 7 RE (Maggiolo et al., 2006; Teste et al., 2007. Using the AMDA science analysis service provided by the Centre de Données de la Physique des Plasmas, we have been able to extract about 200 events of accelerated upgoing ion beams above the polar caps from the Cluster database. Most of these observations are taken at altitudes lower than 7 RE and in the Northern Hemisphere. We investigate the statistical properties of these ion beams. We analyze their geometry, the properties of the plasma populations and of the electric field inside and around the beams, as well as their dependence on solar wind and IMF conditions. We show that ~40 % of the ion beams are collocated with a relatively hot and isotropic plasma population. The density and temperature of the isotropic population are highly variable but suggest that this plasma originates from the plasma sheet. The ion beam properties do not change significantly when the isotropic, hot background population is present. Furthermore, during one single polar cap crossing by Cluster it is possible to detect upgoing ion beams both with and without an accompanying isotropic component. The analysis of the variation of the IMF BZ component prior to the detection of the beams indicates that the delay between a northward/southward turning of IMF and the appearance/disappearance of the beams is respectively ~2 h and 20 min. The observed electrodynamic characteristics of high altitude polar cap ion beams suggest that they are closely connected to polar cap auroral arcs. We discuss the implications of these Cluster observations above the polar cap on the magnetospheric

  12. Current-induced spin polarization in InGaAs and GaAs epilayers with varying doping densities

    Science.gov (United States)

    Luengo-Kovac, M.; Huang, S.; Del Gaudio, D.; Occena, J.; Goldman, R. S.; Raimondi, R.; Sih, V.

    2017-11-01

    The current-induced spin polarization and momentum-dependent spin-orbit field were measured in InxGa1 -xAs epilayers with varying indium concentrations and silicon doping densities. Samples with higher indium concentrations and carrier concentrations and lower mobilities were found to have larger electrical spin generation efficiencies. Furthermore, current-induced spin polarization was detected in GaAs epilayers despite the absence of measurable spin-orbit fields, indicating that the extrinsic contributions to the spin-polarization mechanism must be considered. Theoretical calculations based on a model that includes extrinsic contributions to the spin dephasing and the spin Hall effect, in addition to the intrinsic Rashba and Dresselhaus spin-orbit coupling, are found to reproduce the experimental finding that the crystal direction with the smaller net spin-orbit field has larger electrical spin generation efficiency and are used to predict how sample parameters affect the magnitude of the current-induced spin polarization.

  13. Interaction between subdaily Earth rotation parameters and GPS orbits

    Science.gov (United States)

    Panafidina, Natalia; Seitz, Manuela; Hugentobler, Urs

    2013-04-01

    In processing GPS observations the geodetic parameters like station coordinates and ERPs (Earth rotation parameters) are estimated w.r.t. the celestial reference system realized by the satellite orbits. The interactions/correlations between estimated GPS orbis and other parameters may lead to numerical problems with the solution and introduce systematic errors in the computed values: the well known correlations comprise 1) the correlation between the orbital parameters determining the orientation of the orbital plane in inertial space and the nutation and 2) in the case of estimating ERPs with subdaily resolution the correlation between retrograde diurnal polar motion and nutation (and so the respective orbital elements). In this contribution we study the interaction between the GPS orbits and subdaily model for the ERPs. Existing subdaily ERP model recommended by the IERS comprises ~100 terms in polar motion and ~70 terms in Universal Time at diurnal and semidiurnal tidal periods. We use a long time series of daily normal equation systems (NEQ) obtaine from GPS observations from 1994 till 2007 where the ERPs with 1-hour resolution are transformed into tidal terms and the influence of the tidal terms with different frequencies on the estimated orbital parameters is considered. We found that although there is no algebraic correlation in the NEQ between the individual orbital parameters and the tidal terms, the changes in the amplitudes of tidal terms with periods close to 24 hours can be better accmodated by systematic changes in the orbital parameters than for tidal terms with other periods. Since the variation in Earth rotation with the period of siderial day (23.93h, tide K1) in terrestrial frame has in inertial space the same period as the period of revolution of GPS satellites, the K1 tidal term in polar motion is seen by the satellites as a permanent shift. The tidal terms with close periods (from ~24.13h to ~23.80h) are seen as a slow rotation of the

  14. Orbital angular momentum of general astigmatic modes

    International Nuclear Information System (INIS)

    Visser, Jorrit; Nienhuis, Gerard

    2004-01-01

    We present an operator method to obtain complete sets of astigmatic Gaussian solutions of the paraxial wave equation. In case of general astigmatism, the astigmatic intensity and phase distribution of the fundamental mode differ in orientation. As a consequence, the fundamental mode has a nonzero orbital angular momentum, which is not due to phase singularities. Analogous to the operator method for the quantum harmonic oscillator, the corresponding astigmatic higher-order modes are obtained by repeated application of raising operators on the fundamental mode. The nature of the higher-order modes is characterized by a point on a sphere, in analogy with the representation of polarization on the Poincare sphere. The north and south poles represent astigmatic Laguerre-Gaussian modes, similar to circular polarization on the Poincare sphere, while astigmatic Hermite-Gaussian modes are associated with points on the equator, analogous to linear polarization. We discuss the propagation properties of the modes and their orbital angular momentum, which depends on the degree of astigmatism and on the location of the point on the sphere

  15. The HAMMER: High altitude multiple mission environmental researcher

    Science.gov (United States)

    Hayashi, Darren; Zylla, Cara; Amaro, Ernesto; Colin, Phil; Klause, Thomas; Lopez, Bernardo; Williamson, Danna

    1991-01-01

    At the equator, the ozone layer ranges from 65,000 to 130,000+ feet which is beyond the capabilities of the ER-2, NASA's current high altitude reconnaissance aircraft. The Universities Space Research Association, in cooperation with NASA, is sponsoring an undergraduate program which is geared to designing an aircraft that can study the ozone layer at the equator. This aircraft must be able to satisfy four mission profiles. Mission one is a polar mission which ranges from Chile to the South Pole and back to Chile, a total range of 6000 n. mi. at 100,000 feet with a 2500 lb. payload. The second mission is also a polar mission with a decreased altitude of 70,000 feet and an increased payload of 4000 lb. For the third mission, the aircraft will take-off at NASA Ames, cruise at 100,000 feet carrying a 2500 lb. payload, and land in Puerto Montt, Chile. The final mission requires the aircraft to take-off at NASA Ames, cruise at 100,000 feet with a 1000 lb. payload, make an excursion to 120,000 feet, and land at Howard AFB, Panama. All three missions require that a subsonic Mach number is maintained due to constraints imposed by the air sampling equipment. The aircraft need not be manned for all four missions. Three aircraft configurations were determined to be the most suitable for meeting the above requirements. The performance of each configuration is analyzed to investigate the feasibility of the project requirements. In the event that a requirement can not be obtained within the given constraints, recommendations for proposal modifications are given.

  16. Weights assessment for orbit-on-demand vehicles

    Science.gov (United States)

    Macconochie, I. O.; Martin, J. A.; Breiner, C. A.; Cerro, J. A.

    1985-01-01

    Future manned, reusable earth-to-orbit vehicles may be required to reach orbit within hours or even minutes of a mission decision. A study has been conducted to consider vehicles with such a capability. In the initial phase of the study, 11 vehicles were sized for deployment of 5000 lbs to a polar orbit. From this matrix, two of the most promising concepts were resized for a modified mission and payload. A key feature of the study was the use of consistent mass estimating techniques for a broad range of concepts, allowing direct comparisons of sizes and weights.

  17. Centrifugal acceleration of the polar wind

    Science.gov (United States)

    Horwitz, J. L.; Ho, C. W.; Scarbro, H. D.; Wilson, G. R.; Moore, T. E.

    1994-01-01

    The effect of parallel ion acceleration associated with convection was first applied to energization of test particle polar ions by Cladis (1986). However, this effect is typically neglected in 'self-consistent' models of polar plasma outflow, apart from the fluid simulation by Swift (1990). Here we include approximations for this acceleration, which we broadly characterize as centrifugal in nature, in our time-dependent, semikinetic model of polar plasma outflow and describe the effects on the bulk parameter profiles and distribution functions of H+ and O+. For meridional convection across the pole the approximate parallel force along a polar magnetic field line may be written as F(sub cent, pole) = 1.5m(E(sub i))/B(sub i))squared (r(squared)/r(sup 3)(sub i)) where m is ion mass, r is geometric distance; and E(sub i), B(sub i) and r(sub i) refer to the electric and magnetic field magnitudes and geocentric distance at the ionosphere, respectively. For purely longitudinal convection along a constant L shell the parallel force is F(cent. long) = F(sub cent, pole)(1 - (r/(r(sub i)L))(sup 3/2)/(1 - 3r/(4 r(sub i)L))(sup 5/2). For high latitudes the difference between these two cases is relatively unimportant below approximately 5 R(sub E). We find that the steady state O+ bulk velocities and parallel temperatures strongly increase and decrease, respectively, with convection strength. In particular, the bulk velocities increase from near 0 km/s at 4000 km altitude to approximately 10 km/s at 5 R(sub E) geocentric distance for 50-mV/m ionospheric convection electric field. However, the centrifugal effect on the steady O+ density profiles depends on the exobase ion and electron temperatures: for low-base temperatures (T(sub i) = T(sub e) = 3000 K) the O+ density at high altitudes increases greatly with convection, while for higher base temperatures (T(sub i) = 5000 K, T(sub e) = 9000 K), the high-altitude O+ density decreases somewhat as convection is enhanced. The

  18. Anomalous Hall conductivity: Local orbitals approach

    Czech Academy of Sciences Publication Activity Database

    Středa, Pavel

    2010-01-01

    Roč. 82, č. 4 (2010), 045115/1-045115/9 ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100521 Keywords : anomalous Hall effect * Berry phase correction * orbital polarization momentum Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.772, year: 2010

  19. A Low-Cost Launch Assistance System for Orbital Launch Vehicles

    Directory of Open Access Journals (Sweden)

    Oleg Nizhnik

    2012-01-01

    Full Text Available The author reviews the state of art of nonrocket launch assistance systems (LASs for spaceflight focusing on air launch options. The author proposes an alternative technologically feasible LAS based on a combination of approaches: air launch, high-altitude balloon, and tethered LAS. Proposed LAS can be implemented with the existing off-the-shelf hardware delivering 7 kg to low-earth orbit for the 5200 USD per kg. Proposed design can deliver larger reduction in price and larger orbital payloads with the future advances in the aerostats, ropes, electrical motors, and terrestrial power networks.

  20. Summary of the results from the lunar orbiter laser altimeter after seven years in lunar orbit

    Science.gov (United States)

    Smith, David E.; Zuber, Maria T.; Neumann, Gregory A.; Mazarico, Erwan; Lemoine, Frank G.; Head, James W., III; Lucey, Paul G.; Aharonson, Oded; Robinson, Mark S.; Sun, Xiaoli; Torrence, Mark H.; Barker, Michael K.; Oberst, Juergen; Duxbury, Thomas C.; Mao, Dandan; Barnouin, Olivier S.; Jha, Kopal; Rowlands, David D.; Goossens, Sander; Baker, David; Bauer, Sven; Gläser, Philipp; Lemelin, Myriam; Rosenburg, Margaret; Sori, Michael M.; Whitten, Jennifer; Mcclanahan, Timothy

    2017-02-01

    In June 2009 the Lunar Reconnaissance Orbiter (LRO) spacecraft was launched to the Moon. The payload consists of 7 science instruments selected to characterize sites for future robotic and human missions. Among them, the Lunar Orbiter Laser Altimeter (LOLA) was designed to obtain altimetry, surface roughness, and reflectance measurements. The primary phase of lunar exploration lasted one year, following a 3-month commissioning phase. On completion of its exploration objectives, the LRO mission transitioned to a science mission. After 7 years in lunar orbit, the LOLA instrument continues to map the lunar surface. The LOLA dataset is one of the foundational datasets acquired by the various LRO instruments. LOLA provided a high-accuracy global geodetic reference frame to which past, present and future lunar observations can be referenced. It also obtained high-resolution and accurate global topography that were used to determine regions in permanent shadow at the lunar poles. LOLA further contributed to the study of polar volatiles through its unique measurement of surface brightness at zero phase, which revealed anomalies in several polar craters that may indicate the presence of water ice. In this paper, we describe the many LOLA accomplishments to date and its contribution to lunar and planetary science.

  1. Summary of the Results from the Lunar Orbiter Laser Altimeter after Seven Years in Lunar Orbit

    Science.gov (United States)

    Smith, David E.; Zuber, Maria T.; Neumann, Gregory A.; Mazarico, Erwan; Lemoine, Frank G.; Head, James W., III; Lucey, Paul G.; Aharonson, Oded; Robinson, Mark S.; Sun, Xiaoli; hide

    2016-01-01

    In June 2009 the Lunar Reconnaissance Orbiter (LRO) spacecraft was launched to the Moon. The payload consists of 7 science instruments selected to characterize sites for future robotic and human missions. Among them, the Lunar Orbiter Laser Altimeter (LOLA) was designed to obtain altimetry, surface roughness, and reflectance measurements. The primary phase of lunar exploration lasted one year, following a 3-month commissioning phase. On completion of its exploration objectives, the LRO mission transitioned to a science mission. After 7 years in lunar orbit, the LOLA instrument continues to map the lunar surface. The LOLA dataset is one of the foundational datasets acquired by the various LRO instruments. LOLA provided a high-accuracy global geodetic reference frame to which past, present and future lunar observations can be referenced. It also obtained high-resolution and accurate global topography that were used to determine regions in permanent shadow at the lunar poles. LOLA further contributed to the study of polar volatiles through its unique measurement of surface brightness at zero phase, which revealed anomalies in several polar craters that may indicate the presence of water ice. In this paper, we describe the many LOLA accomplishments to date and its contribution to lunar and planetary science.

  2. High altitude illness

    Science.gov (United States)

    Hartman-Ksycińska, Anna; Kluz-Zawadzka, Jolanta; Lewandowski, Bogumił

    High-altitude illness is a result of prolonged high-altitude exposure of unacclimatized individuals. The illness is seen in the form of acute mountain sickness (AMS) which if not treated leads to potentially life-threatening high altitude pulmonary oedema and high-altitude cerebral oedema. Medical problems are caused by hypobaric hypoxia stimulating hypoxia-inducible factor (HIF) release. As a result, the central nervous system, circulation and respiratory system function impairment occurs. The most important factor in AMS treatment is acclimatization, withdrawing further ascent and rest or beginning to descent; oxygen supplementation, and pharmacological intervention, and, if available, a portable hyperbaric chamber. Because of the popularity of high-mountain sports and tourism better education of the population at risk is essential.

  3. HIGH-TIME-RESOLUTION MEASUREMENTS OF THE POLARIZATION OF THE CRAB PULSAR AT 1.38 GHz

    Energy Technology Data Exchange (ETDEWEB)

    Słowikowska, Agnieszka [Kepler Institute of Astronomy, University of Zielona Góra, Lubuska 2, 65-265 Zielona Góra (Poland); Stappers, Benjamin W. [Jodrell Bank Centre for Astrophysics, University of Manchester, Manchester M13 9PL (United Kingdom); Harding, Alice K. [Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); O' Dell, Stephen L.; Elsner, Ronald F.; Weisskopf, Martin C. [Astrophysics Office, NASA Marshall Space Flight Center, ZP12, Huntsville, AL 35812 (United States); Van der Horst, Alexander J. [Astronomical Institute, University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands)

    2015-01-20

    Using the Westerbork Synthesis Radio Telescope, we obtained high-time-resolution measurements of the full polarization of the Crab pulsar. At a resolution of 1/8192 of the 34 ms pulse period (i.e., 4.1 μs), the 1.38 GHz linear-polarization measurements are in general agreement with previous lower-time-resolution 1.4 GHz measurements of linear polarization in the main pulse (MP), in the interpulse (IP), and in the low-frequency component (LFC). We find the MP and IP to be linearly polarized at about 24% and 21% with no discernible difference in polarization position angle. However, contrary to theoretical expectations and measurements in the visible, we find no evidence for significant variation (sweep) in the polarization position angle over the MP, the IP, or the LFC. We discuss the implications, which appear to be in contradiction to theoretical expectations. We also detect weak circular polarization in the MP and IP, and strong (≈20%) circular polarization in the LFC, which also exhibits very strong (≈98%) linear polarization at a position angle of 40° from that of the MP or IP. The properties are consistent with the LFC, which is a low-altitude component, and the MP and IP, which are high-altitude caustic components. Current models for the MP and IP emission do not readily account for the absence of pronounced polarization changes across the pulse. We measure IP and LFC pulse phases relative to the MP consistent with recent measurements, which have shown that the phases of these pulse components are evolving with time.

  4. Measurement of the Lense-Thirring drag on high-altitude, laser-ranged artificial satellites

    International Nuclear Information System (INIS)

    Ciufolini, I.

    1986-01-01

    We describe a new method of measuring the Lense-Thirring relativistic nodal drag using LAGEOS together with another high-altitude, laser-ranged, similar satellite with appropriately chosen orbital parameters. We propose, for this purpose, that a future satellite such as LAGEOS II have an inclination supplementary to that of LAGEOS. The experiment proposed here would provide a method for experimental verification of the general relativistic formulation of Mach's principle and measurement of the gravitomagnetic field

  5. Terahertz radiation by subpicosecond spin-polarized photocurrent originating from Dirac electrons in a Rashba-type polar semiconductor

    Science.gov (United States)

    Kinoshita, Yuto; Kida, Noriaki; Miyamoto, Tatsuya; Kanou, Manabu; Sasagawa, Takao; Okamoto, Hiroshi

    2018-04-01

    The spin-splitting energy bands induced by the relativistic spin-orbit interaction in solids provide a new opportunity to manipulate the spin-polarized electrons on the subpicosecond timescale. Here, we report one such example in a bulk Rashba-type polar semiconductor BiTeBr. Strong terahertz electromagnetic waves are emitted after the resonant excitation of the interband transition between the Rashba-type spin-splitting energy bands with a femtosecond laser pulse circularly polarized. The phase of the emitted terahertz waves is reversed by switching the circular polarization. This suggests that the observed terahertz radiation originates from the subpicosecond spin-polarized photocurrents, which are generated by the asymmetric depopulation of the Dirac state. Our result provides a way for the current-induced terahertz radiation and its phase control by the circular polarization of incident light without external electric fields.

  6. [Arterial hypertension due to altitude].

    Science.gov (United States)

    Domej, Wolfgang; Trapp, Michael; Miggitsch, Eva Maria; Krakher, Tiziana; Riedlbauer, Rita; Roher, Peter; Schwaberger, Günther

    2008-01-01

    The behavior of blood pressure under hypoxic conditions depends on individual factors, altitude and duration of stay at altitude. While most humans are normotensive at higher altitudes, a few will react with moderate hypertension or hypotension. Excessive elevation of arterial blood pressure is not even to be expected below 4,000 m. Rather, several weeks' stay at higher altitude will decrease systolic and diastolic blood pressure at rest as well as during physical exertion. A high-altitude treatment for rehabilitation purposes at moderate altitude may be recommended for patients with cardio-circulatory disorders. Improvements can last several months even after returning to accustomed altitudes. Furthermore, endurance-trained hypertensive patients with pharmacologically controlled arterial blood pressure might be able to participate in mountain treks without additional health risk.

  7. Objectives of a prospective Ukrainian orbiter mission to the moon

    Science.gov (United States)

    Shkuratov, Yu. G.; Lytvynenko, L. M.; Shulga, V. M.; Yatskiv, Ya. S.; Vidmachenko, A. P.; Kislyulk, V. S.

    2003-06-01

    Ukraine has launch vehicles that are able to deliver about 300 kg to lunar orbit. A future Ukrainian lunar program may propose a polar orbiter. This orbiter should fill principal information gaps in our knowledge about the Moon after the Clementine and Lunar Prospector missions and future missions like Smart-1, Lunar-A, and Selene. We consider that this can be provided by radar studies of the Moon with supporting optical photopolarimetric observations from lunar polar orbit. These experiments allow one to better understand global structure of the lunar surface at a wide range of scales, from microns to kilometers. We propose three instruments for the prospective lunar orbiter. They are a synthetic aperture imaging radar, ground-penetrating radar, and imaging UV-spectropolarimeter. The main purpose of the synthetic aperture imaging radar experiment is to study with high-resolution (50 m) permanently shadowed sites in the lunar polar regions. These sites are cold traps for volatiles, and have a potential for resource utilization. Possible presence of water ice in the regolith in the sites makes them interesting for long-term manned bases on the Moon. Radar and optical imaging and mapping of other interesting regions could be also planned. Multi-frequency, multi-polarization sounding of the lunar surface with ground-penetrating radar can provide data about internal structure of the lunar surface from meters to several hundred meters deep. The ground-penetrating radar can be used for measuring megaregolith properties, detection of cryptomaria, and studies of internal structure of the largest craters. Modest spatial resolution (50 m) of the imaging UV-spectropolarimeter should provide total coverage (or coverage of a large portion) of the lunar surface in oblique viewing at large phase angles. Polarization degree at large (>90°) phase angles bears information about characteristic size of the regolith particles. Additional experiments could use the synthetic aperture

  8. Brain Food at High Altitude.

    Science.gov (United States)

    Jain, Vishal

    2016-01-01

    Scenic view at high altitude is a pleasure to the eyes, but it has some shortcoming effects as well. High altitude can be divided into different categories, i.e., high altitude (3000-5000 ft), very high altitude (5000-8000 ft), and extreme altitude (above 8000 ft). Much of the population resides at high altitude, and others go there for tourism. Military personnel are also posted there to defend boundaries. As we ascent to high altitude, partial pressure of oxygen reduces, whereas concentration remains the same; this reduces the availability of oxygen to different body parts. This pathophysiological condition is known as hypobaric hypoxia (HH) which leads to oxidative stress and further causes cognitive dysfunction in some cases. Hypoxia causes neurodegeneration in different brain regions; however, the hippocampus is found to be more prone in comparison to other brain regions. As the hippocampus is affected most, therefore, spatial memory is impaired most during such condition. This chapter will give a brief review of the damaging effect of high altitude on cognition and also throw light on possible herbal interventions at high altitude, which can improve cognitive performance as well as provide protection against the deteriorating effect of hypobaric hypoxia at high altitude.

  9. Training at altitude in practice.

    Science.gov (United States)

    Dick, F W

    1992-10-01

    There can be little doubt that training at altitude is fundamental to preparing an athlete for competition at altitude. However the value of training at altitude for competition at sea level appears on the one hand to lack total acceptance amongst sports scientists; and on the other to hold some cloak of mystery for coaches who have yet to enjoy first hand experience. The fact is that very few endurance athletes will ignore the critical edge which altitude training affords. Each fraction of a percentage of performance advantage gained through methods which are within the rules of fair play in sport, may shift the balance between failure and achievement. Moreover, there is growing support for application of training at altitude for speed-related disciplines. This paper aims to demystify the subject by dealing with practical aspects of training at altitude. Such aspects include a checklist of what should and should not be done at altitude, when to use altitude relative to target competitions, and specific training examples.

  10. Efficient spin filtering in a disordered semiconductor superlattice in the presence of Dresselhaus spin-orbit coupling

    International Nuclear Information System (INIS)

    Khayatzadeh Mahani, Mohammad Reza; Faizabadi, Edris

    2008-01-01

    The influence of the Dresselhaus spin-orbit coupling on spin polarization by tunneling through a disordered semiconductor superlattice was investigated. The Dresselhaus spin-orbit coupling causes the spin polarization of the electron due to transmission possibilities difference between spin up and spin down electrons. The electron tunneling through a zinc-blende semiconductor superlattice with InAs and GaAs layers and two variable distance In x Ga (1-x) As impurity layers was studied. One hundred percent spin polarization was obtained by optimizing the distance between two impurity layers and impurity percent in disordered layers in the presence of Dresselhaus spin-orbit coupling. In addition, the electron transmission probability through the mentioned superlattice is too much near to one and an efficient spin filtering was recommended

  11. Photo-Induced Electron Spin Polarization in a Narrow Band Gap Semiconductor Nanostructure

    International Nuclear Information System (INIS)

    Peter, A. John; Lee, Chang Woo

    2012-01-01

    Photo-induced spin dependent electron transmission through a narrow gap InSb/InGa x Sb 1−x semiconductor symmetric well is theoretically studied using transfer matrix formulism. The transparency of electron transmission is calculated as a function of electron energy for different concentrations of gallium. Enhanced spin-polarized photon assisted resonant tunnelling in the heterostructure due to Dresselhaus and Rashba spin-orbit coupling induced splitting of the resonant level and compressed spin-polarization are observed. Our results show that Dresselhaus spin-orbit coupling is dominant for the photon effect and the computed polarization efficiency increases with the photon effect and the gallium concentration

  12. Evidence for a new geomagnetic reversal from lava flows in Idaho: discussion of short polarity reversals in the Brunhes and late Matuyama Polarity Chrons

    Science.gov (United States)

    Champion, D.E.; Lanphere, M.A.; Kuntz, M.A.

    1988-01-01

    K-Ar ages and paleomagnetic data for basalt samples from a new core hole (site E) at the Idaho National Engineering Laboratory (INEL) indicate that the age of the reversed polarity event recorded in Snake River Plain lavas is older than 465 ?? 50 ka (1000 years before present) reported previously by Champion et al. (1981). A review of data documenting short reversal records from volcanic and sedimentary rocks shows that there is evidence for eight polarity subchrons in the Brunhes and two besides the Jaramillo in the late Matuyama. These 10 short subchrons begin to indicate the many short events that Cox (1968) hypothesized must exist if polarity interval lengths have a Poisson distribution. The mean sustained polarity interval length since late Matuyama Chron time is 90 000 years. The similarity of this number with the 105-year period of the Earth's orbital eccentricity suggests anew that linkage between geomagnetic, paleoclimatic, and possible underlying Earth orbital parameters should be evaluated. -from Authors

  13. Polarization of photoelectrons produced from atoms by synchrotron radiation

    International Nuclear Information System (INIS)

    Hughes, V.W.; Lu, D.C.; Huang, K.N.

    1981-01-01

    The polarization of photoelectrons from stoms has proved to be an important tool for studying correlation effects in atoms, as well as relativistic effects such as the spin-orbit interaction. Extensive experimental and theoretical studies have been made of the Fano effect, which is the production of polarized electrons by photoionization of unpolarized atoms by circularly polarized light. The experiments have dealt mostly with alkali atoms and with photon energies slightly above the ionization thresholds. Measurements that could be made to utilize polarized radiation are discussed

  14. A Concept of Two-Stage-To-Orbit Reusable Launch Vehicle

    Science.gov (United States)

    Yang, Yong; Wang, Xiaojun; Tang, Yihua

    2002-01-01

    Reusable Launch Vehicle (RLV) has a capability of delivering a wide rang of payload to earth orbit with greater reliability, lower cost, more flexibility and operability than any of today's launch vehicles. It is the goal of future space transportation systems. Past experience on single stage to orbit (SSTO) RLVs, such as NASA's NASP project, which aims at developing an rocket-based combined-cycle (RBCC) airplane and X-33, which aims at developing a rocket RLV, indicates that SSTO RLV can not be realized in the next few years based on the state-of-the-art technologies. This paper presents a concept of all rocket two-stage-to-orbit (TSTO) reusable launch vehicle. The TSTO RLV comprises an orbiter and a booster stage. The orbiter is mounted on the top of the booster stage. The TSTO RLV takes off vertically. At the altitude about 50km the booster stage is separated from the orbiter, returns and lands by parachutes and airbags, or lands horizontally by means of its own propulsion system. The orbiter continues its ascent flight and delivers the payload into LEO orbit. After completing orbit mission, the orbiter will reenter into the atmosphere, automatically fly to the ground base and finally horizontally land on the runway. TSTO RLV has less technology difficulties and risk than SSTO, and maybe the practical approach to the RLV in the near future.

  15. OBSERVATIONS OF LINEAR POLARIZATION IN A SOLAR CORONAL LOOP PROMINENCE SYSTEM OBSERVED NEAR 6173 Å

    Energy Technology Data Exchange (ETDEWEB)

    Saint-Hilaire, Pascal; Martínez Oliveros, Juan-Carlos; Hudson, Hugh S.; Krucker, Säm; Bain, Hazel [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Schou, Jesper [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Couvidat, Sébastien, E-mail: shilaire@ssl.berkeley.edu [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States)

    2014-05-10

    White-light observations by the Solar Dynamics Observatory's Helioseismic and Magnetic Imager of a loop-prominence system occurring in the aftermath of an X-class flare on 2013 May 13 near the eastern solar limb show a linearly polarized component, reaching up to ∼20% at an altitude of ∼33 Mm, about the maximum amount expected if the emission were due solely to Thomson scattering of photospheric light by the coronal material. The mass associated with the polarized component was 8.2 × 10{sup 14} g. At 15 Mm altitude, the brightest part of the loop was 3(±0.5)% linearly polarized, only about 20% of that expected from pure Thomson scattering, indicating the presence of an additional unpolarized component at wavelengths near Fe I (617.33 nm). We estimate the free electron density of the white-light loop system to possibly be as high as 1.8 × 10{sup 12} cm{sup –3}.

  16. A comparison study between observations and simulation results of Barghouthi model for O+ and H+ outflows in the polar wind

    Directory of Open Access Journals (Sweden)

    I. A. Barghouthi

    2011-11-01

    Full Text Available To advance our understanding of the effect of wave-particle interactions on ion outflows in the polar wind region and the resulting ion heating and escape from low altitudes to higher altitudes, we carried out a comparison between polar wind simulations obtained using Barghouthi model with corresponding observations obtained from different satellites. The Barghouthi model describes O+ and H+ outflows in the polar wind region in the range 1.7 RE to 13.7 RE, including the effects of gravity, polarization electrostatic field, diverging geomagnetic field lines, and wave-particle interactions. Wave-particle interactions were included into the model by using a particle diffusion equation, which depends on diffusion coefficients determined from estimates of the typical electric field spectral density at relevant altitudes and frequencies. We provide a formula for the velocity diffusion coefficient that depends on altitude and velocity, in which the velocity part depends on the perpendicular wavelength of the electromagnetic turbulence λ⊥. Because of the shortage of information about λ⊥, it was included into the model as a parameter. We produce different simulations (i.e. ion velocity distributions, ions density, ion drift velocity, ion parallel and perpendicular temperatures for O+ and H+ ions, and for different λ⊥. We discuss the simulations in terms of wave-particle interactions, perpendicular adiabatic cooling, parallel adiabatic cooling, mirror force, and ion potential energy. The main findings of the simulations are as follows: (1 O+ ions are highly energized at all altitudes in the simulation tube due to wave-particle interactions that heat the ions in the perpendicular direction, and part of this gained energy transfer to the parallel direction by mirror force, resulting in accelerating O+ ions along geomagnetic field lines from lower altitudes to higher altitudes. (2 The effect of wave-particle interactions is negligible for H

  17. Polarization measurements of auroral kilometric radiation by Dynamics Explorer-1

    International Nuclear Information System (INIS)

    Shawhan, S.D.; Gurnett, D.A.

    1982-01-01

    The plasma wave instrument (PWI) on the Dynamics Explorer-1 has been used to measure polarization of auroral kilometric radiation (AKR) at frequencies of 50 to 400 kHz in both the northern and the southern nightside auroral regions at altitudes of 1 to 3 R/sub E/ above the AKR source regions. The AKR polarization sense is found to be the same as the right hand polarized auroral hiss found in the frequency range of 0.8 to 6.4 kHz. Consequently, these unambiguous direct polarization measurements of AKR lead to the conclusion that AKR escapes the magnetosphere in the R-X mode. Since DE-1 is close to the source region, it can be inferred that AKR is generated predominately in the R-X mode

  18. ExoMars Trace Gas Orbiter provides atmospheric data during Aerobraking into its final orbit

    Science.gov (United States)

    Svedhem, Hakan; Vago, Jorge L.; Bruinsma, Sean; Müller-Wodarg, Ingo; ExoMars 2016 Team

    2017-10-01

    After the arrival of the Trace Gas Orbiter (TGO) at Mars on 19 October 2016 a number of initial orbit change manoeuvres were executed and the spacecraft was put in an orbit with a 24 hour period and 74 degrees inclination. The spacecraft and its four instruments were thoroughly checked out after arrival and a few measurements and images were taken in November 2016 and in Feb-March 2017. The solar occultation observations have however not yet been possible due to lack of the proper geometry.On 15 March a long period of aerobraking to reach the final 400km semi-circular frozen orbit (370x430km, with a fixed pericentre latitude). This orbit is optimised for the payload observations and for the communication relay with the ExoMars Rover, due to arrive in 2021.The aerobraking is proceeding well and the final orbit is expected to be reached in April 2018. A large data set is being acquired for the upper atmosphere of Mars, from the limit of the sensitivity of the accelerometer, down to lowest altitude of the aerobraking at about 105km. Initial analysis has shown a highly variable atmosphere with a slightly lower density then predicted by existing models. Until the time of the abstract writing no dust storms have been observed.The ExoMars programme is a joint activity by the European Space Agency(ESA) and ROSCOSMOS, Russia. ESA is providing the TGO spacecraft and Schiaparelli (EDM) and two of the TGO instruments and ROSCOSMOS is providing the Proton launcher and the other two TGO instruments. After the arrival of the ExoMars 2020 mission, consisting of a Rover and a Surface platform also launched by a Proton rocket, the TGO will handle the communication between the Earth and the Rover and Surface Platform through its (NASA provided) UHF communication system.

  19. Frozen orbit realization using LQR analogy

    Science.gov (United States)

    Nagarajan, N.; Rayan, H. Reno

    In the case of remote sensing orbits, the Frozen Orbit concept minimizes altitude variations over a given region using passive means. This is achieved by establishing the mean eccentricity vector at the orbital poles i.e., by fixing the mean argument of perigee at 90 deg with an appropriate eccentricity to balance the perturbations due to zonal harmonics J2 and J3 of the Earth's potential. Eccentricity vector is a vector whose magnitude is the eccentricity and direction is the argument of perigee. The launcher dispersions result in an eccentricity vector which is away from the frozen orbit values. The objective is then to formulate an orbit maneuver strategy to optimize the fuel required to achieve the frozen orbit in the presence of visibility and impulse constraints. It is shown that the motion of the eccentricity vector around the frozen perigee can be approximated as a circle. Combining the circular motion of the eccentricity vector around the frozen point and the maneuver equation, the following discrete equation is obtained. X(k+1) = AX(k) + Bu(k), where X is the state (i.e. eccentricity vector components), A the state transition matrix, u the scalar control force (i.e. dV in this case) and B the control matrix which transforms dV into eccentricity vector change. Based on this, it is shown that the problem of optimizing the fuel can be treated as a Linear Quadratic Regulator (LQR) problem in which the maneuver can be solved by using control system design tools like MATLAB by deriving an analogy LQR design.

  20. Verification of possible asymmetry of polarization of thermal neutrons reflected by a mirror

    International Nuclear Information System (INIS)

    Okorokov, A.I.; Runov, V.V.; Gukasov, A.G.; Shchebetov, A.F.

    1976-01-01

    Experiments with a polarizing neutron guide do not confirm the neutron polarization asymmetry observed previously by Berndorfer for neutrons traversing a polarizing neutron guide. In connection with the spin-orbit effects a verification is carried out on single reflection of neutrons by magnetic or nonmagnetic mirrors. With an accuracy of 10 -4 -10 -3 no polarization asymmetry is observed

  1. Geometric phase due to orbit-orbit interaction: rotating LP11 modes in a two-mode fiber

    Science.gov (United States)

    Pradeep Chakravarthy, T.; Naik, Dinesh N.; Viswanathan, Nirmal K.

    2017-10-01

    Accumulation of geometric phase due to non-coplanar propagation of higher-order modes in an optical fiber is experimentally demonstrated. Vertically-polarized LP11 fiber mode, excited in a horizontally-held, torsion-free, step-index, two-mode optical fiber, rotates due to asymmetry in the propagating k-vectors, arising due to off-centered beam location at the fiber input. Perceiving the process as due to rotation of the fiber about the off-axis launch position, the orbital Berry phase accumulation upon scanning the launch position in a closed-loop around the fiber axis manifests as rotational Doppler effect, a consequence of orbit-orbit interaction. The anticipated phase accumulation as a function of the input launch position, observed through interferometry is connected to the mode rotation angle, quantified using the autocorrelation method.

  2. Ground Target Overflight and Orbital Maneuvering via Atmospheric Maneuvers

    Science.gov (United States)

    2014-03-27

    Total deceleration m ∙ s−2 Gravitational acceleration m ∙ s−2 ℎ Altitude m Inclination angle rad Vehicle mass kg Geocentric ...total atmospheric inclination change approached the limit of approximately 36.2° as the number of atmospheric passes increased. This inclination...determine the longitude. By expanding and simplifying Eqs. (3.1) and (3.5) for a circular orbit, the position can be written in the Geocentric Equatorial

  3. Low earth orbit radiation dose distribution in a phantom head

    International Nuclear Information System (INIS)

    Konradi, A.; Badhwar, G.D.; Cash, B.L.; Hardy, K.A.

    1992-01-01

    In order to compare analytical methods with data obtained during exposure to space radiation, a phantom head instrumented with a large number of radiation detectors was flown on the Space Shuttle on three occasions: 8 August 1989 (STS-28), 28 February 1990 (STS-36), and 24 April 1990 (STS-31). The objective of this experiment was to obtain a measurement of the inhomogeneity in the dose distribution within a phantom head volume. The orbits of these missions were complementary-STS-28 and STS-36 had high inclination and low altitude, while STS-31 had a low inclination and high altitude. In the cases of STS-28 and STS-36, the main contribution to the radiation dose comes from galactic cosmic rays (GCR) with a minor to negligible part supplied by the inner belt through the South Atlantic Anomaly (SAA), and for STS-28 an even smaller one from a proton enhancement during a solar flare-associated proton event. For STS-31, the inner belt protons dominate and the GCR contribution is almost negligible. The internal dose distribution is consistent with the mass distribution of the orbiter and the self-shielding and physical location of the phantom head. (author)

  4. Asymmetric distribution of the ionospheric electric potential in the opposite hemispheres as inferred from the SuperDARN observations and FAC-based convection model

    DEFF Research Database (Denmark)

    Lukianova, R.; Hanuise, C.; Christiansen, Freddy

    2008-01-01

    We compare the SuperDARN convection patterns with the predictions of a new numerical model of the global distribution of ionospheric electric potentials. The model utilizes high-precision statistical maps of field-aligned currents (FAC) derived from measurements made by polar-orbiting low-altitud...

  5. On the choice of orbits for an altimetric satellite to study ocean circulation and tides

    Science.gov (United States)

    Parke, Michael E.; Stewart, Robert H.; Farless, David L.; Cartwright, David E.

    1987-01-01

    The choice of an orbit for satellite altimetric studies of the ocean's circulation and tides requires an understanding of the orbital characteristics that influence the accuracy of the satellite's measurements of sea level and the temporal and spatial distribution of the measurements. The orbital characteristics that influence accurate calculations of the satellite's position as a function of time are examined, and the pattern of ground tracks laid down on the ocean's surface as a function of the satellite's altitude and inclination is studied. The results are used to examine the aliases in the measurements of surface geostrophic currents and tides. Finally, these considerations are used to specify possible orbits that may be useful for the upcoming Topex/Poseidon mission.

  6. Endurance training at altitude.

    Science.gov (United States)

    Saunders, Philo U; Pyne, David B; Gore, Christopher J

    2009-01-01

    Since the 1968 Olympic Games when the effects of altitude on endurance performance became evident, moderate altitude training ( approximately 2000 to 3000 m) has become popular to improve competition performance both at altitude and sea level. When endurance athletes are exposed acutely to moderate altitude, a number of physiological responses occur that can comprise performance at altitude; these include increased ventilation, increased heart rate, decreased stroke volume, reduced plasma volume, and lower maximal aerobic power ((.)Vo(2max)) by approximately 15% to 20%. Over a period of several weeks, one primary acclimatization response is an increase in the volume of red blood cells and consequently of (.)Vo(2max). Altitudes > approximately 2000 m for >3 weeks and adequate iron stores are required to elicit these responses. However, the primacy of more red blood cells for superior sea-level performance is not clear-cut since the best endurance athletes in the world, from Ethiopia (approximately 2000 to 3000 m), have only marginally elevated hemoglobin concentrations. The substantial reduction in (.)Vo(2max) of athletes at moderate altitude implies that their training should include adequate short-duration (approximately 1 to 2 min), high-intensity efforts with long recoveries to avoid a reduction in race-specific fitness. At the elite level, athlete performance is not dependent solely on (.)Vo(2max), and the "smallest worthwhile change" in performance for improving race results is as little as 0.5%. Consequently, contemporary statistical approaches that utilize the concept of the smallest worthwhile change are likely to be more appropriate than conventional statistical methods when attempting to understand the potential benefits and mechanisms of altitude training.

  7. Lunar true polar wander inferred from polar hydrogen.

    Science.gov (United States)

    Siegler, M A; Miller, R S; Keane, J T; Laneuville, M; Paige, D A; Matsuyama, I; Lawrence, D J; Crotts, A; Poston, M J

    2016-03-24

    The earliest dynamic and thermal history of the Moon is not well understood. The hydrogen content of deposits near the lunar poles may yield insight into this history, because these deposits (which are probably composed of water ice) survive only if they remain in permanent shadow. If the orientation of the Moon has changed, then the locations of the shadowed regions will also have changed. The polar hydrogen deposits have been mapped by orbiting neutron spectrometers, and their observed spatial distribution does not match the expected distribution of water ice inferred from present-day lunar temperatures. This finding is in contrast to the distribution of volatiles observed in similar thermal environments at Mercury's poles. Here we show that polar hydrogen preserves evidence that the spin axis of the Moon has shifted: the hydrogen deposits are antipodal and displaced equally from each pole along opposite longitudes. From the direction and magnitude of the inferred reorientation, and from analysis of the moments of inertia of the Moon, we hypothesize that this change in the spin axis, known as true polar wander, was caused by a low-density thermal anomaly beneath the Procellarum region. Radiogenic heating within this region resulted in the bulk of lunar mare volcanism and altered the density structure of the Moon, changing its moments of inertia. This resulted in true polar wander consistent with the observed remnant polar hydrogen. This thermal anomaly still exists and, in part, controls the current orientation of the Moon. The Procellarum region was most geologically active early in lunar history, which implies that polar wander initiated billions of years ago and that a large portion of the measured polar hydrogen is ancient, recording early delivery of water to the inner Solar System. Our hypothesis provides an explanation for the antipodal distribution of lunar polar hydrogen, and connects polar volatiles to the geologic and geophysical evolution of the Moon

  8. Dose-response of altitude training: how much altitude is enough?

    Science.gov (United States)

    Levine, Benjamin D; Stray-Gundersen, James

    2006-01-01

    Altitude training continues to be a key adjunctive aid for the training of competitive athletes throughout the world. Over the past decade, evidence has accumulated from many groups of investigators that the "living high--training low" approach to altitude training provides the most robust and reliable performance enhancements. The success of this strategy depends on two key features: 1) living high enough, for enough hours per day, for a long enough period of time, to initiate and sustain an erythropoietic effect of high altitude; and 2) training low enough to allow maximal quality of high intensity workouts, requiring high rates of sustained oxidative flux. Because of the relatively limited access to environments where such a strategy can be practically applied, numerous devices have been developed to "bring the mountain to the athlete," which has raised the key issue of the appropriate "dose" of altitude required to stimulate an acclimatization response and performance enhancement. These include devices using molecular sieve technology to provide a normobaric hypoxic living or sleeping environment, approaches using very high altitudes (5,500m) for shorter periods of time during the day, and "intermittent hypoxic training" involving breathing very hypoxic gas mixtures for alternating 5 minutes periods over the course of 60-90 minutes. Unfortunately, objective testing of the strategies employing short term (less than 4 hours) normobaric or hypobaric hypoxia has failed to demonstrate an advantage of these techniques. Moreover individual variability of the response to even the best of living high--training low strategies has been great, and the mechanisms behind this variability remain obscure. Future research efforts will need to focus on defining the optimal dosing strategy for these devices, and determining the underlying mechanisms of the individual variability so as to enable the individualized "prescription" of altitude exposure to optimize the performance of

  9. Effects of finite coverage on global polarization observables in heavy ion collisions

    Science.gov (United States)

    Lan, Shaowei; Lin, Zi-Wei; Shi, Shusu; Sun, Xu

    2018-05-01

    In non-central relativistic heavy ion collisions, the created matter possesses a large initial orbital angular momentum. Particles produced in the collisions could be polarized globally in the direction of the orbital angular momentum due to spin-orbit coupling. Recently, the STAR experiment has presented polarization signals for Λ hyperons and possible spin alignment signals for ϕ mesons. Here we discuss the effects of finite coverage on these observables. The results from a multi-phase transport and a toy model both indicate that a pseudorapidity coverage narrower than | η | value for the extracted ϕ-meson ρ00 parameter; thus a finite coverage can lead to an artificial deviation of ρ00 from 1/3. We also show that a finite η and pT coverage affect the extracted pH parameter for Λ hyperons when the real pH value is non-zero. Therefore proper corrections are necessary to reliably quantify the global polarization with experimental observables.

  10. Circular Orbit Target Capture Using Space Tether-Net System

    Directory of Open Access Journals (Sweden)

    Guang Zhai

    2013-01-01

    Full Text Available The space tether-net system for on-orbit capture is proposed in this paper. In order to research the dynamic behaviors during system deployment, both free and nonfree deployment dynamics in circular orbit are developed; the system motion with respect to Local Vertical and Local Horizontal frame is also researched with analysis and simulation. The results show that in the case of free deployment, the capture net follows curve trajectories due to the relative orbit dynamic perturbation, and the initial deployment velocities are planned by state transformation equations for static and floating target captures; in the case of non-free deployment, the system undergoes an altitude libration along the Local Vertical, and the analytical solutions that describe the attitude libration are obtained by using variable separation and integration. Finally, the dynamics of postdeployment system is also proved marginally stable if the critical initial conditions are satisfied.

  11. Jupiter's Magnetic Field and Magnetosphere after Juno's First 8 Orbits

    Science.gov (United States)

    Connerney, J. E. P.; Oliversen, R. J.; Espley, J. R.; Gruesbeck, J.; Kotsiaros, S.; DiBraccio, G. A.; Joergensen, J. L.; Joergensen, P. S.; Merayo, J. M. G.; Denver, T.; Benn, M.; Bjarno, J. B.; Malinnikova Bang, A.; Bloxham, J.; Moore, K.; Bolton, S. J.; Levin, S.; Gershman, D. J.

    2017-12-01

    The Juno spacecraft entered polar orbit about Jupiter on July 4, 2016, embarking upon an ambitious mission to map Jupiter's magnetic and gravitational potential fields and probe its deep atmosphere, in search of clues to the planet's formation and evolution. Juno is also instrumented to conduct the first exploration of the polar magnetosphere and to acquire images and spectra of its polar auroras and atmosphere. Juno's 53.5-day orbit trajectory carries her science instruments from pole to pole in approximately 2 hours, with a closest approach to within 1.05 Rj of the center of the planet (one Rj = 71,492 km, Jupiter's equatorial radius), just a few thousand km above the clouds. Repeated periapsis passes will eventually encircle the planet with a dense net of observations equally spaced in longitude (magnetometer sensor suites, located 10 and 12 m from the center of the spacecraft at the end of one of Juno's three solar panel wings. Each contains a vector fluxgate magnetometer (FGM) sensor and a pair of co-located non-magnetic star tracker camera heads, providing accurate attitude determination for the FGM sensors. We present an overview of the magnetometer observations obtained during Juno's first year in orbit in context with prior observations and those acquired by Juno's other science instruments.

  12. Isospin dependence of the spin-orbit splitting in nuclei

    International Nuclear Information System (INIS)

    Isakov, V.I.

    2007-01-01

    The analysis has been made of experimental data on level spectra, single-nucleon transfer reactions near closed shells, and data on polarization effects in charge-exchange (p, n) reactions between isoanalogous states of nuclei with even A. It is concluded that there is a significant difference between the spin-orbit splittings of neutrons and protons in identical orbitals. This conclusion is confirmed in the frame work of different theoretical approaches [ru

  13. Decompression to altitude: assumptions, experimental evidence, and future directions.

    Science.gov (United States)

    Foster, Philip P; Butler, Bruce D

    2009-02-01

    Although differences exist, hypobaric and hyperbaric exposures share common physiological, biochemical, and clinical features, and their comparison may provide further insight into the mechanisms of decompression stress. Although altitude decompression illness (DCI) has been experienced by high-altitude Air Force pilots and is common in ground-based experiments simulating decompression profiles of extravehicular activities (EVAs) or astronauts' space walks, no case has been reported during actual EVAs in the non-weight-bearing microgravity environment of orbital space missions. We are uncertain whether gravity influences decompression outcomes via nitrogen tissue washout or via alterations related to skeletal muscle activity. However, robust experimental evidence demonstrated the role of skeletal muscle exercise, activities, and/or movement in bubble formation and DCI occurrence. Dualism of effects of exercise, positive or negative, on bubble formation and DCI is a striking feature in hypobaric exposure. Therefore, the discussion and the structure of this review are centered on those highlighted unresolved topics about the relationship between muscle activity, decompression, and microgravity. This article also provides, in the context of altitude decompression, an overview of the role of denitrogenation, metabolic gases, gas micronuclei, stabilization of bubbles, biochemical pathways activated by bubbles, nitric oxide, oxygen, anthropometric or physiological variables, Doppler-detectable bubbles, and potential arterialization of bubbles. These findings and uncertainties will produce further physiological challenges to solve in order to line up for the programmed human return to the Moon, the preparation for human exploration of Mars, and the EVAs implementation in a non-zero gravity environment.

  14. The Gravity Field of Mars From MGS, Mars Odyssey, and MRO Radio Science

    Science.gov (United States)

    Genova, Antonio; Goossens, Sander; Lemoine, Frank G.; Mazarico, Erwan; Smith, David E.; Zuber, Maria T.

    2015-01-01

    The Mars Global Surveyor (MGS), Mars Odyssey (ODY), and Mars Reconnaissance Orbiter (MRO) missions have enabled NASA to conduct reconnaissance and exploration of Mars from orbit for sixteen consecutive years. These radio systems on these spacecraft enabled radio science in orbit around Mars to improve the knowledge of the static structure of the Martian gravitational field. The continuity of the radio tracking data, which cover more than a solar cycle, also provides useful information to characterize the temporal variability of the gravity field, relevant to the planet's internal dynamics and the structure and dynamics of the atmosphere [1]. MGS operated for more than 7 years, between 1999 and 2006, in a frozen sun-synchronous, near-circular, polar orbit with the periapsis at approximately 370 km altitude. ODY and MRO have been orbiting Mars in two separate sun-synchronous orbits at different local times and altitudes. ODY began its mapping phase in 2002 with the periapis at approximately 390 km altitude and 4-5pm Local Solar Time (LST), whereas the MRO science mission started in November 2006 with the periapis at approximately 255 km altitude and 3pm LST. The 16 years of radio tracking data provide useful information on the atmospheric density in the Martian upper atmosphere. We used ODY and MRO radio data to recover the long-term periodicity of the major atmospheric constituents -- CO2, O, and He -- at the orbit altitudes of these two spacecraft [2]. The improved atmospheric model provides a better prediction of the annual and semi-annual variability of the dominant species. Therefore, the inclusion of the recovered model leads to improved orbit determination and an improved gravity field model of Mars with MGS, ODY, and MRO radio tracking data.

  15. Spin Orbit Torque in Ferromagnetic Semiconductors

    KAUST Repository

    Li, Hang

    2016-06-21

    Electrons not only have charges but also have spin. By utilizing the electron spin, the energy consumption of electronic devices can be reduced, their size can be scaled down and the efficiency of `read\\' and `write\\' in memory devices can be significantly improved. Hence, the manipulation of electron spin in electronic devices becomes more and more appealing for the advancement of microelectronics. In spin-based devices, the manipulation of ferromagnetic order parameter using electrical currents is a very useful means for current-driven operation. Nowadays, most of magnetic memory devices are based on the so-called spin transfer torque, which stems from the spin angular momentum transfer between a spin-polarized current and the magnetic order parameter. Recently, a novel spin torque effect, exploiting spin-orbit coupling in non-centrosymmetric magnets, has attracted a massive amount of attention. This thesis addresses the nature of spin-orbit coupled transport and torques in non-centrosymmetric magnetic semiconductors. We start with the theoretical study of spin orbit torque in three dimensional ferromagnetic GaMnAs. Using the Kubo formula, we calculate both the current-driven field-like torque and anti-damping-like torque. We compare the numerical results with the analytical expressions in the model case of a magnetic Rashba two-dimensional electron gas. Parametric dependencies of the different torque components and similarities to the analytical results of the Rashba two-dimensional electron gas in the weak disorder limit are described. Subsequently we study spin-orbit torques in two dimensional hexagonal crystals such as graphene, silicene, germanene and stanene. In the presence of staggered potential and exchange field, the valley degeneracy can be lifted and we obtain a valley-dependent Berry curvature, leading to a tunable antidamping torque by controlling the valley degree of freedom. This thesis then addresses the influence of the quantum spin Hall

  16. Determination of polar cusp position by low-energy particle measurements made aboard AUREOLE satellite

    International Nuclear Information System (INIS)

    Gladyshev, V.A.; Jorjio, M.V.; Shuiskaya, F.K.; Crasnier, J.; Sauvaud, J.A.

    1974-01-01

    The Franco-Soviet experiment ARCAD, launched aboard the satellite AUREOLE December 27, 1971, has verified the existence of a particle penetration from the transition zone up to ionospheric altitudes across the polar cusp. The polar cusp is characterized by proton fluxes >10 7 particles/(cm 2 .s.sr.KeV) at 0.5KeV, with energy spectra similar to those in the transition zone. The position and form of the polar cusp are studied from measurements of protons in the range 0.4 to 30KeV during geomagnetically quiet periods (Kp [fr

  17. Bell’s measure and implementing quantum Fourier transform with orbital angular momentum of classical light

    Science.gov (United States)

    Song, Xinbing; Sun, Yifan; Li, Pengyun; Qin, Hongwei; Zhang, Xiangdong

    2015-01-01

    We perform Bell’s measurement for the non-separable correlation between polarization and orbital angular momentum from the same classical vortex beam. The violation of Bell’s inequality for such a non-separable classical correlation has been demonstrated experimentally. Based on the classical vortex beam and non-quantum entanglement between the polarization and the orbital angular momentum, the Hadamard gates and conditional phase gates have been designed. Furthermore, a quantum Fourier transform has been implemented experimentally. PMID:26369424

  18. Altitude and endurance training.

    Science.gov (United States)

    Rusko, Heikki K; Tikkanen, Heikki O; Peltonen, Juha E

    2004-10-01

    The benefits of living and training at altitude (HiHi) for an improved altitude performance of athletes are clear, but controlled studies for an improved sea-level performance are controversial. The reasons for not having a positive effect of HiHi include: (1) the acclimatization effect may have been insufficient for elite athletes to stimulate an increase in red cell mass/haemoglobin mass because of too low an altitude (altitude training period (training effect at altitude may have been compromised due to insufficient training stimuli for enhancing the function of the neuromuscular and cardiovascular systems; and (3) enhanced stress with possible overtraining symptoms and an increased frequency of infections. Moreover, the effects of hypoxia in the brain may influence both training intensity and physiological responses during training at altitude. Thus, interrupting hypoxic exposure by training in normoxia may be a key factor in avoiding or minimizing the noxious effects that are known to occur in chronic hypoxia. When comparing HiHi and HiLo (living high and training low), it is obvious that both can induce a positive acclimatization effect and increase the oxygen transport capacity of blood, at least in 'responders', if certain prerequisites are met. The minimum dose to attain a haematological acclimatization effect is > 12 h a day for at least 3 weeks at an altitude or simulated altitude of 2100-2500 m. Exposure to hypoxia appears to have some positive transfer effects on subsequent training in normoxia during and after HiLo. The increased oxygen transport capacity of blood allows training at higher intensity during and after HiLo in subsequent normoxia, thereby increasing the potential to improve some neuromuscular and cardiovascular determinants of endurance performance. The effects of hypoxic training and intermittent short-term severe hypoxia at rest are not yet clear and they require further study.

  19. Mechanically Reconfigurable Single-Arm Spiral Antenna Array for Generation of Broadband Circularly Polarized Orbital Angular Momentum Vortex Waves.

    Science.gov (United States)

    Li, Long; Zhou, Xiaoxiao

    2018-03-23

    In this paper, a mechanically reconfigurable circular array with single-arm spiral antennas (SASAs) is designed, fabricated, and experimentally demonstrated to generate broadband circularly polarized orbital angular momentum (OAM) vortex waves in radio frequency domain. With the symmetrical and broadband properties of single-arm spiral antennas, the vortex waves with different OAM modes can be mechanically reconfigurable generated in a wide band from 3.4 GHz to 4.7 GHz. The prototype of the circular array is proposed, conducted, and fabricated to validate the theoretical analysis. The simulated and experimental results verify that different OAM modes can be effectively generated by rotating the spiral arms of single-arm spiral antennas with corresponding degrees, which greatly simplify the feeding network. The proposed method paves a reconfigurable way to generate multiple OAM vortex waves with spin angular momentum (SAM) in radio and microwave satellite communication applications.

  20. South Polar Polygons

    Science.gov (United States)

    2005-01-01

    4 July 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a polgyon-cracked surface, into which deep, somewhat kidney-bean-shaped pits have formed. These are landscapes of the martian south polar residual cap. This view was captured during May 2005. Location near: 86.9oS, 5.1oW Image width: 1.5 km (0.9 mi) Illumination from: upper left Season Southern Spring

  1. Calculations of spin-polarized Goos-Hänchen displacement in magnetically confined GaAs/Al x Ga1-x As nanostructure modulated by spin-orbit couplings

    Science.gov (United States)

    Lu, Mao-Wang; Chen, Sai-Yan; Zhang, Gui-Lian; Huang, Xin-Hong

    2018-04-01

    We theoretically investigate Goos-Hänchen (GH) displacement by modelling the spin transport in an archetypal device structure—a magnetically confined GaAs/Al x Ga1-x As nanostructure modulated by spin-orbit coupling (SOC). Both Rashba and Dresselhaus SOCs are taken into account. The degree of spin-polarized GH displacement can be tuned by Rashba or Dresselhaus SOC, i.e. interfacial confining electric field or strain engineering. Based on such a semiconductor nanostructure, a controllable spatial spin splitter can be proposed for spintronics applications.

  2. Calculations of spin-polarized Goos-Hänchen displacement in magnetically confined GaAs/Al x Ga1-x As nanostructure modulated by spin-orbit couplings.

    Science.gov (United States)

    Lu, Mao-Wang; Chen, Sai-Yan; Zhang, Gui-Lian; Huang, Xin-Hong

    2018-04-11

    We theoretically investigate Goos-Hänchen (GH) displacement by modelling the spin transport in an archetypal device structure-a magnetically confined GaAs/Al x Ga 1-x As nanostructure modulated by spin-orbit coupling (SOC). Both Rashba and Dresselhaus SOCs are taken into account. The degree of spin-polarized GH displacement can be tuned by Rashba or Dresselhaus SOC, i.e. interfacial confining electric field or strain engineering. Based on such a semiconductor nanostructure, a controllable spatial spin splitter can be proposed for spintronics applications.

  3. Electron spin polarization in realistic trajectories around the magnetic node of two counter-propagating, circularly polarized, ultra-intense lasers

    Science.gov (United States)

    Del Sorbo, D.; Seipt, D.; Thomas, A. G. R.; Ridgers, C. P.

    2018-06-01

    It has recently been suggested that two counter-propagating, circularly polarized, ultra-intense lasers can induce a strong electron spin polarization at the magnetic node of the electromagnetic field that they setup (Del Sorbo et al 2017 Phys. Rev. A 96 043407). We confirm these results by considering a more sophisticated description that integrates over realistic trajectories. The electron dynamics is weakly affected by the variation of power radiated due to the spin polarization. The degree of spin polarization differs by approximately 5% if considering electrons initially at rest or already in a circular orbit. The instability of trajectories at the magnetic node induces a spin precession associated with the electron migration that establishes an upper temporal limit to the polarization of the electron population of about one laser period.

  4. Electrically tunable spin polarization in silicene: A multi-terminal spin density matrix approach

    International Nuclear Information System (INIS)

    Chen, Son-Hsien

    2016-01-01

    Recent realized silicene field-effect transistor yields promising electronic applications. Using a multi-terminal spin density matrix approach, this paper presents an analysis of the spin polarizations in a silicene structure of the spin field-effect transistor by considering the intertwined intrinsic and Rashba spin–orbit couplings, gate voltage, Zeeman splitting, as well as disorder. Coexistence of the stagger potential and intrinsic spin–orbit coupling results in spin precession, making any in-plane polarization directions reachable by the gate voltage; specifically, the intrinsic coupling allows one to electrically adjust the in-plane components of the polarizations, while the Rashba coupling to adjust the out-of-plan polarizations. Larger electrically tunable ranges of in-plan polarizations are found in oppositely gated silicene than in the uniformly gated silicene. Polarizations in different phases behave distinguishably in weak disorder regime, while independent of the phases, stronger disorder leads to a saturation value. - Highlights: • Density matrix with spin rotations enables multi-terminal arbitrary spin injections. • Gate-voltage tunable in-plane polarizations require intrinsic SO coupling. • Gate-voltage tunable out-of-plane polarizations require Rashba SO coupling. • Oppositely gated silicene yields a large tunable range of in-plan polarizations. • Polarizations in different phases behave distinguishably only in weak disorder.

  5. Polar Polygons

    Science.gov (United States)

    2005-01-01

    18 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark-outlined polygons on a frost-covered surface in the south polar region of Mars. In summer, this surface would not be bright and the polygons would not have dark outlines--these are a product of the presence of seasonal frost. Location near: 77.2oS, 204.8oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  6. TRMM On-Orbit Performance Reassessed After Control Change

    Science.gov (United States)

    Bilanow, Stephen

    2006-01-01

    The Tropical Rainfall Measuring Mission (TRMM) spacecraft, a joint mission between the U.S. and Japan, launched onboard an H-I1 rocket on November 27, 1997, and transitioned in August, 2001, from an average operating altitude of 350 kilometers to 402.5 kilometers. Due to problems using the Earth Sensor Assembly (ESA) at the higher altitude, TRMM switched to a backup attitude control mode. Prior to the orbit boost TRMM controlled pitch and roll to the local vertical using ESA measurements while using gyro data to propagate yaw attitude between yaw updates from the Sun sensors. After the orbit boost, a Kalman filter used 3-axis gyro data with Sun sensor and magnetometers to estimate onboard attitude. While originally intended to meet a degraded attitude accuracy of 0.7 degrees, the new control mode met the original 0.2 degree attitude accuracy requirement after improving onboard ephemeris prediction and adjusting the magnetometer calibration onboard. Independent roll attitude checks using a science instrument, the Precipitation Radar (PR) which was built in Japan, provided a novel insight into the pointing performance. The PR data helped identify the pointing errors after the orbit boost, track the performance improvements, and show subtle effects from ephemeris errors and gyro bias errors. It also helped identify average bias trends throughout the mission. Roll errors tracked by the PR from sample orbits pre-boost and post-boost are shown in Figure 1. Prior to the orbit boost, the largest attitude errors were due to occasional interference in the ESA. These errors were sometime larger than 0.2 degrees in pitch and roll, but usually less, as estimated from a comprehensive review of the attitude excursions using gyro data. Sudden jumps in the onboard roll show up as spikes in the reported attitude since the control responds within tens of seconds to null the pointing error. The PR estimated roll tracks well with an estimate of the roll history propagated using gyro

  7. Strong electron correlation in photoionization of spin-orbit doublets

    International Nuclear Information System (INIS)

    Amusia, M.Ya.; Chernysheva, L.V.; Manson, S.T.; Msezane, A.M.; Radojevic, V.

    2002-01-01

    A new and explicitly many-body aspect of the 'leveraging' of the spin-orbit interaction is demonstrated, spin-orbit activated interchannel coupling, which can significantly alter the photoionization cross section of a spin-orbit doublet. As an example, it is demonstrated via a modified version of the spin-polarized random phase approximation with exchange, that a recently observed unexplained structure in the Xe 3d 5/2 photoionization cross section [A. Kivimaeki et al., Phys. Rev. A 63, 012716 (2000)] is entirely due to this effect. Similar features are predicted for Cs 3d 5/2 and Ba 3d 5/2

  8. The nuclear spin-orbit coupling

    International Nuclear Information System (INIS)

    Bell, J.S.; Skyrme, T.H.R.

    1994-01-01

    Analysis of the nucleon-nucleon scattering around 100 MeV has determined the spin-orbit coupling part of the two-body scattering matrix at that energy, and a reasonable extrapolation to lower energies is possible. This scattering amplitude has been used, in the spirit of Brueckner's nuclear model, to estimate the resultant single-body spin-orbit coupling for a single nucleon interacting with a large nucleus. This resultant potential has a radial dependence approximately proportional to r -1 d ρ /dr, and with a magnitude in good agreement with that required to explain the doublet splittings in nuclei and the polarization of nucleons scattered elastically off nuclei. (author). 14 refs, 2 figs

  9. High Altitude Balloons as a Platform for Space Radiation Belt Science

    Science.gov (United States)

    Mazzino, L.; Buttenschoen, A.; Farr, Q.; Hodgson, C.; Johnson, W.; Mann, I. R.; Rae, J.; University of Alberta High Altitude Balloons (UA-HAB)

    2011-12-01

    The goals of the University of Alberta High Altitude Balloons Program (UA-HAB) are to i) use low cost balloons to address space radiation science, and ii) to utilise the excitement of "space mission" involvement to promote and facilitate the recruitment of undergraduate and graduate students in physics, engineering, and atmospheric sciences to pursue careers in space science and engineering. The University of Alberta High Altitude Balloons (UA-HAB) is a unique opportunity for University of Alberta students (undergraduate and graduate) to engage in the hands-on design, development, build, test and flight of a payload to operate on a high altitude balloon at around 30km altitude. The program development, including formal design and acceptance tests, reports and reviews, mirror those required in the development of an orbital satellite mission. This enables the students to gain a unique insight into how space missions are flown. UA-HAB is a one and half year program that offers a gateway into a high-altitude balloon mission through hands on experience, and builds skills for students who may be attracted to participate in future space missions in their careers. This early education will provide students with the experience necessary to better assess opportunities for pursuing a career in space science. Balloons offer a low-cost alternative to other suborbital platforms which can be used to address radiation belt science goals. In particular, the participants of this program have written grant proposal to secure funds for this project, have launched several 'weather balloon missions', and have designed, built, tested, and launched their particle detector called "Maple Leaf Particle Detector". This detector was focussed on monitoring cosmic rays and space radiation using shielded Geiger tubes, and was flown as one of the payloads from the institutions participating in the High Altitude Student Platform (HASP), organized by the Louisiana State University and the Louisiana

  10. Mapping Vesta Mid-Latitude Quadrangle V-12EW: Mapping the Edge of the South Polar Structure

    Science.gov (United States)

    Hoogenboom, T.; Schenk, P.; Williams, D. A.; Hiesinger, H.; Garry, W. B.; Yingst, R.; Buczkowski, D.; McCord, T. B.; Jaumann, R.; Pieters, C. M.; Gaskell, R. W.; Neukum, G.; Schmedemann, N.; Marchi, S.; Nathues, A.; Le Corre, L.; Roatsch, T.; Preusker, F.; White, O. L.; DeSanctis, C.; Filacchione, G.; Raymond, C. A.; Russell, C. T.

    2011-12-01

    NASA's Dawn spacecraft arrived at the asteroid 4Vesta on July 15, 2011, and is now collecting imaging, spectroscopic, and elemental abundance data during its one-year orbital mission. As part of the geological analysis of the surface, a series of 15 quadrangle maps are being produced based on Framing Camera images (FC: spatial resolution: ~65 m/pixel) along with Visible & Infrared Spectrometer data (VIR: spatial resolution: ~180 m/pixel) obtained during the High-Altitude Mapping Orbit (HAMO). This poster presentation concentrates on our geologic analysis and mapping of quadrangle V-12EW. This quadrangle is dominated by the arcuate edge of the large 460+ km diameter south polar topographic feature first observed by HST (Thomas et al., 1997). Sparsely cratered, the portion of this feature covered in V-12EW is characterized by arcuate ridges and troughs forming a generalized arcuate pattern. Mapping of this terrain and the transition to areas to the north will be used to test whether this feature has an impact or other (e.g., internal) origin. We are also using FC stereo and VIR images to assess whether their are any compositional differences between this terrain and areas further to the north, and image data to evaluate the distribution and age of young impact craters within the map area. The authors acknowledge the support of the Dawn Science, Instrument and Operations Teams.

  11. PoPSat: The Polar Precipitation Satellite Mission

    Science.gov (United States)

    Binder, Matthias J.; Agten, Dries; Arago-Higueras, Nadia; Borderies, Mary; Diaz-Schümmer, Carlos; Jamali, Maryam; Jimenez-Lluva, David; Kiefer, Joshua; Larsson, Anna; Lopez-Gilabert, Lola; Mione, Michele; Mould, Toby JD; Pavesi, Sara; Roth, Georg; Tomicic, Maja

    2017-04-01

    The terrestrial water cycle is one of many unique regulatory systems on planet Earth. It is directly responsible for sustaining biological life on land and human populations by ensuring sustained crop yields. However, this delicate balanced system continues to be influenced significantly by a changing climate, which has had drastic impacts particularly on the polar regions. Precipitation is a key process in the weather and climate system, due to its storage, transport and release of latent heat in the atmosphere. It has been extensively investigated in low latitudes, in which detailed models have been established for weather prediction. However, a gap has been left in higher latitudes above 65°, which show the strongest response to climate changes and where increasing precipitations have been foreseen in the future. In order to establish a global perspective of atmospheric processes, space observation of high-latitude areas is crucial to produce globally consistent data. The increasing demand for those data has driven a critical need to devise a mission which fills the gaps in current climate models. The authors propose the Polar Precipitation Satellite (PoPSat), an innovative satellite mission to provide enhanced observation of light and medium precipitation, focusing on snowfall and light rain in high latitudes. PoPSat is the first mission aimed to provide high resolution 3D structural information about snow and light precipitation systems and cloud structure in the covered areas. The satellite is equipped with a dual band (Ka and W band) phased-array radar. These antennas provide a horizontal resolution of 2 km and 4 km respectively which will exceed all other observations made to date at high-latitudes, while providing the additional capability to monitor snowfall. The data gathered will be compatible and complementary with measurements made during previous missions. PoPSat has been designed to fly on a sun-synchronous, dawn-dusk orbit at 460 km. This orbit

  12. Rashba and Dresselhaus spin-orbit coupling effects on tunnelling through two-dimensional magnetic quantum systems

    International Nuclear Information System (INIS)

    Xu Wen; Guo Yong

    2005-01-01

    We investigate the influence of the Rashba and Dresselhaus spin-orbit coupling interactions on tunnelling through two-dimensional magnetic quantum systems. It is showed that not only Rashba spin-orbit coupling but also Dresselhaus one can affect spin tunnelling properties greatly in such a quantum system. The transmission possibility, the spin polarization and the conductance are obviously oscillated with both coupling strengths. High spin polarization, conductance and magnetic conductance of the structure can be obtained by modulating either Rashba or Dresselhaus coupling strength

  13. High-altitude and high-latitude O+ and H+ outflows: the effect of finite electromagnetic turbulence wavelength

    Directory of Open Access Journals (Sweden)

    I. A. Barghouthi

    2007-11-01

    Full Text Available The energization of ions, due to interaction with electromagnetic turbulence (i.e. wave-particle interactions, has an important influence on H+ and O+ ions outflows in the polar region. The effects of altitude and velocity dependent wave-particle interaction on H+ and O+ ions outflows in the auroral region were investigated by using Monte Carlo method. The Monte Carlo simulation included the effects of altitude and velocity dependent wave-particle interaction, gravity, polarization electrostatic field, and divergence of auroral geomagnetic field within the simulation tube (1.2–10 earth radii, RE. As the ions are heated due to wave-particle interactions (i.e. ion interactions with electromagnetic turbulence and move to higher altitudes, the ion gyroradius ρi may become comparable to the electromagnetic turbulence wavelength λ⊥ and consequently (k⊥ρi becomes larger than unity. This turns the heating rate to be negligible and the motion of the ions is described by using Liouville theorem. The main conclusions are as follows: (1 the formation of H+ and O+ conics at lower altitudes and for all values of λ⊥; (2 O+ toroids appear at 3.72 RE, 2.76 RE and 2 RE, for λ⊥=100, 10, and 1 km, respectively; however, H+ toroids appear at 6.6 RE, 4.4 RE and 3 RE, for λ⊥=100, 10, and 1 km, respectively; and H+ and O+ ion toroids did not appear for the case λ⊥ goes to infinity, i.e. when the effect of velocity dependent wave-particle interaction was not included; (3 As λ⊥ decreases, H+ and O+ ion drift velocity decreases, H+ and O+ ion density increases, H+ and O+ ion perpendicular temperature and H+ and O+ ion parallel temperature decrease; (4 Finally, including the effect of finite electromagnetic turbulence wavelength, i.e. the effect of velocity dependent diffusion coefficient and consequently, the velocity dependent wave-particle interactions produce realistic H+ and O+ ion temperatures and H+ and O+ toroids, and this is, qualitatively

  14. Lunar Topography: Results from the Lunar Orbiter Laser Altimeter

    Science.gov (United States)

    Neumann, Gregory; Smith, David E.; Zuber, Maria T.; Mazarico, Erwan

    2012-01-01

    The Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter (LRO) has been operating nearly continuously since July 2009, accumulating over 6 billion measurements from more than 2 billion in-orbit laser shots. LRO's near-polar orbit results in very high data density in the immediate vicinity of the lunar poles, with full coverage at the equator from more than 12000 orbital tracks averaging less than 1 km in spacing at the equator. LRO has obtained a global geodetic model of the lunar topography with 50-meter horizontal and 1-m radial accuracy in a lunar center-of-mass coordinate system, with profiles of topography at 20-m horizontal resolution, and 0.1-m vertical precision. LOLA also provides measurements of reflectivity and surface roughness down to its 5-m laser spot size. With these data LOLA has measured the shape of all lunar craters 20 km and larger. In the proposed extended mission commencing late in 2012, LOLA will concentrate observations in the Southern Hemisphere, improving the density of the polar coverage to nearly 10-m pixel resolution and accuracy to better than 20 m total position error. Uses for these data include mission planning and targeting, illumination studies, geodetic control of images, as well as lunar geology and geophysics. Further improvements in geodetic accuracy are anticipated from the use of re ned gravity fields after the successful completion of the Gravity Recovery and Interior Laboratory (GRAIL) mission in 2012.

  15. Spin Polarization Inversion at Benzene-Absorbed Fe4N Surface

    KAUST Repository

    Zhang, Qian; Mi, Wenbo; Wang, Xiaocha; Wang, Xuhui

    2015-01-01

    We report a first-principle study on electronic structure and simulation of the spin-polarized scanning tunneling microscopy graphic of a benzene/Fe4N interface. Fe4N is a compound ferromagnet suitable for many spintronic applications. We found that, depending on the particular termination schemes and interface configurations, the spin polarization on the benzene surface shows a rich variety of properties ranging from cosine-type oscillation to polarization inversion. Spin-polarization inversion above benzene is resulting from the hybridizations between C pz and the out-of-plane d orbitals of Fe atom.

  16. Spin Polarization Inversion at Benzene-Absorbed Fe4N Surface

    KAUST Repository

    Zhang, Qian

    2015-05-27

    We report a first-principle study on electronic structure and simulation of the spin-polarized scanning tunneling microscopy graphic of a benzene/Fe4N interface. Fe4N is a compound ferromagnet suitable for many spintronic applications. We found that, depending on the particular termination schemes and interface configurations, the spin polarization on the benzene surface shows a rich variety of properties ranging from cosine-type oscillation to polarization inversion. Spin-polarization inversion above benzene is resulting from the hybridizations between C pz and the out-of-plane d orbitals of Fe atom.

  17. Spin and charge controlled by antisymmetric spin-orbit coupling in a triangular-triple-quantum-dot Kondo system

    Science.gov (United States)

    Koga, M.; Matsumoto, M.; Kusunose, H.

    2018-05-01

    We study a local antisymmetric spin-orbit (ASO) coupling effect on a triangular-triple-quantum-dot (TTQD) system as a theoretical proposal for a new application of the Kondo physics to nanoscale devices. The electric polarization induced by the Kondo effect is strongly correlated with the spin configurations and molecular orbital degrees of freedom in the TTQD. In particular, an abrupt sign reversal of the emergent electric polarization is associated with a quantum critical point in a magnetic field, which can also be controlled by the ASO coupling that changes the mixing weight of different orbital components in the TTQD ground state.

  18. Energy conversion evolution at lunar polar sites

    Indian Academy of Sciences (India)

    robotic and human surface bases. Sunlight is nearly ... orientation and precession of its spin axis rela- tive to its orbit ... atoms, most likely hydrogen, that many people immediately .... to find out the real meaning of the excess polar hydrogen.

  19. Non-perturbative calculation of equilibrium polarization of stored electron beams

    International Nuclear Information System (INIS)

    Yokoya, Kaoru.

    1992-05-01

    Stored electron/positron beams polarize spontaneously owing to the spin-flip synchrotron radiation. In the existing computer codes, the degree of the equilibrium polarization has been calculated using perturbation expansions in terms of the orbital oscillation amplitudes. In this paper a new numerical method is presented which does not employ the perturbation expansion. (author)

  20. Numerical Algorithms for Precise and Efficient Orbit Propagation and Positioning

    Science.gov (United States)

    Bradley, Ben K.

    orbit propagation, yielding savings in computation time and memory. Orbit propagation and position transformation simulations are analyzed to generate a complete set of recommendations for performing the ITRS/GCRS transformation for a wide range of needs, encompassing real-time on-board satellite operations and precise post-processing applications. In addition, a complete derivation of the ITRS/GCRS frame transformation time-derivative is detailed for use in velocity transformations between the GCRS and ITRS and is applied to orbit propagation in the rotating ITRS. EOP interpolation methods and ocean tide corrections are shown to impact the ITRS/GCRS transformation accuracy at the level of 5 cm and 20 cm on the surface of the Earth and at the Global Positioning System (GPS) altitude, respectively. The precession-nutation and EOP simplifications yield maximum propagation errors of approximately 2 cm and 1 m after 15 minutes and 6 hours in low-Earth orbit (LEO), respectively, while reducing computation time and memory usage. Finally, for orbit propagation in the ITRS, a simplified scheme is demonstrated that yields propagation errors under 5 cm after 15 minutes in LEO. This approach is beneficial for orbit determination based on GPS measurements. We conclude with a summary of recommendations on EOP usage and bias-precession-nutation implementations for achieving a wide range of transformation and propagation accuracies at several altitudes. This comprehensive set of recommendations allows satellite operators, astrodynamicists, and scientists to make informed decisions when choosing the best implementation for their application, balancing accuracy and computational complexity.

  1. Sediment volume in the north polar sand seas of Mars

    International Nuclear Information System (INIS)

    Lancaster, N.; Greeley, R.

    1990-01-01

    Data from studies of the cross-sectional area of terrestrial transverse dunes have been combined with maps of dune morphometry derived from Viking orbiter images to generate new estimates of sediment thickness and dune sediment volume in the north polar sand seas of Mars. A relationship between dune spacing and equivalent sediment thickness (EST) was developed from field data on Namibian and North American dunes and was applied to data on dune spacing and dune cover measured on Viking orbiter images to generate maps of dune sediment thickness for Martian north polar sand seas. There are four major sand seas in the north polar region of Mars, covering an area of 6.8 x 10 5 km 2 . Equivalent sediment thickness ranges between 0.5 and 6.1 m with a mean of 1.8 m. The sand seas contain a total of 1158 km 3 of dune sediment, which may have been derived by erosion of polar layered deposits and concentrated in its present location by winds that change direction seasonally

  2. Enhanced optical spin current injection in the hexagonal lattice with intrinsic and Rashba spin–orbit interactions

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Jianfei, E-mail: zoujianfei@hhu.edu.cn; Tang, Chunmei; Zhang, Aimei

    2017-04-04

    We study the photo-induced spin current injection in a hexagonal lattice with both intrinsic and Rashba spin–orbit interactions which is irradiated by a polarized light beam. It is found that the spin current injection rate could be enhanced as the graphene lattice is in the topological insulator state. Furthermore, the spin current injection rate could be remarkably modulated by the degree of polarization of light and its frequency. - Highlights: • The optical spin current could be enhanced by the intrinsic spin–orbit interaction. • The optical spin current could be modulated by the degree of polarization of light. • The maximum of the spin current injection rate is obtained.

  3. Precise Orbital and Geodetic Parameter Estimation using SLR Observations for ILRS AAC

    Directory of Open Access Journals (Sweden)

    Young-Rok Kim

    2013-12-01

    Full Text Available In this study, we present results of precise orbital geodetic parameter estimation using satellite laser ranging (SLR observations for the International Laser Ranging Service (ILRS associate analysis center (AAC. Using normal point observations of LAGEOS-1, LAGEOS-2, ETALON-1, and ETALON-2 in SLR consolidated laser ranging data format, the NASA/ GSFC GEODYN II and SOLVE software programs were utilized for precise orbit determination (POD and finding solutions of a terrestrial reference frame (TRF and Earth orientation parameters (EOPs. For POD, a weekly-based orbit determination strategy was employed to process SLR observations taken from 20 weeks in 2013. For solutions of TRF and EOPs, loosely constrained scheme was used to integrate POD results of four geodetic SLR satellites. The coordinates of 11 ILRS core sites were determined and daily polar motion and polar motion rates were estimated. The root mean square (RMS value of post-fit residuals was used for orbit quality assessment, and both the stability of TRF and the precision of EOPs by external comparison were analyzed for verification of our solutions. Results of post-fit residuals show that the RMS of the orbits of LAGEOS-1 and LAGEOS-2 are 1.20 and 1.12 cm, and those of ETALON-1 and ETALON-2 are 1.02 and 1.11 cm, respectively. The stability analysis of TRF shows that the mean value of 3D stability of the coordinates of 11 ILRS core sites is 7.0 mm. An external comparison, with respect to International Earth rotation and Reference systems Service (IERS 08 C04 results, shows that standard deviations of polar motion Xp and Yp are 0.754 milliarcseconds (mas and 0.576 mas, respectively. Our results of precise orbital and geodetic parameter estimation are reasonable and help advance research at ILRS AAC.

  4. Lunar ranging instrument for Chandrayaan-1

    Indian Academy of Sciences (India)

    ... Committee on Scientific Values · Project Lifescape · Scientific Data of Public Interest ... Lunar Laser Ranging Instrument (LLRI)proposed for the first Indian lunar ... field by precisely measuring the altitude from a polar orbit around the Moon. ... Laboratory for Electro-Optics Systems, Indian Space Research Organization ...

  5. Light-induced spin polarizations in quantum rings

    NARCIS (Netherlands)

    Joibari, F.K.; Blanter, Y.M.; Bauer, G.E.W.

    2014-01-01

    Nonresonant circularly polarized electromagnetic radiation can exert torques on magnetizations by the inverse Faraday effect (IFE). Here, we discuss the enhancement of IFE by spin-orbit interactions. We illustrate the principle by studying a simple generic model system, i.e., the

  6. Comparison of the MIPAS products obtained by four different level 2 processors

    Directory of Open Access Journals (Sweden)

    Piera Raspollini

    2014-01-01

    Full Text Available MIPAS is a midinfrared Fourier Transform spectrometer that sounded the atmospheric emission at limb onboard the ENVISAT satellite. It was launched on 31 March 2002 in a sun-synchronous polar orbit of about 800 km altitude and operated until 8 April 2012. The limb scanning sequence observed by the instrument is made of spectra that sound the atmosphere at different tangent altitudes (the tangent altitude is the minimum altitude reached by the line of sight and is also the altitude from where most of the observed signal originates. The inversion of the measurements allows the determination of the vertical profiles of the atmospheric quantities of interest in the range of the tangent altitudes covered by the limb scanning sequence, which is 6-70 km for the nominal measurement mode. […

  7. Variation in aerodynamic coefficients with altitude

    Directory of Open Access Journals (Sweden)

    Faiza Shahid

    Full Text Available Precise aerodynamics performance prediction plays key role for a flying vehicle to get its mission completed within desired accuracy. Aerodynamic coefficients for same Mach number can be different at different altitude due to difference in Reynolds number. Prediction of these aerodynamics coefficients can be made through experiments, analytical solution or Computational Fluid Dynamics (CFD. Advancements in computational power have generated the concept of using CFD as a virtual Wind Tunnel (WT, hence aerodynamic performance prediction in present study is based upon CFD (numerical test rig. Simulations at different altitudes for a range of Mach numbers with zero angle of attack are performed to predict axial force coefficient behavior with altitude (Reynolds number. Similar simulations for a fixed Mach number ‘3’ and a range of angle of attacks are also carried out to envisage the variation in normal force and pitching moment coefficients with altitude (Reynolds number. Results clearly depict that the axial force coefficient is a function of altitude (Reynolds number and increase as altitude increases, especially for subsonic region. Variation in axial force coefficient with altitude (Reynolds number slightly increases for larger values of angle of attacks. Normal force and pitching moment coefficients do not depend on altitude (Reynolds number at smaller values of angle of attacks but show slight decrease as altitude increases. Present study suggests that variation of normal force and pitching moment coefficients with altitude can be neglected but the variation of axial force coefficient with altitude should be considered for vehicle fly in dense atmosphere. It is recommended to continue this study to more complex configurations for various Mach numbers with side slip and real gas effects. Keywords: Mach number, Reynolds number, Blunt body, Altitude effect, Angle of attacks

  8. Injection of a microsatellite in circular orbits using a three-stage launch vehicle

    Science.gov (United States)

    Marchi, L. O.; Murcia, J. O.; Prado, A. F. B. A.; Solórzano, C. R. H.

    2017-10-01

    The injection of a satellite into orbit is usually done by a multi-stage launch vehicle. Nowadays, the space market demonstrates a strong tendency towards the use of smaller satellites, because the miniaturization of the systems improve the cost/benefit of a mission. A study to evaluate the capacity of the Brazilian Microsatellite Launch Vehicle (VLM) to inject payloads into Low Earth Orbits is presented in this paper. All launches are selected to be made to the east side of the Alcântara Launch Center (CLA). The dynamical model to calculate the trajectory consists of the three degrees of freedom (3DOF) associated with the translational movement of the rocket. Several simulations are performed according to a set of restrictions imposed to the flight. The altitude reached in the separation of the second stage, the altitude and velocity of injection, the flight path angle at the moment of the activation of the third stage and the duration of the ballistic flight are presented as a function of the payload carried.

  9. Comparative DMFT study of the eg-orbital Hubbard model in thin films

    Science.gov (United States)

    Rüegg, Andreas; Hung, Hsiang-Hsuan; Gull, Emanuel; Fiete, Gregory A.

    2014-02-01

    Heterostructures of transition-metal oxides have emerged as a new route to engineer electronic systems with desired functionalities. Motivated by these developments, we study a two-orbital Hubbard model in a thin-film geometry confined along the cubic [001] direction using the dynamical mean-field theory. We contrast the results of two approximate impurity solvers (exact diagonalization and one-crossing approximation) to the results of the numerically exact continuous-time quantum Monte Carlo solver. Consistent with earlier studies, we find that the one-crossing approximation performs well in the insulating regime, while the advantage of the exact-diagonalization-based solver is more pronounced in the metallic regime. We then investigate various aspects of strongly correlated eg-orbital systems in thin-film geometries. In particular, we show how the interfacial orbital polarization dies off quickly a few layers from the interface and how the film thickness affects the location of the interaction-driven Mott transition. In addition, we explore the changes in the electronic structure with varying carrier concentration and identify large variations of the orbital polarization in the strongly correlated regime.

  10. Cassini UVIS Observations of Saturn during the Grand Finale Orbits

    Science.gov (United States)

    Pryor, W. R.; Esposito, L. W.; West, R. A.; Jouchoux, A.; Radioti, A.; Grodent, D. C.; Gerard, J. C. M. C.; Gustin, J.; Lamy, L.; Badman, S. V.

    2017-12-01

    In 2016 and 2017, the Cassini Saturn orbiter executed a final series of high inclination, low-periapsis orbits ideal for studies of Saturn's polar regions. The Cassini Ultraviolet Imaging Spectrograph (UVIS) obtained an extensive set of auroral images, some at the highest spatial resolution obtained during Cassini's long orbital mission (2004-2017). In some cases, two or three spacecraft slews at right angles to the long slit of the spectrograph were required to cover the entire auroral region to form auroral images. We will present selected images from this set showing narrow arcs of emission, more diffuse auroral emissions, multiple auroral arcs in a single image, discrete spots of emission, small scale vortices, large-scale spiral forms, and parallel linear features that appear to cross in places like twisted wires. Some shorter features are transverse to the main auroral arcs, like barbs on a wire. UVIS observations were in some cases simultaneous with auroral observations from the Hubble Space Telescope Space Telescope Imaging Spectrograph (STIS) that will also be presented. UVIS polar images also contain spectral information suitable for studies of the auroral electron energy distribution. The long wavelength part of the UVIS polar images contains a signal from reflected sunlight containing absorption signatures of acetylene and other Saturn hydrocarbons. The hydrocarbon spatial distribution will also be examined.

  11. Radiation doses at high altitudes and during space flights

    International Nuclear Information System (INIS)

    Spurny, F.

    2001-01-01

    There are three main sources of radiation exposure during space flights and at high altitudes--galactic cosmic radiation, solar cosmic radiation and radiation of the earth's radiation belt. Their basic characteristics are presented in the first part of this paper.Man's exposure during space flights is discussed in the second part of the paper. Particular attention is devoted to the quantitative and qualitative characteristics of the radiation exposure on near-earth orbits: both theoretical estimation as well as experimental data are presented. Some remarks on radiation protection rules on-board space vehicles are also given.The problems connected with the radiation protection of air crew and passengers of subsonic and supersonic air transport are discussed in the last part of the paper. General characteristics of on-board radiation fields and their variations with flight altitude, geomagnetic parameters of a flight and the solar activity are presented, both based on theoretical estimates and experimental studies. The questions concerning air crew and passenger radiation protection arising after the publication of ICRP 60 recommendation are also discussed. Activities of different institutions relevant to the topic are mentioned; strategies to manage and check this type of radiation exposure are presented and discussed. Examples of results based on the author's personal experience are given, analyzed and discussed. (author)

  12. The Impact of Altitude on Sleep-Disordered Breathing in Children Dwelling at High Altitude: A Crossover Study.

    Science.gov (United States)

    Hughes, Benjamin H; Brinton, John T; Ingram, David G; Halbower, Ann C

    2017-09-01

    Sleep-disordered breathing (SDB) is prevalent among children and is associated with adverse health outcomes. Worldwide, approximately 250 million individuals reside at altitudes higher than 2000 meters above sea level (masl). The effect of chronic high-altitude exposure on children with SDB is unknown. This study aims to determine the impact of altitude on sleep study outcomes in children with SDB dwelling at high altitude. A single-center crossover study was performed to compare results of high-altitude home polysomnography (H-PSG) with lower altitude laboratory polysomnography (L-PSG) in school-age children dwelling at high altitude with symptoms consistent with SDB. The primary outcome was apnea-hypopnea index (AHI), with secondary outcomes including obstructive AHI; central AHI; and measures of oxygenation, sleep quality, and pulse rate. Twelve participants were enrolled, with 10 included in the final analysis. Median altitude was 1644 masl on L-PSG and 2531 masl on H-PSG. Median AHI was 2.40 on L-PSG and 10.95 on H-PSG. Both obstructive and central respiratory events accounted for the difference in AHI. Oxygenation and sleep fragmentation were worse and pulse rate higher on H-PSG compared to L-PSG. These findings reveal a clinically substantial impact of altitude on respiratory, sleep, and cardiovascular outcomes in children with SDB who dwell at high altitude. Within this population, L-PSG underestimates obstructive sleep apnea and central sleep apnea compared to H-PSG. Given the shortage of high-altitude pediatric sleep laboratories, these results suggest a role for home sleep apnea testing for children residing at high altitude. © Sleep Research Society 2017. Published by Oxford University Press on behalf of the Sleep Research Society. All rights reserved. For permissions, please e-mail journals.permissions@oup.com.

  13. Dynamics and Morphology of Saturn’s North Polar Region During Cassini’s Final Year

    Science.gov (United States)

    Blalock, John J.; Sayanagi, Kunio M.; Ingersoll, Andrew P.; Dyudina, Ulyana A.; Ewald, Shawn; McCabe, Ryan M.; Gunnarson, Jacob; Garland, Justin; Gallego, Angelina

    2017-10-01

    We present an analysis of Saturn’s north polar region utilizing Cassini ISS images captured in visible and near-infrared wavelengths during late 2016 and 2017, including images captured during Cassini’s Grand Finale orbits. To measure the wind field in the region, we utilize the two-dimensional correlation imaging velocimetry (CIV) technique. We also calculate the relative vorticity and divergence from the wind field. To detect changes in the dynamics, we compare measurements of the wind, relative vorticity, and divergence in 2012 and 2013 with those from 2016/2017. We also compare cloud reflectivity between 2012/2013 and 2016/2017 in images that show the north pole under similar illumination conditions. To detect changes in cloud reflectivity, we utilize a Minnaert correction to calculate the zonal mean reflectivity as a function of latitude. Furthermore, we compare the winds and cloud reflectivity at several wavelengths in order to look for changes occurring at different altitudes. Our results indicate that while the dynamics of the north polar region have remained relatively stable, there have been significant morphology changes that have resulted in dramatic color changes. We hypothesize that these changes are a result of the seasonal cycle and linked to the increased production of photochemical hazes in the atmosphere. Our work has been supported by NASA PATM NNX14AK07G, NSF AAG 1212216, and NASA NESSF NNX15AQ70H.

  14. Variation in aerodynamic coefficients with altitude

    Science.gov (United States)

    Shahid, Faiza; Hussain, Mukkarum; Baig, Mirza Mehmood; Haq, Ihtram ul

    Precise aerodynamics performance prediction plays key role for a flying vehicle to get its mission completed within desired accuracy. Aerodynamic coefficients for same Mach number can be different at different altitude due to difference in Reynolds number. Prediction of these aerodynamics coefficients can be made through experiments, analytical solution or Computational Fluid Dynamics (CFD). Advancements in computational power have generated the concept of using CFD as a virtual Wind Tunnel (WT), hence aerodynamic performance prediction in present study is based upon CFD (numerical test rig). Simulations at different altitudes for a range of Mach numbers with zero angle of attack are performed to predict axial force coefficient behavior with altitude (Reynolds number). Similar simulations for a fixed Mach number '3' and a range of angle of attacks are also carried out to envisage the variation in normal force and pitching moment coefficients with altitude (Reynolds number). Results clearly depict that the axial force coefficient is a function of altitude (Reynolds number) and increase as altitude increases, especially for subsonic region. Variation in axial force coefficient with altitude (Reynolds number) slightly increases for larger values of angle of attacks. Normal force and pitching moment coefficients do not depend on altitude (Reynolds number) at smaller values of angle of attacks but show slight decrease as altitude increases. Present study suggests that variation of normal force and pitching moment coefficients with altitude can be neglected but the variation of axial force coefficient with altitude should be considered for vehicle fly in dense atmosphere. It is recommended to continue this study to more complex configurations for various Mach numbers with side slip and real gas effects.

  15. Tunnelling of orbital angular momentum in parallel optical waveguides

    International Nuclear Information System (INIS)

    Alexeyev, C N; Fadeyeva, T A; Yavorsky, M A; Boklag, N A

    2011-01-01

    We study the evolution of circularly polarized optical vortices (OVs) in the system of two coupled few-mode optical fibres. We demonstrate that upon propagation OVs tunnel into the adjacent fibre as a complex superposition of OVs that comprise also OVs of opposite polarization and topological charge. The initial OV may tunnel into the other fibre as the same vortex state of lesser energy. The evolution of the orbital angular momentum in coupled fibres is studied

  16. Use and Protection of GPS Sidelobe Signals for Enhanced Navigation Performance in High Earth Orbit

    Science.gov (United States)

    Parker, Joel J. K.; Valdez, Jennifer E.; Bauer, Frank H.; Moreau, Michael C.

    2016-01-01

    GPS (Global Positioning System) Space Service Volume (SSV) signal environment is from 3,000-36,000 kilometers altitude. Current SSV specifications only capture performance provided by signals transmitted within 23.5(L1) or 26(L2-L5) off-nadir angle. Recent on-orbit data lessons learned show significant PNT (Positioning, Navigation and Timing) performance improvements when the full aggregate signal is used. Numerous military civil operational missions in High Geosynchronous Earth Orbit (HEOGEO) utilize the full signal to enhance vehicle PNT performance

  17. An interstellar origin for Jupiter's retrograde co-orbital asteroid

    Science.gov (United States)

    Namouni, F.; Morais, M. H. M.

    2018-06-01

    Asteroid (514107) 2015 BZ509 was discovered recently in Jupiter's co-orbital region with a retrograde motion around the Sun. The known chaotic dynamics of the outer Solar system have so far precluded the identification of its origin. Here, we perform a high-resolution statistical search for stable orbits and show that asteroid (514107) 2015 BZ509 has been in its current orbital state since the formation of the Solar system. This result indicates that (514107) 2015 BZ509 was captured from the interstellar medium 4.5 billion years in the past as planet formation models cannot produce such a primordial large-inclination orbit with the planets on nearly coplanar orbits interacting with a coplanar debris disc that must produce the low-inclination small-body reservoirs of the Solar system such as the asteroid and Kuiper belts. This result also implies that more extrasolar asteroids are currently present in the Solar system on nearly polar orbits.

  18. High Altitude and Heart

    Directory of Open Access Journals (Sweden)

    Murat Yalcin

    2011-04-01

    Full Text Available Nowadays, situations associated with high altitude such as mountaineering, aviation increasingly draw the attention of people. Gas pressure decreases and hypoxia is encountered when climbing higher. Physiological and pathological responses of human body to different heights are different. Therefore, physiological and pathological changes that may occur together with height and to know the clinical outcomes of these are important . Acute mountain sickness caused by high altitude and high altitude cerebral edema are preventable diseases with appropriate precautions. Atmospheric oxygen decreasing with height, initiates many adaptive mechanisms. These adaptation mechanisms and acclimatization vary widely among individuals because of reasons such as environmental factors, exercise and cold. High altitude causes different changes in the cardiovascular system with various mechanisms. Although normal individuals easily adapt to these changes, this situation can lead to undesirable results in people with heart disease. For this reason, it should be known the effective evaluation of the people with known heart disease before traveling to high altitude and the complications due to the changes with height and the recommendations can be made to these patients. [TAF Prev Med Bull 2011; 10(2.000: 211-222

  19. The EUMETSAT Polar System - Second Generation (EPS-SG) micro-wave imaging (MWI) mission

    Science.gov (United States)

    Bojkov, B. R.; Accadia, C.; Klaes, D.; Canestri, A.; Cohen, M.

    2017-12-01

    The EUMETSAT Polar System (EPS) will be followed by a second generation system called EPS-SG. This new family of missions will contribute to the Joint Polar System being jointly set up with NOAA in the timeframe 2020-2040. These satellites will fly, like Metop (EPS), in a sun synchronous, low earth orbit at 830 km altitude and 09:30 local time descending node, providing observations over the full globe with revisit times of 12 hours. EPS-SG consists of two different satellites configurations, the EPS-SGa series dedicated to IR and MW sounding, and the EPS-SGb series dedicated to microwave imaging and scatterometry. The EPS-SG family will consist of three successive launches of each satellite-type. The Microwave Imager (MWI) will be hosted on Metop-SGb series of satellites, with the primary objective of supporting Numerical Weather Prediction (NWP) at regional and global scales. Other applications will be observation of surface parameters such as sea ice concentration and hydrology applications. The 18 MWI instrument frequencies range from 18.7 GHz to 183 GHz. All MWI channels up to 89 GHz will measure V- and H polarizations. The MWI was also designed to provide continuity of measurements for select heritage microwave imager channels (e.g. SSM/I, AMSR-E). The additional sounding channels such as the 50-55 and 118 GHz bands will provide additional cloud and precipitation information over sea and land. This combination of channels was successfully tested on the NPOESS Aircraft Sounder Testbed - Microwave Sounder (NAST-M) airborne radiometer, and it is the first time that will be implemented in a conical scanning configuration in a single instrument. An overview of the EPS-SG programme and the MWI instrument will be presented.

  20. Acute high-altitude sickness

    Directory of Open Access Journals (Sweden)

    Andrew M. Luks

    2017-02-01

    Full Text Available At any point 1–5 days following ascent to altitudes ≥2500 m, individuals are at risk of developing one of three forms of acute altitude illness: acute mountain sickness, a syndrome of nonspecific symptoms including headache, lassitude, dizziness and nausea; high-altitude cerebral oedema, a potentially fatal illness characterised by ataxia, decreased consciousness and characteristic changes on magnetic resonance imaging; and high-altitude pulmonary oedema, a noncardiogenic form of pulmonary oedema resulting from excessive hypoxic pulmonary vasoconstriction which can be fatal if not recognised and treated promptly. This review provides detailed information about each of these important clinical entities. After reviewing the clinical features, epidemiology and current understanding of the pathophysiology of each disorder, we describe the current pharmacological and nonpharmacological approaches to the prevention and treatment of these diseases.

  1. Polar2Grid 2.0: Reprojecting Satellite Data Made Easy

    Science.gov (United States)

    Hoese, D.; Strabala, K.

    2015-12-01

    Polar-orbiting multi-band meteorological sensors such as those on the Suomi National Polar-orbiting Partnership (SNPP) satellite pose substantial challenges for taking imagery the last mile to forecast offices, scientific analysis environments, and the general public. To do this quickly and easily, the Cooperative Institute for Meteorological Satellite Studies (CIMSS) at the University of Wisconsin has created an open-source, modular application system, Polar2Grid. This bundled solution automates tools for converting various satellite products like those from VIIRS and MODIS into a variety of output formats, including GeoTIFFs, AWIPS compatible NetCDF files, and NinJo forecasting workstation compatible TIFF images. In addition to traditional visible and infrared imagery, Polar2Grid includes three perceptual enhancements for the VIIRS Day-Night Band (DNB), as well as providing the capability to create sharpened true color, sharpened false color, and user-defined RGB images. Polar2Grid performs conversions and projections in seconds on large swaths of data. Polar2Grid is currently providing VIIRS imagery over the Continental United States, as well as Alaska and Hawaii, from various Direct-Broadcast antennas to operational forecasters at the NOAA National Weather Service (NWS) offices in their AWIPS terminals, within minutes of an overpass of the Suomi NPP satellite. Three years after Polar2Grid development started, the Polar2Grid team is now releasing version 2.0 of the software; supporting more sensors, generating more products, and providing all of its features in an easy to use command line interface.

  2. The orbital inclination of A0620 - 00 measured polarimetrically

    International Nuclear Information System (INIS)

    Dolan, J.F.; Tapia, S.

    1989-01-01

    The mass of the degenerate primary in A0620 - 00 is inferred from its spectroscopic mass function to be not less than 3.2 solar masses, making it an excellent candidate for a black hole. The exact value of the mass depends on the orbital inclination. The inclination of a binary system can be determined from the shape of its Stokes parameter light curves if the linear polarization of the system varies as a function of orbital phase. A0620 - 00 over one 8-hour binary period was observed with the 4.5-m equivalent MMT. Its polarization in the visible is variable with orbital phase. The standard theory of Brown et al. (1978) was used to derive an orbital inclination of i = 57 deg (+20 deg, -50 deg), where the error is the 90-percent confidence interval. An inclination of i = 57 deg corresponds to a mass of the compact primary of 6.6 solar masses, but the large uncertainty in the measured value of the inclination allows the derived mass of A0620 - 00 to be as low as 3.8 solar masses. If this is taken to be the maximum mass of any degenerate configuration consistent with general relativity except a black hole, then the mass of A0620 - 00 is still not well enough determined to conclude that it must be a black hole. 21 refs

  3. Certification and safety aspects relating to the transport of passengers on high altitude balloons in Europe

    Science.gov (United States)

    Schoenmaker, Annelie

    2014-07-01

    High-altitude balloons typically fly between 25 and 50 km in altitude, which, while below the Karman line of 100 km, is yet far above the altitudes typically flown by aircraft. For example, the highest-flying commercial aircraft - the Concorde - had a maximum cruising altitude of only 18 km. zero2infinity, a Spanish company, is currently developing a pressurized pod named “bloon” which will be capable of lifting six people, including two pilot crew members and four paying passengers, to an altitude of 36 km through the use of high-altitude balloons. The boundary between Airspace and Outer Space has never been legally defined, mostly because of the lack of activities taking place between the altitude where airplanes fly and the lowest orbiting spacecraft. High-altitude balloons do fly at these in-between altitudes and the prospect of commercializing access to these parts of the stratosphere poses some questions in a new light. Given the relatively low altitude at which they fly, it may well be that these types of balloons would be considered to operate exclusively within air space. However, given the technology involved in crewed high altitude balloon flights, which is more similar to spacecraft engineering than to traditional hot-air or gas ballooning, it is necessary to evaluate the various legal regimes, codes, and regulations that would apply to such flights, especially regarding licenses and liabilities. For high altitude balloon flights commencing in Europe, the European Aviation Safety Agency (EASA) would very likely be the competent certification or licensing agency for these flights, although there would likely be input from various national aviation authorities as well. However, because the European Commission (EC) has not yet issued regulations regarding commercial spaceflight, particularly the use of high altitude balloons, new rules and regulations governing such flights may still need to be drafted and promulgated. With the development of

  4. Spin-Hall conductivity and electric polarization in metallic thin films

    KAUST Repository

    Wang, Xuhui

    2013-02-21

    We predict theoretically that when a normal metallic thin film (without bulk spin-orbit coupling, such as Cu or Al) is sandwiched by two insulators, two prominent effects arise due to the interfacial spin-orbit coupling: a giant spin-Hall conductivity due to the surface scattering and a transverse electric polarization due to the spin-dependent phase shift in the spinor wave functions.

  5. Spin-Hall conductivity and electric polarization in metallic thin films

    KAUST Repository

    Wang, Xuhui; Xiao, Jiang; Manchon, Aurelien; Maekawa, Sadamichi

    2013-01-01

    We predict theoretically that when a normal metallic thin film (without bulk spin-orbit coupling, such as Cu or Al) is sandwiched by two insulators, two prominent effects arise due to the interfacial spin-orbit coupling: a giant spin-Hall conductivity due to the surface scattering and a transverse electric polarization due to the spin-dependent phase shift in the spinor wave functions.

  6. Upward continuation of Dome-C airborne gravity and comparison with GOCE gradients at orbit altitude in east Antarctica

    DEFF Research Database (Denmark)

    Yildiz, Hasan; Forsberg, René; Tscherning, Carl Christian

    2017-01-01

    spherical harmonic models confirmed the quality of the airborne data and that they contain more high-frequency signal than the global models. First, the airborne gravity data were upward continued to GOCE altitude to predict gravity gradients in the local North-East-Up reference frame. In this step...

  7. Reliable retrieval of atmospheric and aquatic parameters in coastal and inland environments from polar-orbiting and geostationary platforms: challenges and opportunities

    Science.gov (United States)

    Stamnes, Knut; Li, Wei; Lin, Zhenyi; Fan, Yongzhen; Chen, Nan; Gatebe, Charles; Ahn, Jae-Hyun; Kim, Wonkook; Stamnes, Jakob J.

    2017-04-01

    Simultaneous retrieval of aerosol and surface properties by means of inverse techniques based on a coupled atmosphere-surface radiative transfer model, neural networks, and optimal estimation can yield considerable improvements in retrieval accuracy in complex aquatic environments compared with traditional methods. Remote sensing of such environments represent specific challenges due (i) the complexity of the atmosphere and water inherent optical properties, (ii) unique bidirectional dependencies of the water-leaving radiance, and (iii) the desire to do retrievals for large solar zenith and viewing angles. We will discuss (a) how challenges related to atmospheric gaseous absorption, absorbing aerosols, and turbid waters can be addressed by using a coupled atmosphere-surface radiative transfer (forward) model in the retrieval process, (b) how the need to correct for bidirectional effects can be accommodated in a systematic and reliable manner, (c) how polarization information can be utilized, (d) how the curvature of the atmosphere can be taken into account, and (e) how neural networks and optimal estimation can be used to obtain fast yet accurate retrievals. Special emphasis will be placed on how information from existing and future sensors deployed on polar-orbiting and geostationary platforms can be obtained in a reliable and accurate manner. The need to provide uncertainty assessments and error budgets will also be discussed.

  8. Photoinduced quantum spin and valley Hall effects, and orbital magnetization in monolayer MoS2

    KAUST Repository

    Tahir, M.

    2014-09-22

    We theoretically demonstrate that 100% valley-polarized transport in monolayers of MoS2 and other group-VI dichalcogenides can be obtained using off-resonant circularly polarized light. By tuning the intensity of the off-resonant light the intrinsic band gap in one valley is reduced, while it is enhanced in the other valley, enabling single valley quantum transport. As a consequence, we predict (i) enhancement of the longitudinal electrical conductivity, accompanied by an increase in the spin polarization of the flowing electrons, (ii) enhancement of the intrinsic spin Hall effect, together with a reduction of the intrinsic valley Hall effect, and (iii) enhancement of the orbital magnetic moment and orbital magnetization. These mechanisms provide appealing opportunities to the design of nanoelectronics based on dichalcogenides.

  9. Photoinduced quantum spin and valley Hall effects, and orbital magnetization in monolayer MoS2

    KAUST Repository

    Tahir, M.; Manchon, Aurelien; Schwingenschlö gl, Udo

    2014-01-01

    We theoretically demonstrate that 100% valley-polarized transport in monolayers of MoS2 and other group-VI dichalcogenides can be obtained using off-resonant circularly polarized light. By tuning the intensity of the off-resonant light the intrinsic band gap in one valley is reduced, while it is enhanced in the other valley, enabling single valley quantum transport. As a consequence, we predict (i) enhancement of the longitudinal electrical conductivity, accompanied by an increase in the spin polarization of the flowing electrons, (ii) enhancement of the intrinsic spin Hall effect, together with a reduction of the intrinsic valley Hall effect, and (iii) enhancement of the orbital magnetic moment and orbital magnetization. These mechanisms provide appealing opportunities to the design of nanoelectronics based on dichalcogenides.

  10. Earth Observatory Satellite system definition study. Report 1: Orbit/launch vehicle trade-off studies and recommendations

    Science.gov (United States)

    1974-01-01

    A summary of the constraints and requirements on the Earth Observatory Satellite (EOS-A) orbit and launch vehicle analysis is presented. The propulsion system (hydrazine) and the launch vehicle (Delta 2910) selected for EOS-A are examined. The rationale for the selection of the recommended orbital altitude of 418 nautical miles is explained. The original analysis was based on the EOS-A mission with the Thematic Mapper and the High Resolution Pointable Imager. The impact of the revised mission model is analyzed to show how the new mission model affects the previously defined propulsion system, launch vehicle, and orbit. A table is provided to show all aspects of the EOS multiple mission concepts. The subjects considered include the following: (1) mission orbit analysis, (2) spacecraft parametric performance analysis, (3) launch system performance analysis, and (4) orbits/launch vehicle selection.

  11. Rarefied-flow pitching moment coefficient measurements of the Shuttle Orbiter

    Science.gov (United States)

    Blanchard, R. C.; Hinson, E. W.

    1988-01-01

    An overview of the process for obtaining the Shuttle Orbiter rarefied-flow pitching moment from flight gyro data is presented. The extraction technique involves differentiation of the output of the pitch gyro after accounting for nonaerodynamic torques, such as those produced by gravity gradient and the Orbiter's auxiliary power unit and adjusting for drift biases. The overview of the extraction technique includes examples of results from each of the steps involved in the process, using the STS-32 mission as a typical sample case. The total pitching moment and moment coefficient (Cm) for that flight are calculated and compared with preflight predictions. The flight results show the anticipated decrease in Cm with increasing altitude. However, the total moment coefficient is less than predicted using preflight estimates.

  12. Polarization in free electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Papadichev, V.A. [Lebedev Physical Institute, Moscow (Russian Federation)

    1995-12-31

    Polarization of electromagnetic radiation is required very often in numerous scientific and industrial applications: studying of crystals, molecules and intermolecular interaction high-temperature superconductivity, semiconductors and their transitions, polymers and liquid crystals. Using polarized radiation allows to obtain important data (otherwise inaccessible) in astrophysics, meteorology and oceanology. It is promising in chemistry and biology for selective influence on definite parts of molecules in chain synthesis reactions, precise control of various processes at cell and subcell levels, genetic engineering etc. Though polarization methods are well elaborated in optics, they can fail in far-infrared, vacuum-ultraviolet and X-ray regions because of lack of suitable non-absorbing materials and damaging of optical elements at high specific power levels. Therefore, it is of some interest to analyse polarization of untreated FEL radiation obtained with various types of undulators, with and without axial magnetic field. The polarization is studied using solutions for electron orbits in various cases: plane or helical undulator with or without axial magnetic field, two plane undulators, a combination of right- and left-handed helical undulators with equal periods, but different field amplitudes. Some examples of how a desired polarization (elliptical circular or linear) can be obtained or changed quickly, which is necessary in many experiments, are given.

  13. High-altitude pulmonary hypertension

    Directory of Open Access Journals (Sweden)

    X-Q. Xu

    2009-03-01

    Full Text Available High-altitude pulmonary hypertension (HAPH is a specific disease affecting populations that live at high elevations. The prevalence of HAPH among those residing at high altitudes needs to be further defined. Whereas reduction in nitric oxide production may be one mechanism for the development of HAPH, the roles of endothelin-1 and prostaglandin I2 pathways in the pathogenesis of HAPH deserve further study. Although some studies have suggested that genetic factors contribute to the pathogenesis of HAPH, data published to date are insufficient for the identification of a significant number of gene polymorphims in HAPH. The clinical presentation of HAPH is nonspecific. Exertional dyspnoea is the most common symptom and signs related to right heart failure are common in late stages of HAPH. Echocardiography is the most useful screening tool and right heart catheterisation is the gold standard for the diagnosis of HAPH. The ideal management for HAPH is migration to lower altitudes. Phosphodiesterase 5 is an attractive drug target for the treatment of HAPH. In addition, acetazolamide is a promising therapeutic agent for high-altitude pulmonary hypertension. To date, no evidence has confirmed whether endothelin-receptor antagonists have efficacy in the treatment of high-altitude pulmonary hypertension.

  14. Creating intense polarized electron beam via laser stripping and spin-orbit interaction

    International Nuclear Information System (INIS)

    Danilov, V.; Ptitsyn, V.; Gorlov, T.

    2010-01-01

    The recent advance in laser field make it possible to excite and strip electrons with definite spin from hydrogen atoms. The sources of hydrogen atoms with orders of magnitude higher currents (than that of the conventional polarized electron cathods) can be obtained from H - sources with good monochromatization. With one electron of H - stripped by a laser, the remained electron is excited to upper state (2P 3/2 and 2P 1/2 ) by a circular polarization laser light from FEL. Then, it is excited to a high quantum number (n=7) with mostly one spin direction due to energy level split of the states with a definite direction of spin and angular momentum in an applied magnetic field and then it is stripped by a strong electric field of an RF cavity. This paper presents combination of lasers and fields to get high polarization and high current electron source.

  15. Mineralogy and Iron Content of the Lunar Polar Regions Using the Kaguya Spectral Profiler and the Lunar Orbiter Laser Altimeter

    Science.gov (United States)

    Lemelin, M.; Lucey, P. G.; Trang, D.; Jha, K.

    2016-12-01

    The lunar polar regions are of high scientific interest, but the extreme lighting conditions have made quantitative analyses using reflectance spectra difficult; some regions are in permanent shadow, and flat surfaces are difficult to correct photometrically due to the extreme grazing incidence and low signal available. Thus, most mineral maps derived from visible and near infrared reflectance spectra have been constrained to within 50° in latitude. The mineralogy of the polar regions, or 44% of the lunar surface, is almost entirely unknown. A few studies have provided compositional analysis based on the spectral shape (where strong absorption bands were present) of lithologies dominated by one or two minerals. In this study, we take a novel approach and use strong signal and well-calibrated reflectance acquired by two different instruments, the Kaguya Spectra Profiler (SP) and the Lunar Orbiter Laser Altimeter (LOLA), in order to derive the first FeO and mineral maps of the polar regions at a spatial resolution of 1 km per pixel. We use reflectance ratios from SP and calibrated reflectance data from LOLA to derive the first polar maps of FeO, which are within 2 wt.% of the FeO measured by the Lunar Prospector Gamma-Ray spectrometer up to 85° in latitude. We then use the reflectance data from SP and Hapke radiative transfer model to compute the abundance of olivine, low-calcium pyroxene, high-calcium pyroxene and plagioclase, using FeO as a constraint. The radiative transfer model yields an error in mineral abundances of 9 wt.%. We use the mineral maps to study the composition of 27 central peaks and 5 basin rings in the polar regions, and relate their composition to their depth of origin in the lunar crust. We find that the central peaks and basin rings in Feldspathic Highlands Terrane are mostly anorthositic in composition, with modal plagioclase content ranging between 66 and 92 wt.%. The central peaks and basin rings in the South Pole-Aitken basin are noritic

  16. A correlative study of simultaneously measured He(++) fluxes in the solar wind and in the magnetosphere utilizing Imp-1 and 1971-089A satellite data

    Science.gov (United States)

    Shelley, E. G.

    1975-01-01

    Simultaneously measured He(++) fluxes in the solar wind and in the magnetosphere were studied using data from the plasma spectrometer on the Imp I satellite and the energetic ion mass spectrometer on the low altitude polar orbiting satellite 1971-89A. A detailed comparison of the He(++) energy spectra measured simultaneously in the solar wind and in the low altitude dayside polar cusp on March 7, 1972 was made. The energy-per-unit-charge range of the energetic ion mass spectrometer on board the polar orbiting satellite was 700 eV to 12 keV. Within this range there was a clear maximum in the He(++) energy spectrum at approximately 1.5 keV/nucleon. There was not a clearly defined maximum in the H(+) spectrum, but the data were consistent with a peak between 0.7 and 1.0 keV/nucleon. Both spectra could be reasonably well fit with a convecting Maxwellian plus a high energy tail; however, the mean velocity for He(++) distribution was significantly greater than that for the H(+) distribution. The simultaneous solar wind measurements showed the mean velocities for both ion species to be approximately 600 km/sec. The discrepancies between the relative velocity distributions in the low altitude cusp and those in the solar wind are consistent with a potential difference of approximately 1.4 kV along their flow direction between the two points of observation.

  17. Role of spin polarization in FM/Al/FM trilayer film at low temperature

    Science.gov (United States)

    Lu, Ning; Webb, Richard

    2014-03-01

    Measurements of electronic transport in diffusive FM/normal metal/FM trilayer film are performed at temperature ranging from 2K to 300K to determine the behavior of the spin polarized current in normal metal under the influence of quantum phase coherence and spin-orbital interaction. Ten samples of Hall bar with length of 200 micron and width of 20 micron are fabricated through e-beam lithography followed by e-gun evaporation of Ni0.8Fe0.2, aluminum and Ni0.8Fe0.2 with different thickness (5nm to 45nm) in vacuum. At low temperature of 4.2K, coherent backscattering, Rashba spin-orbital interaction and spin flip scattering of conduction electrons contribute to magnetoresistance at low field. Quantitative analysis of magnetoresistance shows transition between weak localization and weak anti-localization for samples with different thickness ratio, which indicates the spin polarization actually affects the phase coherence length and spin-orbital scattering length. However, at temperature between 50K and 300K, only the spin polarization dominates the magnetoresistance.

  18. Development, Demonstration and Validation of the Deep Space Orbit Determination Software Using Lunar Prospector Tracking Data

    Directory of Open Access Journals (Sweden)

    Eunji Lee

    2017-09-01

    Full Text Available The deep space orbit determination software (DSODS is a part of a flight dynamic subsystem (FDS for the Korean Pathfinder Lunar Orbiter (KPLO, a lunar exploration mission expected to launch after 2018. The DSODS consists of several sub modules, of which the orbit determination (OD module employs a weighted least squares algorithm for estimating the parameters related to the motion and the tracking system of the spacecraft, and subroutines for performance improvement and detailed analysis of the orbit solution. In this research, DSODS is demonstrated and validated at lunar orbit at an altitude of 100 km using actual Lunar Prospector tracking data. A set of a priori states are generated, and the robustness of DSODS to the a priori error is confirmed by the NASA planetary data system (PDS orbit solutions. Furthermore, the accuracy of the orbit solutions is determined by solution comparison and overlap analysis as about tens of meters. Through these analyses, the ability of the DSODS to provide proper orbit solutions for the KPLO are proved.

  19. Uncertainty Requirement Analysis for the Orbit, Attitude, and Burn Performance of the 1st Lunar Orbit Insertion Maneuver

    Directory of Open Access Journals (Sweden)

    Young-Joo Song

    2016-12-01

    Full Text Available In this study, the uncertainty requirements for orbit, attitude, and burn performance were estimated and analyzed for the execution of the 1st lunar orbit insertion (LOI maneuver of the Korea Pathfinder Lunar Orbiter (KPLO mission. During the early design phase of the system, associate analysis is an essential design factor as the 1st LOI maneuver is the largest burn that utilizes the onboard propulsion system; the success of the lunar capture is directly affected by the performance achieved. For the analysis, the spacecraft is assumed to have already approached the periselene with a hyperbolic arrival trajectory around the moon. In addition, diverse arrival conditions and mission constraints were considered, such as varying periselene approach velocity, altitude, and orbital period of the capture orbit after execution of the 1st LOI maneuver. The current analysis assumed an impulsive LOI maneuver, and two-body equations of motion were adapted to simplify the problem for a preliminary analysis. Monte Carlo simulations were performed for the statistical analysis to analyze diverse uncertainties that might arise at the moment when the maneuver is executed. As a result, three major requirements were analyzed and estimated for the early design phase. First, the minimum requirements were estimated for the burn performance to be captured around the moon. Second, the requirements for orbit, attitude, and maneuver burn performances were simultaneously estimated and analyzed to maintain the 1st elliptical orbit achieved around the moon within the specified orbital period. Finally, the dispersion requirements on the B-plane aiming at target points to meet the target insertion goal were analyzed and can be utilized as reference target guidelines for a mid-course correction (MCC maneuver during the transfer. More detailed system requirements for the KPLO mission, particularly for the spacecraft bus itself and for the flight dynamics subsystem at the ground

  20. Altitude Stress During Participation of Medical Congress

    Science.gov (United States)

    Kim, Soon Bae; Kim, Jong Sung; Kim, Sang Jun; Cho, Su Hee

    2016-01-01

    Medical congresses often held in highlands. We reviewed several medical issues associated with altitude stress especially while physicians have participated medical congress held in high altitude. Altitude stress, also known as an acute mountain sickness (AMS), is caused by acute exposure to low oxygen level at high altitude which is defined as elevations at or above 1,200 m and AMS commonly occurs above 2,500 m. Altitude stress with various symptoms including insomnia can also be experienced in airplane. AMS and drunken state share many common features in symptoms, neurologic manifestations and even show multiple microbleeds in corpus callosum and white matter on MRI. Children are more susceptible to altitude stress than adults. Gradual ascent is the best method for the prevention of altitude stress. Adequate nutrition (mainly carbohydrates) and hydration are recommended. Consumption of alcohol can exacerbate the altitude-induced impairments in judgment and the visual senses and promote psychomotor dysfunction. For prevention or treatment of altitude stress, acetazolamide, phosphodiesterase inhibitors, dexamethasone and erythropoietin are helpful. Altitude stress can be experienced relatively often during participation of medical congress. It is necessary to remind the harmful effect of AMS because it can cause serious permanent organ damage even though the symptoms are negligible in most cases. PMID:27621942

  1. Lessons learned after one year in space for the AAUSAT3 satellite

    DEFF Research Database (Denmark)

    Larsen, Jesper Abildgaard; Mortensen, Hans Peter; Jessen, Troels

    2014-01-01

    The AAUSAT3 satellite is a 1U cubesat, which has been developed by students at Aalborg University, Denmark in collaboration with the Danish Maritime Authority. The satellite was launched into a polar DD-SSO orbit of 800 km altitude on February 25th 2013 on a mission to monitor ships from space...

  2. Performance of portable ventilators at altitude.

    Science.gov (United States)

    Blakeman, Thomas; Britton, Tyler; Rodriquez, Dario; Branson, Richard

    2014-09-01

    Aeromedical transport of critically ill patients requires continued, accurate performance of equipment at altitude. Changes in barometric pressure can affect the performance of mechanical ventilators calibrated for operation at sea level. Deploying ventilators that can maintain a consistent tidal volume (VT) delivery at various altitudes is imperative for lung protection when transporting wounded war fighters to each echelon of care. Three ventilators (Impact 731, Hamilton T1, and CareFusion Revel) were tested at pediatric (50 and 100 mL) and adult (250-750 mL) tidal VTs at 0 and 20 cm H₂O positive end expiratory pressure and at inspired oxygen of 0.21 and 1.0. Airway pressure, volume, and flow were measured at sea level as well as at 8,000, 16,000, and 22,000 ft (corresponding to barometric pressures of 760, 564, 412, and 321 mm Hg) using a calibrated pneumotachograph connected to a training test lung in an altitude chamber. Set VT and delivered VT as well as changes in VT at each altitude were compared by t test. The T1 delivered VT within 10% of set VT at 8,000 ft. The mean VT was less than set VT at sea level as a result of circuit compressible volume with the Revel and the 731. Changes in VT varied widely among the devices at sea level and at altitude. Increasing altitudes resulted in larger VT than set for the Revel and the T1. The 731 compensated for changes in altitude delivered VT within 10% at the adult settings at all altitudes. Altitude compensation is an active software algorithm. Only the 731 actively accounts for changes in barometric pressure to maintain the set VT at all tested altitudes.

  3. The world state of orbital debris measurements and modeling

    Science.gov (United States)

    Johnson, Nicholas L.

    2004-02-01

    For more than 20 years orbital debris research around the world has been striving to obtain a sharper, more comprehensive picture of the near-Earth artificial satellite environment. Whereas significant progress has been achieved through better organized and funded programs and with the assistance of advancing technologies in both space surveillance sensors and computational capabilities, the potential of measurements and modeling of orbital debris has yet to be realized. Greater emphasis on a systems-level approach to the characterization and projection of the orbital debris environment would prove beneficial. On-going space surveillance activities, primarily from terrestrial-based facilities, are narrowing the uncertainties of the orbital debris population for objects greater than 2 mm in LEO and offer a better understanding of the GEO regime down to 10 cm diameter objects. In situ data collected in LEO is limited to a narrow range of altitudes and should be employed with great care. Orbital debris modeling efforts should place high priority on improving model fidelity, on clearly and completely delineating assumptions and simplifications, and on more thorough sensitivity studies. Most importantly, however, greater communications and cooperation between the measurements and modeling communities are essential for the efficient advancement of the field. The advent of the Inter-Agency Space Debris Coordination Committee (IADC) in 1993 has facilitated this exchange of data and modeling techniques. A joint goal of these communities should be the identification of new sources of orbital debris.

  4. Polarization dependent effects in photo-fragmentation dynamics of free molecules

    International Nuclear Information System (INIS)

    Mocellin, A.; Marinho, R.R.T.; Coutinho, L.H.; Burmeister, F.; Wiesner, K.; Naves de Brito, A.

    2003-01-01

    We present multicoincidence spectra of nitrogen, formic acid and methyl methacrylate. We demonstrate how to probe the local symmetry of molecular orbitals from molecules core excited with linearly polarized synchrotron radiation. The intensity distribution of the photoelectron photo-ion photo-ion coincidence (PEPIPICO) spectrum reflects the selectivity and localization of core excitation by polarized light. By simulating the spectra the angular dependence of the fragmentation is determined

  5. Polarization dependent effects in photo-fragmentation dynamics of free molecules

    Energy Technology Data Exchange (ETDEWEB)

    Mocellin, A.; Marinho, R.R.T.; Coutinho, L.H.; Burmeister, F.; Wiesner, K.; Naves de Brito, A

    2003-04-01

    We present multicoincidence spectra of nitrogen, formic acid and methyl methacrylate. We demonstrate how to probe the local symmetry of molecular orbitals from molecules core excited with linearly polarized synchrotron radiation. The intensity distribution of the photoelectron photo-ion photo-ion coincidence (PEPIPICO) spectrum reflects the selectivity and localization of core excitation by polarized light. By simulating the spectra the angular dependence of the fragmentation is determined.

  6. Spin-polarized photoemission from SiGe heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Ferrari, A.; Bottegoni, F.; Isella, G.; Cecchi, S.; Chrastina, D.; Finazzi, M.; Ciccacci, F. [LNESS-Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)

    2013-12-04

    We apply the principles of Optical Orientation to measure by Mott polarimetry the spin polarization of electrons photoemitted from different group-IV heterostructures. The maximum measured spin polarization, obtained from a Ge/Si{sub 0.31}Ge{sub 0.69} strained film, undoubtedly exceeds the maximum value of 50% attainable in bulk structures. The explanation we give for this result lies in the enhanced band orbital mixing between light hole and split-off valence bands as a consequence of the compressive strain experienced by the thin Ge layer.

  7. Classifying spaces of degenerating polarized Hodge structures

    CERN Document Server

    Kato, Kazuya

    2009-01-01

    In 1970, Phillip Griffiths envisioned that points at infinity could be added to the classifying space D of polarized Hodge structures. In this book, Kazuya Kato and Sampei Usui realize this dream by creating a logarithmic Hodge theory. They use the logarithmic structures begun by Fontaine-Illusie to revive nilpotent orbits as a logarithmic Hodge structure. The book focuses on two principal topics. First, Kato and Usui construct the fine moduli space of polarized logarithmic Hodge structures with additional structures. Even for a Hermitian symmetric domain D, the present theory is a refinem

  8. Cardiovascular Effects of Altitude on Performance Athletes.

    Science.gov (United States)

    Shah, Ankit B; Coplan, Neil

    Altitude plays an important role in cardiovascular performance and training for athletes. Whether it is mountaineers, skiers, or sea-level athletes trying to gain an edge by training or living at increased altitude, there are many potential benefits and harms of such endeavors. Echocardiographic studies done on athletes at increased altitude have shown evidence for right ventricular dysfunction and pulmonary hypertension, but no change in left ventricular ejection fraction. In addition, 10% of athletes are susceptible to pulmonary hypertension and high-altitude pulmonary edema. Some studies suggest that echocardiography may be able to identify athletes susceptible to high-altitude pulmonary edema prior to competing or training at increased altitudes. Further research is needed on the long-term effects of altitude training, as repeated, transient episodes of pulmonary hypertension and right ventricular dysfunction may have long-term implications. Current literature suggests that performance athletes are not at higher risk for ventricular arrhythmias when training or competing at increased altitudes. For sea-level athletes, the optimal strategy for attaining the benefits while minimizing the harms of altitude training still needs to be clarified, although-for now-the "live high, train low" approach appears to have the most rationale.

  9. Investigating fundamental physics and space environment with a dedicated Earth-orbiting spacecraft

    Science.gov (United States)

    Peron, Roberto

    -year requirement and thus they need specific arrangements for deorbiting at the end of life or they can simply rely on mother nature for reentry. The goal of this proposed approach is to utilize existing technology developed for acceleration measurement in space and state-of-the-art satellite tracking to precisely determine the orbit of a satellite with well-defined geometrical and mass characteristics (i.e., (A/m) ratio), at the same time accurately measuring over a long period of time the drag deceleration (as well as others non-gravitational effects) acting on the satellite. This will result in a virtually drag-free object that can be exploited to: 1. perform fundamental physics tests by verifying the equation of motion of a test mass in the general relativistic context and placing limits to alternative theories of gravitation; 2. improve the knowledge of selected tidal terms; 3. map, through acceleration measurements, the atmospheric density in the orbital region of interest. In its preliminary incarnation, the satellite would be cylindrical in shape and spinning about its cylinder axis that would be also orthogonal to the orbital plane. The satellite should be placed on a dawn-dusk, sun-synchronous, elliptical orbit spanning the orbital altitudes of interest (e.g., between 500 and 1200 km of altitude). The satellite should be equipped with a 3-axis accelerometer package with an acceleration resolution better than (10^{-11} g) (with (g) the acceleration at the Earth's surface). The expected measurement range is (10^{-8} - 10^{-11} g) considering estimates of drag forces at minimum and maximum solar activity conditions in the altitude range of interest and a preliminary estimate of the satellite (A/m) ratio. The overall concept of the mission will be discussed, concentrating on the fundamental aspects and main scientific return. The main instrumentation to be hosted on-board the spacecraft will be then reviewed, with a focus on current and projected capabilities.

  10. The polarized electron beam at ELSA

    International Nuclear Information System (INIS)

    Hoffmann, M.; Drachenfels, W. von; Frommberger, F.; Gowin, M.; Hillert, W.; Husmann, D.; Keil, J.; Helbing, K.; Michel, T.; Naumann, J.; Speckner, T.; Zeitler, G.

    2001-01-01

    The future medium energy physics program at the electron stretcher accelerator ELSA of Bonn University mainly relies on experiments using polarized electrons in the energy range from 1 to 3.2 GeV. To provide a polarized beam with high polarization and sufficient intensity a dedicated source has been developed and set into operation. To prevent depolarization during acceleration in the circular accelerators several depolarizing resonances have to be corrected for. Intrinsic resonances are compensated using two pulsed betatron tune jump quadrupoles. The influence of imperfection resonances is successfully reduced applying a dynamic closed orbit correction in combination with an empirical harmonic correction on the energy ramp. In order to minimize beam depolarization, both types of resonances and the correction techniques have been studied in detail. It turned out that the polarization in ELSA can be conserved up to 2.5 GeV and partially up to 3.2 GeV which is demonstrated by measurements using a Moeller polarimeter installed in the external GDH1-beamline

  11. Depolarization of the electron spin in storage rings by nonlinear spin-orbit coupling

    International Nuclear Information System (INIS)

    Kewisch, J.

    1985-10-01

    Electrons and positrons which circulate in the storage ring are polarized at the emission of synchrotron radiation by the so called Sokolov-Ternov effect. This polarization is on the one hand of large interest for the study of the weak interaction, on the other hand it can be used for the accurate measurement of the beam energy and by this of the mass of elementary particles. The transverse and longitudinal particle vibrations simultaneously excited by the synchrotron radiation however can effect that this polarization is destroyed. This effect is called spin-orbit coupling. For the calculation of the spin-orbit coupling the computer program SITROS was written. This program is a tracking program: The motion of some sample particles and their spin vectors are calculated for some thousand circulations. From this the mean depolarization and by extrapolation the degree of polarization of the equilibrium state is determined. Contrarily to the known program SLIM which is based on perturbational calculations in SITROS the nonlinear forces in the storage ring can be regarded. By this the calculation of depolarizing higher order resonances is made possible. In this thesis the equations of motion for the orbital and spin motion of the electrons are derived which form the base for the program SITROS. The functions of the program and the approximations necessary for the saving of calculational time are explained. The comparison of the SITROS results with the measurement results obtained at the PETRA storage ring shows that the SITROS program is a useful means for the planning and calculation of storage rings with polarized electron beams. (orig.) [de

  12. Progress in measurement and understanding of beam polarization in electron positron storage rings

    International Nuclear Information System (INIS)

    Barber, D.P.; Bremer, H.D.; Kewisch, J.; Lewin, H.C.; Limberg, T.; Mais, H.; Ripken, G.; Rossmanith, R.; Schmidt, R.

    1983-07-01

    A report is presented on the status of attempts to obtain and measure spin polarization in electron-positron storage rings. Experimental results are presented and their relationship to predictions of calculations discussed. Examples of methods for decoupling orbital and spin motion and thus improving polarization are discussed. (orig.)

  13. Effects of the LDEF orbital environment on the reflectance of optical mirror materials

    Science.gov (United States)

    Herzig, Howard; Fleetwood, Charles, Jr.

    1995-01-01

    Specimens of eight different optical mirror materials were flown in low earth orbit as part of the Long Duration Exposure Facility (LDEF) manifest to determine their ability to withstand exposure to the residual atomic oxygen and other environmental effects at those altitudes. Optical thin films of aluminum, gold, iridium, osmium, platinum, magnesium fluoride-overcoated aluminum and reactively deposited, silicon monoxide-protected aluminum, all of which were vacuum deposited on polished fused silica substrates, were included as part of Experiment S0010, Exposure of Spacecraft Coatings. Two specimens of polished, chemical vapor deposited (CVD) silicon carbide were installed in sites available in Experiment A0114, Interaction of Atomic Oxygen with Solid Surfaces at Orbital Altitudes, which included trays in two of the spacecraft bays, one on the leading edge and the other on the trailing edge. One of the silicon carbide samples was located in each of these trays. This paper will compare specular reflectance data from the preflight and postflight measurements made on each of these samples and attempt to explain the changes in light of the specific environments to which the experiments were exposed.

  14. Development of a methodology for deriving Plasmaspheric Total Electron Content from In-Situ electron density measurements in highly eccentric equatorial orbits

    Science.gov (United States)

    Sadhique, Aliyuthuman; Buckley, Andrew; Gough, Paul; Sussex Space Science Centre Team

    2017-10-01

    The contribution of the Upper Plasmasphere (defined as the altitudes above semi-synchronous orbit height to the Plasmapause height) to the TEC has been and continues to be un-quantified. The PEACE instrument in the Chinese - ESA Double Star TC1 satellite, the mission's orbit's high eccentricity, low perigee, high apogee and the resulting smaller incident angle while in the above altitude range provide the ideal geometric opportunity to build a methodology and to utilize its empirical in-situ electron density measurements to determine the Upper Plasmaspheric TEC component. Furthermore, the variation of the Inclination Angle of TC1 makes it a suitable equatorial mission confined to the Near-Equatorial region, ie 200 - 250 on either sides of the magnetic equator. As the most pronounced absolute TEC values and variations are within this region, it offers an excellent opportunity to build a Upper Plasmaspheric TEC database. This research generates such, first-ever database along its orbital path, using a methodology of approximation equating arcs of the orbits to straight-line TEC Bars, utilizing complex mathematics, also enabling the determination of the whole Plasmaspheric TEC from any eccentric orbital probe. Presented the paper in 15th International Workshop on Technical and Scientific Aspects of MST radar (MST15/iMST2)'' and ``18th EISCAT Symposium (EISCAT18)'' in Tokyo, Japan and The Royal Astronomical Society National Astronomy Meeting 2017.

  15. Density Variations in the Earth's Magnetospheric Cusps

    Science.gov (United States)

    Walsh, B. M.; Niehof, J.; Collier, M. R.; Welling, D. T.; Sibeck, D. G.; Mozer, F. S.; Fritz, T. A.; Kuntz, K. D.

    2016-01-01

    Seven years of measurements from the Polar spacecraft are surveyed to monitor the variations of plasma density within the magnetospheric cusps. The spacecraft's orbital precession from 1998 through 2005 allows for coverage of both the northern and southern cusps from low altitude out to the magnetopause. In the mid- and high- altitude cusps, plasma density scales well with the solar wind density (n(sub cusp)/n(sub sw) approximately 0.8). This trend is fairly steady for radial distances greater then 4 R(sub E). At low altitudes (r less than 4R(sub E)) the density increases with decreasing altitude and even exceeds the solar wind density due to contributions from the ionosphere. The density of high charge state oxygen (O(greater +2) also displays a positive trend with solar wind density within the cusp. A multifluid simulation with the Block-Adaptive-Tree Solar Wind Roe-Type Upwind Scheme MHD model was run to monitor the relative contributions of the ionosphere and solar wind plasma within the cusp. The simulation provides similar results to the statistical measurements from Polar and confirms the presence of ionospheric plasma at low altitudes.

  16. A plasma solenoid driven by an Orbital Angular Momentum laser beam

    OpenAIRE

    Nuter, R.; Korneev, Ph.; Thiele, I.; Tikhonchuk, V.

    2018-01-01

    A tens of Tesla quasi-static axial magnetic field can be produced in the interaction of a short intense laser beam carrying an Orbital Angular Momentum with an underdense plasma. Three-dimensional "Particle In Cell" simulations and analytical model demonstrate that orbital angular momentum is transfered from a tightly focused radially polarized laser beam to electrons without any dissipative effect. A theoretical model describing the balistic interaction of electrons with laser shows that par...

  17. Diagnostic criteria of high-altitude de-adaptation for high-altitude migrants returning to the plains: a multicenter, randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Qi-quan ZHOU

    2012-02-01

    Full Text Available Objective  To investigate the diagnostic method of high-altitude de-adaptation and constitute the diagnostic criteria of high-altitude de-adaptation for people returning to the plains from high-altitude. Methods  Epidemiological survey and clinical multicenter randomized controlled studies were used to determine/perform blood picture, routine urine analysis, routine stool examination, myocardial enzymes, liver and kidney functions, nerve function, sex hormone, microalbuminuria, ECG, echocardiography, pulmonary function tests, and so on, in 3011 subjects after they returned to the plains from high-altitude. The diagnostic criteria of high-altitude de-adaptation were formulated by a comparative analysis of the obtained data with those of healthy subjects living in the same area, altitude, and age. The regularity and characteristics of high-altitude de-adaptation syndrome were found and diagnostic criteria for high-altitude de-adaptation was established based on the results. Results  The investigative results showed that the incidence of high-altitude de-adaptation syndrome was found in 84.36% of population returning to the plains from high-altitude. About 60% of them were considered to have mild reactions, 30% medium, and only 10% were severe. The lower the altitude they returned to, the longer the duration of stay in highland, and the heavier the labor they engaged in high altitude, the higher the incidence rate of high-altitude de-adaptation syndrome was. Patients with high-altitude de-adaptation syndrome exhibited hematological abnormality and abnormal ventricular function, especially the right ventricular diastolic function after returning for 1 year to 5 years. Long-term hypoxia exposure often caused obvious change in cardiac morphology with left and right ventricular hypertrophy, particularly the right ventricle. In addition, low blood pressure and low pulse pressure were found at times. Microalbuminuria was found in some high-altitude de

  18. Spin-orbit-induced spin splittings in polar transition metal dichalcogenide monolayers

    KAUST Repository

    Cheng, Yingchun; Zhu, Zhiyong; Tahir, Muhammad; Schwingenschlö gl, Udo

    2013-01-01

    . We present ab initio electronic structure, phonon, and molecular-dynamics calculations to study the structural stability and spin-orbit-induced spin splitting in the transition metal dichalcogenide monolayers MXY (M = Mo, W and X, Y = S, Se, Te

  19. Analysis of received AIS data from a LEO Cubesat

    DEFF Research Database (Denmark)

    Larsen, Jesper Abildgaard; Mortensen, Hans Peter; Tausen, Mathias

    2014-01-01

    The AAUSAT3 satellite is a 1U cubesat, which has been developed by students at Aalborg Uni- versity, Denmark in collaboration with the Danish Maritime Authority. The satellite was launched into a polar DD-SSO orbit of 800 km altitude on February 25th 2013 on a mission to monitor ships from space...

  20. The Polar Cusp Observed by Cluster Under Constant Imf-Bz Southward

    Science.gov (United States)

    Escoubet, C. P.; Berchem, J.; Pitout, F.; Trattner, K. J.; Richard, R. L.; Taylor, M. G.; Soucek, J.; Grison, B.; Laakso, H. E.; Masson, A.; Dunlop, M. W.; Dandouras, I. S.; Reme, H.; Fazakerley, A. N.; Daly, P. W.

    2011-12-01

    The Earth's magnetic field is influenced by the interplanetary magnetic field (IMF), specially at the magnetopause where both magnetic fields enter in direct contact and magnetic reconnection can be initiated. In the polar regions, the polar cusp that extends from the magnetopause down to the ionosphere is also directly influenced. The reconnection not only allow ions and electrons from the solar wind to enter the polar cusp but also give an impulse to the magnetic field lines threading the polar cusp through the reconnection electric field. A dispersion in energy of the ions is subsequently produced by the motion of field lines and the time-of-flight effect on down-going ions. If reconnection is continuous and operates at constant rate, the ion dispersion is smooth and continuous. On the other hand if the reconnection rate varies, we expect interruption in the dispersion forming energy steps or staircase. Similarly, multiple entries near the magnetopause could also produce steps at low or mid-altitude when a spacecraft is crossing subsequently the field lines originating from these multiple sources. Cluster with four spacecraft following each other in the mid-altitude cusp can be used to distinguish between these "temporal" and "spatial" effects. We will show two Cluster cusp crossings where the spacecraft were separated by a few minutes. The energy dispersions observed in the first crossing were the same during the few minutes that separated the spacecraft. In the second crossing, two ion dispersions were observed on the first spacecraft and only one of the following spacecraft, about 10 min later. The detailed analysis indicates that these steps result from spatial structures.

  1. Possible experiment with two counter-orbiting drag-free satellites to obtain a new test of Einstein's general theory of relativity and improved measurements in geodesy

    International Nuclear Information System (INIS)

    Van Patten, R.A.; Everitt, C.W.F.

    1976-01-01

    In 1918, Lense and Thirring calculated that a moon orbiting a rotating planet would experience a nodal dragging effect due to general relativity. We describe an experiment to measure this effect to 1% with two counter-orbiting drag-free satellites in polar earth orbit. In addition to tracking data from existing ground stations, satellite-to-satellite Doppler ranging data are taken near the poles. New geophysical information is inherent in the polar data

  2. Altitude Lab

    Data.gov (United States)

    Federal Laboratory Consortium — The Altitude Lab evaluates the performance of complete oxygen systems operated in individually controlled hypobaric chambers, which duplicate pressures that would be...

  3. ABOUT TRANSITION ALTITUDE IN RUSSIAN FEDERATION

    Directory of Open Access Journals (Sweden)

    2016-01-01

    Full Text Available This article is about establishing a common transition altitude over all territory of Russian Federation. The main objective is to prove the necessity of a common transition altitude in Russian airspace and to define, which variant of tran- sition altitude (low, medium, high is the most suitable to be implemented in Russia. ICAO and IFALPA points of view, data and experience from different states and regions all over the world were examined in order to show all the advantages and disadvantages of different approaches towards common transition altitude. The research showed that the most appro- priate common transition altitude in Russia will be 10000 feet (3050 meters, it will cover almost all the international aero- dromes and regions in the country. Only several exceptions are needed in mountainous areas. This article can be used to further study of the possibility of implementation of common transition altitude, because it can’t take into consideration all the local features of all the FIRs (Flight Information Regions in Russia. The conclusion is establishing a common transi- tion altitude over such a big part of the world as Russian Federation will lead to improvement of the flight safety, harmoni- zation with ICAO and IFALPA policies and flexibility in airspace design.

  4. Coulomb-free and Coulomb-distorted recolliding quantum orbits in photoelectron holography

    Science.gov (United States)

    Maxwell, A. S.; Figueira de Morisson Faria, C.

    2018-06-01

    We perform a detailed analysis of the different types of orbits in the Coulomb quantum orbit strong-field approximation (CQSFA), ranging from direct to those undergoing hard collisions. We show that some of them exhibit clear counterparts in the standard formulations of the strong-field approximation for direct and rescattered above-threshold ionization, and show that the standard orbit classification commonly used in Coulomb-corrected models is over-simplified. We identify several types of rescattered orbits, such as those responsible for the low-energy structures reported in the literature, and determine the momentum regions in which they occur. We also find formerly overlooked interference patterns caused by backscattered Coulomb-corrected orbits and assess their effect on photoelectron angular distributions. These orbits improve the agreement of photoelectron angular distributions computed with the CQSFA with the outcome of ab initio methods for high energy phtotoelectrons perpendicular to the field polarization axis.

  5. Detection of Earth-rotation Doppler shift from Suomi National Polar-Orbiting Partnership Cross-Track Infrared Sounder.

    Science.gov (United States)

    Chen, Yong; Han, Yong; Weng, Fuzhong

    2013-09-01

    The Cross-Track Infrared Sounder (CrIS) on the Suomi National Polar-Orbiting Partnership Satellite is a Fourier transform spectrometer and provides a total of 1305 channels for sounding the atmosphere. Quantifying the CrIS spectral accuracy, which is directly related to radiometric accuracy, is crucial for improving its data assimilation in numerical weather prediction. In this study, a cross-correlation method is used for detecting the effect of Earth-rotation Doppler shift (ERDS) on CrIS observations. Based on a theoretical calculation, the ERDS can be as large as about 1.3 parts in 10(6) (ppm) near Earth's equator and at the satellite scan edge for a field of regard (FOR) of 1 or 30. The CrIS observations exhibit a relative Doppler shift as large as 2.6 ppm for a FOR pair of 1 and 30 near the equator. The variation of the ERDS with latitude and scan position detected from CrIS observations is similar to that derived theoretically, which indicates that the spectral stability of the CrIS instrument is very high. To accurately calibrate CrIS spectral accuracy, the ERDS effect should be removed. Since the ERDS is easily predictable, the Doppler shift is correctable in the CrIS spectra.

  6. Los Alamos energetic particle sensor systems at geostationary orbit

    International Nuclear Information System (INIS)

    Baker, D.N.; Aiello, W.; Asbridge, J.R.; Belian, R.D.; Higbie, P.R.; Klebesadel, R.W.; Laros, J.G.; Tech, E.R.

    1985-01-01

    The Los Alamos National Laboratory has provided energetic particle sensors for a variety of spacecraft at the geostationary orbit (36,000 km altitude). The sensor system called the Charged Particle Analyzer (CPA) consists of four separate subsystems. The LoE and HiE subsystems measure electrons in the energy ranges 30 to 300 keV and 200 to 2000 keV, respectively. The LoP and HiP subsystems measure ions in the ranges 100 to 600 keV and 0.40 to 150 MeV, respectively. A separate sensor system called the spectrometer for energetic electrons (SEE) measures very high-energy electrons (2 to 15 MeV) using advanced scintillator design. In this paper we describe the relationship of operational anomalies and spacecraft upsets to the directly measured energetic particle environments at 6.6 R/sub E/. We also compare and contrast the CPA and SEE instrument design characteristics with the next generation of Los Alamos instruments to be flown at geostationary altitudes

  7. The HERA polarimeter and the first observation of electron spin polarization at HERA

    International Nuclear Information System (INIS)

    Barber, D.P.; Bremer, H.D.; Boege, M.; Brinkmann, R.; Gianfelice-Wendt, E.; Kaiser, H.; Klanner, R.; Lewin, H.C.; Meyners, N.; Vogel, W.; Brueckner, W.; Buescher, C.; Dueren, M.; Gaul, H.G.; Muecklich, A.; Neunreither, F.; Rith, K.; Scholz, C.; Steffens, E.; Veltri, M.; Wander, W.; Zapfe, K.; Zetsche, F.; Chapman, M.; Milner, R.; Coulter, K.; Delheij, P.P.J.; Haeusser, O.; Henderson, R.; Levy, P.; Vetterli, M.; Gressmann, H.; Janke, T.; Micheel, B.; Westphal, D.; Kaiser, R.; Losev, L.; Nowak, W.D.

    1992-10-01

    Electron spin polarizations of about 8% were observed at HERA in November 1991. In runs during 1992 utilizing special orbit corrections, polarization values close to 60% have been achieved. In this paper the polarimeter, the machine conditions, the data analysis, the first results and plans for future measurements are described. (orig.)

  8. QED effects on individual atomic orbital energies

    Science.gov (United States)

    Kozioł, Karol; Aucar, Gustavo A.

    2018-04-01

    Several issues, concerning QED corrections, that are important in precise atomic calculations are presented. The leading QED corrections, self-energy and vacuum polarization, to the orbital energy for selected atoms with 30 ≤ Z ≤ 118 have been calculated. The sum of QED and Breit contributions to the orbital energy is analyzed. It has been found that for ns subshells the Breit and QED contributions are of comparative size, but for np and nd subshells the Breit contribution takes a major part of the QED+Breit sum. It has also, been found that the Breit to leading QED contributions ratio for ns subshells is almost independent of Z. The Z-dependence of QED and Breit+QED contributions per subshell is shown. The fitting coefficients may be used to estimate QED effects on inner molecular orbitals. We present results of our calculations for QED contributions to orbital energy of valence ns-subshell for group 1 and 11 atoms and discuss about the reliability of these numbers by comparing them with experimental first ionization potential data.

  9. Mesoscopic rings with spin-orbit interactions

    Energy Technology Data Exchange (ETDEWEB)

    Berche, Bertrand; Chatelain, Christophe; Medina, Ernesto, E-mail: berche@lpm.u-nancy.f [Statistical Physics Group, Institut Jean Lamour, UMR CNRS No 7198, Universite Henri Poincare, Nancy 1, B.P. 70239, F-54506 Vandoeuvre les Nancy (France)

    2010-09-15

    A didactic description of charge and spin equilibrium currents on mesoscopic rings in the presence of spin-orbit interaction is presented. Emphasis is made on the non-trivial construction of the correct Hamiltonian in polar coordinates, the calculation of eigenvalues and eigenfunctions and the symmetries of the ground-state properties. Spin currents are derived following an intuitive definition, and then a more thorough derivation is built upon the canonical Lagrangian formulation that emphasizes the SU(2) gauge structure of the transport problem of spin-1/2 fermions in spin-orbit active media. The quantization conditions that follow from the constraint of single-valued Pauli spinors are also discussed. The targeted students are those of a graduate condensed matter physics course.

  10. Understanding the polarization signal of spherical particles for microwave limb radiances

    International Nuclear Information System (INIS)

    Teichmann, C.; Buehler, S.A.; Emde, C.

    2006-01-01

    This paper presents a simple conceptual model to explain that even spherical scatterers lead to a polarization difference signal for microwave limb radiances. The conceptual model relates the polarization difference measured by a limb-looking sensor situated inside a cloud with the anisotropy of the radiation. In the simulations, it was assumed that the cloud consists of spherical ice particles with a radius of 68.5μm which were situated between 10.6 and 12.3km altitude. The frequencies 318 and 500GHz were considered. The results of the conceptual model were compared to the results of the fully polarized scattering model ARTS-1-1. The comparison showed a good qualitative agreement. The polarization difference decreases inside the cloud with increasing height and changes sign. This behavior can be related to a different amount of radiation coming from the atmosphere above and below the cloud, compared to the amount of radiation coming from the sides. The sign of polarization difference of the scattered radiation is opposite for these two radiation sources

  11. DC slice ion imaging study of atomic orbital orientation and alignment in photodissociation

    Science.gov (United States)

    Lee, Suk Kyoung

    A complete study of atomic photofragment polarization has been achieved by using DC slice imaging, a recently developed approach directly providing the central slice of the full 3D product distribution without any mathematical transformation. In this dissertation, the quantum mechanical treatment adapted for the sliced images has been derived to extract the angular momentum polarization anisotropy parameters for any recoil speeds. The important photodissociation dynamics of small polyatomic molecules has been presented based on the thorough interpretation of the observed orientation and alignment. The first demonstration of DC slice imaging of orbital polarization was a study of the 193 nm photodissociation of ethylene sulfide, followed by detailed investigation in ozone and OCS. In ozone, the speed-dependent orientation was measured for O(1D2) atom produced from photodissociation in the 248--285 nm region. The results show negligible orbital orientation following dissociation by circularly polarized light but strong recoil speed-dependent orientation following photolysis by linearly polarized light at all wavelengths studied. The origin of this polarization is ascribed to nonadiabatic transitions at avoided crossings and at long range. The atomic orbital alignment and orientation, including the higher order moments (K = 3, 4), has been carried out for the photodissociation of OCS at 193 nm. The observed speed-dependent beta and polarization parameters of S(1D2) atom support the interpretation that there are two main dissociation processes: a simultaneous two-surface excitation and the initial single-surface excitation followed by the nonadiabatic crossing to the ground state. The angle- and speed-dependent density matrix can be constructed containing the higher order contributions for circularly-polarized dissociation light. It was shown in one case that the higher order contributions should not be overlooked for an accurate picture of the dissociation dynamics in

  12. Azimuth-Variant Signal Processing in High-Altitude Platform Passive SAR with Spaceborne/Airborne Transmitter

    Directory of Open Access Journals (Sweden)

    Huaizong Shao

    2013-03-01

    Full Text Available High-altitude platforms (HAP or near-space vehicle offers several advantages over current low earth orbit (LEO satellite and airplane, because HAP is not constrained by orbital mechanics and fuel consumption. These advantages provide potential for some specific remote sensing applications that require persistent monitoring or fast-revisiting frequency. This paper investigates the azimuth-variant signal processing in HAP-borne bistatic synthetic aperture radar (BiSAR with spaceborne or airborne transmitter for high-resolution remote sensing. The system configuration, azimuth-variant Doppler characteristics and two-dimensional echo spectrum are analyzed. Conceptual system simulation results are also provided. Since the azimuth-variant BiSAR geometry brings a challenge for developing high precision data processing algorithms, we propose an image formation algorithm using equivalent velocity and nonlinear chirp scaling (NCS to address the azimuth-variant signal processing problem. The proposed algorithm is verified by numerical simulation results.

  13. GOCE reentry predictions for the Italian civil protection authorities

    OpenAIRE

    Pardini, Carmen; Anselmo, Luciano

    2014-01-01

    The ESA's GOCE satellite was launched on 17 March 2009. After mapping the geopotential with unrivalled accuracy and detail for four years from an extremely low circular polar orbit, on 21 October 2013 the low thrust ion propulsion motor used to contrast the atmospheric drag was automatically shut down when the pressure in the xenon propellant tank dropped below a critical threshold. Then the satellite entered in "fine-pointing mode" (FPM), a phase of orbital altitude decay with active fine at...

  14. Potential Operating Orbits for the SAFE-400

    International Nuclear Information System (INIS)

    Houts, Mike; Kos, Larry; Poston, David

    2002-01-01

    Safety must be ensured during all phases of space fission system design, development, fabrication, launch, operation, and shutdown. One potential space fission system application is fission electric propulsion (FEP), in which fission energy is converted into electricity and used to power high efficiency (Isp > 3000 s) electric thrusters. For these types of systems it is important to determine which operational scenarios ensure safety while allowing maximum mission performance and flexibility. Space fission systems are essentially non-radioactive at launch, prior to extended operation at high power. Once high power operation begins, system radiological inventory steadily increases as fission products build up. For a given fission product isotope, the maximum radiological inventory is typically achieved once the system has operated for a length of time equivalent to several half-lives. After that time, the isotope decays at the same rate it is produced, and no further inventory builds in. For an FEP mission beginning in Earth orbit, altitude and orbital lifetime increase as the propulsion system operates. Two simultaneous effects of fission propulsion system operation are thus (1) increasing fission product inventory and (2) increasing orbital lifetime. Phrased differently, as fission products build up, more time is required for the fission products to naturally convert back into non-radioactive isotopes. Simultaneously, as fission products build up, orbital lifetime increases, providing more time for the fission products to naturally convert back into nonradioactive isotopes. Operational constraints required to ensure safety can thus be quantified. (authors)

  15. Altitude Testing of Large Liquid Propellant Engines

    Science.gov (United States)

    Maynard, Bryon T.; Raines, Nickey G.

    2010-01-01

    The National Aeronautics and Space Administration entered a new age on January 14, 2004 with President Bush s announcement of the creation the Vision for Space Exploration that will take mankind back to the Moon and on beyond to Mars. In January, 2006, after two years of hard, dedicated labor, engineers within NASA and its contractor workforce decided that the J2X rocket, based on the heritage of the Apollo J2 engine, would be the new engine for the NASA Constellation Ares upper stage vehicle. This engine and vehicle combination would provide assured access to the International Space Station to replace that role played by the Space Shuttle and additionally, would serve as the Earth Departure Stage, to push the Crew Excursion Vehicle out of Earth Orbit and head it on a path for rendezvous with the Moon. Test as you fly, fly as you test was chosen to be the guiding philosophy and a pre-requisite for the engine design, development, test and evaluation program. An exhaustive survey of national test facility assets proved the required capability to test the J2X engine at high altitude for long durations did not exist so therefore, a high altitude/near space environment testing capability would have to be developed. After several agency concepts the A3 High Altitude Testing Facility proposal was selected by the J2X engine program on March 2, 2007 and later confirmed by a broad panel of NASA senior leadership in May 2007. This facility is to be built at NASA s John C. Stennis Space Center located near Gulfport, Mississippi. 30 plus years of Space Shuttle Main Engine development and flight certification testing makes Stennis uniquely suited to support the Vision For Space Exploration Return to the Moon. Propellant handling infrastructure, engine assembly facilities, a trained and dedicated workforce and a broad and varied technical support base will all ensure that the A3 facility will be built on time to support the schedule needs of the J2X engine and the ultimate flight

  16. Toward a Unified View of the Moon's Polar Volatiles from the Lunar Reconnaissance Orbiter

    Science.gov (United States)

    Hayne, Paul

    2016-04-01

    Although the scientific basis for the possibility of water and other volatiles in the cold traps of the lunar polar regions was developed in the 1960's and '70's [1,2], only recently have the data become available to test the theories in detail. Furthermore, comparisons with other planetary bodies, particularly Mercury, have revealed surprising differences that may point to inconsistencies or holes in our understanding of the basic processes involving volatiles on airless bodies [3]. Addressing these gaps in understanding is critical to the future exploration of the Moon, for which water is an important scientific and engineering resource [4]. Launched in 2009, NASA's Lunar Reconnaissance Orbiter (LRO) has been acquiring data from lunar orbit for more than six years. All seven of the remote sensing instruments on the payload have now contributed significantly to advancing understanding of volatiles on the Moon. Here we present results from these investigations, and discuss attempts to synthesize the disparate information to create a self-consistent model for lunar volatiles. In addition to the LRO data, we must take into account results from earlier missions [5,6], ground-based telescopes [7], and sample analyses [8]. The results from these inter-comparisons show that water is likely available in useful quantities, but key additional measurements may be required to resolve remaining uncertainties. [1] Watson, K., Murray, B. C., & Brown, H. (1961), J. Geophys. Res., 66(9), 3033-3045. [2] Arnold, J. R. (1979), J. Geophys. Res. (1978-2012), 84(B10), 5659-5668. [3] Paige, D. A., Siegler, M. A., Harmon, J. K., Neumann, G. A., Mazarico, E. M., Smith, D. E., ... & Solomon, S. C. (2013), Science, 339(6117), 300-303. [4] Hayne, P. O., et al. (2014), Keck Inst. Space Studies Report. [5] Nozette, S., Lichtenberg, C. L., Spudis, P., Bonner, R., Ort, W., Malaret, E., ... & Shoemaker, E. M. (1996), Science, 274(5292), 1495-1498. [6] Pieters, C. M., Goswami, J. N., Clark, R. N

  17. Introduction to altitude/hypoxic training symposium.

    Science.gov (United States)

    Wilber, Randall L

    2007-09-01

    Altitude/hypoxic training has traditionally been an intriguing and controversial area of research and sport performance. This controversial aspect was evident recently in the form of scholarly debates in highly regarded professional journals, as well as the World Anti-Doping Agency's (WADA) consideration of placing "artificially-induced hypoxic conditions" on the 2007 Prohibited List of Substances/Methods. In light of the ongoing controversy surrounding altitude/hypoxic training, this symposium was organized with the following objectives in mind: 1) to examine the primary physiological responses and underlying mechanisms associated with altitude/hypoxic training, including the influence of genetic predisposition; 2) to present evidence supporting the effect of altitude/hypoxic acclimatization on both hematological and nonhematological markers, including erythrocyte volume, skeletal muscle-buffering capacity, hypoxic ventilatory response, and physiological efficiency/economy; 3) to evaluate the efficacy of several contemporary simulated altitude modalities and training strategies, including hypoxic tents, nitrogen apartments, and intermittent hypoxic exposure (IHE) or training, and to address the legal and ethical issues associated with the use of simulated altitude; and 4) to describe different altitude/hypoxic training strategies used by elite-level athletes, including Olympians and military special forces. In addressing these objectives, papers will be presented on the topics of: 1) effect of hypoxic "dose" on physiological responses and sea-level performance (Drs. Benjamin Levine and James Stray-Gundersen), 2) nonhematological mechanisms of improved performance after hypoxic exposure (Dr. Christopher Gore), 3) application of altitude/hypoxic training by elite athletes (Dr. Randall Wilber), and 4) military applications of hypoxic training (Dr. Stephen Muza).

  18. Techniques of production and analysis of polarized synchrotron radiation

    International Nuclear Information System (INIS)

    Mills, D.M.

    1992-01-01

    The use of the unique polarization properties of synchrotron radiation in the hard x-ray spectral region (E>3 KeV) is becoming increasingly important to many synchrotron radiation researchers. The radiation emitted from bending magnets and conventional (planar) insertion devices (IDs) is highly linearly polarized in the plane of the particle's orbit. Elliptically polarized x-rays can also be obtained by going off axis on a bending magnet source, albeit with considerable loss of flux. The polarization properties of synchrotron radiation can be further tailored to the researcher's specific needs through the use of specialized insertion devices such as helical and crossed undulators and asymmetrical wigglers. Even with the possibility of producing a specific polarization, there is still the need to develop x-ray optical components which can manipulate the polarization for both analysis and further modification of the polarization state. A survey of techniques for producing and analyzing both linear and circular polarized x-rays will be presented with emphasis on those techniques which rely on single crystal optical components

  19. The Global Precipitation Measurement (GPM) Spacecraft Power System Design and Orbital Performance

    Science.gov (United States)

    Dakermanji, George; Burns, Michael; Lee, Leonine; Lyons, John; Kim, David; Spitzer, Thomas; Kercheval, Bradford

    2016-01-01

    The Global Precipitation Measurement (GPM) spacecraft was jointly developed by National Aeronautics and Space Administration (NASA) and Japan Aerospace Exploration Agency (JAXA). It is a Low Earth Orbit (LEO) spacecraft launched on February 27, 2014. The spacecraft is in a circular 400 Km altitude, 65 degrees inclination nadir pointing orbit with a three year basic mission life. The solar array consists of two sun tracking wings with cable wraps. The panels are populated with triple junction cells of nominal 29.5% efficiency. One axis is canted by 52 degrees to provide power to the spacecraft at high beta angles. The power system is a Direct Energy Transfer (DET) system designed to support 1950 Watts orbit average power. The batteries use SONY 18650HC cells and consist of three 8s x 84p batteries operated in parallel as a single battery. The paper describes the power system design details, its performance to date and the lithium ion battery model that was developed for use in the energy balance analysis and is being used to predict the on-orbit health of the battery.

  20. Altitude exposures during commercial flight: a reappraisal.

    Science.gov (United States)

    Hampson, Neil B; Kregenow, David A; Mahoney, Anne M; Kirtland, Steven H; Horan, Kathleen L; Holm, James R; Gerbino, Anthony J

    2013-01-01

    Hypobaric hypoxia during commercial air travel has the potential to cause or worsen hypoxemia in individuals with pre-existing cardiopulmonary compromise. Knowledge of cabin altitude pressures aboard contemporary flights is essential to counseling patients accurately about flying safety. The objective of the study was to measure peak cabin altitudes during U.S. domestic commercial flights on a variety of aircraft. A handheld mountaineering altimeter was carried by the investigators in the plane cabin during commercial air travel and peak cabin altitude measured. The values were then compared between aircraft models, aircraft classes, and distances flown. The average peak cabin altitude on 207 flights aboard 17 different aircraft was 6341 +/- 1813 ft (1933 m +/- 553 m), significantly higher than when measured in a similar fashion in 1988. Peak cabin altitude was significantly higher for flights longer than 750 mi (7085 +/- 801 ft) compared to shorter flights (5160 +/- 2290 ft/1573 +/- 698 m). Cabin altitude increased linearly with flight distance for flights up to 750 mi in length, but was independent of flight distance for flights exceeding 750 mi. Peak cabin altitude was less than 5000 ft (1524 m) in 70% of flights shorter than 500 mi. Peak cabin altitudes greater than 8000 ft (2438 m) were measured on approximately 10% of the total flights. Peak cabin altitude on commercial aircraft flights has risen over time. Cabin altitude is lower with flights of shorter distance. Physicians should take these factors into account when determining an individual's need for supplemental oxygen during commercial air travel.

  1. Altitude training improves glycemic control.

    Science.gov (United States)

    Chen, Shu-Man; Lin, Hsueh-Yi; Kuo, Chia-Hua

    2013-08-31

    Under altitude hypoxia condition, energy reliance on anaerobic glycolysis increases to compensate the shortfall caused by reduced fatty acid oxidation. Short-term moderate altitude exposure plus endurance physical activity has been found to improve glucose tolerance (not fasting glucose) in humans, which is associated with the improvement in the whole-body insulin sensitivity. However, most of people cannot accommodate high altitude exposure above 4500 M due to acute mountain sickness and insulin resistance. There is a wide variation among individuals in response to the altitude challenge. In particular, the improvement in glucose tolerance and insulin sensitivity by prolonged altitude hiking activity was not apparent in those individuals with low baseline dehydroepiandrosterone sulfate (DHEA-S) concentration. In rats, exercise training recovery under prolonged hypoxia exposure (14-15% oxygen, 8 h per day for 6 weeks) can also improve insulin sensitivity, secondary to an effective suppression of adiposity. After prolonged hypoxia training, obese abnormality in upregulated baseline levels of AMP-activated protein kinase (AMPK) and AS160 phosphorylation in skeletal muscle can be reversed. In humans, moderate hypoxia increases postprandial blood distribution towards skeletal muscle during a training recovery. This physiological response plays a role in the redistribution of fuel storage among important energy storage sites and may explain its potent effect on the favorable change in body composition. Altitude training can exert strong impact on our metabolic system, and has the potential to be designed as a non-pharmacological or recreational intervention regimen for correcting metabolic syndromes.

  2. Resonant x-ray scattering in manganites: study of the orbital degree of freedom

    International Nuclear Information System (INIS)

    Ishihara, Sumio; Maekawa, Sadamichi

    2002-01-01

    The orbital degree of freedom of electrons and its interplay with spin, charge and lattice degrees of freedom are some of the central issues in colossal magnetoresistive manganites. The orbital degree of freedom has until recently remained hidden, since it does not couple directly to most experimental probes. Development of synchrotron light sources has changed the situation; by the resonant x-ray scattering (RXS) technique the orbital ordering has successfully been observed. In this article, we review progress in the recent studies of RXS in manganites. We start with a detailed review of the RXS experiments applied to the orbital-ordered manganites and other correlated electron systems. We derive the scattering cross section of RXS, where the tensor character of the atomic scattering factor (ASF) with respect to the x-ray polarization is stressed. Microscopic mechanisms of the anisotropic tensor character of the ASF are introduced and numerical results of the ASF and the scattering intensity are presented. The azimuthal angle scan is a unique experimental method to identify RXS from the orbital degree of freedom. A theory of the azimuthal angle and polarization dependence of the RXS intensity is presented. The theoretical results show good agreement with the experiments in manganites. Apart from the microscopic description of the ASF, a theoretical framework of RXS to relate directly to the 3d orbital is presented. The scattering cross section is represented by the correlation function of the pseudo-spin operator for the orbital degree of freedom. A theory is extended to the resonant inelastic x-ray scattering and methods to observe excitations of the orbital degree of freedom are proposed. (author)

  3. Nuclear reactor power for an electrically powered orbital transfer vehicle

    Science.gov (United States)

    Jaffe, L.; Beatty, R.; Bhandari, P.; Chow, E.; Deininger, W.; Ewell, R.; Fujita, T.; Grossman, M.; Kia, T.; Nesmith, B.

    1987-01-01

    To help determine the systems requirements for a 300-kWe space nuclear reactor power system, a mission and spacecraft have been examined which utilize electric propulsion and this nuclear reactor power for multiple transfers of cargo between low earth orbit (LEO) and geosynchronous earth orbit (GEO). A propulsion system employing ion thrusters and xenon propellant was selected. Propellant and thrusters are replaced after each sortie to GEO. The mass of the Orbital Transfer Vehicle (OTV), empty and dry, is 11,000 kg; nominal propellant load is 5000 kg. The OTV operates between a circular orbit at 925 km altitude, 28.5 deg inclination, and GEO. Cargo is brought to the OTV by Shuttle and an Orbital Maneuvering Vehicle (OMV); the OTV then takes it to GEO. The OTV can also bring cargo back from GEO, for transfer by OMV to the Shuttle. OTV propellant is resupplied and the ion thrusters are replaced by the OMV before each trip to GEO. At the end of mission life, the OTV's electric propulsion is used to place it in a heliocentric orbit so that the reactor will not return to earth. The nominal cargo capability to GEO is 6000 kg with a transit time of 120 days; 1350 kg can be transferred in 90 days, and 14,300 kg in 240 days. These capabilities can be considerably increased by using separate Shuttle launches to bring up propellant and cargo, or by changing to mercury propellant.

  4. Nuclear reactor power for an electrically powered orbital transfer vehicle

    International Nuclear Information System (INIS)

    Jaffe, L.; Beatty, R.; Bhandari, P.

    1987-01-01

    To help determine the systems requirements for a 300-kWe space nuclear reactor power system, a mission and spacecraft have been examined which utilize electric propulsion and this nuclear reactor power for multiple transfers of cargo between low Earth orbit (LEO) and geosynchronous Earth orbit (GEO). A propulsion system employing ion thrusters and xenon propellant was selected. Propellant and thrusters are replaced after each sortie to GEO. The mass of the Orbital Transfer Vehicle (OTV), empty and dry, is 11,000 kg; nominal propellant load is 5000 kg. The OTV operates between a circular orbit at 925 km altitude, 28.5 deg inclination, and GEO. Cargo is brought to the OTV by Shuttle and an Orbital Maneuvering Vehicle (OMV); the OTV then takes it to GEO. The OTV can also bring cargo back from GEO, for transfer by OMV to the Shuttle. OTV propellant is resupplied and the ion thrusters are replaced by the OMV before each trip to GEO. At the end of mission life, the OTV's electric propulsion is used to place it in a heliocentric orbit so that the reactor will not return to Earth. The nominal cargo capability to GEO is 6000 kg with a transit time of 120 days; 1350 kg can be transferred in 90 days, and 14,300 kg in 240 days. These capabilities can be considerably increased by using separate Shuttle launches to bring up propellant and cargo, or by changing to mercury propellant

  5. The energy spectra of anomalous oxygen at the time of two successive solar minima

    CERN Document Server

    Kondratyeva, M A; Tretyakova, S P; Zhuravlev, D A

    1999-01-01

    The energy spectra of anomalous oxygen have been determined from nuclear track detectors exposed aboard the Earth-orbiting satellites at altitudes ranging from approx 250-400 km in two consecutive solar minimum periods of 1986-1987 and 1994-1995 with opposite polarity of the solar magnetic field. A comparison of the spectra shows no contradiction to current drift models.

  6. Determination of the orientation of the white dwarf's magnetic axis from X-ray orbital light curves

    International Nuclear Information System (INIS)

    Andronov, I.L.

    1986-01-01

    The directional pattern of soft X-ray radiation produced in a ''polar cap'' on the white dwarf's surface is calculated taking into account the absorption in the axially symmetrical accretion column, homogeneous along its height. An algorithm for the determination of orientation of the magnetic axis of a compact star from orbital curves of soft X-ray flux, is suggested. The values of the orbital inclination i (51 deg <=i<64 deg) and the angle between the rotational and magnetic axes σ (30 deg <=σ<=34 deg) were calculated for the polar AM Herculis for different values of model parameters

  7. A Lookup-Table-Based Approach to Estimating Surface Solar Irradiance from Geostationary and Polar-Orbiting Satellite Data

    Directory of Open Access Journals (Sweden)

    Hailong Zhang

    2018-03-01

    Full Text Available Incoming surface solar irradiance (SSI is essential for calculating Earth’s surface radiation budget and is a key parameter for terrestrial ecological modeling and climate change research. Remote sensing images from geostationary and polar-orbiting satellites provide an opportunity for SSI estimation through directly retrieving atmospheric and land-surface parameters. This paper presents a new scheme for estimating SSI from the visible and infrared channels of geostationary meteorological and polar-orbiting satellite data. Aerosol optical thickness and cloud microphysical parameters were retrieved from Geostationary Operational Environmental Satellite (GOES system images by interpolating lookup tables of clear and cloudy skies, respectively. SSI was estimated using pre-calculated offline lookup tables with different atmospheric input data of clear and cloudy skies. The lookup tables were created via the comprehensive radiative transfer model, Santa Barbara Discrete Ordinate Radiative Transfer (SBDART, to balance computational efficiency and accuracy. The atmospheric attenuation effects considered in our approach were water vapor absorption and aerosol extinction for clear skies, while cloud parameters were the only atmospheric input for cloudy-sky SSI estimation. The approach was validated using one-year pyranometer measurements from seven stations in the SURFRAD (SURFace RADiation budget network. The results of the comparison for 2012 showed that the estimated SSI agreed with ground measurements with correlation coefficients of 0.94, 0.69, and 0.89 with a bias of 26.4 W/m2, −5.9 W/m2, and 14.9 W/m2 for clear-sky, cloudy-sky, and all-sky conditions, respectively. The overall root mean square error (RMSE of instantaneous SSI was 80.0 W/m2 (16.8%, 127.6 W/m2 (55.1%, and 99.5 W/m2 (25.5% for clear-sky, cloudy-sky (overcast sky and partly cloudy sky, and all-sky (clear-sky and cloudy-sky conditions, respectively. A comparison with other state

  8. Simulation study for ground-based Ku-band microwave observations of ozone and hydroxyl in the polar middle atmosphere

    Science.gov (United States)

    Newnham, David; Clilverd, Mark; Kosch, Michael; Verronen, Pekka

    2017-04-01

    Commercial satellite TV broadcasting is possible due to remarkable advances in microwave electronics, enabling weak signals transmitted over 36,000 km from geostationary orbit to be received by inexpensive rooftop dishes. The Ku band satellite frequencies (10.70-14.25 GHz) overlap microwave emissions from ozone (O3) at 11.072 GHz and hydroxyl radical (OH) at 13.44 GHz. These important chemical species in the polar middle atmosphere respond strongly to solar variability and, at high latitudes, geomagnetic activity associated with space weather. Atmospheric model calculations predict that energetic electron precipitation (EEP) driven by magnetospheric substorms produces large changes in polar mesospheric O3 and OH. The EEP typically peaks at geomagnetic latitudes ˜65˚ (e.g. Kilpisjärvi, Finland and Syowa station, Antarctica) and evolves rapidly with time eastwards and over the geomagnetic latitude range 60˚ -80˚ (e.g. reaching Halley, Antarctica). During the substorms OH can increase by more than 1000% at 64-84 km. The substorms leave footprints of 5-55% O3 loss lasting many hours of local time, with strong altitude and seasonal dependences. An atmospheric simulation and retrieval study is performed to determine the specification and design requirements for microwave radiometers capable of measuring O3 and OH profiles from Arctic and Antarctic locations using accessible satellite TV receiver technology. The proposed observations are highly applicable to studies of EEP, atmospheric dynamics, planetaryscale circulation, chemical transport, and the representation of these processes in polar and global climate models. They would provide a lowcost, reliable alternative to increasingly sparse satellite measurements, extending long-term data records and also providing "ground truth" calibration data.

  9. JSC Orbital Debris Website Description

    Science.gov (United States)

    Johnson, Nicholas L.

    2006-01-01

    required. These data also help in the analysis and interpretation of impact features on returned spacecraft surfaces. 4) Mitigation - Controlling the growth of the orbital debris population is a high priority for NASA, the United States, and the major space-faring nations of the world to preserve near-Earth space for future generations. Mitigation measures can take the form of curtailing or preventing the creation of new debris, designing satellites to withstand impacts by small debris, and implementing operational procedures ranging from utilizing orbital regimes with less debris, adopting specific spacecraft attitudes, and even maneuvering to avoid collisions with debris. Downloadable items include several documents in PDF format and executable software.and 5) Reentry - Because of the increasing number of objects in space, NASA has adopted guidelines and assessment procedures to reduce the number of non-operational spacecraft and spent rocket upper stages orbiting the Earth. One method of postmission disposal is to allow reentry of these spacecraft, either from orbital decay (uncontrolled entry) or with a controlled entry. Orbital decay may be achieved by firing engines to lower the perigee altitude so that atmospheric drag will eventually cause the spacecraft to enter. However, the surviving debris impact footprint cannot be guaranteed to avoid inhabited landmasses. Controlled entry normally occurs by using a larger amount of propellant with a larger propulsion system to drive the spacecraft to enter the atmosphere at a steeper flight path angle. It will then enter at a more precise latitude, longitude, and footprint in a nearly uninhabited impact region, generally located in the ocean.

  10. Radar Observations of Convective Systems from a High-Altitude Aircraft

    Science.gov (United States)

    Heymsfield, G.; Geerts, B.; Tian, L.

    1999-01-01

    Reflectivity data collected by the precipitation radar on board the tropical Rainfall Measuring Mission (TRMM) satellite, orbiting at 350 km altitude, are compared to reflectivity data collected nearly simultaneously by a doppler radar aboard the NASA ER-2 flying at 19-20 km altitude, i.e. above even the deepest convection. The TRMM precipitation radar is a scanning device with a ground swath width of 215 km, and has a resolution of about a4.4 km in the horizontal and 250 m in the vertical (125 m in the core swath 48 km wide). The TRMM radar has a wavelength of 217 cm (13.8 GHz) and the Nadir mirror echo below the surface is used to correct reflectivity for loss by attenuation. The ER-2 Doppler radar (EDOP) has two antennas, one pointing to the nadir, 34 degrees forward. The forward pointing beam receives both the normal and the cross-polarized echos, so the linear polarization ratio field can be monitored. EDOP has a wavelength of 3.12 cm (9.6 GHz), a vertical resolution of 37.5 m and a horizontal along-track resolution of about 100 m. The 2-D along track airflow field can be synthesized from the radial velocities of both beams, if a reflectivity-based hydrometer fall speed relation can be assumed. It is primarily the superb vertical resolution that distinguishes EDOP from other ground-based or airborne radars. Two experiments were conducted during 1998 into validate TRMM reflectivity data over convection and convectively-generated stratiform precipitation regions. The Teflun-A (TEXAS-Florida Underflight) experiment, was conducted in April and May and focused on mesoscale convective systems mainly in southeast Texas. TEFLUN-B was conducted in August-September in central Florida, in coordination with CAMEX-3 (Convection and Moisture Experiment). The latter was focused on hurricanes, especially during landfall, whereas TEFLUN-B concentrated on central; Florida convection, which is largely driven and organized by surface heating and ensuing sea breeze circulations

  11. Effects of altitude and exercise on pulmonary capillary integrity: evidence for subclinical high-altitude pulmonary edema.

    Science.gov (United States)

    Eldridge, Marlowe W; Braun, Ruedi K; Yoneda, Ken Y; Walby, William F

    2006-03-01

    Strenuous exercise may be a significant contributing factor for development of high-altitude pulmonary edema, particularly at low or moderate altitudes. Thus we investigated the effects of heavy cycle ergometer exercise (90% maximal effort) under hypoxic conditions in which the combined effects of a marked increase in pulmonary blood flow and nonuniform hypoxic pulmonary vasoconstriction could add significantly to augment the mechanical stress on the pulmonary microcirculation. We postulated that intense exercise at altitude would result in an augmented permeability edema. We recruited eight endurance athletes and examined their bronchoalveolar lavage fluid (BALF) for red blood cells (RBCs), protein, inflammatory cells, and soluble mediators at 2 and 26 h after intense exercise under normoxic and hypoxic conditions. After heavy exercise, under all conditions, the athletes developed a permeability edema with high BALF RBC and protein concentrations in the absence of inflammation. We found that exercise at altitude (3,810 m) caused significantly greater leakage of RBCs [9.2 (SD 3.1)x10(4) cells/ml] into the alveolar space than that seen with normoxic exercise [5.4 (SD 1.2)x10(4) cells/ml]. At altitude, the 26-h postexercise BALF revealed significantly higher RBC and protein concentrations, suggesting an ongoing capillary leak. Interestingly, the BALF profiles following exercise at altitude are similar to that of early high-altitude pulmonary edema. These findings suggest that pulmonary capillary disruption occurs with intense exercise in healthy humans and that hypoxia augments the mechanical stresses on the pulmonary microcirculation.

  12. Average thermospheric wind patterns over the polar regions, as observed by CHAMP

    Directory of Open Access Journals (Sweden)

    H. Lühr

    2007-06-01

    Full Text Available Measurements of the CHAMP accelerometer are utilized to investigate the average thermospheric wind distribution in the polar regions at altitudes around 400 km. This study puts special emphasis on the seasonal differences in the wind patterns. For this purpose 131 days centered on the June solstice of 2003 are considered. Within that period CHAMP's orbit is precessing once through all local times. The cross-track wind estimates of all 2030 passes are used to construct mean wind vectors for 918 equal-area cells. These bin averages are presented in corrected geomagnetic coordinates. Both hemispheres are considered simultaneously providing summer and winter responses for the same prevailing geophysical conditions. The period under study is characterized by high magnetic activity (Kp=4− but moderate solar flux level (F10.7=124. Our analysis reveals clear wind features in the summer (Northern Hemisphere. Over the polar cap there is a fast day-to-night flow with mean speeds surpassing 600 m/s in the dawn sector. At auroral latitudes we find strong westward zonal winds on the dawn side. On the dusk side, however, an anti-cyclonic vortex is forming. The dawn/dusk asymmetry is attributed to the combined action of Coriolis and centrifugal forces. Along the auroral oval the sunward streaming plasma causes a stagnation of the day-to-night wind. This effect is particularly clear on the dusk side. On the dawn side it is evident only from midnight to 06:00 MLT. The winter (Southern Hemisphere reveals similar wind features, but they are less well ordered. The mean day-to-night wind over the polar cap is weaker by about 35%. Otherwise, the seasonal differences are mainly confined to the dayside (06:00–18:00 MLT. In addition, the larger offset between geographic and geomagnetic pole in the south also causes hemispheric differences of the thermospheric wind distribution.

  13. Average thermospheric wind patterns over the polar regions, as observed by CHAMP

    Directory of Open Access Journals (Sweden)

    H. Lühr

    2007-06-01

    Full Text Available Measurements of the CHAMP accelerometer are utilized to investigate the average thermospheric wind distribution in the polar regions at altitudes around 400 km. This study puts special emphasis on the seasonal differences in the wind patterns. For this purpose 131 days centered on the June solstice of 2003 are considered. Within that period CHAMP's orbit is precessing once through all local times. The cross-track wind estimates of all 2030 passes are used to construct mean wind vectors for 918 equal-area cells. These bin averages are presented in corrected geomagnetic coordinates. Both hemispheres are considered simultaneously providing summer and winter responses for the same prevailing geophysical conditions. The period under study is characterized by high magnetic activity (Kp=4− but moderate solar flux level (F10.7=124. Our analysis reveals clear wind features in the summer (Northern Hemisphere. Over the polar cap there is a fast day-to-night flow with mean speeds surpassing 600 m/s in the dawn sector. At auroral latitudes we find strong westward zonal winds on the dawn side. On the dusk side, however, an anti-cyclonic vortex is forming. The dawn/dusk asymmetry is attributed to the combined action of Coriolis and centrifugal forces. Along the auroral oval the sunward streaming plasma causes a stagnation of the day-to-night wind. This effect is particularly clear on the dusk side. On the dawn side it is evident only from midnight to 06:00 MLT. The winter (Southern Hemisphere reveals similar wind features, but they are less well ordered. The mean day-to-night wind over the polar cap is weaker by about 35%. Otherwise, the seasonal differences are mainly confined to the dayside (06:00–18:00 MLT. In addition, the larger offset between geographic and geomagnetic pole in the south also causes hemispheric differences of the thermospheric wind distribution.

  14. Altitude Distribution of the Auroral Acceleration Potential Determined from Cluster Satellite Data at Different Heights

    International Nuclear Information System (INIS)

    Marklund, Goeran T.; Sadeghi, Soheil; Karlsson, Tomas; Lindqvist, Per-Arne; Nilsson, Hans; Forsyth, Colin; Fazakerley, Andrew; Lucek, Elizabeth A.; Pickett, Jolene

    2011-01-01

    Aurora, commonly seen in the polar sky, is a ubiquitous phenomenon occurring on Earth and other solar system planets. The colorful emissions are caused by electron beams hitting the upper atmosphere, after being accelerated by quasistatic electric fields at 1-2 R E altitudes, or by wave electric fields. Although aurora was studied by many past satellite missions, Cluster is the first to explore the auroral acceleration region with multiprobes. Here, Cluster data are used to determine the acceleration potential above the aurora and to address its stability in space and time. The derived potential comprises two upper, broad U-shaped potentials and a narrower S-shaped potential below, and is stable on a 5 min time scale. The scale size of the electric field relative to that of the current is shown to depend strongly on altitude within the acceleration region. To reveal these features was possible only by combining data from the two satellites.

  15. Mafic Materials in Scott Crater? A Test for Lunar Reconnaissance Orbiter

    Science.gov (United States)

    Cooper, Bonnie L.

    2007-01-01

    Clementine 750 nm and multispectral ratio data, along with Lunar Orbiter and radar data, were used to study the crater Scott in the lunar south polar region. The multispectral data provide evidence for mafic materials, impact melts, anorthositic materials, and a small pyroclastic deposit. High-resolution radar data and Lunar Orbiter photography for this area show differences in color and surface texture that correspond with the locations of the hypothesized mafic and anorthositic areas on the crater floor. This region provides a test case for the upcoming Lunar Reconnaissance Orbiter. Verification of the existence of a mafic deposit at this location is relevant to future lunar resource utilization planning.

  16. Dzyaloshinskii-Moriya interaction in the presence of Rashba and Dresselhaus spin-orbit coupling

    Science.gov (United States)

    Valizadeh, Mohammad M.; Satpathy, S.

    2018-03-01

    Chiral order in magnetic structures is currently an area of considerable interest and leads to skyrmion structures and domain walls with certain chirality. The chiral structure originates from the Dzyaloshinskii-Moriya interaction caused by broken inversion symmetry and the spin-orbit interaction. In addition to the Rashba or Dresselhaus interactions, there may also exist substantial spin polarization in magnetic thin films. Here, we study the exchange interaction between two localized magnetic moments in the spin-polarized electron gas with both Rashba and Dresselhaus spin-orbit interaction present. Analytical expressions are found in certain limits in addition to what is known in the literature. The stability of the Bloch and Néel domain walls in magnetic thin films is discussed in light of our results.

  17. PCVs Estimation and their Impacts on Precise Orbit Determination of LEOs

    Science.gov (United States)

    Chunmei, Z.; WANG, X.

    2017-12-01

    In the last decade the precise orbit determination (POD) based on GNSS, such as GPS, has been considered as one of the efficient methods to derive orbits of Low Earth Orbiters (LEOs) that demand accuracy requirements. The Earth gravity field recovery and its related researches require precise dynamic orbits of LEOs. With the improvements of GNSS satellites' orbit and clock accuracy, the algorithm optimization and the refinement of perturbation force models, the antenna phase-center variations (PCVs) of space-borne GNSS receiver have become an increasingly important factor that affects POD accuracy. A series of LEOs such as HY-2, ZY-3 and FY-3 with homebred space-borne GNSS receivers have been launched in the past several years in China. Some of these LEOs load dual-mode GNSS receivers of GPS and BDS signals. The reliable performance of these space-borne receivers has been establishing an important foundation for the future launches of China gravity satellites. Therefore, we first evaluate the data quality of on-board GNSS measurement by examining integrity, multipath error, cycle slip ratio and other quality indices. Then we determine the orbits of several LEOs at different altitudes by the reduced dynamic orbit determination method. The corresponding ionosphere-free carrier phase post-fit residual time series are obtained. And then we establish the PCVs model by the ionosphere-free residual approach and analyze the effects of antenna phase-center variation on orbits. It is shown that orbit accuracy of LEO satellites is greatly improved after in-flight PCV calibration. Finally, focus on the dual-mode receiver of FY-3 satellite we analyze the quality of onboard BDS data and then evaluate the accuracy of the FY-3 orbit determined using only BDS measurement onboard. The accuracy of LEO satellites orbit based on BDS would be well improved with the global completion of BDS by 2020.

  18. Land Surface Temperature- Comparing Data from Polar Orbiting and Geostationary Satellites

    Science.gov (United States)

    Comyn-Platt, E.; Remedios, J. J.; Good, E. J.; Ghent, D.; Saunders, R.

    2012-04-01

    Land Surface Temperature (LST) is a vital parameter in Earth climate science, driving long-wave radiation exchanges that control the surface energy budget and carbon fluxes, which are important factors in Numerical Weather Prediction (NWP) and the monitoring of climate change. Satellites offer a convenient way to observe LST consistently and regularly over large areas. A comparison between LST retrieved from a Geostationary Instrument, the Spinning Enhanced Visible and InfraRed Imager (SEVIRI), and a Polar Orbiting Instrument, the Advanced Along Track Scanning Radiometer (AATSR) is presented. Both sensors offer differing benefits. AATSR offers superior precision and spatial resolution with global coverage but given its sun-synchronous platform only observes at two local times, ~10am and ~10pm. SEVIRI provides the high-temporal resolution (every 15 minutes) required for observing diurnal variability of surface temperatures but given its geostationary platform has a poorer resolution, 3km at nadir, which declines at higher latitudes. A number of retrieval methods are applied to the raw satellite data: First order coefficient based algorithms provided on an operational basis by the LandSAF (for SEVIRI) and the University of Leicester (for AATSR); Second order coefficient based algorithms put forward by the University of Valencia; and an optimal estimation method using the 1DVar software provided by the NWP SAF. Optimal estimation is an iterative technique based upon inverse theory, thus is very useful for expanding into data assimilation systems. The retrievals are assessed and compared on both a fine scale using in-situ data from recognised validation sites and on a broad scale using two 100x100 regions such that biases can be better understood. Overall, the importance of LST lies in monitoring daily temperature extremes, e.g. for estimating permafrost thawing depth or risk of crop damage due to frost, hence the ideal dataset would use a combination of observations

  19. Characteristics of trapped proton anisotropy at Space Station Freedom altitudes

    Science.gov (United States)

    Armstrong, T. W.; Colborn, B. L.; Watts, J. W.

    1990-01-01

    The ionizing radiation dose for spacecraft in low-Earth orbit (LEO) is produced mainly by protons trapped in the Earth's magnetic field. Current data bases describing this trapped radiation environment assume the protons to have an isotropic angular distribution, although the fluxes are actually highly anisotropic in LEO. The general nature of this directionality is understood theoretically and has been observed by several satellites. The anisotropy of the trapped proton exposure has not been an important practical consideration for most previous LEO missions because the random spacecraft orientation during passage through the radiation belt 'averages out' the anisotropy. Thus, in spite of the actual exposure anisotropy, cumulative radiation effects over many orbits can be predicted as if the environment were isotropic when the spacecraft orientation is variable during exposure. However, Space Station Freedom will be gravity gradient stabilized to reduce drag, and, due to this fixed orientation, the cumulative incident proton flux will remain anisotropic. The anisotropy could potentially influence several aspects of Space Station design and operation, such as the appropriate location for radiation sensitive components and experiments, location of workstations and sleeping quarters, and the design and placement of radiation monitors. Also, on-board mass could possible be utilized to counteract the anisotropy effects and reduce the dose exposure. Until recently only omnidirectional data bases for the trapped proton environment were available. However, a method to predict orbit-average, angular dependent ('vector') trapped proton flux spectra has been developed from the standard omnidirectional trapped proton data bases. This method was used to characterize the trapped proton anisotropy for the Space Station orbit (28.5 degree inclination, circular) in terms of its dependence on altitude, solar cycle modulation (solar minimum vs. solar maximum), shielding thickness

  20. Improper ferroelectric polarization in a perovskite driven by intersite charge transfer and ordering

    Science.gov (United States)

    Chen, Wei-Tin; Wang, Chin-Wei; Wu, Hung-Cheng; Chou, Fang-Cheng; Yang, Hung-Duen; Simonov, Arkadiy; Senn, M. S.

    2018-04-01

    It is of great interest to design and make materials in which ferroelectric polarization is coupled to other order parameters such as lattice, magnetic, and electronic instabilities. Such materials will be invaluable in next-generation data storage devices. Recently, remarkable progress has been made in understanding improper ferroelectric coupling mechanisms that arise from lattice and magnetic instabilities. However, although theoretically predicted, a compact lattice coupling between electronic and ferroelectric (polar) instabilities has yet to be realized. Here we report detailed crystallographic studies of a perovskite HgAMn3A'Mn4BO12 that is found to exhibit a polar ground state on account of such couplings that arise from charge and orbital ordering on both the A'- and B-sites, which are themselves driven by a highly unusual MnA '-MnB intersite charge transfer. The inherent coupling of polar, charge, orbital, and hence magnetic degrees of freedom make this a system of great fundamental interest, and demonstrating ferroelectric switching in this and a host of recently reported hybrid improper ferroelectrics remains a substantial challenge.

  1. Chang?E-5T Orbit Determination Using Onboard GPS Observations

    OpenAIRE

    Su, Xing; Geng, Tao; Li, Wenwen; Zhao, Qile; Xie, Xin

    2017-01-01

    In recent years, Global Navigation Satellite System (GNSS) has played an important role in Space Service Volume, the region enclosing the altitudes above 3000 km up to 36,000 km. As an in-flight test for the feasibility as well as for the performance of GNSS-based satellite orbit determination (OD), the Chinese experimental lunar mission Chang?E-5T had been equipped with an onboard high-sensitivity GNSS receiver with GPS and GLONASS tracking capability. In this contribution, the 2-h onboard G...

  2. Accelerating polarized beams in Tevatron

    International Nuclear Information System (INIS)

    Teng, L.C.

    1989-02-01

    In this paper, we will examine the totality of equipment, manpower and cost necessary to obtain a polarized proton beam in the Tevatron. We will not, however, be concerned with the acquisition and acceleration of polarized /bar p/ beams. Furthermore we will consider only a planar main ring without overpass, although it is expected that Siberian snake schemes could be made to apply equally well to non-planar machines. In addition to not wanting to tackle here the task of reformulating the theory for a non-planar closed orbit, we also anticipate that as part of the Tevatron upgrade the main ring will in the not too distant future, be replaced by a planar main injector situated in a separate tunnel. 4 refs., 11 figs., 1 tab

  3. Spin motion at and near orbital resonance in storage rings with Siberian snakes I. At orbital resonance

    International Nuclear Information System (INIS)

    Barber, D.P.; Vogt, M.

    2006-12-01

    Here, and in a sequel, we invoke the invariant spin field to provide an in-depth study of spin motion at and near low order orbital resonances in a simple model for the effects of vertical betatron motion in a storage ring with Siberian Snakes. This leads to a clear understanding, within the model, of the behaviour of the beam polarization at and near so-called snake resonances in proton storage rings. (orig.)

  4. Military Applications of High-Altitude Satellite Orbits in a Multi-Body Dynamical Environment Using Numerical Methods and Dynamical Systems Theory

    Science.gov (United States)

    2016-03-01

    around a libration point in the Earth -Moon system are used as unpredictable transfer pathways when traveling from one Earth orbit to another...spacecraft traveling from one Earth orbit to another in a multi- body environment, as well as characterizing the potential motions in the vicinity of...an inspiring account of how using the gravity of the Moon assisted in placing the satellite in a favorable Earth orbit after a rocket malfunction left

  5. Analysis of high-altitude de-acclimatization syndrome after exposure to high altitudes: a cluster-randomized controlled trial.

    Science.gov (United States)

    He, Binfeng; Wang, Jianchun; Qian, Guisheng; Hu, Mingdong; Qu, Xinming; Wei, Zhenghua; Li, Jin; Chen, Yan; Chen, Huaping; Zhou, Qiquan; Wang, Guansong

    2013-01-01

    The syndrome of high-altitude de-acclimatization commonly takes place after long-term exposure to high altitudes upon return to low altitudes. The syndrome severely affects the returnee's quality of life. However, little attention has been paid to careful characterization of the syndrome and their underlying mechanisms. Male subjects from Chongqing (n = 67, 180 m) and Kunming (n = 70, 1800 m) visited a high-altitude area (3650 m) about 6 months and then returned to low-altitude. After they came back, all subjects were evaluated for high-altitude de-acclimatization syndrome on the 3(rd), 50(th), and 100(th). Symptom scores, routine blood and blood gas tests, and myocardial zymograms assay were used for observation their syndrome. The results showed that the incidence and severity of symptoms had decreased markedly on the 50(th) and 100(th) days, compared with the 3(rd) day. The symptom scores and incidence of different symptoms were lower among subjects returning to Kunming than among those returning to Chongqing. On the 3(rd) day, RBC, Hb, Hct, CK, CK-MB, and LDH values were significantly lower than values recorded at high altitudes, but they were higher than baseline values. On the 50(th) day, these values were not different from baseline values, but LDH levels did not return to baseline until the 100(th) day. These data show that, subjects who suffered high-altitude de-acclimatization syndrome, the recovery fully processes takes a long time (≥ 100(th) days). The appearance of the syndrome is found to be related to the changes in RBC, Hb, Hct, CK, CK-MB, and LDH levels, which should be caused by reoxygenation after hypoxia.

  6. Prospects for polarization at RHIC and SSC

    International Nuclear Information System (INIS)

    Lee, S.Y.

    1991-01-01

    In low to medium energy accelerators, betatron tune jumps and vertical orbit harmonic correction methods have been used to overcome the intrinsic and imperfection resonances. At high energy accelerators, snakes are needed to preserve polarization. We analyze the effects of snake resonances, snake imperfections overlapping resonances on the spin depolarization. We discuss also results of recent snake experiments at the IUCF Cooler Ring. The snake can overcome various kinds of spin depolarization resonances. These experiments pointed out further that partial snake can be used to cure the imperfection resonances in low to medium energy accelerators. We also examine various snake designs. A new generalized snake concept allows for two possible configurations. The compact configuration offers the advantages of shorter total snake length and smaller horizontal orbit displacement. The split snake configuration allows for dual functions of a snake and a 90 degree spin rotator at the mid-section of the snake, which provides helicity state collisions. The requirements for obtaining high luminosity polarized protons at high energy colliders, such as RHIC and SSC, are reviewed

  7. Parabolic heavy ion flow in the polar magnetosphere

    International Nuclear Information System (INIS)

    Horwitz, J.L.

    1987-01-01

    Recent observations by the Dynamics Explorer 1 satellite over the dayside polar cap magnetosphere have indicated downward flows of heavy ions (O + , O ++ , N + , N ++ ) with flow velocities of the order 1 km/s (Lockwood et al., 1985b). These downward flows were interpreted as the result of parabolic flow of these heavy ionospheric ions from a source region associated with the polar cleft topside ionosphere. Here the author utilizes a two-dimensional kinetic model to elicit features of the transport of very low energy O + ions from the cleft ionosphere. Bulk parameter (density, flux, thermal energies, etc.) distributions in the noon-midnight meridian plane illustrate the effects of varying convection electric fields and source energies. The results illustrate that particularly under conditions of weak convection electric fields and weak ion heating in the cleft region, much of the intermediate altitude polar cap magnetosphere may be populated by downward flowing heavy ions. It is further shown how two-dimensional transport effects may alter the characteristic vertical profiles of densities and fluxes from ordinary profiles computed in one-dimensional steady state models

  8. A low cost automatic detection and ranging system for space surveillance in the medium Earth orbit region and beyond.

    Science.gov (United States)

    Danescu, Radu; Ciurte, Anca; Turcu, Vlad

    2014-02-11

    The space around the Earth is filled with man-made objects, which orbit the planet at altitudes ranging from hundreds to tens of thousands of kilometers. Keeping an eye on all objects in Earth's orbit, useful and not useful, operational or not, is known as Space Surveillance. Due to cost considerations, the space surveillance solutions beyond the Low Earth Orbit region are mainly based on optical instruments. This paper presents a solution for real-time automatic detection and ranging of space objects of altitudes ranging from below the Medium Earth Orbit up to 40,000 km, based on two low cost observation systems built using commercial cameras and marginally professional telescopes, placed 37 km apart, operating as a large baseline stereovision system. The telescopes are pointed towards any visible region of the sky, and the system is able to automatically calibrate the orientation parameters using automatic matching of reference stars from an online catalog, with a very high tolerance for the initial guess of the sky region and camera orientation. The difference between the left and right image of a synchronized stereo pair is used for automatic detection of the satellite pixels, using an original difference computation algorithm that is capable of high sensitivity and a low false positive rate. The use of stereovision provides a strong means of removing false positives, and avoids the need for prior knowledge of the orbits observed, the system being able to detect at the same time all types of objects that fall within the measurement range and are visible on the image.

  9. Generation of radio vortex beams with designable polarization using anisotropic frequency selective surface

    Science.gov (United States)

    Yang, Jin; Zhang, Cheng; Ma, Hui Feng; Zhao, Jie; Dai, Jun Yan; Yuan, Wei; Yang, Liu Xi; Cheng, Qiang; Cui, Tie Jun

    2018-05-01

    We propose a strategy to convert a linearly polarized wave from a single point source to an orbital angular momentum (OAM) wave by arbitrary polarization via an anisotropic frequency selective surface (FSS) in the microwave frequency. By tailoring the geometries of FSS elements, reflection-phases in x and y polarizations are engineered and encoded independently, which allows us to design the eventual polarization state of the generated OAM vortex beam by elaborately selecting individual coding sequences for each polarization. Two types of FSSs are designed and experimentally characterized to demonstrate the capability of OAM generation with circular and linear polarizations, respectively, showing excellent performance in a wide bandwidth from 14 to 16 GHz. This method provides opportunities for polarization multiplexing in microwave OAM communication systems.

  10. A model of quasi-free scattering with polarized protons

    International Nuclear Information System (INIS)

    Teodoro, M.R.

    1976-01-01

    A quantitative evaluation, based on a simple model for spin-free coplanar and asymmetric reaction in 16 O, for 215 MeV incoming polarized protons confirms the use of the strong effective polarization of the knocked-out proton by the spin-orbit coupling and of the strong dependence of free, medium energy, proton-proton cross section on the relative orientation of the proton spins. Effective polarizations, momentum distributions and correlation cross sections have been calculated for the 1p sub(1/2), 1 p sub(3/2) and 1s sub(1/2) states in 16 O, using protons totally polarized orthogonal to the scattering plane. Harmonic oscillator and square wells have been used to generate the bound state wave functions, whereas the optical potentials have been taken spin-independent and purely imaginary [pt

  11. Incidence and Symptoms of High Altitude Illness in South Pole Workers: Antarctic Study of Altitude Physiology (ASAP

    Directory of Open Access Journals (Sweden)

    Paul J. Anderson

    2011-01-01

    Full Text Available Introduction Each year, the US Antarctic Program rapidly transports scientists and support personnel from sea level (SL to the South Pole (SP, 2835 m providing a unique natural laboratory to quantify the incidence of acute mountain sickness (AMS, patterns of altitude related symptoms and the field effectiveness of acetazolamide in a highly controlled setting. We hypothesized that the combination of rapid ascent (3 hr, accentuated hypobarism (relative to altitude, cold, and immediate exertion would increase altitude illness risk. Methods Medically screened adults (N = 246, age = 37 ± 11 yr, 30% female, BMI = 26 ± 4 kg/m 2 were recruited. All underwent SL and SP physiological evaluation, completed Lake Louise symptom questionnaires (LLSQ, to define AMS, and answered additional symptom related questions (eg, exertional dyspnea, mental status, cough, edema and general health, during the 1st week at altitude. Acetazolamide, while not mandatory, was used by 40% of participants. Results At SP, the barometric pressure resulted in physiological altitudes that approached 3400 m, while T ° C averaged -42, humidity 0.03%. Arterial oxygen saturation averaged 89% ± 3%. Overall, 52% developed LLSQ defined AMS. The most common symptoms reported were exertional dyspnea-(87%, sleeping difficulty-(74%, headache-(66%, fatigue-(65%, and dizziness/lightheadedness-(46%. Symptom severity peaked on days 1-2, yet in >20% exertional dyspnea, fatigue and sleep problems persisted through day 7. AMS incidence was similar between those using acetazolamide and those abstaining (51 vs. 52%, P = 0.87. Those who used acetazolamide tended to be older, have less altitude experience, worse symptoms on previous exposures, and less SP experience. Conclusion The incidence of AMS at SP tended to be higher than previously reports in other geographic locations at similar altitudes. Thus, the SP constitutes a more intense altitude exposure than might be expected considering physical

  12. Future earth orbit transportation systems/technology implications

    Science.gov (United States)

    Henry, B. Z.; Decker, J. P.

    1976-01-01

    Assuming Space Shuttle technology to be state-of-the-art, projected technological advances to improve the capabilities of single-stage-to-orbit (SSTO) derivatives are examined. An increase of about 30% in payload performance can be expected from upgrading the present Shuttle system through weight and drag reductions and improvements in the propellants and engines. The ODINEX (Optimal Design Integration Executive Computer Program) program has been used to explore design options. An advanced technology SSTO baseline system derived from ODINEX analysis has a conventional wing-body configuration using LOX/LH engines, three with two-position nozzles with expansion ratios of 40 and 200 and four with fixed nozzles with an expansion ratio of 40. Two assisted-takeoff approaches are under consideration in addition to a concept in which the orbital vehicle takes off empty using airbreathing propulsion and carries out a rendezvous with two large cryogenic tankers carrying propellant at an altitude of 6100 m. Further approaches under examination for propulsion, aerothermodynamic design, and design integration are described.

  13. Spin-polarized currents in a two-terminal double quantum ring driven by magnetic fields and Rashba spin-orbit interaction

    Science.gov (United States)

    Dehghan, E.; Khoshnoud, D. Sanavi; Naeimi, A. S.

    2018-06-01

    Aim of this study is to investigate spin transportation in double quantum ring (DQR). We developed an array of DQR to measure the transmission coefficient and analyze the spin transportation through this system in the presence of Rashba spin-orbit interaction (RSOI) and magnetic flux estimated using S-matrix method. In this article, we compute the spin transport and spin-current characteristics numerically as functions of electron energy, angles between the leads, coupling constant of the leads, RSOI, and magnetic flux. Our results suggest that, for typical values of the magnetic flux (ϕ /ϕ0) and Rashba constant (αR), such system can demonstrates many spintronic properties. It is possible to design a new geometry of DQR by incoming electrons polarization in a way to optimize the system to work as a spin-filtering and spin-inverting nano-device with very high efficiency. The results prove that the spin current will strongly modulate with an increase in the magnetic flux and Rashba constant. Moreover it is shown that, when the lead coupling is weak, the perfect spin-inverter does not occur.

  14. A multi-satellite analysis of the direct radiative effects of absorbing aerosols above clouds

    Science.gov (United States)

    Chang, Y. Y.; Christopher, S. A.

    2015-12-01

    Radiative effects of absorbing aerosols above liquid water clouds in the southeast Atlantic as a function of fire sources are investigated using A-Train data coupled with the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard Suomi National Polar-orbiting Partnership (Suomi NPP). Both the VIIRS Active Fire product and the Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) Thermal Anomalies product (MYD14) are used to identify the biomass burning fire origin in southern Africa. The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) are used to assess the aerosol type, aerosol altitude, and cloud altitude. We use back trajectory information, wind data, and the Fire Locating and Modeling of Burning Emissions (FLAMBE) product to infer the transportation of aerosols from the fire source to the CALIOP swath in the southeast Atlantic during austral winter.

  15. Hydrogen Distribution in the Lunar Polar Regions

    Science.gov (United States)

    Sanin, A. B.; Mitrofanov, I. G.; Litvak, M. L.; Bakhtin, B. N.; Bodnarik, J. G.; Boynton, W. V.; Chin, G.; Evans, L. G.; Harshmann, K.; Fedosov, F.; hide

    2016-01-01

    We present a method of conversion of the lunar neutron counting rate measured by the Lunar Reconnaissance Orbiter (LRO) Lunar Exploration Neutron Detector (LEND) instrument collimated neutron detectors, to water equivalent hydrogen (WEH) in the top approximately 1 m layer of lunar regolith. Polar maps of the Moon’s inferred hydrogen abundance are presented and discussed.

  16. Titanium magnetic polarization at the Fe/BaTiO3 interfaces: An effect of ferroelectric polarization discontinuity

    Science.gov (United States)

    Paul, Amitesh; Zheng, Jian-Guo; Aoki, Toshihiro

    2017-10-01

    The exotic magnetic phenomena and the associated functionalities have attracted extensive scientific interest in fundamental physics and cater to the purpose of the novel material search. In this article, with a combination of the electron energy-loss spectroscopy and the X-ray absorption spectroscopy, we have investigated the interfacial Fe atoms and the induced ferromagnetic moment of Ti atoms in Fe/BaTiO3 (BTO) heterostructures. The samples were grown with two different BTO thicknesses, thus resulting in two different states of distorted oxygen environments or different electrostatic potentials. We demonstrate that in these systems, the electronic and magnetic proximity effects remain coupled as the ferroelectric polar discontinuity is held responsible for an induced transfer of the interface electrons. These electrons migrate from the Fe2+ layers to the Ti(4+)-δ layers with the hybridization via O-2p oxide orbitals into Ti orbitals to screen the ferroelectric polarization. These findings, in charge neutral BaO-TiO2 and FeO layers or nonpolar/nopolar interface, essentially underline the central role of the covalent bonding in defining the spin-electronic properties.

  17. Early history of high-altitude physiology.

    Science.gov (United States)

    West, John B

    2016-02-01

    High-altitude physiology can be said to have begun in 1644 when Torricelli described the first mercury barometer and wrote the immortal words "We live submerged at the bottom of an ocean of the element air." Interestingly, the notion of atmospheric pressure had eluded his teacher, the great Galileo. Blaise Pascal was responsible for describing the fall in pressure with increasing altitude, and Otto von Guericke gave a dramatic demonstration of the enormous force that could be developed by atmospheric pressure. Robert Boyle learned of Guericke's experiment and, with Robert Hooke, constructed the first air pump that allowed small animals to be exposed to a low pressure. Hooke also constructed a small low-pressure chamber and exposed himself to a simulated altitude of about 2400 meters. With the advent of ballooning, humans were rapidly exposed to very low pressures, sometimes with tragic results. For example, the French balloon, Zénith, rose to over 8000 m, and two of the three aeronauts succumbed to the hypoxia. Paul Bert was the first person to clearly state that the deleterious effects of high altitude were caused by the low partial pressure of oxygen (PO2), and later research was accelerated by high-altitude stations and expeditions to high altitude. © 2015 New York Academy of Sciences.

  18. Water Vapor, Temperature, and Ice Particles in Polar Mesosphere as Measured by SABER/TIMED and OSIRIS/Odin Instruments

    Science.gov (United States)

    Feofilov, A. G.; Petelina, S. V.; Kutepov, A. A.; Pesnell, W. D.; Goldberg, R. A.

    2009-01-01

    Although many new details on the properties of mesospheric ice particles that farm Polar Mesospheric Clouds (PMCs) and also cause polar mesospheric summer echoes have been recently revealed, certain aspects of mesospheric ice microphysics and dynamics still remain open. The detailed relation between PMC parameters and properties of their environment, as well as interseasonal and interhemispheric differences and trends in PMC properties that are possibly related to global change, are among those open questions. In this work, mesospheric temperature and water vapor concentration measured by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite are used to study the properties of PMCs with respect to the surrounding atmosphere. The cloud parameters, namely location, brightness, and altitude, are obtained from the observations made by the Optical Spectrograph and Infrared Imager System (OSIRIS) on the Odin satellite. About a thousand of simultaneous common volume measurements made by SABER and OSIRIS in both hemispheres from 2002 until 2008 are used. The correlation between PMC brightness (and occurrence rate) and temperatures at PMC altitudes and at the mesopause is analysed. The relation between PMC parameters, frost point temperature, and gaseous water vapor content in and below the cloud is also discussed. Interseasonal and interhemispheric differences and trends in the above parameters, as well as in PMC peak altitudes and mesopause altitudes are evaluated.

  19. Spin Interference in Rectangle Loop Based on Rashba and Dresselhaus Spin-Orbit Interactions

    International Nuclear Information System (INIS)

    Jia-Ting, Ni; Bin, Chen; Xiao-Wan, Liang; Koga, T.

    2009-01-01

    We demonstrate the amplitude and spin polarization of AAS oscillation changing with Rashba spin-orbit interaction (SOI) and Dresselhaus SOI. The amplitude and spin polarization of AB oscillation changing with Rashba SOI and Dresselhaus SOI are demonstrated as well. The ideal quasi-one-dimensional square loop does not exist in reality, therefore to match the experiment better we should consider the shape of the rectangle loop in theory

  20. Monitoring volcanic ash cloud top height through simultaneous retrieval of optical data from polar orbiting and geostationary satellites

    Directory of Open Access Journals (Sweden)

    K. Zakšek

    2013-03-01

    Full Text Available Volcanic ash cloud-top height (ACTH can be monitored on the global level using satellite remote sensing. Here we propose a photogrammetric method based on the parallax between data retrieved from geostationary and polar orbiting satellites to overcome some limitations of the existing methods of ACTH retrieval. SEVIRI HRV band and MODIS band 1 are a good choice because of their high resolution. The procedure works well if the data from both satellites are retrieved nearly simultaneously. MODIS does not retrieve the data at exactly the same time as SEVIRI. To compensate for advection we use two sequential SEVIRI images (one before and one after the MODIS retrieval and interpolate the cloud position from SEVIRI data to the time of MODIS retrieval. The proposed method was tested for the case of the Eyjafjallajökull eruption in April 2010. The parallax between MODIS and SEVIRI data can reach 30 km, which implies an ACTH of approximately 12 km at the beginning of the eruption. At the end of April eruption an ACTH of 3–4 km is observed. The accuracy of ACTH was estimated to be 0.6 km.

  1. The role of Rashba spin-orbit coupling in valley-dependent transport of Dirac fermions

    Energy Technology Data Exchange (ETDEWEB)

    Hasanirok, Kobra; Mohammadpour, Hakimeh

    2017-01-01

    At this work, spin- and valley-dependent electron transport through graphene and silicene layers are studied in the presence of Rashba spin- orbit coupling. We find that the transport properties of the related ferromagnetic/normal/ferromagnetic structure depend on the relevant parameters. A fully valley- and spin- polarized current is obtained. As another result, Rashba spin-orbit interaction plays important role in controlling the transmission characteristics.

  2. DRAGONS - A Micrometeoroid and Orbital Debris Impact Sensor

    Science.gov (United States)

    Liou, J. -C.; Corsaro, R.; Giovane, F.; Anderson, C.; Sadilek, A.; Burchell, M.; Hamilton, J.

    2015-01-01

    The Debris Resistive/Acoustic Grid Orbital Navy-NASA Sensor (DRAGONS) is intended to be a large area impact sensor for in situ measurements of micrometeoroids and orbital debris (MMOD) in the millimeter or smaller size regime. These MMOD particles are too small to be detected by ground-based radars and optical telescopes, but are still large enough to be a serious safety concern for human space activities and robotic missions in the low Earth orbit (LEO) region. The nominal detection area of a DRAGONS unit is 1 m2, consisting of several independently operated panels. The approach of the DRAGONS design is to combine different particle impact detection principles to maximize information that can be extracted from detected events. After more than 10 years of concept and technology development, a 1 m2 DRAGONS system has been selected for deployment on the International Space Station (ISS) in August 2016. The project team achieved a major milestone when the Preliminary Design Review (PDR) was completed in May 2015. Once deployed on the ISS, this multi-year mission will provide a unique opportunity to demonstrate the MMOD detection capability of the DRAGONS technologies and to collect data to better define the small MMOD environment at the ISS altitude.

  3. Design and construction of the POLAR detector

    Science.gov (United States)

    Produit, N.; Bao, T. W.; Batsch, T.; Bernasconi, T.; Britvich, I.; Cadoux, F.; Cernuda, I.; Chai, J. Y.; Dong, Y. W.; Gauvin, N.; Hajdas, W.; Kole, M.; Kong, M. N.; Kramert, R.; Li, L.; Liu, J. T.; Liu, X.; Marcinkowski, R.; Orsi, S.; Pohl, M.; Rapin, D.; Rybka, D.; Rutczynska, A.; Shi, H. L.; Socha, P.; Sun, J. C.; Song, L. M.; Szabelski, J.; Traseira, I.; Xiao, H. L.; Wang, R. J.; Wen, X.; Wu, B. B.; Zhang, L.; Zhang, L. Y.; Zhang, S. N.; Zhang, Y. J.; Zwolinska, A.

    2018-01-01

    The POLAR detector is a space based Gamma Ray Burst (GRB) polarimeter with a wide field of view, which covers almost half the sky. The instrument uses Compton scattering of gamma rays on a plastic scintillator hodoscope to measure the polarization of the incoming photons. The instrument has been successfully launched on board of the Chinese space laboratory Tiangong 2 on September 15, 2016. The construction of the instrument components is described in this article. Details are provided on problems encountered during the construction phase and their solutions. Initial performance of the instrument in orbit is as expected from ground tests and Monte Carlo simulation.

  4. Polarization-induced renormalization of molecular levels at metallic and semiconducting surfaces

    DEFF Research Database (Denmark)

    García Lastra, Juan Maria; Rostgaard, Carsten; Rubio, A.

    2009-01-01

    On the basis of first-principles G0W0 calculations we systematically study how the electronic levels of a benzene molecule are renormalized by substrate polarization when physisorbed on different metallic and semiconducting surfaces. The polarization-induced reduction in the energy gap between oc...... find that error cancellations lead to remarkably good agreement between the G0W0 and Kohn-Sham energies for the occupied orbitals of the adsorbed molecule....

  5. The O2 A-Band in the Fluxes and Polarization of Starlight Reflected by Earth-Like Exoplanets

    International Nuclear Information System (INIS)

    Fauchez, Thomas; Rossi, Loic; Stam, Daphne M.

    2017-01-01

    Earth-like, potentially habitable exoplanets are prime targets in the search for extraterrestrial life. Information about their atmospheres and surfaces can be derived by analyzing the light of the parent star reflected by the planet. We investigate the influence of the surface albedo A s , the optical thickness b cloud , the altitude of water clouds, and the mixing ratio of biosignature O 2 on the strength of the O 2 A-band (around 760 nm) in the flux and polarization spectra of starlight reflected by Earth-like exoplanets. Our computations for horizontally homogeneous planets show that small mixing ratios ( η < 0.4) will yield moderately deep bands in flux and moderate-to-small band strengths in polarization, and that clouds will usually decrease the band depth in flux and the band strength in polarization. However, cloud influence will be strongly dependent on properties such as optical thickness, top altitude, particle phase, coverage fraction, and horizontal distribution. Depending on the surface albedo and cloud properties, different O 2 mixing ratios η can give similar absorption-band depths in flux and band strengths in polarization, especially if the clouds have moderate-to-high optical thicknesses. Measuring both the flux and the polarization is essential to reduce the degeneracies, although it will not solve them, especially not for horizontally inhomogeneous planets. Observations at a wide range of phase angles and with a high temporal resolution could help to derive cloud properties and, once those are known, the mixing ratio of O 2 or any other absorbing gas.

  6. Cosmic-ray-induced radiation environment and dose to man for low-orbit space applications

    International Nuclear Information System (INIS)

    Sandmeier, H.A.; Hansen, G.E.; Battat, M.E.; O'Brien, K.

    1981-09-01

    Neutrons and photons resulting from the interaction of galactic cosmic rays with the material of an orbiting satellite or an orbiting space station at an altitude of some few hundreds of kilometers, and below the level of the radiation belts, have been calculated as a function of geomagnetic latitude and solar activity level. The photon and neutron leakage currents from the top of the atmosphere have been computed. The radiation dose-equivalent rate to an unshielded astronaut has also been calculated. The maximum dose-equivalent rate, near the magnetic poles, was 2 mrem/h. In deep space this would amount to 18 rem/y, indicating that for a prolonged stay in space, shielding would be needed

  7. Risk assessment and late effects of radiation in low-earth orbits

    International Nuclear Information System (INIS)

    Fry, R.J.M.

    1989-01-01

    The radiation dose rates in low-earth orbits are dependent on the altitude and orbital inclination. The doses to which the crews of space vehicles are exposed is governed by the duration of the mission and the shielding, and in low-earth orbit missions protons are the dominant particles encountered. The risk of concern with the low dose rates and the relatively low total doses of radiation that will be incurred on the space station is excess cancer. The National Council on Radiation Protection and Measurements has recently recommended career dose-equivalent limits that take into account sex and age. The new recommendations for career limits range from 1.0 Sv to 4 Sv, depending on sex and on the age at the time of their first space mission, compared to a single career limit of 4.0 Sv previously used by NASA. Risk estimates for radiated-induced cancer are evolving and changes in the current guidance may be required in the next few years. 10 refs., 1 fig., 3 tabs

  8. IPHAS J062746.41+014811.3: A DEEPLY ECLIPSING INTERMEDIATE POLAR

    International Nuclear Information System (INIS)

    Aungwerojwit, A.; Gänsicke, B. T.; Wheatley, P. J.; Pyrzas, S.; Staels, B.; Krajci, T.; Rodríguez-Gil, P.

    2012-01-01

    We present time-resolved photometry of a cataclysmic variable discovered in the Isaac Newton Telescope Photometric Hα Survey of the northern galactic plane, IPHAS J062746.41+014811.3, and classify the system as the fourth deeply eclipsing intermediate polar known with an orbital period of P orb = 8.16 hr and a spin period of P spin = 2210 s. The system shows mild variations of its brightness that appear to be accompanied by a change in the amplitude of the spin modulation at optical wavelengths and a change in the morphology of the eclipse profile. The inferred magnetic moment of the white dwarf is μ wd ∼ (6-7) × 10 33 G cm 3 , and in this case IPHAS J062746.41+014811.3 will evolve either into a short-period EX Hya-like intermediate polar with a large P spin /P orb ratio or, perhaps more likely, into a synchronized polar. Swift observations show that the system is an ultraviolet and X-ray source, with a hard X-ray spectrum that is consistent with those seen in other intermediate polars. The ultraviolet light curve shows orbital modulation and an eclipse, while the low signal-to-noise ratio X-ray light curve does not show a significant modulation on the spin period. The measured X-ray flux is about an order of magnitude lower than would be expected from scaling by the optical fluxes of well-known X-ray-selected intermediate polars.

  9. Martian North Polar Water-Ice Clouds During the Viking Era

    Science.gov (United States)

    Tamppari, L. K.; Bass, D. S.

    2000-01-01

    The Viking Orbiters determined that the surface of Mars' northern residual cap consists of water ice. Observed atmospheric water vapor abundances in the equatorial regions have been related to seasonal exchange between reservoirs such as the polar caps, the regolith and between different phases in the atmosphere. Kahn modeled the physical characteristics of ice hazes seen in Viking Orbiter imaging limb data, hypothesizing that ice hazes provide a method for scavenging water vapor from the atmosphere and accumulating it into ice particles. Given that Jakosky found that these particles had sizes such that fallout times were of order one Martian sol, these water-ice hazes provided a method for returning more water to the regolith than that provided by adsorption alone. These hazes could also explain the rapid hemispheric decrease in atmospheric water in late northern summer as well as the increase during the following early spring. A similar comparison of water vapor abundance versus polar cap brightness has been done for the north polar region. They have shown that water vapor decreases steadily between L(sub s) = 100-150 deg while polar cap albedo increases during the same time frame. As a result, they suggested that late summer water-ice deposition onto the ice cap may be the cause of the cap brightening. This deposition could be due to adsorption directly onto the cap surface or to snowfall. Thus, an examination of north polar waterice clouds could lend insight into the fate of the water vapor during this time period. Additional information is contained in the original extended abstract.

  10. Altitude training considerations for the winter sport athlete.

    Science.gov (United States)

    Chapman, Robert F; Stickford, Jonathon L; Levine, Benjamin D

    2010-03-01

    Winter sports events routinely take place at low to moderate altitudes, and nearly all Winter Olympic Games have had at least one venue at an altitude >1000 m. The acute and chronic effects of altitude can have a substantial effect on performance outcomes. Acutely, the decline in oxygen delivery to working muscle decreases maximal oxygen uptake, negatively affecting performance in endurance events, such as cross-country skiing and biathlon. The reduction in air resistance at altitude can dramatically affect sports involving high velocities and technical skill components, such as ski jumping, speed skating, figure skating and ice hockey. Dissociation between velocity and sensations usually associated with work intensity (ventilation, metabolic signals in skeletal muscle and heart rate) may impair pacing strategy and make it difficult to determine optimal race pace. For competitions taking place at altitude, a number of strategies may be useful, depending on the altitude of residence of the athlete and ultimate competition altitude, as follows. First, allow extra time and practice (how much is yet undetermined) for athletes to adjust to the changes in projectile motion; hockey, shooting, figure skating and ski jumping may be particularly affected. These considerations apply equally in the reverse direction; that is, for athletes practising at altitude but competing at sea level. Second, allow time for acclimatization for endurance sports: 3-5 days if possible, especially for low altitude (500-2000 m); 1-2 weeks for moderate altitude (2000-3000 m); and at least 2 weeks if possible for high altitude (>3000 m). Third, increase exercise-recovery ratios as much as possible, with 1:3 ratio probably optimal, and consider more frequent substitutions for sports where this is allowed, such as ice hockey. Fourth, consider the use of supplemental O(2) on the sideline (ice hockey) or in between heats (skating and Alpine skiing) to facilitate recovery. For competitions at sea

  11. Long-term orbit prediction for Tiangong-1 spacecraft using the mean atmosphere model

    Science.gov (United States)

    Tang, Jingshi; Liu, Lin; Cheng, Haowen; Hu, Songjie; Duan, Jianfeng

    2015-03-01

    China is planning to complete its first space station by 2020. For the long-term management and maintenance, the orbit of the space station needs to be predicted for a long period of time. Since the space station is expected to work in a low-Earth orbit, the error in the a priori atmosphere model contributes significantly to the rapid increase of the predicted orbit error. When the orbit is predicted for 20 days, the error in the a priori atmosphere model, if not properly corrected, could induce a semi-major axis error of up to a few kilometers and an overall position error of several thousand kilometers respectively. In this work, we use a mean atmosphere model averaged from NRLMSISE00. The a priori reference mean density can be corrected during the orbit determination. For the long-term orbit prediction, we use sufficiently long period of observations and obtain a series of the diurnal mean densities. This series contains the recent variation of the atmosphere density and can be analyzed for various periodic components. After being properly fitted, the mean density can be predicted and then applied in the orbit prediction. Here we carry out the test with China's Tiangong-1 spacecraft at the altitude of about 340 km and we show that this method is simple and flexible. The densities predicted with this approach can serve in the long-term orbit prediction. In several 20-day prediction tests, most predicted orbits show semi-major axis errors better than 700 m and overall position errors better than 400 km.

  12. Large-scale irregularities of the winter polar topside ionosphere according to data from Swarm satellites

    Science.gov (United States)

    Lukianova, R. Yu.; Bogoutdinov, Sh. R.

    2017-11-01

    An analysis of the electron density measurements ( Ne) along the flyby trajectories over the high-latitude region of the Northern Hemisphere under winter conditions in 2014 and 2016 has shown that the main large-scale structure observed by Swarm satellites is the tongue of ionization (TOI). At the maximum of the solar cycle ( F 10.7 = 160), the average value of Ne in the TOI region at an altitude of 500 km was 8 × 104 cm-3. Two years later, at F 10.7 = 100, Ne 5 × 104 cm-3 and Ne 2.5 × 104 cm-3 were observed at altitudes of 470 and 530 km, respectively. During the dominance of the azimuthal component of the interplanetary magnetic field, the TOI has been observed mainly on the dawn or dusk side depending on the sign of B y . Simultaneous observations of the convective plasma drift velocity in the polar cap show the transpolar flow drift to the dawn ( B y y generation of large-scale irregularities in the polar ionosphere.

  13. Adding a Mission to the Joint Polar Satellite System (JPSS) Common Ground System (CGS)

    Science.gov (United States)

    Miller, S. W.; Grant, K. D.; Jamilkowski, M. L.

    2014-12-01

    The National Oceanic and Atmospheric Administration (NOAA) and National Aeronautics and Space Administration (NASA) are jointly acquiring the next-generation civilian weather and environmental satellite system: the Joint Polar Satellite System (JPSS). The Joint Polar Satellite System will replace the afternoon orbit component and ground processing system of the current Polar-orbiting Operational Environmental Satellites (POES) managed by NOAA. The JPSS satellites will carry a suite of sensors designed to collect meteorological, oceanographic, climatological and geophysical observations of the Earth. The ground processing system for JPSS is known as the JPSS Common Ground System (JPSS CGS). Developed and maintained by Raytheon Intelligence, Information and Services (IIS), the CGS is a multi-mission enterprise system serving NOAA, NASA and their national and international partners. The CGS provides a wide range of support to a number of missions: 1) Command and control and mission management for the Suomi National Polar-orbiting Partnership (S-NPP) mission today, expanding this support to the JPSS-1 satellite and the Polar Free Flyer mission in 2017 2) Data acquisition via a Polar Receptor Network (PRN) for S-NPP, the Japan Aerospace Exploration Agency's (JAXA) Global Change Observation Mission - Water (GCOM-W1), POES, and the Defense Meteorological Satellite Program (DMSP) and Coriolis/WindSat for the Department of Defense (DoD) 3) Data routing over a global fiber Wide Area Network (WAN) for S-NPP, JPSS-1, Polar Free Flyer, GCOM-W1, POES, DMSP, Coriolis/WindSat, the NASA Space Communications and Navigation (SCaN, which includes several Earth Observing System [EOS] missions), MetOp for the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), and the National Science Foundation (NSF) 4) Environmental data processing and distribution for S-NPP, GCOM-W1 and JPSS-1 With this established infrastructure and existing suite of missions, the CGS

  14. Ionizing radiation environment for the TOMS mission

    Science.gov (United States)

    Lauriente, M.; Maloy, J. O.; Vampola, A. L.

    1992-01-01

    The Total Ozone Mapping Spectrometer (TOMS) will fly on several different spacecraft, each having an orbit which is approximately polar and 800-980 km in altitude. A description is given of the computer-based tools used for characterizing the spacecraft interactions with the ionizing radiation environment in orbit and the susceptibility requirements for ionizing radiation compatibility. The peak flux from the model was used to derive the expected radiation-induced noise in the South Atlantic Anomaly for the new TOMS instruments intended to fly on Advanced Earth Observatory System and Earth Probe.

  15. Interfacial B-site atomic configuration in polar (111) and non-polar (001) SrIrO3/SrTiO3 heterostructures

    Science.gov (United States)

    Anderson, T. J.; Zhou, H.; Xie, L.; Podkaminer, J. P.; Patzner, J. J.; Ryu, S.; Pan, X. Q.; Eom, C. B.

    2017-09-01

    The precise control of interfacial atomic arrangement in ABO3 perovskite heterostructures is paramount, particularly in cases where the subsequent electronic properties of the material exhibit geometrical preferences along polar crystallographic directions that feature inevitably complex surface reconstructions. Here, we present the B-site interfacial structure in polar (111) and non-polar (001) SrIrO3/SrTiO3 interfaces. The heterostructures were examined using scanning transmission electron microscopy and synchrotron-based coherent Bragg rod analysis. Our results reveal the preference of B-site intermixing across the (111) interface due to the polarity-compensated SrTiO3 substrate surface prior to growth. By comparison, the intermixing at the non-polar (001) interface is negligible. This finding suggests that the intermixing may be necessary to mitigate epitaxy along heavily reconstructed and non-stoichiometric (111) perovskite surfaces. Furthermore, this preferential B-site configuration could allow the geometric design of the interfacial perovskite structure and chemistry to selectively engineer the correlated electronic states of the B-site d-orbital.

  16. Interfacial B-site atomic configuration in polar (111 and non-polar (001 SrIrO3/SrTiO3 heterostructures

    Directory of Open Access Journals (Sweden)

    T. J. Anderson

    2017-09-01

    Full Text Available The precise control of interfacial atomic arrangement in ABO3 perovskite heterostructures is paramount, particularly in cases where the subsequent electronic properties of the material exhibit geometrical preferences along polar crystallographic directions that feature inevitably complex surface reconstructions. Here, we present the B-site interfacial structure in polar (111 and non-polar (001 SrIrO3/SrTiO3 interfaces. The heterostructures were examined using scanning transmission electron microscopy and synchrotron-based coherent Bragg rod analysis. Our results reveal the preference of B-site intermixing across the (111 interface due to the polarity-compensated SrTiO3 substrate surface prior to growth. By comparison, the intermixing at the non-polar (001 interface is negligible. This finding suggests that the intermixing may be necessary to mitigate epitaxy along heavily reconstructed and non-stoichiometric (111 perovskite surfaces. Furthermore, this preferential B-site configuration could allow the geometric design of the interfacial perovskite structure and chemistry to selectively engineer the correlated electronic states of the B-site d-orbital.

  17. Middle atmospheric water vapour and dynamics in the vicinity of the polar vortex during the Hygrosonde-2 campaign

    Directory of Open Access Journals (Sweden)

    S. Lossow

    2009-07-01

    Full Text Available The Hygrosonde-2 campaign took place on 16 December 2001 at Esrange/Sweden (68° N, 21° E with the aim to investigate the small scale distribution of water vapour in the middle atmosphere in the vicinity of the Arctic polar vortex. In situ balloon and rocket-borne measurements of water vapour were performed by means of OH fluorescence hygrometry. The combined measurements yielded a high resolution water vapour profile up to an altitude of 75 km. Using the characteristic of water vapour being a dynamical tracer it was possible to directly relate the water vapour data to the location of the polar vortex edge, which separates air masses of different character inside and outside the polar vortex. The measurements probed extra-vortex air in the altitude range between 45 km and 60 km and vortex air elsewhere. Transitions between vortex and extra-vortex usually coincided with wind shears caused by gravity waves which advect air masses with different water vapour volume mixing ratios.

    From the combination of the results from the Hygrosonde-2 campaign and the first flight of the optical hygrometer in 1994 (Hygrosonde-1 a clear picture of the characteristic water vapour distribution inside and outside the polar vortex can be drawn. Systematic differences in the water vapour concentration between the inside and outside of the polar vortex can be observed all the way up into the mesosphere. It is also evident that in situ measurements with high spatial resolution are needed to fully account for the small-scale exchange processes in the polar winter middle atmosphere.

  18. Investigation of Current Induced Spin Polarization in III-V Semiconductor Epilayers

    Science.gov (United States)

    Luengo-Kovac, Marta

    In the development of a semiconductor spintronics device, a thorough understanding of spin dynamics in semiconductors is necessary. In particular, electrical control of electron spins is advantageous for its compatibility with present day electronics. In this thesis, we will discuss the electrical modification of the electron g-factor, which characterizes the strength of the interaction between a spin and a magnetic field, as well as investigate electrically generated spin polarizations as a function of various material parameters. We report on the modification of the electron g-factor by an in-plane electric field in an InGaAs epilayer. We performed external magnetic field scans of the Kerr rotation of the InGaAs film in order to measure the g-factor independently of the spin-orbit fields. The g-factor increases from -0.4473(0.0001) at 0 V/cm to -0.4419( 0.0001) at 50 V/cm applied along the [110] crystal axis. A comparison of temperature and voltage dependent photoluminescence measurements indicate that minimal channel heating occurs at these voltages. Possible explanations for this g-factor modification are discussed, including an increase in the electron temperature that is independent of the lattice temperature and the modification of the donor-bound electron wave function by the electric field. The current-induced spin polarization and momentum-dependent spin-orbit field were measured in InGaAs epilayers with varying indium concentrations and silicon doping densities. Samples with higher indium concentrations and carrier concentrations and lower mobilities were found to have larger electrical spin generation efficiencies. Furthermore, current-induced spin polarization was detected in GaAs epilayers despite the absence of measurable spin-orbit fields, indicating that the spin polarization mechanism is extrinsic. Temperature-dependent measurements of the spin dephasing rates and mobilities were used to characterize the relative strengths of the intrinsic D

  19. Realization of optimized quantum controlled-logic gate based on the orbital angular momentum of light.

    Science.gov (United States)

    Zeng, Qiang; Li, Tao; Song, Xinbing; Zhang, Xiangdong

    2016-04-18

    We propose and experimentally demonstrate an optimized setup to implement quantum controlled-NOT operation using polarization and orbital angular momentum qubits. This device is more adaptive to inputs with various polarizations, and can work both in classical and quantum single-photon regime. The logic operations performed by such a setup not only possess high stability and polarization-free character, they can also be easily extended to deal with multi-qubit input states. As an example, the experimental implementation of generalized three-qubit Toffoli gate has been presented.

  20. Hola! ADEOS

    Science.gov (United States)

    Carlowicz, Michael

    Three months after its launch, Japan's Advanced Earth Observing Satellite (ADEOS) is set to begin day-to-day science operations at the end of November. The global change research satellite, launched August 16 from the Tanegashima Space Center by Japan's National Space Development Agency (NASDA), has settled into a circular polar orbit at 800 km altitude. ADEOS includes instruments from Japan, the United States, and France that will observe ocean chlorophyll production, ocean temperature, atmospheric gases, polarization and direction of solar energy reflected by the Earth, and the distribution of vegetation.

  1. Measurement of product rotational alignment in associative-ionization collisions between polarized Na(3p) atoms

    International Nuclear Information System (INIS)

    Wang, M.; de Vries, M.S.; Weiner, J.

    1986-01-01

    We have studied the effect of reactant Na(3p) polarization on the rotational angular momentum alignment of product Na 2 + ions arising from associative-ionization (AI) collisions. Our results show that sensitivity of the AI rate constant to initial atomic polarization persists even when all hyperfine states are populated with broadband (3 cm -1 ) pulsed laser excitation of Na( 2 P/sub 3/2/) and that the spatial distribution of product rotational angular momentum vectors is anisotropic. We discuss a qualitative description of the collision process consistent with our measurements which indicates that sigma-orbital symmetry is preferred to π-orbital symmetry as the colliding partners approach

  2. Polarized single crystal neutron diffraction study of the zero-magnetization ferromagnet Sm1 -xGdxAl2 (x =0.024 )

    Science.gov (United States)

    Chatterji, T.; Stunault, A.; Brown, P. J.

    2018-02-01

    We have determined the temperature evolution of the spin and orbital moments in the zero-magnetization ferromagnet Sm1 -xGdxAl2 (x = 0.024) by combining polarized and unpolarized single crystal neutron diffraction data. The sensitivity of the polarized neutron technique has allowed the moment values to be determined with a precision of ≈0.1 μB . Our results clearly demonstrate that, when magnetized by a field of 8 T, the spin and orbital moments in Sm1 -xGdxAl2 are oppositely directed, so that the net magnetization is very small. Below 60 K the contributions from spin and orbital motions are both about 2 μB , with that due to orbital motion being slightly larger than that due to spin. Between 60 and 65 K the contributions of each to the magnetization fall rapidly and change sign at Tcomp ≈67 K , above which the aligned moments recover but with the orbital magnetization still slightly higher than the spin one. These results imply that above Tcomp the small resultant magnetization of the Sm3 + ion is oppositely directed to the magnetizing field. It is suggested that this anomaly is due to polarization of conduction electron spin associated with the doping Gd3 + ions.

  3. The effects of different footprint sizes and cloud algorithms on the top-of-atmosphere radiative flux calculation from the Clouds and Earth's Radiant Energy System (CERES instrument on Suomi National Polar-orbiting Partnership (NPP

    Directory of Open Access Journals (Sweden)

    W. Su

    2017-10-01

    Full Text Available Only one Clouds and Earth's Radiant Energy System (CERES instrument is onboard the Suomi National Polar-orbiting Partnership (NPP and it has been placed in cross-track mode since launch; it is thus not possible to construct a set of angular distribution models (ADMs specific for CERES on NPP. Edition 4 Aqua ADMs are used for flux inversions for NPP CERES measurements. However, the footprint size of NPP CERES is greater than that of Aqua CERES, as the altitude of the NPP orbit is higher than that of the Aqua orbit. Furthermore, cloud retrievals from the Visible Infrared Imaging Radiometer Suite (VIIRS and the Moderate Resolution Imaging Spectroradiometer (MODIS, which are the imagers sharing the spacecraft with NPP CERES and Aqua CERES, are also different. To quantify the flux uncertainties due to the footprint size difference between Aqua CERES and NPP CERES, and due to both the footprint size difference and cloud property difference, a simulation is designed using the MODIS pixel-level data, which are convolved with the Aqua CERES and NPP CERES point spread functions (PSFs into their respective footprints. The simulation is designed to isolate the effects of footprint size and cloud property differences on flux uncertainty from calibration and orbital differences between NPP CERES and Aqua CERES. The footprint size difference between Aqua CERES and NPP CERES introduces instantaneous flux uncertainties in monthly gridded NPP CERES measurements of less than 4.0 W m−2 for SW (shortwave and less than 1.0 W m−2 for both daytime and nighttime LW (longwave. The global monthly mean instantaneous SW flux from simulated NPP CERES has a low bias of 0.4 W m−2 when compared to simulated Aqua CERES, and the root-mean-square (RMS error is 2.2 W m−2 between them; the biases of daytime and nighttime LW flux are close to zero with RMS errors of 0.8 and 0.2 W m−2. These uncertainties are within the uncertainties of CERES ADMs

  4. Orbital Normalization of MESSENGER Gamma-Ray Spectrometer Data

    Science.gov (United States)

    Rhodes, E. A.; Peplowski, P. N.; Evans, L. G.; Hamara, D. K.; Boynton, W. V.; Solomon, S. C.

    2011-12-01

    The MESSENGER Gamma-Ray Spectrometer (GRS) measures energy spectra of gamma rays emanating from the surface of Mercury. Analysis of these spectra provides elemental abundances of surface material. The MESSENGER mission necessarily provides some data normalization challenges for GRS analysis. So as to keep the spacecraft cool while orbiting the dayside of the planet, the orbits are highly eccentric, with altitudes varying from 200-500 km to ~ 15,000 km. A small fraction of time is spent at the low altitudes where gamma-ray signals are largest, requiring a large number of orbits to yield sufficient counting statistics for elemental analysis. Also, the sunshade must always shield the spacecraft from the Sun, which causes the orientation of the GRS often to be far from nadir-pointing, so the detector efficiency and attenuation of gamma rays from the planet must be known for a wide range of off-nadir orientations. An efficiency/attenuation map for the expected ranges of orientations and energies was constructed in a ground calibration experiment for a limited range of orientations using a nuclear reactor and radioisotope sources, and those results were extended to other orientations by radiation transport computations using as input a computer-aided design model of the spacecraft and its composition. This normalization has allowed abundance determinations of elements K, Th, and U from radioisotopes of these elements in the Mercury regolith during the first quarter of the year-long mission. These results provide constraints on models of Mercury's chemical and thermal evolution. The normalization of gamma-ray spectra for surface elements not having radioisotopes is considerably more complex; these gamma rays come from neutron inelastic-scatter and capture reactions in the regolith, where the neutrons are generated by cosmic ray impact onto the planet. A radiation transport computation was performed to generate the expected count rates in the neutron-generated gamma

  5. An exact solution for orbit view-periods from a station on a tri-axial ellipsoidal planet

    Science.gov (United States)

    Tang, C. C. H.

    1986-01-01

    This paper presents the concise exact solution for predicting view-periods to be observed from a masked or unmasked tracking station on a tri-axial ellipsoidal surface. The new exact approach expresses the azimuth and elevation angles of a spacecraft in terms of the station-centered geodetic topocentric coordinates in an elegantly concise manner. A simple and efficient algorithm is developed to avoid costly repetitive computations in searching for neighborhoods near the rise and set times of each satellite orbit for each station. Only one search for each orbit is necessary for each station. Sample results indicate that the use of an assumed spherical earth instead of an 'actual' tri-axial ellipsoidal earth could introduce an error up to a few minutes in a view-period prediction for circular orbits of low or medium altitude. For an elliptical orbit of high eccentricity and long period, the maximum error could be even larger. The analytic treatment and the efficient algorithm are designed for geocentric orbits, but they should be applicable to interplanetary trajectories by an appropriate coordinates transformation at each view-period calculation. This analysis can be accomplished only by not using the classical orbital elements.

  6. An exact solution for orbit view-periods from a station on a tri-axial ellipsoidal planet

    Science.gov (United States)

    Tang, C. C. H.

    1986-08-01

    This paper presents the concise exact solution for predicting view-periods to be observed from a masked or unmasked tracking station on a tri-axial ellipsoidal surface. The new exact approach expresses the azimuth and elevation angles of a spacecraft in terms of the station-centered geodetic topocentric coordinates in an elegantly concise manner. A simple and efficient algorithm is developed to avoid costly repetitive computations in searching for neighborhoods near the rise and set times of each satellite orbit for each station. Only one search for each orbit is necessary for each station. Sample results indicate that the use of an assumed spherical earth instead of an 'actual' tri-axial ellipsoidal earth could introduce an error up to a few minutes in a view-period prediction for circular orbits of low or medium altitude. For an elliptical orbit of high eccentricity and long period, the maximum error could be even larger. The analytic treatment and the efficient algorithm are designed for geocentric orbits, but they should be applicable to interplanetary trajectories by an appropriate coordinates transformation at each view-period calculation. This analysis can be accomplished only by not using the classical orbital elements.

  7. Circularly polarized zero-phonon transitions of vacancies in diamond at high magnetic fields

    Science.gov (United States)

    Braukmann, D.; Glaser, E. R.; Kennedy, T. A.; Bayer, M.; Debus, J.

    2018-05-01

    We study the circularly polarized photoluminescence of negatively charged (NV-) and neutral (NV0) nitrogen-vacancy ensembles and neutral vacancies (V0) in diamond crystals exposed to magnetic fields of up to 10 T. We determine the orbital and spin Zeeman splitting as well as the energetic ordering of their ground and first-excited states. The spin-triplet and -singlet states of the NV- are described by an orbital Zeeman splitting of about 9 μ eV /T , which corresponds to a positive orbital g -factor of gL=0.164 under application of the magnetic field along the (001) and (111) crystallographic directions, respectively. The zero-phonon line (ZPL) of the NV- singlet is defined as a transition from the 1E' states, which are split by gLμBB , to the 1A1 state. The energies of the zero-phonon triplet transitions show a quadratic dependence on intermediate magnetic field strengths, which we attribute to a mixing of excited states with nonzero orbital angular momentum. Moreover, we identify slightly different spin Zeeman splittings in the ground (gs) and excited (es) triplet states, which can be expressed by a deviation between their spin g -factors: gS ,es=gS ,gs+Δ g with values of Δ g =0.014 and 0.029 in the (001) and (111) geometries, respectively. The degree of circular polarization of the NV- ZPLs depends significantly on the temperature, which is explained by an efficient spin-orbit coupling of the excited states mediated through acoustic phonons. We further demonstrate that the sign of the circular polarization degree is switched under rotation of the diamond crystal. A weak Zeeman splitting similar to Δ g μBB measured for the NV- ZPLs is also obtained for the NV0 zero-phonon lines, from which we conclude that the ground state is composed of two optically active states with compensated orbital contributions and opposite spin-1/2 momentum projections. The zero-phonon lines of the V0 show Zeeman splittings and degrees of the circular polarization with opposite

  8. Preacclimatization in hypoxic chambers for high altitude sojourns.

    Science.gov (United States)

    Küpper, Thomas E A H; Schöffl, Volker

    2010-09-01

    Since hypoxic chambers are more and more available, they are used for preacclimatization to prepare for sojourns at high altitude. Since there are different protocols and the data differ, there is no general consensus about the standard how to perform preacclimatization by simulated altitude. The paper reviews the different types of exposure and focuses on the target groups which may benefit from preacclimatization. Since data about intermittent hypoxia for some hours per day to reduce the incidence of acute mountain sickness differ, it is suggested to perform preacclimatization by sleeping some nights at a simulated altitude which follows the altitude profile of the "gold standard" for high altitude acclimatization.

  9. Capsize of polarization in dilute photonic crystals.

    Science.gov (United States)

    Gevorkian, Zhyrair; Hakhoumian, Arsen; Gasparian, Vladimir; Cuevas, Emilio

    2017-11-29

    We investigate, experimentally and theoretically, polarization rotation effects in dilute photonic crystals with transverse permittivity inhomogeneity perpendicular to the traveling direction of waves. A capsize, namely a drastic change of polarization to the perpendicular direction is observed in a one-dimensional photonic crystal in the frequency range 10 ÷ 140 GHz. To gain more insights into the rotational mechanism, we have developed a theoretical model of dilute photonic crystal, based on Maxwell's equations with a spatially dependent two dimensional inhomogeneous dielectric permittivity. We show that the polarization's rotation can be explained by an optical splitting parameter appearing naturally in Maxwell's equations for magnetic or electric fields components. This parameter is an optical analogous of Rashba like spin-orbit interaction parameter present in quantum waves, introduces a correction to the band structure of the two-dimensional Bloch states, creates the dynamical phase shift between the waves propagating in the orthogonal directions and finally leads to capsizing of the initial polarization. Excellent agreement between theory and experiment is found.

  10. Shilajit: A panacea for high-altitude problems.

    Science.gov (United States)

    Meena, Harsahay; Pandey, H K; Arya, M C; Ahmed, Zakwan

    2010-01-01

    High altitude problems like hypoxia, acute mountain sickness, high altitude cerebral edema, pulmonary edema, insomnia, tiredness, lethargy, lack of appetite, body pain, dementia, and depression may occur when a person or a soldier residing in a lower altitude ascends to high-altitude areas. These problems arise due to low atmospheric pressure, severe cold, high intensity of solar radiation, high wind velocity, and very high fluctuation of day and night temperatures in these regions. These problems may escalate rapidly and may sometimes become life-threatening. Shilajit is a herbomineral drug which is pale-brown to blackish-brown, is composed of a gummy exudate that oozes from the rocks of the Himalayas in the summer months. It contains humus, organic plant materials, and fulvic acid as the main carrier molecules. It actively takes part in the transportation of nutrients into deep tissues and helps to overcome tiredness, lethargy, and chronic fatigue. Shilajit improves the ability to handle high altitudinal stresses and stimulates the immune system. Thus, Shilajit can be given as a supplement to people ascending to high-altitude areas so that it can act as a "health rejuvenator" and help to overcome high-altitude related problems.

  11. The sleep of elite athletes at sea level and high altitude: a comparison of sea-level natives and high-altitude natives (ISA3600).

    Science.gov (United States)

    Roach, Gregory D; Schmidt, Walter F; Aughey, Robert J; Bourdon, Pitre C; Soria, Rudy; Claros, Jesus C Jimenez; Garvican-Lewis, Laura A; Buchheit, Martin; Simpson, Ben M; Hammond, Kristal; Kley, Marlen; Wachsmuth, Nadine; Gore, Christopher J; Sargent, Charli

    2013-12-01

    Altitude exposure causes acute sleep disruption in non-athletes, but little is known about its effects in elite athletes. The aim of this study was to examine the effects of altitude on two groups of elite athletes, that is, sea-level natives and high-altitude natives. Sea-level natives were members of the Australian under-17 soccer team (n=14). High-altitude natives were members of a Bolivian under-20 club team (n=12). Teams participated in an 18-day (19 nights) training camp in Bolivia, with 6 nights at near sea level in Santa Cruz (430 m) and 13 nights at high altitude in La Paz (3600 m). Sleep was assessed on every day/night using activity monitors. The Australians' sleep was shorter, and of poorer quality, on the first night at altitude compared with sea level. Sleep quality returned to normal by the end of the first week at altitude, but sleep quantity had still not stabilised at its normal level after 2 weeks. The quantity and quality of sleep obtained by the Bolivians was similar, or greater, on all nights at altitude compared with sea level. The Australians tended to obtain more sleep than the Bolivians at sea level and altitude, but the quality of the Bolivians' sleep tended to be better than that of the Australians at altitude. Exposure to high altitude causes acute and chronic disruption to the sleep of elite athletes who are sea-level natives, but it does not affect the sleep of elite athletes who are high-altitude natives.

  12. High-Altitude Illnesses: Physiology, Risk Factors, Prevention, and Treatment

    Directory of Open Access Journals (Sweden)

    Andrew T. Taylor

    2011-01-01

    Full Text Available High-altitude illnesses encompass the pulmonary and cerebral syndromes that occur in non-acclimatized individuals after rapid ascent to high altitude. The most common syndrome is acute mountain sickness (AMS which usually begins within a few hours of ascent and typically consists of headache variably accompanied by loss of appetite, nausea, vomiting, disturbed sleep, fatigue, and dizziness. With millions of travelers journeying to high altitudes every year and sleeping above 2,500 m, acute mountain sickness is a wide-spread clinical condition. Risk factors include home elevation, maximum altitude, sleeping altitude, rate of ascent, latitude, age, gender, physical condition, intensity of exercise, pre-acclimatization, genetic make-up, and pre-existing diseases. At higher altitudes, sleep disturbances may become more profound, mental performance is impaired, and weight loss may occur. If ascent is rapid, acetazolamide can reduce the risk of developing AMS, although a number of high-altitude travelers taking acetazolamide will still develop symptoms. Ibuprofen can be effective for headache. Symptoms can be rapidly relieved by descent, and descent is mandatory, if at all possible, for the management of the potentially fatal syndromes of high-altitude pulmonary and cerebral edema. The purpose of this review is to combine a discussion of specific risk factors, prevention, and treatment options with a summary of the basic physiologic responses to the hypoxia of altitude to provide a context for managing high-altitude illnesses and advising the non-acclimatized high-altitude traveler.

  13. System for indicating fuel-efficient aircraft altitude

    Science.gov (United States)

    Gary, B. L. (Inventor)

    1984-01-01

    A method and apparatus are provided for indicating the altitude at which an aircraft should fly so the W/d ratio (weight of the aircraft divided by the density of air) more closely approaches the optimum W/d for the aircraft. A passive microwave radiometer on the aircraft is directed at different angles with respect to the horizon to determine the air temperature, and therefore the density of the air, at different altitudes. The weight of the aircraft is known. The altitude of the aircraft is changed to fly the aircraft at an altitude at which is W/d ratio more closely approaches the optimum W/d ratio for that aircraft.

  14. Time-dependent theoretical model of the polar wind: Preliminary results

    International Nuclear Information System (INIS)

    Gombosi, T.I.; Cravens, T.E.; Nagy, A.F.

    1985-01-01

    The coupled time dependent continuity, momentum and energy equations of a two ion (O + and H + ) quasineutral plasma were solved in order to extend our understanding of polar wind behavior. This numerical code allows studies of the time dependent behavior of polar wind-type flows into and out of the ionosphere. Initial studies indicate that the typical time constants for electron and ion temperature changes are of the order of minutes and tens of minutes, respectively. The response time of the minor high altitude ion O + is less than an hour, whereas that of the major ion, H + , is many hours. The initial test runs also demonstrate the fact that temporary supersonic flows of both O + and H + are possible, especially in the presence of significant ion heating

  15. The O{sub 2} A-Band in the Fluxes and Polarization of Starlight Reflected by Earth-Like Exoplanets

    Energy Technology Data Exchange (ETDEWEB)

    Fauchez, Thomas [Laboratoire d’Optique Atmosphèrique (LOA), UMR 8518, Université Lille 1, Villeneuve d’Ascq (France); Rossi, Loic; Stam, Daphne M. [Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft (Netherlands)

    2017-06-10

    Earth-like, potentially habitable exoplanets are prime targets in the search for extraterrestrial life. Information about their atmospheres and surfaces can be derived by analyzing the light of the parent star reflected by the planet. We investigate the influence of the surface albedo A {sub s}, the optical thickness b {sub cloud}, the altitude of water clouds, and the mixing ratio of biosignature O{sub 2} on the strength of the O{sub 2} A-band (around 760 nm) in the flux and polarization spectra of starlight reflected by Earth-like exoplanets. Our computations for horizontally homogeneous planets show that small mixing ratios ( η < 0.4) will yield moderately deep bands in flux and moderate-to-small band strengths in polarization, and that clouds will usually decrease the band depth in flux and the band strength in polarization. However, cloud influence will be strongly dependent on properties such as optical thickness, top altitude, particle phase, coverage fraction, and horizontal distribution. Depending on the surface albedo and cloud properties, different O{sub 2} mixing ratios η can give similar absorption-band depths in flux and band strengths in polarization, especially if the clouds have moderate-to-high optical thicknesses. Measuring both the flux and the polarization is essential to reduce the degeneracies, although it will not solve them, especially not for horizontally inhomogeneous planets. Observations at a wide range of phase angles and with a high temporal resolution could help to derive cloud properties and, once those are known, the mixing ratio of O{sub 2} or any other absorbing gas.

  16. Nonequilibrium Spin Dynamics in a Trapped Fermi Gas with Effective Spin-Orbit Interactions

    International Nuclear Information System (INIS)

    Stanescu, Tudor D.; Zhang Chuanwei; Galitski, Victor

    2007-01-01

    We consider a trapped atomic system in the presence of spatially varying laser fields. The laser-atom interaction generates a pseudospin degree of freedom (referred to simply as spin) and leads to an effective spin-orbit coupling for the fermions in the trap. Reflections of the fermions from the trap boundaries provide a physical mechanism for effective momentum relaxation and nontrivial spin dynamics due to the emergent spin-orbit coupling. We explicitly consider evolution of an initially spin-polarized Fermi gas in a two-dimensional harmonic trap and derive nonequilibrium behavior of the spin polarization. It shows periodic echoes with a frequency equal to the harmonic trapping frequency. Perturbations, such as an asymmetry of the trap, lead to the suppression of the spin echo amplitudes. We discuss a possible experimental setup to observe spin dynamics and provide numerical estimates of relevant parameters

  17. Mission Analysis and Orbit Control of Interferometric Wheel Formation Flying

    Science.gov (United States)

    Fourcade, J.

    Flying satellite in formation requires maintaining the specific relative geometry of the spacecraft with high precision. This requirement raises new problem of orbit control. This paper presents the results of the mission analysis of a low Earth observation system, the interferometric wheel, patented by CNES. This wheel is made up of three receiving spacecraft, which follow an emitting Earth observation radar satellite. The first part of this paper presents trades off which were performed to choose orbital elements of the formation flying which fulfils all constraints. The second part presents orbit positioning strategies including reconfiguration of the wheel to change its size. The last part describes the station keeping of the formation. Two kinds of constraints are imposed by the interferometric system : a constraint on the distance between the wheel and the radar satellite, and constraints on the distance between the wheel satellites. The first constraint is fulfilled with a classical chemical station keeping strategy. The second one is fulfilled using pure passive actuators. Due to the high stability of the relative eccentricity of the formation, only the relative semi major axis had to be controlled. Differential drag due to differential attitude motion was used to control relative altitude. An autonomous orbit controller was developed and tested. The final accuracy is a relative station keeping better than few meters for a wheel size of one kilometer.

  18. Application of altitude/hypoxic training by elite athletes.

    Science.gov (United States)

    Wilber, Randall L

    2007-09-01

    At the Olympic level, differences in performance are typically less than 0.5%. This helps explain why many contemporary elite endurance athletes in summer and winter sport incorporate some form of altitude/hypoxic training within their year-round training plan, believing that it will provide the "competitive edge" to succeed at the Olympic level. The purpose of this paper is to describe the practical application of altitude/hypoxic training as used by elite athletes. Within the general framework of the paper, both anecdotal and scientific evidence will be presented relative to the efficacy of several contemporary altitude/hypoxic training models and devices currently used by Olympic-level athletes for the purpose of legally enhancing performance. These include the three primary altitude/hypoxic training models: 1) live high+train high (LH+TH), 2) live high+train low (LH+TL), and 3) live low+train high (LL+TH). The LH+TL model will be examined in detail and will include its various modifications: natural/terrestrial altitude, simulated altitude via nitrogen dilution or oxygen filtration, and hypobaric normoxia via supplemental oxygen. A somewhat opposite approach to LH+TL is the altitude/hypoxic training strategy of LL+TH, and data regarding its efficacy will be presented. Recently, several of these altitude/hypoxic training strategies and devices underwent critical review by the World Anti-Doping Agency (WADA) for the purpose of potentially banning them as illegal performance-enhancing substances/methods. This paper will conclude with an update on the most recent statement from WADA regarding the use of simulated altitude devices.

  19. Radiation environment measurements and single event upset observations in sun-synchronous orbit

    International Nuclear Information System (INIS)

    Dyer, C.S.; Sims, A.J.; Farren, J.; Stephen, J.; Underwood, C.

    1991-01-01

    This paper reports on analysis of data from the Cosmic Radiation Environment and Dosimetry experiment (CREDO) carried in sun-synchronous polar orbit on UoSat-3 which shows the influence of cosmic rays, trapped protons and solar particles and allows comparison with device behavior

  20. The tempo-spatially modulated polarization atmosphere Michelson interferometer.

    Science.gov (United States)

    Zhang, ChunMin; Zhu, HuaChun; Zhao, Baochang

    2011-05-09

    A space-based tempo-spatially modulated polarization atmosphere Michelson interferometer (TSMPAMI) is described. It uses the relative movement between the TSMPAMI and the measured target to change optical path difference. The acquisition method of interferogram is presented. The atmospheric temperatures and horizontal winds can be derived from the optical observations. The measurement errors of the winds and temperatures are discussed through simulations. In the presence of small-scale structures of the atmospheric fields, the errors are found to be significantly influenced by the mismatch of the scenes observed by the adjacent CCD sub-areas aligned along the orbiter's track during successive measurements due to the orbital velocity and the exposure time. For most realistic conditions of the orbit and atmosphere, however, the instrument is proven suitable for measuring the atmospheric parameters. © 2011 Optical Society of America

  1. Respiratory Muscle Training and Exercise Endurance at Altitude.

    Science.gov (United States)

    Helfer, Samuel; Quackenbush, Joseph; Fletcher, Michael; Pendergast, David R

    2016-08-01

    Climbing and trekking at altitude are common recreational and military activities. Physiological effects of altitude are hypoxia and hyperventilation. The hyperventilatory response to altitude may cause respiratory muscle fatigue and reduce sustained submaximal exercise. Voluntary isocapnic hyperpnea respiratory muscle training (VIHT) improves exercise endurance at sea level and at depth. The purpose of this study was to test the hypothesis that VIHT would improve exercise time at altitude [3600 m (11,811 ft)] compared to control and placebo groups. Subjects pedaled an ergometer until exhaustion at simulated altitude in a hypobaric chamber while noninvasive arterial saturation (Sao2), ventilation (VE), and oxygen consumption (Vo2) were measured. As expected, Sao2 decreased to 88 ± 4% saturation at rest and to 81 ± 2% during exercise, and was not affected by VIHT. VIHT resulted in a 40% increase in maximal training VE compared to pre-VIHT. Exercise endurance significantly increased 44% after VIHT (P = altitude post-VIHT increased more (49%) for longer (21 min) and decreased less (11% at 25.4 ± 6.7 min). VIHT improved exercise time at altitude and sustained VE. This suggests that VIHT reduced respiratory muscle fatigue and would be useful to trekkers and military personnel working at altitude. Helfer S, Quackenbush J, Fletcher M, Pendergast DR. Respiratory muscle training and exercise endurance at altitutde. Aerosp Med Hum Perform. 2016; 87(8):704-711.

  2. The sleep of elite athletes at sea level and high altitude: a comparison of sea-level natives and high-altitude natives (ISA3600)

    Science.gov (United States)

    Roach, Gregory D; Schmidt, Walter F; Aughey, Robert J; Bourdon, Pitre C; Soria, Rudy; Claros, Jesus C Jimenez; Garvican-Lewis, Laura A; Buchheit, Martin; Simpson, Ben M; Hammond, Kristal; Kley, Marlen; Wachsmuth, Nadine; Gore, Christopher J; Sargent, Charli

    2013-01-01

    Background Altitude exposure causes acute sleep disruption in non-athletes, but little is known about its effects in elite athletes. The aim of this study was to examine the effects of altitude on two groups of elite athletes, that is, sea-level natives and high-altitude natives. Methods Sea-level natives were members of the Australian under-17 soccer team (n=14). High-altitude natives were members of a Bolivian under-20 club team (n=12). Teams participated in an 18-day (19 nights) training camp in Bolivia, with 6 nights at near sea level in Santa Cruz (430 m) and 13 nights at high altitude in La Paz (3600 m). Sleep was assessed on every day/night using activity monitors. Results The Australians’ sleep was shorter, and of poorer quality, on the first night at altitude compared with sea level. Sleep quality returned to normal by the end of the first week at altitude, but sleep quantity had still not stabilised at its normal level after 2 weeks. The quantity and quality of sleep obtained by the Bolivians was similar, or greater, on all nights at altitude compared with sea level. The Australians tended to obtain more sleep than the Bolivians at sea level and altitude, but the quality of the Bolivians’ sleep tended to be better than that of the Australians at altitude. Conclusions Exposure to high altitude causes acute and chronic disruption to the sleep of elite athletes who are sea-level natives, but it does not affect the sleep of elite athletes who are high-altitude natives. PMID:24282197

  3. TRMM On-Orbit Performance Re-Accessed After Control Change

    Science.gov (United States)

    Bilanow, Steve

    2006-01-01

    The Tropical Rainfall Measuring Mission (TRMM) spacecraft, a joint mission between the U.S. and Japan, launched onboard an HI1 rocket on November 27,1997 and transitioned in August, 2001 from an average operating altitude of 350 kilometers to 402.5 kilometers. Due to problems using the Earth Sensor Assembly (ESA) at the higher altitude, TRMM switched to a backup attitude control mode. Prior to the orbit boost TRMM controlled pitch and roll to the local vertical using ESA measurements while using gyro data to propagate yaw attitude between yaw updates from the Sun sensors. After the orbit boost, a Kalman filter used 3-axis gyro data with Sun sensor and magnetometers to estimate onboard attitude. While originally intended to meet a degraded attitude accuracy of 0.7 degrees, the new control mode met the original 0.2 degree attitude accuracy requirement after improving onboard ephemeris prediction and adjusting the magnetometer calibration onboard. Independent roll attitude checks using a science instrument, the Precipitation Radar (PR) which was built in Japan, provided a novel insight into the pointing performance. The PR data helped identify the pointing errors after the orbit boost, track the performance improvements, and show subtle effects from ephemeris errors and gyro bias errors. It also helped identify average bias trends throughout the mission. Roll errors tracked by the PR from sample orbits pre-boost and post-boost are shown in Figure 1. Prior to the orbit boost the largest attitude errors were due to occasional interference in the ESA. These errors were sometime larger than 0.2 degrees in pitch and roll, but usually less, as estimated from a comprehensive review of the attitude excursions using gyro data. Sudden jumps in the onboard roll show up as spikes in the reported attitude since the control responds within tens of seconds to null the pointing error. The PR estimated roll tracks well with an estimate of the roll history propagated using gyro data

  4. Correlations of mesospheric winds with subtle motion of the Arctic polar vortex

    Directory of Open Access Journals (Sweden)

    Y. Bhattacharya

    2010-01-01

    Full Text Available This paper investigates the relationship between high latitude upper mesospheric winds and the state of the stratospheric polar vortex in the absence of major sudden stratospheric warmings. A ground based Michelson Interferometer stationed at Resolute Bay (74°43' N, 94°58' W in the Canadian High Arctic is used to measure mesopause region neutral winds using the hydroxyl (OH Meinel-band airglow emission (central altitude of ~85 km. These observed winds are compared to analysis winds in the upper stratosphere during November and December of 1995 and 1996; years characterized as cold, stable polar vortex periods. Correlation of mesopause wind speeds with those from the upper stratosphere is found to be significant for the 1996 season when the polar vortex is subtly displaced off its initial location by a strong Aleutian High. These mesopause winds are observed to lead stratospheric winds by approximately two days with increasing (decreasing mesospheric winds predictive of decreasing (increasing stratospheric winds. No statistically significant correlations are found for the 1995 season when there is no such displacement of the polar vortex.

  5. Can High Altitude Influence Cytokines and Sleep?

    Directory of Open Access Journals (Sweden)

    Valdir de Aquino Lemos

    2013-01-01

    Full Text Available The number of persons who relocate to regions of high altitude for work, pleasure, sport, or residence increases every year. It is known that the reduced supply of oxygen (O2 induced by acute or chronic increases in altitude stimulates the body to adapt to new metabolic challenges imposed by hypoxia. Sleep can suffer partial fragmentation because of the exposure to high altitudes, and these changes have been described as one of the responsible factors for the many consequences at high altitudes. We conducted a review of the literature during the period from 1987 to 2012. This work explored the relationships among inflammation, hypoxia and sleep in the period of adaptation and examined a novel mechanism that might explain the harmful effects of altitude on sleep, involving increased Interleukin-1 beta (IL-1β, Interleukin-6 (IL-6, and tumor necrosis factor-alpha (TNF-α production from several tissues and cells, such as leukocytes and cells from skeletal muscle and brain.

  6. Can High Altitude Influence Cytokines and Sleep?

    Science.gov (United States)

    de Aquino Lemos, Valdir; dos Santos, Ronaldo Vagner Thomatieli; Lira, Fabio Santos; Rodrigues, Bruno; Tufik, Sergio; de Mello, Marco Tulio

    2013-01-01

    The number of persons who relocate to regions of high altitude for work, pleasure, sport, or residence increases every year. It is known that the reduced supply of oxygen (O2) induced by acute or chronic increases in altitude stimulates the body to adapt to new metabolic challenges imposed by hypoxia. Sleep can suffer partial fragmentation because of the exposure to high altitudes, and these changes have been described as one of the responsible factors for the many consequences at high altitudes. We conducted a review of the literature during the period from 1987 to 2012. This work explored the relationships among inflammation, hypoxia and sleep in the period of adaptation and examined a novel mechanism that might explain the harmful effects of altitude on sleep, involving increased Interleukin-1 beta (IL-1β), Interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) production from several tissues and cells, such as leukocytes and cells from skeletal muscle and brain. PMID:23690660

  7. Spin-orbit interaction in quantum dots and quantum wires of correlated electrons - a way to spintronics?

    International Nuclear Information System (INIS)

    Birkholz, Jens Eiko

    2008-01-01

    We study the influence of the spin-orbit interaction on the electronic transport through quantum dots and quantum wires of correlated electrons. Starting with a one-dimensional infinite continuum model without Coulomb interaction, we analyze the interplay of the spin-orbit interaction, an external magnetic field, and an external potential leading to currents with significant spin-polarization in appropriate parameter regimes. Since lattice models are known to often be superior to continuum models in describing the experimental situation of low-dimensional mesoscopic systems, we construct a lattice model which exhibits the same low-energy physics in terms of energy dispersion and spin expectation values. Confining the lattice to finite length and connecting it to two semi-infinite noninteracting Fermi liquid leads, we calculate the zero temperature linear conductance using the Landauer-Bttiker formalism and show that spin-polarization effects also evolve for the lattice model by adding an adequate potential structure and can be controlled by tuning the overall chemical potential of the system (quantum wire and leads). Next, we allow for a finite Coulomb interaction and use the functional renormalization group (fRG) method to capture correlation effects induced by the Coulomb interaction. The interacting system is thereby transformed into a noninteracting system with renormalized system parameters. For short wires (∝100 lattice sites), we show that the energy regime in which spin polarization is found is strongly affected by the Coulomb interaction. For long wires (>1000 lattice sites), we find the power-law suppression of the total linear conductance on low energy scales typical for inhomogeneous Luttinger liquids while the degree of spin polarization stays constant. Considering quantum dots which consist of two lattice sites, we observe the well-known Kondo effect and analyze, how the Kondo temperature is affected by the spin-orbit interaction. Moreover, we show

  8. Acute high-altitude illness | Hofmeyr | South African Medical Journal

    African Journals Online (AJOL)

    A substantial proportion of South Africa (SA)'s population lives at high altitude (>1 500 m), and many travel to very high altitudes (>3 500 m) for tourism, business, recreation or religious pilgrimages every year. Despite this, knowledge of acute altitude illnesses is poor among SA doctors. At altitude, the decreasing ambient ...

  9. Theory of Covalent Adsorbate Frontier Orbital Energies on Functionalized Light-Absorbing Semiconductor Surfaces.

    Science.gov (United States)

    Yu, Min; Doak, Peter; Tamblyn, Isaac; Neaton, Jeffrey B

    2013-05-16

    Functional hybrid interfaces between organic molecules and semiconductors are central to many emerging information and solar energy conversion technologies. Here we demonstrate a general, empirical parameter-free approach for computing and understanding frontier orbital energies - or redox levels - of a broad class of covalently bonded organic-semiconductor surfaces. We develop this framework in the context of specific density functional theory (DFT) and many-body perturbation theory calculations, within the GW approximation, of an exemplar interface, thiophene-functionalized silicon (111). Through detailed calculations taking into account structural and binding energetics of mixed-monolayers consisting of both covalently attached thiophene and hydrogen, chlorine, methyl, and other passivating groups, we quantify the impact of coverage, nonlocal polarization, and interface dipole effects on the alignment of the thiophene frontier orbital energies with the silicon band edges. For thiophene adsorbate frontier orbital energies, we observe significant corrections to standard DFT (∼1 eV), including large nonlocal electrostatic polarization effects (∼1.6 eV). Importantly, both results can be rationalized from knowledge of the electronic structure of the isolated thiophene molecule and silicon substrate systems. Silicon band edge energies are predicted to vary by more than 2.5 eV, while molecular orbital energies stay similar, with the different functional groups studied, suggesting the prospect of tuning energy alignment over a wide range for photoelectrochemistry and other applications.

  10. DLR HABLEG- High Altitude Balloon Launched Experimental Glider

    Science.gov (United States)

    Wlach, S.; Schwarzbauch, M.; Laiacker, M.

    2015-09-01

    The group Flying Robots at the DLR Institute of Robotics and Mechatronics in Oberpfaffenhofen conducts research on solar powered high altitude aircrafts. Due to the high altitude and the almost infinite mission duration, these platforms are also denoted as High Altitude Pseudo-Satellites (HAPS). This paper highlights some aspects of the design, building, integration and testing of a flying experimental platform for high altitudes. This unmanned aircraft, with a wingspan of 3 m and a mass of less than 10 kg, is meant to be launched as a glider from a high altitude balloon in 20 km altitude and shall investigate technologies for future large HAPS platforms. The aerodynamic requirements for high altitude flight included the development of a launch method allowing for a safe transition to horizontal flight from free-fall with low control authority. Due to the harsh environmental conditions in the stratosphere, the integration of electronic components in the airframe is a major effort. For regulatory reasons a reliable and situation dependent flight termination system had to be implemented. In May 2015 a flight campaign was conducted. The mission was a full success demonstrating that stratospheric research flights are feasible with rather small aircrafts.

  11. Asynchronous Processing of a Constellation of Geostationary and Polar-Orbiting Satellites for Fire Detection and Smoke Estimation

    Science.gov (United States)

    Hyer, E. J.; Peterson, D. A.; Curtis, C. A.; Schmidt, C. C.; Hoffman, J.; Prins, E. M.

    2014-12-01

    The Fire Locating and Monitoring of Burning Emissions (FLAMBE) system converts satellite observations of thermally anomalous pixels into spatially and temporally continuous estimates of smoke release from open biomass burning. This system currently processes data from a constellation of 5 geostationary and 2 polar-orbiting sensors. Additional sensors, including NPP VIIRS and the imager on the Korea COMS-1 geostationary satellite, will soon be added. This constellation experiences schedule changes and outages of various durations, making the set of available scenes for fire detection highly variable on an hourly and daily basis. Adding to the complexity, the latency of the satellite data is variable between and within sensors. FLAMBE shares with many fire detection systems the goal of detecting as many fires as possible as early as possible, but the FLAMBE system must also produce a consistent estimate of smoke production with minimal artifacts from the changing constellation. To achieve this, NRL has developed a system of asynchronous processing and cross-calibration that permits satellite data to be used as it arrives, while preserving the consistency of the smoke emission estimates. This talk describes the asynchronous data ingest methodology, including latency statistics for the constellation. We also provide an overview and show results from the system we have developed to normalize multi-sensor fire detection for consistency.

  12. Long-term orbit prediction for China's Tiangong-1 spacecraft based on mean atmosphere model

    Science.gov (United States)

    Tang, Jingshi; Liu, Lin; Miao, Manqian

    Tiangong-1 is China's test module for future space station. It has gone through three successful rendezvous and dockings with Shenzhou spacecrafts from 2011 to 2013. For the long-term management and maintenance, the orbit sometimes needs to be predicted for a long period of time. As Tiangong-1 works in a low-Earth orbit with an altitude of about 300-400 km, the error in the a priori atmosphere model contributes significantly to the rapid increase of the predicted orbit error. When the orbit is predicted for 10-20 days, the error in the a priori atmosphere model, if not properly corrected, could induce the semi-major axis error and the overall position error up to a few kilometers and several thousand kilometers respectively. In this work, we use a mean atmosphere model averaged from NRLMSIS00. The a priori reference mean density can be corrected during precise orbit determination (POD). For applications in the long-term orbit prediction, the observations are first accumulated. With sufficiently long period of observations, we are able to obtain a series of the diurnal mean densities. This series bears the recent variation of the atmosphere density and can be analyzed for various periods. After being properly fitted, the mean density can be predicted and then applied in the orbit prediction. We show that the densities predicted with this approach can serve to increase the accuracy of the predicted orbit. In several 20-day prediction tests, most predicted orbits show semi-major axis errors better than 700m and overall position errors better than 600km.

  13. Numerical simulation of altitude impact on pulverized coal combustion

    Energy Technology Data Exchange (ETDEWEB)

    Pei, Xiaohui; He, Boshu; Ling, Ling; Wang, Lei [Beijing Jiaotong Univ., Beijing (China). Inst. of Mechanical, Electronic and Control Engineering

    2013-07-01

    A drop-tube Furnace simulation model has been developed to investigate the pulverized coal combustion characteristics under different altitudes using the commercially available software Fluent. The altitude conditions of 0, 500, 1,000, 1,500 m have been discussed. The results included the fields of temperature, pressure, velocity, the coal burnout, CO burnout and NO emission in the tube furnace. The variation of these parameters with altitude has been analyzed. The coal combustion characteristics were affected by the altitude. The time and space for coal burnout should be increased with the rise of altitude. The valuable results could be referenced in the design of coal- fired furnaces for the high altitude areas.

  14. The Effect of Electrical Polarization on Electronic Structure in LSM Electrodes: An Operando XAS, RIXS and XES Study

    DEFF Research Database (Denmark)

    Traulsen, Marie Lund; Carvalho, H.W.P.; Zielke, Philipp

    2017-01-01

    in the Mn K edge energy towards lower energies. The shift is assigned to a decrease in the average Mn oxidation state, which based on Kβ XES changes from 3.4 at open circuit voltage to 3.2 at −800 mV applied potential. Furthermore, RIXS rendered pronounced changes in the population of the Mn 3d orbitals...... (RIXS) at the Mn K-edge. The study of polarization induced changes in the electronic properties and structure has been carried out at 500°C in 10–20% O2 with electrical polarization applied in the range from −850 mV to 800 mV. Cathodic polarizations in the range −600 mV to −850 mV induced a shift......, due to filling of the Mn d-orbitals during the cathodic polarization. Overall, the study experimentally links the electrical polarization of LSM electrodes to the structural and electronic properties of Mn - these properties are expected to be of major importance for the electrocatalytic performance...

  15. Cluster observations of ion dispersion discontinuities in the polar cusp

    Science.gov (United States)

    Escoubet, C. P.; Berchem, J.; Pitout, F.; Richard, R. L.; Trattner, K. J.; Grison, B.; Taylor, M. G.; Masson, A.; Dunlop, M. W.; Dandouras, I. S.; Reme, H.; Fazakerley, A. N.

    2009-12-01

    The reconnection between the interplanetary magnetic field (IMF) and the Earth’s magnetic field is taking place at the magnetopause on magnetic field lines threading through the polar cusp. When the IMF is southward, reconnection occurs near the subsolar point, which is magnetically connected to the equatorward boundary of the polar cusp. Subsequently the ions injected through the reconnection point precipitate in the cusp and are dispersed poleward. If reconnection is continuous and operates at constant rate, the ion dispersion is smooth and continuous. On the other hand if the reconnection rate varies, we expect interruption in the dispersion forming energy steps or staircase. Similarly, multiple entries near the magnetopause could also produce steps at low or mid-altitude when a spacecraft is crossing subsequently the field lines originating from these multiple sources. In addition, motion of the magnetopause induced by solar wind pressure changes or erosion due to reconnection can also induce a motion of the polar cusp and a disruption of the ions dispersion observed by a spacecraft. Cluster with four spacecraft following each other in the mid-altitude cusp can be used to distinguish between these “temporal” and “spatial” effects. We will present a cusp crossing with two spacecraft, separated by around two minutes. The two spacecraft observed a very similar dispersion with a step in energy in its centre and two other dispersions poleward. We will show that the steps could be temporal (assuming that the time between two reconnection bursts corresponds to the time delay between the two spacecraft) but it would be a fortuitous coincidence. On the other hand the steps and the two poleward dispersions could be explained by spatial effects if we take into account the motion of the open-closed boundary between the two spacecraft crossings.

  16. High Power Microwave Emission of Large and Small Orbit Gyrotron Devices in Rectangular Interaction Structures

    Science.gov (United States)

    Hochman, J. M.; Gilgenbach, R. M.; Jaynes, R. L.; Rintamaki, J. I.; Luginsland, J. W.; Lau, Y. Y.; Spencer, T. A.

    1996-11-01

    Experiments utilize large and small orbit e-beam gyrotron devices in a rectangular-cross-section (RCS) gyrotron. This device is being explored to examine polarization control. Other research issues include pulse shortening, and mode competition. MELBA generates electron beams with parameters of: -800kV, 1-10kA diode current, and 0.5-1.0 μ sec pulselengths. The small orbit gyrotron device is converted to a large orbit experiment by running MELBA's annular electron beam through a magnetic cusp. Initial experiments showed an increase in beam alpha (V_perp/V_par) of a factor of ~ 4 between small and large orbit devices. Experimental results from the RCS gyrotron will be compared for large-orbit and small-orbit electron beams. Beam transport data and frequency measurements will be presented. Computer modeling utilizing the MAGIC and E-gun codes will be shown.

  17. Iridium: Global OTH data communications for high altitude scientific ballooning

    Science.gov (United States)

    Denney, A.

    beneficial points provided by the Iridium platform include pure global accessibility (as well as polar), cost effectiveness because it is available as a COTS (Commercially Off The Shelf) technology, reliability in that the equipment must operate in extreme conditions (near space), integration and development time into current systems must be minimized. As a bonus Motorola and NAL Research Corporation are developing SBD (Short Burst Data) into the Iridium network. This may lead the way to a global IP (Internet Protocol) node based ballooning platform. The Iridium satellite data modems employ the Iridium Low-Earth Orbit (LEO) satellite network. The scope of this paper is to introduce an OTH communications alternative, albeit not necessarily a primary one, to existing ballooning platforms using COTS based emerging technologies. Design aspects, characteristics, actual flight testing statistics, principles of the Iridium modems and communication paths are described including payload and support instrumentation interfacing. Not limited to high altitude ballooning, the Iridium communications platform opens a new era in remote commanding and data retrieval.

  18. Cassini Attitude and Articulation Control Subsystem Fault Protection Challenges During Saturn Proximal Orbits

    Science.gov (United States)

    Bates, David M.

    2015-01-01

    NASA's Cassini Spacecraft, launched on October 15th, 1997 arrived at Saturn on June 30th, 2004, is the largest and most ambitious interplanetary spacecraft in history. As the first spacecraft to achieve orbit at Saturn, Cassini has collected science data throughout its four-year prime mission (2004-08), and has since been approved for a first and second extended mission through 2017. As part of the final extended mission, Cassini will begin an aggressive and exciting campaign of high inclination low altitude flybys within the inner most rings of Saturn, skimming Saturn's outer atmosphere, until the spacecraft is finally disposed of via planned impact with the planet. This final campaign, known as the proximal orbits, presents unique fault protection related challenges, the details of which are discussed in this paper.

  19. Remote Monitoring of the Polarized Target's Control for E1039

    Science.gov (United States)

    Fox, David; SeaQuest Collaboration

    2017-09-01

    The 1039 experiment at FNAL will further our understanding of spin structure by measuring the contribution that sea quarks orbital angular momentum provide to overall nucleon spin. It is accepted that the valence-quarks of nucleons only provide 30% of the total nucleon spin. To study the nucleon's sea quark contribution, E1039 will use the Drell-Yan process by colliding 120 GeV un-polarized beam protons with polarized ammonia targets of hydrogen and deuterium. The asymmetric spin distributions of resulting dimuons will be measured. These asymmetries are sensitive, among other effects, to the orbital angular momentum contribution of the sea quarks. The polarized target requires a multi-stage vacuum pump located near the target. Since access to its present controls will not be possible during running, remote control and monitoring upgrades were required. A secondary control panel was purchased and tested. Information from the programmable logic controller (PLC) must be fed into our data stream to enable remote monitoring and to signal possible alarm conditions. This solution and the program created using explicit TCP/IP messaging to extract data tags from the PLC and log it within our databases will be presented. Supported by U.S. D.O.E. Medium Energy Nuclear Physics under Grant DE-FG02-03ER41243.

  20. Verifying black hole orbits with gravitational spectroscopy

    International Nuclear Information System (INIS)

    Drasco, Steve

    2009-01-01

    Gravitational waves from test masses bound to geodesic orbits of rotating black holes are simulated, using Teukolsky's black hole perturbation formalism, for about ten thousand generic orbital configurations. Each binary radiates power exclusively in modes with frequencies that are integer-linear combinations of the orbit's three fundamental frequencies. General spectral properties are found with a survey of orbits about a black hole taken to be rotating at 80% of the maximal spin. The orbital eccentricity is varied from 0.1 to 0.9. Inclination ranges from 20 deg. to 160 deg. and comes to within 20 deg. of polar. Semilatus rectum is varied from 1.2 to 3 times the value at the innermost stable circular orbits. The following general spectral properties are found: (i) 99% of the radiated power is typically carried by a few hundred modes, and at most by about a thousand modes, (ii) the dominant frequencies can be grouped into a small number of families defined by fixing two of the three integer frequency multipliers, and (iii) the specifics of these trends can be qualitatively inferred from the geometry of the orbit under consideration. Detections using triperiodic analytic templates modeled on these general properties would constitute a verification of radiation from an adiabatic sequence of black hole orbits and would recover the evolution of the fundamental orbital frequencies. In an analogy with ordinary spectroscopy, this would compare to observing the Bohr model's atomic hydrogen spectrum without being able to rule out alternative atomic theories or nuclei. The suitability of such a detection technique is demonstrated using snapshots computed at 12-hour intervals throughout the last three years before merger of a kludged inspiral. The system chosen is typical of those thought to occur in galactic nuclei and to be observable with space-based gravitational wave detectors like LISA. Because of circularization, the number of excited modes decreases as the binary

  1. The low earth orbit radiation environment and its evolution from measurements using the CREAM and CREDO experiments

    International Nuclear Information System (INIS)

    Dyer, C.S.; Sims, A.J.; Truscott, P.R.; Farren, J.; Underwood, C.

    1993-01-01

    Data obtained from Cosmic Radiation Environment Monitors carried on Shuttle missions during 1991/92, as well as on the polar orbiting microsatellite UOSAT-3 since April 1990, show the long term trends in the cosmic-ray and trapped proton environments responsible for single event phenomena. Cosmic-ray fluxes have increased by a factor of two since June 1991, while the solar flare event of Much 1991 created an additional region of trapped radiation which intersects high inclination Shuttle and polar orbits and, although decaying, was still present in December 1992. Deployment at a variety of shielding depths on Shuttle enables the influence of shielding to be explored and shows the influence of secondaries

  2. Probing in-medium spin–orbit interaction with intermediate-energy heavy-ion collisions

    International Nuclear Information System (INIS)

    Xu, Jun; Li, Bao-An

    2013-01-01

    Incorporating for the first time both the spin and isospin degrees of freedom explicitly in transport model simulations of intermediate-energy heavy-ion collisions, we observe that a local spin polarization appears during collision process. Most interestingly, it is found that the nucleon spin up–down differential transverse flow is a sensitive probe of the spin–orbit interaction, providing a novel approach to probe both the density and isospin dependence of the in-medium spin–orbit coupling that is important for understanding the structure of rare isotopes and synthesis of superheavy elements

  3. A New Model of Jupiter's Magnetic Field from Juno's First Nine Orbits

    DEFF Research Database (Denmark)

    Connerney, J. E. P.; Kotsiaros, S.; Oliversen, R. J.

    2018-01-01

    A spherical harmonic model of the magnetic field of Jupiter is obtained from vector magnetic field observations acquired by the Juno spacecraft during its first nine polar orbits about the planet. Observations acquired during eight of these orbits provide the first truly global coverage of Jupiter...... currents. Partial solution of the underdetermined inverse problem using generalized inverse techniques yields a model (“Juno Reference Model through Perijove 9”) of the planetary magnetic field with spherical harmonic coefficients well determined through degree and order 10, providing the first detailed...

  4. Altitude variations of ionospheric currents at auroral latitudes

    International Nuclear Information System (INIS)

    Kamide, Y.; Brekke, A.

    1993-01-01

    On the basis of updated EISCAT experiments, the first full derivation of the ionospheric current density of the auroral electrojets at six different altitudes are presented. It is found that current vectors at different altitudes are quite different, although the eastward and westward currents prevail in the evening and morning sectors, respectively, once the currents are integrated over altitude. The eastward electrojet becomes almost northward whilst the westward electrojet becomes almost southward, at the highest altitude, 125 km, in this study. The physical implications of these characteristics are discussed

  5. Orbital angular momentum of a high-order Bessel light beam

    International Nuclear Information System (INIS)

    Volke-Sepulveda, K; Garces-Chavez, V; Chavez-Cerda, S; Arlt, J; Dholakia, K

    2002-01-01

    The orbital angular momentum density of Bessel beams is calculated explicitly within a rigorous vectorial treatment. This allows us to investigate some aspects that have not been analysed previously, such as the angular momentum content of azimuthally and radially polarized beams. Furthermore, we demonstrate experimentally the mechanical transfer of orbital angular momentum to trapped particles in optical tweezers using a high-order Bessel beam. We set transparent particles of known dimensions into rotation, where the sense of rotation can be reversed by changing the sign of the singularity. Quantitative results are obtained for rotation rates. This paper's animations are available from the Multimedia Enhancements page

  6. Illumination Conditions of the Lunar Polar Regions Using LOLA Topography

    Science.gov (United States)

    Mazarico, E.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.; Torrence, M. H.

    2011-01-01

    We use high-resolution altimetry data obtained by the Lunar Orbiter Laser Altimeter instrument onboard the Lunar Reconnaissance Orbiter to characterize present illumination conditions in the polar regions of the Moon. Compared to previous studies, both the spatial and temporal extent of the simulations are increased significantly, as well as the coverage (fill ratio) of the topographic maps used, thanks to the 28 Hz firing rate of the five-beam instrument. We determine the horizon elevation in a number of directions based on 240 m-resolution polar digital elevation models reaching down to 75 latitude. The illumination of both polar regions extending to 80 can be calculated for any geometry from those horizon longitudinal profiles. We validated our modeling with recent Lunar Reconnaissance Orbiter Wide-Angle Camera images. We assessed the extent of permanently shadowed regions (PSRs, defined as areas that never receive direct solar illumination), and obtained total areas generally larger than previous studies (12,866 and 16,055 km2, in the north and south respectively). We extended our direct illumination model to account for singly-scattered light, and found that every PSR does receive some amount of scattered light during the year. We conducted simulations over long periods (several 18.6-years lunar precession cycles) with a high temporal resolution (6 h), and identified the most illuminated locations in the vicinity of both poles. Because of the importance of those sites for exploration and engineering considerations, we characterized their illumination more precisely over the near future. Every year, a location near the Shackleton crater rim in the south polar region is sunlit continuously for 240 days, and its longest continuous period in total darkness is about 1.5 days. For some locations small height gains ( 10 m) can dramatically improve their average illumination and reduce the night duration, rendering some of those particularly attractive energy-wise as

  7. Widespread spin polarization effects in photoemission from topological insulators

    Energy Technology Data Exchange (ETDEWEB)

    Jozwiak, C.; Chen, Y. L.; Fedorov, A. V.; Analytis, J. G.; Rotundu, C. R.; Schmid, A. K.; Denlinger, J. D.; Chuang, Y.-D.; Lee, D.-H.; Fisher, I. R.; Birgeneau, R. J.; Shen, Z.-X.; Hussain, Z.; Lanzara, A.

    2011-06-22

    High-resolution spin- and angle-resolved photoemission spectroscopy (spin-ARPES) was performed on the three-dimensional topological insulator Bi{sub 2}Se{sub 3} using a recently developed high-efficiency spectrometer. The topological surface state's helical spin structure is observed, in agreement with theoretical prediction. Spin textures of both chiralities, at energies above and below the Dirac point, are observed, and the spin structure is found to persist at room temperature. The measurements reveal additional unexpected spin polarization effects, which also originate from the spin-orbit interaction, but are well differentiated from topological physics by contrasting momentum and photon energy and polarization dependencies. These observations demonstrate significant deviations of photoelectron and quasiparticle spin polarizations. Our findings illustrate the inherent complexity of spin-resolved ARPES and demonstrate key considerations for interpreting experimental results.

  8. Cloud-based opportunities in scientific computing: insights from processing Suomi National Polar-Orbiting Partnership (S-NPP) Direct Broadcast data

    Science.gov (United States)

    Evans, J. D.; Hao, W.; Chettri, S.

    2013-12-01

    The cloud is proving to be a uniquely promising platform for scientific computing. Our experience with processing satellite data using Amazon Web Services highlights several opportunities for enhanced performance, flexibility, and cost effectiveness in the cloud relative to traditional computing -- for example: - Direct readout from a polar-orbiting satellite such as the Suomi National Polar-Orbiting Partnership (S-NPP) requires bursts of processing a few times a day, separated by quiet periods when the satellite is out of receiving range. In the cloud, by starting and stopping virtual machines in minutes, we can marshal significant computing resources quickly when needed, but not pay for them when not needed. To take advantage of this capability, we are automating a data-driven approach to the management of cloud computing resources, in which new data availability triggers the creation of new virtual machines (of variable size and processing power) which last only until the processing workflow is complete. - 'Spot instances' are virtual machines that run as long as one's asking price is higher than the provider's variable spot price. Spot instances can greatly reduce the cost of computing -- for software systems that are engineered to withstand unpredictable interruptions in service (as occurs when a spot price exceeds the asking price). We are implementing an approach to workflow management that allows data processing workflows to resume with minimal delays after temporary spot price spikes. This will allow systems to take full advantage of variably-priced 'utility computing.' - Thanks to virtual machine images, we can easily launch multiple, identical machines differentiated only by 'user data' containing individualized instructions (e.g., to fetch particular datasets or to perform certain workflows or algorithms) This is particularly useful when (as is the case with S-NPP data) we need to launch many very similar machines to process an unpredictable number of

  9. Valley polarized quantum Hall effect and topological insulator phase transitions in silicene

    KAUST Repository

    Tahir, M.; Schwingenschlö gl, Udo

    2013-01-01

    encountered for graphene, in particular the zero band gap and weak spin orbit interaction. We demonstrate a valley polarized quantum Hall effect and topological insulator phase transitions. We use the Kubo formalism to discuss the Hall conductivity and address

  10. Rotatable spin-polarized electron source for inverse-photoemission experiments

    International Nuclear Information System (INIS)

    Stolwijk, S. D.; Wortelen, H.; Schmidt, A. B.; Donath, M.

    2014-01-01

    We present a ROtatable Spin-polarized Electron source (ROSE) for the use in spin- and angle-resolved inverse-photoemission (SR-IPE) experiments. A key feature of the ROSE is a variable direction of the transversal electron beam polarization. As a result, the inverse-photoemission experiment becomes sensitive to two orthogonal in-plane polarization directions, and, for nonnormal electron incidence, to the out-of-plane polarization component. We characterize the ROSE and test its performance on the basis of SR-IPE experiments. Measurements on magnetized Ni films on W(110) serve as a reference to demonstrate the variable spin sensitivity. Moreover, investigations of the unoccupied spin-dependent surface electronic structure of Tl/Si(111) highlight the capability to analyze complex phenomena like spin rotations in momentum space. Essentially, the ROSE opens the way to further studies on complex spin-dependent effects in the field of surface magnetism and spin-orbit interaction at surfaces

  11. Measurements of size and composition of particles in polar stratospheric clouds from infrared solar absorption spectra

    International Nuclear Information System (INIS)

    Kinne, S.; Toon, O.B.; Toon, G.C.; Farmer, C.B.; Browell, E.V.; McCormick, M.P.

    1989-01-01

    The attenuation of solar radiation between 1.8- and 15-μm wavelength was measured with the airborne Jet Propulsion Laboratory Mark IV interferometer during the Airborne Antarctic Ozone Expedition in 1987. The measurements not only provide information about the abundance of stratospheric gases, but also about the optical depths of polar stratospheric clouds (PSCs) at wavelengths of negligible gas absorption. The spectral dependence of the PSC optical depth contains information about PSC particle size and particle composition. Thirty-three PSC cases were analyzed and categorized into two types. Type I clouds contain particles with radii of about 0.5 μm and nitric acid concentrations greater than 40%. Type II clouds contain particles composed of water ice with radii of 6 μm and larger. Cloud altitudes were determined from 1.064-μm backscattering observations of the airborne Langley DIAL lidar system. Based on the PSC geometrical thickness, both mass and particle density were estimated. Type I clouds typically had visible wavelength optical depths of about 0.008, mass densities of about 20 ppb, and about 2 particles/cm 3 . The observed type II clouds had optical depths of about 0.03, mass densities of about 400 ppb mass, and about 0.03 particles/cm 3 . The detected PSC type I clouds extended to altitudes of 21 km and were nearly in the ozone-depleted region of the polar stratosphere. The observed type II cases during September were predominantly found at altitudes below 15 km

  12. Orbital momentum distribution and binding energies for the complete valence shell of molecular bromine

    International Nuclear Information System (INIS)

    Frost, L.; Grisogono, A.M.; Weigold, E.

    1987-08-01

    The binding energy spectrum of Br 2 has been recorded in both the outer and inner valence regions using electron momentum spectroscopy. The measurements are compared with the results of several Green's function calculations using different approximations and based on both polarized and unpolarized wave functions. The inner valence region, observed for the first time, is found to exhibit complex structure that is shown to be due to many-body effects, thus indicating a breakdown of the simple MO picture for ionization in this region. Momentum distributions for the three outer valence orbitals are also measured and compared with spherically averaged calculations using the target Hartree-Fock and plane wave impulse approximations. The effect of polarization functions in the basis set is investigated. Orbital density maps in both momentum and position space have been calculated and compared with the experimental measurements

  13. Geometrical Optics of Beams with Vortices: Berry Phase and Orbital Angular Momentum Hall Effect

    International Nuclear Information System (INIS)

    Bliokh, Konstantin Yu.

    2006-01-01

    We consider propagation of a paraxial beam carrying the spin angular momentum (polarization) and intrinsic orbital angular momentum (IOAM) in a smoothly inhomogeneous isotropic medium. It is shown that the presence of IOAM can dramatically enhance and rearrange the topological phenomena that previously were considered solely in connection to the polarization of transverse waves. In particular, the appearance of a new type of Berry phase that describes the parallel transport of the beam structure along a curved ray is predicted. We derive the ray equations demonstrating the splitting of beams with different values of IOAM. This is the orbital angular momentum Hall effect, which resembles the Magnus effect for optical vortices. Unlike the spin Hall effect of photons, it can be much larger in magnitude and is inherent to waves of any nature. Experimental means to detect the phenomena are discussed

  14. Geometrical optics of beams with vortices: Berry phase and orbital angular momentum Hall effect.

    Science.gov (United States)

    Bliokh, Konstantin Yu

    2006-07-28

    We consider propagation of a paraxial beam carrying the spin angular momentum (polarization) and intrinsic orbital angular momentum (IOAM) in a smoothly inhomogeneous isotropic medium. It is shown that the presence of IOAM can dramatically enhance and rearrange the topological phenomena that previously were considered solely in connection to the polarization of transverse waves. In particular, the appearance of a new type of Berry phase that describes the parallel transport of the beam structure along a curved ray is predicted. We derive the ray equations demonstrating the splitting of beams with different values of IOAM. This is the orbital angular momentum Hall effect, which resembles the Magnus effect for optical vortices. Unlike the spin Hall effect of photons, it can be much larger in magnitude and is inherent to waves of any nature. Experimental means to detect the phenomena are discussed.

  15. Effects of ascent to high altitude on human antimycobacterial immunity.

    Directory of Open Access Journals (Sweden)

    Sarah Eisen

    Full Text Available Tuberculosis infection, disease and mortality are all less common at high than low altitude and ascent to high altitude was historically recommended for treatment. The immunological and mycobacterial mechanisms underlying the association between altitude and tuberculosis are unclear. We studied the effects of altitude on mycobacteria and antimycobacterial immunity.Antimycobacterial immunity was assayed in 15 healthy adults residing at low altitude before and after they ascended to 3400 meters; and in 47 long-term high-altitude residents. Antimycobacterial immunity was assessed as the extent to which participants' whole blood supported or restricted growth of genetically modified luminescent Bacille Calmette-Guérin (BCG mycobacteria during 96 hours incubation. We developed a simplified whole blood assay that could be used by a technician in a low-technology setting. We used this to compare mycobacterial growth in participants' whole blood versus positive-control culture broth and versus negative-control plasma.Measurements of mycobacterial luminescence predicted the number of mycobacterial colonies cultured six weeks later. At low altitude, mycobacteria grew in blood at similar rates to positive-control culture broth whereas ascent to high altitude was associated with restriction (p ≤ 0.002 of mycobacterial growth to be 4-times less than in culture broth. At low altitude, mycobacteria grew in blood 25-times more than negative-control plasma whereas ascent to high altitude was associated with restriction (p ≤ 0.01 of mycobacterial growth to be only 6-times more than in plasma. There was no evidence of differences in antimycobacterial immunity at high altitude between people who had recently ascended to high altitude versus long-term high-altitude residents.An assay of luminescent mycobacterial growth in whole blood was adapted and found to be feasible in low-resource settings. This demonstrated that ascent to or residence at high altitude was

  16. Effective stability around the Cassini state in the spin-orbit problem

    Science.gov (United States)

    Sansottera, Marco; Lhotka, Christoph; Lemaître, Anne

    2014-05-01

    We investigate the long-time stability in the neighborhood of the Cassini state in the conservative spin-orbit problem. Starting with an expansion of the Hamiltonian in the canonical Andoyer-Delaunay variables, we construct a high-order Birkhoff normal form and give an estimate of the effective stability time in the Nekhoroshev sense. By extensively using algebraic manipulations on a computer, we explicitly apply our method to the rotation of Titan. We obtain physical bounds of Titan's latitudinal and longitudinal librations, finding a stability time greatly exceeding the estimated age of the Universe. In addition, we study the dependence of the effective stability time on three relevant physical parameters: the orbital inclination, , the mean precession of the ascending node of Titan orbit, , and the polar moment of inertia,.

  17. Space Van system update

    Science.gov (United States)

    Cormier, Len

    1992-07-01

    The Space Van is a proposed commercial launch vehicle that is designed to carry 1150 kg to a space-station orbit for a price of $1,900,000 per flight in 1992 dollars. This price includes return on preoperational investment. Recurring costs are expected to be about $840,000 per flight. The Space Van is a fully reusable, assisted-single-stage-to orbit system. The most innovative new feature of the Space Van system is the assist-stage concept. The assist stage uses only airbreathing engines for vertical takeoff and vertical landing in the horizontal attitude and for launching the rocket-powered orbiter stage at mach 0.8 and an altitude of about 12 km. The primary version of the orbiter is designed for cargo-only without a crew. However, a passenger version of the Space Van should be able to carry a crew of two plus six passengers to a space-station orbit. Since the Space Van is nearly single-stage, performance to polar orbit drops off significantly. The cargo version should be capable of carrying 350 kg to a 400-km polar orbit. In the passenger version, the Space Van should be able to carry two crew members - or one crew member plus a passenger.

  18. The Mars water cycle at other epochs: History of the polar caps and layered terrain

    Science.gov (United States)

    Jakosky, Bruce M.; Henderson, Bradley G.; Mellon, Michael T.

    1992-01-01

    The atmospheric water cycle at the present epoch involves summertime sublimation of water from the north polar cap, transport of water through the atmosphere, and condensation on one or both winter CO2 caps. Exchange with the regolith is important seasonally, but the water content of the atmosphere appears to be controlled by the polar caps. The net annual transport through the atmosphere, integrated over long timescales, must be the driving force behind the long-term evolution of the polar caps; clearly, this feeds back into the evolution of the layered terrain. We have investigated the behavior of the seasonal water cycle and the net integrated behavior at the pole for the last 10 exp 7 years. Our model of the water cycle includes the solar input, CO2 condensation and sublimation, and summertime water sublimation through the seasonal cycles, and incorporates the long-term variations in the orbital elements describing the Martian orbit.

  19. The Lunar Orbiter Laser Altimeter (LOLA) on NASA's Lunar Reconnaissance Orbiter (LRO) mission

    Science.gov (United States)

    Riris, H.; Cavanaugh, J.; Sun, X.; Liiva, P.; Rodriguez, M.; Neuman, G.

    2017-11-01

    The Lunar Orbiter Laser Altimeter (LOLA) instrument [1-3] on NASA's Lunar Reconnaissance Orbiter (LRO) mission, launched on June 18th, 2009, from Kennedy Space Center, Florida, will provide a precise global lunar topographic map using laser altimetry. LOLA will assist in the selection of landing sites on the Moon for future robotic and human exploration missions and will attempt to detect the presence of water ice on or near the surface, which is one of the objectives of NASA's Exploration Program. Our present knowledge of the topography of the Moon is inadequate for determining safe landing areas for NASA's future lunar exploration missions. Only those locations, surveyed by the Apollo missions, are known with enough detail. Knowledge of the position and characteristics of the topographic features on the scale of a lunar lander are crucial for selecting safe landing sites. Our present knowledge of the rest of the lunar surface is at approximately 1 km kilometer level and in many areas, such as the lunar far side, is on the order of many kilometers. LOLA aims to rectify that and provide a precise map of the lunar surface on both the far and near side of the moon. LOLA uses short (6 ns) pulses from a single laser through a Diffractive Optical Element (DOE) to produce a five-beam pattern that illuminates the lunar surface. For each beam, LOLA measures the time of flight (range), pulse spreading (surface roughness), and transmit/return energy (surface reflectance). LOLA will produce a high-resolution global topographic model and global geodetic framework that enables precise targeting, safe landing, and surface mobility to carry out exploratory activities. In addition, it will characterize the polar illumination environment, and image permanently shadowed regions of the lunar surface to identify possible locations of surface ice crystals in shadowed polar craters.

  20. High-altitude adaptations in vertebrate hemoglobins

    DEFF Research Database (Denmark)

    Weber, Roy E.

    2007-01-01

    Vertebrates at high altitude are subjected to hypoxic conditions that challenge aerobic metabolism. O2 transport from the respiratory surfaces to tissues requires matching between the O2 loading and unloading tensions and theO2-affinity of blood, which is an integrated function of hemoglobin......, birds and ectothermic vertebrates at high altitude....

  1. High-energy polarized proton beams a modern view

    CERN Document Server

    Hoffstaetter, Georg Heinz

    2006-01-01

    This monograph begins with a review of the basic equations of spin motion in particle accelerators. It then reviews how polarized protons can be accelerated to several tens of GeV using as examples the preaccelerators of HERA, a 6.3 km long cyclic accelerator at DESY / Hamburg. Such techniques have already been used at the AGS of BNL / New York, to accelerate polarized protons to 25 GeV. But for acceleration to energies of several hundred GeV as in RHIC, TEVATRON, HERA, LHC, or a VLHC, new problems can occur which can lead to a significantly diminished beam polarization. For these high energies, it is necessary to look in more detail at the spin motion, and for that the invariant spin field has proved to be a useful tool. This is already widely used for the description of high-energy electron beams that become polarized by the emission of spin-flip synchrotron radiation. It is shown that this field gives rise to an adiabatic invariant of spin-orbit motion and that it defines the maximum time average polarizat...

  2. ICESat's First Year of Measurements Over the Polar Ice Sheets

    Science.gov (United States)

    Shuman, C. A.

    2004-05-01

    NASA's Ice, Cloud and Land Elevation Satellite (ICESat) mission was developed to measure changes in elevation of the Greenland and Antarctic ice sheets. Its primary mission goal is to significantly refine estimates of polar ice sheet mass balance. Obtaining precise, spatially dense, ice sheet elevations through time is the first step towards this goal. ICESat data will then enable study of associations between observed ice changes and dynamic or climatic forcing factors, and thus enable improved estimation of the present and future contributions of the ice sheets to global sea level rise. ICESat was launched on January 12, 2003 and acquired science data from February 20th to March 29th with the first of the three lasers of the Geoscience Laser Altimeter System (GLAS). Data acquisition with the second laser began on September 25th and continued until November 18th, 2003. For one-year change detection, the second laser is scheduled for operation from approximately February 17th to March 20th, 2004. Additional operational periods will be selected to 1) enable periodic measurements through the year, and 2) to support of other NASA Earth Science Enterprise missions and activities. To obtain these precise ice sheet elevations, GLAS has a 1064 nm wavelength laser operating at 40 Hz with a designed range precision of about 10 cm. The laser footprints are about 70 m in diameter on the Earth's surface and are spaced every 172 m along-track. The on-board GPS receiver enables radial orbit determinations to an accuracy better than 5 cm. The star-tracking attitude-determination system will enable laser footprints to be located to 6 m horizontally when attitude calibration is completed. The orbital altitude averages 600 km at an inclination of 94 degrees with coverage extending from 86 degrees N and S latitude. The spacecraft attitude can be controlled to point the laser beam to within 50 m of surface reference tracks over the ice sheets and to point off-nadir up to 5 degrees to

  3. Altitude Training in Elite Swimmers for Sea Level Performance (Altitude Project).

    Science.gov (United States)

    Rodríguez, Ferran A; Iglesias, Xavier; Feriche, Belén; Calderón-Soto, Carmen; Chaverri, Diego; Wachsmuth, Nadine B; Schmidt, Walter; Levine, Benjamin D

    2015-09-01

    This controlled, nonrandomized, parallel-groups trial investigated the effects on performance, V˙O2 and hemoglobin mass (tHbmass) of four preparatory in-season training interventions: living and training at moderate altitude for 3 and 4 wk (Hi-Hi3, Hi-Hi), living high and training high and low (Hi-HiLo, 4 wk), and living and training at sea level (SL) (Lo-Lo, 4 wk). From 61 elite swimmers, 54 met all inclusion criteria and completed time trials over 50- and 400-m crawl (TT50, TT400), and 100 (sprinters) or 200 m (nonsprinters) at best stroke (TT100/TT200). Maximal oxygen uptake (V˙O2max) and HR were measured with an incremental 4 × 200 m test. Training load was estimated using cumulative training impulse method and session RPE. Initial measures (PRE) were repeated immediately (POST) and once weekly on return to SL (PostW1 to PostW4). tHbmass was measured in duplicate at PRE and once weekly during the camp with CO rebreathing. Effects were analyzed using mixed linear modeling. TT100 or TT200 was worse or unchanged immediately at POST, but improved by approximately 3.5% regardless of living or training at SL or altitude after at least 1 wk of SL recovery. Hi-HiLo achieved greater improvement 2 (5.3%) and 4 wk (6.3%) after the camp. Hi-HiLo also improved more in TT400 and TT50 2 (4.2% and 5.2%, respectively) and 4 wk (4.7% and 5.5%) from return. This performance improvement was not linked linearly to changes in V˙O2max or tHbmass. A well-implemented 3- or 4-wk training camp may impair performance immediately but clearly improves performance even in elite swimmers after a period of SL recovery. Hi-HiLo for 4 wk improves performance in swimming above and beyond altitude and SL controls through complex mechanisms involving altitude living and SL training effects.

  4. On protection of freedom's solar dynamic radiator from the orbital debris environment. Part 1

    International Nuclear Information System (INIS)

    Rhatigan, J.L.

    1992-01-01

    A great deal of experimentation and analysis has been performed to quantify penetration thresholds of components which will experience orbital debris impacts. Penetration has been found to depend upon mission-specific parameters such as orbital altitude, inclination, and orientation of the component; and upon component specific parameters such as material, density, and the geometry particular to its shielding. Experimental results are highly dependent upon shield configuration and cannot be extrapolated with confidence to alternate shield configurations. Also, current experimental capabilities are limited to velocities which only approach the lower limit of predicted orbital debris velocities. Therefore, prediction of the penetrating particle size for a particular component having a complex geometry remains highly uncertain. This paper describes the approach developed to assess on-orbit survivability, and include the type of particle and particle population expected to defeat the radiator bumpering (i.e., penetrate a fluid flow tube). Results of preliminary hypervelocity impact testing performed on radiator panel samples (in the 6 to 7 km/sec velocity range) are also presented. Plans for further analyses and testing are discussed. These efforts are expected to lead to a radiator design which will perform to Space Station Freedom requirements over the expected lifetime

  5. A comparison of Doppler lidar wind sensors for Earth-orbit global measurement applications

    Science.gov (United States)

    Menzies, Robert T.

    1985-01-01

    Now, there are four Doppler lidar configurations which are being promoted for the measurement of tropospheric winds: (1) the coherent CO2 Lidar, operating in the 9 micrometer region using a pulsed, atmospheric pressure CO2 gas discharge laser transmitter, and heterodyne detection; (2) the coherent Neodymium doped YAG or Glass Lidar, operating at 1.06 micrometers, using flashlamp or diode laser optical pumping of the solid state laser medium, and heterodyne detection; (3) the Neodymium doped YAG/Glass Lidar, operating at the doubled frequency (at 530 nm wavelength), again using flashlamp or diode laser pumping of the laser transmitter, and using a high resolution tandem Fabry-Perot filter and direct detection; and (4) the Raman shifted Xenon Chloride Lidar, operating at 350 nm wavelength, using a pulsed, atmospheric pressure XeCl gas discharge laser transmitter at 308 nm, Raman shifted in a high pressure hydrogen cell to 350 nm in order to avoid strong stratospheric ozone absorption, also using a high resolution tandem Fabry-Perot filter and direct detection. Comparisons of these four systems can include many factors and tradeoffs. The major portion of this comparison is devoted to efficiency. Efficiency comparisons are made by estimating the number of transmitted photons required for a single pulse wind velocity estimate of + or - 1 m/s accuracy in the middle troposphere, from an altitude of 800 km, which is assured to be reasonable for a polar orbiting platform.

  6. Cryogenic implications of orbit selection of the Space Infrared Telescope Facility (SIRTF)

    International Nuclear Information System (INIS)

    Lee, J.H.; Brooke, W.F.; Maa, S.

    1986-01-01

    The Infrared Astronomical Satellite (IRAS) which completed the first all sky survey in the infrared demonstrated the tremendous advantage of space-based infrared astronomy. The ability to cool the telescope optics and focal plane to liquid helium temperatures and the absence of atmospheric disturbances which cause ''seeing'' effects resulted in the discovery of 250,000 IR sources and many interesting phenomena including dust clouds around Vega and the infrared ''cirrus'' at 100 μm. To realize the true benefit of space infrared astronomy, NASA is now studying the Space Infrared Telescope Facility, a long-life space-based observatory, to follow up on the survey results of IRAS. The choice of orbits is a critical program decision. The objective of this paper is to compare the performance of an all superfluid helium SIRTF system in the two possible orbit inclinations, polar orbit (99 0 ) and the low inclination orbit (28.5 0 )

  7. Spin-polarized electron gas in Co2MSi/SrTiO3(M= Ti, V, Cr, Mn, and Fe) heterostructures

    KAUST Repository

    Nazir, S.

    2016-06-08

    Spin-polarized density functional theory is used to study the TiO2 terminated interfaces between the magnetic Heusler alloys Co2Si (M = Ti, V, Cr, Mn, and Fe) and the non-polar band insulator SrTiO3. The structural relaxation at the interface turns out to depend systematically on the lattice mis- match. Charge transfer from the Heusler alloys (mainly the M 3d orbitals) to the Ti dxy orbitals of the TiO2 interface layer is found to gradually grow from M = Ti to Fe, resulting in an electron gas with increasing density of spin-polarized charge carriers. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  8. Polarized View of Supercooled Liquid Water Clouds

    Science.gov (United States)

    Alexandrov, Mikhail D.; Cairns, Brian; Van Diedenhoven, Bastiaan; Ackerman, Andrew S.; Wasilewski, Andrzej P.; McGill, Matthew J.; Yorks, John E.; Hlavka, Dennis L.; Platnick, Steven E.; Arnold, G. Thomas

    2016-01-01

    Supercooled liquid water (SLW) clouds, where liquid droplets exist at temperatures below 0 C present a well known aviation hazard through aircraft icing, in which SLW accretes on the airframe. SLW clouds are common over the Southern Ocean, and climate-induced changes in their occurrence is thought to constitute a strong cloud feedback on global climate. The two recent NASA field campaigns POlarimeter Definition EXperiment (PODEX, based in Palmdale, California, January-February 2013) and Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS, based in Houston, Texas in August- September 2013) provided a unique opportunity to observe SLW clouds from the high-altitude airborne platform of NASA's ER-2 aircraft. We present an analysis of measurements made by the Research Scanning Polarimeter (RSP) during these experiments accompanied by correlative retrievals from other sensors. The RSP measures both polarized and total reflectance in 9 spectral channels with wavelengths ranging from 410 to 2250 nm. It is a scanning sensor taking samples at 0.8deg intervals within 60deg from nadir in both forward and backward directions. This unique angular resolution allows for characterization of liquid water droplet size using the rainbow structure observed in the polarized reflectances in the scattering angle range between 135deg and 165deg. Simple parametric fitting algorithms applied to the polarized reflectance provide retrievals of the droplet effective radius and variance assuming a prescribed size distribution shape (gamma distribution). In addition to this, we use a non-parametric method, Rainbow Fourier Transform (RFT),which allows retrieval of the droplet size distribution without assuming a size distribution shape. We present an overview of the RSP campaign datasets available from the NASA GISS website, as well as two detailed examples of the retrievals. In these case studies we focus on cloud fields with spatial features

  9. Low-altitude ion heating with downflowing and upflowing ions

    Science.gov (United States)

    Shen, Y.; Knudsen, D. J.; Burchill, J. K.; Howarth, A. D.; Yau, A. W.; James, G.; Miles, D.; Cogger, L. L.; Perry, G. W.

    2017-12-01

    Mechanisms that energize ions at the initial stage of ion upflow are still not well understood. We statistically investigate ionospheric ion energization and field-aligned motion at very low altitudes (330-730 km) using simultaneous plasma, magnetic field, wave electric field and optical data from the e-POP satellite. The high-time-resolution (10 ms) dataset enables us to study the micro-structures of ion heating and field-aligned ion motion. The ion temperature and field-aligned bulk flow velocity are derived from 2-D ion distribution functions measured by the SEI instrument. From March 2015 to March 2016, we've found 17 orbits (in total 24 ion heating periods) with clear ion heating signatures passing across the dayside cleft or the nightside auroral regions. Most of these events have consistent ion heating and flow velocity characteristics observed from both the SEI and IRM instruments. The perpendicular ion temperature goes up to 4.5 eV within a 2 km-wide region in some cases, in which the Radio Receiver Instrument (RRI) sees broadband extremely low frequency (BBELF) waves, demonstrating significant wave-ion heating down to as low as 350 km. The e-POP Fast Auroral Imager (FAI) and Magnetic Field (MGF) instruments show that many events are associated with active aurora and are within downward current regions. Contrary to what would be expected from mirror-force acceleration of heated ions, the majority of these heating events (17 out of 24) are associated with the core ion downflow rather than upflow. These statistical results provide us with new sights into ion heating and field-aligned flow processes at very low altitudes.

  10. Towards diagnostic tools for analysing Swarm data through model retrievals

    DEFF Research Database (Denmark)

    Kotsiaros, Stavros; Plank, Gernot; Haagmans, R.

    polar orbits between 300 and 550 km altitude. Goal of the current study is to build tools and to analyze datasets, in order to allow a fast diagnosis of the Swarm system performance in orbit during the commission phase and operations of the spacecraft. The effects on the reconstruction of the magnetic...... field resulting from various error sources are investigated. By using a specially developed software package closed loop simulations are performed aiming at different scenarios. We start from the simple noise-free case and move on to more complex and realistic situations which include attitude errors...

  11. Low Altitude Emission (LAE) of Energetic Neutral Atoms (ENA) Observed by TWINS and its Relation to the CINEMA CubeSat Mission

    Science.gov (United States)

    Bazell, D.; Sotirelis, T.; Nair, H.; Roelof, E. C.; Brandt, P. C.

    2009-12-01

    The brightest source of energetic neutral atoms (ENAs) at energies >1keV is low altitude emission (LAE) from ~200-400km near auroral latitudes where precipitating energetic ions undergo multiple atomic collisions with the monatomic (O) exosphere. This emission is many times brighter than that from the high-altitude ring current region where the energetic ions interact only weakly with the much less dense monatomic (H) hydrogen geocorona. The recently selected NSF CubeSat mission CINEMA [Lin et al., this special session] has, as part of its science payload (STEIN), an ENA imager covering energies 4-100keV. From a high-inclination ~800km orbit, STEIN will view the LAE four times during every 90 minutes. The NASA TWINS stereo ENA imagers (2-40keV) will also view the LAE from their Molniya orbits (apogee radius~7Re). We have been analyzing the TWINS ENA images of LAE and comparing them with in situ ion measurements (1-40keV) from DMSP spacecraft when their tracks take them under the ion precipitation regions imaged by TWINS. We have developed an ENA emissivity function that relates the directionally-dependent emergent ENA spectrum to that of the precipitating ions. The TWINS/DMSP direct comparisons show good agreement. We offer suggestions on joint observing strategies for CINEMA, TWINS and DMSP after the CINEMA launch in the second half of 2011.

  12. SMM mesospheric ozone measurements

    Science.gov (United States)

    Aikin, A. C.

    1990-01-01

    The main objective was to understand the secular and seasonal behavior of ozone in the lower mesosphere, 50 to 70 km. This altitude region is important in understanding the factors which determine ozone behavior. A secondary objective is the study of stratospheric ozone in the polar regions. Use is made of results from the SBUV satellite borne instrument. In the Arctic the interaction between chlorine compounds and low molecular weight hydrocarbons is studied. More than 30,000 profiles were obtained using the UVSP instrument on the SMM spacecraft. Several orbits of ozone data per day were obtained allowing study of the current rise in solar activity from the minimum until the present. Analysis of Nimbus 7 SBUV data in Antarctic spring indicates that ozone is depleted within the polar vortex relative to ozone outside the vortex. This depletion confirms the picture of ozone loss at altitudes where polar stratospheric clouds exist. In addition, there is ozone loss above the cloud level indicating that there is another mechanism in addition to ozone loss initiated by heterogeneous chlorine reactions on cloud particles.

  13. The third post-Newtonian gravitational wave polarizations and associated spherical harmonic modes for inspiralling compact binaries in quasi-circular orbits

    International Nuclear Information System (INIS)

    Blanchet, Luc; Faye, Guillaume; Iyer, Bala R; Sinha, Siddhartha

    2008-01-01

    The gravitational waveform (GWF) generated by inspiralling compact binaries moving in quasi-circular orbits is computed at the third post-Newtonian (3PN) approximation to general relativity. Our motivation is two-fold: (i) to provide accurate templates for the data analysis of gravitational wave inspiral signals in laser interferometric detectors; (ii) to provide the associated spin-weighted spherical harmonic decomposition to facilitate comparison and match of the high post-Newtonian prediction for the inspiral waveform to the numerically-generated waveforms for the merger and ringdown. This extension of the GWF by half a PN order (with respect to previous work at 2.5PN order) is based on the algorithm of the multipolar post-Minkowskian formalism, and mandates the computation of the relations between the radiative, canonical and source multipole moments for general sources at 3PN order. We also obtain the 3PN extension of the source multipole moments in the case of compact binaries, and compute the contributions of hereditary terms (tails, tails-of-tails and memory integrals) up to 3PN order. The end results are given for both the complete plus and cross polarizations and the separate spin-weighted spherical harmonic modes

  14. Tracing the Inter-Hemispheric Coupling During Polar Summer Periods of 2002-2010 Using TIMED/SABER Measurements

    Science.gov (United States)

    Goldberg, Richard; Feoflow, Artem; Pesnell, Dean; Kutepov, Alexander

    2010-01-01

    It has been found that for more than one polar summer season between 2002-2010, the northern polar mesospheric region near and above the mesospheric maximum was warmer than normal. The strongest warming effect of this type was observed to occur during northern summer 2002. Theoretical studies have implied that these "anomalies" were preceded by unusual dynamical processes occurring in the southern hemisphere. We have analyzed temperature distributions measured by the SABER limb scanning infrared radiometer aboard the NASA TIMED satellite between 2002-2010 at altitudes from 15 to 110 km and for latitudes between 83 deg. S to 83 deg. N. We describe the approach to trace the inter-hemispheric temperature correlatoins and to identify the global features that were unique for the "anomalous" northern polar summers.

  15. North Polar Cap

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] This week we will be looking at five examples of laminar wind flow on the north polar cap. On Earth, gravity-driven south polar cap winds are termed 'catabatic' winds. Catabatic winds begin over the smooth expanse of the cap interior due to temperature differences between the atmosphere and the surface. Once begun, the winds sweep outward along the surface of the polar cap toward the sea. As the polar surface slopes down toward sealevel, the wind speeds increase. Catabatic wind speeds in the Antartic can reach several hundreds of miles per hour. In the images of the Martian north polar cap we can see these same type of winds. Notice the streamers of dust moving downslope over the darker trough sides, these streamers show the laminar flow regime coming off the cap. Within the trough we see turbulent clouds of dust, kicked up at the trough base as the winds slow down and enter a chaotic flow regime. The horizontal lines in these images are due to framelet overlap and lighting conditions over the bright polar cap. Image information: VIS instrument. Latitude 86.5, Longitude 64.5 East (295.5 West). 40 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen

  16. Near earth magnetic disturbance in total field at high latitudes. 1: Summary of data from OGO's 2, 4, and 6

    Science.gov (United States)

    Langel, R. A.

    1973-01-01

    Variations in the total (i.e. scalar) magnetic field data from the polar orbiting OGO-2, 4, and 6 spacecraft (altitudes 400-1510 km) are summarized for invariant latitudes above 55 deg. Data from all degrees of magnetic disturbance are included. The data are presented in terms of the quantity delta B(= measured field magnitude minus the field magnitude from a spherical harmonic model of the quiet field).

  17. AltitudeOmics: Resetting of cerebrovascular CO2 reactivity following acclimatization to high altitude

    Directory of Open Access Journals (Sweden)

    Jui-Lin eFan

    2016-01-01

    Full Text Available Previous studies reported enhanced cerebrovascular CO2 reactivity upon ascent to high altitude using linear models. However, there is evidence that this response may be sigmoidal in nature. Moreover, it was speculated that these changes at high altitude are mediated by alterations in acid-base buffering. Accordingly, we reanalyzed previously published data to assess middle cerebral blood flow velocity (MCAv responses to modified rebreathing at sea level (SL, upon ascent (ALT1 and following 16 days of acclimatization (ALT16 to 5,260 m in 21 lowlanders. Using sigmoid curve fitting of the MCAv responses to CO2, we found the amplitude (95% vs. 129%, SL vs. ALT1, 95% confidence intervals (CI [77, 112], [111, 145], respectively, P=0.024 and the slope of the sigmoid response (4.5 vs. 7.5 %/mmHg, SL vs. ALT1, 95% CIs [3.1, 5.9], [6.0, 9.0], respectively, P=0.026 to be enhanced at ALT1, which persisted with acclimatization at ALT16 (amplitude: 177%, 95% CI [139, 215], P<0.001; slope: 10.3 %/mmHg, 95% CI [8.2, 12.5], P=0.003 compared to SL. Meanwhile, the sigmoidal response midpoint was unchanged at ALT1 (SL: 36.5 mmHg; ALT1: 35.4 mmHg, 95% CIs [34.0, 39.0], [33.1, 37.7], respectively, P=0.982, while it was reduced by ~7 mmHg at ALT16 (28.6 mmHg, 95% CI [26.4, 30.8], P=0.001 vs. SL, indicating leftward shift of the cerebrovascular CO2 response to a lower arterial partial pressure of CO2 (PaCO2 following acclimatization to altitude. Sigmoid fitting revealed a leftward shift in the midpoint of the cerebrovascular response curve which could not be observed with linear fitting. These findings demonstrate that