WorldWideScience

Sample records for satellite orbit anomaly

  1. Diagnosing low earth orbit satellite anomalies using NOAA-15 electron data associated with geomagnetic perturbations

    Science.gov (United States)

    Ahmad, Nizam; Herdiwijaya, Dhani; Djamaluddin, Thomas; Usui, Hideyuki; Miyake, Yohei

    2018-05-01

    A satellite placed in space is constantly affected by the space environment, resulting in various impacts from temporary faults to permanent failures depending on factors such as satellite orbit, solar and geomagnetic activities, satellite local time, and satellite construction material. Anomaly events commonly occur during periods of high geomagnetic activity that also trigger plasma variation in the low Earth orbit (LEO) environment. In this study, we diagnosed anomalies in LEO satellites using electron data from the Medium Energy Proton and Electron Detector onboard the National Oceanic and Atmospheric Administration (NOAA)-15 satellite. In addition, we analyzed the fluctuation of electron flux in association with geomagnetic disturbances 3 days before and after the anomaly day. We selected 20 LEO anomaly cases registered in the Satellite News Digest database for the years 2000-2008. Satellite local time, an important parameter for anomaly diagnosis, was determined using propagated two-line element data in the SGP4 simplified general perturbation model to calculate the longitude of the ascending node of the satellite through the position and velocity vectors. The results showed that the majority of LEO satellite anomalies are linked to low-energy electron fluxes of 30-100 keV and magnetic perturbations that had a higher correlation coefficient ( 90%) on the day of the anomaly. The mean local time calculation for the anomaly day with respect to the nighttime migration of energetic electrons revealed that the majority of anomalies (65%) occurred on the night side of Earth during the dusk-to-dawn sector of magnetic local time.

  2. 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...

  3. Spacecraft on-orbit deployment anomalies - What can be done?

    Science.gov (United States)

    Freeman, Michael T.

    1993-04-01

    Modern communications satellites rely heavily upon deployable appendage (i.e. solar arrays, communications antennas, etc.) to perform vital functions that enable the spacecraft to effectively conduct mission objectives. Communications and telemetry antennas provide the radiofrequency link between the spacecraft and the earth ground station, permitting data to be transmitted and received from the satellite. Solar arrays serve as the principle source of electrical energy to the satellite, and recharge internal batteries during operation. However, since satellites cannot carry backup systems, if a solar array fails to deploy, the mission is lost. This article examines the subject of on-orbit anomalies related to the deployment of spacecraft appendage, and possible causes of such failures. Topics discussed shall include mechanical launch loading, on-orbit thermal and solar concerns, reliability of spacecraft pyrotechnics, and practical limitations of ground-based deployment testing. Of particular significance, the article will feature an in-depth look at the lessons learned from the successful recovery of the Telesat Canada Anik-E2 satellite in 1991.

  4. Orbit determination for ISRO satellite missions

    Science.gov (United States)

    Rao, Ch. Sreehari; Sinha, S. K.

    Indian Space Research Organisation (ISRO) has been successful in using the in-house developed orbit determination and prediction software for satellite missions of Bhaskara, Rohini and APPLE. Considering the requirements of satellite missions, software packages are developed, tested and their accuracies are assessed. Orbit determination packages developed are SOIP, for low earth orbits of Bhaskara and Rohini missions, ORIGIN and ODPM, for orbits related to all phases of geo-stationary missions and SEGNIP, for drift and geo-stationary orbits. Software is tested and qualified using tracking data of SIGNE-3, D5-B, OTS, SYMPHONIE satellites with the help of software available with CNES, ESA and DFVLR. The results match well with those available from these agencies. These packages have supported orbit determination successfully throughout the mission life for all ISRO satellite missions. Member-Secretary

  5. History of Satellite Orbit Determination at NSWCDD

    Science.gov (United States)

    2018-01-31

    meeting of the Satellite Division of ION, Palm Springs, CA., 12–15 Sep 1995. Hughey, Raymond H., Jr., “ History of Mathematics and Computing Technology ...TR-17/229 HISTORY OF SATELLITE ORBIT DETERMINATION AT NSWCDD BY EVERETT R. SWIFT WARFARE SYSTEMS ENGINEERING AND INTEGRATION...AND SUBTITLE History of Satellite Orbit Determination at NSWCDD 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER

  6. Anomaly Monitoring Method for Key Components of Satellite

    Directory of Open Access Journals (Sweden)

    Jian Peng

    2014-01-01

    Full Text Available This paper presented a fault diagnosis method for key components of satellite, called Anomaly Monitoring Method (AMM, which is made up of state estimation based on Multivariate State Estimation Techniques (MSET and anomaly detection based on Sequential Probability Ratio Test (SPRT. On the basis of analysis failure of lithium-ion batteries (LIBs, we divided the failure of LIBs into internal failure, external failure, and thermal runaway and selected electrolyte resistance (Re and the charge transfer resistance (Rct as the key parameters of state estimation. Then, through the actual in-orbit telemetry data of the key parameters of LIBs, we obtained the actual residual value (RX and healthy residual value (RL of LIBs based on the state estimation of MSET, and then, through the residual values (RX and RL of LIBs, we detected the anomaly states based on the anomaly detection of SPRT. Lastly, we conducted an example of AMM for LIBs, and, according to the results of AMM, we validated the feasibility and effectiveness of AMM by comparing it with the results of threshold detective method (TDM.

  7. Analysis on Space Environment from the Anomalies of Geosynchronous Satellites

    Directory of Open Access Journals (Sweden)

    Jaejin Lee

    2009-12-01

    Full Text Available While it is well known that space environment can produce spacecraft anomaly, defining space environment effects for each anomalies is difficult. This is caused by the fact that spacecraft anomaly shows various symptoms and reproducing it is impossible. In this study, we try to find the conditions of when spacecraft failures happen more frequently and give satellite operators useful information. Especially, our study focuses on the geosynchronous satellites which cost is high and required high reliability. We used satellite anomaly data given by Satellite News Digest which is internet newspaper providing space industry news. In our analysis, 88 anomaly cases occurred from 1997 to 2008 shows bad corelation with Kp index. Satellite malfunctions were likely to happen in spring and fall and in local time from midnight to dawn. In addition, we found the probability of anomaly increase when high energy electron flux is high. This is more clearly appeared in solar minimum than maximum period.

  8. Orbits of the inner satellites of Neptune

    Science.gov (United States)

    Brozovic, Marina; Showalter, Mark R.; Jacobson, Robert Arthur; French, Robert S.; de Pater, Imke; Lissauer, Jack

    2018-04-01

    We report on the numerically integrated orbits of seven inner satellites of Neptune, including S/2004 N1, the last moon of Neptune to be discovered by the Hubble Space Telescope (HST). The dataset includes Voyager imaging data as well as the HST and Earth-based astrometric data. The observations span time period from 1989 to 2016. Our orbital model accounts for the equatorial bulge of Neptune, perturbations from the Sun and the planets, and perturbations from Triton. The initial orbital integration assumed that the satellites are massless, but the residuals improved significantly as the masses adjusted toward values that implied that the density of the satellites is in the realm of 1 g/cm3. We will discuss how the integrated orbits compare to the precessing ellipses fits, mean orbital elements, current orbital uncertainties, and the need for future observations.

  9. Orbit Propagation and Determination of Low Earth Orbit Satellites

    Directory of Open Access Journals (Sweden)

    Ho-Nien Shou

    2014-01-01

    Full Text Available This paper represents orbit propagation and determination of low Earth orbit (LEO satellites. Satellite global positioning system (GPS configured receiver provides position and velocity measures by navigating filter to get the coordinates of the orbit propagation (OP. The main contradictions in real-time orbit which is determined by the problem are orbit positioning accuracy and the amount of calculating two indicators. This paper is dedicated to solving the problem of tradeoffs. To plan to use a nonlinear filtering method for immediate orbit tasks requires more precise satellite orbit state parameters in a short time. Although the traditional extended Kalman filter (EKF method is widely used, its linear approximation of the drawbacks in dealing with nonlinear problems was especially evident, without compromising Kalman filter (unscented Kalman Filter, UKF. As a new nonlinear estimation method, it is measured at the estimated measurements on more and more applications. This paper will be the first study on UKF microsatellites in LEO orbit in real time, trying to explore the real-time precision orbit determination techniques. Through the preliminary simulation results, they show that, based on orbit mission requirements and conditions using UKF, they can satisfy the positioning accuracy and compute two indicators.

  10. A Magnetic Petrology Database for Satellite Magnetic Anomaly Interpretations

    Science.gov (United States)

    Nazarova, K.; Wasilewski, P.; Didenko, A.; Genshaft, Y.; Pashkevich, I.

    2002-05-01

    A Magnetic Petrology Database (MPDB) is now being compiled at NASA/Goddard Space Flight Center in cooperation with Russian and Ukrainian Institutions. The purpose of this database is to provide the geomagnetic community with a comprehensive and user-friendly method of accessing magnetic petrology data via Internet for more realistic interpretation of satellite magnetic anomalies. Magnetic Petrology Data had been accumulated in NASA/Goddard Space Flight Center, United Institute of Physics of the Earth (Russia) and Institute of Geophysics (Ukraine) over several decades and now consists of many thousands of records of data in our archives. The MPDB was, and continues to be in big demand especially since recent launching in near Earth orbit of the mini-constellation of three satellites - Oersted (in 1999), Champ (in 2000), and SAC-C (in 2000) which will provide lithospheric magnetic maps with better spatial and amplitude resolution (about 1 nT). The MPDB is focused on lower crustal and upper mantle rocks and will include data on mantle xenoliths, serpentinized ultramafic rocks, granulites, iron quartzites and rocks from Archean-Proterozoic metamorphic sequences from all around the world. A substantial amount of data is coming from the area of unique Kursk Magnetic Anomaly and Kola Deep Borehole (which recovered 12 km of continental crust). A prototype MPDB can be found on the Geodynamics Branch web server of Goddard Space Flight Center at http://core2.gsfc.nasa.gov/terr_mag/magnpetr.html. The MPDB employs a searchable relational design and consists of 7 interrelated tables. The schema of database is shown at http://core2.gsfc.nasa.gov/terr_mag/doc.html. MySQL database server was utilized to implement MPDB. The SQL (Structured Query Language) is used to query the database. To present the results of queries on WEB and for WEB programming we utilized PHP scripting language and CGI scripts. The prototype MPDB is designed to search database by major satellite magnetic

  11. 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.

  12. Servicing communication satellites in geostationary orbit

    Science.gov (United States)

    Russell, Paul K.; Price, Kent M.

    1990-01-01

    The econmic benefits of a LEO space station are quantified by identifying alternative operating scenarios utilizing the space station's transportation facilities and assembly and repair facilities. Particular consideration is given to the analysis of the impact of on-orbit assembly and servicing on a typical communications satellite is analyzed. The results of this study show that on-orbit servicing can increase the internal rate of return by as much as 30 percent.

  13. Discriminating satellite IR anomalies associated with the MS 7.1 Yushu earthquake in China

    Science.gov (United States)

    Qin, Kai; Wu, Lixin; Zheng, Shuo; Ma, Weiyu

    2018-03-01

    In the process of exploring pre-earthquake thermal anomalies using satellite infrared data, Blackett et al. (2011) found that the previously reported anomalies before the 2001 Mw 7.7 Gujarat earthquake, in India, were related to positive biases caused by data gaps due to cloud cover and mosaicing of neighboring orbits of MODIS satellite data. They supposed that such effects could also be responsible for other cases. We noted a strip-shaped TIR anomaly on March 17th, 2010, 28 days before the Ms. 7.1 Yushu earthquake (Qin et al., 2011). Here we again investigate multi-year infrared satellite data in different bands to discriminate whether the anomaly is associated with the earthquake, or is only bias caused by the data gaps. From the water vapor images, we find lots of clouds that have TIR anomalies. However, on the cloudiness background, there is an obvious strip-shaped gap matching the tectonic faults almost perfectly. In particular, the animation loops of hourly water vapor images show that the cloud kept moving from west to east, while they never covered the strip-shaped gap. We consider that the cloud with this special spatial pattern should have implied the abnormal signals associated with the seismogenic process. Based on current physical models, the satellite IR anomalies both on TIR and water vapor bands can qualitatively be explained using synthetic mechanisms.

  14. Satellite magnetic anomalies of the Antarctic crust

    Directory of Open Access Journals (Sweden)

    D. E. Alsdorf

    2000-06-01

    Full Text Available Spatially and temporally static crustal magnetic anomalies are contaminated by static core field effects above spherical harmonic degree 12 and dynamic, large-amplitude external fields. To extract crustal magnetic anomalies from the measurements of NASA's Magsat mission, we separate crustal signals from both core and external field effects. In particular, we define Magsat anomalies relative to the degree 11 field and use spectral correlation theory to reduce them for external field effects. We obtain a model of Antarctic crustal thickness by comparing the region's terrain gravity effects to free-air gravity anomalies derived from the Earth Gravity Model 1996 (EGM96. To separate core and crustal magnetic effects, we obtain the pseudo-magnetic effect of the crustal thickness variations from their gravity effect via Poisson's theorem for correlative potentials. We compare the pseudo-magnetic effect of the crustal thickness variations to field differences between degrees 11 and 13 by spectral correlation analysis. We thus identify and remove possible residual core field effects in the Magsat anomalies relative to the degree 11 core field. The resultant anomalies reflect possible Antarctic contrasts due both to crustal thickness and intracrustal variations of magnetization. In addition, they provide important constraints on the geologic interpretation of aeromagnetic survey data, such as are available for the Weddell Province. These crustal anomalies also may be used to correct for long wavelength errors in regional compilations of near-surface magnetic survey data. However, the validity of these applications is limited by the poor quality of the Antarctic Magsat data that were obtained during austral Summer and Fall when south polar external field activity was maximum. Hence an important test and supplement for the Antarctic crustal Magsat anomaly map will be provided by the data from the recently launched Ørsted mission, which will yield coverage

  15. Pre-seismic anomalies from optical satellite observations: a review

    Science.gov (United States)

    Jiao, Zhong-Hu; Zhao, Jing; Shan, Xinjian

    2018-04-01

    Detecting various anomalies using optical satellite data prior to strong earthquakes is key to understanding and forecasting earthquake activities because of its recognition of thermal-radiation-related phenomena in seismic preparation phases. Data from satellite observations serve as a powerful tool in monitoring earthquake preparation areas at a global scale and in a nearly real-time manner. Over the past several decades, many new different data sources have been utilized in this field, and progressive anomaly detection approaches have been developed. This paper reviews the progress and development of pre-seismic anomaly detection technology in this decade. First, precursor parameters, including parameters from the top of the atmosphere, in the atmosphere, and on the Earth's surface, are stated and discussed. Second, different anomaly detection methods, which are used to extract anomalous signals that probably indicate future seismic events, are presented. Finally, certain critical problems with the current research are highlighted, and new developing trends and perspectives for future work are discussed. The development of Earth observation satellites and anomaly detection algorithms can enrich available information sources, provide advanced tools for multilevel earthquake monitoring, and improve short- and medium-term forecasting, which play a large and growing role in pre-seismic anomaly detection research.

  16. Electric propulsion reliability: Statistical analysis of on-orbit anomalies and comparative analysis of electric versus chemical propulsion failure rates

    Science.gov (United States)

    Saleh, Joseph Homer; Geng, Fan; Ku, Michelle; Walker, Mitchell L. R.

    2017-10-01

    With a few hundred spacecraft launched to date with electric propulsion (EP), it is possible to conduct an epidemiological study of EP's on orbit reliability. The first objective of the present work was to undertake such a study and analyze EP's track record of on orbit anomalies and failures by different covariates. The second objective was to provide a comparative analysis of EP's failure rates with those of chemical propulsion. Satellite operators, manufacturers, and insurers will make reliability- and risk-informed decisions regarding the adoption and promotion of EP on board spacecraft. This work provides evidence-based support for such decisions. After a thorough data collection, 162 EP-equipped satellites launched between January 1997 and December 2015 were included in our dataset for analysis. Several statistical analyses were conducted, at the aggregate level and then with the data stratified by severity of the anomaly, by orbit type, and by EP technology. Mean Time To Anomaly (MTTA) and the distribution of the time to (minor/major) anomaly were investigated, as well as anomaly rates. The important findings in this work include the following: (1) Post-2005, EP's reliability has outperformed that of chemical propulsion; (2) Hall thrusters have robustly outperformed chemical propulsion, and they maintain a small but shrinking reliability advantage over gridded ion engines. Other results were also provided, for example the differentials in MTTA of minor and major anomalies for gridded ion engines and Hall thrusters. It was shown that: (3) Hall thrusters exhibit minor anomalies very early on orbit, which might be indicative of infant anomalies, and thus would benefit from better ground testing and acceptance procedures; (4) Strong evidence exists that EP anomalies (onset and likelihood) and orbit type are dependent, a dependence likely mediated by either the space environment or differences in thrusters duty cycles; (5) Gridded ion thrusters exhibit both

  17. Contrast in low-cost operational concepts for orbiting satellites

    Science.gov (United States)

    Walyus, Keith D.; Reis, James; Bradley, Arthur J.

    2002-12-01

    Older spacecraft missions, especially those in low Earth orbit with telemetry intensive requirements, required round-the-clock control center staffing. The state of technology relied on control center personnel to continually examine data, make decisions, resolve anomalies, and file reports. Hubble Space Telescope (HST) is a prime example of this description. Technological advancements in hardware and software over the last decade have yielded increases in productivity and operational efficiency, which result in lower cost. The re-engineering effort of HST, which has recently concluded, utilized emerging technology to reduce cost and increase productivity. New missions, of which NASA's Transition Region and Coronal Explorer Satellite (TRACE) is an example, have benefited from recent technological advancements and are more cost-effective than when HST was first launched. During its launch (1998) and early orbit phase, the TRACE Flight Operations Team (FOT) employed continually staffed operations. Yet once the mission entered its nominal phase, the FOT reduced their staffing to standard weekday business hours. Operations were still conducted at night and during the weekends, but these operations occurred autonomously without compromising their high standards for data collections. For the HST, which launched in 1990, reduced cost operations will employ a different operational concept, when the spacecraft enters its low-cost phase after its final servicing mission in 2004. Primarily due to the spacecraft"s design, the HST Project has determined that single-shift operations will introduce unacceptable risks for the amount of dollars saved. More importantly, significant cost-savings can still be achieved by changing the operational concept for the FOT, while still maintaining round-the-clock staffing. It"s important to note that the low-cost solutions obtained for one satellite may not be applicable for other satellites. This paper will contrast the differences between

  18. VIIRS On-Orbit Optical Anomaly - Investigation, Analysis, Root Cause Determination and Lessons Learned

    Science.gov (United States)

    Iona, Glenn; Butler, James; Guenther, Bruce; Graziani, Larissa; Johnson, Eric; Kennedy, Brian; Kent, Criag; Lambeck, Robert; Waluschka, Eugne; Xiong, Xiaoxiong

    2012-01-01

    A gradual, but persistent, decrease in the optical throughput was detected during the early commissioning phase for the Suomi National Polar-Orbiting Partnership (SNPP) Visible Infrared Imager Radiometer Suite (VIIRS) Near Infrared (NIR) bands. Its initial rate and unknown cause were coincidently coupled with a decrease in sensitivity in the same spectral wavelength of the Solar Diffuser Stability Monitor (SDSM) raising concerns about contamination or the possibility of a system-level satellite problem. An anomaly team was formed to investigate and provide recommendations before commissioning could resume. With few hard facts in hand, there was much speculation about possible causes and consequences of the degradation. Two different causes were determined as will be explained in this paper. This paper will describe the build and test history of VIIRS, why there were no indicators, even with hindsight, of an on-orbit problem, the appearance of the on-orbit anomaly, the initial work attempting to understand and determine the cause, the discovery of the root cause and what Test-As-You-Fly (TAYF) activities, can be done in the future to greatly reduce the likelihood of similar optical anomalies. These TAYF activities are captured in the lessons learned section of this paper.

  19. A method of inversion of satellite magnetic anomaly data

    Science.gov (United States)

    Mayhew, M. A.

    1977-01-01

    A method of finding a first approximation to a crustal magnetization distribution from inversion of satellite magnetic anomaly data is described. Magnetization is expressed as a Fourier Series in a segment of spherical shell. Input to this procedure is an equivalent source representation of the observed anomaly field. Instability of the inversion occurs when high frequency noise is present in the input data, or when the series is carried to an excessively high wave number. Preliminary results are given for the United States and adjacent areas.

  20. Validation of Galileo orbits using SLR with a focus on satellites launched into incorrect orbital planes

    Science.gov (United States)

    Sośnica, Krzysztof; Prange, Lars; Kaźmierski, Kamil; Bury, Grzegorz; Drożdżewski, Mateusz; Zajdel, Radosław; Hadas, Tomasz

    2018-02-01

    The space segment of the European Global Navigation Satellite System (GNSS) Galileo consists of In-Orbit Validation (IOV) and Full Operational Capability (FOC) spacecraft. The first pair of FOC satellites was launched into an incorrect, highly eccentric orbital plane with a lower than nominal inclination angle. All Galileo satellites are equipped with satellite laser ranging (SLR) retroreflectors which allow, for example, for the assessment of the orbit quality or for the SLR-GNSS co-location in space. The number of SLR observations to Galileo satellites has been continuously increasing thanks to a series of intensive campaigns devoted to SLR tracking of GNSS satellites initiated by the International Laser Ranging Service. This paper assesses systematic effects and quality of Galileo orbits using SLR data with a main focus on Galileo satellites launched into incorrect orbits. We compare the SLR observations with respect to microwave-based Galileo orbits generated by the Center for Orbit Determination in Europe (CODE) in the framework of the International GNSS Service Multi-GNSS Experiment for the period 2014.0-2016.5. We analyze the SLR signature effect, which is characterized by the dependency of SLR residuals with respect to various incidence angles of laser beams for stations equipped with single-photon and multi-photon detectors. Surprisingly, the CODE orbit quality of satellites in the incorrect orbital planes is not worse than that of nominal FOC and IOV orbits. The RMS of SLR residuals is even lower by 5.0 and 1.5 mm for satellites in the incorrect orbital planes than for FOC and IOV satellites, respectively. The mean SLR offsets equal -44.9, -35.0, and -22.4 mm for IOV, FOC, and satellites in the incorrect orbital plane. Finally, we found that the empirical orbit models, which were originally designed for precise orbit determination of GNSS satellites in circular orbits, provide fully appropriate results also for highly eccentric orbits with variable linear

  1. GPM GROUND VALIDATION SATELLITE SIMULATED ORBITS LPVEX V1

    Data.gov (United States)

    National Aeronautics and Space Administration — The GPM Ground Validation Satellite Simulated Orbits LPVEx dataset is available in the Orbital database, which takes account for the atmospheric profiles, the...

  2. 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...

  3. ORBITAL DEPENDENCE OF GALAXY PROPERTIES IN SATELLITE SYSTEMS OF GALAXIES

    International Nuclear Information System (INIS)

    Hwang, Ho Seong; Park, Changbom

    2010-01-01

    We study the dependence of satellite galaxy properties on the distance to the host galaxy and the orbital motion (prograde and retrograde orbits) using the Sloan Digital Sky Survey (SDSS) data. From SDSS Data Release 7, we find 3515 isolated satellite systems of galaxies at z -1 . It is found that the radial distribution of early-type satellites in prograde orbit is strongly concentrated toward the host while that of retrograde ones shows much less concentration. We also find the orbital speed of late-type satellites in prograde orbit increases as the projected distance to the host (R) decreases while the speed decreases for those in retrograde orbit. At R less than 0.1 times the host virial radius (R vir,host ), the orbital speed decreases in both prograde and retrograde orbit cases. Prograde satellites are on average fainter than retrograde satellites for both early and late morphological types. The u - r color becomes redder as R decreases for both prograde and retrograde orbit late-type satellites. The differences between prograde and retrograde orbit satellite galaxies may be attributed to their different origin or the different strength of physical processes that they have experienced through hydrodynamic interactions with their host galaxies.

  4. Calculation of precision satellite orbits with nonsingular elements /VOP formulation/

    Science.gov (United States)

    Velez, C. E.; Cefola, P. J.; Long, A. C.; Nimitz, K. S.

    1974-01-01

    Review of some results obtained in an effort to develop efficient, high-precision trajectory computation processes for artificial satellites by optimum selection of the form of the equations of motion of the satellite and the numerical integration method. In particular, the matching of a Gaussian variation-of-parameter (VOP) formulation is considered which is expressed in terms of equinoctial orbital elements and partially decouples the motion of the orbital frame from motion within the orbital frame. The performance of the resulting orbit generators is then compared with the popular classical Cowell/Gauss-Jackson formulation/integrator pair for two distinctly different orbit types - namely, the orbit of the ATS satellite at near-geosynchronous conditions and the near-circular orbit of the GEOS-C satellite at 1000 km.

  5. Satellite Anomalies: Benefits of a Centralized Anomaly Database and Methods for Securely Sharing Information Among Satellite Operators

    Science.gov (United States)

    2014-01-01

    is more or less prone to anomalies. The Atrium Space Insurance Corporation (ASIC) at Lloyd’s of London Insurance Market insures approximately 190...Oceanic and Atmospheric Administration, National Geophysical Data Center, 1993. As of December 6, 2012: http://www.ngdc.noaa.gov/ stp /satellite...National Geophysical Data Center, Online Publications, undated a. As of November 1, 2013: http://www.ngdc.noaa.gov/ stp /solar/onlinepubl.html ———, Space

  6. Satellite Orbital Precessions Caused by the Octupolar Mass Moment ...

    Indian Academy of Sciences (India)

    Abstract. I consider a satellite moving around a non-spherical body of mass M and equatorial radius R, and calculate its orbital precessions caused by the body's octupolar mass moment J4. I consider only the effects averaged over one orbital period T of the satellite. I give exact for- mulas, not restricted to any special values ...

  7. A standard library for modeling satellite orbits on a microcomputer

    Science.gov (United States)

    Beutel, Kenneth L.

    1988-03-01

    Introductory students of astrodynamics and the space environment are required to have a fundamental understanding of the kinematic behavior of satellite orbits. This thesis develops a standard library that contains the basic formulas for modeling earth orbiting satellites. This library is used as a basis for implementing a satellite motion simulator that can be used to demonstrate orbital phenomena in the classroom. Surveyed are the equations of orbital elements, coordinate systems and analytic formulas, which are made into a standard method for modeling earth orbiting satellites. The standard library is written in the C programming language and is designed to be highly portable between a variety of computer environments. The simulation draws heavily on the standards established by the library to produce a graphics-based orbit simulation program written for the Apple Macintosh computer. The simulation demonstrates the utility of the standard library functions but, because of its extensive use of the Macintosh user interface, is not portable to other operating systems.

  8. SPICE Module for the Satellite Orbit Analysis Program (SOAP)

    Science.gov (United States)

    Coggi, John; Carnright, Robert; Hildebrand, Claude

    2008-01-01

    A SPICE module for the Satellite Orbit Analysis Program (SOAP) precisely represents complex motion and maneuvers in an interactive, 3D animated environment with support for user-defined quantitative outputs. (SPICE stands for Spacecraft, Planet, Instrument, Camera-matrix, and Events). This module enables the SOAP software to exploit NASA mission ephemeris represented in the JPL Ancillary Information Facility (NAIF) SPICE formats. Ephemeris types supported include position, velocity, and orientation for spacecraft and planetary bodies including the Sun, planets, natural satellites, comets, and asteroids. Entire missions can now be imported into SOAP for 3D visualization, playback, and analysis. The SOAP analysis and display features can now leverage detailed mission files to offer the analyst both a numerically correct and aesthetically pleasing combination of results that can be varied to study many hypothetical scenarios. The software provides a modeling and simulation environment that can encompass a broad variety of problems using orbital prediction. For example, ground coverage analysis, communications analysis, power and thermal analysis, and 3D visualization that provide the user with insight into complex geometric relations are included. The SOAP SPICE module allows distributed science and engineering teams to share common mission models of known pedigree, which greatly reduces duplication of effort and the potential for error. The use of the software spans all phases of the space system lifecycle, from the study of future concepts to operations and anomaly analysis. It allows SOAP software to correctly position and orient all of the principal bodies of the Solar System within a single simulation session along with multiple spacecraft trajectories and the orientation of mission payloads. In addition to the 3D visualization, the user can define numeric variables and x-y plots to quantitatively assess metrics of interest.

  9. Effects of DeOrbitSail as applied to Lifetime predictions of Low Earth Orbit Satellites

    Science.gov (United States)

    Afful, Andoh; Opperman, Ben; Steyn, Herman

    2016-07-01

    Orbit lifetime prediction is an important component of satellite mission design and post-launch space operations. Throughout its lifetime in space, a spacecraft is exposed to risk of collision with orbital debris or operational satellites. This risk is especially high within the Low Earth Orbit (LEO) region where the highest density of space debris is accumulated. This paper investigates orbital decay of some LEO micro-satellites and accelerating orbit decay by using a deorbitsail. The Semi-Analytical Liu Theory (SALT) and the Satellite Toolkit was employed to determine the mean elements and expressions for the time rates of change. Test cases of observed decayed satellites (Iridium-85 and Starshine-1) are used to evaluate the predicted theory. Results for the test cases indicated that the theory fitted observational data well within acceptable limits. Orbit decay progress of the SUNSAT micro-satellite was analysed using relevant orbital parameters derived from historic Two Line Element (TLE) sets and comparing with decay and lifetime prediction models. This paper also explored the deorbit date and time for a 1U CubeSat (ZACUBE-01). The use of solar sails as devices to speed up the deorbiting of LEO satellites is considered. In a drag sail mode, the deorbitsail technique significantly increases the effective cross-sectional area of a satellite, subsequently increasing atmospheric drag and accelerating orbit decay. The concept proposed in this study introduced a very useful technique of orbit decay as well as deorbiting of spacecraft.

  10. Orbital evolution and origin of the Martian satellites

    International Nuclear Information System (INIS)

    Szeto, A.M.K.

    1983-01-01

    The orbital evolution of the Martian satellites is considered from a dynamical point of view. Celestial mechanics relevant to the calculation of satellite orbital evolution is introduced and the physical parameters to be incorporated in the modeling of tidal dissipation are discussed. Results of extrapolating the satellite orbits backward and forward in time are presented and compared with those of other published work. Collision probability calculations and results for the Martian satellite system are presented and discussed. The implications of these calculations for the origin scenarios of the satellites are assessed. It is concluded that Deimos in its present form could not have been captured, for if it had been, it would have collided with Phobos at some point. An accretion model is therefore preferred over capture, although such a model consistent with the likely carbonaceous chondritic composition of the satellites has yet to be established. 91 references

  11. 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.

  12. 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)

  13. Advances in analysis of pre-earthquake thermal anomalies by analyzing IR satellite data

    Science.gov (United States)

    Ouzounov, D.; Bryant, N.; Filizzola, C.; Pergola, N.; Taylor, P.; Tramutoli, V.

    Presented work addresses the possible relationship between tectonic stress, electro-chemical and thermodynamic processes in the atmosphere and increasing infrared (IR) flux as part of a larger family of electromagnetic (EM) phenomena related to earthquake activity. Thermal infra-red (TIR) surveys performed by polar orbiting (NOAA/AVHRR, MODIS) and geosynchronous weather satellites (GOES, METEOSAT) seems to indicate the appearance (from days to weeks before the event) of "anomalous" space-time TIR transients associated with the place (epicentral area, linear structures and fault systems) and the time of occurrence of a number of major earthquakes with M>5 and focal depths no deeper than 50km. As Earth emitted in 8-14 microns range the TIR signal measured from satellite strongly vary depending on meteorological conditions and other factors (space-time changes in atmospheric transmittance, time/season, solar and satellite zenithal angles and etc) independent from seismic activity, a preliminary definition of "anomalous TIR signal" should be given. To provide reliable discrimination of thermal anomalous area from the natural events (seasonal changes, local morphology) new robust approach (RAT) has been recently proposed (and successfully applied in the field of the monitoring of the major environmental risks) that permits to give a statistically based definition of thermal info-red (TIR) anomaly and reduce of false events detection. New techniques also were specifically developed to assure the precise co-registration of all satellite scenes and permit accurate time-series analysis of satellite observations. As final results we present examples of most recent 2000/2004 worldwide strong earthquakes and the techniques used to capture the tracks of thermal emission mid-IR anomalies and methodology for practical future use of such phenomena in the early warning systems.

  14. Handbook of satellite orbits from Kepler to GPS

    CERN Document Server

    Capderou, Michel

    2014-01-01

    Fifty years after Sputnik, artificial satellites have become indispensable monitors in many areas, such as economics, meteorology, telecommunications, navigation and remote sensing. The specific orbits are important for the proper functioning of the satellites. This book discusses the great variety of satellite orbits, both in shape (circular to highly elliptical) and properties (geostationary, Sun-synchronous, etc.). This volume starts with an introduction into geodesy. This is followed by a presentation of the fundamental equations of mechanics to explain and demonstrate the properties for all types of orbits. Numerous examples are included, obtained through IXION software developed by the author. The book also includes an exposition of the historical background that is necessary to help the reader understand the main stages of scientific thought from Kepler to GPS. This book is intended for researchers, teachers and students working in the field of satellite technology. Engineers, geographers and all those...

  15. Failure analysis of satellite subsystems to define suitable de-orbit devices

    Science.gov (United States)

    Palla, Chiara; Peroni, Moreno; Kingston, Jennifer

    2016-11-01

    Space missions in Low Earth Orbit (LEO) are severely affected by the build-up of orbital debris. A key practice, to be compliant with IADC (Inter-Agency Space Debris Coordination Committee) mitigation guidelines, is the removal of space systems that interfere with the LEO region not later than 25 years after the End of Mission. It is important to note that the current guidelines are not generally legally binding, even if different Space Agencies are now looking at the compliance for their missions. If the guidelines will change in law, it will be mandatory to have a postmission disposal strategy for all satellites, including micro and smaller classes. A potential increased number of these satellites is confirmed by different projections, in particular in the commercial sector. Micro and smaller spacecraft are, in general, not provided with propulsion capabilities to achieve a controlled re-entry, so they need different de-orbit disposal methods. When considering the utility of different debris mitigation methods, it is useful to understand which spacecraft subsystems are most likely to fail and how this may affect the operation of a de-orbit system. This also helps the consideration of which components are the most relevant or should be redundant depending on the satellite mass class. This work is based on a sample of LEO and MEO satellites launched between January 2000 and December 2014 with mass lower than 1000 kg. Failure analysis of satellite subsystems is performed by means of the Kaplan-Meier survival analysis; the parametric fits are conducted with Weibull distributions. The study is carried out by using the satellite database SpaceTrak™ which provides anomalies, failures, and trends information for spacecraft subsystems and launch vehicles. The database identifies five states for each satellite subsystem: three degraded states, one fully operational state, and one failed state (complete failure). The results obtained can guide the identification of the

  16. GNSS satellite transmit power and its impact on orbit determination

    Science.gov (United States)

    Steigenberger, Peter; Thoelert, Steffen; Montenbruck, Oliver

    2018-06-01

    Antenna thrust is a small acceleration acting on Global Navigation Satellite System satellites caused by the transmission of radio navigation signals. Knowledge about the transmit power and the mass of the satellites is required for the computation of this effect. The actual transmit power can be obtained from measurements with a high-gain antenna and knowledge about the properties of the transmit and receive antennas as well as losses along the propagation path. Transmit power measurements for different types of GPS, GLONASS, Galileo, and BeiDou-2 satellites were taken with a 30-m dish antenna of the German Aerospace Center (DLR) located at its ground station in Weilheim. For GPS, total L-band transmit power levels of 50-240 W were obtained, 20-135 W for GLONASS, 95-265 W for Galileo, and 130-185 W for BeiDou-2. The transmit power differs usually only slightly for individual spacecraft within one satellite block. An exception are the GLONASS-M satellites where six subgroups with different transmit power levels could be identified. Considering the antenna thrust in precise orbit determination of GNSS satellites decreases the orbital radius by 1-27 mm depending on the transmit power, the satellite mass, and the orbital period.

  17. Multi-GNSS orbit determination using satellite laser ranging

    Science.gov (United States)

    Bury, Grzegorz; Sośnica, Krzysztof; Zajdel, Radosław

    2018-04-01

    Galileo, BeiDou, QZSS, and NavIC are emerging global navigation satellite systems (GNSSs) and regional navigation satellite systems all of which are equipped with laser retroreflector arrays for range measurements. This paper summarizes the GNSS-intensive tracking campaigns conducted by the International Laser Ranging Service and provides results from multi-GNSS orbit determination using solely SLR observations. We consider the whole constellation of GLONASS, all active Galileo, four BeiDou satellites: 1 MEO, 3 IGSO, and one QZSS. We analyze the influence of the number of SLR observations on the quality of the 3-day multi-GNSS orbit solution. About 60 SLR observations are needed for obtaining MEO orbits of sufficient quality with the root mean square (RMS) of 3 cm for the radial component when compared to microwave-based orbits. From the analysis of a minimum number of tracking stations, when considering the 3-day arcs, 5 SLR stations do not provide a sufficient geometry of observations. The solution obtained using ten stations is characterized with RMS of 4, 9, and 18 cm in the radial, along-track, and cross-track direction, respectively, for MEO satellites. We also investigate the impact of the length of orbital arc on the quality of SLR-derived orbits. Hence, 5- and 7-day arcs constitute the best solution, whereas 3-day arcs are of inferior quality due to an insufficient number of SLR observations and 9-day arcs deteriorate the along-track component. The median RMS from the comparison between 7-day orbital arcs determined using SLR data with microwave-based orbits assumes values in the range of 3-4, 11-16, and 15-27 cm in radial, along-track, and cross-track, respectively, for MEO satellites. BeiDou IGSO and QZSS are characterized by RMS values higher by a factor of 8 and 24, respectively, than MEO orbits.

  18. Precise Orbit Determination of GPS Satellites Using Phase Observables

    Directory of Open Access Journals (Sweden)

    Myung-Kook Jee

    1997-12-01

    Full Text Available The accuracy of user position by GPS is heavily dependent upon the accuracy of satellite position which is usually transmitted to GPS users in radio signals. The real-time satellite position information directly obtained from broadcast ephimerides has the accuracy of 3 x 10 meters which is very unsatisfactory to measure 100km baseline to the accuracy of less than a few mili-meters. There are globally at present seven orbit analysis centers capable of generating precise GPS ephimerides and their orbit quality is of the order of about 10cm. Therefore, precise orbit model and phase processing technique were reviewed and consequently precise GPS ephimerides were produced after processing the phase observables of 28 global GPS stations for 1 day. Initial 6 orbit parameters and 2 solar radiation coefficients were estimated using batch least square algorithm and the final results were compared with the orbit of IGS, the International GPS Service for Geodynamics.

  19. Cultures in orbit: Satellite technologies, global media and local practice

    Science.gov (United States)

    Parks, Lisa Ann

    Since the launch of Sputnik in 1957, satellite technologies have had a profound impact upon cultures around the world. "Cultures in Orbit" examines these seemingly disembodied, distant relay machines in relation to situated social and cultural processes on earth. Drawing upon a range of materials including NASA and UNESCO documents, international satellite television broadcasts, satellite 'development' projects, documentary and science fiction films, remote sensing images, broadcast news footage, World Wide Web sites, and popular press articles I delineate and analyze a series of satellite mediascapes. "Cultures in Orbit" analyzes uses of satellites for live television relay, surveillance, archaeology and astronomy. The project examines such satellite media as the first live global satellite television program Our World, Elvis' Aloha from Hawaii concert, Aboriginal Australian satellite programs, and Star TV's Asian music videos. In addition, the project explores reconnaissance images of mass graves in Bosnia, archaeological satellite maps of Cleopatra's underwater palace in Egypt, and Hubble Space Telescope images. These case studies are linked by a theoretical discussion of the satellite's involvement in shifting definitions of time, space, vision, knowledge and history. The satellite fosters an aesthetic of global realism predicated on instantaneous transnational connections. It reorders linear chronologies by revealing traces of the ancient past on the earth's surface and by searching in deep space for the "edge of time." On earth, the satellite is used to modernize and develop "primitive" societies. Satellites have produced new electronic spaces of international exchange, but they also generate strategic maps that advance Western political and cultural hegemony. By technologizing human vision, the satellite also extends the epistemologies of the visible, the historical and the real. It allows us to see artifacts and activities on earth from new vantage points

  20. CASTOR: Cathode/Anode Satellite Thruster for Orbital Repositioning

    Science.gov (United States)

    Mruphy, Gloria A.

    2010-01-01

    The purpose of CASTOR (Cathode/Anode Satellite Thruster for Orbital Repositioning) satellite is to demonstrate in Low Earth Orbit (LEO) a nanosatellite that uses a Divergent Cusped Field Thruster (DCFT) to perform orbital maneuvers representative of an orbital transfer vehicle. Powered by semi-deployable solar arrays generating 165W of power, CASTOR will achieve nearly 1 km/s of velocity increment over one year. As a technology demonstration mission, success of CASTOR in LEO will pave the way for a low cost, high delta-V orbital transfer capability for small military and civilian payloads in support of Air Force and NASA missions. The educational objective is to engage graduate and undergraduate students in critical roles in the design, development, test, carrier integration and on-orbit operations of CASTOR as a supplement to their curricular activities. This program is laying the foundation for a long-term satellite construction program at MIT. The satellite is being designed as a part of AFRL's University Nanosatellite Program, which provides the funding and a framework in which student satellite teams compete for a launch to orbit. To this end, the satellite must fit within an envelope of 50cmx50cmx60cm, have a mass of less than 50kg, and meet stringent structural and other requirements. In this framework, the CASTOR team successfully completed PDR in August 2009 and CDR in April 2010 and will compete at FCR (Flight Competition Review) in January 2011. The complexity of the project requires implementation of many systems engineering techniques which allow for development of CASTOR from conception through FCR and encompass the full design, fabrication, and testing process.

  1. FROM ORDER TO CHAOS IN EARTH SATELLITE ORBITS

    Energy Technology Data Exchange (ETDEWEB)

    Gkolias, Ioannis; Gachet, Fabien [Department of Mathematics, University of Rome Tor Vergata, I-00133 Rome (Italy); Daquin, Jérôme [IMCCE/Observatoire de Paris, Université Lille1, F-59000 Lille (France); Rosengren, Aaron J., E-mail: gkolias@mat.uniroma2.it [IFAC-CNR, 50019 Sesto Fiorentino, Florence (Italy)

    2016-11-01

    We consider Earth satellite orbits in the range of semimajor axes where the perturbing effects of Earth’s oblateness and lunisolar gravity are of comparable order. This range covers the medium-Earth orbits (MEO) of the Global Navigation Satellite Systems and the geosynchronous orbits (GEO) of the communication satellites. We recall a secular and quadrupolar model, based on the Milankovitch vector formulation of perturbation theory, which governs the long-term orbital evolution subject to the predominant gravitational interactions. We study the global dynamics of this two-and-a-half degrees-of-freedom Hamiltonian system by means of the fast Lyapunov indicator (FLI), used in a statistical sense. Specifically, we characterize the degree of chaoticity of the action space using angle-averaged normalized FLI maps, thereby overcoming the angle dependencies of the conventional stability maps. Emphasis is placed upon the phase-space structures near secular resonances, which are of primary importance to the space debris community. We confirm and quantify the transition from order to chaos in MEO, stemming from the critical inclinations and find that highly inclined GEO orbits are particularly unstable. Despite their reputed normality, Earth satellite orbits can possess an extraordinarily rich spectrum of dynamical behaviors and, from a mathematical perspective, have all the complications that make them very interesting candidates for testing the modern tools of chaos theory.

  2. Orbital and Collisional Evolution of the Irregular Satellites

    Science.gov (United States)

    Nesvorný, David; Alvarellos, Jose L. A.; Dones, Luke; Levison, Harold F.

    2003-07-01

    The irregular moons of the Jovian planets are a puzzling part of the solar system inventory. Unlike regular satellites, the irregular moons revolve around planets at large distances in tilted and eccentric orbits. Their origin, which is intimately linked with the origin of the planets themselves, is yet to be explained. Here we report a study of the orbital and collisional evolution of the irregular satellites from times after their formation to the present epoch. The purpose of this study is to find out the features of the observed irregular moons that can be attributed to this evolution and separate them from signatures of the formation process. We numerically integrated ~60,000 test satellite orbits to map orbital locations that are stable on long time intervals. We found that the orbits highly inclined to the ecliptic are unstable due to the effect of the Kozai resonance, which radially stretches them so that satellites either escape from the Hill sphere, collide with massive inner moons, or impact the parent planet. We also found that prograde satellite orbits with large semimajor axes are unstable due to the effect of the evection resonance, which locks the orbit's apocenter to the apparent motion of the Sun around the parent planet. In such a resonance, the effect of solar tides on a resonant moon accumulates at each apocenter passage of the moon, which causes a radially outward drift of its orbital apocenter; once close to the Hill sphere, the moon escapes. By contrast, retrograde moons with large orbital semimajor axes are long-lived. We have developed an analytic model of the distant satellite orbits and used it to explain the results of our numerical experiments. In particular, we analytically studied the effect of the Kozai resonance. We numerically integrated the orbits of the 50 irregular moons (known by 2002 August 16) for 108 yr. All orbits were stable on this time interval and did not show any macroscopic variations that would indicate

  3. Numerical orbit generators of artificial earth satellites

    Science.gov (United States)

    Kugar, H. K.; Dasilva, W. C. C.

    1984-04-01

    A numerical orbit integrator containing updatings and improvements relative to the previous ones that are being utilized by the Departmento de Mecanica Espacial e Controle (DMC), of INPE, besides incorporating newer modellings resulting from the skill acquired along the time is presented. Flexibility and modularity were taken into account in order to allow future extensions and modifications. Characteristics of numerical accuracy, processing quickness, memory saving as well as utilization aspects were also considered. User's handbook, whole program listing and qualitative analysis of accuracy, processing time and orbit perturbation effects were included as well.

  4. Orbital resonances of Taiwan's FORMOSAT-2 remote sensing satellite

    Science.gov (United States)

    Lin, Shin-Fa; Hwang, Cheinway

    2018-06-01

    Unlike a typical remote sensing satellite that has a global coverage and non-integral orbital revolutions per day, Taiwan's FORMOSAT-2 (FS-2) satellite has a non-global coverage due to the mission requirements of one-day repeat cycle and daily visit around Taiwan. These orbital characteristics result in an integer number of revolutions a day and orbital resonances caused by certain components of the Earth's gravity field. Orbital flight data indicated amplified variations in the amplitudes of FS-2's Keplerian elements. We use twelve years of orbital observations and maneuver data to analyze the cause of the resonances and explain the differences between the simulated (at the pre-launch stage) and real orbits of FS-2. The differences are quantified using orbital perturbation theories that describe secular and long-period orbital evolutions caused by resonances. The resonance-induced orbital rising rate of FS-2 reaches +1.425 m/day, due to the combined (modeled) effect of resonances and atmospheric drags (the relative modeling errors remote sensing mission similar to FS-2, especially in the early mission design and planning phase.

  5. Smaller Satellite Operations Near Geostationary Orbit

    Science.gov (United States)

    2007-09-01

    of that study when a purely mathematical approach is not possible or too cumbersome to emphasize a point clearly. I will approach 7 the...components that are specifically designed to be utilized in CubeSats. Pumpkin Incorporated and Clyde Space are leading developers of COTS equipment...year mission life. From a purely hypothetical approach, assume the high interest targets were operating over Asia, with a number of satellites

  6. Regional positioning using a low Earth orbit satellite constellation

    Science.gov (United States)

    Shtark, Tomer; Gurfil, Pini

    2018-02-01

    Global and regional satellite navigation systems are constellations orbiting the Earth and transmitting radio signals for determining position and velocity of users around the globe. The state-of-the-art navigation satellite systems are located in medium Earth orbits and geosynchronous Earth orbits and are characterized by high launching, building and maintenance costs. For applications that require only regional coverage, the continuous and global coverage that existing systems provide may be unnecessary. Thus, a nano-satellites-based regional navigation satellite system in Low Earth Orbit (LEO), with significantly reduced launching, building and maintenance costs, can be considered. Thus, this paper is aimed at developing a LEO constellation optimization and design method, using genetic algorithms and gradient-based optimization. The preliminary results of this study include 268 LEO constellations, aimed at regional navigation in an approximately 1000 km × 1000 km area centered at the geographic coordinates [30, 30] degrees. The constellations performance is examined using simulations, and the figures of merit include total coverage time, revisit time, and geometric dilution of precision (GDOP) percentiles. The GDOP is a quantity that determines the positioning solution accuracy and solely depends on the spatial geometry of the satellites. Whereas the optimization method takes into account only the Earth's second zonal harmonic coefficient, the simulations include the Earth's gravitational field with zonal and tesseral harmonics up to degree 10 and order 10, Solar radiation pressure, drag, and the lunisolar gravitational perturbation.

  7. Spacecraft anomalies on the CRRES satellite correlated with the environment and insulator samples

    International Nuclear Information System (INIS)

    Violet, M.D.; Frederickson, A.R.

    1993-01-01

    The CRRES satellite has been extensively surveyed for the occurrence of onboard anomalies. CRRES system and instrument responses which were not programmed or commanded are classified as anomalies. The history of anomalies is correlated with the history of plasmas, high energy particles, and electromagnetic fields as measured on CRRES. The anomalies for each instrument on CRRES are compared with those from other instruments. The 674 anomalies, as a group, correlate well with high levels of high energy electron flux and poorly with every other environmental parameter

  8. Excited Landau levels, orbital angular momentum and axial anomaly

    International Nuclear Information System (INIS)

    Teryaev, O.V.

    1993-01-01

    The IR cutoff via the exclusion of the high orbital momentum components for the excited Landau levels leads to the physical interpretation of the cancellation between the explicity and anomalous chiral symmetry breaking. 21 refs

  9. Evolution of the Orbital Elements for Geosynchronous Orbit of Communications Satellite, II

    Directory of Open Access Journals (Sweden)

    Kyu-Hong Choi

    1987-06-01

    Full Text Available For a geostationary satellite north-south station keeping maneuver must control the inclination elements. The effects on the orbit plane of maneuvers and natural perturbations may be represented by a plane plot of Wc versus Ws, since these inclination elements represent the projection of the unit orbit normal onto the equatorial plane. The evolution of the semi-major axis and the inclination elements are obtained.

  10. Solar radio proxies for improved satellite orbit prediction

    Science.gov (United States)

    Yaya, Philippe; Hecker, Louis; Dudok de Wit, Thierry; Fèvre, Clémence Le; Bruinsma, Sean

    2017-12-01

    Specification and forecasting of solar drivers to thermosphere density models is critical for satellite orbit prediction and debris avoidance. Satellite operators routinely forecast orbits up to 30 days into the future. This requires forecasts of the drivers to these orbit prediction models such as the solar Extreme-UV (EUV) flux and geomagnetic activity. Most density models use the 10.7 cm radio flux (F10.7 index) as a proxy for solar EUV. However, daily measurements at other centimetric wavelengths have also been performed by the Nobeyama Radio Observatory (Japan) since the 1950's, thereby offering prospects for improving orbit modeling. Here we present a pre-operational service at the Collecte Localisation Satellites company that collects these different observations in one single homogeneous dataset and provides a 30 days forecast on a daily basis. Interpolation and preprocessing algorithms were developed to fill in missing data and remove anomalous values. We compared various empirical time series prediction techniques and selected a multi-wavelength non-recursive analogue neural network. The prediction of the 30 cm flux, and to a lesser extent that of the 10.7 cm flux, performs better than NOAA's present prediction of the 10.7 cm flux, especially during periods of high solar activity. In addition, we find that the DTM-2013 density model (Drag Temperature Model) performs better with (past and predicted) values of the 30 cm radio flux than with the 10.7 flux.

  11. Satellite Orbit Under Influence of a Drag - Analytical Approach

    Science.gov (United States)

    Martinović, M. M.; Šegan, S. D.

    2017-12-01

    The report studies some changes in orbital elements of the artificial satellites of Earth under influence of atmospheric drag. In order to develop possibilities of applying the results in many future cases, an analytical interpretation of the orbital element perturbations is given via useful, but very long expressions. The development is based on the TD88 air density model, recently upgraded with some additional terms. Some expressions and formulae were developed by the computer algebra system Mathematica and tested in some hypothetical cases. The results have good agreement with iterative (numerical) approach.

  12. Influence of tides in viscoelastic bodies of planet and satellite on the satellite's orbital motion

    Science.gov (United States)

    Emelyanov, N. V.

    2018-06-01

    The problem of influence of tidal friction in both planetary and satellite bodies upon satellite's orbital motion is considered. Using the differential equations in satellite's rectangular planetocentric coordinates, the differential equations describing the changes in semimajor axis and eccentricity are derived. The equations in rectangular coordinates were taken from earlier works on the problem. The calcultations carried out for a number of test examples prove that the averaged solutions of equations in coordinates and precise solutions of averaged equations in the Keplerian elements are identical. For the problem of tides raised on planet's body, it was found that, if satellite's mean motion n is equal to 11/18 Ω, where Ω is the planet's angular rotation rate, the orbital eccentricity does not change. This conclusion is in agreement with the results of other authors. It was also found that there is essential discrepancy between the equations in the elements obtained in this paper and analogous equations published by earlier researchers.

  13. Dynamic and reduced-dynamic precise orbit determination of satellites in low earth orbits

    International Nuclear Information System (INIS)

    Swatschina, P.

    2009-01-01

    The precise positioning of satellites in Low Earth Orbits (LEO) has become a key technology for advanced space missions. Dedicated satellite missions, such as CHAMP, GRACE and GOCE, that aim to map the Earths gravity field and its variation over time with unprecedented accuracy, initiated the demand for highly precise orbit solutions of LEO satellites. Furthermore, a wide range of additional science opportunities opens up with the capability to generate accurate LEO orbits. For all considered satellite missions, the primary measurement system for navigation is a spaceborne GPS receiver. The goal of this thesis is to establish and implement methods for Precise Orbit Determination (POD) of LEO satellites using GPS. Striving for highest precision using yet efficient orbit generation strategies, the attained orbit solutions are aimed to be competitive with the most advanced solutions of other institutions. Dynamic and reduced-dynamic orbit models provide the basic concepts of this work. These orbit models are subsequently adjusted to the highly accurate GPS measurements. The GPS measurements are introduced at the zero difference level in the ionosphere free linear combination. Appropriate procedures for GPS data screening and editing are established to detect erroneous data and to employ measurements of good quality only. For the dynamic orbit model a sophisticated force model, especially designed for LEO satellites, has been developed. In order to overcome the limitations that are induced by the deficiencies of the purely dynamical model, two different types of empirical parameters are introduced into the force model. These reduced-dynamic orbit models allow for the generation of much longer orbital arcs while preserving the spacecraft dynamics to the most possible extent. The two methods for reduced-dynamic orbit modeling are instantaneous velocity changes (pulses) or piecewise constant accelerations. For both techniques highly efficient modeling algorithms are

  14. Tracking target objects orbiting earth using satellite-based telescopes

    Science.gov (United States)

    De Vries, Willem H; Olivier, Scot S; Pertica, Alexander J

    2014-10-14

    A system for tracking objects that are in earth orbit via a constellation or network of satellites having imaging devices is provided. An object tracking system includes a ground controller and, for each satellite in the constellation, an onboard controller. The ground controller receives ephemeris information for a target object and directs that ephemeris information be transmitted to the satellites. Each onboard controller receives ephemeris information for a target object, collects images of the target object based on the expected location of the target object at an expected time, identifies actual locations of the target object from the collected images, and identifies a next expected location at a next expected time based on the identified actual locations of the target object. The onboard controller processes the collected image to identify the actual location of the target object and transmits the actual location information to the ground controller.

  15. 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...

  16. Long-Term Prediction of Satellite Orbit Using Analytical Method

    Directory of Open Access Journals (Sweden)

    Jae-Cheol Yoon

    1997-12-01

    Full Text Available A long-term prediction algorithm of geostationary orbit was developed using the analytical method. The perturbation force models include geopotential upto fifth order and degree and luni-solar gravitation, and solar radiation pressure. All of the perturbation effects were analyzed by secular variations, short-period variations, and long-period variations for equinoctial elements such as the semi-major axis, eccentricity vector, inclination vector, and mean longitude of the satellite. Result of the analytical orbit propagator was compared with that of the cowell orbit propagator for the KOREASAT. The comparison indicated that the analytical solution could predict the semi-major axis with an accuarcy of better than ~35meters over a period of 3 month.

  17. Mapping daily evapotranspiration at field to continental scales using geostationary and polar orbiting satellite imagery

    Directory of Open Access Journals (Sweden)

    M. C. Anderson

    2011-01-01

    Full Text Available Thermal infrared (TIR remote sensing of land-surface temperature (LST provides valuable information about the sub-surface moisture status required for estimating evapotranspiration (ET and detecting the onset and severity of drought. While empirical indices measuring anomalies in LST and vegetation amount (e.g., as quantified by the Normalized Difference Vegetation Index; NDVI have demonstrated utility in monitoring ET and drought conditions over large areas, they may provide ambiguous results when other factors (e.g., air temperature, advection are affecting plant functioning. A more physically based interpretation of LST and NDVI and their relationship to sub-surface moisture conditions can be obtained with a surface energy balance model driven by TIR remote sensing. The Atmosphere-Land Exchange Inverse (ALEXI model is a multi-sensor TIR approach to ET mapping, coupling a two-source (soil + canopy land-surface model with an atmospheric boundary layer model in time-differencing mode to routinely and robustly map daily fluxes at continental scales and 5 to 10-km resolution using thermal band imagery and insolation estimates from geostationary satellites. A related algorithm (DisALEXI spatially disaggregates ALEXI fluxes down to finer spatial scales using moderate resolution TIR imagery from polar orbiting satellites. An overview of this modeling approach is presented, along with strategies for fusing information from multiple satellite platforms and wavebands to map daily ET down to resolutions on the order of 10 m. The ALEXI/DisALEXI model has potential for global applications by integrating data from multiple geostationary meteorological satellite systems, such as the US Geostationary Operational Environmental Satellites, the European Meteosat satellites, the Chinese Fen-yung 2B series, and the Japanese Geostationary Meteorological Satellites. Work is underway to further evaluate multi-scale ALEXI implementations over the US, Europe, Africa

  18. Retrieving Temperature Anomaly in the Global Subsurface and Deeper Ocean From Satellite Observations

    Science.gov (United States)

    Su, Hua; Li, Wene; Yan, Xiao-Hai

    2018-01-01

    Retrieving the subsurface and deeper ocean (SDO) dynamic parameters from satellite observations is crucial for effectively understanding ocean interior anomalies and dynamic processes, but it is challenging to accurately estimate the subsurface thermal structure over the global scale from sea surface parameters. This study proposes a new approach based on Random Forest (RF) machine learning to retrieve subsurface temperature anomaly (STA) in the global ocean from multisource satellite observations including sea surface height anomaly (SSHA), sea surface temperature anomaly (SSTA), sea surface salinity anomaly (SSSA), and sea surface wind anomaly (SSWA) via in situ Argo data for RF training and testing. RF machine-learning approach can accurately retrieve the STA in the global ocean from satellite observations of sea surface parameters (SSHA, SSTA, SSSA, SSWA). The Argo STA data were used to validate the accuracy and reliability of the results from the RF model. The results indicated that SSHA, SSTA, SSSA, and SSWA together are useful parameters for detecting SDO thermal information and obtaining accurate STA estimations. The proposed method also outperformed support vector regression (SVR) in global STA estimation. It will be a useful technique for studying SDO thermal variability and its role in global climate system from global-scale satellite observations.

  19. Satellite laser ranging to low Earth orbiters: orbit and network validation

    Science.gov (United States)

    Arnold, Daniel; Montenbruck, Oliver; Hackel, Stefan; Sośnica, Krzysztof

    2018-04-01

    Satellite laser ranging (SLR) to low Earth orbiters (LEOs) provides optical distance measurements with mm-to-cm-level precision. SLR residuals, i.e., differences between measured and modeled ranges, serve as a common figure of merit for the quality assessment of orbits derived by radiometric tracking techniques. We discuss relevant processing standards for the modeling of SLR observations and highlight the importance of line-of-sight-dependent range corrections for the various types of laser retroreflector arrays. A 1-3 cm consistency of SLR observations and GPS-based precise orbits is demonstrated for a wide range of past and present LEO missions supported by the International Laser Ranging Service (ILRS). A parameter estimation approach is presented to investigate systematic orbit errors and it is shown that SLR validation of LEO satellites is not only able to detect radial but also along-track and cross-track offsets. SLR residual statistics clearly depend on the employed precise orbit determination technique (kinematic vs. reduced-dynamic, float vs. fixed ambiguities) but also reveal pronounced differences in the ILRS station performance. Using the residual-based parameter estimation approach, corrections to ILRS station coordinates, range biases, and timing offsets are derived. As a result, root-mean-square residuals of 5-10 mm have been achieved over a 1-year data arc in 2016 using observations from a subset of high-performance stations and ambiguity-fixed orbits of four LEO missions. As a final contribution, we demonstrate that SLR can not only validate single-satellite orbit solutions but also precise baseline solutions of formation flying missions such as GRACE, TanDEM-X, and Swarm.

  20. 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...

  1. 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...

  2. A high-fidelity N-body ephemeris generator for satellites in Earth orbit

    Science.gov (United States)

    Simmons, David R.

    1991-10-01

    A program is currently used for mission planning called the Analytic Satellite Ephemeris Program (ASEP), which produces projected data for orbits that remain fairly close to Earth. Lunar and solar perturbations are taken into account in another program called GRAVE. This project is a revision of GRAVE which incorporates more flexible means of input for initial data, provides additional kinds of output information, and makes use of structured programming techniques to make the program more understandable and reliable. The computer program ORBIT was tested against tracking data for the first 313 days of operation of the CRRES satellite. A sample graph is given comparing the semi-major axis calculated by the program with the values supplied by NORAD. When calculated for points at which CRRES passes through the ascending node, the argument of perigee, the right ascension of the ascending node, and the mean anomaly all stay within about a degree of the corresponding values from NORAD; the inclination of the orbital plane is much closer. The program value of the eccentricity is in error by no more than 0.0002.

  3. Solar radio proxies for improved satellite orbit prediction

    Directory of Open Access Journals (Sweden)

    Yaya Philippe

    2017-01-01

    Full Text Available Specification and forecasting of solar drivers to thermosphere density models is critical for satellite orbit prediction and debris avoidance. Satellite operators routinely forecast orbits up to 30 days into the future. This requires forecasts of the drivers to these orbit prediction models such as the solar Extreme-UV (EUV flux and geomagnetic activity. Most density models use the 10.7 cm radio flux (F10.7 index as a proxy for solar EUV. However, daily measurements at other centimetric wavelengths have also been performed by the Nobeyama Radio Observatory (Japan since the 1950's, thereby offering prospects for improving orbit modeling. Here we present a pre-operational service at the Collecte Localisation Satellites company that collects these different observations in one single homogeneous dataset and provides a 30 days forecast on a daily basis. Interpolation and preprocessing algorithms were developed to fill in missing data and remove anomalous values. We compared various empirical time series prediction techniques and selected a multi-wavelength non-recursive analogue neural network. The prediction of the 30 cm flux, and to a lesser extent that of the 10.7 cm flux, performs better than NOAA's present prediction of the 10.7 cm flux, especially during periods of high solar activity. In addition, we find that the DTM-2013 density model (Drag Temperature Model performs better with (past and predicted values of the 30 cm radio flux than with the 10.7 flux.

  4. Orbits

    CERN Document Server

    Xu, Guochang

    2008-01-01

    This is the first book of the satellite era which describes orbit theory with analytical solutions of the second order with respect to all possible disturbances. Based on such theory, the algorithms of orbits determination are completely revolutionized.

  5. Gravity Anomalies and Estimated Topography Derived from Satellite Altimetry

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — In many areas of the global ocean, the depth of the seafloor is not well known because survey lines by ships are hundreds of kilometers apart. Satellites carrying...

  6. The Eccentric Satellites Problem: Comparing Milky Way Satellite Orbital Properties to Simulation Results

    Science.gov (United States)

    Haji, Umran; Pryor, Carlton; Applebaum, Elaad; Brooks, Alyson

    2018-01-01

    We compare the orbital properties of the satellite galaxies of the Milky Way to those of satellites found in simulated Milky Way-like systems as a means of testing cosmological simulations of galaxy formation. The particular problem that we are investigating is a discrepancy in the distribution of orbital eccentricities. Previous studies of Milky Way-mass systems analyzed in a semi-analytic ΛCDM cosmological model have found that the satellites tend to have significantly larger fractions of their kinetic energy invested in radial motion with respect to their central galaxy than do the real-world Milky Way satellites. We analyze several high-resolution ("zoom-in") hydrodynamical simulations of Milky Way-mass galaxies and their associated satellite systems to investigate why previous works found Milky Way-like systems to be rare. We find a possible relationship between a quiescent galactic assembly history and a distribution of satellite kinematics resembling that of the Milky Way. This project has been supported by funding from National Science Foundation grant PHY-1560077.

  7. Scope for a small circumsolar annular gravitational contribution to the Pioneer anomaly without affecting planetary orbits

    Science.gov (United States)

    Moore, Guy S. M.; Moore, Richard E. M.

    2013-10-01

    All proposed gravitational explanations of the Pioneer anomaly must crucially face the Equivalence Principle. Thus, if Pioneers 10 and 11 were influenced by anomalous gravitational effects in regions containing other Solar System bodies, then those bodies should likewise be influenced, irrespective of their shape, composition or mass. Although the lack of any observed influence upon planetary orbits severely constrains such explanations, here we aim to construct by computer modeling, hypothetical gravitating annuli having no gravitational impact on planetary orbits from Mercury to Neptune. One model has a central zone, free of radial gravitation in the annular plane, and an ‘onset’ beyond Saturn’s orbit, where sunward annular gravitation increases to match the Pioneer anomaly data. Sharp nulls are included so that Uranus and Neptune escape this influence. Such models can be proportionately reduced in mass: a 1 % contribution to the anomaly requires an annulus of approximately 1 Earth mass. It is thus possible to comply with the JPL assessment of newly recovered data attributing 80 %, or more, of the anomaly to spacecraft heat, which appears to allow small contributions from other causes. Following the possibility of an increasing Kuiper belt density at great ranges, another model makes an outward small anomalous gravitation in the TNO region, tallying with an observed slight indication of such an effect, suggesting that New Horizons may slightly accelerate in this region.

  8. Orbit Determination of the SELENE Satellites Using Multi-Satellite Data Types and Evaluation of SELENE Gravity Field Models

    Science.gov (United States)

    Goossens, S.; Matsumoto, K.; Noda, H.; Araki, H.; Rowlands, D. D.; Lemoine, F. G.

    2011-01-01

    The SELENE mission, consisting of three separate satellites that use different terrestrial-based tracking systems, presents a unique opportunity to evaluate the contribution of these tracking systems to orbit determination precision. The tracking data consist of four-way Doppler between the main orbiter and one of the two sub-satellites while the former is over the far side, and of same-beam differential VLBI tracking between the two sub-satellites. Laser altimeter data are also used for orbit determination. The contribution to orbit precision of these different data types is investigated through orbit overlap analysis. It is shown that using four-way and VLBI data improves orbit consistency for all satellites involved by reducing peak values in orbit overlap differences that exist when only standard two-way Doppler and range data are used. Including laser altimeter data improves the orbit precision of the SELENE main satellite further, resulting in very smooth total orbit errors at an average level of 18m. The multi-satellite data have also resulted in improved lunar gravity field models, which are assessed through orbit overlap analysis using Lunar Prospector tracking data. Improvements over a pre-SELENE model are shown to be mostly in the along-track and cross-track directions. Orbit overlap differences are at a level between 13 and 21 m with the SELENE models, depending on whether l-day data overlaps or I-day predictions are used.

  9. Analysis of Errors in a Special Perturbations Satellite Orbit Propagator

    Energy Technology Data Exchange (ETDEWEB)

    Beckerman, M.; Jones, J.P.

    1999-02-01

    We performed an analysis of error densities for the Special Perturbations orbit propagator using data for 29 satellites in orbits of interest to Space Shuttle and International Space Station collision avoidance. We find that the along-track errors predominate. These errors increase monotonically over each 36-hour prediction interval. The predicted positions in the along-track direction progressively either leap ahead of or lag behind the actual positions. Unlike the along-track errors the radial and cross-track errors oscillate about their nearly zero mean values. As the number of observations per fit interval decline the along-track prediction errors, and amplitudes of the radial and cross-track errors, increase.

  10. Application of Unscented Kalman Filter in Satellite Orbit Simulation

    Institute of Scientific and Technical Information of China (English)

    ZHAO Dongming; CAI Zhiwu

    2006-01-01

    A new estimate method is proposed, which takes advantage of the unscented transform method, thus the true mean and covariance are approximated more accurately. The new method can be applied to non-linear systems without the linearization process necessary for the EKF, and it does not demand a Gaussian distribution of noise and what's more, its ease of implementation and more accurate estimation features enables it to demonstrate its good performance in the experiment of satellite orbit simulation. Numerical experiments show that the application of the unscented Kalman filter is more effective than the EKF.

  11. Heat flux anomalies in Antarctica revealed from satellite magnetic data

    DEFF Research Database (Denmark)

    Maule, Cathrine Fox; Purucker, Michael E.; Olsen, Nils

    2005-01-01

    a method that uses satellite magnetic data to estimate the heat flux underneath the Antarctic ice sheet. We found that the heat flux underneath the ice sheet varies from 40 to 185 megawatts per square meter and that areas of high heat flux coincide with known current volcanism and some areas known to have...

  12. 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.

  13. 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

  14. Initial results of centralized autonomous orbit determination of the new-generation BDS satellites with inter-satellite link measurements

    Science.gov (United States)

    Tang, Chengpan; Hu, Xiaogong; Zhou, Shanshi; Liu, Li; Pan, Junyang; Chen, Liucheng; Guo, Rui; Zhu, Lingfeng; Hu, Guangming; Li, Xiaojie; He, Feng; Chang, Zhiqiao

    2018-01-01

    Autonomous orbit determination is the ability of navigation satellites to estimate the orbit parameters on-board using inter-satellite link (ISL) measurements. This study mainly focuses on data processing of the ISL measurements as a new measurement type and its application on the centralized autonomous orbit determination of the new-generation Beidou navigation satellite system satellites for the first time. The ISL measurements are dual one-way measurements that follow a time division multiple access (TDMA) structure. The ranging error of the ISL measurements is less than 0.25 ns. This paper proposes a derivation approach to the satellite clock offsets and the geometric distances from TDMA dual one-way measurements without a loss of accuracy. The derived clock offsets are used for time synchronization, and the derived geometry distances are used for autonomous orbit determination. The clock offsets from the ISL measurements are consistent with the L-band two-way satellite, and time-frequency transfer clock measurements and the detrended residuals vary within 0.5 ns. The centralized autonomous orbit determination is conducted in a batch mode on a ground-capable server for the feasibility study. Constant hardware delays are present in the geometric distances and become the largest source of error in the autonomous orbit determination. Therefore, the hardware delays are estimated simultaneously with the satellite orbits. To avoid uncertainties in the constellation orientation, a ground anchor station that "observes" the satellites with on-board ISL payloads is introduced into the orbit determination. The root-mean-square values of orbit determination residuals are within 10.0 cm, and the standard deviation of the estimated ISL hardware delays is within 0.2 ns. The accuracy of the autonomous orbits is evaluated by analysis of overlap comparison and the satellite laser ranging (SLR) residuals and is compared with the accuracy of the L-band orbits. The results indicate

  15. Analysis of orbit determination from Earth-based tracking for relay satellites in a perturbed areostationary orbit

    Science.gov (United States)

    Romero, P.; Pablos, B.; Barderas, G.

    2017-07-01

    Areostationary satellites are considered a high interest group of satellites to satisfy the telecommunications needs of the foreseen missions to Mars. An areostationary satellite, in an areoequatorial circular orbit with a period of 1 Martian sidereal day, would orbit Mars remaining at a fixed location over the Martian surface, analogous to a geostationary satellite around the Earth. This work addresses an analysis of the perturbed orbital motion of an areostationary satellite as well as a preliminary analysis of the aerostationary orbit estimation accuracy based on Earth tracking observations. First, the models for the perturbations due to the Mars gravitational field, the gravitational attraction of the Sun and the Martian moons, Phobos and Deimos, and solar radiation pressure are described. Then, the observability from Earth including possible occultations by Mars of an areostationary satellite in a perturbed areosynchronous motion is analyzed. The results show that continuous Earth-based tracking is achievable using observations from the three NASA Deep Space Network Complexes in Madrid, Goldstone and Canberra in an occultation-free scenario. Finally, an analysis of the orbit determination accuracy is addressed considering several scenarios including discontinuous tracking schedules for different epochs and different areoestationary satellites. Simulations also allow to quantify the aerostationary orbit estimation accuracy for various tracking series durations and observed orbit arc-lengths.

  16. GPM GROUND VALIDATION SATELLITE SIMULATED ORBITS C3VP V1

    Data.gov (United States)

    National Aeronautics and Space Administration — The GPM Ground Validation Satellite Simulated Orbits C3VP dataset is available in the Orbital database, which takes account for the atmospheric profiles, the...

  17. GPM GROUND VALIDATION SATELLITE SIMULATED ORBITS MC3E V1

    Data.gov (United States)

    National Aeronautics and Space Administration — The GPM Ground Validation Satellite Simulated Orbits MC3E dataset is available in the Orbital database , which takes account for the atmospheric profiles, the...

  18. GPM GROUND VALIDATION SATELLITE SIMULATED ORBITS TWP-ICE V1

    Data.gov (United States)

    National Aeronautics and Space Administration — The GPM Ground Validation Satellite Simulated Orbits TWP-ICE dataset is available in the Orbital database, which takes account for the atmospheric profiles, the...

  19. Anomalies

    International Nuclear Information System (INIS)

    Bardeen, W.A.

    1985-08-01

    Anomalies have a diverse impact on many aspects of physical phenomena. The role of anomalies in determining physical structure from the amplitude for π 0 decay to the foundations of superstring theory will be reviewed. 36 refs

  20. Spacecraft design project: Low Earth orbit communications satellite

    Science.gov (United States)

    Moroney, Dave; Lashbrook, Dave; Mckibben, Barry; Gardener, Nigel; Rivers, Thane; Nottingham, Greg; Golden, Bill; Barfield, Bill; Bruening, Joe; Wood, Dave

    1991-01-01

    This is the final product of the spacecraft design project completed to fulfill the academic requirements of the Spacecraft Design and Integration 2 course (AE-4871) taught at the U.S. Naval Postgraduate School. The Spacecraft Design and Integration 2 course is intended to provide students detailed design experience in selection and design of both satellite system and subsystem components, and their location and integration into a final spacecraft configuration. The design team pursued a design to support a Low Earth Orbiting (LEO) communications system (GLOBALSTAR) currently under development by the Loral Cellular Systems Corporation. Each of the 14 team members was assigned both primary and secondary duties in program management or system design. Hardware selection, spacecraft component design, analysis, and integration were accomplished within the constraints imposed by the 11 week academic schedule and the available design facilities.

  1. Research on orbit prediction for solar-based calibration proper satellite

    Science.gov (United States)

    Chen, Xuan; Qi, Wenwen; Xu, Peng

    2018-03-01

    Utilizing the mathematical model of the orbit mechanics, the orbit prediction is to forecast the space target's orbit information of a certain time based on the orbit of the initial moment. The proper satellite radiometric calibration and calibration orbit prediction process are introduced briefly. On the basis of the research of the calibration space position design method and the radiative transfer model, an orbit prediction method for proper satellite radiometric calibration is proposed to select the appropriate calibration arc for the remote sensor and to predict the orbit information of the proper satellite and the remote sensor. By analyzing the orbit constraint of the proper satellite calibration, the GF-1solar synchronous orbit is chose as the proper satellite orbit in order to simulate the calibration visible durance for different satellites to be calibrated. The results of simulation and analysis provide the basis for the improvement of the radiometric calibration accuracy of the satellite remote sensor, which lays the foundation for the high precision and high frequency radiometric calibration.

  2. The orbits of satellites of (22) Kalliope and (317) Roxane

    Science.gov (United States)

    Drummond, Jack D.; Reynolds, Odell; Buckman, Miles; Eickhoff, Mark

    2017-10-01

    Between October 2016 and February 2017 we imaged asteroid (22) Kalliope (10.3RC) a=243+/-6 km; P=11.5265+/-0.0204 d; T0=2457725.137+/-0.050; Pole[RA;Dec]=[ 96.2;-68.3]; e=0Roxane S/1 (PC) a=245+/-6 km; P=11.5858+/-0.0203 d; T0=2457721.631+/-0.051; Pole[RA;Dec]=[275.7;+68.8]; e= 0Roxane S/1 (RE) a=251+/-8 km; P=11.4927+/-0.0215 d; T0=2457717.730+/-0.126; Pole[RA;Dec]=[ 95.3; -67.8]; e=0.178+/-0.061ω=124+/-4Roxane S/1 (PE) a=249+/-7 km; P=11.5594+/-0.0190 d; T0=2457717.603+/-0.162; Pole[RADec]=[276.6+69.2]e=0.133+/-0.038ω= 230+/-5Roxane’s moon’s orbital pole is less than 4 degrees from the Ecliptic pole or Roxane’s orbital pole, but more than 22 degrees from Roxane’s rotational pole. Perhaps this indicates that the moon was captured from the Ecliptic plane rather than spun into Roxanne’s equatorial plane.The Starfire Optical Range’s 3.5 m telescope is the smallest ground based telescope used to derive orbits of asteroid satellites. Kalliope and Roxane follow our study of (87) Sylvia and its Romulus (Drummond, Reynolds, and Buckman (2016), Icarus 276, 107-115).

  3. Scripting Module for the Satellite Orbit Analysis Program (SOAP)

    Science.gov (United States)

    Carnright, Robert; Paget, Jim; Coggi, John; Stodden, David

    2008-01-01

    This add-on module to the SOAP software can perform changes to simulation objects based on the occurrence of specific conditions. This allows the software to encompass simulation response of scheduled or physical events. Users can manipulate objects in the simulation environment under programmatic control. Inputs to the scripting module are Actions, Conditions, and the Script. Actions are arbitrary modifications to constructs such as Platform Objects (i.e. satellites), Sensor Objects (representing instruments or communication links), or Analysis Objects (user-defined logical or numeric variables). Examples of actions include changes to a satellite orbit ( v), changing a sensor-pointing direction, and the manipulation of a numerical expression. Conditions represent the circumstances under which Actions are performed and can be couched in If-Then-Else logic, like performing v at specific times or adding to the spacecraft power only when it is being illuminated by the Sun. The SOAP script represents the entire set of conditions being considered over a specific time interval. The output of the scripting module is a series of events, which are changes to objects at specific times. As the SOAP simulation clock runs forward, the scheduled events are performed. If the user sets the clock back in time, the events within that interval are automatically undone. This script offers an interface for defining scripts where the user does not have to remember the vocabulary of various keywords. Actions can be captured by employing the same user interface that is used to define the objects themselves. Conditions can be set to invoke Actions by selecting them from pull-down lists. Users define the script by selecting from the pool of defined conditions. Many space systems have to react to arbitrary events that can occur from scheduling or from the environment. For example, an instrument may cease to draw power when the area that it is tasked to observe is not in view. The contingency

  4. Improving BeiDou precise orbit determination using observations of onboard MEO satellite receivers

    Science.gov (United States)

    Ge, Haibo; Li, Bofeng; Ge, Maorong; Shen, Yunzhong; Schuh, Harald

    2017-12-01

    In recent years, the precise orbit determination (POD) of the regional Chinese BeiDou Navigation Satellite System (BDS) has been a hot spot because of its special constellation consisting of five geostationary earth orbit (GEO) satellites and five inclined geosynchronous satellite orbit (IGSO) satellites besides four medium earth orbit (MEO) satellites since the end of 2012. GEO and IGSO satellites play an important role in regional BDS applications. However, this brings a great challenge to the POD, especially for the GEO satellites due to their geostationary orbiting. Though a number of studies have been carried out to improve the POD performance of GEO satellites, the result is still much worse than that of IGSO and MEO, particularly in the along-track direction. The major reason is that the geostationary characteristic of a GEO satellite results in a bad geometry with respect to the ground tracking network. In order to improve the tracking geometry of the GEO satellites, a possible strategy is to mount global navigation satellite system (GNSS) receivers on MEO satellites to collect the signals from GEO/IGSO GNSS satellites so as that these observations can be used to improve GEO/IGSO POD. We extended our POD software package to simulate all the related observations and to assimilate the MEO-onboard GNSS observations in orbit determination. Based on GPS and BDS constellations, simulated studies are undertaken for various tracking scenarios. The impact of the onboard GNSS observations is investigated carefully and presented in detail. The results show that MEO-onboard observations can significantly improve the orbit precision of GEO satellites from metres to decimetres, especially in the along-track direction. The POD results of IGSO satellites also benefit from the MEO-onboard data and the precision can be improved by more than 50% in 3D direction.

  5. 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

  6. Time series analysis of infrared satellite data for detecting thermal anomalies: a hybrid approach

    Science.gov (United States)

    Koeppen, W. C.; Pilger, E.; Wright, R.

    2011-07-01

    We developed and tested an automated algorithm that analyzes thermal infrared satellite time series data to detect and quantify the excess energy radiated from thermal anomalies such as active volcanoes. Our algorithm enhances the previously developed MODVOLC approach, a simple point operation, by adding a more complex time series component based on the methods of the Robust Satellite Techniques (RST) algorithm. Using test sites at Anatahan and Kīlauea volcanoes, the hybrid time series approach detected ~15% more thermal anomalies than MODVOLC with very few, if any, known false detections. We also tested gas flares in the Cantarell oil field in the Gulf of Mexico as an end-member scenario representing very persistent thermal anomalies. At Cantarell, the hybrid algorithm showed only a slight improvement, but it did identify flares that were undetected by MODVOLC. We estimate that at least 80 MODIS images for each calendar month are required to create good reference images necessary for the time series analysis of the hybrid algorithm. The improved performance of the new algorithm over MODVOLC will result in the detection of low temperature thermal anomalies that will be useful in improving our ability to document Earth's volcanic eruptions, as well as detecting low temperature thermal precursors to larger eruptions.

  7. A study of artificial satellite resonance orbits due to lunisolar perturbations

    International Nuclear Information System (INIS)

    Hughes, S.

    1978-01-01

    A study of artificial satellite resonance orbits due to lunisolar perturbations is given. Particular emphasis is placed on the following aspects: the classification of resonance orbits according to their commensurability condition; the form of the commensurability condition when expressed in terms of the orbital elements of a satellite; the predominant resonant terms for each commensurability condition; and criteria which determine the existence or non-existence of a particular commensurability condition. (author)

  8. 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

  9. Space weather and space anomalies

    Directory of Open Access Journals (Sweden)

    L. I. Dorman

    2005-11-01

    Full Text Available A large database of anomalies, registered by 220 satellites in different orbits over the period 1971-1994 has been compiled. For the first time, data from 49 Russian Kosmos satellites have been included in a statistical analysis. The database also contains a large set of daily and hourly space weather parameters. A series of statistical analyses made it possible to quantify, for different satellite orbits, space weather conditions on the days characterized by anomaly occurrences. In particular, very intense fluxes (>1000 pfu at energy >10 MeV of solar protons are linked to anomalies registered by satellites in high-altitude (>15000 km, near-polar (inclination >55° orbits typical for navigation satellites, such as those used in the GPS network, NAVSTAR, etc. (the rate of anomalies increases by a factor ~20, and to a much smaller extent to anomalies in geostationary orbits, (they increase by a factor ~4. Direct and indirect connections between anomaly occurrence and geomagnetic perturbations are also discussed.

  10. Detection of a weak meddy-like anomaly from high-resolution satellite SST maps

    Directory of Open Access Journals (Sweden)

    Mikhail Emelianov

    2012-09-01

    Full Text Available Despite the considerable impact of meddies on climate through the long-distance transport of properties, a consistent observation of meddy generation and propagation in the ocean is rather elusive. Meddies propagate at about 1000 m below the ocean surface, so satellite sensors are not able to detect them directly and finding them in the open ocean is more fortuitous than intentional. However, a consistent census of meddies and their paths is required in order to gain knowledge about their role in transporting properties such as heat and salt. In this paper we propose a new methodology for processing high-resolution sea surface temperature maps in order to detect meddy-like anomalies in the open ocean on a near-real-time basis. We present an example of detection, involving an atypical meddy-like anomaly that was confirmed as such by in situ measurements.

  11. Determination Gradients of the Earth's Magnetic Field from the Measurements of the Satellites and Inversion of the Kursk Magnetic Anomaly

    Science.gov (United States)

    Karoly, Kis; Taylor, Patrick T.; Geza, Wittmann

    2014-01-01

    We computed magnetic field gradients at satellite altitude, over Europe with emphasis on the Kursk Magnetic Anomaly (KMA). They were calculated using the CHAMP satellite total magnetic anomalies. Our computations were done to determine how the magnetic anomaly data from the new ESA/Swarm satellites could be utilized to determine the structure of the magnetization of the Earths crust, especially in the region of the KMA. Since the ten years of 2 CHAMP data could be used to simulate the Swarm data. An initial East magnetic anomaly gradient map of Europe was computed and subsequently the North, East and Vertical magnetic gradients for the KMA region were calculated. The vertical gradient of the KMA was determined using Hilbert transforms. Inversion of the total KMA was derived using Simplex and Simulated Annealing algorithms. Our resulting inversion depth model is a horizontal quadrangle with upper 300-329 km and lower 331-339 km boundaries.

  12. Analysis of the influence of orbital disturbances applied to an artificial lunar satellite

    International Nuclear Information System (INIS)

    Gonçalves, L D; Rocco, E M; De Moraes, R V

    2015-01-01

    This paper analyzes the influence of the orbital disturbance forces in the trajectory of lunar satellites. The following gravitational and non-gravitational orbital disturbances are considered: the non-homogeneity of the lunar gravitational field; the gravitational attraction due to the third body, considering the Earth and the Sun; the lunar albedo; the solar radiation pressure. Numerical models were developed and implemented in an orbital trajectory simulator aiming to understand the dynamics of the orbital motion of an artificial satellite in lunar orbit when considering the simultaneous effect of all disturbances. Different orbits were simulated in order to characterize the major and the minor influence of each disturbing force as function of the inclination and the right ascension of the ascending node. This study can be very useful in the space mission analysis and in the selection of orbits less affected by environmental disturbances. (paper)

  13. Observation of high energy electrons and protons in the South Atlantic geomagnetic anomaly by Ohzora Satellite

    International Nuclear Information System (INIS)

    Nagata, K.; Murakami, H.; Nakamoto, A.; Hasebe, N.; Kikuche, J.; Doke, T.

    1988-01-01

    Observed results of the high energy electrons (0.19 - 3.2 MeV) and protons (0.58 - 35 MeV) of the South Atlantic Geomagnetic Anomaly are presented. Two silicon Δ E-E telescopes on the ohzora satellite (EXOS-C, 1984-15A) were used to observe the high energy particle and the maximum intensity of electrons and protons. The powers of energy spectra above 1 MeV have different values from energy region below 1 MeV. The electron and proton intensities are greatest at pitch angle maximized at 90 0 . (author) [pt

  14. 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.

  15. Satellite traces, range spread-F occurrence, and gravity wave propagation at the southern anomaly crest

    Energy Technology Data Exchange (ETDEWEB)

    Cabrera, M.A. [Universidad Tecnologica Nacional, Tucuman (Argentina). CIASUR, Facultad Regional Tucuman; Universidad Nacional de Tucuman (Argentina). Lab. de Ionosfera; Pezzopane, M.; Zuccheretti, E. [Istituto Nazionale di Geofisica e Vulcanologia, Rome (Italy); Ezquer, R.G. [Universidad Tecnologica Nacional, Tucuman (Argentina). CIASUR, Facultad Regional Tucuman; Universidad Nacional de Tucuman (Argentina). Lab. de Ionosfera; Consejo Nacional de Investigaciones Cientificas y Tecnicas, Buenos Aires (Argentina)

    2010-07-01

    Range spread-F (RSF) and occurrence of ''satellite'' traces prior to RSF onset were studied at the southern peak of the ionospheric equatorial anomaly (EA). Ionograms recorded in September 2007 at the new ionospheric station of Tucuman, Argentina (26.9 S, 294.6 E, dip latitude 15.5 S), by the Advanced Ionospheric Sounder (AIS) developed at the Istituto Nazionale di Geofisica e Vulcanologia (INGV), were considered. Satellite traces (STs) are confirmed to be a necessary precursor to the appearance of an RSF trace on the ionograms. Moreover, an analysis of isoheight contours of electron density seems to suggest a relationship between RSF occurrence and gravity wave (GW) propagation. (orig.)

  16. Orbit Determination from Tracking Data of Artificial Satellite Using the Method of Differential Correction

    OpenAIRE

    Byoung-Sun Lee; Jung-Hyun Jo; Sang-Young Park; Kyu-Hong Choi; Chun-Hwey Kim

    1988-01-01

    The differential correction process determining osculating orbital elements as correct as possible at a given instant of time from tracking data of artificial satellite was accomplished. Preliminary orbital elements were used as an initial value of the differential correction procedure and iterated until the residual of real observation(O) and computed observation(C) was minimized. Tracking satellite was NOAA-9 or TIROS-N series. Two types of tracking data were prediction data precomputed fro...

  17. World map of ELF/VLF emissions as observed by a low-orbiting satellite

    International Nuclear Information System (INIS)

    Parrot, M.

    1990-01-01

    Statistical studies were performed of the intensities of the ELF/VLF emissions observed by the low-orbiting satellite AUREOL-3. Data were obtained from filterbanks and the frequency range of observations extends from a few tens of Hz up to 15 kHz. The most important phenomena observed are ELF hiss and VLF hiss. Electric and magnetic components are used. Thus, representation of the waves intensities in geographical coordinates was made at different frequencies. The relative ability of natural waves (whistler, hiss) and man-made waves, such as powerful VLF transmitters or powerline harmonic radiations (PLHR), to precipitate particles in the slot region, is studied. Using geomagnetical representation, it is shown that ELF hiss is maximum between 06 and 20 Magnetic Local Time and in the invariant latitude range 50 0 -70 0 as usual, but geographic representation indicates that the waves are intensified at the longitudes of VLF transmitters and near the South Atlantic Anomaly (SAA). The SAA plays a dominant role in the localization of the strongest ELF hiss. Weakest intensities are observed to the east of the SAA. As to the VLF hiss, the maximum intensity is related to regions of enhanced thunderstorm activity, and may be influenced by powerline harmonic radiations (PLHR) over USA. Comparisons with past work, experimental as well as theoretical, are made

  18. Assessing the Impact of Earth Radiation Pressure Acceleration on Low-Earth Orbit Satellites

    Science.gov (United States)

    Vielberg, Kristin; Forootan, Ehsan; Lück, Christina; Kusche, Jürgen; Börger, Klaus

    2017-04-01

    The orbits of satellites are influenced by several external forces. The main non-gravitational forces besides thermospheric drag, acting on the surface of satellites, are accelerations due to the Earth and Solar Radiation Pres- sure (SRP and ERP, respectively). The sun radiates visible and infrared light reaching the satellite directly, which causes the SRP. Earth also emits and reflects the sunlight back into space, where it acts on satellites. This is known as ERP acceleration. The influence of ERP increases with decreasing distance to the Earth, and for low-earth orbit (LEO) satellites ERP must be taken into account in orbit and gravity computations. Estimating acceler- ations requires knowledge about energy emitted from the Earth, which can be derived from satellite remote sensing data, and also by considering the shape and surface material of a satellite. In this sensitivity study, we assess ERP accelerations based on different input albedo and emission fields and their modelling for the satellite missions Challenging Mini-Satellite Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE). As input fields, monthly 1°x1° products of Clouds and the Earth's Radiant En- ergy System (CERES), L3 are considered. Albedo and emission models are generated as latitude-dependent, as well as in terms of spherical harmonics. The impact of different albedo and emission models as well as the macro model and the altitude of satellites on ERP accelerations will be discussed.

  19. GPM GROUND VALIDATION SATELLITE SIMULATED ORBITS LPVEX V1

    Data.gov (United States)

    National Aeronautics and Space Administration — The Satellite Simulator database is available for several campaigns: Light Precipitation Evaluation Experiment (LPVEX), Midlatitude Continental Convective Clouds...

  20. Experimental study on the precise orbit determination of the BeiDou navigation satellite system.

    Science.gov (United States)

    He, Lina; Ge, Maorong; Wang, Jiexian; Wickert, Jens; Schuh, Harald

    2013-03-01

    The regional service of the Chinese BeiDou satellite navigation system is now in operation with a constellation including five Geostationary Earth Orbit satellites (GEO), five Inclined Geosynchronous Orbit (IGSO) satellites and four Medium Earth Orbit (MEO) satellites. Besides the standard positioning service with positioning accuracy of about 10 m, both precise relative positioning and precise point positioning are already demonstrated. As is well known, precise orbit and clock determination is essential in enhancing precise positioning services. To improve the satellite orbits of the BeiDou regional system, we concentrate on the impact of the tracking geometry and the involvement of MEOs, and on the effect of integer ambiguity resolution as well. About seven weeks of data collected at the BeiDou Experimental Test Service (BETS) network is employed in this experimental study. Several tracking scenarios are defined, various processing schemata are designed and carried out; and then, the estimates are compared and analyzed in detail. The results show that GEO orbits, especially the along-track component, can be significantly improved by extending the tracking network in China along longitude direction, whereas IGSOs gain more improvement if the tracking network extends in latitude. The involvement of MEOs and ambiguity-fixing also make the orbits better.

  1. ORBITS AND MASSES OF THE SATELLITES OF THE DWARF PLANET HAUMEA (2003 EL61)

    International Nuclear Information System (INIS)

    Ragozzine, D.; Brown, M. E.

    2009-01-01

    Using precise relative astrometry from the Hubble Space Telescope and the W. M. Keck Telescope, we have determined the orbits and masses of the two dynamically interacting satellites of the dwarf planet (136108) Haumea, formerly 2003 EL61. The orbital parameters of Hi'iaka, the outer, brighter satellite, match well the previously derived orbit. On timescales longer than a few weeks, no Keplerian orbit is sufficient to describe the motion of the inner, fainter satellite Namaka. Using a fully interacting three-point-mass model, we have recovered the orbital parameters of both orbits and the mass of Haumea and Hi'iaka; Namaka's mass is marginally detected. The data are not sufficient to uniquely determine the gravitational quadrupole of the nonspherical primary (described by J 2 ). The nearly coplanar nature of the satellites, as well as an inferred density similar to water ice, strengthen the hypothesis that Haumea experienced a giant collision billions of years ago. The excited eccentricities and mutual inclination point to an intriguing tidal history of significant semimajor axis evolution through satellite mean-motion resonances. The orbital solution indicates that Namaka and Haumea are currently undergoing mutual events and that the mutual event season will last for next several years.

  2. Reconstructing the orbit of the Chelyabinsk meteor using satellite observations

    DEFF Research Database (Denmark)

    Proud, Simon Richard

    2013-01-01

    The large number of objects in a range of orbits around the Sun means that some will inevitably intersect the Earth, becoming a meteor. These objects are commonly comet fragments or asteroids. To determine the type of a particular meteor requires knowledge of its trajectory and orbital path...... that is typically estimated by using ground-based observations such as images or radar measurements. A lack of data can, however, make this difficult and create large uncertainties in the reconstructed orbit. Here I show a new method for estimating a meteor's trajectory, and hence allowing computation of the orbit...

  3. Impacts of Satellite Orbit and Clock on Real-Time GPS Point and Relative Positioning.

    Science.gov (United States)

    Shi, Junbo; Wang, Gaojing; Han, Xianquan; Guo, Jiming

    2017-06-12

    Satellite orbit and clock corrections are always treated as known quantities in GPS positioning models. Therefore, any error in the satellite orbit and clock products will probably cause significant consequences for GPS positioning, especially for real-time applications. Currently three types of satellite products have been made available for real-time positioning, including the broadcast ephemeris, the International GNSS Service (IGS) predicted ultra-rapid product, and the real-time product. In this study, these three predicted/real-time satellite orbit and clock products are first evaluated with respect to the post-mission IGS final product, which demonstrates cm to m level orbit accuracies and sub-ns to ns level clock accuracies. Impacts of real-time satellite orbit and clock products on GPS point and relative positioning are then investigated using the P3 and GAMIT software packages, respectively. Numerical results show that the real-time satellite clock corrections affect the point positioning more significantly than the orbit corrections. On the contrary, only the real-time orbit corrections impact the relative positioning. Compared with the positioning solution using the IGS final product with the nominal orbit accuracy of ~2.5 cm, the real-time broadcast ephemeris with ~2 m orbit accuracy provided <2 cm relative positioning error for baselines no longer than 216 km. As for the baselines ranging from 574 to 2982 km, the cm-dm level positioning error was identified for the relative positioning solution using the broadcast ephemeris. The real-time product could result in <5 mm relative positioning accuracy for baselines within 2982 km, slightly better than the predicted ultra-rapid product.

  4. Impacts of Satellite Orbit and Clock on Real-Time GPS Point and Relative Positioning

    Directory of Open Access Journals (Sweden)

    Junbo Shi

    2017-06-01

    Full Text Available Satellite orbit and clock corrections are always treated as known quantities in GPS positioning models. Therefore, any error in the satellite orbit and clock products will probably cause significant consequences for GPS positioning, especially for real-time applications. Currently three types of satellite products have been made available for real-time positioning, including the broadcast ephemeris, the International GNSS Service (IGS predicted ultra-rapid product, and the real-time product. In this study, these three predicted/real-time satellite orbit and clock products are first evaluated with respect to the post-mission IGS final product, which demonstrates cm to m level orbit accuracies and sub-ns to ns level clock accuracies. Impacts of real-time satellite orbit and clock products on GPS point and relative positioning are then investigated using the P3 and GAMIT software packages, respectively. Numerical results show that the real-time satellite clock corrections affect the point positioning more significantly than the orbit corrections. On the contrary, only the real-time orbit corrections impact the relative positioning. Compared with the positioning solution using the IGS final product with the nominal orbit accuracy of ~2.5 cm, the real-time broadcast ephemeris with ~2 m orbit accuracy provided <2 cm relative positioning error for baselines no longer than 216 km. As for the baselines ranging from 574 to 2982 km, the cm–dm level positioning error was identified for the relative positioning solution using the broadcast ephemeris. The real-time product could result in <5 mm relative positioning accuracy for baselines within 2982 km, slightly better than the predicted ultra-rapid product.

  5. Satellite orbits perturbed by direct solar radiation pressure: general expansion of the disturbing function

    International Nuclear Information System (INIS)

    Hughes, S.

    1977-01-01

    An expression is derived for the solar radiation pressure disturbing function on an Earth satellite orbit which takes into account the variation of the solar radiation flux with distance from the Sun's centre and the absorption of radiation by the satellite. This expression is then expanded in terms of the Keplerian elements of the satellite and solar orbits using Kaula's method (Astr. J.; 67:300 (1962)). The Kaula inclination functions are replaced by an equivalent set of modified Allan (Proc. R. Soc. A.; 288:60 (1965)) inclination functions. The resulting expression reduces to the form commonly used in solar radiation pressure perturbation studies (e.g. Aksnes, Cel. Mech.; 13:89 (1976)), when certain terms are neglected. If, as happens quite often in practice, a satellite's orbit is in near-resonance with certain of these neglected terms, these near-resonant terms can cause changes in the satellite's orbital elements comparable to those produced by the largest term in Aksnes's expression. A new expression for the solar radiation pressure disturbing function expansion is suggested for use in future studies of satellite orbits perturbed by solar radiation pressure. (author)

  6. Modeling Earth Albedo for Satellites in Earth Orbit

    DEFF Research Database (Denmark)

    Bhanderi, Dan; Bak, Thomas

    2005-01-01

    Many satellite are influences by the Earthøs albedo, though very few model schemes exist.in order to predict this phenomenon. Earth albedo is often treated as noise, or ignored completely. When applying solar cells in the attitude hardware, Earth albedo can cause the attitude estimate to deviate...... with as much as 20 deg. Digital Sun sensors with Earth albedo correction in hardware exist, but are expensive. In addition, albedo estimates are necessary in thermal calculations and power budgets. We present a modeling scheme base4d on Eartht reflectance, measured by NASA's Total Ozone Mapping Spectrometer......, in which the Earth Probe Satellite has recorded reflectivity data daily since mid 1996. The mean of these data can be used to calculate the Earth albedo given the positions of the satellite and the Sun. Our results show that the albedo varies highly with the solar angle to the satellite's field of view...

  7. From silk to satellite: Half a century of ocean colour anomalies in the Northeast Atlantic

    KAUST Repository

    Raitsos, Dionysios E.; Pradhan, Yaswant; Lavender, Sam; Hoteit, Ibrahim; McQuatters-Gollop, Abigail L.; Reid, Philip Chris; Richardson, Anthony J.

    2014-01-01

    Changes in phytoplankton dynamics influence marine biogeochemical cycles, climate processes, and food webs, with substantial social and economic consequences. Large-scale estimation of phytoplankton biomass was possible via ocean colour measurements from two remote sensing satellites - the Coastal Zone Colour Scanner (CZCS, 1979-1986) and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS, 1998-2010). Due to the large gap between the two satellite eras and differences in sensor characteristics, comparison of the absolute values retrieved from the two instruments remains challenging. Using a unique in situ ocean colour dataset that spans more than half a century, the two satellite-derived chlorophyll-a (Chl-a) eras are linked to assess concurrent changes in phytoplankton variability and bloom timing over the Northeast Atlantic Ocean and North Sea. Results from this unique re-analysis reflect a clear increasing pattern of Chl-a, a merging of the two seasonal phytoplankton blooms producing a longer growing season and higher seasonal biomass, since the mid-1980s. The broader climate plays a key role in Chl-a variability as the ocean colour anomalies parallel the oscillations of the Northern Hemisphere Temperature (NHT) since 1948. © 2013 John Wiley & Sons Ltd.

  8. Revisiting the South Atlantic Anomaly after 3 years of Swarm satellite mission

    Science.gov (United States)

    Pavón-Carrasco, F. Javier; Campuzano, Saioa A.; De Santis, Angelo

    2017-04-01

    Covering part of Southern America and the South Atlantic Ocean, the South Atlantic Anomaly (SAA) is nowadays one of the most important and largest features of the geomagnetic field at the Earth's surface. It is characterized by lower intensity values than expected for those geomagnetic latitudes. Thanks to the global geomagnetic models, the spatial and temporal geometry of the Earth's magnetic field can be defined at the core-mantle boundary, showing the origin of the SAA as a reversal polarity patch that is growing with a pronounced rate of -2.54ṡ105 nT per century and with western drift. Since the Swarm satellite mission of the European Space Agency was launched at the end of 2013, the three twin satellites are picking up the most accurate values of the geomagnetic field up to now. In this work, we use the satellite magnetic data from Swarm mission along with the observatory ground data of surrounding areas to evaluate the spatial and temporal evolution of the SAA during the Swarm-life.

  9. From silk to satellite: Half a century of ocean colour anomalies in the Northeast Atlantic

    KAUST Repository

    Raitsos, Dionysios E.

    2014-04-23

    Changes in phytoplankton dynamics influence marine biogeochemical cycles, climate processes, and food webs, with substantial social and economic consequences. Large-scale estimation of phytoplankton biomass was possible via ocean colour measurements from two remote sensing satellites - the Coastal Zone Colour Scanner (CZCS, 1979-1986) and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS, 1998-2010). Due to the large gap between the two satellite eras and differences in sensor characteristics, comparison of the absolute values retrieved from the two instruments remains challenging. Using a unique in situ ocean colour dataset that spans more than half a century, the two satellite-derived chlorophyll-a (Chl-a) eras are linked to assess concurrent changes in phytoplankton variability and bloom timing over the Northeast Atlantic Ocean and North Sea. Results from this unique re-analysis reflect a clear increasing pattern of Chl-a, a merging of the two seasonal phytoplankton blooms producing a longer growing season and higher seasonal biomass, since the mid-1980s. The broader climate plays a key role in Chl-a variability as the ocean colour anomalies parallel the oscillations of the Northern Hemisphere Temperature (NHT) since 1948. © 2013 John Wiley & Sons Ltd.

  10. POGO satellite orbit corrections: an opportunity to improve the quality of the geomagnetic field measurements?

    DEFF Research Database (Denmark)

    Stockmann, Reto; Christiansen, Freddy; Olsen, Nils

    2015-01-01

    We present an attempt to improve the quality of the geomagnetic field measurements from the Polar Orbiting Geophysical Observatory (POGO) satellite missions in the late 1960s. Inaccurate satellite positions are believed to be a major source of errors for using the magnetic observations for field...... modelling. To improve the data, we use aniterative approach consisting of two main parts: one is a main field modelling process to obtain the radial fieldgradient to perturb the orbits and the other is the state-of-the-art GPS orbit modelling software BERNESE to calculatenew physical orbits. We report....... With this approach, weeliminate the orbit discontinuities at midnight but only tiny quality improvements could be achieved forgeomagnetically quiet data. We believe that improvements to the data are probably still possible, but it would require the original tracking observations to be found....

  11. Ultraviolet anomalies of the WASP-12 and HD 189733 systems: Trojan satellites as a plasma source

    Science.gov (United States)

    Kislyakova, Kristina; Pilat-Lohinger, Elke; Funk, Barbara; Lammer, Helmut; Fossati, Luca; Eggl, Siegfried; Schwarz, Richard; Boudyada, Mohammed; Erkaev, Nikolai

    2017-04-01

    We suggest an additional possible plasma source in the WASP-12 and HD189733b systems to explain part of the phenomena observed in ultraviolet (UV) light curves during planetary transits. In the proposed scenario, material originates from the molten surface of Trojan satellites on orbits near the Lagrange points L4 and L5. We show that the temperature at the orbital location of WASP-12b is high enough to melt the surface of rocky Trojans and to form shallow lava oceans on them. At the orbital distance of WASP-12b, this leads to the release of elements such as Mg and Ca, which are expected to surround the system. The predicted Mg and Ca outgassing rates from two Io-sized WASP-12b Trojans are ≈ 2.2 × 1027 s-1 and ≈ 2.2 × 1026 s-1, respectively. Trojan outgassing can lead to the observed lack of emission in MgII h&k and CaII H&K line cores of WASP-12. For HD 189733b, the mechanism is only marginally possible due to the lower temperature. The early ingress of HD 189733b observed in the far-UV (FUV) CII doublet couldn't be explained by this mechanism due to absence of carbon within elements outgassed by molten lava. We investigate the long-term stability region of WASP-12b and HD 189733b in case of planar and inclined motion of these satellites and show that unlike the classical exomoons orbiting the planet, Io-sized Trojans can be stable for the whole systems life time.

  12. 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.

  13. Orbit computation of the TELECOM-2D satellite with a Genetic Algorithm

    Science.gov (United States)

    Deleflie, Florent; Coulot, David; Vienne, Alain; Decosta, Romain; Richard, Pascal; Lasri, Mohammed Amjad

    2014-07-01

    In order to test a preliminary orbit determination method, we fit an orbit of the geostationary satellite TELECOM-2D, as if we did not know any a priori information on its trajectory. The method is based on a genetic algorithm coupled to an analytical propagator of the trajectory, that is used over a couple of days, and that uses a whole set of altazimutal data that are acquired by the tracking network made up of the two TAROT telescopes. The adjusted orbit is then compared to a numerical reference. The method is described, and the results are analyzed, as a step towards an operational method of preliminary orbit determination for uncatalogued objects.

  14. Method and associated apparatus for capturing, servicing, and de-orbiting earth satellites using robotics

    Science.gov (United States)

    Cepollina, Frank J. (Inventor); Burns, Richard D. (Inventor); Holz, Jill M. (Inventor); Corbo, James E. (Inventor); Jedhrich, Nicholas M. (Inventor)

    2009-01-01

    This invention is a method and supporting apparatus for autonomously capturing, servicing and de-orbiting a free-flying spacecraft, such as a satellite, using robotics. The capture of the spacecraft includes the steps of optically seeking and ranging the satellite using LIDAR; and matching tumble rates, rendezvousing and berthing with the satellite. Servicing of the spacecraft may be done using supervised autonomy, which is allowing a robot to execute a sequence of instructions without intervention from a remote human-occupied location. These instructions may be packaged at the remote station in a script and uplinked to the robot for execution upon remote command giving authority to proceed. Alternately, the instructions may be generated by Artificial Intelligence (AI) logic onboard the robot. In either case, the remote operator maintains the ability to abort an instruction or script at any time, as well as the ability to intervene using manual override to teleoperate the robot.In one embodiment, a vehicle used for carrying out the method of this invention comprises an ejection module, which includes the robot, and a de-orbit module. Once servicing is completed by the robot, the ejection module separates from the de-orbit module, leaving the de-orbit module attached to the satellite for de-orbiting the same at a future time. Upon separation, the ejection module can either de-orbit itself or rendezvous with another satellite for servicing. The ability to de-orbit a spacecraft further allows the opportunity to direct the landing of the spent satellite in a safe location away from population centers, such as the ocean.

  15. Low-Thrust Out-of-Plane Orbital Station-Keeping Maneuvers for Satellites

    Directory of Open Access Journals (Sweden)

    Vivian M. Gomes

    2012-01-01

    Full Text Available This paper considers the problem of out of plane orbital maneuvers for station keeping of satellites. The main idea is to consider that a satellite is in an orbit around the Earth and that it has its orbit is disturbed by one or more forces. Then, it is necessary to perform a small amplitude orbital correction to return the satellite to its original orbit, to keep it performing its mission. A low thrust propulsion is used to complete this task. It is important to search for solutions that minimize the fuel consumption to increase the lifetime of the satellite. To solve this problem a hybrid optimal control approach is used. The accuracy of the satisfaction of the constraints is considered, in order to try to decrease the fuel expenditure by taking advantage of this freedom. This type of problem presents numerical difficulties and it is necessary to adjust parameters, as well as details of the algorithm, to get convergence. In this versions of the algorithm that works well for planar maneuvers are usually not adequate for the out of plane orbital corrections. In order to illustrate the method, some numerical results are presented.

  16. The Impact of New Trends in Satellite Launches on Orbital Debris Environment

    Science.gov (United States)

    Karacalioglu, Arif Goktug; Stupl, Jan

    2016-01-01

    The main goal of this study is to examine the impact of new trends in satellite launch activities on the orbital debris environment and collision risk. Starting from the launch of the first artificial satellite in 1957, space borne technology has become an indispensable part of our lives. More than 6,000 satellites have been launched into Earth orbit. Though the annual number of satellites launched stayed flat for many decades, the trend has recently changed. The satellite market has been undergoing a major evolution with new space companies replacing the traditional approach of deploying a few large, complex and costly satellites with an approach to use a multitude of smaller, less complex and cheaper satellites. This new approach creates a sharp increase in the number of satellites and so the historic trends are no longer representative. As a foundation for this study, a scenario for satellite deployments based on the publicly announced future satellite missions has been developed. These constellation-deploying companies include, but are not limited to, Blacksky, CICERO, EROS, Landmapper, Leosat, Northstar, O3b, OmniEarth, OneWeb, Orbcomm, OuterNet, PlanetIQ, Planet Labs, Radarsat, RapidEye Next Generation, Sentinel, Skybox, SpaceX, and Spire. Information such as the annual number of launches, the number of orbital planes to be used by the constellation, as well as apogee, perigee, inclination, spacecraft mass and area were included or approximated. Besides the production of satellites, a widespread ongoing effort to enhance orbital injection capabilities will allow delivery of more spacecraft more accurately into Earth orbits. A long list of companies such as Microcosm, Rocket Lab, Firefly Space Systems, Sierra Nevada Corporation and Arca Space Corporation are developing new launch vehicles dedicated for small satellites. There are other projects which intend to develop interstages with propulsive capabilities which will allow the deployment of satellites into

  17. The Study of the Electron Enhancements during Garuda-1 Satellite anomaly

    Science.gov (United States)

    Neflia, Neflia

    Garuda-1 Satellite is one of Indonesian geostationary satellite. On April 5, 2005 Garuda-1 experienced power loss. According to space weather condition, This anomaly could be caused by the enhancement of electron during the day of anomaly and geomagnetic activity. The electron enhancement during quite solar activity have been associated with solar wind speed and IMF. For this study I will use solar wind speed, IMF , AE, Kp, Dst and Plasma Flow Pressure. The result of this study show that before the electron fluxes exceed 1000 pfu on April 5 at 13 UT, solar wind plasma speed exceed 500 km/s from April 4 at 16 UT until April 6 at 21 UT, with maximum speed, 646 km/s, occur on April 5 at 9 UT. AE index also increase from April 4 at 16 UT until April 6 at 09 UT, with maximum AE, 1024 nT, occur on April 5 at 18 and 21 UT. From April 4 at 14 UT until April 5 at 7 UT, Bz index directed southward, with minimum Bz, -8.8 nT, occur at April 5 at 1 UT. Kp index also increase from April 4 at 16 UT until April 6 at 09 UT, with maximum Kp, 7, occur on April 5 at 0-3 UT. Dst decrease from April 4 at 21 UT until April 6 at 09 UT, with minimum Dst occur on April 5 at 5-6 UT. The plasma flow pressure increase from April4 at 18 UT until April 5 at 3 UT, with maximum pressure, 6.9 nPa, occur on April 4 at 21 UT. This result indicate that plasma condition was disturbed which started with geomagnetic subtorm in the Auroral region before electron flux increase.

  18. Evidence of Urban Precipitation Anomalies from Satellite and Ground-Based Measurements

    Science.gov (United States)

    Shepherd, J. Marshall; Manyin, M.; Negri, Andrew

    2004-01-01

    Urbanization is one of the extreme cases of land use change. Most of world's population has moved to urban areas. Although currently only 1.2% of the land is considered urban, the spatial coverage and density of cities are expected to rapidly increase in the near future. It is estimated that by the year 2025, 60% of the world's population will live in cities. Human activity in urban environments also alters weather and climate processes. However, our understanding of urbanization on the total Earth-weather-climate system is incomplete. Recent literature continues to provide evidence that anomalies in precipitation exist over and downwind of major cities. Current and future research efforts are actively seeking to verify these literature findings and understand potential cause-effect relationships. The novelty of this study is that it utilizes rainfall data from multiple satellite data sources (e.g. TRMM precipitation radar, TRMM-geosynchronous-rain gauge merged product, and SSM/I) and ground-based measurements to identify spatial anomalies and temporal trends in precipitation for cities around the world. Early results will be presented and placed within the context of weather prediction, climate assessment, and societal applications.

  19. On the lunar node resonance of the orbital plane evolution of the Earth's satellite orbits

    Science.gov (United States)

    Zhu, Ting-Lei

    2018-06-01

    This paper aims to investigate the effects of lunar node resonance on the circular medium Earth orbits (MEO). The dynamical model is established in classical Hamiltonian systems with the application of Lie transform to remove the non-resonant terms. Resonant condition, stability and phase structures are studied. The lunar node resonance occurs when the secular changing rates of the orbital node (with respect to the equator) and the lunar node (with respect to the ecliptic) form a simple integer ratio. The resonant conditions are satisfied for both inclined and equatorial orbits. The orbital plane would have long period (with typical timescales of several centuries) fluctuation due to the resonance.

  20. Gravity model development for precise orbit computations for satellite altimetry

    Science.gov (United States)

    Marsh, James G.; Lerch, Francis, J.; Smith, David E.; Klosko, Steven M.; Pavlis, Erricos

    1986-01-01

    Two preliminary gravity models developed as a first step in reaching the TOPEX/Poseidon modeling goals are discussed. They were obtained by NASA-Goddard from an analysis of exclusively satellite tracking observations. With the new Preliminary Gravity Solution-T2 model, an improved global estimate of the field is achieved with an improved description of the geoid.

  1. The Use of Resonant Orbits in Satellite Geodesy: A Review

    Czech Academy of Sciences Publication Activity Database

    Klokočník, Jaroslav; Gooding, R. H.; Wagner, C. A.; Kostelecký, J.; Bezděk, Aleš

    2013-01-01

    Roč. 34, č. 1 (2013), s. 43-72 ISSN 0169-3298 Grant - others:ESA(XE) ESA- PECS project No. 98056 Institutional support: RVO:67985815 Keywords : satellite geodesy * Earth's gravitational field * geopotential Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 5.112, year: 2013

  2. Application of KAM Theorem to Earth Orbiting Satellites

    Science.gov (United States)

    2009-03-01

    P m n are the associated Legendre Polynomials, and r, δ and λ are the radius, geocentric latitude and east longitude of the of the satellite...Laskar shows that the cost -to-benefit drops off after windows of order 3-5 [11]. Higher order functions also result in wider peaks, which leads to

  3. The determination of the orbit of the Japanese satellite Ajisai and the GEM-T1 and GEM-T2 gravity field models

    Science.gov (United States)

    Sanchez, Braulio V.

    1990-01-01

    The Japanese Experimental Geodetic Satellite Ajisai was launched on August 12, 1986. In response to the TOPEX-POSEIDON mission requirements, the GSFC Space Geodesy Branch and its associates are producing improved models of the Earth's gravitational field. With the launch of Ajisai, precise laser data is now available which can be used to test many current gravity models. The testing of the various gravity field models show improvements of more than 70 percent in the orbital fits when using GEM-T1 and GEM-T2 relative to results obtained with the earlier GEM-10B model. The GEM-T2 orbital fits are at the 13-cm level (RMS). The results of the tests with the various versions of the GEM-T1 model indicate that the addition of satellite altimetry and surface gravity anomalies as additional data types should improve future gravity field models.

  4. A Geostationary Earth Orbit Satellite Model Using Easy Java Simulation

    Science.gov (United States)

    Wee, Loo Kang; Goh, Giam Hwee

    2013-01-01

    We develop an Easy Java Simulation (EJS) model for students to visualize geostationary orbits near Earth, modelled using a Java 3D implementation of the EJS 3D library. The simplified physics model is described and simulated using a simple constant angular velocity equation. We discuss four computer model design ideas: (1) a simple and realistic…

  5. Thermally induced vibrations of smart solar panel in a low-orbit satellite

    Science.gov (United States)

    Azadi, E.; Fazelzadeh, S. Ahmad; Azadi, M.

    2017-03-01

    In this paper, a smart flexible satellite moving in a circular orbit with two flexible panels are studied. The panels have been modeled as clamped-free-free-free rectangular plates with attached piezoelectric actuators. It is assumed that the satellite has a pitch angle rotation maneuver. Rapid temperature changes at day-night transitions in orbit generate time dependent bending moments. Satellite maneuver and temperature varying induce vibrations in the appendages. So, to simulate the system, heat radiation effects on the appendages have been considered. The nonlinear equations of motion and the heat transfer equations are coupled and solved simultaneously. So, the governing equations of motion are nonlinear and very complicated ones. Finally, the whole system is simulated and the effects of the heat radiation, radius of the orbit, piezoelectric voltages, and piezoelectric locations on the response of the system are studied.

  6. The effect of lunarlike satellites on the orbital infrared light curves of Earth-analog planets.

    Science.gov (United States)

    Moskovitz, Nicholas A; Gaidos, Eric; Williams, Darren M

    2009-04-01

    We have investigated the influence of lunarlike satellites on the infrared orbital light curves of Earth-analog extrasolar planets. Such light curves will be obtained by NASA's Terrestrial Planet Finder (TPF) and ESA's Darwin missions as a consequence of repeat observations to confirm the companion status of a putative planet and determine its orbit. We used an energy balance model to calculate disk-averaged infrared (bolometric) fluxes from planet-satellite systems over a full orbital period (one year). The satellites are assumed to lack an atmosphere, have a low thermal inertia like that of the Moon, and span a range of plausible radii. The planets are assumed to have thermal and orbital properties that mimic those of Earth, while their obliquities and orbital longitudes of inferior conjunction remain free parameters. Even if the gross thermal properties of the planet can be independently constrained (e.g., via spectroscopy or visible-wavelength detection of specular glint from a surface ocean), only the largest (approximately Mars-sized) lunarlike satellites can be detected by light curve data from a TPF-like instrument (i.e., one that achieves a photometric signal-to-noise ratio of 10 to 20 at infrared wavelengths). Nondetection of a lunarlike satellite can obfuscate the interpretation of a given system's infrared light curve so that it may resemble a single planet with high obliquity, different orbital longitude of vernal equinox relative to inferior conjunction, and in some cases drastically different thermal characteristics. If the thermal properties of the planet are not independently established, then the presence of a lunarlike satellite cannot be inferred from infrared data, which would thus demonstrate that photometric light curves alone can only be used for preliminary study, and the addition of spectroscopic data will be necessary.

  7. Attractive manifold-based adaptive solar attitude control of satellites in elliptic orbits

    Science.gov (United States)

    Lee, Keum W.; Singh, Sahjendra N.

    2011-01-01

    The paper presents a novel noncertainty-equivalent adaptive (NCEA) control system for the pitch attitude control of satellites in elliptic orbits using solar radiation pressure (SRP). The satellite is equipped with two identical solar flaps to produce control moments. The adaptive law is based on the attractive manifold design using filtered signals for synthesis, which is a modification of the immersion and invariance (I&I) method. The control system has a modular controller-estimator structure and has separate tunable gains. A special feature of this NCEA law is that the trajectories of the satellite converge to a manifold in an extended state space, and the adaptive law recovers the performance of a deterministic controller. This recovery of performance cannot be obtained with certainty-equivalent adaptive (CEA) laws. Simulation results are presented which show that the NCEA law accomplishes precise attitude control of the satellite in an elliptic orbit, despite large parameter uncertainties.

  8. Using Low Resolution Satellite Imagery for Yield Prediction and Yield Anomaly Detection

    Directory of Open Access Journals (Sweden)

    Oscar Rojas

    2013-04-01

    Full Text Available Low resolution satellite imagery has been extensively used for crop monitoring and yield forecasting for over 30 years and plays an important role in a growing number of operational systems. The combination of their high temporal frequency with their extended geographical coverage generally associated with low costs per area unit makes these images a convenient choice at both national and regional scales. Several qualitative and quantitative approaches can be clearly distinguished, going from the use of low resolution satellite imagery as the main predictor of final crop yield to complex crop growth models where remote sensing-derived indicators play different roles, depending on the nature of the model and on the availability of data measured on the ground. Vegetation performance anomaly detection with low resolution images continues to be a fundamental component of early warning and drought monitoring systems at the regional scale. For applications at more detailed scales, the limitations created by the mixed nature of low resolution pixels are being progressively reduced by the higher resolution offered by new sensors, while the continuity of existing systems remains crucial for ensuring the availability of long time series as needed by the majority of the yield prediction methods used today.

  9. The ITU and managing satellite orbital and spectrum resources in the 21st century

    CERN Document Server

    Allison, Audrey L

    2014-01-01

    Access to satellite orbits and spectrum is managed by the ITU, a United Nations body that strives to extend the benefits of new technologies to the world, while ensuring equitable access to these resources. This book explores how the ITU approaches these dual missions in light of the increasing saturation of the geostationary orbit by a vibrant global satellite industry and the rising interests of developing countries in accessing these limited resources. These issues were the subject of debate at the 2012 World Radiocommunication Conference. This book describes and assesses various regulatory approaches undertaken to manage the increasing requests for access to space and especially access to spectrum and orbital locations in the geosynchronous or “The Clarke” orbit.

  10. The Orbital Dynamics of Synchronous Satellites: Irregular Motions in the 2 : 1 Resonance

    Directory of Open Access Journals (Sweden)

    Jarbas Cordeiro Sampaio

    2012-01-01

    Full Text Available The orbital dynamics of synchronous satellites is studied. The 2 : 1 resonance is considered; in other words, the satellite completes two revolutions while the Earth completes one. In the development of the geopotential, the zonal harmonics J20 and J40 and the tesseral harmonics J22 and J42 are considered. The order of the dynamical system is reduced through successive Mathieu transformations, and the final system is solved by numerical integration. The Lyapunov exponents are used as tool to analyze the chaotic orbits.

  11. Integrated orbit and attitude hardware-in-the-loop simulations for autonomous satellite formation flying

    Science.gov (United States)

    Park, Han-Earl; Park, Sang-Young; Kim, Sung-Woo; Park, Chandeok

    2013-12-01

    Development and experiment of an integrated orbit and attitude hardware-in-the-loop (HIL) simulator for autonomous satellite formation flying are presented. The integrated simulator system consists of an orbit HIL simulator for orbit determination and control, and an attitude HIL simulator for attitude determination and control. The integrated simulator involves four processes (orbit determination, orbit control, attitude determination, and attitude control), which interact with each other in the same way as actual flight processes do. Orbit determination is conducted by a relative navigation algorithm using double-difference GPS measurements based on the extended Kalman filter (EKF). Orbit control is performed by a state-dependent Riccati equation (SDRE) technique that is utilized as a nonlinear controller for the formation control problem. Attitude is determined from an attitude heading reference system (AHRS) sensor, and a proportional-derivative (PD) feedback controller is used to control the attitude HIL simulator using three momentum wheel assemblies. Integrated orbit and attitude simulations are performed for a formation reconfiguration scenario. By performing the four processes adequately, the desired formation reconfiguration from a baseline of 500-1000 m was achieved with meter-level position error and millimeter-level relative position navigation. This HIL simulation demonstrates the performance of the integrated HIL simulator and the feasibility of the applied algorithms in a real-time environment. Furthermore, the integrated HIL simulator system developed in the current study can be used as a ground-based testing environment to reproduce possible actual satellite formation operations.

  12. Improvement in the radial accuracy of altimeter-satellite orbits due to the geopotential

    Czech Academy of Sciences Publication Activity Database

    Klokočník, Jaroslav; Kostelecký, J.; Wagner, C. A.

    2008-01-01

    Roč. 91, 1-4 (2008), s. 106-120 ISSN 0012-8252 R&D Projects: GA AV ČR IAA3003407; GA MŠk(CZ) LC506 Institutional research plan: CEZ:AV0Z10030501 Keywords : orbits of Earth artificial satellites * gravity field of the Earth * radial orbit error Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 6.558, year: 2008

  13. 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.

  14. An orbit determination algorithm for small satellites based on the magnitude of the earth magnetic field

    Science.gov (United States)

    Zagorski, P.; Gallina, A.; Rachucki, J.; Moczala, B.; Zietek, S.; Uhl, T.

    2018-06-01

    Autonomous attitude determination systems based on simple measurements of vector quantities such as magnetic field and the Sun direction are commonly used in very small satellites. However, those systems always require knowledge of the satellite position. This information can be either propagated from orbital elements periodically uplinked from the ground station or measured onboard by dedicated global positioning system (GPS) receiver. The former solution sacrifices satellite autonomy while the latter requires additional sensors which may represent a significant part of mass, volume, and power budget in case of pico- or nanosatellites. Hence, it is thought that a system for onboard satellite position determination without resorting to GPS receivers would be useful. In this paper, a novel algorithm for determining the satellite orbit semimajor-axis is presented. The methods exploit only the magnitude of the Earth magnetic field recorded onboard by magnetometers. This represents the first step toward an extended algorithm that can determine all orbital elements of the satellite. The method is validated by numerical analysis and real magnetic field measurements.

  15. THEMIS satellite observations of hot flow anomalies at Earth's bow shock

    Directory of Open Access Journals (Sweden)

    C. Chu

    2017-03-01

    Full Text Available Hot flow anomalies (HFAs at Earth's bow shock were identified in Time History of Events and Macroscale Interactions During Substorms (THEMIS satellite data from 2007 to 2009. The events were classified as young or mature and also as regular or spontaneous hot flow anomalies (SHFAs. The dataset has 17 young SHFAs, 49 mature SHFAs, 15 young HFAs, and 55 mature HFAs. They span a wide range of magnetic local times (MLTs from approximately 7 to 16.5 MLT. The largest ratio of solar wind to HFA core density occurred near dusk and at larger distances from the bow shock. In this study, HFAs and SHFAs were observed up to 6.3 RE and 6.1 RE (Earth radii, respectively, upstream from the model bow shock. HFA–SHFA occurrence decreases with distance upstream from the bow shock. HFAs of the highest event core ion temperatures were not seen at the flanks. The ratio of HFA ion temperature increase to HFA electron temperature increase is highest around 12 MLT and slightly duskward. For SHFAs, (Tihfa∕Tisw/(Tehfa∕Tesw generally increased with distance from the bow shock. Both mature and young HFAs are more prevalent when there is an approximately radial interplanetary magnetic field. HFAs occur most preferentially for solar wind speeds from 550 to 600 km s−1. The correlation coefficient between the HFA increase in thermal energy density from solar wind values and the decrease in kinetic energy density from solar wind values is 0.62. SHFAs and HFAs do not show major differences in this study.

  16. 78 FR 14920 - Earth Stations Aboard Aircraft Communicating With Fixed-Satellite Service Geostationary-Orbit...

    Science.gov (United States)

    2013-03-08

    ... Consumer and Governmental Affairs Bureau, Reference Information Center shall send a copy of this Report and... ground, ESAAs shall not be authorized for transmission at angles less than 5[deg] measured from the plane..., in the plane of the geostationary satellite orbit (GSO) as it appears at the particular earth station...

  17. A novel emergency system for low earth orbit satellites using Galileo GNSS

    NARCIS (Netherlands)

    Gill, E.K.A.; Helderweirt, A.

    2010-01-01

    Low Earth Orbit (LEO) satellites have a limited direct contact time with the stations of their ground segment. This fundamentally constraints a timeliness reaction of the mission control center in case of emergency situations onboard the LEO spacecraft. To enable such a rapid reaction to emergency

  18. Study on networking issues of medium earth orbit satellite communications systems

    Science.gov (United States)

    Araki, Noriyuki; Shinonaga, Hideyuki; Ito, Yasuhiko

    1993-01-01

    Two networking issues of communications systems with medium earth orbit (MEO) satellites, namely network architectures and location determination and registration methods for hand-held terminals, are investigated in this paper. For network architecture, five candidate architectures are considered and evaluated in terms of signaling traffic. For location determination and registration, two methods are discussed and evaluated.

  19. 78 FR 19172 - Earth Stations Aboard Aircraft Communicating with Fixed-Satellite Service Geostationary-Orbit...

    Science.gov (United States)

    2013-03-29

    ... FEDERAL COMMUNICATIONS COMMISSION 47 CFR Parts 2 and 25 [IB Docket No. 12-376; FCC 12-161] Earth Stations Aboard Aircraft Communicating with Fixed-Satellite Service Geostationary-Orbit Space Stations... the Federal Register of March 8, 2013. The document proposed rules for Earth Stations Aboard Aircraft...

  20. Two satellite study of substorm expansion near geosynchronous orbit

    Directory of Open Access Journals (Sweden)

    Ø. Holter

    2004-12-01

    Full Text Available During several time intervals in 1979–1980 the satellites GEOS-2 and SCATHA were situated relatively close on the nightside of the Earth at geosynchronous distances. Several substorm events were identified during these periods. The event considered in this paper was recorded on 22 May 1979, when the satellites were separated by less than 30min in local time around 21:00 LT. The observed 45 to 60 s delay of magnetic signatures observed at the two s/c indicates a westward expansion of ~7.7°/min. At the two s/c, the magnetic signatures are, in particular for the azimuthal magnetic field components, quite different. At GEOS-2, being close to the magnetic equator, the dominant feature is a dipolarization with a weak field-aligned current signature corresponding to a symmetric current which cancels at the equator. On SCATHA, however, being close to the current sheet boundary, the azimuthal magnetic field indicates a strong field-aligned Birkeland current structure. On both s/c the first indication of an approaching substorm was an increase in the high energy ion flux followed by a reduction in the flux intensity of energetic electrons and a further tailward stretching of the magnetic field, starting ~2min before the onset of the magnetic field dipolarization. The tailward stretching, the observed variations of the magnetic field components, and the subsequent dipolarization are interpreted in terms of an azimuthally tilted field-aligned current system passing the s/c on the tailward side from east to west. The westward expansion and dipolarization observed at the two s/c are consistent with the propagation of a Rayleigh-Taylor type instability. The increased radial ion flux corresponds to the ExB-drift due to the substorm associated electric field.

    Key words. Magnetospheric physics (storms and substorms; plasma waves and instabilities; current systems

  1. Accretion of satellites on to central galaxies in clusters: merger mass ratios and orbital parameters

    Science.gov (United States)

    Nipoti, Carlo; Giocoli, Carlo; Despali, Giulia

    2018-05-01

    We study the statistical properties of mergers between central and satellite galaxies in galaxy clusters in the redshift range 0 identify dark-matter haloes, we construct halo merger trees for different values of the overdensity Δc. While the virial overdensity definition allows us to probe the accretion of satellites at the cluster virial radius rvir, higher overdensities probe satellite mergers in the central region of the cluster, down to ≈0.06rvir, which can be considered a proxy for the accretion of satellite galaxies on to central galaxies. We find that the characteristic merger mass ratio increases for increasing values of Δc: more than 60 per cent of the mass accreted by central galaxies since z ≈ 1 comes from major mergers. The orbits of satellites accreting on to central galaxies tend to be more tangential and more bound than orbits of haloes accreting at the virial radius. The obtained distributions of merger mass ratios and orbital parameters are useful to model the evolution of the high-mass end of the galaxy scaling relations without resorting to hydrodynamic cosmological simulations.

  2. Validation of double Langmuir probe in-orbit performance onboard a nano-satellite

    Science.gov (United States)

    Tejumola, Taiwo Raphael; Zarate Segura, Guillermo Wenceslao; Kim, Sangkyun; Khan, Arifur; Cho, Mengu

    2018-03-01

    Many plasma measurement systems have been proposed and used onboard different satellites to characterize space plasma. Most of these systems employed the technique of Langmuir probes either using the single or double probes methods. Recent growth of lean satellites has positioned it on advantage to be used for space science missions using Langmuir probes because of its simplicity and convenience. However, single Langmuir probes are not appropriate to be used on lean satellites because of their limited conducting area which leads to spacecraft charging and drift of the instrument's electrical ground during measurement. Double Langmuir probes technique can overcome this limitation, as a measurement reference in relation to the spacecraft is not required. A double Langmuir probe measurement system was designed and developed at Kyushu Institute of Technology for HORYU-IV satellite, which is a 10 kg, 30 cm cubic class lean satellite launched into Low Earth Orbit on 17th February 2016. This paper presents the on-orbit performance and validation of the double Langmuir probe measurement using actual on-orbit measured data and computer simulations.

  3. Coarse Initial Orbit Determination for a Geostationary Satellite Using Single-Epoch GPS Measurements

    Directory of Open Access Journals (Sweden)

    Ghangho Kim

    2015-04-01

    Full Text Available A practical algorithm is proposed for determining the orbit of a geostationary orbit (GEO satellite using single-epoch measurements from a Global Positioning System (GPS receiver under the sparse visibility of the GPS satellites. The algorithm uses three components of a state vector to determine the satellite’s state, even when it is impossible to apply the classical single-point solutions (SPS. Through consideration of the characteristics of the GEO orbital elements and GPS measurements, the components of the state vector are reduced to three. However, the algorithm remains sufficiently accurate for a GEO satellite. The developed algorithm was tested on simulated measurements from two or three GPS satellites, and the calculated maximum position error was found to be less than approximately 40 km or even several kilometers within the geometric range, even when the classical SPS solution was unattainable. In addition, extended Kalman filter (EKF tests of a GEO satellite with the estimated initial state were performed to validate the algorithm. In the EKF, a reliable dynamic model was adapted to reduce the probability of divergence that can be caused by large errors in the initial state.

  4. Coarse Initial Orbit Determination for a Geostationary Satellite Using Single-Epoch GPS Measurements

    Science.gov (United States)

    Kim, Ghangho; Kim, Chongwon; Kee, Changdon

    2015-01-01

    A practical algorithm is proposed for determining the orbit of a geostationary orbit (GEO) satellite using single-epoch measurements from a Global Positioning System (GPS) receiver under the sparse visibility of the GPS satellites. The algorithm uses three components of a state vector to determine the satellite’s state, even when it is impossible to apply the classical single-point solutions (SPS). Through consideration of the characteristics of the GEO orbital elements and GPS measurements, the components of the state vector are reduced to three. However, the algorithm remains sufficiently accurate for a GEO satellite. The developed algorithm was tested on simulated measurements from two or three GPS satellites, and the calculated maximum position error was found to be less than approximately 40 km or even several kilometers within the geometric range, even when the classical SPS solution was unattainable. In addition, extended Kalman filter (EKF) tests of a GEO satellite with the estimated initial state were performed to validate the algorithm. In the EKF, a reliable dynamic model was adapted to reduce the probability of divergence that can be caused by large errors in the initial state. PMID:25835299

  5. Variational and symplectic integrators for satellite relative orbit propagation including drag

    Science.gov (United States)

    Palacios, Leonel; Gurfil, Pini

    2018-04-01

    Orbit propagation algorithms for satellite relative motion relying on Runge-Kutta integrators are non-symplectic—a situation that leads to incorrect global behavior and degraded accuracy. Thus, attempts have been made to apply symplectic methods to integrate satellite relative motion. However, so far all these symplectic propagation schemes have not taken into account the effect of atmospheric drag. In this paper, drag-generalized symplectic and variational algorithms for satellite relative orbit propagation are developed in different reference frames, and numerical simulations with and without the effect of atmospheric drag are presented. It is also shown that high-order versions of the newly-developed variational and symplectic propagators are more accurate and are significantly faster than Runge-Kutta-based integrators, even in the presence of atmospheric drag.

  6. The influence of regional surface soil moisture anomalies on forest fires in Siberia observed from satellites

    Energy Technology Data Exchange (ETDEWEB)

    Bartsch, A [Institute of Photogrammetry and Remote Sensing, Vienna University of Technology, 1040 Vienna (Austria); Balzter, H [Department of Geography, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); George, C, E-mail: ab@ipf.tuwien.ac.a [Earth Observation, Centre for Ecology and Hydrology, Crowmarsh Gifford, Wallingford OX10 8BB (United Kingdom)

    2009-10-15

    Forest fires are frequent in the Siberian taiga and are predicted to increase in frequency as a result of increased fire risk under drought conditions, and prolonged fire seasons caused by climate change. There is, however, some uncertainty as to the extent to which drought influences forest fire frequency at a regional scale. Here, we present an analysis of satellite derived soil moisture anomaly data from ERS-1/2 (ERS: Earth Resources Satellite) scatterometer data and burned area maps from MODIS/AVHRR/ATSR (Moderate Resolution Imaging Spectroradiometer/Advanced Very High Resolution Radiometer/Along-Track Scanning Radiometer) over Central Siberia for the years 1992-2000. The purpose of this study is to investigate the relationship of remotely sensed soil moisture deviations from the long-term mean and fire within the boreal biome on a sub-continental scale. Results show that wet surface soil moisture conditions limit the extent of burned area. They can prevent the outbreak of fires but the magnitude of a negative (dry) deviation does not determine the maximum size of fire affected areas. It is known from the literature, however, that an ignition is more likely to occur under low surface wetness conditions, such as those that we observed during July and August in both permafrost and non-permafrost regions. Although the burned area under drier conditions in July is lowest over non-permafrost, the actual number of fires is as high as over continuous permafrost. Approximately 80% of all events occurred under such conditions during that month. The fire size was below 50 km{sup 2} under moist conditions. Larger burned areas have in general not been detected when the surface wetness deviation exceeded +5%.

  7. The influence of regional surface soil moisture anomalies on forest fires in Siberia observed from satellites

    International Nuclear Information System (INIS)

    Bartsch, A; Balzter, H; George, C

    2009-01-01

    Forest fires are frequent in the Siberian taiga and are predicted to increase in frequency as a result of increased fire risk under drought conditions, and prolonged fire seasons caused by climate change. There is, however, some uncertainty as to the extent to which drought influences forest fire frequency at a regional scale. Here, we present an analysis of satellite derived soil moisture anomaly data from ERS-1/2 (ERS: Earth Resources Satellite) scatterometer data and burned area maps from MODIS/AVHRR/ATSR (Moderate Resolution Imaging Spectroradiometer/Advanced Very High Resolution Radiometer/Along-Track Scanning Radiometer) over Central Siberia for the years 1992-2000. The purpose of this study is to investigate the relationship of remotely sensed soil moisture deviations from the long-term mean and fire within the boreal biome on a sub-continental scale. Results show that wet surface soil moisture conditions limit the extent of burned area. They can prevent the outbreak of fires but the magnitude of a negative (dry) deviation does not determine the maximum size of fire affected areas. It is known from the literature, however, that an ignition is more likely to occur under low surface wetness conditions, such as those that we observed during July and August in both permafrost and non-permafrost regions. Although the burned area under drier conditions in July is lowest over non-permafrost, the actual number of fires is as high as over continuous permafrost. Approximately 80% of all events occurred under such conditions during that month. The fire size was below 50 km 2 under moist conditions. Larger burned areas have in general not been detected when the surface wetness deviation exceeded +5%.

  8. Multi-instrument observations of midlatitude summer nighttime anomaly from satellite and ground

    Science.gov (United States)

    Yamamoto, Mamoru; Thampi, Smitha V.; Liu, Huixin; Lin, Charles

    "Midlatitude Summer Nighttime Anomaly (MSNA)" is a phenomenon that the nighttime elec-tron densities exceed the daytime values on almost all days in summer over latitudes of 33-34N of more. We recently found the MSNA over the northeast Asian region from multi-instrument observations. The observations include the tomography analysis based on the chain of digital beacon receivers at Shionomisaki (33.45N, 135.8E), Shigaraki (34.85N, 136.1E), and Fukui (36.06N,136E), the ionosonde network over Japan (especially data from Wakkanai (45.4N, 141.7E)), ground-based GPS TEC observations using the GEONET. Also from satellites, CHAMP in situ electron density measurements, and Formosat3/COSMIC (F3/C) occultation measurements are useful to confirm the presence of MSNA over this region. In the presen-tation we show detailed features of the MSNA based on these multi-instrument, and discuss importance of the neutral atmosphere as a driver of the phenomenon.

  9. Orbit Determination from Tracking Data of Artificial Satellite Using the Method of Differential Correction

    Directory of Open Access Journals (Sweden)

    Byoung-Sun Lee

    1988-06-01

    Full Text Available The differential correction process determining osculating orbital elements as correct as possible at a given instant of time from tracking data of artificial satellite was accomplished. Preliminary orbital elements were used as an initial value of the differential correction procedure and iterated until the residual of real observation(O and computed observation(C was minimized. Tracking satellite was NOAA-9 or TIROS-N series. Two types of tracking data were prediction data precomputed from mean orbital elements of TBUS and real data obtained from tracking 1.707GHz HRPT signal of NOAA-9 using 5 meter auto-track antenna in Radio Research Laboratory. According to tracking data either Gauss method or Herrick-Gibbs method was applied to preliminary orbit determination. In the differential correction stage we used both of the Escobal(1975's analytical method and numerical ones are nearly consistent. And the differentially corrected orbit converged to the same value in spite of the differences between preliminary orbits of each time span.

  10. Analysis of Hansen's Inferior and Superior Partial Anomalies and the Division of the Elliptic Orbit into Two Segments

    Science.gov (United States)

    Sharaf, M. A.; Saad, A. S.

    2017-10-01

    In this paper, a novel analysis was established to prove how Hansen's inferior and superior partial anomalies k and k_1 can divide the elliptic orbit into two segments. The analysis depends on the departures of r (for k) and 1/r (for k1) from their minima. By these departures, we can find: (i) Transformations relating the eccentric anomaly to k and the true anomaly to k1. (ii) Expressions for k and k_1 in terms of the orbital elements. (iii) The interpretation and the intervals of definition of two moduli (X, S) related to k and k_1. (iv) The extreme values of r and the elliptic equations in terms of k and k1. (v) For r' and r'', the modulus X as a measure of the asymmetry of r' (or r'') from r'' (or r'), and the modulus S12 as a measure of the asymmetry of r' and r'' from the minimum value of r. (vi) A description of the segments represented by k and k1. (vii) The relative position of the radius vector at k0° and k1=180°.

  11. 47 CFR 25.261 - Procedures for avoidance of in-line interference events for Non Geostationary Satellite Orbit...

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Procedures for avoidance of in-line interference events for Non Geostationary Satellite Orbit (NGSO) Satellite Network Operations in the Fixed Satellite Service (FSS) Bands. 25.261 Section 25.261 Telecommunication FEDERAL COMMUNICATIONS COMMISSION...

  12. The Impact of New Trends in Satellite Launches on the Orbital Debris Environment

    Science.gov (United States)

    Karacalioglu, Arif Goektug; Stupl, Jan

    2016-01-01

    The main goal of this study is to examine the impact of new trends in satellite launch activities on the orbital debris environment and collision risk. As a foundation for the study, we developed a deployment scenario for satellites and associated rocket bodies based on publicly announced future missions. The upcoming orbital injection technologies, such as the new launch vehicles dedicated for small spacecraft and propulsive interstages, are also considered in this scenario. We then used a simulation tool developed in-house to propagate the objects within this scenario using variable-sized time-steps as small as one second to detect conjunctions between objects. The simulation makes it possible to follow the short- and long-term effects of a particular satellite or constellation in the space environment. Likewise, the effects of changes in the debris environment on a particular satellite or constellation can be evaluated. It is our hope that the results of this paper and further utilization of the developed simulation tool will assist in the investigation of more accurate deorbiting metrics to replace the generic 25-year disposal guidelines, as well as to guide future launches toward more sustainable and safe orbits.

  13. The Effects of Using Solar Radiation Pressure to Alleviate Fuel Requirements for Orbit Changing and Maintenance of the DSCS II F-13 Satellite

    National Research Council Canada - National Science Library

    Paris, Jody A

    2006-01-01

    Orbit disposal and maintenance of aging satellites has become a significant concern over the past few years, as the increasing number of orbiting objects threatens to limit the launching of future satellites...

  14. Multi-Satellite Orbit Determination Using Interferometric Observables with RF Localization Applications

    Science.gov (United States)

    Geeraert, Jeroen L.

    Very long baseline interferometry (VLBI) specifically same-beam interferometry (SBI), and dual-satellite geolocation are two fields of research not previously connected. This is due to the different application of each field, SBI is used for relative interplanetary navigation of two satellites while dual-satellite geolocation is used to locate the source of a radio frequency (RF) signal. In this dissertation however, we leverage both fields to create a novel method for multi-satellite orbit determination (OD) using time difference of arrival (TDOA) and frequency difference of arrival (FDOA) measurements. The measurements are double differenced between the satellites and the stations, in so doing, many of the common errors are canceled which can significantly improve measurement precision. Provided with this novel OD technique, the observability is first analyzed to determine the benefits and limitations of this method. In all but a few scenarios the measurements successfully reduce the covariance when examining the Cramer-Rao Lower Bound (CRLB). Reduced observability is encountered with geostationary satellites as their motion with respect to the stations is limited, especially when only one baseline is used. However, when using satellite pairs with greater relative motion with respect to the stations, even satellites that are close to, but not exactly in a geostationary orbit can be estimated accurately. We find that in a strong majority of cases the OD technique provides lower uncertainties and solutions far more accurate than using conventional OD observables such as range and range-rate while also not being affected by common errors and biases. We specifically examine GEO-GEO, GEO-MEO, and GEO-LEO dual-satellite estimation cases. The work is further extended by developing a relative navigation scenario where the chief satellite is assumed to have perfect knowledge, or some small amount of uncertainty considered but not estimated, while estimating the deputy

  15. Review of a relativity and geodesy mission with counter-orbiting polar satellites

    International Nuclear Information System (INIS)

    Van Patten, R.A.

    1977-01-01

    A new test of general relativity, capable of measuring the Lense-Thirring precession on a satellite orbit was proposed in 1974. We have recently realized that the remarkable geophysical output of this experiment can be enriched by allowing the point of encounter between the two satellites to progress from the poles to the equator during the course of the mission. There is reason to believe that by performing the experiment in this mode, all tesseral harmonics up to about 60th order could be separated and determined to accuracies up to three orders of magnitude better than current knowledge, and still obtain a 1% Lense-Thirring measurement. (orig.) [de

  16. Precise orbit determination for quad-constellation satellites at Wuhan University: strategy, result validation, and comparison

    Science.gov (United States)

    Guo, Jing; Xu, Xiaolong; Zhao, Qile; Liu, Jingnan

    2016-02-01

    This contribution summarizes the strategy used by Wuhan University (WHU) to determine precise orbit and clock products for Multi-GNSS Experiment (MGEX) of the International GNSS Service (IGS). In particular, the satellite attitude, phase center corrections, solar radiation pressure model developed and used for BDS satellites are addressed. In addition, this contribution analyzes the orbit and clock quality of the quad-constellation products from MGEX Analysis Centers (ACs) for a common time period of 1 year (2014). With IGS final GPS and GLONASS products as the reference, Multi-GNSS products of WHU (indicated by WUM) show the best agreement among these products from all MGEX ACs in both accuracy and stability. 3D Day Boundary Discontinuities (DBDs) range from 8 to 27 cm for Galileo-IOV satellites among all ACs' products, whereas WUM ones are the largest (about 26.2 cm). Among three types of BDS satellites, MEOs show the smallest DBDs from 10 to 27 cm, whereas the DBDs for all ACs products are at decimeter to meter level for GEOs and one to three decimeter for IGSOs, respectively. As to the satellite laser ranging (SLR) validation for Galileo-IOV satellites, the accuracy evaluated by SLR residuals is at the one decimeter level with the well-known systematic bias of about -5 cm for all ACs. For BDS satellites, the accuracy could reach decimeter level, one decimeter level, and centimeter level for GEOs, IGSOs, and MEOs, respectively. However, there is a noticeable bias in GEO SLR residuals. In addition, systematic errors dependent on orbit angle related to mismodeled solar radiation pressure (SRP) are present for BDS GEOs and IGSOs. The results of Multi-GNSS combined kinematic PPP demonstrate that the best accuracy of position and fastest convergence speed have been achieved using WUM products, particularly in the Up direction. Furthermore, the accuracy of static BDS only PPP degrades when the BDS IGSO and MEO satellites switches to orbit-normal orientation

  17. Space Network IP Services (SNIS): An Architecture for Supporting Low Earth Orbiting IP Satellite Missions

    Science.gov (United States)

    Israel, David J.

    2005-01-01

    The NASA Space Network (SN) supports a variety of missions using the Tracking and Data Relay Satellite System (TDRSS), which includes ground stations in White Sands, New Mexico and Guam. A Space Network IP Services (SNIS) architecture is being developed to support future users with requirements for end-to-end Internet Protocol (IP) communications. This architecture will support all IP protocols, including Mobile IP, over TDRSS Single Access, Multiple Access, and Demand Access Radio Frequency (RF) links. This paper will describe this architecture and how it can enable Low Earth Orbiting IP satellite missions.

  18. Phase Error Modeling and Its Impact on Precise Orbit Determination of GRACE Satellites

    Directory of Open Access Journals (Sweden)

    Jia Tu

    2012-01-01

    Full Text Available Limiting factors for the precise orbit determination (POD of low-earth orbit (LEO satellite using dual-frequency GPS are nowadays mainly encountered with the in-flight phase error modeling. The phase error is modeled as a systematic and a random component each depending on the direction of GPS signal reception. The systematic part and standard deviation of random part in phase error model are, respectively, estimated by bin-wise mean and standard deviation values of phase postfit residuals computed by orbit determination. By removing the systematic component and adjusting the weight of phase observation data according to standard deviation of random component, the orbit can be further improved by POD approach. The GRACE data of 1–31 January 2006 are processed, and three types of orbit solutions, POD without phase error model correction, POD with mean value correction of phase error model, and POD with phase error model correction, are obtained. The three-dimensional (3D orbit improvements derived from phase error model correction are 0.0153 m for GRACE A and 0.0131 m for GRACE B, and the 3D influences arisen from random part of phase error model are 0.0068 m and 0.0075 m for GRACE A and GRACE B, respectively. Thus the random part of phase error model cannot be neglected for POD. It is also demonstrated by phase postfit residual analysis, orbit comparison with JPL precise science orbit, and orbit validation with KBR data that the results derived from POD with phase error model correction are better than another two types of orbit solutions generated in this paper.

  19. Mars Relays Satellite Orbit Design Considerations for Global Support of Robotic Surface Missions

    Science.gov (United States)

    Hastrup, Rolf; Cesarone, Robert; Cook, Richard; Knocke, Phillip; McOmber, Robert

    1993-01-01

    This paper discusses orbit design considerations for Mars relay satellite (MRS)support of globally distributed robotic surface missions. The orbit results reported in this paper are derived from studies of MRS support for two types of Mars robotic surface missions: 1) the mars Environmental Survey (MESUR) mission, which in its current definition would deploy a global network of up to 16 small landers, and 2)a Small Mars Sample Return (SMSR) mission, which included four globally distributed landers, each with a return stage and one or two rovers, and up to four additional sets of lander/rover elements in an extended mission phase.

  20. Orbital motion in strongly perturbed environments applications to asteroid, comet and planetary satellite orbiters

    CERN Document Server

    Scheeres, Daniel J

    2012-01-01

    The proposed book will provide a detailed, technical introduction to the analysis of orbital motion in strongly perturbed environments, focusing on motion about small Solar System bodies, such as comets and asteroids. The author shows why such small bodies are of interest and why they can be used as a motivation for the general analysis of orbital mechanics. He shows how it is possible to model the small body environment, including specialised cases such as those of binary asteroids, comets and ‘rubble piles’, and how the fundamental equations of motion are derived. The properties of the various solutions to the equations of motion are described and the methods of analysis and their application are discussed. Both ballistic motion and powered motion on and about small bodies are considered and case studies for different small body missions are presented. The author concludes his comprehensive treatment with a discussion of the mechanics of multi-body small body systems and a review of advanced topics and ...

  1. Improved Orbit Determination and Forecasts with an Assimilative Tool for Atmospheric Density and Satellite Drag Specification

    Science.gov (United States)

    Crowley, G.; Pilinski, M.; Sutton, E. K.; Codrescu, M.; Fuller-Rowell, T. J.; Matsuo, T.; Fedrizzi, M.; Solomon, S. C.; Qian, L.; Thayer, J. P.

    2016-12-01

    Much as aircraft are affected by the prevailing winds and weather conditions in which they fly, satellites are affected by the variability in density and motion of the near earth space environment. Drastic changes in the neutral density of the thermosphere, caused by geomagnetic storms or other phenomena, result in perturbations of LEO satellite motions through drag on the satellite surfaces. This can lead to difficulties in locating important satellites, temporarily losing track of satellites, and errors when predicting collisions in space. We describe ongoing work to build a comprehensive nowcast and forecast system for specifying the neutral atmospheric state related to orbital drag conditions. The system outputs include neutral density, winds, temperature, composition, and the satellite drag derived from these parameters. This modeling tool is based on several state-of-the-art coupled models of the thermosphere-ionosphere as well as several empirical models running in real-time and uses assimilative techniques to produce a thermospheric nowcast. This software will also produce 72 hour predictions of the global thermosphere-ionosphere system using the nowcast as the initial condition and using near real-time and predicted space weather data and indices as the inputs. Features of this technique include: • Satellite drag specifications with errors lower than current models • Altitude coverage up to 1000km • Background state representation using both first principles and empirical models • Assimilation of satellite drag and other datatypes • Real time capability • Ability to produce 72-hour forecasts of the atmospheric state In this paper, we will summarize the model design and assimilative architecture, and present preliminary validation results. Validation results will be presented in the context of satellite orbit errors and compared with several leading atmospheric models including the High Accuracy Satellite Drag Model, which is currently used

  2. Geographical representation of radial orbit perturbations due to ocean tides: Implications for satellite altimetry

    Science.gov (United States)

    Bettadpur, Srinivas V.; Eanes, Richard J.

    1994-01-01

    In analogy to the geographical representation of the zeroth-order radial orbit perturbations due to the static geopotential, similar relationships have been derived for radial orbit perturbations due to the ocean tides. At each location these perturbations are seen to be coherent with the tide height variations. The study of this singularity is of obvious importance to the estimation of ocean tides from satellite altimeter data. We derive analytical expressions for the sensitivity of altimeter derived ocean tide models to the ocean tide force model induced errors in the orbits of the altimeter satellite. In particular, we focus on characterizing and quantifying the nonresonant tidal orbit perturbations, which cannot be adjusted into the empirical accelerations or radial perturbation adjustments commonly used during orbit determination and in altimeter data processing. As an illustration of the utility of this technique, we study the differences between a TOPEX/POSEIDON-derived ocean tide model and the Cartwright and Ray 1991 Geosat model. This analysis shows that nearly 60% of the variance of this difference for M(sub 2) can be explained by the Geosat radial orbit eror due to the omission of coefficients from the GEM-T2 background ocean tide model. For O(sub 1), K(sub 1), S(sub 2), and K(sub 2) the orbital effects account for approximately 10 to 40% of the variances of these differences. The utility of this technique to assessment of the ocean tide induced errors in the TOPEX/POSEIDON-derived tide models is also discussed.

  3. A simple orbit-attitude coupled modelling method for large solar power satellites

    Science.gov (United States)

    Li, Qingjun; Wang, Bo; Deng, Zichen; Ouyang, Huajiang; Wei, Yi

    2018-04-01

    A simple modelling method is proposed to study the orbit-attitude coupled dynamics of large solar power satellites based on natural coordinate formulation. The generalized coordinates are composed of Cartesian coordinates of two points and Cartesian components of two unitary vectors instead of Euler angles and angular velocities, which is the reason for its simplicity. Firstly, in order to develop natural coordinate formulation to take gravitational force and gravity gradient torque of a rigid body into account, Taylor series expansion is adopted to approximate the gravitational potential energy. The equations of motion are constructed through constrained Hamilton's equations. Then, an energy- and constraint-conserving algorithm is presented to solve the differential-algebraic equations. Finally, the proposed method is applied to simulate the orbit-attitude coupled dynamics and control of a large solar power satellite considering gravity gradient torque and solar radiation pressure. This method is also applicable to dynamic modelling of other rigid multibody aerospace systems.

  4. Pseudo Last Useful Instant Queuing Strategy for Handovers in Low Earth Orbit Mobile Satellite Networks

    OpenAIRE

    W. Kiamouche; M. Benslama

    2008-01-01

    This paper presents an alternative strategy of queuing handover called Pseudo Last Useful Instant PLUI scheme for Low Earth Orbit Mobile Satellite Systems LEO MSSs. The PLUI scheme uses the same approach as the Last Useful Instant LUI scheme previously proposed in literature, with less complex implementation. Simulation tests were carried out using Dynamic Channel Allocation DCA in order to evaluate the performance of this scheme and also an analytical approach has been p...

  5. First Attempt of Orbit Determination of SLR Satellites and Space Debris Using Genetic Algorithms

    Science.gov (United States)

    Deleflie, F.; Coulot, D.; Descosta, R.; Fernier, A.; Richard, P.

    2013-08-01

    We present an orbit determination method based on genetic algorithms. Contrary to usual estimation methods mainly based on least-squares methods, these algorithms do not require any a priori knowledge of the initial state vector to be estimated. These algorithms can be applied when a new satellite is launched or for uncatalogued objects that appear in images obtained from robotic telescopes such as the TAROT ones. We show in this paper preliminary results obtained from an SLR satellite, for which tracking data acquired by the ILRS network enable to build accurate orbital arcs at a few centimeter level, which can be used as a reference orbit ; in this case, the basic observations are made up of time series of ranges, obtained from various tracking stations. We show as well the results obtained from the observations acquired by the two TAROT telescopes on the Telecom-2D satellite operated by CNES ; in that case, the observations are made up of time series of azimuths and elevations, seen from the two TAROT telescopes. The method is carried out in several steps: (i) an analytical propagation of the equations of motion, (ii) an estimation kernel based on genetic algorithms, which follows the usual steps of such approaches: initialization and evolution of a selected population, so as to determine the best parameters. Each parameter to be estimated, namely each initial keplerian element, has to be searched among an interval that is preliminary chosen. The algorithm is supposed to converge towards an optimum over a reasonable computational time.

  6. Handover aspects for a Low Earth Orbit (LEO) CDMA Land Mobile Satellite (LMS) system

    Science.gov (United States)

    Carter, P.; Beach, M. A.

    1993-01-01

    This paper addresses the problem of handoff in a land mobile satellite (LMS) system between adjacent satellites in a low earth orbit (LEO) constellation. In particular, emphasis is placed on the application of soft handoff in a direct sequence code division multiple access (DS-CDMA) LMS system. Soft handoff is explained in terms of terrestrial macroscopic diversity, in which signals transmitted via several independent fading paths are combined to enhance the link quality. This concept is then reconsidered in the context of a LEO LMS system. A two-state Markov channel model is used to simulate the effects of shadowing on the communications path from the mobile to each satellite during handoff. The results of the channel simulation form a platform for discussion regarding soft handoff, highlighting the potential merits of the scheme when applied in a LEO LMS environment.

  7. Effect of Electrodynamic Forces on the Attitude Stabilization of a Satellite in Ecliptic orbits

    Science.gov (United States)

    Abdel-Aziz, Yehia

    This work is based on the previous paper of the author [1]. The present paper is devoted to the investigation of the attitude dynamics of an ecliptic satellite moving in the magnetic field of the Earth. Eelectrodynamic forces result from the motion of a charged satelite relative to the magnetic field of the Earth. The torque due to electrodynamic effect of the Lorentz forces on the attitude stabilization of the satellite is studied with the detailed model of the Earth's magnetic field. A method for estimating the stable and unstable regions of the equilibrium positions based on Euler's equation is also discussed. The results show that Lorentz forces can affect the stablization of the satellite, in particular for highly eccentric orbits and also for large satellte. [1] Abdel-Aziz, Y. A. Attitude Stabilization of a Rigid Spacecraft in the Geomagnetic Field. AdSpR 40, 18-24, 2007.

  8. Mitigating Aviation Communication and Satellite Orbit Operations Surprises from Adverse Space Weather

    Science.gov (United States)

    Tobiska, W. Kent

    2008-01-01

    Adverse space weather affects operational activities in aviation and satellite systems. For example, large solar flares create highly variable enhanced neutral atmosphere and ionosphere electron density regions. These regions impact aviation communication frequencies as well as precision orbit determination. The natural space environment, with its dynamic space weather variability, is additionally changed by human activity. The increase in orbital debris in low Earth orbit (LEO), combined with lower atmosphere CO2 that rises into the lower thermosphere and causes increased cooling that results in increased debris lifetime, adds to the environmental hazards of navigating in near-Earth space. This is at a time when commercial space endeavors are posed to begin more missions to LEO during the rise of the solar activity cycle toward the next maximum (2012). For satellite and aviation operators, adverse space weather results in greater expenses for orbit management, more communication outages or aviation and ground-based high frequency radio used, and an inability to effectively plan missions or service customers with space-based communication, imagery, and data transferal during time-critical activities. Examples of some revenue-impacting conditions and solutions for mitigating adverse space weather are offered.

  9. TEST BED FOR THE SIMULATION OF MAGNETIC FIELD MEASUREMENTS OF LOW EARTH ORBIT SATELLITES

    Directory of Open Access Journals (Sweden)

    Alberto Gallina

    2018-03-01

    Full Text Available The paper presents a test bed designed to simulate magnetic environment experienced by a spacecraft on low Earth orbit. It consists of a spherical air bearing located inside a Helmholtz cage. The spherical air bearing is used for simulating microgravity conditions of orbiting bodies while the Helmholtz cage generates a controllable magnetic field resembling the one surrounding a satellite during its motion. Dedicated computer software is used to initially calculate the magnetic field on an established orbit. The magnetic field data is then translated into current values and transmitted to programmable power supplies energizing the cage. The magnetic field within the cage is finally measured by a test article mounted on the air bearing. The paper provides a description of the test bed and the test article design. An experimental test proves the good performance of the entire system.

  10. Expansion of the South China Sea basin: Constraints from magnetic anomaly stripes, sea floor topography, satellite gravity and submarine geothermics

    Directory of Open Access Journals (Sweden)

    Xuezhong Yu

    2017-01-01

    Full Text Available The widely distributed E–W-trending magnetic anomaly stripes in the central basin and the N–E-trending magnetic anomaly stripes in the southwest sub-basin provide the most important evidence for Neogene expansion of the South China Sea. The expansion mechanism remains, however, controversial because of the lack of direct drilling data, non-systematic marine magnetic survey data, and irregular magnetic anomaly stripes with two obvious directions. For example, researchers have inferred different ages and episodes of expansion for the central basin and southwest sub-basin. Major controversy centers on the order of basinal expansion and the mechanism of expansion for the entire South China Sea basin. This study attempts to constrain these problems from a comprehensive analysis of the seafloor topography, magnetic anomaly stripes, regional aeromagnetic data, satellite gravity, and submarine geothermics. The mapped seafloor terrain shows that the central basin is a north-south rectangle that is relatively shallow with many seamounts, whereas the southwest sub-basin is wide in northeast, gradually narrows to the southwest, and is relatively deeper with fewer seamounts. Many magnetic anomaly stripes are present in the central basin with variable dimensions and directions that are dominantly EW-trending, followed by the NE-, NW- and NS-trending. Conversely such stripes are few in the southwest sub-basin and mainly NE-trending. Regional magnetic data suggest that the NW-trending Ailaoshan-Red River fault extends into the South China Sea, links with the central fault zone in the South China Sea, which extends further southward to Reed Tablemount. Satellite gravity data show that both the central basin and southwest sub-basin are composed of oceanic crust. The Changlong seamount is particularly visible in the southwest sub-basin and extends eastward to the Zhenbei seamount. Also a low gravity anomaly zone coincides with the central fault zone in the sub

  11. Impact of ITRS 2014 realizations on altimeter satellite precise orbit determination

    Science.gov (United States)

    Zelensky, Nikita P.; Lemoine, Frank G.; Beckley, Brian D.; Chinn, Douglas S.; Pavlis, Despina E.

    2018-01-01

    This paper evaluates orbit accuracy and systematic error for altimeter satellite precise orbit determination on TOPEX, Jason-1, Jason-2 and Jason-3 by comparing the use of four SLR/DORIS station complements from the International Terrestrial Reference System (ITRS) 2014 realizations with those based on ITRF2008. The new Terrestrial Reference Frame 2014 (TRF2014) station complements include ITRS realizations from the Institut National de l'Information Géographique et Forestière (IGN) ITRF2014, the Jet Propulsion Laboratory (JPL) JTRF2014, the Deutsche Geodätisches Forschungsinstitut (DGFI) DTRF2014, and the DORIS extension to ITRF2014 for Precise Orbit Determination, DPOD2014. The largest source of error stems from ITRF2008 station position extrapolation past the 2009 solution end time. The TRF2014 SLR/DORIS complement impact on the ITRF2008 orbit is only 1-2 mm RMS radial difference between 1992-2009, and increases after 2009, up to 5 mm RMS radial difference in 2016. Residual analysis shows that station position extrapolation error past the solution span becomes evident even after two years, and will contribute to about 3-4 mm radial orbit error after seven years. Crossover data show the DTRF2014 orbits are the most accurate for the TOPEX and Jason-2 test periods, and the JTRF2014 orbits for the Jason-1 period. However for the 2016 Jason-3 test period only the DPOD2014-based orbits show a strong and statistically significant margin of improvement. The positive results with DTRF2014 suggest the new approach to correct station positions or normal equations for non-tidal loading before combination is beneficial. We did not find any compelling POD advantage in using non-linear over linear station velocity models in our SLR & DORIS orbit tests on the Jason satellites. The JTRF2014 proof-of-concept ITRS realization demonstrates the need for improved SLR+DORIS orbit centering when compared to the Ries (2013) CM annual model. Orbit centering error is seen as an annual

  12. Incipient-signature identification of mechanical anomalies in a ship-borne satellite antenna system using an ensemble multiwavelet

    International Nuclear Information System (INIS)

    He, Shuilong; Zi, Yanyang; Chen, Jinglong; Chen, Binqiang; He, Zhengjia; Zhao, Chenlu; Yuan, Jing

    2014-01-01

    The instrumented tracking and telemetry ship with a ship-borne satellite antenna (SSA) is the critical device to ensure high quality of space exploration work. To effectively detect mechanical anomalies that can lead to unexpected downtime of the SSA, an ensemble multiwavelet (EM) is presented for identifying the anomaly related incipient-signatures within the measured dynamic signals. Rather than using a predetermined basis as in a conventional multiwavelet, an EM optimizes the matching basis which satisfactorily adapts to the anomaly related incipient-signatures. The construction technique of an EM is based on the conjunction of a two-scale similarity transform (TST) and lifting scheme (LS). For the technique above, the TST improves the regularity by increasing the approximation order of multiscaling functions, while subsequently the LS enhances the smoothness and localizability via utilizing the vanishing moment of multiwavelet functions. Moreover, combining the Hilbert transform with EM decomposition, we identify the incipient-signatures induced by the mechanical anomalies from the measured dynamic signals. A numerical simulation and two successful applications of diagnosis cases (a planetary gearbox and a roller bearing) demonstrate that the proposed technique is capable of dealing with the challenging incipient-signature identification task even though spectral complexity, as well as the strong amplitude/frequency modulation effect, is present in the dynamic signals. (paper)

  13. Seth Nicholson's First Satellite Discovery: Jupiter IX and His Orbit for It

    Science.gov (United States)

    Osterbrock, Donald E.

    2006-12-01

    Seth B. Nicholson was a graduate astronomy student at the University of California in Berkeley when he discovered his first satellite in 1914. He was later to discover three more, after he had joined the Mount Wilson Observatory staff following his PhD in 1915. Nicholson had begun his thesis on the problem of computing an improved orbit for J VIII, which had been discovered by Melotte in England in 1908, a distant irregular satellite like J VI and J VII. Nicholson was taking photographic plates to measure the position of J VIII in the summer of 1914 with the Crossley 36-inch reflector of Lick Observatory. He was a teaching assistant at Berkeley that summer, but would go up to Mount Hamilton to observe on weekends in the dark of the moon, traveling by rail, stage (an automobile on a regular schedule between San Jose and the observatory) and interurban trolley car, and sleeping in a shed near the Crossley dome. He first saw J IX as a much fainter object with the same motion as J VIII on a plate he took in late July 1914, and realized it must be another satellite of the giant planet. Nicholson obtained his first orbit of J IX, which had by then become his new thesis topic, in September, and published a paper on it in early 1915. Its orbit, like that of J VIII, was retrograde and irregular, but it was considerably fainter. Nicholson, a loyal student of Armin O. Leuschner, the head of the Berkeley Astronomy Division, used his teacher's "short method" (or analytic method) to calculate the orbit.

  14. SeaTrack: Ground station orbit prediction and planning software for sea-viewing satellites

    Science.gov (United States)

    Lambert, Kenneth S.; Gregg, Watson W.; Hoisington, Charles M.; Patt, Frederick S.

    1993-01-01

    An orbit prediction software package (Sea Track) was designed to assist High Resolution Picture Transmission (HRPT) stations in the acquisition of direct broadcast data from sea-viewing spacecraft. Such spacecraft will be common in the near future, with the launch of the Sea viewing Wide Field-of-view Sensor (SeaWiFS) in 1994, along with the continued Advanced Very High Resolution Radiometer (AVHRR) series on NOAA platforms. The Brouwer-Lyddane model was chosen for orbit prediction because it meets the needs of HRPT tracking accuracies, provided orbital elements can be obtained frequently (up to within 1 week). Sea Track requires elements from the U.S. Space Command (NORAD Two-Line Elements) for the satellite's initial position. Updated Two-Line Elements are routinely available from many electronic sources (some are listed in the Appendix). Sea Track is a menu-driven program that allows users to alter input and output formats. The propagation period is entered by a start date and end date with times in either Greenwich Mean Time (GMT) or local time. Antenna pointing information is provided in tabular form and includes azimuth/elevation pointing angles, sub-satellite longitude/latitude, acquisition of signal (AOS), loss of signal (LOS), pass orbit number, and other pertinent pointing information. One version of Sea Track (non-graphical) allows operation under DOS (for IBM-compatible personal computers) and UNIX (for Sun and Silicon Graphics workstations). A second, graphical, version displays orbit tracks, and azimuth-elevation for IBM-compatible PC's, but requires a VGA card and Microsoft FORTRAN.

  15. Preliminary Products of Precise Orbit Determination Using Satellite Laser Ranging Observations for ILRS AAC

    Directory of Open Access Journals (Sweden)

    Young-Rok Kim

    2012-09-01

    Full Text Available In this study, we present preliminary results of precise orbit determination (POD using satellite laser ranging (SLR observations for International Laser Ranging Service (ILRS Associate Analysis Center (AAC. Using SLR normal point observations of LAGEOS-1, LAGEOS-2, ETALON-1, and ETALON-2, the NASA/GSFC GEODYN II software are utilized for POD. Weekly-based orbit determination strategy is applied to process SLR observations and the post-fit residuals check, and external orbit comparison are performed for orbit accuracy assessment. The root mean square (RMS value of differences between observations and computations after final iteration of estimation process is used for post-fit residuals check. The result of ILRS consolidated prediction format (CPF is used for external orbit comparison. Additionally, we performed the precision analysis of each ILRS station by post-fit residuals. The post-fit residuals results show that the precisions of the orbits of LAGEOS-1 and LAGEOS-2 are 0.9 and 1.3 cm, and those of ETALON-1 and ETALON-2 are 2.5 and 1.9 cm, respectively. The orbit assessment results by ILRS CPF show that the radial accuracies of LAGEOS-1 and LAGEOS-2 are 4.0 cm and 5.3 cm, and the radial accuracies of ETALON-1 and ETALON-2 are 30.7 cm and 7.2 cm. These results of station precision analysis confirm that the result of this study is reasonable to have implications as preliminary results for administrating ILRS AAC.

  16. Paving the Way for Small Satellite Access to Orbit: Cyclops' Deployment of SpinSat, the Largest Satellite Ever Deployed from the International Space Station

    Science.gov (United States)

    Hershey, Matthew P.; Newswander, Daniel R.; Smith, James P.; Lamb, Craig R.; Ballard, Perry G.

    2015-01-01

    The Space Station Integrated Kinetic Launcher for Orbital Payload Systems (SSIKLOPS), known as "Cyclops" to the International Space Station (ISS) community, successfully deployed the largest satellite ever (SpinSat) from the ISS on November 28, 2014. Cyclops, a collaboration between the NASA ISS Program, NASA Johnson Space Center Engineering, and Department of Defense Space Test Program (DoD STP) communities, is a dedicated 10-100 kg class ISS small satellite deployment system. This paper will showcase the successful deployment of SpinSat from the ISS. It will also outline the concept of operations, interfaces, requirements, and processes for satellites to utilize the Cyclops satellite deployment system.

  17. MODVOLC2: A Hybrid Time Series Analysis for Detecting Thermal Anomalies Applied to Thermal Infrared Satellite Data

    Science.gov (United States)

    Koeppen, W. C.; Wright, R.; Pilger, E.

    2009-12-01

    We developed and tested a new, automated algorithm, MODVOLC2, which analyzes thermal infrared satellite time series data to detect and quantify the excess energy radiated from thermal anomalies such as active volcanoes, fires, and gas flares. MODVOLC2 combines two previously developed algorithms, a simple point operation algorithm (MODVOLC) and a more complex time series analysis (Robust AVHRR Techniques, or RAT) to overcome the limitations of using each approach alone. MODVOLC2 has four main steps: (1) it uses the original MODVOLC algorithm to process the satellite data on a pixel-by-pixel basis and remove thermal outliers, (2) it uses the remaining data to calculate reference and variability images for each calendar month, (3) it compares the original satellite data and any newly acquired data to the reference images normalized by their variability, and it detects pixels that fall outside the envelope of normal thermal behavior, (4) it adds any pixels detected by MODVOLC to those detected in the time series analysis. Using test sites at Anatahan and Kilauea volcanoes, we show that MODVOLC2 was able to detect ~15% more thermal anomalies than using MODVOLC alone, with very few, if any, known false detections. Using gas flares from the Cantarell oil field in the Gulf of Mexico, we show that MODVOLC2 provided results that were unattainable using a time series-only approach. Some thermal anomalies (e.g., Cantarell oil field flares) are so persistent that an additional, semi-automated 12-µm correction must be applied in order to correctly estimate both the number of anomalies and the total excess radiance being emitted by them. Although all available data should be included to make the best possible reference and variability images necessary for the MODVOLC2, we estimate that at least 80 images per calendar month are required to generate relatively good statistics from which to run MODVOLC2, a condition now globally met by a decade of MODIS observations. We also found

  18. Measurements of VLF-particle interactions at the South Atlantic Magnetic Anomaly on board a Brazilian geophysical satellite

    International Nuclear Information System (INIS)

    Gonzalez, W.D.; Pinto Junior, O.; Dutra, S.L.G.; Takahashi, H.

    1988-01-01

    A summary of the proposal for measurements of VLF wave-particle interactions, expected to occur at the South Atlantic magnetic anomaly, to be carried out on board a Brazilian geophysical satellite, will be presented. The expected domain of such interactions refers to electromagnetic VLF waves and to energetic-relativistic inner belt electrons, pitch angle diffusing into the atmosphere via cyclotron resonances. The detectors involve a tri-axial search coil magnetometer and a surface barrier silicon telescope. A modified and preliminary version of this proposed experiment will be carried out on board long duration balloon flights, well before the beginning of the intended satellite measurements. For the ballon flights the particle detector will be replaced by an x-ray detector, which can also monitor parameters related to the electron precipitation. (author) [pt

  19. Orbit Determination of GPS and Koreasat 2 Satellite Using Angle-Only Data and Requirements for Optical Tracking System

    Directory of Open Access Journals (Sweden)

    Woo-Kyoung Lee

    2004-09-01

    Full Text Available Gauss method for the initial orbit determination was tested using angle-only data obtained by orbit propagation using TLE and SGP4/SDP4 orbit propagation model. As the analysis of this simulation, a feasible time span between observation time of satellite resulting the minimum error to the true orbit was found. Initial orbit determination is performed using observational data of GPS 26 and Koreasat 2 from 0.6m telescope of KAO(Korea Astronomy Observatory and precise orbit determination is also performed using simulated data. The result of precise orbit determination shows that the accuracy of resulting orbit is related to the accuracy of the observations and the number of data.

  20. Definition of multipath/RFI experiments for orbital testing with a small applications technology satellite

    Science.gov (United States)

    Birch, J. N.; French, R. H.

    1972-01-01

    An investigation was made to define experiments for collection of RFI and multipath data for application to a synchronous relay satellite/low orbiting satellite configuration. A survey of analytical models of the multipath signal was conducted. Data has been gathered concerning the existing RFI and other noise sources in various bands at VHF and UHF. Additionally, designs are presented for equipment to combat the effects of RFI and multipath: an adaptive delta mod voice system, a forward error control coder/decoder, a PN transmission system, and a wideband FM system. The performance of these systems was then evaluated. Techniques are discussed for measuring multipath and RFI. Finally, recommended data collection experiments are presented. An extensive tabulation is included of theoretical predictions of the amount of signal reflected from a rough, spherical earth.

  1. On-orbit real-time magnetometer bias determination for micro-satellites without attitude information

    Directory of Open Access Journals (Sweden)

    Zhang Zhen

    2015-10-01

    Full Text Available Due to the disadvantages such as complex calculation, low accuracy of estimation, and being non real time in present methods, a new real-time algorithm is developed for on-orbit magnetometer bias determination of micro-satellites without attitude knowledge in this paper. This method uses the differential value approach. It avoids the impact of quartic nature and uses the iterative method to satisfy real-time applications. Simulation results indicate that the new real-time algorithm is more accurate compared with other methods, which are also tested by an experiment system using real noise data. With the new real-time algorithm, a magnetometer calibration can be taken on-orbit and will reduce the demand for computing power effectively.

  2. Advanced Communication Technology Satellite (ACTS) Multibeam Antenna On-Orbit Performance

    Science.gov (United States)

    1995-01-01

    The NASA Lewis Research Center's Advanced Communication Technology Satellite (ACTS) was launched in September 1993. ACTS introduced several new technologies, including a multibeam antenna (MBA) operating at extremely short wavelengths never before used in communications. This antenna, which has both fixed and rapidly reconfigurable high-energy spot beams (150 miles in diameter), serves users equipped with small antenna terminals. Extensive structural and thermal analyses have been performed for simulating the ACTS MBA on-orbit performance. The results show that the reflector surfaces (mainly the front subreflector), antenna support assembly, and metallic surfaces on the spacecraft body will be distorted because of the thermal effects of varying solar heating, which degrade the ACTS MBA performance. Since ACTS was launched, a number of evaluations have been performed to assess MBA performance in the space environment. For example, the on-orbit performance measurements found systematic environmental disturbances to the MBA beam pointing. These disturbances were found to be imposed by the attitude control system, antenna and spacecraft mechanical alignments, and on-orbit thermal effects. As a result, the MBA may not always exactly cover the intended service area. In addition, the on-orbit measurements showed that antenna pointing accuracy is the performance parameter most sensitive to thermal distortions on the front subreflector surface and antenna support assemblies. Several compensation approaches were tested and evaluated to restore on-orbit pointing stability. A combination of autotrack (75 percent of the time) and Earth sensor control (25 percent of the time) was found to be the best way to compensate for antenna pointing error during orbit. This approach greatly minimizes the effects of thermal distortions on antenna beam pointing.

  3. Data manage and communication of lunar orbital X-ray imaging analyzer in CE-1 satellite

    International Nuclear Information System (INIS)

    Wang Jinzhou; Wang Huanyu; Zhang Chengmo; Liang Xiaohua; Gao Min; CaoXuelei; Zhang Jiayu; Peng Wenxi; Cui Xingzhu; Xu Yupeng; Zhang Yongjie

    2006-01-01

    We present the software design for data management and communication software designed for the Lunar Orbital X-ray Imaging Analyzer in CE-1 Satellite. The software uses the appropriate format to assemble science data package and appropriate command respond mode, realizes the data transferring tasks through the 1553B bus on time, event though the channel bandwidth is under the limited. Also, the memory distribution and management of LOXIA (remote terminal) that fitted the communication with BC(Bus Controller) was introduced. Furthermore, for the spatial application, the security and reliability of software are emphasized. (authors)

  4. In-Orbit Trend Analysis of Galileo Satellites for Power Sources Degradation Estimation

    Directory of Open Access Journals (Sweden)

    Bard Frederic

    2017-01-01

    The results are in all cases better than the predictions, which is expected due to the usage of conservatives assumptions in the design to cover (for both IOV and FOC worst case scenario for the entire constellation. It should be noted that the FOC GSAT201 and GSAT202 batteries are degrading slightly faster than the 6 others FOC batteries identified GSAT203, GSAT204, GSAT205, GSAT206, GSAT208 and GSAT209, but still below predictions due to their peculiar unexpected orbit reached after launch (higher DoD up to 42% measured due to longer eclipses. These 2 satellites will require specific degradation monitoring.

  5. A Mobile Communications Space Link Between the Space Shuttle Orbiter and the Advanced Communications Technology Satellite

    Science.gov (United States)

    Fink, Patrick; Arndt, G. D.; Bondyopadhyay, P.; Shaw, Roland

    1994-01-01

    A communications experiment is described as a link between the Space Shuttle Orbiter (SSO) and the Advanced Communications Technology Satellite (ACTS). Breadboarding for this experiment has led to two items with potential for commercial application: a 1-Watt Ka-band amplifier and a Ka-band, circularly polarized microstrip antenna. Results of the hybrid Ka-band amplifier show gain at 30 dB and a saturated output power of 28.5 dBm. A second version comprised of MMIC amplifiers is discussed. Test results of the microstrip antenna subarray show a gain of approximately 13 dB and excellent circular polarization.

  6. Comparison of precision orbit derived density estimates for CHAMP and GRACE satellites

    Science.gov (United States)

    Fattig, Eric Dale

    Current atmospheric density models cannot adequately represent the density variations observed by satellites in Low Earth Orbit (LEO). Using an optimal orbit determination process, precision orbit ephemerides (POE) are used as measurement data to generate corrections to density values obtained from existing atmospheric models. Densities obtained using these corrections are then compared to density data derived from the onboard accelerometers of satellites, specifically the CHAMP and GRACE satellites. This comparison takes two forms, cross correlation analysis and root mean square analysis. The densities obtained from the POE method are nearly always superior to the empirical models, both in matching the trends observed by the accelerometer (cross correlation), and the magnitudes of the accelerometer derived density (root mean square). In addition, this method consistently produces better results than those achieved by the High Accuracy Satellite Drag Model (HASDM). For satellites orbiting Earth that pass through Earth's upper atmosphere, drag is the primary source of uncertainty in orbit determination and prediction. Variations in density, which are often not modeled or are inaccurately modeled, cause difficulty in properly calculating the drag acting on a satellite. These density variations are the result of many factors; however, the Sun is the main driver in upper atmospheric density changes. The Sun influences the densities in Earth's atmosphere through solar heating of the atmosphere, as well as through geomagnetic heating resulting from the solar wind. Data are examined for fourteen hour time spans between November 2004 and July 2009 for both the CHAMP and GRACE satellites. This data spans all available levels of solar and geomagnetic activity, which does not include data in the elevated and high solar activity bins due to the nature of the solar cycle. Density solutions are generated from corrections to five different baseline atmospheric models, as well as

  7. Optical Tracking Data Validation and Orbit Estimation for Sparse Observations of Satellites by the OWL-Net.

    Science.gov (United States)

    Choi, Jin; Jo, Jung Hyun; Yim, Hong-Suh; Choi, Eun-Jung; Cho, Sungki; Park, Jang-Hyun

    2018-06-07

    An Optical Wide-field patroL-Network (OWL-Net) has been developed for maintaining Korean low Earth orbit (LEO) satellites' orbital ephemeris. The OWL-Net consists of five optical tracking stations. Brightness signals of reflected sunlight of the targets were detected by a charged coupled device (CCD). A chopper system was adopted for fast astrometric data sampling, maximum 50 Hz, within a short observation time. The astrometric accuracy of the optical observation data was validated with precise orbital ephemeris such as Consolidated Prediction File (CPF) data and precise orbit determination result with onboard Global Positioning System (GPS) data from the target satellite. In the optical observation simulation of the OWL-Net for 2017, an average observation span for a single arc of 11 LEO observation targets was about 5 min, while an average optical observation separation time was 5 h. We estimated the position and velocity with an atmospheric drag coefficient of LEO observation targets using a sequential-batch orbit estimation technique after multi-arc batch orbit estimation. Post-fit residuals for the multi-arc batch orbit estimation and sequential-batch orbit estimation were analyzed for the optical measurements and reference orbit (CPF and GPS data). The post-fit residuals with reference show few tens-of-meters errors for in-track direction for multi-arc batch and sequential-batch orbit estimation results.

  8. Satellite gravity anomalies and crustal features of the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, D.G.; Krishna, K.S.; Neprochnov, Y.P.; Grinko, B.N.

    -air anomalies due to volcanic constructs that trend in arcuate shape from north to south parallel to 82.5 degrees E are noted as southern continuity of the 85 degrees E Ridge, which terminates at the Afanasy Nikitin seamount. Change in rheology of the crustal...

  9. 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...

  10. The impact of the orbital decay of the LAGEOS satellites on the frame-dragging tests

    Science.gov (United States)

    Iorio, Lorenzo

    2016-01-01

    The laser-tracked geodetic satellites LAGEOS, LAGEOS II and LARES are currently employed, among other things, to measure the general relativistic Lense-Thirring effect in the gravitomagnetic field of the spinning Earth with the hope of providing a more accurate test of such a prediction of the Einstein's theory of gravitation than the existing ones. The secular decay a ˙ of the semimajor axes a of such spacecrafts, recently measured in an independent way to a σȧ ≈ 0.1-0.01 m yr-1 accuracy level, may indirectly impact the proposed relativistic experiment through its connection with the classical orbital precessions induced by the Earth's oblateness J2 . Indeed, the systematic bias due to the current measurement errors σȧ is of the same order of magnitude of, or even larger than, the expected relativistic signal itself; moreover, it grows linearly with the time span T of the analysis. Therefore, the parameter-fitting algorithms must be properly updated in order to suitably cope with such a new source of systematic uncertainty. Otherwise, an improvement of one-two orders of magnitude in measuring the orbital decay of the satellites of the LAGEOS family would be required to reduce this source of systematic uncertainty to a percent fraction of the Lense-Thirring signature.

  11. Interpretation of the Total Magnetic Field Anomalies Measured by the CHAMP Satellite Over a Part of Europe and the Pannonian Basin

    Science.gov (United States)

    Kis, K. I.; Taylor, Patrick T.; Wittmann, G.; Toronyi, B.; Puszta, S.

    2012-01-01

    In this study we interpret the magnetic anomalies at satellite altitude over a part of Europe and the Pannonian Basin. These anomalies are derived from the total magnetic measurements from the CHAMP satellite. The anomalies reduced to an elevation of 324 km. An inversion method is used to interpret the total magnetic anomalies over the Pannonian Basin. A three dimensional triangular model is used in the inversion. Two parameter distributions: Laplacian and Gaussian are investigated. The regularized inversion is numerically calculated with the Simplex and Simulated Annealing methods and the anomalous source is located in the upper crust. A probable source of the magnetization is due to the exsolution of the hematite-ilmenite minerals.

  12. Earth Observatory Satellite system definition study. Report no. 1: Orbit/launch vehicle tradeoff studies and recommendations

    Science.gov (United States)

    1974-01-01

    A study was conducted to determine the recommended orbit for the Earth Observatory Satellite (EOS) Land Resources Mission. It was determined that a promising sun synchronous orbit is 366 nautical miles when using an instrument with a 100 nautical mile swath width. The orbit has a 17 day repeat cycle and a 14 nautical mile swath overlap. Payloads were developed for each mission, EOS A through F. For each mission, the lowest cost booster that was capable of lifting the payload to the EOS orbit was selected. The launch vehicles selected for the missions are identified on the basis of tradeoff studies and recommendations. The reliability aspects of the launch vehicles are analyzed.

  13. Use of negotiated rulemaking in developing technical rules for low-Earth orbit mobile satellite systems

    Science.gov (United States)

    Taylor, Leslie A.

    Technical innovations have converged with the exploding market demand for mobile telecommunications to create the impetus for low-earth orbit (LEO) communications satellite systems. The so-called 'Little LEO's' propose use of VHF and UHF spectrum to provide position - location and data messaging services. The so-called 'Big LEO's' propose to utilize the RDSS bands to provide voice and data services. In the United States, several applications were filed with the U.S. Federal Communications Commission (FCC) to construct and operate these mobile satellite systems. To enable the prompt introduction of such new technology services, the FCC is using innovative approaches to process the applications. Traditionally, when the FCC is faced with 'mutually exclusive' applications, e.g. a grant of one would preclude a grant of the others, it uses selection mechanisms such as comparative hearings or lotteries. In the case of the LEO systems, the FCC has sought to avoid these time-consuming approaches by using negotiated rulemakings. The FCC's objective is to enable the multiple applicants and other interested parties to agree on technical and service rules which will enable the grant of all qualified applications. With regard to the VHF/UHF systems, the Advisory Committee submitted a consensus report to the FCC. The process for the systems operating in the bands above 1 GHz involved more parties and more issues but still provided the FCC useful technical information to guide the adoption of rules for the new mobile satellite service.

  14. Forecasting the impact of an 1859-caliber superstorm on geosynchronous Earth-orbiting satellites: Transponder resources

    Science.gov (United States)

    Odenwald, Sten F.; Green, James L.

    2007-06-01

    We calculate the economic impact on the existing geosynchronous Earth-orbiting satellite population of an 1859-caliber superstorm event were it to occur between 2008 and 2018 during the next solar activity cycle. From a detailed model for transponder capacity and leasing, we have investigated the total revenue loss over the entire solar cycle, as a function of superstorm onset year and intensity. Our Monte Carlo simulations of 1000 possible superstorms, of varying intensity and onset year, suggest that the minimum revenue loss could be of the order of 30 billion. The losses would be larger than this if more that 20 satellites are disabled, if future launch rates do not keep up with the expected rate of retirements, or if the number of spare transponders falls below ˜30%. Consequently, revenue losses can be significantly reduced below 30 billion if the current satellite population undergoes net growth beyond 300 units during Solar Cycle 24 and a larger margin of unused transponders is maintained.

  15. Optimizing Orbit-Instrument Configuration for Global Precipitation Mission (GPM) Satellite Fleet

    Science.gov (United States)

    Smith, Eric A.; Adams, James; Baptista, Pedro; Haddad, Ziad; Iguchi, Toshio; Im, Eastwood; Kummerow, Christian; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Following the scientific success of the Tropical Rainfall Measuring Mission (TRMM) spearheaded by a group of NASA and NASDA scientists, their external scientific collaborators, and additional investigators within the European Union's TRMM Research Program (EUROTRMM), there has been substantial progress towards the development of a new internationally organized, global scale, and satellite-based precipitation measuring mission. The highlights of this newly developing mission are a greatly expanded scope of measuring capability and a more diversified set of science objectives. The mission is called the Global Precipitation Mission (GPM). Notionally, GPM will be a constellation-type mission involving a fleet of nine satellites. In this fleet, one member is referred to as the "core" spacecraft flown in an approximately 70 degree inclined non-sun-synchronous orbit, somewhat similar to TRMM in that it carries both a multi-channel polarized passive microwave radiometer (PMW) and a radar system, but in this case it will be a dual frequency Ku-Ka band radar system enabling explicit measurements of microphysical DSD properties. The remainder of fleet members are eight orbit-synchronized, sun-synchronous "constellation" spacecraft each carrying some type of multi-channel PMW radiometer, enabling no worse than 3-hour diurnal sampling over the entire globe. In this configuration the "core" spacecraft serves as a high quality reference platform for training and calibrating the PMW rain retrieval algorithms used with the "constellation" radiometers. Within NASA, GPM has advanced to the pre-formulation phase which has enabled the initiation of a set of science and technology studies which will help lead to the final mission design some time in the 2003 period. This presentation first provides an overview of the notional GPM program and mission design, including its organizational and programmatic concepts, scientific agenda, expected instrument package, and basic flight

  16. 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

  17. M2 ocean tide parameters and the deceleration of the moon's mean longitude from satellite orbit data

    Science.gov (United States)

    Felsentreger, T. L.; Marsh, J. G.; Williamson, R. G.

    1979-01-01

    An estimation is made of the principal long-period spherical harmonic parameters in the representation of the M2 ocean tide from the orbital histories of the three satellites 1967-92A, Starlette, and GEOS 3. The data used are primarily the evolution of the orbital inclinations of the satellites in conjunction with the longitude of the ascending node from GEOS 3. Analysis procedure and analytic formulation, as well as ocean tidal parameter estimation and deceleration of the lunar mean longitude are outlined. The credibility of the M2 ocean tide solution is further enhanced by the close accord between the computed value for the deceleration of the lunar mean longitude and other recently reported estimates. It is evident from the results presented that studies of close earth satellite orbits are able to provide important information about the tidal forces acting on the earth.

  18. A Simple Time Domain Collocation Method to Precisely Search for the Periodic Orbits of Satellite Relative Motion

    Directory of Open Access Journals (Sweden)

    Xiaokui Yue

    2014-01-01

    Full Text Available A numerical approach for obtaining periodic orbits of satellite relative motion is proposed, based on using the time domain collocation (TDC method to search for the periodic solutions of an exact J2 nonlinear relative model. The initial conditions for periodic relative orbits of the Clohessy-Wiltshire (C-W equations or Tschauner-Hempel (T-H equations can be refined with this approach to generate nearly bounded orbits. With these orbits, a method based on the least-squares principle is then proposed to generate projected closed orbit (PCO, which is a reference for the relative motion control. Numerical simulations reveal that the presented TDC searching scheme is effective and simple, and the projected closed orbit is very fuel saving.

  19. Investigating On-Orbit Attitude Determination Anomalies for the Solar Dynamics Observatory Mission

    Science.gov (United States)

    Vess, Melissa F.; Starin, Scott R.; Chia-Kuo, Alice Liu

    2011-01-01

    The Solar Dynamics Observatory (SDO) was launched on February 11, 2010 from Kennedy Space Center on an Atlas V launch vehicle into a geosynchronous transfer orbit. SDO carries a suite of three scientific instruments, whose observations are intended to promote a more complete understanding of the Sun and its effects on the Earth's environment. After a successful launch, separation, and initial Sun acquisition, the launch and flight operations teams dove into a commissioning campaign that included, among other things, checkout and calibration of the fine attitude sensors and checkout of the Kalman filter (KF) and the spacecraft s inertial pointing and science control modes. In addition, initial calibration of the science instruments was also accomplished. During that process of KF and controller checkout, several interesting observations were noticed and investigated. The SDO fine attitude sensors consist of one Adcole Digital Sun Sensor (DSS), two Galileo Avionica (GA) quaternion-output Star Trackers (STs), and three Kearfott Two-Axis Rate Assemblies (hereafter called inertial reference units, or IRUs). Initial checkout of the fine attitude sensors indicated that all sensors appeared to be functioning properly. Initial calibration maneuvers were planned and executed to update scale factors, drift rate biases, and alignments of the IRUs. After updating the IRU parameters, the KF was initialized and quickly reached convergence. Over the next few hours, it became apparent that there was an oscillation in the sensor residuals and the KF estimation of the IRU bias. A concentrated investigation ensued to determine the cause of the oscillations, their effect on mission requirements, and how to mitigate them. The ensuing analysis determined that the oscillations seen were, in fact, due to an oscillation in the IRU biases. The low frequencies of the oscillations passed through the KF, were well within the controller bandwidth, and therefore the spacecraft was actually

  20. Precise orbit determination for BDS3 experimental satellites using iGMAS and MGEX tracking networks

    Science.gov (United States)

    Li, Xingxing; Yuan, Yongqiang; Zhu, Yiting; Huang, Jiande; Wu, Jiaqi; Xiong, Yun; Zhang, Xiaohong; Li, Xin

    2018-04-01

    In this contribution, we focus on the precise orbit determination (POD) for BDS3 experimental satellites with the international GNSS Monitoring and Assessment System (iGMAS) and Multi-GNSS Experiment (MGEX) tracking networks. The datasets of DOY (day of year) 001-230 in 2017 are analyzed with different processing strategies. By comparing receiver clock biases and receiver B1I-B3I DCBs, it is confirmed that there is no obvious systematic bias between experimental BDS3 and BDS2 in the common B1I and B3I signals, which indicates that experimental BDS3 and BDS2 can be treated as one system when performing combined POD. With iGMAS-only BDS3 stations, the 24-h overlap RMS of BDS3 + BDS2 + GPS combined POD is 24.3, 16.1 and 8.4 cm in along-track, cross-track and radial components, which is better than BDS3-only POD by 80-90% and better than BDS3+BDS2 combined POD by about 10%. With more stations (totally 20 stations from both iGMAS and MGEX) and the proper ambiguity resolution strategy (GEO ambiguities are float and BDS3 ambiguities are fixed), the performance of BDS3 POD can be further improved to 14.6, 7.9 and 3.7 cm, respectively, in along-track, cross-track and radial components, which is comparable to the performance of BDS2 POD. The 230-day SLR validations of C32, C33 and C34 show that the mean differences of - 3.48 , 7.81 and 8.19 cm can be achieved, while the STD is 13.35, 13.46 and 13.11 cm, respectively. Furthermore, the 230-day overlap comparisons reveal that C31 most likely still uses an orbit-normal mode and exhibits similar orbit modeling problems in orbit-normal periods as found in most of the BDS2 satellites.

  1. Uncertainty Evaluations of the CRCS In-orbit Field Radiometric Calibration Methods for Thermal Infrared Channels of FENGYUN Meteorological Satellites

    Science.gov (United States)

    Zhang, Y.; Rong, Z.; Min, M.; Hao, X.; Yang, H.

    2017-12-01

    Meteorological satellites have become an irreplaceable weather and ocean-observing tool in China. These satellites are used to monitor natural disasters and improve the efficiency of many sectors of Chinese national economy. It is impossible to ignore the space-derived data in the fields of meteorology, hydrology, and agriculture, as well as disaster monitoring in China, a large agricultural country. For this reason, China is making a sustained effort to build and enhance its meteorological observing system and application system. The first Chinese polar-orbiting weather satellite was launched in 1988. Since then China has launched 14 meteorological satellites, 7 of which are sun synchronous and 7 of which are geostationary satellites; China will continue its two types of meteorological satellite programs. In order to achieve the in-orbit absolute radiometric calibration of the operational meteorological satellites' thermal infrared channels, China radiometric calibration sites (CRCS) established a set of in-orbit field absolute radiometric calibration methods (FCM) for thermal infrared channels (TIR) and the uncertainty of this method was evaluated and analyzed based on TERRA/AQUA MODIS observations. Comparisons between the MODIS at pupil brightness temperatures (BTs) and the simulated BTs at the top of atmosphere using radiative transfer model (RTM) based on field measurements showed that the accuracy of the current in-orbit field absolute radiometric calibration methods was better than 1.00K (@300K, K=1) in thermal infrared channels. Therefore, the current CRCS field calibration method for TIR channels applied to Chinese metrological satellites was with favorable calibration accuracy: for 10.5-11.5µm channel was better than 0.75K (@300K, K=1) and for 11.5-12.5µm channel was better than 0.85K (@300K, K=1).

  2. Building an adaptive agent to monitor and repair the electrical power system of an orbital satellite

    Science.gov (United States)

    Tecuci, Gheorghe; Hieb, Michael R.; Dybala, Tomasz

    1995-01-01

    Over several years we have developed a multistrategy apprenticeship learning methodology for building knowledge-based systems. Recently we have developed and applied our methodology to building intelligent agents. This methodology allows a subject matter expert to build an agent in the same way in which the expert would teach a human apprentice. The expert will give the agent specific examples of problems and solutions, explanations of these solutions, or supervise the agent as it solves new problems. During such interactions, the agent learns general rules and concepts, continuously extending and improving its knowledge base. In this paper we present initial results on applying this methodology to build an intelligent adaptive agent for monitoring and repair of the electrical power system of an orbital satellite, stressing the interaction with the expert during apprenticeship learning.

  3. TCP/IP Interface for the Satellite Orbit Analysis Program (SOAP)

    Science.gov (United States)

    Carnright, Robert; Stodden, David; Coggi, John

    2009-01-01

    The Transmission Control Protocol/ Internet protocol (TCP/IP) interface for the Satellite Orbit Analysis Program (SOAP) provides the means for the software to establish real-time interfaces with other software. Such interfaces can operate between two programs, either on the same computer or on different computers joined by a network. The SOAP TCP/IP module employs a client/server interface where SOAP is the server and other applications can be clients. Real-time interfaces between software offer a number of advantages over embedding all of the common functionality within a single program. One advantage is that they allow each program to divide the computation labor between processors or computers running the separate applications. Secondly, each program can be allowed to provide its own expertise domain with other programs able to use this expertise.

  4. Optical Tracking Data Validation and Orbit Estimation for Sparse Observations of Satellites by the OWL-Net

    Directory of Open Access Journals (Sweden)

    Jin Choi

    2018-06-01

    Full Text Available An Optical Wide-field patroL-Network (OWL-Net has been developed for maintaining Korean low Earth orbit (LEO satellites’ orbital ephemeris. The OWL-Net consists of five optical tracking stations. Brightness signals of reflected sunlight of the targets were detected by a charged coupled device (CCD. A chopper system was adopted for fast astrometric data sampling, maximum 50 Hz, within a short observation time. The astrometric accuracy of the optical observation data was validated with precise orbital ephemeris such as Consolidated Prediction File (CPF data and precise orbit determination result with onboard Global Positioning System (GPS data from the target satellite. In the optical observation simulation of the OWL-Net for 2017, an average observation span for a single arc of 11 LEO observation targets was about 5 min, while an average optical observation separation time was 5 h. We estimated the position and velocity with an atmospheric drag coefficient of LEO observation targets using a sequential-batch orbit estimation technique after multi-arc batch orbit estimation. Post-fit residuals for the multi-arc batch orbit estimation and sequential-batch orbit estimation were analyzed for the optical measurements and reference orbit (CPF and GPS data. The post-fit residuals with reference show few tens-of-meters errors for in-track direction for multi-arc batch and sequential-batch orbit estimation results.

  5. Climatologies from satellite measurements: the impact of orbital sampling on the standard error of the mean

    Directory of Open Access Journals (Sweden)

    M. Toohey

    2013-04-01

    Full Text Available Climatologies of atmospheric observations are often produced by binning measurements according to latitude and calculating zonal means. The uncertainty in these climatological means is characterised by the standard error of the mean (SEM. However, the usual estimator of the SEM, i.e., the sample standard deviation divided by the square root of the sample size, holds only for uncorrelated randomly sampled measurements. Measurements of the atmospheric state along a satellite orbit cannot always be considered as independent because (a the time-space interval between two nearest observations is often smaller than the typical scale of variations in the atmospheric state, and (b the regular time-space sampling pattern of a satellite instrument strongly deviates from random sampling. We have developed a numerical experiment where global chemical fields from a chemistry climate model are sampled according to real sampling patterns of satellite-borne instruments. As case studies, the model fields are sampled using sampling patterns of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS and Atmospheric Chemistry Experiment Fourier-Transform Spectrometer (ACE-FTS satellite instruments. Through an iterative subsampling technique, and by incorporating information on the random errors of the MIPAS and ACE-FTS measurements, we produce empirical estimates of the standard error of monthly mean zonal mean model O3 in 5° latitude bins. We find that generally the classic SEM estimator is a conservative estimate of the SEM, i.e., the empirical SEM is often less than or approximately equal to the classic estimate. Exceptions occur only when natural variability is larger than the random measurement error, and specifically in instances where the zonal sampling distribution shows non-uniformity with a similar zonal structure as variations in the sampled field, leading to maximum sensitivity to arbitrary phase shifts between the sample distribution and

  6. Application of Vision Metrology to In-Orbit Measurement of Large Reflector Onboard Communication Satellite for Next Generation Mobile Satellite Communication

    Science.gov (United States)

    Akioka, M.; Orikasa, T.; Satoh, M.; Miura, A.; Tsuji, H.; Toyoshima, M.; Fujino, Y.

    2016-06-01

    Satellite for next generation mobile satellite communication service with small personal terminal requires onboard antenna with very large aperture reflector larger than twenty meters diameter because small personal terminal with lower power consumption in ground base requires the large onboard reflector with high antenna gain. But, large deployable antenna will deform in orbit because the antenna is not a solid dish but the flexible structure with fine cable and mesh supported by truss. Deformation of reflector shape deteriorate the antenna performance and quality and stability of communication service. However, in case of digital beam forming antenna with phased array can modify the antenna beam performance due to adjustment of excitation amplitude and excitation phase. If we can measure the reflector shape precisely in orbit, beam pattern and antenna performance can be compensated with the updated excitation amplitude and excitation phase parameters optimized for the reflector shape measured every moment. Softbank Corporation and National Institute of Information and Communications Technology has started the project "R&D on dynamic beam control technique for next generation mobile communication satellite" as a contracted research project sponsored by Ministry of Internal Affairs and Communication of Japan. In this topic, one of the problem in vision metrology application is a strong constraints on geometry for camera arrangement on satellite bus with very limited space. On satellite in orbit, we cannot take many images from many different directions as ordinary vision metrology measurement and the available area for camera positioning is quite limited. Feasibility of vision metrology application and general methodology to apply to future mobile satellite communication satellite is to be found. Our approach is as follows: 1) Development of prototyping simulator to evaluate the expected precision for network design in zero order and first order 2) Trial

  7. Simultaneous Laser Ranging and Communication from an Earth-Based Satellite Laser Ranging Station to the Lunar Reconnaissance Orbiter in Lunar Orbit

    Science.gov (United States)

    Sun, Xiaoli; Skillman, David R.; Hoffman, Evan D.; Mao, Dandan; McGarry, Jan F.; Neumann, Gregory A.; McIntire, Leva; Zellar, Ronald S.; Davidson, Frederic M.; Fong, Wai H.; hide

    2013-01-01

    We report a free space laser communication experiment from the satellite laser ranging (SLR) station at NASA Goddard Space Flight Center (GSFC) to the Lunar Reconnaissance Orbiter (LRO) in lunar orbit through the on board one-way Laser Ranging (LR) receiver. Pseudo random data and sample image files were transmitted to LRO using a 4096-ary pulse position modulation (PPM) signal format. Reed-Solomon forward error correction codes were used to achieve error free data transmission at a moderate coding overhead rate. The signal fading due to the atmosphere effect was measured and the coding gain could be estimated.

  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. LauncherOne: Virgin Orbit's Dedicated Launch Vehicle for Small Satellites & Impact to the Space Enterprise Vision

    Science.gov (United States)

    Vaughn, M.; Kwong, J.; Pomerantz, W.

    Virgin Orbit is developing a space transportation service to provide an affordable, reliable, and responsive dedicated ride to orbit for smaller payloads. No longer will small satellite users be forced to make a choice between accepting the limitations of flight as a secondary payload, paying dramatically more for a dedicated launch vehicle, or dealing with the added complexity associated with export control requirements and international travel to distant launch sites. Virgin Orbit has made significant progress towards first flight of a new vehicle that will give satellite developers and operators a better option for carrying their small satellites into orbit. This new service is called LauncherOne (See the figure below). LauncherOne is a two stage, air-launched liquid propulsion (LOX/RP) rocket. Air launched from a specially modified 747-400 carrier aircraft (named “Cosmic Girl”), this system is designed to conduct operations from a variety of locations, allowing customers to select various launch azimuths and increasing available orbital launch windows. This provides small satellite customers an affordable, flexible and dedicated option for access to space. In addition to developing the LauncherOne vehicle, Virgin Orbit has worked with US government customers and across the new, emerging commercial sector to refine concepts for resiliency, constellation replenishment and responsive launch elements that can be key enables for the Space Enterprise Vision (SEV). This element of customer interaction is being led by their new subsidiary company, VOX Space. This paper summarizes technical progress made on LauncherOne in the past year and extends the thinking of how commercial space, small satellites and this new emerging market can be brought to bear to enable true space system resiliency.

  10. K-Band Phased Array Developed for Low- Earth-Orbit Satellite Communications

    Science.gov (United States)

    Anzic, Godfrey

    1999-01-01

    Future rapid deployment of low- and medium-Earth-orbit satellite constellations that will offer various narrow- to wide-band wireless communications services will require phased-array antennas that feature wide-angle and superagile electronic steering of one or more antenna beams. Antennas, which employ monolithic microwave integrated circuits (MMIC), are perfectly suited for this application. Under a cooperative agreement, an MMIC-based, K-band phased-array antenna is being developed with 50/50 cost sharing by the NASA Lewis Research Center and Raytheon Systems Company. The transmitting array, which will operate at 19 gigahertz (GHz), is a state-of-the-art design that features dual, independent, electronically steerable beam operation ( 42 ), a stand-alone thermal management, and a high-density tile architecture. This array can transmit 622 megabits per second (Mbps) in each beam from Earth orbit to small Earth terminals. The weight of the total array package is expected to be less than 8 lb. The tile integration technology (flip chip MMIC tile) chosen for this project represents a major advancement in phased-array engineering and holds much promise for reducing manufacturing costs.

  11. On-line Flagging of Anomalies and Adaptive Sequential Hypothesis Testing for Fine-feature Characterization of Geosynchronous Satellites

    Science.gov (United States)

    Chaudhary, A.; Payne, T.; Kinateder, K.; Dao, P.; Beecher, E.; Boone, D.; Elliott, B.

    The objective of on-line flagging in this paper is to perform interactive assessment of geosynchronous satellites anomalies such as cross-tagging of a satellites in a cluster, solar panel offset change, etc. This assessment will utilize a Bayesian belief propagation procedure and will include automated update of baseline signature data for the satellite, while accounting for the seasonal changes. Its purpose is to enable an ongoing, automated assessment of satellite behavior through its life cycle using the photometry data collected during the synoptic search performed by a ground or space-based sensor as a part of its metrics mission. The change in the satellite features will be reported along with the probabilities of Type I and Type II errors. The objective of adaptive sequential hypothesis testing in this paper is to define future sensor tasking for the purpose of characterization of fine features of the satellite. The tasking will be designed in order to maximize new information with the least number of photometry data points to be collected during the synoptic search by a ground or space-based sensor. Its calculation is based on the utilization of information entropy techniques. The tasking is defined by considering a sequence of hypotheses in regard to the fine features of the satellite. The optimal observation conditions are then ordered in order to maximize new information about a chosen fine feature. The combined objective of on-line flagging and adaptive sequential hypothesis testing is to progressively discover new information about the features of a geosynchronous satellites by leveraging the regular but sparse cadence of data collection during the synoptic search performed by a ground or space-based sensor. Automated Algorithm to Detect Changes in Geostationary Satellite's Configuration and Cross-Tagging Phan Dao, Air Force Research Laboratory/RVB By characterizing geostationary satellites based on photometry and color photometry, analysts can

  12. 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.

  13. Study of high-resolution satellite geoid and gravity anomaly data over the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Majumdar, T. J.; Krishna, K.S.; Chatterjee, S.; Bhattacharya, R.; Michael, L.

    research vessels. Solid line shows location of the profile along which interpreted seismic results and var i- ous products of satellite gravity data are shown in Fi gure 4. RESEARCH COMMUNICATIONS CURRENT SCIENCE, VOL. 90, NO. 2 , 25 JANUARY 2006... depth le v els. Location o f the profile is shown with solid line in Figure 3. of the Bay of Bengal can be reasonably co n sidered in mapping the structural features of the region. Thereby the results can be used to study the tectonics...

  14. An analytic algorithm for global coverage of the revisiting orbit and its application to the CFOSAT satellite

    Science.gov (United States)

    Xu, Ming; Huang, Li

    2014-08-01

    This paper addresses a new analytic algorithm for global coverage of the revisiting orbit and its application to the mission revisiting the Earth within long periods of time, such as Chinese-French Oceanic Satellite (abbr., CFOSAT). In the first, it is presented that the traditional design methodology of the revisiting orbit for some imaging satellites only on the single (ascending or descending) pass, and the repeating orbit is employed to perform the global coverage within short periods of time. However, the selection of the repeating orbit is essentially to yield the suboptimum from the rare measure of rational numbers of passes per day, which will lose lots of available revisiting orbits. Thus, an innovative design scheme is proposed to check both rational and irrational passes per day to acquire the relationship between the coverage percentage and the altitude. To improve the traditional imaging only on the single pass, the proposed algorithm is mapping every pass into its ascending and descending nodes on the specified latitude circle, and then is accumulating the projected width on the circle by the field of view of the satellite. The ergodic geometry of coverage percentage produced from the algorithm is affecting the final scheme, such as the optimal one owning the largest percentage, and the balance one possessing the less gradient in its vicinity, and is guiding to heuristic design for the station-keeping control strategies. The application of CFOSAT validates the feasibility of the algorithm.

  15. The CACAO Method for Smoothing, Gap Filling, and Characterizing Seasonal Anomalies in Satellite Time Series

    Science.gov (United States)

    Verger, Aleixandre; Baret, F.; Weiss, M.; Kandasamy, S.; Vermote, E.

    2013-01-01

    Consistent, continuous, and long time series of global biophysical variables derived from satellite data are required for global change research. A novel climatology fitting approach called CACAO (Consistent Adjustment of the Climatology to Actual Observations) is proposed to reduce noise and fill gaps in time series by scaling and shifting the seasonal climatological patterns to the actual observations. The shift and scale CACAO parameters adjusted for each season allow quantifying shifts in the timing of seasonal phenology and inter-annual variations in magnitude as compared to the average climatology. CACAO was assessed first over simulated daily Leaf Area Index (LAI) time series with varying fractions of missing data and noise. Then, performances were analyzed over actual satellite LAI products derived from AVHRR Long-Term Data Record for the 1981-2000 period over the BELMANIP2 globally representative sample of sites. Comparison with two widely used temporal filtering methods-the asymmetric Gaussian (AG) model and the Savitzky-Golay (SG) filter as implemented in TIMESAT-revealed that CACAO achieved better performances for smoothing AVHRR time series characterized by high level of noise and frequent missing observations. The resulting smoothed time series captures well the vegetation dynamics and shows no gaps as compared to the 50-60% of still missing data after AG or SG reconstructions. Results of simulation experiments as well as confrontation with actual AVHRR time series indicate that the proposed CACAO method is more robust to noise and missing data than AG and SG methods for phenology extraction.

  16. Lithospheric thickness jumps at the S-Atlantic continental margins from satellite gravity data and modelled isostatic anomalies

    Science.gov (United States)

    Shahraki, Meysam; Schmeling, Harro; Haas, Peter

    2018-01-01

    Isostatic equilibrium is a good approximation for passive continental margins. In these regions, geoid anomalies are proportional to the local dipole moment of density-depth distributions, which can be used to constrain the amount of oceanic to continental lithospheric thickening (lithospheric jumps). We consider a five- or three-layer 1D model for the oceanic and continental lithosphere, respectively, composed of water, a sediment layer (both for the oceanic case), the crust, the mantle lithosphere and the asthenosphere. The mantle lithosphere is defined by a mantle density, which is a function of temperature and composition, due to melt depletion. In addition, a depth-dependent sediment density associated with compaction and ocean floor variation is adopted. We analyzed satellite derived geoid data and, after filtering, extracted typical averaged profiles across the Western and Eastern passive margins of the South Atlantic. They show geoid jumps of 8.1 m and 7.0 m for the Argentinian and African sides, respectively. Together with topography data and an averaged crustal density at the conjugate margins these jumps are interpreted as isostatic geoid anomalies and yield best-fitting crustal and lithospheric thicknesses. In a grid search approach five parameters are systematically varied, namely the thicknesses of the sediment layer, the oceanic and continental crusts and the oceanic and the continental mantle lithosphere. The set of successful models reveals a clear asymmetry between the South Africa and Argentine lithospheres by 15 km. Preferred models predict a sediment layer at the Argentine margin of 3-6 km and at the South Africa margin of 1-2.5 km. Moreover, we derived a linear relationship between, oceanic lithosphere, sediment thickness and lithospheric jumps at the South Atlantic margins. It suggests that the continental lithospheres on the western and eastern South Atlantic are thicker by 45-70 and 60-80 km than the oceanic lithospheres, respectively.

  17. 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.

  18. Kinematic Orbit Determination Method Optimization and Test Analysis for BDS Satellites with Short-arc Tracking Data

    Directory of Open Access Journals (Sweden)

    GUO Rui

    2017-04-01

    Full Text Available Rapid orbit recovery is a puzzle for the BDS satellites after orbit maneuvers. Two kinematic orbit determination methods are studied, with two orbit determination models being established. The receiver system error and serious multipath error exist in the BDS system. The co-location method is proposed to estimate and calibrate the receiver system errors. A CNMC (code noise and multipath correction method is introduced to weaken the multipath error. Therefore the data quality is controlled efficiently for the receivers in the short tracking arc. The GEO/IGSO/MEO real data is emploied to carry out tests and validation. Using 10 min short tracking arc, the kinematic precise orbit determination accuracy is about 3.27 m for the GEOs, and 8.19 m for the IGSOs, and 5.9 m for the MEOs. Rapid orbit determination is achieved, which satisfying the orbit requirements from the BDS RDSS services. The kinematic precise orbit determination method also supports the RDSS service walking up to the global world.

  19. Comparison of satellite altimetry sea level anomalies and hydrographic observations in the Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    Francisco Mir Calafat

    2012-08-01

    Full Text Available Steric sea level (SSL computed from hydrographic observations in the Mediterranean Sea is compared against altimetric sea level anomalies (SLA at seasonal and inter-annual time scales for the period 1993-2008. SSL (referenced to 300 m is computed using two data sets: in situ profiles and gridded products obtained from interpolated observations. The impact of expendable/mechanical bathythermograph (XBT/MBT biases affecting some of the in situ profiles is investigated by comparing both corrected and uncorrected data. For the period 2003-2008 the mass component is estimated from GRACE observations and subtracted from SLA. The analysis of the spatio-temporal distribution of profiles shows that the number of profiles with data below 300 m is a small percentage of the total and that their spatial coverage of the Mediterranean basin is very limited. This is an important handicap for regions where the contribution of the deep layers to SSL is significant. Overall, SSL and SLA are shown to be consistent in the Mediterranean at seasonal time scales, although the annual amplitude of the SSL from in situ profiles and interpolated data is considerably smaller than that of the SLA. The agreement at inter-annual time scales is less good. At some particular locations SSL computed from individual profiles is more correlated with SLA than the gridded products. At basin and sub-basin scales, however, interpolated and in situ observations provide similar results in terms of their correlation with observed SLA. The XBT/MBT bias corrections have little effect on the SSL at the time scales considered in this study.

  20. Small-Body Extensions for the Satellite Orbit Analysis Program (SOAP)

    Science.gov (United States)

    Carnright, Robert; Stodden, David; Coggi, John

    2008-01-01

    An extension to the SOAP software allows users to work with tri-axial ellipsoid-based representations of planetary bodies, primarily for working with small, natural satellites, asteroids, and comets. SOAP is a widely used tool for the visualization and analysis of space missions. The small body extension provides the same visualization and analysis constructs for use with small bodies. These constructs allow the user to characterize satellite path and instrument cover information for small bodies in both 3D display and numerical output formats. Tri-axial ellipsoids are geometric shapes the diameters of which are different in each of three principal x, y, and z dimensions. This construct provides a better approximation than using spheres or oblate spheroids (ellipsoids comprising two common equatorial diameters as a distinct polar diameter). However, the tri-axial ellipsoid is considerably more difficult to work with from a modeling perspective. In addition, the SOAP small-body extensions allow the user to actually employ a plate model for highly irregular surfaces. Both tri-axial ellipsoids and plate models can be assigned to coordinate frames, thus allowing for the modeling of arbitrary changes to body orientation. A variety of features have been extended to support tri-axial ellipsoids, including the computation and display of the spacecraft sub-orbital point, ground trace, instrument footprints, and swathes. Displays of 3D instrument volumes can be shown interacting with the ellipsoids. Longitude/latitude grids, contour plots, and texture maps can be displayed on the ellipsoids using a variety of projections. The distance along an arbitrary line of sight can be computed between the spacecraft and the ellipsoid, and the coordinates of that intersection can be plotted as a function of time. The small-body extension supports the same visual and analytical constructs that are supported for spheres and oblate spheroids in SOAP making the implementation of the more

  1. Orbital

    OpenAIRE

    Yourshaw, Matthew Stephen

    2017-01-01

    Orbital is a virtual reality gaming experience designed to explore the use of traditional narrative structure to enhance immersion in virtual reality. The story structure of Orbital was developed based on the developmental steps of 'The Hero's Journey,' a narrative pattern identified by Joseph Campbell. Using this standard narrative pattern, Orbital is capable of immersing the player quickly and completely for the entirety of play time. MFA

  2. A probabilistic analysis of the implications of instrument failures on ESA's Swarm mission for its individual satellite orbit deployments

    Science.gov (United States)

    Jackson, Andrew

    2015-07-01

    On launch, one of Swarm's absolute scalar magnetometers (ASMs) failed to function, leaving an asymmetrical arrangement of redundant spares on different spacecrafts. A decision was required concerning the deployment of individual satellites into the low-orbit pair or the higher "lonely" orbit. I analyse the probabilities for successful operation of two of the science components of the Swarm mission in terms of a classical probabilistic failure analysis, with a view to concluding a favourable assignment for the satellite with the single working ASM. I concentrate on the following two science aspects: the east-west gradiometer aspect of the lower pair of satellites and the constellation aspect, which requires a working ASM in each of the two orbital planes. I use the so-called "expert solicitation" probabilities for instrument failure solicited from Mission Advisory Group (MAG) members. My conclusion from the analysis is that it is better to have redundancy of ASMs in the lonely satellite orbit. Although the opposite scenario, having redundancy (and thus four ASMs) in the lower orbit, increases the chance of a working gradiometer late in the mission; it does so at the expense of a likely constellation. Although the results are presented based on actual MAG members' probabilities, the results are rather generic, excepting the case when the probability of individual ASM failure is very small; in this case, any arrangement will ensure a successful mission since there is essentially no failure expected at all. Since the very design of the lower pair is to enable common mode rejection of external signals, it is likely that its work can be successfully achieved during the first 5 years of the mission.

  3. Evaluation of DNA bending models in their capacity to predict electrophoretic migration anomalies of satellite DNA sequences.

    Science.gov (United States)

    Matyášek, Roman; Fulneček, Jaroslav; Kovařík, Aleš

    2013-09-01

    DNA containing a sequence that generates a local curvature exhibits a pronounced retardation in electrophoretic mobility. Various theoretical models have been proposed to explain relationship between DNA structural features and migration anomaly. Here, we studied the capacity of 15 static wedge-bending models to predict electrophoretic behavior of 69 satellite monomers derived from four divergent families. All monomers exhibited retarded mobility in PAGE corresponding to retardation factors ranging 1.02-1.54. The curvature varied both within and across the groups and correlated with the number, position, and lengths of A-tracts. Two dinucleotide models provided strong correlation between gel mobility and curvature prediction; two trinucleotide models were satisfactory while remaining dinucleotide models provided intermediate results with reliable prediction for subsets of sequences only. In some cases, similarly shaped molecules exhibited relatively large differences in mobility and vice versa. Generally less accurate predictions were obtained in groups containing less homogeneous sequences possessing distinct structural features. In conclusion, relatively universal theoretical models were identified suitable for the analysis of natural sequences known to harbor relatively moderate curvature. These models could be potentially applied to genome wide studies. However, in silico predictions should be viewed in context of experimental measurement of intrinsic DNA curvature. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Cosmic rays and other space weather effects influenced on satellite operation, technologies, biosphere and people health

    Science.gov (United States)

    Lev, Dorman

    2016-07-01

    Satellite anomalies (or malfunctions), including total distortion of electronics and loose of some satellites cost for Insurance Companies billions dollars per year. During especially active periods the probability of big satellite anomalies and their loosing increased very much. Now, when a great number of civil and military satellites are continuously worked for our practice life, the problem of satellite anomalies became very important. Many years ago about half of satellite anomalies were caused by technical reasons (for example, for Russian satellites Kosmos), but with time with increasing of production quality, this part became smaller and smaller. The other part, which now is dominated, caused by different space weather effects (energetic particles of CR and generated/trapped in the magnetosphere, and so on). We consider only satellite anomalies not caused by technical reasons: the total number of such anomalies about 6000 events, and separately for high and low altitude orbit satellites (5000 and about 800 events, correspondingly for high and low altitude satellites). No relation was found between low and high altitude satellite anomalies. Daily numbers of satellite anomalies, averaged by a superposed epoch method around sudden storm commencements and solar proton event onsets for high (>1500 km) and low (railway operation (possible, through induction currents), catastrophes in long-distance electric power lines and transformators, and in other ground technologies.

  5. Orbit and clock determination of BDS regional navigation satellite system based on IGS M-GEX and WHU BETS tracking network

    Science.gov (United States)

    GENG, T.; Zhao, Q.; Shi, C.; Shum, C.; Guo, J.; Su, X.

    2013-12-01

    BeiDou Navigation Satellite System (BDS) began to provide the regional open service on December 27th 2012 and will provide the global open service by the end of 2020. Compared to GPS, the space segment of BDS Regional System consists of 5 Geostationary Earth Orbit satellites (GEO), 5 Inclined Geosynchronous Orbit satellites (IGSO) and 4 Medium Earth orbit (MEO) satellites. Since 2011, IGS Multiple-GNSS Experiment (M-GEX) focuses on tracking the newly available GNSS signals. This includes all signals from the modernized satellites of the GPS and GLONASS systems, as well as signals of the BDS, Galileo and QZSS systems. Up to now, BDS satellites are tracked by around 25 stations with a variety of different antennas and receivers from different GNSS manufacture communities in M-GEX network. Meanwhile, there are 17 stations with Unicore Communications Incorporation's GPS/BDS receivers in BeiDou Experimental Tracking Stations (BETS) network by Wuhan University. In addition, 5 BDS satellites have been tracking by the International Laser Ranging Service (ILRS). BDS performance is expected to be further studied by the GNSS communities. Following an introduction of the BDS system and above different tracking network, this paper discusses the achieved BDS characterization and performance assessment. Firstly, the BDS signal and measurement quality are analyzed with different antennas and receivers in detail compared to GPS. This includes depth of coverage for satellite observation, carrier-to-noise-density ratios, code noise and multipath, carrier phase errors. Secondly, BDS Precise Orbit Determination (POD) is processed. Different arc lengths and sets of orbit parameters are tested using Position And Navigation Data Analysis software (PANDA) which is developed at the Wuhan University. GEO, IGSO and MEO satellites orbit quality will be assessed using overlap comparison, 2-day orbit fit and external validations with Satellite Laser Range (SLR). Then BDS satellites are equipped

  6. Power system design and in orbit performance of Algeria's first micro satellite Alsat-1

    Energy Technology Data Exchange (ETDEWEB)

    Bekhti, Mohammed [Centre National des Techniques Spatiales, BP13, Arzew 31200 (Algeria); Sweeting, M.N. [Centre for Satellite Engineering Research, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom)

    2008-07-15

    On the 28th November 2002, Algeria's first enhanced micro satellite was launched into a 686 km low earth orbit onboard a Cosmos 3M rocket from Plesetsk. The spacecraft was designed, manufactured and launched as a technology transfer programme between the National Centre of Space Techniques (CNTS) Algeria and Surrey Satellite Technology Limited (SSTL) United Kingdom in the timescale of 18 months. This paper will describe the design and in orbit performance of the mission power system, stressing the decisions taken in order to meet the mission requirements within the 18 months, concept to launch programme. Most of the design and construction techniques used in the production of the Alsat-1 power system were based on SSTL heritage over the years. It will be shown how off the shelf components either for the generation or storage of the onboard energy can be applied successfully to such missions. (author)

  7. Satellites

    International Nuclear Information System (INIS)

    Burns, J.A.; Matthews, M.S.

    1986-01-01

    The present work is based on a conference: Natural Satellites, Colloquium 77 of the IAU, held at Cornell University from July 5 to 9, 1983. Attention is given to the background and origins of satellites, protosatellite swarms, the tectonics of icy satellites, the physical characteristics of satellite surfaces, and the interactions of planetary magnetospheres with icy satellite surfaces. Other topics include the surface composition of natural satellites, the cratering of planetary satellites, the moon, Io, and Europa. Consideration is also given to Ganymede and Callisto, the satellites of Saturn, small satellites, satellites of Uranus and Neptune, and the Pluto-Charon system

  8. 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

  9. Precise orbit determination of the Sentinel-3A altimetry satellite using ambiguity-fixed GPS carrier phase observations

    Science.gov (United States)

    Montenbruck, Oliver; Hackel, Stefan; Jäggi, Adrian

    2017-11-01

    The Sentinel-3 mission takes routine measurements of sea surface heights and depends crucially on accurate and precise knowledge of the spacecraft. Orbit determination with a targeted uncertainty of less than 2 cm in radial direction is supported through an onboard Global Positioning System (GPS) receiver, a Doppler Orbitography and Radiopositioning Integrated by Satellite instrument, and a complementary laser retroreflector for satellite laser ranging. Within this study, the potential of ambiguity fixing for GPS-only precise orbit determination (POD) of the Sentinel-3 spacecraft is assessed. A refined strategy for carrier phase generation out of low-level measurements is employed to cope with half-cycle ambiguities in the tracking of the Sentinel-3 GPS receiver that have so far inhibited ambiguity-fixed POD solutions. Rather than explicitly fixing double-difference phase ambiguities with respect to a network of terrestrial reference stations, a single-receiver ambiguity resolution concept is employed that builds on dedicated GPS orbit, clock, and wide-lane bias products provided by the CNES/CLS (Centre National d'Études Spatiales/Collecte Localisation Satellites) analysis center of the International GNSS Service. Compared to float ambiguity solutions, a notably improved precision can be inferred from laser ranging residuals. These decrease from roughly 9 mm down to 5 mm standard deviation for high-grade stations on average over low and high elevations. Furthermore, the ambiguity-fixed orbits offer a substantially improved cross-track accuracy and help to identify lateral offsets in the GPS antenna or center-of-mass (CoM) location. With respect to altimetry, the improved orbit precision also benefits the global consistency of sea surface measurements. However, modeling of the absolute height continues to rely on proper dynamical models for the spacecraft motion as well as ground calibrations for the relative position of the altimeter reference point and the CoM.

  10. OLFAR, a radio telescope based on nano satellites in moon orbit

    NARCIS (Netherlands)

    Engelen, S.; Verhoeven, C.J.M.; Bentum, Marinus Jan

    2010-01-01

    It seems very likely that missions with nano-satellites in professional scientific or commercial applications will not be single-satellite missions. Well structured formations or less structured swarms of nano-satellites will be able to perform tasks that cannot be done in the “traditional‿ way. The

  11. Asteroid Origins Satellite (AOSAT) I: An On-orbit Centrifuge Science Laboratory

    Science.gov (United States)

    Lightholder, Jack; Thoesen, Andrew; Adamson, Eric; Jakubowski, Jeremy; Nallapu, Ravi; Smallwood, Sarah; Raura, Laksh; Klesh, Andrew; Asphaug, Erik; Thangavelautham, Jekan

    2017-04-01

    Exploration of asteroids, comets and small moons (small bodies) can answer fundamental questions relating to the formation of the solar system, the availability of resources, and the nature of impact hazards. Near-earth asteroids and the small moons of Mars are potential targets of human exploration. But as illustrated by recent missions, small body surface exploration remains challenging, expensive, and fraught with risk. Despite their small size, they are among the most extreme planetary environments, with low and irregular gravity, loosely bound regolith, extreme temperature variation, and the presence of electrically charged dust. Here we describe the Asteroid Origins Satellite (AOSAT-I), an on-orbit, 3U CubeSat centrifuge using a sandwich-sized bed of crushed meteorite fragments to replicate asteroid surface conditions. Demonstration of this CubeSat will provide a low-cost pathway to physical asteroid model validation, shed light on the origin and geophysics of asteroids, and constrain the design of future landers, rovers, resource extractors, and human missions. AOSAT-I will conduct scientific experiments within its payload chamber while operating in two distinct modes: (1) as a nonrotating microgravity laboratory to investigate primary accretion, and (2) as a rotating centrifuge producing artificial milligravity to simulate surface conditions on asteroids, comets and small moons. AOSAT-I takes advantage of low-cost, off-the-shelf components, modular design, and the rapid assembly and instrumentation of the CubeSat standard, to answer fundamental questions in planetary science and reduce cost and risk of future exploration.

  12. Effects of Orbital Lifetime Reduction on the Long-Term Earth Satellite Population as Modeled by EVOLVE 4.0

    Science.gov (United States)

    Krisko, Paula H.; Opiela, John N.; Liou, Jer-Chyi; Anz-Meador, Phillip D.; Theall, Jeffrey R.

    1999-01-01

    The latest update of the NASA orbital debris environment model, EVOLVE 4.0, has been used to study the effect of various proposed debris mitigation measures, including the NASA 25-year guideline. EVOLVE 4.0, which includes updates of the NASA breakup, solar activity, and the orbit propagator models, a GEO analysis option, and non-fragmentation debris source models, allows for the statistical modeling and predicted growth of the particle population >1 mm in characteristic length in LEO and GEO orbits. The initial implementation of this &odel has been to study the sensitivity of the overall LEO debris environment to mitigation measures designed to limit the lifetime of intact objects in LEO orbits. The mitigation measures test matrix for this study included several commonly accepted testing schemes, i.e., the variance of the maximum LEO lifetime from 10 to 50 years, the date of the initial implementation of this policy, the shut off of all explosions at some specified date, and the inclusion of disposal orbits. All are timely studies in that all scenarios have been suggested by researchers and satellite operators as options for the removal of debris from LEO orbits.

  13. A Novel Double Cluster and Principal Component Analysis-Based Optimization Method for the Orbit Design of Earth Observation Satellites

    Directory of Open Access Journals (Sweden)

    Yunfeng Dong

    2017-01-01

    Full Text Available The weighted sum and genetic algorithm-based hybrid method (WSGA-based HM, which has been applied to multiobjective orbit optimizations, is negatively influenced by human factors through the artificial choice of the weight coefficients in weighted sum method and the slow convergence of GA. To address these two problems, a cluster and principal component analysis-based optimization method (CPC-based OM is proposed, in which many candidate orbits are gradually randomly generated until the optimal orbit is obtained using a data mining method, that is, cluster analysis based on principal components. Then, the second cluster analysis of the orbital elements is introduced into CPC-based OM to improve the convergence, developing a novel double cluster and principal component analysis-based optimization method (DCPC-based OM. In DCPC-based OM, the cluster analysis based on principal components has the advantage of reducing the human influences, and the cluster analysis based on six orbital elements can reduce the search space to effectively accelerate convergence. The test results from a multiobjective numerical benchmark function and the orbit design results of an Earth observation satellite show that DCPC-based OM converges more efficiently than WSGA-based HM. And DCPC-based OM, to some degree, reduces the influence of human factors presented in WSGA-based HM.

  14. Initial Results from On-Orbit Testing of the Fram Memory Test Experiment on the Fastsat Micro-Satellite

    Science.gov (United States)

    MacLeond, Todd C.; Sims, W. Herb; Varnavas,Kosta A.; Ho, Fat D.

    2011-01-01

    The Memory Test Experiment is a space test of a ferroelectric memory device on a low Earth orbit satellite that launched in November 2010. The memory device being tested is a commercial Ramtron Inc. 512K memory device. The circuit was designed into the satellite avionics and is not used to control the satellite. The test consists of writing and reading data with the ferroelectric based memory device. Any errors are detected and are stored on board the satellite. The data is sent to the ground through telemetry once a day. Analysis of the data can determine the kind of error that was found and will lead to a better understanding of the effects of space radiation on memory systems. The test is one of the first flight demonstrations of ferroelectric memory in a near polar orbit which allows testing in a varied radiation environment. The initial data from the test is presented. This paper details the goals and purpose of this experiment as well as the development process. The process for analyzing the data to gain the maximum understanding of the performance of the ferroelectric memory device is detailed.

  15. Design Concepts for a Small Space-Based GEO Relay Satellite for Missions Between Low Earth and near Earth Orbits

    Science.gov (United States)

    Bhasin, Kul B.; Warner, Joseph D.; Oleson, Steven; Schier, James

    2014-01-01

    The main purpose of the Small Space-Based Geosynchronous Earth orbiting (GEO) satellite is to provide a space link to the user mission spacecraft for relaying data through ground networks to user Mission Control Centers. The Small Space Based Satellite (SSBS) will provide services comparable to those of a NASA Tracking Data Relay Satellite (TDRS) for the same type of links. The SSBS services will keep the user burden the same or lower than for TDRS and will support the same or higher data rates than those currently supported by TDRS. At present, TDRSS provides links and coverage below GEO; however, SSBS links and coverage capability to above GEO missions are being considered for the future, especially for Human Space Flight Missions (HSF). There is also a rising need for the capability to support high data rate links (exceeding 1 Gbps) for imaging applications. The communication payload on the SSBS will provide S/Ka-band single access links to the mission and a Ku-band link to the ground, with an optical communication payload as an option. To design the communication payload, various link budgets were analyzed and many possible operational scenarios examined. To reduce user burden, using a larger-sized antenna than is currently in use by TDRS was considered. Because of the SSBS design size, it was found that a SpaceX Falcon 9 rocket could deliver three SSBSs to GEO. This will greatly reduce the launch costs per satellite. Using electric propulsion was also evaluated versus using chemical propulsion; the power system size and time to orbit for various power systems were also considered. This paper will describe how the SSBS will meet future service requirements, concept of operations, and the design to meet NASA users' needs for below and above GEO missions. These users' needs not only address the observational mission requirements but also possible HSF missions to the year 2030. We will provide the trade-off analysis of the communication payload design in terms of

  16. A 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

    Science.gov (United States)

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

    1976-01-01

    In 1918, Lense and Thirring calculated that a moon in orbit around a massive rotating planet would experience a nodal dragging effect due to general relativity. We describe an experiment to measure this effect by means of two counter-orbiting drag-free satellites in polar orbit about the earth. For a 2-1/2 year experiment, the measurement should approach an accuracy of 1%. An independent measurement of the geodetic precession of the orbit plane due to the motion about the sun may also be possible to about 10% accuracy. In addition to precision tracking data from existing ground stations, satellite-to-satellite Doppler data are taken at points of passing near the poles to yield an accurate measurement of the separation distance between the two satellites. New geophysical information on both earth harmonics and tidal effects is inherent in this polar ranging data.

  17. Optical Orbit Determination of a Geosynchronous Earth Orbit Satellite Effected by Baseline Distances between Various Ground-based Tracking Stations Ⅱ: COMS Case with Analysis of Actual Observation Data

    Directory of Open Access Journals (Sweden)

    Ju Young Son

    2015-09-01

    Full Text Available We estimated the orbit of the Communication, Ocean and Meteorological Satellite (COMS, a Geostationary Earth Orbit (GEO satellite, through data from actual optical observations using telescopes at the Sobaeksan Optical Astronomy Observatory (SOAO of the Korea Astronomy and Space Science Institute (KASI, Optical Wide field Patrol (OWL at KASI, and the Chungbuk National University Observatory (CNUO from August 1, 2014, to January 13, 2015. The astrometric data of the satellite were extracted from the World Coordinate System (WCS in the obtained images, and geometrically distorted errors were corrected. To handle the optically observed data, corrections were made for the observation time, light-travel time delay, shutter speed delay, and aberration. For final product, the sequential filter within the Orbit Determination Tool Kit (ODTK was used for orbit estimation based on the results of optical observation. In addition, a comparative analysis was conducted between the precise orbit from the ephemeris of the COMS maintained by the satellite operator and the results of orbit estimation using optical observation. The orbits estimated in simulation agree with those estimated with actual optical observation data. The error in the results using optical observation data decreased with increasing number of observatories. Our results are useful for optimizing observation data for orbit estimation.

  18. On the Accuracy of the Conjugation of High-Orbit Satellites with Small-Scale Regions in the Ionosphere

    Science.gov (United States)

    Safargaleev, V. V.; Safargaleeva, N. N.

    2018-03-01

    The degree of uncertainty that arises when mapping high-orbit satellites of the Cluster type into the ionosphere using three geomagnetic field models (T89, T98, and T01) has been estimated. Studies have shown that uncertainty is minimal in situations when a satellite in the daytime is above the equatorial plane of the magnetosphere at the distance of no more than 5 R E from the Earth's surface and is projected into the ionosphere of the northern hemisphere. In this case, the dimensions of the uncertainty region are about 50 km, and the arbitrariness of the choice of the model for projecting does not play a decisive role in organizing satellite support based on optical observations when studying such large-scale phenomena as, e.g., WTS, as well as heating experiments at the EISCAT heating facility for the artificial modification of the ionosphere and the generation of artificial fluctuations in the VLF band. In all other cases, the uncertainty in determining the position of the base of the field line on which the satellite is located is large, and additional information is required to correctly compare the satellite with the object in the ionosphere.

  19. GPM GROUND VALIDATION SATELLITE SIMULATED ORBITS MC3E V1

    Data.gov (United States)

    National Aeronautics and Space Administration — The Satellite Simulator database is available for several campaigns: Light Precipitation Evaluation Experiment (LPVEX), Midlatitude Continental Convective Clouds...

  20. GPM GROUND VALIDATION SATELLITE SIMULATED ORBITS TWP-ICE V1

    Data.gov (United States)

    National Aeronautics and Space Administration — The Satellite Simulator database is available for several campaigns: Light Precipitation Evaluation Experiment (LPVEX), Midlatitude Continental Convective Clouds...

  1. GPM GROUND VALIDATION SATELLITE SIMULATED ORBITS C3VP V1

    Data.gov (United States)

    National Aeronautics and Space Administration — The Satellite Simulator database is available for several campaigns: Light Precipitation Evaluation Experiment (LPVEX), Midlatitude Continental Convective Clouds...

  2. Atmospheric influences on infrared-laser signals used for occultation measurements between Low Earth Orbit satellites

    Directory of Open Access Journals (Sweden)

    S. Schweitzer

    2011-10-01

    Full Text Available LEO-LEO infrared-laser occultation (LIO is a new occultation technique between Low Earth Orbit (LEO satellites, which applies signals in the short wave infrared spectral range (SWIR within 2 μm to 2.5 μm. It is part of the LEO-LEO microwave and infrared-laser occultation (LMIO method that enables to retrieve thermodynamic profiles (pressure, temperature, humidity and altitude levels from microwave signals and profiles of greenhouse gases and further variables such as line-of-sight wind speed from simultaneously measured LIO signals. Due to the novelty of the LMIO method, detailed knowledge of atmospheric influences on LIO signals and of their suitability for accurate trace species retrieval did not yet exist. Here we discuss these influences, assessing effects from refraction, trace species absorption, aerosol extinction and Rayleigh scattering in detail, and addressing clouds, turbulence, wind, scattered solar radiation and terrestrial thermal radiation as well. We show that the influence of refractive defocusing, foreign species absorption, aerosols and turbulence is observable, but can be rendered small to negligible by use of the differential transmission principle with a close frequency spacing of LIO absorption and reference signals within 0.5%. The influences of Rayleigh scattering and terrestrial thermal radiation are found negligible. Cloud-scattered solar radiation can be observable under bright-day conditions, but this influence can be made negligible by a close time spacing (within 5 ms of interleaved laser-pulse and background signals. Cloud extinction loss generally blocks SWIR signals, except very thin or sub-visible cirrus clouds, which can be addressed by retrieving a cloud layering profile and exploiting it in the trace species retrieval. Wind can have a small influence on the trace species absorption, which can be made negligible by using a simultaneously retrieved or a moderately accurate background wind speed profile. We

  3. Solution Method and Precision Analysis of Double-difference Dynamic Precise Orbit Determination of BeiDou Navigation Satellite System

    Directory of Open Access Journals (Sweden)

    LIU Weiping

    2016-02-01

    Full Text Available To resolve the high relativity between the transverse element of GEO orbit and double-difference ambiguity, the classical double-difference dynamic method is improved and the method, which is to determine precise BeiDou satellite orbit using carrier phase and pseudo-range smoothed by phase, is proposed. The feasibility of the method is discussed and the influence of the method about ambiguity fixing is analyzed. Considering the characteristic of BeiDou, the method, which is to fix double-difference ambiguity of BeiDou satellites by QIF, is derived. The real data analysis shows that the new method, which can reduce the relativity and assure the precision, is better than the classical double-difference dynamic method. The result of ambiguity fixing is well by QIF, but the ambiguity fixing success rate is not high on the whole. So the precision of BeiDou orbit can't be improved clearly after ambiguity fixing.

  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. 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.

  6. 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.

  7. Results from On-Orbit Testing of the Fram Memory Test Experiment on the Fastsat Micro-Satellite

    Science.gov (United States)

    MacLeod, Todd C.; Sims, W. Herb; Varnavas, Kosta A.; Ho, Fat D.

    2011-01-01

    NASA is planning on going beyond Low Earth orbit with manned exploration missions. The radiation environment for most Low Earth orbit missions is harsher than at the Earth's surface but much less harsh than deep space. Development of new electronics is needed to meet the requirements of high performance, radiation tolerance, and reliability. The need for both Volatile and Non-volatile memory has been identified. Emerging Non-volatile memory technologies (FRAM, C-RAM,M-RAM, R-RAM, Radiation Tolerant FLASH, SONOS, etc.) need to be investigated for use in Space missions. An opportunity arose to fly a small memory experiment on a high inclination satellite (FASTSAT). An off-the-shelf 512K Ramtron FRAM was chosen to be tested in the experiment.

  8. Long-Term Rotational Dynamics of Defunct Earth-Orbiting Satellites

    Data.gov (United States)

    National Aeronautics and Space Administration — While extensive research has been conducted to predict the trajectories of defunct high altitude satellites, the attitude dynamics of these objects are not well...

  9. Global-scale Observations of the Limb and Disk (GOLD) Mission: Science from Geostationary Orbit on-board a Commercial Communications Satellite

    Science.gov (United States)

    Eastes, R.; Deaver, T.; Krywonos, A.; Lankton, M. R.; McClintock, W. E.; Pang, R.

    2011-12-01

    Geostationary orbits are ideal for many science investigations of the Earth system on global scales. These orbits allow continuous observations of the same geographic region, enabling spatial and temporal changes to be distinguished and eliminating the ambiguity inherent to observations from low Earth orbit (LEO). Just as observations from geostationary orbit have revolutionized our understanding of changes in the troposphere, they will dramatically improve our understanding of the space environment at higher altitudes. However, geostationary orbits are infrequently used for science missions because of high costs. Geostationary satellites are large, typically weighing tons. Consequently, devoting an entire satellite to a science mission requires a large financial commitment, both for the spacecraft itself and for sufficient science instrumentation to justify a dedicated spacecraft. Furthermore, the small number of geostationary satellites produced for scientific missions increases the costs of each satellite. For these reasons, it is attractive to consider flying scientific instruments on satellites operated by commercial companies, some of whom have fleets of ~40 satellites. However, scientists' lack of understanding of the capabilities of commercial spacecraft as well as commercial companies' concerns about risks to their primary mission have impeded the cooperation necessary for the shared use of a spacecraft. Working with a commercial partner, the GOLD mission has successfully overcome these issues. Our experience indicates that there are numerous benefits to flying on commercial communications satellites (e.g., it is possible to downlink large amounts of data) and the costs are low if the experimental requirements adequately match the capabilities and available resources of the host spacecraft. Consequently, affordable access to geostationary orbit aboard a communications satellite now appears possible for science payloads.

  10. Ground Track Acquisition and Maintenance Maneuver Modeling for Low-Earth Orbit Satellite

    Directory of Open Access Journals (Sweden)

    Byoung-Sun Lee

    1997-12-01

    Full Text Available This paper presents a comprehensive analytical approach for determining key maneuver parameters associated with the acquisition and maintenance of the ground track for a low-earth orbit. A livearized model relating changes in the drift rate of the ground track directly to changes in the orbital semi-major axis is also developed. The effect of terrestrial atmospheric drag on the semi-major axis is also explored, being quantified through an analytical expression for the decay rate as a function of density. The non-singular Lagrange planetary equations, further simplified for nearly circular orbits, provide the desired relationships between the corrective in-plane impulsive velocity increments and the corresponding effects on the orbit elements. The resulting solution strategy offers excellent insight into the dynamics affecting the timing, magnitude, and frequency of these maneuvers. Simulations are executed for the ground track acquisition and maintenance maneuver as a pre-flight planning and analysis.

  11. Next-Generation NASA Earth-Orbiting Relay Satellites: Fusing Optical and Microwave Communications

    Science.gov (United States)

    Israel, David J.; Shaw, Harry

    2018-01-01

    NASA is currently considering architectures and concepts for the generation of relay satellites that will replace the Tracking and Data Relay Satellite (TDRS) constellation, which has been flying since 1983. TDRS-M, the last of the second TDRS generation, launched in August 2017, extending the life of the TDRS constellation beyond 2030. However, opportunities exist to re-engineer the concepts of geosynchronous Earth relay satellites. The needs of the relay satellite customers have changed dramatically over the last 34 years since the first TDRS launch. There is a demand for greater bandwidth as the availability of the traditional RF spectrum for space communications diminishes and the demand for ground station access grows. The next generation of NASA relay satellites will provide for operations that have factored in these new constraints. In this paper, we describe a heterogeneous constellation of geosynchronous relay satellites employing optical and RF communications. The new constellation will enable new optical communications services formed by user-to-space relay, space relay-to-space relay and space relay-to-ground links. It will build upon the experience from the Lunar Laser Communications Demonstration from 2013 and the Laser Communications Relay Demonstration to be launched in 2019.Simultaneous to establishment of the optical communications space segment, spacecraft in the TDRS constellation will be replaced with RF relay satellites with targeted subsets of the TDRS capabilities. This disaggregation of the TDRS service model will allow for flexibility in replenishing the needs of legacy users as well as addition of new capabilities for future users. It will also permit the U.S. government access to launch capabilities such as rideshare and to hosted payloads that were not previously available.In this paper, we also explore how the next generation of Earth relay satellites provides a significant boost in the opportunities for commercial providers to the

  12. Next-Generation NASA Earth-Orbiting Relay Satellites: Fusing Microwave and Optical Communications

    Science.gov (United States)

    Israel, David J.

    2018-01-01

    NASA is currently considering architectures and concepts for the generation of relay satellites that will replace the Tracking and Data Relay Satellite (TDRS) constellation, which has been flying since 1983. TDRS-M, the last of the second TDRS generation, launched in August 2017, extending the life of the TDRS constellation beyond 2030. However, opportunities exist to re-engineer the concepts of geosynchronous Earth relay satellites. The needs of the relay satellite customers have changed dramatically over the last 34 years since the first TDRS launch. There is a demand for greater bandwidth as the availability of the traditional RF spectrum for space communications diminishes and the demand for ground station access grows. The next generation of NASA relay satellites will provide for operations that have factored in these new constraints. In this paper, we describe a heterogeneous constellation of geosynchronous relay satellites employing optical and RF communications. The new constellation will enable new optical communications services formed by user-to-space relay, space relay-to-space relay and space relay-to-ground links. It will build upon the experience from the Lunar Laser Communications Demonstration from 2013 and the Laser Communications Relay Demonstration to be launched in 2019.Simultaneous to establishment of the optical communications space segment, spacecraft in the TDRS constellation will be replaced with RF relay satellites with targeted subsets of the TDRS capabilities. This disaggregation of the TDRS service model will allow for flexibility in replenishing the needs of legacy users as well as addition of new capabilities for future users. It will also permit the U.S. government access to launch capabilities such as rideshare and to hosted payloads that were not previously available. In this paper, we also explore how the next generation of Earth relay satellites provides a significant boost in the opportunities for commercial providers to the

  13. Contraction of high eccentricity satellite orbits using uniformly regular KS canonical elements with oblate diurnally varying atmosphere.

    Science.gov (United States)

    Raj, Xavier James

    2016-07-01

    Accurate orbit prediction of an artificial satellite under the influence of air drag is one of the most difficult and untraceable problem in orbital dynamics. The orbital decay of these satellites is mainly controlled by the atmospheric drag effects. The effects of the atmosphere are difficult to determine, since the atmospheric density undergoes large fluctuations. The classical Newtonian equations of motion, which is non linear is not suitable for long-term integration. Many transformations have emerged in the literature to stabilize the equations of motion either to reduce the accumulation of local numerical errors or allowing the use of large integration step sizes, or both in the transformed space. One such transformation is known as KS transformation by Kustaanheimo and Stiefel, who regularized the nonlinear Kepler equations of motion and reduced it into linear differential equations of a harmonic oscillator of constant frequency. The method of KS total energy element equations has been found to be a very powerful method for obtaining numerical as well as analytical solution with respect to any type of perturbing forces, as the equations are less sensitive to round off and truncation errors. The uniformly regular KS canonical equations are a particular canonical form of the KS differential equations, where all the ten KS Canonical elements αi and βi are constant for unperturbed motion. These equations permit the uniform formulation of the basic laws of elliptic, parabolic and hyperbolic motion. Using these equations, developed analytical solution for short term orbit predictions with respect to Earth's zonal harmonic terms J2, J3, J4. Further, these equations were utilized to include the canonical forces and analytical theories with air drag were developed for low eccentricity orbits (e 0.2) orbits by assuming the atmosphere to be oblate only. In this paper a new non-singular analytical theory is developed for the motion of high eccentricity satellite

  14. Earth rotation, station coordinates and orbit determination from satellite laser ranging

    Science.gov (United States)

    Murata, Masaaki

    The Project MERIT, a special program of international colaboration to Monitor Earth Rotation and Intercompare the Techniques of observation and analysis, has come to an end with great success. Its major objective was to evaluate the ultimate potential of space techniques such as VLBI and satellite laser ranging, in contrast with the other conventional techniques, in the determination of rotational dynamics of the earth. The National Aerospace Laboratory (NAL) has officially participated in the project as an associate analysis center for satellite laser technique for the period of the MERIT Main Campaign (September 1983-October 1984). In this paper, the NAL analysis center results are presented.

  15. Incorporation of star measurements for the determination of orbit and attitude parameters of a geosynchronous satellite: An iterative application of linear regression

    Science.gov (United States)

    Phillips, D.

    1980-01-01

    Currently on NOAA/NESS's VIRGS system at the World Weather Building star images are being ingested on a daily basis. The image coordinates of the star locations are measured and stored. Subsequently, the information is used to determine the attitude, the misalignment angles between the spin axis and the principal axis of the satellite, and the precession rate and direction. This is done for both the 'East' and 'West' operational geosynchronous satellites. This orientation information is then combined with image measurements of earth based landmarks to determine the orbit of each satellite. The method for determining the orbit is simple. For each landmark measurement one determines a nominal position vector for the satellite by extending a ray from the landmark's position towards the satellite and intersecting the ray with a sphere with center coinciding with the Earth's center and with radius equal to the nominal height for a geosynchronous satellite. The apparent motion of the satellite around the Earth's center is then approximated with a Keplerian model. In turn the variations of the satellite's height, as a function of time found by using this model, are used to redetermine the successive satellite positions by again using the Earth based landmark measurements and intersecting rays from these landmarks with the newly determined spheres. This process is performed iteratively until convergence is achieved. Only three iterations are required.

  16. 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.

  17. Analytical theory for artificial satellites. [nominal orbit expressed by means of Chebyshev polynomials

    Science.gov (United States)

    Deprit, A.

    1975-01-01

    A theory for generating segmented ephemerides is discussed as a means for fast generation and simple retrieval of nominal orbit data. Over a succession of finite intervals of time, the orbit is represented by a best approximation expressed by Chebyshev polynomials. Storage of coefficients tables for Chebyshev polynomials is seen as a method to reduce data and decrease transmission costs. A general algorithm was constructed and computer programs were designed. The possibility of storing an ephemeris for a few days in the on-board computer, or in microprocessors attached to the data collectors is suggested.

  18. An algorithm for enhanced formation flying of satellites in low earth orbit

    Science.gov (United States)

    Folta, David C.; Quinn, David A.

    1998-01-01

    With scientific objectives for Earth observation programs becoming more ambitious and spacecraft becoming more autonomous, the need for innovative technical approaches on the feasibility of achieving and maintaining formations of spacecraft has come to the forefront. The trend to develop small low-cost spacecraft has led many scientists to recognize the advantage of flying several spacecraft in formation to achieve the correlated instrument measurements formerly possible only by flying many instruments on a single large platform. Yet, formation flying imposes additional complications on orbit maintenance, especially when each spacecraft has its own orbit requirements. However, advances in automation and technology proposed by the Goddard Space Flight Center (GSFC) allow more of the burden in maneuver planning and execution to be placed onboard the spacecraft, mitigating some of the associated operational concerns. The purpose of this paper is to present GSFC's Guidance, Navigation, and Control Center's (GNCC) algorithm for Formation Flying of the low earth orbiting spacecraft that is part of the New Millennium Program (NMP). This system will be implemented as a close-loop flight code onboard the NMP Earth Orbiter-1 (EO-1) spacecraft. Results of this development can be used to determine the appropriateness of formation flying for a particular case as well as operational impacts. Simulation results using this algorithm integrated in an autonomous `fuzzy logic' control system called AutoCon™ are presented.

  19. Gravity field models from kinematic orbits of CHAMP, GRACE and GOCE satellites

    Czech Academy of Sciences Publication Activity Database

    Bezděk, Aleš; Sebera, Josef; Klokočník, Jaroslav; Kostelecký, J.

    2014-01-01

    Roč. 53, č. 3 (2014), s. 412-429 ISSN 0273-1177 R&D Projects: GA MŠk LH13071; GA ČR GA13-36843S Institutional support: RVO:67985815 Keywords : gravity field models * kinematic orbits * generalized least squares Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.358, year: 2014

  20. Comparison of satellite-derived LAI and precipitation anomalies over Brazil with a thermal infrared-based Evaporative Stress Index for 2003-2013

    Science.gov (United States)

    Anderson, Martha C.; Zolin, Cornelio A.; Hain, Christopher R.; Semmens, Kathryn; Tugrul Yilmaz, M.; Gao, Feng

    2015-07-01

    Shortwave vegetation index (VI) and leaf area index (LAI) remote sensing products yield inconsistent depictions of biophysical response to drought and pluvial events that have occurred in Brazil over the past decade. Conflicting reports of severity of drought impacts on vegetation health and functioning have been attributed to cloud and aerosol contamination of shortwave reflectance composites, particularly over the rainforested regions of the Amazon basin which are subject to prolonged periods of cloud cover and episodes of intense biomass burning. This study compares timeseries of satellite-derived maps of LAI from the Moderate Resolution Imaging Spectroradiometer (MODIS) and precipitation from the Tropical Rainfall Mapping Mission (TRMM) with a diagnostic Evaporative Stress Index (ESI) retrieved using thermal infrared remote sensing over South America for the period 2003-2013. This period includes several severe droughts and floods that occurred both over the Amazon and over unforested savanna and agricultural areas in Brazil. Cross-correlations between absolute values and standardized anomalies in monthly LAI and precipitation composites as well as the actual-to-reference evapotranspiration (ET) ratio used in the ESI were computed for representative forested and agricultural regions. The correlation analyses reveal strong apparent anticorrelation between MODIS LAI and TRMM precipitation anomalies over the Amazon, but better coupling over regions vegetated with shorter grass and crop canopies. The ESI was more consistently correlated with precipitation patterns over both landcover types. Temporal comparisons between ESI and TRMM anomalies suggest longer moisture buffering timescales in the deeper rooted rainforest systems. Diagnostic thermal-based retrievals of ET and ET anomalies, such as used in the ESI, provide independent information on the impacts of extreme hydrologic events on vegetation health in comparison with VI and precipitation-based drought

  1. Test results and in-orbit operation of the Infrared Astronomical Satellite circumvention circuit

    Science.gov (United States)

    Long, E. C.; Langford, D.

    1984-01-01

    The IRAS circumvention circuit (CC) eliminates the unwanted charged-particle pulses from the IR signal. The operation of the CC along with preflight and in-orbit testing is described. Ground testing of the brassboard circuit using a simulated preamplifier output showed that the CC would perform the circumvention function as designed. When all flight detectors and preamplifiers became available, the CC was tested using a gamma source to simulate charged-particle sources; with the low energy deposited in the detectors (20 keV average) the noise was reduced by up to 5 times with the CC turned on. In-orbit results show that the CC decreases the unwanted charged-particle background noise by up to two orders of magnitude. The difference in the results with the CC on and off is so great that the science team has recommended that no data be taken with the CC off.

  2. Effects of valence nucleon orbits and charge symmetry breaking interaction on the Nolen-Schiffer anomaly of mirror nuclei

    International Nuclear Information System (INIS)

    Suzuki, T.; Sagawa, H.; Arima, A.

    1992-01-01

    Coulomb energy differences (Nolen-Schiffer anomalies) of mirror nuclei 17 O- 17 F and 41 Ca- 41 Sc are studied by using realistic Hartree-Fock and Woods-Saxon single-particle wave functions which are determined precisely through the analysis of the magnetic form factors of electron scattering. These single-particle wave functions are used to evaluate the Coulomb energy differences due to charge symmetry breaking forces, with new coupling constants determined by the analysis of the scattering lengths of pp and nn system which have been successfully applied to the Coulomb energy difference of 3 He- 3 H. We also evaluated the effects of the charge symmetry breaking forces using Hartree-Fock wave functions. Together with various other contributions, our calculated values of the Coulomb energy differences, which showed deviations of 3-9% from the experimental values in the previous analysis of Nolen and Schiffer, agree with the experimental values within 1% (2%) accuracy for A=17 (41). (orig.)

  3. Evaluation of geomagnetic field models using magnetometer measurements for satellite attitude determination system at low earth orbits: Case studies

    Science.gov (United States)

    Cilden-Guler, Demet; Kaymaz, Zerefsan; Hajiyev, Chingiz

    2018-01-01

    In this study, different geomagnetic field models are compared in order to study the errors resulting from the representation of magnetic fields that affect the satellite attitude system. For this purpose, we used magnetometer data from two Low Earth Orbit (LEO) spacecraft and the geomagnetic models IGRF-12 (Thébault et al., 2015) and T89 (Tsyganenko, 1989) models to study the differences between the magnetic field components, strength and the angle between the predicted and observed vector magnetic fields. The comparisons were made during geomagnetically active and quiet days to see the effects of the geomagnetic storms and sub-storms on the predicted and observed magnetic fields and angles. The angles, in turn, are used to estimate the spacecraft attitude and hence, the differences between model and observations as well as between two models become important to determine and reduce the errors associated with the models under different space environment conditions. We show that the models differ from the observations even during the geomagnetically quiet times but the associated errors during the geomagnetically active times increase. We find that the T89 model gives closer predictions to the observations, especially during active times and the errors are smaller compared to the IGRF-12 model. The magnitude of the error in the angle under both environmental conditions was found to be less than 1°. For the first time, the geomagnetic models were used to address the effects of the near Earth space environment on the satellite attitude.

  4. Global Monitoring RSEM System for Crop Production by Incorporating Satellite-based Photosynthesis Rates and Anomaly Data of Sea Surface Temperature

    Science.gov (United States)

    Kaneko, D.; Sakuma, H.

    2014-12-01

    The first author has been developing RSEM crop-monitoring system using satellite-based assessment of photosynthesis, incorporating meteorological conditions. Crop production comprises of several stages and plural mechanisms based on leaf photosynthesis, surface energy balance, and the maturing of grains after fixation of CO2, along with water exchange through soil vegetation-atmosphere transfer. Grain production in prime countries appears to be randomly perturbed regionally and globally. Weather for crop plants reflects turbulent phenomena of convective and advection flows in atmosphere and surface boundary layer. It has been difficult for scientists to simulate and forecast weather correctly for sufficiently long terms to crop harvesting. However, severely poor harvests related to continental events must originate from a consistent mechanism of abnormal energetic flow in the atmosphere through both land and oceans. It should be remembered that oceans have more than 100 times of energy storage compared to atmosphere and ocean currents represent gigantic energy flows, strongly affecting climate. Anomalies of Sea Surface Temperature (SST), globally known as El Niño, Indian Ocean dipole, and Atlantic Niño etc., affect the seasonal climate on a continental scale. The authors aim to combine monitoring and seasonal forecasting, considering such mechanisms through land-ocean biosphere transfer. The present system produces assessments for all continents, specifically monitoring agricultural fields of main crops. Historical regions of poor and good harvests are compared with distributions of SST anomalies, which are provided by NASA GSFC. Those comparisons fairly suggest that the Worst harvest in 1993 and the Best in 1994 relate to the offshore distribution of low temperature anomalies and high gaps in ocean surface temperatures. However, high-temperature anomalies supported good harvests because of sufficient solar radiation for photosynthesis, and poor harvests because

  5. Characteristics of equatorial ionization anomaly (EIA) in relation to transionospheric satellite links around the northern crest in the Indian longitude sector

    Science.gov (United States)

    Das, A.; Paul, K. S.; Halder, S.; Basu, K.; Paul, A.

    2014-02-01

    The poleward gradient of the equatorial ionization anomaly (EIA) introduces more intense propagation effects on transionospheric satellite links in comparison to the equatorward gradient. Characterization of the poleward gradient was performed during March-April, August-October 2011 and March-April 2012 using GPS total electron content (TEC) recorded from a chain of stations located more or less along the same meridian (88.5° E) at Calcutta, Baharampore, Farakka and Siliguri. The poleward gradients calculated on magnetically quiet days at elevation in excess of 50° at 14:00, 15:00 and 16:00 LT were found to have a strong correlation with GPS S4 observed from Calcutta during post-sunset-to-midnight hours. A threshold value of poleward TEC gradient is calculated above which there is a probability of scintillation at Calcutta with S4 ≥ 0.4.

  6. Characteristics of equatorial ionization anomaly (EIA in relation to transionospheric satellite links around the northern crest in the Indian longitude sector

    Directory of Open Access Journals (Sweden)

    A. Das

    2014-02-01

    Full Text Available The poleward gradient of the equatorial ionization anomaly (EIA introduces more intense propagation effects on transionospheric satellite links in comparison to the equatorward gradient. Characterization of the poleward gradient was performed during March–April, August–October 2011 and March–April 2012 using GPS total electron content (TEC recorded from a chain of stations located more or less along the same meridian (88.5° E at Calcutta, Baharampore, Farakka and Siliguri. The poleward gradients calculated on magnetically quiet days at elevation in excess of 50° at 14:00, 15:00 and 16:00 LT were found to have a strong correlation with GPS S4 observed from Calcutta during post-sunset-to-midnight hours. A threshold value of poleward TEC gradient is calculated above which there is a probability of scintillation at Calcutta with S4 ≥ 0.4.

  7. Detecting ecosystem performance anomalies for land management in the upper colorado river basin using satellite observations, climate data, and ecosystem models

    Science.gov (United States)

    Gu, Yingxin; Wylie, B.K.

    2010-01-01

    This study identifies areas with ecosystem performance anomalies (EPA) within the Upper Colorado River Basin (UCRB) during 2005-2007 using satellite observations, climate data, and ecosystem models. The final EPA maps with 250-m spatial resolution were categorized as normal performance, underperformance, and overperformance (observed performance relative to weather-based predictions) at the 90% level of confidence. The EPA maps were validated using "percentage of bare soil" ground observations. The validation results at locations with comparable site potential showed that regions identified as persistently underperforming (overperforming) tended to have a higher (lower) percentage of bare soil, suggesting that our preliminary EPA maps are reliable and agree with ground-based observations. The 3-year (2005-2007) persistent EPA map from this study provides the first quantitative evaluation of ecosystem performance anomalies within the UCRB and will help the Bureau of Land Management (BLM) identify potentially degraded lands. Results from this study can be used as a prototype by BLM and other land managers for making optimal land management decisions. ?? 2010 by the authors.

  8. VizieR Online Data Catalog: The orbits of Jupiter's irregular satellites (Brozovic+, 2017)

    Science.gov (United States)

    Brozovic, M.; Jacobson, R. A.

    2018-05-01

    The large majority of astrometric observations originate from Earth-based telescopes, although there are a handful of observations of Himalia and Callirrhoe from the New Horizons spacecraft flyby of Jupiter. The modern Hipparcos Catalog (Perryman et al. 1997A&A...323L..49P) based astrometry is reported as positions in the ICRF. We convert the older measurements to the ICRF positions. The references to optical observations up to the year 2000 are documented in Jacobson (2000AJ....120.2679J). We continued to use the Jacobson (2000AJ....120.2679J) observational biases for the early measurements. We have since extended the data set with observations published in the Minor Planet Electronic Circulars (MPEC), the International Astronomical Union Circulars (IAUC), the Natural Satellites Data Center (NSDC) database (Arlot & Emelyanov 2009A&A...503..631A), the United States Naval Observatory Flagstaff Station catalog, and the Pulkovo Observatory database. (5 data files).

  9. On-line Flagging of Anomalies and Adaptive Sequential Hypothesis Testing for Fine-feature Characterization of Geosynchronous Satellites

    Science.gov (United States)

    2015-10-18

    model-based evidence. This work resolves cross-tag using three methods (Z-test for dependent data, classical sequential analysis and Brownian motion...Slider Movement The two-facet model is used as the Inversion Model. It represents a three-axis stabilized satellite as two facets, namely a body...the sequential analysis. If is independent and has an approximately normal distribution then Brownian motion drift analysis is used. If is

  10. THE ANGLO-AUSTRALIAN PLANET SEARCH. XXI. A GAS-GIANT PLANET IN A ONE YEAR ORBIT AND THE HABITABILITY OF GAS-GIANT SATELLITES

    International Nuclear Information System (INIS)

    Tinney, C. G.; Wittenmyer, Robert A.; Bailey, Jeremy A.; Horner, J.; Butler, R. Paul; Jones, Hugh R. A.; O'Toole, Simon J.; Carter, Brad D.

    2011-01-01

    We have detected the Doppler signature of a gas-giant exoplanet orbiting the star HD 38283, in an eccentric orbit with a period of almost exactly one year (P = 363.2 ± 1.6 d, m sin i = 0.34 ± 0.02 M Jup , e = 0.41 ± 0.16). The detection of a planet with period very close to one year critically relied on year-round observation of this circumpolar star. Discovering a planet in a 1 AU orbit around a G dwarf star has prompted us to look more closely at the question of the habitability of the satellites of such planets. Regular satellites orbit all the giant planets in our solar system, suggesting that their formation is a natural by-product of the planet formation process. There is no reason for exomoon formation not to be similarly likely in exoplanetary systems. Moreover, our current understanding of that formation process does not preclude satellite formation in systems where gas giants undergo migration from their formation locations into the terrestrial planet habitable zone. Indeed, regular satellite formation and Type II migration are both linked to the clearing of a gap in the protoplanetary disk by a planet, and so may be inextricably linked. Migration would also multiply the chances of capturing both irregular satellites and Trojan companions sufficiently massive to be habitable. The habitability of such exomoons and exo-Trojans will critically depend on their mass, whether or not they host a magnetosphere, and (for the exomoon case) their orbital radius around the host exoplanet.

  11. In-flight performance analysis of MEMS GPS receiver and its application to precise orbit determination of APOD-A satellite

    Science.gov (United States)

    Gu, Defeng; Liu, Ye; Yi, Bin; Cao, Jianfeng; Li, Xie

    2017-12-01

    An experimental satellite mission termed atmospheric density detection and precise orbit determination (APOD) was developed by China and launched on 20 September 2015. The micro-electro-mechanical system (MEMS) GPS receiver provides the basis for precise orbit determination (POD) within the range of a few decimetres. The in-flight performance of the MEMS GPS receiver was assessed. The average number of tracked GPS satellites is 10.7. However, only 5.1 GPS satellites are available for dual-frequency navigation because of the loss of many L2 observations at low elevations. The variations in the multipath error for C1 and P2 were estimated, and the maximum multipath error could reach up to 0.8 m. The average code noises are 0.28 m (C1) and 0.69 m (P2). Using the MEMS GPS receiver, the orbit of the APOD nanosatellite (APOD-A) was precisely determined. Two types of orbit solutions are proposed: a dual-frequency solution and a single-frequency solution. The antenna phase center variations (PCVs) and code residual variations (CRVs) were estimated, and the maximum value of the PCVs is 4.0 cm. After correcting the antenna PCVs and CRVs, the final orbit precision for the dual-frequency and single-frequency solutions were 7.71 cm and 12.91 cm, respectively, validated using the satellite laser ranging (SLR) data, which were significantly improved by 3.35 cm and 25.25 cm. The average RMS of the 6-h overlap differences in the dual-frequency solution between two consecutive days in three dimensions (3D) is 4.59 cm. The MEMS GPS receiver is the Chinese indigenous onboard receiver, which was successfully used in the POD of a nanosatellite. This study has important reference value for improving the MEMS GPS receiver and its application in other low Earth orbit (LEO) nanosatellites.

  12. Attitude Control and Orbital Dynamics Challenges of Removing the First 3-Axis Stabilized Tracking and Data Relay Satellite from the Geosynchronous ARC

    Science.gov (United States)

    Benet, Charles A.; Hofman, Henry; Williams, Thomas E.; Olney, Dave; Zaleski, Ronald

    2011-01-01

    Launched on April 4, 1983 onboard STS 6 (Space Shuttle Challenger), the First Tracking and Data Relay Satellite (TDRS 1) was retired above the Geosynchronous Orbit (GEO) on June 27, 2010 after having provided real-time communications with a variety of low-orbiting spacecraft over a 26-year period. To meet NASA requirements limiting orbital debris 1, a team of experts was assembled to conduct an End-Of-Mission (EOM) procedure to raise the satellite 350 km above the GEO orbit. Following the orbit raising via conventional station change maneuvers, the team was confronted with having to deplete the remaining propellant and passivate all energy storage or generation sources. To accomplish these tasks within the time window, communications (telemetry and control links), electrical power, propulsion, and thermal constraints, a spacecraft originally designed as a three-axis stabilized satellite was turned into a spinner. This paper (a companion paper to Innovative Approach Enabled the Retirement of TDRS 1, paper # 1699, IEEE 2011 Aerospace Conference, March 5-12, 2011 sup 2) focuses on the challenges of maintaining an acceptable spinning dynamics, while repetitively firing thrusters. Also addressed are the effects of thruster firings on the orbit characteristics and how they were mitigated by a careful scheduling of the fuel depletion operations. Periodic thruster firings for spin rate adjustment, nutation damping, and precession of the momentum vector were also required in order to maintain effective communications with the satellite. All operations were thoroughly rehearsed and supported by simulations thus lending a high level of confidence in meeting the NASA EOM goals.

  13. On-Orbit Camera Misalignment Estimation Framework and Its Application to Earth Observation Satellite

    Directory of Open Access Journals (Sweden)

    Seungwoo Lee

    2015-03-01

    Full Text Available Despite the efforts for precise alignment of imaging sensors and attitude sensors before launch, the accuracy of pre-launch alignment is limited. The misalignment between attitude frame and camera frame is especially important as it is related to the localization error of the spacecraft, which is one of the essential factors of satellite image quality. In this paper, a framework for camera misalignment estimation is presented with its application to a high-resolution earth-observation satellite—Deimos-2. The framework intends to provide a solution for estimation and correction of the camera misalignment of a spacecraft, covering image acquisition planning to mathematical solution of camera misalignment. Considerations for effective image acquisition planning to obtain reliable results are discussed, followed by a detailed description on a practical method for extracting many GCPs automatically using reference ortho-photos. Patterns of localization errors that commonly occur due to the camera misalignment are also investigated. A mathematical model for camera misalignment estimation is described comprehensively. The results of simulation experiments showing the validity and accuracy of the misalignment estimation model are provided. The proposed framework was applied to Deimos-2. The real-world data and results from Deimos-2 are presented.

  14. Modelling and prediction of crop losses from NOAA polar-orbiting operational satellites

    Directory of Open Access Journals (Sweden)

    Felix Kogan

    2016-05-01

    Full Text Available Weather-related crop losses have always been a concern for farmers, governments, traders, and policy-makers for the purpose of balanced food supply/demands, trade, and distribution of aid to the nations in need. Among weather disasters, drought plays a major role in large-scale crop losses. This paper discusses utility of operational satellite-based vegetation health (VH indices for modelling cereal yield and for early warning of drought-related crop losses. The indices were tested in Saratov oblast (SO, one of the principal grain growing regions of Russia. Correlation and regression analysis were applied to model cereal yield from VH indices during 1982–2001. A strong correlation between mean SO's cereal yield and VH indices were found during the critical period of cereals, which starts two–three weeks before and ends two–three weeks after the heading stage. Several models were constructed where VH indices served as independent variables (predictors. The models were validated independently based on SO cereal yield during 1982–2012. Drought-related cereal yield losses can be predicted three months in advance of harvest and six–eight months in advance of official grain production statistic is released. The error of production losses prediction is 7%–10%. The error of prediction drops to 3%–5% in the years of intensive droughts.

  15. The Response of Equatorial Ionization Anomaly in 120°E to the Geomagnetic Storm of 18 August 2003 at Different Altitudes From Multiple Satellite Observations

    Science.gov (United States)

    Luo, Weihua; Zhu, Zhengping; Xiong, Chao; Chang, Shanshan

    2017-12-01

    In this paper, the variations of equatorial ionization anomaly (EIA) in 120°E region during the 17-20 August 2003 storm are investigated from measurements of satellites at different altitudes from Challenging Minisatellite Payload (CHAMP), Gravity Recovery and Climate Experiment (GRACE), scientific satellite of the Republic of China (ROCSAT-1), and Defense Meteorological Satellite Program missions. The results showed that (1) at CHAMP and GRACE altitudes, the EIA was inhibited before the storm sudden commencement (SSC) and also during the storm recovery phase, but it was enhanced significantly during the storm main phase of the storm. (2) The variations of EIA strength and interhemispheric density asymmetry of the two crests were similar at CHAMP and GRACE altitudes, while the location asymmetry of the two crests was different at CHAMP and GRACE altitudes. (3) The irregularities and long-duration scintillation were recorded before the SSC of the storm, when the EIA was inhibited. The irregularities at different altitudes and short-duration scintillation were observed during the main phase of the storm, when the EIA was enhanced significantly. (4) The EIA enhancement can be attributed to the enhanced electric field due to prompt penetration interplanetary electric fields and the storm time neutral wind, while the suppression of EIA on 17 August can be attributed to the absence of the equatorward neutral wind, which varied with the altitudes. The EIA inhibition during the recovery phase may be caused mainly by the neutral wind. Our results suggest that the neutral wind is the crucial factor causing the variations in EIA and the occurrence of scintillation.

  16. The stars: an absolute radiometric reference for the on-orbit calibration of PLEIADES-HR satellites

    Science.gov (United States)

    Meygret, Aimé; Blanchet, Gwendoline; Mounier, Flore; Buil, Christian

    2017-09-01

    The accurate on-orbit radiometric calibration of optical sensors has become a challenge for space agencies who gather their effort through international working groups such as CEOS/WGCV or GSICS with the objective to insure the consistency of space measurements and to reach an absolute accuracy compatible with more and more demanding scientific needs. Different targets are traditionally used for calibration depending on the sensor or spacecraft specificities: from on-board calibration systems to ground targets, they all take advantage of our capacity to characterize and model them. But achieving the in-flight stability of a diffuser panel is always a challenge while the calibration over ground targets is often limited by their BDRF characterization and the atmosphere variability. Thanks to their agility, some satellites have the capability to view extra-terrestrial targets such as the moon or stars. The moon is widely used for calibration and its albedo is known through ROLO (RObotic Lunar Observatory) USGS model but with a poor absolute accuracy limiting its use to sensor drift monitoring or cross-calibration. Although the spectral irradiance of some stars is known with a very high accuracy, it was not really shown that they could provide an absolute reference for remote sensors calibration. This paper shows that high resolution optical sensors can be calibrated with a high absolute accuracy using stars. The agile-body PLEIADES 1A satellite is used for this demonstration. The star based calibration principle is described and the results are provided for different stars, each one being acquired several times. These results are compared to the official calibration provided by ground targets and the main error contributors are discussed.

  17. Protocoles d'accès multiple orientés qualité de service en constellation de satellite à orbite basse

    OpenAIRE

    Ibrahim , Abbas

    2002-01-01

    Pendant les dernières années, le réseau cellulaire est devenu accessible presque partout. Pour compléter ce réseau cellulaire terrestre, plusieurs systèmes basés sur des satellites à basse orbite (LEO Low Earth Orbit) et moyenne orbite (MEO Medium Earth Orbit) ont été développés pour offrir une couverture globale. Les services multimédias sont largement demandés sur une échelle globale.Notre but est de développer une couche d'accès MAC au canal satellitaire tout en respectant les contraintes ...

  18. Probing the earth's gravity field by means of satellite-to-satellite tracking

    Science.gov (United States)

    Vonbun, F. O.

    1977-01-01

    Two satellite-to-satellite tracking (sst) tests are described in detail: (1) the ATS-6/Geos-3 and (2) the ATS-6/Apollo-Soyuz experiment. The main purpose of these two experiments was to track via ATS-6 the Geos-3, as well as the Apollo-Soyuz and to use these tracking data to determine both of the orbits at the same time, each of the orbits alone, and to test the two sst links to study local gravity anomalies. A second purpose was to test communications, command and data transmission from the ground via ATS-6 to these spacecraft and back again to the ground.

  19. 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

  20. A simultaneous estimation of the mass of Mars and its natural satellites, Phobos and Deimos, from the orbital perturbations on the Mariner 9, Viking 1, and Viking 2 orbiters

    Science.gov (United States)

    Lemoine, F. G.; Smith, D. E.; Fricke, S. K.; Mccarthy, J. J.

    1993-01-01

    The natural satellites of Mars, Phobos and Deimos, caused perturbations on the orbits of the Mariner 9, and the Viking spacecraft that were used to estimate the satellite masses. The Viking spacecraft were specifically targeted to make close flybys (within a few hundred kilometers) of Phobos in February 1977 and of Deimos in October 1977. These close encounters were used to estimate the moon's gravitational constant, GM (the universal constant of gravitation multiplied by the satellite mass). However, the Viking and Mariner 9 spacecraft made numerous flybys of Phobos and Deimos at distances of a few thousand kilometers. The tracking data from these more 'distant' encounters were processed to estimate the masses of Mars, Phobos, and Deimos.

  1. Comparison of the Northeast Arctic cod year class strength (at the age of 3+) with the SST anomalies in main spawning ground (the Norwegian Shelf Waters) by results of analysis satellite monitoring data during last years.

    Science.gov (United States)

    Vanyushin, George

    2015-04-01

    Continuous long-term database (1998-2014) on the sea surface temperature (SST) comprising results of regional satellite monitoring (the Norwegian and the Barents seas) is used to resolve several applied problems. Authors have analyzed indirect influence the SST (the NOAA satellite data) on modern cod total stock biomass (abundance of the Northeast Arctic cod at age 3+). In this study, we went on the consideration of the relationship between the SST anomalies for March-April in the main spawning ground of the cod off the Lofoten islands in the Norwegian Shelf Waters and forecasting assessment of future cod generation success and its future abundance of 3 year old. Mean monthly SST and SST anomalies are computed for the selected area on the basis of the weekly SST maps which made by using the NOAA satellites data for the period 1998-2014. Comparison of the SST anomalies in the main spawning ground with abundance of the cod year class at age 3+ shows that survival of the cod generations was inhibited on the whole as negative (below -0,1C) well as positive SST anomalies (above +1,3C) during March and April. Finally, the results indicate that poor and low middle generations of cod at age 3+ (2002, 2004, 2010) occurred in years with negative or extremely high positive the SST anomalies in the spawning area. The SST anomalies in years which were close to normal significances provide conditions for appearance middle or strong generations of cod (2001-2003, 2005-2009, 2011-2013). So, the SST and SST anomalies (by the NOAA satellite data) characterize of increase in input of warm Atlantic waters which form numerous eddies along the main stream thus creating favorable conditions for spawning and development of the cod larvae and fry and provide them with food stock, finally direct influence on forming total stock biomass of cod and helping its population forecast. Key words: satellite monitoring of SST, the Northeast Arctic cod, spawning ground, forecast of the cod year class

  2. Accounting of fundamental components of the rotation parameters of the Earth in the formation of a high-accuracy orbit of navigation satellites

    Science.gov (United States)

    Markov, Yu. G.; Mikhailov, M. V.; Pochukaev, V. N.

    2012-07-01

    An analysis of perturbing factors influencing the motion of a navigation satellite (NS) is carried out, and the degree of influence of each factor on the GLONASS orbit is estimated. It is found that fundamental components of the Earth's rotation parameters (ERP) are one substantial factor commensurable with maximum perturbations. Algorithms for the calculation of orbital perturbations caused by these parameters are given; these algorithms can be implemented in a consumer's equipment. The daily prediction of NS coordinates is performed on the basis of real GLONASS satellite ephemerides transmitted to a consumer, using the developed prediction algorithms taking the ERP into account. The obtained accuracy of the daily prediction of GLONASS ephemerides exceeds by tens of times the accuracy of the daily prediction performed using algorithms recommended in interface control documents.

  3. 多系统GNSS卫星轨道快速积分方法%A Rapid Orbit Integration Algorithm for Multi-GNSS Satellites

    Institute of Scientific and Technical Information of China (English)

    范磊; 李敏; 宋伟伟; 施闯; 王成

    2016-01-01

    A rapid and efficient orbit numerical integration algorithm with high accuracy is needed in multi-GNSS rapid precise orbit determination.In order to improve the compute efficiency, an adaptive step-changed Admas integration method and a synchronous integration algoritm for multi-GNSS satellites are developed in this paper.To validate the precision and efficiency of the proposed method, the multi-GNSS precise orbit products calculated by Wuhan University (WHU) and Center for Orbit Determination in Europe (CODE) are used for orbit fitting.Results show that, the average 3DRMS of GPS, GLONASS, BDS and Galileo satellites are all below 20mm.Comparing with the traditional step-fixed orbit integraion method applied for each satellite separately, the computational efficiency of the proposed method is improved significantly: without damaging the accuracy, it takes only 0.09s for a single satellite, which is 14 times faster than the traditional method.Besides, further improvement can be achieved when the number of satellites is increased.%快速高效且高精度的轨道数值积分算法是多系统GNSS卫星联合快速精密定轨的重要基础.本文从自适应变换Admas积分步长和多卫星同步积分两方面研究了多系统GNSS卫星轨道快速积分方法.为了验证该方法的精度和效率,利用武汉大学(WHU)与欧洲定轨中心(CODE)发布的事后精密星历进行轨道动力学拟合.试验结果表明:GPS/GLONASS/BDS/Galileo 4个系统卫星平均三维RMS均优于20mm;在不损失传统方法精度的前提下,单颗卫星平均积分与拟合耗时仅需0.09s,较传统逐颗卫星固定步长积分算法提升了14倍,并且随着卫星数的增加,效率提升越明显.

  4. Analysis of Groundwater Anomalies Estimated by GRACE and GLDAS Satellite-based Hydrological Model in the Gulf of Mexico

    Science.gov (United States)

    Lotfata, A.; Ambinakudige, S.

    2017-12-01

    Coastal regions face a higher risk of flooding. A rise in sea-level increases flooding chances in low-lying areas. A major concern is the effect of sea-level rise on the depth of the fresh water/salt water interface in the aquifers of the coastal regions. A sea-level change rise impacts the hydrological system of the aquifers. Salt water intrusion into fresh water aquifers increase water table levels. Flooding prone areas in the coast are at a higher risk of salt water intrusion. The Gulf coast is one of the most vulnerable flood areas due to its natural weather patterns. There is not yet a local assessment of the relation between groundwater level and sea-level rising. This study investigates the projected sea-level rise models and the anomalous groundwater level during January 2002 to December 2016. We used the NASA Gravity Recovery and Climate Experiment (GRACE) and Global Land Data Assimilation System (GLDAS) satellite data in the analysis. We accounted the leakage error and the measurement error in GRACE data. GLDAS data was used to calculate the groundwater storage from the total water storage estimated using GRACE data (ΔGW=ΔTWS (soil moisture, surface water, groundwater, and canopy water) - ΔGLDAS (soil moisture, surface water, and canopy water)). The preliminary results indicate that the total water storage is increasing in parts of the Gulf of Mexico. GRACE data show high soil wetness and groundwater levels in Mississippi, Alabama and Texas coasts. Because sea-level rise increases the probability of flooding in the Gulf coast and affects the groundwater, we will analyze probable interactions between sea-level rise and groundwater in the study area. To understand regional sea-level rise patterns, we will investigate GRACE Ocean data along the Gulf coasts. We will quantify ocean total water storage, its salinity, and its relationship with the groundwater level variations in the Gulf coast.

  5. Comparison of precise orbit determination methods of zero-difference kinematic, dynamic and reduced-dynamic of GRACE-A satellite using SHORDE software

    Science.gov (United States)

    Li, Kai; Zhou, Xuhua; Guo, Nannan; Zhao, Gang; Xu, Kexin; Lei, Weiwei

    2017-09-01

    Zero-difference kinematic, dynamic and reduced-dynamic precise orbit determination (POD) are three methods to obtain the precise orbits of Low Earth Orbit satellites (LEOs) by using the on-board GPS observations. Comparing the differences between those methods have great significance to establish the mathematical model and is usefull for us to select a suitable method to determine the orbit of the satellite. Based on the zero-difference GPS carrier-phase measurements, Shanghai Astronomical Observatory (SHAO) has improved the early version of SHORDE and then developed it as an integrated software system, which can perform the POD of LEOs by using the above three methods. In order to introduce the function of the software, we take the Gravity Recovery And Climate Experiment (GRACE) on-board GPS observations in January 2008 as example, then we compute the corresponding orbits of GRACE by using the SHORDE software. In order to evaluate the accuracy, we compare the orbits with the precise orbits provided by Jet Propulsion Laboratory (JPL). The results show that: (1) If we use the dynamic POD method, and the force models are used to represent the non-conservative forces, the average accuracy of the GRACE orbit is 2.40cm, 3.91cm, 2.34cm and 5.17cm in radial (R), along-track (T), cross-track (N) and 3D directions respectively; If we use the accelerometer observation instead of non-conservative perturbation model, the average accuracy of the orbit is 1.82cm, 2.51cm, 3.48cm and 4.68cm in R, T, N and 3D directions respectively. The result shows that if we use accelerometer observation instead of the non-conservative perturbation model, the accuracy of orbit is better. (2) When we use the reduced-dynamic POD method to get the orbits, the average accuracy of the orbit is 0.80cm, 1.36cm, 2.38cm and 2.87cm in R, T, N and 3D directions respectively. This method is carried out by setting up the pseudo-stochastic pulses to absorb the errors of atmospheric drag and other

  6. Real-time clock and orbit calculation of the GPS satellite constellation based on observation data of RTIGS-station network

    International Nuclear Information System (INIS)

    Thaler, G.

    2011-01-01

    Due to the development of faster communication networks and improving computer technology beside postprocessing techniques real-time applications and services are more and more created and used in the eld of precise positioning and navigation using global navigation satellite systems (GNSS) like GPS. Data formats like RTCM (NTRIP) or RTIGS serve in this manner as basic tool to transmit real-time GNSS observation data to a eld of users. To handle this trend to real-time, the International GNSS Service (IGS) or more precisely the Real-Time Working Group (RTWG) of the IGS started to establish a global GNSS station network several years ago. These reference stations (RTIGS stations) transmit their observation data in real-time via the open internet to registerd users to support the development of potential new real-time products and services. One example for such a new real-time application based on the observations of the RTIGS network is the software RTIGU-Control developed within this PHD thesis. RTIGU-Control fulls 2 main tasks. The rst task is the monitoring (integrity) of the predicted IGS orbit and clock products (IGU products) using real-time observations from the station network. The second task deals with calculating more precise satellite and station clock corrections compared to the predicted values of the IGU solutions based on the already very precise IGU orbit solutions. In a rst step RTIGU-Control calculates based on the IGU orbit predictions together with code-smoothed station observations precise values for the satellite and station clock corrections.The code-smoothed observations are additionally corrected for several corrections eecting the GNSS observations (for example the delay of the signal propagation time due to the atmosphere, relativistic eects, etc.). The second calculation step deals with monitoring the IGU predicted orbits using the calculated clock solution in the calculation step before and again the corrected real-time observations

  7. Orbits of massive satellite galaxies - II. Bayesian estimates of the Milky Way and Andromeda masses using high-precision astrometry and cosmological simulations

    Science.gov (United States)

    Patel, Ekta; Besla, Gurtina; Mandel, Kaisey

    2017-07-01

    In the era of high-precision astrometry, space observatories like the Hubble Space Telescope (HST) and Gaia are providing unprecedented 6D phase-space information of satellite galaxies. Such measurements can shed light on the structure and assembly history of the Local Group, but improved statistical methods are needed to use them efficiently. Here we illustrate such a method using analogues of the Local Group's two most massive satellite galaxies, the Large Magellanic Cloud (LMC) and Triangulum (M33), from the Illustris dark-matter-only cosmological simulation. We use a Bayesian inference scheme combining measurements of positions, velocities and specific orbital angular momenta (j) of the LMC/M33 with importance sampling of their simulated analogues to compute posterior estimates of the Milky Way (MW) and Andromeda's (M31) halo masses. We conclude that the resulting host halo mass is more susceptible to bias when using measurements of the current position and velocity of satellites, especially when satellites are at short-lived phases of their orbits (I.e. at pericentre). Instead, the j value of a satellite is well conserved over time and provides a more reliable constraint on host mass. The inferred virial mass of the MW (M31) using j of the LMC (M33) is {{M}}_{vir, MW} = 1.02^{+0.77}_{-0.55} × 10^{12} M⊙ ({{M}}_{vir, M31} = 1.37^{+1.39}_{-0.75} × 10^{12} M⊙). Choosing simulated analogues whose j values are consistent with the conventional picture of a previous (<3 Gyr ago), close encounter (<100 kpc) of M33 about M31 results in a very low virial mass for M31 (˜1012 M⊙). This supports the new scenario put forth in Patel, Besla & Sohn, wherein M33 is on its first passage about M31 or on a long-period orbit. We conclude that this Bayesian inference scheme, utilizing satellite j, is a promising method to reduce the current factor of 2 spread in the mass range of the MW and M31. This method is easily adaptable to include additional satellites as new 6D

  8. 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

  9. Geostationary Satellite (GOES) Images

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Visible and Infrared satellite imagery taken from radiometer instruments on SMS (ATS) and GOES satellites in geostationary orbit. These satellites produced...

  10. Analytic model for the long-term evolution of circular Earth satellite orbits including lunar node regression

    Science.gov (United States)

    Zhu, Ting-Lei; Zhao, Chang-Yin; Zhang, Ming-Jiang

    2017-04-01

    This paper aims to obtain an analytic approximation to the evolution of circular orbits governed by the Earth's J2 and the luni-solar gravitational perturbations. Assuming that the lunar orbital plane coincides with the ecliptic plane, Allan and Cook (Proc. R. Soc. A, Math. Phys. Eng. Sci. 280(1380):97, 1964) derived an analytic solution to the orbital plane evolution of circular orbits. Using their result as an intermediate solution, we establish an approximate analytic model with lunar orbital inclination and its node regression be taken into account. Finally, an approximate analytic expression is derived, which is accurate compared to the numerical results except for the resonant cases when the period of the reference orbit approximately equals the integer multiples (especially 1 or 2 times) of lunar node regression period.

  11. SATELLITE CONSTELLATION DESIGN PARAMETER

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. SATELLITE CONSTELLATION DESIGN PARAMETER. 1. ORBIT CHARACTERISTICS. ORBITAL HEIGHT >= 20,000 KM. LONGER VISIBILITY; ORBITAL PERIOD. PERTURBATIONS(MINIMUM). SOLAR RADIATION PRESSURE (IMPACTS ECCENTRICITY); LUNI ...

  12. ATS-6 engineering performance report. Volume 2: Orbit and attitude controls

    Science.gov (United States)

    Wales, R. O. (Editor)

    1981-01-01

    Attitude control is reviewed, encompassing the attitude control subsystem, spacecraft attitude precision pointing and slewing adaptive control experiment, and RF interferometer experiment. The spacecraft propulsion system (SPS) is discussed, including subsystem, SPS design description and validation, orbital operations and performance, in-orbit anomalies and contingency operations, and the cesium bombardment ion engine experiment. Thruster failure due to plugging of the propellant feed passages, a major cause for mission termination, are considered among the critical generic failures on the satellite.

  13. Satellite Anomalies Due to Environment

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These events range from minor operational problems to permanent spacecraft failures. Australia, Canada, Germany, India, Japan, United Kingdom, and the United States...

  14. Venus - Ishtar gravity anomaly

    Science.gov (United States)

    Sjogren, W. L.; Bills, B. G.; Mottinger, N. A.

    1984-01-01

    The gravity anomaly associated with Ishtar Terra on Venus is characterized, comparing line-of-sight acceleration profiles derived by differentiating Pioneer Venus Orbiter Doppler residual profiles with an Airy-compensated topographic model. The results are presented in graphs and maps, confirming the preliminary findings of Phillips et al. (1979). The isostatic compensation depth is found to be 150 + or - 30 km.

  15. Studies of Geomagnetic Pulsations Using Magnetometer Data from the CHAMP Low-Earth-Orbit Satellite and Ground-Based Stations: a Review

    Directory of Open Access Journals (Sweden)

    P R Sutcliffe

    2011-06-01

    Full Text Available We review research on geomagnetic pulsations carried out using magnetic field measurements from the CHAMP low-Earth-orbit (LEO satellite and ground-based stations in South Africa and Hungary. The high quality magnetic field measurements from CHAMP made it possible to extract and clearly resolve Pi2 and Pc3 pulsations in LEO satellite data. Our analyses for nighttime Pi2 pulsations are indicative of a cavity mode resonance. However, observations of daytime Pi2 pulsation events identified in ground station data show no convincing evidence of their occurrence in CHAMP data. We also studied low-latitude Pc3 pulsations and found that different types of field line resonant structure occur, namely discrete frequencies driven by a narrow band source and L-dependent frequencies driven by a broad band source.

  16. LEOcom: communication system for low earth orbit satellites for voice, data and facsimile; LEOcom - sistema de comunicacao por satelites de orbita terrestre baixa para voz, dados e facsimile

    Energy Technology Data Exchange (ETDEWEB)

    Giacaglia, G.E.O.; Lamas, W.Q. [Universidade de Taubate (UNITAU), SP (Brazil). Programa de Pos-graduacao em Engenharia Mecanica], E-mail: giorgio@unitau.br; Ceballos, D.C. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil); Pereira, J.J. [Comando-Geral de Tecnologia Aeroespacial (CTA), Sao Jose dos Campos, SP (Brazil)

    2009-07-01

    This paper provides a basic description of a Communication System for Low Earth Orbit Satellites that can provide voice, data and facsimile to hundreds of countries located in equatorial land between + and - 20 deg latitude, reaching higher latitudes, depending on the location of the onshore terminal. As a point high, it emphasizes its opportunity to support the control of networks transmission of electricity, in any area, and plants generation, located in remote areas, and support any type of operation in these regions. It is the aim of this work to reactivate a good project for Brazil and the tropical world.

  17. Eye and orbital cavity

    International Nuclear Information System (INIS)

    Panfilova, G.V.; Koval', G.Yu.

    1984-01-01

    Radioanatomy of eyes and orbit is described. Diseases of the orbit (developmental anomalies, inflammatory diseases, lacrimal apparatus deseases, toxoplasmosis, tumors and cysts et al.), methods of foreign body localization in the eye are considered. Roentgenograms of the orbit and calculation table for foreign body localization in spherical eyes of dissimilar diameter are presented

  18. Satellite Communications

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Satellite Communications. Arthur C Clarke wrote a seminal paper in 1945 in wireless world. Use three satellites in geo-synchronous orbit to enable intercontinental communications. System could be realised in '50 to 100 years'

  19. Gravitational anomalies

    Energy Technology Data Exchange (ETDEWEB)

    Leutwyler, H; Mallik, S

    1986-12-01

    The effective action for fermions moving in external gravitational and gauge fields is analyzed in terms of the corresponding external field propagator. The central object in our approach is the covariant energy-momentum tensor which is extracted from the regular part of the propagator at short distances. It is shown that the Lorentz anomaly, the conformal anomaly and the gauge anomaly can be expressed in terms of the local polynomials which determine the singular part of the propagator. (There are no coordinate anomalies). Except for the conformal anomaly, for which we give explicit representations only in dless than or equal to4, we consider an arbitrary number of dimensions.

  20. Gridded 5-day mean sea surface height anomaly and significant wave height from Jason-1 and OSTM/Jason-2 satellites (NODC Accession 0065055)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This accession contains the gridded 5-day mean sea surface height anomaly (SSHA) and Ku Band significant wave height (SWH-KU) observed from Jason-1 and OSTM/Jason-2...

  1. Probing the earth's gravity field using Satellite-to-Satellite Tracking (SST)

    Science.gov (United States)

    Vonbun, F. O.

    1976-01-01

    Satellite-to-Satellite (SST) tests, namely: (a) the ATS-6/GEOS-3 and (b) the ATS-6/Apollo-Soyuz experiment and some of the results obtained are described. The main purpose of these two experiments was first to track via ATS-6 the GEOS-3 as well as the Apollo-Soyuz and to use these tracking data to determine (a) both orbits, that is, ATS-6, GEOS-3 and/or the Apollo-Soyuz orbits at the same time; (b) each of these orbits alone; and (c) test the ATS-6/GEOS-3 and/or Apollo-Soyuz SST link to study local gravity anomalies; and, second, to test communications, command, and data transmission from the ground via ATS-6 to these spacecraft and back again to the ground. The Apollo-Soyuz Geodynamics Experiment is discussed in some detail.

  2. Comparison of circular orbit and Fourier power series ephemeris representations for backup use by the upper atmosphere research satellite onboard computer

    Science.gov (United States)

    Kast, J. R.

    1988-01-01

    The Upper Atmosphere Research Satellite (UARS) is a three-axis stabilized Earth-pointing spacecraft in a low-Earth orbit. The UARS onboard computer (OBC) uses a Fourier Power Series (FPS) ephemeris representation that includes 42 position and 42 velocity coefficients per axis, with position residuals at 10-minute intervals. New coefficients and 32 hours of residuals are uploaded daily. This study evaluated two backup methods that permit the OBC to compute an approximate spacecraft ephemeris in the event that new ephemeris data cannot be uplinked for several days: (1) extending the use of the FPS coefficients previously uplinked, and (2) switching to a simple circular orbit approximation designed and tested (but not implemented) for LANDSAT-D. The FPS method provides greater accuracy during the backup period and does not require additional ground operational procedures for generating and uplinking an additional ephemeris table. The tradeoff is that the high accuracy of the FPS will be degraded slightly by adopting the longer fit period necessary to obtain backup accuracy for an extended period of time. The results for UARS show that extended use of the FPS is superior to the circular orbit approximation for short-term ephemeris backup.

  3. ARM Radiosondes for National Polar-Orbiting Operational Environmental Satellite System Preparatory Project Validation Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Borg, Lori [Univ. of Wisconsin, Madison, WI (United States); Tobin, David [Univ. of Wisconsin, Madison, WI (United States); Reale, Anthony [National Oceanic and Atmospheric Administration (NOAA), Washington, DC (United States); Knuteson, Robert [Univ. of Wisconsin, Madison, WI (United States); Feltz, Michelle [Univ. of Wisconsin, Madison, WI (United States); Liu, Mark [National Oceanic and Atmospheric Administration (NOAA), Washington, DC (United States); Holdridge, Donna J [Argonne National Lab. (ANL), Argonne, IL (United States); Mather, James [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2017-06-01

    This IOP has been a coordinated effort involving the U.S. Department of Energy (DOE) Atmospheric Radiation (ARM) Climate Research Facility, the University of Wisconsin (UW)-Madison, and the JPSS project to validate SNPP NOAA Unique Combined Atmospheric Processing System (NUCAPS) temperature and moisture sounding products from the Cross-track Infrared Sounder (CrIS) and the Advanced Technology Microwave Sounder (ATMS). In this arrangement, funding for radiosondes was provided by the JPSS project to ARM. These radiosondes were launched coincident with the SNPP satellite overpasses (OP) at four of the ARM field sites beginning in July 2012 and running through September 2017. Combined with other ARM data, an assessment of the radiosonde data quality was performed and post-processing corrections applied producing an ARM site Best Estimate (BE) product. The SNPP targeted radiosondes were integrated into the NOAA Products Validation System (NPROVS+) system, which collocated the radiosondes with satellite products (NOAA, National Aeronautics and Space Administration [NASA], European Organisation for the Exploitation of Meteorological Satellites [EUMETSAT], Geostationary Operational Environmental Satellite [GOES], Constellation Observing System for Meteorology, Ionosphere, and Climate [COSMIC]) and Numerical Weather Prediction (NWP forecasts for use in product assessment and algorithm development. This work was a fundamental, integral, and cost-effective part of the SNPP validation effort and provided critical accuracy assessments of the SNPP temperature and water vapor soundings.

  4. Viewing marine bacteria, their activity and response to environmental drivers from orbit: satellite remote sensing of bacteria.

    Science.gov (United States)

    Grimes, D Jay; Ford, Tim E; Colwell, Rita R; Baker-Austin, Craig; Martinez-Urtaza, Jaime; Subramaniam, Ajit; Capone, Douglas G

    2014-04-01

    Satellite-based remote sensing of marine microorganisms has become a useful tool in predicting human health risks associated with these microscopic targets. Early applications were focused on harmful algal blooms, but more recently methods have been developed to interrogate the ocean for bacteria. As satellite-based sensors have become more sophisticated and our ability to interpret information derived from these sensors has advanced, we have progressed from merely making fascinating pictures from space to developing process models with predictive capability. Our understanding of the role of marine microorganisms in primary production and global elemental cycles has been vastly improved as has our ability to use the combination of remote sensing data and models to provide early warning systems for disease outbreaks. This manuscript will discuss current approaches to monitoring cyanobacteria and vibrios, their activity and response to environmental drivers, and will also suggest future directions.

  5. Holonomy anomalies

    International Nuclear Information System (INIS)

    Bagger, J.; Nemeschansky, D.; Yankielowicz, S.

    1985-05-01

    A new type of anomaly is discussed that afflicts certain non-linear sigma models with fermions. This anomaly is similar to the ordinary gauge and gravitational anomalies since it reflects a topological obstruction to the reparametrization invariance of the quantum effective action. Nonlinear sigma models are constructed based on homogeneous spaces G/H. Anomalies arising when the fermions are chiral are shown to be cancelled sometimes by Chern-Simons terms. Nonlinear sigma models are considered based on general Riemannian manifolds. 9 refs

  6. Saturn satellites

    International Nuclear Information System (INIS)

    Ruskol, E.L.

    1981-01-01

    The characteristics of the Saturn satellites are discussed. The satellites close to Saturn - Janus, Mimas, Enceladus, Tethys, Dione and Rhea - rotate along the circular orbits. High reflectivity is attributed to them, and the density of the satellites is 1 g/cm 3 . Titan is one of the biggest Saturn satellites. Titan has atmosphere many times more powerful than that of Mars. The Titan atmosphere is a peculiar medium with a unique methane and hydrogen distribution in the whole Solar system. The external satellites - Hyperion, Japetus and Phoebe - are poorly investigated. Neither satellite substance density, nor their composition are known. The experimental data on the Saturn rings obtained on the ''Pioneer-11'' and ''Voyager-1'' satellites are presented [ru

  7. Boomerang Satellites

    Science.gov (United States)

    Hesselbrock, Andrew; Minton, David A.

    2017-10-01

    We recently reported that the orbital architecture of the Martian environment allows for material in orbit around the planet to ``cycle'' between orbiting the planet as a ring, or as coherent satellites. Here we generalize our previous analysis to examine several factors that determine whether satellites accreting at the edge of planetary rings will cycle. In order for the orbiting material to cycle, tidal evolution must decrease the semi-major axis of any accreting satellites. In some systems, the density of the ring/satellite material, the surface mass density of the ring, the tidal parameters of the system, and the rotation rate of the primary body contribute to a competition between resonant ring torques and tidal dissipation that prevent this from occurring, either permanently or temporarily. Analyzing these criteria, we examine various bodies in our solar system (such as Saturn, Uranus, and Eris) to identify systems where cycling may occur. We find that a ring-satellite cycle may give rise to the current Uranian ring-satellite system, and suggest that Miranda may have formed from an early, more massive Uranian ring.

  8. Verified solutions for the gravitational attraction to an oblate spheroid: Implications for planet mass and satellite orbits

    Science.gov (United States)

    Hofmeister, Anne M.; Criss, Robert E.; Criss, Everett M.

    2018-03-01

    Forces external to the oblate spheroid shape, observed from planetary to galactic scales, are demonstrably non-central, which has important ramifications for planetary science. We simplify historic formulae and derive new analytical solutions for the gravitational potential and force outside a constant density oblate. Numerical calculations that sum point mass contributions in a >109 element mesh confirm our equations. We show that contours of constant force and potential about oblate bodies are closely approximated by two confocal families whose foci (f) respectively are (9/10)½ae and (3/5)½ae for a body with f = ae. This leads to useful approximations that address internal density variations. We demonstrate that the force on a general point is not directed towards the oblate's center, nor are forces simply proportional to the inverse square of that distance, despite forces in the equatorial and axial directions pointing towards the center. Our results explain complex dynamics of galactic systems. Because most planets and stars have an aspect ratio >0.9, the spherical approximation is reasonable except for orbits within ∼2 body radii. We show that applying the "generalized" potential, which assumes central forces, yields J2 values half those expected for oblate bodies, and probably underestimates masses of Uranus and Neptune by ∼0.2%. We show that the inner Saturnian moons are subject to non-central forces, which may affect calculations of their orbital precession. Our new series should improve interpretation of flyby data.

  9. 卫星轨道Kalman滤波稳健估计%obust Kalman Filtering for Satellite Orbit Determination

    Institute of Scientific and Technical Information of China (English)

    文援兰; 王威; 杨元喜

    2001-01-01

    Kalman filtering is affected by the gross error that is inevitable in the observation of satellite. First robust kalman filtering is derived and its robustness is analyzed, then the observations of Lageos is processed. It verifies that robust kalman filtering has the capability to resist the gross error.%卫星观测数据中不可避免地存在着粗差,一般的Kalman滤波易受观测粗差的影响。首先推导Kalman滤波稳健估计公式,并分析了它的稳健性。然后用Kalman滤波稳健估计对Lageos卫星的激光实测资料进行了处理,证明它具有明显的抗粗差的能力和稳健性。

  10. Evolution of almost circular orbits of satellites under the action of noncentral gravitational field of the Earth and lunisolar perturbations

    Science.gov (United States)

    Dulliev, A. M.

    2011-02-01

    Based on the results of paper [1] by G.V. Mozhaev, joint perturbations produced by nonsphericity of the Earth and by attraction of the Moon and the Sun are investigated using the method of averaging. Arbitrary number of spherical harmonics was taken into account in the force function of the Earth’s gravitational filed, and only the principal term was retained in the perturbing function of the Sun. In the perturbing function of the Moon two parallactic terms were considered in addition to the dominant term. The flight altitude was chosen in such a way that perturbations produced by the Sun and Moon would have the second order of smallness relative to the polar oblateness of the Earth. As a result, the formulas for calculation of satellite coordinates are derived that give a high precision on long time intervals.

  11. Local time dependences of electron flux changes during substorms derived from mulit-satellite observation at synchronous orbit

    International Nuclear Information System (INIS)

    Nagai, T.

    1982-01-01

    Energetic electron (energy higher than 2 MeV) observation by a synchronous satellite chain (which consists of GOES 2, GOES 3, and GMS covering the local time extent of approximately 10 hr) have been used to study the large-scale characteristics of the dynamic behavior in the near-earth magnetosphere for substorms, in which low-latitude positive bay aspects are clearly seen in the ground magnetic data. Simultaneous multi-satellite observations have clearly demonstrated the local time dependence of electron flux changes during substorms and the longitudinal extent of electron flux variations. Before a ground substorm onset the energetic electron flux decreases in a wide longitudinal region of the nighttime and the flux decrease is seen even on the afternoonside. For the flux behavior associated with the onset of the substorm expansion phase, there exists a demarcation line, the LT position of which can be represented as LT = 24.3-1.5 K/sub p/. The flux shows a recovery to a normal level east of the demarcation line, and it shows a decrease west of the demarcation line. The region of the flux decrease during the expansion phase is restricted, and it is observed mainly on the afternoonside. The afternoonside flux decrease has a different characteristic from the nightside flux decrease preceding the expansion phase. The nighside flux decrease-recovery sequence is observed in a wide region of more than 6 hr in the nighttime and the center of this variation exists in the premidnight region. It should be noted that the afternoonside flux decrease is not observed for every substorm and the nightside signature noted that the afternoonside flux sometimes becomes a dominent feature even on the afternoonside

  12. Arcs électriques sur panneaux solaires de satellite

    OpenAIRE

    Amorim, Emmanuel

    2002-01-01

    Tout au long de leur durée de vie, les satellites sont en interaction constante avec l'environnement spatial. En orbite géostationnaire, les surfaces des satellites sont par exemple chargées par les particules de la magnétosphère, en particulier par les électrons. Récemment, des pertes de puissance ont été constatées sur certains satellites situés en orbite géostationnaire. Ces anomalies ont été corrélées avec des périodes d'environnement chargeant et s'expliqueraient par une décharge électro...

  13. Daily observations of the development of the ionospheric equatorial anomaly by means of differential Doppler shift method

    International Nuclear Information System (INIS)

    Huang, Y.N.; Cheng, K.; Chen, S.W.

    1987-01-01

    The differential Doppler frequency shifts observed by receiving coherent radio signals at frequencies of 150 and 400 MHz transmitted from the polar orbiting satellites of U.S. Navy Navigation Satellite System have been used to deduce the latitudinal variations of the ionospheric total electron content (TEC) near the ionospheric equatorial anomaly crest region. All latitudinal variations of TEC thus obtained for each passage of an NNSS satellite are used to construct daily contour plots of TEC in a latitude versus local time coordinates. It has been shown that these contour plot of TEC can be used to investigate the behavior of TEC around equatorial anomaly crest region. Some results are presented and discussed. 18 references

  14. Reanalyses of the radiation belt electron phase space density using nearly equatorial CRRES and polar-orbiting Akebono satellite observations

    Science.gov (United States)

    Ni, Binbin; Shprits, Yuri; Nagai, Tsugunobu; Thorne, Richard; Chen, Yue; Kondrashov, Dmitri; Kim, Hee-jeong

    2009-05-01

    Data assimilation techniques provide algorithms that allow for blending of incomplete and inaccurate data with physics-based dynamic models to reconstruct the electron phase space density (PSD) in the radiation belts. In this study, we perform reanalyses of the radial PSD profile using two independent data sources from the nearly equatorial CRRES Medium Electron A (MEA) observations and the polar-orbiting Akebono Radiation Monitor (RDM) measurements for a 50-day period from 18 August to 6 October 1990. We utilize the University of California, Los Angeles, One-Dimensional Versatile Electron Radiation Belt (UCLA 1-D VERB) code and a Kalman filtering approach. Comparison of the reanalyses obtained independently using the CRRES MEA and Akebono RDM measurements shows that the dynamics of the PSD can be accurately reconstructed using Kalman filtering even when available data are sparse, inaccurate, and contaminated by random errors. The reanalyses exhibit similarities in the locations and magnitudes of peaks in radial profiles of PSD and the rate and radial extent of the dropouts during storms. This study shows that when unidirectional data are not available, pitch angle averaged flux measurements can be used to infer the long-term behavior (climatology) of the radiation belts. The methodology of obtaining PSD from pitch angle averaged and unidirectional fluxes using the Tsyganenko and Stern (1996) magnetic field model is described in detail.

  15. Orbits 2nd order singularity-free solutions

    CERN Document Server

    Xu, Guochang

    2014-01-01

    In its 2nd edition, this book covers the theory of satellite orbits, derives the complete solutions of orbital disturbances, describes the algorithms of orbits determination and the applications of the theory to the phenomenon of physical satellite formation.

  16. Towards high temporal and moderate spatial resolutions in the remote sensing retrieval of evapotranspiration by combining geostationary and polar orbit satellite data

    Science.gov (United States)

    Barrios, José Miguel; Ghilain, Nicolas; Arboleda, Alirio; Gellens-Meulenberghs, Françoise

    2014-05-01

    Evapotranspiration (ET) is the water flux going from the surface into the atmosphere as result of soil and surface water evaporation and plant transpiration. It constitutes a key component of the water cycle and its quantification is of crucial importance for a number of applications like water management, climatic modelling, agriculture monitoring and planning, etc. Estimating ET is not an easy task; specially if large areas are envisaged and various spatio-temporal patterns of ET are present as result of heterogeneity in land cover, land use and climatic conditions. In this respect, spaceborne remote sensing (RS) provides the only alternative to continuously measure surface parameters related to ET over large areas. The Royal Meteorological Institute (RMI) of Belgium, in the framework of EUMETSAT's "Land Surface Analysis-Satellite Application Facility" (LSA-SAF), has developed a model for the estimation of ET. The model is forced by RS data, numerical weather predictions and land cover information. The RS forcing is derived from measurements by the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard the Meteosat Second Generation (MSG) satellite. This ET model is operational and delivers ET estimations over the whole field of view of the MSG satellite (Europe, Africa and Eastern South America) (http://landsaf.meteo.pt) every 30 minutes. The spatial resolution of MSG is 3 x 3 km at subsatellite point and about 4 x 5 km in continental Europe. The spatial resolution of this product may constrain its full exploitation as the interest of potential users (farmers and natural resources scientists) may lie on smaller spatial units. This study aimed at testing methodological alternatives to combine RS imagery (geostationary and polar orbit satellites) for the estimation of ET such that the spatial resolution of the final product is improved. In particular, the study consisted in the implementation of two approaches for combining the current ET estimations with

  17. Initial assessment of the effects of energetic-ion injections in the magnetosphere due to the transport of satellite-power-system components from low earth orbit to geosynchronous earth orbit

    International Nuclear Information System (INIS)

    Curtis, S.A.; Grebowsky, J.M.

    1980-07-01

    Potentially serious environmental effects exist when cargo orbital transfer vehicle (COTV) ion propulsion is used on the scale proposed in the preliminary definition studies of the Satellite Power System. These effects of the large scale injections of ion propulsion exhaust in the plasmasphere and in the outer magnetosphere are shown to be highly model dependent with major differences existing in the predicted effects of two models - the ion cloud model and the ion sheath model. The expected total number density deposition of the propellant Ar + in the plasmasphere, the energy spectra of the deposited Ar + and time-dependent behavior of the Ar + injected into the plasmasphere by a fleet of COTV vehicles differ drastically between the two models. The major environmental effect of the former model is communication disturbance due to plasma density irregularities, in contrast to the spectacular predictions of the latter model which include power line tripping and pipe line corrosion. The ion sheath model is demonstrated to be applicable to the proposed Ar + beam physics if the beam is divergent and turbulent whereas the ion cloud model is not a realistic approximation for such a beam because the frozen-field assumption on which it is based is not valid. Finally, it is shown that the environmental effects of ion propulsion may be mitigated by the appropriate adjustment of the beam parameters

  18. GLONASS orbit/clock combination in VNIIFTRI

    Science.gov (United States)

    Bezmenov, I.; Pasynok, S.

    2015-08-01

    An algorithm and a program for GLONASS satellites orbit/clock combination based on daily precise orbits submitted by several Analytic Centers were developed. Some theoretical estimates for combine orbit positions RMS were derived. It was shown that under condition that RMS of satellite orbits provided by the Analytic Centers during a long time interval are commensurable the RMS of combine orbit positions is no greater than RMS of other satellite positions estimated by any of the Analytic Centers.

  19. Effect of Ionosphere on Geostationary Communication Satellite Signals

    Science.gov (United States)

    Erdem, Esra; Arikan, Feza; Gulgonul, Senol

    2016-07-01

    Geostationary orbit (GEO) communications satellites allow radio, television, and telephone transmissions to be sent live anywhere in the world. They are extremely important in daily life and also for military applications. Since, satellite communication is an expensive technology addressing crowd of people, it is critical to improve the performance of this technology. GEO satellites are at 35,786 kilometres from Earth's surface situated directly over the equator. A satellite in a geostationary orbit (GEO) appears to stand still in the sky, in a fixed position with respect to an observer on the earth, because the satellite's orbital period is the same as the rotation rate of the Earth. The advantage of this orbit is that ground antennas can be fixed to point towards to satellite without their having to track the satellite's motion. Radio frequency ranges used in satellite communications are C, X, Ku, Ka and even EHG and V-band. Satellite signals are disturbed by atmospheric effects on the path between the satellite and the receiver antenna. These effects are mostly rain, cloud and gaseous attenuation. It is expected that ionosphere has a minor effect on the satellite signals when the ionosphere is quiet. But there are anomalies and perturbations on the structure of ionosphere with respect to geomagnetic field and solar activity and these conditions may cause further affects on the satellite signals. In this study IONOLAB-RAY algorithm is adopted to examine the effect of ionosphere on satellite signals. IONOLAB-RAY is developed to calculate propagation path and characteristics of high frequency signals. The algorithm does not have any frequency limitation and models the plasmasphere up to 20,200 km altitude, so that propagation between a GEO satellite and antenna on Earth can be simulated. The algorithm models inhomogeneous, anisotropic and time dependent structure of the ionosphere with a 3-D spherical grid geometry and calculates physical parameters of the

  20. Trends in communications satellites

    CERN Document Server

    Curtin, Denis J

    1979-01-01

    Trends in Communications Satellites offers a comprehensive look at trends and advances in satellite communications, including experimental ones such as NASA satellites and those jointly developed by France and Germany. The economic aspects of communications satellites are also examined. This book consists of 16 chapters and begins with a discussion on the fundamentals of electrical communications and their application to space communications, including spacecraft, earth stations, and orbit and wavelength utilization. The next section demonstrates how successful commercial satellite communicati

  1. Tethered Satellite System Contingency Investigation Board

    Science.gov (United States)

    1992-11-01

    The Tethered Satellite System (TSS-1) was launched aboard the Space Shuttle Atlantis (STS-46) on July 31, 1992. During the attempted on-orbit operations, the Tethered Satellite System failed to deploy successfully beyond 256 meters. The satellite was retrieved successfully and was returned on August 6, 1992. The National Aeronautics and Space Administration (NASA) Associate Administrator for Space Flight formed the Tethered Satellite System (TSS-1) Contingency Investigation Board on August 12, 1992. The TSS-1 Contingency Investigation Board was asked to review the anomalies which occurred, to determine the probable cause, and to recommend corrective measures to prevent recurrence. The board was supported by the TSS Systems Working group as identified in MSFC-TSS-11-90, 'Tethered Satellite System (TSS) Contingency Plan'. The board identified five anomalies for investigation: initial failure to retract the U2 umbilical; initial failure to flyaway; unplanned tether deployment stop at 179 meters; unplanned tether deployment stop at 256 meters; and failure to move tether in either direction at 224 meters. Initial observations of the returned flight hardware revealed evidence of mechanical interference by a bolt with the level wind mechanism travel as well as a helical shaped wrap of tether which indicated that the tether had been unwound from the reel beyond the travel by the level wind mechanism. Examination of the detailed mission events from flight data and mission logs related to the initial failure to flyaway and the failure to move in either direction at 224 meters, together with known preflight concerns regarding slack tether, focused the assessment of these anomalies on the upper tether control mechanism. After the second meeting, the board requested the working group to complete and validate a detailed integrated mission sequence to focus the fault tree analysis on a stuck U2 umbilical, level wind mechanical interference, and slack tether in upper tether

  2. DOWN'S ANOMALY.

    Science.gov (United States)

    PENROSE, L.S.; SMITH, G.F.

    BOTH CLINICAL AND PATHOLOGICAL ASPECTS AND MATHEMATICAL ELABORATIONS OF DOWN'S ANOMALY, KNOWN ALSO AS MONGOLISM, ARE PRESENTED IN THIS REFERENCE MANUAL FOR PROFESSIONAL PERSONNEL. INFORMATION PROVIDED CONCERNS (1) HISTORICAL STUDIES, (2) PHYSICAL SIGNS, (3) BONES AND MUSCLES, (4) MENTAL DEVELOPMENT, (5) DERMATOGLYPHS, (6) HEMATOLOGY, (7)…

  3. Investigation of the Crust of the Pannonian Basin, Hungary Using Low-Altitude CHAMP Horizontal Gradient Magnetic Anomalies

    Science.gov (United States)

    Taylor, Patrick T.; Kis, Karoly I.; Puszta, Sandor; Wittmann, Geza; Kim, Hyung Rae; Toronyi, B.

    2011-01-01

    The Pannonian Basin is a deep intra-continental basin that formed as part of the Alpine orogeny. It is some 600 by 500 km in area and centered on Hungary. This area was chosen since it has one of the thinnest continental crusts in Europe and is the region of complex tectonic structures. In order to study the nature of the crustal basement we used the long-wavelength magnetic anomalies acquired by the CHAMP satellite. The SWARM constellation, scheduled to be launched next year, will have two lower altitude satellites flying abreast, with a separation of between ca. 150 to 200 km. to record the horizontal magnetic gradient. Since the CHAMP satellite has been in orbit for eight years and has obtained an extensive range of data, both vertically and horizontally there is a large enough data base to compute the horizontal magnetic gradients over the Pannonian Basin region using these many CHAMP orbits. We recomputed a satellite magnetic anomaly map, using the spherical-cap method of Haines (1985), the technique of Alsdorf et al. (1994) and from spherical harmonic coefficients of MF6 (Maus et aI., 2008) employing the latest and lowest altitude CHAMP data. We then computed the horizontal magnetic anomaly gradients (Kis and Puszta, 2006) in order to determine how these component data will improve our interpretation and to preview what the SW ARM mission will reveal with reference to the horizontal gradient anomalies. The gradient amplitude of an 1000 km northeast-southwest profile through our horizontal component anomaly map varied from 0 to 0.025 nT/km with twin positive anomalies (0.025 and 0.023 nT/km) separated by a sharp anomaly negative at o nT/km. Horizontal gradient indicate major magnetization boundaries in the crust (Dole and Jordan, 1978 and Cordell and Grauch, 1985). Our gradient anomaly was modeled with a twodimensional body and the anomaly, of some 200 km, correlates with a 200 km area of crustal thinning in the southwestern Pannonian Basin.

  4. Orbital studies of lunar magnetism

    Science.gov (United States)

    Mcleod, M. G.; Coleman, P. J., Jr.

    1982-01-01

    Limitations of present lunar magnetic maps are considered. Optimal processing of satellite derived magnetic anomaly data is also considered. Studies of coastal and core geomagnetism are discussed. Lunar remanent and induced lunar magnetization are included.

  5. The relationship of thermospheric density anomaly with electron temperature, small-scale FAC, and ion up-flow in the cusp region, as observed by CHAMP and DMSP satellites

    Directory of Open Access Journals (Sweden)

    G. N. Kervalishvili

    2013-03-01

    Full Text Available We present in a statistical study a comparison of thermospheric mass density enhancements (ρrel with electron temperature (Te, small-scale field-aligned currents (SSFACs, and vertical ion velocity (Vz at high latitudes around noon magnetic local time (MLT. Satellite data from CHAMP (CHAllenging Minisatellite Payload and DMSP (Defense Meteorological Satellite Program sampling the Northern Hemisphere during the years 2002–2005 are used. In a first step we investigate the distribution of the measured quantities in a magnetic latitude (MLat versus MLT frame. All considered variables exhibit prominent peak amplitudes in the cusp region. A superposed epoch analysis was performed to examine causal relationship between the quantities. The occurrence of a thermospheric relative mass density anomaly, ρrel >1.2, in the cusp region is defining an event. The location of the density peak is taken as a reference latitude (Δ MLat = 0°. Interestingly, all the considered quantities, SSFACs, Te, and Vz are co-located with the density anomaly. The amplitudes of the peaks exhibit different characters of seasonal variation. The average relative density enhancement of the more prominent density peaks considered in this study amounts to 1.33 during all seasons. As expected, SSFACs are largest in summer with average amplitudes equal to 2.56 μA m−2, decaying to 2.00 μA m−2 in winter. The event related enhancements of Te and Vz are both largest in winter (Δ Te =730 K, Vz =136 m s−1 and smallest in summer (Δ Te = 377 K, Vz = 57 m s−1. Based on the similarity of the seasonal behaviour we suggest a close relationship between these two quantities. A correlation analysis supports a linear relation with a high coefficient greater than or equal to 0.93, irrespective of season. Our preferred explanation is that dayside reconnection fuels Joule heating of the thermosphere causing air upwelling and at the same time heating of the electron gas that pulls up ions

  6. Regional magnetic anomaly constraints on continental rifting

    Science.gov (United States)

    Vonfrese, R. R. B.; Hinze, W. J.; Olivier, R.; Bentley, C. R.

    1985-01-01

    Radially polarized MAGSAT anomalies of North and South America, Europe, Africa, India, Australia and Antarctica demonstrate remarkably detailed correlation of regional magnetic lithospheric sources across rifted margins when plotted on a reconstruction of Pangea. These major magnetic features apparently preserve their integrity until a superimposed metamorphoric event alters the magnitude and pattern of the anomalies. The longevity of continental scale magnetic anomalies contrasts markedly with that of regional gravity anomalies which tend to reflect predominantly isostatic adjustments associated with neo-tectonism. First observed as a result of NASA's magnetic satellite programs, these anomalies provide new and fundamental constraints on the geologic evolution and dynamics of the continents and oceans. Accordingly, satellite magnetic observations provide a further tool for investigating continental drift to compliment other lines of evidence in paleoclimatology, paleontology, paleomagnetism, and studies of the radiometric ages and geometric fit of the continents.

  7. Satellite Geomagnetism

    DEFF Research Database (Denmark)

    Olsen, Nils; Stolle, Claudia

    2012-01-01

    Observations of Earth’s magnetic field from space began more than 50 years ago. A continuous monitoring of the field using low Earth orbit (LEO) satellites, however, started only in 1999, and three satellites have taken highprecision measurements of the geomagnetic field during the past decade....... The unprecedented time-space coverage of their data opened revolutionary new possibilities for monitoring, understanding, and exploring Earth’s magnetic field. In the near future, the three-satellite constellation Swarm will ensure continuity of such measurement and provide enhanced possibilities to improve our...... ability to characterize and understand the many sources that contribute to Earth’s magnetic field. In this review, we summarize investigations of Earth’s interior and environment that have been possible through the analysis of high-precision magnetic field observations taken by LEO satellites....

  8. Utilization of downscaled microwave satellite data and GRACE Total Water Storage anomalies for improving streamflow prediction in the Lower Mekong Basin

    Science.gov (United States)

    Lakshmi, V.; Gupta, M.; Bolten, J. D.

    2016-12-01

    The Mekong river is the world's eighth largest in discharge with draining an area of 795,000 km² from the Eastern watershed of the Tibetan Plateau to the Mekong Delta including, Myanmar, Laos PDR, Thailand, Cambodia, Vietnam and three provinces of China. The populations in these countries are highly dependent on the Mekong River and they are vulnerable to the availability and quality of the water resources within the Mekong River Basin. Soil moisture is one of the most important hydrological cycle variables and is available from passive microwave satellite sensors (such as AMSR-E, SMOS and SMAP), but their spatial resolution is frequently too coarse for effective use by land managers and decision makers. The merging of satellite observations with numerical models has led to improved land surface predictions. Although performance of the models have been continuously improving, the laboratory methods for determining key hydraulic parameters are time consuming and expensive. The present study assesses a method to determine the effective soil hydraulic parameters using a downscaled microwave remote sensing soil moisture product based on the NASA Advanced Microwave Scanning Radiometer (AMSR-E). The soil moisture downscaling algorithm is based on a regression relationship between 1-km MODIS land surface temperature and 1-km Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) to produce an enhanced spatial resolution ASMR-E-based soil moisture product. Since the optimized parameters are based on the near surface soil moisture information, further constraints are applied during the numerical simulation through the assimilation of GRACE Total Water Storage (TWS) within the land surface model. This work improves the hydrological fluxes and the state variables are optimized and the optimal parameter values are then transferred for retrieving hydrological fluxes. To evaluate the performance of the system in helping improve

  9. Effects of high-orbit spaceflight on signaling cascades and apoptosis in immune cells from mice flied on board the BION-M1 satellite

    Science.gov (United States)

    Novoselova, Elena; Shenkman, Boris; Lunin, Sergey; Parfenyuk, Svetlana; Novoselova, Tatyana; Fesenko, Eugeny

    The study was designed to evaluate immune cell activity in male C57bl mice after a 30-day high-orbit spaceflight (550 km, higher than conventional manned spaceflights) on board the BION-M1 satellite (Roskosmos Program, Russia). For the present study, thymus, spleens and plasma samples were collected from mice 12 h after landing and, additionally, 7 days subsequently. Assessing the activity of NF-kappaB signaling cascade by measuring Rel A (p65) protein phosphorylation in splenic lymphocytes, we showed that the NF-kappaB activity was significantly increased at 12 h after landing. Contrariwise, one week after landing, the NF-kappaB activity was markedly decreased, even below to the control values. Interestingly, after landing there were no significant changes in SAPK/JNK cascade activity in splenic lymphocytes as well as in the expression of transcription factor IRF3 in thymus cells. To assess the apoptosis status in thymus lymphocytes, levels of p53 protein and its phosphorylated form were measured in thymic lymphocytes. It is known that p53 plays an important role in the cellular response to DNA damage, genomic aberrations, and other characteristic of apoptosis. The results showed that the high-orbit spaceflight environment caused some increase in level of p53 protein, but most notably, activated phosphorylated form of p53 protein. Calculated ratio of active and inactive forms of the protein (ph-p53/p53) 12 h after landing increased by more than 2-fold, indicating the apparent induction of apoptosis in thymus cells. Interestingly, 7 days after the landing, this ratio was not restored, but rather increased: the specified ratio was 4 times higher as compared to the ground-based control. We can conclude that response to the prolonged high-orbit spaceflight is not like the classic "stress response", which is usually observed under various stressful factors. It is known that the stress response is surely accompanied by increased SAPK/JNK cascade activity as well as the

  10. South Atlantic Anomaly evolution by means of Swarm data

    Science.gov (United States)

    Pavon-Carrasco, F. Javier; Qamili, Enkelejda; De Santis, Angelo

    2015-04-01

    The study of the South Atlantic Anomaly (SAA) is an important challenge nowadays not only for the geomagnetic and paleomagnetic community, but also for other areas focused on the Earth Observation. This large magnetic anomaly is characterized by values of geomagnetic field intensity around 30% lower than expected for those latitudes and covers a large area in the South Atlantic Ocean between Southwest Brazil and South Africa. This great depression of the geomagnetic field strength at the Earth's surface has an internal deep origin: it is caused by a prominent patch of reversed polarity flux in the outer core. Since the Earth's magnetic field has an important protective role for the all geosphere because it deflects a large part of the solar radiation that would otherwise reach the Earth's surface, a large increase of the SAA could have dramatic consequences for human health and technologies. In the last three decades, an almost constant monitoring of the SAA has been carried out using satellite data showing a clear picture of the behaviour and evolution of the SAA, which area is growing alarmingly during the most recent years at the Earth's surface and at the core mantle boundary. In this context, the ESA Swarm mission (constituted by a constellation of three satellites in near-polar low orbits at two different altitudes) is providing detailed measurements of the intensity and directional elements of the geomagnetic field with high-precision and resolution never reached in the former space missions. This work aims to analyse in detail in space and time the SAA from the Earth's surface up to the satellite altitude. In order to carry out this study, comprehensive geomagnetic models at regional and global scale will be performed using the dataset provided by the Swarm satellites and all the available ground data. This kind of study is crucial to understand the evolution of the Earth's magnetic field in this area, and to possibly predict its future behaviour.

  11. Scientific Satellites

    Science.gov (United States)

    1967-01-01

    noise signal level exceeds 10 times the normal background. EXPERIMENTS FOR SATELLITE ASTRONOMY 615 ANTENNA MONOPOLE -., PREAMPLFE = BANDPASS-FILTER...OUTPUT TO AND DETECTOR TELEMETRYCHANNELS (18) CALIBRATION NOISE MATRIX CLOCK NOISE SOURCE ’ON’ SOURCE COMMAND F ROM PROGRAMERP ANTENNA MONOPOLE FIGURE 13...Animal Tempera- ture Sensing for Studying the Effect of Prolonged Orbital Flight on the Circadian Rhythms of Pocket Mice . Unmanned Spacecraft Meeting

  12. Dyonic anomalies

    International Nuclear Information System (INIS)

    Henningson, Mans; Johansson, Erik P.G.

    2005-01-01

    We consider the problem of coupling a dyonic p-brane in d=2p+4 space-time dimensions to a prescribed (p+2)-form field strength. This is particularly subtle when p is odd. For the case p=1, we explicitly construct a coupling functional, which is a sum of two terms: one which is linear in the prescribed field strength, and one which describes the coupling of the brane to its self-field and takes the form of a Wess-Zumino term depending only on the embedding of the brane world-volume into space-time. We then show that this functional is well-defined only modulo a certain anomaly, related to the Euler class of the normal bundle of the brane world-volume

  13. Precision orbit determination performance for CryoSat-2

    Science.gov (United States)

    Schrama, Ernst

    2018-01-01

    In this paper we discuss our efforts to perform precision orbit determination (POD) of CryoSat-2 which depends on Doppler and satellite laser ranging tracking data. A dynamic orbit model is set-up and the residuals between the model and the tracking data is evaluated. The average r.m.s. of the 10 s averaged Doppler tracking pass residuals is approximately 0.39 mm/s; and the average of the laser tracking pass residuals becomes 1.42 cm. There are a number of other tests to verify the quality of the orbit solution, we compare our computed orbits against three independent external trajectories provided by the CNES. The CNES products are part of the CryoSat-2 products distributed by ESA. The radial differences of our solution relative to the CNES precision orbits shows an average r.m.s. of 1.25 cm between Jun-2010 and Apr-2017. The SIRAL altimeter crossover difference statistics demonstrate that the quality of our orbit solution is comparable to that of the POE solution computed by the CNES. In this paper we will discuss three important changes in our POD activities that have brought the orbit performance to this level. The improvements concern the way we implement temporal gravity accelerations observed by GRACE; the implementation of ITRF2014 coordinates and velocities for the DORIS beacons and the SLR tracking sites. We also discuss an adjustment of the SLR retroreflector position within the satellite reference frame. An unexpected result is that we find a systematic difference between the median of the 10 s Doppler tracking residuals which displays a statistically significant pattern in the South Atlantic Anomaly (SSA) area where the median of the velocity residuals varies in the range of -0.15 to +0.15 mm/s.

  14. Some design considerations for planetary relay communications satellites.

    Science.gov (United States)

    Barber, T. A.; Bourke, R. D.

    1966-01-01

    Items affecting information transmitted from payload landed on remote planet to Earth via communications satellite including orbit, transmission policy and orbit injection error effect on communication capability

  15. Satellite services system overview

    Science.gov (United States)

    Rysavy, G.

    1982-01-01

    The benefits of a satellite services system and the basic needs of the Space Transportation System to have improved satellite service capability are identified. Specific required servicing equipment are discussed in terms of their technology development status and their operative functions. Concepts include maneuverable television systems, extravehicular maneuvering unit, orbiter exterior lighting, satellite holding and positioning aid, fluid transfer equipment, end effectors for the remote manipulator system, teleoperator maneuvering system, and hand and power tools.

  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. A Satellite Mortality Study to Support Space Systems Lifetime Prediction

    Science.gov (United States)

    Fox, George; Salazar, Ronald; Habib-Agahi, Hamid; Dubos, Gregory

    2013-01-01

    Estimating the operational lifetime of satellites and spacecraft is a complex process. Operational lifetime can differ from mission design lifetime for a variety of reasons. Unexpected mortality can occur due to human errors in design and fabrication, to human errors in launch and operations, to random anomalies of hardware and software or even satellite function degradation or technology change, leading to unrealized economic or mission return. This study focuses on data collection of public information using, for the first time, a large, publically available dataset, and preliminary analysis of satellite lifetimes, both operational lifetime and design lifetime. The objective of this study is the illustration of the relationship of design life to actual lifetime for some representative classes of satellites and spacecraft. First, a Weibull and Exponential lifetime analysis comparison is performed on the ratio of mission operating lifetime to design life, accounting for terminated and ongoing missions. Next a Kaplan-Meier survivor function, standard practice for clinical trials analysis, is estimated from operating lifetime. Bootstrap resampling is used to provide uncertainty estimates of selected survival probabilities. This study highlights the need for more detailed databases and engineering reliability models of satellite lifetime that include satellite systems and subsystems, operations procedures and environmental characteristics to support the design of complex, multi-generation, long-lived space systems in Earth orbit.

  18. Chiral anomalies and differential geometry

    International Nuclear Information System (INIS)

    Zumino, B.

    1983-10-01

    Some properties of chiral anomalies are described from a geometric point of view. Topics include chiral anomalies and differential forms, transformation properties of the anomalies, identification and use of the anomalies, and normalization of the anomalies. 22 references

  19. Defense Meteorological Satellite Program (DMSP) - Space Weather Sensors

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Defense Meteorological Satellite Program (DMSP) maintains a constellation of sun-synchronous, near-polar orbiting satellites. The orbital period is 101 minutes...

  20. Harmonically excited orbital variations

    International Nuclear Information System (INIS)

    Morgan, T.

    1985-01-01

    Rephrasing the equations of motion for orbital maneuvers in terms of Lagrangian generalized coordinates instead of Newtonian rectangular cartesian coordinates can make certain harmonic terms in the orbital angular momentum vector more readily apparent. In this formulation the equations of motion adopt the form of a damped harmonic oscillator when torques are applied to the orbit in a variationally prescribed manner. The frequencies of the oscillator equation are in some ways unexpected but can nonetheless be exploited through resonant forcing functions to achieve large secular variations in the orbital elements. Two cases are discussed using a circular orbit as the control case: (1) large changes in orbital inclination achieved by harmonic excitation rather than one impulsive velocity change, and (2) periodic and secular changes to the longitude of the ascending node using both stable and unstable excitation strategies. The implications of these equations are also discussed for both artificial satellites and natural satellites. For the former, two utilitarian orbits are suggested, each exploiting a form of harmonic excitation. 5 refs

  1. Meteorological satellite systems

    CERN Document Server

    Tan, Su-Yin

    2014-01-01

    “Meteorological Satellite Systems” is a primer on weather satellites and their Earth applications. This book reviews historic developments and recent technological advancements in GEO and polar orbiting meteorological satellites. It explores the evolution of these remote sensing technologies and their capabilities to monitor short- and long-term changes in weather patterns in response to climate change. Satellites developed by various countries, such as U.S. meteorological satellites, EUMETSAT, and Russian, Chinese, Japanese and Indian satellite platforms are reviewed. This book also discusses international efforts to coordinate meteorological remote sensing data collection and sharing. This title provides a ready and quick reference for information about meteorological satellites. It serves as a useful tool for a broad audience that includes students, academics, private consultants, engineers, scientists, and teachers.

  2. Robustness analysis method for orbit control

    Science.gov (United States)

    Zhang, Jingrui; Yang, Keying; Qi, Rui; Zhao, Shuge; Li, Yanyan

    2017-08-01

    Satellite orbits require periodical maintenance due to the presence of perturbations. However, random errors caused by inaccurate orbit determination and thrust implementation may lead to failure of the orbit control strategy. Therefore, it is necessary to analyze the robustness of the orbit control methods. Feasible strategies which are tolerant to errors of a certain magnitude can be developed to perform reliable orbit control for the satellite. In this paper, first, the orbital dynamic model is formulated by Gauss' form of the planetary equation using the mean orbit elements; the atmospheric drag and the Earth's non-spherical perturbations are taken into consideration in this model. Second, an impulsive control strategy employing the differential correction algorithm is developed to maintain the satellite trajectory parameters in given ranges. Finally, the robustness of the impulsive control method is analyzed through Monte Carlo simulations while taking orbit determination error and thrust error into account.

  3. Utilization of the NASA Operational Simulator for Small Satellites (NOS3) for V&V of STF-1’s Semiautonomous On-Orbit Operations

    OpenAIRE

    Grubb, Matthew; Lucas, John; Morris, Justin; Zemerick, Scott

    2017-01-01

    The NASA Operational Simulator for Small Satellites (NOS3) is a suite of software tools that significantly aids the SmallSat community with software development, integration and test (I&T), mission operations/training, verification and validation (V&V), and software systems check-out. NOS3 has been utilized extensively for NASA’s Simulation-to-Flight 1 (STF-1) cubesat mission with respect to V&V of its semiautonomous science operations. NOS3 provides a software development environment, a mult...

  4. Thermal infrared anomalies of several strong earthquakes.

    Science.gov (United States)

    Wei, Congxin; Zhang, Yuansheng; Guo, Xiao; Hui, Shaoxing; Qin, Manzhong; Zhang, Ying

    2013-01-01

    In the history of earthquake thermal infrared research, it is undeniable that before and after strong earthquakes there are significant thermal infrared anomalies which have been interpreted as preseismic precursor in earthquake prediction and forecasting. In this paper, we studied the characteristics of thermal radiation observed before and after the 8 great earthquakes with magnitude up to Ms7.0 by using the satellite infrared remote sensing information. We used new types of data and method to extract the useful anomaly information. Based on the analyses of 8 earthquakes, we got the results as follows. (1) There are significant thermal radiation anomalies before and after earthquakes for all cases. The overall performance of anomalies includes two main stages: expanding first and narrowing later. We easily extracted and identified such seismic anomalies by method of "time-frequency relative power spectrum." (2) There exist evident and different characteristic periods and magnitudes of thermal abnormal radiation for each case. (3) Thermal radiation anomalies are closely related to the geological structure. (4) Thermal radiation has obvious characteristics in abnormal duration, range, and morphology. In summary, we should be sure that earthquake thermal infrared anomalies as useful earthquake precursor can be used in earthquake prediction and forecasting.

  5. Kohn anomalies in superconductors

    International Nuclear Information System (INIS)

    Flatte, M.E.

    1994-01-01

    The detailed behavior of phonon dispersion curves near momenta which span the electronic Fermi sea in a superconductor is presented. An anomaly, similar to the metallic Kohn anomaly, exists in a superconductor's dispersion curves when the frequency of the photon spanning the Fermi sea exceeds twice the superconducting energy gap. This anomaly occurs at approximately the same momentum but is stronger than the normal-state Kohn anomaly. It also survives at finite temperature, unlike the metallic anomaly. Determination of Fermi-surface diameters from the location of these anomalies, therefore, may be more successful in the superconducting phase than in the normal state. However, the superconductor's anomaly fades rapidly with increased phonon frequency and becomes unobservable when the phonon frequency greatly exceeds the gap. This constraint makes these anomalies useful only in high-temperature superconductors such as La 1.85 Sr 0.15 CuO 4

  6. Live Satellite Communications... An Exciting Teaching Aid

    Science.gov (United States)

    Journal of Aerospace Education, 1976

    1976-01-01

    Describes ways that orbiting satellites carrying amateur radios can be used in the classroom at various grade levels to supplement physics, mathematics, electronics, and social science curricula. (MLH)

  7. Simulating cosmic radiation absorption and secondary particle production of solar panel layers of Low Earth Orbit (LEO) satellite with GEANT4

    Science.gov (United States)

    Yiǧitoǧlu, Merve; Veske, Doǧa; Nilüfer Öztürk, Zeynep; Bilge Demirköz, Melahat

    2016-07-01

    All devices which operate in space are exposed to cosmic rays during their operation. The resulting radiation may cause fatal damages in the solid structure of devices and the amount of absorbed radiation dose and secondary particle production for each component should be calculated carefully before the production. Solar panels are semiconductor solid state devices and are very sensitive to radiation. Even a short term power cut-off may yield a total failure of the satellite. Even little doses of radiation can change the characteristics of solar cells. This deviation can be caused by rarer high energetic particles as well as the total ionizing dose from the abundant low energy particles. In this study, solar panels planned for a specific LEO satellite, IMECE, are analyzed layer by layer. The Space Environment Information System (SPENVIS) database and GEANT4 simulation software are used to simulate the layers of the panels. The results obtained from the simulation will be taken in account to determine the amount of radiation protection and resistance needed for the panels or to revise the design of the panels.

  8. Tracheobronchial Branching Anomalies

    International Nuclear Information System (INIS)

    Hong, Min Ji; Kim, Young Tong; Jou, Sung Shick; Park, A Young

    2010-01-01

    There are various congenital anomalies with respect to the number, length, diameter, and location of tracheobronchial branching patterns. The tracheobronchial anomalies are classified into two groups. The first one, anomalies of division, includes tracheal bronchus, cardiac bronchus, tracheal diverticulum, pulmonary isomerism, and minor variations. The second one, dysmorphic lung, includes lung agenesis-hypoplasia complex and lobar agenesis-aplasia complex

  9. Tracheobronchial Branching Anomalies

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Min Ji; Kim, Young Tong; Jou, Sung Shick [Soonchunhyang University, Cheonan Hospital, Cheonan (Korea, Republic of); Park, A Young [Soonchunhyang University College of Medicine, Asan (Korea, Republic of)

    2010-04-15

    There are various congenital anomalies with respect to the number, length, diameter, and location of tracheobronchial branching patterns. The tracheobronchial anomalies are classified into two groups. The first one, anomalies of division, includes tracheal bronchus, cardiac bronchus, tracheal diverticulum, pulmonary isomerism, and minor variations. The second one, dysmorphic lung, includes lung agenesis-hypoplasia complex and lobar agenesis-aplasia complex

  10. Solar satellites

    Energy Technology Data Exchange (ETDEWEB)

    Poher, C.

    1982-01-01

    A reference system design, projected costs, and the functional concepts of a satellite solar power system (SSPS) for converting sunlight falling on solar panels of a satellite in GEO to a multi-GW beam which could be received by a rectenna on earth are outlined. Electricity transmission by microwaves has been demonstrated, and a reference design system for supplying 5 GW dc to earth was devised. The system will use either monocrystalline Si or concentrator GaAs solar cells for energy collection in GEO. Development is still needed to improve the lifespan of the cells. Currently, the cell performance degrades 50 percent in efficiency after 7-8 yr in space. Each SSPS satellite would weigh either 34,000 tons (Si) or 51,000 tons (GaAs), thereby requiring the fabrication of a heavy lift launch vehicle or a single-stage-to-orbit transport in order to minimize launch costs. Costs for the solar panels have been estimated at $500/kW using the GaAs technology, with transport costs for materials to GEO being $40/kg.

  11. Solar satellites

    Science.gov (United States)

    Poher, C.

    A reference system design, projected costs, and the functional concepts of a satellite solar power system (SSPS) for converting sunlight falling on solar panels of a satellite in GEO to a multi-GW beam which could be received by a rectenna on earth are outlined. Electricity transmission by microwaves has been demonstrated, and a reference design system for supplying 5 GW dc to earth was devised. The system will use either monocrystalline Si or concentrator GaAs solar cells for energy collection in GEO. Development is still needed to improve the lifespan of the cells. Currently, the cell performance degrades 50 percent in efficiency after 7-8 yr in space. Each SSPS satellite would weigh either 34,000 tons (Si) or 51,000 tons (GaAs), thereby requiring the fabrication of a heavy lift launch vehicle or a single-stage-to-orbit transport in order to minimize launch costs. Costs for the solar panels have been estimated at $500/kW using the GaAs technology, with transport costs for materials to GEO being $40/kg.

  12. Geostationary satellites collocation

    CERN Document Server

    Li, Hengnian

    2014-01-01

    Geostationary Satellites Collocation aims to find solutions for deploying a safe and reliable collocation control. Focusing on the orbital perturbation analysis, the mathematical foundations for orbit and control of the geostationary satellite are summarized. The mathematical and physical principle of orbital maneuver and collocation strategies for multi geostationary satellites sharing with the same dead band is also stressed. Moreover, the book presents some applications using the above algorithms and mathematical models to help readers master the corrective method for planning station keeping maneuvers. Engineers and scientists in the fields of aerospace technology and space science can benefit from this book. Hengnian Li is the Deputy Director of State Key Laboratory of Astronautic Dynamics, China.

  13. Modeling water and heat balance components of large territory for vegetation season using information from polar-orbital and geostationary meteorological satellites

    Science.gov (United States)

    Muzylev, Eugene; Startseva, Zoya; Uspensky, Alexander; Volkova, Elena; Kukharsky, Alexander; Uspensky, Sergey

    2015-04-01

    To date, physical-mathematical modeling processes of land surface-atmosphere interaction is considered to be the most appropriate tool for obtaining reliable estimates of water and heat balance components of large territories. The model of these processes (Land Surface Model, LSM) developed for vegetation period is destined for simulating soil water content W, evapotranspiration Ev, vertical latent LE and heat fluxes from land surface as well as vertically distributed soil temperature and moisture, soil surface Tg and foliage Tf temperatures, and land surface skin temperature (LST) Ts. The model is suitable for utilizing remote sensing data on land surface and meteorological conditions. In the study these data have been obtained from measurements by scanning radiometers AVHRR/NOAA, MODIS/EOS Terra and Aqua, SEVIRI/geostationary satellites Meteosat-9, -10 (MSG-2, -3). The heterogeneity of the land surface and meteorological conditions has been taken into account in the model by using soil and vegetation characteristics as parameters and meteorological characteristics as input variables. Values of these characteristics have been determined from ground observations and remote sensing information. So, AVHRR data have been used to build the estimates of effective land surface temperature (LST) Ts.eff and emissivity E, vegetation-air temperature (temperature at the vegetation level) Ta, normalized vegetation index NDVI, vegetation cover fraction B, the leaf area index LAI, and precipitation. From MODIS data the values of LST Tls, Å, NDVI, LAI have been derived. From SEVIRI data there have been retrieved Tls, E, Ta, NDVI, LAI and precipitation. All named retrievals covered the vast territory of the part of the agricultural Central Black Earth Region located in the steppe-forest zone of European Russia. This territory with coordinates 49°30'-54°N, 31°-43°E and a total area of 227,300 km2 has been chosen for investigation. It has been carried out for years 2009

  14. Prospects of application of survey satellite image for meteorology

    Science.gov (United States)

    Kapochkina, A. B.; Kapochkin, B. B.; Kucherenko, N. V.

    The maximal interest is represented with the information from geostationary satellites. These satellites repeat shootings the chosen territories, allowing to study dynamics of images. Most interesting shootings in IR a range. Studying of survey image is applied to studying linear elements of clouds (LEC). It is established, that "LEC " arise only above breaks of an earth's crust. In research results of the complex analysis of the satellite data, hydrometeorological supervision, seismicity, supervision over deformations of a surface of the Earth are used. It is established that before formation "LEC " in a ground layer arise anomalies of temperature and humidity. The situation above Europe 16 May, 2001 is considered. "LEC " in Europe block carry of air weights from the west to the east. Synoptic conditions above the Great Britain July, 7-10, 2000 is considered. Moving "LEC" trace distribution of deformation waves to an earth's crust. Satellite shootings Europe before earthquake in Greece 14.08.2003 are considered. These days ground supervision were conducted and the data of the geostationary satellite were analyzed. During moving "LEC " occur failures (destruction houses & of gas mains), earthquake. The situation above Iberian peninsula 12-16.11.2001 is considered. "LEC" arose before flooding in Europe. The situation before flooding in Germany June, 6-8, 2002 and flooding on the river Kuban June, 16-23, 2002 is considered. In case of occurrence of tectonic compression of an earth's crust there are "LEC ", tracer intensive movements of air upwards and downwards above negative and positive anomalies of the form of a terrestrial surface, accordingly. Such meteorological situations are dangerous to flights of aircraft, the fast gravitational anomalies influencing into orbits of movement of satellites trace. The situation above equatorial Atlantic 26.03.2003 years is considered. At tectonic compression of continental scale overcast covers the whole continents for more

  15. Trends in mobile satellite communication

    Science.gov (United States)

    Johannsen, Klaus G.; Bowles, Mike W.; Milliken, Samuel; Cherrette, Alan R.; Busche, Gregory C.

    1993-01-01

    Ever since the U.S. Federal Communication Commission opened the discussion on spectrum usage for personal handheld communication, the community of satellite manufacturers has been searching for an economically viable and technically feasible satellite mobile communication system. Hughes Aircraft Company and others have joined in providing proposals for such systems, ranging from low to medium to geosynchronous orbits. These proposals make it clear that the trend in mobile satellite communication is toward more sophisticated satellites with a large number of spot beams and onboard processing, providing worldwide interconnectivity. Recent Hughes studies indicate that from a cost standpoint the geosynchronous satellite (GEOS) is most economical, followed by the medium earth orbit satellite (MEOS) and then by the low earth orbit satellite (LEOS). From a system performance standpoint, this evaluation may be in reverse order, depending on how the public will react to speech delay and collision. This paper discusses the trends and various mobile satellite constellations in satellite communication under investigation. It considers the effect of orbital altitude and modulation/multiple access on the link and spacecraft design.

  16. Optimize the Coverage Probability of Prediction Interval for Anomaly Detection of Sensor-Based Monitoring Series

    Directory of Open Access Journals (Sweden)

    Jingyue Pang

    2018-03-01

    Full Text Available Effective anomaly detection of sensing data is essential for identifying potential system failures. Because they require no prior knowledge or accumulated labels, and provide uncertainty presentation, the probability prediction methods (e.g., Gaussian process regression (GPR and relevance vector machine (RVM are especially adaptable to perform anomaly detection for sensing series. Generally, one key parameter of prediction models is coverage probability (CP, which controls the judging threshold of the testing sample and is generally set to a default value (e.g., 90% or 95%. There are few criteria to determine the optimal CP for anomaly detection. Therefore, this paper designs a graphic indicator of the receiver operating characteristic curve of prediction interval (ROC-PI based on the definition of the ROC curve which can depict the trade-off between the PI width and PI coverage probability across a series of cut-off points. Furthermore, the Youden index is modified to assess the performance of different CPs, by the minimization of which the optimal CP is derived by the simulated annealing (SA algorithm. Experiments conducted on two simulation datasets demonstrate the validity of the proposed method. Especially, an actual case study on sensing series from an on-orbit satellite illustrates its significant performance in practical application.

  17. Branchial anomalies in children.

    Science.gov (United States)

    Bajaj, Y; Ifeacho, S; Tweedie, D; Jephson, C G; Albert, D M; Cochrane, L A; Wyatt, M E; Jonas, N; Hartley, B E J

    2011-08-01

    Branchial cleft anomalies are the second most common head and neck congenital lesions seen in children. Amongst the branchial cleft malformations, second cleft lesions account for 95% of the branchial anomalies. This article analyzes all the cases of branchial cleft anomalies operated on at Great Ormond Street Hospital over the past 10 years. All children who underwent surgery for branchial cleft sinus or fistula from January 2000 to December 2010 were included in this study. In this series, we had 80 patients (38 female and 42 male). The age at the time of operation varied from 1 year to 14 years. Amongst this group, 15 patients had first branchial cleft anomaly, 62 had second branchial cleft anomaly and 3 had fourth branchial pouch anomaly. All the first cleft cases were operated on by a superficial parotidectomy approach with facial nerve identification. Complete excision was achieved in all these first cleft cases. In this series of first cleft anomalies, we had one complication (temporary marginal mandibular nerve weakness. In the 62 children with second branchial cleft anomalies, 50 were unilateral and 12 were bilateral. In the vast majority, the tract extended through the carotid bifurcation and extended up to pharyngeal constrictor muscles. Majority of these cases were operated on through an elliptical incision around the external opening. Complete excision was achieved in all second cleft cases except one who required a repeat excision. In this subgroup, we had two complications one patient developed a seroma and one had incomplete excision. The three patients with fourth pouch anomaly were treated with endoscopic assisted monopolar diathermy to the sinus opening with good outcome. Branchial anomalies are relatively common in children. There are three distinct types, first cleft, second cleft and fourth pouch anomaly. Correct diagnosis is essential to avoid inadequate surgery and multiple procedures. The surgical approach needs to be tailored to the type

  18. Probability of satellite collision

    Science.gov (United States)

    Mccarter, J. W.

    1972-01-01

    A method is presented for computing the probability of a collision between a particular artificial earth satellite and any one of the total population of earth satellites. The collision hazard incurred by the proposed modular Space Station is assessed using the technique presented. The results of a parametric study to determine what type of satellite orbits produce the greatest contribution to the total collision probability are presented. Collision probability for the Space Station is given as a function of Space Station altitude and inclination. Collision probability was also parameterized over miss distance and mission duration.

  19. Global gravitational anomalies

    International Nuclear Information System (INIS)

    Witten, E.

    1985-01-01

    A general formula for global gauge and gravitational anomalies is derived. It is used to show that the anomaly free supergravity and superstring theories in ten dimensions are all free of global anomalies that might have ruined their consistency. However, it is shown that global anomalies lead to some restrictions on allowed compactifications of these theories. For example, in the case of O(32) superstring theory, it is shown that a global anomaly related to π 7 (O(32)) leads to a Dirac-like quantization condition for the field strength of the antisymmetric tensor field. Related to global anomalies is the question of the number of fermion zero modes in an instanton field. It is argued that the relevant gravitational instantons are exotic spheres. It is shown that the number of fermion zero modes in an instanton field is always even in ten dimensional supergravity. (orig.)

  20. Anomaly-free models for flavour anomalies

    Science.gov (United States)

    Ellis, John; Fairbairn, Malcolm; Tunney, Patrick

    2018-03-01

    We explore the constraints imposed by the cancellation of triangle anomalies on models in which the flavour anomalies reported by LHCb and other experiments are due to an extra U(1)^' gauge boson Z^' . We assume universal and rational U(1)^' charges for the first two generations of left-handed quarks and of right-handed up-type quarks but allow different charges for their third-generation counterparts. If the right-handed charges vanish, cancellation of the triangle anomalies requires all the quark U(1)^' charges to vanish, if there are either no exotic fermions or there is only one Standard Model singlet dark matter (DM) fermion. There are non-trivial anomaly-free models with more than one such `dark' fermion, or with a single DM fermion if right-handed up-type quarks have non-zero U(1)^' charges. In some of the latter models the U(1)^' couplings of the first- and second-generation quarks all vanish, weakening the LHC Z^' constraint, and in some other models the DM particle has purely axial couplings, weakening the direct DM scattering constraint. We also consider models in which anomalies are cancelled via extra vector-like leptons, showing how the prospective LHC Z^' constraint may be weakened because the Z^' → μ ^+ μ ^- branching ratio is suppressed relative to other decay modes.

  1. First branchial groove anomaly.

    Science.gov (United States)

    Kumar, M; Hickey, S; Joseph, G

    2000-06-01

    First branchial groove anomalies are very rare. We report a case of a first branchial groove anomaly presented as an infected cyst in an 11-month-old child. Management of such lesions is complicated because of their close association with the facial nerve. Surgical management must include identification and protection of the facial nerve. Embryology and facial nerve disposition in relation to the anomaly are reviewed.

  2. Chartering Launchers for Small Satellites

    Science.gov (United States)

    Hernandez, Daniel

    The question of how to launch small satellites has been solved over the years by the larger launchers offering small satellites the possibility of piggy-backing. Specific fixtures have been developed and commercialized: Arianespace developed the ASAP interface, the USAF studied ESPA, NASA has promoted Shuttle launch possibilities, Russian authorities and companies have been able to find solutions with many different launchers... It is fair to say that most launcher suppliers have worked hard and finally often been able to find solutions to launch most small satellites into orbit. It is also true, however, that most of these small satellites were technology demonstration missions capable of accepting a wide range of orbit and launch characteristics: orbit altitude and inclination, launch date, etc. In some cases the small satellite missions required a well-defined type of orbit and have therefore been obliged to hire a small launcher on which they were the prime passenger. In our paper we would like to propose an additional solution to all these possibilities: launchers could plan well in advance (for example about 3 years), trips to precisely defined orbits to allow potential passengers to organize themselves and be ready on the D-Day. On the scheduled date the chartered launcher goes to the stated orbit while on another date, another chartered launcher goes to another orbit. The idea is to organize departures for space like trains or airplanes leaving on known schedules for known destinations.

  3. The Italian contribution to the CSES satellite

    Science.gov (United States)

    Conti, Livio

    2016-04-01

    We present the Italian contribution to the CSES (China Seismo-Electromagnetic Satellite) mission. The CSES satellite aims at investigating electromagnetic field, plasma and particles in the near-Earth environment in order to study in particular seismic precursors, particles fluxes (from Van Allen belts, cosmic rays, solar wind, etc.), anthropogenic electromagnetic pollution and more in general the atmosphere-ionosphere-magnetosphere coupling mechanisms that can affect the climate changes. The launch of CSES - the first of a series of several satellite missions - is scheduled by the end of 2016. The CSES satellite has been financed by the CNSA (China National Space Agency) and developed by CEA (China Earthquake Administration) together with several Chinese research institutes and private companies such as the DFH (that has developed the CAST2000 satellite platform). Italy participates to the CSES satellite mission with the LIMADOU project funded by ASI (Italian Space Agency) in collaboration with the Universities of Roma Tor Vergata, Uninettuno, Trento, Bologna and Perugia, as well as the INFN (Italian National Institute of Nuclear Physics), INGV (Italian National Institute of Geophysics and Volcanology) and INAF-IAPS (Italian National Institute of Astrophysics and Planetology). Many analyses have shown that satellite observations of electromagnetic fields, plasma parameters and particle fluxes in low Earth orbit may be useful in order to study the existence of electromagnetic emissions associated with the occurrence of earthquakes of medium and high magnitude. Although the earthquakes forecasting is not possible today, it is certainly a major challenge - and perhaps even a duty - for science in the near future. The claims that the reported anomalies (of electromagnetic, plasma and particle parameters) are seismic precursors are still intensely debated and analyses for confirming claimed correlations are still lacking. In fact, ionospheric currents, plasma

  4. Living antennas on communication satellites

    DEFF Research Database (Denmark)

    Lumholt, Michael

    2003-01-01

    Crises change the global pattern of communication. The communications problems occur because the satellites are optimized to cover specific geographic areas, and these areas cannot be altered once the satellites are in Earth orbit. An effective solution to the problem is to equip communication sa...... satellites with "living" antennas that can adjust their radiation coverage areas according to the new demands. The development of living antennas is, therefore, among the focus areas identified and supported by the European Space Agency, ESA....

  5. Theory of satellite geodesy applications of satellites to geodesy

    CERN Document Server

    Kaula, William M

    2000-01-01

    The main purpose of this classic text is to demonstrate how Newtonian gravitational theory and Euclidean geometry can be used and developed in the earth's environment. The second is to collect and explain some of the mathematical techniques developed for measuring the earth by satellite.Book chapters include discussions of the earth's gravitational field, with special emphasis on spherical harmonies and the potential of the ellipsoid; matrices and orbital geometry; elliptic motion, linear perturbations, resonance, and other aspects of satellite orbit dynamics; the geometry of satellite obser

  6. Monitoramento de propriedades rurais através de dados multisensores em nível orbital / Monitoring of rural properties using multisensor satellite data

    Directory of Open Access Journals (Sweden)

    Rener Ribeiro Fernandes

    2011-04-01

    classification and object-oriented in order to better discriminate the land use of the study area, comparing their results to those obtained by thematic classification by maximum likelihood. The values were tabulated, noting that in 2002, 33.43% of the vegetation of the structure had been changed, this percentage increased to 40.32% in 2004, 51.85% in 2006. In 2008 the conversion of natural vegetation type values up to 60.69% by analysis of supervised classification using maximum likelihood and 70.64% for object-oriented classification. The method of object-orientad classification showed the most promissing final results enabled by the use of high-resolution data of the sensor HRC satellite CBERS-2B.

  7. Orbit Functions

    Directory of Open Access Journals (Sweden)

    Anatoliy Klimyk

    2006-01-01

    Full Text Available In the paper, properties of orbit functions are reviewed and further developed. Orbit functions on the Euclidean space E_n are symmetrized exponential functions. The symmetrization is fulfilled by a Weyl group corresponding to a Coxeter-Dynkin diagram. Properties of such functions will be described. An orbit function is the contribution to an irreducible character of a compact semisimple Lie group G of rank n from one of its Weyl group orbits. It is shown that values of orbit functions are repeated on copies of the fundamental domain F of the affine Weyl group (determined by the initial Weyl group in the entire Euclidean space E_n. Orbit functions are solutions of the corresponding Laplace equation in E_n, satisfying the Neumann condition on the boundary of F. Orbit functions determine a symmetrized Fourier transform and a transform on a finite set of points.

  8. Gravitational anomalies in the solar system?

    Science.gov (United States)

    Iorio, Lorenzo

    2015-02-01

    Mindful of the anomalous perihelion precession of Mercury discovered by Le Verrier in the second half of the nineteenth century and its successful explanation by Einstein with his General Theory of Relativity in the early years of the twentieth century, discrepancies among observed effects in our Solar system and their theoretical predictions on the basis of the currently accepted laws of gravitation applied to known matter-energy distributions have the potential of paving the way for remarkable advances in fundamental physics. This is particularly important now more than ever, given that most of the universe seems to be made of unknown substances dubbed Dark Matter and Dark Energy. Should this not be directly the case, Solar system's anomalies could anyhow lead to advancements in either cumulative science, as shown to us by the discovery of Neptune in the first half of the nineteenth century, and technology itself. Moreover, investigations in one of such directions can serendipitously enrich the other one as well. The current status of some alleged gravitational anomalies in the Solar system is critically reviewed. They are: (a) Possible anomalous advances of planetary perihelia. (b) Unexplained orbital residuals of a recently discovered moon of Uranus (Mab). (c) The lingering unexplained secular increase of the eccentricity of the orbit of the Moon. (d) The so-called Faint Young Sun Paradox. (e) The secular decrease of the mass parameter of the Sun. (f) The Flyby Anomaly. (g) The Pioneer Anomaly. (h) The anomalous secular increase of the astronomical unit.

  9. Dental Anomalies: An Update

    Directory of Open Access Journals (Sweden)

    Fatemeh Jahanimoghadam

    2016-01-01

    Full Text Available Dental anomalies are usual congenital malformation that can happen either as isolated findings or as a part of a syndrome. Developmental anomalies influencing the morphology exists in both deciduous and permanent dentition and shows different forms such as gemination, fusion, concrescence, dilaceration, dens evaginatus (DE, enamel pearls, taurodontism or peg-shaped laterals. All These anomalies have clinical significance concerning aesthetics, malocclusion and more necessary preparing of the development of dental decays and oral diseases. Through a search in PubMed, Google, Scopus and Medline, a total of eighty original research papers during 1928-2016 were found with the keywords such as dental anomaly, syndrome, tooth and hypodontia. One hundred review titles were identified, eighty reviews were retrieved that were finally included as being relevant and of sufficient quality. In this review, dental anomalies including gemination, fusion, concrescence, dilaceration, dens invaginatus, DE, taurodontism, enamel pearls, fluorosis, peg-shaped laterals, dentinal dysplasia, regional odontodysplasia and hypodontia are discussed. Diagnosing dental abnormality needs a thorough evaluation of the patient, involving a medical, dental, familial and clinical history. Clinical examination and radiographic evaluation and in some of the cases, specific laboratory tests are also needed. Developmental dental anomalies require careful examination and treatment planning. Where one anomaly is present, clinicians should suspect that other anomalies may also be present. Moreover, careful clinical and radiographical examination is required. Furthermore, more complex cases need multidisciplinary planning and treatment.

  10. Satellite communications network design and analysis

    CERN Document Server

    Jo, Kenneth Y

    2011-01-01

    This authoritative book provides a thorough understanding of the fundamental concepts of satellite communications (SATCOM) network design and performance assessments. You find discussions on a wide class of SATCOM networks using satellites as core components, as well as coverage key applications in the field. This in-depth resource presents a broad range of critical topics, from geosynchronous Earth orbiting (GEO) satellites and direct broadcast satellite systems, to low Earth orbiting (LEO) satellites, radio standards and protocols.This invaluable reference explains the many specific uses of

  11. Computing Thermal Imbalance Forces On Satellites

    Science.gov (United States)

    Vigue, Yvonne; Schutz, Robert E.; Sewell, Granville; Abusali, Pothai A. M.

    1994-01-01

    HEAT.PRO computer program calculates imbalance force caused by heating of surfaces of satellite. Calculates thermal imbalance force and determines its effect on orbit of satellite, especially where shadow cast by Earth Causes periodic changes in thermal environment around satellite. Written in FORTRAN 77.

  12. Lithospheric stretching and the long wavelength free-air gravity anomaly of the Eastern Continental margin of India and the 85 degree E Ridge, Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Rajesh, S.; Majumdar, T.J.; Krishna, K.S.

    Or as envisaged, was it originated from the Crozet hotspot We address these issues by using satellite altimeter-derived gravity anomaly and its analytical upward continuation anomalies with forward modeling of ship-borne data. Results on analytical continuation...

  13. VLBI Observations of Geostationary Satellites

    Science.gov (United States)

    Artz, T.; Nothnagel, A.; La Porta, L.

    2013-08-01

    For a consistent realization of a Global Geodetic Observing System (GGOS), a proper tie between the individual global reference systems used in the analysis of space-geodetic observations is a prerequisite. For instance, the link between the terrestrial, the celestial and the dynamic reference system of artificial Earth orbiters may be realized by Very Long O Baseline Interferometry (VLBI) observations of one or several satellites. In the preparation phase for a dedicated satellite mission, one option to realize this is using a geostationary (GEO) satellite emitting a radio signal in X-Band and/or S-Band and, thus, imitating a quasar. In this way, the GEO satellite can be observed by VLBI together with nearby quasars and the GEO orbit can, thus, be determined in a celestial reference frame. If the GEO satellite is, e.g., also equipped with a GNSS-type transmitter, a further tie between GNSS and VLBI may be realized. In this paper, a concept for the generation of a radio signal is shown. Furthermore, simulation studies for estimating the GEO position are presented with a GEO satellite included in the VLBI schedule. VLBI group delay observations are then simulated for the quasars as well as for the GEO satellite. The analysis of the simulated observations shows that constant orbit changes are adequately absorbed by estimated orbit parameters. Furthermore, the post-fit residuals are comparable to those from real VLBI sessions.

  14. Introduction to anomalies

    International Nuclear Information System (INIS)

    Alvarez-Gaume, L.

    1986-01-01

    These lectures are dedicated to the study of the recent progress and implications of anomalies in quantum field theory. In this introduction the author recapitulates some of the highlights in the history of the subject. The outline of these lectures is as follows: Section II contains a quick review of spinors in Euclidean and Minkowski space, some other group theory results relevant for the computation of anomalies in various dimensions, and an exposition of the index theorem. Section III starts the analysis of fermion determinants and chiral effective actions by deriving the non-Abelian anomaly from index theory. Using the results of Section II, the anomaly cancellation recently discovered by Green and Schwarz will be presented in Section IV as well as the connection of these results of Section III with the descent equations and the Wess-Zumino-Witten Lagrangians. Section V contains the generalization of anomalies to σ-models and some of its application in string theory. Section VI will deal with the anomalies from the Hamiltonian point of view. An exact formula for the imaginary part of the effective action for chiral fermions in the presence of arbitrary external gauge and gravitational fields will be derived in Section VII, and used in Section VIII for the study of global anomalies. 85 references

  15. ORBITAL INJURIES

    Directory of Open Access Journals (Sweden)

    Andrej Kansky

    2002-12-01

    Full Text Available Background. Orbit is involved in 40% of all facial fractures. There is considerable variety in severity, ranging from simple nondisplaced to complex comminuted fractures. Complex comminuted fractures (up to 20% are responsible for the majority of complications and unfavorable results. Orbital fractures are classified as internal orbital fractures, zygomatico-orbital fractures, naso-orbito-ethmoidal fractures and combined fractures. The ophtalmic sequelae of midfacial fractures are usually edema and ecchymosis of the soft tissues, subconjuctival hemorrhage, diplopia, iritis, retinal edema, ptosis, enophthalmos, ocular muscle paresis, mechanical restriction of ocular movement and nasolacrimal disturbances. More severe injuries such as optic nerve trauma and retinal detachments have also been reported. Within the wide range of orbital fractures small group of complex fractures causes most of the sequelae. Therefore identification of severe injuries and adequate treatment is of major importance. The introduction of craniofacial techniques made possible a wide exposure even of large orbital wall defects and their reconstruction by bone grafts. In spite of significant progress, repair of complex orbital wall defects remains a problem even for the experienced surgeons.Results. In 1999 121 facial injuries were treated at our department (Clinical Centre Ljubljana Dept. Of Maxillofacial and Oral Surgery. Orbit was involved in 65% of cases. Isolated inner orbital fractures presented 4% of all fractures. 17 (14% complex cases were treated, 5 of them being NOE, 5 orbital (frame and inner walls, 3 zygomatico-orbital, 2 FNO and 2 maxillo-orbital fractures.Conclusions. Final result of the surgical treatment depends on severity of maxillofacial trauma. Complex comminuted fractures are responsable for most of the unfavorable results and ocular function is often permanently damaged (up to 75% in these fractures.

  16. 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).

  17. [Orbital inflammation].

    Science.gov (United States)

    Mouriaux, F; Coffin-Pichonnet, S; Robert, P-Y; Abad, S; Martin-Silva, N

    2014-12-01

    Orbital inflammation is a generic term encompassing inflammatory pathologies affecting all structures within the orbit : anterior (involvement up to the posterior aspect of the globe), diffuse (involvement of intra- and/or extraconal fat), apical (involvement of the posterior orbit), myositis (involvement of only the extraocular muscles), dacryoadenitis (involvement of the lacrimal gland). We distinguish between specific inflammation and non-specific inflammation, commonly referred to as idiopathic inflammation. Specific orbital inflammation corresponds to a secondary localization of a "generalized" disease (systemic or auto-immune). Idiopathic orbital inflammation corresponds to uniquely orbital inflammation without generalized disease, and thus an unknown etiology. At the top of the differential diagnosis for specific or idiopathic orbital inflammation are malignant tumors, represented most commonly in the adult by lympho-proliferative syndromes and metastases. Treatment of specific orbital inflammation begins with treatment of the underlying disease. For idiopathic orbital inflammation, treatment (most often corticosteroids) is indicated above all in cases of visual loss due to optic neuropathy, in the presence of pain or oculomotor palsy. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  18. Anomalies on orbifolds

    Energy Technology Data Exchange (ETDEWEB)

    Arkani-Hamed, Nima; Cohen, Andrew G.; Georgi, Howard

    2001-03-16

    We discuss the form of the chiral anomaly on an S1/Z2 orbifold with chiral boundary conditions. We find that the 4-divergence of the higher-dimensional current evaluated at a given point in the extra dimension is proportional to the probability of finding the chiral zero mode there. Nevertheless the anomaly, appropriately defined as the five dimensional divergence of the current, lives entirely on the orbifold fixed planes and is independent of the shape of the zero mode. Therefore long distance four dimensional anomaly cancellation ensures the consistency of the higher dimensional orbifold theory.

  19. Skyrmions and anomalies

    International Nuclear Information System (INIS)

    Rho, M.

    1987-02-01

    The author summarizes the works presented at the meeting on skyrmions and anomalies. He divides the principal issues of this workshop into five categories: QCD effective lagrangians, chiral bags and the Cheshire cat principle, strangeness problem, phenomenology, mathematical structure

  20. Anomaly Detection in Sequences

    Data.gov (United States)

    National Aeronautics and Space Administration — We present a set of novel algorithms which we call sequenceMiner, that detect and characterize anomalies in large sets of high-dimensional symbol sequences that...

  1. Kohn anomaly in graphene

    International Nuclear Information System (INIS)

    Milosevic, I.; Kepcija, N.; Dobardzic, E.; Damnjanovic, M.; Mohr, M.; Maultzsch, J.; Thomsen, C.

    2011-01-01

    Symmetry based analysis of the Kohn anomaly is performed. Kohn phonon frequencies and displacements are calculated by force constant method. It is shown that Kohn phonon vibrations cause electronic band gap opening.

  2. Spin and orbital moments in UGa3

    International Nuclear Information System (INIS)

    Kambe, S; Kato, H; Sakai, H; Tokunaga, Y; Walstedt, R E; Matsuda, T D; Aoki, D; Haga, Y; Onuki, Y

    2003-01-01

    The antiferromagnetic (AF) state of UGa 3 is studied using 69 Ga nuclear magnetic resonance. We have observed a drastic change of the hyperfine coupling constant at the Ga site around the AF transition (T N = 67 K) in UGa 3 . The internal field at the Ga site appears at slightly lower temperature ∼63 K, indicating another anomaly around 63 K. A possible origin of the anomaly is discussed, in terms of orbital ordering

  3. MASSIVE SATELLITES OF CLOSE-IN GAS GIANT EXOPLANETS

    International Nuclear Information System (INIS)

    Cassidy, Timothy A.; Johnson, Robert E.; Mendez, Rolando; Arras, Phil; Skrutskie, Michael F.

    2009-01-01

    We study the orbits, tidal heating and mass loss from satellites around close-in gas giant exoplanets. The focus is on large satellites which are potentially observable by their transit signature. We argue that even Earth-size satellites around hot Jupiters can be immune to destruction by orbital decay; detection of such a massive satellite would strongly constrain theories of tidal dissipation in gas giants, in a manner complementary to orbital circularization. The star's gravity induces significant periodic eccentricity in the satellite's orbit. The resulting tidal heating rates, per unit mass, are far in excess of Io's and dominate radioactive heating out to planet orbital periods of months for reasonable satellite tidal Q. Inside planet orbital periods of about a week, tidal heating can completely melt the satellite. Lastly, we compute an upper limit to the satellite mass loss rate due to thermal evaporation from the surface, valid if the satellite's atmosphere is thin and vapor pressure is negligible. Using this upper limit, we find that although rocky satellites around hot Jupiters with orbital periods less than a few days can be significantly evaporated in their lifetimes, detectable satellites suffer negligible mass loss at longer orbital periods.

  4. Algebraic structure of chiral anomalies

    International Nuclear Information System (INIS)

    Stora, R.

    1985-09-01

    I will describe first the algebraic aspects of chiral anomalies, exercising however due care about the topological delicacies. I will illustrate the structure and methods in the context of gauge anomalies and will eventually make contact with results obtained from index theory. I will go into two sorts of generalizations: on the one hand, generalizing the algebraic set up yields e.g. gravitational and mixed gauge anomalies, supersymmetric gauge anomalies, anomalies in supergravity theories; on the other hand most constructions applied to the cohomologies which characterize anomalies easily extend to higher cohomologies. Section II is devoted to a description of the general set up as it applies to gauge anomalies. Section III deals with a number of algebraic set ups which characterize more general types of anomalies: gravitational and mixed gauge anomalies, supersymmetric gauge anomalies, anomalies in supergravity theories. It also includes brief remarks on σ models and a reminder on the full BRST algebra of quantized gauge theories

  5. Anomalies and gravity

    International Nuclear Information System (INIS)

    Mielke, Eckehard W.

    2006-01-01

    Anomalies in Yang-Mills type gauge theories of gravity are reviewed. Particular attention is paid to the relation between the Dirac spin, the axial current j5 and the non-covariant gauge spin C. Using diagrammatic techniques, we show that only generalizations of the U(1)- Pontrjagin four-form F and F = dC arise in the chiral anomaly, even when coupled to gravity. Implications for Ashtekar's canonical approach to quantum gravity are discussed

  6. Fivebrane gravitational anomalies

    International Nuclear Information System (INIS)

    Becker, Katrin; Becker, Melanie

    2000-01-01

    Freed, Harvey, Minasian and Moore (FHMM) have proposed a mechanism to cancel the gravitational anomaly of the M-theory fivebrane coming from diffeomorphisms acting on the normal bundle. This procedure is based on a modification of the conventional M-theory Chern-Simons term. We apply the FHMM mechanism in the ten-dimensional type IIA theory. We then analyze the relation to the anomaly cancellation mechanism for the type IIA fivebrane proposed by Witten

  7. The Holographic Weyl anomaly

    CERN Document Server

    Henningson, M; Henningson, Mans; Skenderis, Kostas

    1998-01-01

    We calculate the Weyl anomaly for conformal field theories that can be described via the adS/CFT correspondence. This entails regularizing the gravitational part of the corresponding supergravity action in a manner consistent with general covariance. Up to a constant, the anomaly only depends on the dimension d of the manifold on which the conformal field theory is defined. We present concrete expressions for the anomaly in the physically relevant cases d = 2, 4 and 6. In d = 2 we find for the central charge c = 3 l/ 2 G_N in agreement with considerations based on the asymptotic symmetry algebra of adS_3. In d = 4 the anomaly agrees precisely with that of the corresponding N = 4 superconformal SU(N) gauge theory. The result in d = 6 provides new information for the (0, 2) theory, since its Weyl anomaly has not been computed previously. The anomaly in this case grows as N^3, where N is the number of coincident M5 branes, and it vanishes for a Ricci-flat background.

  8. Discussions on attitude determination and control system for micro/nano/pico-satellites considering survivability based on Hodoyoshi-3 and 4 experiences

    Science.gov (United States)

    Nakasuka, Shinichi; Miyata, Kikuko; Tsuruda, Yoshihiro; Aoyanagi, Yoshihide; Matsumoto, Takeshi

    2018-04-01

    The recent advancement of micro/nano/pico-satellites technologies encourages many universities to develop three axis stabilized satellites. As three axis stabilization is high level technology requiring the proper functioning of various sensors, actuators and control software, many early satellites failed in their initial operation phase because of shortage of solar power generation or inability to realize the initial step of missions because of unexpected attitude control system performance. These results come from failure to design the satellite attitude determination and control system (ADCS) appropriately and not considering "satellite survivability." ADCS should be designed such that even if some sensors or actuators cannot work as expected, the satellite can survive and carry out some of its missions, even if not full. This paper discusses how to realize ADCS while taking satellite survivability into account, based on our experiences of design and in-orbit operations of Hodoyoshi-3 and 4 satellites launched in 2014, which suffered from various component anomalies but could complete their missions.

  9. Gravity Probe B orbit determination

    International Nuclear Information System (INIS)

    Shestople, P; Ndili, A; Parkinson, B W; Small, H; Hanuschak, G

    2015-01-01

    The Gravity Probe B (GP-B) satellite was equipped with a pair of redundant Global Positioning System (GPS) receivers used to provide navigation solutions for real-time and post-processed orbit determination (OD), as well as to establish the relation between vehicle time and coordinated universal time. The receivers performed better than the real-time position requirement of 100 m rms per axis. Post-processed solutions indicated an rms position error of 2.5 m and an rms velocity error of 2.2 mm s −1 . Satellite laser ranging measurements provided independent verification of the GPS-derived GP-B orbit. We discuss the modifications and performance of the Trimble Advance Navigation System Vector III GPS receivers. We describe the GP-B precision orbit and detail the OD methodology, including ephemeris errors and the laser ranging measurements. (paper)

  10. Magsat - A new satellite to survey the earth's magnetic field

    Science.gov (United States)

    Mobley, F. F.; Eckard, L. D.; Fountain, G. H.; Ousley, G. W.

    1980-01-01

    The Magsat satellite was launched on Oct. 30, 1979 into a sun-synchronous dawn-dusk orbit, of 97 deg inclination, 350 km perigee, and 550 km apogee. It contains a precision vector magnetometer and a cesium-vapor scalar magnetometer at the end of a 6-m long graphite epoxy scissors boom. The magnetometers are accurate to 2 nanotesla. A pair of star cameras are used to define the body orientation to 10 arc sec rms. An 'attitude transfer system' measures the orientation of the magnetometer sensors relative to the star cameras to approximately 5 arc sec rms. The satellite position is determined to 70 meters rms by Doppler tracking. The overall objective is to determine each component of the earth's vector magnetic field to an accuracy of 6 nanotesla rms. The Magsat satellite gathers a complete picture of the earth's magnetic field every 12 hours. The vector components are sampled 16 times per second with a resolution of 0.5 nanotesla. The data will be used by the U.S. Geological Survey to prepare 1980 world magnetic field charts and to detect large-scale magnetic anomalies in the earth's crust for use in planning resource exploration strategy.

  11. 47 CFR 25.280 - Inclined orbit operations.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Inclined orbit operations. 25.280 Section 25.280 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Operations § 25.280 Inclined orbit operations. (a) Satellite operators may commence...

  12. 47 CFR 25.282 - Orbit raising maneuvers.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Orbit raising maneuvers. 25.282 Section 25.282 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS... geostationary satellite orbit under this part is also authorized to transmit in connection with short-term...

  13. EMAG2v3: Earth Magnetic Anomaly Grid (2-arc-minute resolution)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — EMAG2v3 is a global Earth Magnetic Anomaly Grid compiled from satellite, ship, and airborne magnetic measurements. It is a significant update of the previous release...

  14. EMAG2: Earth Magnetic Anomaly Grid (2-arc-minute resolution)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — EMAG2 is a global Earth Magnetic Anomaly Grid compiled from satellite, ship, and airborne magnetic measurements. It is a significant update of our previous candidate...

  15. RARE BRANCHIAL ARCH ANOMALIES

    Directory of Open Access Journals (Sweden)

    Jayanta Kumar

    2016-03-01

    Full Text Available AIM Amongst the branchial arch anomalies third arch anomaly occurs rarely and more so the fourth arch anomalies. We present our experience with cases of rare branchial arch anomalies. PATIENTS AND METHODS From June 2006 to January 2016, cases having their external opening in the lower third of sternocleidomastoid muscle with the tract going through thyroid gland and directing to pyriform sinus (PFS or cysts with internal opening in the PFS were studied. RESULTS No fourth arch anomaly was encountered. One cyst with internal opening which later on formed a fistula, three fistulae from beginning and two sinuses were encountered. The main stay of diagnosis was the fistula in the PFS and the tract lying posterior to the internal carotid artery. Simple excision technique with a small incision around the external opening was done. There was no recurrence. CONCLUSION Third arch fistula is not very rare as it was thought. Internal fistula is found in most of the cases. Though radiological investigations are helpful, fistulae can be diagnosed clinically and during operation. Extensive operation of the neck, mediastinum and pharynx is not required.

  16. Interstellar depletion anomalies and ionization potentials

    International Nuclear Information System (INIS)

    Tabak, R.G.

    1979-01-01

    Satellite observations indicate that (1) most elements are depleted from the gas phase when compared to cosmic abundances, (2) some elements are several orders of magnitude more depleted than others, and (3) these depletions vary from cloud to cloud. Since the most likely possibility is that the 'missing' atoms are locked into grains, depletions occur either by accretion onto core particles in interstellar clouds or earlier, during the period of primary grain formation. If the latter mechanism is dominant, then the most important depletion parameter is the condensation temperature of the elements and their various compounds. However, this alone is not sufficient to explain all the observed anomalies. It is shown that electrostatic effects - under a wide variety of conditions- can enormously enhance the capture cross-section of the grain. It is suggested that this mechanism can also account for such anomalies as the apparent 'overabundance' of the alkali metals in the gas phase. (orig.)

  17. Beyond reliability, multi-state failure analysis of satellite subsystems: A statistical approach

    International Nuclear Information System (INIS)

    Castet, Jean-Francois; Saleh, Joseph H.

    2010-01-01

    Reliability is widely recognized as a critical design attribute for space systems. In recent articles, we conducted nonparametric analyses and Weibull fits of satellite and satellite subsystems reliability for 1584 Earth-orbiting satellites launched between January 1990 and October 2008. In this paper, we extend our investigation of failures of satellites and satellite subsystems beyond the binary concept of reliability to the analysis of their anomalies and multi-state failures. In reliability analysis, the system or subsystem under study is considered to be either in an operational or failed state; multi-state failure analysis introduces 'degraded states' or partial failures, and thus provides more insights through finer resolution into the degradation behavior of an item and its progression towards complete failure. The database used for the statistical analysis in the present work identifies five states for each satellite subsystem: three degraded states, one fully operational state, and one failed state (complete failure). Because our dataset is right-censored, we calculate the nonparametric probability of transitioning between states for each satellite subsystem with the Kaplan-Meier estimator, and we derive confidence intervals for each probability of transitioning between states. We then conduct parametric Weibull fits of these probabilities using the Maximum Likelihood Estimation (MLE) approach. After validating the results, we compare the reliability versus multi-state failure analyses of three satellite subsystems: the thruster/fuel; the telemetry, tracking, and control (TTC); and the gyro/sensor/reaction wheel subsystems. The results are particularly revealing of the insights that can be gleaned from multi-state failure analysis and the deficiencies, or blind spots, of the traditional reliability analysis. In addition to the specific results provided here, which should prove particularly useful to the space industry, this work highlights the importance

  18. Seafloor spreading magnetic anomalies south off Sri Lanka

    Digital Repository Service at National Institute of Oceanography (India)

    Desa, M.; Ramana, M.V.; Ramprasad, T.

    Cretaceous is estimated to have evolved with variable half-spreading rates ranging from 5.5 to 1.53 cm/yr. The trends of the fracture zones inferred from the offsets in the magnetic anomalies have been constrained using the satellite gravity mosaic...

  19. Low Risk Anomalies?

    DEFF Research Database (Denmark)

    Schneider, Paul; Wagner, Christian; Zechner, Josef

    . Empirically, we find that option-implied ex-ante skewness is strongly related to ex-post residual coskewness and alphas. Beta- and volatility-based low risk anomalies are largely driven by a single principal component, which is in turn largely explained by skewness. Controlling for skewness renders the alphas......This paper shows that stocks' CAPM alphas are negatively related to CAPM betas if investors demand compensation for negative skewness. Thus, high (low) beta stocks appear to underperform (outperform). This apparent anomaly merely reflects compensation for residual coskewness ignored by the CAPM...... of betting-against-beta and -volatility insignificant....

  20. Positively deflected anomaly mediation

    International Nuclear Information System (INIS)

    Okada, Nobuchika

    2002-01-01

    We generalize the so-called 'deflected anomaly mediation' scenario to the case where threshold corrections of heavy messengers to the sparticle squared masses are positive. A concrete model realizing this scenario is also presented. The tachyonic slepton problem can be fixed with only a pair of messengers. The resultant sparticle mass spectrum is quite different from that in the conventional deflected anomaly mediation scenario, but is similar to the one in the gauge mediation scenario. The lightest sparticle is mostly B-ino

  1. Congenital laryngeal anomalies,

    Directory of Open Access Journals (Sweden)

    Michael J. Rutter

    2014-12-01

    Full Text Available Introduction: It is essential for clinicians to understand issues relevant to the airway management of infants and to be cognizant of the fact that infants with congenital laryngeal anomalies are at particular risk for an unstable airway. Objectives: To familiarize clinicians with issues relevant to the airway management of infants and to present a succinct description of the diagnosis and management of an array of congenital laryngeal anomalies. Methods: Revision article, in which the main aspects concerning airway management of infants will be analyzed. Conclusions: It is critical for clinicians to understand issues relevant to the airway management of infants.

  2. Man-Made Debris In and From Lunar Orbit

    Science.gov (United States)

    Johnson, Nicholas L.; McKay, Gordon A. (Technical Monitor)

    1999-01-01

    During 1966-1976, as part of the first phase of lunar exploration, 29 manned and robotic missions placed more than 40 objects into lunar orbit. Whereas several vehicles later successfully landed on the Moon and/or returned to Earth, others were either abandoned in orbit or intentionally sent to their destruction on the lunar surface. The former now constitute a small population of lunar orbital debris; the latter, including four Lunar Orbiters and four Lunar Module ascent stages, have contributed to nearly 50 lunar sites of man's refuse. Other lunar satellites are known or suspected of having fallen from orbit. Unlike Earth satellite orbital decays and deorbits, lunar satellites impact the lunar surface unscathed by atmospheric burning or melting. Fragmentations of lunar satellites, which would produce clouds of numerous orbital debris, have not yet been detected. The return to lunar orbit in the 1990's by the Hagoromo, Hiten, Clementine, and Lunar Prospector spacecraft and plans for increased lunar exploration early in the 21st century, raise questions of how best to minimize and to dispose of lunar orbital debris. Some of the lessons learned from more than 40 years of Earth orbit exploitation can be applied to the lunar orbital environment. For the near-term, perhaps the most important of these is postmission passivation. Unique solutions, e.g., lunar equatorial dumps, may also prove attractive. However, as with Earth satellites, debris mitigation measures are most effectively adopted early in the concept and design phase, and prevention is less costly than remediation.

  3. Orbital Resonances in the Vinti Solution

    Science.gov (United States)

    Zurita, L. D.

    As space becomes more congested, contested, and competitive, high-accuracy orbital predictions become critical for space operations. Current orbit propagators use the two-body solution with perturbations added, which have significant error growth when numerically integrated for long time periods. The Vinti Solution is a more accurate model than the two-body problem because it also accounts for the equatorial bulge of the Earth. Unfortunately, the Vinti solution contains small divisors near orbital resonances in the perturbative terms of the Hamiltonian, which lead to inaccurate orbital predictions. One approach to avoid the small divisors is to apply transformation theory, which is presented in this research. The methodology of this research is to identify the perturbative terms of the Vinti Solution, perform a coordinate transformation, and derive the new equations of motion for the Vinti system near orbital resonances. An analysis of these equations of motion offers insight into the dynamics found near orbital resonances. The analysis in this research focuses on the 2:1 resonance, which includes the Global Positioning System. The phase portrait of a nominal Global Positioning System satellite orbit is found to contain a libration region and a chaotic region. Further analysis shows that the dynamics of the 2:1 resonance affects orbits with semi-major axes ranging from -5.0 to +5.4 kilometers from an exactly 2:1 resonant orbit. Truth orbits of seven Global Positioning System satellites are produced for 10 years. Two of the satellites are found to be outside of the resonance region and three are found to be influenced by the libration dynamics of the resonance. The final satellite is found to be influenced by the chaotic dynamics of the resonance. This research provides a method of avoiding the small divisors found in the perturbative terms of the Vinti Solution near orbital resonances.

  4. Orbital transport

    International Nuclear Information System (INIS)

    Oertel, H. Jr.; Koerner, H.

    1993-01-01

    The Third Aerospace Symposium in Braunschweig presented, for the first time, the possibility of bringing together the classical disciplines of aerospace engineering and the natural science disciplines of meteorology and air chemistry in a european setting. In this way, aspects of environmental impact on the atmosphere could be examined quantitatively. An essential finding of the european conference, is the unrestricted agreement of the experts that the given launch frequencies of the present orbital transport result in a negligible amount of pollutants being released in the atmosphere. The symposium does, however, call attention to the increasing need to consider the effect of orbital and atmospheric environmental impact of a future increase in launch frequencies of orbital transport in connection with future space stations. The Third Aerospace Symposium, 'Orbital Transport, Technical, Meteorological and Chemical Aspects', constituted a first forum of discussion for engineers and scientists. Questions of new orbital transport technologies and their environmental impact were to be discussed towards a first consensus. Through the 34 reports and articles, the general problems of space transportation and environmental protection were addressed, as well as particular aspects of high temperatures during reentry in the atmosphere of the earth, precision navigation of flight vehicles or flow behavior and air chemistry in the stratosphere. (orig./CT). 342 figs

  5. Existence of undiscovered Uranian satellites

    International Nuclear Information System (INIS)

    Boice, D.C.

    1986-04-01

    Structure in the Uranian ring system as observed in recent occultations may contain indirect evidence for the existence of undiscovered satellites. Using the Alfven and Arrhenius (1975, 1976) scenario for the formation of planetary systems, the orbital radii of up to nine hypothetical satellites interior to Miranda are computed. These calculations should provide interesting comparisons when the results from the Voyager 2 encounter with Uranus are made public. 15 refs., 1 fig., 1 tab

  6. Assessing Asset Pricing Anomalies

    NARCIS (Netherlands)

    W.A. de Groot (Wilma)

    2017-01-01

    markdownabstractOne of the most important challenges in the field of asset pricing is to understand anomalies: empirical patterns in asset returns that cannot be explained by standard asset pricing models. Currently, there is no consensus in the academic literature on the underlying causes of

  7. Anomaly Busters II

    International Nuclear Information System (INIS)

    Anon.

    1985-01-01

    The anomaly busters had struck on the first day of the Kyoto meeting with Yoji Totsuka of Tokyo speaking on baryon number nonjjonservation and 'related topics'. The unstable proton is a vital test of grand unified pictures pulling together the electroweak and quark/gluon forces in a single field theory

  8. Anomaly Busters II

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1985-11-15

    The anomaly busters had struck on the first day of the Kyoto meeting with Yoji Totsuka of Tokyo speaking on baryon number nonjjonservation and 'related topics'. The unstable proton is a vital test of grand unified pictures pulling together the electroweak and quark/gluon forces in a single field theory.

  9. The reactor antineutrino anomalies

    Energy Technology Data Exchange (ETDEWEB)

    Haser, Julia; Buck, Christian; Lindner, Manfred [Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany)

    2016-07-01

    Major discoveries were made in the past few years in the field of neutrino flavour oscillation. Nuclear reactors produce a clean and intense flux of electron antineutrinos and are thus an essential neutrino source for the determination of oscillation parameters. Most currently the reactor antineutrino experiments Double Chooz, Daya Bay and RENO have accomplished to measure θ{sub 13}, the smallest of the three-flavour mixing angles. In the course of these experiments two anomalies emerged: (1) the reanalysis of the reactor predictions revealed a deficit in experimentally observed antineutrino flux, known as the ''reactor antineutrino anomaly''. (2) The high precision of the latest generation of neutrino experiments resolved a spectral shape distortion relative to the expected energy spectra. Both puzzles are yet to be solved and triggered new experimental as well as theoretical studies, with the search for light sterile neutrinos as most popular explanation for the flux anomaly. This talk outlines the two reactor antineutrino anomalies. Discussing possible explanations for their occurrence, recent and upcoming efforts to solve the reactor puzzles are highlighted.

  10. Echocardiography in Ebstein's anomaly

    NARCIS (Netherlands)

    W.J. Gussenhoven (Wilhelmina Johanna)

    1984-01-01

    textabstractIn this thesis the value of echocardiography is evaluated for the diagnosis of Ebstein's anomaly of the tricuspid valve. This congenital heart defect, first described in 1866 by Wilhelm Ebstein, is characterized by an apical displacement of the septal and inferior tricuspid valve

  11. Bolivian Bouguer Anomaly Grid

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A 1 kilometer Bouguer anomaly grid for the country of Bolivia.Number of columns is 550 and number of rows is 900. The order of the data is from the lower left to the...

  12. Generalized zero point anomaly

    International Nuclear Information System (INIS)

    Nogueira, Jose Alexandre; Maia Junior, Adolfo

    1994-01-01

    It is defined Zero point Anomaly (ZPA) as the difference between the Effective Potential (EP) and the Zero point Energy (ZPE). It is shown, for a massive and interacting scalar field that, in very general conditions, the renormalized ZPA vanishes and then the renormalized EP and ZPE coincide. (author). 3 refs

  13. Minnesota Bouguer Anomaly Grid

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A 1.5 kilometer Bouguer anomaly grid for the state of Minnesota. Number of columns is 404 and number of rows is 463. The order of the data is from the lower left to...

  14. Satellite failures revisited

    Science.gov (United States)

    Balcerak, Ernie

    2012-12-01

    In January 1994, the two geostationary satellites known as Anik-E1 and Anik-E2, operated by Telesat Canada, failed one after the other within 9 hours, leaving many northern Canadian communities without television and data services. The outage, which shut down much of the country's broadcast television for hours and cost Telesat Canada more than $15 million, generated significant media attention. Lam et al. used publicly available records to revisit the event; they looked at failure details, media coverage, recovery effort, and cost. They also used satellite and ground data to determine the precise causes of those satellite failures. The researchers traced the entire space weather event from conditions on the Sun through the interplanetary medium to the particle environment in geostationary orbit.

  15. Characterization of NPP Visible/Infrared Imager Radiometer Suite (VIIRS) Reflective Solar Bands Dual Gain Anomaly

    Science.gov (United States)

    Lee, Shihyan; McIntire, Jeff; Oudari, Hassan

    2012-01-01

    The Visible/Infrared Imager Radiometer Suite (VIIRS) contains six dual gain bands in the reflective solar spectrum. The dual gain bands are designed to switch gain mode at pre-defined thresholds to achieve high resolution at low radiances while maintaining the required dynamic range for science. During pre-launch testing, an anomaly in the electronic response before transitioning from high to low gain was discovered and characterized. On-orbit, the anomaly was confirmed using MODIS data collected during Simultaneous Nadir Overpasses (SNOs). The analysis of the Earth scene data shows that dual gain anomaly can be determined at the orbital basis. To characterize the dual gain anomaly, the anomaly region and electronic offsets were tracked per week during the first 8 month of VIIRS operation. The temporal analysis shows the anomaly region can drift 20 DN and is impacted by detectors DC Restore. The estimated anomaly flagging regions cover 2.5 % of the high gain dynamic range and are consistent with prelaunch and on-orbit LUT. The prelaunch results had a smaller anomaly range (30-50 DN) and are likely the results of more stable electronics from the shorter data collection time. Finally, this study suggests future calibration efforts to focus on the anomaly's impact on science products and possible correction method to reduce uncertainties.

  16. A low earth orbit dynamic model for the proton anisotropy validation

    Science.gov (United States)

    Badavi, Francis F.

    2011-11-01

    Ionizing radiation measurements at low earth orbit (LEO) form the ideal tool for the experimental validation of radiation environmental models, nuclear transport code algorithms and nuclear reaction cross sections. Indeed, prior measurements on the space transportation system (STS; shuttle) have provided vital information impacting both the environmental models and the nuclear transport code development by requiring dynamic models of the LEO environment. Previous studies using computer aided design (CAD) models of the international space station (ISS) have demonstrated that the dosimetric prediction for a spacecraft at LEO requires the description of an environmental model with accurate anisotropic as well as dynamic behavior. This paper describes such a model for the trapped proton. The described model is a component of a suite of codes collectively named GEORAD (GEOmagnetic RADiation) which computes cutoff rigidity, trapped proton and trapped electron environments. The web version of GEORAD is named OLTARIS (On-line Tool for the Assessment of Radiation in Space). GEORAD suite is applicable to radiation environment prediction at LEO, medium earth orbit (MEO) and geosynchronous earth orbit (GEO) at quiet solar periods. GEORAD interest is in the study of long term effect of the trapped environment and therefore it does not account for any short term external field contribution due to solar activity. With the concentration of the paper on the LEO protons only, the paper presents the validation of the trapped proton model within GEORAD with reported measurements from the compact environment anomaly sensor (CEASE) science instrument package, flown onboard the tri-service experiment-5 (TSX-5) satellite during the period of June 2000 to July 2006. The spin stabilized satellite was flown in a 410 × 1710 km, 69° inclination elliptical orbit, allowing it to be exposed to a broad range of the LEO regime. The paper puts particular emphasize on the validation of the

  17. Angles-only relative orbit determination in low earth orbit

    Science.gov (United States)

    Ardaens, Jean-Sébastien; Gaias, Gabriella

    2018-06-01

    The paper provides an overview of the angles-only relative orbit determination activities conducted to support the Autonomous Vision Approach Navigation and Target Identification (AVANTI) experiment. This in-orbit endeavor was carried out by the German Space Operations Center (DLR/GSOC) in autumn 2016 to demonstrate the capability to perform spaceborne autonomous close-proximity operations using solely line-of-sight measurements. The images collected onboard have been reprocessed by an independent on-ground facility for precise relative orbit determination, which served as ultimate instance to monitor the formation safety and to characterize the onboard navigation and control performances. During two months, several rendezvous have been executed, generating a valuable collection of images taken at distances ranging from 50 km to only 50 m. Despite challenging experimental conditions characterized by a poor visibility and strong orbit perturbations, angles-only relative positioning products could be continuously derived throughout the whole experiment timeline, promising accuracy at the meter level during the close approaches. The results presented in the paper are complemented with former angles-only experience gained with the PRISMA satellites to better highlight the specificities induced by different orbits and satellite designs.

  18. Fuzzy Logic Controller for Small Satellites Navigation

    National Research Council Canada - National Science Library

    Della Pietra, G; Falzini, S; Colzi, E; Crisconio, M

    2005-01-01

    .... The navigator aims at operating satellites in orbit with a minimum ground support and very good performances, by the adoption of innovative technologies, such as attitude observation GPS, attitude...

  19. Defense Meteorological Satellite Program (DMSP) Film

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The United States Air Force Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) is a polar orbiting meteorological sensor with two...

  20. Selected Geomagnetic Measurements From Several Satellites

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — More than 17 million selected magnetic observations from several orbiting low-altitude satellites are contained in this digital collection. Except for MAGSAT, all...

  1. Real-Time and Post-Processed Orbit Determination and Positioning

    Science.gov (United States)

    Bar-Sever, Yoaz E. (Inventor); Bertiger, William I. (Inventor); Dorsey, Angela R. (Inventor); Harvey, Nathaniel E. (Inventor); Lu, Wenwen (Inventor); Miller, Kevin J. (Inventor); Miller, Mark A. (Inventor); Romans, Larry J. (Inventor); Sibthorpe, Anthony J. (Inventor); Weiss, Jan P. (Inventor); hide

    2016-01-01

    Novel methods and systems for the accurate and efficient processing of real-time and latent global navigation satellite systems (GNSS) data are described. Such methods and systems can perform orbit determination of GNSS satellites, orbit determination of satellites carrying GNSS receivers, positioning of GNSS receivers, and environmental monitoring with GNSS data.

  2. Algebraic study of chiral anomalies

    Indian Academy of Sciences (India)

    Chiral anomalies; gauge theories; bundles; connections; quantum field ... The algebraic structure of chiral anomalies is made globally valid on non-trivial bundles by the introduction of a fixed background connection. ... Current Issue : Vol.

  3. Ferret Workflow Anomaly Detection System

    National Research Council Canada - National Science Library

    Smith, Timothy J; Bryant, Stephany

    2005-01-01

    The Ferret workflow anomaly detection system project 2003-2004 has provided validation and anomaly detection in accredited workflows in secure knowledge management systems through the use of continuous, automated audits...

  4. Precise GPS orbits for geodesy

    Science.gov (United States)

    Colombo, Oscar L.

    1994-01-01

    The Global Positioning System (GPS) has become, in recent years, the main space-based system for surveying and navigation in many military, commercial, cadastral, mapping, and scientific applications. Better receivers, interferometric techniques (DGPS), and advances in post-processing methods have made possible to position fixed or moving receivers with sub-decimeter accuracies in a global reference frame. Improved methods for obtaining the orbits of the GPS satellites have played a major role in these achievements; this paper gives a personal view of the main developments in GPS orbit determination.

  5. Analysis of South Atlantic Anomaly perturbations on Sentinel-3A Ultra Stable Oscillator. Impact on DORIS phase measurement and DORIS station positioning

    Science.gov (United States)

    Jalabert, Eva; Mercier, Flavien

    2018-07-01

    DORIS measurements rely on the precise knowledge of the embedded oscillator which is called the Ultra Stable Oscillator (DORIS USO). The important radiations in the South Atlantic Anomaly (SAA) perturb the USO behavior by causing rapid frequency variations when the satellite is flying through the SAA. These variations are not taken into account in standard DORIS processing, since the USO is modelled as a third degree polynomial over 7-10 days. Therefore, there are systematic measurements errors when the satellite passes through SAA. In standard GNSS processing, the clock is directly estimated at each epoch. On Sentinel-3A, the GPS receiver and the DORIS receiver use the same USO. It is thus possible to estimate the behavior of the USO using GPS measurements. This estimated USO behavior can be used in the DORIS processing, instead of the third degree polynomial, hence allowing an estimation of the orbit sensitivity to these USO anomalies. This study shows two main results. First, the SAA effect on the DORIS USO is observed well using GPS measurements. Second, the USO behavior observed with GPS can be used to mitigate the SAA effect. Indeed, when used in Sentinel-3A processing, the resulting DORIS orbit shows improved phase measurements and station positioning for stations inside the SAA (Arequipa and Cachoeira). The phase measurements residuals are improved by up to 10 cm, and station vertical positioning (i.e. on the estimated Up component in the North-East-Up station frame) is improved by up to a few centimeters. However, the orbit itself is not sensitive to the correction because only two stations (out of almost 60) are SAA-sensitive on Sentinel-3A.

  6. The escape of natural satellites from Mercury and Venus

    International Nuclear Information System (INIS)

    Kumar, S.S.

    1977-01-01

    It is suggested that the slow rotations of Mercury and Venus may be connected with the absence of natural satellites around them. If Mercury or Venus possessed a satellite at the time of formation, the tidal evolution would have caused the satellite to recede. At a sufficiently large distance from the planet, the Sun's gravitational influence makes the satellite orbit unstable. The natural satellites of Mercury and Venus might have escaped as a consequence of this instability. (Auth.)

  7. Escape of natural satellites from Mercury and Venus

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, S S [Virginia Univ., Charlottesville (USA)

    1977-09-01

    It is suggested that the slow rotations of Mercury and Venus may be connected with the absence of natural satellites around them. If Mercury or Venus possessed a satellite at the time of formation, the tidal evolution would have caused the satellite to recede. At a sufficiently large distance from the planet, the Sun's gravitational influence makes the satellite orbit unstable. The natural satellites of Mercury and Venus might have escaped as a consequence of this instability.

  8. Ground test of satellite constellation based quantum communication

    OpenAIRE

    Liao, Sheng-Kai; Yong, Hai-Lin; Liu, Chang; Shentu, Guo-Liang; Li, Dong-Dong; Lin, Jin; Dai, Hui; Zhao, Shuang-Qiang; Li, Bo; Guan, Jian-Yu; Chen, Wei; Gong, Yun-Hong; Li, Yang; Lin, Ze-Hong; Pan, Ge-Sheng

    2016-01-01

    Satellite based quantum communication has been proven as a feasible way to achieve global scale quantum communication network. Very recently, a low-Earth-orbit (LEO) satellite has been launched for this purpose. However, with a single satellite, it takes an inefficient 3-day period to provide the worldwide connectivity. On the other hand, similar to how the Iridium system functions in classic communication, satellite constellation (SC) composed of many quantum satellites, could provide global...

  9. Branchial Cleft Anomalies

    Science.gov (United States)

    McPhail, Neil; Mustard, Robert A.

    1966-01-01

    The embryology, anatomy and pathology of branchial cleft anomalies are discussed and 87 cases reviewed. The most frequent anomaly was branchial cleft cyst, of which there were 77 cases. Treatment in all cases consisted of complete excision. There were five cases of external branchial sinus and five cases of complete branchial fistula. Sinograms were helpful in demonstrating these lesions. Excision presented little difficulty. No proved case of branchiogenic carcinoma has been found in the Toronto General Hospital. Five cases are described in which the original diagnosis was branchiogenic carcinoma—in four of these a primary tumour has already been found. The authors believe that the diagnosis of branchiogenic carcinoma should never be accepted until repeated examinations over a period of at least five years have failed to reveal a primary tumour. ImagesFig. 1Fig. 2Fig. 3Fig. 4Fig. 5 PMID:5901161

  10. Sky alert! when satellites fail

    CERN Document Server

    Johnson, Les

    2013-01-01

    How much do we depend on space satellites? Defense, travel, agriculture, weather forecasting, mobile phones and broadband, commerce...the list seems endless. But what would our live be like if the unimaginable happened and, by accident or design, those space assets disappeared? Sky Alert! explores what our world would be like, looking in turn at areas where the loss could have catastrophic effects. The book - demonstrates our dependence on space technology and satellites; - outlines the effect on our economy, defense, and daily lives if satellites and orbiting spacecraft were destroyed; - illustrates the danger of dead satellites, spent rocket stages, and space debris colliding with a functioning satellites; - demonstrates the threat of dramatically increased radiation levels associated with geomagnetic storms; - introduces space as a potential area of conflict between nations.

  11. Forward Technology Solar Cell Experiment First On-Orbit Data

    Science.gov (United States)

    Walters, R. J.; Garner, J. C.; Lam, S. N.; Vazquez, J. A.; Braun, W. R.; Ruth, R. E.; Warner, J. H.; Lorentzen, J. R.; Messenger, S. R.; Bruninga, R.; hide

    2007-01-01

    This paper presents first on orbit measured data from the Forward Technology Solar Cell Experiment (FTSCE). FTSCE is a space experiment housed within the 5th Materials on the International Space Station Experiment (MISSE-5). MISSE-5 was launched aboard the Shuttle return to flight mission (STS-114) on July 26, 2005 and deployed on the exterior of the International Space Station (ISS). The experiment will remain in orbit for nominally one year, after which it will be returned to Earth for post-flight testing and analysis. While on orbit, the experiment is designed to measure a 36 point current vs. voltage (IV) curve on each of the experimental solar cells, and the data is continuously telemetered to Earth. The experiment also measures the solar cell temperature and the orientation of the solar cells to the sun. A range of solar cell technologies are included in the experiment including state-of-the-art triple junction InGaP/GaAs/Ge solar cells from several vendors, thin film amorphous Si and CuIn(Ga)Se2 cells, and next-generation technologies like single-junction GaAs cells grown on Si wafers and metamorphic InGaP/InGaAs/Ge triple-junction cells. In addition to FTSCE, MISSE-5 also contains a Thin-Film Materials experiment. This is a passive experiment that will provide data on the effect of the space environment on more than 200 different materials. FTSCE was initially conceived in response to various on-orbit and ground test anomalies associated with space power systems. The Department of Defense (DoD) required a method of rapidly obtaining on orbit validation data for new space solar cell technologies, and NRL was tasked to devise an experiment to meet this requirement. Rapid access to space was provided by the MISSE Program which is a NASA Langley Research Center program. MISSE-5 is a completely self-contained experiment system with its own power generation and storage system and communications system. The communications system, referred to as PCSat, transmits

  12. Penile Anomalies in Adolescence

    Directory of Open Access Journals (Sweden)

    Dan Wood

    2011-01-01

    Full Text Available This article considers the impact and outcomes of both treatment and underlying condition of penile anomalies in adolescent males. Major congenital anomalies (such as exstrophy/epispadias are discussed, including the psychological outcomes, common problems (such as corporal asymmetry, chordee, and scarring in this group, and surgical assessment for potential surgical candidates. The emergence of new surgical techniques continues to improve outcomes and potentially raises patient expectations. The importance of balanced discussion in conditions such as micropenis, including multidisciplinary support for patients, is important in order to achieve appropriate treatment decisions. Topical treatments may be of value, but in extreme cases, phalloplasty is a valuable option for patients to consider. In buried penis, the importance of careful assessment and, for the majority, a delay in surgery until puberty has completed is emphasised. In hypospadias patients, the variety of surgical procedures has complicated assessment of outcomes. It appears that true surgical success may be difficult to measure as many men who have had earlier operations are not reassessed in either puberty or adult life. There is also a brief discussion of acquired penile anomalies, including causation and treatment of lymphoedema, penile fracture/trauma, and priapism.

  13. Penile anomalies in adolescence.

    Science.gov (United States)

    Wood, Dan; Woodhouse, Christopher

    2011-03-07

    This article considers the impact and outcomes of both treatment and underlying condition of penile anomalies in adolescent males. Major congenital anomalies (such as exstrophy/epispadias) are discussed, including the psychological outcomes, common problems (such as corporal asymmetry, chordee, and scarring) in this group, and surgical assessment for potential surgical candidates. The emergence of new surgical techniques continues to improve outcomes and potentially raises patient expectations. The importance of balanced discussion in conditions such as micropenis, including multidisciplinary support for patients, is important in order to achieve appropriate treatment decisions. Topical treatments may be of value, but in extreme cases, phalloplasty is a valuable option for patients to consider. In buried penis, the importance of careful assessment and, for the majority, a delay in surgery until puberty has completed is emphasised. In hypospadias patients, the variety of surgical procedures has complicated assessment of outcomes. It appears that true surgical success may be difficult to measure as many men who have had earlier operations are not reassessed in either puberty or adult life. There is also a brief discussion of acquired penile anomalies, including causation and treatment of lymphoedema, penile fracture/trauma, and priapism.

  14. Euro-African MAGSAT anomaly-tectonic observations

    Science.gov (United States)

    Hinze, W. J.; Olivier, R.; Vonfrese, R. R. B.

    1985-01-01

    Preliminary satellite (MAGSAT) scalar magnetic anomaly data are compiled and differentially reduced to radial polarization by equivalent point source inversion for comparison with tectonic data of Africa, Europe and adjacent marine areas. A number of associations are evident to constrain analyses of the tectonic features and history of the region. The Precambrian shields of Africa and Europe exhibit varied magnetic signatures. All shields are not magnetic highs and, in fact, the Baltic shield is a marked minimum. The reduced-to-the-pole magnetic map shows a marked tendency for northeasterly striking anomalies in the eastern Atlantic and adjacent Africa, which is coincident to the track of several hot spots for the past 100 million years. However, there is little consistency in the sign of the magnetic anomalies and the track of the hot spots. Comparison of the radially polarized anomalies of Africa and Europe with other reduced-to-the-pole magnetic satellite anomaly maps of the Western Hemisphere support the reconstruction of the continents prior to the origin of the present-day Atlantic Ocean in the Mesozoic Era.

  15. 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.

  16. Data distribution in the OLFAR satellite swarm

    NARCIS (Netherlands)

    Budianu, A.; Willink-Castro, T.J.; Engelen, S.; Rajan, R.T.; Rajan, Raj; Smith, D.M.P.; Meijerink, Arjan; Bentum, Marinus Jan

    2013-01-01

    The Orbiting Low Frequency Antennas for Radio Astronomy (OLFAR) project aims to develop a radio telescope for very low frequencies (below 30 MHz) by using a swarm of 50 or more nano-satellites. Spread in a 100-km diameter cloud, the satellites will form a very large aperture capable of sensing the

  17. Anomaly General Circulation Models.

    Science.gov (United States)

    Navarra, Antonio

    The feasibility of the anomaly model is assessed using barotropic and baroclinic models. In the barotropic case, both a stationary and a time-dependent model has been formulated and constructed, whereas only the stationary, linear case is considered in the baroclinic case. Results from the barotropic model indicate that a relation between the stationary solution and the time-averaged non-linear solution exists. The stationary linear baroclinic solution can therefore be considered with some confidence. The linear baroclinic anomaly model poses a formidable mathematical problem because it is necessary to solve a gigantic linear system to obtain the solution. A new method to find solution of large linear system, based on a projection on the Krylov subspace is shown to be successful when applied to the linearized baroclinic anomaly model. The scheme consists of projecting the original linear system on the Krylov subspace, thereby reducing the dimensionality of the matrix to be inverted to obtain the solution. With an appropriate setting of the damping parameters, the iterative Krylov method reaches a solution even using a Krylov subspace ten times smaller than the original space of the problem. This generality allows the treatment of the important problem of linear waves in the atmosphere. A larger class (nonzonally symmetric) of basic states can now be treated for the baroclinic primitive equations. These problem leads to large unsymmetrical linear systems of order 10000 and more which can now be successfully tackled by the Krylov method. The (R7) linear anomaly model is used to investigate extensively the linear response to equatorial and mid-latitude prescribed heating. The results indicate that the solution is deeply affected by the presence of the stationary waves in the basic state. The instability of the asymmetric flows, first pointed out by Simmons et al. (1983), is active also in the baroclinic case. However, the presence of baroclinic processes modifies the

  18. Dynamique des orbites fortement elliptiques

    OpenAIRE

    Lion , Guillaume

    2013-01-01

    Most of the orbits of artificial satellites around the Earth have relatively low eccentricities. The calculation of their trajectories is very well under control, either by means of numerical methods when it comes to focus on accuracy and comparing observations, or either through analytical or semi-analytical theories to optimize the speed of calculations. This second category is used, in particular, for computing many long-term trajectories that could help to ensure the security and safety o...

  19. Electrophotometric observations of artificial satellites

    International Nuclear Information System (INIS)

    Vovchyk, Yeva; Blagodyr, Yaroslav; Kraynyuk, Gennadiy; Bilinsky, Andriy; Lohvynenko, Alexander; Klym, Bogdan; Pochapsky, Yevhen

    2004-01-01

    Problems associated with polarimetric observations of low Earth orbit artificial satellites as important solar system objects are discussed. The instrumentation (the optical and mechanical parts, the control and drive electronics, and the application software) for performing such observations is also described

  20. Peculiarities of the ionosphere monitoring from low-flying satellites

    International Nuclear Information System (INIS)

    Danilkin, N.P.; Denisenko, P.F.; Mal'tseva, O.A.

    1998-01-01

    Peculiarities of the HF-radiowave propagation between ground stations and low-flying satellites near and below the maximum of the F area are studied through the method of mathematical modeling. It is established that the signal may propagate by three trajectories. The first one is below the satellite orbit. The turn altitudes of the second and the third beams are above the satellite orbit. Availability of three trajectories leads to the three-digit dependence of the group ways on the working frequency F. The P(f) curves for different satellite distances from a reception point and its orbit altitudes for the isotropic and magnetoactive ionosphere are presented

  1. In-Orbit Operation of the ASTRO-H SXS

    Science.gov (United States)

    Tsujimoto, Masahiro; Mitsuda, Kazuhisa; Kelley, Richard L.; den Herder, Jan-Willem A.; Akamatsu, Hiroki; Bialas, Thomas G.; Boyce, Kevin R.; Brown, Gregory V.; Chiao, Meng P.; Costantini, Elisa; hide

    2016-01-01

    We summarize all of the in-orbit operations of the soft x-ray spectrometer (SXS) onboard the ASTROH (Hitomi) satellite. The satellite was launched on February 17, 2016, and the communication with the satellite ceased on March 26, 2016. The SXS was still in the commissioning phase, in which the set-ups were progressively changed. This paper is intended to serve as a concise reference of the events in orbit in order to properly interpret the SXS data taken during its short lifetime and as a test case for planning the in-orbit operation for future microcalorimeter missions.

  2. Centriolar satellites

    DEFF Research Database (Denmark)

    Tollenaere, Maxim A X; Mailand, Niels; Bekker-Jensen, Simon

    2015-01-01

    Centriolar satellites are small, microscopically visible granules that cluster around centrosomes. These structures, which contain numerous proteins directly involved in centrosome maintenance, ciliogenesis, and neurogenesis, have traditionally been viewed as vehicles for protein trafficking...... highlight newly discovered regulatory mechanisms targeting centriolar satellites and their functional status, and we discuss how defects in centriolar satellite components are intimately linked to a wide spectrum of human diseases....

  3. Dynamical friction for dark halo satellites: effects of tidal massloss and growing host potential

    OpenAIRE

    Zhao, HongSheng

    2004-01-01

    How fast a satellite decays its orbit depends on how slowly its mass is lost by tide. Motivated by inner halo satellite remnants like the Sgr and Omega Cen, we develop fully analytical models to study the orbital decay and tidal massloss of satellites. The orbital decay rate is often severely overestimated if applying the ChandraSekhar's formula without correcting for (a) the evaporation and tidal loss of the satellite and (b) the contraction of satellite orbits due to adiabatic growth of the...

  4. Deep space optical communication via relay satellite

    Science.gov (United States)

    Dolinar, S.; Vilnrotter, V.; Gagliardi, R.

    1981-01-01

    The application of optical communications for a deep space link via an earth-orbiting relay satellite is discussed. The system uses optical frequencies for the free-space channel and RF links for atmospheric transmission. The relay satellite is in geostationary orbit and contains the optics necessary for data processing and formatting. It returns the data to earth through the RF terrestrial link and also transmits an optical beacon to the satellite for spacecraft return pointing and for the alignment of the transmitting optics. Future work will turn to modulation and coding, pointing and tracking, and optical-RF interfacing.

  5. Satellite Power Systems (SPS) concept definition study. Volume 5: Special emphasis studies. [rectenna and solar power satellite design studies

    Science.gov (United States)

    Hanley, G. M.

    1980-01-01

    Satellite configurations based on the Satellite Power System baseline requirements were analyzed and a preferred concept selected. A satellite construction base was defined, precursor operations incident to establishment of orbital support facilities identified, and the satellite construction sequence and procedures developed. Rectenna construction requirement were also addressed. Mass flow to orbit requirements were revised and traffic models established based on construction of 60 instead of 120 satellites. Analyses were conducted to determine satellite control, resources, manufacturing, and propellant requirements. The impact of the laser beam used for space-to-Earth power transmission upon the intervening atmosphere was examined as well as the inverse effect. The significant space environments and their effects on spacecraft components were investigated to define the design and operational limits imposed by the environments on an orbit transfer vehicle. The results show that LEO altitude 300 nmi and transfer orbit duration 6 months are preferrable.

  6. Asteroid Satellites

    Science.gov (United States)

    Merline, W. J.

    2001-11-01

    Discovery and study of small satellites of asteroids or double asteroids can yield valuable information about the intrinsic properties of asteroids themselves and about their history and evolution. Determination of the orbits of these moons can provide precise masses of the primaries, and hence reliable estimates of the fundamental property of bulk density. This reveals much about the composition and structure of the primary and will allow us to make comparisons between, for example, asteroid taxonomic type and our inventory of meteorites. The nature and prevalence of these systems will also give clues as to the collisional environment in which they formed, and have further implications for the role of collisions in shaping our solar system. A decade ago, binary asteroids were more of a theoretical curiosity. In 1993, the Galileo spacecraft allowed the first undeniable detection of an asteroid moon, with the discovery of Dactyl, a small moon of Ida. Since that time, and particularly in the last year, the number of known binaries has risen dramatically. Previously odd-shaped and lobate near-Earth asteroids, observed by radar, have given way to signatures indicating, almost certainly, that at least four NEAs are binary systems. The tell-tale lightcurves of several other NEAs reveal a high likelihood of being double. Indications are that among the NEAs, there may be a binary frequency of several tens of percent. Among the main-belt asteroids, we now know of 6 confirmed binary systems, although their overall frequency is likely to be low, perhaps a few percent. The detections have largely come about because of significant advances in adaptive optics systems on large telescopes, which can now reduce the blurring of the Earth's atmosphere to compete with the spatial resolution of space-based imaging (which itself, via HST, is now contributing valuable observations). Most of these binary systems have similarities, but there are important exceptions. Searches among other

  7. First branchial cleft anomaly.

    Science.gov (United States)

    Al-Fallouji, M. A.; Butler, M. F.

    1983-01-01

    A 15-year-old girl presented with a cystic swelling since birth behind the ramus of the right mandible and diagnosed clinically as a dermoid cyst. Surgical exploration, however, showed that it was closely related to the external auditory canal, with an extension running medially behind the parotid gland and ending in the bony middle ear. The facial nerve was closely related to the deep part of the cyst. Such an anatomical position indicates that this was a first branchial cleft anomaly. Surgical excision of the cyst was performed. PMID:6622327

  8. German telecommunications satellite (Deutscher fernmelde satellit) (DFS-1 and -2)

    Science.gov (United States)

    Hiendlmeier, G.; Schmeller, H.

    1991-01-01

    The German Telecommunications Satellite (DFS) Program is to provide telecommunications service for high data rate transmission of text and video data to the Federal Republic of Germany within the 11-14 GHz and 20-30 GHz bands. The space segment of this program is composed of three satellites, DFS-1, DFS-2, and DFS-3, which will be located at 23.5 degrees E longitude of the geostationary orbit. The DFS will be launched from the Center Spatial Guyanis in French Giana on an Ariane launch vehicle. The mission follows the typical injection sequence: parking orbit, transfer orbit, and earth orbit. Attitude maneuvers will be performed to orient the spacecraft prior to Apogee Kick Motor (AKM) firing. After AKM firing, drift phase orbital and attitude maneuvers will be performed to place the spacecraft in its final geostationary position. The Deep Space Network (DSN) will support the transfer and drift orbit mission phases. Information is presented in tabular form for the following areas: DSN support, compatibility testing, frequency assignments, telemetry, command, and tracking support responsibilities.

  9. Quantification of Impact of Orbital Drift on Inter-Annual Trends in AVHRR NDVI Data

    Directory of Open Access Journals (Sweden)

    Jyoteshwar R. Nagol

    2014-07-01

    Full Text Available The Normalized Difference Vegetation Index (NDVI time-series data derived from Advanced Very High Resolution Radiometer (AVHRR have been extensively used for studying inter-annual dynamics of global and regional vegetation. However, there can be significant uncertainties in the data due to incomplete atmospheric correction and orbital drift of the satellites through their active life. Access to location specific quantification of uncertainty is crucial for appropriate evaluation of the trends and anomalies. This paper provides per pixel quantification of orbital drift related spurious trends in Long Term Data Record (LTDR AVHRR NDVI data product. The magnitude and direction of the spurious trends was estimated by direct comparison with data from MODerate resolution Imaging Spectrometer (MODIS Aqua instrument, which has stable inter-annual sun-sensor geometry. The maps show presence of both positive as well as negative spurious trends in the data. After application of the BRDF correction, an overall decrease in positive trends and an increase in number of pixels with negative spurious trends were observed. The mean global spurious inter-annual NDVI trend before and after BRDF correction was 0.0016 and −0.0017 respectively. The research presented in this paper gives valuable insight into the magnitude of orbital drift related trends in the AVHRR NDVI data as well as the degree to which it is being rectified by the MODIS BRDF correction algorithm used by the LTDR processing stream.

  10. Orbit analysis

    International Nuclear Information System (INIS)

    Michelotti, L.

    1995-01-01

    The past fifteen years have witnessed a remarkable development of methods for analyzing single particle orbit dynamics in accelerators. Unlike their more classic counterparts, which act upon differential equations, these methods proceed by manipulating Poincare maps directly. This attribute makes them well matched for studying accelerators whose physics is most naturally modelled in terms of maps, an observation that has been championed most vigorously by Forest. In the following sections the author sketchs a little background, explains some of the physics underlying these techniques, and discusses the best computing strategy for implementing them in conjunction with modeling accelerators

  11. Brane orbits

    CERN Document Server

    Bergshoeff, Eric A; Riccioni, Fabio

    2012-01-01

    We complete the classification of half-supersymmetric branes in toroidally compactified IIA/IIB string theory in terms of representations of the T-duality group. As a by-product we derive a last wrapping rule for the space-filling branes. We find examples of T-duality representations of branes in lower dimensions, suggested by supergravity, of which none of the component branes follow from the reduction of any brane in ten-dimensional IIA/IIB string theory. We discuss the constraints on the charges of half-supersymmetric branes, determining the corresponding T-duality and U-duality orbits.

  12. Orbit analysis

    Energy Technology Data Exchange (ETDEWEB)

    Michelotti, L.

    1995-01-01

    The past fifteen years have witnessed a remarkable development of methods for analyzing single particle orbit dynamics in accelerators. Unlike their more classic counterparts, which act upon differential equations, these methods proceed by manipulating Poincare maps directly. This attribute makes them well matched for studying accelerators whose physics is most naturally modelled in terms of maps, an observation that has been championed most vigorously by Forest. In the following sections the author sketchs a little background, explains some of the physics underlying these techniques, and discusses the best computing strategy for implementing them in conjunction with modeling accelerators.

  13. Orbital Debris and NASA's Measurement Program

    Science.gov (United States)

    Africano, J. L.; Stansbery, E. G.

    2002-05-01

    Since the launch of Sputnik in 1957, the number of manmade objects in orbit around the Earth has dramatically increased. The United States Space Surveillance Network (SSN) tracks and maintains orbits on over nine thousand objects down to a limiting diameter of about ten centimeters. Unfortunately, active spacecraft are only a small percentage ( ~ 7%) of this population. The rest of the population is orbital debris or ``space junk" consisting of expended rocket bodies, dead payloads, bits and pieces from satellite launches, and fragments from satellite breakups. The number of these smaller orbital debris objects increases rapidly with decreasing size. It is estimated that there are at least 130,000 orbital debris objects between one and ten centimeters in diameter. Most objects smaller than 10 centimeters go untracked! As the orbital debris population grows, the risk to other orbiting objects, most importantly manned space vehicles, of a collision with a piece of debris also grows. The kinetic energy of a solid 1 cm aluminum sphere traveling at an orbital velocity of 10 km/sec is equivalent to a 400 lb. safe traveling at 60 mph. Fortunately, the volume of space in which the orbiting population resides is large, collisions are infrequent, but they do occur. The Space Shuttle often returns to earth with its windshield pocked with small pits or craters caused by collisions with very small, sub-millimeter-size pieces of debris (paint flakes, particles from solid rocket exhaust, etc.), and micrometeoroids. To get a more complete picture of the orbital-debris environment, NASA has been using both radar and optical techniques to monitor the orbital debris environment. This paper gives an overview of the orbital debris environment and NASA's measurement program.

  14. First data from X-ray astronomy satellite

    International Nuclear Information System (INIS)

    Cox, J.

    1984-01-01

    EXOSAT, the European Space Agency's first x-ray astronomy satellite which was launched last year, has sent back information on x-ray sources. The article briefly discusses the observations made by the satellite concerning Cygnus x-1 and the galactic supernova remnant Cassiopeia A. EXOSAT is the first x-ray astronomy satellite to be operated in a deep space orbit

  15. Einstein, Entropy and Anomalies

    Science.gov (United States)

    Sirtes, Daniel; Oberheim, Eric

    2006-11-01

    This paper strengthens and defends the pluralistic implications of Einstein's successful, quantitative predictions of Brownian motion for a philosophical dispute about the nature of scientific advance that began between two prominent philosophers of science in the second half of the twentieth century (Thomas Kuhn and Paul Feyerabend). Kuhn promoted a monistic phase-model of scientific advance, according to which a paradigm driven `normal science' gives rise to its own anomalies, which then lead to a crisis and eventually a scientific revolution. Feyerabend stressed the importance of pluralism for scientific progress. He rejected Kuhn's model arguing that it fails to recognize the role that alternative theories can play in identifying exactly which phenomena are anomalous in the first place. On Feyerabend's account, Einstein's predictions allow for a crucial experiment between two incommensurable theories, and are an example of an anomaly that could refute the reigning paradigm only after the development of a competitor. Using Kuhn's specification of a disciplinary matrix to illustrate the incommensurability between the two paradigms, we examine the different research strategies available in this peculiar case. On the basis of our reconstruction, we conclude by rebutting some critics of Feyerabend's argument.

  16. Mobility management in satellite networks

    Science.gov (United States)

    Johanson, Gary A.

    1995-01-01

    This paper addresses the methods used or proposed for use in multi-beam and/or multi-satellite networks designed to provide Mobile Satellite Services (MSS). Specific topics include beam crossover in the North American Mobile Satellite (MSAT) system as well as registration and live call hand-off for a multi-regional geosynchronous (GEO) satellite based system and a global coverage Low Earth Orbiting (LEO) system. In the MSAT system, the individual satellite beams cover very large geographic areas so the need for live call hand-off was not anticipated. This paper discusses the methods used to keep track of the beam location of the users so that incoming call announcements or other messages may be directed to them. Proposed new GEO systems with large numbers of beams will provide much smaller geographic coverage in individual beams and thus the need arises to keep track of the user's location as well as to provide live call hand-off as the user traverses from beam to beam. This situation also occurs in proposed LEO systems where the problems are worsened by the need for satellite to satellite hand-off as well as beam to beam hand-off within a single satellite. The paper discusses methods to accomplish these handoffs and proposes system architectures to address the various hand-off scenarios.

  17. Exobiology of icy satellites

    Science.gov (United States)

    Simakov, M. B.

    At the beginning of 2004 the total number of discovered planets near other stars was 119 All of them are massive giants and met practically in all orbits In a habitable zone from 0 8 up to 1 1 AU at less 11 planets has been found starting with HD 134987 and up to HD 4203 It would be naive to suppose existence of life in unique known to us amino-nucleic acid form on the gas-liquid giant planets Nevertheless conditions for onset and evolutions of life can be realized on hypothetical satellites extrasolar planets All giant planets of the Solar system have a big number of satellites 61 of Jupiter 52 of Saturn known in 2003 A small part of them consist very large bodies quite comparable to planets of terrestrial type but including very significant share of water ice Some from them have an atmosphere E g the mass of a column of the Titan s atmosphere exceeds 15 times the mass of the Earth atmosphere column Formation or capture of satellites is a natural phenomenon and satellite systems definitely should exist at extrasolar planets A hypothetical satellite of the planet HD 28185 with a dense enough atmosphere and hydrosphere could have biosphere of terrestrial type within the limits of our notion about an origin of terrestrial biosphere As an example we can see on Titan the largest satellite of Saturn which has a dense nitrogen atmosphere and a large quantity of liquid water under ice cover and so has a great exobiological significance The most recent models of the Titan s interior lead to the conclusion that a substantial liquid layer

  18. Solar Radiation Pressure Binning for the Geosynchronous Orbit

    Science.gov (United States)

    Hejduk, M. D.; Ghrist, R. W.

    2011-01-01

    Orbital maintenance parameters for individual satellites or groups of satellites have traditionally been set by examining orbital parameters alone, such as through apogee and perigee height binning; this approach ignored the other factors that governed an individual satellite's susceptibility to non-conservative forces. In the atmospheric drag regime, this problem has been addressed by the introduction of the "energy dissipation rate," a quantity that represents the amount of energy being removed from the orbit; such an approach is able to consider both atmospheric density and satellite frontal area characteristics and thus serve as a mechanism for binning satellites of similar behavior. The geo-synchronous orbit (of broader definition than the geostationary orbit -- here taken to be from 1300 to 1800 minutes in orbital period) is not affected by drag; rather, its principal non-conservative force is that of solar radiation pressure -- the momentum imparted to the satellite by solar radiometric energy. While this perturbation is solved for as part of the orbit determination update, no binning or division scheme, analogous to the drag regime, has been developed for the geo-synchronous orbit. The present analysis has begun such an effort by examining the behavior of geosynchronous rocket bodies and non-stabilized payloads as a function of solar radiation pressure susceptibility. A preliminary examination of binning techniques used in the drag regime gives initial guidance regarding the criteria for useful bin divisions. Applying these criteria to the object type, solar radiation pressure, and resultant state vector accuracy for the analyzed dataset, a single division of "large" satellites into two bins for the purposes of setting related sensor tasking and orbit determination (OD) controls is suggested. When an accompanying analysis of high area-to-mass objects is complete, a full set of binning recommendations for the geosynchronous orbit will be available.

  19. Infrared Astronomy Satellite

    Science.gov (United States)

    Ferrera, G. A.

    1981-09-01

    In 1982, the Infrared Astronomy Satellite (IRAS) will be launched into a 900-km sun-synchronous (twilight) orbit to perform an unbiased, all-sky survey of the far-infrared spectrum from 8 to 120 microns. Observations telemetered to ground stations will be compiled into an IR astronomy catalog. Attention is given the cryogenically cooled, 60-cm Ritchey-Chretien telescope carried by the satellite, whose primary and secondary mirrors are fabricated from beryllium by means of 'Cryo-Null Figuring'. This technique anticipates the mirror distortions that will result from cryogenic cooling of the telescope and introduces dimensional compensations for them during machining and polishing. Consideration is also given to the interferometric characterization of telescope performance and Cryo/Thermal/Vacuum simulated space environment testing.

  20. Satellite disintegration dynamics

    Science.gov (United States)

    Dasenbrock, R. R.; Kaufman, B.; Heard, W. B.

    1975-01-01

    The subject of satellite disintegration is examined in detail. Elements of the orbits of individual fragments, determined by DOD space surveillance systems, are used to accurately predict the time and place of fragmentation. Dual time independent and time dependent analyses are performed for simulated and real breakups. Methods of statistical mechanics are used to study the evolution of the fragment clouds. The fragments are treated as an ensemble of non-interacting particles. A solution of Liouville's equation is obtained which enables the spatial density to be calculated as a function of position, time and initial velocity distribution.

  1. Satellite to study earth's magnetic field

    Science.gov (United States)

    1979-01-01

    The Magnetic Field Satellite (Magsat) designed to measure the near earth magnetic field and crustal anomalies is briefly described. A scalar magnetometer to measure the magnitude of the earth's crustal magnetic field and a vector magnetometer to measure magnetic field direction as well as magnitude are included. The mission and its objectives are summarized along with the data collection and processing system.

  2. Activities of Canadian Satellite Communications, Inc.

    Science.gov (United States)

    1992-12-01

    Canadian Satellite Communications (Cancom) has as its core business the provision of television and radio signals to cable systems in Canada, with the objective of making affordable broadcast signals available to remote and/or small communities. Cancom also provides direct-to-home services to backyard receiving dishes, as well as satellite digital data business communications services, satellite business television, and satellite network services. Its business communication services range from satellite links for big-city businesses with small branch operations located far from major centers, to a mobile messaging and tracking system for the trucking industry. Revenues in 1992 totalled $48,212,000 and net income was just over $7 million. Cancom bought 10 percent interest in Leosat Corp. of Washington, DC, who are seeking approval to operate a position locator network from low-orbit satellites. Cancom has also become a partner in SovCan Star Satellite Communications Inc., which will build an international satellite system in partnership with Russia. The first satellite in this east-west business network will be placed in a Russian orbital slot over the Atlantic by 1996, and a second satellite will follow for the Pacific region. This annual report of Cancom's activities for 1992 includes financial statements and a six year financial review.

  3. An Orbit Propagation Software for Mars Orbiting Spacecraft

    Directory of Open Access Journals (Sweden)

    Young-Joo Song

    2004-12-01

    Full Text Available An orbit propagation software for the Mars orbiting spacecraft has been developed and verified in preparations for the future Korean Mars missions. Dynamic model for Mars orbiting spacecraft has been studied, and Mars centered coordinate systems are utilized to express spacecraft state vectors. Coordinate corrections to the Mars centered coordinate system have been made to adjust the effects caused by Mars precession and nutation. After spacecraft enters Sphere of Influence (SOI of the Mars, the spacecraft experiences various perturbation effects as it approaches to Mars. Every possible perturbation effect is considered during integrations of spacecraft state vectors. The Mars50c gravity field model and the Mars-GRAM 2001 model are used to compute perturbation effects due to Mars gravity field and Mars atmospheric drag, respectively. To compute exact locations of other planets, JPL's DE405 ephemerides are used. Phobos and Deimos's ephemeris are computed using analytical method because their informations are not released with DE405. Mars Global Surveyor's mapping orbital data are used to verify the developed propagator performances. After one Martian day propagation (12 orbital periods, the results show about maximum ±5 meter errors, in every position state components(radial, cross-track and along-track, when compared to these from the Astrogator propagation in the Satellite Tool Kit. This result shows high reliability of the developed software which can be used to design near Mars missions for Korea, in future.

  4. Radiation Measured for Chinese Satellite SJ-10 Space Mission

    Science.gov (United States)

    Zhou, Dazhuang; Sun, Yeqing; Zhang, Binquan; Zhang, Shenyi; Sun, Yueqiang; Liang, Jinbao; Zhu, Guangwu; Jing, Tao; Yuan, Bin; Zhang, Huanxin; Zhang, Meng; Wang, Wei; Zhao, Lei

    2018-02-01

    Space biological effects are mainly a result of space radiation particles with high linear energy transfer (LET); therefore, accurate measurement of high LET space radiation is vital. The radiation in low Earth orbits is composed mainly of high-energy galactic cosmic rays (GCRs), solar energetic particles, particles of radiation belts, the South Atlantic Anomaly, and the albedo neutrons and protons scattered from the Earth's atmosphere. CR-39 plastic nuclear track detectors sensitive to high LET are the best passive detectors to measure space radiation. The LET method that employs CR-39 can measure all the radiation LET spectra and quantities. CR-39 detectors can also record the incident directions and coordinates of GCR heavy ions that pass through both CR-39 and biosamples, and the impact parameter, the distance between the particle's incident point and the seed's spore, can then be determined. The radiation characteristics and impact parameter of GCR heavy ions are especially beneficial for in-depth research regarding space radiation biological effects. The payload returnable satellite SJ-10 provided an excellent opportunity to investigate space radiation biological effects with CR-39 detectors. The space bio-effects experiment was successfully conducted on board the SJ-10 satellite. This paper introduces space radiation in low Earth orbits and the LET method in radiation-related research and presents the results of nuclear tracks and biosamples hitting distributions of GCR heavy ions, the radiation LET spectra, and the quantities measured for the SJ-10 space mission. The SJ-10 bio-experiment indicated that radiation may produce significant bio-effects.

  5. On satellite lines anomalies in OH excited states

    International Nuclear Information System (INIS)

    Elitzur, M.

    1976-01-01

    It is argued that different pumps produce similar distributions of populations in the first two excited states of OH. The pattern observed recently in G 219.3 - 07 by Whiteoak and Gardner can be due either to radiative or collisional pump. (author)

  6. Low Risk Anomalies?

    DEFF Research Database (Denmark)

    Schneider, Paul; Wagner, Christian; Zechner, Josef

    This paper shows theoretically and empirically that beta- and volatility-based low risk anomalies are driven by return skewness. The empirical patterns concisely match the predictions of our model that endogenizes the role of skewness for stock returns through default risk. With increasing downside...... risk, the standard capital asset pricing model (CAPM) increasingly overestimates expected equity returns relative to firms' true (skew-adjusted) market risk. Empirically, the profitability of betting against beta/volatility increases with firms' downside risk, and the risk-adjusted return differential...... of betting against beta/volatility among low skew firms compared to high skew firms is economically large. Our results suggest that the returns to betting against beta or volatility do not necessarily pose asset pricing puzzles but rather that such strategies collect premia that compensate for skew risk...

  7. Water radon anomaly fields

    Energy Technology Data Exchange (ETDEWEB)

    Yin, H.

    1980-01-01

    A striking aspect of water radon levels in relation to earthquakes is that before the Tangshan quake there was a remarkable synchronicity of behavior of many wells within 200 km of Tangshan. However, for many wells anomalous values persisted after the earthquake, particularly outside the immediate region of the quake. It is clear that radon may be produced by various processes; some candidates are pressure, shear, vibration, temperature and pressure, mixing of water-bearing strata, breakdown of mineral crystal structure, and the like, although it is not clear which of these are primary. It seems that a possible explanation of the persistence of the anomaly in the case of Tangshan may be that the earthquake released strain in the vicinity of Tangshan but increased it further along the geological structures involved, thus producing a continued radon buildup.

  8. Nolen-Schiffer anomaly

    International Nuclear Information System (INIS)

    Pieper, S.C.; Wiringa, R.B.

    1995-01-01

    The Argonne v 18 potential contains a detailed treatment of the pp, pn and nn electromagnetic potential, including Coulomb, vacuum polarization, Darwin Foldy and magnetic moment terms, all with suitable form factors and was fit to pp and pn data using the appropriate nuclear masses. In addition, it contains a nuclear charge-symmetry breaking (CSB) term adjusted to reproduce the difference in the experimental pp and nn scattering lengths. We have used these potential terms to compute differences in the binding energies of mirror isospin-1/2 nuclei (Nolen-Schiffer [NS] anomaly). Variational Monte Carlo calculations for the 3 He- 3 H system and cluster variational Monte Carlo for the 15 O- 15 N and 17 F- 17 O systems were made. In the first case, the best variational wave function for the A = 3 nuclei was used. However, because our 16 O wave function does not reproduce accurately the 16 O rms radius, to which the NS anomaly is very sensitive, we adjusted the A = 15 and A = 17 wave functions to reproduce the experimental density profiles. Our computed energy differences for these three systems are 0.757 ± .001, 3.544 ± .018 and 3.458 ± .040 MeV respectively, which are to be compared with the experimental differences of 0.764, 3.537, and 3.544 MeV. Most of the theoretical uncertainties are due to uncertainties in the experimental rms radii. The nuclear CSB potential contributes 0.066, 0.188, and 0.090 MeV to these totals. We also attempted calculations for A = 39 and A = 41. However, in these cases, the experimental uncertainties in the rms radius make it impossible to extract useful information about the contribution of the nuclear CSB potential

  9. Interim Service ISDN Satellite (ISIS) simulator development for advanced satellite designs and experiments

    Science.gov (United States)

    Pepin, Gerard R.

    1992-01-01

    The simulation development associated with the network models of both the Interim Service Integrated Services Digital Network (ISDN) Satellite (ISIS) and the Full Service ISDN Satellite (FSIS) architectures is documented. The ISIS Network Model design represents satellite systems like the Advanced Communications Technology Satellite (ACTS) orbiting switch. The FSIS architecture, the ultimate aim of this element of the Satellite Communications Applications Research (SCAR) Program, moves all control and switching functions on-board the next generation ISDN communications satellite. The technical and operational parameters for the advanced ISDN communications satellite design will be obtained from the simulation of ISIS and FSIS engineering software models for their major subsystems. Discrete event simulation experiments will be performed with these models using various traffic scenarios, design parameters, and operational procedures. The data from these simulations will be used to determine the engineering parameters for the advanced ISDN communications satellite.

  10. Satellite Communications

    CERN Document Server

    Pelton, Joseph N

    2012-01-01

    The field of satellite communications represents the world's largest space industry. Those who are interested in space need to understand the fundamentals of satellite communications, its technology, operation, business, economic, and regulatory aspects. This book explains all this along with key insights into the field's future growth trends and current strategic challenges. Fundamentals of Satellite Communications is a concise book that gives all of the key facts and figures as well as a strategic view of where this dynamic industry is going. Author Joseph N. Pelton, PhD, former Dean of the International Space University and former Director of Strategic Policy at Intelstat, presents a r

  11. Satellite recovery - Attitude dynamics of the targets

    Science.gov (United States)

    Cochran, J. E., Jr.; Lahr, B. S.

    1986-01-01

    The problems of categorizing and modeling the attitude dynamics of uncontrolled artificial earth satellites which may be targets in recovery attempts are addressed. Methods of classification presented are based on satellite rotational kinetic energy, rotational angular momentum and orbit and on the type of control present prior to the benign failure of the control system. The use of approximate analytical solutions and 'exact' numerical solutions to the equations governing satellite attitude motions to predict uncontrolled attitude motion is considered. Analytical and numerical results are presented for the evolution of satellite attitude motions after active control termination.

  12. 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.

  13. A Study on the Tracking and Position Predictions of Artificial Satellite (II

    Directory of Open Access Journals (Sweden)

    Pil-Ho Park

    1991-06-01

    Full Text Available We developed a software system called IODS (ISSA Orbit Determination System, which can predict the orbit of arbitrary artificial satellite using the numerical method. For evaluating the orbit prediction accuracy of IODS, the orbital data predicted for the meteorological satellite NOAA-11 and the stationary satellite INTELSAT-V are intercompared with those tracked at the Central Bureau of Meteorology and the Kum-San Satellites Communication Station. And the Perturbation affecting the orbit of these artificial satellites are quantitatively analyzed. The orbital variation and the eclipse phenomina due to the earth shadow are analyzed for a hypothetical geostationary satellite called KORSAT-1 which is assumed to be located in longitude 110°E.

  14. Calculated surface-energy anomaly in the 3d metals

    DEFF Research Database (Denmark)

    Aldén, M.; Skriver, Hans Lomholt; Mirbt, S.

    1992-01-01

    Local-spin-density theory and a Green’s-function technique based on the linear muffin-tin orbitals method have been used to calculate the surface energy of the 3d metals. The theory explains the variation of the values derived from measurements of the surface tension of liquid metals including...... the pronounced anomaly occurring between vanadium and nickel in terms of a decrease in the d contribution caused by spin polarization....

  15. Axial anomaly at finite temperature

    International Nuclear Information System (INIS)

    Chaturvedi, S.; Gupte, Neelima; Srinivasan, V.

    1985-01-01

    The Jackiw-Bardeen-Adler anomaly for QED 4 and QED 2 are calculated at finite temperature. It is found that the anomaly is independent of temperature. Ishikawa's method [1984, Phys. Rev. Lett. vol. 53 1615] for calculating the quantised Hall effect is extended to finite temperature. (author)

  16. Anomaly mediation deformed by axion

    Energy Technology Data Exchange (ETDEWEB)

    Nakayama, Kazunori, E-mail: kazunori@hep-th.phys.s.u-tokyo.ac.jp [Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwa 277-8583 (Japan); Yanagida, Tsutomu T. [Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwa 277-8583 (Japan)

    2013-05-13

    We show that in supersymmetric axion models the axion supermultiplet obtains a sizable F-term due to a non-supersymmetric dynamics and it generally gives the gaugino masses comparable to the anomaly mediation contribution. Thus the gaugino mass relation predicted by the anomaly mediation effect can be significantly modified in the presence of axion to solve the strong CP problem.

  17. Novel topological invariants and anomalies

    International Nuclear Information System (INIS)

    Hirayama, M.; Sugimasa, N.

    1987-01-01

    It is shown that novel topological invariants are associated with a class of Dirac operators. Trace formulas which are similar to but different from Callias's formula are derived. Implications of these topological invariants to anomalies in quantum field theory are discussed. A new class of anomalies are calculated for two models: one is two dimensional and the other four dimensional

  18. Asymptotic Behavior of an Elastic Satellite with Internal Friction

    International Nuclear Information System (INIS)

    Haus, E.; Bambusi, D.

    2015-01-01

    We study the dynamics of an elastic body whose shape and position evolve due to the gravitational forces exerted by a pointlike planet. The main result is that, if all the deformations of the satellite dissipate some energy, then under a suitable nondegeneracy condition there are only three possible outcomes for the dynamics: (i) the orbit of the satellite is unbounded, (ii) the satellite falls on the planet, (iii) the satellite is captured in synchronous resonance i.e. its orbit is asymptotic to a motion in which the barycenter moves on a circular orbit, and the satellite moves rigidly, always showing the same face to the planet. The result is obtained by making use of LaSalle’s invariance principle and by a careful kinematic analysis showing that energy stops dissipating only on synchronous orbits. We also use in quite an extensive way the fact that conservative elastodynamics is a Hamiltonian system invariant under the action of the rotation group

  19. 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.

  20. Shadow imaging of geosynchronous satellites

    Science.gov (United States)

    Douglas, Dennis Michael

    Geosynchronous (GEO) satellites are essential for modern communication networks. If communication to a GEO satellite is lost and a malfunction occurs upon orbit insertion such as a solar panel not deploying there is no direct way to observe it from Earth. Due to the GEO orbit distance of ~36,000 km from Earth's surface, the Rayleigh criteria dictates that a 14 m telescope is required to conventionally image a satellite with spatial resolution down to 1 m using visible light. Furthermore, a telescope larger than 30 m is required under ideal conditions to obtain spatial resolution down to 0.4 m. This dissertation evaluates a method for obtaining high spatial resolution images of GEO satellites from an Earth based system by measuring the irradiance distribution on the ground resulting from the occultation of the satellite passing in front of a star. The representative size of a GEO satellite combined with the orbital distance results in the ground shadow being consistent with a Fresnel diffraction pattern when observed at visible wavelengths. A measurement of the ground shadow irradiance is used as an amplitude constraint in a Gerchberg-Saxton phase retrieval algorithm that produces a reconstruction of the satellite's 2D transmission function which is analogous to a reverse contrast image of the satellite. The advantage of shadow imaging is that a terrestrial based redundant set of linearly distributed inexpensive small telescopes, each coupled to high speed detectors, is a more effective resolved imaging system for GEO satellites than a very large telescope under ideal conditions. Modeling and simulation efforts indicate sub-meter spatial resolution can be readily achieved using collection apertures of less than 1 meter in diameter. A mathematical basis is established for the treatment of the physical phenomena involved in the shadow imaging process. This includes the source star brightness and angular extent, and the diffraction of starlight from the satellite

  1. Satellite myths

    Science.gov (United States)

    Easton, Roger L.; Hall, David

    2008-01-01

    Richard Corfield's article “Sputnik's legacy” (October 2007 pp23-27) states that the satellite on board the US Vanguard rocket, which exploded during launch on 6 December 1957 two months after Sputnik's successful take-off, was “a hastily put together contraption of wires and circuitry designed only to send a radio signal back to Earth”. In fact, the Vanguard satellite was developed over a period of several years and put together carefully using the best techniques and equipment available at the time - such as transistors from Bell Laboratories/Western Electric. The satellite contained not one but two transmitters, in which the crystal-controlled oscillators had been designed to measure both the temperature of the satellite shell and of the internal package.

  2. Distant retrograde orbits and the asteroid hazard

    Science.gov (United States)

    Perozzi, Ettore; Ceccaroni, Marta; Valsecchi, Giovanni B.; Rossi, Alessandro

    2017-08-01

    Distant Retrograde Orbits (DROs) gained a novel wave of fame in space mission design because of their numerous advantages within the framework of the US plans for bringing a large asteroid sample in the vicinity of the Earth as the next target for human exploration. DROs are stable solutions of the three-body problem that can be used whenever an object, whether of natural or artificial nature, is required to remain in the neighborhood of a celestial body without being gravitationally captured by it. As such, they represent an alternative option to Halo orbits around the collinear Lagrangian points L1 and L2. Also known under other names ( e.g., quasi-satellite orbits, cis-lunar orbits, family- f orbits) these orbital configurations found interesting applications in several mission profiles, like that of a spacecraft orbiting around the small irregularly shaped satellite of Mars Phobos or the large Jovian moon Europa. In this paper a basic explanation of the DRO dynamics is presented in order to clarify some geometrical properties that characterize them. Their accessibility is then discussed from the point of view of mission analysis under different assumptions. Finally, their relevance within the framework of the present asteroid hazard protection programs is shown, stressing the significant increase in warning time they would provide in the prediction of impactors coming from the direction of the Sun.

  3. A possible flyby anomaly for Juno at Jupiter

    Science.gov (United States)

    Acedo, L.; Piqueras, P.; Moraño, J. A.

    2018-05-01

    In the last decades there have been an increasing interest in improving the accuracy of spacecraft navigation and trajectory data. In the course of this plan some anomalies have been found that cannot, in principle, be explained in the context of the most accurate orbital models including all known effects from classical dynamics and general relativity. Of particular interest for its puzzling nature, and the lack of any accepted explanation for the moment, is the flyby anomaly discovered in some spacecraft flybys of the Earth over the course of twenty years. This anomaly manifest itself as the impossibility of matching the pre and post-encounter Doppler tracking and ranging data within a single orbit but, on the contrary, a difference of a few mm/s in the asymptotic velocities is required to perform the fitting. Nevertheless, no dedicated missions have been carried out to elucidate the origin of this phenomenon with the objective either of revising our understanding of gravity or to improve the accuracy of spacecraft Doppler tracking by revealing a conventional origin. With the occasion of the Juno mission arrival at Jupiter and the close flybys of this planet, that are currently been performed, we have developed an orbital model suited to the time window close to the perijove. This model shows that an anomalous acceleration of a few mm/s2 is also present in this case. The chance for overlooked conventional or possible unconventional explanations is discussed.

  4. GPS Based Reduced-Dynamic Orbit Determination for Low Earth Orbiters with Ambiguity Fixing

    Directory of Open Access Journals (Sweden)

    Yang Yang

    2015-01-01

    Full Text Available With the ever-increasing number of satellites in Low Earth Orbit (LEO for scientific missions, the precise determination of the position and velocity of the satellite is a necessity. GPS (Global Positioning System based reduced-dynamic orbit determination (RPOD method is commonly used in the post processing with high precision. This paper presents a sequential RPOD strategy for LEO satellite in the framework of Extended Kalman Filter (EKF. Precise Point Positioning (PPP technique is used to process the GPS observations, with carrier phase ambiguity resolution using Integer Phase Clocks (IPCs products. A set of GRACE (Gravity Recovery And Climate Experiment mission data is used to test and validate the RPOD performance. Results indicate that orbit determination accuracy could be improved by 15% in terms of 3D RMS error in comparison with traditional RPOD method with float ambiguity solutions.

  5. CASA Uno GPS orbit and baseline experiments

    Science.gov (United States)

    Schutz, B. E.; Ho, C. S.; Abusali, P. A. M.; Tapley, B. D.

    1990-01-01

    CASA Uno data from sites distributed in longitude from Australia to Europe have been used to determine orbits of the GPS satellites. The characteristics of the orbits determined from double difference phase have been evaluated through comparisons of two-week solutions with one-week solutions and by comparisons of predicted and estimated orbits. Evidence of unmodeled effects is demonstrated, particularly associated with the orbit planes that experience solar eclipse. The orbit accuracy has been assessed through the repeatability of unconstrained estimated baseline vectors ranging from 245 km to 5400 km. Both the baseline repeatability and the comparison with independent space geodetic methods give results at the level of 1-2 parts in 100,000,000. In addition, the Mojave/Owens Valley (245 km) and Kokee Park/Ft. Davis (5409 km) estimates agree with VLBI and SLR to better than 1 part in 100,000,000.

  6. Generating Animated Displays of Spacecraft Orbits

    Science.gov (United States)

    Candey, Robert M.; Chimiak, Reine A.; Harris, Bernard T.

    2005-01-01

    Tool for Interactive Plotting, Sonification, and 3D Orbit Display (TIPSOD) is a computer program for generating interactive, animated, four-dimensional (space and time) displays of spacecraft orbits. TIPSOD utilizes the programming interface of the Satellite Situation Center Web (SSCWeb) services to communicate with the SSC logic and database by use of the open protocols of the Internet. TIPSOD is implemented in Java 3D and effects an extension of the preexisting SSCWeb two-dimensional static graphical displays of orbits. Orbits can be displayed in any or all of the following seven reference systems: true-of-date (an inertial system), J2000 (another inertial system), geographic, geomagnetic, geocentric solar ecliptic, geocentric solar magnetospheric, and solar magnetic. In addition to orbits, TIPSOD computes and displays Sibeck's magnetopause and Fairfield's bow-shock surfaces. TIPSOD can be used by the scientific community as a means of projection or interpretation. It also has potential as an educational tool.

  7. Pathology of orbital bones. The XXXII Edward Jackson Memorial Lecture.

    Science.gov (United States)

    Blodi, F C

    1976-01-01

    The orbital bones may show nearly all the pathologic changes observed in the skull and in the face. The congenital anomalies in this area are numerous and involve various forms of craniostenoses. Among the benign osseous tumors the osteoma is most frequently encountered in the orbit. Fibrous dysplasia is a tumefaction of indeterminate behavior that often involves the orbit. Osteosarcoma or other malignant neoplasms are rarely seen in this area. Eosinophilic granuloma and Hand-Schüller-Christian disease are tumor-like lesions that may involve the orbit.

  8. Thermal Radiation Anomalies Associated with Major Earthquakes

    Science.gov (United States)

    Ouzounov, Dimitar; Pulinets, Sergey; Kafatos, Menas C.; Taylor, Patrick

    2017-01-01

    Recent developments of remote sensing methods for Earth satellite data analysis contribute to our understanding of earthquake related thermal anomalies. It was realized that the thermal heat fluxes over areas of earthquake preparation is a result of air ionization by radon (and other gases) and consequent water vapor condensation on newly formed ions. Latent heat (LH) is released as a result of this process and leads to the formation of local thermal radiation anomalies (TRA) known as OLR (outgoing Longwave radiation, Ouzounov et al, 2007). We compare the LH energy, obtained by integrating surface latent heat flux (SLHF) over the area and time with released energies associated with these events. Extended studies of the TRA using the data from the most recent major earthquakes allowed establishing the main morphological features. It was also established that the TRA are the part of more complex chain of the short-term pre-earthquake generation, which is explained within the framework of a lithosphere-atmosphere coupling processes.

  9. Precise Orbit Determination of QZS-1

    Science.gov (United States)

    Hugentobler, U.; Steigenberger, P.; Rodriguez-Solano, C.; Hauschild, A.

    2011-12-01

    QZS-1, the first satellite of the Japanese Quasi Zenith Satellite System (QZSS) was launched in September 2010. Transmission of the standard codes started in December 2010 and the satellite was declared healthy in June 2011. Five stations of the COoperative Network for GIOVE Observation (CONGO) were upgraded to provide QZSS tracking capability. These five stations provide the basis for the precise orbit determination (POD) of the QZS-1 spacecraft. The stability and consistency of different orbital arc lengths is analyzed based on orbit fit residuals, day boundary discontinuities, and Satellite Laser Ranging residuals. As QZS-1 simultaneously transmits navigation signals on three frequencies in the L1, L2, and L5 band, different ionosphere-free linear combinations can be formed. The differences of the orbits computed from these different observables (ionosphere-free linear combination of L1/L2 and L1/L5) as well as the stability of the differential code biases estimated within the POD are studied. Finally, results of the attitude determination based on the navigation signal transmission from two different antennas onboard QZS-1 are presented.

  10. Preliminary Analyses of Beidou Signal-In Anomaly Since 2013

    Science.gov (United States)

    Wu, Y.; Ren, J.; Liu, W.

    2016-06-01

    As BeiDou navigation system has been operational since December 2012. There is an increasing desire to use multiple constellation to improve positioning performance. The signal-in-space (SIS) anomaly caused by the ground control and the space vehicle is one of the major threats to affect the integrity. For a young Global Navigation Satellite System, knowledge about SIS anomalies in history is very important for not only assessing the SIS integrity performance of a constellation but also providing the assumption for ARAIM (Advanced Receiver Autonomous Integrity Monitoring). In this paper, the broadcast ephemerides and the precise ones are pre-processed for avoiding the false anomaly identification. The SIS errors over the period of Mar. 2013-Feb. 2016 are computed by comparing the broadcast ephemerides with the precise ones. The time offsets between GPST (GPS time) and BDT (BeiDou time) are estimated and removed by an improved estimation algorithm. SIS worst-UREs are computed and a RMS criteria are investigated to identify the SIS anomalies. The results show that the probability of BeiDou SIS anomalies is in 10-3 level in last three years. Even though BeiDou SIS integrity performance currently cannot match the GPS integrity performances, the result indicates that BeiDou has a tendency to improve its integrity performance.

  11. Periodic orbits around areostationary points in the Martian gravity field

    International Nuclear Information System (INIS)

    Liu Xiaodong; Baoyin Hexi; Ma Xingrui

    2012-01-01

    This study investigates the problem of areostationary orbits around Mars in three-dimensional space. Areostationary orbits are expected to be used to establish a future telecommunication network for the exploration of Mars. However, no artificial satellites have been placed in these orbits thus far. The characteristics of the Martian gravity field are presented, and areostationary points and their linear stability are calculated. By taking linearized solutions in the planar case as the initial guesses and utilizing the Levenberg-Marquardt method, families of periodic orbits around areostationary points are shown to exist. Short-period orbits and long-period orbits are found around linearly stable areostationary points, but only short-period orbits are found around unstable areostationary points. Vertical periodic orbits around both linearly stable and unstable areostationary points are also examined. Satellites in these periodic orbits could depart from areostationary points by a few degrees in longitude, which would facilitate observation of the Martian topography. Based on the eigenvalues of the monodromy matrix, the evolution of the stability index of periodic orbits is determined. Finally, heteroclinic orbits connecting the two unstable areostationary points are found, providing the possibility for orbital transfer with minimal energy consumption.

  12. Anomalies in instanton calculus

    International Nuclear Information System (INIS)

    Anselmi, D.

    1995-01-01

    I develop a formalism for solving topological field theories explicitly, in the case when the explicit expression of the instantons is known. I solve topological Yang-Mills theory with the k=1 instanton of Belavin et al. and topological gravity with the Eguchi-Hanson instanton. It turns out that naively empty theories are indeed nontrivial. Many unexpected interesting hidden quantities (punctures, contact terms, nonperturbative anomalies with or without gravity) are revealed. Topological Yang-Mills theory with G=SU(2) is not just Donaldson theory, but contains a certain link theory. Indeed, local and non-local observables have the property of marking cycles. Moreover, from topological gravity one learns that an object can be considered BRST exact only if it is so all over the moduli space M , boundary included. Being BRST exact in any interior point of M is not sufficient to make an amplitude vanish. Presumably, recursion relations and hierarchies can be found to solve topological field theories in four dimensions, in particular topological Yang-Mills theory with G=SU(2) on R 4 and topological gravity with the full set of asymptotically locally Euclidean manifolds. ((orig.))

  13. Global aspects of gauge anomalies

    International Nuclear Information System (INIS)

    Zhang, H.

    1988-01-01

    This dissertation discusses the global aspects of gauge anomalies in even dimensions. After a very brief description of local gauge anomalies, the possible global gauge anomalies for various gauge theories are discussed using homotopy theory. One of the main results obtained in a general formula for the SU(n - k) global gauge anomaly coefficient in arbitrary 2n dimensions. The result is expressed in terms of the James number of the Stiefel manifold SU(n + 1)/SU(n - k) and the generalized Dynkin indices. From this, the possibilities of SU(n), SU(n - 1), and SU(2) global gauge anomalies in arbitrary 2n dimensions have been determined. We have also determined the possibilities of global gauge anomalies for the gauge groups SP(2N) and SO(N) in certain general dimensions, as well as for the exceptional gauge groups in specific dimensions. Moreover, several general propositions are formulated and proved which are very useful in the study of global gauge anomalies

  14. The Future of the South Atlantic Anomaly and Implications for Radiation Damage in Space

    Science.gov (United States)

    Heirtzler, J. R.; Smith, David E. (Technical Monitor)

    2000-01-01

    South Atlantic Anomaly of the geomagnetic field plays a dominant role in where radiation damage occurs in near Earth orbits. The historic and recent variations of the geomagnetic field in the South Atlantic are used to estimate the extent of the South Atlantic Anomaly until the year 2000. This projection indicates that radiation damage to spacecraft and humans in space will greatly increase and cover a much larger geographic area than present.

  15. Cibola flight experiment satellite

    Science.gov (United States)

    Davies, P.; Liddle, Doug; Paffett, John; Sweeting, Martin; Curiel, A.; Sun, Wei; Eves, Stuart

    2004-11-01

    In order to achieve an "economy of scale" with respect to payload capacity the major trend in telecommunications satellites is for larger and larger platforms. With these large platforms the level of integration between platform and payload is increasing leading to longer delivery schedules. The typical lifecycle for procurement of these large telecommunications satellites is now 3-6 years depending on the level of non-recurring engineering needed. Surrey Satellite Technology Ltd (SSTL) has designed a low-cost platform aimed at telecommunications and navigation applications. SSTL's Geostationary Minisatellite Platform (GMP) is a new entrant addressing the lower end of the market with payloads up to 250kg requiring less than 1.5 kW power. The British National Space Centre through the MOSAIC Small Satellite Initiative supported the development of GMP. The main design goals for GMP are low-cost for the complete mission including launch and operations and a platform allowing flexible payload accommodation. GMP is specifically designed to allow rapid development and deployment with schedules typically between 1 and 2 years from contract signature to flight readiness. GMP achieves these aims by a modular design where the level of integration between the platform and payload is low. The modular design decomposes the satellite into three major components - the propulsion bay, the avionics bay and the payload module. Both the propulsion and avionics bays are reusable, largely unchanged, and independent of the payload configuration. Such a design means that SSTL or a 3rd party manufacturer can manufacture the payload in parallel to the platform with integration taking place quite late in the schedule. In July 2003 SSTL signed a contract for ESA's first Galileo navigation satellite known as GSTBV2/A. The satellite is based on GMP and ESA plan to launch it into a MEO orbit late in 2005. The second flight of GMP is likely to be in 2006 carrying a geostationary payload

  16. 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

    A conservative design approach was adopted by the International Space Station Program for specifying total ionizing radiation dose requirements for use in selecting and qualifying materials for construction of the International Space Station. The total ionizing dose design environment included in SSP 30512 Space Station Ionizing Radiation Design Environment is based on trapped proton and electron fluence derived from the solar maximum versions of the AE-8 and AP-8 models, respectively, specified for a circular orbit at 500 km altitude and 51.7 degree inclination. Since launch, the range of altitudes utilized for Space Station operations vary from a minimum of approximately 330 km to a maximum of approximately 405 km with a mean operational altitude less than 400 km. The design environment, therefore, overestimates the radiation environment because the particle flux in the South Atlantic Anomaly is the primary contributor to radiation dose in low Earth orbit and flux within the Anomaly is altitude dependent. In addition, a 2X multiplier is often applied to the design environment to cover effects from the contributions of galactic cosmic rays, solar energetic particle events, geomagnetic storms, and uncertainties in the trapped radiation models which are not explicitly included in the design environment. Application of this environment may give radiation dose overestimates on the order of 1OX to 30X for materials exposed to the space environment, suggesting that materials originally qualified for ten year exposures on orbit may be used for longer periods without replacement. In this paper we evaluate the "as flown" radiation environments derived from historical records of the ISS flight trajectory since launch and compare the results with the SSP 30512 design environment to document the magnitude of the radiation dose overestimate provided by the design environment. "As flown" environments are obtained from application of the AE-8/AP-8 trapped particle models along

  17. Revolving scheme for solving a cascade of Abel equations in dynamics of planar satellite rotation

    Directory of Open Access Journals (Sweden)

    Sergey V. Ershkov

    2017-05-01

    Full Text Available The main objective for this research was the analytical exploration of the dynamics of planar satellite rotation during the motion of an elliptical orbit around a planet. First, we revisit the results of J. Wisdom et al. (1984, in which, by the elegant change of variables (considering the true anomaly f as the independent variable, the governing equation of satellite rotation takes the form of an Abel ordinary differential equation (ODE of the second kind, a sort of generalization of the Riccati ODE. We note that due to the special character of solutions of a Riccati-type ODE, there exists the possibility of sudden jumping in the magnitude of the solution at some moment of time. In the physical sense, this jumping of the Riccati-type solutions of the governing ODE could be associated with the effect of sudden acceleration/deceleration in the satellite rotation around the chosen principle axis at a definite moment of parametric time. This means that there exists not only a chaotic satellite rotation regime (as per the results of J. Wisdom et al. (1984, but a kind of gradient catastrophe (Arnold, 1992 could occur during the satellite rotation process. We especially note that if a gradient catastrophe could occur, this does not mean that it must occur: such a possibility depends on the initial conditions. In addition, we obtained asymptotical solutions that manifest a quasi-periodic character even with the strong simplifying assumptions e→0, p=1, which reduce the governing equation of J. Wisdom et al. (1984 to a kind of Beletskii’s equation.

  18. An introduction to gravitational anomalies

    International Nuclear Information System (INIS)

    Alvarez-Gaume', L.

    1984-01-01

    The outline of these lectures is as follows: We will first analyze the abelian anomaly from the point of view of the Atiyah-Singer index theorem. This is clearly not the first time that this analysis has been carried out, but it will give us a chance of introducing a general method of computing anomalies based on supersymmetric quantum mechanics. Then we will present the general strategy for identifying and computing the anomalies in the energy-momentum tensor and what can be learned from them

  19. Gravitational Anomaly and Transport Phenomena

    International Nuclear Information System (INIS)

    Landsteiner, Karl; Megias, Eugenio; Pena-Benitez, Francisco

    2011-01-01

    Quantum anomalies give rise to new transport phenomena. In particular, a magnetic field can induce an anomalous current via the chiral magnetic effect and a vortex in the relativistic fluid can also induce a current via the chiral vortical effect. The related transport coefficients can be calculated via Kubo formulas. We evaluate the Kubo formula for the anomalous vortical conductivity at weak coupling and show that it receives contributions proportional to the gravitational anomaly coefficient. The gravitational anomaly gives rise to an anomalous vortical effect even for an uncharged fluid.

  20. Remote monitoring of cathodic protection rectifiers of the Bolivia-Brazil Gas Pipeline using low orbit satellite telephone; Monitoracao remota de retificadores de protecao catodica do Gasoduto Bolivia-Brasil utilizando telefone via satelite de baixa orbita

    Energy Technology Data Exchange (ETDEWEB)

    Coelho, Jorge Fernando Pereira [TBG - Transportadora Brasileira Gasoduto Bolivia Brasil S.A., Rio de Janeiro, RJ (Brazil)

    2003-07-01

    The present paper has for objective to present the information collected during definitions, development, implementation, testing and operation phases of the Pilot System for monitoring of the Cathodic Protection Rectifiers MS-10 and SP-09, installed on the Bolivia-Brazil Gas Pipeline. The adopted solution for the Pilot System includes, basically, communication through low-earth satellite telephone, inter linked to the public telephone net, acquisition and data transmission system (Remote Terminal Unit) and data reception in the Supervision and Control Room. (author)