WorldWideScience

Sample records for satellite orbital effects

  1. 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.

  2. Effect of TTC on Satellite Orbital Mechanics

    CERN Document Server

    Pinheiro, Mario J

    2016-01-01

    The modified dynamical equation of motions introduced in previous publication topological torsion current (TTC) [Mario J. Pinheiro (2013) 'A Variational Method in Out-of-Equilibrium Physical Systems', Scientific Reports {\\bf 3}, Article number: 3454] predicts a so-far unforeseen anomalous acceleration detected in spacecrafts during close planetary flybys in retrograde direction, and a null-effect when the spacecraft approach the planet in posigrade direction.

  3. Eclipse intervals for satellites in circular orbit under the effects of Earth’s oblateness and solar radiation pressure

    Directory of Open Access Journals (Sweden)

    M.N. Ismail

    2015-06-01

    Full Text Available In this work, the circumstances of eclipse for a circular satellites’ orbit are studied. The time of passage of the ingress and egress points is calculated. Finally, the eclipse intervals of satellites’ orbit are calculated. An application was done taken into account the effects of solar radiation pressure and Earth’s oblateness on the orbital elements of circular orbit satellite.

  4. Low Earth orbit communications satellite

    Science.gov (United States)

    Moroney, D.; Lashbrook, D.; Mckibben, B.; Gardener, N.; Rivers, T.; Nottingham, G.; Golden, B.; Barfield, B.; Bruening, J.; Wood, D.

    1992-01-01

    A current thrust in satellite communication systems considers a low-Earth orbiting constellations of satellites for continuous global coverage. Conceptual design studies have been done at the time of this design project by LORAL Aerospace Corporation under the program name GLOBALSTAR and by Motorola under their IRIDIUM program. This design project concentrates on the spacecraft design of the GLOBALSTAR low-Earth orbiting communication system. Overview information on the program was gained through the Federal Communications Commission licensing request. The GLOBALSTAR system consists of 48 operational satellites positioned in a Walker Delta pattern providing global coverage and redundancy. The operational orbit is 1389 km (750 nmi) altitude with eight planes of six satellites each. The orbital planes are spaced 45 deg., and the spacecraft are separated by 60 deg. within the plane. A Delta 2 launch vehicle is used to carry six spacecraft for orbit establishment. Once in orbit, the spacecraft will utilize code-division multiple access (spread spectrum modulation) for digital relay, voice, and radio determination satellite services (RDSS) yielding position determination with accuracy up to 200 meters.

  5. Satellite orbit determination and gravity field recovery from satellite-to-satellite tracking

    Science.gov (United States)

    Wakker, K. F.; Ambrosius, B. A. C.; Leenman, H.

    1989-07-01

    Studies on satellite-to-satellite tracking (SST) with POPSAT (a geodetic satellite concept) and a ERS-class (Earth observation) satellite, a Satellite-to-Satellite Tracking (SST) gravity mission, and precise gravity field determination methods and mission requirements are reported. The first two studies primarily address the application of SST between the high altitude POPSAT and an ERS-class or GRM (Geopotential Research Mission) satellite to the orbit determination of the latter two satellites. Activities focussed on the determination of the tracking coverage of the lower altitude satellite by ground based tracking systems and by POPSAT, orbit determination error analysis and the determination of the surface forces acting on GRM. The third study surveys principles of SST, uncertainties of existing drag models, effects of direct luni-solar attraction and tides on orbit and the gravity gradient observable. Detailed ARISTOTELES (which replaced POPSAT) orbit determination error analyses were performed for various ground based tracking networks.

  6. The study of gravity gradient effect on attitude of low earth orbit satellite

    Science.gov (United States)

    Hamzah, Nor Hazadura; Yaacob, Sazali; Muthusamy, Hariharan; Hamzah, Norhizam; Ghazali, Najah

    2013-04-01

    Simulations and mathematical models are increasingly used to assist the process of decision making in engineering design. The objective of this paper is to simulate the linear attitude dynamics of small satellites under gravity gradient torque which is inherent in low earth orbit. The equations were first derived in their nonlinear form, and then manipulated and simulated in their linear form. Simulation results demonstrate the importance of choosing the appropriate values of satellite's moment of inertia in designing phase of a satellite.

  7. Effect of NOAA satellite orbital drift on AVHRR-derived phenological metrics

    Science.gov (United States)

    Ji, Lei; Brown, Jesslyn F.

    2017-10-01

    The U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center routinely produces and distributes a remote sensing phenology (RSP) dataset derived from the Advanced Very High Resolution Radiometer (AVHRR) 1-km data compiled from a series of National Oceanic and Atmospheric Administration (NOAA) satellites (NOAA-11, -14, -16, -17, -18, and -19). Each NOAA satellite experienced orbital drift during its duty period, which influenced the AVHRR reflectance measurements. To understand the effect of the orbital drift on the AVHRR-derived RSP dataset, we analyzed the impact of solar zenith angle (SZA) on the RSP metrics in the conterminous United States (CONUS). The AVHRR weekly composites were used to calculate the growing-season median SZA at the pixel level for each year from 1989 to 2014. The results showed that the SZA increased towards the end of each NOAA satellite mission with the highest increasing rate occurring during NOAA-11 (1989-1994) and NOAA-14 (1995-2000) missions. The growing-season median SZA values (44°-60°) in 1992, 1993, 1994, 1999, and 2000 were substantially higher than those in other years (28°-40°). The high SZA in those years caused negative trends in the SZA time series, that were statistically significant (at α = 0.05 level) in 76.9% of the CONUS area. A pixel-based temporal correlation analysis showed that the phenological metrics and SZA were significantly correlated (at α = 0.05 level) in 4.1-20.4% of the CONUS area. After excluding the 5 years with high SZA (>40°) from the analysis, the temporal SZA trend was largely reduced, significantly affecting less than 2% of the study area. Additionally, significant correlation between the phenological metrics and SZA was observed in less than 7% of the study area. Our study concluded that the NOAA satellite orbital drift increased SZA, and in turn, influenced the phenological metrics. Elimination of the years with high median SZA reduced the influence of orbital drift

  8. Effect of NOAA satellite orbital drift on AVHRR-derived phenological metrics

    Science.gov (United States)

    Ji, Lei; Brown, Jesslyn

    2017-01-01

    The U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center routinely produces and distributes a remote sensing phenology (RSP) dataset derived from the Advanced Very High Resolution Radiometer (AVHRR) 1-km data compiled from a series of National Oceanic and Atmospheric Administration (NOAA) satellites (NOAA-11, −14, −16, −17, −18, and −19). Each NOAA satellite experienced orbital drift during its duty period, which influenced the AVHRR reflectance measurements. To understand the effect of the orbital drift on the AVHRR-derived RSP dataset, we analyzed the impact of solar zenith angle (SZA) on the RSP metrics in the conterminous United States (CONUS). The AVHRR weekly composites were used to calculate the growing-season median SZA at the pixel level for each year from 1989 to 2014. The results showed that the SZA increased towards the end of each NOAA satellite mission with the highest increasing rate occurring during NOAA-11 (1989–1994) and NOAA-14 (1995–2000) missions. The growing-season median SZA values (44°–60°) in 1992, 1993, 1994, 1999, and 2000 were substantially higher than those in other years (28°–40°). The high SZA in those years caused negative trends in the SZA time series, that were statistically significant (at α = 0.05 level) in 76.9% of the CONUS area. A pixel-based temporal correlation analysis showed that the phenological metrics and SZA were significantly correlated (at α = 0.05 level) in 4.1–20.4% of the CONUS area. After excluding the 5 years with high SZA (>40°) from the analysis, the temporal SZA trend was largely reduced, significantly affecting less than 2% of the study area. Additionally, significant correlation between the phenological metrics and SZA was observed in less than 7% of the study area. Our study concluded that the NOAA satellite orbital drift increased SZA, and in turn, influenced the phenological metrics. Elimination of the years with high median SZA reduced the

  9. Investigating the Effects of Non-Gravitational Force Modelling on GPS Satellite Orbits

    Science.gov (United States)

    Petrie, E. J.; King, R. W.; Herring, T.; Ziebart, M. K.

    2011-12-01

    Non-gravitational forces such as solar radiation pressure, earth radiation pressure, antenna thrust and thermal re-radiation are relatively small contributors to the overall GPS satellite orbital force budget. However, if neglected, these small non-gravitationally induced accelerations produce significant errors in satellite positions and velocities when integrated over time. For applications where centimetre level orbital accuracy is required (i.e. ppb accuracy ground positioning), these forces must be accounted for either through realistic a priori physical models and/or appropriate parameter estimation. Current GPS processing approaches typically use an approximate solar radiation pressure force, together with estimated parameters that are meant to account for non-modeled forces. These parameters often fall into the categories of scaling and sinusoidal once-per-revolution parameters. Here we investigate the effects of using more detailed physically based models of radiation forces and interaction between these models and the parameterisation of the non-modeled forces. Ideally, with a complete physical model, additional parameters are not required. Reduction of the number of empirical parameters estimated can result in large effects on the stability of the terrestrial reference frame determined with GPS. These analyses are done using an adapted version of the GAMIT processing software which includes a Fourier series model for radiation forces developed at University College London.

  10. Detecting extrasolar moons akin to Solar System satellites with an Orbital Sampling Effect

    CERN Document Server

    Heller, René

    2014-01-01

    Despite years of high accuracy observations, none of the available theoretical techniques has yet allowed the confirmation of a moon beyond the Solar System. Methods are currently limited to masses about an order of magnitude higher than the mass of any moon in the Solar System. I here present a new method sensitive to exomoons similar to the known moons. Due to the projection of transiting exomoon orbits onto the celestial plane, satellites appear more often at larger separations from their planet. After about a dozen randomly sampled observations, a photometric orbital sampling effect (OSE) starts to appear in the phase-folded transit light curve, indicative of the moons' radii and planetary distances. Two additional outcomes of the OSE emerge in the planet's transit timing variations (TTV-OSE) and transit duration variations (TDV-OSE), both of which permit measurements of a moon's mass. The OSE is the first effect that permits characterization of multi-satellite systems. I derive and apply analytical OSE d...

  11. Diffusive chaos in navigation satellites orbits

    CERN Document Server

    Daquin, J; Tsiganis, K

    2016-01-01

    The navigation satellite constellations in medium-Earth orbit exist in a background of third-body secular resonances stemming from the perturbing gravitational effects of the Moon and the Sun. The resulting chaotic motions, emanating from the overlapping of neighboring resonant harmonics, induce especially strong perturbations on the orbital eccentricity, which can be transported to large values, thereby increasing the collision risk to the constellations and possibly leading to a proliferation of space debris. We show here that this transport is of a diffusive nature and we present representative diffusion maps that are useful in obtaining a global comprehension of the dynamical structure of the navigation satellite orbits.

  12. Orbit Determination Using Satellite-to-Satellite Tracking Data

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Satellite-to-Satellite Tracking (SST) data can be used to determine the orbits of spacecraft in two ways. One is combined orbit determination, which combines SST data with ground-based tracking data and exploits the enhanced tracking geometry. The other is the autonomous orbit determination, which uses only SST. The latter only fits some particular circumstances since it suffers the rank defect problem in other circumstances. The proof of this statement is presented. The na ture of the problem is also investigated in order to find an effective solution. Several methods of solution are discussed. The feasibility of the methods is demonstrated by their apphcation to a simulation.

  13. Sun-synchronous satellite orbit determination

    Science.gov (United States)

    Ma, Der-Ming; Zhai, Shen-You

    2004-02-01

    The linearized dynamic equations used for on-board orbit determination of Sun-synchronous satellite are derived. Sun-synchronous orbits are orbits with the secular rate of the right ascension of the ascending node equal to the right ascension rate of the mean sun. Therefore the orbit is no more a closed circle but a tight helix about the Earth. In the paper, instead of treating the orbit as a closed circle, the actual helix orbit is taken as nominal trajectory. The details of the linearized equations of motion for the satellite in the Sun-synchronous orbit are derived. The linearized equations are obtained by perturbing the Keplerian motion with the J2 correction and the effect of sun's attraction being neglected. Combined with the GPS navigation equations, the Kalman filter formulation is given. The particular application considered is the circular Sun-synchronous orbit with the altitude of 800 km and inclination of 98.6°. The numerical example simulated by MATLAB® shows that only the pseudo-range data used in the algorithm still gives acceptable results. Based on the simulation results, we can use the on-board GPS receivers' signal only as an alternative to determine the orbit of Sun-Synchronous satellite and therefore circumvents the need for extensive ground support.

  14. 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.

  15. Detecting extrasolar moons akin to solar system satellites with an orbital sampling effect

    Energy Technology Data Exchange (ETDEWEB)

    Heller, René, E-mail: rheller@physics.mcmaster.ca [Department of Physics and Astronomy, McMaster University (Canada)

    2014-05-20

    Despite years of high accuracy observations, none of the available theoretical techniques has yet allowed the confirmation of a moon beyond the solar system. Methods are currently limited to masses about an order of magnitude higher than the mass of any moon in the solar system. I here present a new method sensitive to exomoons similar to the known moons. Due to the projection of transiting exomoon orbits onto the celestial plane, satellites appear more often at larger separations from their planet. After about a dozen randomly sampled observations, a photometric orbital sampling effect (OSE) starts to appear in the phase-folded transit light curve, indicative of the moons' radii and planetary distances. Two additional outcomes of the OSE emerge in the planet's transit timing variations (TTV-OSE) and transit duration variations (TDV-OSE), both of which permit measurements of a moon's mass. The OSE is the first effect that permits characterization of multi-satellite systems. I derive and apply analytical OSE descriptions to simulated transit observations of the Kepler space telescope assuming white noise only. Moons as small as Ganymede may be detectable in the available data, with M stars being their most promising hosts. Exomoons with the ten-fold mass of Ganymede and a similar composition (about 0.86 Earth radii in radius) can most likely be found in the available Kepler data of K stars, including moons in the stellar habitable zone. A future survey with Kepler-class photometry, such as Plato 2.0, and a permanent monitoring of a single field of view over five years or more will very likely discover extrasolar moons via their OSEs.

  16. Secular motion around synchronously orbiting planetary satellites.

    Science.gov (United States)

    Lara, Martin; San-Juan, Juan F; Ferrer, Sebastián

    2005-12-01

    We investigate the secular motion of a spacecraft around the natural satellite of a planet. The satellite rotates synchronously with its mean motion around the planet. Our model takes into account the gravitational potential of the satellite up to the second order, and the third-body perturbation in Hill's approximation. Close to the satellite, the ratio of rotation rate of the satellite to mean motion of the orbiter is small. When considering this ratio as a small parameter, the Coriolis effect is a first-order perturbation, while the third-body tidal attraction, the ellipticity effect, and the oblateness perturbation remain at higher orders. Then, we apply perturbation theory and find that a third-order approach is enough to show the influence of the satellite's ellipticity in the pericenter dynamics. Finally, we discuss the averaged system in the three-dimensional parametric space, and provide a global description of the flow.

  17. 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...

  18. Orbit Propagation and Determination of Low Earth Orbit Satellites

    OpenAIRE

    Ho-Nien Shou

    2014-01-01

    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 t...

  19. An Assessment of Relativistic Effects for Low Earth Orbiters: The GRACE Satellites

    Science.gov (United States)

    2007-01-01

    IOP PUBLISHING METROLOGIA Metrologia 44 (2007) 484–490 doi:10.1088/0026-1394/44/6/007 An assessment of relativistic effects for low Earth orbiters...for the larger-eccentricity orbit is shown in figure 2(b). Metrologia , 44 (2007) 484–490 485 K M Larson et al Figure 1. Amplitude of the once/rev...486 Metrologia , 44 (2007) 484–490 Assessment of relativistic effects for low Earth orbiters combination was launched on TOPEX in 1992. Unfortunately

  20. High Precision Orbit Determination of CHAMP Satellite

    Institute of Scientific and Technical Information of China (English)

    ZHAO Qile; LIU Jingnan; GE Maorong

    2006-01-01

    The precision orbit determination of challenging minisatellite payload(CHAMP) satellite was done based on position and navigation data analyst(PANDA) software which is developed in Wuhan University, using the onboard GPS data of year 2002 from day 126 to 131. The orbit accuracy was assessed by analyzing the difference from GFZ post-processed science orbits (PSO), the GPS carrier and pseudo-range data residuals and the satellite laser ranging (SLR) residuals.

  1. 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.

  2. Study on relative orbital configuration in satellite formation flying

    Institute of Scientific and Technical Information of China (English)

    Junfeng Li; Xin Meng; Yunfeng Gao; Xiang Li

    2005-01-01

    In this paper, the relative orbital configurations of satellites in formation flying with non-perturbation and J2 perturbation are studied, and an orbital elements method is proposed to obtain the relative orbital configurations of satellites in formation. Firstly, under the condition of nonperturbation, we obtain many shapes of relative orbital configurations when the semi-major axes of satellites are equal.These shapes can be lines, ellipses or distorted closed curves.Secondly, on the basis of the analysis of J2 effect on relative orbital configurations, we find out that J2 effect can induce two kinds of changes of relative orbital configurations. They are distortion and drifting, respectively. In addition, when J2perturbation is concerned, we also find that the semi-major axes of the leading and following satellites should not be the same exactly in order to decrease the J2 effect. The relationship of relative orbital elements and J2 effect is obtained through simulations. Finally, the minimum relation perturbation conditions are established in order to reduce the influence of the J2 effect. The results show that the minimum relation perturbation conditions can reduce the J2 effect significantly when the orbital element differences are small enough, and they can become rules for the design of satellite formation flying.

  3. Ionospheric refraction effects on TOPEX orbit determination accuracy using the Tracking and Data Relay Satellite System (TDRSS)

    Science.gov (United States)

    Radomski, M. S.; Doll, C. E.

    1991-01-01

    This investigation concerns the effects on Ocean Topography Experiment (TOPEX) spacecraft operational orbit determination of ionospheric refraction error affecting tracking measurements from the Tracking and Data Relay Satellite System (TDRSS). Although tracking error from this source is mitigated by the high frequencies (K-band) used for the space-to-ground links and by the high altitudes for the space-to-space links, these effects are of concern for the relatively high-altitude (1334 kilometers) TOPEX mission. This concern is due to the accuracy required for operational orbit-determination by the Goddard Space Flight Center (GSFC) and to the expectation that solar activity will still be relatively high at TOPEX launch in mid-1992. The ionospheric refraction error on S-band space-to-space links was calculated by a prototype observation-correction algorithm using the Bent model of ionosphere electron densities implemented in the context of the Goddard Trajectory Determination System (GTDS). Orbit determination error was evaluated by comparing parallel TOPEX orbit solutions, applying and omitting the correction, using the same simulated TDRSS tracking observations. The tracking scenarios simulated those planned for the observation phase of the TOPEX mission, with a preponderance of one-way return-link Doppler measurements. The results of the analysis showed most TOPEX operational accuracy requirements to be little affected by space-to-space ionospheric error. The determination of along-track velocity changes after ground-track adjustment maneuvers, however, is significantly affected when compared with the stringent 0.1-millimeter-per-second accuracy requirements, assuming uncoupled premaneuver and postmaneuver orbit determination. Space-to-space ionospheric refraction on the 24-hour postmaneuver arc alone causes 0.2 millimeter-per-second errors in along-track delta-v determination using uncoupled solutions. Coupling the premaneuver and postmaneuver solutions

  4. Effects of Plasma Drag on Low Earth Orbiting Satellites due to Heating of Earth's Atmosphere by Coronal Mass Ejections

    CERN Document Server

    Nwankwo, Victor U J

    2013-01-01

    Solar events, such as coronal mass ejections (CMEs) and solar flares, heat up the upper atmosphere and near-Earth space environment. Due to this heating and expansion of the outer atmosphere by the energetic ultraviolet, X-ray and particles expelled from the sun, the low Earth-Orbiting satellites (LEOS) become vulnerable to an enhanced drag force by the ions and molecules of the expanded atmosphere. Out of various types of perturbations, Earth directed CMEs play the most significant role. They are more frequent and intense during the active (solar maximum) phase of the sun's approximately 11-year cycle. As we are approaching another solar maximum later in 2013, it may be instructive to analyse the effects of the past solar cycles on the orbiting satellites using the archival data of space environment parameters as indicators. In this paper, we compute the plasma drag on a model LEOS due to the atmospheric heating by CMEs and other solar events as a function of the solar parameters. Using the current forecast ...

  5. Synthetically adaptive robust filtering for satellite orbit determination

    Institute of Scientific and Technical Information of China (English)

    YANG; Yuanxi

    2004-01-01

    The quality of the satellite orbit determination is rested on the knowledge of perturbing forces acting on the satellite and stochastic properties of the observations, and the ability of controlling various kinds of errors. After a brief discussion on the dynamic and geometric orbit determinations, Sage adaptive filtering and robust filtering are reviewed. A new synthetically adaptive robust filtering based on a combination of robust filtering and Sage filtering is developed. It is shown, by derivations and calculations, that the synthetically adaptive robust filtering for orbit determination is not only robust but also simple in calculation. It controls the effects of the outliers of tracking observations and the satellite dynamical disturbance on the parameter estimates of the satellite orbit.

  6. LARES succesfully launched in orbit: satellite and mission description

    CERN Document Server

    Paolozzi, Antonio

    2013-01-01

    On February 13th 2012, the LARES satellite of the Italian Space Agency (ASI) was launched into orbit with the qualification flight of the new VEGA launcher of the European Space Agency (ESA). The payload was released very accurately in the nominal orbit. The name LARES means LAser RElativity Satellite and summarises the objective of the mission and some characteristics of the satellite. It is, in fact, a mission designed to test Einstein's General Relativity Theory (specifically 'frame dragging' and Lense-Thirring effect). The satellite is passive and covered with optical retroreflectors that send back laser pulses to the emitting ground station. This allows accurate positioning of the satellite, which is important for measuring the very small deviations from Galilei-Newton's laws. In 2008, ASI selected the prime industrial contractor for the LARES system with a heavy involvement of the universities in all phases of the programme, from the design to the construction and testing of the satellite and separation...

  7. Autonomous satellite constellation orbit determination using the star sensor and inter-satellite links data

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A method of autonomous orbit determination for a satellite constellation using a star sensor combined with inter satellite links(ISLs) is studied.Two types of simulated observation data,Three-Satellite Constellation ISLs and background stellar observations by a CCD star sensor,are first produced.Based on these data,an observation equation is built for the constellation joint autonomous orbit determination,in which the simulations are run.The accuracy of this method with different orbital determination models are analyzed and compared with regard to the effect of potential measurement errors.The results show that autonomous satellite constellation orbit determination using star sensor measurement and ISLs data is feasible.Finally,this paper arrives at several conclusions which contribute to extending this method to a more general satellite constellation.

  8. MONTE CARLO SIMULATION FOR MODELING THE EFFECT OF GROUND SEGMENT LOCATION ON IN-ORBIT RESPONSIVENESS OF LEO SUNSYNCHRONOUS SATELLITE S

    Institute of Scientific and Technical Information of China (English)

    M. Navabi; Hossein Bonyan Khamseh

    2011-01-01

    Responsiveness is a challenge for space systems to sustain competitive advantage over alternate non-spaceborne technologies.For a satellite in its operational orbit,in-orbit responsiveness is defined as the capability of the satellite to respond to a given demand in a timely manner.In this paper,it is shown that Average Wait Time (AWT) to pick up user demand from ground segment is the appropriate metric to evaluate the effect of ground segment location on in-orbit responsiveness of Low Earth Orbit (LEO) sunsynchronous satellites.This metric depends on pattern of ground segment access to satellite and distribution of user demands in time domain.A mathematical model is presented to determine pattern of ground segment access to satellite and concept of cumulative distribution function is used to simulate distribution of user demands for markets with different total demand scenarios.Monte Carlo simulations are employed to take account of uncertainty in distribution and total volume of user demands.Sampling error and standard deviation are used to ensure validity of AWT metric obtained from Monte Carlo simulations.Incorporation of the proposed metric in the ground segment site location process results in more responsive satellite systems which,in turn,lead to greater customer satisfaction levels and attractiveness of spaceborne systems for different applications.Finally,simulation results for a case study are presented.

  9. Effects on satellite orbits in the gravitational field of an axisymmetric central body with a mass monopole and arbitrary spin multipole moments

    CERN Document Server

    Meichsner, J

    2015-01-01

    Perturbations of satellite orbits in the gravitational field of a body with a mass monopole and arbitrary spin multipole moments are considered for an axisymmetric and stationary situation. Periodic and secular effects caused by the central gravitomagnetic field are derived by a first order perturbation theory. For a central spin-dipole field these results reduce to the well known Lense-Thirring effects.

  10. Dual RF Astrodynamic GPS Orbital Navigator Satellite

    Science.gov (United States)

    Kanipe, David B.; Provence, Robert Steve; Straube, Timothy M.; Reed, Helen; Bishop, Robert; Lightsey, Glenn

    2009-01-01

    Dual RF Astrodynamic GPS Orbital Navigator Satellite (DRAGONSat) will demonstrate autonomous rendezvous and docking (ARD) in low Earth orbit (LEO) and gather flight data with a global positioning system (GPS) receiver strictly designed for space applications. ARD is the capability of two independent spacecraft to rendezvous in orbit and dock without crew intervention. DRAGONSat consists of two picosatellites (one built by the University of Texas and one built by Texas A and M University) and the Space Shuttle Payload Launcher (SSPL); this project will ultimately demonstrate ARD in LEO.

  11. The Orbits of Saturn's Small Satellites

    Science.gov (United States)

    Spitale, J. N.; Jacobson, R. A.; Porco, C. C.; Owen, W. M.; Charnoz, S.

    2005-05-01

    We report on the orbits of the small, inner Saturnian satellites, either recovered or newly-discovered in recent Cassini imaging observations (excluding Helene, Telesto and Calypso, which will be discussed by another group). Using combined Cassini and Voyager observations, the mean motions of Pan and Atlas have been refined by several orders of magnitude. The Atlas orbit is based on a numerical integration perturbed by all of the massive Saturnian satellites including Prometheus, Pandora, Janus, and Epimetheus. We find that the dominant perturber is Prometheus. Cassini, Voyager, HST, and Earth-based data have been used to refine the orbits of Janus, Epimetheus, Prometheus and Pandora. The orbits of the co-orbitals, Janus and Epimetheus, remain stable; their orbital swap does not occur until Februrary, 2006. The orbits of Prometheus and Pandora remain close to recent values (Jacobson and French 2004, Icarus, 172, 382). Six new objects have been discovered to date -- three (S/2004 S3, S4, S6) in close proximity to the F ring, two (S/2004 S1(Methone), S/2004 S2(Pallene)) between the orbits of Mimas and Enceladus, and one (S/2004 S5(Polydeuces)) co-orbital with Dione, trailing by ˜60 deg (Porco et al., Science 307, 25 Feb 2005). One of the F-ring objects -- S/2004 S3 -- was seen over a 118-day interval, but none of those objects, including S/2004 S3, were subsequently recovered in an F-ring movie acquired on 15 November 2004 (29 days after the last sighting of S/2004 S3) with an image scale of 4 km/pixel, in which all were expected to appear. Consequently, we are confident only that Methone, Pallene and Polydeuces are solid satellites; S/2004 S3, S4 and S6 may be transient clumps. Our orbital fits, both precessing ellipse models and orbital integrations, suggest that Pallene is the same object as S/1981 S14, imaged by Voyager 2 on 23 August 1981, contrary to our initial reports (IAU circular 8389). The orbital inclination and eccentricity of Methone are considerably

  12. From order to chaos in Earth satellite orbits

    CERN Document Server

    Gkolias, Ioannis; Gachet, Fabien; Rosengren, Aaron J

    2016-01-01

    We consider Earth satellite orbits in the range of semi-major 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 angles-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 first importance to the space debris...

  13. Characterizing the Effects of Low Order Perturbations on Geodetic Satellite Precision Orbit Determination

    Science.gov (United States)

    2015-08-07

    relativistic corrections comprise of Schwarzschild terms, Lense- Thirring precession (frame-dragging), and de Sitter ( geodesic ) precession. The Schwarzschild...Lense-Thirring, and de Sitter terms can be seen on lines 1, 2, and 3 respectively in Equation 1.13 ∆ −→̈ r = GME c2r3 {[ 2(β + γ) GME r − γ−→̇r · −→̇r...satellite. Figure 3. RSS Position Differences for Various Lunar Gravity Field Model Solutions It can be seen that all four lines representing each RSS

  14. From Order to Chaos in Earth Satellite Orbits

    Science.gov (United States)

    Gkolias, Ioannis; Daquin, Jérôme; Gachet, Fabien; Rosengren, Aaron J.

    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.

  15. A satellite orbital testbed for SATCOM using mobile robots

    Science.gov (United States)

    Shen, Dan; Lu, Wenjie; Wang, Zhonghai; Jia, Bin; Wang, Gang; Wang, Tao; Chen, Genshe; Blasch, Erik; Pham, Khanh

    2016-05-01

    This paper develops and evaluates a satellite orbital testbed (SOT) for satellite communications (SATCOM). SOT can emulate the 3D satellite orbit using the omni-wheeled robots and a robotic arm. The 3D motion of satellite is partitioned into the movements in the equatorial plane and the up-down motions in the vertical plane. The former actions are emulated by omni-wheeled robots while the up-down motions are performed by a stepped-motor-controlled-ball along a rod (robotic arm), which is attached to the robot. The emulated satellite positions will go to the measure model, whose results will be used to perform multiple space object tracking. Then the tracking results will go to the maneuver detection and collision alert. The satellite maneuver commands will be translated to robots commands and robotic arm commands. In SATCOM, the effects of jamming depend on the range and angles of the positions of satellite transponder relative to the jamming satellite. We extend the SOT to include USRP transceivers. In the extended SOT, the relative ranges and angles are implemented using omni-wheeled robots and robotic arms.

  16. An autonomous orbit determination method for MEO and LEO satellite

    Science.gov (United States)

    Zhang, Hui; Wang, Jin; Yu, Guobin; Zhong, Jie; Lin, Ling

    2014-09-01

    A reliable and secure navigation system and assured autonomous capability of satellite are in high demand in case of emergencies in space. This paper introduces a novel autonomous orbit determination method for Middle-Earth-Orbit and Low-Earth-Orbit (MEO and LEO) satellite by observing space objects whose orbits are known. Generally, the geodetic satellites, such as LAGEOS and ETALONS, can be selected as the space objects here. The precision CCD camera on tracking gimbal can make a series of photos of the objects and surrounding stars when MEO and LEO satellite encounters the space objects. Then the information processor processes images and attains sightings and angular observations of space objects. Several clusters of such angular observations are incorporated into a batch least squares filter to obtain an orbit determination solution. This paper describes basic principle and builds integrated mathematical model. The accuracy of this method is analyzed by means of computer simulation. Then a simulant experiment system is built, and the experimental results demonstrate the feasibility and effectiveness of this method. The experimental results show that this method can attain the accuracy of 150 meters with angular observations of 1 arcsecond system error.

  17. Improvement of orbit determination accuracy for Beidou Navigation Satellite System with Two-way Satellite Time Frequency Transfer

    Science.gov (United States)

    Tang, Chengpan; Hu, Xiaogong; Zhou, Shanshi; Guo, Rui; He, Feng; Liu, Li; Zhu, Lingfeng; Li, Xiaojie; Wu, Shan; Zhao, Gang; Yu, Yang; Cao, Yueling

    2016-10-01

    The Beidou Navigation Satellite System (BDS) manages to estimate simultaneously the orbits and clock offsets of navigation satellites, using code and carrier phase measurements of a regional network within China. The satellite clock offsets are also directly measured with Two-way Satellite Time Frequency Transfer (TWSTFT). Satellite laser ranging (SLR) residuals and comparisons with the precise ephemeris indicate that the radial error of GEO satellites is much larger than that of IGSO and MEO satellites and that the BDS orbit accuracy is worse than GPS. In order to improve the orbit determination accuracy for BDS, a new orbit determination strategy is proposed, in which the satellite clock measurements from TWSTFT are fixed as known values, and only the orbits of the satellites are solved. However, a constant systematic error at the nanosecond level can be found in the clock measurements, which is obtained and then corrected by differencing the clock measurements and the clock estimates from orbit determination. The effectiveness of the new strategy is verified by a GPS regional network orbit determination experiment. With the IGS final clock products fixed, the orbit determination and prediction accuracy for GPS satellites improve by more than 50% and the 12-h prediction User Range Error (URE) is better than 0.12 m. By processing a 25-day of measurement from the BDS regional network, an optimal strategy for the satellite-clock-fixed orbit determination is identified. User Equivalent Ranging Error is reduced by 27.6% for GEO satellites, but no apparent reduction is found for IGSO/MEO satellites. The SLR residuals exhibit reductions by 59% and 32% for IGSO satellites but no reductions for GEO and MEO satellites.

  18. Analysis of the Lunar Gravity Field by Using GL0660B Model and Its Effect on Lunar Satellite Orbit

    Directory of Open Access Journals (Sweden)

    HUANG Kunxue

    2016-07-01

    Full Text Available The lunar gravity field provides a way to research moon's evolution and probes the interior structure of the moon. It is an important factor influencing the lunar satellite precise orbit determination as well. The new lunar gravity model GL0660B from GRAIL mission dramatically improves the gravity spectrum and spectral ranges. Using the model GL0660B, it can be computed that the corresponding degree-wise RMS and correlation of topography, with which the quality of model GL0660B can be analyzed. Then different characters of the lunar gravity field comparing with other lunar gravity fields are analyzed. Besides, gravity anomaly distribution figures at different height of the models are given, and the character and difference of the lunar gravity models at different height are compared. In addition, lunar satellite orbit revolutionary at different height are modeled by GEODYN. The result shows that the trend of lunar satellite eccentricity changes is a complex and long cycle of change trend. It is different affected by the perturbation of the mascons of different height, which causes different changes of apolune, perilune and eccentricity.

  19. China's FY-3 Polar Orbit Meteorological Satellite And Its Applications

    Institute of Scientific and Technical Information of China (English)

    Zhang Jiashen; Fang Meng; Sun Anlai

    2009-01-01

    @@ FY-3 is China's second generation of polar orbit meteorological satellite. FY-3A,the first of the FY-3 series,was launched on May 27,2008 from Taiyuan Satellite Launeh Center. After 5 months of in-orbit test,the satellite and its ground application system were put into trial operation on November 18,2008,marking the successful technical upgrading of China's polar-orbit meteorological satellite.

  20. Benefits Derived From Laser Ranging Measurements for Orbit Determination of the GPS Satellite Orbit

    Science.gov (United States)

    Welch, Bryan W.

    2007-01-01

    While navigation systems for the determination of the orbit of the Global Position System (GPS) have proven to be very effective, the current research is examining methods to lower the error in the GPS satellite ephemerides below their current level. Two GPS satellites that are currently in orbit carry retro-reflectors onboard. One notion to reduce the error in the satellite ephemerides is to utilize the retro-reflectors via laser ranging measurements taken from multiple Earth ground stations. Analysis has been performed to determine the level of reduction in the semi-major axis covariance of the GPS satellites, when laser ranging measurements are supplemented to the radiometric station keeping, which the satellites undergo. Six ground tracking systems are studied to estimate the performance of the satellite. The first system is the baseline current system approach which provides pseudo-range and integrated Doppler measurements from six ground stations. The remaining five ground tracking systems utilize all measurements from the current system and laser ranging measurements from the additional ground stations utilized within those systems. Station locations for the additional ground sites were taken from a listing of laser ranging ground stations from the International Laser Ranging Service. Results show reductions in state covariance estimates when utilizing laser ranging measurements to solve for the satellite s position component of the state vector. Results also show dependency on the number of ground stations providing laser ranging measurements, orientation of the satellite to the ground stations, and the initial covariance of the satellite's state vector.

  1. Single-event and total-dose effects in geo-stationary transfer orbit during solar-activity maximum period measured by the Tsubasa satellite

    Science.gov (United States)

    Koshiishi, H.; Kimoto, Y.; Matsumoto, H.; Goka, T.

    The Tsubasa satellite developed by the Japan Aerospace Exploration Agency was launched in Feb 2002 into Geo-stationary Transfer Orbit GTO Perigee 500km Apogee 36000km and had been operated well until Sep 2003 The objective of this satellite was to verify the function of commercial parts and new technologies of bus-system components in space Thus the on-board experiments were conducted in the more severe radiation environment of GTO rather than in Geo-stationary Earth Orbit GEO or Low Earth Orbit LEO The Space Environment Data Acquisition equipment SEDA on board the Tsubasa satellite had the Single-event Upset Monitor SUM and the DOSimeter DOS to evaluate influences on electronic devices caused by radiation environment that was also measured by the particle detectors of the SEDA the Standard DOse Monitor SDOM for measurements of light particles and the Heavy Ion Telescope HIT for measurements of heavy ions The SUM monitored single-event upsets and single-event latch-ups occurred in the test sample of two 64-Mbit DRAMs The DOS measured accumulated radiation dose at fifty-six locations in the body of the Tsubasa satellite Using the data obtained by these instruments single-event and total-dose effects in GTO during solar-activity maximum period especially their rapid changes due to solar flares and CMEs in the region from L 1 1 through L 11 is discussed in this paper

  2. Orbital Perturbations of the Galilean Satellites During Planetary Encounters

    CERN Document Server

    Deienno, R; Vokrouhlicky, D; Yokoyama, T

    2014-01-01

    The Nice model of the dynamical instability and migration of the giant planets can explain many properties of the present Solar System, and can be used to constrain its early architecture. In the jumping-Jupiter version of the Nice model, required from the terrestrial planet constraint and dynamical structure of the asteroid belt, Jupiter has encounters with an ice giant. Here we study the survival of the Galilean satellites in the jumping-Jupiter model. This is an important concern because the ice-giant encounters, if deep enough, could dynamically perturb the orbits of the Galilean satellites, and lead to implausible results. We performed numerical integrations where we tracked the effect of planetary encounters on the Galilean moons. We considered three instability cases from Nesvorny & Morbidelli (2012) that differed in the number and distribution of encounters. We found that in one case, where the number of close encounters was relatively small, the Galilean satellite orbits were not significantly af...

  3. Lunar gravitational field estimation and the effects of mismodeling upon lunar satellite orbit prediction. M.S. Thesis

    Science.gov (United States)

    Davis, John H.

    1993-01-01

    Lunar spherical harmonic gravity coefficients are estimated from simulated observations of a near-circular low altitude polar orbiter disturbed by lunar mascons. Lunar gravity sensing missions using earth-based nearside observations with and without satellite-based far-side observations are simulated and least squares maximum likelihood estimates are developed for spherical harmonic expansion fit models. Simulations and parameter estimations are performed by a modified version of the Smithsonian Astrophysical Observatory's Planetary Ephemeris Program. Two different lunar spacecraft mission phases are simulated to evaluate the estimated fit models. Results for predicting state covariances one orbit ahead are presented along with the state errors resulting from the mismodeled gravity field. The position errors from planning a lunar landing maneuver with a mismodeled gravity field are also presented. These simulations clearly demonstrate the need to include observations of satellite motion over the far side in estimating the lunar gravity field. The simulations also illustrate that the eighth degree and order expansions used in the simulated fits were unable to adequately model lunar mascons.

  4. A new method for determination of satellite orbits by transfer

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The original idea of a new method for determination of satellite orbits by transfer is from Two-Way Satellite Time and Frequency Transfer (TWSTFT). The original method is called "determination of satellite orbit by transfer". The method is not only for determination of satellite orbit but also for the time transfer with high accuracy and precision. The advantage is that the accuracy and the precision for determination of satellite orbit are very high and the new method is favorable for various applications. The combination of various signals disseminated and received forms various modes of satellite orbit determinations. If receivers at stations receive the own station-disseminated signals via a satellite transponder, it forms an orbit determination mode called "receiving the own station-disseminated signals mode". If receivers at all stations receive the signals disseminated from the master station via satellite transponders, it forms an orbit determination mode called "receiving the master station-disseminated signals mode". If all of receivers at stations receive all stations-disseminated signals via satellite transponders, it forms an orbit determination mode called "receiving all stations-disseminated signals mode". Also there are other combinations of signals for satellite orbit determination. For dif- ferent orbit determination modes with different signal combinations, their rigorous formulae of proc- essing are hereby presented in this paper. The accurate and the precise satellite orbit determination for both of the modes, "receiving the own station-disseminated signals mode" and "receiving the master station-disseminated signals mode" is attempted. It shows that the accuracy and precision for both of modes are nearly the same, the ranging accuracy is better than 1 cm, and the observation residuals of satellite orbit determination are better than 9 cm in the observation duration of 1 day.

  5. A new method for determination of satellite orbits by transfer

    Institute of Scientific and Technical Information of China (English)

    LI ZhiGang; YANG XuHai; AI GuoXiang; SI HuLi; QIAO RongChuan; FENG ChuGang

    2009-01-01

    The original idea of a new method for determination of satellite orbits by transfer is from Two-Way Satellite Time and Frequency Transfer (TWSTFT).The original method is called "determination of satellite orbit by transfer".The method is not only for determination of satellite orbit but also for the time transfer with high accuracy and precision.The advantage is that the accuracy and the precision for determination of satellite orbit are very high and the new method is favorable for various applications.The combination of various signals disseminated and received forms various modes of satellite orbit determinations.If receivers at stations receive the own station-disseminated signals via a satellite transponder,it forms an orbit determination mode called "receiving the own station-disseminated signals mode".If receivers at all stations receive the signals disseminated from the master station via satellite transponders,it forms an orbit determination mode called "receiving the master station-disseminated signals mode".If all of receivers at stations receive all stations-disseminated signals via satellite transponders,it forms an orbit determination mode called "receiving all stations-disseminated signals mode".Also there are other combinations of signals for satellite orbit determination.For different orbit determination modes with different signal combinations,their rigorous formulae of processing are hereby presented in this paper.The accurate and the precise satellite orbit determination for both of the modes,"receiving the own station-disseminated signals mode" and "receiving the master station-disseminated signals mode" is attempted.It shows that the accuracy and precision for both of modes are nearly the same,the ranging accuracy is better than 1 cm,and the observation residuals of satellite orbit determination are better than 9 cm in the observation duration of 1 day.

  6. LiAISON: Linked, Autonomous Interplanetary Satellite Orbit Navigation Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A new navigation technique known as LiAISON (Linked Autonomous Interplanetary Satellite Orbit Navigation) may be used to propel the benefits of GPS to new orbits,...

  7. 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...

  8. NUMERICAL INTEGRATION OF A SATELLITE ORBIT WITH KS TRANSFORMATION

    OpenAIRE

    Piñeros, Jhonathan Murcia; Koffi, Maxime; Kuga, Helio Koiti

    2017-01-01

    A satellite orbit is mainly influenced by central body gravitational forces. For a satellite in LEO (Low Earth Orbit), MEO (Medium Earth Orbit) or GEO (Geosynchronous Earth Orbit) the Earth´s gravity distribution and other perturbations determine the position and velocity changes in function of time. If the motion is around a spherical body with homogenous mass distribution and without perturbative forces, the orbit must be cyclic like the Two Body Problem (TBP) or Keplerian Orbit. Different ...

  9. Circumnutations of sunflower hypocotyls in satellite orbit

    Science.gov (United States)

    Brown, A. H.; Chapman, D. K.; Lewis, R. F.; Venditti, A. L.

    1990-01-01

    The principal objective of the research reported here was to determine whether a plant's periodic growth oscillations, called circumnutations, would persist in the absence of a significant gravitational or inertial force. The definitive experiment was made possible by access to the condition of protracted near weightlessness in an earth satellite. The experiment, performed during the first flight of Spacelab on the National Aeronautics and Space Administration shuttle, Columbia, in November and December, 1983, tested a biophysical model, proposed in 1967, that might account for circumnutation as a gravity-dependent growth response. However, circumnutations were observed in microgravity. They continued for many hours without stimulation by a significant g-force. Therefore, neither a gravitational nor an inertial g-force was an absolute requirement for initiation [correction of initation] or continuation of circumnutation. On average, circumnutation was significantly more vigorous in satellite orbit than on earth-based clinostats. Therefore, at least for sunflower (Helianthus annuus L.) circumnutation, clinostatting is not the functional equivalent of weightlessness.

  10. Satellite orbital conjunction reports assessing threatening encounters in space (SOCRATES)

    Science.gov (United States)

    Kelso, T. S.; Alfano, S.

    2006-05-01

    While many satellite operators are aware of the possibility of a collision between their satellite and another object in earth orbit, most seem unaware of the frequency of near misses occurring each day. Until recently, no service existed to advise satellite operators of an impending conjunction of a satellite payload with another satellite, putting the responsibility for determining these occurrences squarely on the satellite operator's shoulders. This problem has been further confounded by the lack of a timely, comprehensive data set of satellite orbital element sets and computationally efficient tools to provide predictions using industry-standard software. As a result, hundreds of conjunctions within 1 km occur each week, with little or no intervention, putting billions of dollars of space hardware at risk, along with their associated missions. As a service to the satellite operator community, the Center for Space Standards & Innovation (CSSI) offers SOCRATES-Satellite Orbital Conjunction Reports Assessing Threatening Encounters in Space. Twice each day, CSSI runs a list of all satellite payloads on orbit against a list of all objects on orbit using the catalog of all unclassified NORAD two-line element sets to look for conjunctions over the next seven days. The runs are made using STK/CAT-Satellite Tool Kit's Conjunction Analysis Tools-together with the NORAD SGP4 propagator in STK. This paper will discuss how SOCRATES works and how it can help satellite operators avoid undesired close approaches through advanced mission planning.

  11. 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.

  12. Monitoring objects orbiting earth using satellite-based telescopes

    Energy Technology Data Exchange (ETDEWEB)

    Olivier, Scot S.; Pertica, Alexander J.; Riot, Vincent J.; De Vries, Willem H.; Bauman, Brian J.; Nikolaev, Sergei; Henderson, John R.; Phillion, Donald W.

    2015-06-30

    An ephemeris refinement system includes satellites with imaging devices in earth orbit to make observations of space-based objects ("target objects") and a ground-based controller that controls the scheduling of the satellites to make the observations of the target objects and refines orbital models of the target objects. The ground-based controller determines when the target objects of interest will be near enough to a satellite for that satellite to collect an image of the target object based on an initial orbital model for the target objects. The ground-based controller directs the schedules to be uploaded to the satellites, and the satellites make observations as scheduled and download the observations to the ground-based controller. The ground-based controller then refines the initial orbital models of the target objects based on the locations of the target objects that are derived from the observations.

  13. Orbital perturbations of the Galilean satellites during planetary encounters

    Energy Technology Data Exchange (ETDEWEB)

    Deienno, Rogerio; Nesvorný, David [Southwest Research Institute, Boulder, CO (United States); Vokrouhlický, David [Institute of Astronomy, Charles University, Prague (Czech Republic); Yokoyama, Tadashi, E-mail: rogerio.deienno@gmail.com [Universidade Estadual Paulista, Rio Claro, SP (Brazil)

    2014-08-01

    The Nice model of the dynamical instability and migration of the giant planets can explain many properties of the present solar system, and can be used to constrain its early architecture. In the jumping-Jupiter version of the Nice model, required from the terrestrial planet constraint and dynamical structure of the asteroid belt, Jupiter has encounters with an ice giant. Here, we study the survival of the Galilean satellites in the jumping-Jupiter model. This is an important concern because the ice-giant encounters, if deep enough, could dynamically perturb the orbits of the Galilean satellites and lead to implausible results. We performed numerical integrations where we tracked the effect of planetary encounters on the Galilean moons. We considered three instability cases from Nesvorný and Morbidelli that differed in the number and distribution of encounters. We found that in one case, where the number of close encounters was relatively small, the Galilean satellite orbits were not significantly affected. In the other two, the orbital eccentricities of all moons were excited by encounters, Callisto's semimajor axis changed, and, in a large fraction of trials, the Laplace resonance of the inner three moons was disrupted. The subsequent evolution by tides damps eccentricities and can recapture the moons in the Laplace resonance. A more important constraint is represented by the orbital inclinations of the moons, which can be excited during the encounters and not appreciably damped by tides. We find that one instability case taken from Nesvorný and Morbidelli clearly does not meet this constraint. This shows how the regular satellites of Jupiter can be used to set limits on the properties of encounters in the jumping-Jupiter model, and help us to better understand how the early solar system evolved.

  14. Orbital Perturbations of the Galilean Satellites during Planetary Encounters

    Science.gov (United States)

    Deienno, Rogerio; Nesvorný, David; Vokrouhlický, David; Yokoyama, Tadashi

    2014-08-01

    The Nice model of the dynamical instability and migration of the giant planets can explain many properties of the present solar system, and can be used to constrain its early architecture. In the jumping-Jupiter version of the Nice model, required from the terrestrial planet constraint and dynamical structure of the asteroid belt, Jupiter has encounters with an ice giant. Here, we study the survival of the Galilean satellites in the jumping-Jupiter model. This is an important concern because the ice-giant encounters, if deep enough, could dynamically perturb the orbits of the Galilean satellites and lead to implausible results. We performed numerical integrations where we tracked the effect of planetary encounters on the Galilean moons. We considered three instability cases from Nesvorný & Morbidelli that differed in the number and distribution of encounters. We found that in one case, where the number of close encounters was relatively small, the Galilean satellite orbits were not significantly affected. In the other two, the orbital eccentricities of all moons were excited by encounters, Callisto's semimajor axis changed, and, in a large fraction of trials, the Laplace resonance of the inner three moons was disrupted. The subsequent evolution by tides damps eccentricities and can recapture the moons in the Laplace resonance. A more important constraint is represented by the orbital inclinations of the moons, which can be excited during the encounters and not appreciably damped by tides. We find that one instability case taken from Nesvorný & Morbidelli clearly does not meet this constraint. This shows how the regular satellites of Jupiter can be used to set limits on the properties of encounters in the jumping-Jupiter model, and help us to better understand how the early solar system evolved.

  15. State Geography Using NOAA Polar-Orbiting Satellites.

    Science.gov (United States)

    Stadler, Stephen J.

    1985-01-01

    NOAA polar-orbiting satellites have the capability of providing views of entire states. This article describes the characteristics of data from these satellites, indicates their advantages and disadvantages, and shows how the satellite data can be used in a statewide representation of physical geography for students at the introductory level. (RM)

  16. Methods of rapid orbit forecasting after maneuvers for geostationary satellites

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A geostationary(GEO) satellite may serve as a navigation satellite,but there is a problem that maneuvers frequently occur and the forces are difficult to model.Based on the technique of determining satellite orbits by transfer,a predicted orbit with high accuracy may be achieved by the method of statis-tical orbit determination in case of no maneuver force.The predicted orbit will soon be invalid after the maneuver starts,and it takes a long time to get a valid orbit after the maneuver ends.In order to improve ephemeris usability,the method of rapid orbit forecasting after maneuvers is studied.First,GEO satellite movement is analyzed in case of maneuvers based on the observation from the orbit meas-urement system by transfer.Then when a GEO satellite is in the free status just after maneuvers,the short arc observation is used to forecast the orbit.It is assumed that the common system bias and biases of each station are constant,which can be obtained from orbit determination with long arc observations.In this way,only 6 orbit elements would be solved by the method of statistical orbit determination,and the ephemeris with high accuracy may be soon obtained.Actual orbit forecasting with short arc observation for SINOSAT-1 satellite shows that,with the tracking network available,the precision of the predicted orbit(RMS of O-C) can reach about 5 m with 15 min arc observation,and about 3 m with 30 min arc observation.

  17. Evaluation of CHAMP Satellite Orbit with SLR Measurements

    Institute of Scientific and Technical Information of China (English)

    QIN Xianping; YANG Yuanxi

    2005-01-01

    The technique of Evaluating CHAMP satellite orbit with SLR measurements is presented. As an independent evaluation of the orbit solution, SLR data observed from January 1 to 16, 2002 are processed to compute the residuals after fixing the GFZ's post science orbits solutions. The SLR residuals are computed as the differences of the SLR measurements minus the corresponding distances between the SLR station and the GPS-derived orbit positions. On the basis of the SLR residuals analysis, it is found that the accuracy of GFZ's post science orbits is better than 10 em and that there is no systematic error in GFZ's post science orbits.

  18. Methods of rapid orbit forecasting after maneuvers for geostationary satellites

    Institute of Scientific and Technical Information of China (English)

    YANG XuHai; LI ZhiGang; FENG ChuGang; GUO Ji; SHI HuLi; AI GuoXiang; WU FengLei; QIAO RongChuan

    2009-01-01

    A geostationary (GEO) satellite may serve as a navigation satellite,but there is a problem that maneuvers frequently occur and the forces are difficult to model.Based on the technique of determining setellite orbits by transfer,a predicted orbit with high accuracy may be achieved by the method of statistical orbit determination in case of no maneuver force.The predicted orbit will soon be invalid after the maneuver starts,and it takes a long time to get a valid orbit after the maneuver ends.In order to improve ephemeris usability,the method of rapid orbit forecasting after maneuvers is studied.First,GEO satellite movement is analyzed in case of maneuvers based on the observation from the orbit measurement system by transfer.Then when a GEO satellite is in the free status just after maneuvers,the short arc observation is used to forecast the orbit.It is assumed that the common system bias and biases of each station are constant,which can be obtained from orbit determination with long arc observations.In this way,only 6 orbit elements would be solved by the method of statistical orbit determination,and the ephemeris with high accuracy may be soon obtained.Actual orbit forecasting with short arc observation for SlNOSAT-1 satellite shows that,with the tracking network available,the precision of the predicted orbit (RMS of O-C) can reach about 5 m with 15 min arc observation,and about 3 m with 30 min arc observation.

  19. 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.

  20. Algorithm of orbit determination using one or two GPS satellites

    Institute of Scientific and Technical Information of China (English)

    刘艳芳; 洪炳荣; 郭建宁; 巨涛

    1999-01-01

    The problem of orbit determination using one or two GPS satellites is discussed. Methods of getting initial values based on linear translation is presented; the Secant method and the descend Newton iterative procedure and the continuation algorithm are used synthetically to solve the nonlinear equations. Computer simulation shows that this algorithm can give preliminary state of satellite orbit with a certain precision in short time.

  1. Electric Propulsion for Low Earth Orbit Communication Satellites

    Science.gov (United States)

    Oleson, Steven R.

    1997-01-01

    Electric propulsion was evaluated for orbit insertion, satellite positioning and de-orbit applications on big (hundreds of kilograms) and little (tens of kilograms) low earth orbit communication satellite constellations. A simple, constant circumferential thrusting method was used. This technique eliminates the complex guidance and control required when shading of the solar arrays must be considered. Power for propulsion was assumed to come from the existing payload power. Since the low masses of these satellites enable multiple spacecraft per launch, the ability to add spacecraft to a given launch was used as a figure of merit. When compared to chemical propulsion ammonia resistojets, ion, Hall, and pulsed plasma thrusters allowed an additional spacecraft per launch Typical orbit insertion and de-orbit times were found to range from a few days to a few months.

  2. Satellite de-orbiting via controlled solar radiation pressure

    Science.gov (United States)

    Deienno, Rogerio; Sanchez, Diogo Merguizo; de Almeida Prado, Antonio Fernando Bertachini; Smirnov, Georgi

    2016-06-01

    The goal of the present research was to study the use of solar radiation pressure to place a satellite in an orbit that makes it to re-enter the atmosphere of the Earth. This phase of the mission is usual, since the orbital space around the Earth is crowded and all satellites have to be discarded after the end of their lifetimes. The technique proposed here is based on a device that can increase and decrease the area-to-mass ratio of the satellite when it is intended to reduce its altitude until a re-entry point is reached. Equations that predict the evolution of the eccentricity and semi-major axis of the orbit of the satellite are derived and can be used to allow the evaluation of the time required for the decay of the satellite. Numerical simulations are made, and they show the time required for the decay as a function of the area-to-mass ratio and the evolution of the most important orbital elements. The results show maps that indicate regions of fast decays as a function of the area-to-mass ratio and the initial inclination of the orbit of the satellite. They also confirmed the applicability of the equations derived here. The numerical results showed the role played by the evection and the Sun-synchronous resonances in the de-orbiting time.

  3. Orbital List Ephemerides Design of LEO Navigation Augmentation Satellite

    Directory of Open Access Journals (Sweden)

    FANG Shanchuan

    2016-08-01

    Full Text Available A set of reliable LEO (low earth orbit broadcast ephemerides is required to be designed specifically if LEOs, with current GEOs, are also utilized as navigation augmentation satellites. The classical nine state parameters-based GLONASS-type broadcast ephemerides model can only represent precisely the 30-minute orbital motions of the medium and high earth orbiters. To directly deal with LEOs, a modified 21-parameter broadcast ephemerides model is proposed. First, the short-term variations of the main perturbation forces of LEOs are analyzed. Then a set of simple quadratic polynomials and harmonic functions is adopted to compensate mathematically atmospheric drag perturbation and other effects. A thoroughly simulation for the LEOs of altitude 500~1200 km is given to demonstrate the impact of the numbers of ephemerides parameters, the length of the fitting arcs and the sample rates on the fitting precision. The results of 20-minute fitting arc (approximately 1/5 of orbital period show that the average RMS of the fitting user range error (FURE is less than 0.05 m for LEOs higher than 700 km and within 0.03 m for LEOs of altitude 1000 km.

  4. Orientation and resonance locks for satellites in the elliptic orbit.

    Science.gov (United States)

    Liu, H.-S.

    1972-01-01

    In order to achieve the maximum strength of higher resonance locks for satellites in the elliptic orbit, the condition of satellite orientation during the process of deployment is established. It is shown that for maximum strength locks the axis of the minimum moment of inertia of satellites should point toward the attracting body at plus or minus (5/8) pi and 0 values of the true anomaly f. This condition of deployment is applicable to all cases of resonance rotation regardless of the value of lock number k and orbit eccentricity e.

  5. Lunar Orbit Stability for Small Satellite Mission Design

    Science.gov (United States)

    Dono, Andres

    2015-01-01

    The irregular nature of the lunar gravity field will severely affect the orbit lifetime and behavior of future lunar small satellite missions. These spacecraft need stable orbits that do not require large deltaV budgets for station-keeping maneuvers. The initial classical elements of any lunar orbit are critical to address its stability and to comply with mission requirements. This publication identifies stable regions according to different initial conditions at the time of lunar orbit insertion (LOI). High fidelity numerical simulations with two different gravity models were performed. We focus in low altitude orbits where the dominant force in orbit propagation is the existence of unevenly distributed lunar mass concentrations. These orbits follow a periodic oscillation in some of the classical elements that is particularly useful for mission design. A set of orbital maintenance strategies for various mission concepts is presented.

  6. 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...

  7. The Orbits of Jupiter’s Irregular Satellites

    Science.gov (United States)

    Brozović, Marina; Jacobson, Robert A.

    2017-04-01

    We report on the improved ephemerides for the irregular Jovian satellites. We used a combination of numerically integrated equations of motion and a weighted least-squares algorithm to fit the astrometric measurements. The orbital fits for 59 satellites are summarized in terms of state vectors, post-fit residuals, and mean orbital elements. The current data set appears to be sensitive to the mass of Himalia, which is constrained to the range of GM = 0.13–0.28 km3 s‑2. Here, GM is the product of the Newtonian constant of gravitation, G and the body's mass, M. Our analysis of the orbital uncertainties indicates that 11 out of 59 satellites are lost owing to short data arcs. The lost satellites hold provisional International Astronomical Union (IAU) designations and will likely need to be rediscovered.

  8. Orbit control of a stratospheric satellite with parameter uncertainties

    Science.gov (United States)

    Xu, Ming; Huo, Wei

    2016-12-01

    When a stratospheric satellite travels by prevailing winds in the stratosphere, its cross-track displacement needs to be controlled to keep a constant latitude orbital flight. To design the orbit control system, a 6 degree-of-freedom (DOF) model of the satellite is established based on the second Lagrangian formulation, it is proven that the input/output feedback linearization theory cannot be directly implemented for the orbit control with this model, thus three subsystem models are deduced from the 6-DOF model to develop a sequential nonlinear control strategy. The control strategy includes an adaptive controller for the balloon-tether subsystem with uncertain balloon parameters, a PD controller based on feedback linearization for the tether-sail subsystem, and a sliding mode controller for the sail-rudder subsystem with uncertain sail parameters. Simulation studies demonstrate that the proposed control strategy is robust to uncertainties and satisfies high precision requirements for the orbit flight of the satellite.

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

    Science.gov (United States)

    2006-03-01

    of Aeronautics and Astronautics Graduate School of Engineering and Management Air Force Institute of Technology Air University Air Education and...Space Operations Center ( SPOC ) and other space partners of all conjunctions associated with disposal operations. 5. Post Mission Disposal. Satellites... Education Series, American Institute of Aeronautics and Astronautics, 1987. 3. Betts J. T. “Optimal Interplanetary Orbit Transfers by Direct

  10. 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

  11. 月球重力场环境对月球卫星轨道影响分析%The effect of lunar gravity environment on lunar satellite orbit

    Institute of Scientific and Technical Information of China (English)

    童科伟; 李文清; 刘伟; 高朝辉; 王俊峰

    2012-01-01

    文章分析了月球复杂的重力场环境对月球卫星轨道运行的影响。通过月球卫星冻结轨道与地球卫星冻结轨道的对比分析,结果表明月球重力场存在较大异常,并由此引起月球卫星轨道发生较大漂移。另外,月球冻结轨道在带谐项影响下还存在中等周期的漂移,仅简单考虑带谐项系数无法求得完美的月球冻结系数。由于月球重力场异常对绕月卫星的影响与地球轨道卫星情况相比存在很大差异,因此月球轨道卫星的长期运行与控制策略的设计必须充分考虑此影响%The effect of lunar gravity environment on the lunar satellite orbit is analyzed. The differences between the frozen orbit for lunar and earth satellites are compared first. It is shown that the lunar gravity anomaly is responsible for a large drift to the lunar satellite orbit, the lunar tesseral harmonics are responsible for a moderate period drift to the lunar frozen orbit. Because the effect of lunar gravity anomaly on lunar satellites is quite different from the case for the earth, so for the long-term orbit operation and control for lunar satellites, a different strategy must be adopted than the traditional methods designed for the earth satellite orbit.

  12. Precise orbit determination for the GOCE satellite using GPS

    Science.gov (United States)

    Bock, H.; Jäggi, A.; Švehla, D.; Beutler, G.; Hugentobler, U.; Visser, P.

    Apart from the gradiometer as the core instrument, the first ESA Earth Explorer Core Mission GOCE (Gravity field and steady-state Ocean Circulation Explorer) will carry a 12-channel GPS receiver dedicated for precise orbit determination (POD) of the satellite. The EGG-C (European GOCE Gravity-Consortium), led by the Technical University in Munich, is building the GOCE HPF (High-level Processing Facility) dedicated to the Level 1b to Level 2 data processing. One of the tasks of this facility is the computation of the Precise Science Orbit (PSO) for GOCE. The PSO includes a reduced-dynamic and a kinematic orbit solution. The baseline for the PSO is a zero-difference procedure using GPS satellite orbits, clocks, and Earth Rotation Parameters (ERPs) from CODE (Center for Orbit Determination in Europe), one of the IGS (International GNSS Service) Analysis Centers. The scheme for reduced-dynamic and kinematic orbit determination is based on experiences gained from CHAMP and GRACE POD and is realized in one processing flow. Particular emphasis is put on maximum consistency in the analysis of day boundary overlapping orbital arcs, as well as on the higher data sampling rate with respect to CHAMP and GRACE and on differences originating from different GPS antenna configurations. We focus on the description of the procedure used for the two different orbit determinations and on the validation of the procedure using real data from the two GRACE satellites as well as simulated GOCE data.

  13. The EMC impact of SPS operations on low Earth orbit satellites

    Science.gov (United States)

    Grant, W. B.; Morrison, E. L., Jr.; Davis, K. C.

    1980-01-01

    The susceptibility of various operational and planned low Earth orbit satellites to solar power satellite (SPS) operations was examined. Functional degradation for the electronic systems on LANDSAT, the global positioning system, and the space telescope is described in relation to the amplitude of the SPS illumination components. Analyses include the modes of coupling to devices and subsystems, and performance effects in relation to satellite mission.

  14. Tether de-orbiting of satellites at end of mission

    Science.gov (United States)

    Sanmartin, Juan R.; Sánchez-Torres, Antonio

    2012-07-01

    The accumulation of space debris around the Earth has become critical for Space security. The BETs project, financed by the European Commission through its FP7-Space program, is focusing on preventing generation of new debris by de-orbiting satellites at end of mission. The de-orbiting system considered, involving an electrodynamic bare tape-tether, uses no propellant and no power supply, while generating power for on-board use during de-orbiting. As an example, preliminary results are here presented on a specific orbit/satellite case: 1300 km altitude and 65 degrees inclination, and 500 kg mass. Design tether dimensions are 8 km length, 1.5 cm width, and 0.05 mm thickness; subsystem masses are limited to twice tether mass. Simple calculations, using orbit-averaging, solar mid-cycle phase, and ionospheric and geomagnetic field models, yield 2.6 months time for de-orbiting down to 200 km, with a probability of about 1 percent of debris cutting the tape. References: Sanmartin, J.R., Lorenzini, E.C., and Martinez-Sanchez, M., Electrodynamic Tether Applications and Constraints, J. Space. Rockets 47, 442-456, 2010. Sanmartin, J.R. et al., A universal system to de-orbit satellites at end of life, Journal of Space Technology and Science, to appear.

  15. Experimental Study on the Precise Orbit Determination of the BeiDou Navigation Satellite System

    Directory of Open Access Journals (Sweden)

    Jens Wickert

    2013-03-01

    Full Text Available 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.

  16. Precise Relative Orbit Determination of Twin GRACE Satellites

    Institute of Scientific and Technical Information of China (English)

    ZHAO Qile; HU Zhigang; GUO Jing; LI Min; GE Maorong

    2010-01-01

    When formation flying spacecrafts are used as platform to gain earth oriented observation, precise baselines between these spacecrafts are always essential. Gravity recovery and climate experiment (GRACE) mission is aimed at mapping the global gravity field and its variation. Accurate baseline of GRACE satellites is necessary for the gravity field modeling. The determination of kinematic and reduced dynamic relative orbits of twin satellites has been studied in this paper, and an accuracy of 2 mm for dynamic relative orbits and 5 mm for kinematic ones can be obtained, whereby most of the double difference onboard GPS ambiguities are resolved.

  17. Orbital rotations of a satellite. Case study: GOCE

    Science.gov (United States)

    Baur, O.; Grafarend, E. W.

    Considering a satellite orbit as a space curve in terms of Differential Geometry, we succeeded to merge orbital rotation and curvature/torsion by means of Cartan connection. Here we transform the Frenet frame of reference of the space curve to the Kepler frame of reference ("along track", "cross track", "quasi-radial") of the satellite orbit by means of Meusnier's Lemma. As a case study, we identify the spectrum of orbital rotation frequencies relative to a GOCE satellite configuration. In particular, we identify more than one rotational period. For a moving frame of reference of type Frenet, periods in the range of the time of revolution of the satellite as well as half the time of revolution appear, whereas even periods of a third the revolution time become visible for the Kepler frame of reference. We describe moving frame rotations with respect to the quasi-inertial frame of reference, namely the angular velocities around the base vectors, by means of curvature measures. This allows to calculate frame rotations by geometric orbit information only (GPS track), i.e. apart from gradiometer measurements. Among other things, we identify the angular velocity relative to the second base vector becoming strictly zero in case of the Frenet frame of reference.

  18. Smaller Satellite Operations Near Geostationary Orbit

    Science.gov (United States)

    2007-09-01

    Hubble_Space_Telescope>. 29 Heiner Klinkrad . Space Debris: Models and Risk Analysis. Chichester, UK. Springer, 2006. 32. 31 threshold, the satellites would be...Heiner Klinkrad . Space Debris: Models and Risk Analysis. Chichester, UK. Springer, 2006. 32. 35 Appendix B. 39 throughout such a maneuver36, which...46 Heiner Klinkrad . Space Debris: Models and Risk Analysis. Chichester, UK. Springer, 2006. 32. 47 S. Kilston. Ikonos-2, Block-1

  19. Copernicus POD Service: Orbit Determination of the Sentinel Satellites

    Science.gov (United States)

    Peter, Heike; Fernández, Jaime; Ayuga, Francisco; Féménias, Pierre

    2016-04-01

    The Copernicus POD (Precise Orbit Determination) Service is part of the Copernicus Processing Data Ground Segment (PDGS) of the Sentinel-1, -2 and -3 missions. A GMV-led consortium is operating the Copernicus POD Service being in charge of generating precise orbital products and auxiliary data files for their use as part of the processing chains of the respective Sentinel PDGS. Sentinel-1A was launched in April 2014 while Sentinel-2A was on June 2015 and both are routinely operated since then. Sentinel-3A is expected to be launched in February 2016 and Sentinel-1B is planned for spring 2016. Thus the CPOD Service will be operating three to four satellites simultaneously in spring 2016. The satellites of the Sentinel-1, -2, and -3 missions are all equipped with dual frequency high precision GPS receivers delivering the main observables for POD. Sentinel-3 satellites will additionally be equipped with a laser retro reflector for Satellite Laser Ranging and a receiver for DORIS tracking. All three types of observables (GPS, SLR and DORIS) will be used routinely for POD. The POD core of the CPOD Service is NAPEOS (Navigation Package for Earth Orbiting Satellites) the leading ESA/ESOC software for precise orbit determination. The careful selection of models and inputs is important to achieve the different but very demanding requirements in terms of orbital accuracy and timeliness for the Sentinel -1, -2 & -3 missions. The three missions require orbital products with various latencies from 30 minutes up to 20-30 days. The accuracy requirements are also different and partly very challenging, targeting 5 cm in 3D for Sentinel-1 and 2-3 cm in radial direction for Sentinel-3. Although the characteristics and the requirements are different for the three missions the same core POD setup is used to the largest extent possible. This strategy facilitates maintenance of the complex system of the CPOD Service. Updates in the dynamical modelling of the satellite orbits, e

  20. Earth Observing Satellite Orbit Design Via Particle Swarm Optimization

    Science.gov (United States)

    2014-08-01

    Earth Observing Satellite Orbit Design Via Particle Swarm Optimization Sharon Vtipil ∗ and John G. Warner ∗ US Naval Research Laboratory, Washington...number of passes per day given a satellite’s orbital altitude and inclination. These are used along with particle swarm optimization to determine optimal...well suited to use within a meta-heuristic optimization method such as the Particle Swarm Optimizer (PSO). This method seeks to find the optimal set

  1. Atmospheric Drag Perturbation in an Autonomous Orbit Determination for Satellite

    Institute of Scientific and Technical Information of China (English)

    XUE shen-fang; JIN Sheng-zhen; NING Shu-nian; SUN Cai-hong

    2005-01-01

    In this paper, an autonomous orbit determination method for satellite using a large field of view star sensor is presented. The simulation of orbit under atmospheric drag perturbation are given with expanded Kalman filtering.The large field of view star sensor has the same precision as star sensor and a sufficient filed of view. Therefore ,the refraction stars can be observed more accurately in real time. The geometric relation between the refracted starlight and the earth can be determined by tangent altitude of the refraction starlight. And then the earth enter can be determined in satellite body frame. The simulation shows that the precision of the mean square deviation of satellite's position and velocity is 5m and 0.01m/s respectively. The calculated decrement of the semi-major axis in one day is close to the theoretical result, and the absolute error is in the range of decimeter when the altitude of orbit is 750 km. The simulateion of orbit of different initial semi-major axis shows that the higher the altitude of orbit is, the smaller the decrement of the semi-major axis is, and when the altitude of orbit is 1700 km the decimeter of the semi-major axis is 10-7km.

  2. Selection of the best initial orbital elements of satellite based on fuzzy integration evaluation method

    Institute of Scientific and Technical Information of China (English)

    Yang Yong'an; Zhang Hongwei; Feng Zuren; Luo Yongjin

    2006-01-01

    The fuzzy integration evaluation method (FIEM) is studied in order to select the best orbital elements from the multi-group initial orbits determined by a satellite TT&C (Tracking, Telemetry and Control) center with all kinds of data sources. By employing FIEM together with the experience of TT&C experts, the index system to evaluate the selection of the best initial orbits is established after the data sources and orbit determination theories are studied. Besides, the concrete steps in employing the method are presented. Moreover, by taking the objects to be evaluated as evaluation experts, the problem of how to generate evaluation matrices is solved. Through practical application, the method to select the best initial orbital elements has been proved to be flexible and effective. The originality of the method is to find a new evaluation criterion (comparing the actually tracked orbits) replacing the traditional one (comparing the nominal orbits) for selecting the best orbital elements.

  3. Precise Orbit Determination of Earth's Satellites for Climate Change Investigation

    Science.gov (United States)

    Vespe, Francesco

    The tremendous improvement of the gravity field models which we are achieving with the last Earth's satellite missions like, CHAMP, GRACE and GOCE devoted to its recovery could make feasibile the use of precise orbit determination (POD) of Earth satellites as a tool for sensing global changes of some key atmosphere parameters like refractivity and extinction. Such improvements indeed, coupled with the huge number of running Earth's satellites and combinations of their orbital parameters (namely the nodes) in a gravity field free fashion (hereafter GFF) can magnify the solar radiation pressure acting on medium earth orbit satellites :GPS, Etalon and, in near real future GALILEO and its smooth modulation through the Earth's atmosphere (penumbra). We would remind that The GFF technique is able to cancel out with "n" satellite orbital parameters the first n-1 even zonal harmonics of the gravity field. Previously it was demonstrated that the signal we want to detect could in principle emerge from the noise threshold but, more refined models of the atmosphere would be needed to perform a more subtle analysis. So we will re-compute the signal features of penumbra by applying more refined atmospheric models. The analysis will be performed by including in GFF Earth's satellites equipped with DORIS systems (Jason, Spot 2-3-4-5, ENVISAT etc.) other than those ranged with SLR and GPS. The introduction of DORIS tracked satellites indeed will allow to cancel higher and higher order of even zonal harmonics and will make still more favourable the signal to noise budget. The analysis will be performed over a time span of at least few tens of years just to enhance probable climate signatures.

  4. Long-term evolution of navigation satellite orbits: GPS/GLONASS/GALILEO

    Science.gov (United States)

    Chao, C.; Gick, R.

    Earlier studies conducted a The Aerospace Corporation discovered that the GPSt Block II satellites placed in disposal orbits can eventually, perhaps in 20 to 40 years, reenter into the operating constellation. This is because the disposal orbits, while circular initially, evolve int o orbits with significant eccentricity mostly as the result of sun-moon gravitational perturbations. Options of minimizing the eccentricity growth include reducing initial eccentricity of the disposal orbit and inserting into an orbit with a favorable argument of perigee. A recent study was performed to examine whether the same long-term eccentricity evolution exists for the disposal orbits of other navigation satellite systems such as GLONASS and GALILEO. The non-operational GPS Block I satellites are included in the study as well, because the orbits are at 63.4 deg inclination, which is different from that of the GPS Block II satellites. Similar to the earlier studies, long-term perturbations and stability of these orbits were understood through analytical and numerical investigations. Two-hundred-year semi-analytic integration revealed interesting facts about the orbit stability. Initially near circular, these types of orbits may evolve into orbits with large eccentricity (as much as 0.7 over 150 years). Analytical approximations through doubly-averaged equations reveal that the cause is due to the resonance induced by Sun/moon and J2 secular perturbations. A total of 113 non-operational GLONASS satellites and upper stages and 10 GPS/Block I satellites were propagated for 200 years using a high-precision semi-analytical propagator (MEANPROP). Results show that the GLONASS satellites will start to enter the operating GPS constellation after 40 years. The uncovered resonance effect is strongly dependent on o bit inclination and altitude. The effect becomes morer pronounced for GALILEO orbits due to a higher altitude, 3000 km above GPS. Strategies to minimize the significant

  5. 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......, based upon measurements from satellite sensors. The meteor that fell on 15 February 2013 is used as an example and the resulting orbit is in broad agreement with estimates from other observations. This new technique represents an alternative method for trajectory determination that may be particularly...

  6. Orbits of the small inner satellites of Jupiter

    Science.gov (United States)

    Synnott, S. P.

    1984-01-01

    Voyager images led to the discovery of the three small inner satellites of Jupiter, Adrastea, Metis, and Thebe. Attention is presently given to orbital parameter estimates and associated uncertainties that have been determined from Voyager imaging data, the achievable angular accuracy of which is about 0.00005 rad.

  7. 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...

  8. Autonomous robotic operations for on-orbit satellite servicing

    Science.gov (United States)

    Ogilvie, Andrew; Allport, Justin; Hannah, Michael; Lymer, John

    2008-04-01

    The Orbital Express Demonstration System (OEDS) flight test successfully demonstrated technologies required to autonomously service satellites on-orbit. The mission's integrated robotics solution, the Orbital Express Demonstration Manipulator System (OEDMS) developed by MDA, performed critical flight test operations. The OEDMS comprised a six-jointed robotic manipulator arm and its avionics, non-proprietary servicing and ORU (Orbital Replacement Unit) interfaces, a vision and arm control system for autonomous satellite capture, and a suite of Ground Segment and Flight Segment software allowing script generation and execution under supervised or full autonomy. The arm was mounted on ASTRO, the servicer spacecraft developed by Boeing. The NextSat, developed by Ball Aerospace, served as the client satellite. The OEDMS demonstrated two key goals of the OEDS flight test: autonomous free-flyer capture and berthing of a client satellite, and autonomous transfer of ORUs from servicer to client and back. The paper provides a description of the OEDMS and the key operations it performed.

  9. Improving satellite vulnerability assessment to untrackable orbital debris

    Science.gov (United States)

    Welty, Nathan; Schaefer, Frank; Rudolph, Martin; Destefanis, Roberto; Grassi, Lilith

    2012-07-01

    The projected growth in the untrackable orbital debris population will place an increased emphasis on satellite vulnerability assessments during both design and mission operations. This study presents an enhanced method for assessing satellite vulnerability to untrackable orbital debris that expands on traditional practices. By looking beyond structural penetration of the spacecraft, the method predicts the survivability of individual components and the associated degradation of system functionality resulting from untrackable debris impacts. A new risk assessment tool, the Particle Impact Risk and Vulnerability Assessment Tool (PIRAT), has been developed based on this method and is also presented here. It interfaces with both the NASA ORDEM2000 and ESA MASTER-2009 debris models and has been validated against the benchmark test cases from the Inter-Agency Space Debris Coordination Committee (IADC). This study concludes with an example vulnerability assessment using PIRAT for a generic Earth observation satellite in a Sun-synchronous low-Earth orbit. The results illustrate the additional insight provided by this method that can be used to improve the robustness of future satellite designs and mitigate the overall mission risk posed by untrackable orbital debris.

  10. An Earth Orbiting Satellite Service and Repair Facility

    Science.gov (United States)

    Berndt, Andrew; Cardoza, Mike; Chen, John; Daley, Gunter; Frizzell, Andy; Linton, Richard; Rast, Wayne

    1989-01-01

    A conceptual design was produced for the Geosynchronous Satellite Servicing Platform (GSSP), an orbital facility capable of repairing and servicing satellites in geosynchronous orbit. The GSSP is a man-tended platform, which consists of a habitation module, operations module, service bay and truss assembly. This design review includes an analysis of life support systems, thermal and power requirements, robotic and automated systems, control methods and navigation, and communications systems. The GSSP will utilize existing technology available at the time of construction, focusing mainly on modifying and integrating existing systems. The entire facility, along with two satellite retrieval vehicles (SRV), will be placed in geosynchronous orbit by the Advanced Launch System. The SRV will be used to ferry satellites to and from the GSSP. Technicians will be transferred from Earth to the GSSP and back in an Apollo-derived Crew Transfer Capsule (CTC). These missions will use advanced telerobotic equipment to inspect and service satellites. Four of these missions are tentatively scheduled per year. At this rate, the GSSP will service over 650 satelites during the projected 25 year lifespan.

  11. Advances in precision orbit determination of GRACE satellites

    Science.gov (United States)

    Bettadpur, Srinivas; Save, Himanshu; Kang, Zhigui

    The twin Gravity Recovery And Climate Experiment (GRACE) satellites carry a complete suite of instrumentation essential for precision orbit determination (POD). Dense, continuous and global tracking is provided by the Global Positioning System receivers. The satellite orientation is measured using two star cameras. High precision measurements of non-gravitational accel-erations are provided by accelerometers. Satellite laser ranging (SLR) retroreflectors are used for collecting data for POD validation. Additional validation is provided by the highly precise K-Band ranging system measuring distance changes between the twin GRACE satellites. This paper presents the status of POD for GRACE satellites. The POD quality will be vali-dated using the SLR and K-Band ranging data. The POD quality improvement from upgraded modeling of the GPS observations, including the transition to the new IGS05 standards, will be discussed. In addition, the contributions from improvements in the gravity field modeling -partly arising out of GRACE science results -will be discussed. The aspects of these improve-ments that are applicable for the POD of other low-Earth orbiting satellites will be discussed as well.

  12. Packet routing algorithm for polar orbit LEO satellite constellation network

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Broadband satellite networks are capable of providing global coverage and support various services. The networks constructed by Low Earth Orbit (LEO) satellite constellations have attracted great interests because of their short round-trip delays and wide bandwidths. A challenging problem is to develop a simple and efficient packet routing algorithm for the LEO satellite constellation network. This paper presents a SpiderWeb Topological Network (SWTN) and a distributed packet routing algorithm for the LEO satellite constellation network based on the SWTN. The algorithm gives the minimum propagation delay paths with low computational complexity and requires no routing tables, which is practical for on-board processing. The performance of the algorithm is demonstrated through simulations.

  13. Orbit Control of Fly-around Satellite with Highly Eccentric Orbit Using Solar Radiation Pressure

    Science.gov (United States)

    Yong-gang, Hou; Chang-yin, Zhao; Ming-jiang, Zhang; Rong-yu, Sun

    2017-01-01

    The method of controlling highly eccentric accompanying flight orbit using the solar wing is proposed in this paper. The formation is maintained by controlling the orbit of the accompanying satellite (follower). The accompanying satellite rotates around its inertial principal axis with a constant angular velocity. The control on the accompanying satellite is divided into the in-plane control and out-of-plane control. The in-plane control is superior to the out-of-plane control. The out-of-plane control force is applied when the in-plane error is eliminated or the in-plane control force can not be supplied due to some geometrical factors. By the sliding mode control method, the magnitude and direction of the control force required by the in-plane orbit control are calculated. Then accordingly, the expression of the solar wing orientation with respect to the satellite body in the control process is derived, so that by adjusting the orientation of the solar wing, the required control force can be obtained. Finally, the verification on this method is performed by numerical simulations, including the orbit adjustment, error elimination, and the orbit maintenance. It is shown that this method can keep the error less than 5 m, and it is feasible for the space formation flight.

  14. Astrometric positioning and orbit determination of geostationary satellites

    Science.gov (United States)

    Montojo, F. J.; López Moratalla, T.; Abad, C.

    2011-03-01

    In the project titled “Astrometric Positioning of Geostationary Satellite” (PASAGE), carried out by the Real Instituto y Observatorio de la Armada (ROA), optical observation techniques were developed to allow satellites to be located in the geostationary ring with angular accuracies of up to a few tenths of an arcsec. These techniques do not necessarily require the use of large telescopes or especially dark areas, and furthermore, because optical observation is a passive method, they could be directly applicable to the detection and monitoring of passive objects such as space debris in the geostationary ring.By using single-station angular observations, geostationary satellite orbits with positional uncertainties below 350 m (2 sigma) were reconstructed using the Orbit Determination Tool Kit software, by Analytical Graphics, Inc. This software is used in collaboration with the Spanish Instituto Nacional de Técnica Aeroespacial.Orbit determination can be improved by taking into consideration the data from other stations, such as angular observations alone or together with ranging measurements to the satellite. Tests were carried out combining angular observations with the ranging measurements obtained from the Two-Way Satellite Time and Frequency Transfer technique that is used by ROA’s Time Section to carry out time transfer with other laboratories. Results show a reduction of the 2 sigma uncertainty to less than 100 m.

  15. 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.

  16. Control of satellite clusters in elliptic orbit with limited communication.

    Science.gov (United States)

    Chichka, David F; Belanger, Gene; Speyer, Jason L

    2004-05-01

    The cooperative control of satellite clusters in elliptical, low-Earth orbit is studied, with the goal of minimizing the necessary information passed among the individual satellites in the cluster. We investigate two possible control paradigms in this paper. The system is described using linearized equations of motion, allowing it to be expressed as a time-varying linear system. The control objective is to attain a required formation at a specified point along the orbit. A decentralized controller is used, in which each satellite maintains a local estimate of the overall state of the cluster. These estimates, along with any control information, are shared after any satellite executes a control action. The second paradigm is an extension of the first, in which state estimates are never shared, and only the control information is passed. In each case, less information being passed results in a higher computational burden on each satellite. Simulation results show cyclic errors, likely induced by higher-order terms in eccentricity and inclinations. The controller that shares state estimates performs much better than the controller that passes only control information.

  17. Geosynchronous Earth Orbit/Low Earth Orbit Space Object Inspection and Debris Disposal: A Preliminary Analysis Using a Carrier Satellite With Deployable Small Satellites

    OpenAIRE

    Crockett, Derick A.

    2013-01-01

    Detailed observations of geosynchronous satellites from earth are very limited. To better inspect these high altitude satellites, the use of small, refuelable satellites is proposed. The small satellites are stationed on a carrier platform in an orbit near the population of geosynchronous satellites. A carrier platform equipped with deployable, refuelable SmallSats is a viable option to inspect geosynchronous satellites. The propellant requirement to transfer to a targeted geosynchronous sate...

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

    Science.gov (United States)

    Karacalioglu, Arif Goktug; Stupl, Jan

    2016-01-01

    their desired orbits beyond the restrictions of the launch vehicle used. These near future orbital injection technologies are also covered in the developed scenario. Using the above-mentioned background information, this study aims to examine how the orbital debris environment will be affected from the new dynamics of the emerging space markets. We developed a simulation tool that is capable of propagating the objects in a given deployment scenario with variable-sized time-steps as small as one second. Over the course of the run, the software also detects collisions; additional debris objects are then created according to the NASA breakup model and are fed back into the simulation framework. Examining the simulation results, the total number of particles to accumulate in different orbits can be monitored and the number of conjunctions can be tracked to assess the collision risks. The simulation makes it possible to follow the short- and long-term effects of a particular satellite or constellation on the space environment. Likewise, the effects of changes in the debris environment on a particular satellite or constellation can be evaluated. It is authors 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.

  19. The effect of temperature cycling typical of low earth orbit satellites on thin films of YBa2Cu3O(7-x)

    Science.gov (United States)

    Mogro-Campero, A.; Turner, L. G.; Bogorad, A.; Herschitz, R.

    1990-01-01

    The refrigeration of superconductors in space poses a challenging problem. The problem could be less severe if superconducting materials would not have to be cooled when not in use. Thin films of the YBa2Cu3O(7-x) (YBCO) superconductor were subjected to thermal cycling, which was carried out to simulate a large number of eclipses of a low earth orbit satellite. Electrical measurements were performed to find the effect of the temperature cycling. Thin films of YBCO were formed by coevaporation of Y, BaF2, and Cu and postannealing in wet oxygen at 850 C for 3.5 h. The substrates used were (100) SrTiO3, polycrystalline alumina, and oxidized silicon; the last two have an evaporated zirconia layer. Processing and microstructure studies of these types of films have been published. THe zero resistance transition temperatures of the samples used in this study were 91, 82, and 86 K, respectively. The samples were characterized by four point probe electrical measurements as a function of temperature. The parameters measured were: the zero resistance transition temperature, the 10 to 90 percent transition width, and the room temperature resistance, normalized to that measured before temperature cycling. The results for two samples are presented. Each sample had a cumulative exposure. Cycling in atmospheric pressure nitrogen was performed at a rate of about 60 cycles per day, whereas in vacuum the rate was only about 10 cycles per day. The results indicate only little or no changes in the parameters measured. Degradation of superconducting thin films of YBCO has been reported due to storage in nitrogen. It is believed that the relatively good performance of films after temperature cycling is related to the fact that BaF2 was used as an evaporation source. The latest result on extended temperature cycling indicates significant degradation. Further tests of extended cycling will be carried out to provide additional data and to clarify this preliminary finding.

  20. Laser beaming demonstrations to high-orbit satellites

    Science.gov (United States)

    Lipinski, Ronald J.; Meister, Dorothy C.; Tucker, Steve D.; Fugate, Robert Q.; Leatherman, Phillip; Maes, Carl F.; Lange, W. Joseph; Cowan, William D.; Meulenberg, Andrew; Cleis, Richard A.; Spinhirne, James M.; Ruane, Raymond E.; Michie, Robert B.; Vonderhaar, Donald F.

    1994-05-01

    A team of Phillips Laboratory, COMSAT Laboratories, and Sandia National Laboratories plans to demonstrate state-of-the-art laser-beaming demonstrations to high-orbit satellites. The demonstrations will utilize the 1.5-m diameter telescope with adaptive optics at the AFPL Starfire Optical Range (SOR) and a ruby laser provided by the Air Force and Sandia (1 - 50 kW and 6 ms at 694.3 nm). The first targets will be corner-cube retro-reflectors left on the moon by the Apollo 11, 14, and 15 landings. We attempt to use adaptive optics for atmospheric compensation to demonstrate accurate and reliable beam projection with a series of shots over a span of time and shot angle. We utilize the return signal from the retro- reflectors to help determine the beam diameter on the moon and the variations in pointing accuracy caused by atmospheric tilt. This is especially challenging because the retro-reflectors need to be in the lunar shadow to allow detection over background light. If the results from this experiment are encouraging, we will at a later date direct the beam at a COMSAT satellite in geosynchronous orbit as it goes into the shadow of the earth. We utilize an onboard monitor to measure the current generated in the solar panels on the satellite while the beam is present. A threshold irradiance of about 4 W/m2 on orbit is needed for this demonstration.

  1. An Orbiting Standards Platform for communication satellite system RF measurements

    Science.gov (United States)

    Wallace, R. G.; Woodruff, J. J.

    1978-01-01

    The Orbiting Standards Platform (OSP) is a proposed satellite dedicated to performing RF measurements on space communications systems. It would consist of a quasi-geostationary spacecraft containing an ensemble of calibrated RF sources and field strength meters operating in several microwave bands, and would be capable of accurately and conveniently measuring critical earth station and satellite RF performance parameters, such as EIRP, gain, figure of merit (G/T), crosspolarization, beamwidth, and sidelobe levels. The feasibility and utility of the OSP concept has been under joint study by NASA, NBS, Comsat and NTIA. A survey of potential OSP users was conducted by NTIA as part of this effort. The response to this survey, along with certain trends in satellite communications system design, indicates a growing need for such a measurement service.

  2. Validation of GOCE Satellite Gravity Gradient Observations by Orbital Analysis

    Science.gov (United States)

    Visser, P.

    The upcoming European Space Agency ESA Gravity Field and Steady-State Ocean Circular Explorer GOCE mission foreseen to be launched in 2007 will carry a highly sensitive gradiometer consisting of 3 orthogonal pairs of ultra-sensitive accelerometers A challenging calibration procedure has been developed to calibrate the gradiometer not only before launch by a series of on-ground tests but also after launch by making use of on-board cold-gas thrusters to provoke a long series of gradiometer shaking events which will provide observations for its calibration This calibration can be checked by a combined analysis of GPS Satellite-to-Satellite Tracking SST and Satellite Gravity Gradient SGG observations An assessment has been made of how well SGG calibration parameters can be estimated in a combined orbit and gravity field estimation from these observations

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  4. 47 CFR 25.146 - Licensing and operating authorization provisions for the non-geostationary satellite orbit fixed...

    Science.gov (United States)

    2010-10-01

    ... provisions for the non-geostationary satellite orbit fixed-satellite service (NGSO FSS) in the bands 10.7 GHz... Licensing and operating authorization provisions for the non-geostationary satellite orbit fixed-satellite... submitted for the proposed non-geostationary satellite orbit fixed-satellite service (NGSO FSS) system...

  5. On-orbit target tracking and inspection by satellite formation

    Institute of Scientific and Technical Information of China (English)

    Guang Zhai; Jingrui Zhang; Zhicheng Zhou

    2013-01-01

    A new type of estimator is developed for the satel-lite formation to track and inspect on-orbit targets. The fol ower satel ite in the formation works without relative sensors, and its target pointing commands are derived based on relative orbital dynamics. The centralized estimator based on truth measurement is designed, however, this estimator is proved unstable because of the lack of necessary measurement information. After that, an alternative estimator based on pseudo measurement is designed, and its observability and control ability are analyzed to qualitatively evaluate the convergence performance. Final y, an on-orbit target inspection scenario is numerical y simulated to verify the perfor-mance of the estimator based on pseudo measurement.

  6. Demonstration on the indexes design of gravity satellite orbit parameters in the low-low satellite-to-satellite tracking mode

    Directory of Open Access Journals (Sweden)

    Liu Xiaogang

    2013-02-01

    Full Text Available Combining with the exigent demand of the development of satellite gravimetry system in China, aiming at the determination of technical indexes of gravity satellite orbit parameters, on the basis of the numerical experiments and results analysis, the design indexes of gravity satellite orbit height, inter-satellite range and the orbit inclination are analyzed and calculated, and the issues towards twin gravity satellites such as coherence requirement of the orbit semi-major axes, control requirement of the pitch angle and time interval requirement to keep twin satellites formation in mobility are discussed. Results show that the satellite orbit height is 400 km to 500 km, the inter-satellite range is about 220 km, the satellite orbit inclination is between polar orbit and sun-synchronous orbit, the semi-major axes difference of twin satellites orbit is within ±70. 146 m, the pitch angle of twin satellites is about 0.9 degree, and the time interval to keep twin satellites formation in mobility is 7 days to 15 days.

  7. Nodding feed antenna for communications with satellites in synchronous orbit

    Science.gov (United States)

    Smetana, J.; Zavesky, R.

    1978-01-01

    The design, fabrication, and performance of a parabolic, ground receiving antenna system with a feed that nods in one axis producing a maximum beam deviation 1.1 deg from boresight is described. The antenna design was: (1)to lower the weight (and the subsequent cost) of the supporting structure and the actuator motors for a tracking antenna by moving just the feed; (2) to use a manual tracking system eliminating the need for expensive electronic controls or computers; (3) to provide for several hours of unattended operation; and (4)to permit operation of the antenna by unskilled personnel. Also described are some physical and orbital phenomenon that effect the operation or design of the antenna. One is the motion of a nearly geostationary satellite due to gravitational forces from the sun, the moon, and other stellar bodies. Others are the rotation of the nodding axis and the feed polarization as a function of the location of the station on the earth. A comparison of per unit cost was made for one unit and a quantity of 100.

  8. Satellite broadcasting experiments and in-orbit performance of BSE

    Science.gov (United States)

    Shimoseko, S.; Yamamoto, M.; Kajikawa, M.; Arai, K.

    1981-09-01

    The Japanese medium-scale Broadcasting Satellite for Experimental Purposes (BSE) was launched in April 1978 and placed in a geostationary orbit at 110 deg E longitude. Two transmitters with bandwidths of 50 MHz and 80 MHz were mounted on the BSE transponder to conduct experiments on various television signals; no significant variation in transmission characteristics was observed during the two-year period. Rain attenuation characteristics in the 12 GHz band were studied and a value of 6.6 dB was registered in Owase, one of the most rainy areas in Japan. The strength of the rain scatter wave of the BSE uplink signal was measured to investigate the characteristics between broadcasting satellite uplink and a terrestrial link in the 14 GHz band. Uplink power control, important for the efficient operation of satellite communications systems, was shown to compensate the variations in receiving power due to fluctuations in the beam pointing of the satellite antenna. Routine operations were performed to check the three-axis attitude control, stationkeeping, housekeeping, and the bus equipment. The electrical power, secondary propulsion, thermal control, and communication subsystems were also evaluated. The first operations 1 broadcasting satellite is scheduled to be launched early in 1984.

  9. 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.

  10. Shift control method for the local time at descending node based on sun-synchronous orbit satellite

    Institute of Scientific and Technical Information of China (English)

    Yang Yong'an; Feng Zuren; Sun Linyan; Tan Wei

    2009-01-01

    This article analyzes the shift factors of the descending node local time for sun-synchronous satellites and proposes a shift control method to keep the local time shift within an allowance range. It is found that the satellite orbit design and the orbit injection deviation are the causes for the initial shift velocity, whereas the atmospheric drag and the sun gravitational perturbation produce the shift acceleration. To deal with these shift factors, a shift control method is put forward, through such methods as orbit variation design, orbit altitude, and inclination keeping control. The simulation experiment and practical application have proved the effectiveness of this control method.

  11. 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.

  12. Operational high latitude surface irradiance products from polar orbiting satellites

    Science.gov (United States)

    Godøy, Øystein

    2016-12-01

    It remains a challenge to find an adequate approach for operational estimation of surface incoming short- and longwave irradiance at high latitudes using polar orbiting meteorological satellite data. In this presentation validation results at a number of North Atlantic and Arctic Ocean high latitude stations are presented and discussed. The validation results have revealed that although the method works well and normally fulfil the operational requirements, there is room for improvement. A number of issues that can improve the estimates at high latitudes have been identified. These improvements are partly related to improved cloud classification using satellite data and partly related to improved handling of multiple reflections over bright surfaces (snow and sea ice), especially in broken cloud conditions. Furthermore, the availability of validation sites over open ocean and sea ice is a challenge.

  13. Artificial Crater Formation on Satellite Surfaces Using an Orbiting Railgun

    Science.gov (United States)

    Dissly, R. W.; Miller, K. L.; Carlson, R. J.

    2003-01-01

    The specification of greater than 45kW of disposable power available on the JIMO spacecraft raises the possibility of a new class of instrumentation that has utility at such power levels. In this presentation we discuss the concept of an electromagnetic mass driver that can launch projectiles from orbit around one of the Galilean satellites directed on a trajectory that will impact the satellite surface. The resulting impact will create a crater that will provide information on the mechanical properties of surface and near-surface materials, expose subsurface materials for remote spectral identification, and form a vapor cloud that can be sensed for composition either remotely or in-situ. An analog for such a controlled cratering experiment is Deep Impact, a mission to observe the crater and ensuing ejecta cloud formed by a ballistic projectile into a comet surface in July, 2005.

  14. Artificial Crater Formation on Satellite Surfaces Using an Orbiting Railgun

    Science.gov (United States)

    Dissly, R. W.; Miller, K. L.; Carlson, R. J.

    2003-01-01

    The specification of greater than 45kW of disposable power available on the JIMO spacecraft raises the possibility of a new class of instrumentation that has utility at such power levels. In this presentation we discuss the concept of an electromagnetic mass driver that can launch projectiles from orbit around one of the Galilean satellites directed on a trajectory that will impact the satellite surface. The resulting impact will create a crater that will provide information on the mechanical properties of surface and near-surface materials, expose subsurface materials for remote spectral identification, and form a vapor cloud that can be sensed for composition either remotely or in-situ. An analog for such a controlled cratering experiment is Deep Impact, a mission to observe the crater and ensuing ejecta cloud formed by a ballistic projectile into a comet surface in July, 2005.

  15. Aerodynamic Stability of Satellites in Elliptic Low Earth Orbits

    CERN Document Server

    Bailey, Matthew; Mancas, Stefan C; Udrea, Bogdan; Umeadi, Uchenna

    2013-01-01

    Topical observations of the thermosphere at altitudes below $200 \\, km$ are of great benefit in advancing the understanding of the global distribution of mass, composition, and dynamical responses to geomagnetic forcing, and momentum transfer via waves. The perceived risks associated with such low altitude and short duration orbits has prohibited the launch of Discovery-class missions. Miniaturization of instruments such as mass spectrometers and advances in the nano-satellite technology, associated with relatively low cost of nano-satellite manufacturing and operation, open an avenue for performing low altitude missions. The time dependent coefficients of a second order non-homogeneous ODE which describes the motion have a double periodic shape. Hence, they will be approximated using Jacobi elliptic functions. Through a change of variables the original ODE will be converted into Hill's ODE for stability analysis using Floquet theory. We are interested in how changes in the coefficients of the ODE affect the ...

  16. 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.

  17. Orbit and Attitude Control of Asymmetric Satellites in Polar Near-Circular Orbit

    Directory of Open Access Journals (Sweden)

    Wei Zhao

    2009-10-01

    Full Text Available In this paper, the general problem about the orbit and attitude dynamic model is discussed. A feedback linearization control method is introduced for this model. Due to the asymmetric structure, the orbital properties of such satellites are the same as traditional symmetric ones, but the attitude properties are greatly different from the symmetric counterparts. With perturbations accumulate with time, the attitude angles increase periodically with time, but the orbital elements change much slower than the attitude angles. In the attitude dynamic model, chaos could appear. Traditional linear controllers can not compensate enough for asymmetric satellite when the mission is complex, especially in maneuver missions. Thus nonlinear control method is required to solve such problem in large scale. A feedback linearization method, one robust nonlinear control method, is introduced and applied to the asymmetric satellite in this paper. Some simulations are also given and the results show that feedback linearization controller not only stabilizes the system, but also exempt the chaos in the system.

  18. 低轨卫星精密定轨中重力场模型误差的补偿%Reducing Influence of Gravity Model Error in Precise Orbit Determination of Low Earth Orbit Satellites

    Institute of Scientific and Technical Information of China (English)

    郭金来; 胡敏; 赵齐乐; 郭道玉

    2007-01-01

    Based on the orbit integration and orbit fitting method, the influence of the characters of the gravity model, with different precisions, on the movement of low Earth orbit satellites was studied. The way and the effect of absorbing the influence of gravity model error on CHAMP and GRACE satellite orbits, using linear and periodical empirical acceleration models and the so-called "pseudo-stochastic pulses" model, were also analyzed.

  19. Formation flying orbit design for the distributed synthetic aperture radar satellite

    Institute of Scientific and Technical Information of China (English)

    CHEN Jie; ZHOU Yinqing; LI Chunsheng

    2004-01-01

    Formation flying orbit design is one of the key technologies for system design and performance analysis of the distributed SAR satellites. The approximately analytic solution of the passive stable formation flying orbit elements is explored based on the expansion form of Kepler's equation. A new method of orbital parameters design for three-dimensional formation flying SAR satellites is presented, and the precision of the orbital elements is analyzed. Formation flying orbit elements are calculated for the L-Band distributed SAR satellites using the formulas deduced in this paper. The accuracy of the orbital elements is validated by the computer simulation results presented in this paper.

  20. 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.

  1. Guidance and adaptive-robust attitude & orbit control of a small information satellite

    Science.gov (United States)

    Somov, Ye.; Butyrin, S.; Somov, S.; Somova, T.; Testoyedov, N.; Rayevsky, V.; Titov, G.; Yakimov, Ye.; Ovchinnikov, A.; Mathylenko, M.

    2017-01-01

    We consider a small information satellite which may be placed on an orbit with altitude from 600 up to 1000 km. The satellite attitude and orbit control system contains a strap-down inertial navigation system, cluster of four reaction wheels, magnetic driver and a correcting engine unit with eight electro-reaction engines. We study problems on design of algorithms for spatial guidance, in-flight identification and adaptive-robust control of the satellite motion on sun-synchronous orbit.

  2. 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.

  3. A mission-oriented orbit design method of remote sensing satellite for region monitoring mission based on evolutionary algorithm

    Science.gov (United States)

    Shen, Xin; Zhang, Jing; Yao, Huang

    2015-12-01

    Remote sensing satellites play an increasingly prominent role in environmental monitoring and disaster rescue. Taking advantage of almost the same sunshine condition to same place and global coverage, most of these satellites are operated on the sun-synchronous orbit. However, it brings some problems inevitably, the most significant one is that the temporal resolution of sun-synchronous orbit satellite can't satisfy the demand of specific region monitoring mission. To overcome the disadvantages, two methods are exploited: the first one is to build satellite constellation which contains multiple sunsynchronous satellites, just like the CHARTER mechanism has done; the second is to design non-predetermined orbit based on the concrete mission demand. An effective method for remote sensing satellite orbit design based on multiobjective evolution algorithm is presented in this paper. Orbit design problem is converted into a multi-objective optimization problem, and a fast and elitist multi-objective genetic algorithm is utilized to solve this problem. Firstly, the demand of the mission is transformed into multiple objective functions, and the six orbit elements of the satellite are taken as genes in design space, then a simulate evolution process is performed. An optimal resolution can be obtained after specified generation via evolution operation (selection, crossover, and mutation). To examine validity of the proposed method, a case study is introduced: Orbit design of an optical satellite for regional disaster monitoring, the mission demand include both minimizing the average revisit time internal of two objectives. The simulation result shows that the solution for this mission obtained by our method meet the demand the users' demand. We can draw a conclusion that the method presented in this paper is efficient for remote sensing orbit design.

  4. On the co-orbital motion in the planar restricted three-body problem: the quasi-satellite motion revisited

    Science.gov (United States)

    Pousse, Alexandre; Robutel, Philippe; Vienne, Alain

    2017-08-01

    In the framework of the planar and circular restricted three-body problem, we consider an asteroid that orbits the Sun in quasi-satellite motion with a planet. A quasi-satellite trajectory is a heliocentric orbit in co-orbital resonance with the planet, characterized by a nonzero eccentricity and a resonant angle that librates around zero. Likewise, in the rotating frame with the planet, it describes the same trajectory as the one of a retrograde satellite even though the planet acts as a perturbator. In the last few years, the discoveries of asteroids in this type of motion made the term "quasi-satellite" more and more present in the literature. However, some authors rather use the term "retrograde satellite" when referring to this kind of motion in the studies of the restricted problem in the rotating frame. In this paper, we intend to clarify the terminology to use, in order to bridge the gap between the perturbative co-orbital point of view and the more general approach in the rotating frame. Through a numerical exploration of the co-orbital phase space, we describe the quasi-satellite domain and highlight that it is not reachable by low eccentricities by averaging process. We will show that the quasi-satellite domain is effectively included in the domain of the retrograde satellites and neatly defined in terms of frequencies. Eventually, we highlight a remarkable high eccentric quasi-satellite orbit corresponding to a frozen ellipse in the heliocentric frame. We extend this result to the eccentric case (planet on an eccentric motion) and show that two families of frozen ellipses originate from this remarkable orbit.

  5. On Comparing Precision Orbit Solutions of Geodetic Satellites Given Several Ocean Tide and Geopotential Models

    Science.gov (United States)

    2014-08-01

    definitive orbit solution. However, these results vary for different satellite orbits and time past the initial fit span. I. Introduction The ability to...closely follow the definitive orbit solution. However, these results vary for different satellite orbits and time past the initial fit span. 15. SUBJECT...using data obtained from the GRACE mission. Principal investigators for GRACE at the University of Texas at Austin Center for Space Research ( CSR

  6. Physical and Orbital Properties of Some of Saturn's Small Satellites

    Science.gov (United States)

    Porco, C. C.; Thomas, P.; Spitale, J.; Jacobson, R. A.; Denk, T.; Charnoz, S.; Richardson, D. C.; Dones, L.; Baker, E.; Weiss, J. W.

    2005-08-01

    We present Cassini imaging results on the orbits and physical properties for the small ring-region moons Pan, Atlas, and the Cassini-discovered Keeler gap moon, S/2005 S1 (1), as well as the newly discovered/recovered moons orbiting among the major satellites, Methone (S/2004 S1), Pallene (S/2004 S2), and the Dione co-orbital S/2004 S5 Polydeuces (2,3,4). We find that Atlas is undergoing a 700-km amplitude longitudinal perturbation by Prometheus, Methone is undergoing a 30,000-km amplitude longitudinal perturbation by Mimas, and Pallene is undergoing a long-term 75-km amplitude longitudinal perturbation by Enceladus. Orbital integrations involving Atlas return a mass of GMAtlas = (0.43 ± 0.18) X 10-3 km3/sec2, three times larger than previously reported (4). Reasonably high resolution images have also allowed refinement of physical dimensions and spectral properties of these small moons. Results will be presented. At the time of writing, we find that Atlas has polar and equatorial diameters of 19 km, 38 km and 46 km, respectively. Its volume is (1.5 ± 0.4) X 104 km3, yielding a density of 0.43 ± 0.20 gm/cm3. Pan's polar diameter is 23 km, and differences in its equatorial axes are not well constrained; they both appear to be ˜ 35 km. Pan's volume is (1.4 ± 0.7) X 104 km3. Using the most currently reliable mass, GMPan = (0.33 ± 0.05) × 10-3 km3/sec2 (4), Pan's density is roughly 0.4 ± 0.2 gm/cm3. Both Pan and Atlas appear to be synchronous rotators, but libration cannot be ruled out yet. Given its shape, it is possible that Atlas is in a secondary spin-orbit resonance that could force a libration. Preliminary idealized rubble pile simulations have been performed which show that, at the orbits of Atlas and Pan, a simple self-gravitating ice-particle aggregate, with equal equatorial dimensions, would be stable against tides; a body with sufficiently unequal equatorial dimensions would not. [1] IAUC 8524. [2] IAUC 8389. [Correction: Pallene (S/2004 S2) is the

  7. Satellite Orbital Precessions Caused by the Octupolar Mass Moment of a Non-Spherical Body Arbitrarily Oriented in Space

    Indian Academy of Sciences (India)

    G. Renzetti

    2013-12-01

    I consider a satellite moving around a non-spherical body of mass and equatorial radius , and calculate its orbital precessions caused by the body’s octupolar mass moment 4. I consider only the effects averaged over one orbital period of the satellite. I give exact formulas, not restricted to any special values of either the eccentricity or the inclination of the satellite’s orbit. I do not assume any preferential orientation for the body’s spin axis $\\hat{\\mathbf{k}}$ because in many cases of potential interest (exoplanets, neutron stars, black holes) it is poorly known or unknown at all.

  8. 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.

  9. 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.

  10. Expressions Module for the Satellite Orbit Analysis Program

    Science.gov (United States)

    Edmonds, Karina

    2008-01-01

    The Expressions Module is a software module that has been incorporated into the Satellite Orbit Analysis Program (SOAP). The module includes an expressions- parser submodule built on top of an analytical system, enabling the user to define logical and numerical variables and constants. The variables can capture output from SOAP orbital-prediction and geometric-engine computations. The module can combine variables and constants with built-in logical operators (such as Boolean AND, OR, and NOT), relational operators (such as >, functions and operations, including logarithms, trigonometric functions, Bessel functions, minimum/ maximum operations, and floating- point-to-integer conversions. The module supports combinations of time, distance, and angular units and has a dimensional- analysis component that checks for correct usage of units. A parser based on the Flex language and the Bison program looks for and indicates errors in syntax. SOAP expressions can be built using other expressions as arguments, thus enabling the user to build analytical trees. A graphical user interface facilitates use.

  11. GBT Reveals Satellite of Milky Way in Retrograde Orbit

    Science.gov (United States)

    2003-05-01

    New observations with National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT) suggest that what was once believed to be an intergalactic cloud of unknown distance and significance, is actually a previously unrecognized satellite galaxy of the Milky Way orbiting backward around the Galactic center. Path of Complex H Artist's rendition of the path of satellite galaxy Complex H (in red) in relation to the orbit of the Sun (in yellow) about the center of the Milky Way Galaxy. The outer layers of Complex H are being stripped away by its interaction with the Milky Way. The hydrogen atmosphere (in blue) is shown surrounding the visible portion (in white) of the Galaxy. CREDIT: Lockman, Smiley, Saxton; NRAO/AUI Jay Lockman of the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia, discovered that this object, known as "Complex H," is crashing through the outermost parts of the Milky Way from an inclined, retrograde orbit. Lockman's findings will be published in the July 1 issue of the Astrophysical Journal, Letters. "Many astronomers assumed that Complex H was probably a distant neighbor of the Milky Way with some unusual velocity that defied explanation," said Lockman. "Since its motion appeared completely unrelated to Galactic rotation, astronomers simply lumped it in with other high velocity clouds that had strange and unpredictable trajectories." High velocity clouds are essentially what their name implies, fast-moving clouds of predominately neutral atomic hydrogen. They are often found at great distances from the disk of the Milky Way, and may be left over material from the formation of our Galaxy and other galaxies in our Local Group. Over time, these objects can become incorporated into larger galaxies, just as small asteroids left over from the formation of the solar system sometimes collide with the Earth. Earlier studies of Complex H were hindered because the cloud currently is passing almost exactly behind the outer disk of

  12. The High-ORbit Ultraviolet-visible Satellite, HORUS

    Science.gov (United States)

    Scowen, Paul A.; Cooke, Brian; Beasley, Matthew; Siegmund, Oswald

    2013-09-01

    The High-ORbit Ultraviolet-visible Satellite (HORUS) is a 2.4-meter class space telescope that will conduct a comprehensive and systematic study of the astrophysical processes and environments relevant for the births and life cycles of stars and their planetary systems, to investigate and understand the range of environments, feedback mechanisms, and other factors that most affect the outcome of the star and planet formation process. HORUS will provide 100× greater imaging efficiency and combines the resolution of STIS with the throughput of COS. The HORUS mission will contribute vital information on how solar systems form and whether habitable planets should be common or rare. It also will investigate the structure, evolution, and destiny of galaxies and the universe. This program relies on focused capabilities unique to space that no other planned NASA mission will provide: near-ultraviolet (UV)/visible (200-1100nm) wide-field (14' square), diffraction-limited imaging; and high-sensitivity, high-resolution FUV (100- 320nm) spectroscopy. From its baseline orbit at L2 HORUS will enjoy a stable environment for thermal and pointing control, and long-duration target visibility. The core HORUS design will provide wide field of view imagery and high efficiency point source far-ultraviolet (FUV) spectroscopy using a combination of spectral selection and field sharing.

  13. 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

  14. The National Polar-orbiting Operational Environmental Satellite System

    Science.gov (United States)

    Bloom, H.

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

  15. Forecast analysis on satellites that need de-orbit technologies: future scenarios for passive de-orbit devices

    Science.gov (United States)

    Palla, Chiara; Kingston, Jennifer

    2016-09-01

    Propulsion-based de-orbit is a space-proven technology; however, this strategy can strongly limit operational lifetime, as fuel mass is dedicated to the de-orbiting. In addition previous reliability studies have identified the propulsion subsystem as one of the major contributors driving satellite failures. This issue brings the need to develop affordable de-orbit technologies with a limited reliance on the system level performance of the host satellite, ideally largely passive methods. Passive disposal strategies which take advantage of aerodynamic drag as the de-orbit force are particularly attractive because they are independent of spacecraft propulsion capabilities. This paper investigates the future market for passive de-orbit devices in LEO to aid in defining top-level requirements for the design of such devices. This is performed by considering the compliances of projected future satellites with the Inter Agency Space Debris Coordination Committee de-orbit time, to quantify the number of spacecraft that are compliant or non-compliant with the guidelines and, in this way, determine their need for the previously discussed devices. The study is performed by using the SpaceTrak™ database which provides future launch schedules, and spacecraft information; the de-orbit analysis is carried out by means of simulations with STELA. A case study of a passive strategy is given by the de-orbit mechanism technological demonstrator, which is currently under development at Cranfield University and designed to deploy a drag sail at the end of the ESEO satellite mission.

  16. Scheduler for monitoring objects orbiting earth using satellite-based telescopes

    Energy Technology Data Exchange (ETDEWEB)

    Olivier, Scot S; Pertica, Alexander J; Riot, Vincent J; De Vries, Willem H; Bauman, Brian J; Nikolaev, Sergei; Henderson, John R; Phillion, Donald W

    2015-04-28

    An ephemeris refinement system includes satellites with imaging devices in earth orbit to make observations of space-based objects ("target objects") and a ground-based controller that controls the scheduling of the satellites to make the observations of the target objects and refines orbital models of the target objects. The ground-based controller determines when the target objects of interest will be near enough to a satellite for that satellite to collect an image of the target object based on an initial orbital model for the target objects. The ground-based controller directs the schedules to be uploaded to the satellites, and the satellites make observations as scheduled and download the observations to the ground-based controller. The ground-based controller then refines the initial orbital models of the target objects based on the locations of the target objects that are derived from the observations.

  17. 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.

  18. 不同高度范围月球卫星轨道受摄分析%Effects of Perturbations on Lunar Satellite Orbits at Different Altitudes

    Institute of Scientific and Technical Information of China (English)

    冯晶琅; 袁建平; 陈记争

    2011-01-01

    Aim. Lunar missions need comprehensive knowledge of the perturbation effects of: (1) deviation of moon from being spherical, (2) Earth, (3) sun; the introduction of the full paper points out that, since, to our knowledge, only fragmentary information exists in the open literature[2,3] , this paper intends to provide the comprehensive knowledge needed. We explain our research results in sections 1 and 2. Section 1 studies the magnitudes of changes in lunar non-spherical perturbation, earth perturbation and sun perturbation at different altitudes. Section 2 analyzes the effects of the three perturbations on the changes in orbital elements and perilune altitudes; it also simulares their effects on orbital elements at different altitudes; the simulation results, given in Figs. 2 through 5 and Tables 2 and 3, and their analysis show preliminarily that: ( 1 ) the higher the altitudes of lunar orbits, the greater are the changes in eccentricity, semi-major axis and perilune altitude caused by neglecting the earth perturbation, while the effects of lunar non-spherical perturbation decrease; (2) when the altitude is above 5300 kin, the effect of sun perturbation can not be ignored.%目前月球探测任务具有多样性,需要采用不同高度的月球卫星轨道,因此研究摄动力对不同高度月球卫星轨道的影响具有重要意义.文章首先分析了月球非球形摄动、地球引力摄动和太阳引力摄动三种摄动力大小随高度的变化规律.在此基础上,仿真计算了这三种摄动对不同高度月球卫星轨道的影响,得到了轨道要素和近月点高度在不同轨道高度范围内随这三种摄动力的变化规律.最后在近月点高度为百米级精度的条件下,给出了不同高度范围需要考虑的摄动力,为新型月球任务轨道设计和轨道控制提供参考.

  19. The zero gravity curve and surface and radii for geostationary and geosynchronous satellite orbits

    Directory of Open Access Journals (Sweden)

    Sjöberg L.E.

    2017-02-01

    Full Text Available A geosynchronous satellite orbits the Earth along a constant longitude. A special case is the geostationary satellite that is located at a constant position above the equator. The ideal position of a geostationary satellite is at the level of zero gravity, i.e. at the geocentric radius where the gravitational force of the Earth equals the centrifugal force. These forces must be compensated for several perturbing forces, in particular for the lunisolar tides. Considering that the gravity field of the Earth varies not only radially but also laterally, this study focuses on the variations of zero gravity not only on the equator (for geostationary satellites but also for various latitudes. It is found that the radius of a geostationary satellite deviates from its mean value of 42164.2 km only within ±2 m, mainly due to the spherical harmonic coefficient J22, which is related with the equatorial flattening of the Earth. Away from the equator the zero gravity surface deviates from the ideal radius of a geosynchronous satellite, and more so for higher latitudes. While the radius of the former surface increases towards infinity towards the poles, the latter decreases about 520 m from the equator to the pole. Tidal effects vary these radii within ±2.3 km.

  20. H-- Filtering Algorithms Case Study GPS-Based Satellite Orbit Determination

    Science.gov (United States)

    Kuang, Jinlu; Tan, Soonhie

    In this paper the new Hfiltering algorithms for the design of navigation systems for autonomous LEO satellite is introduced. The nominal orbit (i.e., position and velocity) is computed by integrating the classical orbital differential equations of the LEO satellite by using the 7th-8th order Runge- Kutta algorithms. The perturbations due to the atmospheric drag force, the lunar-solar attraction and the solar radiation pressure are included together with the Earth gravity model (EGM-96). The spherical harmonic coefficients of the EGM-96 are considered up to 72 for the order and degree. By way of the MATLAB GPSoft software, the simulated pseudo ranges between the user LEO satellite and the visible GPS satellites are generated when given the appropriate angle of mask. The effects of the thermal noises, tropospheric refraction, ionospheric refraction, and multipath of the antenna are also compensated numerically in the simulated pseudo ranges. The dynamic Position-Velocity (PV) model is obtained by modeling the velocity as nearly constant being the white noise process. To further accommodate acceleration in the process model, the Position-Velocity-Acceleration (PVA) model is investigated by assuming the acceleration to be the Gaussian- Markov process. The state vector for the PV model becomes 8-dimensional (3-states for positions, 3-states for velocities, 1-state for range (clock) bias error, 1-state for range (clock) drift error). The state vector for the PV model becomes 11-dimensional with the addition of three more acceleration states. Three filtering approaches are used to smooth the orbit solution based upon the GPS pseudo range observables. The numerical simulation shows that the observed orbit root-mean-square errors of 60 meters by using the least squares adjustment method are improved to be less than 5 meters within 16 hours of tracking time by using the Hfiltering algorithms. The results are compared with the ones obtained by using the Extended Kalman

  1. The Coverage Analysis for Low Earth Orbiting Satellites at Low Elevation

    Directory of Open Access Journals (Sweden)

    Shkelzen Cakaj

    2014-07-01

    Full Text Available Low Earth Orbit (LEO satellites are used for public networking and for scientific purposes. Communication via satellite begins when the satellite is positioned in its orbital position. Ground stations can communicate with LEO satellites only when the satellite is in their visibility region. The duration of the visibility and the communication vary for each LEO satellite pass over the station, since LEO satellites move too fast over the Earth. The satellite coverage area is defined as a region of the Earth where the satellite is seen at a minimum predefined elevation angle. The satellite’s coverage area on the Earth depends on orbital parameters. The communication under low elevation angles can be hindered by natural barriers. For safe communication and for savings within a link budget, the coverage under too low elevation is not always provided. LEO satellites organized in constellations act as a convenient network solution for real time global coverage. Global coverage model is in fact the complementary networking process of individual satellite’s coverage. Satellite coverage strongly depends on elevation angle. To conclude about the coverage variation for low orbiting satellites at low elevation up to 10º, the simulation for attitudes from 600km to 1200km is presented through this paper.

  2. Approximate analytic method for high-apogee twelve-hour orbits of artificial Earth's satellites

    Science.gov (United States)

    Vashkovyaka, M. A.; Zaslavskii, G. S.

    2016-09-01

    We propose an approach to the study of the evolution of high-apogee twelve-hour orbits of artificial Earth's satellites. We describe parameters of the motion model used for the artificial Earth's satellite such that the principal gravitational perturbations of the Moon and Sun, nonsphericity of the Earth, and perturbations from the light pressure force are approximately taken into account. To solve the system of averaged equations describing the evolution of the orbit parameters of an artificial satellite, we use both numeric and analytic methods. To select initial parameters of the twelve-hour orbit, we assume that the path of the satellite along the surface of the Earth is stable. Results obtained by the analytic method and by the numerical integration of the evolving system are compared. For intervals of several years, we obtain estimates of oscillation periods and amplitudes for orbital elements. To verify the results and estimate the precision of the method, we use the numerical integration of rigorous (not averaged) equations of motion of the artificial satellite: they take into account forces acting on the satellite substantially more completely and precisely. The described method can be applied not only to the investigation of orbit evolutions of artificial satellites of the Earth; it can be applied to the investigation of the orbit evolution for other planets of the Solar system provided that the corresponding research problem will arise in the future and the considered special class of resonance orbits of satellites will be used for that purpose.

  3. 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.

  4. Precise Orbit Determination of the two LAGEOS and LARES satellites and the LARASE activities

    Science.gov (United States)

    Massimo Lucchesi, David; Peron, Roberto; Anselmo, Luciano; Bassan, Massimo; Magnafico, Carmelo; Nobili, Anna Maria; Pardini, Carmen; Pucacco, Giuseppe; Stanga, Ruggero; Visco, Massimo

    2016-04-01

    The LAser RAnged Satellites Experiment (LARASE) research program aims to provide an original contribution in testing and verifying Einstein's theory of General Relativity (GR) in its Weak-Field and Slow-Motion (WFSM) limit by means of the powerful Satellite Laser Ranging (SLR) technique. Therefore, in this perspective, a Precise Orbit Determination (POD) of a dedicated set of passive laser-ranged satellites is required. In particular, the joint analysis of the orbit of the two LAGEOS (LAser GEOdynamic Satellite) satellites with that of the more recently launched LARES (LAser RElativity Satellite) satellite will be exploited in order to obtain precise measurements of the gravitational interaction in the field of the Earth. A major point to be reached within the activities of LARASE is to provide the relativistic measurements with an error budget of the various systematic effects (both gravitational and non-gravitational) that be robust and reliable. This requires a careful analysis of the various disturbing effects on the orbit of the considered satellites, especially for the new LARES. This activity has been planned both for the gravitational and the non-gravitational perturbations (NGP). Therefore, we started to re-visit, update and improve previous dynamical models, especially for the NGP, and we also developed new models in such a way to improve the current dynamical models used in space geodesy to account for the main perturbations acting on the orbit of LAGEOS and LARES. We focused especially on the spin dynamics, the drag effects (especially for LARES, because of its much lower height with respect to the two LAGEOS) and, at a preliminary level, the thermal ones that, as it is well known from the literature, are very important for the LAGEOS satellites. These studies are of fundamental importance not only for the objective of a reliable error budget, but also in order to improve the POD. In this context, because of the importance of the LAGEOS satellites in

  5. Basic performance of BeiDou-2 navigation satellite system used in LEO satellites precise orbit determination

    Directory of Open Access Journals (Sweden)

    Liu Junhong

    2014-10-01

    Full Text Available The visibility for low earth orbit (LEO satellites provided by the BeiDou-2 system is analyzed and compared with the global positioning system (GPS. In addition, the spaceborne receivers’ observations are simulated by the BeiDou satellites broadcast ephemeris and LEO satellites orbits. The precise orbit determination (POD results show that the along-track component accuracy is much better over the service area than the non-service area, while the accuracy of the other two directions keeps at the same level over different areas. However, the 3-dimensional (3D accuracy over the two areas shows almost no difference. Only taking into consideration the observation noise and navigation satellite ephemeris errors, the 3D accuracy of the POD is about 30 cm. As for the precise relative orbit determination (PROD, the 3D accuracy is much better over the eastern hemisphere than that of the western hemisphere. The baseline length accuracy is 3.4 mm over the service area, and it is still better than 1 cm over the non-service area. This paper demonstrates that the BeiDou regional constellation could provide global service to LEO satellites for the POD and the PROD. Finally, the benefit of geostationary earth orbit (GEO satellites is illustrated for POD.

  6. Basic performance of BeiDou-2 navigation satellite system used in LEO satellites precise orbit determination

    Institute of Scientific and Technical Information of China (English)

    Liu Junhong; Gu Defeng; Ju Bing; Yao Jing; Duan Xiaojun; Yi Dongyun

    2014-01-01

    The visibility for low earth orbit (LEO) satellites provided by the BeiDou-2 system is analyzed and compared with the global positioning system (GPS). In addition, the spaceborne receivers’ observations are simulated by the BeiDou satellites broadcast ephemeris and LEO satel-lites orbits. The precise orbit determination (POD) results show that the along-track component accuracy is much better over the service area than the non-service area, while the accuracy of the other two directions keeps at the same level over different areas. However, the 3-dimensional (3D) accuracy over the two areas shows almost no difference. Only taking into consideration the observation noise and navigation satellite ephemeris errors, the 3D accuracy of the POD is about 30 cm. As for the precise relative orbit determination (PROD), the 3D accuracy is much better over the eastern hemisphere than that of the western hemisphere. The baseline length accuracy is 3.4 mm over the service area, and it is still better than 1 cm over the non-service area. This paper demon-strates that the BeiDou regional constellation could provide global service to LEO satellites for the POD and the PROD. Finally, the benefit of geostationary earth orbit (GEO) satellites is illustrated for POD.

  7. Design of a Representative Low Earth Orbit Satellite to Improve Existing Debris Models

    Science.gov (United States)

    Clark, S.; Dietrich, A.; Werremeyer, M.; Fitz-Coy, N.; Liou, J.-C.

    2012-01-01

    This paper summarizes the process and methodologies used in the design of a small-satellite, DebriSat, that represents materials and construction methods used in modern day Low Earth Orbit (LEO) satellites. This satellite will be used in a future hypervelocity impact test with the overall purpose to investigate the physical characteristics of modern LEO satellites after an on-orbit collision. The major ground-based satellite impact experiment used by DoD and NASA in their development of satellite breakup models was conducted in 1992. The target used for that experiment was a Navy Transit satellite (40 cm, 35 kg) fabricated in the 1960 s. Modern satellites are very different in materials and construction techniques from a satellite built 40 years ago. Therefore, there is a need to conduct a similar experiment using a modern target satellite to improve the fidelity of the satellite breakup models. The design of DebriSat will focus on designing and building a next-generation satellite to more accurately portray modern satellites. The design of DebriSat included a comprehensive study of historical LEO satellite designs and missions within the past 15 years for satellites ranging from 10 kg to 5000 kg. This study identified modern trends in hardware, material, and construction practices utilized in recent LEO missions, and helped direct the design of DebriSat.

  8. Orbital performance of communication satellite microwave power amplifiers (MPAs)

    Science.gov (United States)

    Strauss, R.

    1993-01-01

    This paper presents background data on the performance of microwave power amplifiers (MPAs) used as transmitters in currently operating commercial communication satellites. Specifically aspects of two competing MPA types are discussed. These are well known TWTA (travelling wave tube amplifier) and the SSPA (solid state power amplifier). Extensive in-orbit data has been collected from over 2000 MPAs in 1991 and 1993. The study in 1991 invovlved 75 S/C (spacecraft) covering 463 S/C years. The 1993 'second-look' study encompassed a slightly different population of 72 S/C with 497 S/C years of operation. A surprising result of both studies was that SSPAs, although quite reliable, did not achieve the reliability of TWTAs were one-third more reliable in the 1993 study. This was at C-band with comparable power amplifiers, e.g. 6-16W of RF output power and similar gains. Data at K(sub u)-band is for TWTAs only since there are no SSPAs in the current S/C inventory. The other complementary result was that the projected failure rates used as S/C payload design guidelines were, on average, somewhat higher for TWTAs than the actual failure rates uncovered by this study. SSPA rates were as projected.

  9. Real-time precise orbit determination of LEO satellites using a single-frequency GPS receiver: Preliminary results of Chinese SJ-9A satellite

    Science.gov (United States)

    Sun, Xiucong; Han, Chao; Chen, Pei

    2017-10-01

    Spaceborne Global Positioning System (GPS) receivers are widely used for orbit determination of low-Earth-orbiting (LEO) satellites. With the improvement of measurement accuracy, single-frequency receivers are recently considered for low-cost small satellite missions. In this paper, a Schmidt-Kalman filter which processes single-frequency GPS measurements and broadcast ephemerides is proposed for real-time precise orbit determination of LEO satellites. The C/A code and L1 phase are linearly combined to eliminate the first-order ionospheric effects. Systematic errors due to ionospheric delay residual, group delay variation, phase center variation, and broadcast ephemeris errors, are lumped together into a noise term, which is modeled as a first-order Gauss-Markov process. In order to reduce computational complexity, the colored noise is considered rather than estimated in the orbit determination process. This ensures that the covariance matrix accurately represents the distribution of estimation errors without increasing the dimension of the state vector. The orbit determination algorithm is tested with actual flight data from the single-frequency GPS receiver onboard China's small satellite Shi Jian-9A (SJ-9A). Preliminary results using a 7-h data arc on October 25, 2012 show that the Schmidt-Kalman filter performs better than the standard Kalman filter in terms of accuracy.

  10. Analysis of Characteristics of QZSS Satellite Orbit and Clock Products during Yaw Attitude Model Switching

    Directory of Open Access Journals (Sweden)

    ZHOU Peiyuan

    2016-03-01

    Full Text Available Yaw attitude model switching of navigation satellites have great impact on its orbit and clock products derived from precise orbit determination. Firstly, the yaw attitude and solar radiation model of QZSS is given briefly. Then, using QZSS precise orbit and clock products provided by IGS MGEX analysis center, precision of orbit and clock is analyzed by satellite laser ranging residuals and polynomial fit residuals respectively. Finally, spectral analysis and modified Allan variance is carried out on clock products to reveal its periodic variations. Research on QZSS satellite orbit and clock products of 2014 shows that there are two eclipse seasons of 20 days and the beta angle is fluctuating with a period of half-year. And there is significant correlation between the precision of orbit and clock products and beta angle. Moreover, the satellite clock offset has periodic variations similar to orbit periods and its amplitude is changing with the beta angle which indicates problems of current orbit determination strategies. In view of similarities between QZSS and BeiDou IGSO and MEO satellites in yaw attitude model, the conclusion is beneficial to improve BeiDou precise orbit determination.

  11. A method of autonomous orbit determination for satellite using star sensor

    Institute of Scientific and Technical Information of China (English)

    MA; Jianbo; XU; Jin

    2005-01-01

    In this paper a method of autonomous orbit determination using star sensor is studied. By building relatively consummate dynamical models which simulate attitude motion of satellite and observation from satellite to background stars, the simulant computation of this method is executed, and it is shown that the method of autonomous orbit determination is feasible. Academic and calculation analyses have been done for the relation between the direction of star sensor with respect to satellite-body coordinate system and the accuracy of autonomous orbit determination.

  12. 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... avoidance of in-line interference events for Non Geostationary Satellite Orbit (NGSO) Satellite...

  13. 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.

  14. Effects of Geopotential and Atmospheric Drag Effects on Frozen Orbits Using Nonsingular Variables

    Directory of Open Access Journals (Sweden)

    Paula Cristiane Pinto Mesquita Pardal

    2014-01-01

    Full Text Available The concept of frozen orbit has been applied in space missions mainly for orbital tracking and control purposes. This type of orbit is important for orbit design because it is characterized by keeping the argument of perigee and eccentricity constant on average, so that, for a given latitude, the satellite always passes at the same altitude, benefiting the users through this regularity. Here, the system of nonlinear differential equations describing the motion is studied, and the effects of geopotential and atmospheric drag perturbations on frozen orbits are taken into account. Explicit analytical expressions for secular and long period perturbations terms are obtained for the eccentricity and the argument of perigee. The classical equations of Brouwer and Brouwer and Hori theories are used. Nonsingular variables approach is used, which allows obtaining more precise previsions for CBERS (China Brazil Earth Resources Satellite satellites family and similar satellites (SPOT, Landsat, ERS, and IRS orbital evolution.

  15. Multi-technique combination of space geodesy observations: Impact of the Jason-2 satellite on the GPS satellite orbits estimation

    Science.gov (United States)

    Zoulida, Myriam; Pollet, Arnaud; Coulot, David; Perosanz, Félix; Loyer, Sylvain; Biancale, Richard; Rebischung, Paul

    2016-10-01

    In order to improve the Precise Orbit Determination (POD) of the GPS constellation and the Jason-2 Low Earth Orbiter (LEO), we carry out a simultaneous estimation of GPS satellite orbits along with Jason-2 orbits, using GINS software. Along with GPS station observations, we use Jason-2 GPS, SLR and DORIS observations, over a data span of 6 months (28/05/2011-03/12/2011). We use the Geophysical Data Records-D (GDR-D) orbit estimation standards for the Jason-2 satellite. A GPS-only solution is computed as well, where only the GPS station observations are used. It appears that adding the LEO GPS observations results in an increase of about 0.7% of ambiguities fixed, with respect to the GPS-only solution. The resulting GPS orbits from both solutions are of equivalent quality, agreeing with each other at about 7 mm on Root Mean Square (RMS). Comparisons of the resulting GPS orbits to the International GNSS Service (IGS) final orbits show the same level of agreement for both the GPS-only orbits, at 1.38 cm in RMS, and the GPS + Jason2 orbits at 1.33 cm in RMS. We also compare the resulting Jason-2 orbits with the 3-technique Segment Sol multi-missions d'ALTimétrie, d'orbitographie et de localisation précise (SSALTO) POD products. The orbits show good agreement, with 2.02 cm of orbit differences global RMS, and 0.98 cm of orbit differences RMS on the radial component.

  16. Designing nonuniform satellite systems for continuous global coverage using equatorial and polar circular orbits

    Science.gov (United States)

    Ulybyshev, S. Yu.

    2016-07-01

    We present a method for designing nonuniform satellite systems for continuous global coverage using a combination of equatorial and near-polar satellite segments in circular orbits. Equations are derived to determine the basic design parameters of the satellite system itself and the conditions of its closure at the joint of near-polar and equatorial segments. We analyze specific features of near-polar and equatorial satellite systems and their advantages and disadvantages compared with existing classes of near-polar phased and kinematically correct satellite systems. We estimate the minimum required number of spacecrafts in satellite systems for a given fold of coverage and present calculated dependences for classes of near-polar phased and equatorial satellite systems with different types of closure. For the class of kinematically correct satellite systems, we analyze the characteristics of systems with a minimum spacecraft flight height and reveal that the number of satellites in the orbital plane depends on the flight height for different folds of coverage. We bring examples of the best near-polar equatorial satellite systems of global coverage for different folds and a class of satellite systems with a fixed number of spacecrafts and orbital planes in them.

  17. Orbits of massive satellite galaxies - I. A close look at the Large Magellanic Cloud and a new orbital history for M33

    Science.gov (United States)

    Patel, Ekta; Besla, Gurtina; Sohn, Sangmo Tony

    2017-02-01

    The Milky Way (MW) and M31 both harbour massive satellite galaxies, the Large Magellanic Cloud (LMC) and M33, which may comprise up to 10 per cent of their host's total mass. Massive satellites can change the orbital barycentre of the host-satellite system by tens of kiloparsec and are cosmologically expected to harbour dwarf satellite galaxies of their own. Assessing the impact of these effects crucially depends on the orbital histories of the LMC and M33. Here, we revisit the dynamics of the MW-LMC system and present the first detailed analysis of the M31-M33 system utilizing high-precision proper motions and statistics from the dark-matter-only Illustris cosmological simulation. With the latest Hubble Space Telescope proper motion measurements of M31, we reliably constrain M33's interaction history with its host. In particular, like the LMC, M33 is either on its first passage (tinf picture and provide further insight about their host masses. We conclude that, cosmologically, massive satellites such as the LMC and M33 are likely completing their first orbits about their hosts. We also find that the orbital energies of such analogues prefer an MW halo mass ˜1.5 × 1012 M⊙ and an M31 halo mass ≥1.5 × 1012 M⊙. Despite conventional wisdom, we conclude it is highly improbable that M33 made a close (<100 kpc) approach to M31 recently (tperi < 3 Gyr ago). Such orbits are rare (<1 per cent) within the 4σ error space allowed by observations. This conclusion cannot be explained by perturbative effects through four-body encounters amongst the MW, M31, M33, and the LMC. This surprising result implies that we must search for a new explanation for M33's strongly warped gas and stellar discs.

  18. Satellite co-locations as a link between SLR, GPS and Low Earth Orbiting (LEO) satellites

    Science.gov (United States)

    Melachroinos, S. A.; Lemoine, F. G.; Chinn, D. S.; Nicolas, J. B.; Zelensky, N. P.; Wimert, J.; Radway, Y.

    2013-12-01

    The procedure applied for the determination of the International Terrestrial Reference Frame (ITRF) requires the combination of all four major techniques of Space Geodesy. This combination is only possibly realized by the introduction of the local-ties between co-located techniques. A local-tie is the lever arm vector between the marker points on the sites where two or more space geodesy instruments operate. The local ties are used as additional observations with proper variances. They are usually derived from local surveys using either classical geodesy or the global navigation satellite systems (GNSS). The Global Positioning System (GPS) plays a major role in the ITRF combination by linking together all the other three techniques SLR, DORIS and VLBI (Altamimi and Collilieux 2009). However, discrepancies between local ties and space geodesy estimates are well known although the reasons for these discrepancies are often not clear. These discrepancies could be either due to errors in local ties and in coordinate estimates or in both. In this study, we use the tracking to G05-35 and G06-36 and one LEO by SLR sites and their combined orbits, earth rotation parameters (ERPs) and station positions in order to establish space-based co-location ties on the stations. The LEO satellite used in this experiment is Jason-2, which carries both GPS and SLR. Therefore from the data-processing point of view the LEO satellite is used as a fast moving station (Thaller et al. 2011). Jason-2 is also equipped with DORIS, but it will be included into another combined analysis. Subsequently, we compare the consistency of our space-based co-locations to the ones from ITRF08 and SLRF08 - IGb08 solutions.

  19. Satellite quenching time-scales in clusters from projected phase space measurements matched to simulated orbits

    Science.gov (United States)

    Oman, Kyle A.; Hudson, Michael J.

    2016-12-01

    We measure the star formation quenching efficiency and time-scale in cluster environments. Our method uses N-body simulations to estimate the probability distribution of possible orbits for a sample of observed Sloan Digital Sky Survey galaxies in and around clusters based on their position and velocity offsets from their host cluster. We study the relationship between their star formation rates and their likely orbital histories via a simple model in which star formation is quenched once a delay time after infall has elapsed. Our orbit library method is designed to isolate the environmental effect on the star formation rate due to a galaxy's present-day host cluster from `pre-processing' in previous group hosts. We find that quenching of satellite galaxies of all stellar masses in our sample (109-10^{11.5}M_{⊙}) by massive (> 10^{13} M_{⊙}) clusters is essentially 100 per cent efficient. Our fits show that all galaxies quench on their first infall, approximately at or within a Gyr of their first pericentric passage. There is little variation in the onset of quenching from galaxy-to-galaxy: the spread in this time is at most ˜2 Gyr at fixed M*. Higher mass satellites quench earlier, with very little dependence on host cluster mass in the range probed by our sample.

  20. 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.

  1. 78 FR 14952 - Earth Stations Aboard Aircraft Communicating with Fixed-Satellite Service Geostationary-Orbit...

    Science.gov (United States)

    2013-03-08

    ... From the Federal Register Online via the Government Publishing Office FEDERAL COMMUNICATIONS COMMISSION 47 CFR Part 2 Earth Stations Aboard Aircraft Communicating with Fixed-Satellite Service Geostationary-Orbit Space Stations AGENCY: Federal Communications Commission. ACTION: Proposed rule....

  2. Synchronization and Antisynchronization of a Planar Oscillation of Satellite in an Elliptic Orbit via Active Control

    Directory of Open Access Journals (Sweden)

    Mohammad Shahzad

    2011-01-01

    Full Text Available We have investigated the synchronization and antisynchronization behaviour of two identical planar oscillation of a satellite in elliptic orbit evolving from different initial conditions using the active control technique based on the Lyapunov stability theory and the Routh-Hurwitz criteria. The designed controller, with our own choice of the coefficient matrix of the error dynamics that satisfy the Lyapunov stability theory and the Routh-Hurwitz criteria, is found to be effective in the stabilization of the error states at the origin, thereby, achieving synchronization and antisynchronization between the states variables of two nonlinear dynamical systems under consideration. The results are validated by numerical simulations using mathematica.

  3. 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.

  4. 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.

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

    Institute of Scientific and Technical Information of China (English)

    Zhang Zhen; Xiong Jianping; Jin Jin

    2015-01-01

    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 mag-netometer 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 iter-ative 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.

  6. 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.

  7. Orbital Maneuvers Using Low Thrust to Place a Satellite in a Constellation

    Directory of Open Access Journals (Sweden)

    Vivian Martins Gomes

    2007-01-01

    Full Text Available This paper considers the problem of low thrust suboptimal maneuvers to insert a satellite in a constellation. It is assumed that a satellite constellation is given with all the Keplerian elements of the satellite members having known values. Then, it is necessary to maneuver a new satellite from a parking orbit to its position in the constellation. The control available to perform this maneuver is the application of a low thrust to the satellite and the objective is to perform this maneuver with minimum fuel consumption.

  8. Orbital parameters of infalling satellite haloes in the hierarchical $\\Lambda$CDM model

    CERN Document Server

    Jiang, Lilian; Sawala, Till; Frenk, Carlos S

    2014-01-01

    We present distributions of orbital parameters of infalling satellites of $\\Lambda$CDM haloes in the mass range $10^{12}-10^{14}$M$_\\odot$, which represent the initial conditions for the subsequent evolution of substructures within the host halo. We use merger trees constructed in a high resolution cosmological N-body simulation to trace satellite haloes, and identify the time of infall. We find signficant trends in the distribution of orbital parameters with both the host halo mass and the ratio of satellite-to-host halo masses. For all host halo masses, satellites whose infall mass is a larger fraction of the host halo mass have more eccentric, radially biased orbits. At fixed satellite-to-host halo mass ratio, high mass haloes are biased towards accreting satellites on slightly more biased orbits. To charactise the orbital distributions fully requires fitting the correlated bivariate distribution of two chosen orbital parameters (e.g. radial and tangential velocity or energy and angular momentu). We provid...

  9. 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.

  10. Preliminary Analysis of a Novel SAR Based Emergency System for Earth Orbit Satellites using Galileo

    NARCIS (Netherlands)

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

    2010-01-01

    This paper presents a preliminary analysis of a novel Search and Rescue (SAR) based emergency system for Low Earth Orbit (LEO) satellites using the Galileo Global Navigation Satellite System (GNSS). It starts with a description of the space user SAR system including a concept description, mission ar

  11. Development of an in-orbit refocusing mechanism for the meteosat second generation weather satellites

    NARCIS (Netherlands)

    Verhoeff, P.; Mierlo, H.A. van; Braam, B.C.; Hopman, J.; Werkhoven, W.P. van; Kluse, M. le

    1998-01-01

    A Refocusing Mechanism (REM) has been designed and built for the SEVIRI instrument, the imager in the Meteosat Second Generation (MSG) satellite. The purpose of the mechanism is in-orbit focal adjustment of a mirror assembly which forms part of SEVIRI. As the MSG satellite observes the earth and its

  12. On-orbit control of the Communications Technology Satellite (CTS)/HERMES

    Science.gov (United States)

    Raine, H. R.

    1980-01-01

    A variety of control functions for the CIS HERMES satellite are reviewed. Its mission, to demonstrate high power SHF (12 GHz) transmission is discussed. The satellite was controlled in geostationary orbit for nearly four years from the satellite control center in Ottawa, Canada. Highlights of these operations are outlined. The interactions between many of the automatic onboard control functions and control from the ground are described. Special emphasis is placed on the characteristics and performance of the three axis attitude control system.

  13. Modeling radiation conditions in orbits of projected system of small satellites for radiation monitoring

    Science.gov (United States)

    Panasyuk, M. I.; Podzolko, M. V.; Kovtyukh, A. S.; Osedlo, V. I.; Tulupov, V. I.; Yashin, I. V.

    2016-11-01

    Calculated estimates are presented for the accumulated radiation doses behind the shields of various thicknesses in the orbits of projected at Skobeltsyn Institute of Nuclear Physics, Moscow State University system of small satellites for radiation monitoring. The results are analyzed and compared with the calculation data for other actively exploited near-Earth orbits.

  14. Energy integral method for gravity field determination from satellite orbit coordinates

    NARCIS (Netherlands)

    Visser, P.N.A.M.; Sneeuw, N.; Gerlach, C.

    2003-01-01

    A fast iterative method for gravity field determination from low Earth satellite orbit coordinates has been developed and implemented successfully. The method is based on energy conservation and avoids problems related to orbit dynamics and initial state. In addition, the particular geometry of a re

  15. GPS-based precise orbit determination and accelerometry for low flying satellites

    NARCIS (Netherlands)

    Van den IJssel, J.A.A.

    2014-01-01

    Atmospheric density models are currently the limiting factor in the accuracy of the dynamic orbit determination and prediction of satellites in a low Earth orbit. Any improvement in these models would greatly aid in applications such as re-entry prediction, ground-track maintenance of Earth observat

  16. A decade of ERS satellite orbits and altimetry

    NARCIS (Netherlands)

    Scharroo, R.

    2002-01-01

    The First European Remote Sensing Satellite, ERS-1, was launched in July 1991, fol- lowed by ERS-2 in April 1995. Both satellites carry a radar altimeter to serve oper- ational applications and scientific research in the fields of geodesy, oceanography, glaciology and meteorology. Together, the sate

  17. LEO卫星星下点轨迹保持策略优化研究%Optimal research on satellite track keeping strategy for low earth orbit satellite

    Institute of Scientific and Technical Information of China (English)

    崔鹏; 傅忠谦

    2013-01-01

    The most LEO(low earth orbit) satellites run in the sun-synchronous orbit.In order to keep their orbit character and achieve the work condition of satellite equipment,satellite track must be kept by orbit control.This paper analyses the local time of descending node is kept by inclination biased and effect for satellite track of inclination biased and decrease of major semi-axis and chronic change of inclination.It gives the keeping method and compute model of adding major semi-axis biased.The simulation results show that the method achieves the demand of track keeping,and the frequency of orbit control is decreased.There is important meaning in practice application.%在轨运行的LEO(low earth orbit)卫星绝大多数是太阳同步回归轨道,为了保持其轨道特性并满足星上载荷工作条件,必须进行星下点轨迹保持.分析了倾角偏置实现降交点地方时保持的同时对星下点轨迹漂移的影响,以及半长轴衰减和倾角长期变化引起的星下点轨迹漂移,给出了增大半长轴偏置量的星下点轨迹保持方法和计算模型.仿真结果显示,此方法不但满足轨迹保持要求,而且减小了轨道维持频度,在工程应用中有重要的意义.

  18. Orbits of Massive Satellite Galaxies: I. A Close Look at the Large Magellanic Cloud and a New Orbital History for M33

    CERN Document Server

    Patel, Ekta; Sohn, Tony

    2016-01-01

    The Milky Way (MW) and M31 both harbor massive satellite galaxies, the Large Magellanic Cloud (LMC) and M33, which may comprise up to 10 per cent of their host's total mass. Massive satellites can change the orbital barycentre of the host-satellite system by tens of kiloparsecs and are cosmologically expected to harbor dwarf satellite galaxies of their own. Assessing the impact of these effects depends crucially on the orbital histories of the LMC and M33. Here, we revisit the dynamics of the MW-LMC system and present the first detailed analysis of the M31-M33 system utilizing high precision proper motions and statistics from the dark matter-only Illustris cosmological simulation. With the latest Hubble Space Telescope proper motion measurements of M31, we reliably constrain M33's interaction history with its host. In particular, like the LMC, M33 is either on its first passage (t_{inf} =2x10^12 Msun), it is on a long period orbit of about 6 Gyr. Cosmological analogs of the LMC and M33 identified in Illustris...

  19. Spectrum and orbit conservation as a factor in future mobile satellite system design

    Science.gov (United States)

    Bowen, Robert R.

    1990-01-01

    Access to the radio spectrum and geostationary orbit is essential to current and future mobile satellite systems. This access is difficult to obtain for current systems, and may be even more so for larger future systems. In this environment, satellite systems that minimize the amount of spectrum orbit resource required to meet a specific traffic requirement are essential. Several spectrum conservation techniques are discussed, some of which are complementary to designing the system at minimum cost. All may need to be implemented to the limits of technological feasibility if network growth is not to be constrained because of the lack of available spectrum-orbit resource.

  20. 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.; Krainak, Michael A.; Zuber, Maria T.; Smith, David E.

    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.

  1. Precise orbit determination of the Fengyun-3C satellite using onboard GPS and BDS observations

    Science.gov (United States)

    Li, Min; Li, Wenwen; Shi, Chuang; Jiang, Kecai; Guo, Xiang; Dai, Xiaolei; Meng, Xiangguang; Yang, Zhongdong; Yang, Guanglin; Liao, Mi

    2017-04-01

    The GNSS Occultation Sounder instrument onboard the Chinese meteorological satellite Fengyun-3C (FY-3C) tracks both GPS and BDS signals for orbit determination. One month's worth of the onboard dual-frequency GPS and BDS data during March 2015 from the FY-3C satellite is analyzed in this study. The onboard BDS and GPS measurement quality is evaluated in terms of data quantity as well as code multipath error. Severe multipath errors for BDS code ranges are observed especially for high elevations for BDS medium earth orbit satellites (MEOs). The code multipath errors are estimated as piecewise linear model in 2° × 2° grid and applied in precise orbit determination (POD) calculations. POD of FY-3C is firstly performed with GPS data, which shows orbit consistency of approximate 2.7 cm in 3D RMS (root mean square) by overlap comparisons; the estimated orbits are then used as reference orbits for evaluating the orbit precision of GPS and BDS combined POD as well as BDS-based POD. It is indicated that inclusion of BDS geosynchronous orbit satellites (GEOs) could degrade POD precision seriously. The precisions of orbit estimates by combined POD and BDS-based POD are 3.4 and 30.1 cm in 3D RMS when GEOs are involved, respectively. However, if BDS GEOs are excluded, the combined POD can reach similar precision with respect to GPS POD, showing orbit differences about 0.8 cm, while the orbit precision of BDS-based POD can be improved to 8.4 cm. These results indicate that the POD performance with onboard BDS data alone can reach precision better than 10 cm with only five BDS inclined geosynchronous satellite orbit satellites and three MEOs. As the GNOS receiver can only track six BDS satellites for orbit positioning at its maximum channel, it can be expected that the performance of POD with onboard BDS data can be further improved if more observations are generated without such restrictions.

  2. Optimization of orbital assignment and specification of service areas in satellite communications

    Science.gov (United States)

    Wang, Cou-Way; Levis, Curt A.; Buyukdura, O. Merih

    1987-01-01

    The mathematical nature of the orbital and frequency assignment problem for communications satellites is explored, and it is shown that choosing the correct permutations of the orbit locations and frequency assignments is an important step in arriving at values which satisfy the signal-quality requirements. Two methods are proposed to achieve better spectrum/orbit utilization. The first, called the delta S concept, leads to orbital assignment solutions via either mixed-integer or restricted basis entry linear programming techniques; the method guarantees good single-entry carrier-to-interference ratio results. In the second, a basis for specifying service areas is proposed for the Fixed Satellite Service. It is suggested that service areas should be specified according to the communications-demand density in conjunction with the delta S concept in order to enable the system planner to specify more satellites and provide more communications supply.

  3. 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...

  4. Fundamentals of the route theory for satellite constellation design for Earth discontinuous coverage. Part 4: Compound satellite structures on orbits with synchronized nodal regression

    Science.gov (United States)

    Razoumny, Yury N.

    2016-12-01

    Basing on the theory results considered in the previous papers of the series for traditional one-tiered constellation formed on the orbits with the same values of altitudes and inclinations for all the satellites of the constellation, the method for constellation design using compound satellite structures on orbits with different altitudes and inclinations and synchronized nodal regression is developed. Compound, multi-tiered, satellite structures (constellations) are based on orbits with different values of altitude and inclination providing nodal regression synchronization. It is shown that using compound satellite constellations for Earth periodic coverage makes it possible to sufficiently improve the Earth coverage, as compared to the traditional constellations based on the orbits with common altitude and inclination for all the satellites of the constellation, and, as a consequence, to get new opportunities for the satellite constellation design for different types of prospective space systems regarding increasing the quality of observations or minimization of the number of the satellites required.

  5. Precise Ground-In-the-Loop Orbit Control for Low Earth Observation Satellites

    Science.gov (United States)

    Arbinger, C.; D'Amico, S.; Eineder, M.

    The growing interest in earth observation missions equipped with space-borne optical and synthetic aperture radar (SAR) sensors drives the accuracy requirements with respect to orbit determination and control. Especially SAR interferometry with its capability to resolve the velocity of on-ground objects (e.g. for traffic monitoring, ocean currents and glacier monitoring) and to determine highly precise digital elevation models is of significant interest for scientific applications. These goals may be achieved using along-track and repeat-pass interferometry with a satellite formation, based on the precise orbit control of one satellite with respect to the osculating trajectory of the second satellite. Such a control concept will be realized by the German TerraSAR-X mission, with an expected launch in 2006, using a virtual formation, where a single satellite will be controlled in a tight manner with respect to a predefined osculating reference trajectory. This is very challenging, since common orbit disturbances, like for close twin formations, do not cancel out in this scenario. The predefined trajectory in the TerraSAR-X case could also be the orbit of a second satellite. The paper describes the generation of such a virtual reference orbit, discusses the ground-in-the-loop control concept and presents results from a long-term simulation.

  6. 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.

  7. 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.

  8. Improved Orbit Determination and Forecasts with an Assimilative Tool for Satellite Drag Specification

    Science.gov (United States)

    Pilinski, M.; Crowley, G.; Sutton, E.; Codrescu, M.

    2016-09-01

    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. As the population of satellites in Earth orbit grows, higher space-weather prediction accuracy is required for critical missions, such as accurate catalog maintenance, collision avoidance for manned and unmanned space flight, reentry prediction, satellite lifetime prediction, defining on-board fuel requirements, and satellite attitude dynamics. 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. In this paper, we will review the driving requirements for our model, 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. As part of the analysis, we compare the drag observed by

  9. Monitoring of the orbital position of a geostationary satellite by the spatially separated reception of signals of digital satellite television

    Science.gov (United States)

    Kaliuzny, M. P.; Bushuev, F. I.; Sibiriakova, Ye. S.; Shulga, O. V.; Shakun, L. S.; Bezrukovs, V.; Kulishenko, V. F.; Moskalenko, S. S.; Malynovsky, Ye. V.; Balagura, O. A.

    2017-02-01

    The results of the determination of the geostationary satellite "Eutelsat-13B" orbital position obtained during 2015-2016 years using European stations' network for reception of DVB-S signals from the satellite are presented. The network consists of five stations located in Ukraine and Latvia. The stations are equipped with a radio engineering complex developed by the RI "MAO". The measured parameter is a time difference of arrival (TDOA) of the DVB-S signals to the stations of the network. The errors of TDOA determination and satellite coordinates, obtained using a numerical model of satellite motion, are equal ±2.6 m and ±35 m respectively. Software implementation of the numerical model is taken from the free space dynamics library OREKIT.

  10. Orbits and Masses of the Satellites of the Dwarf Planet Haumea = 2003 EL61

    CERN Document Server

    Ragozzine, Darin

    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 non-spherical primary (described by $J_2$). The nearly co-planar 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 inc...

  11. Precise orbit determination of a maneuvered GEO satellite using CAPS ranging data

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Wheel-off-loadings and orbital maneuvers of the GEO satellite result in additional accelerations to the satellite itself. Complex and difficult to model, these time varying accelerations are an important error source of precise orbit determination (POD). In most POD practices, only non-maneuver orbital arcs are treated. However, for some applications such as satellite navigation RDSS services, uninterrupted orbital ephemeris is demanded, requiring the development of POD strategies to be processed both during and after an orbital maneuver. We in this paper study the POD for a maneuvered GEO satellite, using high precision and high sampling rate ranging data obtained with Chinese Area Positioning System (CAPS). The strategy of long arc POD including maneuver arcs is studied by using telemetry data to model the maneuver thrust process. Combining the thrust and other orbital perturbations, a long arc of 6 days’ CAPS ranging data is analyzed. If the telemetry data are not available or contain significant errors, attempts are made to estimate thrusting parameters using CAPS ranging data in the POD as an alternative to properly account for the maneuver. Two strategies achieve reasonably good data fitting level in the tested arc with the maximal position difference being about 20 m.

  12. Precise orbit determination of a maneuvered GEO satellite using CAPS ransing data

    Institute of Scientific and Technical Information of China (English)

    HUANG Yong; HU XiaoGong; HUANG Cheng; YANG QiangWen; JIAO WenHai

    2009-01-01

    Wheel-off-loadings and orbital maneuvers of the GEO satellite result in additional accelerations to the satellite itself.Complex and difficult to model,these time varying accelerations are an important error source of precise orbit determination (POD).In most POD practices,only non-maneuver orbital arcs are treated.However,for some applications such as satellite navigation RDSS services,uninterrupted orbital ephemeris is demanded,requiring the development of POD strategies to be processed both during and after an orbital maneuver.We in this paper study the POD for a maneuvered GEO satellite,using high precision and high sampling rate ranging data obtained with Chinese Area Positioning System (CAPS).The strategy of long arc POD including maneuver arcs is studied by using telemetry data to model the maneuver thrust process.Combining the thrust and other orbital perturbations,a long arc of 6 days' CAPS ranging data is analyzed.If the telemetry data are not available or contain significant errors,attempts are made to estimate thrusting parameters using CAPS ranging data in the POD as an alternative to properly account for the maneuver.Two strategies achieve reasonably good data fitting level in the tested arc with the maximal position difference being about 20m.

  13. Precise orbit determination of a maneuvered GEO satellite using CAPS ranging data

    Science.gov (United States)

    Huang, Yong; Hu, Xiaogong; Huang, Cheng; Yang, Qiangwen; Jiao, Wenhai

    2009-03-01

    Wheel-off-loadings and orbital maneuvers of the GEO satellite result in additional accelerations to the satellite itself. Complex and difficult to model, these time varying accelerations are an important error source of precise orbit determination (POD). In most POD practices, only non-maneuver orbital arcs are treated. However, for some applications such as satellite navigation RDSS services, uninterrupted orbital ephemeris is demanded, requiring the development of POD strategies to be processed both during and after an orbital maneuver. We in this paper study the POD for a maneuvered GEO satellite, using high precision and high sampling rate ranging data obtained with Chinese Area Positioning System (CAPS). The strategy of long arc POD including maneuver arcs is studied by using telemetry data to model the maneuver thrust process. Combining the thrust and other orbital perturbations, a long arc of 6 days’ CAPS ranging data is analyzed. If the telemetry data are not available or contain significant errors, attempts are made to estimate thrusting parameters using CAPS ranging data in the POD as an alternative to properly account for the maneuver. Two strategies achieve reasonably good data fitting level in the tested arc with the maximal position difference being about 20 m.

  14. Satellite quenching timescales in clusters from projected phase space measurements matched to simulated orbits

    CERN Document Server

    Oman, Kyle A

    2016-01-01

    We measure the star formation quenching efficiency and timescale in cluster environments. Our method uses N-body simulations to estimate the probability distribution of possible orbits for a sample of observed SDSS galaxies in and around clusters based on their position and velocity offsets from their host cluster. We study the relationship between their star formation rates and their likely orbital histories via a simple model in which star formation is quenched once a delay time after infall has elapsed. Our orbit library method is designed to isolate the environmental effect on the star formation rate due to a galaxy's present-day host cluster from `pre-processing' in previous group hosts. We find that quenching of satellite galaxies of all stellar masses in our sample ($10^{9}-10^{11.5}\\,{\\rm M}_\\odot$) by massive ($> 10^{13}\\,{\\rm M}_\\odot$) clusters is essentially $100$ per cent efficient. Our fits show that all galaxies quench on their first infall, approximately at or within a Gyr of their first peric...

  15. Integrated Orbit, Attitude, and Structural Control Systems Design for Space Solar Power Satellites

    Science.gov (United States)

    Wie, Bong; Roithmayr, Carlos M.

    2001-01-01

    The major objective of this study is to develop an integrated orbit, attitude, and structural control systems architecture for very large Space Solar Power Satellites (SSPS) in geosynchronous orbit. This study focuses on the 1.2-GW Abacus SSPS concept characterized by a 3.2 x 3.2 km solar-array platform, a 500-m diameter microwave beam transmitting antenna, and a 500 x 700 m earth-tracking reflector. For this baseline Abacus SSPS configuration, we derive and analyze a complete set of mathematical models, including external disturbances such as solar radiation pressure, microwave radiation, gravity-gradient torque, and other orbit perturbation effects. The proposed control systems architecture utilizes a minimum of 500 1-N electric thrusters to counter, simultaneously, the cyclic pitch gravity-gradient torque, the secular roll torque caused by an offset of the center-of-mass and center-of-pressure, the cyclic roll/yaw microwave radiation torque, and the solar radiation pressure force whose average value is about 60 N.

  16. 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

  17. Satellite formation design in orbits of high eccentricity for missions with performance criteria specified over a region of interest

    Science.gov (United States)

    Roscoe, Christopher William Thomas

    Several methods are presented for the design of satellite formations for science missions in high-eccentricity reference orbits with quantifiable performance criteria specified throughout only a portion the orbit, called the Region of Interest (RoI). A modified form of the traditional average along-track drift minimization condition is introduced to account for the fact that performance criteria are only specified within the RoI, and a robust formation design algorithm (FDA) is defined to improve performance in the presence of formation initialization errors. Initial differential mean orbital elements are taken as the design variables and the Gim-Alfriend state transition matrix (G-A STM) is used for relative motion propagation. Using mean elements and the G-A STM allows for explicit inclusion of J2 perturbation effects in the design process. The methods are applied to the complete formation design problem of the NASA Magnetospheric Multiscale (MMS) mission and results are verified using the NASA General Mission Analysis Tool (GMAT). Since satellite formations in high-eccentricity orbits will spend long times at high altitude, third-body perturbations are an important design consideration as well. A detailed analytical analysis of third-body perturbation effects on satellite formations is also performed and averaged dynamics are derived for the particular case of the lunar perturbation. Numerical results of the lunar perturbation analysis are obtained for the example application of the MMS mission and verified in GMAT.

  18. An Autonomous Orbit Determination System for Earth Satellites

    Science.gov (United States)

    1989-12-01

    these points is warranted. For example, low-Earth orbits ( LEO ) can be expected to approach e - 0 with time, so it is particularly useful to examine how...0.77887 e + 0.52875 e x y z 7 Canis Major A A A Cairs) M-0.18485 e + 0.93984 e - 0.28728 e (Sirus) -xyz A A A 8 a Leo -0.86275 e + 0.46061 e...Filters for Orbit Determination and Estimation, PhD Dissertation. University of Illinois, Urbana-Champaign IL, 1986 (AD-A170680). 12. Brouwer , Dirk

  19. Estimated Satellite Cluster Elements in Near Circular Orbit

    Science.gov (United States)

    1988-12-01

    values of the covariance matriz P to see if the filter performs as well as it believes it is performing [4:page 3391. 1.1.. Thuth Model The truth...between satellites will bc affected. Since the measurements contain no informa- L tion on absolute downrange position, it is impossible to estimate

  20. In-Orbit Earth Radiation Budget Satellite (ERBS) Battery Switch

    Science.gov (United States)

    Ahmad, Anisa; Enciso, Marlon; Rao, Gopalakrishna

    2000-01-01

    A viewgraph presentation outlines the Earth Radiation Budget Satellite (ERBS) power system and battery history. ERBS spacecraft and battery cell failures are listed with the reasons for failure. The battery management decision and stabilization of the batteries is discussed. Present battery operations are shown to be successful.

  1. MIT Orbital Transfer Vehicle (MOTV): CASTOR Satellite: Design Document

    Science.gov (United States)

    2010-11-18

    with Chocolate Satellite ................................................... 38 Figure 2.1-1: Ground System Layout...292 Figure 6.2-8: Analog Output Channels ........................................................................... 293 Figure 6.2-9: Turn PID Off...connections. Diagrams of the pin connections are included. The Grounding section identifies the type of grounding connections (i.e. analog , digital

  2. The Orbits of Saturn's Small Satellites Derived from Combined Historic and Cassini Imaging Observations

    Science.gov (United States)

    Spitale, J. N.; Jacobson, R. A.; Porco, C. C.; Owen, W. M., Jr.

    2006-08-01

    We report on the orbits of the small, inner Saturnian satellites, either recovered or newly discovered in recent Cassini imaging observations. The orbits presented here reflect improvements over our previously published values in that the time base of Cassini observations has been extended, and numerical orbital integrations have been performed in those cases in which simple precessing elliptical, inclined orbit solutions were found to be inadequate. Using combined Cassini and Voyager observations, we obtain an eccentricity for Pan 7 times smaller than previously reported because of the predominance of higher quality Cassini data in the fit. The orbit of the small satellite (S/2005 S1 [Daphnis]) discovered by Cassini in the Keeler gap in the outer A ring appears to be circular and coplanar; no external perturbations are apparent. Refined orbits of Atlas, Prometheus, Pandora, Janus, and Epimetheus are based on Cassini , Voyager, Hubble Space Telescope, and Earth-based data and a numerical integration perturbed by all the massive satellites and each other. Atlas is significantly perturbed by Prometheus, and to a lesser extent by Pandora, through high-wavenumber mean-motion resonances. Orbital integrations involving Atlas yield a mass of GMAtlas=(0.44+/-0.04)×10-3 km3 s -2, 3 times larger than reported previously (GM is the product of the Newtonian constant of gravitation G and the satellite mass M). Orbital integrations show that Methone is perturbed by Mimas, Pallene is perturbed by Enceladus, and Polydeuces librates around Dione's L5 point with a period of about 791 days. We report on the nature and orbits of bodies sighted in the F ring, two of which may have persisted for a year or more.

  3. Long-term evolution of the inclined geosynchronous orbit in Beidou Navigation Satellite System

    Science.gov (United States)

    Tang, Jingshi; Hou, Xiyun; Liu, Lin

    2017-02-01

    China's Beidou Navigation Satellite System (BDS), unlike other navigation satellite systems, uses several inclined geosynchronous orbits (IGSO) to enhance the accuracy of regional or global navigation. In order to maintain a safe space environment in the vicinity of its operational orbit, it is necessary that the decommissioned satellites be well disposed of. To understand the underlying dynamics that affect the BDS IGSO, we study this problem from two aspects. In this paper, we first theoretically analyze the problem using the simplified models with 1 and 2 degrees of freedoms (1-/2-dof). Then we extensively investigate the numerically propagated orbits for 200 and 1000 years, applying the results from these simplified models and seeking proper explanations for the underlying dynamics. We especially focus on the eccentricity evolution, which is a major concern regarding the collision hazard. We expect to understand the underlying dynamics governing the long-term evolution of BDS IGSO and gain helpful insight into future disposal strategies.

  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. 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…

  6. GPS-derived orbits for the GOCE satellite

    NARCIS (Netherlands)

    Bock, H.; Jäggi, A.; Meyer, U.; Visser, P.N.A.M.; Van den IJssel, J.A.A.; Van Helleputte, T.; Heinze, M.; Hugentobler, U.

    2011-01-01

    The first ESA (European Space Agency) Earth explorer core mission GOCE (Gravity field and steady-state Ocean Circulation Explorer) was launched on 17 March 2009 into a sun-synchronous dusk–dawn orbit with an exceptionally low initial altitude of about 280 km. The onboard 12-channel dual-frequency GP

  7. Real-Time Orbit Determination for Future Korean Regional Navigation Satellite System

    Science.gov (United States)

    Shin, Kihae; Oh, Hyungjik; Park, Sang-Young; Park, Chandeok

    2016-03-01

    This paper presents an algorithm for Real-Time Orbit Determination (RTOD) of navigation satellites for the Korean Regional Navigation Satellite System (KRNSS), when the navigation satellites generate ephemeris by themselves in abnormal situations. The KRNSS is an independent Regional Navigation Satellite System (RNSS) that is currently within the basic/preliminary research phase, which is intended to provide a satellite navigation service for South Korea and neighboring countries. Its candidate constellation comprises three geostationary and four elliptical inclined geosynchronous orbit satellites. Relative distance ranging between the KRNSS satellites based on Inter-Satellite Ranging (ISR) is adopted as the observation model. The extended Kalman filter is used for real-time estimation, which includes fine-tuning the covariance, measurement noise, and process noise matrices. Simulation results show that ISR precision of 0.3-0.7 m, ranging capability of 65,000 km, and observation intervals of less than 20 min are required to accomplish RTOD accuracy to within 1 m. Furthermore, close correlation is confirmed between the dilution of precision and RTOD accuracy.

  8. 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.

  9. Dawn Mission’s Search for satellites at Ceres: Upper limits on size of orbital objects

    Science.gov (United States)

    McFadden, Lucy-Ann A.; Skillman, David R.; Memarsadeghi, Nargess; Carsenty, Uri; Schroeder, Stefan E.; Li, Jian-Yang Y.; Rayman, Marc D.

    2015-11-01

    Hundreds of asteroids have small secondary satellites or are double, or even multiple body systems; yet dwarf planet Ceres doesn’t and isn’t. Ground-based and space-based telescopic searches have placed upper limits on the size of any secondary bodies gravitationally bound to Ceres of 1-2 km (Gehrels et al 1987, Bieryla et al. 2011). The Dawn project’s satellite working group designed and conducted a search during approach to Ceres and during high orbit concentrating its search close to Ceres’ limb where previous searches could not reach. Over 2000 images for both science and optical navigation were searched. In addition, a dedicated satellite search was conducted during two commanded off-nadir pointings. The acquired images extend 5.5° x 5.5° on either side of Ceres, at a range of ~ 145,000 km and solar phase angle at Ceres of 18°. No moving objects associated with Ceres were detected. The search extended down to Ceres’ limb (previous searches went to 500 km above the limb) and extended the upper limit for the non-detection to 30 +/- 6 and 45 +/-9 meter radius for effective exposure times of 114s and 19s respectively. An additional small search was conducted using the spacecraft's star tracker from which no objects were found. The Dawn mission’s search reduced the previous detection limit from Hubble Space Telescope images by two orders of magnitude. Why some asteroids have satellites and others don’t is a matter for dynamical speculation.

  10. CARTEL: A method to calibrate S-band ranges with geostationary satellites. Results of orbit determination

    Science.gov (United States)

    Guitart, A.; Mesnard, B.

    1986-05-01

    A satellite tracking campaign was organized, with 4 S-band stations, for 1 wk. The relative geometry of the network with respect to the satellites was an opportunity to show how the most precise orbit can be computed with the operational software. This precise orbit served as a reference to evaluate what can be achieved with one station with range and angular measurements, a typical configuration used for stationkeeping of geostationary satellites. Orbit computation implied numerical integration with gravitational (Earth, Moon, and Sun) and solar radiation pressure forces acting on the satellite. Arc lengths of 2 days gave initial state vectors which were compared every day. Precision of 10 m is achieved. However, an analysis of the influence of parameters in the orbit computations reveals that the absolute accuracy is of the order of 100 m, since modeling perturbations were neglected in the operational software (e.g., polar motion). In a relative sense, the reference orbit allows estimation of systematic errors for other tracking antennas.

  11. INSIGHT (interaction of low-orbiting satellites with the surrounding ionosphere and thermosphere)

    Science.gov (United States)

    Schlicht, Anja; Reussner, Elisabeth; Lühr, Hermann; Stolle, Claudia; Xiong, Chao; Schmidt, Michael; Blossfeld, Mathis; Erdogan, Eren; Pancetta, Francesca; Flury, Jakob

    2016-04-01

    In the framework of the DFG special program "Dynamic Earth" the project INSIGHT, started in September 2015, is studying the interactions between the ionosphere and thermosphere as well as the role of the satellites and their instruments in observing the space environment. Accelerometers on low-Earth orbiters (LEOs) are flown to separate non-gravitational forces acting on the satellite from influences of gravitational effects. Amongst others these instruments provide valuable information for improving our understanding of thermospheric properties like densities and winds. An unexpected result, for example, is the clear evidence of geomagnetic field control on the neutral upper atmosphere. The charged particles of the ionosphere act as mediators between the magnetic field and the thermosphere. In the framework of INSIGHT the climatology of the thermosphere will be established and the coupling between the ionosphere and thermosphere is studied. There are indications that the accelerometers are influenced by systematic errors not identified up to now. For GRACE it is one of the discussed reasons, why this mission so far did not reach the baseline accuracy. Beutler et al. 2010 discussed the limited use of the GRACE accelerometer measurements in comparison to stochastic pulses in gravity field recovery. Analysis of the accelerometer measurements show many structures in the high frequency region which can be traced back to switching processes of electric circuits in the spacecraft, like heater and magnetic torquer switching, or so called twangs, which can be associated with discharging of non-conducting surfaces of the satellite. As all observed signals have the same time dependency a common origin is very likely, namely the coupling of time variable electric currents into the accelerometer signal. In GOCE gravity field gradients non-gravitational signatures around the magnetic poles are found indicating that even at lower frequencies problems occur. INSIGHT will identify

  12. UoGAS - A Get Away Special Satellite with Orbit-Raising Capability

    OpenAIRE

    Lorenz, Ralph

    1988-01-01

    The low cost of satellite deployment from Shuttle GAS canister makes it an attractive launch option. However, the low deployment altitude severely constrains lifetime so the UoGAS (University of Surrey Get Away Special) spacecraft will incorporate a propulsion system. Lifetime extension methods are considered and a start-of-mission orbit-raising manoeuvre is selected. An orbit dynamics simulation method (taking into account the atmospheric drag) is discussed and results presented. Mission pro...

  13. 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

  14. System Design and In-orbit Verification of the HJ-1-C SAR Satellite

    Directory of Open Access Journals (Sweden)

    Zhang Run-ning

    2014-06-01

    Full Text Available HJ-1-C is a SAR satellite owned by the Chinese Environment and Natural Disaster Monitoring constellation, and works together with the optical satellites HJ-1-A/B for monitoring environment and natural disasters. In this paper, the system design and characteristics of the first Chinese civil SAR satellite are described. In addition, the interface relation between SAR payload and platform is studied. Meanwhile, the data transmission capability, attitude, power, and temperature control that support SAR imaging are reviewed. Finally, the corresponding in-orbit verification results are presented.

  15. An analysis of the wide area differential method of geostationary orbit satellites

    Institute of Scientific and Technical Information of China (English)

    CAI ChengLin; LI XiaoHui; WU HaiTao

    2009-01-01

    This work aims to obtain a wide area differential method for geostationary orbit (GEO) constellation. A comparison between the dilution of precision (DOP) of four-dimensional (4D) calculation including satellite clock errors and ephemeris errors and that of three-dimensional (3D) calculation only including ephemeris errors with the inverse positioning theory of GPS shows the conclusion that all the 3D PDOPs are greatly reduced. Based on this, a basic idea of correcting satellite clock errors and ephem-eris errors apart is put forward, and moreover, a specific method of separation is proposed. Satellite clock errors are separated in a master station with time synchronization, and all the remaining pseudo-range errors after the satellite clock errors have been deducted are used to work out ephemeris corrections of all GEO satellites. By a comparative analysis of user positioning accuracy before and after differential, the wide area differential method is verified to be quite valid for GEO constellation.

  16. Interaction of 4-rotational gauge field with orbital moment, gravi-diamagnetic effect and orbit experiment

    CERN Document Server

    Babourova, Olga V

    2010-01-01

    A direct interaction of the 4-rotational (Lorentzian) gauge field with the angular orbital momentum of an external field is considered. This interaction appears in a new Poincar\\'{e} gauge theory of gravitation, in which tetrads are not true gauge fields, but represent to be some functions of the translational and 4-rotational gauge fields. The given interaction leads to a new effect: the existence of an electronic orbits precession under the action of an intensive external gravitational field (gravi-diamagnetic effect), and also substantiates the existence of the direct interaction of the proper angular momentum of a gyroscope with the torsion field, which theoretically can be generated by the rotational angular momentum of the planet the Earth. The latter interaction can be detected by the experiment "Gravity Probe B" (GP-B) on a satellite orbit

  17. Dynamical evolution of interplanetary dust particles trapped in Earth's horseshoe and quasi-satellite co-orbital resonance regions

    Science.gov (United States)

    Kortenkamp, Stephen J.

    2016-10-01

    We use numerical integrations to model the orbital evolution of IDPs decaying from the asteroid belt into the inner solar system under the influence of radiation pressure, Poynting-Roberston light drag, and solar wind drag. In our models the ratio of radiation pressure to solar gravity ranges from 0.0025 up to 0.02, corresponding to IDP diameters ranging from about 200 microns down to about 25 microns, respectively. In this size range nearly 100% of IDPs become temporarily trapped in mean-motion resonances just outside Earth's orbit. While trapped in these outer resonances the orbital eccentricities of IDPs significantly increases. This causes most IDPs to eventually escape the resonances, allowing their orbits to continue decaying inwards past 1 AU. We've shown previously (Kortenkamp, Icarus 226, 1550-1558, 2013) that significant fractions of IDPs in this size range can subsequently become trapped in Earth's co-orbital horseshoe and quasi-satellite resonance regions, with semi-major axes just inside of 1 AU. Here, we present new results on the long-term effects of Earth's varying orbital eccentricity and inclination on the trapping and evolution of these co-orbital IDPs.

  18. Evaluation and modeling of autonomous attitude thrust control for the Geostation Operational Environmental Satellite (GOES)-8 orbit determination

    Science.gov (United States)

    Forcey, W.; Minnie, C. R.; Defazio, R. L.

    1995-01-01

    The Geostationary Operational Environmental Satellite (GOES)-8 experienced a series of orbital perturbations from autonomous attitude control thrusting before perigee raising maneuvers. These perturbations influenced differential correction orbital state solutions determined by the Goddard Space Flight Center (GSFC) Goddard Trajectory Determination System (GTDS). The maneuvers induced significant variations in the converged state vector for solutions using increasingly longer tracking data spans. These solutions were used for planning perigee maneuvers as well as initial estimates for orbit solutions used to evaluate the effectiveness of the perigee raising maneuvers. This paper discusses models for the incorporation of attitude thrust effects into the orbit determination process. Results from definitive attitude solutions are modeled as impulsive thrusts in orbit determination solutions created for GOES-8 mission support. Due to the attitude orientation of GOES-8, analysis results are presented that attempt to absorb the effects of attitude thrusting by including a solution for the coefficient of reflectivity, C(R). Models to represent the attitude maneuvers are tested against orbit determination solutions generated during real-time support of the GOES-8 mission. The modeling techniques discussed in this investigation offer benefits to the remaining missions in the GOES NEXT series. Similar missions with large autonomous attitude control thrusting, such as the Solar and Heliospheric Observatory (SOHO) spacecraft and the INTELSAT series, may also benefit from these results.

  19. Vision-based localization for on-orbit servicing of a partially cooperative satellite

    Science.gov (United States)

    Oumer, Nassir W.; Panin, Giorgio; Mülbauer, Quirin; Tseneklidou, Anastasia

    2015-12-01

    This paper proposes ground-in-the-loop, model-based visual localization system based on transmitted images to ground, to aid rendezvous and docking maneuvers between a servicer and a target satellite. In particular, we assume to deal with a partially cooperative target, i.e. passive and without fiducial markers, but supposed at least to keep a controlled attitude, up to small fluctuations, so that the approach mainly involves translational motion. For the purpose of localization, video cameras provide an effective and relatively inexpensive solution, working at a wide range of distances with an increasing accuracy and robustness during the approach. However, illumination conditions in space are especially challenging, due to the direct sunlight exposure and to the glossy surface of a satellite, that creates strong reflections and saturations and therefore a high level of background clutter and missing detections. We employ a monocular camera for mid-range tracking (20 - 5 m) and stereo camera at close-range (5 - 0.5 m), with the respective detection and tracking methods, both using intensity edges and robustly dealing with the above issues. Our tracking system has been extensively verified at the facility of the European Proximity Operations Simulator (EPOS) of DLR, which is a very realistic ground simulation able to reproduce sunlight conditions through a high power floodlight source, satellite surface properties using multilayer insulation foils, as well as orbital motion trajectories with ground-truth data, by means of two 6 DOF industrial robots. Results from this large dataset show the effectiveness and robustness of our method against the above difficulties.

  20. 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 s

  1. Long-term evolution of the inclined geosynchronous orbit in Beidou Navigation Satellite System

    Science.gov (United States)

    Tang, Jingshi; Hou, Xiyun; Liu, Lin

    2016-07-01

    China's Beidou Navigation Satellite System (BDS), unlike other navigation satellite systems, uses several inclined geosynchronous orbits (IGSO) to enhance the accuracy of regional or global navigation. In order to maintain a safe space environment in the vicinity of its operational orbit, it is necessary that the decommissioned satellites be well disposed of. Following up the study on the specific BDS IGSO satellites in the previous COSPAR Scientific Assembly, we now extend the study to understand the underlying dynamics and discuss the long-term evolution of such orbits from a more general perspective. In this paper, we first theoretically analyze the problem using simplified models of 1 and 2 degrees of freedoms (1-/2-dof). Then we extensively investigate the numerically propagated orbits for 200 and 1000 years, applying the results from these simplified models and seeking proper explanations for the underlying dynamics. We especially focus on the eccentricity evolution, which is a major concern regarding the collision hazard. We expect to understand the underlying dynamics governing the long-term evolution of BDS IGSO and gain helpful insight into future disposal strategies.

  2. 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.

  3. 78 FR 19172 - Earth Stations Aboard Aircraft Communicating with Fixed-Satellite Service Geostationary-Orbit...

    Science.gov (United States)

    2013-03-29

    ... From the Federal Register Online via the Government Publishing Office FEDERAL COMMUNICATIONS COMMISSION 47 CFR Parts 2 and 25 Earth Stations Aboard Aircraft Communicating with Fixed-Satellite Service Geostationary-Orbit Space Stations AGENCY: Federal Communications Commission. ACTION: Proposed rule;...

  4. 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.

  5. 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

  6. Tests of daily time variable Earth gravity field solutions for precise orbit determination of altimetry satellites

    Science.gov (United States)

    Rudenko, Sergei; Gruber, Christian

    2016-04-01

    This study makes use of current GFZ monthly and daily gravity field products from 2002 to 2014 based on radial basis functions (RBF) instead of time variable gravity field modeling for precise orbit determination of altimetry satellites. Since some monthly solutions are missing in the GFZ GRACE RL05a solution and in order to reach a better quality for the precise orbit determination, daily generated RBF solutions obtained from Kalman filtered GRACE data processing and interpolated in case of gaps have been used. Moreover, since the geopotential coefficients of low degrees are better determined using SLR observations to geodetic satellites like Lageos, Stella, Starlette and Ajisai than from GRACE observations, these terms are co-estimated in the RBF solutions by using apriori SLR-derived values up to degree and order 4. Precise orbits for altimetry satellites Envisat (2002-2012), Jason-1 (2002-2013) and Jason-2 (2008-2014) are then computed over the given time intervals using this approach and compared with the orbits obtained when using other models such as EIGEN-6S4. An analysis of the root-mean-square values of the observation fits of SLR and DORIS observations and the orbit arcs overlaps will allow us to draw a conclusion on the quality of the RBF solution and to use these new trajectories for sea level trend estimates and geophysical application.

  7. Dynamical friction and scratches of orbiting satellite galaxies on host systems

    CERN Document Server

    Ogiya, Go

    2015-01-01

    We study the dynamical response of extended systems, hosts, to smaller systems, satellites, orbiting around the hosts using extremely high-resolution N-body simulations with up to one billion particles. This situation corresponds to minor mergers which are ubiquitous in the scenario of hierarchical structure formation in the universe. According to Chandrasekhar (1943), satellites create density wakes along the orbit and the wakes cause a deceleration force on satellites, i.e. dynamical friction. This study proposes an analytical model to predict the dynamical response of hosts in the density distribution and finds not only traditional wakes but also mirror images of over- and underdensities centered on the host. Controlled N-body simulations with high resolutions verify the predictions of the analytical model directly. We apply our analytical model to the expected dynamical response of nearby interacting galaxy pairs, the Milky Way - Large Magellanic Cloud system and the M31 - M33 system.

  8. Dynamical friction and scratches of orbiting satellite galaxies on host systems

    Science.gov (United States)

    Ogiya, Go; Burkert, Andreas

    2016-04-01

    We study the dynamical response of extended systems, hosts, to smaller systems, satellites, orbiting around the hosts using extremely high-resolution N-body simulations with up to one billion particles. This situation corresponds to minor mergers which are ubiquitous in the scenario of hierarchical structure formation in the universe. According to Chandrasekhar, satellites create density wakes along the orbit and the wakes cause a deceleration force on satellites, i.e. dynamical friction. This study proposes an analytical model to predict the dynamical response of hosts as reflected in their density distribution and finds not only traditional wakes but also mirror images of over- and underdensities centred on the host. Our controlled N-body simulations with high resolutions verify the predictions of the analytical model. We apply our analytical model to the expected dynamical response of nearby interacting galaxy pairs, the Milky Way-Large Magellanic Cloud system and the M31-M33 system.

  9. Simulation of the Impacts of Single LEO Satellite Orbit Parameters on the Distribution and Number of Occultation Events

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Focusing on carrying out GPS occultation observations with a receiver set on LEO satellite, this paper develops the LEO orbit simulation system based on which the occultation events can be simulated taking into account the geometric relationship of the satellites and the field of view of the receiver antenna. In this paper, the impacts of 4 types of LEO orbit parameters including argument of latitude (AOL), right ascension of ascending node (RAAN), orbit height and orbit inclination on the distribution and number of occultation events observed with a single LEO satellite are discussed through simulation and some conclusions are drawn.

  10. The role of high-resolution geomagnetic field models for investigating ionospheric currents at low Earth orbit satellites

    Science.gov (United States)

    Stolle, Claudia; Michaelis, Ingo; Rauberg, Jan

    2016-07-01

    Low Earth orbiting geomagnetic satellite missions, such as the Swarm satellite mission, are the only means to monitor and investigate ionospheric currents on a global scale and to make in situ measurements of F region currents. High-precision geomagnetic satellite missions are also able to detect ionospheric currents during quiet-time geomagnetic conditions that only have few nanotesla amplitudes in the magnetic field. An efficient method to isolate the ionospheric signals from satellite magnetic field measurements has been the use of residuals between the observations and predictions from empirical geomagnetic models for other geomagnetic sources, such as the core and lithospheric field or signals from the quiet-time magnetospheric currents. This study aims at highlighting the importance of high-resolution magnetic field models that are able to predict the lithospheric field and that consider the quiet-time magnetosphere for reliably isolating signatures from ionospheric currents during geomagnetically quiet times. The effects on the detection of ionospheric currents arising from neglecting the lithospheric and magnetospheric sources are discussed on the example of four Swarm orbits during very quiet times. The respective orbits show a broad range of typical scenarios, such as strong and weak ionospheric signal (during day- and nighttime, respectively) superimposed over strong and weak lithospheric signals. If predictions from the lithosphere or magnetosphere are not properly considered, the amplitude of the ionospheric currents, such as the midlatitude Sq currents or the equatorial electrojet (EEJ), is modulated by 10-15 % in the examples shown. An analysis from several orbits above the African sector, where the lithospheric field is significant, showed that the peak value of the signatures of the EEJ is in error by 5 % in average when lithospheric contributions are not considered, which is in the range of uncertainties of present empirical models of the EEJ.

  11. Cryogenic On-Orbit Liquid Depot Storage, Acquisition, and Transfer Satellite (COLD-SAT)

    Science.gov (United States)

    Schuster, John R.; Russ, Edwin J.; Wachter, Joseph P.

    1990-01-01

    The Cryogenic On-Orbit Liquid Depot Storage, Acquisition, and Transfer Satellite (COLD-SAT) will perform subcritical liquid hydrogen handling experiments under low gravity conditions to provide engineering data for future space transportation missions. Comprising the four Class 1 enabling experiments are tank press control, tank chilldown, tank no-vent fill, and liquid acquisition device fill/refill. The nine Class 2 enhancing experiments are tanker thermal performance, pressurization, low-gravity setting and outflow, liquid acquisition device performance, transfer line chilldown, outflow subcooling, low-gravity vented fill, fluid dumping, and advanced instrumentation. Consisting of an experiment module mated to a spacecraft bus, COLD-SAT will be placed in an initial 1300 km circular orbit by an Atlas commercial launch vehicle, and will perform experiments in a semi-autonomous mode for a period of up to six months. The three-axis controlled spacecraft bus provides electric power, control and data management, communications, and attitude control along with propulsive acceleration levels ranging from 10(exp -6) to 10(exp -4) g. It is desired to understand the effects that low acceleration levels might have on the heat and mass transfer processes involved in some of the experiments. The experiment module contains the three liquid hydrogen tanks, valves, pressurization and pumping equipment, and instrumentation. Within the highly insulated tanks are specialized fluid management equipment that might be used in future space transportation systems. At launch all the liquid hydrogen for the experiments is contained in the largest tank, which has helium-purged insulation to prevent cryo-pumping of air on the launch pad. The tank is loaded by the hydrogen tanking system used for the Centaur upper stage of the Atlas. After reaching orbit the two smaller tanks become receivers for fluid transfers, and when tanked, become the vessels for performing many of the experiments.

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

    Science.gov (United States)

    Stockmann, Reto; Christiansen, Freddy; Olsen, Nils; Jackson, Andrew

    2015-06-01

    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 an iterative approach consisting of two main parts: one is a main field modelling process to obtain the radial field gradient to perturb the orbits and the other is the state-of-the-art GPS orbit modelling software BERNESE to calculate new physical orbits. We report results based on a single-day approach showing a clear increase of the data quality. That single-day approach leads, however, to undesirable orbital jumps at midnight. Furthermore, we report results obtained for a much larger data set comprising almost all of the data from the three missions. With this approach, we eliminate the orbit discontinuities at midnight but only tiny quality improvements could be achieved for geomagnetically quiet data. We believe that improvements to the data are probably still possible, but it would require the original tracking observations to be found.

  13. Preliminary Results of the Ground/Orbiter Lasercomm Demonstration Experiment between Table Mountain and teh ETS-V1 Satellite

    Science.gov (United States)

    Wilson, K. E.; Lesh, J. R.; Araki, K.; Arimoto, Y.

    1996-01-01

    The Ground/Orbiter Lasercomm Demonstration (GOLD) is an optical communications demonstration between the Japanese Engineering Test Satellite (ETS-V1) and an optical ground transmitting and receiving station at the Table Mountain FAcility in Wrightwood California. Laser transmissions to the satellite are performed approximately four hours every third night when the satellite is at apogee above Table Mountain.

  14. Preliminary Results of the Ground/Orbiter Lasercomm Demonstration Experiment between Table Mountain and teh ETS-V1 Satellite

    Science.gov (United States)

    Wilson, K. E.; Lesh, J. R.; Araki, K.; Arimoto, Y.

    1996-01-01

    The Ground/Orbiter Lasercomm Demonstration (GOLD) is an optical communications demonstration between the Japanese Engineering Test Satellite (ETS-V1) and an optical ground transmitting and receiving station at the Table Mountain FAcility in Wrightwood California. Laser transmissions to the satellite are performed approximately four hours every third night when the satellite is at apogee above Table Mountain.

  15. Orbit Determination with Angle-only Data from the First Korean Optical Satellite Tracking System, OWL-Net

    Science.gov (United States)

    Choi, J.; Jo, J.

    2016-09-01

    The optical satellite tracking data obtained by the first Korean optical satellite tracking system, Optical Wide-field patrol - Network (OWL-Net), had been examined for precision orbit determination. During the test observation at Israel site, we have successfully observed a satellite with Laser Retro Reflector (LRR) to calibrate the angle-only metric data. The OWL observation system is using a chopper equipment to get dense observation data in one-shot over 100 points for the low Earth orbit objects. After several corrections, orbit determination process was done with validated metric data. The TLE with the same epoch of the end of the first arc was used for the initial orbital parameter. Orbit Determination Tool Kit (ODTK) was used for an analysis of a performance of orbit estimation using the angle-only measurements. We have been developing batch style orbit estimator.

  16. 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.

  17. The Orbit and Future Motion of Earth Quasi-Satellite 2016 HO3

    Science.gov (United States)

    Chodas, Paul

    2016-10-01

    The newly discovered small asteroid 2016 HO3 is not only co-orbital with the Earth, it is currently trapped as a quasi-satellite, and it will remain a constant companion of our planet for centuries to come. Although it orbits the Sun, not the Earth, in a frame rotating with the Earth the asteroid appears to make yearly loops around our planet, and also bobs up and down through the ecliptic due to its 8-degree orbital inclination. What makes this asteroid a quasi-satellite is the fact that the Earth's gravity influences its motion so that it never wanders farther away than about 100 lunar distances. In the rotating frame, the asteroid's yearly cycles librate back and forth along the Earth's orbit, with a period of about 45 years. One other asteroid, 2003 YN107, followed a similar librational pattern from 1997 to 2006, but has since departed our vicinity. 2016 HO3, on the other hand, will continue to librate about our planet for centuries to come, making it the best and most stable example of a quasi-satellite to date.

  18. Precise Orbit Determination of BeiDou Satellites with Contributions from Chinese National Continuous Operating Reference Stations

    Directory of Open Access Journals (Sweden)

    Ming Chen

    2017-08-01

    Full Text Available The precise orbit determination (POD for BeiDou satellites is usually limited by the insufficient quantity and poor distribution of ground tracking stations. To cope with this problem, this study used the GPS and BeiDou joint POD method based on Chinese national continuous operating reference stations (CNCORS and IGS/MGEX stations. The results show that the 3D RMS of the differences of overlapping arcs is better than 22 cm for geostationary orbit (GEO satellites and better than 10 cm for inclined geosynchronous orbit (IGSO and medium earth orbit (MEO satellites. The radial RMS is better than 2 cm for all three types of BeiDou satellites. The results of satellite laser ranging (SLR residuals show that the RMS of the IGSO and MEO satellites is better than 5 cm, whereas the GEO satellite has a systematic bias. This study investigates the contributions of CNCORS to the POD of BeiDou satellites. The results show that after the incorporation of CNCORS, the precision of overlapping arcs of the GEO, IGSO, and MEO satellites is improved by 15.5%, 57.5%, and 5.3%, respectively. In accordance with the improvement in the precision of overlapping arcs, the accuracy of the IGSO and MEO satellites assessed by the SLR is improved by 30.1% and 4.8%, respectively. The computation results and analysis demonstrate that the inclusion of CNCORS yields the biggest contribution in the improvement of orbit accuracy for IGSO satellites, when compared to GEO satellites, while the orbit improvement for MEO satellites is the lowest due to their global coverage.

  19. Chinese Surveying and Control Network for Earth-Orbit Satellites and Deep Space Detection

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The relationship between the surveying and control network(CSN) for earth-orbit satellite and spatial geodesy, and the relationship between the CSN for deep space celestial bodies and detectors, and deep space detection are briefly summarized, and so are the basic technical needs of the deep space surveying and control network(DSN). Then, the techniques, the constituents and the distributing of Chinese satellite CSN (CSCSN) and other radio observing establishments in China are introduced. Lastly, with the primary CSCSN and other observing establishments, some projects for China to rebuild a more perfect CSCSN, and to establish a DSN are analyzed and stated.

  20. On-Orbit Performance of the Far Ultraviolet Spectroscopic Explorer (FUSE) Satellite

    CERN Document Server

    Sahnow, D J; Ake, T; Andersen, J; Andersson, B G; André, M; Artis, D; Berman, A; Blair, W; Brownsberger, K R; Calvani, H; Chayer, P; Conard, S; Feldman, P; Friedman, S; Fullerton, A W; Gaines, G; Gawne, W; Green, J; Gummin, M; Jennings, T; Joyce, J B; Kaiser, M E; Kruk, J W; Lindler, D; Massa, D L; Murphy, E; Oegerle, W R; Ohl, R; Roberts, B; Romelfanger, M; Roth, K C; Sankrit, R; Sembach, K R; Shelton, R; Siegmund, O; Silva, C; Sonneborn, G; Vaclavik, S; Weaver, H; Wilkinson, E

    2000-01-01

    Launch of the Far Ultraviolet Spectroscopic Explorer (FUSE) has been followed by an extensive period of calibration and characterization as part of the preparation for normal satellite operations. Major tasks carried out during this period include initial coalignment, focusing and characterization of the four instrument channels, and a preliminary measurement of the resolution and throughput performance of the instrument. We describe the results from this test program, and present preliminary estimates of the on-orbit performance of the FUSE satellite based on a combination of this data and prelaunch laboratory measurements.

  1. 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

  2. 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.

  3. Joint Polar Satellite System (JPSS) Micrometeoroid and Orbital Debris (MMOD) Assessment

    Science.gov (United States)

    Squire, Michael D.; Cooke, William J.; Williamsen, Joel; Kessler, Donald; Vesely, William E.; Hull, Scott H.; Schonberg, William; Peterson, Glenn E.; Jenkin, Alan B.; Cornford, Steven L.

    2015-01-01

    The Joint Polar Satellite System (JPSS) Project requested the NASA Engineering and Safety Center (NESC) conduct an independent evaluation of the Micrometeoroid and Orbital Debris (MMOD) models used in the latest JPSS MMOD risk assessment. The principal focus of the assessment was to compare Orbital Debris Engineering Model version 3 (ORDEM 3.0) with the Meteoroid and Space Debris Terrestrial Environment Reference version 2009 (MASTER-2009) and Aerospace Debris Environment Projection Tool (ADEPT) and provide recommendations to the JPSS Project regarding MMOD protection. The outcome of the NESC assessment is contained in this report.

  4. 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.

  5. 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

  6. 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 ...

  7. 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.

  8. Quantum Cryptography for Secure Communications to Low-Earth Orbit Satellites

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, R.J.; Buttler, W.T.; Kwiat, P.G.; Lamoreaux, S.K.; Morgan, G.L.; Peterson, C.G.; Twyeffort, E.; Simmons, C.M.; Nordholt, J.E.

    1999-06-03

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). Quantum cryptography is an emerging technology in which two parties may simultaneously generate shared, secret cryptographic key material using the transmission of quantum states of light. The security of these transmissions is based on the inviolability of the laws of quantum mechanics. An adversary can neither successfully tap the quantum transmissions, nor evade detection. Key material is built up using the transmission of a single-photon per bit. We have developed an experimental quantum cryptography system based on the transmission of non-orthogonal single-photon polarization states to generate shared key material over line-of-sight optical links. Our results provide strong evidence that cryptographic key material could be generated on demand between a ground station and a satellite (or between two satellites), allowing a satellite to be securely re-keyed on in orbit.

  9. Minimum Number of Observation Points for LEO Satellite Orbit Estimation by OWL Network

    Science.gov (United States)

    Park, Maru; Jo, Jung Hyun; Cho, Sungki; Choi, Jin; Kim, Chun-Hwey; Park, Jang-Hyun; Yim, Hong-Suh; Choi, Young-Jun; Moon, Hong-Kyu; Bae, Young-Ho; Park, Sun-Youp; Kim, Ji-Hye; Roh, Dong-Goo; Jang, Hyun-Jung; Park, Young-Sik; Jeong, Min-Ji

    2015-12-01

    By using the Optical Wide-field Patrol (OWL) network developed by the Korea Astronomy and Space Science Institute (KASI) we generated the right ascension and declination angle data from optical observation of Low Earth Orbit (LEO) satellites. We performed an analysis to verify the optimum number of observations needed per arc for successful estimation of orbit. The currently functioning OWL observatories are located in Daejeon (South Korea), Songino (Mongolia), and Oukaïmeden (Morocco). The Daejeon Observatory is functioning as a test bed. In this study, the observed targets were Gravity Probe B, COSMOS 1455, COSMOS 1726, COSMOS 2428, SEASAT 1, ATV-5, and CryoSat-2 (all in LEO). These satellites were observed from the test bed and the Songino Observatory of the OWL network during 21 nights in 2014 and 2015. After we estimated the orbit from systematically selected sets of observation points (20, 50, 100, and 150) for each pass, we compared the difference between the orbit estimates for each case, and the Two Line Element set (TLE) from the Joint Space Operation Center (JSpOC). Then, we determined the average of the difference and selected the optimal observation points by comparing the average values.

  10. Low-Thrust Transfer Design of Low-Observable Geostationary Earth Orbit Satellite

    Directory of Open Access Journals (Sweden)

    Bing Hua

    2015-01-01

    Full Text Available With radar and surface-to-air missiles posing an increasing threat to on-orbit spacecraft, low-observable satellites play an important role in low-thrust transfers. This paper presents the design for a low-thrust geostationary earth orbit (GEO transfer control strategy which takes into consideration the low-observable constraint and discusses Earth shadow and perturbation. A control parameter optimization addresses the orbit transfer problem, and five thrust modes are used. Simulation results show that the method outlined in this paper is simple and feasible and results in reduced transfer time with a small amount of calculation. The method therefore offers a useful reference for low-thrust GEO transfer design.

  11. Chaos in navigation satellite orbits caused by the perturbed motion of the Moon

    CERN Document Server

    Rosengren, Aaron J; Rossi, Alessandro; Valsecchi, Giovanni B

    2015-01-01

    Numerical simulations carried out over the past decade suggest that the orbits of the Global Navigation Satellite Systems are unstable, resulting in an apparent chaotic growth of the eccentricity. Here we show that the irregular and haphazard character of these orbits reflects a similar irregularity in the orbits of many celestial bodies in our Solar System. We find that secular resonances, involving linear combinations of the frequencies of nodal and apsidal precession and the rate of regression of lunar nodes, occur in profusion so that the phase space is threaded by a devious stochastic web. As in all cases in the Solar System, chaos ensues where resonances overlap. These results may be significant for the analysis of disposal strategies for the four constellations in this precarious region of space.

  12. Coherence and phase structure of compressional ULF waves at low-Earth-orbit observed by the Swarm satellites

    Science.gov (United States)

    Heilig, Balázs; Sutcliffe, Peter R.

    2016-04-01

    Different types of ultra low frequency (ULF waves), such as dayside compressional Pc3-Pc4 waves, Pc2 and Pc1 waves, Pc3-Pc4 field line resonances, night side and day side Pi2s, etc. have been successfully identified in the topside ionosphere. ULF observations in this region can help us to understand the wave structure in the magnetosphere, wave propagation, and also the effects of the ionosphere (transmission, reflection, mode conversion). Because of the fast orbiting of the LEO satellites Fourier analysis is not applicable, special techniques (wavelet analysis, maximum entropy method) are needed to resolve ULF signals, as well as to discriminate between spatial and wave structures. In this paper we present results of a study of Pc3 compressional waves observed at low-Earth-orbit (LEO) by the Swarm satellites. The particular emphasis has been to investigate the distribution of wave coherence and phase difference as functions of magnetic latitude and local time. This is the first time that a study of this nature has been carried out using magnetic field data from multiple LEO satellites. We believe that our study provides the first observational evidence to support the prediction by the inductive thin ionosphere model that incident Alfvén mode waves are partially converted into compressional mode waves by the ionosphere.

  13. SATURNʼS INNER SATELLITES: ORBITS, MASSES, AND THE CHAOTIC MOTION OF ATLAS FROM NEW CASSINI IMAGING OBSERVATIONS

    National Research Council Canada - National Science Library

    Cooper, Nicholas J; Renner, Stéfan; Murray, Carl D; Evans, Michael W

    2015-01-01

    We present numerically derived orbits and mass estimates for the inner Saturnian satellites, Atlas, Prometheus, Pandora, Janus, and Epimetheus from a fit to 2580 new Cassini Imaging Science Subsystem...

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

    CERN Document Server

    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 $\\dot a$ of the semimajor axes $a$ of such spacecrafts, recently measured in an independent way to a $\\sigma_{\\dot a}\\approx 0.1-0.01$ 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 $J_2$. \\textcolor{black}{Indeed,} the systematic bias due to the current measurement errors $\\sigma_{\\dot a}$ 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. \\textcolor{black}{Therefore, the parameter-fitting algorit...

  15. Test of the gravitational redshift with stable clocks in eccentric orbits: application to Galileo satellites 5 and 6

    CERN Document Server

    Delva, P; Bertone, S; Richard, E; Wolf, P

    2015-01-01

    In this paper we propose to use satellites Galileo~5 and~6 to perform a test of the gravitational redshift. The best test to date was performed with the Gravity Probe A experiment (1976) with an accuracy of $1.4\\times 10^{-4}$. Here we show that considering realistic noise and systematic effects, and thanks to a highly eccentric orbit, it is possible to improve the GP-A limit to an accuracy around $(3-4)\\times 10^{-5}$ after one year of integration of Galileo~5 and~6 data.

  16. Secular resonances between bodies on close orbits: a case study of the Himalia prograde group of jovian irregular satellites

    CERN Document Server

    Li, Daohai

    2016-01-01

    The gravitational interaction between two objects on similar orbits can effect noticeable changes in the orbital evolution even if the ratio of their masses to that of the central body is vanishingly small. Christou (2005) observed an occasional resonant lock in the differential node $\\Delta \\Omega$ between two members in the Himalia irregular satellite group of Jupiter in the $N$-body simulations (corresponding mass ratio $\\sim 10^{-9}$). Using a semianalytical approach, we have reproduced this phenomenon. We also demonstrate the existence of two additional types of resonance, involving angle differences $\\Delta\\omega$ and $\\Delta (\\Omega+\\varpi)$ between two group members. These resonances cause secular oscillations in eccentricity and/or inclination on timescales $\\sim$ 1 Myr. We locate these resonances in $(a,e,i)$ space and analyse their topological structure. In subsequent $N$-body simulations, we confirm these three resonances and find a fourth one involving $\\Delta \\varpi$. In addition, we study the o...

  17. Linear Magnetoelectric Effect by Orbital Magnetism

    NARCIS (Netherlands)

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

    2012-01-01

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

  18. 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.

  19. Indonesia coverage simulation of SAR satellite at near-equatorial orbit

    Science.gov (United States)

    Septanto, Harry; Utama, Satriya; Heru Triharjanto, Robertus; Suhermanto

    2017-01-01

    Properties of SAR (Synthetic Aperture Radar) that able to penetrate the cloud and does not depend on the sunlight are a number of advantages when utilized for monitoring tropical region like the IMC (Indonesian Maritime Continent). Moreover, since having areas along equatorial belt, the IMC is at a shortcoming from perspective of highly inclined LEO (Low Earth Orbit) satellite. It would result shorter and infrequent pass times when compared with a near-equatorial LEO satellite whose low inclination. This paper reports on the investigation of a near-equatorial LEO SAR satellite coverage property through simulations. The simulations is run in nine scenarios of orbit parameter that consist of combinations of attitude {500 km, 600 km, 700 km} and inclination {80, 90, 100}. The target area is defined as 50 km x 50 km around Jakarta. Meanwhile, the SAR sensor simulation is run with swath width of 40 km, incidence angle around 250-290 and Stripmap mode. Minimum, Maximum and Mean Access Revisit of the target for each scenarios are resulted.

  20. The Measurement of Landfill Gas Emissions with the Orbiting Carbon Observatory and CarbonSAT Satellites

    Science.gov (United States)

    Vigil, S. A.; Bovensmann, H.

    2010-12-01

    Landfill gas is a significant contributor to anthropogenic emissions of CH4 and CO2. The U.S. Environmental Protection Agency has estimated the total U.S. 2007 emissions of the CH4 component of landfill gas at 132.9 Tg CO2 Equivalent. This compares to total CH4 emission from all US sources in 2007 at 585.3 Tg CO2 Equivalent. Worldwide CH4 emissions from landfill gas have been estimated at 668 Tg CO2 Equivalent. Satellite remote sensing can also be used to characterize landfill gas emissions. The NASA Orbiting Carbon Observatory (OCO-2) and the proposed CarbonSAT (University of Bremen) satellites are particularly suited for this purpose. The Orbiting Carbon Observatory (OCO) was designed to provided high spatial resolution ( developed countries. In general, landfills in the developed countries have landfill gas control system ground based landfill gas monitoring systems. These ground-based measurements can be used to calibrate OCO-2 and CarbonSAT landfill gas measurements. OCO-2 and CarbonSAT can be used to measure landfill emissions from the large landfills and open dumps of the emerging megacities in the developing world where accurate ground measurements are not available. For example Mexico City generates 26,000 MT of municipal solid waste that is disposed of in two uncontrolled landfills. Similar conditions exist in Asia, Latin America, and Africa. Satellite based measurements of these landfill gas emissions could help prioritize greenhouse gas remediation projects for these countries.

  1. ARMA Prediction of SBAS Ephemeris and Clock Corrections for Low Earth Orbiting Satellites

    Directory of Open Access Journals (Sweden)

    Jeongrae Kim

    2015-01-01

    Full Text Available For low earth orbit (LEO satellite GPS receivers, space-based augmentation system (SBAS ephemeris/clock corrections can be applied to improve positioning accuracy in real time. The SBAS correction is only available within its service area, and the prediction of the SBAS corrections during the outage period can extend the coverage area. Two time series forecasting models, autoregressive moving average (ARMA and autoregressive (AR, are proposed to predict the corrections outside the service area. A simulated GPS satellite visibility condition is applied to the WAAS correction data, and the prediction accuracy degradation, along with the time, is investigated. Prediction results using the SBAS rate of change information are compared, and the ARMA method yields a better accuracy than the rate method. The error reductions of the ephemeris and clock by the ARMA method over the rate method are 37.8% and 38.5%, respectively. The AR method shows a slightly better orbit accuracy than the rate method, but its clock accuracy is even worse than the rate method. If the SBAS correction is sufficiently accurate comparing with the required ephemeris accuracy of a real-time navigation filter, then the predicted SBAS correction may improve orbit determination accuracy.

  2. A preliminary estimate of geoid-induced variations in repeat orbit satellite altimeter observations

    Science.gov (United States)

    Brenner, Anita C.; Beckley, B. D.; Koblinsky, C. J.

    1990-01-01

    Altimeter satellites are often maintained in a repeating orbit to facilitate the separation of sea-height variations from the geoid. However, atmospheric drag and solar radiation pressure cause a satellite orbit to drift. For Geosat this drift causes the ground track to vary by + or - 1 km about the nominal repeat path. This misalignment leads to an error in the estimates of sea surface height variations because of the local slope in the geoid. This error has been estimated globally for the Geosat Exact Repeat Mission using a mean sea surface constructed from Geos 3 and Seasat altimeter data. Over most of the ocean the geoid gradient is small, and the repeat-track misalignment leads to errors of only 1 to 2 cm. However, in the vicinity of trenches, continental shelves, islands, and seamounts, errors can exceed 20 cm. The estimated error is compared with direct estimates from Geosat altimetry, and a strong correlation is found in the vicinity of the Tonga and Aleutian trenches. This correlation increases as the orbit error is reduced because of the increased signal-to-noise ratio.

  3. Tracking and Data Relay Satellite (TDRS) Orbit Estimation Using an Extended Kalman Filter

    Science.gov (United States)

    Ward, Douglas T.; Dang, Ket D.; Slojkowski, Steve; Blizzard, Mike; Jenkins, Greg

    2007-01-01

    Alternatives to the Tracking and Data Relay Satellite (TDRS) orbit estimation procedure were studied to develop a technique that both produces more reliable results and is more amenable to automation than the prior procedure. The Earth Observing System (EOS) Terra mission has TDRS ephemeris prediction 3(sigma) requirements of 75 meters in position and 5.5 millimeters per second in velocity over a 1.5-day prediction span. Meeting these requirements sometimes required reruns of the prior orbit determination (OD) process, with manual editing of tracking data to get an acceptable solution. After a study of the available alternatives, the Flight Dynamics Facility (FDF) began using the Real-Time Orbit Determination (RTOD(Registered TradeMark)) Kalman filter program for operational support of TDRSs in February 2007. This extended Kalman filter (EKF) is used for daily support, including within hours after most thrusting, to estimate the spacecraft position, velocity, and solar radiation coefficient of reflectivity (C(sub R)). The tracking data used are from the Bilateration Ranging Transponder System (BRTS), selected TDRS System (TDRSS) User satellite tracking data, and Telemetry, Tracking, and Command (TT&C) data. Degraded filter results right after maneuvers and some momentum unloads provided incentive for a hybrid OD technique. The results of combining EKF strengths with the Goddard Trajectory Determination System (GTDS) Differential Correction (DC) program batch-least-squares solutions, as recommended in a 2005 paper on the chain-bias technique, are also presented.

  4. A preliminary estimate of geoid-induced variations in repeat orbit satellite altimeter observations

    Science.gov (United States)

    Brenner, Anita C.; Beckley, B. D.; Koblinsky, C. J.

    1990-01-01

    Altimeter satellites are often maintained in a repeating orbit to facilitate the separation of sea-height variations from the geoid. However, atmospheric drag and solar radiation pressure cause a satellite orbit to drift. For Geosat this drift causes the ground track to vary by + or - 1 km about the nominal repeat path. This misalignment leads to an error in the estimates of sea surface height variations because of the local slope in the geoid. This error has been estimated globally for the Geosat Exact Repeat Mission using a mean sea surface constructed from Geos 3 and Seasat altimeter data. Over most of the ocean the geoid gradient is small, and the repeat-track misalignment leads to errors of only 1 to 2 cm. However, in the vicinity of trenches, continental shelves, islands, and seamounts, errors can exceed 20 cm. The estimated error is compared with direct estimates from Geosat altimetry, and a strong correlation is found in the vicinity of the Tonga and Aleutian trenches. This correlation increases as the orbit error is reduced because of the increased signal-to-noise ratio.

  5. A Critical Examination of Current On-Orbit Satellite Collision Risk Analysis Under Constraints of Public Data

    Science.gov (United States)

    Whitworth, Brandon; Moon, Mark; Pace, William; Baker, Robert

    2010-09-01

    The collision of Cosmos 2251 and Iridium 33 on 10 February 2009, made real the dangers of space operations without accurate situational awareness. A critical examination of the state of the art in collision risk assessment for on-orbit assets quickly reveals that it is inadequate to have provided satellite operators the opportunity to prevent the Cosmos-Iridium collision. Satellite operators need reliable information in a timely manner in order to take appropriate action. The shortfalls of publicly available orbit information place all spacecraft and missions at risk. The accuracy limitations of the General Perturbations(GP) catalog and orbit model(SGP-4) limit the effectiveness of current open source efforts. Beyond the accuracy limits, the relatively low frequency of updates for debris included in the catalog increases the uncertainty in time-space for inactive space objects such as Cosmos 2251. The current state of the art collision risk assessment includes advanced techniques such as expanding the GP model with covariance information which will allow uncertainty in the model to be accounted for in the on-orbit risk calculations. Covariance information can be estimated from consecutively published element sets for the same orbital object. A challenge to covariance estimation is that maneuvers or long periods of time between updates can skew the computed data. Once reliable covariance information is known and an efficient algorithm can be applied to find all of the close approaches between all cataloged objects then it is possible to estimate the collision risk for each close encounter with the tri-variate normal distribution. Unknown covariance will need to be handled in an appropriate way for a complete solution. Covariance information alone cannot solve the problem due to the relatively slow rate of update for all objects by the Space Surveillance Network(SSN) and there is no centralized source for planned and executed orbit changes for powered spacecraft. The

  6. An Assessment of the Space Radiation Environment in a Near Equatorial Low Earth Orbit Based on Razaksat-1 Satellite

    CERN Document Server

    Suparta, Wayan

    2015-01-01

    The Malaysian satellite RazakSAT-1 was designed to operate in a near-equatorial orbit (NEqO) and low earth orbit (LEO). However, after one year of operation in 2010, communication to the satellite was lost. This study attempted to identify whether space radiation sources could have caused the communication loss by comparing RazakSAT-1 with two functional satellites. Data on galactic cosmic rays (GCR), trapped protons, trapped electrons, and solar energetic particles (SEPs) obtained from Space Environment Information System (SPENVIS) was analyzed.

  7. Semianalytic Integration of High-Altitude Orbits under Lunisolar Effects

    Directory of Open Access Journals (Sweden)

    Martin Lara

    2012-01-01

    Full Text Available The long-term effect of lunisolar perturbations on high-altitude orbits is studied after a double averaging procedure that removes both the mean anomaly of the satellite and that of the moon. Lunisolar effects acting on high-altitude orbits are comparable in magnitude to the Earth’s oblateness perturbation. Hence, their accurate modeling does not allow for the usual truncation of the expansion of the third-body disturbing function up to the second degree. Using canonical perturbation theory, the averaging is carried out up to the order where second-order terms in the Earth oblateness coefficient are apparent. This truncation order forces to take into account up to the fifth degree in the expansion of the lunar disturbing function. The small values of the moon’s orbital eccentricity and inclination with respect to the ecliptic allow for some simplification. Nevertheless, as far as the averaging is carried out in closed form of the satellite’s orbit eccentricity, it is not restricted to low-eccentricity orbits.

  8. On-orbit Geometric Parameters Refinement of Mapping Satellite-1 Triple Line Array Camera

    Directory of Open Access Journals (Sweden)

    GENG Hongyi

    2016-03-01

    Full Text Available To find the model and method of on-orbit geometric refinement suitable for the triple line array camera of Mapping Satellite-1, this paper first analyzed the impact of the exterior orientation line element error on the geometric parameters refinement, then eliminated the high-frequency noise by the preprocessing of the attitude data, and compensated the low-frequency flutter of satellite platform in the course of flying by sine function and designed the constant angular error model for the lens of the triple line array camera. In addition, an interior orientation model, using directly pixel coordinates as observations, was constructed based on conventional additional parameter model and the combination of the best refinement model parameters and the solution strategy were determined by the unilateral control extrapolative location. The experiments show that the planar accuracy and vertical accuracy are about 1 GSD and 0.8 GSD by the proposed refinement plan and the rational distribution of GCPS.

  9. Alkaline regenerative fuel cell energy storage system for manned orbital satellites

    Science.gov (United States)

    Martin, R. E.; Gitlow, B.; Sheibley, D. W.

    1982-01-01

    It is pointed out that the alkaline regenerative fuel cell system represents a highly efficient, lightweight, reliable approach for providing energy storage in an orbiting satellite. In addition to its energy storage function, the system can supply hydrogen and oxygen for attitude control of the satellite and for life support. A summary is presented of the results to date obtained in connection with the NASA-sponsored fuel cell technology advancement program, giving particular attention to the requirements of the alkaline regenerative fuel cell and the low-earth mission. Attention is given to system design guidelines, weight considerations, gold-platinum cathode cell performance, matrix development, the electrolyte reservoir plate, and the cyclical load profile tests.

  10. On-orbit flight results from the reconfigurable cibola flight experiment satellite (CFEsat)

    Energy Technology Data Exchange (ETDEWEB)

    Caffrey, Michael [Los Alamos National Laboratory; Morgan, Keith [Los Alamos National Laboratory; Roussel-dupre, Diane [LANL; Robinson, Scott [Los Alamos National Laboratory; Nelson, Anthony [Los Alamos National Laboratory; Salazar, Anthony [Los Alamos National Laboratory; Wirthlin, Michael [BYU; Howes, William [BYU; Richins, Daniel [BYU

    2009-01-01

    The Cibola Flight Experiment (CFE) is an experimental small satellite developed at the Los Alamos National Laboratory to demonstrate the feasibility of using FPGA-based reconfigurable computing for sensor processing in a space environment. The CFE satellite was launched on March 8, 2007 in low-earth orbit and has operated extremely well since its deployment. The nine Xilinx Virtex FPGAs used in the payload have been used for several high-throughput sensor processing applications and for single-event upset (SEU) monitoring and mitigation. This paper will describe the CFE system and summarize its operational results. In addition, this paper will describe the results from several SEU detection circuits that were performed on the spacecraft.

  11. Parallel satellite orbital situational problems solver for space missions design and control

    Science.gov (United States)

    Atanassov, Atanas Marinov

    2016-11-01

    Solving different scientific problems for space applications demands implementation of observations, measurements or realization of active experiments during time intervals in which specific geometric and physical conditions are fulfilled. The solving of situational problems for determination of these time intervals when the satellite instruments work optimally is a very important part of all activities on every stage of preparation and realization of space missions. The elaboration of universal, flexible and robust approach for situation analysis, which is easily portable toward new satellite missions, is significant for reduction of missions' preparation times and costs. Every situation problem could be based on one or more situation conditions. Simultaneously solving different kinds of situation problems based on different number and types of situational conditions, each one of them satisfied on different segments of satellite orbit requires irregular calculations. Three formal approaches are presented. First one is related to situation problems description that allows achieving flexibility in situation problem assembling and presentation in computer memory. The second formal approach is connected with developing of situation problem solver organized as processor that executes specific code for every particular situational condition. The third formal approach is related to solver parallelization utilizing threads and dynamic scheduling based on "pool of threads" abstraction and ensures a good load balance. The developed situation problems solver is intended for incorporation in the frames of multi-physics multi-satellite space mission's design and simulation tools.

  12. An analysis of the wide area differential method of geostationary orbit satellites

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    This work aims to obtain a wide area differential method for geostationary orbit (GEO) constellation. A comparison between the dilution of precision (DOP) of four-dimensional (4D) calculation including sa- tellite clock errors and ephemeris errors and that of three-dimensional (3D) calculation only including ephemeris errors with the inverse positioning theory of GPS shows the conclusion that all the 3D PDOPs are greatly reduced. Based on this, a basic idea of correcting satellite clock errors and ephem- eris errors apart is put forward, and moreover, a specific method of separation is proposed. Satellite clock errors are separated in a master station with time synchronization, and all the remaining pseu- do-range errors after the satellite clock errors have been deducted are used to work out ephemeris corrections of all GEO satellites. By a comparative analysis of user positioning accuracy before and after differential, the wide area differential method is verified to be quite valid for GEO constellation.

  13. Near-Earth asteroid satellite spins under spin-orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Naidu, Shantanu P.; Margot, Jean-Luc [Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095 (United States)

    2015-02-01

    We develop a fourth-order numerical integrator to simulate the coupled spin and orbital motions of two rigid bodies having arbitrary mass distributions under the influence of their mutual gravitational potential. We simulate the dynamics of components in well-characterized binary and triple near-Earth asteroid systems and use surface of section plots to map the possible spin configurations of the satellites. For asynchronous satellites, the analysis reveals large regions of phase space where the spin state of the satellite is chaotic. For synchronous satellites, we show that libration amplitudes can reach detectable values even for moderately elongated shapes. The presence of chaotic regions in the phase space has important consequences for the evolution of binary asteroids. It may substantially increase spin synchronization timescales, explain the observed fraction of asychronous binaries, delay BYORP-type evolution, and extend the lifetime of binaries. The variations in spin rate due to large librations also affect the analysis and interpretation of light curve and radar observations.

  14. On the scale estimation using truncated swath measurements from low Earth orbiting satellites

    Science.gov (United States)

    Liu, Qi

    2013-05-01

    Truncation effect caused by limited swath width of low Earth orbiting (LEO) satellites results in inevitable underestimation of object scale when using pixel-counting methods. A new approach is proposed to obtain more accurate object scale through truncated measurements. The approach is based upon the mean object area fraction (MOAF), which depicts the relative population of object points in a varying-size domain and proves to be less sensitive to truncation effect. The MOAF-equivalent radius (MER) is deduced by comparing the actual MOAF with the standard one inferred from a circle object. Numerical simulations are implemented to demonstrate the MER characteristics. In contrast to area-equivalent radius (AER) that is merely determined by the absolute amount of object points, MER relies on the overall spatial structure of the object. For objects with irregular shapes, the MER value is generally smaller than AER in the absence of truncation. Nevertheless, taking the actual AER as true scale, MER has significantly reduced biases compared to AER once the object is truncated. This advantage can be reinforced when focusing on size statistics of analogous objects, because negative and positive biases associated with various truncation situations coexist in MER, against the uniform negative biases of AER. When applied to MODIS cloud mask data that are restricted in individual granules, MER has consistently larger values than AER for most truncated clouds. Compared with the explicitly problematic estimation from AER due to truncation, MER offers a notable elevation on the estimated cloud size and gets closer to the truth.

  15. Bulk density of asteroid 243 Ida from the orbit of its satellite Dactyl

    Science.gov (United States)

    Belton, M.J.S.; Chapmant, C.R.; Thomas, P.C.; Davies, M.E.; Greenberg, R.; Klaasen, K.; Byrnes, D.; D'Amario, L.; Synnott, S.; Johnson, T.V.; McEwen, A.; Merline, W.J.; Davis, D.R.; Petit, J.-M.; Storrs, A.; Veverka, J.; Zellner, B.

    1995-01-01

    DURING its reconnaissance of the asteroid 243 Ida, the Galileo spacecraft returned images of a second object, 1993(243)1 Dactyl1 - the first confirmed satellite of an asteroid. Sufficient data were obtained on the motion of Dactyl to determine its orbit as a function of Ida's mass. Here we apply statistical and dynamical arguments to constrain the range of possible orbits, and hence the mass of Ida. Combined with the volume of Ida2, this yields a bulk density of 2.6??0.5 g cm-3. Allowing for the uncertainty in the porosity of Ida, this density range is consistent with a bulk chondritic composition, and argues against some (but not all) classes of meteoritic igneous rock types that have been suggested as compositionally representative of S-type asteroids like Ida.

  16. Prediction Model for the Life of Nickel-cadmium Batteries in Geosynchronous Orbit Satellites

    Science.gov (United States)

    Engleman, J. H.; Zirkes-Falco, M. B.; Bogner, R. S.; Pickett, D. F., Jr.

    1984-01-01

    A mathematical model is described which predicts the service life of nickel-cadmium batteries designed for geosynchronous orbit satellites. Regression analysis technique is used to analyze orbital data on second generation trickle charged batteries. The model gives average cell voltage as a function of design parameters, operating parameters and time. The voltage model has the properties of providing a good fit to the data, good predictive capability, and agreement with known battery performance characteristics. Average cell voltage can be predicted to within 0.02 volts for up to 8 years. This modeling shows that these batteries will operate reliably for 10 years. Third-generation batteries are expected to operate even longer.

  17. 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.

  18. Space debris proximity analysis in powered and orbital phases during satellite launch

    Science.gov (United States)

    Bandyopadhyay, Priyankar; Sharma, R. K.; Adimurthy, V.

    2004-01-01

    This paper describes the methodology of the space debris proximity analysis in powered and orbital phase at the time of a satellite launch. The details of the SPADEPRO analysis package, developed for this purpose, are presented. It consists of modules which provide the functions related to ephemeris generation and reconstruction of primary object (launch vehicle or its payload upon insertion), determination of close approaches with resident space objects, computation of the state vector variance of the primary and the secondary objects to represent the knowledge uncertainty, and computation of the collision risk given the variance. This has been successfully applied during the recent launches of the Indian Space Research Organization.

  19. 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.

  20. Satellite's Trajectory Propagation At NearCircular Orbits Using TLE Files In The Simplified SGP Model

    Directory of Open Access Journals (Sweden)

    V. A. Chagina

    2016-01-01

    Full Text Available The article describes the satellite's trajectory calculation algorithm for near-circular orbits using TLE (two-line element files in the simplified SGP model. The aim of the algorithm is to obtain the array of satellite's azimuth and elevation required to control the antennas of ground station. The initial conditions of motion in TLE format are very widespread nowadays, they are being used by many calculation software, nevertheless there is a deficit of information concerned with this format in Russian literature. The report presented at NASA web-sites by Dr. T.S. Kelso contains the descriptions of satellite's trajectory calculation algorithms in case of various models (SGP, SGP4, SDP4 etc. The realization of these algorithms demands for the executer's experience because speaking about Russian and the American scientific schools there are differences both in measure units and in approaches to satellite's trajectory calculation.Moreover, in opposite to series of related publications all the calculation sequence to obtain the values of antenna pointing is given in this article, the described algorithm is pretty simple and clear. It is not enough to have the satellite's coordinates and velocity in Earth inertial equatorial system to calculate azimuth and elevation. One has to bind the ground station situated at the surface of the Earth, which is involved in complicated motion, to a point in inertial space using Local Sidereal Time. Several issues propose the utilization of Astronomical Almanac. But the exploitation of the Almanac is not convenient when it is required to get the arrays of values of antenna control angles as functions of time. The article contains the methodology given in foreign issues which allow the calculation of Local Sidereal Time. This methodology is an adjacent part of the trajectory calculation problem with respect to ground station.The calculation results obtained using the described algorithm were compared with the data

  1. 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.

  2. Launch in orbit of the NINA-2 apparatus aboard the satellite MITA

    Science.gov (United States)

    Casolino, M.; NINA-2 Collaboration

    2001-08-01

    The satellite MITA was launched on July the 15th , 2000 from the cosmodrome of Plesetsk (Russia) with a Cosmos-3M rocket. MITA carries the payload NINA-2 for the study of solar and galactic cosmic rays. The detector used in this mission is identical to the one already flying on the Russian satellite Resurs-O1 n.4 in a 840 km sunsynchronous orbit, but makes use of the extensive computer and telemetry capabilities of MITA bus to improve the active data acquisition time. The scientific objectives of NINA are the study of cosmic nuclei from hydrogen to iron in the energy range between 10 MeV/n and 1 GeV/n during solar maximum period. The device is capable of charge identification up to iron with isotope sensitivity up to oxigen. The 87.3 degrees, 460 km altitude polar orbit allows investigations of cosmic rays of solar and galactic origin as well as the trapped component. In this work we present preliminary results concerning particle identification capabilities and nuclear differential spectra for helium, carbon and oxygen in the energy range between 10 and 50 MeV/n.

  3. NIR- and SWIR-based on-orbit vicarious calibrations for satellite ocean color sensors.

    Science.gov (United States)

    Wang, Menghua; Shi, Wei; Jiang, Lide; Voss, Kenneth

    2016-09-05

    The near-infrared (NIR) and shortwave infrared (SWIR)-based atmospheric correction algorithms are used in satellite ocean color data processing, with the SWIR-based algorithm particularly useful for turbid coastal and inland waters. In this study, we describe the NIR- and two SWIR-based on-orbit vicarious calibration approaches for satellite ocean color sensors, and compare results from these three on-orbit vicarious calibrations using satellite measurements from the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP). Vicarious calibration gains for VIIRS spectral bands are derived using the in situ normalized water-leaving radiance nLw(λ) spectra from the Marine Optical Buoy (MOBY) in waters off Hawaii. The SWIR vicarious gains are determined using VIIRS measurements from the South Pacific Gyre region, where waters are the clearest and generally stable. Specifically, vicarious gain sets for VIIRS spectral bands of 410, 443, 486, 551, and 671 nm derived from the NIR method using the NIR 745 and 862 nm bands, the SWIR method using the SWIR 1238 and 1601 nm bands, and the SWIR method using the SWIR 1238 and 2257 nm bands are (0.979954, 0.974892, 0.974685, 0.965832, 0.979042), (0.980344, 0.975344, 0.975357, 0.965531, 0.979518), and (0.980820, 0.975609, 0.975761, 0.965888, 0.978576), respectively. Thus, the NIR-based vicarious calibration gains are consistent with those from the two SWIR-based approaches with discrepancies mostly within ~0.05% from three data processing methods. In addition, the NIR vicarious gains (745 and 862 nm) derived from the two SWIR methods are (0.982065, 1.00001) and (0.981811, 1.00000), respectively, with the difference ~0.03% at the NIR 745 nm band. This is the fundamental basis for the NIR-SWIR combined atmospheric correction algorithm, which has been used to derive improved satellite ocean color products over open oceans and turbid coastal/inland waters. Therefore, a unified

  4. Dwarf spheroidal satellites of the Milky Way from dark matter free tidal dwarf galaxy progenitors: maps of orbits

    CERN Document Server

    Casas, R A; Ramírez, K Pena; Kroupa, P

    2012-01-01

    The long term time evolution of tidal dwarf satellite galaxies with two different initial densities orbiting a host galaxy that resembles the Milky Way has been studied using a large set of Newtonian N-Body simulations. From the simulations two maps of the orbital conditions that lead to quasi-equilibrium objects were constructed. It has been found that several orbits of the satellites allow for the existence, for about 1 Gyr or more, of out-of-equilibrium bodies with high apparent mass-to-light ratios. Within this framework the satellites in the quasi-stable phase reproduce the observed satellite properties for about 16% of the orbit for high density progenitors, and for about 66% for progenitors with lower densities An additional simulation for a single satellite with initial mass of 10^7 Msun and Plummer radius of 0.15 kpc leads to remnants in the quasi- equilibrium phase that simultaneously reproduce remarkably well the observational quantities of the UFDGs of the Milky Way. This satellite in the quasi-st...

  5. 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.

  6. Analysis of stability boundaries of satellite's equilibrium attitude in a circular orbit

    Science.gov (United States)

    Novikov, M. A.

    2016-03-01

    An asymmetric satellite equipped with control momentum gyroscopes (CMGs) with the center of mass of the system moving uniformly in a circular orbit was considered. The stability of a relative equilibrium attitude of the satellite was analyzed using Lyapunov's direct method. The Lyapunov function V is a positive definite integral of the total energy of the perturbed motion of the system. The asymptotic stability analysis of the stationary motion of the conservative system was based on the Barbashin-Krasovskii theorem on the nonexistence of integer trajectories of the set dot V, which was obtained using the differential equations of motion of the satellite with CMGs. By analyzing the sign definiteness of the quadratic part of V, it was found earlier by V.V. Sazonov that the stability region is described by four strict inequalities. The asymptotic stability at the stability boundary was analyzed by sequentially turning these inequalities into equalities with terms of orders higher than the second taken into account in V. The sign definiteness analysis of the inhomogeneous function V at the stability boundary involved a huge amount of computations related to the multiplication, expansion, substitution, and factorization of symbolic expressions. The computations were performed by applying a computer algebra system on a personal computer.

  7. Commentary to "LARES successfully launched in orbit: Satellite and mission description" by A. Paolozzi and I. Ciufolini

    CERN Document Server

    Iorio, Lorenzo

    2014-01-01

    We comment on some statements in a recent paper by Paolozzi and Ciufolini concerning certain remarks raised by us on the realistic accuracy obtainable in testing the general relativistic Lense-Thirring effect in the gravitational field of the Earth with the newly launched LARES satellite together with the LAGEOS and LAGEOS II spacecraft in orbit for a long time. The orbital configuration of LARES is different from that of the originally proposed LAGEOS-3. Indeed, while the latter one should have been launched to the same altitude of LAGEOS (i.e. about $h_{\\rm L}=5890$ km) in an orbital plane displaced by $180$ deg with respect to that of LAGEOS ($I_{\\rm L}=110$ deg, $I_{\\rm L3}=70$ deg), LARES currently moves at a much smaller altitude (about $h_{\\rm LR}=1440$ km) and at a slightly different inclination ($I_{\\rm LR} = 69.5$ deg). As independently pointed out in the literature by different authors, the overall accuracy of a LARES-LAGEOS-LAGEOS II Lense-Thirring test may be unfavorably \\textcolor{black}{impacte...

  8. Precise orbit determination for Jason-1 satellite using on-board GPS data with cm-level accuracy

    Institute of Scientific and Technical Information of China (English)

    PENG DongJu; WU Bin

    2009-01-01

    The joint US/French Jason-1 satellite altimeter mission, launched from the Vandenberg Air Force Base on December 7, 2001, continues the time series of centimeter-level ocean topography observations as the follow-on to the highly successful T/P radar altimeter satellite. Orbit error especially the radial orbit error is a major component in the overall budget of all altimeter satellite missions, in order to continue the T/P standard of observations. Jason-1 has a radial orbit error budget requirement of 2.5 cm. in this work, two cycles (December 19, 2002 to January 7, 2003) of the Jason-1 on-board GPS data were processed using the zero-difference (ZD) dynamic precise orbit determination (POD) technique. The resulting Jason-1 orbit accuracy was assessed by comparison with the precise orbit ephemeris (POE)produced by JPL, orbit overlaps and SLR residuals. These evaluations indicate that the RMS radial accuracy is in the range of 1-2 cm.

  9. Simulation of Motion of Satellite under the Effect of Oblateness of Earth and Atmospheric Drag

    CERN Document Server

    Sharma, Jaita; Pirzada, U M; Shah, Vishant

    2016-01-01

    The equations governing motion of the satellite under the effect of oblateness of Earth and atmospheric drag have been simulated, for a fixed initial position and three different initial velocities, till satellite collapses on Earth. Simulation of motion of artificial Earth satellite subject to the combined effects of oblate Earth and atmospheric drag is presented. The atmospheric model considered here takes in to account of exponential variation of the density with initial distance of Satellite from Earth's surface, scale height and radial distance. The minimum and maximum values of orbital elements and their variation over a time for different initial velocities have been reported.

  10. A compact and low cost TT&C S-Band Ground Station for low orbit satellites

    Science.gov (United States)

    Pacola, Luiz C.; Ferrari, Carlos A.

    Instituto Nacional de Pesquisas Espaciais (INPE's) S-Band Ground Station for satellite control and monitoring is revised consdiering the current software and hardware technology. A Ground Station concept for low orbit satellites is presented. The front-end uses a small antenna and low cost associated equipment without loss of performance. The baseband equipment is highly standardized and developed on a personal computer IBM compatible using extensively Digital Signal Processing (DSP). A link budget for ranging, telecommand and telemetry is also presented.

  11. Energetic electron enhancements below the radiation belt and X-ray contamination at low-orbiting satellites

    CERN Document Server

    Suvorova, Alla V; Huang, Chien-Ming

    2014-01-01

    The work concerns a problem of electron-induced contaminant at relatively low latitudes to high-energy astrophysical measurements on board the low-orbiting satellites. We show the results of a statistical analysis of the energetic electron enhancements in energy range 30-300 keV observed by a fleet of NOAA/POES low-orbiting satellites over the time period from 1999 to 2012. We demonstrate geographical distributions of great and moderate long-lasting enhancements caused by different type of the solar wind drivers.

  12. A vector method for synthesis of orbits and the structure of satellite constellations for multiswath periodic coverage of the Earth

    Science.gov (United States)

    Saulskiy, V. K.

    2016-07-01

    Single satellites and multisatellite constellations for the periodic coverage of the Earth are considered. The main feature is the use of several cameras with different swath widths. A vector method is proposed which makes it possible to find orbits minimizing the periodicities of coverage of a given area of Earth uniformly for all swaths. Their number is not limited, but the relative dimensions should satisfy the Fibonacci series or some new numerical sequences. The results apply to constellations of any number of satellites. Formulas were derived for calculating their structure, i.e., relative position in the constellation. Examples of orbits and the structure of constellations for the Earth's multiswath coverage are presented.

  13. Stimulated Radiative Molecular Association in the Early Solar System: Orbital Radii of Satellites of Uranus, Jupiter, Neptune, and Saturn

    CERN Document Server

    Lombardi, James C

    2015-01-01

    The present investigation relates the orbital radii of regular satellites of Uranus, Jupiter, Neptune, and Saturn to photon energies in the spectra of atomic and molecular hydrogen. To explain these observations a model is developed involving stimulated radiative molecular association (SRMA) reactions among the photons and atoms in the protosatellite disks of the planets. In this model thermal energy is extracted from each disk due to a resonance at radii where there is a match between the temperature in the disk and a photon energy. Matter accumulates at these radii, and satellites and rings are ultimately formed. Orbital radii of satellites of Uranus, Jupiter, and Neptune are related to photon energies ($E_{PM}$ values) in the spectrum of molecular hydrogen. Orbital radii of satellites of Saturn are related to photon energies ($E_{PA}$ values) in the spectrum of atomic hydrogen. The first hint that such relationships exist is found in the linearity of the graphs of orbital radii of uranian satellites vs. or...

  14. On the co-orbital motion in the Planar Restricted Three-Body Problem: the Quasi-satellite motion revisited

    CERN Document Server

    Pousse, Alexandre; Vienne, Alain

    2016-01-01

    In the framework of the planar and circular Restricted Three-Body Problem, we consider an asteroid that orbits the Sun in quasi-satellite motion with a planet. A quasi-satellite trajectory is a heliocentric orbit in co-orbital resonance with the planet, characterized by a non zero eccentricity and a resonant angle that librates around zero. Likewise, in the rotating frame with the planet it describes the same trajectory as the one of a retrograde satellite even though the planet acts as a perturbator. In the last few years, the discoveries of asteroids in this type of motion made the term "quasi-satellite" more and more present in the literature. However, some authors rather use the term "retrograde satellite" when referring to this kind of motion in the studies of the restricted problem in the rotating frame. In this paper we intend to clarify the terminology to use, in order to bridge the gap between the perturbative co-orbital point of view and the more general approach in the rotating frame. Through a num...

  15. Research on long-term autonomous orbit determination for navigation constellation using inter-satellite orientation observation information

    Science.gov (United States)

    Li, Bo; Xu, Bo; Wang, Hai-Hong

    2009-12-01

    Long-term autonomous orbit determination is one of the key techniques of autonomous navigation for navigation constellation. Based only on cross-link range observation, which is not able to overcome the defect of entire constellation rotation and translation relative to inertial reference frame, the accuracy of autonomous orbit determination is reduced with time. In order to solve this problem, the approach of using inter-satellite orientation observation is put forward to estimate the constellation rotation and translation with the benefit of absolute position information provided by stars. In view of the fact that most navigation satellites moving in near circular orbits, and also in order to reduce the calculation burden of onboard computer, nonsingular orbital elements are chosen as state variables and analytical method is used to calculate the transition matrix in this paper. In addition, the extended Kalman filter is designed to fuse information of satellite dynamic model, cross-link range observation and inter-satellite orientation observation to determine the orbit. The simulation results based on the IGS Final Products of GPS constellation indicate that, at the certain error condition of range and orientation measurement, the URE of constellation is better than 2 meters within 120 days.

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

    Science.gov (United States)

    2013-03-08

    ... forwarding and receiving communications signals via a system of satellites or reselling satellite... specialized telecommunications services, such as satellite tracking, communications telemetry, and radar... of Subjects in 47 CFR Parts 2 and 25 Frequency allocations, Satellites. Federal Communications...

  17. Earth Oblateness and Relative Sun Motion Considerations in the Determination of an Ideal Orbit for the Nimbus Meteorological Satellite

    Science.gov (United States)

    Bandeen, William R.

    1961-01-01

    It is desired that the Nimbus meteorological satellite always cross the equator around local noon and, half-an-orbit later, cross the equator in the other direction around local midnight. The application of the phenomenon of nodal regression toward this end is discussed, and an analysis of the parameters angles of inclination, periods, and heights of such "ideal" circular orbits is presented. Also, the relative motion of the apparent versus the fictitious mean sun is briefly discussed.

  18. 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.

  19. Centimeter-level precise orbit determination for the HY-2A satellite using DORIS and SLR tracking data

    Science.gov (United States)

    Kong, Qiaoli; Guo, Jinyun; Sun, Yu; Zhao, Chunmei; Chen, Chuanfa

    2017-01-01

    The HY-2A satellite is the first ocean dynamic environment monitoring satellite of China. Centimeter-level radial accuracy is a fundamental requirement for its scientific research and applications. To achieve this goal, we designed the strategies of precise orbit determination (POD) in detail. To achieve the relative optimal orbit for HY-2A, we carried out POD using DORIS-only, SLR-only, and DORIS + SLR tracking data, respectively. POD tests demonstrated that the consistency level of DORIS-only and SLR-only orbits with respect to the CNES orbits were about 1.81 cm and 3.34 cm in radial direction in the dynamic sense, respectively. We designed 6 cases of different weight combinations for DORIS and SLR data, and found that the optimal relative weight group was 0.2 mm/s for DORIS and 15.0 cm for SLR, and RMS of orbit differences with respect to the CNES orbits in radial direction and three-dimensional (3D) were 1.37 cm and 5.87 cm, respectively. These tests indicated that the relative radial and 3D accuracies computed using DORIS + SLR data with the optimal relative weight set were obviously higher than those computed using DORIS-only and SLR-only data, and satisfied the requirement of designed precision. The POD for HY-2A will provide the invaluable experience for the following HY-2B, HY-2C, and HY-2D satellites.

  20. On-orbit calibration of soft X-ray detector on Chang'E-2 satellite

    Science.gov (United States)

    Xiao, Hong; Peng, Wen-Xi; Wang, Huan-Yu; Cui, Xing-Zhu; Guo, Dong-Ya

    2015-10-01

    The X-ray spectrometer is one of the satellite payloads on the Chang'E-2 satellite. The soft X-ray detector is one of the devices on the X-ray spectrometer, designed to detect the major rock-forming elements within the 0.5-10 keV range on the lunar surface. In this paper, energy linearity and energy resolution calibration is done using a weak 55Fe source. Temperature and time effects are found not to give a large error. The total uncertainty of calibration is estimated to be within 5% after correction. Supported by National Science Foundation of Ministry of Education

  1. On-orbit calibration of soft X-ray detector on Chang'E-2 satellite

    CERN Document Server

    Xiao, Hong; Wang, Huanyu; Cui, Xingzhu; Guo, Dongya

    2015-01-01

    X-ray spectrometer is one of the satellite payloads on Chang'E-2 satellite. The soft X-ray detector is one of the device on X-ray spectrometer which is designed to detect the major rock-forming elements within 0.5-10keV range on lunar surface. In this paper, energy linearity and energy resolution calibration is done using a weak Fe55 source, while temperature and time effect is considered not take big error. The total uncertainty is estimated to be within 5% after correction.

  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. APPLICATION OF VISION METROLOGY TO IN-ORBIT MEASUREMENT OF LARGE REFLECTOR ONBOARD COMMUNICATION SATELLITE FOR NEXT GENERATION MOBILE SATELLITE COMMUNICATION

    Directory of Open Access Journals (Sweden)

    M. Akioka

    2016-06-01

    Full Text Available 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

  4. 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

  5. Tracking Low Earth Orbit Small Debris with GPS Satellites as Bistatic Radar

    Science.gov (United States)

    Mahmud, M.; Qaisar, S.; Benson, C.

    2016-09-01

    Space debris is a growing problem and collisions are potentially lethal to satellites. Trajectories for small objects are predicted based on infrequent measurements, and the scale and therefore cost of maneuver required to avoid collisions is a function of trajectory accuracy. Frequent and precise observations will improve trajectory accuracy. In this paper, we extend on aspects of the feasibility of tracking space debris in Low Earth Orbit using emissions from GNSS satellites as bistatic radar illuminators. The wavelengths of GNSS signals are of order 20 cm and our primary focus is to track debris smaller than this, thereby maintaining phase stability of the scattered signals, enabling very long coherent processing intervals. However, the signals scattered by debris will be very weak at a terrestrial receiver, requiring the computationally expensive integration of a large number of signals, over an extended duration and with a large phased array. Detection of such weak signals in the presence of relatively strong direct-arrival signals requires extremely high cross-correlation protection. We show that sufficient cross-correlation protection can be obtained due to the large and varying Doppler shift, and also illustrate a novel processing approach utilizing downshifting of the collected signal to audio frequency. This technique dramatically reduces the cost and complexity of updating debris trajectories. The processing cost of preserving an uncertainty volume of many hundreds of meters around the predicted debris track is very modest, and searching within that uncertainty volume is undertaken at audio sampling rates. Moreover, we explore techniques that further lower the already modest cost of the non-linear search within the preserved uncertainty volume. We conclude with an outline of a system using these techniques that could provide centimetre level tracking of large quantities of small orbital objects at a modest cost.

  6. 'Orbital volume restoration rate after orbital fracture'; a CT-based orbital volume measurement for evaluation of orbital wall reconstructive effect.

    Science.gov (United States)

    Wi, J M; Sung, K H; Chi, M

    2017-01-13

    PurposeTo evaluate the effect of orbital reconstruction and factors related to the effect of orbital reconstruction by assessing of orbital volume using orbital computed tomography (CT) in cases of orbital wall fracture.MethodsIn this retrospective study, 68 patients with isolated blowout fractures were evaluated. The volumes of orbits and herniated orbital tissues were determined by CT scans using a three-dimensional reconstruction technique (the Eclipse Treatment Planning System). Orbital CT was performed preoperatively, immediately after surgery, and at final follow ups (minimum of 6 months). We evaluated the reconstructive effect of surgery making a new formula, 'orbital volume reconstruction rate' from orbital volume differences between fractured and contralateral orbits before surgery, immediately after surgery, and at final follow up.ResultsMean volume of fractured orbits before surgery was 23.01±2.60 cm(3) and that of contralateral orbits was 21.31±2.50 cm(3) (P=0.005). Mean volume of the fractured orbits immediately after surgery was 21.29±2.42 cm(3), and that of the contralateral orbits was 21.33±2.52 cm(3) (P=0.921). Mean volume of fractured orbits at final follow up was 21.50±2.44 cm(3), and that of contralateral orbits was 21.32±2.50 cm(3) (P=0.668). The mean orbital volume reconstruction rate was 100.47% immediately after surgery and 99.17% at final follow up. No significant difference in orbital volume reconstruction rate was observed with respect to fracture site or orbital implant type. Patients that underwent operation within 14 days of trauma had a better reconstruction rate at final follow up than patients who underwent operation over 14 days after trauma (P=0.039).ConclusionComputer-based measurements of orbital fracture volume can be used to evaluate the reconstructive effect of orbital implants and provide useful quantitative information. Significant reduction of orbital volume is observed immediately after orbital wall

  7. Representativeness of total column water vapour retrievals from instruments on polar orbiting satellites

    Science.gov (United States)

    Diedrich, Hannes; Wittchen, Falco; Preusker, René; Fischer, Jürgen

    2016-07-01

    The remote sensing of total column water vapour (TCWV) from polar orbiting, sun-synchronous satellite spectrometers such as the Medium Resolution Imaging Spectrometer (MERIS) on board of ENVISAT and the Moderate Imaging Spectroradiometer (MODIS) on board of Aqua and Terra enables observations on a high spatial resolution and a high accuracy over land surfaces. The observations serve studies about small-scale variations of water vapour as well as the detection of local and global trends. However, depending on the swath width of the sensor, the temporal sampling is low and the observations of TCWV are limited to cloud-free land scenes. This study quantifies the representativeness of a single TCWV observation at the time of the satellite overpass under cloud-free conditions by investigating the diurnal cycle of TCWV using 9 years of a 2-hourly TCWV data set from global GNSS (Global Navigation Satellite Systems) stations. It turns out that the TCWV observed at 10:30 local time (LT) is generally lower than the daily mean TCWV by 0.65 mm (4 %) on average for cloud-free cases. Averaging over all GNSS stations, the monthly mean TCWV at 10:30 LT, constrained to cases that are cloud-free, is 5 mm (25 %) lower than the monthly mean TCWV at 10:30 LT of all cases. Additionally, the diurnal variability of TCWV is assessed. For the majority of GNSS stations, the amplitude of the averaged diurnal cycle ranges between 1 and 5 % of the daily mean with a minimum between 06:00 and 10:00 LT and maximum between 16:00 and 20:00 LT. However, a high variability of TCWV on an individual day is detected. On average, the TCWV standard deviation is about 15 % regarding the daily mean.

  8. Charge efficiency of Ni/H2 cells during transfer orbit of Telstar 4 satellites

    Science.gov (United States)

    Fang, W. C.; Maurer, Dean W.; Vyas, B.; Thomas, M. N.

    1994-02-01

    The TELSTAR 4 communication satellites being manufactured by Martin Marietta Astro Space (Astro Space) for AT&T are three axis stabilized spacecraft scheduled to be launched on expendable vehicles such as the Atlas or Ariane rockets. Typically, these spacecraft consist of a box that holds the electronics and supports the antenna reflectors and the solar array wings. The wings and reflectors are folded against the sides of the box during launch and the spacecraft is spun for attitude control in that phase; they are then deployed after achieving the final orbit. The launch phase and transfer orbits required to achieve the final geosynchronous orbit typically take 4 to 5 days during which time the power required for command, telemetry, attitude control, heaters, etc., is provided by two 50 AH nickel hydrogen batteries augmented by the exposed outboard solar panels. In the past, this situation has presented no problem since there was a considerable excess of power available from the array. In the case of large high powered spacecraft such as TELSTAR 4, however, the design power levels in transfer orbit approach the time-averaged power available from the exposed surface area of the solar arrays, resulting in a very tight power margin. To compound the difficulty, the array output of the spinning spacecraft in transfer orbit is shaped like a full wave rectified sine function and provides very low charging rates to the batteries during portions of the rotation. In view of the typically low charging efficiency of alkaline nickel batteries at low rates, it was decided to measure the efficiency during a simulation of the TELSTAR 4 conditions at the expected power levels and temperatures on three nickel hydrogen cells of similar design. The unique feature of nickel hydrogen cells that makes the continuous measurement of efficiency possible is that hydrogen is one of the active materials and thus, cell pressure is a direct measure of the state of charge or available capacity

  9. Saturn's inner satellites: Orbits, masses, and the chaotic motion of atlas from new Cassini imaging observations

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, N. J.; Murray, C. D. [Astronomy Unit, School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London, E1 4NS (United Kingdom); Renner, S. [Université Lille 1, Laboratoire d' Astronomie de Lille (LAL), 1 impasse de l' Observatoire, F-59000 Lille (France); Evans, M. W. [Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States)

    2015-01-01

    We present numerically derived orbits and mass estimates for the inner Saturnian satellites, Atlas, Prometheus, Pandora, Janus, and Epimetheus from a fit to 2580 new Cassini Imaging Science Subsystem astrometric observations spanning 2004 February to 2013 August. The observations are provided as machine-readable and Virtual Observatory tables. We estimate GM{sub Atlas} = (0.384 ± 0.001) × 10{sup −3} km{sup 3} s{sup −2}, a value 13% smaller than the previously published estimate but with an order of magnitude reduction in the uncertainty. We also find GM{sub Prometheus} = (10.677 ± 0.006) × 10{sup −3} km{sup 3} s{sup −2}, GM{sub Pandora} = (9.133 ± 0.009) × 10{sup −3} km{sup 3} s{sup −2}, GM{sub Janus} = (126.51 ± 0.03) × 10{sup −3} km{sup 3} s{sup −2}, and GM{sub Epimetheus} = (35.110 ± 0.009) × 10{sup −3} km{sup 3} s{sup −2}, consistent with previously published values, but also with significant reductions in uncertainties. We show that Atlas is currently librating in both the 54:53 co-rotation-eccentricity resonance (CER) and the 54:53 inner Lindblad (ILR) resonance with Prometheus, making it the latest example of a coupled CER-ILR system, in common with the Saturnian satellites Anthe, Aegaeon, and Methone, and possibly Neptune's ring arcs. We further demonstrate that Atlas's orbit is chaotic, with a Lyapunov time of ∼10 years, and show that its chaotic behavior is a direct consequence of the coupled resonant interaction with Prometheus, rather than being an indirect effect of the known chaotic interaction between Prometheus and Pandora. We provide an updated analysis of the second-order resonant perturbations involving Prometheus, Pandora, and Epimetheus based on the new observations, showing that these resonant arguments are librating only when Epimetheus is the innermost of the co-orbital pair, Janus and Epimetheus. We also find evidence that the known chaotic changes in the orbits of Prometheus and Pandora are not

  10. Saturnʼs Inner Satellites: Orbits, Masses, and the Chaotic Motion of Atlas from New Cassini Imaging Observations

    Science.gov (United States)

    Cooper, N. J.; Renner, S.; Murray, C. D.; Evans, M. W.

    2015-01-01

    We present numerically derived orbits and mass estimates for the inner Saturnian satellites, Atlas, Prometheus, Pandora, Janus, and Epimetheus from a fit to 2580 new Cassini Imaging Science Subsystem astrometric observations spanning 2004 February to 2013 August. The observations are provided as machine-readable and Virtual Observatory tables. We estimate G{{M}Atlas} = (0.384 ± 0.001) × 10-3 km3 s-2, a value 13% smaller than the previously published estimate but with an order of magnitude reduction in the uncertainty. We also find G{{M}Prometheus} = (10.677 ± 0.006) × 10-3 km3 s-2, G{{M}Pandora} = (9.133 ± 0.009) × 10-3 km3 s-2, G{{M}Janus} = (126.51 ± 0.03) × 10-3 km3 s-2, and G{{M}Epimetheus} = (35.110 ± 0.009) × 10-3 km3 s-2, consistent with previously published values, but also with significant reductions in uncertainties. We show that Atlas is currently librating in both the 54:53 co-rotation-eccentricity resonance (CER) and the 54:53 inner Lindblad (ILR) resonance with Prometheus, making it the latest example of a coupled CER-ILR system, in common with the Saturnian satellites Anthe, Aegaeon, and Methone, and possibly Neptune's ring arcs. We further demonstrate that Atlas's orbit is chaotic, with a Lyapunov time of ˜10 years, and show that its chaotic behavior is a direct consequence of the coupled resonant interaction with Prometheus, rather than being an indirect effect of the known chaotic interaction between Prometheus and Pandora. We provide an updated analysis of the second-order resonant perturbations involving Prometheus, Pandora, and Epimetheus based on the new observations, showing that these resonant arguments are librating only when Epimetheus is the innermost of the co-orbital pair, Janus and Epimetheus. We also find evidence that the known chaotic changes in the orbits of Prometheus and Pandora are not confined to times of apse anti-alignment.

  11. On-orbit Demonstration of a Sun Sensor on the Micro-Satellite MAIDO-1

    Directory of Open Access Journals (Sweden)

    Hiroshi Okubo

    2011-12-01

    Full Text Available 0 0 1 219 1249 International Islamic University 10 2 1466 14.0 Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Times New Roman";} A 50-kg-class microsatellite “MAIDO-1 (SOHLA-1” was launched, along with six other piggyback subsatellites, by a Japanese H-2A rocket on January 23, 2009. The fundamental and detailed designs of the satellite were developed by university students under the technical guidance of the Japan Aerospace Exploration Agency (JAXA. A string-type sun sensor (Fudai Sun Sensor; FSS was also developed by the students with the technical assistance of JAXA and Advanced Engineering Services (AES Co. Ltd. The FSS was mounted on the satellite as an experimental component. This paper reports the development of MAIDO-1 and FSS as well as the satellite operation by the students and the results of on-orbit experiments. ABSTRAK: Satu mikrosatelit kelas 50 kg “MAIDO-1 (SOHLA-1” telah dilancarkan, bersama enam lagi subsatelit gendong, dengan menggunakan roket H-2A (Jepun pada 23 Januari, 2009. Reka bentuk satelit yang asas dan terperinci dibangunkan oleh para pelajar universiti di bawah bimbingan teknikal Agensi Explorasi Aeroangkasa Jepun (Japan Aerospace Exploration Agency (JAXA. Sejenis penderia matahari bertali (Fudai Sun Sensor; FSS juga dibangunkan oleh para penuntut dengan bantuan teknikal dari pihak JAXA dan Advanced Engineering Services (AES Sdn. Bhd. FSS telah dilekapkan ke satelit sebagai komponen eksperimental. Kertas ini membentangkan perkembangan MAIDO-1 dan FSS, operasi satelit oleh pelajar-pelajar dan keputusan eksperimen semasa dalam orbit.

  12. The impact of orbital sampling, monthly averaging and vertical resolution on climate chemistry model evaluation with satellite observations

    Directory of Open Access Journals (Sweden)

    A. M. Aghedo

    2011-07-01

    Full Text Available Ensemble climate model simulations used for the Intergovernmental Panel on Climate Change (IPCC assessments have become important tools for exploring the response of the Earth System to changes in anthropogenic and natural forcings. The systematic evaluation of these models through global satellite observations is a critical step in assessing the uncertainty of climate change projections. This paper presents the technical steps required for using nadir sun-synchronous infrared satellite observations for multi-model evaluation and the uncertainties associated with each step. This is motivated by need to use satellite observations to evaluate climate models. We quantified the implications of the effect of satellite orbit and spatial coverage, the effect of variations in vertical sensitivity as quantified by the observation operator and the impact of averaging the operators for use with monthly-mean model output. We calculated these biases in ozone, carbon monoxide, atmospheric temperature and water vapour by using the output from two global chemistry climate models (ECHAM5-MOZ and GISS-PUCCINI and the observations from the Tropospheric Emission Spectrometer (TES instrument on board the NASA-Aura satellite from January 2005 to December 2008.

    The results show that sampling and monthly averaging of the observation operators produce zonal-mean biases of less than ±3 % for ozone and carbon monoxide throughout the entire troposphere in both models. Water vapour sampling zonal-mean biases were also within the insignificant range of ±3 % (that is ±0.14 g kg−1 in both models. Sampling led to a temperature zonal-mean bias of ±0.3 K over the tropical and mid-latitudes in both models, and up to −1.4 K over the boundary layer in the higher latitudes. Using the monthly average of temperature and water vapour operators lead to large biases over the boundary layer in the southern-hemispheric higher latitudes and in the upper

  13. The impact of orbital sampling, monthly averaging and vertical resolution on climate chemistry model evaluation with satellite observations

    Directory of Open Access Journals (Sweden)

    A. M. Aghedo

    2011-03-01

    Full Text Available Ensemble climate model simulations used for the Intergovernmental Panel on Climate Change (IPCC assessments have become important tools for exploring the response of the Earth System to changes in anthropogenic and natural forcings. The systematic evaluation of these models through global satellite observations is a critical step in assessing the uncertainty of climate change projections. This paper presents the technical steps required for using nadir sun-synchronous infrared satellite observations for multi-model evaluation and the uncertainties associated with each step. This is motivated by need to use satellite observations to evaluate climate models. We quantified the implications of the effect of satellite orbit and spatial coverage, the effect of variations in vertical sensitivity as quantified by the observation operator and the impact of averaging the operators for use with monthly-mean model output. We calculated these biases in ozone, carbon monoxide, atmospheric temperature and water vapour by using the output from two global chemistry climate models (ECHAM5-MOZ and GISS-PUCCINI and the observations from the Tropospheric Emission Spectrometer (TES satellite from January 2005 to December 2008.

    The results show that sampling and monthly averaging of the observation operators produce biases of less than ±3% for ozone and carbon monoxide throughout the entire troposphere in both models. Water vapour sampling biases were also within the insignificant range of ±3% (that is ±0.14 g kg−1 in both models. Sampling led to a temperature bias of ±0.3 K over the tropical and mid-latitudes in both models, and up to −1.4 K over the boundary layer in the higher latitudes. Using the monthly average of temperature and water vapour operators lead to large biases over the boundary layer in the southern-hemispheric higher latitudes and in the upper troposphere, respectively. Up to 8% bias was calculated in the upper

  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. Secular resonances between bodies on close orbits: a case study of the Himalia prograde group of jovian irregular satellites

    Science.gov (United States)

    Li, Daohai; Christou, Apostolos A.

    2016-06-01

    The gravitational interaction between two objects on similar orbits can effect noticeable changes in the orbital evolution even if the ratio of their masses to that of the central body is vanishingly small. Christou (Icarus 174:215-229, 2005) observed an occasional resonant lock in the differential node Δ Ω between two members in the Himalia irregular satellite group of Jupiter in the N-body simulations (corresponding mass ratio ˜ 10^{-9}). Using a semianalytical approach, we have reproduced this phenomenon. We also demonstrate the existence of two additional types of resonance, involving angle differences Δ ω and Δ (Ω +π) between two group members. These resonances cause secular oscillations in eccentricity and/or inclination on timescales ˜ 1 Myr. We locate these resonances in ( a, e, i) space and analyse their topological structure. In subsequent N-body simulations, we confirm these three resonances and find a fourth one involving Δ π. In addition, we study the occurrence rates and the stability of the four resonances from a statistical perspective by integrating 1000 test particles for 100 Myr. We find ˜ 10 to 30 librators for each of the resonances. Particularly, the nodal resonance found by Christou is the most stable: 2 particles are observed to stay in libration for the entire integration.

  16. The Innovative DE orbiting Aerobrake System "IDEAS " for Small Satellites: The Use of Gossamer Technolgy for a Cleaner Space

    Science.gov (United States)

    Santerre, B.; Bonnefond, T.; Dupuy, C.

    2008-08-01

    From the birth of space adventure until now, a huge number of objects have been put in orbit. Today, space environment is more and more crowded. The assessed number of objects sizing more than 1 cm is 300000. About 9600 objects are referenced, with only 500 useful. 22% of satellites are non operating satellites. For these reasons, space debris is becoming a real concern. The Inter Agency Space Debris Cordination (IDAC), composed of 11 space agencies, has defined a code of conduct to limit the space debris. In 2004, CNES decided to apply this code of conduct. As a consequence, the in-orbit life time (after operative life) of every satellite must be limited to 25 years. In the frame of this code of conduct, Astrium Space Transportation is developing in collaboration with CNES, a solution for slow deorbiting of small satellites using passive aerobraking. The Gossamer technology has been identified as the best solution to fulfil this functional requirement and to limit cost and performance impacts for the satellite. The interest of using gossamer technologies for small satellite aerobraking system was demonstrated by a feasibility study performed by Astrium Space Transportation during 2005. The main advantages of the retained solution are the easy accommodation on satellite, the simple electrical interface with the satellite, the ability to be operated even on an underperforming spacecraft (as long as telemetry can be received) and the absence of need of any specific satellite control. The trade-off between several inflatable technologies led to the selection of kapton/aluminium/kapton laminates, mainly because of the specific requirements of the mission (low available electrical power, long passive-life duration before deployment, no attitude control during deployment = non defined thermal conditions). This technology is currently developed and will be qualified for an application on a CNES satellite, called Microscope, that is asked to reduce its natural deorbiting

  17. 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

  18. A study of L-dependent Pc3 pulsations observed by low Earth orbiting CHAMP satellite

    Directory of Open Access Journals (Sweden)

    D. C. Ndiitwani

    2010-02-01

    Full Text Available Field line resonances (FLR driven by compressional waves are an important mechanism for the generation of ULF geomagnetic pulsations observed at all latitudes during local daytime. References to observations of toroidal standing Alfvén mode oscillations with clearly L-dependent frequencies from spacecraft in the outer magnetosphere for L>3 are limited in the literature. Such observations in the inner magnetosphere for L<3 have not yet been reported in the literature. This study offers two interesting case studies of observations of ULF waves by the low Earth orbiting CHAMP satellite. The magnetic field measurements from CHAMP, which are of unprecedented accuracy and resolution, are compared to Hermanus magnetometer data for times when CHAMP crosses the ground station L-shell, namely for 13 February 2002 and 18 February 2003. The data were analysed for Pc3 pulsation activity using the Maximum Entropy Spectral Analysis (MESA method to visualise FLRs in the vector magnetometer data. For the first time observations of Pc3 toroidal oscillations with clearly L-dependent frequencies for lower L-shell values (L<3 observed by an LEO satellite are reported. These observations show FLR frequencies increasing as a function of decreasing latitude down to L=1.6 and then decreasing as a result of the larger plasma density of the upper ionosphere. The L-dependent frequency oscillations were observed in the presence of a broadband compressional wave spectrum. Our observations thus confirm the well-known magnetohydrodynamic (MHD wave theoretical prediction of a compressional wave being the driver of the field line resonance.

  19. Solution set on the natural satellite formation orbits under first-order earth's non-spherical perturbation

    Institute of Scientific and Technical Information of China (English)

    Humei Wang; Wei Yang; Junfeng Li

    2005-01-01

    Using the reference orbital element approach, the precise governing equations for the relative motion of formation flight are formulated. A number of ideal formations with respect to an elliptic orbit can be designed based on the relative motion analysis from the equations. The features of the oscillating reference orbital elements are studied by using the perturbation theory. The changes in the relative orbit under perturbation are divided into three categories, termed scale enlargement, drift and distortion respectively. By properly choosing the initial mean orbital elements for the leader and follower satellites, the deviations from originally regular formation orbit caused by the perturbation can be suppressed. Thereby the natural formation is set up. It behaves either like non-disturbed or need little control to maintain.The presented reference orbital element approach highlights the kinematics properties of the relative motion and is convenient to incorporate the results of perturbation analysis on orbital elements. This method of formation design has advantages over other methods in seeking natural formation and in initializing formation.

  20. 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.

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

    Directory of Open Access Journals (Sweden)

    S. Schweitzer

    2011-05-01

    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, recently introduced by Kirchengast and Schweitzer (2011, that enables to retrieve thermodynamic profiles (pressure, temperature, humidity and accurate 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. For enabling trace species retrieval based on differential transmission, the LIO signals are spectrally located as pairs, one in the centre of a suitable absorption line of a target species (absorption signal and one close by but outside of any absorption lines (reference signal. 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 the atmospheric influences on the transmission and differential transmission of LIO signals. Refraction effects, trace species absorption (by target species, and cross-sensitivity to foreign species, aerosol extinction and Rayleigh scattering are studied in detail. The influences of clouds, turbulence, wind, scattered solar radiation and terrestrial thermal radiation are discussed as well. We show that the influence of defocusing, foreign species absorption, aerosols and turbulence is observable, but can be rendered small to negligible by use of the differential transmission principle and by a design with close frequency spacing of absorption and reference signals within 0.5 %. The influences of Rayleigh scattering and thermal radiation on the received signal intensities are found negligible. Cloud-scattered solar radiation can be observable under bright-day conditions but this

  2. Computation and Prediction of plasma drag on Orbiting Satellites due to Space Environmental Perturbation by Coronal Mass Ejections (CMEs)

    Science.gov (United States)

    Nwankwo, Victor U. J.; Chakrabarti, Sandip Kumar

    2012-07-01

    Certain earth pointing Coronal Mass Ejections (CMEs) induce geomagnetic storms, which significantly affect human activities. Satellites orbiting earth are particularly vulnerable to blasts of solar energy resulting from this phenomenon. It is known that the huge amount of energetic ultraviolet radiation from this space environmental disturbance can heat up the outer atmosphere, causing it to expand. This can cause a significant drag on Earth-Orbiting satellites and even degrade the precision of Global Positioning Systems (GPS) measurements. However, CMEs are more damaging. They are more frequent during the active (solar maximum) Phase of the sun's approximately 11-year cycle. As we approach another maximum in 2012-2013, it is instructive to make an estimate of average daily production of energetic proton flux based on GOES data on earth-pointing CMEs in the past solar cycle. We also compute the drag on satellites due to atmospheric perturbations by CMEs and make predictions of how the existing satellite orbits could be affected near the peak of next solar cycle maximum.

  3. Possible Effect of the Earth’s Inertial Induction on the Orbital Decay of LAGEOS

    Indian Academy of Sciences (India)

    Ujjal Dey; Samanwita Kar; Amitabha Ghosh

    2016-09-01

    The theory of velocity dependent inertial induction, based upon extended Mach's principle, has been able to generate many interesting results related to celestial mechanics and cosmological problems. Because of the extremely minute magnitude of the effect its presence can be detected through the motion of accurately observed bodies like Earth satellites. LAGEOS I and II are medium altitude satellites with nearly circular orbits. The motions of these satellites are accurately recorded and the past data of a few decades help to test many theories including the general theory of relativity. Therefore, it is hoped that the effect of the Earth's inertial induction can have any detectable effect on the motion of these satellites. It is established that the semi-major axis of LAGEOS I is decreasing at the rate of 1.3 mm/d. As the atmospheric drag is negligible at that altitude, a proper explanation of the secular change has been wanting, and, therefore, this paper examines the effect of the Earth's inertial induction effect on LAGEOS I. Past researches have established that Yarkovsky thermal drag, charged and neutral particle drag might be the possible mechanisms for this orbital decay. Inertial induction is found to generate a perturbing force that results in 0.33 mm/d decay of the semi-major axis. Some other changes are also predicted and the phenomenon also helps to explain the observed changes in the orbits of a few other satellites. The results indicate the feasibility of the theory of inertial induction i.e. the dynamic gravitation phenomenon of the Earth on its satellites as a possible partial cause for orbital decay.

  4. Possible Effect of the Earth's Inertial Induction on the Orbital Decay of LAGEOS

    Science.gov (United States)

    Dey, Ujjal; Kar, Samanwita; Ghosh, Amitabha

    2016-09-01

    The theory of velocity dependent inertial induction, based upon extended Mach's principle, has been able to generate many interesting results related to celestial mechanics and cosmological problems. Because of the extremely minute magnitude of the effect its presence can be detected through the motion of accurately observed bodies like Earth satellites. LAGEOS I and II are medium altitude satellites with nearly circular orbits. The motions of these satellites are accurately recorded and the past data of a few decades help to test many theories including the general theory of relativity. Therefore, it is hoped that the effect of the Earth's inertial induction can have any detectable effect on the motion of these satellites. It is established that the semi-major axis of LAGEOS I is decreasing at the rate of 1.3 mm/d. As the atmospheric drag is negligible at that altitude, a proper explanation of the secular change has been wanting, and, therefore, this paper examines the effect of the Earth's inertial induction effect on LAGEOS I. Past researches have established that Yarkovsky thermal drag, charged and neutral particle drag might be the possible mechanisms for this orbital decay. Inertial induction is found to generate a perturbing force that results in 0.33 mm/d decay of the semi major axis. Some other changes are also predicted and the phenomenon also helps to explain the observed changes in the orbits of a few other satellites. The results indicate the feasibility of the theory of inertial induction i.e. the dynamic gravitation phenomenon of the Earth on its satellites as a possible partial cause for orbital decay.

  5. The Solar Poynting-Robertson Effect On Particles Orbiting Solar System Bodies: Circular Orbits

    Science.gov (United States)

    Rubincam, David P.

    2013-01-01

    The Poynting-Robertson effect from sunlight impinging directly on a particle which orbits a Solar System body (planet, asteroid, comet) is considered from the Sun's rest frame. There appear to be no significant first-order terms in V(sub b)/c for circular orbits, where V(sub b) is the body's speed in its orbit about the Sun and c is the speed of light, when the particle's orbital semimajor axis is much smaller than the body's orbital semimajor axis about the Sun as is mainly the case in the Solar System.

  6. A preliminary study on dead geostationary satellite removal

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The collision between satellites IRIDIUM 33 and COSMOS 2251 indicated that the clash of two on-orbit satellites was becoming an inevitable reality. Our calculation with the two-line orbit element by NORAD showed that some two geostationary satellites had approached very close in July 2009. Therefore, more attention should be given to avoid such collisions. This paper analyzes the orbital long-term variation of a dead satellite drifting in the geostationary orbit. Also, the negative effects posed by dead satellites upon the on-orbit operational geostationary satellites are studied. Then the paper proposes a novel idea to launch a satellite sweeper whose purpose is to collect the on-orbit dead satellites and help them de-orbit to a "graveyard". The satellite sweeper consists of a parent satellite and a child satellite. The child satellite collects a dead satellite and transfers it to a higher orbit. The parent satellite stationed in the geostationary orbit is in charge of refueling the child satellite. The strategy of maneuver and rendezvous is presented and a series of formulas are derived. The analysis results show that our method to clean the geostationary orbital zone is practical and fuel-saving. With the help of just a few satellite sweepers, we can gain a clean environment of geostationary orbit environment again.

  7. A Virtual Environment for Satellite Modeling and Orbital Analysis in a Distributed Interactive Simulation

    Science.gov (United States)

    1993-12-01

    center of mass to the center of the earth. Interactive modification of the heading or pitch components of satellite orientation is not factored in to... satellite orientation and orientation by simulating thruster-firing activities. Both systems accept actual satellite telemetry for propagating models in the...model by applying rigid body dynamics. Model satellite sensor capabilities to determine FOV. Process actual satellite orientation data. _ __ Incorporate

  8. Saturn's inner satellites : orbits, masses and the chaotic motion of Atlas from new Cassini imaging observations

    CERN Document Server

    Cooper, N J; Murray, C D; Evans, M W

    2014-01-01

    We present numerically-derived orbits and mass estimates for the inner Saturnian satellites, Atlas, Prometheus, Pandora, Janus and Epimetheus from a fit to 2580 new Cassini ISS astrometric observations spanning February 2004 to August 2013. The observations are provided in a supplementary table. We estimate GM_ Atlas=0.384+/-0.001 x 10^(-3)km^3s^(-2), a value 13% smaller than the previously published estimate but with an order of magnitude reduction in the uncertainty. We also find GM_ Prometheus=10.677+/-0.006x10(-3)km^3s^(-2), GM_Pandora=9.133+/-0.009x10^(-3)km^3s^(-2), GM_Janus=126.51+/-0.03x10^(-3)km^3s^(-2) and GM_Epimetheus=35.110+/-0.009x10^(-3)km^3s^(-2), consistent with previously published values, but also with significant reductions in uncertainties. We show that Atlas is currently librating in both the 54:53 co-rotation-eccentricity resonance (CER) and the 54:53 inner Lindblad (ILR) resonance with Prometheus, making it the latest example of a coupled CER-ILR system, in common with the Saturnian sa...

  9. Low Earth orbit satellite-to-ground optical scintillation: comparison of experimental observations and theoretical predictions.

    Science.gov (United States)

    Yura, Harold T; Kozlowski, David A

    2011-07-01

    Scintillation measurements of a 1064 nm laser at a 5 kHz sampling rate were made by an optical ground station at the European Space Agency observatory in Tenerife, Spain while tracking a low Earth orbit satellite during the spring and summer of 2010. The scintillation index (SI), the variance of irradiance normalized to the square of the mean, and power spectra measurements were compared to theoretical predictions based on the Kolmogorov spectrum, the Maui3 nighttime turbulence profile, weak scintillation finite-beam wave theory, included receiver, and source aperture averaging with no free-fitting parameters. Good agreement was obtained, not only for the magnitude of the observed fluctuations, but also for the corresponding elevation angle dependence and shape of the power spectra. Little variation was seen for the SI between daytime and nighttime links. For all elevation angles, ascending and descending, the observed scintillation over extensive regions of the atmosphere is consistent with log-normal statistics. Additionally, it appears from the results presented here that the nighttime turbulence profile for the atmosphere above the observatory in Tenerife is similar to that above Haleakala in Maui, Hawaii.

  10. Analysis of Orbit Perturbations and Frozen Orbit for Lunar Satellite%月球卫星轨道摄动及冻结轨道研究

    Institute of Scientific and Technical Information of China (English)

    童科伟; 刘伟; 高朝辉; 王俊峰; 王笃俊

    2012-01-01

    利用理论分析、数值仿真与相图分析,论述了月球卫星冻结轨道与地球卫星冻结轨道的区别,分析结果表明,月球重力场存在较大异常,会引起月球卫星轨道发生较大漂移。月球冻结轨道在田谐项影响下,还存在中等周期的漂移。仅简单考虑带谐项系数,无法求得完美的月球冻结系数。月球重力场异常对绕月卫星的影响与地球相比存在很大区别。月球轨道卫星的长期运行与控制策略的设计,不能按照地球轨道卫星的传统方法。目前使用的月球引力模型精度较差,尽管基于这些不可靠的引力模型,可以得出很多有用结论,但对未来高精度的月球探测任务来说,还存在不足,需要在将来的月球探测任务中,探测高精度的月球重力场,以利于未来月球探测航天系统的任务分析与设计。%The differences between lunar satellite frozen orbit and earth satellite frozen orbit are analyzed based on analytic theory,numerical simulation and phase portrait analysis.The results show that the lunar gravity anomaly causes large drift of lunar satellite orbit,the lunar tesseral harmonics causes middle period drift of lunar frozen orbit.Phase portrait analysis and numerical analysis methods can be used to solve perfect lunar frozen coefficients instead of only using zonal harmonics.Lunar gravity anomaly causes significant difference when compared with earth orbit.For long term operation and control of lunar satellite a different strategy must be used.Though some useful results can be obtained based on currently used lower precision lunar gravity field models,they are not adequate for the future high precision lunar exploration mission.It is urgent to detect high precision lunar gravity field model for the mission analysis and design of future lunar exploration space system.

  11. Effects of orbit progression on the radiation exposures from solar proton fluxes in low Earth orbit under geomagnetic storm conditions.

    Science.gov (United States)

    Nealy, J E; Wilson, J W; Shea, M A; Smart, D F

    1996-01-01

    The present study examines the effects of orbit progression on the exposures within a Space Station Freedom module in a 51.6-degree inclined orbit at 450 km. The storm evolution is modeled after the November 1960 event, and the solar proton flux evolution is taken from the August 1972 solar proton event. The effects of a strong magnetic shock, such as was observed during the October 1989 event, is also modeled. The statistics on hourly average storm fields for the last forty years reveal that the largest geomagnetic storms approach a Dst value of -500 nanotesla at the storm peak. Similarly, one of the largest satellite-measured proton flux (> 10 MeV) for space exposures is the event of August 1972. The effects of orbit progression (advance of the line of nodes) is examined for the above conditions to study the variation of exposures under differing times of occurrence of the solar proton peak intensity, attainment of geomagnetic storm maximum, and the location of the line of nodes of the last geomagnetically protected orbit. The impact of the inherent inhomogeneity of the space station module is examined as a limiting factor on exposure with regard to the need of additional parasitic shielding.

  12. Workshop on Satellite Power Systems (SPS) effects on optical and radio astronomy

    Energy Technology Data Exchange (ETDEWEB)

    Stokes, G.M.; Ekstrom, P.A. (eds.)

    1980-04-01

    The impacts of the SPS on astronomy were concluded to be: increased sky brightness, reducing the effective aperture of terrestrial telescopes; microwave leakage radiation causing erroneous radioastronomical signals; direct overload of radioastronomical receivers at centimeter wavelengths; and unintentional radio emissions associated with massive amounts of microwave power or with the presence of large, warm structures in orbit causing the satellites to appear as individual stationary radio sources; finally, the fixed location of the geostationary satellite orbits would result in fixed regions of the sky being unusable for observations. (GHT)

  13. Orbital effects due to gravitational induction

    CERN Document Server

    Bini, Donato; Giordano, Domenico

    2015-01-01

    We study the motion of test particles in the metric of a localized and slowly rotating astronomical source, within the framework of linear gravitoelectromagnetism, grounded on a Post-Minkowskian approximation of general relativity. Special attention is paid to gravitational inductive effects due to time-varying gravitomagnetic fields. We show that, within the limits of the approximation mentioned above, there are cumulative effects on the orbit of the particles either for planetary sources or for binary systems. They turn out to be negligible.

  14. Comparison of the Defense Meteorological Satellite Program (DMSP) and the NOAA Polar-Orbiting Operational Environmental Satellite (POES) Program,

    Science.gov (United States)

    1985-10-01

    Space Segment..... ..... o. . . . .... . . .. . .. VI-53 VII. ANALYSES OF ORBITAL REQUIREMENTS ........ .o.... VII-l A. Timeliness and Geographic ...in situ platforms, and deter- mination of geographic location of those platforms, such as oceanic buoys, ships automatic stations, aircraft, and...Readout Stations (CRSs). The maximum access period is approximately 15 minutes of each orbit. During this contact time, the C segement must: " Command the

  15. Trimer effects in fragment molecular orbital-linear combination of molecular orbitals calculation of one-electron orbitals for biomolecules.

    Science.gov (United States)

    Kobori, Tomoki; Sodeyama, Keitaro; Otsuka, Takao; Tateyama, Yoshitaka; Tsuneyuki, Shinji

    2013-09-07

    The fragment molecular orbital (FMO)-linear combination of molecular orbitals (LCMO) method incorporates as an efficient post-process calculation of one-electron orbitals of the whole system after the FMO total energy calculation. A straightforward way to increase the accuracy is inclusion of the trimer effect. Here, we derive a comprehensive formulation called the FMO3-LCMO method. To keep the computational costs of the trimer term low enough, we use a matrix-size reduction technique. We evaluated the accuracy and efficiency of the FMO3-LCMO scheme in model biological systems (alanine oligomer and chignolin). The results show that delocalized electronic orbitals with covalent and hydrogen bonds are better described at the trimer level, and the FMO3-LCMO method is applicable to quantitative evaluations of a wide range of frontier orbitals in large biosystems.

  16. 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)

  17. Zero initial partial derivatives of satellite orbits with respect to force parameters violate the physics of motion of celestial bodies

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Satellite orbits have been routinely used to produce models of the Earth’s gravity field. In connection with such productions, the partial derivatives of a satellite orbit with respect to the force parameters to be determined, namely, the unknown harmonic coefficients of the gravitational model, have been first computed by setting the initial values of partial derivatives to zero. In this note, we first design some simple mathematical examples to show that setting the initial values of partial derivatives to zero is generally erroneous mathematically. We then prove that it is prohibited physically. In other words, set-ting the initial values of partial derivatives to zero violates the physics of motion of celestial bodies.

  18. Zero initial partial derivatives of satellite orbits with respect to force parameters violate the physics of motion of celestial bodies

    Institute of Scientific and Technical Information of China (English)

    XU PeiLiang

    2009-01-01

    Satellite orbits have been routinely used to produce models of the Earth's gravity field. In connection with such productions, the partial derivatives of a satellite orbit with respect to the force parameters to be determined, namely, the unknown harmonic coefficients of the gravitational model, have been first computed by setting the initial values of partial derivatives to zero. In this note, we first design some simple mathematical examples to show that setting the initial values of partial derivatives to zero is generally erroneous mathematically. We then prove that it is prohibited physically. In other words, set-ting the initial values of partial derivatives to zero violates the physics of motion of celestial bodies.

  19. Mapping the Space Radiation Environment in LEO Orbit by the SATRAM Timepix Payload On Board the Proba-V Satellite

    Science.gov (United States)

    Granja, Carlos; Polansky, Stepan; Sospisil, Stanislav; Owens, Alan; Mellab, Karim

    2016-08-01

    The compact spacecraft payload SATRAM is operating in LEO orbit since 2013 on board the Proba-V satellite from ESA and provides high-resolution wide-range radiation monitoring of the satellite environment. Equipped with the pixel detector Timepix, the technology demonstration payload determines the composition (particle types) and spectral characterization (stopping power) of the mixed radiation field with quantum imaging sensitivity, charged particle tracking, energy loss and directionality capability. With a polar orbit (sun synchronous, 98° inclination) and altitude of 820 km the space radiation field is continuously sampled over the entire planet every few days. Results are given in the form of spatial- and time- correlated maps of dose rate and particle flux. Comparison is made between quiescent and geomagnetic storm activity periods.

  20. SATURNʼS INNER SATELLITES: ORBITS, MASSES, AND THE CHAOTIC MOTION OF ATLAS FROM NEW CASSINI IMAGING OBSERVATIONS

    OpenAIRE

    Cooper, Nicholas J.; Renner, Stéfan; Murray, Carl D.; Evans, Michael W.

    2015-01-01

    International audience; We present numerically derived orbits and mass estimates for the inner Saturnian satellites, Atlas, Prometheus, Pandora, Janus, and Epimetheus from a fit to 2580 new Cassini Imaging Science Subsystem astrometric observations spanning 2004 February to 2013 August. The observations are provided as machine-readable and Virtual Observatory tables. We estimate GM Atlas = (0.384 ± 0.001) × 10 −3 km 3 s −2 , a value 13% smaller than the previously published estimate but with ...

  1. 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

  2. Cultural Effects and Uses of Communication Satellites.

    Science.gov (United States)

    Schramm, Wilbur

    The communication satellite already has developed a mature technology. It carries a substantial part of the world's long range communication, and is now useable for special cultural and educational purposes. Major cultural effects come from its contribution to increasing enormously the flow of information in the world. It will increase human…

  3. Orbital relaxation effects on Kohn–Sham frontier orbital energies in density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, DaDi [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Zheng, Xiao, E-mail: xz58@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Li, Chen [Department of Chemistry, Duke University, Durham, North Carolina 27708 (United States); Yang, Weitao, E-mail: weitao.yang@duke.edu [Department of Chemistry, Duke University, Durham, North Carolina 27708 (United States); Key Laboratory of Theoretical Chemistry of Environment, School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China)

    2015-04-21

    We explore effects of orbital relaxation on Kohn–Sham frontier orbital energies in density functional theory by using a nonempirical scaling correction approach developed in Zheng et al. [J. Chem. Phys. 138, 174105 (2013)]. Relaxation of Kohn–Sham orbitals upon addition/removal of a fractional number of electrons to/from a finite system is determined by a systematic perturbative treatment. The information of orbital relaxation is then used to improve the accuracy of predicted Kohn–Sham frontier orbital energies by Hartree–Fock, local density approximation, and generalized gradient approximation methods. The results clearly highlight the significance of capturing the orbital relaxation effects. Moreover, the proposed scaling correction approach provides a useful way of computing derivative gaps and Fukui quantities of N-electron finite systems (N is an integer), without the need to perform self-consistent-field calculations for (N ± 1)-electron systems.

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

    NARCIS (Netherlands)

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

    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

  5. Opportunities for Coordinated Observations of CO2 with the Orbiting Carbon Observatory (OCO) and Greenhouse Gases Observing Satellite (GOSAT)

    Science.gov (United States)

    Crisp, David

    2008-01-01

    The Orbiting Carbon Observatory (OCO) and the Greenhouse Gases Observing Satellite (GOSAT) are the first two satellites designed to make global measurements of atmospheric carbon dioxide (CO2) with the precision and sampling needed identify and monitor surface sources and sinks of this important greenhouse gas. Because the operational phases of the OCO and GOSAT missions overlap in time, there are numerous opportunities for comparing and combining the data from these two satellites to improve our understanding of the natural processes and human activities that control the atmospheric CO2 and it variability over time. Opportunities for cross-calibration, cross-validation, and coordinated observations that are currently under consideration are summarized here.

  6. The small satellite NINA-MITA to study galactic and solar cosmic rays in low-altitude polar orbit

    Science.gov (United States)

    Furano, G.; Bidoli, V.; Casolino, M.; de Pascale, M. P.; Iannucci, A.; Morselli, A.; Picozza, P.; Reali, E.; Sparvoli, R.; Bakaldin, A.; Galper, A.; Koldashov, M.; Korotkov, M.; Leonov, A.; Mikhailov, V.; Murashov, A.; Voronov, S.; Mazzenga, G.; Ricci, M.; Castellini, G.; Barbiellini, M.; Boezio, M.; Bonvicini, V.; Cirami, R.; Vacchi, A.; Zampa, N.; Ambriola, M.; Bellotti, R.; Cafagna, F.; Ciacio, F.; Circella, M.; de Marzo, C.; Adriani, O.; Papini, P.; Piccardi, S.; Spillantini, P.

    The satellite MITA, carrying on board the scientific payload NINA-2, was launched on July the 15th, 2000 from the cosmodrome of Plesetsk (Russia) with a Cosmos-3M rocket. The satellite and the payload are currently operating within nominal parameters. NINA-2 is the first scientific payload for the technological flight of the Italian small satellite MITA. The detector used in this mission is identical to the one already flying on the Russian satellite Resurs-O1 n.4 in a 840-km sun-synchronous orbit, but makes use of the extensive computer and telemetry capabilities of MITA bus to improve the active data acquisition time. NINA physics objectives are to study cosmic nuclei from hydrogen to iron in the energy range between 10 MeV/n and 1 GeV/n during the years 2000-2003, that is the solar maximum period. The device is capable of charge identification up to iron with isotope sensitivity up to oxigen. The 87.3 degrees, 460 km altitude polar orbit allows investigations of cosmic rays of solar and galactic origin, so to study long and short term solar transient phenomena, and the study of the trapped radiation at higher geomagnetic cutoff.

  7. 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.

  8. Using Equinoctial Orbital Elements and Quasi-average Element Method to Construct Analytical Solutions for Geostationary Satellite

    Science.gov (United States)

    Liu, Bin; Tang, Jingshi; Hou, Xiyun; Liu, Lin

    2016-07-01

    The eccentricity and the inclination of the satellite in geosynchronous orbit are both small, under this condition, perturbations from the Earth's non-spherical gravitational field result in orbit resonances due to incommensurable small denominators, that is, the problem of small eccentricity, small inclination and commensurability small incommensurable denominator exist simultaneously. Usually we adopt the classic Kepler orbital elements to describe an orbit, However, in the case of small eccentricities and small inclinations, the geometric meaning of the perigee and ascending node of an GEO is no longer clear, and the equations of motion have small denominators which results in the failure of the usual mean orbit element perturbation solution. This phenomenon of singularity is caused by the inappropriate choice of independent variables and has nothing to do with the dynamics. Such singularities can be avoided by choosing the appropriate independent variables (called non-singularity orbital elements). Incommensurable singularity appears in the process of solving the perturbation equations by the mean element methodology. The quasi-average element methodology retains the main advantages of the mean element method and reasonably revises its definition. Quasi-average orbits, without short periodic terms, while including the long-term items are taken as the reference orbit. The reference orbit in this transformation has long-term variations which are similar to the long periodic terms within a short-time duration. So we can avoid the failure of the perturbation solution caused by the periodic terms when using the classical perturbation method or the mean element method. From the perspective of mechanics, it can eliminate the incommensurable singularity, and the perturbation solution will remain valid. This paper aims at introducing the calculation method to eliminate the singularity problem of e=0,i=0 and commensurability singularity by using the quasi-average element

  9. 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

  10. An Evaluation of Semianalytical Satellite Theory against Long Arcs of Real Data for Highly Eccentric Orbits.

    Science.gov (United States)

    1987-01-01

    made several valuable sugges- tions that were helpful in interpreting the semimajor axis comparisons. Mr. Leo Early was a saving source of information...orbit types: (1) low Earth orbits, ( LEO ) below 5000 km; (2) geosynchronous orbits (GEO), at 35,700 km altitude; (3) Molniya orbits, about 500 km by 40,000...of the more extensive analytical theory of Lane and Cranford which used the solution of Brouwer for its gravitational model and a power density

  11. 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

    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...

  12. A Study on the Relationship between the Orbital Lifetime and Inclination of Low Lunar Satellites

    Institute of Scientific and Technical Information of China (English)

    Hai-Hong Wang; Lin Liu

    2005-01-01

    A detailed theoretical analysis on the orbital lifetime and orbital inorbital lifetime are given. Numerical simulations under the real force model were carried out, which not only validate the theoretical analysis and also give some valuable results for the orbit design of the LMOs.

  13. 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 (account under developing of the anomaly frequency models and forecasting. We consider also influence of CR on frequency of gene mutations and evolution of biosphere (we show that if it will be no CR, the Earth's civilization will be start only after milliards years later, what will be too late), CR role in thunderstorm phenomena and discharges, space weather effects on space technologies and radiation effects from solar and galactic CR in dependence of cutoff rigidities and altitude, influence magnetic storms accompanied by CR Forbush-effects on people health (increasing frequency of infarct myocardial and brain strokes), increasing frequency of car

  14. Effects of spin-orbit coupling on quantum transport

    NARCIS (Netherlands)

    Bardarson, Jens Hjorleifur

    2008-01-01

    The effect of spin-orbit coupling on various quantum transport phenomena is considered. The main topics discussed are: * How spin-orbit coupling can induce shot noise through trajectory splitting. * How spin-orbit coupling can degrade electron-hole entanglement (created by a tunnel barrier) by mo

  15. Onboard and Real-Time Artificial Satellite Orbit Determination Using GPS

    Directory of Open Access Journals (Sweden)

    Ana Paula Marins Chiaradia

    2013-01-01

    Full Text Available An algorithm for real-time and onboard orbit determination applying the Extended Kalman Filter (EKF method is developed. Aiming at a very simple and still fairly accurate orbit determination, an analysis is performed to ascertain an adequacy of modeling complexity versus accuracy. The minimum set of to-be-estimated states to reach the level of accuracy of tens of meters is found to have at least the position, velocity, and user clock offset components. The dynamical model is assessed through several tests, covering force model, numerical integration scheme and step size, and simplified variational equations. The measurement model includes only relevant effects to the order of meters. The EKF method is chosen to be the simplest real-time estimation algorithm with adequate tuning of its parameters. In the developed procedure, the obtained position and velocity errors along a day vary from 15 to 20 m and from 0.014 to 0.018 m/s, respectively, with standard deviation from 6 to 10 m and from 0.006 to 0.008 m/s, respectively, with the SA either on or off. The results, as well as analysis of the final adopted models used, are presented in this work.

  16. Modeling atmospheric drag effect on Mangalyaan Mars orbiter during geocentric, heliocentric and areocentric trajectories

    Science.gov (United States)

    Nwankwo, Victor U. J.; Chakrabarti, Sandip Kumar

    2016-07-01

    Interplanetary missions are susceptible to gravitational and non-gravitational perturbing forces at every trajectory phase, assuming that the man made rockets and thrusters work as expected. These forces are mainly due to planetary and solar-forcing-induced perturbations during geocentric, heliocentric and Martian trajectories, and before orbit insertion. In this study, we analyzed perturbing forces and their possible effects on interplanetary and/or Mars mission satellites, before Orbit Insertion. We also model the significance of atmospheric drag force on Mangalyaan Mars orbiter mission, as a function of appropriate space environmental parameters during its 28 days in Earth's orbit (around and during perigee passage), 300 days of heliocentric and 100 days of Martian trajectory based on Earth-Mars atmosphere density ratio.

  17. General Purpose Satellites: a concept for affordable low earth orbit vehicles

    OpenAIRE

    Boyd, Austin W.; Fuhs, Allen E.

    1997-01-01

    A general purpose satellite has been designed which will be launched from the Space Shuttle using a NASA Get-Away-Special (GAS) canister. The design is based upon the use of a new extended GAS canister and a low profile launch mechanism. The satellite is cylindrical. measuring 19 inches in diameter and 35 inches long. The maximum vehicle weight is 250 pounds, of which 50 pounds is dedicated to user payloads. The remaining 200 pounds encompasses the satellite structure and support ...

  18. System Design and In-orbit Verification of the HJ-1-C SAR Satellite

    OpenAIRE

    Zhang Run-ning; Jiang Xiu-peng

    2014-01-01

    HJ-1-C is a SAR satellite owned by the Chinese Environment and Natural Disaster Monitoring constellation, and works together with the optical satellites HJ-1-A/B for monitoring environment and natural disasters. In this paper, the system design and characteristics of the first Chinese civil SAR satellite are described. In addition, the interface relation between SAR payload and platform is studied. Meanwhile, the data transmission capability, attitude, power, and temperature control that supp...

  19. Effect of LEO Satellite's Orbit Parameter on GPS Occultation Event's Number and Distribution%LEO卫星轨道参数对GPS掩星数量和分布的影响

    Institute of Scientific and Technical Information of China (English)

    赵世军; 孙学金; 朱有成; 廖仿玉

    2002-01-01

    利用低地球轨道LEO(Low Eanh Orbit)卫星所载GPS接收机探测地球大气的分层结构是上世纪80年代后期才发展起来的新技术.不同的LEO卫星,将使发生的掩星事件数量和分布有所差别.在一定的大气折射指数分布模型和现有GPS星座的假设条件下,利用射线追踪法模拟了掩星事件,并讨论了LEO卫星的轨道倾角和高度对掩星事件发生的数量和分布的影响,其结论对实际发射LEO卫星时的参数选取具有参考价值.

  20. The on-orbit calibration of geometric parameters of the Tian-Hui 1 (TH-1) satellite

    Science.gov (United States)

    Wang, Jianrong; Wang, Renxiang; Hu, Xin; Su, Zhongbo

    2017-02-01

    The on-orbit calibration of geometric parameters is a key step in improving the location accuracy of satellite images without using Ground Control Points (GCPs). Most methods of on-orbit calibration are based on the self-calibration using additional parameters. When using additional parameters, different number of additional parameters may lead to different results. The triangulation bundle adjustment is another way to calibrate the geometric parameters of camera, which can describe the changes in each geometric parameter. When triangulation bundle adjustment method is applied to calibrate geometric parameters, a prerequisite is that the strip model can avoid systematic deformation caused by the rate of attitude changes. Concerning the stereo camera, the influence of the intersection angle should be considered during calibration. The Equivalent Frame Photo (EFP) bundle adjustment based on the Line-Matrix CCD (LMCCD) image can solve the systematic distortion of the strip model, and obtain high accuracy location without using GCPs. In this paper, the triangulation bundle adjustment is used to calibrate the geometric parameters of TH-1 satellite cameras based on LMCCD image. During the bundle adjustment, the three-line array cameras are reconstructed by adopting the principle of inverse triangulation. Finally, the geometric accuracy is validated before and after on-orbit calibration using 5 testing fields. After on-orbit calibration, the 3D geometric accuracy is improved to 11.8 m from 170 m. The results show that the location accuracy of TH-1 without using GCPs is significantly improved using the on-orbit calibration of the geometric parameters.

  1. 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.

  2. Satellite's Motion under the Effect of Magnetic Torque

    Directory of Open Access Journals (Sweden)

    Rashmi Bhardwaj

    2006-01-01

    Full Text Available Non-integrability of planar oscillation of a satellite in an elliptic orbit under the influence of magnetic torque has been studied. The amplitude of the oscillation remains constant upto the second order of approximation. The analysis regarding the stability of the stationary planar oscillation of a satellite near the resonance frequency shows that discontinuity occurs in the amplitude of the oscillation at a frequency of the external periodic force which is less than the frequency of the natural oscillation.

  3. On the Stability of Satellite Planes I: Effects of Mass, Velocity, Halo Shape and Alignment

    CERN Document Server

    Fernando, Nuwanthika; Guglielmo, Magda; Lewis, Geraint F; Ibata, Rodrigo A; Power, Chris

    2016-01-01

    The recently discovered vast thin plane of dwarf satellites orbiting the Andromeda Galaxy (M31) adds to the mystery of the small scale distribution of the Local Group's galaxy population. Such well defined planar structures are apparently rare occurrences in cold dark matter cosmological simulations, and we lack a coherent explanation of their formation and existence. In this paper, we explore the long-term survivability of thin planes of dwarfs in galactic halos, focusing, in particular, on systems mimicking the observed Andromeda distribution. The key results show that, in general, planes of dwarf galaxies are fragile, sensitive to the shape of the dark matter halo and other perturbing effects. In fact, long lived planes of satellites only exist in polar orbits in spherical dark matter halos, presenting a challenge to the observed Andromeda plane which is significantly tilted with respect to the optical disk. Our conclusion is that, in standard cosmological models, planes of satellites are generally short l...

  4. The application of the instantaneous states reduction to the orbital monitoring of pivotal arcs of the Chang’E-1 satellite

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In the Chinese lunar exploration project,the Chang’E-1 (CE-1) satellite was jointly monitored by the United S-band range and Doppler and the VLBI technique. A real-time reduction of the tracking data is realized to deduce the time series of the instantaneous state vectors (ISV) (position and velocity vec-tors) of the CE-1 satellite,and is applied to the orbital monitoring of pivotal arcs. This paper introduces this real-time data reduction method and its application to the orbital monitoring of pivotal arcs of the CE-1 satellite in order to serve as a source of criticism and reference.

  5. Fast and accurate prediction for aerodynamic forces and moments acting on satellites flying in Low-Earth Orbit

    Science.gov (United States)

    Jin, Xuhon; Huang, Fei; Hu, Pengju; Cheng, Xiaoli

    2016-11-01

    A fundamental prerequisite for satellites operating in a Low Earth Orbit (LEO) is the availability of fast and accurate prediction of non-gravitational aerodynamic forces, which is characterised by the free molecular flow regime. However, conventional computational methods like the analytical integral method and direct simulation Monte Carlo (DSMC) technique are found failing to deal with flow shadowing and multiple reflections or computationally expensive. This work develops a general computer program for the accurate calculation of aerodynamic forces in the free molecular flow regime using the test particle Monte Carlo (TPMC) method, and non-gravitational aerodynamic forces actiong on the Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite is calculated for different freestream conditions and gas-surface interaction models by the computer program.

  6. Small oscillations of test bodies on circular orbits in Schwarzschild and Kerr metrics (The Shirokov effect)

    Energy Technology Data Exchange (ETDEWEB)

    Vladimirov, Yu.S.; Rodichev, S.V. (Moskovskij Gosudarstvennyj Univ. (USSR))

    1981-10-01

    The Shirokov effect has been recalculated and analyzed by the monad method of assignment of systems of reference. The effect consists in the following: if test masses of the system of reference (for example, a satellite without drift) freely rotating along a circular orbit are imparted low velocities in the radial direction or perpendicular to the orbit plane, weak oscillations of a test body appear, periods of these weak oscillations differing. Their difference depends on the radius of the circular orbit and gravitational radius of a central source. It is shown, that difference of oscillation periods has the same nature as phenomenon of drift of Mercury, perigelium. Motion of the test body in the opposite direction angular source velocity increases difference of oscillation periods and motion in the direction of angular source velocity decreases it. Analogously this effect has been calculated in the Kerr metric.

  7. The orbits of the uranian satellites and rings, the gravity field of the uranian system, and the orientation of the pole of Uranus

    Energy Technology Data Exchange (ETDEWEB)

    Jacobson, R. A., E-mail: robert.jacobson@jpl.nasa.gov [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099 (United States)

    2014-11-01

    French et al. determined the orbits of the Uranian rings, the orientation of the pole of Uranus, and the gravity harmonics of Uranus from Earth-based and Voyager ring occultations. Jacobson et al. determined the orbits of the Uranian satellites and the masses of Uranus and its satellites from Earth-based astrometry and observations acquired with the Voyager 2 spacecraft; they used the gravity harmonics and pole from French et al. Jacobson and Rush reconstructed the Voyager 2 trajectory and redetermined the Uranian system gravity parameters, satellite orbits, and ring orbits in a combined analysis of the data used previously augmented with additional Earth-based astrometry. Here we report on an extension of that work that incorporates additional astrometry and ring occultations together with improved data processing techniques.

  8. Phase Residual Estimations for PCVs of Spaceborne GPS Receiver Antenna and Their Impacts on Precise Orbit Determination of GRACE Satellites

    Institute of Scientific and Technical Information of China (English)

    TU Jia; GU Defeng; WU Yi; YI Dongyun

    2012-01-01

    In-flight phase center systematic errors of global positioning system (GPS) receiver antenna are the main restriction for improving the precision of precise orbit determination using dual-frequency GPS.Residual approach is one of the valid methods for in-flight calibration of GPS receiver antenna phase center variations (PCVs) from ground calibration.In this paper,followed by the correction model of spaceborne GPS receiver antenna phase center,ionosphere-free PCVs can be directly estimated by ionosphere-free carrier phase post-fit residuals of reduced dynamic orbit determination.By the data processing of gravity recovery and climate experiment (GRACE) satellites,the following conclusions are drawn.Firstly,the distributions of ionosphere-free carrier phase post-fit residuals from different periods have the similar systematic characteristics.Secondly,simulations show that the influence of phase residual estimations for ionosphere-free PCVs on orbit determination can reach the centimeter level.Finally,it is shown by in-flight data processing that phase residual estimations of current period could not only be used for the calibration for GPS receiver antenna phase center of foretime and current period,but also be used for the forecast of ionosphere-free PCVs in future period,and the accuracy of orbit determination can be well improved.

  9. Degravitation, Orbital Dynamics and the Effective Barycentre

    CERN Document Server

    Dirkes, Alain

    2016-01-01

    In this article we present a particular theory of gravity in which Einstein's field equations are modified by promoting Newton's constant $G$ to a covariant differential operator $G_\\Lambda(\\Box_g)$. The general idea was obviously outlined for the first time in [13-16] and originates from the quest of finding a mechanism that is able to degravitate the vacuum energy on cosmological scales. We suggest in this manuscript a precise covariant coupling model which acts like a high-pass filter with a macroscopic distance filter scale $\\sqrt{\\Lambda}$. In the context of this specific theory of gravity we review some cosmological aspects before we briefly recall the effective relaxed Einstein equations outlined for the first time in [1]. We present a general procedure to determine the gravitational potentials for a far away wave zone field point. Moreover we work out the modified orbital dynamics of a binary-system as well as the effective 1.5 post-Newtonian barycentre for a generic $n$-body system. We notice that it...

  10. 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.

  11. Spectral signatures of the ionospheric Alfvén resonator to be observed by low-Earth orbit satellite

    Science.gov (United States)

    Surkov, V. V.; Pilipenko, V. A.

    2016-03-01

    Interference of an incident and reflected Alfvén pulses propagating inside the ionospheric Alfvén resonator (IAR) is studied on the basis of a simple one-dimensional model. Particular emphasis has been placed on the analysis of spectral features of ultralow frequency (˜1-15 Hz) electric perturbations recently observed by Communications/Navigation Outage Forecasting System satellite. This "fingerprint" multiband spectral structure was observed when satellite descended in the terminator vicinity. Among factors affecting spectral structure the satellite position and distance from the IAR boundaries are most significant. It is concluded that the observed spectrograms exhibit modulation with "period" depending on propagation delay time of reflected Alfvén pulses in such a way that this effect can mask a spectral resonance structure resulted from excitation of IAR eigenmodes. The proposed interference effect is capable to produce a spectral pattern resembling a fingerprint which is compatible with the satellite observations.

  12. Satellite abundances around bright isolated galaxies II: radial distribution and environmental effects

    CERN Document Server

    Wang, Wenting; Henriques, Bruno M B; White, Simon D M

    2014-01-01

    We use the SDSS/DR8 galaxy sample to study the radial distribution of satellite galaxies around isolated primaries, comparing to semi-analytic models of galaxy formation based on the Millennium and Millennium-II simulations. SDSS satellites behave differently around high- and low-mass primaries: those orbiting objects with $M_*>10^{11}M_\\odot$ are mostly red and are less concentrated towards their host than the inferred dark matter halo, an effect that is very pronounced for the few blue satellites. On the other hand, less massive primaries have steeper satellite profiles that agree quite well with the expected dark matter distribution and are dominated by blue satellites, even in the inner regions where strong environmental effects are expected. In fact, such effects appear to be strong only for primaries with $M_* > 10^{11}M_\\odot$. This behaviour is not reproduced by current semi-analytic simulations, where satellite profiles always parallel those of the dark matter and satellite populations are predominan...

  13. Early On-Orbit Performance of the Visible Infrared Imaging Radiometer Suite Onboard the Suomi National Polar-Orbiting Partnership (S-NPP) Satellite

    Science.gov (United States)

    Cao, Changyong; DeLuccia, Frank J.; Xiong, Xiaoxiong; Wolfe, Robert; Weng, Fuzhong

    2014-01-01

    The Visible Infrared Imaging Radiometer Suite (VIIRS) is one of the key environmental remote-sensing instruments onboard the Suomi National Polar-Orbiting Partnership spacecraft, which was successfully launched on October 28, 2011 from the Vandenberg Air Force Base, California. Following a series of spacecraft and sensor activation operations, the VIIRS nadir door was opened on November 21, 2011. The first VIIRS image acquired signifies a new generation of operational moderate resolution-imaging capabilities following the legacy of the advanced very high-resolution radiometer series on NOAA satellites and Terra and Aqua Moderate-Resolution Imaging Spectroradiometer for NASA's Earth Observing system. VIIRS provides significant enhancements to the operational environmental monitoring and numerical weather forecasting, with 22 imaging and radiometric bands covering wavelengths from 0.41 to 12.5 microns, providing the sensor data records for 23 environmental data records including aerosol, cloud properties, fire, albedo, snow and ice, vegetation, sea surface temperature, ocean color, and nigh-time visible-light-related applications. Preliminary results from the on-orbit verification in the postlaunch check-out and intensive calibration and validation have shown that VIIRS is performing well and producing high-quality images. This paper provides an overview of the onorbit performance of VIIRS, the calibration/validation (cal/val) activities and methodologies used. It presents an assessment of the sensor initial on-orbit calibration and performance based on the efforts from the VIIRS-SDR team. Known anomalies, issues, and future calibration efforts, including the long-term monitoring, and intercalibration are also discussed.

  14. 利用TLE数据分析LEO卫星轨道异常的新方法-综合判据法%New Method to Analyse the Orbital Abnormal of LEO Satellite Using TLE Data——Compositive Criterion

    Institute of Scientific and Technical Information of China (English)

    杨旭; 刘静; 吴相彬; 王荣兰; 于友成; 王人冬; 张耀; 李大卫

    2011-01-01

    及时准确地发现在轨卫星的轨道异常意义重大.通过有效的异常算法,能够找出发生轨道异常的碎片或航天器,为空间碎片碰撞预警系统分析和验证碰撞事件提供数据支持.通过对利用TLE(Two Line Elements)数据分析LEO在轨卫星轨道异常的方法研究,提出了一个利用单个卫星相邻根数时间差控制加综合判据的判别方法.分析表明,相对于取单一因素阈值的判别方法,综合判据法能够最大限度地减少漏判,并且保持相对较高的判断准确率.%Finding the orbital abnormal of orbiting satellite accurately and in time has great meanings. The presented method can find the orbital abnormal of debris or spacecraft effectively, which provide data supports to analyse and verify the collision event computed by space debris collision avoidance system. The orbital abnormal also includes the orbit maneuver and other orbit change.This paper discussed how to analyse the orbital abnormal of LEO satellites using TLE data. Then,a method of using the satellite adjacent elements plus compositive criterion are presented. The basic idea of compositive criterion method is to get each sub criterion and turnover rate using a certain period data of satellites, and each satellite has its own criterion instead of using an settled criterion to all satellites. Analysis showed that compared to using a single element threshold method, the compositive criterion method decreases the missing discrimination and also has a high accuracy of right discrimination. This paper also briefly analyzed other kinds of orbit using the same method.

  15. An autonomous navigation algorithm for high orbit satellite using star sensor and ultraviolet earth sensor.

    Science.gov (United States)

    Baohua, Li; Wenjie, Lai; Yun, Chen; Zongming, Liu

    2013-01-01

    An autonomous navigation algorithm using the sensor that integrated the star sensor (FOV1) and ultraviolet earth sensor (FOV2) is presented. The star images are sampled by FOV1, and the ultraviolet earth images are sampled by the FOV2. The star identification algorithm and star tracking algorithm are executed at FOV1. Then, the optical axis direction of FOV1 at J2000.0 coordinate system is calculated. The ultraviolet image of earth is sampled by FOV2. The center vector of earth at FOV2 coordinate system is calculated with the coordinates of ultraviolet earth. The autonomous navigation data of satellite are calculated by integrated sensor with the optical axis direction of FOV1 and the center vector of earth from FOV2. The position accuracy of the autonomous navigation for satellite is improved from 1000 meters to 300 meters. And the velocity accuracy of the autonomous navigation for satellite is improved from 100 m/s to 20 m/s. At the same time, the period sine errors of the autonomous navigation for satellite are eliminated. The autonomous navigation for satellite with a sensor that integrated ultraviolet earth sensor and star sensor is well robust.

  16. 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.

  17. Low-latitude Pi2 oscillations observed by polar Low Earth Orbiting satellite

    Science.gov (United States)

    Thomas, Neethal; Vichare, Geeta; Sinha, A. K.; Rawat, Rahul

    2015-09-01

    Low-latitude Pi2 pulsations in the topside ionosphere are investigated using vector magnetic field measurements from LEO satellite, CHAMP, and underneath ground station. Substorm-associated Pi2s are initially identified using high-resolution data from Indian station Shillong, during 2007-2009, and are further classified into three subgroups of Pi2 band (6-25 mHz), based on its frequency. During nighttime, coherent in-phase oscillations are observed in the compressional component at satellite and horizontal component at underneath ground station for all the Pi2 events, irrespective of the Pi2 frequency. We observe that the identification of daytime Pi2s at CHAMP (compressional component) depends on the frequency of Pi2 oscillation; i.e., 40%, 45%, and 100% of Pi2 events observed in dayside ground station with frequency between 6-10 mHz, 10-15 mHz, and 15-25 mHz were identified at satellite, respectively. At CHAMP during daytime, the presence of a dominant power in the lower frequencies of Pi2 band, which is unique to satellite, is consistently observed and can modify the Pi2 oscillations. Pi2s having frequency >15 mHz are less affected by these background frequencies, and a clear signature of daytime Pi2s at CHAMP is possible to observe, provided that contribution from non-Pi2 frequencies at satellite from the lower end of Pi2 band is eliminated. Daytime Pi2s identified in the topside ionosphere showed coherent but mostly opposite phase oscillations with underneath ground station, and satellite-to-ground amplitude ratio is, in general, found to be less than 1. Present results indicate that a combination of fast cavity-mode oscillations and an instantaneous transmission of Pi2 electric field from high- to low-latitude ionosphere is responsible for the observation of daytime Pi2s.

  18. Effects on biological systems of reflected light from a satellite power system

    Science.gov (United States)

    White, M.

    1981-01-01

    Light reflection produced by the satellite power system and the possible effects of that light on the human eye, plants, and animals were studied. For the human eye, two cases of reflected light, might cause eye damage if viewed for too long. These cases are: (1) if, while in low Earth orbit, the orbital transfer vehicle is misaligned to reflect the Sun to Earth there exists a maximum safe fixation time for the naked eye of 42.4 secs; (2) reflection from the aluminum paint on the back of the orbital transfer vehicle, while in or near low Earth orbit, can be safely viewed by the naked eye for 129 sec. For plants and animals the intensity and timing of light are not a major problem. Ways for reducing and/or eliminating the irradiances are proposed.

  19. 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.

  20. Orbiting Retrievable Far and Extreme Ultraviolet Spectrometer - Shuttle Pallet Satellite (ORFEUS-SPAS)

    Science.gov (United States)

    1993-01-01

    The objective of the ORFEUS mission is to launch a deployable/retrievable astronomical platform and obtain ultraviolet spectra for both astrophysically interesting sources and the intervening interstellar medium. Also, the IMAX cameras will obtain footage of both the Shuttle and the ORFEUS-SPAS satellite during the deployment/retrieval operations phase of the ORFEUS-SPAS mission.

  1. Faster Estimation and Analysis of Doppler Frequency Shift from Medium Elliptic Orbit Satellites%中椭圆轨道卫星多普勒频移快速估计及分析

    Institute of Scientific and Technical Information of China (English)

    乔文龙; 章坚武; 包建荣; 姜斌

    2016-01-01

    卫星通信中,星地双方高速移动及快速角度变化等因素,将造成较大多普勒频移及频谱扩展等现象,恶化星地通信性能.在Walker星座计算多普勒频移算法的基础上,提出了改进的中椭圆轨道卫星多普勒频移的快速简化计算方法.相对于传统卫星在宇宙空间的三维坐标复杂公式计算方法,所提方法通过长半轴、偏心率等参数直接计算卫星半径,较大降低了计算复杂度.最后,仿真对比和分析高椭圆轨道通信卫星的多普勒频移曲线,较好地解释了中椭圆轨道多普勒频移特性.同时,仿真星地在相对运动情况下的多普勒频移特性,验证了其有效性,以便于实际卫星通信场合快速估计多普勒频移而有效辅助信号接收.%In satellite communications, the high-speed movement, the rapid angle change and some other factors of between the satellites and the ground stations would usually, cause fairly large Doppler frequency shifting, spectrum spreading, and other phenomena, thus deteriorating the satellite-ground communication performance. Based on the Doppler frequency shift algorithm under the Walker constellation a modified calculation method of the Doppler shift in the medium elliptical orbit satellite is proposed. Compared with traditional formula methods needing to know three-dimensional coordinates of the satellites in space, the computational complexity is greatly reduced through directly calculating the radius of the satellite by the semi-major axis of ellipse, eccentricity and other parameters. Finally, simulation comparison and analysis of the Doppler frequency shift curves in high elliptical orbit communication satellites fairly interprets the characteristics of medium elliptical orbit Doppler frequency shift. In addition, simulation on the characteristics of medium elliptical orbit Doppler frequency shift for the relative motion of between satellite and ground station indicates the effectiveness of this

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

    DEFF Research Database (Denmark)

    Olsen, Jørgen Lundegaard

    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...

  3. On Comparing Precision Orbit Solutions of Geodetic Satellites Given Several Atmospheric Density Models

    Science.gov (United States)

    2014-08-01

    mechanics 1998, 1998, pp. 1275–1293. [3] P. W. Binning, M. T. Soyka, and J. W. Middour, “Orbit determination using space to ground Differential GPS in...upper atmosphere models,” Planetary and Space Science, Vol. 47, No. 12, 1999, pp. 1465–1473. [12] S. Krzysztof, “Impact of the Atmospheric Drag on

  4. The Combined Release and Radiation Effects Satellite (CRRES) program: A unique series of scientific experiments

    Science.gov (United States)

    Reasoner, David L.; McCook, Morgan W.; Vaughan, William W.

    The Defense Department and NASA have joined in a program to study the space environment which surrounds the earth and the effects of space radiation on modern satellite electronic systems. The Combined Release and Radiation Effects Satellite (CRRES) will carry an array of active experiments including chemical releases and a complement of sophisticated scientific instruments to accomplish these objectives. Other chemical release active experiments will be performed with sub-orbital rocket probes. The chemical releases will 'paint' the magnetic and electric fields of earthspace with clouds of glowing ions. Earthspace will be a laboratory, and the releases will be studied with an extensive network of ground-, aircraft-, and satellite-based diagnostic instruments. Some of the topics discussed include the following: the effects of earthspace; the need for active experiments; types of chemical releases; the CRRES program schedule; international support and coordinated studies; photographing chemical releases; information on locating chemical releases for observation by the amateur; and CRRES as a program.

  5. Interpretations of de-orbit, deactivation, and shutdown guidelines applicable to GEO satellites

    Science.gov (United States)

    Honda, L.; Perkins, J.; Sun, Sheng

    As the population of space debris in orbit around the Earth grows, the probability for catastrophic collisions increases. Many agencies such as the IADC, FCC, and UN have proposed space debris mitigation guidelines or recommendations. For example, a minimum increase in perigee altitude of 235km + (1000 Cr A / m) where Cr is the solar radiation pressure coefficient, A/m is the aspect area to dry mass ratio, and 235 km is the sum of the upper altitude of the geostationary orbit (GEO) protected region (200 km) and the maximum descent of a re-orbited spacecraft due to lunar-solar & geopotential perturbations (35 km) with an eccentricity less than or equal to 0.003. While this particular recommendation is reasonably straightforward, the assumptions an operator chooses may change the result by 25 km. Other recommendations are more ambiguous. For example, once the space vehicle has been de-orbited to the required altitude, all on-board stored energy sources must be discharged by venting propellants and pressurants, discharging batteries and disabling the ability to charge them, and performing other appropriate measures. “ Vented” is not usually defined. In addition, the broadcasting capability of the spacecraft must be disabled. Boeing and its customers are working together to devise de-orbit and deactivation sequences that meet the spirit of the recommendations. This paper derives and proposes a generic minimum deorbit altitude, appropriate depletion and venting pressures based on tank design, propellant and pressurant type, and an acceptable shutdown procedure and final configuration that avoid interference with those still in the GEO belt well into the future. The goal of this paper is to open a dialogue with the global community to establish reasonable guidelines that are straightforward, safe, and achievable before an absolute requirement is set.

  6. An Approach for Optimizing the On-Orbit Servicing Architecture for a Given Client Satellite Constellation

    Science.gov (United States)

    2005-03-01

    In February of 1980, NASA launched the Solar Maximum Mission spacecraft to collect observations of solar flares, sunspots, magnetic fields, and the...spacecraft autonomously delivered supplies to and returned waste from the Mir space station, the second generation of Russian manned orbiting facilities...Vehicle Routing Problems The classic vehicle routing problem ( VRP ) is a combinatorial optimization problem that minimizes the cost of routing a

  7. Galileo satellite antenna modeling

    Science.gov (United States)

    Steigenberger, Peter; Dach, Rolf; Prange, Lars; Montenbruck, Oliver

    2015-04-01

    The space segment of the European satellite navigation system Galileo currently consists of six satellites. Four of them belong to the first generation of In-Orbit Validation (IOV) satellites whereas the other two are Full Operational Capability (FOC) satellites. High-precision geodetic applications require detailed knowledge about the actual phase center of the satellite and receiver antenna. The deviation of this actual phase center from a well-defined reference point is described by phase center offsets (PCOs) and phase center variations (PCVs). Unfortunately, no public information is available about the Galileo satellite antenna PCOs and PCVs, neither for the IOV, nor the FOC satellites. Therefore, conventional values for the IOV satellite antenna PCOs have been adopted for the Multi-GNSS experiment (MGEX) of the International GNSS Service (IGS). The effect of the PCVs is currently neglected and no PCOs for the FOC satellites are available yet. To overcome this deficiency in GNSS observation modeling, satellite antenna PCOs and PCVs are estimated for the Galileo IOV satellites based on global GNSS tracking data of the MGEX network and additional stations of the legacy IGS network. Two completely independent solutions are computed with the Bernese and Napeos software packages. The PCO and PCV values of the individual satellites are analyzed and the availability of two different solutions allows for an accuracy assessment. The FOC satellites are built by a different manufacturer and are also equipped with another type of antenna panel compared to the IOV satellites. Signal transmission of the first FOC satellite has started in December 2014 and activation of the second satellite is expected for early 2015. Based on the available observations PCO estimates and, optionally PCVs of the FOC satellites will be presented as well. Finally, the impact of the new antenna model on the precision and accuracy of the Galileo orbit determination is analyzed.

  8. Research on the Orbit Keeping of Satellite%卫星运行轨道保持研究

    Institute of Scientific and Technical Information of China (English)

    冯艳; 张忠峰

    2011-01-01

    With the known control law, the initial value range of state variables are determined by genetic algorithm.Then fixed point can be accurately obtained by Newton-Raphson's iteration.Finally attraction region of fixed point of orbit keeping is obtained by cell-to-cell mapping method.The results indicate that the orbit of satellite can keep if the state variables and control law satisfy given conditions.%在控制量已知的条件下,首先用遗传算法确定了卫星轨道保持所需初始状态量的范围,再用Newton-Raphson迭代法精确求得不动点,最后用胞映射法计算得到轨道保持不动点的吸引域.结果表明:只要控制量和状态量满足特定条件,卫星的运行轨道就能保持.

  9. Visualization tools for extremely high resolution DEM from the LRO and other orbiter satellites

    Science.gov (United States)

    Montgomery, J.; McDonald, John

    2012-10-01

    Recent space missions have included laser altimetry instrumentation that provides precise high-resolution global topographic data products. These products are critical in analyzing geomorphological surface processes of planets and moons. Although highly valued, the high-resolution data is often overlooked by researchers due to the high level of IT sophistication necessary to use the high-resolution data products, which can be as large as several hundred gigabytes. Researchers have developed software tools to assist in viewing and manipulating data products derived from altimetry data, however current software tools require substantial off-line processing, provide rudimentary visualization or are not suited for viewing the new high-resolution data. We have adapted mVTK, a novel software visualization tool, to work with NASA's recently acquired Lunar Reconnaissance Orbiter data. mVTK is a software visualization package that dynamically creates cylindrical cartographic map projections from gridded high-resolution altimetry data in real-time. The projections are interactive 2D shade relief, false color maps that allow the user to make simple slope and distance measurements on the actual underlying high-resolution data. We have tested mVTK on several laser altimetry data sets including binned gridded record data from NASA's Mars Global Surveyor and Lunar Reconnaissance Orbiter space missions.

  10. Time and frequency requirement for the earth and ocean physics applications program. [characteristics and orbital mechanics of artificial satellites for data acquisition

    Science.gov (United States)

    Vonbun, F. O.

    1972-01-01

    The application of time and frequency standards to the Earth and Ocean Physics Applications Program (EOPAP) is discussed. The goals and experiments of the EOPAP are described. Methods for obtaining frequency stability and time synchronization are analyzed. The orbits, trajectories, and characteristics of the satellites used in the program are reported.

  11. Orbital fibroblast chemokine modulation: effects of dexamethasone and cyclosporin A

    OpenAIRE

    BURNSTINE, M.; Elner, S.; Elner, V.

    1998-01-01

    AIM—Orbital inflammation is common, but the mechanisms underlying leucocytic infiltration of orbital tissue are poorly understood. Human orbital fibroblasts (OF) express chemokines, interleukin 8 (IL-8) and monocyte chemotactic protein 1 (MCP-1), when exposed to proinflammatory cytokines. The effects of dexamethasone (DEX) and cyclosporin A (CSA) on OF IL-8 and MCP-1 were examined.
METHODS—Cultured human OF were incubated with recombinant interleukin 1β (rIL-1β; 0.2, 2.0, 20 ng/ml) alone or i...

  12. ASC Champ Orbit Model

    DEFF Research Database (Denmark)

    Riis, Troels; Jørgensen, John Leif

    1999-01-01

    This documents describes a test of the implementation of the ASC orbit model for the Champ satellite.......This documents describes a test of the implementation of the ASC orbit model for the Champ satellite....

  13. Fast converging with high accuracy estimates of satellite attitude and orbit based on magnetometer augmented with gyro, star sensor and GPS via extended Kalman filter

    Directory of Open Access Journals (Sweden)

    Tamer Mekky Ahmed Habib

    2011-12-01

    Full Text Available The primary goal of this work is to extend the work done in, Tamer (2009, to provide high accuracy satellite attitude and orbit estimates needed for imaging purposes and also before execution of spacecraft orbital maneuvers for the next Egyptian scientific satellite. The problem of coarse satellite attitude and orbit estimation based on magnetometer measurements has been treated in the literature. The current research expands the field of application from coarse and slow converging estimates to accurate and fast converging attitude and orbit estimates within 0.1°, and 10 m for attitude angles and spacecraft location respectively (1-σ. The magnetometer is used for both spacecraft attitude and orbit estimation, aided with gyro to provide angular velocity measurements, star sensor to provide attitude quaternion, and GPS receiver to provide spacecraft location. The spacecraft under consideration is subject to solar radiation pressure forces and moments, aerodynamics forces and moments, earth’s oblateness till the fourth order (i.e. J4, gravity gradient moments, and residual magnetic dipole moments. The estimation algorithm developed is powerful enough to converge quickly (actually within 10 s despite very large initial estimation errors with sufficiently high accuracy estimates.

  14. Stimulated Radiative Molecular Association in the Early Solar System. II. Orbital Radii of the Planets and Other Satellites of the Sun

    CERN Document Server

    Lombardi, James C

    2015-01-01

    In a previous investigation, the orbital radii of regular satellites of Uranus, Jupiter, Neptune, and Saturn are shown to be directly related to photon energies in the spectra of atomic and molecular hydrogen. To explain these observations a model was developed involving stimulated radiative molecular association (SRMA) reactions among photons and atoms in the protosatellite disks of the planets. In the present investigation, the previously developed model is applied to the planets and important satellites of the Sun. A key component of the model involves resonance associated with SRMA. Through this resonance, thermal energy is extracted from the protosun's protoplanetary disk at specific distances from the protosun wherever there is a match between the local thermal energy of the disk and the energy of photons impinging on the disk. Orbital radii of the planets and satellites are related to photon energies ($E_P$ values) in the spectrum of atomic hydrogen. An expression determined previously is used to relat...

  15. 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.

  16. New orbits of irregular satellites designed for the predictions of stellar occultations up to 2020, based on thousands of new observations

    Science.gov (United States)

    Gomes-Júnior, A. R.; Assafin, M.; Beauvalet, L.; Desmars, J.; Vieira-Martins, R.; Camargo, J. I. B.; Morgado, B. E.; Braga-Ribas, F.

    2016-10-01

    Gomes-Júnior et al. published 3613 positions for the eight largest irregular satellites of Jupiter and 1787 positions for the largest irregular satellite of Saturn, Phoebe. These observations were made between 1995 and 2014 and have an estimated error of about 60-80 mas. Based on this set of positions, we derived new orbits for the eight largest irregular satellites of Jupiter: Himalia, Elara, Pasiphae, Carme, Lysithea, Sinope, Ananke and Leda. For Phoebe we updated the ephemeris from Desmars et al. using 75 per cent more positions than the previous one. Because of their orbital characteristics, it is common belief that the irregular satellites were captured by the giant planets in the early Solar system, but there is no consensus for a single model explaining where they were formed. Size, shape, albedo and composition would help to trace back their true origin, but these physical parameters are yet poorly known for irregular satellites. The observation of stellar occultations would allow for the determination of such parameters. Indeed Jupiter will cross the galactic plane in 2019-2020 and Saturn in 2018, improving a lot the chances of observing such events in the near future. Using the derived ephemerides and the UCAC4 catalogue we managed to identify 5442 candidate stellar occultations between 2016 January and 2020 December for the nine satellites studied here. We discussed how the successful observation of a stellar occultation by these objects is possible and present some potential occultations.

  17. 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.

  18. Effective management strategy for establishing an operating room satellite pharmacy.

    Science.gov (United States)

    Brakebill, J I; Schoeneman, P F; Buchanan, B

    1988-11-01

    The steps involved in justifying and implementing an operating room (OR) pharmacy satellite are described. A hospital administrator's viewpoint on the project is included. Objectives of the satellite were to reduce inventory costs, improve control of distribution, reduce loss of revenue and improve patient charging, improve IV compounding and labeling, and significantly improve narcotic control and accountability. The satellite provides comprehensive services 12 hours a day, five days a week. Effective after-hours procedures have been developed to provide efficient drug distribution when the pharmacy is closed. Achieved benefits of the satellite include decreased drug inventory, improved patient charging, accurate labeling, improved IV compounding, and improved pharmacy/surgery relations. The OR pharmacy satellite is a successful cost-effective operation.

  19. Centimeter Precise Orbit Determination for SWARM Satellite via Reduced-dynamic Method%SWARM卫星简化动力学厘米级精密定轨

    Institute of Scientific and Technical Information of China (English)

    张兵兵; 聂琳娟; 吴汤婷; 冯建迪; 邱耀东

    2016-01-01

    联合星载GPS双频观测值与简化的动力学模型,在卫星运动方程中引入适当的伪随机脉冲参数,对SWARM卫星进行精密定轨.采用星载GPS相位观测值残差、重叠轨道以及与外部轨道对比等3种方法对SWARM卫星简化动力学定轨结果进行检核.结果表明:SWARM星载GPS相位观测值残差RMS为7~10mm;径向、切向以及法向6h重叠轨道差值RMS均在1cm左右,3个方向均无明显的系统误差.通过与欧空局(ESA)发布的精密轨道进行对比分析,径向轨道差值RMS为2~5cm,切向轨道差值RMS为2~5cm,法向轨道差值RMS为2~4cm,3D轨道差值RMS为4~7cm;SWARM-B定轨精度优于SWARM-A与SWARM-C.因此,采用简化动力学法与本文提供的定轨策略进行SWARM卫星精密定轨是切实可行的,定轨结果良好且稳定,定轨精度达到厘米级.%Combining dual-frequency satellite-borne GPS observations with reduced dynamic models,and introducing proper pseudo-stochastic pulse parameters into the satellite’s motion equation,SWARM satellite precise orbit determination is implemented.The orbit accuracy is assessed using three methods, which include analysis satellite-borne GPS phase observation residuals,orbit overlaps and external orbit comparisons.The results indicate that the SWARM satellite-borne GPS phase observation residual RMS is in the range of 7 to 10 mm,radial,along-track and cross-track orbit overlap difference RMS of 6 hours are about 1 cm,three directions have no significant systematic errors,comparisons with orbits computed by European Space Agency (ESA),Radial orbit difference RMS is in the range of 2 to 5 cm,along-track orbit difference RMS is in the range of 2 to 5 cm,cross-track orbit difference RMS is in the range of 2 to 4 cm,3D orbit difference RMS is in the range of 4 to 7 cm,SWARM-B orbit accuracy is better than SWARM-A and SWARM-C.This evaluations indicate that SWARM satellite precise orbit determination is practicable by using reduced

  20. Satellite Observations of Coastal Processes from a Geostationary Orbit: Application to estuarine, coastal, and ocean resource management

    Science.gov (United States)

    Tzortziou, M.; Mannino, A.; Schaeffer, B. A.

    2016-12-01

    Coastal areas are among the most vulnerable yet economically valuable ecosystems on Earth. Estuaries and coastal oceans are critically important as essential habitat for marine life, as highly productive ecosystems and a rich source of food for human consumption, as a strong economic driver for coastal communities, and as a highly dynamic interface between land and ocean carbon and nutrient cycles. Still, our present capabilities to remotely observe coastal ocean processes from space are limited in their temporal, spatial, and spectral resolution. These limitations, in turn, constrain our ability to observe and understand biogeochemical processes in highly dynamic coastal ecosystems, or predict their response and resilience to current and future pressures including sea level rise, coastal urbanization, and anthropogenic pollution.On a geostationary orbit, and with high spatial resolution and hyper-spectral capabilities, NASA's Decadal Survey mission GEO-CAPE (GEO-stationary for Coastal and Air Pollution Events) will provide, for the first time, a satellite view of the short-term changes and evolution of processes along the economically invaluable but, simultaneously, particularly vulnerable near-shore waters of the United States. GEO-CAPE will observe U.S. lakes, estuaries, and coastal regions at sufficient temporal and spatial scales to resolve near-shore processes, tides, coastal fronts, and eddies, track sediments and pollutants, capture diurnal biogeochemical processes and rates of transformation, monitor harmful algal blooms and large oil spills, observe episodic events and coastal hazards. Here we discuss the GEO-CAPE applications program and the new capabilities afforded by this future satellite mission, to identify potential user communities, incorporate end-user needs into future mission planning, and allow integration of science and management at the coastal interface.

  1. Effects of CubeSat Deployments in Low-Earth Orbit

    Science.gov (United States)

    Matney, M. J.; Vavrin, A. B.; Manis, A. P.

    2017-01-01

    Long-term models, such as NASA's LEGEND (LEO (Low-Earth Orbit)-to-GEO (Geosynchrous Earth Orbit) Environment Debris) model, are used to make predictions about how space activities will affect the long-term evolution of the debris environment. Part of this process is to predict how spacecraft and rocket bodies will be launched and left in the environment in the future. This has usually been accomplished by repeating past launch history to simulate future launches. It was partially upon the basis of the results of such models that both national and international orbital debris mitigation guidelines - especially the "25-year rule" for post-mission disposal - were determined. The proliferation of Cubesat launches in recent years, however, has raised concerns that we are seeing a fundamental shift in how humans launch satellites into space that may alter the assumptions upon which our current mitigation guidelines are based. The large number of Cubesats, and their short lifetime and general inability to perform collision avoidance, potentially makes them an important new source of debris. The NASA Orbital Debris Program Office (ODPO) has conducted a series of LEGEND computations to investigate the long-term effects of adding Cubesats to the environment. Several possible future scenarios were simulated to investigate the effects of the size of future Cubesat launches and the efficiency of post-mission disposal on the proliferation of catastrophic collisions over the next 200 years. These results are compared to a baseline "business-as-usual" scenario where launches are assumed to continue as in the past without major Cubesat deployments. Using these results, we make observations about the continued use of the 25-year rule and the importance of the universal application of post-mission disposal. We also discuss how the proliferation of Cubesats may affect satellite traffic at lower altitudes.

  2. Orbital stability zones about asteroids. II - The destabilizing effects of eccentric orbits and of solar radiation

    Science.gov (United States)

    Hamilton, Douglas P.; Burns, Joseph A.

    1992-03-01

    Recently, Hamilton and Burns (1991) characterized the size and shape of a stability zone around an asteroid on a circular heliocentric orbit within which asteroid material could remain bound for an extended period of time. The present paper considers two additional effects: the asteroid's nonzero heliocentric eccentricity and solar radiation pressure. Results of numerical analyses show that, for an asteroid on an eccentric orbit, the stability zone scales roughly as the size of the Hill sphere calculated at the asteroid's pericenter. It was also found that solar radiation pressure is a very efficient mechanism for removing small (on the order of 0.1 mm) particles from circular asteroidal zone. Particles larger than a few centimeters are only slightly affected by radiation pressure. The results are applied to the Gaspra 951 asteroid.

  3. Satellites formation configuration design and orbit maneuver algorithm optimization%卫星编队构型设计与轨道机动算法优化

    Institute of Scientific and Technical Information of China (English)

    夏红伟; 李莉; 曲耀斌; 贾大玲; 周利均; 王常虹

    2013-01-01

      卫星编队与轨道机动是完成在轨监视与捕获等空间任务的关键技术。针对追踪航天器在相对目标航天器的绕飞过程中特殊构型的编队飞行问题,提出了三种特殊的编队构型机动方案;针对近距离轨道逼近问题,分析了同平面轨道变轨策略和轨道转移能耗最优化问题,在此基础上给出了三脉冲升降轨机动方法,并可以根据需要将其扩展为 N 脉冲机动。以目标星运行轨道高度780 km 为例进行仿真分析,结果表明平行四边形编队中追踪星在各交点处完成变轨所需的速度脉冲向量分别为0.1172 m/s、0.1843 m/s,而花形编队和菱形编队中追踪星在各交点处完成变轨所需的速度脉冲向量均为0.1978 m/s,从而验证了所提出方法的有效性。%Satellites formation and orbit maneuver are key techniques of the space missions such as orbital monitoring, orbital capture. Aiming at the formation flight problem of special configuration when the tracking spacecraft were flying around the target spacecraft, three special formation configurations were given. To solve the problem of close orbit approximation, the strategy of the plane orbital transfer and the energy consumption optimization problem of the orbital transfer were analyzed. The orbit ascend and descend method of three-pulse on that basis was also given, and it can be extended to N-pulse maneuver. Simulations were made when the orbit altitude of target spacecraft was 780 km, and the results show that the needed speed pulse vectors are 0.1172 m/s and 0.1843 m/s respectively when the tracking spacecraft transfers at the nodes in the parallelogram formation, while the needed speed pulse vector is 0.1978 m/s in the flower shape or diamond formation. The results also verify the effectiveness of the proposed method.

  4. Comparison of Orbit-Based and Time-Offset-Based Geometric Correction Models for SAR Satellite Imagery Based on Error Simulation.

    Science.gov (United States)

    Hong, Seunghwan; Choi, Yoonjo; Park, Ilsuk; Sohn, Hong-Gyoo

    2017-01-17

    Geometric correction of SAR satellite imagery is the process to adjust the model parameters that define the relationship between ground and image coordinates. To achieve sub-pixel geolocation accuracy, the adoption of the appropriate geometric correction model and parameters is important. Until now, various geometric correction models have been developed and applied. However, it is still difficult for general users to adopt a suitable geometric correction models having sufficient precision. In this regard, this paper evaluated the orbit-based and time-offset-based models with an error simulation. To evaluate the geometric correction models, Radarsat-1 images that have large errors in satellite orbit information and TerraSAR-X images that have a reportedly high accuracy in satellite orbit and sensor information were utilized. For Radarsat-1 imagery, the geometric correction model based on the satellite position parameters has a better performance than the model based on time-offset parameters. In the case of the TerraSAR-X imagery, two geometric correction models had similar performance and could ensure sub-pixel geolocation accuracy.

  5. Comparison of Orbit-Based and Time-Offset-Based Geometric Correction Models for SAR Satellite Imagery Based on Error Simulation

    Science.gov (United States)

    Hong, Seunghwan; Choi, Yoonjo; Park, Ilsuk; Sohn, Hong-Gyoo

    2017-01-01

    Geometric correction of SAR satellite imagery is the process to adjust the model parameters that define the relationship between ground and image coordinates. To achieve sub-pixel geolocation accuracy, the adoption of the appropriate geometric correction model and parameters is important. Until now, various geometric correction models have been developed and applied. However, it is still difficult for general users to adopt a suitable geometric correction models having sufficient precision. In this regard, this paper evaluated the orbit-based and time-offset-based models with an error simulation. To evaluate the geometric correction models, Radarsat-1 images that have large errors in satellite orbit information and TerraSAR-X images that have a reportedly high accuracy in satellite orbit and sensor information were utilized. For Radarsat-1 imagery, the geometric correction model based on the satellite position parameters has a better performance than the model based on time-offset parameters. In the case of the TerraSAR-X imagery, two geometric correction models had similar performance and could ensure sub-pixel geolocation accuracy. PMID:28106729

  6. Comparison of Orbit-Based and Time-Offset-Based Geometric Correction Models for SAR Satellite Imagery Based on Error Simulation

    Directory of Open Access Journals (Sweden)

    Seunghwan Hong

    2017-01-01

    Full Text Available Geometric correction of SAR satellite imagery is the process to adjust the model parameters that define the relationship between ground and image coordinates. To achieve sub-pixel geolocation accuracy, the adoption of the appropriate geometric correction model and parameters is important. Until now, various geometric correction models have been developed and applied. However, it is still difficult for general users to adopt a suitable geometric correction models having sufficient precision. In this regard, this paper evaluated the orbit-based and time-offset-based models with an error simulation. To evaluate the geometric correction models, Radarsat-1 images that have large errors in satellite orbit information and TerraSAR-X images that have a reportedly high accuracy in satellite orbit and sensor information were utilized. For Radarsat-1 imagery, the geometric correction model based on the satellite position parameters has a better performance than the model based on time-offset parameters. In the case of the TerraSAR-X imagery, two geometric correction models had similar performance and could ensure sub-pixel geolocation accuracy.

  7. Orbital motions as gradiometers for post-Newtonian tidal effects

    CERN Document Server

    Iorio, Lorenzo

    2014-01-01

    The direct long-term changes occurring in the orbital dynamics of a local gravitationally bound binary system $S$ due to the post-Newtonian tidal acceleration caused by an external massive source are investigated. A class of systems made of a test particle $m$ rapidly orbiting with orbital frequency $n_{\\rm b}$ an astronomical body of mass $M$ which, in turn, slowly revolves around a distant object of mass $M^{'}$ with orbital frequency $n_{\\rm b}^{'}\\ll n_{\\rm b}$ is considered. The characteristic frequencies of the non-Keplerian orbital variations of $m$ and of $M$ itself are assumed to be negligible with respect to both $n_{\\rm b}$ and $n_{\\rm b}^{'}$. General expressions for the resulting Newtonian and post-Newtonian tidal orbital shifts of $m$ are obtained. The future missions BepiColombo and JUICE to Mercury and Ganymede, respectively, are considered in view of a possible detection. The largest effects, of the order of $\\approx 0.1-0.5$ milliarcseconds per year (mas yr$^{-1}$), occur for the Ganymede or...

  8. From horseshoe to quasi-satellite and back again: the curious dynamics of Earth co-orbital asteroid 2015 SO2

    CERN Document Server

    Marcos, C de la Fuente

    2015-01-01

    Earth co-orbitals of the horseshoe type are interesting objects to study for practical reasons. They are relatively easy to access from our planet and that makes them attractive targets for sample return missions. Here, we show that near-Earth asteroid (NEA) 2015 SO2 is a transient co-orbital to the Earth that experiences a rather peculiar orbital evolution characterised by recurrent, alternating horseshoe and quasi-satellite episodes. It is currently following a horseshoe trajectory, the ninth asteroid known to do so. Besides moving inside the 1:1 mean motion resonance with the Earth, it is subjected to a Kozai resonance with the value of the argument of perihelion librating around 270 degrees. Contrary to other NEAs, asteroid 2015 SO2 may have remained in the vicinity of Earth's co-orbital region for a few hundreds of thousands of years.

  9. 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 ...

  10. The Effect of Seasonal and Long-Period Geopotential Variations on the GPS Orbits

    Science.gov (United States)

    Melachroinos, Stavros A.; Lemoine, Frank G.; Chinn, Douglas S.; Zelensky, Nikita P.; Nicholas, Joseph B.; Beckley, Brian D.

    2013-01-01

    We examine the impact of using seasonal and long-period time-variable gravity field (TVG) models on GPS orbit determination, through simulations from 1994 to 2012. The models of time-variable gravity that we test include the GRGS release RL02 GRACE-derived 10-day gravity field models up to degree and order 20 (grgs20x20), a 4 x 4 series of weekly coefficients using GGM03S as a base derived from SLR and DORIS tracking to 11 satellites (tvg4x4), and a harmonic fit to the above 4 x 4 SLR-DORIS time series (goco2s_fit2). These detailed models are compared to GPS orbit simulations using a reference model (stdtvg) based on the International Earth Rotation Service (IERS) and International GNSS Service (IGS) repro1 standards. We find that the new TVG modeling produces significant along, cross-track orbit differences as well as annual, semi-annual, draconitic and long-period effects in the Helmert translation parameters (Tx, Ty, Tz) of the GPS orbits with magnitudes of several mm. We show that the simplistic TVG modeling approach used by all of the IGS Analysis Centers, which is based on the models provided by the IERS standards, becomes progressively less adequate following 2006 when compared to the seasonal and long-period TVG models.

  11. Suppression of spin-orbit effects in 1D system

    OpenAIRE

    Entin, M. V.; Magarill, L. I.

    2004-01-01

    We report the absence of spin effects such as spin-galvanic effect, spin polarization and spin current under static electric field and inter-spin-subband absorption in 1D system with spin-orbit interaction of arbitrary form. It was also shown that the accounting for the direct interaction of electron spin with magnetic field violates this statement.

  12. Mapping enzymatic catalysis using the effective fragment molecular orbital method

    DEFF Research Database (Denmark)

    Svendsen, Casper Steinmann; Fedorov, Dmitri G.; Jensen, Jan Halborg

    2013-01-01

    We extend the Effective Fragment Molecular Orbital (EFMO) method to the frozen domain approach where only the geometry of an active part is optimized, while the many-body polarization effects are considered for the whole system. The new approach efficiently mapped out the entire reaction path of ...

  13. New orbits of irregular satellites designed for the predictions of stellar occultations up to 2020, based on thousands of new observations

    CERN Document Server

    Gomes-Júnior, A R; Beauvalet, L; Desmars, J; Vieira-Martins, R; Camargo, J I B; Morgado, B E; Braga-Ribas, F

    2016-01-01

    Gomes-J\\'unior et al. (2015) published 3613 positions for the 8 largest irregular satellites of Jupiter and 1787 positions for the largest irregular satellite of Saturn, Phoebe. These observations were made between 1995 and 2014 and have an estimated error of about 60 to 80 mas. Based on this set of positions, we derived new orbits for the eight largest irregular satellites of Jupiter: Himalia, Elara, Pasiphae, Carme, Lysithea, Sinope, Ananke and Leda. For Phoebe we updated the ephemeris from Desmars et al. (2013) using 75% more positions than the previous one. Due to their orbital characteristics, it is common belief that the irregular satellites were captured by the giant planets in the early Solar System, but there is no consensus for a single model explaining where they were formed. Size, shape, albedo and composition would help to trace back their true origin, but these physical parameters are yet poorly known for irregular satellites. The observation of stellar occultations would allow for the determina...

  14. LOOPUS Mob-D: System concept for a public mobile satellite system providing integrated digital services for the Northern Hemisphere from an elliptical orbit

    Science.gov (United States)

    Kuhlen, H.; Horn, P.

    1990-08-01

    A new concept for a satellite based public mobile communications system LOOPUS Mob-D is introduced where most of the 'classical' problems in mobile satellite systems are approached in a different way. The LOOPUS system will offer a total capacity of 6000 high rate channel in three service areas (Europe, Asia, and North America) covering the entire Northern Hemisphere with a set of group special mobile (GSM) compatible mobile services eventually providing the 'office in the car'. Special characteristics of the LOOPUS orbit and the communications network architecture are highlighted.

  15. Design of a Low-Cost Single-Board Computer System for Use In Low-Earth Orbit Small Satellite Missions

    OpenAIRE

    Milani, Dino

    1996-01-01

    A single-board computer system created specifically to meet the demands of a new generation of small satellite missions is being designed, built and tested by students at the University of New Hampshire. The Satellite Single-Board Computer (SSBC) is an Intel 80C186 based system that is qualified for explicit use in low-earth orbit missions. The SSBC serves as a low-cost, high-quality alternative to commercially available systems which are usually very costly and designed for much harsher spac...

  16. Observed Orbit Effects during Long Range Beam-Beam Studies

    CERN Document Server

    Alemany, R; Buffat, X; Calaga, R; Fitterer, M; Giachino, R; Hemelsoet, GH; Herr, W; Papotti, G; Pieloni, T; Poyer, M; Schaumann, M; Trad, G; Wollmann, D

    2012-01-01

    Possible limitations due to long range beam-beam effects at the LHC have been studied and are presented in this note. With a larger number of bunches and collisions in all interaction points, the crossing angles were reduced to enhance long range beam-beam effects. The analysis of the effects on the dynamic aperture and losses are documented in [1]. This note concentrates on the bunch-by-bunch orbit effects observed during the experiment.

  17. Effects of rubber shock absorber on the flywheel micro vibration in the satellite imaging system

    Science.gov (United States)

    Deng, Changcheng; Mu, Deqiang; Jia, Xuezhi; Li, Zongxuan

    2016-12-01

    When a satellite is in orbit, its flywheel will generate micro vibration and affect the imaging quality of the camera. In order to reduce this effect, a rubber shock absorber is used, and a numerical model and an experimental setup are developed to investigate its effect on the micro vibration in the study. An integrated model is developed for the system, and a ray tracing method is used in the modeling. The spot coordinates and displacements of the image plane are obtained, and the modulate transfer function (MTF) of the system is calculated. A satellite including a rubber shock absorber is designed, and the experiments are carried out. Both simulation and experiments results show that the MTF increases almost 10 %, suggesting the rubber shock absorber is useful to decrease the flywheel vibration.

  18. 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.

  19. Orbital ordering and the dilute effect in copper fluoride

    Energy Technology Data Exchange (ETDEWEB)

    Tatami, N. [Department of Physics, Tohoku University, Sendai, Miyagi 980-8578 (Japan)]. E-mail: tatam@iiyo.phys.tohoku.ac.jp; Ando, Y. [Department of Physics, Tohoku University, Sendai, Miyagi 980-8578 (Japan); Niioka, S. [Department of Physics, Tohoku University, Sendai, Miyagi 980-8578 (Japan); Kira, H. [Department of Physics, Tohoku University, Sendai, Miyagi 980-8578 (Japan); Onodera, M. [Department of Physics, Tohoku University, Sendai, Miyagi 980-8578 (Japan); Nakao, H. [Department of Physics, Tohoku University, Sendai, Miyagi 980-8578 (Japan); Iwasa, K. [Department of Physics, Tohoku University, Sendai, Miyagi 980-8578 (Japan); Murakami, Y. [Department of Physics, Tohoku University, Sendai, Miyagi 980-8578 (Japan); Kakiuchi, T. [GraduateUniversity for Advanced Studies, Tsukuba 305-0801 (Japan); Wakabayashi, Y. [Photon Factory, IMSS, KEK, Tsukuba, Ibaraki 305-0801 (Japan); Sawa, H. [Photon Factory, IMSS, KEK, Tsukuba, Ibaraki 305-0801 (Japan); Itoh, S. [Neutron Science Laboratory, IMSS, KEK, Tsukuba, Ibaraki 305-0801 (Japan)

    2007-03-15

    We have investigated the dilute effect on a typical orbital ordering system KCuF{sub 3} by partially substituting Zn for Cu. The crystal structure has been examined as a function of Cu concentration at room temperature by X-ray diffraction. It is found that the phase transition from a tetragonal structure to a cubic one occurs with decreasing Cu concentration. This structural phase transition is confirmed to be an orbital order-disorder transition by the resonant X-ray scattering (RXS) technique.

  20. On the stability of satellite planes - I. Effects of mass, velocity, halo shape and alignment

    Science.gov (United States)

    Fernando, Nuwanthika; Arias, Veronica; Guglielmo, Magda; Lewis, Geraint F.; Ibata, Rodrigo A.; Power, Chris

    2017-02-01

    The recently discovered vast thin plane of dwarf satellites orbiting the Andromeda Galaxy (M31) adds to the mystery of the small-scale distribution of the Local Group's galaxy population. Such well-defined planar structures are apparently rare occurrences in cold dark matter cosmological simulations, and we lack a coherent explanation of their formation and existence. In this paper, we explore the long-term survivability of thin planes of dwarfs in galactic haloes, focusing, in particular, on systems mimicking the observed Andromeda distribution. The key results show that, in general, planes of dwarf galaxies are fragile, sensitive to the shape of the dark matter halo and other perturbing effects. In fact, long-lived planes of satellites only exist in polar orbits in spherical dark matter haloes, presenting a challenge to the observed Andromeda plane that is significantly tilted with respect to the optical disc. Our conclusion is that, in the standard cosmological models, planes of satellites are generally short lived, and hence we must be located at a relatively special time in the evolution of the Andromeda Plane, lucky enough to see its coherent pattern.

  1. 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.

  2. New fire diurnal cycle characterizations to improve fire radiative energy assessments made from low-Earth orbit satellites sampling

    Science.gov (United States)

    Andela, N.; Kaiser, J. W.; van der Werf, G. R.; Wooster, M. J.

    2015-03-01

    Accurate near real time fire emissions estimates are required for air quality forecasts. To date, most approaches are based on satellite-derived estimates of fire radiative power (FRP), which can be converted to fire radiative energy (FRE) which is directly related to fire emissions. Uncertainties in these FRE estimations are often substantial. This is for a large part because the most often used low-Earth orbit satellite-based instruments like the MODerate-resolution Imaging Spectroradiometer (MODIS) have a relatively poor sampling of the usually pronounced fire diurnal cycle. In this paper we explore the spatial variation of this fire diurnal cycle and its drivers. Specifically, we assess how representing the fire diurnal cycle affects FRP and FRE estimations when using data collected at MODIS overpasses. Using data assimilation we explored three different methods to estimate hourly FRE, based on an incremental sophistication of parameterizing the fire diurnal cycle. We sampled data from the geostationary Meteosat Spinning Enhanced Visible and Infrared Imager (SEVIRI) at MODIS detection opportunities to drive the three approaches. The full SEVIRI time-series, providing full coverage of the diurnal cycle, were used to evaluate the results. Our study period comprised three years (2010-2012), and we focussed on Africa and the Mediterranean basin to avoid the use of potentially lower quality SEVIRI data obtained at very far off-nadir view angles. We found that the fire diurnal cycle varies substantially over the study region, and depends on both fuel and weather conditions. For example, more "intense" fires characterized by a fire diurnal cycle with high peak fire activity, long duration over the day, and with nighttime fire activity are most common in areas of large fire size (i.e., large burned area per fire event). These areas are most prevalent in relatively arid regions. Ignoring the fire diurnal cycle as done currently in some approaches caused structural

  3. On-orbit geometric calibration and geometric quality assessment for the high-resolution geostationary optical satellite GaoFen4

    Science.gov (United States)

    Wang, Mi; Cheng, Yufeng; Chang, Xueli; Jin, Shuying; Zhu, Ying

    2017-03-01

    The Chinese GaoFen4 (GF4) remote sensing satellite, launched at the end of December 2015, is China's first civilian high-resolution geostationary optical satellite and has the world's highest resolution from geostationary orbit. High accuracy geometric calibration is the key factor in the geometrical quality of satellite imagery. This paper proposes an on-orbit geometric calibration approach for the high-resolution geostationary optical satellite GF4 in which a stepwise calibration is performed, external parameters are estimated, and internal parameters are then estimated in a generalized camera frame determined by external parameters. First, the correlation of the imaging error sources and the rigorous imaging model of GF4 are introduced. Second, the geometric calibration model based on the two-dimensional detector directional angle and the parameters estimation method for the planar array camera are presented. LandSat 8 digital orthophoto maps (DOM) and GDEM2 digital elevation models (DEM) are used to validate the efficiency of the proposed method and to make a geometric quality assessment of GF4. The results indicate that changing imaging time and imaging area will dramatically affect the absolute positioning accuracy because of the change of the camera's installation angles caused by thermal environment changes around the satellite in a high orbit. After calibration, the internal distortion is well-compensated, and the positioning accuracy with relatively few ground control points (GCPs) is demonstrated to be better than 1.0 pixels for both the panchromatic and near-infrared sensor and the intermediate infrared sensor.

  4. Analysis of the Lunar Gravity Field by Using GL0660B Model and Its Effect on Lunar Satellite Orbit%月球重力场模型GL0660B特征分析及其对绕月卫星轨道的影响

    Institute of Scientific and Technical Information of China (English)

    黄昆学; 常晓涛; 朱广彬; 李武东

    2016-01-01

    The lunar gravity field provides a way to research moon’s evolution and probes the interior structure of the moon.It is an important factor influencing the lunar satellite precise orbit determination as well.The new lunar gravity model GL0660B from GRAIL mission dramatically improves the gravity spectrum and spectral ranges.Using the model GL0660B,it can be computed that the corresponding degree-wise RMS and correlation of topography,with which the quality of model GL0660B can be analyzed.Then different characters of the lunar gravity field comparing with other lunar gravity fields are analyzed. Besides,gravity anomaly distribution figures at different height of the models are given,and the character and difference of the lunar gravity models at different height are compared.In addition,lunar satellite orbit revolutionary at different height are modeled by GEODYN.The result shows that the trend of lunar satellite eccentricity changes is a complex and long cycle of change trend.It is different affected by the perturbation of the mascons of different height,which causes different changes of apolune,perilune and eccentricity.%月球重力场可用来研究月球演化过程和内部结构,是影响绕月卫星精密定轨的重要因素。基于GRAIL任务数据解算的GL0660B重力场模型,极大提高了月球重力场空间频谱信号的强度和范围。本文首先通过计算相应重力场的阶方差和地形相关性分析,对GL0660B模型进行了精度分析;其次,利用GL0660B模型和其他几个月球重力场模型进行比较,对月球重力场的特征进行了分析;然后通过绘制GL0660B模型和 LP150Q模型在月球外部不同高度处的重力异常图,分析比较了月球重力场模型在不同高度上所反映的月球重力场的特征和差异;最后,利用 GEODYN 软件模拟计算了不同高度卫星的轨道变化。可以看出绕月卫星离心率随时间的变化,以及周期性变化趋势,而且

  5. Inertial effect on spin–orbit coupling and spin transport

    Energy Technology Data Exchange (ETDEWEB)

    Basu, B., E-mail: sribbasu@gmail.com; Chowdhury, Debashree, E-mail: debashreephys@gmail.com

    2013-08-15

    We theoretically study the renormalization of inertial effects on the spin dependent transport of conduction electrons in a semiconductor by taking into account the interband mixing on the basis of k{sup →}⋅p{sup →} perturbation theory. In our analysis, for the generation of spin current we have used the extended Drude model where the spin–orbit coupling plays an important role. We predict enhancement of the spin current resulting from the renormalized spin–orbit coupling effective in our model in cubic and non-cubic crystals. Attention has been paid to clarify the importance of gauge fields in the spin transport of this inertial system. A theoretical proposition of a perfect spin filter has been done through the Aharonov–Casher like phase corresponding to this inertial system. For a time dependent acceleration, effect of k{sup →}⋅p{sup →} perturbation on the spin current and spin polarization has also been addressed. Furthermore, achievement of a tunable source of polarized spin current through the non uniformity of the inertial spin–orbit coupling strength has also been discussed. -- Highlights: •Study of the renormalization of inertial spin dependent transport of electrons. •Enhancement of the spin current due to the renormalized spin–orbit coupling. •A theoretical proposition of a perfect spin filter. •For a time dependent acceleration, spin current, spin polarization is addressed.

  6. 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...... 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....

  7. Full particle orbit effects in regular and stochastic magnetic fields

    Science.gov (United States)

    Ogawa, Shun; Cambon, Benjamin; Leoncini, Xavier; Vittot, Michel; del Castillo-Negrete, Diego; Dif-Pradalier, Guilhem; Garbet, Xavier

    2016-07-01

    We present a numerical study of charged particle motion in a time-independent magnetic field in cylindrical geometry. The magnetic field model consists of an unperturbed reversed-shear (non-monotonic q-profile) helical part and a perturbation consisting of a superposition of modes. Contrary to most of the previous studies, the particle trajectories are computed by directly solving the full Lorentz force equations of motion in a six-dimensional phase space using a sixth-order, implicit, symplectic Gauss-Legendre method. The level of stochasticity in the particle orbits is diagnosed using averaged, effective Poincare sections. It is shown that when only one mode is present, the particle orbits can be stochastic even though the magnetic field line orbits are not stochastic (i.e., fully integrable). The lack of integrability of the particle orbits in this case is related to separatrix crossing and the breakdown of the global conservation of the magnetic moment. Some perturbation consisting of two modes creates resonance overlapping, leading to Hamiltonian chaos in magnetic field lines. Then, the particle orbits exhibit a nontrivial dynamics depending on their energy and pitch angle. It is shown that the regions where the particle motion is stochastic decrease as the energy increases. The non-monotonicity of the q-profile implies the existence of magnetic ITBs (internal transport barriers) which correspond to shearless flux surfaces located in the vicinity of the q-profile minimum. It is shown that depending on the energy, these magnetic ITBs might or might not confine particles. That is, magnetic ITBs act as an energy-dependent particle confinement filter. Magnetic field lines in reversed-shear configurations exhibit topological bifurcations (from homoclinic to heteroclinic) due to separatrix reconnection. We show that a similar but more complex scenario appears in the case of particle orbits that depend in a non-trivial way on the energy and pitch angle of the

  8. Full particle orbit effects in regular and stochastic magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Ogawa, Shun, E-mail: shun.ogawa@cpt.univ-mrs.fr [Aix Marseille Univ., Univ. Toulon, CNRS, CPT, Marseille (France); CEA, IRFM, F-13108 St. Paul-lez-Durance Cedex (France); Cambon, Benjamin; Leoncini, Xavier; Vittot, Michel [Aix Marseille Univ., Univ. Toulon, CNRS, CPT, Marseille (France); Castillo-Negrete, Diego del [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6169 (United States); Dif-Pradalier, Guilhem; Garbet, Xavier [CEA, IRFM, F-13108 St. Paul-lez-Durance Cedex (France)

    2016-07-15

    We present a numerical study of charged particle motion in a time-independent magnetic field in cylindrical geometry. The magnetic field model consists of an unperturbed reversed-shear (non-monotonic q-profile) helical part and a perturbation consisting of a superposition of modes. Contrary to most of the previous studies, the particle trajectories are computed by directly solving the full Lorentz force equations of motion in a six-dimensional phase space using a sixth-order, implicit, symplectic Gauss-Legendre method. The level of stochasticity in the particle orbits is diagnosed using averaged, effective Poincare sections. It is shown that when only one mode is present, the particle orbits can be stochastic even though the magnetic field line orbits are not stochastic (i.e., fully integrable). The lack of integrability of the particle orbits in this case is related to separatrix crossing and the breakdown of the global conservation of the magnetic moment. Some perturbation consisting of two modes creates resonance overlapping, leading to Hamiltonian chaos in magnetic field lines. Then, the particle orbits exhibit a nontrivial dynamics depending on their energy and pitch angle. It is shown that the regions where the particle motion is stochastic decrease as the energy increases. The non-monotonicity of the q-profile implies the existence of magnetic ITBs (internal transport barriers) which correspond to shearless flux surfaces located in the vicinity of the q-profile minimum. It is shown that depending on the energy, these magnetic ITBs might or might not confine particles. That is, magnetic ITBs act as an energy-dependent particle confinement filter. Magnetic field lines in reversed-shear configurations exhibit topological bifurcations (from homoclinic to heteroclinic) due to separatrix reconnection. We show that a similar but more complex scenario appears in the case of particle orbits that depend in a non-trivial way on the energy and pitch angle of the

  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. 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

  11. Modeling the Orbital Sampling Effect of Extrasolar Moons

    CERN Document Server

    Heller, René; Jackson, Brian

    2016-01-01

    The orbital sampling effect (OSE) appears in phase-folded transit light curves of extrasolar planets with moons. Analytical OSE models have hitherto neglected stellar limb darkening and non-zero transit impact parameters and assumed that the moon is on a circular, co-planar orbit around the planet. Here, we present an analytical OSE model for eccentric moon orbits, which we implement in a numerical simulator with stellar limb darkening that allows for arbitrary transit impact parameters. We also describe and publicly release a fully numerical OSE simulator (PyOSE) that can model arbitrary inclinations of the transiting moon orbit. Both our analytical solution for the OSE and PyOSE can be used to search for exomoons in long-term stellar light curves such as those by Kepler and the upcoming PLATO mission. Our updated OSE model offers an independent method for the verification of possible future exomoon claims via transit timing variations and transit duration variations. Photometrically quiet K and M dwarf star...

  12. Attitude control system design and on-orbit performance analysis of nano-satellite--‘‘Tian Tuo 1’’

    Institute of Scientific and Technical Information of China (English)

    Ran Dechao; Sheng Tao; Cao Lu; Chen Xiaoqian; Zhao Yong

    2014-01-01

    ‘‘Tian Tuo 1’’ (TT-1) nano-satellite is the first single-board nano-satellite that was suc-cessfully launched in China. The main objective of TT-1 is technology demonstration and scientific measurements. The satellite carries out the significant exploration of single-board architecture fea-sibility validation, and it is tailored to the low-cost philosophy by adopting numerous commercial-off-the-shelf (COTS) components. The satellite is featured with three-axis stabilization control capability. A pitch bias momentum wheel and three magnetic coils are adopted as control actuators. The sun sensors, magnetometers and a three-axis gyro are employed as the measurement sensors. The quaternion estimator (QUEST) and unscented Kalman filter (UKF) method are adopted for the nano-satellite attitude determination. On-orbit data received by ground station is conducted to analysis the performance of attitude determination and control system (ADCS). The results show that the design of ADCS for TT-1 is suitable, robust and feasible.

  13. Cycle life evaluation of 3 Ah Li xMn 2O 4-based lithium-ion secondary cells for low-earth-orbit satellites . I. Full cell results

    Science.gov (United States)

    Brown, Shelley; Ogawa, Keita; Kumeuchi, Youichi; Enomoto, Shinsuke; Uno, Masatoshi; Saito, Hirobumi; Sone, Yoshitsugu; Abraham, Daniel; Lindbergh, Göran

    Lithium-ion batteries are a candidate for the energy storage system onboard low-earth-orbit satellites. Cycle life performance under both orbital and terrestrial conditions must be investigated in order to evaluate any inadvertent effects due to the former and the validity of the latter, with a successful comparison allowing for the extension of terrestrial experimental matrices in order to identify the effects of ageing. The orbital performance of Li xMn 2O 4-based pouch cells onboard the microsatellite REIMEI was monitored and compared with terrestrial experiments, with the cells found to be unaffected by orbital conditions. A lifetime matrix of different cycling depths-of-discharge (DODs: 0, 20, 40%) and temperatures (25, 45 ° C) was undertaken with periodic reference performance tests. A decrease in both the cell end-of-discharge cycling voltage and capacity was accelerated by both higher temperatures and larger DODs. Impedance spectra measured for all ageing conditions indicated that the increase was small, manifested in a state-of-charge dependent increase of the high-frequency semi-circle and a noticeable increase in the high-frequency real axis intercept. An evaluation of the change of both the resistance and capacity of 3 Ah cells led to the development of a potential prognostic state-of-health indicator. The use of elevated temperatures to accelerate cell ageing was validated.

  14. Cycle life evaluation of 3 Ah Li{sub x}Mn{sub 2}O{sub 4}-based lithium-ion secondary cells for low-earth-orbit satellites. I. Full cell results

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Shelley; Lindbergh, Goeran [School of Chemical Science and Engineering, Department of Chemical Engineering and Technology, Teknikringen 42, Royal Institute of Technology, Stockholm SE-100 44 (Sweden); Ogawa, Keita [Advanced Engineering Services Co., Ltd., 1-6-1 Takezono, Tsukuba, Ibaraki 305-0032 (Japan); Kumeuchi, Youichi; Enomoto, Shinsuke [NEC-Tokin Corporation, 1120 Shimokuzawa, Sagamihara, Kanagawa 229-1198 (Japan); Uno, Masatoshi; Saito, Hirobumi; Sone, Yoshitsugu [Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510 (Japan); Abraham, Daniel [Chemical Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)

    2008-12-01

    Lithium-ion batteries are a candidate for the energy storage system onboard low-earth-orbit satellites. Cycle life performance under both orbital and terrestrial conditions must be investigated in order to evaluate any inadvertent effects due to the former and the validity of the latter, with a successful comparison allowing for the extension of terrestrial experimental matrices in order to identify the effects of ageing. The orbital performance of Li{sub x}Mn{sub 2}O{sub 4}-based pouch cells onboard the microsatellite REIMEI was monitored and compared with terrestrial experiments, with the cells found to be unaffected by orbital conditions. A lifetime matrix of different cycling depths-of-discharge (DODs: 0, 20, 40%) and temperatures (25, 45 C) was undertaken with periodic reference performance tests. A decrease in both the cell end-of-discharge cycling voltage and capacity was accelerated by both higher temperatures and larger DODs. Impedance spectra measured for all ageing conditions indicated that the increase was small, manifested in a state-of-charge dependent increase of the high-frequency semi-circle and a noticeable increase in the high-frequency real axis intercept. An evaluation of the change of both the resistance and capacity of 3 Ah cells led to the development of a potential prognostic state-of-health indicator. The use of elevated temperatures to accelerate cell ageing was validated. (author)

  15. Effect of Gravitational Frame Dragging on Orbiting Qubits

    CERN Document Server

    Lanzagorta, Marco

    2012-01-01

    In this paper we discuss the effect of gravitational frame dragging on orbiting qubits. In particular, we consider the Kerr spacetime geometry and spin-1/2 qubits moving in an equatorial radial fall with zero angular momentum and equatorial circular orbits. We ignore the ${\\cal O}(\\hbar)$ order effects due to spin-curvature coupling, which allows us to consider the motion of the spin-1/2 particles as Kerr geometry geodesics. We derive analytical expressions for the infinitesimal Wigner rotation and numerical results for their integration across the length of the particle's trajectory. To this end, we consider the bounds on the finite Wigner rotation imposed by Penrose's cosmic censorship hypothesis.

  16. Satellite propulsion spectral signature detection and analysis through Hall effect thruster plume and atmospheric modeling

    Science.gov (United States)

    Wheeler, Pamela; Cobb, Richard; Hartsfield, Carl; Prince, Benjamin

    2016-09-01

    Space Situational Awareness (SSA) is of utmost importance in today's congested and contested space environment. Satellites must perform orbital corrections for station keeping, devices like high efficiency electric propulsion systems such as a Hall effect thrusters (HETs) to accomplish this are on the rise. The health of this system is extremely important to ensure the satellite can maintain proper position and perform its intended mission. Electron temperature is a commonly used diagnostic to determine the efficiency of a hall thruster. Recent papers have coordinated near infrared (NIR) spectral measurements of emission lines in xenon and krypton to electron temperature measurements. Ground based observations of these spectral lines could allow the health of the thruster to be determined while the satellite is in operation. Another issue worth considering is the availability of SSA assets for ground-based observations. The current SSA architecture is limited and task saturated. If smaller telescopes, like those at universities, could successfully detect these signatures they could augment data collection for the SSA network. To facilitate this, precise atmospheric modeling must be used to pull out the signature. Within the atmosphere, the NIR has a higher transmission ratio and typical HET propellants are approximately 3x the intensity in the NIR versus the visible spectrum making it ideal for ground based observations. The proposed research will focus on developing a model to determine xenon and krypton signatures through the atmosphere and estimate the efficacy through ground-based observations. The model will take power modes, orbit geometries, and satellite altitudes into consideration and be correlated with lab and field observations.

  17. Anisotropic Paramagnetic Meissner Effect by Spin-Orbit Coupling

    Science.gov (United States)

    Espedal, Camilla; Yokoyama, Takehito; Linder, Jacob

    2016-03-01

    Conventional s -wave superconductors repel an external magnetic field. However, a recent experiment [A. Di Bernardo et al., Phys. Rev. X 5, 041021 (2015)] has tailored the electromagnetic response of superconducting correlations via adjacent magnetic materials. We consider another route of altering the Meissner effect where spin-orbit interactions induce an anisotropic Meissner response that changes sign depending on the field orientation. The tunable electromagnetic response opens new paths in the utilization of hybrid systems comprising magnets and superconductors.

  18. Analyzing perturbation characteristic and orbital maintenance strategy for super low altitude satellite%超低轨道卫星摄动特性分析及轨道维持方法

    Institute of Scientific and Technical Information of China (English)

    温生林; 闫野; 易腾

    2015-01-01

    针对超低轨道卫星长时间在轨飞行的轨道维持问题,分析了超低轨道平均偏心率矢量变化特性,提出了一种超低轨道维持的控制方法。分析了 J2、J3摄动以及大气阻力摄动作用下超低轨道卫星偏心率矢量的变化特性;基于能量守恒原理设计了超低轨道高度维持的控制策略;通过仿真算例验证了控制策略的有效性。结果表明:在地球非球形引力摄动、大气阻力摄动和速度脉冲作用下超低轨道平均偏心率的变化是稳定的,所设计的轨道维持方法不仅能够实现超低轨道高度维持,确保平均偏心率矢量收敛至平衡位置,且用于轨道维持的燃料消耗合理,能够满足长时间的超低轨道飞行要求。%Aiming at the orbital maintenance problem of super low altitude satellite for the long duration of the flight,the variation characteristics of the average eccentricity vector were analyzed and an orbital maintenance method was presented.Firstly,the change of average eccentricity vector characteristic of super low altitude satellite under the J2 ,J3 zonal terms and the atmospheric drag was analyzed.Then an orbital maintenance strategy based on energy conservation principle was proposed.Finally,the effectiveness of orbital maintenance strategy was validated by simulation examples.Simulation results show that the changes of average eccentricity is stable under the perturbation of the earth non-spherical gravity,the atmospheric drag and the impulsive maneuver,and the proposed orbital maintenance method can effectively achieve super low altitude maintenance and make the average eccentricity vector converge to equilibrium point.Besides,the fuel consumption for orbital maintenance is reasonable and the long duration flight in super low orbit can be achieved.

  19. Design of Geodetic SVLBI Satellite Orbit and Its Tracking Network%SVLBI用于大地测量的卫星轨道及其跟踪网设计

    Institute of Scientific and Technical Information of China (English)

    魏二虎; 刘经南; KULKARNI M.N.; FREY Sándor

    2008-01-01

    SVLBI (space very long baseline interferometry) has some important potential applications in geodesy and geodynam- ics, for which one of the most difficult tasks is to precisely determine the orbit of an SVLBI satellite. This work studies several technologies that will possibly be able to determine the orbit of a space VLBI satellite. Then, according to the types and charac- teristics of the satellite and the requirements for geodetic study and the geometry of the GNSS (GPS, GALILEO) satellite to track the space VLBI satellite, the six Keplerian elements of the SVLBI satellite (TEST-SVLBI) are determined. A program is designed to analyze the coverage area of space of different altitudes by the stations of the network, with which the tracking network of TEST-SVLBI is designed. The efficiency of tracking TEST-SVLBI by the network is studied, and the results are presented.

  20. Inertial effect on spin-orbit coupling and spin transport

    Science.gov (United States)

    Basu, B.; Chowdhury, Debashree

    2013-08-01

    We theoretically study the renormalization of inertial effects on the spin dependent transport of conduction electrons in a semiconductor by taking into account the interband mixing on the basis of k→ṡp→ perturbation theory. In our analysis, for the generation of spin current we have used the extended Drude model where the spin-orbit coupling plays an important role. We predict enhancement of the spin current resulting from the renormalized spin-orbit coupling effective in our model in cubic and non-cubic crystals. Attention has been paid to clarify the importance of gauge fields in the spin transport of this inertial system. A theoretical proposition of a perfect spin filter has been done through the Aharonov-Casher like phase corresponding to this inertial system. For a time dependent acceleration, effect of k→ ṡp→ perturbation on the spin current and spin polarization has also been addressed. Furthermore, achievement of a tunable source of polarized spin current through the non uniformity of the inertial spin-orbit coupling strength has also been discussed.

  1. Evaluation of pulsed RFI effects on digital satellite repeaters

    Science.gov (United States)

    Huang, T. C.; Braun, W. R.

    1980-01-01

    This paper presents an analytical approach for assessing the effect of pulsed RFI on the error probability of a coherent phase-shift keyed signal through a nonlinear satellite repeater. The RFI is assumed to affect the uplink channel and to consist of CW pulses with random power levels and arriving randomly in time with a Poisson distribution. A model to approximate the effect of intermodulation products is introduced and the error probability conditioned on the output of the satellite repeater is computed. The classical moment technique is then used as an efficient method of averaging the conditional error probability over the numerous random parameters associated with the uplink signal.

  2. Satellites of spiral galaxies

    Science.gov (United States)

    Zaritsky, Dennis; Smith, Rodney; Frenk, Carlos; White, Simon D. M.

    1993-01-01

    We present a survey of satellites around a homogeneous set of late-type spirals with luminosity similar to that of the Milky Way. On average, we find fewer than 1.5 satellites per primary, but we argue that we can treat the survey as an ensemble and so derive the properties of the halo of a 'typical' isolated spiral. The projected density profile of the ensemble falls off approximately as 1/r. Within 50 kpc the azimuthal distribution of satellites shows some evidence for the 'Holmberg effect', an excess near the minor axis of the primary; however, at larger projected distances, the distribution appears isotropic. There is a weak but significant correlation between the size of a satellite and its distance from its primary, as expected if satellites are tidally truncated. Neither Hubble type nor spectral characteristics correlate with apparent separation. The ensemble of satellites appears to be rotating at about 30 km/s in the same direction as the galactic disk. Satellites on prograde orbits tend to be brighter than those on retrograde orbits. The typical velocity difference between a satellite and its primary shows no clear dependence either on apparent separation, or on the rotation speed of the primary. Thus our survey demonstrates that isolated spiral galaxies have massive halos that extend to many optical radii.

  3. 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.

  4. Effect of higher orbital angular momenta in the baryon spectrum

    CERN Document Server

    Garcilazo, H; Fernández, F

    2001-01-01

    We have performed a Faddeev calculation of the baryon spectrum for the chiral constituent quark model including higher orbital angular momentum states. We have found that the effect of these states is important, although a description of the baryon spectrum of the same quality as the one given by including only the lowest-order configurations can be obtained. We have studied the effect of the pseudoscalar quark-quark interaction on the relative position of the positive- and negative-parity excitations of the nucleon as well as the effect of varying the strength of the color-magnetic interaction.

  5. A Method to Predict the Orbital Lifetimes of Free Tethers and Tether-Trailing Satellites using Artificial Neural Networks

    Science.gov (United States)

    1992-08-28

    completely developed the method in a memoir on the perturbations of comets moving in elliptical orbits.76 As a result, orbital element variational...6848.48 70.09 160.98 159.94 -0.65 159.84 -0.71 " lAits with Free Tethers. i = 28.5 0. Results obtained for free tethers originating in nonstandard orbits

  6. The Effects of Solar Maximum on the Earth's Satellite Population and Space Situational Awareness

    Science.gov (United States)

    Johnson, Nicholas L.

    2012-01-01

    The rapidly approaching maximum of Solar Cycle 24 will have wide-ranging effects not only on the number and distribution of resident space objects, but also on vital aspects of space situational awareness, including conjunction assessment processes. The best known consequence of high solar activity is an increase in the density of the thermosphere, which, in turn, increases drag on the vast majority of objects in low Earth orbit. The most prominent evidence of this is seen in a dramatic increase in space object reentries. Due to the massive amounts of new debris created by the fragmentations of Fengyun-1C, Cosmos 2251 and Iridium 33 during the recent period of Solar Minimum, this effect might reach epic levels. However, space surveillance systems are also affected, both directly and indirectly, historically leading to an increase in the number of lost satellites and in the routine accuracy of the calculation of their orbits. Thus, at a time when more objects are drifting through regions containing exceptionally high-value assets, such as the International Space Station and remote sensing satellites, their position uncertainties increase. In other words, as the possibility of damaging and catastrophic collisions increases, our ability to protect space systems is degraded. Potential countermeasures include adjustments to space surveillance techniques and the resetting of collision avoidance maneuver thresholds.

  7. Orbit Determination of KOMPSAT-1 and Cryosat-2 Satellites Using Optical Wide-field Patrol Network (OWL-Net) Data with Batch Least Squares Filter

    Science.gov (United States)

    Lee, Eunji; Park, Sang-Young; Shin, Bumjoon; Cho, Sungki; Choi, Eun-Jung; Jo, Junghyun; Park, Jang-Hyun

    2017-03-01

    The optical wide-field patrol network (OWL-Net) is a Korean optical surveillance system that tracks and monitors domestic satellites. In this study, a batch least squares algorithm was developed for optical measurements and verified by Monte Carlo simulation and covariance analysis. Potential error sources of OWL-Net, such as noise, bias, and clock errors, were analyzed. There is a linear relation between the estimation accuracy and the noise level, and the accuracy significantly depends on the declination bias. In addition, the time-tagging error significantly degrades the observation accuracy, while the time-synchronization offset corresponds to the orbital motion. The Cartesian state vector and measurement bias were determined using the OWL-Net tracking data of the KOMPSAT-1 and Cryosat-2 satellites. The comparison with known orbital information based on two-line elements (TLE) and the consolidated prediction format (CPF) shows that the orbit determination accuracy is similar to that of TLE. Furthermore, the precision and accuracy of OWL-Net observation data were determined to be tens of arcsec and sub-degree level, respectively.

  8. Xichang Satellite Launch Center

    Institute of Scientific and Technical Information of China (English)

    LiuJie

    2004-01-01

    Xichang Satellite Launch Center(XSLC) is mainly for geosynchronous orbit launches. The main purpose of XSLC is to launch spacecraft, such as broadcasting,communications and meteorological satellites, into geo-stationary orbit.Most of the commercial satellite launches of Long March vehicles have been from Xichang Satellite Launch Center. With 20 years' development,XSLC can launch 5 kinds of launch vehicles and send satellites into geostationary orbit and polar orbit. In the future, moon exploration satellites will also be launched from XSLC.

  9. Combining Slater-type orbitals and effective core potentials

    Science.gov (United States)

    Lesiuk, Michał; Tucholska, Aleksandra M.; Moszynski, Robert

    2017-05-01

    We present a general methodology to evaluate matrix elements of the effective core potentials (ECPs) within a one-electron basis set of Slater-type orbitals (STOs). The scheme is based on translation of individual STO distributions in the framework of the Barnett-Coulson method. We discuss different types of integrals which naturally appear and reduce them to a few basic quantities which can be calculated recursively or purely numerically. Additionally, we consider evaluation of the STOs matrix elements involving the core polarization potentials and effective spin-orbit potentials. Construction of the STOs basis sets designed specifically for use with ECPs is discussed and differences in comparison with all-electron basis sets are briefly summarized. We verify the validity of the present approach by calculating excitation energies, static dipole polarizabilities, and valence orbital energies for the alkaline-earth metals (Ca, Sr, and Ba). Finally, we evaluate interaction energies, permanent dipole moments, and ionization energies for barium and strontium hydrides, and compare them with the best available experimental and theoretical data.

  10. Best Mitigation Paths To Effectively Reduce Earth's Orbital Debris

    Science.gov (United States)

    Wiegman, Bruce M.

    2009-01-01

    This slide presentation reviews some ways to reduce the problem posed by debris in orbit around the Earth. It reviews the orbital debris environment, the near-term needs to minimize the Kessler syndrome, also known as collisional cascading, a survey of active orbital debris mitigation strategies, the best paths to actively remove orbital debris, and technologies that are required for active debris mitigation.

  11. 全球导航星座的远地/深空导航应用研究%The application research of global navigation constellation for HEO (high earth orbit) satellites and deep-space satellites

    Institute of Scientific and Technical Information of China (English)

    赵雯雯; 张立新; 蒙艳松; 宋志强

    2011-01-01

    It has been widely studied that GNSS(global navigation satellite system) offers navigation for Ground-Based users and LEO(low earth orbit.) users. At present, it mainly depends on Ground-Based measurement and control system that HEO satellites and deep-space satellites determine their orbits and attitude, and synchronize their time. The Ground-Based measurement and control system which has complex equipment and high investment can't support abundant aerocrafts at the same time, and can't operate autonomously. This article studied the possibility of orbit determination, attitude determination, and time synchronization with global navigation constellation for HEO satellites and deep-space satellites, and consequently achieved the extended applications of global navigation constellation. It found out a high efficient way for global navigation constellation to operating as time and space reference for constellation networks, in order that constellation networks autonomously operate and navigate. And it also putted forward a solution to realize passive navigation for HEO satellites and deep-space satellites by skillfully designing the links between satellites, without increasing equipment on satellites. The research focused on the number of visible satellites and GDOP(geometric dilution of precision) value. The precision of positioning and time determination was also analyzed in order to provide new ideas for the construction of global navigation constellation.%全球卫星导航系统为低轨和地面用户提供导航服务已有广泛的研究.中高轨卫星以及深空卫星的定轨、定姿和时间同步,目前主要利用地面测控系统完成,存在设备复杂、投资高、无法同时支持大量飞行器、无法自主运行等缺点.本文研究中高轨卫星和深空卫星利用全球导航星座进行定轨、定姿和授时服务的可行性,实现其扩展应用,寻求全球导航星座作为天基网时空基准的高效途径,使得天基网的

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

    CERN Document Server

    Laundal, Karl M; Olsen, Nils

    2016-01-01

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

  13. Mapping enzymatic catalysis using the effective fragment molecular orbital method

    DEFF Research Database (Denmark)

    Svendsen, Casper Steinmann; Fedorov, Dmitri G.; Jensen, Jan Halborg

    2013-01-01

    We extend the Effective Fragment Molecular Orbital (EFMO) method to the frozen domain approach where only the geometry of an active part is optimized, while the many-body polarization effects are considered for the whole system. The new approach efficiently mapped out the entire reaction path...... determine the reaction barrier of chorismate mutase to be [Formula: see text] kcal mol(-1) for MP2/cc-pVDZ and [Formula: see text] for MP2/cc-pVTZ in an ONIOM approach using EFMO-RHF/6-31G(d) for the high and low layers, respectively....

  14. Are Tidal Effects Responsible for Exoplanetary Spin-Orbit Alignment?

    CERN Document Server

    Li, Gongjie

    2015-01-01

    The obliquities of planet-hosting stars are clues about the formation of planetary systems. Previous observations led to the hypothesis that for close-in giant planets, spin-orbit alignment is enforced by tidal interactions. Here, we examine two problems with this hypothesis. First, Mazeh and coworkers recently used a new technique -- based on the amplitude of starspot-induced photometric variability -- to conclude that spin-orbit alignment is common even for relatively long-period planets, which would not be expected if tides were responsible. We re-examine the data and find a statistically significant correlation between photometric variability and planetary orbital period that is qualitatively consistent with tidal interactions. However it is still difficult to explain quantitatively, as it would require tides to be effective for periods as long as tens of days. Second, Rogers and Lin argued against a particular theory for tidal re-alignment by showing that initially retrograde systems would fail to be re-...

  15. Orbital effects of spatial variations of fundamental coupling constants

    CERN Document Server

    Iorio, Lorenzo

    2011-01-01

    We deal with the effects induced on the orbit of a test particle revolving around a central body by putative spatial variations of fundamental coupling constants $\\zeta$. In particular, we assume a dipole gradient for $\\zeta(\\bds r)/\\bar{\\zeta}$ along a generic direction $\\bds{\\hat{k}}$ in space. We analytically work out the long-term variations of all the six standard Keplerian orbital elements parameterizing the orbit of a test particle in a gravitationally bound two-body system. It turns out that, apart from the semi-major axis $a$, the eccentricity $e$, the inclination $I$, the longitude of the ascending node $\\Omega$, the longitude of pericenter $\\pi$ and the mean anomaly $\\mathcal{M}$ undergo non-zero long-term changes. By using the usual decomposition along the radial ($R$), transverse ($T$) and normal ($N$) directions, we also analytically work out the long-term changes $\\Delta R,\\Delta T,\\Delta N$ and $\\Delta v_R,\\Delta v_T,\\Delta v_N$ experienced by the position and the velocity vectors $\\bds r$ and...

  16. ARE TIDAL EFFECTS RESPONSIBLE FOR EXOPLANETARY SPIN–ORBIT ALIGNMENT?

    Energy Technology Data Exchange (ETDEWEB)

    Li, Gongjie [Harvard-Smithsonian Center for Astrophysics, The Institute for Theory and Computation, 60 Garden Street, Cambridge, MA 02138 (United States); Winn, Joshua N., E-mail: gli@cfa.harvard.edu [Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)

    2016-02-10

    The obliquities of planet-hosting stars are clues about the formation of planetary systems. Previous observations led to the hypothesis that for close-in giant planets, spin–orbit alignment is enforced by tidal interactions. Here, we examine two problems with this hypothesis. First, Mazeh and coworkers recently used a new technique—based on the amplitude of starspot-induced photometric variability—to conclude that spin–orbit alignment is common even for relatively long-period planets, which would not be expected if tides were responsible. We re-examine the data and find a statistically significant correlation between photometric variability and planetary orbital period that is qualitatively consistent with tidal interactions. However it is still difficult to explain quantitatively, as it would require tides to be effective for periods as long as tens of days. Second, Rogers and Lin argued against a particular theory for tidal re-alignment by showing that initially retrograde systems would fail to be re-aligned, in contradiction with the observed prevalence of prograde systems. We investigate a simple model that overcomes this problem by taking into account the dissipation of inertial waves and the equilibrium tide, as well as magnetic braking. We identify a region of parameter space where re-alignment can be achieved, but it only works for close-in giant planets, and requires some fine tuning. Thus, while we find both problems to be more nuanced than they first appeared, the tidal model still has serious shortcomings.

  17. Introduction of the in-orbit test and its performance for the first meteorological imager of the Communication, Ocean, and Meteorological Satellite

    Science.gov (United States)

    Kim, D. H.; Ahn, M. H.

    2014-08-01

    The first geostationary Earth observation satellite of Korea - the Communication, Ocean, and Meteorological Satellite (COMS) - was successfully launched on 27 June 2010. After arrival at its operational orbit, the satellite underwent an in-orbit test (IOT) that lasted for about 8 months. During the IOT period, the main payload for the weather application, the meteorological imager, went through successful tests for demonstrating its function and performance, and the test results are introduced here. The radiometric performance of the meteorological imager (MI) is tested by means of signal-to-noise ratio (SNR) for the visible channel, noise-equivalent differential temperature (NEdT) for the infrared channels, and pixel-to-pixel nonuniformity for both the visible and infrared channels. In the case of the visible channel, the SNR of all eight detectors is obtained using the ground-measured parameters with the background signals obtained in orbit. The overall performance shows a value larger than 26 at 5% albedo, exceeding the user requirement of 10 by a significant margin. Also, the relative variability of detector responsivity among the eight visible channels meets the user requirement, showing values within 10% of the user requirement. For the infrared channels, the NEdT of each detector is well within the user requirement and is comparable with or better than the legacy instruments, except for the water vapor channel, which is slightly noisier than the legacy instruments. The variability of detector responsivity of infrared channels is also below the user requirement, within 40% of the requirement, except for the shortwave infrared channel. The improved performance result is partly due to the stable and low detector temperature obtained due to spacecraft design, i.e., by installing a single solar panel on the opposite side of the MI.

  18. 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.

  19. 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.

  20. Time-transfer experiments between satellite laser ranging ground stations via one-way laser ranging to the Lunar Reconnaissance Orbiter

    Science.gov (United States)

    Mao, D.; Sun, X.; Skillman, D. R.; Mcgarry, J.; Hoffman, E.; Neumann, G. A.; Torrence, M. H.; Smith, D. E.; Zuber, M. T.

    2014-12-01

    Satellite laser ranging (SLR) has long been used to measure the distance from a ground station to an Earth-orbiting satellite in order to determine the spacecraft position in orbit, and to conduct other geodetic measurements such as plate motions. This technique can also be used to transfer time between the station and satellite, and between remote SLR sites, as recently demonstrated by the Time Transfer by Laser Link (T2L2) project by the Centre National d'Etudes Spatiaes (CNES) and Observatorire de la Cote d'Azur (OCA) as well as the Laser Time Transfer (LTT) project by the Shanghai Astronomical Observatory, where two-way and one-way measurements were obtained at the same time. Here we report a new technique to transfer time between distant SLR stations via simultaneous one-way laser ranging (LR) to the Lunar Reconnaissance Orbiter (LRO) spacecraft at lunar distance. The major objectives are to establish accurate ground station times and to improve LRO orbit determination via these measurements. The results of these simultaneous LR measurements are used to compare the SLR station times or transfer time from one to the other using times-of-flight estimated from conventional radio frequency tracking of LRO. The accuracy of the time transfer depends only on the difference of the times-of-flight from each ground station to the spacecraft, and is expected to be at sub-nano second level. The technique has been validated by both a ground-based experiment and an experiment that utilized LRO. Here we present the results to show that sub-nanosecond precision and accuracy are achievable. Both experiments were carried out between the primary LRO-LR station, The Next Generation Satellite Laser Ranging (NGSLR) station, and its nearby station, Mobile Laser System (MOBLAS-7), both at Greenbelt, Maryland. The laser transmit time from both stations were recorded by the same event timer referenced to a Hydrogen maser. The results have been compared to data from a common All

  1. The SATRAM Timepix spacecraft payload in open space on board the Proba-V satellite for wide range radiation monitoring in LEO orbit

    Science.gov (United States)

    Granja, Carlos; Polansky, Stepan; Vykydal, Zdenek; Pospisil, Stanislav; Owens, Alan; Kozacek, Zdenek; Mellab, Karim; Simcak, Marek

    2016-06-01

    The Space Application of Timepix based Radiation Monitor (SATRAM) is a spacecraft platform radiation monitor on board the Proba-V satellite launched in an 820 km altitude low Earth orbit in 2013. The is a technology demonstration payload is based on the Timepix chip equipped with a 300 μm silicon sensor with signal threshold of 8 keV/pixel to low-energy X-rays and all charged particles including minimum ionizing particles. For X-rays the energy working range is 10-30 keV. Event count rates can be up to 106 cnt/(cm2 s) for detailed event-by-event analysis or over 1011 cnt/(cm2 s) for particle-counting only measurements. The single quantum sensitivity (zero-dark current noise level) combined with per-pixel spectrometry and micro-scale pattern recognition analysis of single particle tracks enables the composition (particle type) and spectral characterization (energy loss) of mixed radiation fields to be determined. Timepix's pixel granularity and particle tracking capability also provides directional sensitivity for energetic charged particles. The payload detector response operates in wide dynamic range in terms of absorbed dose starting from single particle doses in the pGy level, particle count rate up to 106-10 /cm2/s and particle energy loss (threshold at 150 eV/μm). The flight model in orbit was successfully commissioned in 2013 and has been sampling the space radiation field in the satellite environment along its orbit at a rate of several frames per minute of varying exposure time. This article describes the design and operation of SATRAM together with an overview of the response and resolving power to the mixed radiation field including summary of the principal data products (dose rate, equivalent dose rate, particle-type count rate). The preliminary evaluation of response of the embedded Timepix detector to space radiation in the satellite environment is presented together with first results in the form of a detailed visualization of the mixed radiation

  2. Satellite (Natural)

    Science.gov (United States)

    Murdin, P.

    2000-11-01

    In its most general sense, any celestial object in orbit around a similar larger object. Thus, for example, the Magellanic Clouds are satellite galaxies of our own Milky Way galaxy. Without qualification, the term is used to mean a body in orbit around a planet; an alternative term is moon. The term natural satellite distinguishes these bodies from artificial satellites—spacecraft placed in orbi...

  3. Spin-orbit and tensor mean-field effects on spin-orbit splitting including self-consistent core polarizations

    CERN Document Server

    Zalewski, M; Satula, W; Werner, T R

    2008-01-01

    A new strategy of fitting the coupling constants of the nuclear energy density functional is proposed, which shifts attention from ground-state bulk to single-particle properties. The latter are analyzed in terms of the bare single-particle energies and mass, shape, and spin core-polarization effects. Fit of the isoscalar spin-orbit and both isoscalar and isovector tensor coupling constants directly to the f5/2-f7/2 spin-orbit splittings in 40Ca, 56Ni, and 48Ca is proposed as a practical realization of this new programme. It is shown that this fit requires drastic changes in the isoscalar spin-orbit strength and the tensor coupling constants as compared to the commonly accepted values but it considerably and systematically improves basic single-particle properties including spin-orbit splittings and magic-gap energies. Impact of these changes on nuclear binding energies is also discussed.

  4. Autonomous navigation method of high elliptical orbit satellite based on celestial navigation and GPS%基于天文/GPS的HEO卫星自主导航方法

    Institute of Scientific and Technical Information of China (English)

    王鹏; 张迎春

    2015-01-01

    为了实现大椭圆轨道(HEO)卫星高精度自主导航,提出一种将直接敏感地平天文导航与全球定位系统(GPS)相结合的组合导航方法.首先,分析卫星轨道��2运动模型及其所受空间摄动,建立卫星轨道动力学模型;然后,分析单一使用天文导航和GPS的优缺点,根据HEO卫星对GPS的可见性,提出在远地点只采用天文导航,而在近地点采用以天文导航为主、适时引入GPS信号进行位速测量辅助修正的方法.通过计算机仿真和结果分析表明了所提出的设计方法导航精度比单一天文导航提高72.4%∼85.6%.%In order to realize autonomous and continuous navigation information outputs for high elliptical orbit(HEO) satellite, new integrated navigation system is proposed based on celestial navigation of directly sensing stellar and global positioning system(GPS) navigation. Firstly, satellite orbit motion model is established on the satellite orbit dynamics��2 model and suffered space perturbation. Moreover, performances of single-use celestial navigation or GPS are analyzed. When the satellite is near the apogee, observation system is established by using only celestial navigation. When the satellite is near the perigee, the estimate covariance is revised through incoming GPS signal to improve the celestial navigation estimate. The autonomous navigation system is designed and simulating. The results of computer simulation show that the navigation accuracy is improved by 72.4%∼85.6%compared with the celestial navigation method.

  5. Orbitronics: the Intrinsic Orbital Hall Effect in p-Doped Silicon

    Energy Technology Data Exchange (ETDEWEB)

    Bernevig, B.Andrei; Hughes, Taylor L.; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-01-15

    The spin Hall effect depends crucially on the intrinsic spin-orbit coupling of the energy band. Because of the smaller spin-orbit coupling in silicon, the spin Hall effect is expected to be much reduced. We show that the electric field in p-doped silicon can induce a dissipationless orbital current in a fashion reminiscent of the spin Hall effect. The vertex correction due to impurity scattering vanishes and the effect is therefore robust against disorder. The orbital Hall effect can lead to the accumulation of local orbital momentum at the edge of the sample, and can be detected by the Kerr effect.

  6. 北斗卫星单系统精密定轨方法对比分析%Comparison and Analysis of BeiDou Satellite Single-system Precise Orbit Determination

    Institute of Scientific and Technical Information of China (English)

    刘伟平; 郝金明; 邓科; 陈逸伦

    2016-01-01

    提出了联合使用载波相位和相位平滑伪距实现北斗卫星双差动力法精密定轨,给出了北斗卫星非差动力法和双差动力法精密定轨的数据处理流程,分析了两种方法的异同.结合实测数据,对比了两种方法的实际定轨效果,结果表明:一定测站布局下,利用两种方法, GEO(Geostationary Earth Orbit Satellite)卫星3维精密定轨精度均能达到1 m左右量级, IGSO(Inclined Geosynchronous Earth Orbit Satellite)和MEO(Medium Earth Orbit Satellite)卫星优于0.5 m,3类卫星的径向定轨精度均优于10 cm.较之非差动力法,双差动力法对GEO卫星精密定轨精度具有一定的改善作用,两者在IGSO卫星精密定轨上效果基本相当,但在MEO卫星定轨上,非差动力法结果更优.%The method of double-difference dynamic precise orbit determination for BeiDou satellites by using both carrier phase and smoothed pseudo-range is presented. The data processing flows of zero-difference and double-difference dynamic precise orbit determination for BeiDou satellites are presented. And the two methods are analyzed. The precision of two methods is compared based on the real data. The results show that in the condition of stations layout and by using the two methods, the three-dimension precision of GEO (Geostationary Earth Orbit Satellite) can reach about 1 m, and those of IGSO (Inclined Geosynchronous Earth Orbit Satellite) and MEO (Medium Earth Orbit Satellite) can be better than 0.5 m. And the radial precision of the three kinds of orbit satellites can be all better than 10 cm. Compared with the zero-difference dynamic method, the orbit precision of GEO is better with the double-difference dynamic method, and that of IGSO is comparable, but that of MEO is worse.

  7. N-body Simulations of Satellite Formation around Giant Planets: Origin of Orbital Configuration of the Galilean Moons

    CERN Document Server

    Ogihara, Masahiro

    2012-01-01

    As the number of discovered extrasolar planets has been increasing, diversity of planetary systems requires studies of new formation scenarios. It is important to study satellite formation in circumplanetary disks, which is often viewed as analogous to formation of rocky planets in protoplanetary disks. We investigated satellite formation from satellitesimals around giant planets through N-body simulations that include gravitational interactions with a circumplanetary gas disk. Our main aim is to reproduce the observable properties of the Galilean satellites around Jupiter through numerical simulations, as previous N-body simulations have not explained the origin of the resonant configuration. We performed accretion simulations based on the work of Sasaki et al. (2010), in which an inner cavity is added to the model of Canup & Ward (2002, 2006). We found that several satellites are formed and captured in mutual mean motion resonances outside the disk inner edge and are stable after rapid disk gas dissipat...

  8. 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.

  9. Rayleigh radiance computations for satellite remote sensing: accounting for the effect of sensor spectral response function.

    Science.gov (United States)

    Wang, Menghua

    2016-05-30

    To understand and assess the effect of the sensor spectral response function (SRF) on the accuracy of the top of the atmosphere (TOA) Rayleigh-scattering radiance computation, new TOA Rayleigh radiance lookup tables (LUTs) over global oceans and inland waters have been generated. The new Rayleigh LUTs include spectral coverage of 335-2555 nm, all possible solar-sensor geometries, and surface wind speeds of 0-30 m/s. Using the new Rayleigh LUTs, the sensor SRF effect on the accuracy of the TOA Rayleigh radiance computation has been evaluated for spectral bands of the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi National Polar-orbiting Partnership (SNPP) satellite and the Joint Polar Satellite System (JPSS)-1, showing some important uncertainties for VIIRS-SNPP particularly for large solar- and/or sensor-zenith angles as well as for large Rayleigh optical thicknesses (i.e., short wavelengths) and bands with broad spectral bandwidths. To accurately account for the sensor SRF effect, a new correction algorithm has been developed for VIIRS spectral bands, which improves the TOA Rayleigh radiance accuracy to ~0.01% even for the large solar-zenith angles of 70°-80°, compared with the error of ~0.7% without applying the correction for the VIIRS-SNPP 410 nm band. The same methodology that accounts for the sensor SRF effect on the Rayleigh radiance computation can be used for other satellite sensors. In addition, with the new Rayleigh LUTs, the effect of surface atmospheric pressure variation on the TOA Rayleigh radiance computation can be calculated precisely, and no specific atmospheric pressure correction algorithm is needed. There are some other important applications and advantages to using the new Rayleigh LUTs for satellite remote sensing, including an efficient and accurate TOA Rayleigh radiance computation for hyperspectral satellite remote sensing, detector-based TOA Rayleigh radiance computation, Rayleigh radiance calculations for high altitude

  10. Chang'e-1 Satellite Completed Its Preset Objectives

    Institute of Scientific and Technical Information of China (English)

    He Ying

    2008-01-01

    @@ By October 23, Chang'e-1 satellite with a one-year design lifetime has been operating in lunar orbit for one year, completed more than 4000 orbits, covering the entire moon 12 times. The satellite's platform works normally at present and all systems and equipment onboard work in their main mode. The satellite has obtained a large quantity of scientific data and achieved the preset objectives of precise orbit maneuver, successful moon orbiting, effective exploration and oneyear lifetime. The Chang'e-1 mission is a complete success.

  11. GIM在LEO卫星单频GPS定轨中的应用%The Application of GIM in Precise Orbit Determination for LEO Satellites with Single-frequency GPS Measurements

    Institute of Scientific and Technical Information of China (English)

    彭冬菊; 吴斌

    2012-01-01

    With the availability of precise GPS ephemeris and clock solution, the ionospheric range delay is left as the dominant error sources in the post-processing of space-borne GPS data from single-frequency receivers. Thus, the removal of ionospheric effects is a major prerequisite for an improved orbit reconstruction of LEO satellites equipped with low cost single-frequency GPS receivers. In this paper, the use of Global Ionospheric Maps (GIM) in kinematic and dynamic orbit determination for LEO satellites with single-frequency GPS measurements is discussed first, and then, estimating the scale factor of ionosphere to remove the ionospheric effects in C/A code pseudo-range measurements in both kinematic and adynamia orbit defemination approaches is addressed. As it is known the ionospheric path delay of space-borne GPS signals is strongly dependent on the orbit altitudes of LEO satellites, we selected real space-borne GPS data from CHAMP, GRACE, TerraSAR-X and SAC-C satellites with altitudes between 300 km and 800 km as sample data in this paper. It is demonstrated that the approach of eliminating ionospheric effects in space-borne C/A code pseudo-range by estimating the scale factor of ionosphere is highly effective. Employing this approach, the accuracy of both kinematic and dynamic orbits can be improved notably. Among those five LEO satellites, CHAMP with the lowest orbit altitude has the most remarkable orbit accuracy improvements, which are 55.6% and 47.6% for kinematic and dynamic approaches, respectively. SAC-C with the highest orbit altitude has the least orbit accuracy improvements accordingly, which are 47.8% and 38.2%, respectively.%电离层延迟误差是单频GPS (Global Positioning System)数据最主要的误差源,为提高基于单频GPS数据的LEO (Low Earth Orbiting)卫星定轨精度,必须消除/减弱GPS观测数据中电离层延迟影响.研究了全球电离层模型GIM (Global Ionospheric Maps)在基于单频GPS伪距数据的低轨卫星

  12. The Effects of Moon¡¯s Uneven Mass Distribution on the Critical Inclinations of a Lunar Orbiter

    Science.gov (United States)

    Rahoma, Walid A.; Abd El-Salam, Fawzy A.

    2014-12-01

    The uneven mass distribution of the Moon highly perturbs the lunar spacecrafts. This uneven mass distribution leads to peculiar dynamical features of the lunar orbiters. The critical inclination is the value of inclination which keeps the deviation of the argument of pericentre from the initial values to be zero. Considerable investigations have been performed for critical inclination when the gravity field is assumed to be symmetric around the equator, namely for oblate gravity field to which Earth¡¯s satellites are most likely to be subjected. But in the case of a lunar orbiter, the gravity field of mass distribution is rather asymmetric, that is, sectorial, and tesseral, harmonic coefficients are big enough so they can¡¯t be neglected. In the present work, the effects of the first sectorial and tesseral harmonic coefficients in addition to the first zonal harmonic coefficients on the critical inclination of a lunar artificial satellite are investigated. The study is carried out using the Hamiltonian framework. The Hamiltonian of the problem is cconstructed and the short periodic terms are eliminated using Delaunay canonical variables. Considering the above perturbations, numerical simulations for a hypothetical lunar orbiter are presented. Finally, this study reveals that the critical inclination is quite different from the critical inclination of traditional sense and/or even has multiple solutions. Consequently, different families of critical inclination are obtained and analyzed.

  13. Effect of weak fluid inertia upon Jeffery orbits

    Science.gov (United States)

    Einarsson, Jonas

    2016-11-01

    We consider the rotation of small neutrally buoyant axisymmetric particles in a viscous steady shear flow. When inertial effects are negligible the problem exhibits infinitely many periodic solutions, the "Jeffery orbits." We compute how inertial effects lift their degeneracy by perturbatively solving the coupled particle-flow equations. We obtain an equation of motion valid at small shear Reynolds numbers, for spheroidal particles with arbitrary aspect ratios. At small shear Reynolds numbers the preferred Jeffery orbit is tumbling for prolate spheroids, and log-rolling for moderately oblate particles (aspect ratio λ > 1 / 7 . 3). For thinner oblate particles both log-rolling and tumbling are stable, separated by an unstable limit cycle. We solved this long-standing problem by considering the symmetries that constrain the solution. In this case the symmetries reduced the problem to only four scalar integrals. Here I introduce an alternative method that accounts for the symmetries and tensorial nature of the governing equations, enables perturbative calculation of Stokes' equations, and is suitable for computer algebra.

  14. Chaotic orbit effects in a stationary single particle probabilistic density

    Science.gov (United States)

    Ogawa, Shun; Leoncini, Xavier; Vittot, Michel; Dif-Pradalier, Guilhem; Garbet, Xavier

    2016-10-01

    Chaotic particle orbit effects in a stationary density function or macroscopic quantities are investigated. A considered field consists with static magnetic field and null electric field in a cylinder, then a test particle is driven by the Lorentz force. We firstly consider an axisymmetric magnetic field, where three integrals of motion coexist. So that the test particle motion is completely integrable, and its Hamiltonian is reduced to an effective one degree of freedom Hamiltonian. For some initial states, the effective potential of this reduced Hamiltonian has a saddle point and a separatrix bringing about some chaos when a perturbation is added to the magnetic field. We investigate how this chaos modifies the stationary density function. We acknowledge support of the A *MIDEX project (n ∘ ANR-11- IDEX-0001-02) funded by the ``investissements d'Avenir'' French Government program, managed by the French National Research Agency (ANR).

  15. Satellite theory

    Science.gov (United States)

    Kozai, Y.

    1981-04-01

    The dynamical characteristics of the natural satellite of Mars, Jupiter, Saturn, Uranus and Neptune are analyzed on the basis of the solar tidal perturbation factor and the oblateness factor of the primary planet for each satellite. For the inner satellites, for which the value of the solar tidal factor is much smaller than the planetary oblateness factor, it is shown that the eccentricity and inclination of satellite orbits are generally very small and almost constant; several pairs of inner satellites are also found to exhibit commensurable mean motions, or secular accelerations in mean longitude. In the case of the outer satellites, for which solar perturbations are dominant, secular perturbations and long-period perturbations may be derived by the solution of equations of motion reduced to one degree of freedom. The existence of a few satellites, termed intermediary satellites, for which the solar tidal perturbation is on the order of the planetary oblateness factor, is also observed, and the pole of the orbital plane of the satellite is noted to execute a complex motion around the pole of the planet or the orbital plane of the planet.

  16. Chaos at Uranus Spreads Dust Across the Regular Satellites

    Science.gov (United States)

    Tamayo, Dan; Burns, J. A.; Nicholson, P. D.; Hamilton, D. P.

    2012-05-01

    The short collision timescales between the Uranian irregular satellites argue for the past generation of vast quantities of dust at the outer reaches of Uranus’ Hill sphere (Bottke et al. 2010). Uranus’ extreme obliquity (98 degrees) renders the orbits of large objects unstable to eccentricity perturbations in the radial range a ≈ 60 - 75 Rp. (Tremaine et al. 2009). We study the effect on dust by investigating how the instability is modified by radiation pressure. We find that dust particles generated at the orbits of the irregular satellites move inward as radiation forces cause their orbits to decay (Burns et al. 1979). When they reach the unstable region, grain orbits undergo chaotic large-amplitude eccentricity oscillations that bring their pericenters inside the orbits of the regular satellites. We argue that the impact probabilities and expected spatial distribution across the satellite surfaces might explain the observed hemispherical color asymmetries common to the outer four regular satellites.

  17. Introduction to the in orbit test and its performance of the first meteorological imager of the Communication, Ocean, and Meteorological Satellite

    Science.gov (United States)

    Kim, D.; Ahn, M. H.

    2013-12-01

    The first geostationary earth observation satellite of Korea, named Communication, Ocean, and Meteorological Satellite (COMS), is successfully launched on 27 June 2010 in Korea Standard Time. After arrival of its operational orbit, the satellite underwent in orbit test (IOT) lasting for about 8 months. During the IOT period, the meteorological imager went through tests for its functional and performance demonstration. With the successful acquisition of the first visible channel image, signal chain from the payload to satellite bus and to the ground is also verified. While waiting for the outgassing operation, several functional tests for the payload are also performed. By taking an observation of different sizes of image, of various object targets such as the Sun, moon, and internal calibration target, it has been demonstrated that the payload performs as commanded, satisfying its functional requirements. After successful operation of outgassing which lasted about 40 days, the first set of infrared images is also successfully acquired and the full performance test started. The radiometric performance of the meteorological imager is tested by signal to noise ratio (SNR) for the visible channel, noise equivalent differential temperature (NEdT) for the infrared channels, and pixel to pixel non-uniformity. In case of the visible channel, SNR of all 8 detectors are obtained using the ground measured parameters and background signals obtained in orbit and are larger than 26 at 5% albedo, exceeding the user requirement value of 10 with a significant margin. The values at 100% albedo also meet the user requirements. Also, the relative variability of detector responsivity among the 8 visible channels meets the user requirement, showing values of about 10% of the user requrirement. For the infrared channels, the NEdT of each detector is well within the user requirement and is comparable with or better than the legacy instruments, except the water vapor channel which is

  18. Orbital magnetism of graphene nanostructures: Bulk and confinement effects

    Science.gov (United States)

    Heße, Lisa; Richter, Klaus

    2014-11-01

    We consider the orbital magnetic properties of noninteracting charge carriers in graphene-based nanostructures in the low-energy regime. The magnetic response of such systems results both from bulk contributions and from confinement effects that can be particularly strong in ballistic quantum dots. First we provide a comprehensive study of the magnetic susceptibility χ of bulk graphene in a magnetic field for the different regimes arising from the relative magnitudes of the energy scales involved, i.e., temperature, Landau-level spacing, and chemical potential. We show that for finite temperature or chemical potential, χ is not divergent although the diamagnetic contribution χ0 from the filled valance band exhibits the well-known -B-1 /2 dependence. We further derive oscillatory modulations of χ , corresponding to de Haas-van Alphen oscillations of conventional two-dimensional electron gases. These oscillations can be large in graphene, thereby compensating the diamagnetic contribution χ0 and yielding a net paramagnetic susceptibility for certain energy and magnetic field regimes. Second, we predict and analyze corresponding strong, confinement-induced susceptibility oscillations in graphene-based quantum dots with amplitudes distinctly exceeding the corresponding bulk susceptibility. Within a semiclassical approach we derive generic expressions for orbital magnetism of graphene quantum dots with regular classical dynamics. Graphene-specific features can be traced back to pseudospin interference along the underlying periodic orbits. We demonstrate the quality of the semiclassical approximation by comparison with quantum-mechanical results for two exemplary mesoscopic systems, a graphene disk with infinite mass-type edges, and a rectangular graphene structure with armchair and zigzag edges, using numerical tight-binding calculations in the latter case.

  19. 皮卫星在轨能量平衡仿真研究%Study on simulation of on-orbit energy balance of pico-satellite

    Institute of Scientific and Technical Information of China (English)

    金小军; 赵翔宇; 辜渝嘉; 金仲和

    2009-01-01

    针对浙江大学皮卫星由于输入能量条件差以及采用非调节母线和体装式结构,使其能量平衡计算相对于传统卫星更加复杂的特点和电源电路的特殊设计,对电源系统进行了建模. 通过实时计算太阳电池、蓄电池和负载的在轨工作参数以及分析实时的电流平衡、电压平衡和能量平衡,最终得到真实的能量平衡仿真模型. 对理想运行条件、实际环境条件和考虑卫星姿态失效的最差条件分别进行了仿真. 结果表明,在理想条件下可以完全保证整星能量平衡;在实际环境下最大平衡功率能忍受实际负载约10%的拉偏;在最差姿态条件下已几乎没有裕量,但能完全保证卫星安全模式下的负载功率能量平衡.%Considering that the computation of energy balance of the Zheda pico-satellite is more complex than that of conventional satellites due to its weak input energy and the use of the non-conditioning bus and the body-mounted structure, the power system was modeled based on the features of the pico-satellite and the specific design of the power circuit.The on-orbit running parameters of the solar array, the battery and the load were calculated in real time, and the real-time current balance, voltage balance and energy balance were analyzed, which lead to the practical simulation model of energy balance.Simulations of the ideal condition, the practical condition and the worst condition with the invalidation of the satellite attitude were made respectively.The results showed that the satellite can fully attain energy balance under the ideal condition and can tolerate 10% of the load power under the practical condition.Under the worst condition, the satellite had little margin of energy, but it can fully attain energy balance under the safe mode of the satellite.

  20. Traffic planning for the Anik-E satellites

    Science.gov (United States)

    Gray, Douglas A.

    Traffic planning is required to insure effective use of the dual band Anik E series of communications satellites. A trilateral orbital agreement reached with the United States and Mexico allows Canada four dual band satellite positions. This paper outlines the traffic planning process, describes satellite coordination, and provides highlights of the implementation of the Trilateral Orbital Plan. Constraints affecting traffic assignments include satellite health, the need for satellite diversity, and existing earth network facilities. Anik E will provide voice, television, and data communications over 24 C-band channels.

  1. Passive Micro Vibration Isolator Utilizing Flux Pinning Effect for Satellites

    Science.gov (United States)

    Shibata, Takuma; Sakai, Shin-ichiro

    2016-09-01

    Information related to the origin of space and evolution of galaxy can be obtained using the observation satellites. In recent years, high pointing accuracy is demanded for getting more detailed data about distant stars and galaxies. As a result, vibration isolators that consist of a main structure and a TTM (Tip Tilt Mirror) have been adopted for observation satellites. However, cutting the low frequency vibrations off passively with the conventional methods is difficult. A vibration isolator that uses pinning effect is proposed for solving this problem. The pinning effect is acquired by cooling the type-II superconductor below the critical temperature and it generates a pinning force to maintain the relative distance and attitude between a type- II superconductor and a material that generates magnetic flux. The mission part and the bus part of the satellite are equipped with superconductors and permanent magnets and these parts perform short distance formation flight by applying the effect. This method can cut vibrations from low to high frequency bands off passively. In addition, Meissner effect can prevent collision of the mission and bus parts. In order to investigate the performance of this system, experiments and simulations are carried out and the results are discussed.

  2. Correlation effects and orbital magnetism of Co clusters

    CERN Document Server

    Di Marco, L Peters I; Şaşıoğlu, E; Altun, A; Rossen, S; Friedrich, C; Blügel, S; Katsnelson, M I; Kirilyuk, A; Eriksson, O

    2016-01-01

    Recent experiments on isolated Co clusters have shown huge orbital magnetic moments in comparison with their bulk and surface counterparts. These clusters hence provide the unique possibility to study the evolution of the orbital magnetic moment with respect to the cluster size and how competing interactions contribute to the quenching of orbital magnetism. We investigate here different theoretical methods to calculate the spin and orbital moments of Co clusters, and assess the performances of the methods in comparison with experiments. It is shown that density functional theory in conventional local density or generalized gradient approximations, or even with a hybrid functional, severely underestimates the orbital moment. As natural extensions/corrections we considered the orbital polarization correction, the LDA+U approximation as well as the LDA+DMFT method. Our theory shows that of the considered methods, only the LDA+DMFT method provides orbital moments in agreement with experiment, thus emphasizing the...

  3. Environmental assessment for the satellite power system concept development and evaluation program: nonmicrowave health and ecological effects

    Energy Technology Data Exchange (ETDEWEB)

    White, M R

    1980-11-01

    A Concept Development and Evaluation Program is being carried out for a proposed Satellite Power System (SPS). For purposes of this evaluation, a preliminary reference system has been developed. SPS, as described in the reference system, would collect solar energy on satellites in geosychronous orbit in space. The energy would be converted to microwaves and beamed to an earth-receiving antenna (rectenna). One task in the environmental part of the program is the assessment of the nonmicrowave effects on health and the environment. These effects would result from all phases of SPS development and operation. This report covers the current knowledge regarding these effects, and is based on the reference system. The assessment is summarized as to scope, methodology, impacts of terrestrial development, launch and recovery of spacecraft, space activities (including health effects of the space environment, ionizing radiation, electromagnetic exposure, spacecraft charging and environmental interactions, occupational hazards, etc.) and construction and operation of rectenna (ground receiving station).

  4. Interplay of spin-orbit and entropic effects in cerium

    Energy Technology Data Exchange (ETDEWEB)

    Lanata, Nicola [Rutgers University; Yao, Yong-Xin [Ames Laboratory; Wang, Cai-Zhuang [Ames Laboratory; Ho, Kai-Ming [Ames Laboratory; Kotliar, Gabriel [Rutgers University

    2014-10-01

    We perform first-principles calculations of elemental cerium and compute its pressure-temperature phase diagram, finding good quantitative agreement with the experiments. Our calculations indicate that, while a signature of the volume-collapse transition appears in the free energy already at low temperatures, at higher temperatures this signature is enhanced because of the entropic effects, and originates an actual thermodynamical instability. Furthermore, we find that the catalyst determining this feature is—in all temperature regimes—a pressure-induced effective reduction of the f-level degeneracy due to the spin-orbit coupling. Our analysis suggests also that the lattice vibrations might be crucial in order to capture the behavior of the pressure-temperature transition line at large temperatures.

  5. Design and analysis of the satellite laser communications network

    Science.gov (United States)

    Ren, Pei-an; Qian, Fengchen; Liu, Qiang; Jin, Linlin

    2015-02-01

    A satellite laser communications network structure with two layers and multiple domains has been proposed, which performance has been simulated by OPENT. To simulation, we design several OPNET models of the network's components based on a satellite constellation with two layers and multiple domains, as network model, node model, MAC layer protocol and optical antenna model. The network model consists of core layer and access layer. The core network consists of four geostationary orbit (GEO) satellites which are uniformly distributed in the geostationary orbit. The access network consists of 6 low Earth orbit (LEO) satellites which is the walker delta (walk-δ) constellation with three orbit planes. In access layer, each plane has two satellites, and the constellation is stably. The satellite constellation presented for space laser network can meet the demand of coverage in the middle and low latitude by a few satellites. Also several terminal device models such as the space laser transmitter, receiver, protocol layer module and optical antenna have been designed according to the inter-satellite links in different orbits t from GEO to LEO or GEO to ground. The influence to network of different transmitting throughput, receiving throughput, network protocol and average time delay are simulated. Simulation results of network coverage, connectivity and traffic load performance in different scenes show that the satellite laser network presented by the paper can be fit for high-speed satellite communications. Such analysis can provide effective reference for the research of satellite laser networking and communication protocol.

  6. Fault Diagnosis Based on RO-NUIO/LMI for Flexible Satellite Attitude Control Systems during Orbit Control%基于RO-NUIO/LMI的挠性卫星轨控期间姿控系统故障诊断

    Institute of Scientific and Technical Information of China (English)

    侯倩; 程月华; 姜斌; 陆宁云

    2011-01-01

    During satellite orbit maneuver, the orbit control force causes disturbing torque and affects attitude of a satellite if the control force does not pass through the mass center of the satellite. In this paper, a set of reduced order nonlinear unknown input observers (RO-NUIO) are designed to detect and isolate faults. During the design process, the system is divided into three sub-systems to ensure that some states are not affected by the disturbance. Observers are designed by using the observable information. Meanwhile, some parameters of the observers can be obtained by using the LMI approach to reduce effects of nonlinear part on observers. The existence conditions of the observer proposed in this paper only depend on the inherent feature of the system. Combination of the reduced order idea and the LMI method make the structure of observers easy to be applied to nonlinear satellite attitude control systems. Numerical simulation is carried out to demonstrate the efficiency of the proposed fault diagnosis scheme for satellite attitude control systems.%卫星轨控期间,由于推力偏心,会产生较大的干扰力矩,直接影响卫星姿态.针对轨道控制期间的挠性卫星姿态控制系统,设计了干扰解耦的降阶非线性未知输入观测器(RO-NUIO),用于故障检测与故障隔离.在设计过程中,首先通过坐标变换,使得不可观的状态及部分可观状态不受干扰影响,然后针对不可观的子系统利用可观状态的信息设计观测器,观测器中的部分参数利用LMI方法获得,可以弱化非线性部分对观测器的影响.所设计观测器的存在条件仅依赖于系统本身特性,无需在线验证.观测器采用降阶设计,同时借助LMI思想,结构简单,适合于非线性卫星姿态控制系统.仿真结果验证了降阶非线性未知输入观测器实现卫星姿态控制故障诊断的可行性与有效性.

  7. Hill Problem Analytical Theory to the Order Four: Application to the Computation of Frozen Orbits around Planetary Satellites

    Directory of Open Access Journals (Sweden)

    Martin Lara

    2009-01-01

    Full Text Available Frozen orbits of the Hill problem are determined in the double-averaged problem, where short and long-period terms are removed by means of Lie transforms. Due to the perturbation method we use, the initial conditions of corresponding quasi-periodic solutions in the nonaveraged problem are computed straightforwardly. Moreover, the method provides the explicit equations of the transformation that connects the averaged and nonaveraged models. A fourth-order analytical theory is necessary for the accurate computation of quasi-periodic frozen orbits.

  8. Feasibility Analysis on the Utilization of the Iridium Satellite Communications Network for Resident Space Objects in Low Earth Orbit

    Science.gov (United States)

    2013-03-21

    equatorial speed. Ideally, the GEO satellite remains directly overhead in the absence of perturbing forces. Of course , perturbing forces exist and cause a...respectively. Assuming a mean Earth radius of 6371 km, the Earth- central angles and can be found from trigonometry using the footprint

  9. Solar irradiance observed on the FY-3 satellites - instrument overview and primary observation results of in-orbit experiments

    Science.gov (United States)

    Wang, H.; Fang, W.; Li, H.

    2015-12-01

    Solar driving mechanism for Earth climate has been a controversial problem for centuries. Data of Solar Irradiance (SI) is required by the investigations of the solar driving mechanism, including Total Solar Irradiance (TSI) and Spectral Solar Irradiance (SSI). SI observations with short term accuracy and long term precision are essential to separate solar forcing from human-induced factors. TSI and SSI have been measured on Chinese FY-3 satellites, including FY-3A, FY-3B and FY-3C. FY-3A satellite launched in May, 2008 is the first satellite. FY-3B satellite launched in November, 2010 is the second satellite and FY-3C satellite launched in September, 2013 is the third satellite. SSI has been measured by SBUS (Solar Backscatter Ultraviolet Sounder) in the ultraviolet spectrum in the FY-3 mission. When a solar diffuser plate is deployed to reflect the incoming sunlight, SI is measured at 12 discrete, 1.1 nm wide wavelength bands between 250 nm and 340 nm. The SSI measurements are performed using a double monochromator operated in a stepped wavelength scan mode. SBUS collects SSI weekly at 12 discrete wave-lengths near polar area. Moreover, SSI is measured by SBUS every month covering 160-400 nm continuous spectral region. SSI has been recorded in SBUS missions since the ascending phase of Solar Cycle 24. Approximately the same variation tendencies of SSI were detected by SBUS in specific spectrum compared with data from SOLSTICE/SORCE. TSI have been recorded by Total Solar Irradiance Monitors (TSIM) in FY-3 missions. The sun was measured by TSIM/FY-3A and TSIM/FY-3B in a scanning manner. TSI data quality is improved by TSIM/FY-3C which has a pointing system. TSIM/FY-3C measures the sun with nearly zero solar pointing errors. TSI variations detected by TSIM/FY-3C are nearly the same with VIRGO/SOHO and TIM/SORCE. The TSIM experiments have observed the sun for about 7 years. A slowly increasing TSI trend has been detected by TSIMs in the Solar Cycle 24. We present the

  10. Effects of Turbulent Aberrations on Probability Distribution of Orbital Angular Momentum for Optical Communication

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yi-Xin; CANG Ji

    2009-01-01

    Effects of atmospheric turbulence tilt, defocus, astigmatism and coma aberrations on the orbital angular mo-mentum measurement probability of photons propagating in weak turbulent regime are modeled with Rytov approximation. By considering the resulting wave as a superposition of angular momentum eigenstates, the or-bital angular momentum measurement probabilities of the transmitted digit axe presented. Our results show that the effect of turbulent tilt aberration on the orbital angular momentum measurement probabilities of photons is the maximum among these four kinds of aberrations. As the aberration order increases, the effects of turbulence aberrations on the measurement probabilities of orbital angular momentum generally decrease, whereas the effect of turbulence defoens can be ignored. For tilt aberration, as the difference between the measured orbital angular momentum and the original orbital angular momentum increases, the orbital angular momentum measurement probabifity decreases.

  11. The Organism/Organic Exposure to Orbital Stresses (O/OREOS) satellite: radiation exposure in low-earth orbit and supporting laboratory studies of iron tetraphenylporphyrin chloride.

    Science.gov (United States)

    Cook, Amanda M; Mattioda, Andrew L; Ricco, Antonio J; Quinn, Richard C; Elsaesser, Andreas; Ehrenfreund, Pascale; Ricca, Alessandra; Jones, Nykola C; Hoffmann, Søren V

    2014-02-01

    We report results from the exposure of the metalloporphyrin iron tetraphenylporphyrin chloride (FeTPPCl) to the outer space environment, measured in situ aboard the Organism/Organic Exposure to Orbital Stresses nanosatellite. FeTPPCl was exposed for a period of 17 months (3700 h of direct solar exposure), which included broad-spectrum solar radiation (∼122 nm to the near infrared). Motivated by the potential role of metalloporphyrins as molecular biomarkers, the exposure of thin-film samples of FeTPPCl to the space environment in low-Earth orbit was monitored in situ via ultraviolet/visible spectroscopy and reported telemetrically. The space data were complemented by laboratory exposure experiments that used a high-fidelity solar simulator covering the spectral range of the spaceflight measurements. We found that thin-film samples of FeTPPCl that were in contact with a humid headspace gas (0.8-2.3% relative humidity) were particularly susceptible to destruction upon irradiation, degrading up to 10 times faster than identical thin films in contact with dry headspace gases; this degradation may also be related to the presence of oxides of nitrogen in those cells. In the companion terrestrial experiments, simulated solar exposure of FeTPPCl films in contact with either Ar or CO2:O2:Ar (10:0.01:1000) headspace gas resulted in growth of a band in the films' infrared spectra at 1961 cm(-1). We concluded that the most likely carriers of this band are allene (C3H4) and chloropropadiene (C3H3Cl), putative molecular fragments of the destruction of the porphyrin ring. The thin films studied in space and in solar simulator-based experiments show qualitatively similar spectral evolution as a function of contacting gaseous species but display significant differences in the time dependence of those changes. The relevance of our findings to planetary science, biomarker research, and the photostability of organic materials in astrobiologically relevant environments is

  12. Tidal satellite perturbations and the Lense-Thirring effect

    CERN Document Server

    Iorio, L; Iorio, Lorenzo; Pavlis, Erricos C.

    2001-01-01

    The tiny general relativistic Lense-Thirring effect can be measured by means of a suitable combination of the orbital residuals of the nodes of LAGEOS and LAGEOS II and the perigee of LAGEOS II. This observable is affected, among other factors, by the Earth' s solid and ocean tides. They induce long-period orbital perturbations that, over observational periods of few years, may alias the detection of the gravitomagnetic secular trend of interest. In this paper we calculate explicitly the most relevant tidal perturbations acting upon LAGEOSs and assess their influence on the detection of the Lense-Thirring effect. The present day level of knowledge of the solid and ocean tides allow us to conclude that their influence on it ranges from almost 4% over 4 years to less than 2% over 7 years.

  13. Atomic oxygen effects on POSS polyimides in low earth orbit.

    Science.gov (United States)

    Minton, Timothy K; Wright, Michael E; Tomczak, Sandra J; Marquez, Sara A; Shen, Linhan; Brunsvold, Amy L; Cooper, Russell; Zhang, Jianming; Vij, Vandana; Guenthner, Andrew J; Petteys, Brian J

    2012-02-01

    Kapton polyimde is extensively used in solar arrays, spacecraft thermal blankets, and space inflatable structures. Upon exposure to atomic oxygen in low Earth orbit (LEO), Kapton is severely eroded. An effective approach to prevent this erosion is to incorporate polyhedral oligomeric silsesquioxane (POSS) into the polyimide matrix by copolymerizing POSS monomers with the polyimide precursor. The copolymerization of POSS provides Si and O in the polymer matrix on the nano level. During exposure of POSS polyimide to atomic oxygen, organic material is degraded, and a silica passivation layer is formed. This silica layer protects the underlying polymer from further degradation. Laboratory and space-flight experiments have shown that POSS polyimides are highly resistant to atomic-oxygen attack, with erosion yields that may be as little as 1% those of Kapton. The results of all the studies indicate that POSS polyimide would be a space-survivable replacement for Kapton on spacecraft that operate in the LEO environment.

  14. Topside ionospheric effects of the annular solar eclipse of 15th January 2010 as observed by DEMETER satellite

    Science.gov (United States)

    Maji, Surya K.; Chakrabarti, Sandip K.; Sanki, Dipak; Pal, Sujay

    2017-06-01

    We present effects of the annular solar eclipse of 15th January 2010 on the topside ionosphere using the DEMETER satellite data. Measurements of the electron-ion density and electron temperature by the ISL (Instrument Sonde de Langmuir) and IAP (Instrument Analyseur de Plasma) instruments on board the DEMETER satellite during the eclipse time over the low latitude (±40) Indian ocean area are presented. We found the peak decrease in electron density to be about 35% and the peak decrease in ion density to be about 40% from the reference orbits at the altitude of the satellite (∼660 km). Electron and ion temperatures were found to have decreased by 200-300 K at the same altitude. Instead of simple decrease as in ion density, electron temperature showed a complex wave-like oscillation as the solar eclipse progressed. Electron density decreased to a minimum value before the maximum obscuration and starts to increase before passing through another minimum at the time of maximum obscuration. Both the minima are located at the ±10° geomagnetic latitude. Variations of electron and ion densities were found to follow the average solar illumination experienced by the satellite and its conjugate points at satellite altitude, while the electron temperature showed no such correlation.

  15. Effects of solar radiation on the orbits of small particles

    Science.gov (United States)

    Lyttleton, R. A.

    1976-01-01

    A modification of the Robertson (1937) equations of particle motion in the presence of solar radiation is developed which allows for partial reflection of sunlight as a result of rapid and varying particle rotations caused by interaction with the solar wind. The coefficients and forces in earlier forms of the equations are compared with those in the present equations, and secular rates of change of particle orbital elements are determined. Orbital dimensions are calculated in terms of time, probable sizes and densities of meteoric and cometary particles are estimated, and times of infall to the sun are computed for a particle moving in an almost circular orbit and a particle moving in an elliptical orbit of high eccentricity. Changes in orbital elements are also determined for particles from a long-period sun-grazing comet. The results show that the time of infall to the sun from a highly eccentric orbit is substantially shorter than from a circular orbit with a radius equal to the mean distance in the eccentric orbit. The possibility is considered that the free orbital kinetic energy of particles drawn into the sun may be the energy source for the solar corona.

  16. Effects of Colored Noise on Periodic Orbits in a One-Dimensional Map

    Institute of Scientific and Technical Information of China (English)

    LI Feng-Guo; AI Bao-Quan

    2011-01-01

    Noise can induce inverse period-doubling transition and chaos. The effects of the colored noise on periodic orbits, of the different periodic sequences in the logistic map, are investigated. It is found that the dynamical behaviors of the orbits, induced by an exponentially correlated colored noise, are different in the mergence of transition, and the effects of the noise intensity on their dynamical behaviors are different from the effects of the correlation time of noise.Remarkably, the noise can induce new periodic orbits, namely, two new orbits emerge in the period-four sequence at the bifurcation parameter value μ = 3.5, four new orbits in the period-eight sequence at μ = 3.55, and three new orbits in the period-six sequence at μ = 3.846, respectively. Moreover, the dynamical behaviors of the new orbits clearly show the resonancelike response to the colored noise.

  17. Out-of-band effects of satellite ocean color sensors.

    Science.gov (United States)

    Wang, Menghua; Naik, Puneeta; Son, SeungHyun

    2016-03-20

    We analyze the sensor out-of-band (OOB) effects for satellite ocean color sensors of the sea-viewing wild field-of-view sensor (SeaWiFS), the moderate resolution imaging spectroradiometer (MODIS), and the visible infrared imaging radiometer suite (VIIRS) for phytoplankton-dominated open oceans and turbid coastal and inland waters, following the approach of Wang et al. [Appl. Opt.40, 343 (2001)APOPAI0003-693510.1364/AO.40.000343]. The applicability of the open ocean water reflectance model of Morel and Maritorena [J. Geophys. Res.106, 7163 (2001)JGREA20148-022710.1029/2000JC000319] (MM01) for the sensor OOB effects is analyzed for oligotrophic waters in Hawaii. The MM01 model predicted OOB contributions for oligotrophic waters are consistent with the result from in situ measurements. The OOB effects cause an apparent shift in sensor band center wavelengths in radiometric response, which depends on the sensor spectral response function and the target radiance being measured. Effective band center wavelength is introduced and calculated for three satellite sensors and for various water types. Using the effective band center wavelengths, satellite and in situ measured water optical property data can be more meaningfully and accurately compared. It is found that, for oligotrophic waters, the OOB effect is significant for the SeaWiFS 555 nm band (and somewhat 510 nm band), MODIS 412 nm band, and VIIRS 551 nm band. VIIRS and SeaWiFS have similar sensor OOB performance. For coastal and inland waters, however, the OOB effect is generally not significant for all three sensors, even though some small OOB effects do exist. This study highlights the importance of understanding the sensor OOB effect and the necessity of a complete prelaunch sensor characterization on the quality of ocean color products. Furthermore, it shows that hyperspectral in situ optics measurements are preferred for the purpose of accurately validating satellite-measured normalized water

  18. 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.

  19. Orbital Precession Effect in the Reissner-Nordstr(o)m Field with a Global Monopole

    Institute of Scientific and Technical Information of China (English)

    GONG Tian-Xi; WANG Yong-Jiu

    2009-01-01

    Using an elegant mathematical method advanced by us,we calculate the orbital precession effect in the gravitational field of the centre mass with electric charge and a global monopole.Analysing the results,we obtain that the orbital precession effect increases on account of the global symmetry breaking,but the orbital precession effect aroused by the electric charge of the field source reduces the orbital precession effect aroused by the mass of the field source.Generalizing the effect in the Schwarzschild field,we obtain interesting results by discussing the parameters of the celestial body,which provide a feasible experimental verification of the general relativity.

  20. Neptune's small satellites

    Science.gov (United States)

    Thomas, P.

    1992-04-01

    The small satellites of Neptune and other planets discovered during the Voyager 2 mission are discussed in terms of their composition and relationship to the planetary systems. The satellite Proteus is described in terms of its orbit, five other satellites are described, and they are compared to ther small satellites and systems. Neptune's satellites are hypothesized to be related to the ring system, and the satellite Galatea is related to the confinement of the rings.