WorldWideScience

Sample records for satellite orbit analysis

  1. Satellite orbits design using frequency analysis

    Science.gov (United States)

    Noullez, A.; Tsiganis, K.; Tzirti, S.

    2015-07-01

    We present here a new method for the efficient computation of periodic orbits, which are of particular interest for low-altitude satellite orbits design in high degree/order, non-axisymmetric gravity models. Our method consists of an iterative filtering scheme, that is itself based on 'Prony's method' of frequency analysis, and is independent of the complexity of the gravity model. Applying this method to the case of a low-altitude lunar orbiter, we show that it converges rapidly, in all models and for all values of altitude and initial inclination studied. Thus, as demonstrated below, one could use it to correct the initial conditions of a desired mission orbit - usually defined within the framework of a simplified model (e.g. the 'J2 problem') - ensuring minimal orbital eccentricity variations and, for very low altitudes, collision avoidance. At the same time, an accurate quasi-periodic decomposition of the orbit is computed, giving a measure of the periodic fluctuations of the orbital parameters.

  2. Precision Analysis of LEO Satellite Orbit Prediction

    Directory of Open Access Journals (Sweden)

    WANG Yafei

    2016-09-01

    Full Text Available The accuracy of different fitting intervals on the predicted orbit of different arc lengths was analyzed by using the dynamic fitting method and taken HY-2A satellite as an example. According to two orbit products, one was the precise orbit obtained by CNES and the other was rapid orbit computed by adopting zero-different reduced dynamic method, obtaining the precise predicted orbit. By the results, we can get that the 3DRMS is near 6dm by using 12h or 24h fitting orbit to forecast 12h arc; the 3DRMS is near 1m when forecasting 24h arc.

  3. Performance Analysis of BDS Satellite Orbits during Eclipse Periods: Results of Satellite Laser Ranging Validation

    Directory of Open Access Journals (Sweden)

    PENG Hanbing

    2016-06-01

    Full Text Available The performance of BeiDou satellite orbits during eclipse periods is an important part of the performance analysis of BeiDou Navigation Satellite System (BDS. Accuracy evaluation of satellite orbits in ephemeris of BDS during eclipse periods can provide support for the service performance assessment. It also helps to find possible deficiencies in the orbit modeling during eclipse periods, which may further contribute to the improvements of functional models for precise orbit determination. The effects of eclipse periods on the orbits of the three types of satellites of BDS are analyzed with the satellite laser ranging (SLR observations ranging from January 2014 to July 2015. At the same time, the orbit radial accuracy of BDS broadcast and precise ephemeris are validated. The results show that, obvious orbit accuracy decrease can be observed in both broadcast and precise ephemeris for IGSO/MEO satellites during eclipse periods (especially the yaw-maneuver periods. And orbit radial errors of IGSO/MEO satellites in broadcast ephemeris reach 1.5~2.0 m, and exceed 10.0 cm for that in precise ephemeris. Performance decrease of the GEO satellite orbit during eclipse arcs can hardly be revealed by the orbit radial residual series. During non-eclipse periods, radial accuracy of IGSO/MEO and GEO satellite orbits in broadcast ephemeris are better than 0.5 m and 0.9 m respectively. The radial accuracy of IGSO/MEO satellite orbits in precise ephemeris are better than 10.0 cm and that of the GEO satellite is about 50.0 cm with a systematic bias of 40.0 cm around.

  4. 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.

  5. Analysis of the orbital motion of the asteroid Apophis' satellite

    Science.gov (United States)

    Ivashkin, V. V.; Lang, A.

    2017-07-01

    We have analyzed the orbital disturbed spacecraft motion near an asteroid. The equations of the asteroidocentric spacecraft motion have been used with regard to three perturbations from celestial bodies, the asteroid's nonsphericity, and solar radiation pressure. It has been shown that the orbital parameters of the main spacecraft and a small satellite with a radio beacon can be selected such that the orbits are rather stable for a fairly long period of time, i.e., a few weeks for the main spacecraft with an orbit initial radius of 0.5 km and a few years before approaching Apophis with the Earth in 2029, for a small satellite at an orbit initial radius of 1.5 km. The initial orientation of the spacecraft orbital plane perpendicular to the sunward direction is optimal from the point of view of the stability of the spacecraft flight near an asteroid.

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

    OpenAIRE

    ZHOU Peiyuan; Du, Lan; FANG Shanchuan; Lu, Yu; Zhang, Zhongkai; Li, Fupeng

    2016-01-01

    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 carrie...

  7. Analysis of Filtering Methods for Satellite Autonomous Orbit Determination Using Celestial and Geomagnetic Measurement

    Directory of Open Access Journals (Sweden)

    Xiaolin Ning

    2012-01-01

    Full Text Available Satellite autonomous orbit determination (OD is a complex process using filtering method to integrate observation and orbit dynamic equations effectively and estimate the position and velocity of a satellite. Therefore, the filtering method plays an important role in autonomous orbit determination accuracy and time consumption. Extended Kalman filter (EKF, unscented Kalman filter (UKF, and unscented particle filter (UPF are three widely used filtering methods in satellite autonomous OD, owing to the nonlinearity of satellite orbit dynamic model. The performance of the system based on these three methods is analyzed under different conditions. Simulations show that, under the same condition, the UPF provides the highest OD accuracy but requires the highest computation burden. Conclusions drawn by this study are useful in the design and analysis of autonomous orbit determination system of satellites.

  8. Satellite orbit predictor

    Science.gov (United States)

    Friedman, Morton l.; Garrett, James, Major

    An analog aid to determine satellite coverage of Emergency Locator Transmitters Emergency Position Indicating Radio Beacon (ELT/EPIRB) distress incidence is discussed. The satellite orbit predictor is a graphical aid for determining the relationship between the satellite orbit, antenna coverage of the spacecraft and coverage of the Local User Terminal. The predictor allows the user to quickly visualize if a selected position will probably be detected and is composed of a base map and a satellite track overlay for each satellite.A table of equator crossings for each satellite is included.

  9. Solution Method and Precision Analysis of Multi-days Orbit Combination of BeiDou Satellites

    Directory of Open Access Journals (Sweden)

    LIU Weiping

    2016-10-01

    Full Text Available Multi-days orbit of BeiDou satellites is gotten by the routine method of stacking observation data at present, which limits calculation efficiency. And moreover, the dynamic model of BeiDou satellites is not perfect because of the short running time, which also limits the precision of multi-days orbit. The method of multi-days BeiDou satellite orbit combination is present. In this method, normal equation stacking is used to combining some consecutive one-day BeiDou satellite orbits to one multi-days orbit, which can improve calculation efficiency. Meanwhile, pseudo-stochastic pulse is used to compensate the deficiency of dynamic model. The analysis shows that it is the pseudo-stochastic pulse at one-day boundary that improves the precision of BeiDou satellite orbits obviously. And the tangential and normal precision is improved more than the radial. The orbit precision of GEO and IGSO is improved more than that of MEO. And the precision of BeiDou satellite orbit can be improved by extending the orbit arc length with certain limits, which is especially in the tangential direction.

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

    OpenAIRE

    Shkelzen Cakaj; Bexhet Kamo; Algenti Lala; Alban Rakipi

    2014-01-01

    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 regio...

  12. Relative Orbital Element Estimation and Observability Analysis for Formation Flying Satellites using Inter-Satellite Range Measurements Only

    NARCIS (Netherlands)

    Maessen, D.C.; Gill, E.K.A.

    2010-01-01

    This paper investigates to what extent the relative orbital elements of two satellites flying in formation can be estimated making use of inter-satellite range measurements only. Since the determination of relative orbital elements does not require the orientation of the relative orbit with respect

  13. Orbital analysis of LAGEOS and LAGEOS II laser ranged satellites: relativistic effects and geophysical issues

    Science.gov (United States)

    Peron, Roberto

    2005-03-01

    We present here the results of a recent analysis of LAGEOS and LAGEOS II laser range data. The higher accuracy in determining the orbits of these satellites makes it possible to see very tiny relativistic effects like frame-dragging and a wide variety of other phenomena at work. In particular, it is apparent the need of better understanding some effects of non-gravitational origin. The importance of these orbital fits as a geophysical probe is also stressed with a particular example. The analysis is carried out with GEODYN II Software, whose broad structure and use is described.

  14. Energy Balance and Power Performance Analysis for Satellite in Low Earth Orbit

    Directory of Open Access Journals (Sweden)

    Sung-Soo Jang

    2010-09-01

    Full Text Available The electrical power system (EPS of Korean satellites in low-earth-orbit is designed to achieve energy balance based on a one-orbit mission scenario. This means that the battery has to be fully charged at the end of a one-orbit mission. To provide the maximum solar array (SA power generation, the peak power tracking (PPT method has been developed for a spacecraft power system. The PPT is operated by a software algorithm, which tracks the peak power of the SA and ensures the battery is fully charged in one orbit. The EPS should be designed to avoid the stress of electronics in order to handle the main bus power from the SA power. This paper summarizes the results of energy balance to achieve optimal power sizing and the actual trend analysis of EPS performance in orbit. It describes the results of required power for the satellite operation in the worst power conditions at the end-of-life, the methods and input data used in the energy balance, and the case study of energy balance analyses for the normal operation in orbit. Both 10:35 AM and 10:50 AM crossing times are considered, so the power performance in each case is analyzed with the satellite roll maneuver according to the payload operation concept. In addition, the data transmission to the Korea Ground Station during eclipse is investigated at the local-time-ascending-node of 11:00 AM to assess the greatest battery depth-of-discharge in normal operation.

  15. Orbital and Photometric Analysis of the Inner Uranian Satellites from Hubble Images

    Science.gov (United States)

    French, Robert S.; Showalter, Mark R.; de Pater, Imke; Lissauer, Jack J.

    2017-10-01

    We continue our exploration of the dynamics of the thirteen densely-packed inner Uranian satellites. Using over 830 long-exposure images taken during 2003-2013 by the Hubble Space Telescope through broadband filters, we have obtained astrometry for twelve of the thirteen moons (excluding Cordelia) and derived Keplerian orbital elements including the influence of Uranus’s oblateness. Analysis of the libration caused by the Belinda:Perdita 44:43 mean-motion resonance implies that Belinda has roughly 26 times the mass of Perdita. We also see evidence of forced eccentricity in the orbits of several moons due to currently unknown perturbations. We will present our most recent findings on these topics as well as the photometrically-obtained rotational state of Perdita.

  16. 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.

  17. Satellite Power Systems (SPS) concept definition study. Volume 5: Transportation and operations analysis. [heavy lift launch and orbit transfer vehicles for orbital assembly

    Science.gov (United States)

    Hanley, G.

    1978-01-01

    The development of transportation systems to support the operations required for the orbital assembly of a 5-gigawatt satellite is discussed as well as the construction of a ground receiving antenna (rectenna). Topics covered include heavy lift launch vehicle configurations for Earth-to LEO transport; the use of chemical, nuclear, and electric orbit transfer vehicles for LEO to GEO operations; personnel transport systems; ground operations; end-to-end analysis of the construction, operation, and maintenance of the satellite and rectenna; propellant production and storage; and payload packaging.

  18. 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.

  19. 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.

  20. Orbital decay analysis, reentry predictions and risk assessment for the GOCE satellite

    Science.gov (United States)

    Pardini, Carmen; Anselmo, Luciano

    The ESA’s GOCE satellite was launched on 17 March 2009. After mapping the geopotential with unrivalled accuracy and detail for four years from an extremely low circular polar orbit, on 21 October 2013 the low thrust ion propulsion motor used to contrast the atmospheric drag was automatically shut down when the pressure in the xenon propellant tank dropped below a critical threshold. Then the satellite entered in “fine-pointing mode” (FPM), a phase of orbital altitude decay with active fine attitude control carried out by a set of magnetotorquers. According to the pre-launch specifications, the attitude control system was expected to compensate the gravity gradient and the aerodynamic torques up to an average drag force along the orbit of 20 mN. However the system proved itself much more robust than envisaged, remaining operational until reentry, with drag forces exceeding 2000 mN. The uncommon nature of the GOCE reentry campaign, sharing an uncontrolled orbital decay with a finely controlled attitude along the atmospheric drag direction, made the reentry predictions for this satellite an interesting case study, in particular because nobody was able to say a priori if and when the attitude control would have failed, leading to an unrestrained tumbling. Therefore, even though the casualty expectancy for this reentry was slightly above the internationally recognized alert threshold of 1/10,000, i.e. around 1/5000, it presented a number of challenges and opportunities from the prediction and risk evaluation points of view. As in previous cases, ISTI/CNR was in charge of reentry predictions for the Italian civil protection authorities and exchanged information with the other agencies involved in the framework of the international reentry campaign promoted by the Inter-Agency Space Debris Coordination Committee (IADC). Considering the peculiar nature of the GOCE reentry, the definition of reliable uncertainty windows was not easy, in particular taking into account

  1. The Preliminary Result and Analysis for BD Orbit Determination with Inter-satellite Link Data

    Directory of Open Access Journals (Sweden)

    SONG Xiaoyong

    2017-05-01

    Full Text Available The experimental satellite of BD navigation system has assembled inter-satellite link (ISL payloads and has obtained the real ISL observation data. The paper presents the preprocessing method of ISL and the POD method and result for Ka only observation and the combination Ka observation with L-band. It's showed that:the radial orbit error is less than 0.5 m with Ka only observation; the radial orbit error is less than 0.3 m with the observation by combining the Ka ISL with L-band data which has improved the orbit accuracy remarkably in contrast to L-band only data; the accuracy of calibrating device delay is better than 0.1 m。

  2. Analysis of Damage Probability for Collision Between Space Debris and a Satellite in Low-Earth Orbit

    Directory of Open Access Journals (Sweden)

    Jae-Eun Lee

    2007-06-01

    Full Text Available Space environment becomes more hazardous for satellite because of increasing number of space debris. This research is to analyze collision hazards between KOMPSAT 3 in low-earth orbit and space debris generated by the explosion of FengYun satellite on the January 11, 2007. Based on the observed data of the space debris from FengYun satellite, the mass and number distribution of the debris are estimated including undetectable debris from the explosion of FengYun satellite. The spatial density and flux for the space debris can be calculated according to size. This study also brings out the analysis for the assessment of collision probability and damage probability. The algorithm developed in the current paper can be used to estimate the level of risk due to space debris for the satellites that will be launched in the future.

  3. Satellite Laser Ranging Satellite Orbit Product from NASA CDDIS

    Data.gov (United States)

    National Aeronautics and Space Administration — SLR Satellite Orbit solutions available from the Crustal Dynamics Data Information System (CDDIS). Precise Orbit Determination (POD) solutions in Standard Product 3...

  4. 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...

  5. 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.

  6. Orbital positioning and stationkeeping of geostationary satellites

    Science.gov (United States)

    Donat, H.

    Orbit, launcher, and satellite related constraints on launch windows are reviewed. The flight sequence and orbital position optimization of spin and three axis stabilized satellites are described. Geostationary orbit perturbations and evolution, and orbit correction are considered. North-south and east-west stationkeeping strategies are outlined. Stationkeeping of Telecom-1 and TDF-1 is illustrated.

  7. 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.

  8. Sampling analysis for the Earth Radiation Budget Satellite System mission based on orbital coverage and cloud variability

    Science.gov (United States)

    Harrison, E. F.; Gibson, G. G.; Minnis, P.

    1978-01-01

    The reported study represents an extension of an investigation by Harrison et al. (1976). Based on the results of sampling studies, two 98 deg inclined orbits coupled with a 56 deg inclination orbit appear to satisfy the science requirements on both regional and zonal scales. The NOAA sun-synchronous satellites in the TIROS-N series could adequately cover the high latitudes and a satellite having an inclination of 56 deg could provide sampling in the mid and low latitude areas where variations in radiation energetics are most dynamic. Attention is given to studies of time and space coverage, zonal evaluations, a regional analysis, and statistics describing the regional variations of cloud cover. A table is presented with data concerning the uncertainty of monthly mean reflected irradiance due to cloud variability for selected northern hemisphere regions.

  9. Geo satellite attitude and orbit control: fixed orbit control thrasters

    OpenAIRE

    Ermoshkin, Yu; V. Raevsky; Urusov, V.

    2009-01-01

    The paper describes the enhanced application ofhigh-economical electro-jet orbit control thrusters for geostationary satellites; in particular, generation of controlling moments to the benefit of satellite attitude determination and control subsystems in the course of orbit control maneuvers ongoing. The scheme with thrusters fixed on a satellite body is analyzed. Possible orbit control session procedures are proposed on the basis of controlling moments generation. Advantages and disadvantage...

  10. Linked Autonomous Interplanetary Satellite Orbit Navigation

    Science.gov (United States)

    Parker, Jeffrey S.; Anderson, Rodney L.; Born, George H.; Leonard, Jason M.; McGranaghan, Ryan M.; Fujimoto, Kohei

    2013-01-01

    A navigation technology known as LiAISON (Linked Autonomous Interplanetary Satellite Orbit Navigation) has been known to produce very impressive navigation results for scenarios involving two or more cooperative satellites near the Moon, such that at least one satellite must be in an orbit significantly perturbed by the Earth, such as a lunar halo orbit. The two (or more) satellites track each other using satellite-to-satellite range and/or range-rate measurements. These relative measurements yield absolute orbit navigation when one of the satellites is in a lunar halo orbit, or the like. The geometry between a lunar halo orbiter and a GEO satellite continuously changes, which dramatically improves the information content of a satellite-to-satellite tracking signal. The geometrical variations include significant out-of-plane shifts, as well as inplane shifts. Further, the GEO satellite is almost continuously in view of a lunar halo orbiter. High-fidelity simulations demonstrate that LiAISON technology improves the navigation of GEO orbiters by an order of magnitude, relative to standard ground tracking. If a GEO satellite is navigated using LiAISON- only tracking measurements, its position is typically known to better than 10 meters. If LiAISON measurements are combined with simple radiometric ground observations, then the satellite s position is typically known to better than 3 meters, which is substantially better than the current state of GEO navigation. There are two features of LiAISON that are novel and advantageous compared with conventional satellite navigation. First, ordinary satellite-to-satellite tracking data only provides relative navigation of each satellite. The novelty is the placement of one navigation satellite in an orbit that is significantly perturbed by both the Earth and the Moon. A navigation satellite can track other satellites elsewhere in the Earth-Moon system and acquire knowledge about both satellites absolute positions and velocities

  11. Analysis distribution of galactic cosmic rays particle energy with polar orbit satellite for Geant4 application

    Science.gov (United States)

    Suparta, W.; Putro, W. S.

    2014-04-01

    Galactic Cosmic Rays (GCR) are photon waves originating from astrophysical sources which traverse through the interstellar/interplanetary medium and reaching the terrestrial atmosphere. The energies of Galactic Cosmic Ray particles up to and exceeding 1012 eV, and this spectrum are peaked around 1 GeV. The National Aeronautics and Space Administration (NASA) provide satellite mission for monitoring the energy GCR particles in polar orbit, so-called the ACE and OMNI. In this paper, we analyze results from measurement error of GCR sensor. The error result is obtained by comparing the measurements from GCR sensor with ground-based neutron monitors at Bartol University. The measurements were taken for two periods during a Solar Particle Event (SPE) maximum on 14 July 2000 and 28 October 2003. The largest value of measurement error from GCR sensor in this study is OMNI satellites. After the error results were obtained, they were applied into Geant4 simulation. This simulation shows the shape of particle energy distribution of GCR sensors. The simulation has been tested and can be operated very well under Linux based platform.

  12. 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.

  13. Low Earth Orbit Satellite’s Orbit Propagation and Determination

    Science.gov (United States)

    2014-01-01

    Institute of Technology Email: honien.shou@xuite.net Abstract This paper represents orbit propagation and determination of Low Eearth Orbit(LEO...Arichandran, S. H. Tan, T. Bretschneider, High – Presicion Onboard Orbit Determination for Small Satellites - the GPS-Based XNS on X-SAT. 6th Symposium on

  14. 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.

  15. Artificial satellites orbiting planetary satellites: critical inclination and sun-synchronous orbits

    Science.gov (United States)

    da Costa, Maria Lívia G. T. X.; Vilhena de Moraes, Rodolpho; Carvalho, Jean Paulo S.; Prado, Antônio Fernando B. A.

    2017-10-01

    The behavior of critical inclinations and sun-synchronous orbits of artificial satellites orbiting planetary satellites are analyzed considering, simultaneously, the influence of the harmonics J 2 and C 22, both due to the non-uniform mass distribution of the natural satellite. In the present research, the central bodies of interest are the Moon and two of the Galilean moons: Io and Europa.

  16. 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.

  17. Analysis of a Simulated Optical GSO Survey Observation for the Effective Maintenance of the Catalogued Satellites and the Orbit Determination Strategy

    Directory of Open Access Journals (Sweden)

    Jin Choi

    2015-09-01

    Full Text Available A strategy is needed for a regional survey of geosynchronous orbits (GSOs to monitor known space objects and detect uncataloged space objects. On the basis of the Inter-Agency Debris Committee’s recommendation regarding the protected region of geosynchronous Earth orbit (GEO, target satellites with perigee and apogee of GEO ± 200 km and various inclinations are selected for analysis. The status of the GSO region was analyzed using the satellite distribution based on the orbital characteristics in publicly available two-line element data. Natural perturbation effects cause inactive satellites to drift to two stable longitudinal points. Active satellites usually maintain the designed positions as a result of regular or irregular maneuver operations against their natural drift. To analyze the detection rate of a single optical telescope, 152 out of 412 active satellites and 135 out of 288 inactive satellites in the GSO region were selected on the basis of their visibility at the observation site in Daejeon, Korea. By using various vertical view ranges and various numbers of observations of the GSO region, the detection efficiencies were analyzed for a single night, and the numbers of follow-up observations were determined. The orbital estimation accuracies were also checked using the arc length and number of observed data points to maintain the GSO satellite catalog.

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

    Directory of Open Access Journals (Sweden)

    Ju Young Son

    2015-09-01

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

  19. Precise orbit determination of Beidou Satellites at GFZ

    Science.gov (United States)

    Deng, Zhiguo; Ge, Maorong; Uhlemann, Maik; Zhao, Qile

    2014-05-01

    In December 2012 the Signal-In-Space Interface Control Document (ICD) of the BeiDou Navigation Satellite System (BeiDou system) was published. Currently the initial BeiDou regional navigation satellite system consisting of 14 satellites was completed, and provides observation data of five Geostationary-Earth-Orbit (GEO)satellites, five Inclined-GeoSynchronous-Orbit (IGSO) satellites and four Medium-Earth-Orbit (MEO) satellites. The Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences (GFZ) contributes as one of the analysis centers to the International GNSS Service (IGS) since many years. In 2012 the IGS began the "Multi GNSS EXperiment" (MGEX), which supports the new GNSS, such as Galileo, Compass, and QZSS. Based on tracking data of BeiDou-capable receivers from the MGEX and chinese BeiDou networks up to 45 global distributed stations are selected to estimate orbit and clock parameters of the GPS/BeiDou satellites. Some selected results from the combined GPS/BeiDou data processing with 10 weeks of data from 2013 are shown. The quality of the orbit and clock products are assessed by means of orbit overlap statistics, clock stabilities as well as an independent validation with SLR measurements. At the end an outlook about GFZ AC's future Multi-GNSS activities will be given.

  20. The orbit estimation for Larets satellite

    Science.gov (United States)

    Rutkowska, M.

    2006-10-01

    The LARETS satellite was launched on September 26, 2004 into a circular orbit at an altitude of 690 km and with an inclination of 98.2 degree. The aim of this study is the computation of the orbit of the satellite LARETS with the highest accuracy possible. The paper discusses the influence of the modelling of different physical effects on the motion of LARETS, in particular in terms of orbit quality. All computations are performed with the NASA program GEODYN II (Eddy et al.,1990).

  1. Satellite orbits in Levi-Civita space

    Science.gov (United States)

    Humi, Mayer

    2018-03-01

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

  2. Equilibrium Temperature of a Satellite in LowEarth Orbit

    Directory of Open Access Journals (Sweden)

    T. M. Hegab

    2015-01-01

    Full Text Available The efficiency of artificial satellite equipment, essentially, depends on its temperature condition, which in the case of low-Earth orbit varies quite widely. The satellite temperature changes because of the fact that along with a portion of the orbit where the satellite perceives heat flows, caused by solar radiation directly incident on its surface and solar radiation, reflected from the Earth's surface; in general cases of the low earth orbit there is its shaded portion where the satellite receives only a relatively low intensive self-radiation of the Earth. The level of possible values of satellite temperature at different portions of low earth orbit can be estimated by the equilibrium temperature determined from the balance equation of heat flows, perceived and radiated by its surface.The analysis of heat flows, which act on the surface of an artificial satellite of conditional spherical shape, allows us to obtain the dependences, in order to find a satellite equilibrium temperature at different heights of its position above Earth's surface and an angle between the directions from the center of the Earth towards the Sun, and the satellite as it moves out of the shadow of the Earth and at different height of its position at the shaded portion of the orbit as well. These dependencies are used for graphing to show the changes of the equilibrium temperature of the low-Earth orbiting satellite.The presented technique allows us to evaluate the possible range of temperature change of the low-Earth orbiting satellite.

  3. GOCE Satellite Orbit in a Computational Aspect

    Science.gov (United States)

    Bobojc, Andrzej; Drozyner, Andrzej

    2013-04-01

    The presented work plays an important role in research of possibility of the Gravity Field and Steady-State Ocean Circulation Explorer Mission (GOCE) satellite orbit improvement using a combination of satellite to satellite tracking high-low (SST- hl) observations and gravity gradient tensor (GGT) measurements. The orbit improvement process will be started from a computed orbit, which should be close to a reference ("true") orbit as much as possible. To realize this objective, various variants of GOCE orbit were generated by means of the Torun Orbit Processor (TOP) software package. The TOP software is based on the Cowell 8th order numerical integration method. This package computes a satellite orbit in the field of gravitational and non-gravitational forces (including the relativistic and empirical accelerations). The three sets of 1-day orbital arcs were computed using selected geopotential models and additional accelerations generated by the Moon, the Sun, the planets, the Earth and ocean tides, the relativity effects. Selected gravity field models include, among other things, the recent models from the GOCE mission and the models such as EIGEN-6S, EIGEN-5S, EIGEN-51C, ITG-GRACE2010S, EGM2008, EGM96. Each set of 1-day orbital arcs corresponds to the GOCE orbit for arbitrary chosen date. The obtained orbits were compared to the GOCE reference orbits (Precise Science Orbits of the GOCE satellite delivered by the European Space Agency) using the root mean squares (RMS) of the differences between the satellite positions in the computed orbits and in the reference ones. These RMS values are a measure of performance of selected geopotential models in terms of GOCE orbit computation. The RMS values are given for the truncated and whole geopotential models. For the three variants with the best fit to the reference orbits, the empirical acceleration models were added to the satellite motion model. It allowed for further improving the fitting of computed orbits to the

  4. 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.

  5. Analysis of Scaling Parameters of the Batch Unscented Transformation for Precision Orbit Determination using Satellite Laser Ranging Data

    Directory of Open Access Journals (Sweden)

    Jae-Hyuk Kim

    2011-09-01

    Full Text Available The current study analyzes the effects of the scaling parameters of the batch unscented transformation on precision satellite orbit determination. Satellite laser ranging (SLR data are used in the orbit determination algorithm, which consists of dynamics model, observation model and filtering algorithm composed of the batch unscented transformation. TOPEX/Poseidon SLR data are used by utilizing the normal point (NP data observed from ground station. The filtering algorithm includes a repeated series of processes to determine the appropriate scaling parameters for the batch unscented transformation. To determine appropriate scaling parameters, general ranges of the scaling parameters of α, β, κ, λ are established. Depending on the range settings, each parameter was assigned to the filtering algorithm at regular intervals. Appropriate scaling parameters are determined for observation data obtained from several observatories, by analyzing the relationship between tuning properties of the scaling parameters and estimated orbit precision. The orbit determination of satellite using the batch unscented transformation can achieve levels of accuracy within several tens of cm with the appropriate scaling parameters. The analyses in the present study give insights into the roles of scaling parameters in the batch unscented transformation method.

  6. Initial Analysis and Modeling Results from the Polar Orbiting Geomagnetic Survey (POGS) Satellite

    Science.gov (United States)

    1993-08-01

    satellites, DMA ha made the deision to dismantle itu Vound-besed global sateite-raucking network and ita dMa proceing spport Igp beginnn in October 1993...depend on the time-dependent Disturbance Storm Time index Dst(r), when it becomes available, as follows: q,()= a.,. + PmDa(?) ( Ita ) s’(T)= y.a + 8-.D...the Dst Ring-Current Myth, Journal of Geophysical Research (in Press) Cappellari, J. 0., C. E. Velez , and A. J. Fuchs; Mathematical Theory of the

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

    DEFF Research Database (Denmark)

    Proud, Simon Richard

    2013-01-01

    , 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...... useful in areas where ground-based observations are sparse. Key Points Global satellite coverage allows rapid analysis of meteors Cloud/trail altitude can be determined by satellite Remote sensing data can be used to reconstruct meteor orbital elements......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...

  8. 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.

  9. 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.

  10. 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.

  11. Electrode structure analysis and surface characterization for lithium-ion cells simulated low-Earth-orbit satellite operation. I. Electrochemical behavior and structure analysis

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xianming; Yamada, Chisa; Naito, Hitoshi; Segami, Go; Kibe, Kouichi [Institute of Space Technology and Aeronautics, Japan Aerospace Exploration Agency, Tsukuba Space Center, Sengen 2-1-1, Ibaraki 305-8505 (Japan); Sakiyama, Yoko; Takahashi, Yoshikazu; Hironaka, Toshiya; Hayashi, Eiji [Toray Research Center, Inc., Sonoyama 3-3-7, Otsu, Shiga 520-8567 (Japan)

    2007-05-01

    Lithium-ion cells for satellite applications operate under a special condition, and are expected to behave differently from those for commercial purposes. To understand the performance-degradation mechanism of lithium-ion cells experienced cycle-life testing in a simulated low-Earth-orbit (LEO) satellite operation, we conducted the structure analysis and surface characterization of the aged LiCoO{sub 2} cathode and graphite anode obtained from a lithium-ion cell with 4350-cycle LEO simulation experience. The analysis results were compared with a fresh cell which served as control. This paper provides a review of testing results on electrochemical and structure analysis. The capacity-verification and impedance measure results indicated that the LiCoO{sub 2} cathode, rather than graphite anode, was responsible for the performance degradation of the aged cell. This conclusion was confirmed by the structure analysis. The qualitative analysis of the XRD spectra disclosed that the aged cathode exhibited a much larger structure change than the aged anode. We also detected the lithium ions that were irreversibly reserved in graphite anode in XRD and {sup 7}Li nuclear magnetic resonance (NMR) analysis of aged graphite anode. These results lead us to deduce that the serious structure change in LiCoO{sub 2} cathode was primarily responsible for the performance degradation of the aged cell. (author)

  12. A refined orbit for the satellite of asteroid (107) Camilla

    Science.gov (United States)

    Pajuelo, Myriam Virginia; Carry, Benoit; Vachier, Frederic; Berthier, Jerome; Descamp, Pascal; Merline, William J.; Tamblyn, Peter M.; Conrad, Al; Storrs, Alex; Margot, Jean-Luc; Marchis, Frank; Kervella, Pierre; Girard, Julien H.

    2015-11-01

    The satellite of the Cybele asteroid (107) Camilla was discovered in March 2001 using the Hubble Space Telescope (Storrs et al., 2001, IAUC 7599). From a set of 23 positions derived from adaptive optics observations obtained over three years with the ESO VLT, Keck-II and Gemini-North telescopes, Marchis et al. (2008, Icarus 196) determined its orbit to be nearly circular.In the new work reported here, we compiled, reduced, and analyzed observations at 39 epochs (including the 23 positions previously analyzed) by adding additional observations taken from data archives: HST in 2001; Keck in 2002, 2003, and 2009; Gemini in 2010; and VLT in 2011. The present dataset hence contains twice as many epochs as the prior analysis and covers a time span that is three times longer (more than a decade).We use our orbit determination algorithm Genoid (GENetic Orbit IDentification), a genetic based algorithm that relies on a metaheuristic method and a dynamical model of the Solar System (Vachier et al., 2012, A&A 543). The method uses two models: a simple Keplerian model to minimize the search-time for an orbital solution, exploring a wide space of solutions; and a full N-body problem that includes the gravitational field of the primary asteroid up to 4th order.The orbit we derive fits all 39 observed positions of the satellite with an RMS residual of only milli-arcseconds, which corresponds to sub-pixel accuracy. We found the orbit of the satellite to be circular and roughly aligned with the equatorial plane of Camilla. The refined mass of the system is (12 ± 1) x 10^18 kg, for an orbital period of 3.71 days.We will present this improved orbital solution of the satellite of Camilla, as well as predictions for upcoming stellar occultation events.

  13. Centimeter Precise Orbit Determination for SWARM Satellite via Reduced-dynamic Method

    Directory of Open Access Journals (Sweden)

    ZHANG Bingbing

    2016-11-01

    Full Text Available 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-dynamic method and orbit determining strategy in the article, the orbit solution is well and stable, the orbit accuracy reaches centimeter level.

  14. 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.

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

    Science.gov (United States)

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

    2017-07-01

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

  16. GPM GROUND VALIDATION SATELLITE SIMULATED ORBITS LPVEX V1

    Data.gov (United States)

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

  17. 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...

  18. The accuracy of orbit estimation for the low-orbit satellites LARETS and WESTPAC

    Science.gov (United States)

    Rutkowska, Milena

    The LARETS satellite was launched on September 26, 2004, into a circular orbit at an altitude of 690 km and with an inclination of 98.2°. This mission is a successor to the WESTPAC satellite which was launched to an altitude of 835 km six years before. The study is based on the observations taken by the global network of laser stations during the period from December 30, 2003 to March 17, 2004 for LARETS. This study is aimed at the precise orbit computation of LARETS. The experience acquired during the orbit estimation of WESTPAC was applied to the orbit investigation of LARETS. The WESTPAC was merely used for reference and initial parameters of the force model [Rutkowska, M., Noomenn, R., Global orbit analysis of the satellite WESTPAC, Adv. Space Res., 30(2), 265-270, 2002]. The orbit of LARETS was estimated with an rms-of-fit to the SLR measurements of 3.9 cm, using the following computation model: the CSR TEG-4 gravity field up to degree and order (200,200), the Ray tide model, the MSIS86 model for atmospheric density [Hedin, A.E., MSIS-86 Thermospheric Model, J. Geophys. Res., 92 (A5), 4649-4662, 1987], and the solution of 8-hourly CD-values. It has been verified that the modeling of the gravity field up to degree and order (100,100) which gives the same rms-of-fit value. Estimated orbits for both satellites are compared to each other in Fig. 2. All computations are performed with the NASA program GEODYN II [Eddy, W.F, McCarthy, J.J., Pavlis, D.E., Marshall, J.A., Luthce, S.B., Tsaoussi, L.S., GEODYN II System Operations Manual, vol. 1-5, ST System Corp., Lanham MD, USA, 1990].

  19. 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.

  20. Chaotic motions of a tethered satellite system in circular orbit

    Science.gov (United States)

    Jin, D. P.; PANG, Z. J.; Wen, H.; Yu, B. S.

    2016-09-01

    This paper studies the chaotic motions of a tethered satellite system by utilizing a ground-based experimental system. Based on dynamics similarity principle, a dynamical equivalent model between the on-orbit tethered satellite and its ground physical model is obtained. As a result, the space dynamics environment of the tethered satellite can be simulated via the thrust forces and the torque of a momentum wheel on the satellite simulator. The numerical results of the on-orbit tethered satellite show the chaotic motions of the attitude motion of mother satellite. The experiment shows that the torque of momentum wheel as a negative damping is able to suppress the chaotic motion.

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

    Science.gov (United States)

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

    1974-01-01

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

  2. 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.

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

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... 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 ...

  4. On preparing UKIRT to observe satellites and orbital debris

    Science.gov (United States)

    Kendrick, Richard L.; Bold, Matthew

    2016-07-01

    In 2013 the process of developing an Orbital Debris and Satellite observation capability for the United Kingdom Infrared Telescope was initiated. This process involved the modification of various operational aspects of the observatory. After a year of implementing the modifications the observatory was capable of providing deep space observations of orbital debris and satellites in a queue based format. The telescope has been operating with this capability for the past 2.5 years and has generated terabytes of observational data on orbital debris and satellites that are in the GEO satellite belt distributed across the Pacific Ocean.

  5. Galilean satellite remote sensing by the Galileo Jupiter Orbiter

    Science.gov (United States)

    Yeates, C. M.; Klaasen, K. P.; Clarke, T. C.

    1983-01-01

    The derivation of a mission design strategy for the Galileo Jupiter Orbiter which best satisfies the requirements for remote sensing of the surfaces of the Galilean satellites during a 20-month orbital tour of the Jovian system is described. The celestial mechanics of a spacecraft orbiting about Jupiter and interacting with the Galilean satellites is discussed. A satellite tour strategy designed to optimize the accomplishment of remote sensing, field and particle science, and radio science objectives is developed. Finally, an assessment is made of how well these objectives can be met given the spacecraft, the capabilities of the scientific instruments, and the structure of the satellite tour.

  6. Secular resonances between bodies on close orbits II: prograde and retrograde orbits for irregular satellites

    Science.gov (United States)

    Li, Daohai; Christou, Apostolos A.

    2017-09-01

    In extending the analysis of the four secular resonances between close orbits in Li and Christou (Celest Mech Dyn Astron 125:133-160, 2016) (Paper I), we generalise the semianalytical model so that it applies to both prograde and retrograde orbits with a one-to-one map between the resonances in the two regimes. We propose the general form of the critical angle to be a linear combination of apsidal and nodal differences between the two orbits b_1 Δ π + b_2 Δ Ω, forming a collection of secular resonances in which the ones studied in Paper I are among the strongest. Test of the model in the orbital vicinity of massive satellites with physical and orbital parameters similar to those of the irregular satellites Himalia at Jupiter and Phoebe at Saturn shows that {>}20 and {>}40% of phase space is affected by these resonances, respectively. The survivability of the resonances is confirmed using numerical integration of the full Newtonian equations of motion. We observe that the lowest order resonances with b_1+|b_2|≤ 3 persist, while even higher-order resonances, up to b_1+|b_2|≥ 7, survive. Depending on the mass, between 10 and 60% of the integrated test particles are captured in these secular resonances, in agreement with the phase space analysis in the semianalytical model.

  7. Satellite orbit determination using satellite gravity gradiometry observations in GOCE mission perspective

    Directory of Open Access Journals (Sweden)

    A. Bobojć

    2003-01-01

    Full Text Available Between the years 2004 and 2005 the launch of the first gradiometric satellite is planned. This satellite will be an important element of the Gravity Field and Steady – State Ocean Circulation Explorer Mission (GOCE. This mission is one of the reasons for performing the simulation research of the Satellite Gravity Gradiometry. Our work contains the theory description and simulation results of the satellite orbit determination using the gravity tensor observations. In the process of the satellite orbit determination the initial dynamic state vector corrections are obtained. These corrections are estimated by means of the gravity gradiometry measurements. The performed simulations confirm the possibility of satellite orbit determination by means of the gravity tensor observations.Key words. satellite geodesy, satellite gradiometry, satellite orbits

  8. A simplex method for the orbit determination of maneuvering satellites

    Science.gov (United States)

    Chen, JianRong; Li, JunFeng; Wang, XiJing; Zhu, Jun; Wang, DanNa

    2018-02-01

    A simplex method of orbit determination (SMOD) is presented to solve the problem of orbit determination for maneuvering satellites subject to small and continuous thrust. The objective function is established as the sum of the nth powers of the observation errors based on global positioning satellite (GPS) data. The convergence behavior of the proposed method is analyzed using a range of initial orbital parameter errors and n values to ensure the rapid and accurate convergence of the SMOD. For an uncontrolled satellite, the orbit obtained by the SMOD provides a position error compared with GPS data that is commensurate with that obtained by the least squares technique. For low Earth orbit satellite control, the precision of the acceleration produced by a small pulse thrust is less than 0.1% compared with the calibrated value. The orbit obtained by the SMOD is also compared with weak GPS data for a geostationary Earth orbit satellite over several days. The results show that the position accuracy is within 12.0 m. The working efficiency of the electric propulsion is about 67% compared with the designed value. The analyses provide the guidance for subsequent satellite control. The method is suitable for orbit determination of maneuvering satellites subject to small and continuous thrust.

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

    Science.gov (United States)

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

    2017-12-01

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

  10. Orbital oscillations of an elastic vertically-tethered satellite

    Science.gov (United States)

    Aslanov, V. S.

    2011-10-01

    The motion of a satellite in a circular orbit with respect to its center of mass is considered. The satellite bears an elastic tether system unrolled along the local vertical. The load at the end of the tether oscillates harmonically. The satellite motion under the action of the gravitational moment and the moment due to the tether tension force is studied. The bifurcation diagram is constructed and the hetero- and homoclinic separatrix trajectories are determined. Mel'nikov's method is used to study the satellite chaotic behavior near separatrices under the action of the periodic tether tension force. The results of the present paper can be used to analyze tether systems of gravitational stabilization and to study the orbital behavior of a satellite with an unrolled tether system with respect to the satellite center of mass.

  11. Orbital and attitude evolution of SCD-1 and SCD-2 Brazilian satellites

    Science.gov (United States)

    Murcia, J. O.; Carrara, V.; Kuga, H. K.

    2017-10-01

    The SCD-1 and SCD-2 satellites were launched in 1993 and 1998, respectively, with use of the Launcher “Pegasus” of the OSC (Orbital Sciences Corporation). 21 and 16 years later, the satellites are still in orbit around the Earth and providing data for users. Mission and Operational data from Satellite Tracking Center Network are stored in mission files in the Satellite Control Center (SCC) and made available to the users. The SCC also stores history files of the satellite orbit and attitude ephemeris, besides the on-board telemetry, temperatures, equipment status, etc. This work will present some analysis of the orbit ephemeris evolution based upon the Two-Line Elements sets (TLE’s) obtained from NORAD (North American Aerospace Defense Command). Attitude evolution along time is also presented for both satellites from SCC data. The orbit decay will be explained as resulting mainly due to the solar activity during the satellite lifetime. This work aims to report the history of more than 20 years of continuous operation of SCD-1 and SCD-2. At the end, an estimation of the orbital decay is forecast with the use of NASA’s DAS software.

  12. 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...

  13. Are artificial satellites orbits influenced by an expanding Earth?

    Directory of Open Access Journals (Sweden)

    G. Scalera

    2006-06-01

    Full Text Available Albeit in the past great theoretical and experimental efforts were made in proposing and searching for G time-decreasing, a major role could be played by an increase of M. A recent analysis (Scalera, 2003a converges toward an upper limit of the Earth’s mass variation in the order of magnitude of M/M=10-9 /yr. It is here discussed the possible role that can be played by parameters linked to the expanding Earth in the effects we observe in the orbital motion of the artificial satellites. The important result in this short note is the discrimination between the reality of the glacial rebound process and/or the relaxation of the 100m excess of equatorial bulge testified by the high rate of j2 , and the improbable role that glacial rebound can have in driving PM and TPW. It is recommended that the new technology of drag-free satellites be used (Gravity-Probe B is the first step to reveal possible residual orbital parameter variations ascribable to formerly unrecognized fictitious drag terms due to Earth radial increase.

  14. Electrode structure analysis and surface characterization for lithium-ion cells simulated low-Earth-orbit satellite operation. II: Electrode surface characterization

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xianming; Yamada, Chisa; Naito, Hitoshi; Segami, Go; Kibe, Koichi [Institute of Space Technology and Aeronautics, Japan Aerospace Exploration Agency, Tsukuba Space Center, Sengen 2-1-1, Ibaraki 305-8505 (Japan); Hironaka, Toshiya; Hayashi, Eiji; Sakiyama, Yoko; Takahashi, Yoshikazu [Toray Research Center, Inc., Sonoyama 3-3-7, Otsu, Shiga 520-8567 (Japan)

    2007-06-01

    As a sequence work to investigate the performance-degradation mechanism of an aged commercial laminated lithium-ion cell experiencing 4350-cycle charge-discharge in a simulated low-Earth-orbit (LEO) satellite operation, we performed the surface characterization of LiCoO{sub 2} cathode and graphite anode by Fourier transform infrared-Attenuated total reflection (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS) analysis in this work. Overall, the graphite anode had a larger change in surface chemistry than that of the LiCoO{sub 2} cathode. Except the common surface components, we detected Co metal at the aged graphite surface in the first time. This Co metal deposition was believed to originate from Co{sup 2+} dissolution from LiCoO{sub 2} cathode during prolonged cycling, and detrimental to structure stability of LiCoO{sub 2} cathode which was a main cause of cell capacity loss. The amount of surface-film component was also estimated by FTIR analysis. Though the total amount of surface film increased, the organic (inorganic) surface film decreased (increased) with prolonged cycling. (author)

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

    Directory of Open Access Journals (Sweden)

    T. Moretto

    2002-07-01

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

  16. Relative Orbit Elements for Satellites in Elliptical Orbits

    Science.gov (United States)

    2010-03-01

    flying missions [9, 35, 63, 75, 95, 107, 111], such as the European PRISMA mission [22], NASA’s Magnetosphere Multiscale mission [21, 34, 62, 80, 109...Magnetosphere Multiscale (MMS) Mission, 1999. [22] D’Amico, S., Gill, E., and Montenbruck, O., “Relative Orbit Control Design for the PRISMA Formation

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

    Science.gov (United States)

    Steigenberger, Peter; Thoelert, Steffen; Montenbruck, Oliver

    2017-11-01

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

  18. Satellite orbit estimation using DORIS data: comparison of reduced-dynamic and dynamic orbit modeling and discussion of modeling aspects

    Science.gov (United States)

    Stepanek, Petr; Rodriguez-Solano, Carlos; Filler, Vratislav; Hugentobler, Urs

    2013-04-01

    Reduced-dynamic orbit modeling is currently used to compute the routine solutions of the GOP analysis center, which are of similar accuracy as solutions from the other centers utilizing a precise non-conservative force modeling. GOP works with a modified version of the Bernese GPS Software that has not supported non-conservative orbit modeling but utilized empirical and pseudo-stochastic orbit modeling. This limitation is now overcome by new scientific modification of the software, which opens the unique possibility to compare both approaches using the same software platform. The precise dynamic LEO orbit modeling includes the attitude models and the nominal satellite macro-models, with modeling of non-conservative acceleration, i.e., Sun radiation pressure, Earth radiation pressure and atmospheric drag. Both dynamic and reduced-dynamic approaches are used by different analysis centers providing DORIS solutions. The focus of this study is the analysis of the differences between these two approaches for LEO satellite orbit estimation and the verification of the nominal satellite attitude model quality, checked through the necessity of employing 1-per revolution empirical parameters. In addition, the impact of indirect and direct Earth radiation pressure models are assessed, including an analytical model as well as a latitude dependent and a latitude-longitude dependent model. All the presented studies are based on the comparison of estimated DORIS orbits with the multi-technique orbits estimated by other groups as well as on internal arc overlaps and orbit validation using SLR data. Not only orbits estimated with fixed network are analyzed but also the impact of the orbital models on the free-network solutions is investigated.

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

    Science.gov (United States)

    Parks, Lisa Ann

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

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

    OpenAIRE

    Young-Rok Kim; Sang-Young Park; Eun-Seo Park; Hyung-Chul Lim

    2012-01-01

    In this study, we present preliminary results of precise orbit determination (POD) using satellite laser ranging (SLR) observations for International Laser Ranging Service (ILRS) Associate Analysis Center (AAC). Using SLR normal point observations of LAGEOS-1, LAGEOS-2, ETALON-1, and ETALON-2, the NASA/GSFC GEODYN II software are utilized for POD. Weekly-based orbit determination strategy is applied to process SLR observations and the post-fit residuals check, and external orbit comparison ar...

  1. A systematic method of generating Galilean satellite-to-satellite transfers for Orbiter/Lander missions

    Science.gov (United States)

    Soldner, J. K.; Feingold, H.

    1981-01-01

    A Galilean satellite tour design strategy is presented which minimizes the approach velocities at the target satellites. A technique is developed such that once a Hohmann transfer is established between any two adjacent Galilean satellites, transfer trajectories to the remaining Galilean satellites can be derived in a systematic manner. A relationship between spacecraft orbital period and perijove radius is used to develop an algorithm which produces transfer trajectories by simply accounting for the satellites' angular position. The algorithm is incorporated into a FORTRAN code which demonstrates that a finite number of realizable trajectories exist in the specialized Galilean satellite tours due to resonance phasing. The basic assumption is made that the orbits of all the Galilean satellites are circular and coplanar.

  2. Synthetic Representation of the Motion of Co-orbitals of the Galilean Satellites

    Science.gov (United States)

    Scott, Bryan; Bills, Bruce

    2015-05-01

    Two of Saturn's satellites (Tethys and Dione) each have two co-orbital companions at their L4 and L5 triangular equilibrium points. This prompts us to ask: do any of Jupiter's Galilean satellites have co-orbitals? In our analysis, the motions of the Galilean satellites are specified by the model E5 of Lieske, truncated to include the dominant terms. This model includes the oblate figure of Jupiter, mutual perturbations between pairs of satellites, and perturbations from Saturn and the Sun. The initial positions and velocities of co-orbital test particles are specified by a rotation of the state vector of the Galilean satellite with which it shares an orbit, on a reference date, through a given angle, and the equations of motion are integrated. Integrations are carried out for 100,000 days, which is several hundred times the longest forcing period. A linearized stability analysis of motion about the L4 or L5 Lagrange points, of the circular restricted three body problem, predicts oscillations in angular separation at two main frequencies. In the six body problem that we consider here, these same frequencies appear, along with characteristic families of harmonics. Numerically integrated co-orbitals trajectories in the rotating frame exhibit the expected tadpole behavior. The Fourier amplitude spectrum of the numerically integrated angular separation between the co-orbital and its parent satellite exhibits two sets of characteristic features. The first set consists of the prominent lines in the spectrum of the variability in satellite mean motion. The second consists of the restricted three body predicted frequencies, and the families of related spectral lines which emerge for pertrubations in the restricted problem. Our integrations suggest that the motion of co-orbitals of the Galilean satellites is well approximated by this simple scheme.

  3. 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.

  4. About Tidal Evolution of Quasi-Periodic Orbits of Satellites

    Science.gov (United States)

    Ershkov, Sergey V.

    2017-06-01

    Tidal interactions between Planet and its satellites are known to be the main phenomena, which are determining the orbital evolution of the satellites. The modern ansatz in the theory of tidal dissipation in Saturn was developed previously by the international team of scientists from various countries in the field of celestial mechanics. Our applying to the theory of tidal dissipation concerns the investigating of the system of ODE-equations (ordinary differential equations) that govern the orbital evolution of the satellites; such an extremely non-linear system of 2 ordinary differential equations describes the mutual internal dynamics for the eccentricity of the orbit along with involving the semi-major axis of the proper satellite into such a monstrous equations. In our derivation, we have presented the elegant analytical solutions to the system above; so, the motivation of our ansatz is to transform the previously presented system of equations to the convenient form, in which the minimum of numerical calculations are required to obtain the final solutions. Preferably, it should be the analytical solutions; we have presented the solution as a set of quasi- periodic cycles via re-inversing of the proper ultra- elliptical integral. It means a quasi-periodic character of the evolution of the eccentricity, of the semi-major axis for the satellite orbit as well as of the quasi-periodic character of the tidal dissipation in the Planet.

  5. Relative Orbit Determination of Multiple Satellites Using Double Differenced Measurements

    Science.gov (United States)

    Geeraert, J. L.; McMahon, J. W.

    The location of operational space assets around the Earth is still of primary concern in the SSA community due to the ever increasing density of man-made objects and potential for collisions. In this paper we demonstrate using the double differenced measurements of time difference of arrival (TDOA) and frequency difference of arrival (FDOA) for relative orbit determination of multiple satellites. A close proximity two-spacecraft formation with bounded orbits is presented to demonstrate the TDOA and FDOA OD capabilities. Two scenarios are examined, the first is with the chief satellite assumed to have perfectly known state knowledge, and the second assumes some small uncertainty on the chief satellite. In the first scenario a square-root unscented Kalman filter is used to estimate the state of the deputy about the chief, and in the second scenario the deputy satellite is estimated while the uncertainty of the chief satellite is considered using the square-root unscented Schmidt-Kalman filter. The OD results are compared with conventional range and range-rate measurements and we find that, with three baselines or more, the TDOA and FDOA provides the lowest uncertainty OD solutions except for the case where the chief is in a GEO orbit. When only one baseline is used, the TDOA and FDOA measurements are favorable with lower orbits and a longer observation spans.

  6. Regional positioning using a low Earth orbit satellite constellation

    Science.gov (United States)

    Shtark, Tomer; Gurfil, Pini

    2018-02-01

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

  7. Centriolar satellites: busy orbits around the centrosome.

    Science.gov (United States)

    Bärenz, Felix; Mayilo, Dmytro; Gruss, Oliver J

    2011-12-01

    Since its first description by Theodor Boveri in 1888, the centrosome has been studied intensely, and it revealed detailed information about its structure, molecular composition and its various functions. The centrosome consists of two centrioles, which generally appear in electron microscopy as barrel-shaped structures usually composed of nine microtubule triplets. An amorphous mass of pericentriolar material surrounds the centrioles and accumulates many proteins important for the integrity and function of centrosomes, such as the γ-tubulin ring complex (γ-TuRC) that mediates microtubule nucleation and capping. In animal somatic cells, the centrosome generally accounts for the major microtubule organizing center, and the duplicated pair of centrosomes determines the poles of the microtubule-based mitotic spindle. Despite detailed insights into the centrosome's structure and function, it has been a complete mystery until a few years ago how centrosomes duplicate and assemble. Moreover, it is still largely unclear if and how centrosomal proteins or protein complexes are exchanged, replaced or qualitatively altered. Previously identified cytoplasmic granules, named "pericentriolar" or "centriolar satellites", might fulfil such functions in protein targeting and exchange, and communication between the centrosomes and the cytoplasm. In this review, we summarize current knowledge about the structure, molecular composition and possible roles of the satellites that seem to surround the core of the centrosome in most animal cells. Copyright © 2011 Elsevier GmbH. All rights reserved.

  8. NAVSPASUR orbital processing for satellite break-up events

    Science.gov (United States)

    Schumacher, Paul W., Jr.

    1991-01-01

    Satellite breakups via explosion or collision can instantly increase the trackable orbiting population by up to several hundred objects, temporarily perturbing the routine space surveillance operations at U.S. Space Command (USSPACWCOM) and the Naval Space Surveillance Center (NAVSPASUR). This paper is a survey of some of the procedures and techniques used by NAVSPASUR to respond to such events. First, the overall data flow at NAVSPASUR is described highlighting the places at which human analysts may intervene with special processing. So-called manual intervention is required in a variety of non-nominal situations, including breakups. Second, a description is given of some of the orbital analysis and other software tools available to NAVSPASUR analysts. These tools were developed in-house over the past thirty years and can be employed in a highly flexible manner. The basic design philosophy for these tools was to implement simple concepts as efficiently as possible and to allow the analyst maximum use of his personal expertise. Finally, several historical breakup scenarios are discussed briefly. These scenarios provide examples of the types of questions that are fairly easy to answer in the present operational environment, as well as examples of questions that are very difficult to answer.

  9. On temporal averaging of polar orbiting satellite data

    Science.gov (United States)

    Zheng, L.; Levy, G.

    1997-05-01

    The spatial and temporal sampling of polar-orbiting satellites results in errors in some level 3 data products of mean global fields. The problem has been identified in data from the Special Sensor Microwave Imager, Active Microwave Instrument, and the Microwave Sounding Unit and therefore is believed to be ubiquitous to many global data sets from polar-orbiting satellites. Zeng and Levy [1995] have shown that improper spatial smoothing of the monthly mean winds generated from scatterometer data may introduce unacceptable errors in monthly surface flux estimates. They have proposed an effective interpolating and filtering procedure for AMI data. We investigate the severity of the problem and discuss the adaptation of such a scheme to general satellite application.

  10. Comparison of the reduced dynamical orbit parametrization and precise non-conservative orbit force modeling for DORIS satellites

    Science.gov (United States)

    Stepanek, P.; Rodriguez-Solano, C.; Filler, V.; Hugentobler, U.

    2011-12-01

    The focus of the studies is the analysis of the comparison between two different approaches for LEO satellite orbit estimation employing DORIS measurements. The first one is the reduced-dynamical model, based on the orbit modeling by using the empirical and the pseudo-stochastic parameters. The second approach includes the attitude models and the CNES-developed satellite macromodels, with modeling of non-conservative acceleration, i.e., Sun radiation pressure, Earth radiation pressure and atmospheric drag. Both approaches are used at analysis centers providing DORIS solutions. The reduced-dynamical modeling is currently used by the GOP analysis center, which achieves similar accuracy of the free-network solutions as the other centers utilizing a precise non-conservative force modeling. The GOP works with a modified version of the Bernese GPS Software that has not included the non-conservative modeling. This limitation is now overcome by the new scientific modification of the software, which opens the unique possibility to compare both approaches by using the same software platform. We compare external and internal precision of the estimated orbits. We also analyze the individual satellite free-network DORIS solutions and time-series of derived parameters, i.e., station coordinates, TRF scale, the geocenter variations and the Earth rotation parameters. The studies highlight the main differences in the results that should answer the question whether the modeling of non-conservative forces including the CNES box-wing satellite models actually brings a significant improvement to the DORIS solutions.

  11. 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.

  12. 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

  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. Autonomous Orbit Determination for Lagrangian Navigation Satellite Based on Neural Network Based State Observer

    Directory of Open Access Journals (Sweden)

    Youtao Gao

    2017-01-01

    Full Text Available In order to improve the accuracy of the dynamical model used in the orbit determination of the Lagrangian navigation satellites, the nonlinear perturbations acting on Lagrangian navigation satellites are estimated by a neural network. A neural network based state observer is applied to autonomously determine the orbits of Lagrangian navigation satellites using only satellite-to-satellite range. This autonomous orbit determination method does not require linearizing the dynamical mode. There is no need to calculate the transition matrix. It is proved that three satellite-to-satellite ranges are needed using this method; therefore, the navigation constellation should include four Lagrangian navigation satellites at least. Four satellites orbiting on the collinear libration orbits are chosen to construct a constellation which is used to demonstrate the utility of this method. Simulation results illustrate that the stable error of autonomous orbit determination is about 10 m. The perturbation can be estimated by the neural network.

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

    DEFF Research Database (Denmark)

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

    2002-01-01

    Three geomagnetic satellite missions currently provide high precision magnetic field measurements from low altitude polar orbiting spacecraft. We demonstrate how these data can be used to determine the intensity and location of the horizontal currents that flow in the ionosphere, predominantly...... in the auroral electrojets. First, we examine the results during a recent geomagnetic storm. The currents derived from two satellites at different altitudes are in very good agreement, which verifies good stability of the method. Further, a very high degree of correlation (correlation coefficients of 0.......8-0.9) is observed between the amplitudes of the derived currents and the commonly used auroral electro-jet indices based on magnetic measurements at ground. This points to the potential of defining an auroral activity index based on the satellite observations, which could be useful for space weather monitoring...

  16. 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.

  17. Precise satellite orbit determination with particular application to ERS-1

    Science.gov (United States)

    Fernandes, Maria Joana Afonso Pereira

    The motivation behind this study is twofold. First to assess the accuracy of ERS-1 long arc ephemerides using state of the art models. Second, to develop improved methods for determining precise ERS-1 orbits using either short or long arc techniques. The SATAN programs, for the computation of satellite orbits using laser data were used. Several facilities were added to the original programs: the processing of PRARE range and altimeter data, and a number of algorithms that allow more flexible solutions by adjusting a number of additional parameters. The first part of this study, before the launch of ERS-1, was done with SEAS AT data. The accuracy of SEASAT orbits computed with PRARE simulated data has been determined. The effect of temporal distribution of tracking data along the arc and the extent to which altimetry can replace range data have been investigated. The second part starts with the computation of ERS-1 long arc solutions using laser data. Some aspects of modelling the two main forces affecting ERS-l's orbit are investigated. With regard to the gravitational forces, the adjustment of a set of geopotential coefficients has been considered. With respect to atmospheric drag, extensive research has been carried out on determining the influence on orbit accuracy of the measurements of solar fluxes (P10.7 indices) and geomagnetic activity (Kp indices) used by the atmospheric model in the computation of atmospheric density at satellite height. Two new short arc methods have been developed: the Constrained and the Bayesian method. Both methods are dynamic and consist of solving for the 6 osculating elements. Using different techniques, both methods overcome the problem of normal matrix ill- conditioning by constraining the solution. The accuracy and applicability of these methods are discussed and compared with the traditional non-dynamic TAR method.

  18. Robustness analysis method for orbit control

    Science.gov (United States)

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

    2017-08-01

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

  19. Weakly Accreting Circumplanetary Disks and Satellites in Resonant Orbits

    Science.gov (United States)

    Fujii, Yuri I.; Kobayashi, Hiroshi; Takahashi, Sanemichi Z.; Gressel, Oliver

    2017-10-01

    During the formation phase of gas giants, circumplanetary gaseous disks form around the planets. Circumplanetary disks are important not only for mass supply to gas giants but also for formation of regular satellites. The size-scale of circumplanetary disks is smaller than that of protoplanetary disks and this makes magnetic diffusion quicker. Thus, it is more difficult to sustain the magnetorotational instability (MRI) in circumplanetary disks. In the absence of significant angular momentum transport, continuous mass flow from the parental protoplanetary disk leads to the formation of a massive circumplanetary disk. We have developed an evolutionary disk model for this scenario and have estimated the orbital evolution of moons within the disk. In a certain temperature range, we find that inward migration of a satellite can be stopped by a disk structure resulting from the opacity transitions. We also find that the second and third migrating satellites can be captured in mean motion resonances. In this way, a compact system in Laplace resonance, which are similar to inner three bodies of Galilean satellites, can be formed in our disk models.

  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. The exterior tidal potential acting on a satellite. [satellite orbits/satellite perturbation - gravitation effects

    Science.gov (United States)

    Musen, P.

    1975-01-01

    A theory is presented that points out the existence of several long period and 'cross effects' in the coefficients in the expansion of the geopotential and in the motion of satellites. The tidal potential, defined as small periodic variations in the geopotential, was calculated. The influence of these geopotential variations on satellite perturbation is examined. Spherical harmonics were employed.

  2. The Photometric Brightness Variation of Geostationary Orbit Satellite

    Directory of Open Access Journals (Sweden)

    Haingja Seo

    2013-09-01

    Full Text Available Photometric observation is one of the most effective techniques for determining the physical characteristics of unknown space objects and space debris. In this research, we examine the change in brightness of the Communication, Ocean, Meteorological Satellite-1 (COMS-1 Geostationary Orbit Satellite (GEO, and compare it to our estimate model. First, we calculate the maximum brightness time using our calculation method and then derive the light curve shape using our rendering model. The maximum brightness is then calculated using the induced equation from Pogson's formula. For a comparison with our estimation, we carried out photometric observation using an optical telescope. The variation in brightness and the shape of the light curve are similar to the calculations achieved using our model, but the maximum brightness shows a slightly different value from our calculation result depending on the input parameters. This paper examines the photometric phenomenon of the variation in brightness of a GEO satellite, and the implementation of our approach to understanding the characteristics of space objects.

  3. 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.

  4. Orbit/launch vehicle tradeoff studies. Earth Observatory Satellite system definition study (EOS)

    Science.gov (United States)

    1974-01-01

    An evaluation of the Earth Observatory Satellite (EOS) design, performance, and cost factors which affect the choices of an orbit and a launch vehicle is presented. Primary emphasis is given to low altitude (300 to 900 nautical miles) land resources management applications for which payload design factors are defined. The subjects considered are: (1) a mission model, (2) orbit analysis and characterization, (3) characteristics and capabilities of candidate conventional launch vehicles, and space shuttle support. Recommendations are submitted for the EOS-A mission, the Single Multispectral Scanner payload, the Single Multispectral Scanner plus Thematic Mapper payload, the Dual Multispectral Scanner payload, and the Dual Multispectral Scanner plus Thematic Mapper payload.

  5. SAT-LAB: A MATLAB Graphical User Interface for simulating and visualizing Keplerian satellite orbits

    Science.gov (United States)

    Piretzidis, Dimitrios; Sideris, Michael G.

    2017-04-01

    SAT-LAB is a MATLAB-based Graphical User Interface (GUI), developed for simulating and visualizing satellite orbits. The primary purpose of SAT-LAB is to provide software with a user-friendly interface that can be used for both academic and scientific purposes. For the simulation of satellite orbits, a simple Keplerian propagator is used. The user can select the six Keplerian elements, and the simulation and visualization of the satellite orbit is performed simultaneously, in real time. The satellite orbit and the state vector, i.e., satellite position and velocity, at each epoch is given in the Inertial Reference Frame (IRF) and the Earth-Fixed Reference Frame (EFRF). For the EFRF, both the 3D Cartesian coordinates and the ground tracks of the orbit are provided. Other visualization options include selection of the appearance of the Earth's coastline and topography/bathymetry, the satellite orbit, position, velocity and radial distance, and the IRF and EFRF axes. SAT-LAB is also capable of predicting and visualizing orbits of operational satellites. The software provides the ability to download orbital elements and other information of operational satellites in the form of Two-Line Element sets. The user can choose among 41 satellite categories, including geodetic, communications, navigation, and weather satellites, as well as space debris from past satellite missions or collisions. Real-time tracking of the position of operational satellites is also available. All the capabilities of SAT-LAB software are demonstrated by providing simulation examples of geostationary, highly elliptical and near polar orbits. Also, visualization examples of operational satellite orbits, such as GNSS and LEO satellites, are given.

  6. GPM GROUND VALIDATION SATELLITE SIMULATED ORBITS C3VP V1

    Data.gov (United States)

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

  7. GPM GROUND VALIDATION SATELLITE SIMULATED ORBITS MC3E V1

    Data.gov (United States)

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

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

    Data.gov (United States)

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

  9. Software and hardware implements for tracking low earth orbit (LEO) satellites

    OpenAIRE

    Rahal, Wassila Leila; Banabadji, Noureddine; Belbachir, Ahmed Hafid

    2008-01-01

    International audience; In this paper, we present a novel, precise and efficient tracking system for Low Earth Orbit (LEO) Satellites. We have developed a software (LAAR-Track) and a hardware interface for orbit determination based on using orbital elements, which are given by the NORAD (North American Aerospace Defence). Orbital perturbations, such as the atmospheric drag, the influence of the moon and the sun and the geopotential field have been considered for satellites trajectory determin...

  10. Orbit determination of the Next-Generation Beidou satellites with Intersatellite link measurements and a priori orbit constraints

    Science.gov (United States)

    Ren, Xia; Yang, Yuanxi; Zhu, Jun; Xu, Tianhe

    2017-11-01

    Intersatellite Link (ISL) technology helps to realize the auto update of broadcast ephemeris and clock error parameters for Global Navigation Satellite System (GNSS). ISL constitutes an important approach with which to both improve the observation geometry and extend the tracking coverage of China's Beidou Navigation Satellite System (BDS). However, ISL-only orbit determination might lead to the constellation drift, rotation, and even lead to the divergence in orbit determination. Fortunately, predicted orbits with good precision can be used as a priori information with which to constrain the estimated satellite orbit parameters. Therefore, the precision of satellite autonomous orbit determination can be improved by consideration of a priori orbit information, and vice versa. However, the errors of rotation and translation in a priori orbit will remain in the ultimate result. This paper proposes a constrained precise orbit determination (POD) method for a sub-constellation of the new Beidou satellite constellation with only a few ISLs. The observation model of dual one-way measurements eliminating satellite clock errors is presented, and the orbit determination precision is analyzed with different data processing backgrounds. The conclusions are as follows. (1) With ISLs, the estimated parameters are strongly correlated, especially the positions and velocities of satellites. (2) The performance of determined BDS orbits will be improved by the constraints with more precise priori orbits. The POD precision is better than 45 m with a priori orbit constrain of 100 m precision (e.g., predicted orbits by telemetry tracking and control system), and is better than 6 m with precise priori orbit constraints of 10 m precision (e.g., predicted orbits by international GNSS monitoring & Assessment System (iGMAS)). (3) The POD precision is improved by additional ISLs. Constrained by a priori iGMAS orbits, the POD precision with two, three, and four ISLs is better than 6, 3, and 2

  11. In-orbit assessment of laser retro-reflector efficiency onboard high orbiting satellites

    Science.gov (United States)

    Wilkinson, Matthew; Appleby, Graham

    2011-08-01

    The navigation and geodetic satellites that orbit the Earth at altitudes of approximately 20,000 km are tracked routinely by many of the Satellite Laser Ranging (SLR) stations of the International Laser Ranging Service (ILRS). In order to meet increasing demands on SLR stations for daytime and nighttime observations, any new mission needs to ensure a strong return signal so that the target is easily acquirable. The ILRS has therefore set a minimum effective cross-section of 100 million square metres for the on-board laser retro-reflector arrays (LRAs) and further recommends the use of 'uncoated' cubes in the arrays. Given the large number of GNSS satellites that are currently supported by SLR, it is informative to make an assessment of the relative efficiencies of the various LRAs employed. This paper uses the laser ranging observations themselves to deduce and then compare the efficiencies of the LRAs on the COMPASS-M1 navigation satellite, two satellites from the GPS and three from the GLONASS constellations, the two GIOVE test satellites from the upcoming Galileo constellation, the two Etalon geodetic spheres and the geosynchronous communications test satellite, ETS-8. All the LRAs on this set of satellites employ back-coated retro-reflector cubes, except those on the COMPASS-M1 and ETS-8 vehicles which are uncoated. A measure of return signal strength, and thus of LRA-efficiency, is calculated using the laser-range full-rate data archive from 2007 to 2010, scaled to remove the effects of variations in satellite range, atmospheric attenuation and retro-reflector target total surface area. Observations from five SLR stations are used in this study; they are Herstmonceux (UK), Yarragadee (Australia), Monument Peak and McDonald (USA) and Wettzell (Germany). Careful consideration is given to the treatment of the observations from each station in order to take account of local working practices and system upgrades. The results show that the uncoated retro

  12. 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.

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

    Science.gov (United States)

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

    2017-12-01

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

  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. 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

  16. Combining Regional Monitoring Stations with Space-based Data to Determine the MEO Satellite Orbit

    Directory of Open Access Journals (Sweden)

    WANG Le

    2017-05-01

    Full Text Available The ground monitoring stations of BeiDou Navigation Satellite System (BDS are regional distribution and the number of these stations is small. The more global ground stations cannot be built in the short term. The ground regional monitoring stations are difficult to observe the global Medium Earth Orbit Satellite (MEO continuously, which leads to low precision of orbits in BDS real-time broadcast ephemeris. Based on the above problems, in view of real time satellite GNSS data of low earth orbit satellite can effectively make up the lack of regional monitoring stations in space overlay, a method is proposed that the GNSS receivers of LEO satellites used as high dynamic space-based monitoring stations combining with the data of the ground monitoring stations to calculate and forecast the MEO satellite orbits. The numeral results show that, using the data of seven regional monitoring stations add 1 to 3 LEO satellites, the precision of the MEO orbit determination can be increased by about 21%, 34% and 55% respectively. It also shows that, the ground regional monitoring stations combined with the data of LEO satellites can effectively improve the orbit precision of MEO satellite. It is suggested that using the data combined with ground stations and LEO satellites to improve the precision of broadcast ephemeris of MEO in BDS.

  17. Determination of the orbit of the CHAMP satellite based on the laser observations

    Science.gov (United States)

    Lejba, P.

    This work presents the results of orbit determination of the CHAMP satellite from observations of 14 the best SLR stations for year 2002 All computations were based on the Earth combined gravity field model EIGEN-CG01C Reigber et al 2005 In computations was taken the orbital programme GEODYN-II created and accesibled by NASA The got RMS value of the orbit of the CHAMP satellite is better than 30 cm The obtained results show that the orbit of the CHAMP satellite is highly perturbed by the Earth s gravity field and by the atmosphere of the Earth

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

    Science.gov (United States)

    1974-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Maru Park

    2015-12-01

    Full Text Available 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.

  20. Time Synchronization and Performance of BeiDou Satellite Clocks in Orbit

    Directory of Open Access Journals (Sweden)

    Han Chunhao

    2013-01-01

    Full Text Available The time model of Beidou satellite clocks is analyzed. The general relations of satellite clocks with the system time are studied. The error sources of two-way radio time transfer between satellites and uplink stations are analyzed. The uncertainty of type A is about 0.3 ns in Beidou system. All the satellite clocks in orbit of Beidou satellite navigation system are evaluated by the clock offsets observed by the two-way radio time transfer. The frequency stabilities at a sample time of 10000 s and 1 day for all the satellite clocks are better than . It means that the performance of Beidou satellite clocks in orbit is consistent with the ground test, and the results in orbit are a little better than those in ground vacuum.

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

    Directory of Open Access Journals (Sweden)

    Young-Rok Kim

    2012-09-01

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

  2. Satellite communications network design and analysis

    CERN Document Server

    Jo, Kenneth Y

    2011-01-01

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

  3. Energetic Electron Enhancements below the Radiation Belt and X-Ray Contamination at Low-Orbiting Satellites

    Directory of Open Access Journals (Sweden)

    Alla V. Suvorova

    2014-01-01

    Full Text Available 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.

  4. On the Use of Controlled Radiation Pressure to Send a Satellite to a Graveyard Orbit

    Science.gov (United States)

    Silva Neto, J. B.; Sanchez, D. M.; Prado, A. F. B. A.; Smirnov, G. V.

    2017-10-01

    A very important topic in modern astrodynamics is the removal of satellites from their orbits, after the end of their missions. In this work, we propose the use of the solar radiation pressure to change the orbital energy of a satellite, to remove it from the operational region to a graveyard orbit. A mechanism for changing the area-to-mass ratio of the satellite and/or its reflectivity coefficient is used to accomplish this task. We derive an analytical model to find the maximum eccentricity achieved during the removal trajectory, for different initial conditions for the argument of perigee and the longitude of the ascending node. After that, the best trajectories, i.e., trajectories with low eccentricity, are integrated using a numerical model. These low eccentricity trajectories are important because satellites with disposal orbits with low eccentricity pose a lower risk of crossing the operational region during the de-orbiting.

  5. MUSIC/FAST, A PRE-DESIGN AND PRE-MISSION ANALYSIS TOOL FOR THE EARTH ATMOSPHERIC RE-ENTRY OF SPACECRAFT, CAPSULES AND DE-ORBITED SATELLITES

    OpenAIRE

    Sourgen, Frédéric; Prévereaud, Ysolde; Vérant, Jean-Luc; LAROCHE, Emmanuel; Moschetta, Jean-Marc

    2015-01-01

    The paper proposes an overview of the physical models developed/selected and implemented in the ONERA aerothermodynamic (ATD) engineering code FAST. This tool is used to quickly determine the pressure and heat flux surface distribution at the wall, as well as aerodynamic forces and moments coefficients in hypersonic regime for free-molecular, transitional and continuum flows, for realistic designs of space vehicles ranging from capsules to spacecrafts and for generic shapes of orbital debris ...

  6. Electrodynamical compensation of disturbing torque and attitude stabilization of a satellite in J2 perturbed orbit

    Science.gov (United States)

    Tikhonov, A. A.; Antipov, K. A.; Korytnikov, D. G.; Nikitin, D. Yu.

    2017-12-01

    The paper deals with a satellite in a circular near-Earth orbit, perturbed due to J2 Earth's oblateness. The satellite interacts with the geomagnetic field by the moments of Lorentz and magnetic forces. The octupole approximation of the Earth's magnetic field is used. The possibility of electrodynamical attitude control for the satellite's stabilization in the orbital frame is analyzed. Once the problem of electrodynamical compensation of disturbing torque is solved, we can obtain the control algorithms for the satellite electromagnetic parameters which allows to stabilize the satellite attitude position in the orbital frame in the presence of disturbing gravity gradient torque. The total stability of the satellite programmed motion is proved analytically and verified by computer modeling.

  7. Reprocessing the Elliptical Orbiting Galileo Satellites E14 and E18: Preliminary Results

    Science.gov (United States)

    Männel, Benjamin

    2017-04-01

    In August 2014, the two Galileo satellites FOC-1 (E18) and FOC-2 (E14) were - due to a technical problem - launched into a wrong, elliptic orbit. In a recovery mission a series of orbit maneuvers were performed to raise the perigee to an altitude where both spacecrafts could be introduced to the Galileo navigation service. After this period of orbit maintenance both satellites started to transmit navigation signals at November 29, 2014 (E18) and March 17, 2015 (E14). However, as it was not possible to recover the nominal orbits due to propellant limitations, both spacecrafts orbit the Earth with a numerical eccentricity of 0.16 and an inclination of 50.2°. Very soon, it was assumed that both satellites could be highly useful for studies on general relativity, especially as the Galileo spacecrafts are equipped with very stable passive hydrogen masers. A prerequisite for dedicated studies in this field are highly accurate satellite orbits and clock corrections. Preliminary results for orbit and satellite clock determination will be presented based on an initial reprocessing over the past 2.5 years. The presentation focuses firstly on orbit modeling aspects with respect to the elliptically orbits. Secondly the derived clock corrections for the on-board passive clocks are assessed with respect to the reference clock at ground stations. The results will be discussed also with respect to the proposed Galileo-based studies on the gravitational redshift.

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

    Science.gov (United States)

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

    2018-01-01

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

  9. 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.

  10. Time Resolved Atmospheric Carbon Satellite Observations from Geostationary Orbit

    Science.gov (United States)

    Edwards, David; Worden, Helen

    This presentation describes proposed satellite carbon measurements from CHRONOS (Commercially Hosted spectroRadiometer Observations and New Opportunities for Science). The primary goal of this mission is to measure the atmospheric pollutants carbon monoxide (CO) and methane (CH4) from geostationary orbit, with hourly observations of North America at high spatial resolution. Carbon monoxide is produced by combustion processes such as urban activity and wildfires, and serves as a proxy for other combustion pollutants that are not easily measured. Both CO and CH4 are chemical precursors of tropospheric ozone pollution. Methane has diverse anthropogenic sources ranging from fossil fuel production, animal husbandry, agriculture and waste management. The impact of gas exploration in the Western States of the USA and oil extraction from the Canadian tar sands will be particular foci of the mission, as will the poorly-quantified natural CH4 emissions from wetlands and thawing permafrost. In addition to characterizing pollutant sources, improved understanding of the domestic CH4 budget is a priority for policy decisions related to short-lived climate forcers. A primary motivation for targeting CO is its value as a tracer of atmospheric pollution. The CHRONOS measurements will provide insight into local and long-range transport across the North American continent, as well as the processes governing the entrainment and venting of pollution in and out of the planetary boundary layer. As a result of significantly improved characterization of diurnal changes in atmospheric composition, CHRONOS observations will find direct societal applications for air quality regulation and forecasting. We present a quantification of this expected improvement in the prediction of near-surface concentrations when CHRONOS measurements are used in Observation System Simulation Experiments (OSSEs). If CHRONOS and the planned NASA Earth Venture TEMPO (Tropospheric Emissions: Monitoring of Pollution

  11. Analysis of multiple access techniques in multi-satellite and multi-spot mobile satellite systems

    Science.gov (United States)

    Corazza, Giovanni E.; Ferrarelli, Carlo; Vatalaro, Francesco

    1995-01-01

    In this paper the analysis of mobile satellite systems adopting constellations of multi-spot satellites over non-geostationary orbits is addressed. A link design procedure is outlined, taking into account system spectrum efficiency, probability of bit error and outage probability. A semi-analytic approach to the evaluation of outage probability in the presence of fading and imperfect power control is described, and applied to single channel per carrier (SCPC) and code division multiple access (CDMA) techniques. Some results are shown for the Globalstar, Iridium and Odyssey orbital configurations.

  12. Development of Integrated Orbit and Attitude Software-in-the-loop Simulator for Satellite Formation Flying

    Directory of Open Access Journals (Sweden)

    Han-Earl Park

    2013-03-01

    Full Text Available An integrated orbit and attitude control algorithm for satellite formation flying was developed, and an integrated orbit and attitude software-in-the-loop (SIL simulator was also developed to test and verify the integrated control algorithm. The integrated algorithm includes state-dependent Riccati equation (SDRE control algorithm and PD feedback control algorithm as orbit and attitude controller respectively and configures the two algorithms with an integrating effect. The integrated SIL simulator largely comprises an orbit SIL simulator for orbit determination and control, and attitude SIL simulator for attitude determination and control. The two SIL simulators were designed considering the performance and characteristics of related hardware-in-the-loop (HIL simulators and were combined into the integrated SIL simulator. To verify the developed integrated SIL simulator with the integrated control algorithm, an orbit simulation and integrated orbit and attitude simulation were performed for a formation reconfiguration scenario using the orbit SIL simulator and the integrated SIL simulator, respectively. Then, the two simulation results were compared and analyzed with each other. As a result, the user satellite in both simulations achieved successful formation reconfiguration, and the results of the integrated simulation were closer to those of actual satellite than the orbit simulation. The integrated orbit and attitude control algorithm verified in this study enables us to perform more realistic orbit control for satellite formation flying. In addition, the integrated orbit and attitude SIL simulator is able to provide the environment of easy test and verification not only for the existing diverse orbit or attitude control algorithms but also for integrated orbit and attitude control algorithms.

  13. Global Navigation Satellite System (GNSS) Final Orbit/Reference Frame Product Summary from NASA CDDIS

    Data.gov (United States)

    National Aeronautics and Space Administration — This derived product set consists of Global Navigation Satellite System Final Orbit/Reference Frame Product Summary from the NASA Crustal Dynamics Data Information...

  14. Global Navigation Satellite System (GNSS) Rapid Orbit/Clock/ERP Product Summary from NASA CDDIS

    Data.gov (United States)

    National Aeronautics and Space Administration — This derived product set consists of Global Navigation Satellite System Rapid Orbit/Reference Frame Product Summary from the NASA Crustal Dynamics Data Information...

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

    National Research Council Canada - National Science Library

    McConnell, Michael L

    2005-01-01

    ...) and Air Force Space Command (AFSPC) are looking to developing programs to provide an on-orbit servicing capability for future satellite systems under development, such as the Space-Based Radar (SBR) system...

  16. High precision and convenient extension simulation platform for satellite attitude and orbit system

    Science.gov (United States)

    Cui, Hongzheng; Han, Chao; Chen, Pei; Luo, Qinqin

    2012-01-01

    In this paper, a high precision and convenient extension simulation platform for satellite attitude and orbit system is developed, to demonstrate the satellite attitude and orbit system for given space mission, and test the new underdeveloped algorithms for attitude/orbit dynamics, attitude determination, orbit navigation, and attitude/orbit control. The simulation platform is based on Matlab/Simulink software, using the technique of Simulink modeling, importing C/Fortran code in Matlab/Simulink, and embedded Matlab function, with beautiful reusability, inheritability and expansibility. The paper orderly presents the background behind the development of the platform, the platform design architecture and capability, the validity of the platform, the inheritability and expansibility of the platform, the platform implementation example for Chinese weather satellite (FY-3), and the future development for the platform.

  17. 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

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. GPM GROUND VALIDATION SATELLITE SIMULATED ORBITS LPVEX V1

    Data.gov (United States)

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

  3. Stable Satellite Orbits for Global Coverage of the Moon

    Science.gov (United States)

    Ely, Todd; Lieb, Erica

    2006-01-01

    A document proposes a constellation of spacecraft to be placed in orbit around the Moon to provide navigation and communication services with global coverage required for exploration of the Moon. There would be six spacecraft in inclined elliptical orbits: three in each of two orthogonal orbital planes, suggestive of a linked-chain configuration. The orbits have been chosen to (1) provide 99.999-percent global coverage for ten years and (2) to be stable under perturbation by Earth gravitation and solar-radiation pressure, so that no deterministic firing of thrusters would be needed to maintain the orbits. However, a minor amount of orbit control might be needed to correct for such unmodeled effects as outgassing of the spacecraft.

  4. CDDIS_DORIS_products_orbit

    Data.gov (United States)

    National Aeronautics and Space Administration — Precise satellite orbits derived from analysis of Doppler Orbitography by Radiopositioning Integrated on Satellite (DORIS) data. These products are the generated by...

  5. International Network of Passive Correlation Ranging for Orbit Determination of a Geostationary Satellite

    Science.gov (United States)

    Kaliuzhnyi, Mykola; Bushuev, Felix; Shulga, Oleksandr; Sybiryakova, Yevgeniya; Shakun, Leonid; Bezrukovs, Vladislavs; Moskalenko, Sergiy; Kulishenko, Vladislav; Malynovskyi, Yevgen

    2016-12-01

    An international network of passive correlation ranging of a geostationary telecommunication satellite is considered in the article. The network is developed by the RI "MAO". The network consists of five spatially separated stations of synchronized reception of DVB-S signals of digital satellite TV. The stations are located in Ukraine and Latvia. The time difference of arrival (TDOA) on the network stations of the DVB-S signals, radiated by the satellite, is a measured parameter. The results of TDOA estimation obtained by the network in May-August 2016 are presented in the article. Orbital parameters of the tracked satellite are determined using measured values of the TDOA and two models of satellite motion: the analytical model SGP4/SDP4 and the model of numerical integration of the equations of satellite motion. Both models are realized using the free low-level space dynamics library OREKIT (ORbit Extrapolation KIT).

  6. 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

  7. 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

  8. Development of a surface isolation estimation technique suitable for application of polar orbiting satellite data

    Science.gov (United States)

    Davis, P. A.; Penn, L. M. (Principal Investigator)

    1981-01-01

    A technique is developed for the estimation of total daily insolation on the basis of data derivable from operational polar-orbiting satellites. Although surface insolation and meteorological observations are used in the development, the algorithm is constrained in application by the infrequent daytime polar-orbiter coverage.

  9. Orbit IMU alignment: Error analysis

    Science.gov (United States)

    Corson, R. W.

    1980-01-01

    A comprehensive accuracy analysis of orbit inertial measurement unit (IMU) alignments using the shuttle star trackers was completed and the results are presented. Monte Carlo techniques were used in a computer simulation of the IMU alignment hardware and software systems to: (1) determine the expected Space Transportation System 1 Flight (STS-1) manual mode IMU alignment accuracy; (2) investigate the accuracy of alignments in later shuttle flights when the automatic mode of star acquisition may be used; and (3) verify that an analytical model previously used for estimating the alignment error is a valid model. The analysis results do not differ significantly from expectations. The standard deviation in the IMU alignment error for STS-1 alignments was determined to the 68 arc seconds per axis. This corresponds to a 99.7% probability that the magnitude of the total alignment error is less than 258 arc seconds.

  10. 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 ...

  11. A dynamics and control algorithm for low Earth orbit precision formation flying satellites

    Science.gov (United States)

    Eyer, Jesse Koovik

    An innovative dynamics and control algorithm is developed for a dual-nanosatellite formation flying mission. The principal function of this algorithm is to use regular GPS state measurements to determine the controlled satellite's tracking error from a set of reference trajectories in the local-vertical/local-horizontal reference frame. A linear state-feedback control law---designed using a linear quadratic regulator method---calculates the optimal thrusts necessary to correct this error and communicates the thrust directions to the attitude control system and the thrust durations to the propulsion system. The control system is developed to minimize the conflicting metrics of tracking error and DeltaV requirements. To reconfigure the formation, an optimization algorithm is designed using the analytical solution to the state-space equation and the Hill-Clohessy-Wiltshire state transition matrix to solve for dual-thrust reconfiguration maneuvers. The resulting trajectories require low DeltaV, use finite-time thrusts and are accurate in a fully nonlinear orbital environment. This algorithm will be used to control the CanX-4&5 formation flying demonstration mission. In addition, an iterative method which numerically generates quasi periodic trajectories for a satellite formation is presented. This novel technique utilizes a shooting approach to the Newton method to close the relative deputy trajectory over a specific number of orbits, then fits the actual perturbed motion of the deputy with a Fourier series to enforce periodicity. This process is applied to two well-known satellite formations: a projected circular orbit and a J2-invariant formation. Compared to conventional formations, these resulting quasi-periodic trajectories require a dramatically lower control effort to maintain and could therefore be used to extend DeltaV-limited formation flying missions. Finally, an analytical study of the stability of the formation flying algorithm is conducted. To facilitate

  12. 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......, 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......, and that the longitude of the satellite position is significant to the model output. The results also show that the calculated albedo is generally lower than it would be expected based only on the reflectivity data....

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

    Science.gov (United States)

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

    2017-06-12

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

  14. 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

    2017-11-01

    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.

  15. 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.

  16. 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.

  17. ORAN- ORBITAL AND GEODETIC PARAMETER ESTIMATION ERROR ANALYSIS

    Science.gov (United States)

    Putney, B.

    1994-01-01

    The Orbital and Geodetic Parameter Estimation Error Analysis program, ORAN, was developed as a Bayesian least squares simulation program for orbital trajectories. ORAN does not process data, but is intended to compute the accuracy of the results of a data reduction, if measurements of a given accuracy are available and are processed by a minimum variance data reduction program. Actual data may be used to provide the time when a given measurement was available and the estimated noise on that measurement. ORAN is designed to consider a data reduction process in which a number of satellite data periods are reduced simultaneously. If there is more than one satellite in a data period, satellite-to-satellite tracking may be analyzed. The least squares estimator in most orbital determination programs assumes that measurements can be modeled by a nonlinear regression equation containing a function of parameters to be estimated and parameters which are assumed to be constant. The partitioning of parameters into those to be estimated (adjusted) and those assumed to be known (unadjusted) is somewhat arbitrary. For any particular problem, the data will be insufficient to adjust all parameters subject to uncertainty, and some reasonable subset of these parameters is selected for estimation. The final errors in the adjusted parameters may be decomposed into a component due to measurement noise and a component due to errors in the assumed values of the unadjusted parameters. Error statistics associated with the first component are generally evaluated in an orbital determination program. ORAN is used to simulate the orbital determination processing and to compute error statistics associated with the second component. Satellite observations may be simulated with desired noise levels given in many forms including range and range rate, altimeter height, right ascension and declination, direction cosines, X and Y angles, azimuth and elevation, and satellite-to-satellite range and

  18. Simple and Small De-orbiting Package for Nano-Satellites Using an Inflatable Balloon

    Science.gov (United States)

    Nakasuka, Shinichi; Senda, Kei; Watanabe, Akihito; Yajima, Takashi; Sahara, Hironori

    The paper proposes a de-orbiting system using inflatable balloon especially dedicated for nano-satellites. The system consists of a balloon of laminated aluminum film, gas supply system and electronics system which inflates the balloon when a certain signal comes from the satellite at the end of its life time. The balloon, once deployed, keeps its shape even after the gas expires. The package can be very small, low-cost and requires very little power for activation, which makes this system very attractive especially for university education satellites for which the satellite weight/size as well as cost are major concern. The BBM system has been developed and several ground experiments have been performed including deployment in vacuum environment and thermal cycle tests. We recognized that this system concept is viable and very promising as a de-orbiting system in the future when the satellite is ordered to have some method to avoid becoming space debris.

  19. A KAM Tori Algorithm for Earth Satellite Orbits

    Science.gov (United States)

    Wiesel, William E.

    2017-12-01

    This paper offers a new approach for constructing Kolmogorov - Arnold - Moser (KAM) tori for orbits in the full potential for a non-spherical planet. The Hamilton - Jacobi equation is solved numerically by a Newton-Rhapson iteration, achieving convergence to machine precision, and still retaining literal variable dependence. Similar iteration methods allow correcting the orbital frequencies, and permit the calculation of the state transition matrix for the full problem. Some initial numerical examples are offered.

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

    DEFF Research Database (Denmark)

    Stockmann, Reto; Christiansen, Freddy; Olsen, Nils

    2015-01-01

    We present an attempt to improve the quality of the geomagnetic field measurements from the Polar Orbiting Geophysical Observatory (POGO) satellite missions in the late 1960s. Inaccurate satellite positions are believed to be a major source of errors for using the magnetic observations for field...... modelling. To improve the data, we use aniterative approach consisting of two main parts: one is a main field modelling process to obtain the radial fieldgradient to perturb the orbits and the other is the state-of-the-art GPS orbit modelling software BERNESE to calculatenew physical orbits. We report...... 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...

  1. CDDIS_GNSS_products_orbit_ultrarapid

    Data.gov (United States)

    National Aeronautics and Space Administration — Precise satellite orbits derived from analysis of Global Navigation Satellite System (GNSS) data. Analysis Centers (ACs) of the International GNSS Service (IGS)...

  2. CDDIS_GNSS_products_orbit_rapid

    Data.gov (United States)

    National Aeronautics and Space Administration — Precise satellite orbits derived from analysis of Global Navigation Satellite System (GNSS) data. Analysis Centers (ACs) of the International GNSS Service (IGS)...

  3. CDDIS_GNSS_products_orbit_final

    Data.gov (United States)

    National Aeronautics and Space Administration — Precise satellite orbits derived from analysis of Global Navigation Satellite System (GNSS) data. Analysis Centers (ACs) of the International GNSS Service (IGS)...

  4. CDDIS_GNSS_products_orbit_realtime

    Data.gov (United States)

    National Aeronautics and Space Administration — Precise satellite orbits derived from analysis of Global Navigation Satellite System (GNSS) data. Analysis Centers (ACs) of the International GNSS Service (IGS)...

  5. Non-numeric computation for high eccentricity orbits. [Earth satellite orbit perturbation

    Science.gov (United States)

    Sridharan, R.; Renard, M. L.

    1975-01-01

    Geocentric orbits of large eccentricity (e = 0.9 to 0.95) are significantly perturbed in cislunar space by the sun and moon. The time-history of the height of perigee, subsequent to launch, is particularly critical. The determination of 'launch windows' is mostly concerned with preventing the height of perigee from falling below its low initial value before the mission lifetime has elapsed. Between the extremes of high accuracy digital integration of the equations of motion and of using an approximate, but very fast, stability criteria method, this paper is concerned with the developement of a method of intermediate complexity using non-numeric computation. The computer is used as the theory generator to generalize Lidov's theory using six osculating elements. Symbolic integration is completely automatized and the output is a set of condensed formulae well suited for repeated applications in launch window analysis. Examples of applications are given.

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

    Directory of Open Access Journals (Sweden)

    Vivian M. Gomes

    2012-01-01

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

  7. Swarm Satellite Antenna Phase Center Correction and Its Influence on the Precision Orbit Determination

    Directory of Open Access Journals (Sweden)

    TIAN Yingguo

    2016-12-01

    Full Text Available Receiver antenna phase center bias is a source of error must be considered in precise orbit determination using GPS. And PCV generally need multi-day observations data for joint estimation, so the estimation methods and its efficiency are particularly important. For the traditional PCV estimation method imperfect, such as the low computational efficiency, need to store days of normal equations and a priori information, this paper proposes an improved PCV synthesis method. By recursive way, the method doesn't need to store multi-day normal equations and the priori information about orbit, provide timely information PCV, then improve the efficiency of obtaining the PCV value, and provides a new way to achieve the Swarm satellite PCV solution. By the Swarm satellite precise orbit determination (POD, the result shows that the rapid PCV synthesis method can improve the efficiency of PCV synthesis, reducing the need for storage space. By comparing with external precision orbit, the result show that after the PCV correction, radial, tangential and normal precision of Swarm satellite orbit is improved, especially the normal precision most obviously, the average of about 23.3 mm; after the PCV correction, Swarm satellite orbit precision of all directions was superior to 2 cm.

  8. Monitoring of the Orbital Position of a Geostationary Satellite by the Spatially Separated Reception of Signals of Digital Satellite Television

    Directory of Open Access Journals (Sweden)

    Kaliuzny, M.P.

    2017-01-01

    Full Text Available 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 ±2.6m and ±35m respectively. Software implementation of the numerical model is taken from the free space dynamics library OREKIT.

  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. Early Mission Orbit Determination Error Analysis Results for Low-Earth Orbiting Missions using TDRSS Differenced One-way Doppler Tracking Data

    Science.gov (United States)

    Marr, Greg C.

    2003-01-01

    Differencing multiple, simultaneous Tracking and Data Relay Satellite System (TDRSS) one-way Doppler passes can yield metric tracking data usable for orbit determination for (low-cost) spacecraft which do not have TDRSS transponders or local oscillators stable enough to allow the one-way TDRSS Doppler tracking data to be used for early mission orbit determination. Orbit determination error analysis results are provided for low Earth orbiting spacecraft for various early mission tracking scenarios.

  11. Economic analysis requirements in support of orbital debris regulatory policy

    Science.gov (United States)

    Greenberg, Joel S.

    1996-10-01

    As the number of Earth orbiting objects increases so does the potential for generating orbital debris with the consequent increase in the likelihood of impacting and damaging operating satellites. Various debris remediation approaches are being considered that encompass both in-orbit and return-to-Earth schema and have varying degrees of operations, cost, international competitiveness, and safety implications. Because of the diversity of issues, concerns and long-term impacts, there is a clear need for the setting of government policies that will lead to an orderly abatement of the potential orbital debris hazards. These policies may require the establishment of a supportive regulatory regime. The Department of Transportation is likely to have regulatory responsibilities relating to orbital debris stemming from its charge to protect the public health and safety, safety of property, and national security interests and foreign policy interests of the United States. This paper describes DOT's potential regulatory role relating to orbital debris remediation, the myriad of issues concerning the need for establishing government policies relating to orbital debris remediation and their regulatory implications, the proposed technological solutions and their economic and safety implications. Particular emphasis is placed upon addressing cost-effectiveness and economic analyses as they relate to economic impact analysis in support of regulatory impact analysis.

  12. 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

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

    Czech Academy of Sciences Publication Activity Database

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

    2013-01-01

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

  14. Low earth orbit satellite (LEOsat) for information exchange and ...

    African Journals Online (AJOL)

    The functions of the communication networks were to facilitate disaster management, humanitarian relief, distance education and training, health care delivery, governance; and to over-come geographic isolation and reliance on obsolete communication systems. The POSAT satellite was equipp-ed with facility for ...

  15. Orbit determination of the Sentinel satellites - preparations for GPS L2C-tracking

    Science.gov (United States)

    Peter, Heike; Fernández, Jaime; Fernández, Carlos; Féménias, Pierre

    2017-04-01

    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. Since April 2014 four Sentinel satellites have been launched (1A, 2A, 3A, and 1B). Sentinel-2B is expected to be launched in March 2017. Thus the CPOD Service will be operating five satellites simultaneously in spring 2017. 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 are additionally equipped with a laser retro reflector for Satellite Laser Ranging and a receiver for DORIS tracking. This allows an additional external validation of the Sentinel-3 orbit accuracy. 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. The main quality control of the CPOD orbits is done by validating them with independent orbit solutions provided by the Copernicus POD Quality Working Group. The cross-comparison of orbit solutions from different institutions is essential to monitor and to improve the orbit accuracy. The GPS receivers on the B-satellites have the capability to track L2C signal. The option is, however, not yet activated, because if enabled the old L2 signal can no longer be tracked by the receiver. The measurements of many old GPS IIA and IIR satellites would have to be discarded because of the missing second frequency. To be prepared for the future, tests and simulations are foreseen to learn about the impact of the new observable on the POD results. This paper

  16. 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…

  17. Accretion of satellites onto central galaxies in clusters: merger mass ratios and orbital parameters

    Science.gov (United States)

    Nipoti, Carlo; Giocoli, Carlo; Despali, Giulia

    2018-02-01

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

  18. 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.

  19. Determination of GNSS satellite transmit power and impact on orbit determination

    Science.gov (United States)

    Steigenberger, Peter; Thölert, Steffen; Montenbruck, Oliver

    2017-04-01

    Precise orbit determination of GNSS satellites requires a best possible modeling of forces acting on the satellite. Antenna thrust is a small acceleration caused by the transmission of navigation signals of a GNSS satellite. It depends on the mass of the satellite and the total power of the transmitted signals and results in a mainly radial force changing the orbital radius by up to 2 cm. Within the International GNSS Service (IGS), antenna thrust is currently only considered for GPS and GLONASS. Transmit power levels for the different types of GPS satellites are based on the minimum received power near the Earth's surface as specified in the GPS interface control document. Empirical scaling factors take into account deviations from observed power levels resulting in IGS model values between 76 and 249 W. For GLONASS, a transmit power of 100 W is assumed. However, antenna thrust is currently ignored within the IGS for the emerging navigation systems Galileo, BeiDou, and QZSS due to unknown transmit power levels. The effective isotropically radiated power (EIRP) of a GNSS satellite can be measured with a high gain antenna. Based on the gain pattern of the satellite antenna, the transmit power can be obtained. EIRP measurements were gathered with a 30 m high gain antenna operated by Deutsches Zentrum für Luft- und Raumfahrt (German Aerospace Center, DLR) at its ground station in Weilheim (Germany). In this presentation, we discuss the measurement setup and present the transmit power estimates for GPS, GLONASS, Galileo, and BeiDou satellites in the L1, L2, L5/E5 and E6 frequency bands. Differences of the various satellite types as well as the scatter of the individual satellites within one type are analyzed. The GPS results are compared to the values of the current IGS model. Finally, the impact of taking into account antenna thrust based on the estimated transmit power on precise orbit determination is assessed.

  20. 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.

  1. Asymptotic stability of a satellite with electrodynamic attitude control in the orbital frame

    Science.gov (United States)

    Aleksandrov, A. Yu.; Tikhonov, A. A.

    2017-10-01

    A satellite in a circular near-Earth orbit is under consideration. The three-axis stabilization of the satellite in the orbital coordinate system with the use of electrodynamic attitude control system is studied. No constraints are imposed on the Earth's magnetic field approximation. The gravity gradient disturbing torque acting on the satellite attitude dynamics is taken into account as the largest disturbing torque. With the use of the Lyapunov direct method, conditions under which electrodynamic control solves the problem are obtained. The restrictions on the control parameter values for which one can guarantee the asymptotic stability of the programmed satellite motion are found and represented in an explicit form. Comparison of the results of numerical simulation and analytical investigation demonstrate effectiveness of the proposed approach.

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

    Directory of Open Access Journals (Sweden)

    Hyungjik Oh

    2016-03-01

    Full Text Available 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.

  3. 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.

  4. The family of Quasi-satellite periodic orbits in the co-planar RTBP

    Science.gov (United States)

    Pousse, Alexandre; Robutel, Philippe; Vienne, Alain

    2015-05-01

    In the framework of the Restricted Three-body Problem (RTBP), we consider a primary whose mass is equal to one, a secondary on circular or eccentric motion with a mass ɛ and a massless third body. The three bodies are in coplanar motion and in co-orbital resonance.We actually know three classes of regular co-orbital motions: in rotating frame with the secondary, the tadpole orbits (TP) librate around Lagrangian equilibria L4 or L5 the horseshoe orbits (HS) encompass the three equilibrium points L3, L4 and L5 the quasi-satellite orbits (QS) are remote retrograde satellite around the secondary, but outside of its Hill sphere.Contrarily to TP orbits which emerge from a fixed point in rotating frame, QS orbits emanate from a one-parameter family of periodic orbits, denoted family-f by Henon (1969). In the averaged problem, this family can be understood as a family of fixed points. However, the eccentricity of these orbits can reach high values. Consequently a development in eccentricity will not be efficient.Using the method developed by Nesvorný et al. (2002) which is valid for every values of eccentricity, we study the QS periodic orbits family with a numerical averaging.In the circular case, I will present the validity domain of the average approximation and a particular orbit. Then, I will highlight an unexpected result for very high eccentricity on families of periodic orbits that originate from L3, L4 and L5. Finally, I will sketch out an analytic method adapted to QS motion and exhibit associated results in the eccentric case.

  5. Attitude guidance and control of the navigation satellites at passage of singular orbit sites

    Science.gov (United States)

    Fateev, Alexey; Vassilyev, Alexander; Somov, Sergey

    2017-01-01

    The solar-terrestrial reference frame is applied during a navigation satellite flight using onboard measured units of directions on the Sun and Earth, which are beginning in the satellite (Object) mass center. The angle between these units traditionally is named as the angle SOE (Sun - Object - Earth). We consider problems of attitude guidance and control at the spacecraft operation on specific parts of the orbit (singular orbit sites) at following values of the SOE angles — close to 0 deg (small SOE angles) and close to 180 deg (large SOE angles) with a view to minimizing the impact of solar pressure forces on the SC mass center motion.

  6. On-orbit low gravity cryogenic scientific investigations using the COLD-SAT Satellite

    Science.gov (United States)

    Bailey, W. J.

    1990-01-01

    The Cryogenic On-Orbit Liquid Depot Storage, Acquisition and Transfer (COLD-SAT) Satellite is an experimental spacecraft designed to investigate the systems and technologies required for an efficient, effective, and reliable management of cryogenic fluids in reduced-gravity space environment. This paper defines the technology needs and the accompanying experimental three-month baseline mission of the COLD-SAT Satellite; describes the experiment subsystems, major features, and rationale for satisfying primary and secondary experimental requirements, using LH2 as the test fluid; and presents the conceptual design of the COLD-SAT spacecraft subsystems which support the on-orbit experiment.

  7. The Use of X-Ray Pulsars for Aiding GPS Satellite Orbit Determination

    Science.gov (United States)

    2005-03-01

    called “ recycled ” pulsars , are extremely old pulsars (1 - 14 Gyr4) whose spin rates have been rejuvenated from the accretion of mass and angular momentum...THE USE OF X-RAY PULSARS FOR AIDING GPS SATELLITE ORBIT DETERMINATION THESIS Dennis W. Woodfork, II Captain, USAF AFIT/GA/ENG/05-01 DEPARTMENT OF THE...Department of Defense, or the United States Government. AFIT/GA/ENG/05-01 THE USE OF X-RAY PULSARS FOR AIDING GPS SATELLITE ORBIT DETERMINATION THESIS

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

    Directory of Open Access Journals (Sweden)

    Jarbas Cordeiro Sampaio

    2012-01-01

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

  9. Thermosphere Density Variability, Drag Coefficients, and Precision Satellite Orbits

    Science.gov (United States)

    2013-07-29

    Journal of Spacecraft and Rockets, 44 (6), 1220- 1225, 2007. Vallado, D. A., Fundamentals of Astrodynamics and Applications , Chap. 8, App. B, Microcosm...Nov 1998. 4. TITLE. Enter title and subtitle with volume number and part number, if applicable . On classified documents, enter the title...in space? How do these changes affect the motion of satellites? These are some of the fundamental questions that this research will address. 2

  10. Building large telescopes in orbit using small satellites

    Science.gov (United States)

    Saunders, Chris; Lobb, Dan; Sweeting, Martin; Gao, Yang

    2017-12-01

    In many types of space mission there is a constant desire for larger and larger instrument apertures, primarily for the purposes of increased resolution or sensitivity. In the Radio Frequency domain, this is currently addressed by antennas that unfold or deploy on-orbit. However, in the optical and infrared domains, this is a significantly more challenging problem, and has up to now either been addressed by simply having large monolithic mirrors (which are fundamentally limited by the volume and mass lifting capacity of any launch vehicle) or by complex 'semi-folding' designs such as the James Webb Space Telescope. An alternative is to consider a fractionated instrument which is launched as a collection of individual smaller elements which are then assembled (or self-assemble) once in space, to form a much larger overall instrument. SSTL has been performing early concept assessment work on such systems for high resolution science observations from high orbits (potentially also for persistent surveillance of Earth). A point design of a 25 m sparse aperture (annular ring) telescope is presented. Key characteristics of 1) multiple small elements launched separately and 2) on-orbit assembly to form a larger instrument are included in the architecture. However, on-orbit assembly brings its own challenges in terms of guidance navigation and control, robotics, docking mechanisms, system control and data handling, optical alignment and stability, and many other elements. The number and type of launchers used, and the technologies and systems used heavily affect the outcome and general cost of the telescope. The paper describes one of the fractionated architecture concepts currently being studied by SSTL, including the key technologies and operational concepts that may be possible in the future.

  11. Coorbital motion in the co-planar RTBP: family of Quasi-satellite periodic orbits

    Science.gov (United States)

    Pousse, A.; Robutel, P.; Vienne, A.

    2015-10-01

    In the framework of the Restricted Three-body Problem (RTBP), we consider a primary whose mass is equal to one, a secondary on circular or eccentric motion with a mass # and a massless third body. The three bodies are in coplanar motion and in co-orbital resonance. We actually know three classes of regular coorbital motions: in rotating frame with the secondary, the tadpole orbits (TP) librate around Lagrangian equilibria L4 or L5; the horseshoe orbits (HS) encompass the three equilibrium points L3, L4 and L5; the quasi-satellite orbits (QS) are remote retrograde satellite around the secondary, but outside of its Hill sphere. Contrarily to TP orbits which emerge from a fixed point in rotating frame, QS orbits emanate from a oneparameter family of periodic orbits, denoted family-f by Henon (1969). In the averaged problem, this family can be understood as a family of fixed points. However, the eccentricity of these orbits can reach high values. Consequently a development in eccentricity will not be efficient. Using the method developed by Nesvorny et al. (2002) which is valid for every values of eccentricity, we study the QS periodic orbits family with a numerical averaging. In the circular case, I will present the validity domain of the average approximation and a particular orbit. Then, I will highlight an unexpected result for very high eccentricity on families of periodic orbits that originate from L3, L4 and L5. Finally, I will sketch out an analytic method adapted to QS motion and exhibit associated results in the eccentric case.

  12. 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.

  13. Applications of Geostatistics in Optimal Design of Satellite Altimetry Orbits and Measurement Configurations

    Science.gov (United States)

    Herzfeld, Ute C.; Wallin, Bruce F.; Stachura, Maciej

    2011-07-01

    The Geoscience Laser Altimeter System (GLAS) aboard NASA's Ice, Cloud and land Elevation Satellite (ICESat) is a pulse-limited laser that records measurements in a geophysical track-line ground pattern of single discrete points along a sub-satellite track. Spacing between tracks depends on latitude and repeat cycle. Derivation of digital elevation models (DEMs) of the ice surface from GLAS data requires interpolation, which due to the spatial data distribution is mathematically an extrapolation problem, best solved using a form of geostatistical estimation. In this article, we investigate the relationships between observing ice surface elevations with single-beam and multi-beam altimetry, regional coverage and spatial resolution, orbit ground track design and repeat-track spacing, analysis with ordinary and advanced universal Kriging algorithms and resultant DEM accuracy. The study is a contribution to the ICESat-2 ad-hoc Science Definition Team tasks and analyzes GLAS data and several potential multi-beam configurations proposed for the ICESat-2 instrumentation. Measurement of elevation change at the accuracy required by the U.S. National Research Council (2007) "Decadal Survey" recommendations requires understanding the effects of spatial variability of the elevation measurement, in particular for complex, rough or steep natural surfaces. This problem, which is important to correctly assess the cryosphere's contribution to sea-level rise, is treated using scale-dependent simulation. Results indicate that multi-beam laser measurements are needed and provide a solution to the trade-off problem between repeat-mission and geodetical coverage. More generally, the article demonstrates links between space mission planning, orbit design, spatial distribution of measurements from future instrumentation and improved mathematical data processing algorithms.

  14. Design on an enhanced interactive satellite communications system analysis program

    Science.gov (United States)

    Andersen, Kevin Robert

    1991-09-01

    This thesis describes the design of a user-friendly interactive satellite communications analysis program for use on a personal computer. The user inputs the various parameters of a satellite orbit, ground station location and communications equipment. The output generated allows a user to view the satellite ground trace and footprint, calculate satellite rise and set times, and analyze the performance of the communications link. The link analysis allows the user to input various signal losses and jamming interference. Care was taken to ensure that the program is simple to operate and that it provides on-line help for each segment. A principle goal of this thesis effort is to provide an educational tool that familiarizes the user with the communications segment of a space system. The initial success of the program based upon student response validates the use of object-oriented like software tools that enhance user understanding of complex subjects.

  15. 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

  16. 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

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

    Science.gov (United States)

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

    2018-03-01

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

  18. 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.

  19. Preliminary Assessment of New Orbital Debris Shielding for Unmanned Satellites

    Science.gov (United States)

    Wilkinson, J.; Stokes, H.; Walker, R.

    The numerous rocket launches and spacecraft deployments carried out since the dawn of the space age have generated a large orbiting population of man-made debris. Without the adoption of mitigation measures, it is likely that this population will continue to increase in the future. The ever-growing collision threat posed to operating spacecraft from these debris objects is therefore fast becoming a driver in the design of new spacecraft missions. DERA, under contract from the European Space Agency (ESA), is developing new techniques to provide mass- and cost-effective solutions to this spacecraft protection problem. Direct shielding methods such as enhancing a spacecraft's thermal blankets with strong materials and adapting the honeycomb panel structure are being investigated, as are indirect shielding methods such as reconfiguration of critical or susceptible units. This paper reports the latest results of the direct shielding research.

  20. 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.

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

    Science.gov (United States)

    Montenbruck, Oliver; Hackel, Stefan; Jäggi, Adrian

    2017-11-01

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

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

    Science.gov (United States)

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

    2011-01-01

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

  3. 47 CFR 25.146 - Licensing and operating authorization provisions for the non-geostationary satellite orbit fixed...

    Science.gov (United States)

    2010-10-01

    ... FSS system shall not claim protection from GSO FSS and BSS networks operating in accordance with this... model the system in computer sharing simulations, including, at a minimum, NGSO hand-over and satellite... submitted for the proposed non-geostationary satellite orbit fixed-satellite service (NGSO FSS) system in...

  4. Modeling And Simulation Of Prolate Dual-Spin Satellite Dynamics In An Inclined Elliptical Orbit: Case Study Of Palapa B2R Satellite

    OpenAIRE

    Muliadi, J.; Jenie, S. D.; Budiyono, A.

    2008-01-01

    In response to the interest to re-use Palapa B2R satellite nearing its End of Life (EOL) time, an idea to incline the satellite orbit in order to cover a new region has emerged in the recent years. As a prolate dual-spin vehicle, Palapa B2R has to be stabilized against its internal energy dissipation effect. This work is focused on analyzing the dynamics of the reusable satellite in its inclined orbit. The study discusses in particular the stability of the prolate dual-spin satellite under th...

  5. The role of onboard intelligence and of orbital servicing in the increase of satellite lifetime

    Science.gov (United States)

    Cougnet, P. C.; Sotta, J. P.

    1984-01-01

    The continued increase in satellite lifetime is now or is going to become critical with respect to the maintenance of system reliability and the risk of mission obsolescence. Resource to redundant equipment becomes more and more penalizing particularly because of the limited capacities of the launch methods. Futhermore, the classic satellite concept does not permit avoiding mission obsolescence or long duration life. To remedy these problems, two possible complementary methods are presented. One involves the use of satellite onboard intelligence to enable better management of its configuration and platform subsystems in order to assure a high level of availability to he satellite. The other solution is orbital servicing which permits periodic adjustment of reliability and platform autonomy as well as the eventual exchange of the payload. This solution calls for new techniques: rendezvous, assembling, and the space robot.

  6. In-Orbit Test Results of the Optical Intersatellite Link, SILEX. A Milestone in Satellite Communication

    Science.gov (United States)

    Tolker-Nielsen, T.; Oppenhaeuser, G.

    2002-01-01

    The Semi conductor Inter satellite Link EXperiment, SILEX, consists of two terminals, one terminal embarked on the French LEO observation satellite SPOT4 and one terminal embarked on ESA's GEO telecommunication satellite ARTEMIS. The objective of SILEX is to perform optical communication experiments in orbit and on an operational basis transmit SPOT4 Earth observation data to ARTEMIS, which will relay the data to ground via its Ka band feeder link. SPOT4 was successfully launched on 22nd March 1998. The ARTEMIS launch on 12th July 2001 left ARTEMIS in an orbit with too low apogee, necessitating orbit raising to a circular parking orbit, altitude 31000km, using a large fraction of the chemical propellant on board. The remaining 5000km to GEO stationary orbit will be achieved using the low thrust innovative electric propulsion system necessitating specific attitude control software. The final orbit raising will last about 6 months and the expected lifetime of ARTEMIS after station acquisition is 5 years. While waiting for the establishment of the new attitude control software and the beginning of the final orbit raising maneuvers a test program has been undertaken in November/December 2001 to characterize the performances of the SILEX system. Testing was performed every fifth day when ARTEMIS was visible over Europe. The test program involves Optical Ground Station acquisition and tracking, inter-satellite link acquisition and tracking, bit error rate measurements and transmission of Earth observation data. The paper reports on results of the in orbit testing, giving comparisons with predictions. The conclusion of the test program is that the SILEX system has excellent performances qualifying the system for operational use by SPOTIMAGE in parallel with a detailed technological experimentation program involving the two SILEX terminals, ESA's optical ground station on Tenerife, and also NASDA's OICETS, once ARTEMIS has acquired its final orbital position. The results

  7. Precise Orbit Determination of LEO Satellite Using Dual-Frequency GPS Data

    Directory of Open Access Journals (Sweden)

    Yoola Hwang

    2009-06-01

    Full Text Available KOrea Multi-purpose SATellite (KOMPSAT-5 will be launched at 550km altitude in 2010. Accurate satellite position (20 cm and velocity (0.03 cm/s are required to treat highly precise Synthetic Aperture Radar (SAR image processing. Ionosphere delay was eliminated using dual frequency GPS data and double differenced GPS measurement removed common clock errors of both GPS satellites and receiver. SAC-C carrier phase data with 0.1 Hz sampling rate was used to achieve precise orbit determination (POD with ETRI GNSS Precise Orbit Determination (EGPOD software, which was developed by ETRI. Dynamic model approach was used and satellite's position, velocity, and the coefficients of solar radiation pressure and drag were adjusted once per arc using Batch Least Square Estimator (BLSE filter. Empirical accelerations for sinusoidal radial, along-track, and cross track terms were also estimated once per revolution for unmodeled dynamics. Additionally piece-wise constant acceleration for cross-track direction was estimated once per arc. The performance of POD was validated by comparing with JPL's Precise Orbit Ephemeris (POE.

  8. MODAL ANALYSIS OF A SATELLITE WITH DIFFERENT MATERIALS

    OpenAIRE

    Aguiar, Lucas Rafael Carneiro de; Carneiro, Sergio Henrique da Silva; Paiano, Salvatore

    2017-01-01

    For placing an object in any Earth orbit, it is extremely necessary to follow safety rules. The non-use of this can be destroyable for the launching system. Because of that, the launching company Kosmotras® requires that the satellite UniSat7 from GAUSS srl® pursue a high level of structural security. The Kosmotras® requests a modal analysis and that the natural frequencies of the satellite must be higher than 20 Hertz in longitudinal direction and 10 Hertz in lateral. For achieving this resu...

  9. Solar Power Satellite system in formation on a common geostationary orbit

    Science.gov (United States)

    Salazar, F. J. T.; Winter, O. C.

    2017-10-01

    The diurnal day-night cycle severely limits the Terrestrial solar power. To overcome this limitation, a Solar Power Satellite (SPS) system, consisting of a sunlight reflector and a microwave energy generator-transmitter in formation, is presented in this work. The microwave transmitting satellite (MTS) is placed on a common geostationary orbit (GEO) in the Earth’s equatorial plane, and the sunlight reflector uses the solar radiation pressure to achieve quasi-periodic orbits about the MTS, so that the sunlight is always redirected to the MTS, which converts the solar energy in electromagnetic power and transmits it by microwaves to an Earth-receiving antenna. Assuming the sun line direction constant at dierent seasons (i.e. autumn/spring equinoxes and winter and summer solstices), previous studies have shown the existence of a family of displaced ecliptic orbits above or below the equatorial plane of the Earth around a GEO. In this study, the position of the Sun is assumed on the ecliptic plane with a mean obliquity (inclination of Earth’s equator with respect to the ecliptic) of 23.5◦. A linear solution as an initial condition for the full equations of motions about a GEO, which yields bounded orbit for the sunlight reflector about the MTS in the Earth-satellite two-body problem with solar radiation pressure. To redirect the sunlight to the MTS, the law of reflection is satisfied by the space mirror attitude.

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

    National Research Council Canada - National Science Library

    Paris, Jody A

    2006-01-01

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

  11. Earth Observing Satellite Orbit Design Via Particle Swarm Optimization

    Science.gov (United States)

    2014-08-01

    West Point, 2011. 9Vallado, D. A., Fundamentals of astrodynamics and applications , Vol. 12, Springer, 2001. 10Kennedy, J. and Eberhart, R., “Particle...Optimization and Differential Evolution Algorithms: Technical Analysis, Applications and Hybridization Perspectives,” Advances of Computational Intelligence in

  12. 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.

  13. Mission planning for on-orbit servicing through multiple servicing satellites: A new approach

    Science.gov (United States)

    Daneshjou, K.; Mohammadi-Dehabadi, A. A.; Bakhtiari, M.

    2017-09-01

    In this paper, a novel approach is proposed for the mission planning of on-orbit servicing such as visual inspection, active debris removal and refueling through multiple servicing satellites (SSs). The scheduling has been done with the aim of minimization of fuel consumption and mission duration. So a multi-objective optimization problem is dealt with here which is solved by employing particle swarm optimization algorithm. Also, Taguchi technique is employed for robust design of effective parameters of optimization problem. The day that the SSs have to leave parking orbit, transfer duration from parking orbit to final orbit, transfer duration between one target to another, and time spent for the SS on each target are the decision parameters which are obtained from the optimization problem. The raised idea is that in addition to the aforementioned decision parameters, eccentricity and inclination related to the initial orbit and also phase difference between the SSs on the initial orbit are identified by means of optimization problem, so that the designer has not much role on determining them. Furthermore, it is considered that the SS and the target rendezvous at the servicing point and the SS does not perform any phasing maneuver to reach the target. It should be noted that Lambert theorem is used for determination of the transfer orbit. The results show that the proposed approach reduces the fuel consumption and the mission duration significantly in comparison with the conventional approaches.

  14. 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.

  15. Orbital positioning of domestic satellites. [area coverage and radio frequency interference optimization

    Science.gov (United States)

    Gubin, S.; Kane, D.

    1973-01-01

    An important factor in establishing domestic or regional communication satellite systems which share a given frequency band is the positioning of the satellites in the arc of the geostationary orbit that is visible to the area to be served. A description is given of the results of orbit spacing studies performed with respect to the eight different space systems proposed to provide U.S. domestic communication services. Some tentative guidelines which may be of general use are proposed. Four sets of computer models were studied, taking into account quasi-homogeneous models, a five-system model, a heterogeneous model with 3-degree spacings, and a heterogeneous model with unequal spacings and with coordination.

  16. Three-Dimensional Orbits of Earth Satellites, Including Effects of Earth Oblateness and Atmospheric Rotation

    Science.gov (United States)

    Nielsen, Jack N.; Goodwin, Frederick K.; Mersman, William A.

    1958-01-01

    The principal purpose of the present paper is to present sets of equations which may be used for calculating complete trajectories of earth satellites from outer space to the ground under the influence of air drag and gravity, including oblateness effects, and to apply these to several examples of entry trajectories starting from a circular orbit. Equations of motion, based on an "instantaneous ellipse" technique, with polar angle as independent variable, were found suitable for automatic computation of orbits in which the trajectory consists of a number of revolutions. This method is suitable as long as the trajectory does not become nearly vertical. In the terminal phase of the trajectories, which are nearly vertical, equations of motion in spherical polar coordinates with time as the independent variable were found to be more suitable. In the first illustrative example the effects of the oblateness component of the earth's gravitational field and of atmospheric rotation were studied for equatorial orbits. The satellites were launched into circular orbits at a height of 120 miles, an altitude sufficiently high that a number of revolutions could be studied. The importance of the oblateness component of the earth's gravitational field is shown by the fact that a satellite launched at circular orbital speed, neglecting oblateness, has a perigee some 67,000 feet lower when oblateness forces are included in the equations of motion than when they are not included. Also, the loss in altitude per revolution is double that of a satellite following an orbit not subject to oblateness. The effect of atmospheric rotation on the loss of altitude per revolution was small. As might be surmised, the regression of the line of nodes as predicted by celestial mechanics is unchanged when drag is included. It is clear that the inclination of the orbital plane to the equator will be relatively unaffected by drag for no atmospheric rotation since the drag lies in the orbital plane in

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

    Science.gov (United States)

    2014-08-01

    Astrodynamics, drag, atmospheric density, geodesy 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF PAGES 12 19a...due to estimation error of these parameters rather than to physical forces. Ultimately, the orbit 8 solution that is treated as truth largely does not...Translation of ’Le satellite de geodesie ’Starlette’,’ Groupe de Recherches de Geodesie Spatiale, Centre National d’Etudes Spatiales, Bretigny-sur-Orge

  18. Lunar Gravitational Field Estimation and the Effects of Mismodeling Upon Lunar Satellite Orbit Prediction

    Science.gov (United States)

    1993-06-01

    Elliptical Satellite Initial Conditions for "Truth" Model Observations ............................................................................. 115 ...km (3.651789462 x 10- AU) e0 0.05994874611 i0 900 (103.10484938493500) GO 900 (304.19968053947210) Ob0 3150 (297.23942697989870) M 11 115 L&UNA...orbiter data could 155 LUINAR GRAVITATIONAL FMM~ EST rAlON ADAI• rlEORBrT IPR- nIMON provide the best estimate of the remaining second degree harmonic

  19. Analysis of the Accuracy of Beidou Combined Orbit Determination Enhanced by LEO and ISL

    Directory of Open Access Journals (Sweden)

    FENG Laiping

    2017-05-01

    Full Text Available In order to improve the precision of BeiDou orbit determination under the conditions of regional ground monitoring station and make good use of increasingly rich on-board data and upcoming ISL technology, a method of BeiDou precision orbit determination is proposed which combines the use of ground monitoring stations data, low earth orbit satellite(LEOs data and Inter-Satellite Link(ISL data. The effects of assisting data of LEOs and ISL on the precision orbit determination of navigation satellite are discussed. Simulation analysis is carried out mainly from the number of LEOs, orbit slot configuration and ISL. The results show that the orbit precision of BeiDou will greatly improve about 73% with a small number of LEOs, while improvement of clock bias is not remarkable; the uniform orbit slot configuration of the same number of LEOs has a modest effect on the accuracy of combined orbit determination; compared with LEOs, the increase of ISL will significantly improve the accuracy of orbit determination with a higher efficiency.

  20. 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.

  1. Angles-Only Initial Relative Orbit Determination Performance Analysis using Cylindrical Coordinates

    Science.gov (United States)

    Geller, David K.; Lovell, T. Alan

    2017-03-01

    The solution of the initial relative orbit determination problem using angles-only measurements is important for orbital proximity operations, satellite inspection and servicing, and the identification of unknown space objects in similar orbits. In this paper, a preliminary relative orbit determination performance analysis is conducted utilizing the linearized relative orbital equations of motion in cylindrical coordinates. The relative orbital equations of motion in cylindrical coordinates are rigorously derived in several forms included the exact nonlinear two-body differential equations of motion, the linear-time-varying differential equations of motion for an elliptical orbit chief, and the linear-time-invariant differential equations of motion for a circular orbit chief. Using the nonlinear angles-only measurement equation in cylindrical coordinates, evidence of full-relative-state observability is found, contrary to the range observability problem exhibited in Cartesian coordinates. Based on these results, a geometric approach to assess initial relative orbit determination performance is formulated. To facilitate a better understanding of the problem, the focus is on the 2-dimensional initial orbit determination problem. The results clearly show the dependence of the relative orbit determination performance on the geometry of the relative motion and on the time-interval between observations. Analysis is conducted for leader-follower orbits and flyby orbits where the deputy passes directly above or below the chief.

  2. Orbit uncertainty propagation and sensitivity analysis with separated representations

    Science.gov (United States)

    Balducci, Marc; Jones, Brandon; Doostan, Alireza

    2017-09-01

    Most approximations for stochastic differential equations with high-dimensional, non-Gaussian inputs suffer from a rapid (e.g., exponential) increase of computational cost, an issue known as the curse of dimensionality. In astrodynamics, this results in reduced accuracy when propagating an orbit-state probability density function. This paper considers the application of separated representations for orbit uncertainty propagation, where future states are expanded into a sum of products of univariate functions of initial states and other uncertain parameters. An accurate generation of separated representation requires a number of state samples that is linear in the dimension of input uncertainties. The computation cost of a separated representation scales linearly with respect to the sample count, thereby improving tractability when compared to methods that suffer from the curse of dimensionality. In addition to detailed discussions on their construction and use in sensitivity analysis, this paper presents results for three test cases of an Earth orbiting satellite. The first two cases demonstrate that approximation via separated representations produces a tractable solution for propagating the Cartesian orbit-state uncertainty with up to 20 uncertain inputs. The third case, which instead uses Equinoctial elements, reexamines a scenario presented in the literature and employs the proposed method for sensitivity analysis to more thoroughly characterize the relative effects of uncertain inputs on the propagated state.

  3. 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.

  4. 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.

  5. Improved Ionospheric Model Algorithm for LEO Satellite Single-frequency Precise Orbit Determination

    Directory of Open Access Journals (Sweden)

    TIAN Yingguo

    2016-07-01

    Full Text Available Ionospheric delay correction is the core issue of LEO satellite single-frequency precise orbit determination. At present, "the method of ionosphere scale factor" is mainly adopted in the LEO satellite ionospheric delay correction, but the method doesn't consider the electron density peak height along with the variation of factors, such as latitude and longitude, day and night, seasons, solar activity, etc. IRI2012 model while considering the influence of the above factors on the electron density peak height, but because of the height criteria inconsistent with ionosphere single layer model, there is usually a systematic deviation and can't be used directly. Therefore, this paper puts forward to an improved ionospheric delay correction method, the ionosphere thin layer height as the constraint condition of IRI2012 model of electron density peak height of the mean parameter estimation. Based on Swarm satellite single-frequency observation data, the effectiveness of the method was verified. The results showed that: with the improved model of the ionosphere, the precision of Swarm satellite obit radial, tangential and normal was improved in varying degrees, especially for the radial and normal most obviously, improved on average by 31.6% and 32.0%, respectively. At the same time, the systemic deviation of the orbit reduced significantly, especially for the radial and normal, reduced on average by 65.0% and 54.7%, respectively.

  6. 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.

  7. 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.

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

    Directory of Open Access Journals (Sweden)

    M. C. Anderson

    2011-01-01

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

  9. Global Navigation Satellite System (GNSS) Ultra-Rapid Orbit/Clock/ERP Product Comparison Summary from NASA CDDIS

    Data.gov (United States)

    National Aeronautics and Space Administration — This derived product set consists of Global Navigation Satellite System Rapid Orbit/Reference Frame Product Summary from the NASA Crustal Dynamics Data Information...

  10. 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...

  11. Global Navigation Satellite System (GNSS) Ultra-Rapid Orbit/Clock/ERP Product Summary from NASA CDDIS

    Data.gov (United States)

    National Aeronautics and Space Administration — This derived product set consists of Global Navigation Satellite System Rapid Orbit/Reference Frame Product Summary from the NASA Crustal Dynamics Data Information...

  12. Satellite splat II: an inelastic collision with a surface-launched projectile and the maximum orbital radius for planetary impact

    Science.gov (United States)

    Blanco, Philip R.; Mungan, Carl E.

    2016-07-01

    Starting with conservation of energy and angular momentum, we derive a convenient method for determining the periapsis distance of an orbiting object, by expressing its velocity components in terms of the local circular speed. This relation is used to extend the results of our previous paper, examining the effects of an adhesive inelastic collision between a projectile launched from the surface of a planet (of radius R) and an equal-mass satellite in a circular orbit of radius r s. We show that there is a maximum orbital radius r s ≈ 18.9R beyond which such a collision cannot cause the satellite to impact the planet. The difficulty of bringing down a satellite in a high orbit with a surface-launched projectile provides a useful topic for a discussion of orbital angular momentum and energy. The material is suitable for an undergraduate intermediate mechanics course.

  13. 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.

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

    Science.gov (United States)

    Osterbrock, Donald E.

    2006-12-01

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

  15. Analysis of Orbital Lifetime Prediction Parameters in Preparation for Post-Mission Disposal

    Directory of Open Access Journals (Sweden)

    Ha–Yeon Choi

    2015-12-01

    Full Text Available Atmospheric drag force is an important source of perturbation of Low Earth Orbit (LEO orbit satellites, and solar activity is a major factor for changes in atmospheric density. In particular, the orbital lifetime of a satellite varies with changes in solar activity, so care must be taken in predicting the remaining orbital lifetime during preparation for post-mission disposal. In this paper, the System Tool Kit (STK® Long-term Orbit Propagator is used to analyze the changes in orbital lifetime predictions with respect to solar activity. In addition, the STK® Lifetime tool is used to analyze the change in orbital lifetime with respect to solar flux data generation, which is needed for the orbital lifetime calculation, and its control on the drag coefficient control. Analysis showed that the application of the most recent solar flux file within the Lifetime tool gives a predicted trend that is closest to the actual orbit. We also examine the effect of the drag coefficient, by performing a comparative analysis between varying and constant coefficients in terms of solar activity intensities.

  16. Analysis and Optimization of BDS GEO/IGSO/MEO Ground Monitoring Stations Configuration for Determining GNSS Orbit

    Directory of Open Access Journals (Sweden)

    ZHANG Longping

    2017-05-01

    Full Text Available Orbit determination accuracy of GNSS satellites depends on the satellites dynamics models and GNSS orbit determination geometry. Because of the weak geometry, higher orbit height of GEO and IGSO and relatively low accuracy of the dynamics models, the geometry information may play an important role in improving the GNSS orbit. The method for analysis the configuration and the influence of BDS GEO/IGSO/MEO ground monitoring stations distribution are discussed. Firstly, based on the reduced-dynamic orbit determination theory, the precision improvement of GNSS orbit from multi-epoch geometry observations is revealed. Secondly, the geometric condition of an ideal configuration for BDS satellites orbit determination is studied and the influence factors (quantity, range, density are obtained. Thirdly, the method based on the discrete probability distribution is proposed to analyse the configuration of the ground monitoring stations. Finally, the indicators of discrete probability density and configuration of BDS orbit determination are optimized by adding five Chinese regional stations. It is showed that the improvement of GEO and IGSO satellites is more significant relative to MEO satellites. The accuracy of GEO/IGSO/MEO satellites is improved by 10%, 16%, 4% respectively.

  17. 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.

  18. 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.

  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. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

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

    Science.gov (United States)

    2014-08-01

    TERMS Orbit determination, Astrodynamics , geopotential, geodesy 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF PAGES...covariance estimation and analysis software- OCEAN,” Astrodynamics 1997 , 1997, pp. 1567–1586. 2Soyka, M. T., Middour, J. W., and Fein, J., “Simultaneous...W., “Orbit determination using space to ground Differential GPS in NRL’s OCEAN package,” Astrodynamics 1999 , 2000, pp. 421–434. 4Seago, J. H

  6. 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

  7. 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.

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

    Directory of Open Access Journals (Sweden)

    Byoung-Sun Lee

    1997-12-01

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

  9. Optical Orbit Determination of a Geosynchronous Earth Orbit Satellite Effected by Baseline Distances between Various Ground-based Tracking Stations I: COMS simulation case

    Directory of Open Access Journals (Sweden)

    Ju Young Son

    2015-09-01

    Full Text Available To protect and manage the Korean space assets including satellites, it is important to have precise positions and orbit information of each space objects. While Korea currently lacks optical observatories dedicated to satellite tracking, the Korea Astronomy and Space Science Institute (KASI is planning to establish an optical observatory for the active generation of space information. However, due to geopolitical reasons, it is difficult to acquire an adequately sufficient number of optical satellite observatories in Korea. Against this backdrop, this study examined the possible locations for such observatories, and performed simulations to determine the differences in precision of optical orbit estimation results in relation to the relative baseline distance between observatories. To simulate more realistic conditions of optical observation, white noise was introduced to generate observation data, which was then used to investigate the effects of baseline distance between optical observatories and the simulated white noise. We generated the optical observations with white noise to simulate the actual observation, estimated the orbits with several combinations of observation data from the observatories of various baseline differences, and compared the estimated orbits to check the improvement of precision. As a result, the effect of the baseline distance in combined optical GEO satellite observation is obvious but small compared to the observation resolution limit of optical GEO observation.

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

    OpenAIRE

    Xiaokui Yue; Xuechuan Wang; Honghua Dai

    2014-01-01

    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 the...

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

    Science.gov (United States)

    1974-01-01

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

  12. Long-Term Thermospheric Trends Based on Satellite Drag Analysis

    Science.gov (United States)

    Marcos, F. A.; Grossbard, N. J.

    2004-05-01

    A new database of thermospheric densities has been derived for the period 1970 - 2000 from satellite orbital decay analysis. The data are generated from actual radar tracking observations, rather than from the less accurate historical element sets, to form precise orbit and drag/density data with improved accuracy and one-day resolution. Satellites with high eccentricities were used to achieve long lifetimes and relatively localized latitude and local time resolution. Data are compared to three empirical models (Jacchia, NRLMSIS and NASA MET). The data were normalized to remove systematic model errors vs solar activity detected in all three models. A linear regression through the normalized data was obtained for each satellite. The weighted average of these fits show, at 400 km altitude, a downward trend of about 5% over 30 years with a 95% confidence interval of about 25%. The data are also analyzed as a function of altitude, solar flux and geomagnetic activity, and compared to theoretical predictions. Assuming a linear fit, these results tend to agree with other recent studies indicating a long-term cooling trend in the thermosphere.

  13. a Permanent Magnet Hall Thruster for Satellite Orbit Maneuvering with Low Power

    Science.gov (United States)

    Ferreira, Jose Leonardo

    Plasma thrusters are known to have some advantages like high specific impulse. Electric propulsion is already recognized as a successful technology for long duration space missions. It has been used as primary propulsion system on earth-moon orbit trnsfer missions, comets and asteroids exploration and on commercially geosyncronous satellite attitude control systems. Closed Drift Plasma Thrusters, also called Hall Thrusters or SPT (Stationary Plasma Thruster) was conceived inthe USSR and, since then, they have been developed in several countries such as France, USA, Japan and Brazil. In this work, introductory remarks are made with focus on the most significant contributions of the electric propulsion to the progress of space missions and its future role on the brazillian space program. The main features of an inedit Permanent Magnet Hall Thruster (PMHT) developed at the Plasma Laboratory of the University of Brasilia is presented. The idea of using an array of permanent magnets, instead of an eletromagnet, to produce a radial magnetic field inside the cylindrical plasma drift channel of the thruster is a very important improvement, because it allows the possibility of developing a Hall Thruster with electric power consumption low enough to be used in small and medium size satellites. The new Halĺplasma source characterization is presented with plasma density, temperature and potential space profiles. Ion temperature mesurements based on Doppler broadening of spectral lines and ion energy measurements of the ejected plasma plume are also shown. Based on the mesured parameters of the accelerated plasma we constructed a merit figure for the PMHT. We also perform numerical simulations of satellite orbit raising from an altitude of 700 km to 36000 km using a PMHT operating in the 100 mN to 500 mN thrust range. In order to perform these caculations, integration techniques of spacecraft trajectory were used. The main simulation parameters were: orbit raising time

  14. Satellite image analysis using neural networks

    Science.gov (United States)

    Sheldon, Roger A.

    1990-01-01

    The tremendous backlog of unanalyzed satellite data necessitates the development of improved methods for data cataloging and analysis. Ford Aerospace has developed an image analysis system, SIANN (Satellite Image Analysis using Neural Networks) that integrates the technologies necessary to satisfy NASA's science data analysis requirements for the next generation of satellites. SIANN will enable scientists to train a neural network to recognize image data containing scenes of interest and then rapidly search data archives for all such images. The approach combines conventional image processing technology with recent advances in neural networks to provide improved classification capabilities. SIANN allows users to proceed through a four step process of image classification: filtering and enhancement, creation of neural network training data via application of feature extraction algorithms, configuring and training a neural network model, and classification of images by application of the trained neural network. A prototype experimentation testbed was completed and applied to climatological data.

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

    Science.gov (United States)

    Woods-Vedeler, Jessica (Technical Monitor); Moore, Chris (Technical Monitor); Wie, Bong; Roithmayr, Carlos

    2001-01-01

    The major objective of this study is to develop an integrated orbit, attitude, and structural control system 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 500 700 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 system 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 o.set 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.

  17. Recognizing methods for epicenter-neighboring orbits with ionospheric information from DEMETER satellite data

    Science.gov (United States)

    Zang, Sicong; Pi, Dechang; Zhang, Xuemin; Shen, Xuhui

    2017-09-01

    Due to the temporal and spatial restriction of existing approaches, a recognizing method focuses on all strong seismic activities in globe during the lifecycle of DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) is proposed for epicenter-neighboring orbits from the point of view of the Fourth Paradigm. Satellite orbits are regarded as the analyzing objects to reduce the unbalance between the quantity of non-seismic and abnormal data. Two criteria, α3 and α4 are put forward to quantify the asymmetry and stability of ionospheric parameters along the orbit and t location-scale distribution is carried out to fit the quantitative indicators. Moreover, during the distribution fitting, the probable cause of two typical types of exceptions are analyzed and explained. In order to determine which magnitude the abnormal α3 and α4 are caused by, suitable pairs of thresholds are calculated by means of dynamic time warping (DTW) distance. Finally, three groups of experiments are applied to validate the effectiveness of this method.

  18. A Robust Method to Detect BeiDou Navigation Satellite System Orbit Maneuvering/Anomalies and Its Applications to Precise Orbit Determination.

    Science.gov (United States)

    Ye, Fei; Yuan, Yunbin; Tan, Bingfeng; Ou, Jikun

    2017-05-16

    The failure to detect anomalies and maneuvering of the orbits of navigation satellite sensors will deteriorate the performance of positioning and orbit determination. Motivated by the influence of the frequent maneuvering of BDS GEO and IGSO satellites, this paper analyzes the limitations of existing methods, where BDS orbit maneuvering and anomalies can be detected, and develops a method to solve this problem based on the RMS model of orbit mutual differences proposed in this paper. The performance of this method was assessed by comparison with the health flag of broadcast ephemeris, precise orbit products of GFZ, the O-C values of a GNSS station and a conventional method. The results show that the performance of the method developed in this paper is better than that of the conventional method when the periodicity and trend items are obvious. Meanwhile, three additional verification results show that the method developed in this paper can find error information in the merged broadcast ephemeris provided by iGMAS. Furthermore, from the testing results, it can be seen that the detection of anomaly and maneuvering items do not affect each other based on the robust thresholds constructed in this paper. In addition, the precise orbit of the maneuvering satellites can be determined under the circumstances that the maneuver information detected in this paper is used, and the root mean square (RMS) of orbit overlap comparison for GEO-03/IGSO-03 in Radial, Along, Cross, 1D-RMS are 0.7614/0.4460 m, 1.8901/0.3687 m, 0.3392/0.2069 m, 2.0657/0.6145 m, respectively.

  19. A Robust Method to Detect BeiDou Navigation Satellite System Orbit Maneuvering/Anomalies and Its Applications to Precise Orbit Determination

    Directory of Open Access Journals (Sweden)

    Fei Ye

    2017-05-01

    Full Text Available The failure to detect anomalies and maneuvering of the orbits of navigation satellite sensors will deteriorate the performance of positioning and orbit determination. Motivated by the influence of the frequent maneuvering of BDS GEO and IGSO satellites, this paper analyzes the limitations of existing methods, where BDS orbit maneuvering and anomalies can be detected, and develops a method to solve this problem based on the RMS model of orbit mutual differences proposed in this paper. The performance of this method was assessed by comparison with the health flag of broadcast ephemeris, precise orbit products of GFZ, the O-C values of a GNSS station and a conventional method. The results show that the performance of the method developed in this paper is better than that of the conventional method when the periodicity and trend items are obvious. Meanwhile, three additional verification results show that the method developed in this paper can find error information in the merged broadcast ephemeris provided by iGMAS. Furthermore, from the testing results, it can be seen that the detection of anomaly and maneuvering items do not affect each other based on the robust thresholds constructed in this paper. In addition, the precise orbit of the maneuvering satellites can be determined under the circumstances that the maneuver information detected in this paper is used, and the root mean square (RMS of orbit overlap comparison for GEO-03/IGSO-03 in Radial, Along, Cross, 1D-RMS are 0.7614/0.4460 m, 1.8901/0.3687 m, 0.3392/0.2069 m, 2.0657/0.6145 m, respectively.

  20. 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.

  1. Stability of the determination of the preliminary-orbit elements of a geodetic satellite according to its two geocentric positions by means of the Gauss method

    Science.gov (United States)

    Sangare, T.

    An effort is made to establish a correlation between small variations of the initial geocentric quantities and variations of the orbital elements of a geodetic satellite calculated by means of the Gauss method. Specifically, the problem is to correlate variations of the geocentric radius vector (calculated through the topocentric radius vector) with variations of the semimajor axis of the orbit. The problem is solved numerically for the polar orbits of geodetic satellites observed from the equatorial region. The optimal orbit orientation is determined.

  2. Real-time, autonomous precise satellite orbit determination using the global positioning system

    Science.gov (United States)

    Goldstein, David Ben

    2000-10-01

    The desire for autonomously generated, rapidly available, and highly accurate satellite ephemeris is growing with the proliferation of constellations of satellites and the cost and overhead of ground tracking resources. Autonomous Orbit Determination (OD) may be done on the ground in a post-processing mode or in real-time on board a satellite and may be accomplished days, hours or immediately after observations are processed. The Global Positioning System (GPS) is now widely used as an alternative to ground tracking resources to supply observation data for satellite positioning and navigation. GPS is accurate, inexpensive, provides continuous coverage, and is an excellent choice for autonomous systems. In an effort to estimate precise satellite ephemeris in real-time on board a satellite, the Goddard Space Flight Center (GSFC) created the GPS Enhanced OD Experiment (GEODE) flight navigation software. This dissertation offers alternative methods and improvements to GEODE to increase on board autonomy and real-time total position accuracy and precision without increasing computational burden. First, GEODE is modified to include a Gravity Acceleration Approximation Function (GAAF) to replace the traditional spherical harmonic representation of the gravity field. Next, an ionospheric correction method called Differenced Range Versus Integrated Doppler (DRVID) is applied to correct for ionospheric errors in the GPS measurements used in GEODE. Then, Dynamic Model Compensation (DMC) is added to estimate unmodeled and/or mismodeled forces in the dynamic model and to provide an alternative process noise variance-covariance formulation. Finally, a Genetic Algorithm (GA) is implemented in the form of Genetic Model Compensation (GMC) to optimize DMC forcing noise parameters. Application of GAAF, DRVID and DMC improved GEODE's position estimates by 28.3% when applied to GPS/MET data collected in the presence of Selective Availability (SA), 17.5% when SA is removed from the GPS

  3. 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.

  4. 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

  5. The Design and Analysis Program for the Development of LEO Satellite Electrical Power Subsystem

    Directory of Open Access Journals (Sweden)

    Sang-Kon Lee

    2007-06-01

    Full Text Available The design and analysis of satellite power subsystem is an important driver for the mass, size, and capability of the satellite. Every other satellite subsystem is affected by the power subsystem, and in particular, important issues such as launch vehicle selection, thermal design, and structural design are largely influenced by the capabilities and limitations of the power system. This paper introduces a new electrical power subsystem design program for the rapid development of LEO satellite and shows an example of design results using other LEO satellite design data. The results shows that the proposed design program can be used the optimum sizing and the analytical prediction of the on-orbit performance of satellite electrical power subsystem.

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

    Science.gov (United States)

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

    2016-06-01

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

  7. 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

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

    Science.gov (United States)

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

    2013-01-01

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

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

    Science.gov (United States)

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

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

  10. Performance of BDS-3: Measurement Quality Analysis, Precise Orbit and Clock Determination

    Directory of Open Access Journals (Sweden)

    Xin Xie

    2017-05-01

    Full Text Available Since 2015, China has successfully launched five experimental BeiDou global navigation system (BDS-3 satellites for expanding the regional system to global coverage. An initial performance assessment and characterization analysis of the BDS-3 is presented. Twenty days of tracking data have been collected from eleven monitoring stations. The tracking characteristics and measurement quality are analyzed and compared with the regional BDS (BDS-2 in terms of observed carrier-to-noise density ratio, pseudo-range multipath, and noise. The preliminary results suggest that the measurement quality of BDS-3 outperforms the BDS-2 for the same type of satellites. In addition, the analysis of multipath combinations reveals that the problem of satellite-induced code biases found in BDS-2 seems to have been solved for BDS-3. Precise orbit and clock determination are carried out and evaluated. The orbit overlap comparison show a precision of 2–6 dm in 3D root mean square (RMS and 6–14 cm in the radial component for experimental BDS-3 satellites. External validations with satellite laser ranging (SLR show residual RMS on the level of 1–3 dm. Finally, the performance of the new-generation onboard atomic clocks is evaluated and results confirm an increased stability compared to BDS-2 satellite clocks.

  11. Low-earth-orbit Satellite Internet Protocol Communications Concept and Design

    Science.gov (United States)

    Slywezak, Richard A.

    2004-01-01

    This report presents a design concept for a low-Earth-orbit end-to-end Internet-Protocol- (IP-) based mission. The goal is to maintain an up-to-date communications infrastructure that makes communications seamless with the protocols used in terrestrial computing. It is based on the premise that the use of IPs will permit greater interoperability while also reducing costs and providing users the ability to retrieve data directly from the satellite. However, implementing an IP-based solution also has a number of challenges, since wireless communications have different characteristics than wired communications. This report outlines the design of a low-Earth-orbit end-to-end IP-based mission; the ideas and concepts of Space Internet architectures and networks are beyond the scope of this document. The findings of this report show that an IP-based mission is plausible and would provide benefits to the user community, but the outstanding issues must be resolved before a design can be implemented.

  12. Orbit dynamics and geographical coverage capabilities of satellite-based solar occultation experiments for global monitoring of stratospheric constituents

    Science.gov (United States)

    Brooks, D. R.

    1980-01-01

    Orbit dynamics of the solar occultation technique for satellite measurements of the Earth's atmosphere are described. A one-year mission is simulated and the orbit and mission design implications are discussed in detail. Geographical coverage capabilities are examined parametrically for a range of orbit conditions. The hypothetical mission is used to produce a simulated one-year data base of solar occultation measurements; each occultation event is assumed to produce a single number, or 'measurement' and some statistical properties of the data set are examined. A simple model is fitted to the data to demonstrate a procedure for examining global distributions of atmospheric constitutents with the solar occultation technique.

  13. Orbit Determination Using SLR Data for STSAT-2C: Short-arc Analysis

    Science.gov (United States)

    Kim, Young-Rok; Park, Eunseo; Kucharski, Daniel; Lim, Hyung-Chul

    2015-09-01

    In this study, we present the results of orbit determination (OD) using satellite laser ranging (SLR) data for the Science and Technology Satellite (STSAT)-2C by a short-arc analysis. For SLR data processing, the NASA/GSFC GEODYN II software with one year (2013/04 - 2014/04) of normal point observations is used. As there is only an extremely small quantity of SLR observations of STSAT-2C and they are sparsely distribution, the selection of the arc length and the estimation intervals for the atmospheric drag coefficients and the empirical acceleration parameters was made on an arc-to-arc basis. For orbit quality assessment, the post-fit residuals of each short-arc and orbit overlaps of arcs are investigated. The OD results show that the weighted root mean square post-fit residuals of short-arcs are less than 1 cm, and the average 1-day orbit overlaps are superior to 50/600/900 m for the radial/cross-track/along-track components. These results demonstrate that OD for STSAT-2C was successfully achieved with cm-level range precision. However its orbit quality did not reach the same level due to the availability of few and sparse measurement conditions. From a mission analysis viewpoint, obtaining the results of OD for STSAT-2C is significant for generating enhanced orbit predictions for more frequent tracking.

  14. Orbit Determination Using SLR Data for STSAT-2C:Short-arc Analysis

    Directory of Open Access Journals (Sweden)

    Young-Rok Kim

    2015-09-01

    Full Text Available In this study, we present the results of orbit determination (OD using satellite laser ranging (SLR data for the Science and Technology Satellite (STSAT-2C by a short-arc analysis. For SLR data processing, the NASA/GSFC GEODYN II software with one year (2013/04 – 2014/04 of normal point observations is used. As there is only an extremely small quantity of SLR observations of STSAT-2C and they are sparsely distribution, the selection of the arc length and the estimation intervals for the atmospheric drag coefficients and the empirical acceleration parameters was made on an arc-to-arc basis. For orbit quality assessment, the post-fit residuals of each short-arc and orbit overlaps of arcs are investigated. The OD results show that the weighted root mean square post-fit residuals of short-arcs are less than 1 cm, and the average 1-day orbit overlaps are superior to 50/600/900 m for the radial/cross-track/along-track components. These results demonstrate that OD for STSAT-2C was successfully achieved with cm-level range precision. However its orbit quality did not reach the same level due to the availability of few and sparse measurement conditions. From a mission analysis viewpoint, obtaining the results of OD for STSAT-2C is significant for generating enhanced orbit predictions for more frequent tracking.

  15. Determination of orbits and SLR stations’ coordinates on the basis of laser observations of the satellites Starlette and Stella

    Science.gov (United States)

    Lejba, P.; Schillak, S.; Wnuk, E.

    Orbits of two low satellites Starlette and Stella have been determined on the basis of the observational data collected in 2001 from the best 14 Satellite Laser Ranging stations. The coordinates of seven SLR stations have been determined in the ITRF2000 coordinates frame and compared with the results calculated for the same stations on the basis of Lageos data. All the calculations have been made assuming two models of the Earth gravity field EGM96 and EIGEN-GRACE02S. It has been shown that the best results of satellite orbits determination are obtained with the latest model of the Earth gravity field proposed on the basis of the GRACE mission results. With respect to the results obtained assuming the EGM96 model, the improvement reaches 10-50% both in the values of orbital RMS, and the station coordinates. All the calculations have been performed with the use of GEODYN-II program. The RMS of the orbits of Starlette and Stella varies from 1.02 to 1.90 cm. Such RMS values permit determination of the laser stations to a high accuracy. The results presented in this work show that the data obtained for low satellites such as Starlette or Stella can be successfully applied for determination of the SLR station coordinates.

  16. Shape Shifting Satellites in Binary Near-Earth Asteroids: Do Meteoroid Impacts Play a Role in BYORP Orbital Evolution?

    Science.gov (United States)

    Rubincam, David Parry

    2012-01-01

    Less than catastrophic meteoroid impacts over 10(exp 5) years may change the shape of small rubble-pile satellites in binary NEAs, lengthening the average BYORP (binary Yarkovsky-Radzievskii-Paddack) rate of orbital evolution. An estimate of shape-shifting meteoroid fluxes give numbers close enough to causing random walks in the semimajor axis of binary systems to warrant further investigation

  17. Detection, identification, and classification of mosquito larval habitats using remote sensing scanners in earth-orbiting satellites*

    Science.gov (United States)

    Hayes, Richard O.; Maxwell, Eugene L.; Mitchell, Carl J.; Woodzick, Thomas L.

    1985-01-01

    A method of identifying mosquito larval habitats associated with fresh-water plant communities, wetlands, and other aquatic locations at Lewis and Clark Lake in the states of Nebraska and South Dakota, USA, using remote sensing imagery obtained by multispectral scanners aboard earth-orbiting satellites (Landsat 1 and 2) is described. The advantages and limitations of this method are discussed. PMID:2861917

  18. Impact risk analysis for a spacecraft in Cosmo-Skymed orbit

    Science.gov (United States)

    Giacomuzzo, Cinzia; Francesconi, Alessandro; Anselmo, Luciano

    2010-10-01

    This paper presents a case study of Micrometeoroids and Orbital Debris risk assessment for a spacecraft flying in an orbit close to that of the Italian Cosmo-Skymed constellation. The aim of the analysis was to calculate the failure flux impinging on the satellite external shell, taking into account both geometry and materials of satellite surfaces. Furthermore the analysis included the evaluation of the contribution to debris population at the selected orbit of the fragments produced by a Chinese Anti-SATellite experiment, which caused the catastrophic break-up of the satellite Fengyun 1C in January 2007. A first computation was carried out using ESABASE2/Debris v.1.4.2. This software made it possible to perform geometrical analysis of a satellite subjected to a given debris environment, but the most up to date available models, ORDEM2000 and MASTER2001, gave significantly different results. An independent procedure for risk assessment analysis was implemented to further analyse such issue and to provide damage equation adequate to represent the behaviour of the selected structural aluminium honeycomb sandwich panels covered by Multi-Layer Insulation. Debris fluxes were calculated applying MASTER2005 and ORDEM2000 environment models, then results were compared to those of ESABASE2. Failure fluxes were calculated implementing special damage equations for honeycomb structures available from the open technical literature. The expected flux contribution of catalogued debris from the Chinese Anti-SATellite (ASAT) experiment was estimated independently using the code SDIRAT (Space Debris Impact Risk Analysis Tool) developed at the Institute of Information Science and Technologies (ISTI).

  19. Radiation Dose Analysis of Galactic Cosmic Ray in Low Earth Orbit/Near Equatorial Orbit

    Science.gov (United States)

    Suparta, W.; Zulkeple, S. K.

    2014-10-01

    Space environment contained harmful radiation that posed risk to spacecraft orbiting the Earth. In this paper, we looked into radiation doses caused by galactic cosmic ray (GCR) towards satellites orbiting in low earth orbit (LEO) near Earth's equator (NEqO) and compared them with doses caused by solar energetic particles (SEP) and trapped particles to determine the damage level of GCR. The radiation doses included linear energy transfer (LET) and nonionizing energy loss (NIEL) through a 1mm gallium arsenide (GaAs) planar geometry by using Space Environment Information System (SPENVIS) method. The orbital data followed Malaysian Razaksat satellite at 685km altitude and 9° inclination during selected solar minimum and solar maximum from solar cycles 21 to 24. We found that trapped particles gave the highest LET and no SEP was detected in SPENVIS. The LET values tend to be higher during solar minimum for trapped particles and GCR, corresponding to their anti-correlated fluxes with the solar activity. However, the NIEL values for GCR in solar cycle 23 did not follow the anti-correlation pattern.

  20. Using Polar-orbiting Environmental Satellite data to specify the radiation environment up to 1200 km altitude

    Science.gov (United States)

    O'Brien, T. P.; Mazur, J. E.; Guild, T. B.; Looper, M. D.

    2015-08-01

    Data from the Deal dosimeter payload on the Rapid Pathfinder satellite provide daily maps of the radiation environment on a sphere at 1200 km altitude. Through the use of magnetic coordinates, these dosimeter maps can be projected down to lower altitudes, providing valuable information for satellite anomaly resolution for vehicles in low Earth orbit (LEO). Unfortunately, the Deal data are not widely available, and the mission has a limited lifetime. As an alternative, we present a method to estimate the Deal daily maps using belt index data from NOAA's Polar-orbiting Environmental Satellite (POES) vehicles. The method addresses only trapped radiation but could readily be supplemented with POES's own measurements of solar particle radiation reaching LEO.

  1. Visibility Analysis of Domestic Satellites on Proposed Ground Sites for Optical Surveillance

    Directory of Open Access Journals (Sweden)

    Jung Hyun Jo1

    2011-12-01

    Full Text Available The objectives of this study are to analyze the satellite visibility at the randomly established ground sites, to determine the five optimal ground sites to perform the optical surveillance and tracking of domestic satellites, and to verify the acquisition of the optical observation time sufficient to maintain the precise ephemeris at optimal ground sites that have been already determined. In order to accomplish these objectives, we analyzed the visibility for sun-synchronous orbit satellites, low earth orbit satellites, middle earth orbit satellites and domestic satellites as well as the continuous visibility along with the fictitious satellite ground track, and calculate the effective visibility. For the analysis, we carried out a series of repetitive process using the satellite tool kit simulation software developed by Analytical Graphics Incorporated. The lighting states of the penumbra and direct sun were set as the key constraints of the optical observation. The minimum of the observation satellite elevation angle was set to be 20 degree, whereas the maximum of the sun elevation angle was set to be -10 degree which is within the range of the nautical twilight. To select the candidates for the optimal optical observation, the entire globe was divided into 84 sectors in a constant interval, the visibility characteristics of the individual sectors were analyzed, and 17 ground sites were arbitrarily selected and analyzed further. Finally, five optimal ground sites (Khurel Togoot Observatory, Assy-Turgen Observatory, Tubitak National Observatory, Bisdee Tier Optical Astronomy Observatory, and South Africa Astronomical Observatory were determined. The total observation period was decided as one year. To examine the seasonal variation, the simulation was performed for the period of three days or less with respect to spring, summer, fall and winter. In conclusion, we decided the optimal ground sites to perform the optical surveillance and tracking

  2. State/orbit estimation from real Doppler data for solid apogee motor burning phase of geostationary satellite

    Science.gov (United States)

    Ono, S.

    Methods for the state/orbit sequential estimation from real Doppler data for the solid ABM burning phase are presented. The estimations were performed for Engineering Test Satellite 2, and for 2 satellites which both failed during this ABM phase. The state estimations were performed by deterministic and stochastic methods using real Doppler data intermittently acquired at the neighboring tracking stations. The deterministic method conquers this intermittence and estimates well the motor acceleration, but the attitude change is strongly influenced by the neighboring geometry. The stochastic Kalman sequential filter, constructed with spin dynamics considerations, conquers the intermittence and the neighboring geometry and excellently estimates the acceleration and the attitude drift due to an unbalance with reasonably converging variances. The estimated state/orbit at ABM burn out agrees well with the drift orbit and the attitude independently determined by the batch method.

  3. Frozen orbits for satellites close to an earth-like planet

    Science.gov (United States)

    Coffey, Shannon L.; Deprit, Andre; Deprit, Etienne

    1994-05-01

    We say that a planet is Earth-like if the coefficient of the second order zonal harmonic dominates all other coefficients in the gravity field. This paper concerns the zonal problem for satellites around an Earth-like planet, all other perturbations excluded. The potential contains all zonal coefficients J2 through J9. The model problem is averaged over the mean anomaly by a Lie transformation to the second order; we produce the resulting Hamiltonian as a Fourier series in the argument of perigee whose coefficients are algebraic functions of the eccentricity - not truncated power series. We then proceed to a global exploration of the equilibria in the averaged problem. These singularities which aerospace engineers know by the name of frozen orbits are located by solving the equilibria equations in two ways, (1) analytically in the neighborhood of either the zero eccentricity or the critical inclination, and (2) numerically by a Newton-Raphson iteration applied to an approximate position read from the color map of the phase flow. The analytical solutions we supply in full to assist space engineers in designing survey missions. We pay special attention to the manner in which additional zonal coefficients affect the evolution of bifurcations we had traced earlier in the main problem (J2 only). In particular, we examine the manner in which the odd zonal J3 breaks the discrete symmetry inherent to the even zonal problem. In the even case, we find that Vinti's problem (J4 + J22 = 0) p resents a degeneracy in the form of non-isolated equilibria; we surmise that the degeneracy is a reflection of the fact that Vinti's problem is separable. By numerical continuation we have discovered three families of frozen orbits in the full zonal problem under consideration; (1) a family of stable equilibria starting from the equatorial plane and tending to the critical inclination; (2) an unstable family arising from the bifurcation at the critical inclination; (3) a stable family also

  4. A Statistical Study of the Spatial Extent of Relativistic Electron Precipitation With Polar Orbiting Environmental Satellites

    Science.gov (United States)

    Shekhar, Sapna; Millan, Robyn; Smith, David

    2017-11-01

    Relativistic electron precipitation (REP) in the atmosphere can contribute significantly to electron loss from the outer radiation belts. In order to estimate the contribution to this loss, it is important to estimate the spatial extent of the precipitation region. We observed REP with the zenith pointing (0°) Medium Energy Proton Electron Detector (MEPED) on board Polar Orbiting Environmental Satellites (POES), for 15 years (2000-2014) and used both single-satellite and multisatellite measurements to estimate an average extent of the region of precipitation in L shell and magnetic local time (MLT). In the duration of 15 years (2000-2014), 31,035 REP events were found in this study. Events were found to split into two classes; one class of events coincided with proton precipitation in the P1 channel (30-80 keV), were located in the dusk and early morning sector, and were more localized in L shell (dL < 0.5), whereas the other class of events did not coincide with proton precipitation, were located mostly in the midnight sector, and were wider in L shell (dL ˜ 1-2.5). Both classes were highly localized in MLT (dMLT ≤ 3 h), occurring mostly during the declining phase of the solar cycle and geomagnetically active times. The events located in the midnight sector for both classes were found to be associated with tail magnetic field stretching which could be due to the fact that they tend to occur mostly during geomagnetically active times or could imply that precipitation is caused by current sheet scattering.

  5. The effect of proton radiation on the EMCCD for a low Earth orbit satellite mission

    Science.gov (United States)

    Smith, Ken; Daigle, Olivier; Scott, Alan; Piche, Louis; Hudson, Danya

    2016-08-01

    We report on the proton radiation effects on a 1k x 1k e2v EMCCD utilized in the Nüvü EM N2 1024 camera. Radiation testing was performed at the TRIUMF Proton Irradiation Facility in Canada, where the e2v CCD201-20 EMCCD received a 105 MeV proton fluence up to 5.2x109 protons/cm2, emulating a 1 year's radiation dose of solar protons in low earth orbit with nominal shielding that would be expected from a small or microsatellite. The primary space-based application is for Space Situational Awareness (SSA), where a small telescope images faint orbiting Resident Space Objects (RSOs) on the EMCCD, resulting in faint streaks at the photon level of signal in the images. Of particular concern is the effect of proton radiation on low level CTE, where very low level signals could be severely impaired if not lost. Although other groups have reported on the characteristics of irradiated EMCCDs, their CTE results are not portable to this application. To understand the real impact of proton irradiation the device must be tested under realistic operating conditions with representative backgrounds, clock periods, and signal levels. Testing was performed both in the laboratory and under a night sky on the ground in order to emulate a complex star background environment containing RSOs. The degradation is presented and mitigation techniques are proposed. As compared to conventional CCDs, the EMCCD with high gain allows faint and moving RSOs to be detected with a relatively small telescope aperture, at improved signal to noise ratio at high frame rates. This allows the satellite platform to take sharp images immediately upon slewing to the target without the need for complex and relatively slow attitude stabilization systems.

  6. Orbit Determination Using SLR Data for STSAT-2C:Short-arc Analysis

    OpenAIRE

    Young-Rok Kim; Eunseo Park; Daniel Kucharski; Hyung-Chul Lim

    2015-01-01

    In this study, we present the results of orbit determination (OD) using satellite laser ranging (SLR) data for the Science and Technology Satellite (STSAT)-2C by a short-arc analysis. For SLR data processing, the NASA/GSFC GEODYN II software with one year (2013/04 – 2014/04) of normal point observations is used. As there is only an extremely small quantity of SLR observations of STSAT-2C and they are sparsely distribution, the selection of the arc length and the estimation intervals ...

  7. Capacity Model and Constraints Analysis for Integrated Remote Wireless Sensor and Satellite Network in Emergency Scenarios.

    Science.gov (United States)

    Zhang, Wei; Zhang, Gengxin; Dong, Feihong; Xie, Zhidong; Bian, Dongming

    2015-11-17

    This article investigates the capacity problem of an integrated remote wireless sensor and satellite network (IWSSN) in emergency scenarios. We formulate a general model to evaluate the remote sensor and satellite network capacity. Compared to most existing works for ground networks, the proposed model is time varying and space oriented. To capture the characteristics of a practical network, we sift through major capacity-impacting constraints and analyze the influence of these constraints. Specifically, we combine the geometric satellite orbit model and satellite tool kit (STK) engineering software to quantify the trends of the capacity constraints. Our objective in analyzing these trends is to provide insights and design guidelines for optimizing the integrated remote wireless sensor and satellite network schedules. Simulation results validate the theoretical analysis of capacity trends and show the optimization opportunities of the IWSSN.

  8. Capacity Model and Constraints Analysis for Integrated Remote Wireless Sensor and Satellite Network in Emergency Scenarios

    Directory of Open Access Journals (Sweden)

    Wei Zhang

    2015-11-01

    Full Text Available This article investigates the capacity problem of an integrated remote wireless sensor and satellite network (IWSSN in emergency scenarios. We formulate a general model to evaluate the remote sensor and satellite network capacity. Compared to most existing works for ground networks, the proposed model is time varying and space oriented. To capture the characteristics of a practical network, we sift through major capacity-impacting constraints and analyze the influence of these constraints. Specifically, we combine the geometric satellite orbit model and satellite tool kit (STK engineering software to quantify the trends of the capacity constraints. Our objective in analyzing these trends is to provide insights and design guidelines for optimizing the integrated remote wireless sensor and satellite network schedules. Simulation results validate the theoretical analysis of capacity trends and show the optimization opportunities of the IWSSN.

  9. Orbital

    OpenAIRE

    Yourshaw, Matthew Stephen

    2017-01-01

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

  10. Orbital analysis of two-color laser ranging

    Science.gov (United States)

    Schillak, S. R.

    2013-12-01

    The poster presents the results of analysis of Zimmerwald SLR data for two colors 423nm and 846 nm. Two-color laser ranging were performed by Zimmerwald SLR station from August 2002 to January 2008. The results in each color were treated as two independent stations 7810 Blue and 7810 Infrared. The station positions were determined by NASA Goddard's orbital program GEODYN-II from results of LAGEOS-1 and LAGEOS-2 satellites. The NEU positions stability were equal to 3.5 mm (N), 3.2 mm (E), 16.5 mm (U) for blue and 3.2 mm (N), 2.9 mm (E), 14.6 (U) for infrared. In the period of study were 47 common monthly points for both colors. The difference between N, E, U components in blue and infrared for common points were equal to 0.8×2.0 mm, 0.4×1.9 mm and -4.8×8.7 mm respectively. The differences between Range Biases for both colors independently for LAGEOS-1 and LAGEOS-2 were equal to -5.7×8.6 mm and for -5.0×9.5 mm respectively. The same for both satellites annual wave with amplitude 10 mm was detected. This effect can to be explain by differences in atmospheric correction for each color. This same analysis for station Concepcion (7405) couldn't to be performed due to only 8 common points. In future very important should be laser ranging in two-colors 532 nm and 1064 nm for confirmation presented here results, especially that a new sensitive APD detectors for 1064 nm are now available. The atmospheric correction is critical for SLR accuracy upgrading.

  11. Space Debris Attitude Simulation - IOTA (In-Orbit Tumbling Analysis)

    Science.gov (United States)

    Kanzler, R.; Schildknecht, T.; Lips, T.; Fritsche, B.; Silha, J.; Krag, H.

    Today, there is little knowledge on the attitude state of decommissioned intact objects in Earth orbit. Observational means have advanced in the past years, but are still limited with respect to an accurate estimate of motion vector orientations and magnitude. Especially for the preparation of Active Debris Removal (ADR) missions as planned by ESA's Clean Space initiative or contingency scenarios for ESA spacecraft like ENVISAT, such knowledge is needed. The In-Orbit Tumbling Analysis tool (IOTA) is a prototype software, currently in development within the framework of ESA's “Debris Attitude Motion Measurements and Modelling” project (ESA Contract No. 40000112447), which is led by the Astronomical Institute of the University of Bern (AIUB). The project goal is to achieve a good understanding of the attitude evolution and the considerable internal and external effects which occur. To characterize the attitude state of selected targets in LEO and GTO, multiple observation methods are combined. Optical observations are carried out by AIUB, Satellite Laser Ranging (SLR) is performed by the Space Research Institute of the Austrian Academy of Sciences (IWF) and radar measurements and signal level determination are provided by the Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR). Developed by Hyperschall Technologie Göttingen GmbH (HTG), IOTA will be a highly modular software tool to perform short- (days), medium- (months) and long-term (years) propagation of the orbit and attitude motion (six degrees-of-freedom) of spacecraft in Earth orbit. The simulation takes into account all relevant acting forces and torques, including aerodynamic drag, solar radiation pressure, gravitational influences of Earth, Sun and Moon, eddy current damping, impulse and momentum transfer from space debris or micro meteoroid impact, as well as the optional definition of particular spacecraft specific influences like tank sloshing, reaction wheel behaviour

  12. Improved Reliability of Orbital Rendezvous Operations by Using Small Satellites for Reconnaissance

    Science.gov (United States)

    Rughani, Rahul

    This research explores the use of cubesats as an alternative to fixed radar platforms when performing rendezvous operations between spacecraft in orbit. In order to be a viable alternative, this system needs to be at least as reliable as current systems in use, less costly, and most importantly it must be safe. The main goal of this research is to investigate the application of this system architecture in Low Earth Orbit (LEO), however it can also be applied in Geostationary Orbit (GEO) as will be shown later on. To do this, reliability, safety, and orbit simulations were created in Matlab and run for various formations of cubesats. The system reliability was modeled using an aggregation of the reliabilities of the individual components, with the reliability decreasing exponentially over time. The orbital dynamics of the rendezvous motion was modeled using the Clohessy-Wiltshire linearized approximations for relative motion. Safety analysis was performed by analyzing the orbital characteristics of the system given small perturbations at critical points in the mission, observing how this changes the dynamics of the system and whether or not these changes could make the system unsafe, or dangerous to other spacecraft. The results of these simulations yielded interesting results, demonstrating that such a system architecture can in fact be cheaper, more reliable, and safer than current systems in use, so long as a minimum number of cubesats are employed. Not only can the system be more reliable than current systems, it also has the ability to gather much more accurate data due to the multiple vantage points available. This research also investigates a potential design for the cubesat to be used for this mission. It has been designed in order to acquire targets and function even in the case when the target spacecraft is damaged and unresponsive, or sending bad data to operators on the ground. This ability to rendezvous with a non-cooperative spacecraft is not possible

  13. Thermal Analysis of Iodine Satellite (iSAT)

    Science.gov (United States)

    Mauro, Stephanie

    2015-01-01

    This paper presents the progress of the thermal analysis and design of the Iodine Satellite (iSAT). The purpose of the iSAT spacecraft (SC) is to demonstrate the ability of the iodine Hall Thruster propulsion system throughout a one year mission in an effort to mature the system for use on future satellites. The benefit of this propulsion system is that it uses a propellant, iodine, that is easy to store and provides a high thrust-to-mass ratio. The spacecraft will also act as a bus for an earth observation payload, the Long Wave Infrared (LWIR) Camera. Four phases of the mission, determined to either be critical to achieving requirements or phases of thermal concern, are modeled. The phases are the Right Ascension of the Ascending Node (RAAN) Change, Altitude Reduction, De-Orbit, and Science Phases. Each phase was modeled in a worst case hot environment and the coldest phase, the Science Phase, was also modeled in a worst case cold environment. The thermal environments of the spacecraft are especially important to model because iSAT has a very high power density. The satellite is the size of a 12 unit cubesat, and dissipates slightly more than 75 Watts of power as heat at times. The maximum temperatures for several components are above their maximum operational limit for one or more cases. The analysis done for the first Design and Analysis Cycle (DAC1) showed that many components were above or within 5 degrees Centigrade of their maximum operation limit. The battery is a component of concern because although it is not over its operational temperature limit, efficiency greatly decreases if it operates at the currently predicted temperatures. In the second Design and Analysis Cycle (DAC2), many steps were taken to mitigate the overheating of components, including isolating several high temperature components, removal of components, and rearrangement of systems. These changes have greatly increased the thermal margin available.

  14. Integrated Adaptive Analysis and Visualization of Satellite Network Data Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to develop a system that enables integrated and adaptive analysis and visualization of satellite network management data. Integrated analysis and...

  15. Advanced Communication Technology Satellite (ACTS) multibeam antenna analysis and experiment

    Science.gov (United States)

    Acosta, Roberto J.; Lagin, Alan R.; Larko, Jeffrey M.; Narvaez, Adabelle

    1992-01-01

    One of the most important aspects of a satellite communication system design is the accurate estimation of antenna performance degradation. Pointing error, end coverage gain, peak gain degradation, etc. are the main concerns. The thermal or dynamic distortions of a reflector antenna structural system can affect the far-field antenna power distribution in a least four ways. (1) The antenna gain is reduced; (2) the main lobe of the antenna can be mispointed thus shifting the destination of the delivered power away from the desired locations; (3) the main lobe of the antenna pattern can be broadened, thus spreading the RF power over a larger area than desired; and (4) the antenna pattern sidelobes can increase, thus increasing the chances of interference among adjacent beams of multiple beam antenna system or with antenna beams of other satellites. The in-house developed NASA Lewis Research Center thermal/structural/RF analysis program was designed to accurately simulate the ACTS in-orbit thermal environment and predict the RF antenna performance. The program combines well establish computer programs (TRASYS, SINDA and NASTAN) with a dual reflector-physical optics RF analysis program. The ACTS multibeam antenna configuration is analyzed and several thermal cases are presented and compared with measurements (pre-flight).

  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. Technique for Geolocation of EMI Emitters by O3B Satellites

    Science.gov (United States)

    2016-06-01

    electronic warfare GEO geosynchronous orbit GHz gigahertz GPS Global Positioning System HEO highly elliptical orbit HTS high throughput satellite Hz...altitude MEO medium Earth orbit SATCOM satellite communications SIGINT signals intelligence SMAD Space Mission Analysis and Design STK Systems Tool...having a basic understanding of satellite communications (SATCOM) and orbital mechanics, as the underlying concepts used in techniques for geolocation of

  18. Estimates of Minimum Energy Requirements for Range-Controlled Return of a Nonlifting Satellite from a Circular Orbit

    Science.gov (United States)

    Jackson, Charlie M., Jr.

    1961-01-01

    Existing expressions are used to obtain the minimum propellant fraction required for return from a circular orbit as a function of vacuum trajectory range. trajectory are matched to those of the atmospheric trajectory to obtain a complete return from orbit to earth. The results are restricted by the assumptions of (1) impulsive velocity change, (2) nearly circular transfer trajectory, ( 3) spherical earth, atmosphere, and gravitational field, (4) exponential atmospheric density variation with attitude, and (5) a nonrotating atmosphere. The solutions for the parameters of the vacuum Calculations are made t o determine the effects of longitudinal and lateral range on required propeUant fraction and reentry loading for a nonrotating earth and for several orbital altitudes. the single- and two-impulse method of return is made and the results indicate a "trade off" between propellant fraction required and landing- position accuracy. A comparison of An example of a return mission from a polar orbit is discussed where the initial deorbit point is the intersection of the North Pole horizon with the satellite orbit. Some effects of a rotating earth are also considered. It is found that, for each target-orbital-plane longitudinal difference, there exists a target latitude for which the required propellant fraction is a minimum.

  19. Space Shuttle Orbiter windshield bird impact analysis

    Science.gov (United States)

    Edelstein, Karen S.; McCarty, Robert E.

    The NASA Space Shuttle Orbiter's windshield employs three glass panes separated by air gaps. The brittleness of the glass offers much less birdstrike energy-absorption capability than the laminated polycarbonate windshields of more conventional aircraft; attention must accordingly be given to the risk of catastrophic bird impact, and to methods of strike prevention that address bird populations around landing sites rather than the modification of the window's design. Bird populations' direct reduction, as well as careful scheduling of Orbiter landing times, are suggested as viable alternatives. The question of birdstrike-resistant glass windshield design for hypersonic aerospacecraft is discussed.

  20. The Operational Utility of Space Environmental Measurements From Polar-Orbiting, Sun-Synchronous Satellites in AFWA Models and Applications

    Science.gov (United States)

    Citrone, P. J.; Bonadonna, M. F.; Cade, T.; Nobis, T. E.; Denig, W. F.

    2005-12-01

    Satellite-based measurements of the space environment provide vital data inputs to advanced space weather models and applications used by the Air Force Weather Agency (AFWA) to generate mission-tailored space weather intelligence in support of U.S. military operations. Since the 1970's, the Defense Meteorological Satellite Program (DMSP) has provided in-situ measurements of the topside ionosphere and of the differential energy flux of precipitating electrons and ions into the auroral and polar regions. Recently, DMSP has deployed a new class of ultraviolet remote sensors which offer opportunities for improved space environmental monitoring. The DMSP polar-orbiting, sun-synchronous satellite measurements provide critical data inputs for current and future AFWA space weather models that specify and forecast the global thermosphere, ionosphere, and magnetosphere. The AFWA Space Weather Technology Branch is pursuing an ongoing effort to transition to operations advanced research technologies associated with space environmental forecasting, to include related software applications used by AFWA to generate mission-tailored visualization products that depict space weather impacts on military systems. The Space Environmental Sensor Suite (SESS) on the National Polar-orbiting Operational Environmental Satellite System (NPOESS) will offer improved capabilities in terms of characterization and timeliness for space environmental data required by AFWA to meet new and emerging Department of Defense space weather operational requirements.

  1. Boomerang Satellites

    Science.gov (United States)

    Hesselbrock, Andrew; Minton, David A.

    2017-10-01

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

  2. Global Navigation Satellite System (GNSS) Ultra-Rapid Orbit Product (sub-daily files, generated 4 times/day) from NASA CDDIS

    Data.gov (United States)

    National Aeronautics and Space Administration — This derived product set consists of Global Navigation Satellite System Ultra-Rapid Orbit Product (daily files, generated daily) from the NASA Crustal Dynamics Data...

  3. 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.

  4. Military Applications of High-Altitude Satellite Orbits in a Multi-Body Dynamical Environment Using Numerical Methods and Dynamical Systems Theory

    Science.gov (United States)

    2016-03-01

    multi-body dynamical model. Other potential applications of the tools in the present investigation include mis - sions that start in the near-Earth...MILITARY APPLICATIONS OF HIGH-ALTITUDE SATELLITE ORBITS IN A MULTI-BODY DYNAMICAL ENVIRONMENT USING NUMERICAL METHODS AND DYNAMICAL SYSTEMS THEORY...16-M-247 MILITARY APPLICATIONS OF HIGH-ALTITUDE SATELLITE ORBITS IN A MULTI-BODY DYNAMICAL ENVIRONMENT USING NUMERICAL METHODS AND DYNAMICAL SYSTEMS

  5. Inter-satellite laser link simulation analysis

    Science.gov (United States)

    Tong, Lanjuan; Guan, Hui; Wang, Zhilin

    2015-11-01

    The characteristic of satellite communication link was firstly described and four application modes were put forward. By comparison, it is suggested that microwave link is used in satellite-to-ground communication and laser link is used in inter-satellite communication. Secondly the condition and composition of laser link establishment was analyzed and laser link model was set up, and the principle and composition of APT system was described. Finally, based on STK and MATLAB platform, the process of inter-satellite laser link establishment was designed, and setting the scene of TDRS capturing and tracking user's satellite as an example, simulation was realized and demonstrated.

  6. Orbital

    Science.gov (United States)

    Hanson, Robert M.

    2003-06-01

    ORBITAL requires the following software, which is available for free download from the Internet: Netscape Navigator, version 4.75 or higher, or Microsoft Internet Explorer, version 5.0 or higher; Chime Plug-in, version compatible with your OS and browser (available from MDL).

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

    Data.gov (United States)

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

  8. GPM GROUND VALIDATION SATELLITE SIMULATED ORBITS MC3E V1

    Data.gov (United States)

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

  9. GPM GROUND VALIDATION SATELLITE SIMULATED ORBITS C3VP V1

    Data.gov (United States)

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

  10. 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.

  11. Prototype Design and Mission Analysis for a Small Satellite Exploiting Environmental Disturbances for Attitude Stabilization

    Science.gov (United States)

    2016-03-01

    Responsive Satellite PD Proportional-Derivative P-POD Poly-Picosatellite Orbital Deployer RAAN Right Ascension of Ascending Node RW Reaction Wheel SSA...length, mission duration and even the orbital altitudes got bigger, wider, and higher. The performance requirements dictated bigger satellites , so...Equatorial Orbit (GEO) belt are large antennas and solar panels on satellites , large telescopes as payloads on spacecraft and the football-field

  12. 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

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

    Science.gov (United States)

    Schweitzer, S.; Kirchengast, G.; Proschek, V.

    2011-10-01

    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 conclude that

  14. 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

  15. Orbiter CCTV video signal noise analysis

    Science.gov (United States)

    Lawton, R. M.; Blanke, L. R.; Pannett, R. F.

    1977-01-01

    The amount of steady state and transient noise which will couple to orbiter CCTV video signal wiring is predicted. The primary emphasis is on the interim system, however, some predictions are made concerning the operational system wiring in the cabin area. Noise sources considered are RF fields from on board transmitters, precipitation static, induced lightning currents, and induced noise from adjacent wiring. The most significant source is noise coupled to video circuits from associated circuits in common connectors. Video signal crosstalk is the primary cause of steady state interference, and mechanically switched control functions cause the largest induced transients.

  16. Utilization of landmark data in attitude/orbit determination. [for earth stabilized satellites

    Science.gov (United States)

    Siddalingaiah, H.; Desai, P. S.

    1975-01-01

    A mathematical model is reported for determination of satellite position, velocity, and attitude using landmark coordinates as observables. This model, although developed with respect to earth stabilized missions, Tiros-N and Nimbus-G in particular, is applicable to any earth stabilized satellite in general.

  17. Nonlinear Least Squares Method for Gyros Bias and Attitude Estimation Using Satellite Attitude and Orbit Toolbox for Matlab

    Science.gov (United States)

    Silva, W. R.; Kuga, H. K.; Zanardi, M. C.

    2015-10-01

    The knowledge of the attitude determination is essential to the safety and control of the satellite and payload, and this involves approaches of nonlinear estimation techniques. Here one focuses on determining the attitude and the gyros drift of a real satellite CBERS-2 (China Brazil Earth Resources Satellite) using simulated measurements provided by propagator PROPAT Satellite Attitude and Orbit Toolbox for Matlab. The method used for the estimation was the Nonlinear Least Squares Estimation (NLSE). The attitude dynamical model is described by nonlinear equations involving the Euler angles. The attitude sensors available are two DSS (Digital Sun Sensor), two IRES (Infra-Red Earth Sensor), and one triad of mechanical gyros. The two IRES give direct measurements of roll and pitch angles with a certain level of error. The two DSS are nonlinear functions of roll, pitch, and yaw attitude angles. Gyros are very important sensors, as they provide direct incremental angles or angular velocities. However gyros present several sources of error of which the drift is the most troublesome. Results show that one can reach accuracies in attitude determination within the prescribed requirements, besides providing estimates of the gyro drifts which can be further used to enhance the gyro error model.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-07-07

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

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

    Science.gov (United States)

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

    2011-01-01

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

  20. [Analysis of variation of orbital openings in contemporary skulls].

    Science.gov (United States)

    Gawlikowska-Sroka, Aleksandra

    2013-01-01

    The size and symmetry of the eye-socket have puzzled many medical and biological scientists. The orbit is a very complicated skull part because of the great number of bones involved in its structure, and its specific physiological function. The aim of our study was to estimate variations in the shape, size and position of the orbital openings in contemporary human skulls by using computer software. The material consisted of 80 male human skulls of the European population from the beginning of the 20th century. X-ray photographs were taken in the P-A projection, then the images were scanned and calibrated by means of MicroStation 95 Academic Edition software. Tools for measuring the vector elements were used to assess measurements: n-mf, mf-ml, mf-ek, spa--sbk and the area of the orbital opening. The orbital index and the index of morphological asymmetry were assessed. Michalski's tables were used to establish orbit features. The statistical analysis was performed using the Statistica computer software package. Measurements of the eye--socket position in relation to the mid-line were significantly more frequently larger on the left-hand side, which means a more lateral position of orbits on that side. The measurements of breadth, height and area were more frequently larger on the right side. The asymmetry index was significant for orbit width. The majority of the examined orbits were classified as hypsikonch, according to the orbital index. According to Michalski's scale, the dominant size data described orbital openings in the European population from the West Pomeranian region. The awareness of variability in this area is necessary for the correct interpretation of patients' examination results, reconstruction planning, in forensic medicine, and anthropology.

  1. TriTel-S: Development of a complex dosimetry instrument for a satellite in geostationary transfer orbit

    Energy Technology Data Exchange (ETDEWEB)

    Hirn, A. [Hungarian Academy of Sciences KFKI Atomic Energy Research Institute, P.O. Box 49, H-1525 Budapest (Hungary)], E-mail: hirn@aeki.kfki.hu; Pazmandi, T.; Deme, S.; Apathy, I. [Hungarian Academy of Sciences KFKI Atomic Energy Research Institute, P.O. Box 49, H-1525 Budapest (Hungary); Bodnar, L. [BL-Electronics, Sport u. 5, H-2083 Solymar (Hungary); Csoke, A. [Hungarian Academy of Sciences KFKI Atomic Energy Research Institute, P.O. Box 49, H-1525 Budapest (Hungary)

    2008-02-15

    One of the many risks of long-duration space flights is the excessive exposure to cosmic radiation, which may have serious consequences particularly during solar flares and higher solar activity. Since space radiation mainly consists of charged heavy particles, the equivalent dose differs significantly from the absorbed dose. The objectives of this project, which began in the KFKI Atomic Energy Research Institute of the Hungarian Academy of Sciences several years ago, are to develop a three-dimensional silicon detector telescope (TriTel) and to develop software for data evaluation of the measured energy deposition spectra. A version of TriTel will be installed onboard a European satellite (ESEO) in a highly eccentric orbit crossing, the Van Allen belts. The instrument will encounter high fluxes of trapped electron radiation in a considerable part of the orbit. In order to give a rough estimate of the expected fluxes and spectra of protons and electrons in orbit, calculations were made with the Space Environment Information System (SPENVIS) online tool. The number of electron coincidences and the deposited energy spectra of electrons were calculated with the Monte Carlo simulation-based software MUlti-LAyered Shielding SImulation Software (MULASSIS). The description of the instrument, the expected environment in orbit and the evaluation of the results of the preliminary simulations are discussed in this paper.

  2. 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.

  3. Analysis of orbitally excited B-mesons

    CERN Document Server

    Albrecht, Zoltan; Quast, Gunter

    2003-01-01

    This thesis reports on the study of orbitally excited B** mesons in DELPHI b-events taken in the years 1994 to 2000 with the DELPHI detector at the LEP collider. The analyses presented represent the result of applying much improved and extended techniques of spectroscopy since the first DELPHI publication in 1995. A major improvement has occurred in the area of particle identification, where a neural network approach has been implemented in the DELPHI software package. Developments in the area of neural networks have led to much improved enrichment of the excited B states. The Bˆ{**} neural networks identify, on a track-by-track basis, the decay pion/kaon originating from the Bˆ{**} decay, suppressing background and keeping signal events in an efficient way. To improve detector resolution, a further application of neural networks has been applied to reconstruct the underlying Q-value. The corresponding network gives a correction on existing measurements of the Q-value in the form of a probability density fu...

  4. 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.

  5. A System Design and Analysis for Satellite Communication Link

    Directory of Open Access Journals (Sweden)

    Tae Jin Chung

    2000-12-01

    Full Text Available A satellite RF communication link is analyzed based on a simple fundamental equations by systematic approach in this paper. The number of variables related to a design and analysis of satellite RF link is often a dozen or more, thus it is a tedious and time-consuming task. With the given input data, the important parameters are calculated step by step and three communication characteristics such as communication channel capacity, carrier-to-noise ratio (CNR at the satellite and ground station are analyzed. It gives very useful information to the system engineers for designing and analyzing the overall satellite communication system in the conceptual design phase.

  6. 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.

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

    Science.gov (United States)

    2015-08-07

    the field of the earth of the general-relativistic precession of the LAGEOS II pericenter and new constraints on non-newtonian gravity,” Physical ...Journal of Geodesy , Vol. 72, No. 6, 1998, pp. 333–342. [19] “Etalon-1, and -2,” http://ilrs.gsfc.nasa.gov/missions/satellite_missions...current_missions/g129_general.html, 2012. [24] L. Kanner and Associates, “Translation of ’Le satellite de geodesie ’Starlette’,’ Groupe de Recherches

  8. Independent Orbiter Assessment (IOA): Weibull analysis report

    Science.gov (United States)

    Raffaelli, Gary G.

    1987-01-01

    The Auxiliary Power Unit (APU) and Hydraulic Power Unit (HPU) Space Shuttle Subsystems were reviewed as candidates for demonstrating the Weibull analysis methodology. Three hardware components were identified as analysis candidates: the turbine wheel, the gearbox, and the gas generator. Detailed review of subsystem level wearout and failure history revealed the lack of actual component failure data. In addition, component wearout data were not readily available or would require a separate data accumulation effort by the vendor. Without adequate component history data being available, the Weibull analysis methodology application to the APU and HPU subsystem group was terminated.

  9. Nonlinear Uncertainty Propagation of Satellite State Error for Tracking and Conjunction Risk Assessment

    Science.gov (United States)

    2017-12-18

    quantification in non-linear systems with application to orbit trajectory prediction and satellite conjunction analysis. This statistical approach...approaches for orbit state estimation assume the probability of the satellite location is Gaussian in 3-dimensions, and propagates it as growing...important for identifying objects and finding them after several orbits . However, when predicting rare events, such as satellite collisions, rare

  10. Quad-Tree Visual-Calculus Analysis of Satellite Coverage

    Science.gov (United States)

    Lo, Martin W.; Hockney, George; Kwan, Bruce

    2003-01-01

    An improved method of analysis of coverage of areas of the Earth by a constellation of radio-communication or scientific-observation satellites has been developed. This method is intended to supplant an older method in which the global-coverage-analysis problem is solved from a ground-to-satellite perspective. The present method provides for rapid and efficient analysis. This method is derived from a satellite-to-ground perspective and involves a unique combination of two techniques for multiresolution representation of map features on the surface of a sphere.

  11. 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... proposed rule that appeared in the Federal Register of March 8, 2013. The document proposed rules for Earth...

  12. 78 FR 14952 - Earth Stations Aboard Aircraft Communicating with Fixed-Satellite Service Geostationary-Orbit...

    Science.gov (United States)

    2013-03-08

    ... COMMISSION 47 CFR Part 2 Earth Stations Aboard Aircraft Communicating with Fixed-Satellite Service... of Earth Stations Aboard Aircraft (ESAA) in the 14.0-14.5 GHz band from secondary to primary and... stations of the FSS on a primary basis in the 11.7-12.2 GHz band (space-to-Earth), on an unprotected basis...

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

    Science.gov (United States)

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

    2017-10-01

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

  14. Remotely sensed soil temperatures beneath snow-free skin-surface using thermal observations from tandem polar-orbiting satellites: An analytical three-time-scale model

    DEFF Research Database (Denmark)

    Zhan, Wenfeng; Zhou, Ji; Ju, Weimin

    2014-01-01

    -surface. This study shows that thermal remote sensing can be used to estimate soil temperatures. Our results provide insights into thermal observations collected with tandem polar-orbiting satellites when used toward obtaining soil temperatures under clear-sky conditions without the use of any ground......, including the daily-averaged temperature, thermal inertia, upward surface flux factor, and day-to-day change rate. Thus, under clear-sky conditions, the four thermal measurements in a diurnal cycle recorded with tandem polar-orbiting satellites are sufficient for reconstructing the DTC of both land surface...... and soil temperatures. Polar-orbiting satellite data from MODIS are used to show the model's capability. The results demonstrate that soil temperatures with a spatial resolution of 1km under snow-free conditions can be generated at any time of a clear-sky day. Validation is performed by using a comparison...

  15. 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.

  16. Near-Earth Object Survey Orbit Quality Analysis

    Science.gov (United States)

    Buie, Marc W.

    2013-05-01

    Abstract (2,250 Maximum Characters): The Sentinel Mission is currently under development by the B612 Foundation and Ball Aerospace. The mission concept is based on a space-based infrared telescope in an independent orbit similar to that of Venus. Being in an orbit interior to the Earth greatly reduces the time to complete the survey of the near-Earth region compared to a similar survey that could be accomplished from ground-based or orbiting observatory near the Earth. One of the key mission design elements is the cadence of observation. This involves the tiling pattern for how the instrument field-of-view maps out the sky and the repeat interval between successive observations. This presentation will show a quantitative analysis of orbit determination from this type of platform and show how the expected distribution of NEOs will be observed and the orbit qualities that will result. From this analysis, limits can then be placed on the degree of confusion that the cadence can tolerate before linking different epochs becomes problematic.

  17. A Land Product Characterization System for Comparative Analysis of Satellite Data and Products

    Directory of Open Access Journals (Sweden)

    Kevin Gallo

    2017-12-01

    Full Text Available A Land Product Characterization System (LPCS has been developed to provide land data and products to the community of individuals interested in validating space-based land products by comparing them with similar products available from other sensors or surface-based observations. The LPCS facilitates the application of global multi-satellite and in situ data for characterization and validation of higher-level, satellite-derived, land surface products (e.g., surface reflectance, normalized difference vegetation index, and land surface temperature. The LPCS includes data search, inventory, access, and analysis functions that will permit data to be easily identified, retrieved, co-registered, and compared statistically through a single interface. The system currently includes data and products available from Landsat 4 through 8, Moderate Resolution Imaging Spectroradiometer (MODIS Terra and Aqua, Suomi National Polar-Orbiting Partnership (S-NPP/Joint Polar Satellite System (JPSS Visible Infrared Imaging Radiometer Suite (VIIRS, and simulated data for the Geostationary Operational Environmental Satellite (GOES-16 Advanced Baseline Imager (ABI. In addition to the future inclusion of in situ data, higher-level land products from the European Space Agency (ESA Sentinel-2 and -3 series of satellites, and other high and medium resolution spatial sensors, will be included as available. When fully implemented, any of the sensor data or products included in the LPCS would be available for comparative analysis.

  18. NOAA/NESDIS Satellite Derived Surface Oil Analysis Products

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NESDIS Experimental Marine Pollution Surveillance Report (EMPSR) and the Daily Composite product are new products of the NOAA Satellite Analysis Branch and...

  19. Measurement, analysis and correction of the closed orbit distortion ...

    Indian Academy of Sciences (India)

    2013-02-01

    Feb 1, 2013 ... Abstract. The paper presents the measurement, analysis and correction of closed orbit distortion. (COD) in Indus-2 at 550 MeV injection energy and 2 GeV synchrotron radiation user run energy. The measured COD was analysed and fitted to understand major sources of errors in terms of the effective ...

  20. Measurement, analysis and correction of the closed orbit distortion ...

    Indian Academy of Sciences (India)

    The paper presents the measurement, analysis and correction of closed orbit distortion (COD) in Indus-2 at 550 MeV injection energy and 2 GeV synchrotron radiation user run energy. The measured COD was analysed and fitted to understand major sources of errors in terms of the effective quadrupole misalignments.

  1. Effects of Full Order Geopotential Hessian on Precision Orbit Determination of Geodetic Satellites

    Science.gov (United States)

    2014-08-01

    Astrodynamics, geopotential, geodesy 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF PAGES 12 19a. NAME OF RESPONSIBLE PERSON...Orientation Parameters, Fundamental Physical Constants, Monitoring Earth Rotation and Polar Motion, and Time-Varying Geocenter Coordinates. For a full list...Tech. rep., DTIC Document, 2010. 15Kanner, L. and Associates, “Translation of ’Le satellite de geodesie ’Starlette’,’ Groupe de Recherches de Geodesie

  2. 78 FR 14920 - Earth Stations Aboard Aircraft Communicating With Fixed-Satellite Service Geostationary-Orbit...

    Science.gov (United States)

    2013-03-08

    ... COMMISSION 47 CFR Parts 2 and 25 Earth Stations Aboard Aircraft Communicating With Fixed-Satellite Service... technical and licensing rules for Earth Stations Aboard Aircraft (ESAA), i.e., earth stations on aircraft...-11.2 GHz, 11.45-11.7 GHz, 11.7-12.2 GHz (space-to-Earth or downlink) and 14.0-14.5 GHz (Earth-to...

  3. The National Polar-orbiting Operational Environmental Satellite System - Restructured Capabilities for Operational Ocean Remote Sensing

    Science.gov (United States)

    2008-09-01

    aerosols, cloud cover, surface albedo , and snow cover. Performance at the sensor level is expected to be comparable to MODIS [8], and as such represents...and research satellites with ocean observation capabilities such as the Moderate Resolution Imaging Spectroradiometer ( MODIS ) on the NASA Terra...used to exploit ocean surface observations from the AVHRR and MODIS sensors. Certain sensor effects (near-field response; cross-talk; sensor

  4. Independent Orbiter Assessment (IOA): Analysis of the pyrotechnics subsystem

    Science.gov (United States)

    Robinson, W. W.

    1988-01-01

    The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. This report documents the independent analysis results corresponding to the Orbiter Pyrotechnics hardware. The IOA analysis process utilized available pyrotechnics hardware drawings and schematics for defining hardware assemblies, components, and hardware items. Each level of hardware was evaluated and analyzed for possible failure modes and effects. Criticality was assigned based upon the severity of the effect for each failure mode.

  5. Analytical and Experimental Study Using Output-Only Modal Testing for On-Orbit Satellite Appendages

    OpenAIRE

    Mashiul Alam; Ramin Sedaghati; Yvan Soucy; Rama B. Bhat

    2009-01-01

    Output-only modal testing is an effective technique to identify the modal parameters of structural systems under ambient or operational conditions and has potential applications in civil, mechanical, and aerospace engineering. It may effectively be used for model validation, model updating, quality control, and health monitoring through the determination of modal characteristics of the structures. This approach to modal testing has great potential for ground and on-orbit modal testing of spac...

  6. Stabilization and real world satellite problem. [transformations for stabilizing orbital equations

    Science.gov (United States)

    Velez, C. E.

    1975-01-01

    The use of transformations of orbital equations has been considered in connection with requirements for more accurate data. The reported investigation is concerned with an evaluation of the relative merits of such transformations. The formulations tested include the classical Cowell formulation, the time regularized formulation, stabilization by the use of integrals, and stabilization by the use of elements. It is found that irrespective of efficiency considerations, stabilizing transformation makes it possible to obtain precisions which are unattainable with the Cowell formulations.

  7. Feasibility study for a Cryogenic On-Orbit Liquid Depot-Storage, Acquisition and Transfer (COLD-SAT) satellite

    Science.gov (United States)

    Rybak, S. C.; Willen, G. S.; Follett, W. H.; Hanna, G. J.; Cady, E. C.; Distefano, E.; Meserole, J. S.

    1990-01-01

    This feasibility study presents the conceptual design of a spacecraft for performing a series of cryogenic fluid management flight experiments. This spacecraft, the Cryogenic On-Orbit Liquid Depot-Storage, Acquisition, and Transfer (COLD-SAT) satellite, will use liquid hydrogen as the test fluid, be launched on a Delta expendable launch vehicle, and conduct a series of experiments over a two to three month period. These experiments will investigate the physics of subcritical cryogens in the low gravity space environment to characterize their behavior and to correlate the data with analytical and numerical models of in-space cryogenic fluid management systems. Primary technologies addressed by COLD-SAT are: (1) pressure control; (2) chilldown; (3) no-vent fill; (4) liquid acquisition device fill; (5) pressurization; (6) low-g fill and drain; (7) liquid acquisition device expulsion; (8) line chilldown; (9) thermodynamic state control; and (10) fluid dumping.

  8. A New Method to Retrieve the Orbital Parameters of the Galilean Satellites Using Small Telescopes: A Teaching Experiment

    Science.gov (United States)

    Sanchez-Lavega, Agustin; Ordoñez-Etxebarria, Iñaki; del Rio-Gaztelurrutia, Teresa

    2014-11-01

    We show in this communication how it is possible to deduce the radius of the orbits of Galilean satellites around Jupiter using a small number of well-planned observations. This allows the instructor to propose a complete student activity that involves planning an observation, the observation itself, processing and analyzing the images and deduction of relevant magnitudes [1]. This work was performed in the Aula EspaZio Gela under the Master in Space Science and Technology [2].References[1] I. Ordoñez-Etxebarria, T. del Río Gaztelurrutia and A. Sánchez Lavega, European Journal of Physics, Eur. J. Phys., 35, 045020 (14pp), (2014)[2] A. Sánchez-Lavega et al., European Journal of Engineering Education, doi:10.1080/03043797.2013.788611 (2013)AcknowledgementsThis work was supported by a grant from Diputaciõn Foral de Bizkaia — Bizkaiko Foru Aldundia to the Aula Espazio Gela.

  9. Satellite Geomagnetism

    DEFF Research Database (Denmark)

    Olsen, Nils; Stolle, Claudia

    2012-01-01

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

  10. An analysis of near-circular lunar mapping orbits

    Indian Academy of Sciences (India)

    Keywords. Lunar mapping; orbit maintenance; orbit life time; lunar gravity model; spherical harmonics. ... The aim is to select the appropriate near-circular orbit characteristics,which extend orbit life through passive orbit maintenance.The spherical harmonic terms that make major contributions to the orbital behaviour are ...

  11. A Cooperative Multi-Satellite Mission for Controlled Active Debris Removal from Low Earth Orbit

    Science.gov (United States)

    2015-03-07

    area for components and structural fragments surviving reentry shall not exceed 1 in 10,000.” Bon- nal et al. [13] quantify the risks presented by...engine survive reentry. The resulting casualty area and kinetic energy at impact for the propellant tank are 10.15 m2 and 25.9 kJ, and for the engine...support complex het- erogeneous multi-satellite mission design. From the authors experience in formation flying mission design [59], [60], [61], [62

  12. Analysis of Geolocation Approaches Using Satellites

    Science.gov (United States)

    2014-03-01

    carbon nanotube experiment, or ALICE for short. In addition to its recent satellite launch, AFIT hosts a CubeSat design course during which students...an exact solution to the TDOA equations will be discussed. Advantages and disadvantages of this method will also be discussed. An explicit solution...allows for a means for error checking. The advantages and disadvantages of this method will be discussed in further detail. 8 Taylor series estimation

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

    Science.gov (United States)

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

    2018-01-01

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

  14. 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....

  15. Estimation de fiabilité en ligne d'un satellite en orbite

    OpenAIRE

    Cabarbaye, André; Laulheret, Roland

    2015-01-01

    International audience;   Cet article présente une démarche de mise en œuvre du Health Monitoring dans le domaine spatial qui fait actuellement l'objet d'une action de recherche et développement menée par le CNES. Faisant suite à une première publication sur la modélisation des phénomènes de dégradation des satellites, il montre comment enrichir les estimations prévisionnelles de fiabilité des éléments non soumis à usure par l'exploitation du retour d'expérience au moyen de techniques bayésie...

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

    DEFF Research Database (Denmark)

    Olsen, Jørgen Lundegaard

    provide good sensitivity to canopy water content, which can make vegetation stress detection possible. Furthermore, the high frequency observations in the optical spectrum now available from geostationary instruments have the potential for detection of changes in vegetation related surface properties...... on short timescales, which are challenging from polar orbiting instruments. Geostationary NDVI and the NIR and SWIR based Shortwave Infrared Water Stress Index (SIWSI) indices are compared with extensive field data from the Dahra site, supplemented by data from the Agoufou and Demokeya sites. The indices...... are also compared with output from hydrological modelling of the Senegal River basin and a gridded rainfall product. It was shown that NIR/SWIR based indices are better suited for assessing water stress related changes in vegetation status, as compared to the more commonly applied NDVI. The hypothesis...

  17. Satellite nuclear power station: An engineering analysis

    Science.gov (United States)

    Williams, J. R.; Clement, J. D.; Rosa, R. J.; Kirby, K. D.; Yang, Y. Y.

    1973-01-01

    A nuclear-MHD power plant system which uses a compact non-breeder reactor to produce power in the multimegawatt range is analyzed. It is shown that, operated in synchronous orbit, the plant would transmit power safely to the ground by a microwave beam. Fuel reprocessing would take place in space, and no radioactive material would be returned to earth. Even the effect of a disastrous accident would have negligible effect on earth. A hydrogen moderated gas core reactor, or a colloid-core, or NERVA type reactor could also be used. The system is shown to approach closely the ideal of economical power without pollution.

  18. Preliminary Orbit Determination System (PODS) for Tracking and Data Relay Satellite System (TDRSS)-tracked target Spacecraft using the homotopy continuation method

    Science.gov (United States)

    Kirschner, S. M.; Samii, M. V.; Broaddus, S. R.; Doll, C. E.

    1988-09-01

    The Preliminary Orbit Determination System (PODS) provides early orbit determination capability in the Trajectory Computation and Orbital Products System (TCOPS) for a Tracking and Data Relay Satellite System (TDRSS)-tracked spacecraft. PODS computes a set of orbit states from an a priori estimate and six tracking measurements, consisting of any combination of TDRSS range and Doppler tracking measurements. PODS uses the homotopy continuation method to solve a set of nonlinear equations, and it is particularly effective for the case when the a priori estimate is not well known. Since range and Doppler measurements produce multiple states in PODS, a screening technique selects the desired state. PODS is executed in the TCOPS environment and can directly access all operational data sets. At the completion of the preliminary orbit determination, the PODS-generated state, along with additional tracking measurements, can be directly input to the differential correction (DC) process to generate an improved state. To validate the computational and operational capabilities of PODS, tests were performed using simulated TDRSS tracking measurements for the Cosmic Background Explorer (COBE) satellite and using real TDRSS measurements for the Earth Radiation Budget Satellite (ERBS) and the Solar Mesosphere Explorer (SME) spacecraft. The effects of various measurement combinations, varying arc lengths, and levels of degradation of the a priori state vector on the PODS solutions were considered.

  19. 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.

  20. Magnetospheric Multiscale (MMS) Mission Commissioning Phase Orbit Determination Error Analysis

    Science.gov (United States)

    Chung, Lauren R.; Novak, Stefan; Long, Anne; Gramling, Cheryl

    2009-01-01

    The Magnetospheric MultiScale (MMS) mission commissioning phase starts in a 185 km altitude x 12 Earth radii (RE) injection orbit and lasts until the Phase 1 mission orbits and orientation to the Earth-Sun li ne are achieved. During a limited time period in the early part of co mmissioning, five maneuvers are performed to raise the perigee radius to 1.2 R E, with a maneuver every other apogee. The current baseline is for the Goddard Space Flight Center Flight Dynamics Facility to p rovide MMS orbit determination support during the early commissioning phase using all available two-way range and Doppler tracking from bo th the Deep Space Network and Space Network. This paper summarizes th e results from a linear covariance analysis to determine the type and amount of tracking data required to accurately estimate the spacecraf t state, plan each perigee raising maneuver, and support thruster cal ibration during this phase. The primary focus of this study is the na vigation accuracy required to plan the first and the final perigee ra ising maneuvers. Absolute and relative position and velocity error hi stories are generated for all cases and summarized in terms of the ma ximum root-sum-square consider and measurement noise error contributi ons over the definitive and predictive arcs and at discrete times inc luding the maneuver planning and execution times. Details of the meth odology, orbital characteristics, maneuver timeline, error models, and error sensitivities are provided.

  1. Structural Health Monitoring Analysis for the Orbiter Wing Leading Edge

    Science.gov (United States)

    Yap, Keng C.

    2010-01-01

    This viewgraph presentation reviews Structural Health Monitoring Analysis for the Orbiter Wing Leading Edge. The Wing Leading Edge Impact Detection System (WLE IDS) and the Impact Analysis Process are also described to monitor WLE debris threats. The contents include: 1) Risk Management via SHM; 2) Hardware Overview; 3) Instrumentation; 4) Sensor Configuration; 5) Debris Hazard Monitoring; 6) Ascent Response Summary; 7) Response Signal; 8) Distribution of Flight Indications; 9) Probabilistic Risk Analysis (PRA); 10) Model Correlation; 11) Impact Tests; 12) Wing Leading Edge Modeling; 13) Ascent Debris PRA Results; and 14) MM/OD PRA Results.

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

    Directory of Open Access Journals (Sweden)

    Seungwoo Lee

    2015-03-01

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

  3. Evolution of Satellite Imagers and Sounders for Low Earth Orbit and Technology Directions at NASA

    Science.gov (United States)

    Pagano, Thomas S.; McClain, Charles R.

    2010-01-01

    Imagers and Sounders for Low Earth Orbit (LEO) provide fundamental global daily observations of the Earth System for scientists, researchers, and operational weather agencies. The imager provides the nominal 1-2 km spatial resolution images with global coverage in multiple spectral bands for a wide range of uses including ocean color, vegetation indices, aerosol, snow and cloud properties, and sea surface temperature. The sounder provides vertical profiles of atmospheric temperature, water vapor cloud properties, and trace gases including ozone, carbon monoxide, methane and carbon dioxide. Performance capabilities of these systems has evolved with the optical and sensing technologies of the decade. Individual detectors were incorporated on some of the first imagers and sounders that evolved to linear array technology in the '80's. Signal-to-noise constraints limited these systems to either broad spectral resolution as in the case of the imager, or low spatial resolution as in the case of the sounder. Today's area 2-dimensional large format array technology enables high spatial and high spectral resolution to be incorporated into a single instrument. This places new constraints on the design of these systems and enables new capabilities for scientists to examine the complex processes governing the Earth System.

  4. Transiting planets - light-curve analysis for eccentric orbits

    Science.gov (United States)

    Kipping, David M.

    2008-09-01

    Transiting planet light curves have historically been used predominantly for measuring the depth and hence ratio of the planet-star radii, p. Equations have previously been presented by Seager & Mallén-Ornelas for the analysis of the total and trough transit light-curve time to derive the ratio of semimajor axis to stellar radius, a/R*, in the case of circular orbits. Here, a new analytic model is proposed which operates for the more general case of an eccentric orbit. We aim to investigate three major effects our model predicts: (i) the degeneracy in transit light-curve solutions for eccentricity, e > 0; (ii) the asymmetry of the light curve and the resulting shift in the mid-transit time, TMID; (iii) the effect of eccentricity on the ingress and egress slopes. It is also shown that a system with changing eccentricity and inclination may produce a long-term transit time variation (LTTV). Furthermore, we use our model in a re-analysis of HD209458b archived data by Richardson et al., where we include the confirmed non-zero eccentricity and derive a 24-μm planetary radius of RP = 1.275RJ +/- 0.082RJ (where RJ = 1 Jovian radius), which is ~1 per cent larger than if we assume a circular orbit.

  5. 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.

  6. Modal test - Measurement and analysis requirements. [for Viking Orbiter

    Science.gov (United States)

    Wada, B. K.

    1975-01-01

    Data from the Viking Orbiter Modal Test Program are used to illustrate modal test measurement and analysis requirements. The test was performed using a multiple shake dwell technique where data were acquired one channel at a time and recorded on paper tape. Up to ten shakers were used simultaneously, with a complete set of data consisting of 290 strain-gage readings and 125 accelerometer readings. The data analysis provided information sufficient to minimize errors in the data. The list of analyses in order of value is orthogonality, residual mass, frequency sweep, data checks to assure good test data, multilevel trends, global kinetic energy, and global strain energy.

  7. Defense Weather Satellites: Analysis of Alternatives is Useful for Certain Capabilities, but Ineffective Coordination Limited Assessment of Two Critical Capabilities

    Science.gov (United States)

    2016-03-10

    through fiscal year 2012, including the National Polar- orbiting Operational Satellite System (NPOESS), a tri-agency program between DOD, NOAA, and...morning polar orbit and started a separate program, the Defense Weather Satellite System. The program was cancelled in fiscal year 2012 because of cost...and timing considerations. NOAA has developed the Joint Polar Satellite System to meet its responsibility for coverage in the afternoon orbit . 2

  8. Electric field computation analysis for the Electric Field Detector (EFD) on board the China Seismic-Electromagnetic Satellite (CSES)

    Science.gov (United States)

    Diego, P.; Bertello, I.; Candidi, M.; Mura, A.; Coco, I.; Vannaroni, G.; Ubertini, P.; Badoni, D.

    2017-11-01

    The floating potential variability of the Electric Field Detector (EFD) probes, on board the Chinese Seismo-Electromagnetic Satellite (CSES), has been modeled, and the effects of several structural and environmental elements have been determined. The expected floating potentials of the probes are computed considering the ambient ionospheric plasma parameter variations. In addition, the ion collection variability, due to the different probe attitudes along the orbit, and its effect on each floating potential, are considered. Particular attention is given to the analysis of the shadow produced by the stubs, in order to determine the artificial electric field introduced by instrumental effects which has to be subtracted from the real measurements. The modulation of the altered electric field, due to the effect on shadowing of the ion drift, as measured by the ESA satellite Swarm A in a similar orbit, is also modeled. Such simulations are made in preparation of real EFD data analysis performed during the upcoming flight of CSES.

  9. Long-term effects of main-body’s obliquity on satellite formation perturbed by third-body gravity in elliptical and inclined orbit

    Science.gov (United States)

    Bakhtiari, Majid; Daneshjou, Kamran; Fakoor, Mahdi

    2017-03-01

    A new non-simplified model of formation flying is derived in the presence of an oblate main-body and third-body perturbation. In the proposed model, considering the perturbation of the third-body in an inclined orbit, the effect of obliquity (axial tilt) of the main-body is becoming important and has been propounded in the absolute motion of a reference satellite and the relative motion of a follower satellite. From a new point of view, J 2 perturbed relative motion equations and considering a disturbing body in an elliptic inclined three dimensional orbit, are derived using Lagrangian mechanics based on accurate introduced perturbed reference satellite motion. To validate the accuracy of the model presented in this study, an auxiliary model was constructed as the Main-body Center based Relative Motion (MCRM) model. Finally, the importance of the main-body’s obliquity is demonstrated by several examples related to the Earth-Moon system in relative motion and lunar satellite formation keeping. The main-body’s obliquity has a remarkable effect on formation keeping in the examined in-track and projected circular orbit (PCO) formations.

  10. 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.

  11. 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 ...

  12. Overview And In-Orbit Behavior Of The First Lithium-Ion Batteries Used Onboard Eutelsat W3A Geo Telecommunications Satellite

    Science.gov (United States)

    Mattesco, Patrick; Peiro, Philippe; Thakur, Vijay; Borthomieu, Yannick

    2011-10-01

    The Lithium-ion (Li-ion) battery has been perceived several years ago by Astrium as a very promising technology in terms of technical, industrial and cost aspects for its Eurostar E3000 platform dedicated to telecommunications satellite for payload power from 5 up to 18 kW. One of the main advantages of such energy storage technology is the capacity to deliver very high power and energy density with quite low dissipation when compared to the other qualified technologies. On March 16, 2004, a Proton Launcher placed successfully into orbit the W3A spacecraft for Eutelsat (first Eurostar E3000 satellite equipped with Li-ion batteries). This was the achievement of the work, initiated with the support of ESA and CNES in 1996 with Stentor program. In 2011, 25 Li-ion batteries are in orbit on 15 Eurostar E3000 satellites. This paper is an update of the one presented at the Seventh European Space Power Conference in 2005 [1]. First part is a recall of the battery development, battery design, and battery management during system tests and pre-launch phases. In the second part, the seven years behaviour in orbit for the two W3A lithium batteries is provided (less than one year in orbit data was available at the time of [1]).

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

    Science.gov (United States)

    Song, Young-Joo; Bae, Jonghee; Kim, Young-Rok; Kim, Bang-Yeop

    2016-12-01

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

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

    Directory of Open Access Journals (Sweden)

    Young-Joo Song

    2016-12-01

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

  15. Computer-aided communication satellite system analysis and optimization

    Science.gov (United States)

    Stagl, T. W.; Morgan, N. H.; Morley, R. E.; Singh, J. P.

    1973-01-01

    The capabilities and limitations of the various published computer programs for fixed/broadcast communication satellite system synthesis and optimization are discussed. A satellite Telecommunication analysis and Modeling Program (STAMP) for costing and sensitivity analysis work in application of communication satellites to educational development is given. The modifications made to STAMP include: extension of the six beam capability to eight; addition of generation of multiple beams from a single reflector system with an array of feeds; an improved system costing to reflect the time value of money, growth in earth terminal population with time, and to account for various measures of system reliability; inclusion of a model for scintillation at microwave frequencies in the communication link loss model; and, an updated technological environment.

  16. An analysis of near-circular lunar mapping orbits

    Indian Academy of Sciences (India)

    Numerical investigations have been carried out to analyse the evolution of lunar circular orbits and the influence of the higher order harmonics of the lunar gravity field. The aim is to select the appropriate near-circular orbit characteristics, which extend orbit life through passive orbit maintenance. The spherical harmonic ...

  17. CODE's five-system orbit and clock solution—the challenges of multi-GNSS data analysis

    Science.gov (United States)

    Prange, Lars; Orliac, Etienne; Dach, Rolf; Arnold, Daniel; Beutler, Gerhard; Schaer, Stefan; Jäggi, Adrian

    2017-04-01

    This article describes the processing strategy and the validation results of CODE's MGEX (COM) orbit and satellite clock solution, including the satellite systems GPS, GLONASS, Galileo, BeiDou, and QZSS. The validation with orbit misclosures and SLR residuals shows that the orbits of the new systems Galileo, BeiDou, and QZSS are affected by modelling deficiencies with impact on the orbit scale (e.g., antenna calibration, Earth albedo, and transmitter antenna thrust). Another weakness is the attitude and solar radiation pressure (SRP) modelling of satellites moving in the orbit normal mode—which is not yet correctly considered in the COM solution. Due to these issues, we consider the current state COM solution as preliminary. We, however, use the long-time series of COM products for identifying the challenges and for the assessment of model-improvements. The latter is demonstrated on the example of the solar radiation pressure (SRP) model, which has been replaced by a more generalized model. The SLR validation shows that the new SRP model significantly improves the orbit determination of Galileo and QZSS satellites at times when the satellite's attitude is maintained by yaw-steering. The impact of this orbit improvement is also visible in the estimated satellite clocks—demonstrating the potential use of the new generation satellite clocks for orbit validation. Finally, we point out further challenges and open issues affecting multi-GNSS data processing that deserves dedicated studies.

  18. Results and Analysis of BDS Precise Orbit Determination with the Enhancement of Fengyun-3C

    Directory of Open Access Journals (Sweden)

    ZENG Tian

    2017-07-01

    Full Text Available Global navigation satellite system occultation sounder (GNOS Fengyun-3C was launched successfully on September 23, 2013, which carried GPS/BDS receiver for the first time. This provides the convenience to study the enhancement results of low earth orbiter satellite (LEO to BDS precise orbit determination (POD. First the data characteristics and code observation noise of GNOS are analyzed. Then the enhancement experiments in the case of global and regional ground observation stations layout are processed with four POD schemes: BDS single system, GPS/BDS double system, BDS single system with GNOS observations, GPS/BDS double system with GNOS observations. The precision of BDS orbits and clock are compared via overlapping arcs. Results show that in the case of global station layout the along directional precision of GEO satellite has the biggest improvement, with the improvement percentage 60%. Then the precision of cross direction and the along direction of remaining satellites shows the second biggest improvement. The orbit precision of only BDS POD in part of arcs some satellite even suffers a slight decline. The root mean square (RMS of overlapping clock difference of visible arcs in GPS/BDS POD experiments is improved 0.1 ns level. As to the experiments of regional station layout with 7 ground observation stations, the orbit and clock overlapping precision and orbit predicting precision are analyzed. Results show that the predicting precision of BDS GEO satellites in the along direction is improved 85%. The remaining also has a substantial improvement, with the average percentage 21.7%. RMS of overlapping clock difference of visible arcs is improved 0.5 ns level.

  19. Real-time, Quasi-Global, Multi-Satellite Precipitation Analysis Using TRMM and other Satellite Observations

    Science.gov (United States)

    Adler, Robert F.; Huffman, George; Curtis, Scott; Bolvin, David; Nelkin, Eric

    2003-01-01

    A TRMM-based 3-hr analyses that use TRMM observations to calibrate polar-orbit microwave observations from SSM/I (and other satellites) and geosynchronous IR observations and merges the various calibrated observations into a final, 3-hr resolution map is described. This TRMM standard product will be available for the entire TRMM period (January 1998-present) in 2003 as part of Version 6 of the TRMM products. A real-time version of this merged product is being produced and is available at 0.25" latitude-longitude resolution over the latitude range from 50 N-500S. Examples will be shown, including its use in monitoring flood conditions and in relating weather-scale patterns to climate-scale patterns. Plans to incorporate the TRMM data and 3-hourly analysis into the Global Precipitation Climatology Project (GPCP) products are outlined. The outcome in the near future should be an improved global analysis and climatology on monthly scales for the 23 year period and finer time scale analyses for more recent periods, including 3-hourly analyses over the globe. These technique developments are potential prototypes for analyses with the Global Precipitation Measurement (GPM) mission.

  20. Verification of a Micro-Thrusting Model to Maintain Satellites in Low Orbit.

    Science.gov (United States)

    1987-06-01

    10 KG OF FUEL 38420 38440 38-160 38-180 38500 381520 TIMIE OF VERNAL EQUINOX (M .J.D.) Figure 13. mission Life versus Time of Vernal Equinox (100...8217 E39 B E 39 E 3E 3BE 3E 3E 3E -/N- 10KCOFFE 10 500510 50 INTA ATLIEMAS(-. Fiue4. iso if ess.aelt .12 The final analysis is concerned with the mean

  1. Toward seamless multiview scene analysis from satellite to street level

    NARCIS (Netherlands)

    Lefevre, Sebastien; Tuia, Devis; Wegner, Jan Dirk; Produit, Timothee; Nassar, Ahmed Samy

    2017-01-01

    In this paper, we discuss and review how combined multiview imagery from satellite to street level can benefit scene analysis. Numerous works exist that merge information from remote sensing and images acquired from the ground for tasks such as object detection, robots guidance, or scene

  2. Health scorecard of spacecraft platforms: Track record of on-orbit anomalies and failures and preliminary comparative analysis

    Science.gov (United States)

    Wise, Marcie A.; Saleh, Joseph H.; Haga, Rachel A.

    2011-01-01

    Choosing the "right" satellite platform for a given market and mission requirements is a major investment decision for a satellite operator. With a variety of platforms available on the market from different manufacturers, and multiple offerings from the same manufacturer, the down-selection process can be quite involved. In addition, because data for on-obit failures and anomalies per platform is unavailable, incomplete, or fragmented, it is difficult to compare options and make an informed choice with respect to the critical attribute of field reliability of different platforms. In this work, we first survey a large number of geosynchronous satellite platforms by the major satellite manufacturers, and we provide a brief overview of their technical characteristics, timeline of introduction, and number of units launched. We then analyze an extensive database of satellite failures and anomalies, and develop for each platform a "health scorecard" that includes all the minor and major anomalies, and complete failures—that is failure events of different severities—observed on-orbit for each platform. We identify the subsystems that drive these failure events and how much each subsystem contributes to these events for each platform. In addition, we provide the percentage of units in each platform which have experienced failure events, and, after calculating the total number of years logged on-orbit by each platform, we compute its corresponding average failure and anomaly rate. We conclude this work with a preliminary comparative analysis of the health scorecards of different platforms. The concept of a "health scorecard" here introduced provides a useful snapshot of the failure and anomaly track record of a spacecraft platform on orbit. As such, it constitutes a useful and transparent benchmark that can be used by satellite operators to inform their acquisition choices ("inform" not "base" as other considerations are factored in when comparing different spacecraft

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

    Science.gov (United States)

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

    1993-01-01

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

  4. VLBI observations of GNSS-satellites: from scheduling to analysis.

    Science.gov (United States)

    Plank, Lucia; Hellerschmied, Andreas; McCallum, Jamie; Böhm, Johannes; Lovell, Jim

    2017-01-01

    The possibility of observing satellites with the very long baseline interferometry (VLBI) technique has been discussed for several years in the geodetic community, with observations of either existing satellites of the global navigation satellite systems or of satellites dedicated to realise a space tie. Such observations were carried out using the Australian telescopes in Hobart and Ceduna which, for the first time, integrated all the necessary steps: planning the observations (automated scheduling), correlation of the data and the generation of a series of time delay observables suitable for a subsequent geodetic analysis. We report on the development of new and the adaptation of existing routines for observing and data processing, focusing on technology development. The aim was to use methods that are routinely used in geodetic VLBI. A series of test experiments of up to six hours duration was performed, allowing to improve the observations from session to session and revealing new problems still to be solved. The newly developed procedures and programs now enable more observations. Further development assumed, this bears the prospect of being directly applied to the observation of dedicated space-tie satellites.

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

    DEFF Research Database (Denmark)

    Olsen, Jørgen Lundegaard

    . By detrending time series for the Senegal River basin, spatially coherent patterns of index trends were found, suggesting that real information is present in the daily anomalies of both NDVI and SIWSI. It was found necessary with spatial aggregation on quite coarse scale for significant analysis results when...... index (NDVI), which combines red and near infrared (NIR) spectral regions. From NDVI data a greening of the Sahel have been identified since the 80s and attributed to increasing trends in annual rainfall for large parts of the region. One part of this thesis analyses time series of parameterized MODIS...... that short term variations in anomalies from seasonally detrended time series of indices could carry information on vegetation stress was examined and confirmed. However, it was not found sufficiently robust on pixel level to be implemented for monitoring vegetation water stress on a per-pixel basis...

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

    Science.gov (United States)

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

    2017-09-01

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

  7. A Survey and Performance Analysis of Orbit Propagators for LEO, GEO, and Highly Elliptical Orbits

    Science.gov (United States)

    Shuster, Simon P.

    On-orbit targeting, guidance, and navigation relies on state vector propagation algorithms that must strike a balance between accuracy and computational efficiency. To better understand this balance, the relative position accuracy and computational requirements of numerical and analytical propagation methods are analyzed for a variety of orbits. For numerical propagation, several differential equation formulations (Cowell, Encke-time, Encke-beta, and Equinoctial Elements) are compared over a range of integration step sizes for a given set of perturbations and numerical integration methods. This comparison is repeated for two numerical integrators: a Runge-Kutta 4th order and a NLZD4/4. For analytical propagation, SGP4, which relies on mean orbital elements, is compared for element sets averaged with different amounts of orbit data.

  8. Feasibility Analysis Of Free Space Earth To Satellite Optical Link In Tropical Region

    Directory of Open Access Journals (Sweden)

    Norhanis Aida M. Nor

    2012-01-01

    Full Text Available Free Space Optics (FSO becomes a great attention because of the chances in transmitting data up to 2.5Gbps. There are a lot of advantages offered by FSO such as easily deployment with saving time and cost and no electromagnetic interference. In spite of the advantages, FSO has an uncontrolled drawback which is highly sensitive to atmospheric phenomena because uses air as tranmission medium. Current studies and researches are only focusing on FSO terrestrial link with short path length and based on data from temperate region. Therefore, this paper is aiming to provide feasibility analysis of FSO link from earth to satellite especially Low Earth Orbit (LEO based on atmospheric data in tropical region. The analysis will include the losses from geometrical attenuation, absorption, scintillation, haze attenuation, and rain attenuation. ABSTRAK: Ruang Bebas Optik (Free Space Optics (FSO mendapat perhatian kerana kebolehannya memancarkan data pada kelajuan tinggi. Di sebalik kelebihannya, FSO amat sensitif terhadap fenomena atmosfera kerana ia menggunakan udara sebagai perantara transmisi. Penyelidikan dan kajian terkini hanya memfokus kepada jalinan darat FSO dengan kepanjangan jarak pendek dan bergantung kepada kawasan tenang.  Oleh itu, kertas ini menyasarkan untuk memberikan analisis kebolehlaksanaan  jalinan FSO dari bumi ke satelit terutamanya Orbit Rendah Bumi (Low Earth Orbit (LEO bergantung kepada data atmosfera di kawasan tropika. Analisa termasuklah kehilangannya akibat pengecilan geometri, penyerapan, kelipan, pelemahan jerebu dan pelemahan hujan.KEYWORDS:  feasibility; Free Space Optics; availability; atmospheric attenuation; beam divergence angle; elevation angle

  9. Attitude control system design and on-orbit performance analysis of nano-satellite—“Tian Tuo 1”

    Directory of Open Access Journals (Sweden)

    Ran Dechao

    2014-06-01

    Full Text Available “Tian Tuo 1” (TT-1 nano-satellite is the first single-board nano-satellite that was successfully 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 feasibility 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.

  10. A Tapestry of Orbits

    Science.gov (United States)

    King-Hele, D. G.

    2005-07-01

    Satellites as they cross the night sky look like moving stars, which can be accurately tracked by an observer with binoculars as well as by giant radars and large cameras. These observations help to determine the satellite's orbit, which is sensitive to the drag of the upper atmosphere and to any irregularities in the gravity field of the Earth. Analysis of the orbit can be used to evaluate the density of the upper atmosphere and to define the shape of the Earth. Desmond King-Hele was the pioneer of this technique of orbit analysis, and this book tells us how the research began, before the launch of Sputnik in 1957. For thirty years King-Hele and his colleagues at the Royal Aircraft Establishment, Farnborough, developed and applied the technique to reveal much about the Earth and air at a very modest cost. In the 1960s the upper-atmosphere density was thoroughly mapped out for 100 to 2000 km, revealing immense variation of density with solar activity and between day and night. In the 1970s and 1980s a picture of the upper-atmosphere winds emerged, and the profile of the pear-shaped Earth was accurately charted. The number of satellites now orbiting the earth is over 5000. This book is the story of how this inexpensive research of their orbits developed to yield a rich harvest of knowledge about the Earth and its atmosphere, in a scientific narrative that is enlivened with many personal experiences.

  11. Aerothermodynamic Analysis of a Reentry Brazilian Satellite

    CERN Document Server

    Santos, Wilson F N

    2012-01-01

    This work deals with a computational investigation on the small ballistic reentry Brazilian vehicle SARA (acronyms for SAt\\'elite de Reentrada Atmosf\\'erica). Hypersonic flows over the vehicle SARA at zero-degree angle of attack in a chemical equilibrium and thermal non-equilibrium are modeled by the Direct Simulation Monte Carlo (DSMC) method, which has become the main technique for studying complex multidimensional rarefied flows, and that properly accounts for the non-equilibrium aspects of the flows. The emphasis of this paper is to examine the behavior of the primary properties during the high altitude portion of SARA reentry. In this way, velocity, density, pressure and temperature field are investigated for altitudes of 100, 95, 90, 85 and 80 km. In addition, comparisons based on geometry are made between axisymmetric and planar two-dimensional configurations. Some significant differences between these configurations were noted on the flowfield structure in the reentry trajectory. The analysis showed t...

  12. Geostationary satellites collocation

    CERN Document Server

    Li, Hengnian

    2014-01-01

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

  13. Analysis of the Effect of UTI-UTC to High Precision Orbit Propagation

    Directory of Open Access Journals (Sweden)

    Dongseok Shin

    1999-12-01

    Full Text Available As the spatial resolution of remote sensing satellites becomes higher, very accurate determination of the position of a LEO (Low Earth Orbit satellite is demanding more than ever. Non-symmetric Earth gravity is the major perturbation force to LEO satellites. Since the orbit propagation is performed in the celestial frame while Earth gravity is defined in the terrestrial frame, it is required to convert the coordinates of the satellite from one to the other accurately. Unless the coordinate conversion between the two frames is performed accurately the orbit propagation calculates incorrect Earth gravitational force at a specific time instant, and hence, causes errors in orbit prediction. The coordinate conversion between the two frames involves precession, nutation, Earth rotation and polar motion. Among these factors, unpredictability and uncertainty of Earth rotation, called UTI-UTC, is the largest error source. In this paper, the effect of UTI-UTC on the accuracy of the LEO propagation is introduced, tested and analzed. Considering the maximum unpredictability of UTI-UTC, 0.9 seconds, the meaningful order of non-spherical Earth harmonic functions is derived.

  14. Automatic Satellite Telemetry Analysis for SSA using Artificial Intelligence Techniques

    Science.gov (United States)

    Stottler, R.; Mao, J.

    In April 2016, General Hyten, commander of Air Force Space Command, announced the Space Enterprise Vision (SEV) (http://www.af.mil/News/Article-Display/Article/719941/hyten-announces-space-enterprise-vision/). The SEV addresses increasing threats to space-related systems. The vision includes an integrated approach across all mission areas (communications, positioning, navigation and timing, missile warning, and weather data) and emphasizes improved access to data across the entire enterprise and the ability to protect space-related assets and capabilities. "The future space enterprise will maintain our nation's ability to deliver critical space effects throughout all phases of conflict," Hyten said. Satellite telemetry is going to become available to a new audience. While that telemetry information should be valuable for achieving Space Situational Awareness (SSA), these new satellite telemetry data consumers will not know how to utilize it. We were tasked with applying AI techniques to build an infrastructure to process satellite telemetry into higher abstraction level symbolic space situational awareness and to initially populate that infrastructure with useful data analysis methods. We are working with two organizations, Montana State University (MSU) and the Air Force Academy, both of whom control satellites and therefore currently analyze satellite telemetry to assess the health and circumstances of their satellites. The design which has resulted from our knowledge elicitation and cognitive task analysis is a hybrid approach which combines symbolic processing techniques of Case-Based Reasoning (CBR) and Behavior Transition Networks (BTNs) with current Machine Learning approaches. BTNs are used to represent the process and associated formulas to check telemetry values against anticipated problems and issues. CBR is used to represent and retrieve BTNs that represent an investigative process that should be applied to the telemetry in certain circumstances

  15. 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

  16. Comparative Analysis of Urban Heat Island Effects For Large Hungarian Cities Using Satellite Imagery

    Science.gov (United States)

    Dezso, Zs.; Bartholy, J.; Pongracz, R.; Barcza, Z.

    In order to find potential mitigation strategies that facilitate the urban population to adapt to new environmental conditions urban heat islands and other climatological impacts of urbanization must be investigated. In this study detailed comparison of the urban heat island effects for the Budapest agglomeration area (capital of Hungary) and other large cities of the Carpathian Basin is provided. A new approach has been applied, namely satellite images have served as a basic tool in the present analysis. Part of the NASA's Earth Observing System satellite TERRA was launched to a po- lar orbit in December 1999. Measurements include surface temperature (both land and ocean), global vegetation, cloud characteristics, snow cover, and temperature and moisture profiles. MODIS is capable of viewing the entire globe daily at high reso- lutions, ranging from 250 m to 1 km per pixel. First validated observations started in February 2000, and regular measurements are available from July 2000. In this pa- per daytime and nighttime surface temperature time series measured in the Carpathian Basin have been analysed. First, several large cities have been selected and their pixel representations (including their rural environment) have been determined. Then, these representative areas have been divided into urban and rural pixels which have provided spatial averages of observed surface temperature values. The preliminary results sug- gest that intensity of the urban heat island detected in Hungarian cities ranges between 1K and 3K, the most intense periods include the summer season and nighttime. Fine resolution satellite images provide an excellent tool to investigate heat island struc- tures for each selected city. Using the selected representative area of these Hungarian cities spatial structures of their urban heat island have been determined depending on seasons and different macrocirculation conditions. Further analysis have been carried out by identifying special pixels

  17. 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...

  18. [Clinical analysis of orbital complications of acute rhinosinusitis in adults].

    Science.gov (United States)

    Li, Na; Yu, Long-gang; Jiang, Yan; Han, Min; Chen, Min; Yan, Shu; Zhang, Xiao-wen

    2013-02-01

    To investigate the clinical features, diagnosis and therapy of surgical intervention for orbital complications of acute rhinosinusitis in adults. Four adults with orbital complications of acute rhinosinusitis were retrospectively reviewed. The patients underwent transnasal endoscopic sinus surgery or combined with eyebrow incision after conservative treatments failed. There were 2 cases with orbital abscess, 2 cases with subperiosteal abscess. Two of them suffered from diabetes. After operation, constitutional symptoms and ocular symptoms disappeared in all 4 patients. CT was rechecked during the postoperative follow-up. The imaging showed that the orbital and nasal lesions were obviously relieved or disappeared. The orbital complications of acute rhinosinusitis in adults are clinically rare. The patients are usually with low immunity or underlying conditions, such as diabetes. Based on the basis of controlling basic diseases, the treatment outcome of orbital complications of acute rhinosinusitis in adults is affirmative by surgery and conservative managements.

  19. Estimation of Biomass Burning Emissions by Fusing Fire Radiative Power Observed from Polar-orbiting and Geostationary Satellites across the Continental United States

    Science.gov (United States)

    Li, F.; Zhang, X.; Kondragunta, S.

    2016-12-01

    Trace gases and aerosols released from biomass burning significantly disturb the energy balance of the Earth and also degrade regional air quality. However, biomass burning emissions (BBE) have been poorly estimated using the traditional bottom-up approach because of the substantial uncertainties in the burned area and fuel loads. Recently, Fire Radiative Power (FRP) derived from satellite fire observations enables the estimation of BBE at multiple spatial scales in near real time. Nonetheless, it is very challenging to accurately produce reliable FRP diurnal cycles from either polar-orbiting satellites or geostationary satellites for the calculation of the temporally integrated FRP, Fire Radiative Energy (FRE). Here we reconstruct FRP diurnal cycles by fusing FRP observed from polar-orbiting and geostationary satellites and estimate BBE from 2011 to 2015 across the Continental United States. Specifically, FRP from the Geostationary Operational Environmental Satellite (GOES) is preprocessed and calibrated using the collocated and concurred observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) over Landsat TM burn scars. The climatologically diurnal FRP curves are then calculated from the calibrated GOES FRP for the 25 Bailey's ecoregions. By fitting MODIS FRP and the calibrated GOES FRP to the climatological curves, FRP diurnal cycles are further reconstructed for individual days at a 0.25-degree grid. Both FRE estimated from FRP diurnal cycles and ecoregion specified FRE combustion rates are used to estimate hourly BBE. The estimated BBE is finally evaluated using QFED and GFED4.0 inventories and emissions modeled using Landsat TM 30m burn severities and 30m fuel loading from Fuel Characteristic Classification System. The results show that BBE estimates are greatly improved by using the reconstructed FRP diurnal cycles from high temporal (GOES) and high spatial resolution (MODIS) FRP observations.

  20. 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.

  1. Validation of GNSS orbits using SLR observations

    Science.gov (United States)

    Urschl, C.; Gurtner, W.; Hugentobler, U.; Schaer, S.; Beutler, G.

    Satellite Laser Ranging (SLR) observations allow for a completely independent validation of orbits derived using microwave measurements as provided by the International GPS Service (IGS). The orbit validation is based on the difference between the observed range (SLR measurements) and the computed range (assuming that the satellite positions are know from the IGS). The resulting range residuals are primarily an indicator for the radial accuracy of the microwave orbits. This validation method is well-known and several validation results have been published in the last 10 years. The IGS analysis center CODE (Center for Orbit Determination in Europe) provides on a routine base daily range residuals for all GNSS satellites observed by both, SLR and microwave techniques. We present results of our recent range residual analysis for two GPS satellites (PRN G05, G06) and three GLONASS satellites (PRN R03, R22, R24). Microwave orbits provided by IGS and CODE are used as well as SLR normal point observations of 13 globally distributed sites. The resulting range residual time series of about 3.3 years, starting in January 2001, for GPS satellites and of about 10 months, starting in June 2003, for GLONASS satellites are analyzed. The comparison of the range residuals with previous analysis results shows the impact of several improvements, i.e., the increasing quality of the microwave orbit as well as the use of new laser retroreflector arrays on GLONASS satellites launched after 1995. The validation of the CODE orbits shows a standard deviation of 2.7 cm for the GPS satellites and of 4.9 cm for the GLONASS satellites. A bias of about -5.8 cm for GPS satellites and of -2.3 cm for GLONASS satellites between the SLR measurements and the microwave orbits was determined. The cause of these biases is not yet fully understood. Pass-specific systematics in the range residuals were found, but it was not possible to assign them to station- or satellite-specific error sources

  2. Targeting Villages for Rural Development Using Satellite Image Analysis.

    Science.gov (United States)

    Varshney, Kush R; Chen, George H; Abelson, Brian; Nowocin, Kendall; Sakhrani, Vivek; Xu, Ling; Spatocco, Brian L

    2015-03-01

    Satellite imagery is a form of big data that can be harnessed for many social good applications, especially those focusing on rural areas. In this article, we describe the common problem of selecting sites for and planning rural development activities as informed by remote sensing and satellite image analysis. Effective planning in poor rural areas benefits from information that is not available and is difficult to obtain at any appreciable scale by any means other than algorithms for estimation and inference from remotely sensed images. We discuss two cases in depth: the targeting of unconditional cash transfers to extremely poor villages in sub-Saharan Africa and the siting and planning of solar-powered microgrids in remote villages in India. From these cases, we draw out some common lessons broadly applicable to informed rural development.

  3. Quantitative analysis of geomorphic processes using satellite image data at different scales

    Science.gov (United States)

    Williams, R. S., Jr.

    1985-01-01

    When aerial and satellite photographs and images are used in the quantitative analysis of geomorphic processes, either through direct observation of active processes or by analysis of landforms resulting from inferred active or dormant processes, a number of limitations in the use of such data must be considered. Active geomorphic processes work at different scales and rates. Therefore, the capability of imaging an active or dormant process depends primarily on the scale of the process and the spatial-resolution characteristic of the imaging system. Scale is an important factor in recording continuous and discontinuous active geomorphic processes, because what is not recorded will not be considered or even suspected in the analysis of orbital images. If the geomorphic process of landform change caused by the process is less than 200 m in x to y dimension, then it will not be recorded. Although the scale factor is critical, in the recording of discontinuous active geomorphic processes, the repeat interval of orbital-image acquisition of a planetary surface also is a consideration in order to capture a recurring short-lived geomorphic process or to record changes caused by either a continuous or a discontinuous geomorphic process.

  4. Orbit analysis of a geostationary gravitational wave interferometer detector array

    CERN Document Server

    Tinto, Massimo; Kuga, Helio K; Alves, Marcio E S; Aguiar, Odylio D

    2014-01-01

    We analyze the trajectories of three geostationary satellites forming the GEOstationary GRAvitational Wave Interferometer (GEOGRAWI)~\\cite{tinto}, a space-based laser interferometer mission aiming to detect and study gravitational radiation in the ($10^{-4} - 10$) Hz band. The combined effects of the gravity fields of the Earth, the Sun and the Moon make the three satellites deviate from their nominally stationary, equatorial and equilateral configuration. Since changes in the satellites relative distances and orientations could negatively affect the precision of the laser heterodyne measurements, we have derived the time-dependence of the inter-satellite distances and velocities, the variations of the polar angles made by the constellation's three arms with respect to a chosen reference frame, and the time changes of the triangle's enclosed angles. We find that, during the time between two consecutive station-keeping maneuvers (about two weeks), the relative variations of the inter-satellite distances do not...

  5. Analysis of the Origin and Evolution of the Small Satellites of Pluto

    Science.gov (United States)

    Pires Dos Santos, Pryscilla Maria; Morbidelli, A.; Nesvorny, D.; Giuliatti Winter, S. M.

    2012-10-01

    At this time the origin of the small satellites of Pluto remains elusive. In this work we envisioned an alternative scenario. Pluto-Charon was already formed and embedded into a massive planetesimal disk, then planetesimals got captured by Pluto-Charon binary from the heliocentric disk. For a dynamically "cold" disk, temporary capture in the Pluto-Charon system can occur with non-negligible probability. We conjecture that if the captured planetesimals got disrupted during their Pluto-bound phase by a collision with other planetesimals of the disk, then these events could have generated a debris disk. This disk damped under internal collisional evolution, until turning itself into an accretional disk that could form small satellites on circular orbits, co-planar with Charon. Objects large enough to carry a sufficient amount of mass to generate the small satellites of Pluto have collisional lifetimes orders of magnitude longer than the typical capture time ( 100 years). Thus, this scenario, although add new arguments to an unsolved problem, cannot also explain the origin of the small satellites of Pluto, which remains elusive. Additionality, we will also present some preliminary results on the analysis of the evolution of the Pluto system in the framework of the "new" Nice model (see, e.g. Levison et al, 2008). Their results explain very well the distribution of Plutinos, bodies trapped in 2:3 mean motion resonance with Neptune. By assuming that the bodies observed today in the Pluto system were put together before the Late Heavy Bombardment period (Gomes et al, 2005), through encounter histories of Pluto and its members during the dynamical evolution of the giant planets, we analyse if this multiple system is destroyed by such interactions. In fact, understanding the evolution of the plutinos provides hints to the understanding of the history of the outer Solar system.

  6. Analytic robust stability analysis of SVD orbit feedback

    CERN Document Server

    Pfingstner, Jürgen

    2012-01-01

    Orbit feedback controllers are indispensable for the operation of modern particle accelerators. Many such controllers are based on the decoupling of the inputs and outputs of the system to be controlled with the help of the singular value decomposition (SVD controller). It is crucial to verify the stability of SVD controllers, also in the presence of mismatches between the used accelerator model and the real machine (robust stability problem). In this paper, analytical criteria for guaranteed stability margins of SVD orbit feedback systems for three different types of model mismatches are presented: scaling errors of actuators and BPMs (beam position monitors) and additive errors of the orbit response matrix. For the derivation of these criteria, techniques from robust control theory have been used, e.g the small gain theorem. The obtained criteria can be easily applied directly to other SVD orbit feedback systems. As an example, the criteria were applied to the orbit feedback system of the Compact Linear ...

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

    Directory of Open Access Journals (Sweden)

    Ming Xu

    2012-10-01

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

  8. CryoSat-2 satellite radar altimetry for river analysis and modelling

    DEFF Research Database (Denmark)

    Schneider, Raphael

    from previous and current satellite altimetry missions, which are in short-repeat orbits with cycles of 10 to 35 days. The orbit configuration of CryoSat-2 is a challenge for hydrologic applications. Short-repeat missions allow deriving time series at locations where the satellite ground track......The global coverage of in situ observations of surface water dynamics is insufficient to effectively manage water resources. Moreover, the availability of these data is decreasing, due to the lack of gauging stations and data sharing. Satellite radar altimetry, initially developed to monitor ocean...... water levels, also offers measurements of water levels of rivers and lakes on a global scale. Because of the continuous upstart of new missions, and sensor and processing innovations, the importance of satellite altimetry data for the hydrologic community is increasing. CryoSat-2, launched...

  9. METIS-ESA solar orbiter mission internal straylight analysis

    Science.gov (United States)

    Verroi, E.; Da Deppo, V.; Naletto, G.; Fineschi, S.; Antonucci, E.

    2017-11-01

    METIS is the Multi Element Telescope for Imaging and Spectroscopy for the ESA Solar Orbiter. Its target is the solar corona from a near-Sun orbit in two different spectral bands: the HI UV narrow band at 121.6 nm, and the VL visible light band. METIS adopts a novel inverted externally occulted configuration, where the disk light is shielded by an annular occulter, and an annular aspherical mirror M1 collects the signal coming from the corona. After M1 the coronal light passes through an internal occulter and is then reflected by a second annular mirror M2 toward a narrow filter for the 121.6 nm HI line selection. The visible light reflected by the filter is used to feed a visible light (580 - 640 nm) polarimetric channel. The photospheric light passing through the entrance aperture is back-rejected by a spherical rejection mirror. Since the coronal light is enormously fainter than the photospheric one, a very tough suppression is needed for the internal stray light, in particular the requirement for the stray light suppression is more stringent in the VL than in the UV, because the emission of the corona with respect to the disk emission is different in the two cases, and the requirements are a suppression of at least 10-9 times for the VL and a suppression of at least 10-7 times for the UV channel. This paper presents the stray light analysis for this new coronographic configuration. The complexity of the optomechanical design of METIS, combined with the faintness of the coronal light with respect to the solar disk noise, make a standard ray tracing approach not feasible because it is not sufficient to stop at the first generation of scattered rays in order to check the requirements. Also scattered rays down to the fourth generation must be treated as sources of new scattering light, to analyze the required level of accuracy. If used in a standard ray tracing scattering analysis, this approach is absolutely beyond the computational capabilities today available

  10. Multi-Channel Satellite Image Analysis Using a Variational Approach

    Science.gov (United States)

    Alvarez, L.; Castaño, C. A.; García, M.; Krissian, K.; Mazorra, L.; Salgado, A.; Sánchez, J.

    2008-06-01

    Currently, meteorological satellites provide multichannel image sequences including visible, temperature and water vapor channels. Based on a variational approach, we propose mathematical models to address some of the usual challenges in satellite image analysis such as: (i) the estimation and smoothing of the cloud structures by decoupling them into different layers depending on their altitudes, (ii) the estimation of the cloud structure motion by combining information from all the channels, and (iii) the 3D visualization of both the cloud structure and the estimated displacements. We include information of all the channels in a single variational motion estimation model. The associated Euler-Lagrange equations yield to a nonlinear system of partial differential equations that we solve numerically using finite-difference schemes. We illustrate the performance of the proposed models with numerical experiments on two multichannel satellite sequences of the North Atlantic, one of them from the Hurricane Vince. Based on a realistic synthetic ground truth motion, we show that our multichannel approach overcomes the single channel estimation for both the average Euclidean and angular errors.

  11. Non Linear Error Analysis from Orbit Measurements in SPS and RHIC

    CERN Document Server

    Cardona, Javier F

    2005-01-01

    Recently, an "action and phase" analysis of SPS orbits measurements proved to be sensitive to sextupole components intentionally activated at specific locations in the ring. In this paper we attempt to determine the strenght of such sextupoles from the measured orbits and compare them with the set values. Action and phase analysis of orbit trayectories generated by RHIC models with non linearities will also be presented and compare with RHIC experiments.

  12. Orbiter subsystem hardware/software interaction analysis. Volume 8: Forward reaction control system

    Science.gov (United States)

    Becker, D. D.

    1980-01-01

    The results of the orbiter hardware/software interaction analysis for the AFT reaction control system are presented. The interaction between hardware failure modes and software are examined in order to identify associated issues and risks. All orbiter subsystems and interfacing program elements which interact with the orbiter computer flight software are analyzed. The failure modes identified in the subsystem/element failure mode and effects analysis are discussed.

  13. 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.

  14. Orbit Determination Error Analysis Results for the Triana Sun-Earth L2 Libration Point Mission

    Science.gov (United States)

    Marr, G.

    2003-01-01

    Using the NASA Goddard Space Flight Center's Orbit Determination Error Analysis System (ODEAS), orbit determination error analysis results are presented for all phases of the Triana Sun-Earth L1 libration point mission and for the science data collection phase of a future Sun-Earth L2 libration point mission. The Triana spacecraft was nominally to be released by the Space Shuttle in a low Earth orbit, and this analysis focuses on that scenario. From the release orbit a transfer trajectory insertion (TTI) maneuver performed using a solid stage would increase the velocity be approximately 3.1 km/sec sending Triana on a direct trajectory to its mission orbit. The Triana mission orbit is a Sun-Earth L1 Lissajous orbit with a Sun-Earth-vehicle (SEV) angle between 4.0 and 15.0 degrees, which would be achieved after a Lissajous orbit insertion (LOI) maneuver at approximately launch plus 6 months. Because Triana was to be launched by the Space Shuttle, TTI could potentially occur over a 16 orbit range from low Earth orbit. This analysis was performed assuming TTI was performed from a low Earth orbit with an inclination of 28.5 degrees and assuming support from a combination of three Deep Space Network (DSN) stations, Goldstone, Canberra, and Madrid and four commercial Universal Space Network (USN) stations, Alaska, Hawaii, Perth, and Santiago. These ground stations would provide coherent two-way range and range rate tracking data usable for orbit determination. Larger range and range rate errors were assumed for the USN stations. Nominally, DSN support would end at TTI+144 hours assuming there were no USN problems. Post-TTI coverage for a range of TTI longitudes for a given nominal trajectory case were analyzed. The orbit determination error analysis after the first correction maneuver would be generally applicable to any libration point mission utilizing a direct trajectory.

  15. 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.

  16. A Study on the Strategies of the Positioning of a Satellite on Observed Images by the Astronomical Telescope and the Observation and Initial Orbit Determination of Unidentified Space Objects

    Directory of Open Access Journals (Sweden)

    Jin Choi

    2011-12-01

    Full Text Available An optical tracking system has advantages for observing geostationary earth orbit (GEO satellites relatively over other types of observation system. Regular surveying for unidentified space objects with the optical tracking system can be an early warning tool for the safety of five Korean active GEO satellites. Two strategies of positioning on the observed image of Communication, Ocean and Meteorological Satellite 1 are tested and compared. Photometric method has a half root mean square error against streak method. Also null eccentricity method for initial orbit determination (IOD is tested with simulation data and real observation data. Under 10 minutes observation time interval, null eccentricity method shows relatively better IOD results than the other time interval. For follow-up observation of unidentified space objects, at least two consecutive observations are needed in 5 minutes to determine orbit for geosynchronous orbit space objects.

  17. Ascent Trajectory Optimization for Air-Launched Launch Vehicle with Small Sun-Synchronous Orbit Satellite Based on Pseudo-spectral Method

    Directory of Open Access Journals (Sweden)

    L. Wang

    2015-01-01

    Full Text Available Economical space transportation systems to launch small satellites into Earth’s orbits are researched in many countries. Using aerospace systems, included aircraft and air-launched launch vehicle, is one of the low cost technical solutions. The airborne launch vehicle application to launch a small satellite with the purpose of remote sensing requires high precision exit on specified sun-synchronous orbit. So a problem is stated to construct an optimal ascent trajectory and optimal control.In this paper, the mathematical motion model of the air-launched launch vehicle with the external disturbances caused by the Earth’s non-sphericity, drag and wind is put forward based on the three-stage flight program with passive intermediate section. A discrete process based on pseudo-spectral method is used to solve the problem, which allows converting the initial problem into a nonlinear programming problem with dynamic constraints and aims for the criteria of maximization of the final mass released onto the target orbit.Application of the proposed solution procedure is illustrated by calculating the optimal control and the corresponding trajectory for two-stage liquid launch vehicle, which places the small spacecraft on the orbit of sun-synchronous at the height of 512 km. The numerical simulation results have demonstrated the effectiveness of the proposed algorithm and allow us to analyze three-stage trajectory parameters with intermediate passive flight phase. It can be noted that in the resulting ascent trajectory, the intermediate passive flight part is a suborbital trajectory with low energy integral, perigee of which is under the surface of the Earth.

  18. Micrometeoroid and Orbital Debris (MMOD) Shield Ballistic Limit Analysis Program

    Science.gov (United States)

    Ryan, Shannon

    2013-01-01

    This software implements penetration limit equations for common micrometeoroid and orbital debris (MMOD) shield configurations, windows, and thermal protection systems. Allowable MMOD risk is formulated in terms of the probability of penetration (PNP) of the spacecraft pressure hull. For calculating the risk, spacecraft geometry models, mission profiles, debris environment models, and penetration limit equations for installed shielding configurations are required. Risk assessment software such as NASA's BUMPERII is used to calculate mission PNP; however, they are unsuitable for use in shield design and preliminary analysis studies. The software defines a single equation for the design and performance evaluation of common MMOD shielding configurations, windows, and thermal protection systems, along with a description of their validity range and guidelines for their application. Recommendations are based on preliminary reviews of fundamental assumptions, and accuracy in predicting experimental impact test results. The software is programmed in Visual Basic for Applications for installation as a simple add-in for Microsoft Excel. The user is directed to a graphical user interface (GUI) that requires user inputs and provides solutions directly in Microsoft Excel workbooks.

  19. Satellite time series analysis using Empirical Mode Decomposition

    Science.gov (United States)

    Pannimpullath, R. Renosh; Doolaeghe, Diane; Loisel, Hubert; Vantrepotte, Vincent; Schmitt, Francois G.

    2016-04-01

    Geophysical fields possess large fluctuations over many spatial and temporal scales. Satellite successive images provide interesting sampling of this spatio-temporal multiscale variability. Here we propose to consider such variability by performing satellite time series analysis, pixel by pixel, using Empirical Mode Decomposition (EMD). EMD is a time series analysis technique able to decompose an original time series into a sum of modes, each one having a different mean frequency. It can be used to smooth signals, to extract trends. It is built in a data-adaptative way, and is able to extract information from nonlinear signals. Here we use MERIS Suspended Particulate Matter (SPM) data, on a weekly basis, during 10 years. There are 458 successive time steps. We have selected 5 different regions of coastal waters for the present study. They are Vietnam coastal waters, Brahmaputra region, St. Lawrence, English Channel and McKenzie. These regions have high SPM concentrations due to large scale river run off. Trend and Hurst exponents are derived for each pixel in each region. The energy also extracted using Hilberts Spectral Analysis (HSA) along with EMD method. Normalised energy computed for each mode for each region with the total energy. The total energy computed using all the modes are extracted using EMD method.

  20. First ISON observations for satellite conjunction analysis in the Western Hemisphere

    Science.gov (United States)

    Zalles, R.; Molotov, I.; Kokina, T.; Zolotov, V.; Condori, R.

    2018-01-01

    In this paper we report on observations of a pair of approaching space objects in the beginning of June 2016, observed jointly by the Tarija Observatory in Bolivia and the Mexican observatory of Sinaloa University in Cosala in the context of the ISON collaboration. These objects were the STAR ONE C1 (2007-056A) active satellite in GEO position 65\\ deg west, and the passive satellite LES 6 (1968-081D). The large number of measurements obtained in a few nights allowed a precise orbit reconstruction. The passive satellite LES 6 (with a brigtness amplitude variation of 3 magnitudes) was too faint for the small aperture of the Cosala telescope.

  1. Analysis of the US Air Force Defense Meteorological Satellite Program Imagery for Global Lightning

    Science.gov (United States)

    Scharfen, Gregory R.

    1999-01-01

    The U. S. Air Force operates the Defense Meteorological Satellite Program (DMSP), a system of near-polar orbiting satellites designed for use in operational weather forecasting and other applications. DMSP satellites carry a suite of sensors that provide images of the earth and profiles of the atmosphere. The National Snow and Ice Data Center (NSIDC) at the University of Colorado has been involved with the archival of DMSP data and its use for several research projects since 1979. This report summarizes the portion of this involvement funded by NASA.

  2. Military Space Mission Design and Analysis in a Multi-Body Environment: An Investigation of High-Altitude Orbits as Alternative Transfer Paths, Parking Orbits for Reconstitution, and Unconventional Mission Orbits

    Science.gov (United States)

    2017-03-23

    MILITARY SPACE MISSION DESIGN AND ANALYSIS IN A MULTI- BODY ENVIRONMENT: AN INVESTIGATION OF HIGH-ALTITUDE ORBITS AS ALTERNATIVE TRANSFER PATHS...subject to copyright protection in the United States. AFIT-ENY-MS-17-M-246 MILITARY SPACE MISSION DESIGN AND ANALYSIS IN A MULTI- BODY ENVIRONMENT: AN...SPACE MISSION DESIGN AND ANALYSIS IN A MULTI- BODY ENVIRONMENT: AN INVESTIGATION OF HIGH-ALTITUDE ORBITS AS ALTERNATIVE TRANSFER PATHS, PARKING ORBITS FOR

  3. Satellite Communications

    Indian Academy of Sciences (India)

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

  4. Exoplanet orbital eccentricities derived from LAMOST-Kepler analysis.

    Science.gov (United States)

    Xie, Ji-Wei; Dong, Subo; Zhu, Zhaohuan; Huber, Daniel; Zheng, Zheng; De Cat, Peter; Fu, Jianning; Liu, Hui-Gen; Luo, Ali; Wu, Yue; Zhang, Haotong; Zhang, Hui; Zhou, Ji-Lin; Cao, Zihuang; Hou, Yonghui; Wang, Yuefei; Zhang, Yong

    2016-10-11

    The nearly circular (mean eccentricity [Formula: see text]) and coplanar (mean mutual inclination [Formula: see text]) orbits of the solar system planets motivated Kant and Laplace to hypothesize that planets are formed in disks, which has developed into the widely accepted theory of planet formation. The first several hundred extrasolar planets (mostly Jovian) discovered using the radial velocity (RV) technique are commonly on eccentric orbits ([Formula: see text]). This raises a fundamental question: Are the solar system and its formation special? The Kepler mission has found thousands of transiting planets dominated by sub-Neptunes, but most of their orbital eccentricities remain unknown. By using the precise spectroscopic host star parameters from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) observations, we measure the eccentricity distributions for a large (698) and homogeneous Kepler planet sample with transit duration statistics. Nearly half of the planets are in systems with single transiting planets (singles), whereas the other half are multiple transiting planets (multiples). We find an eccentricity dichotomy: on average, Kepler singles are on eccentric orbits with [Formula: see text] 0.3, whereas the multiples are on nearly circular [Formula: see text] and coplanar [Formula: see text] degree) orbits similar to those of the solar system planets. Our results are consistent with previous studies of smaller samples and individual systems. We also show that Kepler multiples and solar system objects follow a common relation [[Formula: see text](1-2)[Formula: see text

  5. System Modeling and Operational Characteristic Analysis for an Orbital Friction Vibration Actuator Used in Orbital Vibration Welding

    Directory of Open Access Journals (Sweden)

    XU, F.

    2013-05-01

    Full Text Available Orbital Friction Vibration Actuator (OFVA is a core component of Orbital Friction Welding (OFW, which is a novel apertureless welding technology utilizing friction heat to implement solid-state joining. In this paper, topology and operational principle of OFVA are introduced, the analytical formulas of the electromagnetic force for the x and y directions, which can drive the mover to generate a circular motion trajectory, are derived, and the characteristic of static electromagnetic force is predicted by analytical method and 2-D (two-dimensional FEM (finite element method, 3-D and measurement. The coupled magnetic field-circuit-motion simulation models which are driven by current and voltage source are established, respectively, and some of its operational characteristics are analyzed. Simulation and experiment validate theoretical analysis and the feasibility of the fabricated prototype, demonstrate the good performance of the OFVA, and provide valuable reference for engineering applications.

  6. Organism/Organic Exposure to Orbital Stresses (OOREOS) Satellite: Radiation Exposure in LEO and Supporting Laboratory Studies

    Science.gov (United States)

    Mattioda, Andrew Lige; Cook, Amanda Marie; Quinn, Richard C.; Elsaesser, Andreas; Ehrenfreund, Pascale; Ricca,Alessandra; Jones, Nykola C.; Hoffman, Soren; Ricco,Antonio

    2014-01-01

    We will present the results from the exposure of the metalloporphyrin iron tetraphenylporphyrin chloride (FeTPPCI), anthraufin (C(sub 14)H(sub 8)(O sub 4) (Anth) and Isoviolanthrene (C(sub 34H sub 18) (IVA) to the outher space environment, measured in situ aboard the Organism/Organic Exposure to Orbital Stresses nanosatellite. The compounds were exposed for a period of 17 months (3700 hours of direct solar exposure) including broad-spectrum solar radiation (approx. 122 nm to the near infrared). The organic films are enclosed in hermetically sealed sample cells that contain one of four astrobiologically relevant microenvironments. Transmission spectra (200-1000 nm) were recorded for each film, at first daily and subsequently every 15 days, along with a solar spectrum and the dark response of the detector array. In addition to analysis via UV-Vis spectroscopy, the laboratory controls were also monitored via infrared and far-UV spectroscopy. The results presented will include the finding that the FeTPPCI and IVA organic films in contact with a humid headspace gas (0.8-2.3%) exhibit faster degradation times, upon irradiation, in comparison with identical films under dry headspaces gases, whereas the Anth thin film exhibited a higher degree of photostability. In the companion laboratory experiments, simulated solar exposure of FeTPI films in contact with either Ar or CO(sub -2):O(sub -2):Ar (10:0.01:1000) headspace gas results in growth of a band in the films infrared spectra at 1961 cm(sup 1). Our assignment of this new spectral feature and the corresponding rational will be presented. The relevance of O/OREOS findings to planetary science, biomarker research, and the photostability of organic materials in astrobiologically relevant environments will also be discussed.

  7. Analysis of data collected by the Tatyana II satellite

    Science.gov (United States)

    Lilianaa, Rivera; Oscar, Martínez; Eduardo, Mendoza-Torres; Humberto, Salazar

    2011-04-01

    The Tatyana II satellite is the second one of the University Satellite Program, which is led by the Moscow State University with the participation of the Benemerita Universidad Autonoma de Puebla. This satellite has ultraviolet, red-infrared and charged particles detectors. In this work preliminary results based on the data collected by these detectors on board the satellite over a period of ~3.5 months are presented.

  8. Ricci-based chaos analysis for roto-translatory motion of a Kelvin-type gyrostat satellite

    Science.gov (United States)

    Abtahi, Seyed Mahdi; Sadati, Seyed Hossein; Salarieh, Hassan

    2014-03-01

    The chaotic dynamics of roto-translatory motion of a triaxial Kelvin-type gyrostat satellite under gravity gradient perturbations is considered. The Hamiltonian approach is used for modelling of the coupled spin-orbit equations of motion. The complex Hamiltonian of the system is reduced via the extended Deprit canonical transformation using the Serret-Andoyer variables. Therefore, this reduction leads to the derivation of the perturbation form of the Hamiltonian that can be used in the Ricci curvature criterion based on the Riemannian manifold geometry for the analysis of chaos phenomenon. The results obtained from Ricci method as well as the values from the Lyapunov exponent demonstrate the presence of a strange attraction and chaotic responses in the perturbed system. The simulation results based on numerical methods such as Poincaré section, trajectories of phase portrait and time series responses quantitatively confirm the heteroclinic bifurcation and chaotic behaviour in the rotational-translational dynamics of the gyrostat satellite system.

  9. Analysis of complications after surgical repair of orbital fractures.

    Science.gov (United States)

    Brucoli, Matteo; Arcuri, Francesco; Cavenaghi, Roberta; Benech, Arnaldo

    2011-07-01

    The term "orbital blow-out fracture" is referred to as the mechanism by which an impact to the eyeball is transposed as a mechanical energy to the orbital walls, causing them to fracture. Despite a proper surgical technique, a successful anatomic reconstruction of the orbit, and an accurate follow-up, 3 complications are still frequently observed at long-term follow-up: diplopia, enophthalmos, and hypesthesia of the infraorbital nerve territory. In this retrospective study, we analyze the incidence, the specific characterization, and the potential risk factors of these 3 complications. The records of 75 patients who underwent surgical repair of isolated orbital blow-out fracture from January 2001 to December 2007 at the Maxillofacial Surgery Unit of the Novara Major Hospital were reviewed retrospectively. Patients who had other coexisting facial fractures or orbital rim involvement were excluded from this study. The mean follow-up reached 39 months (range, 6-81 months). Enophthalmos was measured by a Hertel exophthalmometer; diplopia was evaluated by an optometrist with cover test, red glass test, and Hess-Lancaster test; and hypesthesia of the infraorbital nerve territory was checked by clinical examination. The studied parameters included patient's age and sex, time interval between trauma and surgery, location of the fracture, and implant material. The χ test for nonparametric data was used, and a P value of less than 0.05 was considered statistically significant. Sex, location of the fracture, and implant material were not considered statistically significant (P > 0.05). The unique variable that influenced our data was the time interval between trauma and surgery (P > 0.05). Although the surgical technique was executed properly and the immediate postoperative recovery was uneventful, diplopia, enophthalmos, and infraorbital nerve dysfunction were the frequent complications. We stress the fact that orbital blow-out fracture is generally not considered a

  10. Integration of a satellite ground support system based on analysis of the satellite ground support domain

    Science.gov (United States)

    Pendley, R. D.; Scheidker, E. J.; Levitt, D. S.; Myers, C. R.; Werking, R. D.

    1994-01-01

    This analysis defines a complete set of ground support functions based on those practiced in real space flight operations during the on-orbit phase of a mission. These functions are mapped against ground support functions currently in use by NASA and DOD. Software components to provide these functions can be hosted on RISC-based work stations and integrated to provide a modular, integrated ground support system. Such modular systems can be configured to provide as much ground support functionality as desired. This approach to ground systems has been widely proposed and prototyped both by government institutions and commercial vendors. The combined set of ground support functions we describe can be used as a standard to evaluate candidate ground systems. This approach has also been used to develop a prototype of a modular, loosely-integrated ground support system, which is discussed briefly. A crucial benefit to a potential user is that all the components are flight-qualified, thus giving high confidence in their accuracy and reliability.

  11. DS-CDMA satellite diversity reception for personal satellite communication: Downlink performance analysis

    Science.gov (United States)

    DeGaudenzi, Riccardo; Giannetti, Filippo

    1995-01-01

    The downlink of a satellite-mobile personal communication system employing power-controlled Direct Sequence Code Division Multiple Access (DS-CDMA) and exploiting satellite-diversity is analyzed and its performance compared with a more traditional communication system utilizing single satellite reception. The analytical model developed has been thoroughly validated by means of extensive Monte Carlo computer simulations. It is shown how the capacity gain provided by diversity reception shrinks considerably in the presence of increasing traffic or in the case of light shadowing conditions. Moreover, the quantitative results tend to indicate that to combat system capacity reduction due to intra-system interference, no more than two satellites shall be active over the same region. To achieve higher system capacity, differently from terrestrial cellular systems, Multi-User Detection (MUD) techniques are likely to be required in the mobile user terminal, thus considerably increasing its complexity.

  12. Satellite Based Analysis of Surface Urban Heat Island Intensity

    Directory of Open Access Journals (Sweden)

    Gémes Orsolya

    2016-06-01

    Full Text Available The most obvious characteristics of urban climate are higher air and surface temperatures compared to rural areas and large spatial variation of meteorological parameters within the city. This research examines the long term and seasonal development of urban surface temperature using satellite data during a period of 30 years and within a year. The medium resolution Landsat data were (preprocessed using open source tools. Besides the analysis of the long term and seasonal changes in land surface temperature within a city, also its relationship with changes in the vegetation cover was investigated. Different urban districts and local climate zones showed varying strength of correlation. The temperature difference between urban surfaces and surroundings is defined as surface urban heat island (SUHI. Its development shows remarkable seasonal and spatial anomalies. The satellite images can be applied to visualize and analyze the SUHI, although they were not collected at midday and early afternoon, when the phenomenon is normally at its maximum. The applied methodology is based on free data and software and requires minimal user interaction. Using the results new urban developments (new built up and green areas can be planned, that help mitigate the negative effects of urban climate.

  13. Rainfall frequency analysis for ungauged sites using satellite precipitation products

    Science.gov (United States)

    Gado, Tamer A.; Hsu, Kuolin; Sorooshian, Soroosh

    2017-11-01

    The occurrence of extreme rainfall events and their impacts on hydrologic systems and society are critical considerations in the design and management of a large number of water resources projects. As precipitation records are often limited or unavailable at many sites, it is essential to develop better methods for regional estimation of extreme rainfall at these partially-gauged or ungauged sites. In this study, an innovative method for regional rainfall frequency analysis for ungauged sites is presented. The new method (hereafter, this is called the RRFA-S) is based on corrected annual maximum series obtained from a satellite precipitation product (e.g., PERSIANN-CDR). The probability matching method (PMM) is used here for bias correction to match the CDF of satellite-based precipitation data with the gauged data. The RRFA-S method was assessed through a comparative study with the traditional index flood method using the available annual maximum series of daily rainfall in two different regions in USA (11 sites in Colorado and 18 sites in California). The leave-one-out cross-validation technique was used to represent the ungauged site condition. Results of this numerical application have found that the quantile estimates obtained from the new approach are more accurate and more robust than those given by the traditional index flood method.

  14. Geostationary Orbital Crowding: An Analysis of Problems and Solutions

    Science.gov (United States)

    1990-05-16

    it was given 79 monopoly power by its original signatories to operate and maintain a single worldwide satellite network for public international...Books, 1988), p. 5. Figure 3.4. Regions of the International Telecomunications Union 96 Space WARC-1979 Convening in Geneva, Switzerland on the 24th of

  15. Gaia in-orbit realignment: overview and data analysis

    NARCIS (Netherlands)

    Mora, A.; Vosteen, L.L.A.

    2012-01-01

    The ESA Gaia spacecraft has two Shack-Hartmann wavefront sensors (WFS) on its focal plane. They are required to refocus the telescope in-orbit due to launch settings and gravity release. They require bright stars to provide good signal to noise patterns. The centroiding precision achievable poses a

  16. Progress in the analysis of experimental chaos through periodic orbits

    Energy Technology Data Exchange (ETDEWEB)

    Badii, R. (Paul Scherrer Institute, CH-5232 Villigen (Switzerland)); Brun, E. (Physics Institute, University of Zuerich, CH-8057 Zuerich (Switzerland)); Finardi, M. (Paul Scherrer Institute, CH-5232 Villigen (Switzerland)); Flepp, L.; Holzner, R.; Parisi, J.; Reyl, C.; Simonet, J. (Physics Institute, University of Zuerich, CH-8057 Zuerich (Switzerland))

    1994-10-01

    The understanding of chaotic systems can be considerably improved with the knowledge of their periodic-orbit structure. The identification of the low-order unstable periodic orbits embedded in a strange attractor induces a hierarchical organization of the dynamics which is invariant under smooth coordinate changes. The applicability of this technique is by no means limited to analytical or numerical calculations, but has been recently extended to experimental time series. As a specific example, the authors review some of the major results obtained on a nuclear-magnetic-resonance laser which have led to an extension of the conventional (Bloch-Kirchhoff) equations of motion, to the construction of approximate generating partitions, and to an efficient control of the chaotic system around various unstable periodic orbits. The determination of the symbolic dynamics, with the precision achieved by recording all unstable cycles up to order 9, improves the topological and metric characterization of a heteroclinic crisis. The periodic-orbit approach permits detailed study of chaotic motion, thereby leading to an improved classification scheme which subsumes the older ones, based on estimates of scalar quantities such as fractal dimensions and metric entropies.

  17. Risk Analysis of On-Orbit Spacecraft Refueling Concepts

    Science.gov (United States)

    Cirillo, William M.; Stromgren, Chel; Cates, Grant R.

    2010-01-01

    On-orbit refueling of spacecraft has been proposed as an alternative to the exclusive use of Heavy-lift Launch Vehicles to enable human exploration beyond Low Earth Orbit (LEO). In these scenarios, beyond LEO spacecraft are launched dry (without propellant) or partially dry into orbit, using smaller or fewer element launch vehicles. Propellant is then launched into LEO on separate launch vehicles and transferred to the spacecraft. Refueling concepts are potentially attractive because they reduce the maximum individual payload that must be placed in Earth orbit. However, these types of approaches add significant complexity to mission operations and introduce more uncertainty and opportunities for failure to the mission. In order to evaluate these complex scenarios, the authors developed a Monte Carlo based discrete-event model that simulates the operational risks involved with such strategies, including launch processing delays, transportation system failures, and onorbit element lifetimes. This paper describes the methodology used to simulate the mission risks for refueling concepts, the strategies that were evaluated, and the results of the investigation. The results of the investigation show that scenarios that employ refueling concepts will likely have to include long launch and assembly timelines, as well as the use of spare tanker launch vehicles, in order to achieve high levels of mission success through Trans Lunar Injection.

  18. 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.

  19. Orbiter subsystem hardware/software interaction analysis. Volume 8: AFT reaction control system, part 2

    Science.gov (United States)

    Becker, D. D.

    1980-01-01

    The orbiter subsystems and interfacing program elements which interact with the orbiter computer flight software are analyzed. The failure modes identified in the subsystem/element failure mode and effects analysis are examined. Potential interaction with the software is examined through an evaluation of the software requirements. The analysis is restricted to flight software requirements and excludes utility/checkout software. The results of the hardware/software interaction analysis for the forward reaction control system are presented.

  20. Analysis of the SPS Long Term Orbit Drifts

    Energy Technology Data Exchange (ETDEWEB)

    Velotti, Francesco [CERN; Bracco, Chiara [CERN; Cornelis, Karel [CERN; Drøsdal, Lene [CERN; Fraser, Matthew [CERN; Gianfelice-Wendt, Eliana [Fermilab; Goddard, Brennan [CERN; Kain, Verena [CERN; Meddahi, Malika [CERN

    2016-06-01

    The Super Proton Synchrotron (SPS) is the last accelerator in the Large Hadron Collider (LHC) injector chain, and has to deliver the two high-intensity 450 GeV proton beams to the LHC. The transport from SPS to LHC is done through the two Transfer Lines (TL), TI2 and TI8, for Beam 1 (B1) and Beam 2 (B2) respectively. During the first LHC operation period Run 1, a long term drift of the SPS orbit was observed, causing changes in the LHC injection due to the resulting changes in the TL trajectories. This translated into longer LHC turnaround because of the necessity to periodically correct the TL trajectories in order to preserve the beam quality at injection into the LHC. Different sources for the SPS orbit drifts have been investigated: each of them can account only partially for the total orbit drift observed. In this paper, the possible sources of such drift are described, together with the simulated and measured effect they cause. Possible solutions and countermeasures are also discussed.

  1. Finite Element Analysis for Satellite Structures Applications to Their Design, Manufacture and Testing

    CERN Document Server

    Abdelal, Gasser F; Gad, Ahmed H

    2013-01-01

    Designing satellite structures poses an ongoing challenge as the interaction between analysis, experimental testing, and manufacturing phases is underdeveloped. Finite Element Analysis for Satellite Structures: Applications to Their Design, Manufacture and Testing explains the theoretical and practical knowledge needed to perform design of satellite structures. By layering detailed practical discussions with fully developed examples, Finite Element Analysis for Satellite Structures: Applications to Their Design, Manufacture and Testing provides the missing link between theory and implementation.   Computational examples cover all the major aspects of advanced analysis; including modal analysis, harmonic analysis, mechanical and thermal fatigue analysis using finite element method. Test cases are included to support explanations an a range of different manufacturing simulation techniques are described from riveting to shot peening to material cutting. Mechanical design of a satellites structures are covered...

  2. 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

    done by Freud .’ Prior to his psychoanalysis investigations, Freud attempted to ".... represent psychical processes as quantitatively determinate states...parent vehicle for (1) tether initiated reentry or orbit transfer of a subsatellite, and/or (2) local area operations requiring return to the space...performing flow analyses routinely use empirically- derived expressions to calculate convection heat transfer coefficients.ś Another example occurs in

  3. Suspended Cell Culture ANalysis (SCAN) Tool to Enhance ISS On-Orbit Capabilities Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Aurora Flight Sciences and partner, Draper Laboratory, propose to develop an on-orbit immuno-based label-free Suspension Cell Culture ANalysis tool, SCAN tool, which...

  4. Attitude Analysis and Robust Adaptive Backstepping Sliding Mode Control of Spacecrafts Orbiting Irregular Asteroids

    Directory of Open Access Journals (Sweden)

    Chunhui Liang

    2014-01-01

    Full Text Available Attitude stability analysis and robust control algorithms for spacecrafts orbiting irregular asteroids are investigated in the presence of model uncertainties and external disturbances. Rigid spacecraft nonlinear attitude models are considered and detailed attitude stability analysis of spacecraft subjected to the gravity gradient torque in an irregular central gravity field is included in retrograde orbits and direct orbits using linearized system model. The robust adaptive backstepping sliding mode control laws are designed to make the attitude of the spacecrafts stabilized and responded accurately to the expectation in the presence of disturbances and parametric uncertainties. Numerical simulations are included to illustrate the spacecraft performance obtained using the proposed control laws.

  5. Mission design of a Pioneer Jupiter Orbiter

    Science.gov (United States)

    Friedman, L. D.; Nunamaker, R. R.

    1975-01-01

    The Mission analysis and design work performed in order to define a Pioneer mission to orbit Jupiter is described. This work arose from the interaction with a science advisory 'Mission Definition' team and led to the present mission concept. Building on the previous Jupiter Orbiter-Satellite Tour development at JPL a magnetospheric survey mission concept is developed. The geometric control of orbits which then provide extensive local time coverage of the Jovian system is analyzed and merged with the various science and program objectives. The result is a 'flower-orbit' mission design, yielding three large apoapse excursions at various local times and many interior orbits whose shape and orientation is under continual modification. This orbit design, together with a first orbit defined by delivery of an atmospheric probe, yields a mission of high scientific interest.

  6. Modeling Navigation System Performance of a Satellite-Observing Star Tracker Tightly Integrated with an Inertial Measurement Unit

    Science.gov (United States)

    2015-03-26

    70 4.1.1 Overall Model Approach . . . . . . . . . . . . . 71 4.2 Satellite Trajectory Model . . . . . . . . . . . . . . . . . 72... trajectory by providing a posi- tion update to an IMU. Willhite’s thesis also used satellite availability analysis by Kaptuch [41]. He showed that the...the process of global coverage of a constellation assuming circular orbits of the satellites . Satellites that orbit in the same plane with overlapping

  7. Analysis of raw AIS spectrum recordings from a LEO satellite

    DEFF Research Database (Denmark)

    Larsen, Jesper Abildgaard; Mortensen, Hans Peter

    2014-01-01

    The AAUSAT3 satellite is a 1U cubesat, which has been developed by students at Aalborg University, Denmark in collaboration with the Danish Maritime Authority. The satellite was launched in February 2013 on a mission to monitor ships from space using their AIS broadcast signals as an indication...

  8. An Analysis of Military Use of Commercial Satellite Communications

    Science.gov (United States)

    2008-09-01

    allowing multiple satellites to be launched at the same time (from two to seven depending on the launch vehicle). Initially a colossal economic... Rhodes , C., Scheiern, M., Feldman, P., Frelinger, D., Uy, R. (2000). Employing Commercial Satellite Communications: Wideband Investment Options for

  9. GNSS global real-time augmentation positioning: Real-time precise satellite clock estimation, prototype system construction and performance analysis

    Science.gov (United States)

    Chen, Liang; Zhao, Qile; Hu, Zhigang; Jiang, Xinyuan; Geng, Changjiang; Ge, Maorong; Shi, Chuang

    2018-01-01

    Lots of ambiguities in un-differenced (UD) model lead to lower calculation efficiency, which isn't appropriate for the high-frequency real-time GNSS clock estimation, like 1 Hz. Mixed differenced model fusing UD pseudo-range and epoch-differenced (ED) phase observations has been introduced into real-time clock estimation. In this contribution, we extend the mixed differenced model for realizing multi-GNSS real-time clock high-frequency updating and a rigorous comparison and analysis on same conditions are performed to achieve the best real-time clock estimation performance taking the efficiency, accuracy, consistency and reliability into consideration. Based on the multi-GNSS real-time data streams provided by multi-GNSS Experiment (MGEX) and Wuhan University, GPS + BeiDou + Galileo global real-time augmentation positioning prototype system is designed and constructed, including real-time precise orbit determination, real-time precise clock estimation, real-time Precise Point Positioning (RT-PPP) and real-time Standard Point Positioning (RT-SPP). The statistical analysis of the 6 h-predicted real-time orbits shows that the root mean square (RMS) in radial direction is about 1-5 cm for GPS, Beidou MEO and Galileo satellites and about 10 cm for Beidou GEO and IGSO satellites. Using the mixed differenced estimation model, the prototype system can realize high-efficient real-time satellite absolute clock estimation with no constant clock-bias and can be used for high-frequency augmentation message updating (such as 1 Hz). The real-time augmentation message signal-in-space ranging error (SISRE), a comprehensive accuracy of orbit and clock and effecting the users' actual positioning performance, is introduced to evaluate and analyze the performance of GPS + BeiDou + Galileo global real-time augmentation positioning system. The statistical analysis of real-time augmentation message SISRE is about 4-7 cm for GPS, whlile 10 cm for Beidou IGSO/MEO, Galileo and about 30 cm

  10. Dynamics analysis of electrodynamic satellite tethers. Equations of motion and numerical solution algorithms for the tether

    Science.gov (United States)

    Nacozy, P. E.

    1984-01-01

    The equations of motion are developed for a perfectly flexible, inelastic tether with a satellite at its extremity. The tether is attached to a space vehicle in orbit. The tether is allowed to possess electrical conductivity. A numerical solution algorithm to provide the motion of the tether and satellite system is presented. The resulting differential equations can be solved by various existing standard numerical integration computer programs. The resulting differential equations allow the introduction of approximations that can lead to analytical, approximate general solutions. The differential equations allow more dynamical insight of the motion.

  11. Orbital Debris: A Policy Perspective

    Science.gov (United States)

    Johnson, Nicholas L.

    2007-01-01

    A viewgraph presentation describing orbital debris from a policy perspective is shown. The contents include: 1) Voyage through near-Earth Space-animation; 2) What is Orbital Debris?; 3) Orbital Debris Detectors and Damage Potential; 4) Hubble Space Telescope; 5) Mir Space Station Solar Array; 6) International Space Station; 7) Space Shuttle; 8) Satellite Explosions; 9) Satellite Collisions; 10) NASA Orbital Debris Mitigation Guidelines; 11) International Space Station Jettison Policy; 12) Controlled/Uncontrolled Satellite Reentries; 13) Return of Space Objects; 14) Orbital Debris and U.S. National Space Policy; 15) U.S Government Policy Strategy; 16) Bankruptcy of the Iridium Satellite System; 17) Inter-Agency Space Debris Coordination Committee (IADC); 18) Orbital Debris at the United Nations; 19) Chinese Anti-satellite System; 20) Future Evolution of Satellite Population; and 21) Challenge of Orbital Debris

  12. An inadvertent capture cell for orbital debris and micrometeorites - The main electronics box thermal blanket of the solar maximum satellite

    Science.gov (United States)

    Rietmeijer, F. J. M.; Schramm, L. S.; Barrett, R. A.; Mckay, D. S.; Zook, H. A.

    1986-01-01

    The physical properties of impact features in the Solar Max main electronics box thermal blanket are consistent with hypervelocity impacts of particles in the near-earth space environment. The majority of particles are orbital debris and include spacecraft paints and bismuth-rich particles. At least 30 percent of all impact features are caused by micrometeorites, which include silicates and sulfides. Some micrometeorites survive impact with only minor shock-metamorphic effects or chemical fractionation. Currently calibration experiments are under way to relate flux to particle diameter (or mass).

  13. Coherent uncertainty analysis of aerosol measurements from multiple satellite sensors

    Directory of Open Access Journals (Sweden)

    M. Petrenko

    2013-07-01

    Full Text Available Aerosol retrievals from multiple spaceborne sensors, including MODIS (on Terra and Aqua, MISR, OMI, POLDER, CALIOP, and SeaWiFS – altogether, a total of 11 different aerosol products – were comparatively analyzed using data collocated with ground-based aerosol observations from the Aerosol Robotic Network (AERONET stations within the Multi-sensor Aerosol Products Sampling System (MAPSS, http://giovanni.gsfc.nasa.gov/mapss/ and http://giovanni.gsfc.nasa.gov/aerostat/. The analysis was performed by comparing quality-screened satellite aerosol optical depth or thickness (AOD or AOT retrievals during 2006–2010 to available collocated AERONET measurements globally, regionally, and seasonally, and deriving a number of statistical measures of accuracy. We used a robust statistical approach to detect and remove possible outliers in the collocated data that can bias the results of the analysis. Overall, the proportion of outliers in each of the quality-screened AOD products was within 7%. Squared correlation coefficient (R2 values of the satellite AOD retrievals relative to AERONET exceeded 0.8 for many of the analyzed products, while root mean square error (RMSE values for most of the AOD products were within 0.15 over land and 0.07 over ocean. We have been able to generate global maps showing regions where the different products present advantages over the others, as well as the relative performance of each product over different land cover types. It was observed that while MODIS, MISR, and SeaWiFS provide accurate retrievals over most of the land cover types, multi-angle capabilities make MISR the only sensor to retrieve reliable AOD over barren and snow/ice surfaces. Likewise, active sensing enables CALIOP to retrieve aerosol properties over bright-surface closed shrublands more accurately than the other sensors, while POLDER, which is the only one of the sensors capable of measuring polarized aerosols, outperforms other sensors in certain

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

    Science.gov (United States)

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

    2018-03-01

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

  15. A Monte Carlo error analysis program for near-Mars, finite-burn, orbital transfer maneuvers

    Science.gov (United States)

    Green, R. N.; Hoffman, L. H.; Young, G. R.

    1972-01-01

    A computer program was developed which performs an error analysis of a minimum-fuel, finite-thrust, transfer maneuver between two Keplerian orbits in the vicinity of Mars. The method of analysis is the Monte Carlo approach where each off-nominal initial orbit is targeted to the desired final orbit. The errors in the initial orbit are described by two covariance matrices of state deviations and tracking errors. The function of the program is to relate these errors to the resulting errors in the final orbit. The equations of motion for the transfer trajectory are those of a spacecraft maneuvering with constant thrust and mass-flow rate in the neighborhood of a single body. The thrust vector is allowed to rotate in a plane with a constant pitch rate. The transfer trajectory is characterized by six control parameters and the final orbit is defined, or partially defined, by the desired target parameters. The program is applicable to the deboost maneuver (hyperbola to ellipse), orbital trim maneuver (ellipse to ellipse), fly-by maneuver (hyperbola to hyperbola), escape maneuvers (ellipse to hyperbola), and deorbit maneuver.

  16. Analysis of error in TOMS total ozone as a function of orbit and attitude parameters

    Science.gov (United States)

    Gregg, W. W.; Ardanuy, P. E.; Braun, W. C.; Vallette, B. J.; Bhartia, P. K.; Ray, S. N.

    1991-01-01

    Computer simulations of orbital scenarios were performed to examine the effects of orbital altitude, equator crossing time, attitude uncertainty, and orbital eccentricity on ozone observations by future satellites. These effects were assessed by determining changes in solar and viewing geometry and earth daytime coverage loss. The importance of these changes on ozone retrieval was determined by simulating uncertainties in the TOMS ozone retrieval algorithm. The major findings are as follows: (1) Drift of equator crossing time from local noon would have the largest effect on the quality of ozone derived from TOMS. The most significant effect of this drift is the loss of earth daytime coverage in the winter hemisphere. The loss in coverage increases from 1 degree latitude for + or - 1 hour from noon, 6 degrees for + or - 3 hours from noon, to 53 degrees for + or - 6 hours from noon. An additional effect is the increase in ozone retrieval errors due to high solar zenith angles. (2) To maintain contiguous earth coverage, the maximum scan angle of the sensor must be increased with decreasing orbital altitude. The maximum scan angle required for full coverage at the equator varies from 60 degrees at 600 km altitude to 45 degrees at 1200 km. This produces an increase in spacecraft zenith angle, theta, which decreases the ozone retrieval accuracy. The range in theta was approximately 72 degrees for 600 km to approximately 57 degrees at 1200 km. (3) The effect of elliptical orbits is to create gaps in coverage along the subsatellite track. An elliptical orbit with a 200 km perigee and 1200 km apogee produced a maximum earth coverage gap of about 45 km at the perigee at nadir. (4) An attitude uncertainty of 0.1 degree in each axis (pitch, roll, yaw) produced a maximum scan angle to view the pole, and maximum solar zenith angle).

  17. Spin–Orbit Alignment of Exoplanet Systems: Ensemble Analysis Using Asteroseismology

    DEFF Research Database (Denmark)

    Campante, T. L.; Lund, M. N.; Kuszlewicz, James S.

    2016-01-01

    The angle ψ between a planet’s orbital axis and the spin axis of its parent star is an important diagnostic of planet formation, migration, and tidal evolution. We seek empirical constraints on ψ by measuring the stellar inclination i s via asteroseismology for an ensemble of 25 solar-type hosts...... observed with NASA’s Kepler satellite. Our results for i s are consistent with alignment at the 2 σ level for all stars in the sample, meaning that the system surrounding the red-giant star Kepler-56 remains as the only unambiguous misaligned multiple-planet system detected to date. The availability...

  18. Orbital data applications for space objects conjunction assessment and situation analysis

    CERN Document Server

    Chen, Lei; Liang, Yan-Gang; Li, Ke-Bo

    2017-01-01

    This book introduces readers to the application of orbital data on space objects in the contexts of conjunction assessment and space situation analysis, including theories and methodologies. It addresses the main topics involved in space object conjunction assessment, such as: orbital error analysis of space objects; close approach analysis; the calculation, analysis and application of collision probability; and the comprehensive assessment of collision risk. In addition, selected topics on space situation analysis are also presented, including orbital anomaly and space event analysis, and so on. The book offers a valuable guide for researchers and engineers in the fields of astrodynamics, space telemetry, tracking and command (TT&C), space surveillance, space situational awareness, and space debris, as well as for graduates majoring in flight vehicle design and related fields.

  19. Swarm Utilisation Analysis: LEO satellite observations for the ESA's SSA Space Weather network

    Science.gov (United States)

    Kervalishvili, Guram; Stolle, Claudia; Rauberg, Jan; Olsen, Nils; Vennerstrøm, Susanne; Gullikstad Johnsen, Magnar; Hall, Chris

    2017-04-01

    ESA's (European Space Agency) constellation mission Swarm was successfully launched on 22 November 2013. The three satellites achieved their final constellation on 17 April 2014 and since then Swarm-A and Swarm-C orbiting the Earth at about 470 km (flying side-by-side) and Swarm-B at about 520 km altitude. Each of Swarm satellite carries instruments with high precision to measure magnetic and electric fields, neutral and plasma densities, and TEC (Total Electron Content) for which a dual frequency GPS receiver is used. SUA (Swarm Utilisation Analysis) is a project of the ESA's SSA (Space Situational Awareness) SWE (Space Weather) program. Within this framework GFZ (German Research Centre for Geosciences, Potsdam, Germany) and DTU (National Space Institute, Kongens Lyngby, Denmark) have developed two new Swarm products ROT (Rate Of change of TEC) and PEJ (Location and intensity level of Polar Electrojets), respectively. ROT is derived as the first time derivative from the Swarm measurements of TEC at 1 Hz sampling. ROT is highly relevant for users in navigation and communications: strong plasma gradients cause GPS signal degradation or even loss of GPS signal. Also, ROT is a relevant space weather asset irrespective of geomagnetic activity, e.g., high amplitude values of ROT occur during all geomagnetic conditions. PEJ is derived from the Swarm measurements of the magnetic field strength at 1 Hz sampling. PEJ has a high-level importance for power grid companies since the polar electrojet is a major cause for ground-induced currents. ROT and PEJ together with five existing Swarm products TEC, electron density, IBI (Ionospheric Bubble Index), FAC (Field-Aligned Current), and vector magnetic field build the SUA service prototype. This prototype will be integrated into ESA's SSA Space Weather network as a federated service and will be available soon from ESA's SSA SWE Ionospheric Weather and Geomagnetic Conditions Expert Service Centres (ESCs).

  20. Communication Satellite Systems Conference, 11th, San Diego, CA, March 17-20, 1986, Technical Papers

    Science.gov (United States)

    1986-03-01

    User-oriented satellite systems for the 1990's are considered along with a satellite system for aeronautical data communications, the colocation of geostationary communication satellites, an application of intersatellite links to domestic satellite systems, global interconnectivity in the next two decades, an analysis of the Geostar position determination system, and possible architectures for a European data relay satellite system. Attention is given to optimum antenna beam pointing for communication satellites, communications satellites versus fiber optics, spread spectrum-based synchronization of digital satellite transmissions, the Geostationary Satellite Orbit Analysis Program (GSOAP), technology achievements and projections for communication satellites of the future, and trends and development of low noise amplifiers using new FET device. Other topics explored are related to the Omninet mobile satellite system, the Space Transportation System, Japan's launch vehicles, the French military satellite system, and geostationary communications platform payload concepts.

  1. Low-cost, high-resolution, single-structure array telescopes for imaging of low-earth-orbit satellites

    Science.gov (United States)

    Massie, N. A.; Oster, Yale; Poe, Greg; Seppala, Lynn; Shao, Mike

    1992-01-01

    Telescopes that are designed for the unconventional imaging of near-earth satellites must follow unique design rules. The costs must be reduced substantially over those of the conventional telescope designs, and the design must accommodate a technique to circumvent atmospheric distortion of the image. Apertures of 12 m and more along with altitude-altitude mounts that provide high tracking rates are required. A novel design for such a telescope, optimized for speckle imaging, has been generated. Its mount closely resembles a radar mount, and it does not use the conventional dome. Costs for this design are projected to be considerably lower than those for the conventional designs. Results of a design study are presented with details of the electro-optical and optical designs.

  2. Satellite Test of the Equivalence Principle Uncertainty Analysis

    Science.gov (United States)

    Worden, Paul; Mester, John

    2009-12-01

    STEP, the Satellite Test of the Equivalence Principle, is intended to test the apparent equivalence of gravitational and inertial mass to 1 part in 1018 (Worden et al. in Adv. Space Res. 25(6):1205-1208, 2000). This will be an increase of more than five orders of magnitude over ground-based experiments and lunar laser ranging observations (Su et al. in Phys. Rev. D 50:3614-3636, 1994; Williams et al. in Phys. Rev. D 53:6730-6739, 1996; Schlamminger et al. in Phys. Rev. Lett. 100:041101, 2008). It is essential to have a comprehensive and consistent model of the possible error sources in an experiment of this nature to be able to understand and set requirements, and to evaluate design trade-offs. In the following pages we describe existing software for such an error model and the application of this software to the STEP experiment. In particular we address several issues, including charge and patch effect forces, where our understanding has improved since the launch of GP-B owing to the availability of GP-B data and preliminary analysis results (Everitt et al. in Space Sci. Rev., 2009, this issue; Silbergleit et al. in Space Sci. Rev., 2009, this issue; Keiser et al. in Space Sci. Rev., 2009, this issue; Heifetz et al. in Space Sci. Rev., 2009, this issue; Muhlfelder et al. in Space Sci. Rev., 2009, this issue).

  3. On the Mitigation of Solar Index Variability for High Precision Orbit Determination in Low Earth Orbit

    Science.gov (United States)

    2016-09-16

    causing increased difficulty in achieving and maintaining high precision orbit predictions for satellites operating in low Earth orbit . In particular, the...Geodetic satellites with high precision satellite laser ranging data are used as test cases for the Naval Research Laboratory’s Orbit Covariance Estimation...forces imparted upon a satellite . For satellites in Low Earth Orbit (LEO), atmospheric drag forces are typically the largest source of force modeling error

  4. Satellite and ground-based sensors for the Urban Heat Island analysis in the city of Rome

    DEFF Research Database (Denmark)

    Fabrizi, Roberto; Bonafoni, Stefania; Biondi, Riccardo

    2010-01-01

    to the layer of air closest to the surface. UHI spatial characteristics have been assessed using air temperatures measured by both weather stations and brightness temperature maps from the Advanced Along Track Scanning Radiometer (AATSR) on board ENVISAT polar-orbiting satellite. In total, 634 daytime......,Atmospheric humidity,Urban Heat Island,Luminance,Brightness temperatures,Polar-orbiting satellites,Geodetic satellites,Spatial characteristics,Heat island......In this work, the trend of the Urban Heat Island (UHI) of Rome is analyzed by both ground-based weather stations and a satellite-based infrared sensor. First, we have developed a suitable algorithm employing satellite brightness temperatures for the estimation of the air temperature belonging...

  5. Orbital Cellulitis and Subperiosteal Abscess: A 5-year Outcomes Analysis.

    Science.gov (United States)

    Erickson, Benjamin P; Lee, Wendy W

    2015-06-01

    Orbital cellulitis and subperiosteal abscess (SPA) are historically associated with poor outcomes. We seek to characterize current associations with abscess formation, surgical failure and vision loss. All cases of orbital cellulitis presenting to an affiliated hospital between April 2008 and 2013 were critically reviewed. Thirty patients met inclusion criteria. Average age was 28.7 ± 24.4. The male to female ratio was 2:1. Abscesses were identified in 56.7% of patients. Adults were less likely than children to present with abscesses (28.6% vs. 81.3%, p = 0.008). Of the other factors analyzed, only antibiotic use before admission (70.5% vs. 23.1%, p = 0.03) and maximum restriction (-2.5 ± 1.2 vs. -0.9 ± 0.7, p = 0.008) were associated with SPA. Temperature at presentation (37.9 ± 0.9 vs. 37.1 ± 0.4, p = 0.04), relative proptosis (5.8 ± 3.3 mm vs. 2.1 ± 1.1, p = 0.002) and abscess volume (4.3 ± 1.3 mm(3) vs. 0.7 ± 0.5 mm(3), p = 0.0004) were associated with progression to surgery. Reoperation was required in 26.7% of patients. Of these, two-thirds had combined superior/medial abscesses that re-accumulated after isolated endonasal surgery. Two of the 3 patients with profound vision loss had a dental etiology. Only young age, prior antibiotics and degree of restriction predicted the presence of an abscess. Re-accumulation was more common than anticipated, and drainage of superior/medial abscesses by endoscopic surgery alone had the strongest association with surgical failure. Patients with odontogenic abscesses must be treated with particular caution.

  6. Ground Contact Analysis for Korea’s Fictitious Lunar Orbiter Mission

    Directory of Open Access Journals (Sweden)

    Young-Joo Song

    2013-12-01

    Full Text Available In this research, the ground contact opportunity for the fictitious low lunar orbiter is analyzed to prepare for a future Korean lunar orbiter mission. The ground contact opportunity is basically derived from geometrical relations between the typical ground stations at the Earth, the relative positions of the Earth and Moon, and finally, the lunar orbiter itself. Both the cut-off angle and the orbiter’s Line of Sight (LOS conditions (weather orbiter is located at near or far side of the Moon seen from the Earth are considered to determine the ground contact opportunities. Four KOMPSAT Ground Stations (KGSs are assumed to be Korea’s future Near Earth Networks (NENs to support lunar missions, and world-wide separated Deep Space Networks (DSNs are also included during the contact availability analysis. As a result, it is concluded that about 138 times of contact will be made between the orbiter and the Daejeon station during 27.3 days of prediction time span. If these contact times are converted into contact duration, the duration is found to be about 8.55 days, about 31.31% of 27.3 days. It is discovered that selected four KGSs cannot provide continuous tracking of the lunar orbiter, meaning that international collaboration is necessary to track Korea’s future lunar orbiter effectively. Possible combinations of world-wide separated DSNs are also suggested to compensate for the lack of contact availability with only four KGSs, as with primary and backup station concepts. The provided algorithm can be easily modified to support any type of orbit around the Moon, and therefore, the presented results could aid further progress in the design field of Korea’s lunar orbiter missions.

  7. Orbits 2nd order singularity-free solutions

    CERN Document Server

    Xu, Guochang

    2014-01-01

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

  8. The General Mission Analysis Tool (GMAT): A New Resource for Supporting Debris Orbit Determination, Tracking and Analysis

    Science.gov (United States)

    Jah, Moriba; Huges, Steven; Wilkins, Matthew; Kelecy, Tom

    2009-03-01

    The General Mission Analysis Tool (GMAT) was initially developed at NASA's Goddard Space Flight Center (GSFC) as a high accuracy orbital analysis tool to support a variety of space missions. A formal agreement has recently been established between NASA and the Air Force Research Laboratory (AFRL) to further develop GMAT to include orbit determination (OD) capabilities. A variety of estimation strategies and dynamic models will be included in the new version of GMAT. GMAT will accommodate orbit determination, tracking and analysis of orbital debris through a combination of model, processing and implementation requirements. The GMAT processing architecture natively supports parallel processing such that allow it can efficiently accommodate the OD and tracking of numerous objects resulting from breakups. A full first release of the augmented GMAT capability is anticipated in September 2009 and it will be available for community use at no charge.

  9. On Directional Measurement Representation in Orbit Determination

    Science.gov (United States)

    2016-09-13

    Precision Orbit Determination (OD) is often critical for successful satellite operations supporting a wide variety of missions. Directional or angles only...representations. The three techniques are then compared experimentally for a geostationary and a low Earth orbit satellite using simulated data to evaluate their... Orbit Determination (OD) is often critical for successful satellite operations supporting a wide variety of missions. Precision OD involves

  10. An automated data management/analysis system for space shuttle orbiter tiles. [stress analysis

    Science.gov (United States)

    Giles, G. L.; Ballas, M.

    1982-01-01

    An engineering data management system was combined with a nonlinear stress analysis program to provide a capability for analyzing a large number of tiles on the space shuttle orbiter. Tile geometry data and all data necessary of define the tile loads environment accessed automatically as needed for the analysis of a particular tile or a set of tiles. User documentation provided includes: (1) description of computer programs and data files contained in the system; (2) definitions of all engineering data stored in the data base; (3) characteristics of the tile anaytical model; (4) instructions for preparation of user input; and (5) a sample problem to illustrate use of the system. Description of data, computer programs, and analytical models of the tile are sufficiently detailed to guide extension of the system to include additional zones of tiles and/or additional types of analyses

  11. Analysis of BeiDou Satellite Measurements with Code Multipath and Geometry-Free Ionosphere-Free Combinations

    Directory of Open Access Journals (Sweden)

    Qile Zhao

    2016-01-01

    Full Text Available Using GNSS observable from some stations in the Asia-Pacific area, the carrier-to-noise ratio (CNR and multipath combinations of BeiDou Navigation Satellite System (BDS, as well as their variations with time and/or elevation were investigated and compared with those of GPS and Galileo. Provided the same elevation, the CNR of B1 observables is the lowest among the three BDS frequencies, while B3 is the highest. The code multipath combinations of BDS inclined geosynchronous orbit (IGSO and medium Earth orbit (MEO satellites are remarkably correlated with elevation, and the systematic “V” shape trends could be eliminated through between-station-differencing or modeling correction. Daily periodicity was found in the geometry-free ionosphere-free (GFIF combinations of both BDS geostationary Earth orbit (GEO and IGSO satellites. The variation range of carrier phase GFIF combinations of GEO satellites is −2.0 to 2.0 cm. The periodicity of carrier phase GFIF combination could be significantly mitigated through between-station differencing. Carrier phase GFIF combinations of BDS GEO and IGSO satellites might also contain delays related to satellites. Cross-correlation suggests that the GFIF combinations’ time series of some GEO satellites might vary according to their relative geometries with the sun.

  12. Spin–Orbit Alignment of Exoplanet Systems: Ensemble Analysis Using Asteroseismology

    DEFF Research Database (Denmark)

    Campante, T. L.; Lund, M. N.; Kuszlewicz, James S.

    2016-01-01

    The angle ψ between a planet’s orbital axis and the spin axis of its parent star is an important diagnostic of planet formation, migration, and tidal evolution. We seek empirical constraints on ψ by measuring the stellar inclination i s via asteroseismology for an ensemble of 25 solar-type hosts...... observed with NASA’s Kepler satellite. Our results for i s are consistent with alignment at the 2 σ level for all stars in the sample, meaning that the system surrounding the red-giant star Kepler-56 remains as the only unambiguous misaligned multiple-planet system detected to date. The availability...... of a measurement of the projected spin–orbit angle λ for two of the systems allows us to estimate ψ . We find that the orbit of the hot Jupiter HAT-P-7b is likely to be retrograde ( ##IMG## [http://ej.iop.org/images/0004-637X/819/1/85/apj522683ieqn1.gif] $psi =116rc. 4_-14.7^+30.2$ ), whereas that of Kepler-25c...

  13. Analysis of satellite precipitation over East Africa during last decades

    Science.gov (United States)

    Cattani, Elsa; Wenhaji Ndomeni, Claudine; Merino, Andrés; Levizzani, Vincenzo

    2016-04-01

    Daily accumulated precipitation time series from satellite retrieval algorithms (e.g., ARC2 and TAMSAT) are exploited to extract the spatial and temporal variability of East Africa (EA - 5°S-20°N, 28°E-52°E) precipitation during last decades (1983-2013). The Empirical Orthogonal Function (EOF) analysis is applied to precipitation time series to investigate the spatial and temporal variability in particular for October-November-December referred to as the short rain season. Moreover, the connection among EA's precipitation, sea surface temperature, and soil moisture is analyzed through the correlation with the dominant EOF modes of variability. Preliminary results concern the first two EOF's modes for the ARC2 data set. EOF1 is characterized by an inter-annual variability and a positive correlation between precipitation and El Niño, positive Indian Ocean Dipole mode, and soil moisture, while EOF2 shows a dipole structure of spatial variability associated with a longer scale temporal variability. This second dominant mode is mostly linked to sea surface temperature variations in the North Atlantic Ocean. Further analyses are carried out by computing the time series of the joint CCI/CLIVAR/JCOMM Expert Team on Climate Change Detection and Indices (ETCCDI, http://etccdi.pacificclimate.org/index.shtml), i.e. RX1day, RX5day, CDD, CDD, CWD, SDII, PRCPTOT, R10, R20. The purpose is to identify the occurrenes of extreme events (droughts and floods) and extract precipitation temporal variation by trend analysis (Mann-Kendall technique). Results for the ARC2 data set demonstrate the existence of a dipole spatial pattern in the linear trend of the time series of PRCPTOT (annual precipitation considering days with a rain rate > 1 mm) and SDII (average precipitation on wet days over a year). A negative trend is mainly present over West Ethiopia and Sudan, whereas a positive trend is exhibited over East Ethiopia and Somalia. CDD (maximum number of consecutive dry days) and

  14. Current and Future Applications of Multispectral (RGB) Satellite Imagery for Weather Analysis and Forecasting Applications

    Science.gov (United States)

    Molthan, Andrew L.; Fuell, Kevin K.; LaFontaine, Frank; McGrath, Kevin; Smith, Matt

    2013-01-01

    Current and future satellite sensors provide remotely sensed quantities from a variety of wavelengths ranging from the visible to the passive microwave, from both geostationary and low ]Earth orbits. The NASA Short ]term Prediction Research and Transition (SPoRT) Center has a long history of providing multispectral imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA fs Terra and Aqua satellites in support of NWS forecast office activities. Products from MODIS have recently been extended to include a broader suite of multispectral imagery similar to those developed by EUMETSAT, based upon the spectral channels available from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) aboard METEOSAT ]9. This broader suite includes products that discriminate between air mass types associated with synoptic ]scale features, assists in the identification of dust, and improves upon paired channel difference detection of fog and low cloud events. Future instruments will continue the availability of these products and also expand upon current capabilities. The Advanced Baseline Imager (ABI) on GOES ]R will improve the spectral, spatial, and temporal resolution of our current geostationary capabilities, and the recent launch of the Suomi National Polar ]Orbiting Partnership (S ]NPP) carries instruments such as the Visible Infrared Imager Radiometer Suite (VIIRS), the Cross ]track Infrared Sounder (CrIS), and the Advanced Technology Microwave Sounder (ATMS), which have unrivaled spectral and spatial resolution, as precursors to the JPSS era (i.e., the next generation of polar orbiting satellites. New applications from VIIRS extend multispectral composites available from MODIS and SEVIRI while adding new capabilities through incorporation of additional CrIS channels or information from the Near Constant Contrast or gDay ]Night Band h, which provides moonlit reflectance from clouds and detection of fires or city lights. This presentation will

  15. Trends in communications satellites

    CERN Document Server

    Curtin, Denis J

    1979-01-01

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

  16. An Analysis of the Orbital Distribution of Solid Rocket Motor Slag

    Science.gov (United States)

    Horstman, Matthew F.; Mulrooney, Mark

    2007-01-01

    The contribution made by orbiting solid rocket motors (SRMs) to the orbital debris environment is both potentially significant and insufficiently studied. A combination of rocket motor design and the mechanisms of the combustion process can lead to the emission of sufficiently large and numerous by-products to warrant assessment of their contribution to the orbital debris environment. These particles are formed during SRM tail-off, or the termination of burn, by the rapid expansion, dissemination, and solidification of the molten Al2O3 slag pool accumulated during the main burn phase of SRMs utilizing immersion-type nozzles. Though the usage of SRMs is low compared to the usage of liquid fueled motors, the propensity of SRMs to generate particles in the 100 m and larger size regime has caused concern regarding their contributing to the debris environment. Particle sizes as large as 1 cm have been witnessed in ground tests conducted under vacuum conditions and comparable sizes have been estimated via ground-based telescopic and in-situ observations of sub-orbital SRM tail-off events. Using sub-orbital and post recovery observations, a simplistic number-size-velocity distribution of slag from on-orbit SRM firings was postulated. In this paper we have developed more elaborate distributions and emission scenarios and modeled the resultant orbital population and its time evolution by incorporating a historical database of SRM launches, propellant masses, and likely location and time of particulate deposition. From this analysis a more comprehensive understanding has been obtained of the role of SRM ejecta in the orbital debris environment, indicating that SRM slag is a significant component of the current and future population.

  17. A Ballistic Limit Analysis Program for Shielding Against Micrometeoroids and Orbital Debris

    Science.gov (United States)

    Ryan, Shannon; Christiansen, Erie

    2010-01-01

    A software program has been developed that enables the user to quickly and simply perform ballistic limit calculations for common spacecraft structures that are subject to hypervelocity impact of micrometeoroid and orbital debris (MMOD) projectiles. This analysis program consists of two core modules: design, and; performance. The design module enables a user to calculate preliminary dimensions of a shield configuration (e.g., thicknesses/areal densities, spacing, etc.) for a ?design? particle (diameter, density, impact velocity, incidence). The performance module enables a more detailed shielding analysis, providing the performance of a user-defined shielding configuration over the range of relevant in-orbit impact conditions.

  18. Vegetation Cover Change in Yosemite National Park (California) Detected using Landsat Satellite Image Analysis

    Science.gov (United States)

    Potter, Christopher

    2015-01-01

    Landsat image analysis over the past 20+ years showed that consistent increases in the satellite normalized difference vegetation index (NDVI) during relatively dry years were confined to large wildfire areas that burned in the late 1980s and 1990s.

  19. GPM GROUND VALIDATION TRMM MULTI-SATELLITE PRECIPITATION ANALYSIS (TMPA) IPHEX V7

    Data.gov (United States)

    National Aeronautics and Space Administration — This GPM Ground Validation TRMM Multi-satellite Precipitation Analysis (TMPA) IPHEx dataset is a subset of the TMPA 3B42RT gridded precipitation product selected for...

  20. Orbital Debris Quarterly News. Volume 13; No. 1

    Science.gov (United States)

    Liou, J.-C. (Editor); Shoots, Debi (Editor)

    2009-01-01

    Topics discussed include: new debris from a decommissioned satellite with a nuclear power source; debris from the destruction of the Fengyun-1C meteorological satellite; quantitative analysis of the European Space Agency's Automated Transfer Vehicle 'Jules Verne' reentry event; microsatellite impact tests; solar cycle 24 predictions and other long-term projections and geosynchronus (GEO) environment for the Orbital Debris Engineering Model (ORDEM2008). Abstracts from the NASA Orbital Debris Program Office, examining satellite reentry risk assessments and statistical issues for uncontrolled reentry hazards, are also included.

  1. Very high resolution satellite data: New challenges in image analysis

    Digital Repository Service at National Institute of Oceanography (India)

    Sathe, P.V.; Muraleedharan, P.M.

    Early years of coming century will see a large number of satellites with very high spatial resolution reaching beyond 1 m in the visible range of electromagnetic spectrum. Such images will come very close to giving a ground-based view of a terrain...

  2. Analysis of urban decay from low resolution satellite remote sensing ...

    African Journals Online (AJOL)

    This paper analyzed the spatial and temporal pattern of urban decay in different parts of a traditional organic city through data extracted from satellite remote sensing images. It analyzed temporal differences in urban quality in the city using uniform parameter of urban blight measurement. It presented a classification scheme ...

  3. Triple Difference Approach to Low Earth Orbiter Precision Orbit Determination

    Science.gov (United States)

    Kwon, Jay-Hyoun; Grejner-Brzezinska, Dorota A.; Yom, Jae-Hong; Cheon, Lee-Dong

    2003-03-01

    A precise kinematic orbit determination (P-KOD) procedure for Low Earth Orbiter(LEO) using the GPS ion-free triple differenced carrier phases is presented. Because the triple differenced observables provide only relative information, the first epoch's positions of the orbit should be held fixed. Then, both forward and backward filtering was executed to mitigate the effect of biases of the first epoch's position. P-KOD utilizes the precise GPS orbits and ground stations data from International GPS Service (IGS) so that the only unknown parameters to be solved are positions of the satellite at each epoch. Currently, the 3-D accuracy of P-KOD applied to CHAMP (CHAllenging Minisatellite Payload) shows better than 35 cm compared to the published rapid scientific orbit (RSO) solution from GFZ (GeoForschungsZentrum Potsdam). The data screening for cycle slips is a particularly challenging procedure for LEO, which moves very fast in the middle of the ionospheric layer. It was found that data screening using SNR (signal to noise ratio) generates best results based on the residual analysis using RSO. It is expected that much better accuracy are achievable with refined prescreening procedure and optimized geometry of the satellites and ground stations.

  4. Effective field analysis using the full angular spin-orbit torque magnetometry dependence

    Science.gov (United States)

    Schulz, Tomek; Lee, Kyujoon; Krüger, Benjamin; Lo Conte, Roberto; Karnad, Gurucharan V.; Garcia, Karin; Vila, Laurent; Ocker, Berthold; Ravelosona, Dafiné; Kläui, Mathias

    2017-06-01

    Spin-orbit torques promise ultraefficient magnetization switching used for advanced devices based on emergent quasiparticles such as domain walls and skyrmions. Recently, the spin structure dynamics, materials, and systems with tailored spin-orbit torques are being developed. A method, which allows one to detect the acting torques in a given system as a function of the magnetization direction is the torque magnetometry method based on a higher harmonics analysis of the anomalous Hall effect. Here we show that the effective fields acting on magnetic domain walls that govern the efficiency of their dynamics require a sophisticated analysis taking into account the full angular dependence of the torques. Using a one-dimensional model, we compared the spin-orbit torque efficiencies by depinning measurements and spin torque magnetometry. We show that the effective fields can be accurately determined and we find good agreement. Thus, our method allows us now to rapidly screen materials and predict the resulting quasiparticle dynamics.

  5. Simplified sum-over-states calculations and missing-orbital analysis on hyperpolarizabilities of benzene derivatives

    Science.gov (United States)

    Tomonari, Mutsumi; Ookubo, Norio; Takada, Toshikazu; Feyereisen, Martin W.; Almlöf, Jan

    1993-03-01

    The simplified sum-over-states (SOS) and missing-orbital analysis methods are introduced. The former aims to calculate the molecular polarizabilities in the framework of ab initio SCF theory, and the latter to analyze the calculated polarizabilities. The utility of the combination of these methods is demonstrated for the benzene derivatives, e.g. p-nitroaniline (PNA) and p-cyanoaniline (PCA). The calculated first-order hyperpolarizabilities (β) agree well with those of both CPHF calculations and experimental results. The missing-orbital analysis shows that β for PCA is contributed by both forward and backward charge transfer (CT) related to "out-of-plane" and "in-plane" orbitals, respectively. In contrast, β for PNA is confirmed to be explained fully by the conventional two-state model characterized by strong forward CT.

  6. Global Characterization of CO2 Column Retrievals from Shortwave-Infrared Satellite Observations of the Orbiting Carbon Observatory-2 Mission

    Directory of Open Access Journals (Sweden)

    Charles Miller

    2011-02-01

    Full Text Available The global characteristics of retrievals of the column-averaged CO2 dry air mole fraction, XCO2, from shortwave infrared observations has been studied using the expected measurement performance of the NASA Orbiting Carbon Observatory-2 (OCO-2 mission. This study focuses on XCO2 retrieval precision and averaging kernels and their sensitivity to key parameters such as solar zenith angle (SZA, surface pressure, surface type and aerosol optical depth (AOD, for both nadir and sunglint observing modes. Realistic simulations have been carried out and the single sounding retrieval errors for XCO2 have been derived from the formal retrieval error covariance matrix under the assumption that the retrieval has converged to the correct answer and that the forward model can adequately describe the measurement. Thus, the retrieval errors presented in this study represent an estimate of the retrieval precision. For nadir observations, we find single-sounding retrieval errors with values typically less than 1 part per million (ppm over most land surfaces for SZAs less than 70° and up to 2.5 ppm for larger SZAs. Larger errors are found over snow/ice and ocean surfaces due to their low albedo in the spectral regions of the CO2 absorption bands and, for ocean, also in the O2 A band. For sunglint observations, errors over the ocean are significantly smaller than in nadir mode with values in the range of 0.3 to 0.6 ppm for small SZAs which can decrease to values as small as 0.15 for the largest SZAs. The vertical sensitivity of the retrieval that is represented by the column averaging kernel peaks near the surface and exhibits values near unity throughout most of the troposphere for most anticipated scenes. Nadir observations over dark ocean or snow/ice surfaces and observations with large AOD and large SZA show a decreased sensitivity to near-surface CO2. All simulations are carried out for a mid-latitude summer atmospheric profile, a given aerosol type and

  7. 'Ku-satellites, C-satellites, and landlines - A critical analysis for NBC's future

    Science.gov (United States)

    Kivell, D.

    1983-10-01

    The factors considered in the choice and design of a K-band satellite distribution system for the NBC television network are reviewed. The K-band system is found to fulfill the requirements of transponder availability (four channels normally and eight channels simultaneously on football weekends), freedom from interference, and bandwidth (to accommodate multiplexed analog components, digital television, or two signals per transponder) more adequately than a C-band system and at lower cost (46 vs. 50 million dollars/year) than the present landline system, accounting for projected increases in landline fees resulting from the divestiture of ATT. Ground stations with one 3-m and one 6, 8, or 11-m antenna each have been shown to provide adequate video signal-to-noise ratios despite rain-attenuation effects, as well as the potential for uplink operation. A centralized, computer-controlled management and switching system with a common clock and redundant single-channel-per-carrier channels has been designed, and full operation of the K-band distribution system is planned for January, 1985.

  8. Consideration of Collision "Consequence" in Satellite Conjunction Assessment and Risk Analysis

    Science.gov (United States)

    Hejduk, M.; Laporte, F.; Moury, M.; Newman, L.; Shepperd, R.

    2017-01-01

    Classic risk management theory requires the assessment of both likelihood and consequence of deleterious events. Satellite conjunction risk assessment has produced a highly-developed theory for assessing collision likelihood but holds a completely static solution for collision consequence, treating all potential collisions as essentially equally worrisome. This may be true for the survival of the protected asset, but the amount of debris produced by the potential collision, and therefore the degree to which the orbital corridor may be compromised, can vary greatly among satellite conjunctions. This study leverages present work on satellite collision modeling to develop a method by which it can be estimated, to a particular confidence level, whether a particular collision is likely to produce a relatively large or relatively small amount of resultant debris and how this datum might alter conjunction remediation decisions. The more general question of orbital corridor protection is also addressed, and a preliminary framework presented by which both collision likelihood and consequence can be jointly considered in the risk assessment process.

  9. Error Analysis of Satellite Precipitation-Driven Modeling of Flood Events in Complex Alpine Terrain

    Directory of Open Access Journals (Sweden)

    Yiwen Mei

    2016-03-01

    Full Text Available The error in satellite precipitation-driven complex terrain flood simulations is characterized in this study for eight different global satellite products and 128 flood events over the Eastern Italian Alps. The flood events are grouped according to two flood types: rain floods and flash floods. The satellite precipitation products and runoff simulations are evaluated based on systematic and random error metrics applied on the matched event pairs and basin-scale event properties (i.e., rainfall and runoff cumulative depth and time series shape. Overall, error characteristics exhibit dependency on the flood type. Generally, timing of the event precipitation mass center and dispersion of the time series derived from satellite precipitation exhibits good agreement with the reference; the cumulative depth is mostly underestimated. The study shows a dampening effect in both systematic and random error components of the satellite-driven hydrograph relative to the satellite-retrieved hyetograph. The systematic error in shape of the time series shows a significant dampening effect. The random error dampening effect is less pronounced for the flash flood events and the rain flood events with a high runoff coefficient. This event-based analysis of the satellite precipitation error propagation in flood modeling sheds light on the application of satellite precipitation in mountain flood hydrology.

  10. Arctic sea-level reconstruction analysis using recent satellite altimetry

    DEFF Research Database (Denmark)

    Svendsen, Peter Limkilde; Andersen, Ole Baltazar; Nielsen, Allan Aasbjerg

    2014-01-01

    We present a sea-level reconstruction for the Arctic Ocean using recent satellite altimetry data. The model, forced by historical tide gauge data, is based on empirical orthogonal functions (EOFs) from a calibration period; for this purpose, newly retracked satellite altimetry from ERS-1 and -2...... and Envisat has been used. Despite the limited coverage of these datasets, we have made a reconstruction up to 82 degrees north for the period 1950–2010. We place particular emphasis on determining appropriate preprocessing for the tide gauge data, and on validation of the model, including the ability...... to reconstruct known data. The relationship between the reconstruction and climatic variables, such as atmospheric pressure, and climate oscillations, including the Arctic Oscillation (AO), is examined....

  11. Numerical Analysis of Constrained, Time-Optimal Satellite Reorientation

    Directory of Open Access Journals (Sweden)

    Robert G. Melton

    2012-01-01

    Full Text Available Previous work on time-optimal satellite slewing maneuvers, with one satellite axis (sensor axis required to obey multiple path constraints (exclusion from keep-out cones centered on high-intensity astronomical sources reveals complex motions with no part of the trajectory touching the constraint boundaries (boundary points or lying along a finite arc of the constraint boundary (boundary arcs. This paper examines four cases in which the sensor axis is either forced to follow a boundary arc, or has initial and final directions that lie on the constraint boundary. Numerical solutions, generated via a Legendre pseudospectral method, show that the forced boundary arcs are suboptimal. Precession created by the control torques, moving the sensor axis away from the constraint boundary, results in faster slewing maneuvers. A two-stage process is proposed for generating optimal solutions in less time, an important consideration for eventual onboard implementation.

  12. Performance Modeling and Analysis of Parallel Processing and Low Earth Orbit Satellite Communication Systems

    Science.gov (United States)

    1994-01-01

    134 xii 9.8.1 The SatLab M oel...BONeS SatLab Interface M odule (BSIM ) ............................................................ 142 9.8.2.7 Satemnm router M odule...parallel processing systems can be grouped into one of two architectural categories: processor-to-iemory (P-M) or processing element-to-processing

  13. A Performance Analysis of the IRIDIUM Low Earth Orbit Satellite System

    Science.gov (United States)

    1998-06-01

    GLOBALSTAR network is being developed by a group of companies that includes Loral, QUALCOMM, SS/L, AirTouch and numerous others [Com93]. The network will...other. It is acceptable to model this group of independent traffic sources as a single traffic source with a Poisson mean arrival rate. The location of...Assumptions The simulation model was developed using the commercial software packages SATLAB and DESIGNER by Cadence Design Systems, Inc. [Cad95]. The

  14. Frozen orbits at high eccentricity and inclination: application to Mercury orbiter

    Science.gov (United States)

    Delsate, N.; Robutel, P.; Lemaître, A.; Carletti, T.

    2010-11-01

    We hereby study the stability of a massless probe orbiting around an oblate central body (planet or planetary satellite) perturbed by a third body, assumed to lay in the equatorial plane (Sun or Jupiter for example) using a Hamiltonian formalism. We are able to determine, in the parameters space, the location of the frozen orbits, namely orbits whose orbital elements remain constant on average, to characterize their stability/unstability and to compute the periods of the equilibria. The proposed theory is general enough, to be applied to a wide range of probes around planet or natural planetary satellites. The BepiColombo mission is used to motivate our analysis and to provide specific numerical data to check our analytical results. Finally, we also bring to the light that the coefficient J 2 is able to protect against the increasing of the eccentricity due to the Kozai-Lidov effect and the coefficient J 3 determines a shift of the equilibria.

  15. BeiDou Satellites Assistant Determination by Receiving Other GNSS Downlink Signals

    Directory of Open Access Journals (Sweden)

    Lei Chen

    2016-01-01

    Full Text Available GNSS’s orbit determinations always rely on ground station or intersatellite links (ISL. In the emergency of satellite-to-ground links and ISL break-off, BeiDou navigation satellite system (BDS satellites cannot determine their orbits. In this paper, we propose to add a spaceborne annular beam antenna for receiving the global positioning system (GPS and global navigation satellite system (GLONASS signals; therefore, the BDS satellites may be capable of determining their orbits by GPS/GLONASS signals. Firstly, the spectrum selection, the power isolation, the range of Doppler frequency shift, and changing rate are taken into account for the feasibility. Specifically, the L2 band signals are chosen for receiving and processing in order to prevent the overlapping of the receiving and transmitting signals. Secondly, the minimum number of visible satellites (MNVS, carrier-to-noise ratio (C/N0, dilution of precision (GDOP, and geometric distance root-mean-square (gdrms are evaluated for acquiring the effective receiving antennas’ coverage ranges. Finally, the scheme of deploying 3 receiving antennas is proved to be optimal by analysis and simulations over the middle earth orbit (MEO, geostationary earth orbit (GEO, and the inclined geosynchronous satellite orbit (IGSO. The antennas’ structures and patterns are designed to draw a conclusion that installing GPS and GLONASS receivers on BDS satellites for emergent orbits determination is cost-effective.

  16. Satellite image analysis for surveillance, vegetation and climate change

    Energy Technology Data Exchange (ETDEWEB)

    Cai, D Michael [Los Alamos National Laboratory

    2011-01-18

    Recently, many studies have provided abundant evidence to show the trend of tree mortality is increasing in many regions, and the cause of tree mortality is associated with drought, insect outbreak, or fire. Unfortunately, there is no current capability available to monitor vegetation changes, and correlate and predict tree mortality with CO{sub 2} change, and climate change on the global scale. Different survey platforms (methods) have been used for forest management. Typical ground-based forest surveys measure tree stem diameter, species, and alive or dead. The measurements are low-tech and time consuming, but the sample sizes are large, running into millions of trees, covering large areas, and spanning many years. These field surveys provide powerful ground validation for other survey methods such as photo survey, helicopter GPS survey, and aerial overview survey. The satellite imagery has much larger coverage. It is easier to tile the different images together, and more important, the spatial resolution has been improved such that close to or even higher than aerial survey platforms. Today, the remote sensing satellite data have reached sub-meter spatial resolution for panchromatic channels (IKONOS 2: 1 m; Quickbird-2: 0.61 m; Worldview-2: 0.5 m) and meter spatial resolution for multi-spectral channels (IKONOS 2: 4 meter; Quickbird-2: 2.44 m; Worldview-2: 2 m). Therefore, high resolution satellite imagery can allow foresters to discern individual trees. This vital information should allow us to quantify physiological states of trees, e.g. healthy or dead, shape and size of tree crowns, as well as species and functional compositions of trees. This is a powerful data resource, however, due to the vast amount of the data collected daily, it is impossible for human analysts to review the imagery in detail to identify the vital biodiversity information. Thus, in this talk, we will discuss the opportunities and challenges to use high resolution satellite imagery and

  17. Families of Keplerian orbits

    Energy Technology Data Exchange (ETDEWEB)

    Butikov, Eugene I [St Petersburg State University, St Petersburg (Russian Federation)

    2003-03-01

    Various properties of Keplerian orbits traced by satellites that are launched from one and the same spatial point with different initial velocities are discussed. Two families of elliptical orbits are investigated, namely the sets of orbits produced by a common direction but different magnitudes of the initial velocities, and by a common magnitude but various directions of the initial velocities. For the latter family, the envelope of all the orbits is found, which is the boundary of the spatial region occupied by the orbits.

  18. Families of Keplerian orbits

    CERN Document Server

    Butikov, E I

    2003-01-01

    Various properties of Keplerian orbits traced by satellites that are launched from one and the same spatial point with different initial velocities are discussed. Two families of elliptical orbits are investigated, namely the sets of orbits produced by a common direction but different magnitudes of the initial velocities, and by a common magnitude but various directions of the initial velocities. For the latter family, the envelope of all the orbits is found, which is the boundary of the spatial region occupied by the orbits.

  19. Micro-Satellite Configuration of Discoid and Asymmetrical, Gyroless with Thrusters Three-Axis Robust Control and Stability Analysis

    Directory of Open Access Journals (Sweden)

    Ho-Nien Shou

    2014-01-01

    Full Text Available The center of mass of the micro-satellite can offset due to fuel consumption in the course of propulsion, with the interference of external orbital environment such as gravity gradient torque and solar radiation torque. If the structural shape is discoid and asymmetrical, the attitude control may be difficult. The only solution is to design a robust controller, so that the attitude pointing of the satellite can meet the mission requirements with the interference of internal parameter perturbation and external disturbance. Meanwhile, in order to reduce the weight and manufacturing cost of satellite, in the design of satellite attitude angular rate determination, the project used unscented kalman filter (UKF algorithm, coarse sun sensor (CSS and earth horizon sensor (EHS as measurement components to obtain the satellite attitude without rate gyro.

  20. Instantaneous Reference Frame Realization by Means of Combination of Space Geodesy Techniques Onboard Jason-2 Satellite

    Science.gov (United States)

    Svehla, Drazen; Flohrer, Claudia; Otten, Michiel; Springer, Tim; Zandbergen, René; Dow, John

    2010-05-01

    Terrestrial reference frames are realized by sets of station coordinates that are estimated over a longer period of time using a combination of different space geodesy techniques. However, in the precise orbit determination (POD) of LEO satellites using GPS, reference stations on the ground are not directly used to estimate the orbit of the LEO satellite. Compared to SLR and DORIS, LEO POD based on GPS uses an intermediate reference frame represented by the GPS satellite orbits and epoch-wise estimates of high-rate GPS satellite clocks. Any error in the GPS satellite orbits and clocks, or this intermediate space-based reference frame, will directly propagate into LEO orbit and directly alias into gravity field determination (as in the case of GOCE) or altimetry results (as in the case of JASON-2). To demonstrate this, one can take two different GPS orbit and clock solutions from two of the most accurate IGS Analysis Centers and compare the estimated LEO orbits in the spectral domain. The quality of the instantaneous reference frame realized by the GPS satellites will more strongly affect LEO satellites in very low orbits (like GOCE) than satellites in a high LEO orbit (like JASON-2), due to the use of kinematic or very reduced-dynamic POD approaches for the lower orbit altitudes. POD for JASON-2 satellite require a rather modest number of estimated orbital parameters and it is comparable to the GPS orbit parameterisation. Furthermore, as concerns non-gravitational forces, satellites in a high LEO orbit are mainly affected by the solar radiation pressure, whereas satellites in very low LEO orbit, considering solar radiation, are mainly affected by the air-drag. Satellites in the higher orbits are very good candidates for the combination of space geodesy techniques, like GPS, DORIS and SLR. With the collocation of different space geodesy techniques onboard JASON-2 satellite, one can connect all GPS satellites in the GPS constellation in only about 90 minutes, and all