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  • 1
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    The GPS flight experiment on TOPEX/POSEIDEN (1994)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The precision orbit determination (POD) experiment on TOPEX/POSEIDON using the Global Positioning System (GPS) is yielding concrete results. Orbit consistency and accuracy tests indicate that GPS is routinely providing satellite altitude with an accuracy of better than 3 cm. Here we review the GPS experiment, its basic concepts, POD techniques and key results, and discuss the possible cost and performance benefits that may flow to future missions.
    Keywords: SPACECRAFT INSTRUMENTATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 19; p. 2171-2174
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  • 2
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    Strategies for sub-decimeter satellite tracking with GPS (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Decimeter tracking of low earth orbiters can be achieved with a variety of differential GPS techniques. A precisely known global network of GPS ground receivers and a receiver aboard the user satellite are needed, and all techniques must simultaneously estimate the user and GPS satellite orbits. Three basic strategies include a purely geometric, a fully dynamic, and a hybrid strategy, the last of which combines dynamic GPS solutions with a geometric user solution. Two powerful extensions of the hybrid strategy show the most promise. The first uses a quasi-optimal synthesis of dynamics and geometry in the user solution, while the second uses a novel gravity adjustment method to exploit data from repeat ground tracks in a computationally efficient way. The best of these techniques promise to deliver sub-decimeter accuracy down to the lowest possible orbits.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
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  • 3
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    Precise tracking of remote sensing satellites with the Global Positioning System (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The Global Positioning System (GPS) can be applied in a number of ways to track remote sensing satellites at altitudes below 3000 km with accuracies of better than 10 cm. All techniques use a precise global network of GPS ground receivers operating in concert with a receiver aboard the user satellite, and all estimate the user orbit, GPS orbits, and selected ground locations simultaneously. The GPS orbit solutions are always dynamic, relying on the laws of motion, while the user orbit solution can range from purely dynamic to purely kinematic (geometric). Two variations show considerable promise. The first one features an optimal synthesis of dynamics and kinematics in the user solution, while the second introduces a novel gravity model adjustment technique to exploit data from repeat ground tracks. These techniques, to be demonstrated on the Topex/Poseidon mission in 1992, will offer subdecimeter tracking accuracy for dynamically unpredictable satellites down to the lowest orbital altitudes.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); 28; 108-116
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  • 4
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    Near-optimal strategies for sub-decimeter satellite tracking with GPS (1986)
    In:  Other Sources
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    Publication Date: 2013-08-29
    Description: Decimeter tracking of low Earth orbiters using differential Global Positioning System (GPS) techniques is discussed. A precisely known global network of GPS ground receivers and a receiver aboard the user satellite are needed, and all techniques simultaneously estimate the user and GPS satellite orbits. Strategies include a purely geometric, a fully dynamic, and a hybrid strategy. The last combines dynamic GPS solutions with a geometric user solution. Two powerful extensions of the hybrid strategy show the most promise. The first uses an optimized synthesis of dynamics and geometry in the user solution, while the second uses a gravity adjustment method to exploit data from repeat ground tracks. These techniques promise to deliver subdecimeter accuracy down to the lowest satellite altitudes.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: ESA Proceedings of the Second International Symposium on Spacecraft Flight Dynamics; p 233-238
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  • 5
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    The limits of direct satellite tracking with GPS (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The expected accuracy of the direct user orbit solution and the magnitude of the principal error sources are evaluated using the techniques of covariance analysis. Utilization of advanced GPS receivers, measurement calibration methods, and geophysical models developed for high-precision GPS-based geodesy and differential satellite tracking are assumed in order to explore the limiting accuracy of the above technique. In addition, the dependence of user orbit accuracy on such factors as data arc length, the time interval between the end of the ground data arc used for GPS orbit solutions and the beginning of the user data arc, and data types used are studied. For comparison, results from the analysis of a full differential orbit solution are also presented. It is shown that submeter real-time accuracy can be readily achieved for a user above 700 km altitude, even when the user solution is based on a GPS ephemeris that is more than 12 h old.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: Navigation (ISSN 0028-1522); 37; 65-79
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  • 6
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    The limits of direct satellite tracking with GPS (1988)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Recent advances in high precision differential GPS-based satellite tracking can be usefully applied to the more conventional direct tracking of low earth satellites. To properly evaluate the limiting accuracy of direct GPS-based tracking, it is necessary to take full account of the correlations between the a priori errors in GPS states, Y-bias, and solar pressure parameters. These can be obtained by careful analysis of the GPS orbit determination process. When up-to-date assumptions are used in the analyses of GPS and user orbit solutions, it is found that submeter accuracy can be readily achieved for a user above 1000 km altitude, even when the user solution is obtained with data taken 12 hours after the data used in the GPS orbit solutions.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: AIAA PAPER 88-0576
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  • 7
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    Topex orbit determination and gravity recovery using GPS data from repeat orbits (1988)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A covariance analysis is presented for a differential GPS-based technique for satellite tracking and gravity recovery to be demonstrated on Topex in the early 1990's. The technique employs data from an ensemble of repeat ground tracks to recover a unique satellite epoch state for each track and a set of invariant local gravity parameters common to all tracks. For satellites above about 800 km altitude, where gravity modeling is the dominant systematic error, averaging of random error over many arcs and adjustment of the gravity model reduces the final satellite position error. The local gravity parameters can then be used to produce a refined global gravity model. The analysis indicates that errors ranging from 5 to 8 cm in Topex altitude and 0.05 to 0.2 mgal for the gravity field can be achieved, depending on the number of repeat arcs used.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: AIAA PAPER 88-0575
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  • 8
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    GPS-based orbit determination and point positioning under selective availability (1990)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: Selective availability (SA) degrades the positioning accuracy for nondifferential users of the GPS Standard Positioning Service (SPS). The often quoted SPS accuracy available under normal conditions is 100 m 2DRMS. In the absence of more specific information, many prospective SPS users adopt the 100 m value in their planning, which exaggerates the error in many cases. SA error is examined for point positioning and dynamic orbit determination for an orbiting user. To minimize SA error, nondifferential users have several options: expand their field of view; observe as many GPS satellites as possible; smooth the error over time; and employ precise GPS ephemerides computed independently, as by NASA and the NGS, rather than the broadcast ephemeris. Simulations show that 3D point position error can be kept to 30 m, and this can be smoothed to 3 m in a few hours.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: International Technical Meeting of the Satellite Division of the Institute of Navigation; Sept. 19-21, 1990; Colorado Springs, CO; United States
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  • 9
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    From Data to Knowledge in Earth Science, Planetary Science, and Astronomy (2004)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper examines three NASA science data archive systems from the Earth, planetary, and astronomy domains, and discusses the various efforts underway to provide their science communities with not only better access to their holdings, but also with the services they need to interpret the data and understand their physical meaning. The paper identifies problems common to all three domains and suggests ways that common standards, technologies, and even implementations be leveraged to benefit each other.
    Keywords: Documentation and Information Science
    Type: European Space Agency and ESRIN Centre; Oct 05, 2004 - Oct 07, 2004; Frascati; Italy
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  • 10
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    Toward decimeter Topex orbit determination using GPS (1990)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Several practical aspects of precision GPS-based Topex orbit determination are investigated. Multipath signals contaminating Topex pseudorange data are greatly reduced by placing the GPS antenna on a conducting backplate consisting of concentric choke rings to attenuate signals coming in from the Topex horizon and below, and by elevating it on a boom to keep it well above all reflecting surfaces. A proper GPS antenna cutoff view angle is chosen so that a sufficient number of GPS satellites with good geometry are in view while reception of reflected signals is minimized. The geometrical strength of the tracking data is optimized by properly selecting GPS satellites to be observed so as to provide data with moderate continuity, low PDOP, and common visibility with ground tracking sites. The tracking performance is greatly enhanced when three complementary sites are added to the minimum ground tracking network consisting of the three NASA DSN sites.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: AAS PAPER 89-359 , AAS/AIAA Astrodynamics Conference 1989; Aug 07, 1989 - Aug 10, 1989; Stowe, VT; United States
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