Antenna phase center calibration for precise positioning of LEO satellites |
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| Authors: | Oliver Montenbruck Miquel Garcia-Fernandez Yoke Yoon Steffen Schön Adrian Jäggi |
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| Institution: | 1.German Space Operations Center, Deutsches Zentrum für Luft- und Raumfahrt,We?ling,Germany;2.Institut für Erdmessung, Leibniz Universit?t Hannover,Hannover,Germany;3.Astronomisches Institut der Universit?t Bern,Bern,Switzerland |
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| Abstract: | Phase center variations of the receiver and transmitter antenna constitute a remaining uncertainty in the high precision orbit
determination (POD) of low Earth orbit (LEO) satellites using GPS measurements. Triggered by the adoption of absolute phase
patterns in the IGS processing standards, a calibration of the Sensor Systems S67-1575-14 antenna with GFZ choke ring has
been conducted that serves as POD antenna on various geodetic satellites such as CHAMP, GRACE and TerraSAR-X. Nominal phase
patterns have been obtained with a robotic measurement system in a field campaign and the results were used to assess the
impact of receiver antenna phase patterns on the achievable positioning accuracy. Along with this, phase center distortions
in the actual spacecraft environment were characterized based on POD carrier phase residuals for the GRACE and TerraSAR-X
missions. It is shown that the combined ground and in-flight calibration can improve the carrier phase modeling accuracy to
a level of 4 mm which is close to the pure receiver noise. A 3.5 cm (3D rms) consistency of kinematic and reduced dynamic
orbit determination solutions is achieved for TerraSAR-X, which presumably reflects the limitations of presently available
GPS ephemeris products. The reduced dynamic solutions themselves match the observations of high grade satellite laser ranging
stations to 1.5 cm but are potentially affected by cross-track biases at the cm-level. With respect to the GPS based relative
navigation of TerraSAR-X/TanDEM-X formation, the in-flight calibration of the antenna phase patterns is considered essential
for an accurate modeling of differential carrier phase measurements and a mm level baseline reconstruction.
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| Keywords: | Antennas Phase center variation Orbit determination LEO satellites TerraSAR-X CHAMP GRACE |
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