Measurements of Global Navigation Satellite Systems (GNSS) refer to the electrical phase centers of the GNSS transmitting and receiving antennas. The phase center offsets (PCOs) between the electrical and mechanical reference points must be known to an accuracy of better than 1 mm for high-precision applications. PCOs can be calibrated in an anechoic chamber before the launch of a satellite. Such calibrations are available, for example, for the Galileo satellites and some of the GPS satellites.
Fig. 1: The phase center offset (PCO) of a GNSS satellite describes the position of the mean phase center with respect to the center of mass.
For other satellites or to validate the terrestrial calibrations, PCOs can also be determined from the observations of a global GNSS network. Figure 2 compares such estimated values with the chamber calibrations of the Galileo satellites. The consistency of the two methods is generally in the range of less than one centimeter, with larger differences only occurring for the first generation of Galileo IOV satellites.
Fig. 2: Comparison of the horizontal Galileo antenna offsets of different satellite generations for different signal frequencies. IOV: In-Orbit Validation; FOC: Full Operation Capability; FOCe: FOC in eccentric orbit.
Steigenberger, P., Thoelert, S., Dach, R., & Montenbruck, O. (2023). Validation of GPS III transmit antenna calibrations. Advances in Space Research, 73(5), 2488–2498. https://doi.org/10.1016/j.asr.2023.11.048
Montenbruck, O., Steigenberger, P., & Mayer-Gürr, T. (2023). Manufacturer calibrations of GPS transmit antenna phase patterns: a critical review. Journal of Geodesy, 98(1), 2. https://doi.org/10.1007/s00190-023-01809-y
Steigenberger, P., & Montenbruck, O. (2023). Consistency of Galileo satellite antenna phase center offsets. Journal of Geodesy, 97(6). https://doi.org/10.1007/s00190-023-01750-0
Steigenberger, P., Fritsche, M., Dach, R., Schmid, R., Montenbruck, O., Uhlemann, M., & Prange, L. (2016). Estimation of satellite antenna phase center offsets for Galileo. Journal of Geodesy, 90(8), 773–785. https://doi.org/10.1007/s00190-016-0909-6
Contact
Dr.-Ing. Benjamin Braun
German Aerospace Center (DLR)
Space Operations and Astronaut Training
Spaceflight Technology
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