Copernicus Sentinel-1 change of GPS antenna reference point for POD

23 July 2020

The Copernicus Sentinel-1 POD configuration will evolve by end of July 2020 to improve the orbital accuracy of Sentinel-1 PRE, NRT and NTC products by correcting the GPS Antenna Reference Point (ARP) location. The impact on the POD was identified by the CPOD Quality Working Group (QWG), by the presence of non-negligible empirical forces and significant differences between Sentinel-1A and Sentinel-1B, but a thorough investigation was necessary to identify the root cause of it. The new ARP values are documented in the Sentinel-1 Properties for GPS POD document.

This updated configuration will correct systematic differences of a few centimetres observed in cross-comparisons between orbital products of different processing centres of the CPOD QWG. The new values have been validated by cross-comparisons performed in the frame of the CPOD Regular Service Reviews since June 2019 and have shown improved results in terms of accuracy and consistency. They have been further validated by external analysis carried out by other members of the CPOD QWG (e.g. Peter et al. (2020). Copernicus Sentinel-1 satellites: sensitivity of antenna offset estimation to orbit and observation modelling. Advances in Geosciences. 50. 87-100. 10.5194/adgeo-50-87-2020.

The change of configuration for both Sentinel-1A and -1B will coincide with the following change of cycles: 29/07/2020 17:10 for S-1A, and 30/07/2020 17:01 for S-1B. It will impact the following products: predicted (AUX_PREORB), restituted (AUX_RESORB) and precise (AUX_POEORB) orbit ephemerides. The change will be applied according to the validity period of products, thus keeping consistency between the different types of products irrespectively of their generation date. Moreover, the fact that the change will take place on the change of cycle will allow identifying any impact in the inSAR processing as well.

This change of configuration is duly documented in the Sentinels POD product handbook and corresponds to the CPOD version 1.7.0.

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