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CryoSat Baseline C FDM L1b products now generated with the L0 Platform Attitude information

09 June 2015

CryoSat users are informed that the Baseline C L1b FDM products are now generated with full information on the attitude (antenna bench roll, pitch and yaw angles). For Baseline C production ranging from 01 April 2015 to noon 4 June 2015 the attitude information was not yet available, but this issue has now been fixed with the installation of an upgraded version of the processor.

The computation of the satellite attitude requires the use of the Star Tracker Data. With the Baseline C, the Star Tracker Data are obtained by post-processing the raw L0 data used on board the satellite. This new approach consists in bias removal and noise reduction in order to improve the retrieval of the interferometer baseline position and antennas real beam directions. The Refined Star Tracker Attitude (STR_ATTREF) data is unfortunately not available yet at time of the near-real time production (< 3h) leading to Baseline C L1b FDM products without attitude information inside.

In agreement with the CryoSat Quality Working Group, it has been decided to resume the usage of Raw Star Tracker L0 products for the single FDM processing and the change has now been implemented.

As a consequence, the values of the Star Tracker Usage (Fields 14, 2, 14, for respectively L1b, L2, In-Depth L2 Products MDS Record), become mode dependent as follows:

For LRM/SAR/SARin

  • 0 : No Star Tracker data used for product generation and attitude initialisation done by using default values
  • 4: Star Tracker data used for product generation and these data are the same used by the satellite through its AOCS (Attitude Orbit Control System)

For FDM

  • 0 : No Star Tracker data used for product generation and attitude initialisation done by using default values
  • 1 : Data of Star Tracker 1 used for product generation
  • 2 : Data of Star Tracker 2 used for product generation
  • 3 : Data of Star Tracker 3 used for product generation

Users shall please note that the Baseline C LRM, SAR and SARin processing will keep using the Refined Star Tracker Attitude data.