Frequently Asked Questions
Yes. Pending the proper correction of collocation between ATSR forward and nadir views to be undertaken in a Level 1 B reprocessing next year, the empirical adjustments for each sensor estimated within the ARC project have applied to RRDP extracts.
The adjustments used to shift the forward view to give improved alignment with the nadir view are:
- ATSR-1: +3 pixels across-track (xi) and no along-track shift
- ATSR-2: +1 pixel across-track (xi) and -1 pixels along-track (xj)
- AATSR: -1 pixel across-track (xi) and -2 pixels along-track (xj)
No, the latest calibration has not been applied.
For AATSR, the RRDP contains the GC1 and VC1 filenames to allow a RRDP participant to apply the latest calibration using the method recommended by Dave Smith from RAL Space (see http://www.aatsrops.rl.ac.uk/EDSX/OtherInfo/) for further details. This web page also contains information on how to scale ATSR-2 to AATSR and on how to scale AATSR to MERIS if required.
The AATSR nadir and forward 12 µm BTs in the RRDP have been adjusted by +0.2 K, which is an interim measure to reduce this problem and make the channels more consistent with previous ATSRs. This measure is thought to reduce the magnitude of the remaining calibration uncertainty to O(0.1 K). If a more precise adjustment is required, results from the ARC project suggest that an additional adjustment as a function of the total column water vapour in the observed scene is useful. Details can be provided on request.