Improvement of Envisat RA-2 reprocessed data v2.1
28 August 2012
An anomaly has been identified in the altimeter instrumental processing of the ENVISAT RA2 GDR v2.1 reprocessed products (see the validation report and in particular section '6.1. Impact of the reprocessing and PTR drift').
The altimeter internal delay measured by means of the altimeter internal calibration (PTR: In Flight Time Delay Calibration Factor) was not determined correctly and this had a subsequent, and significant, impact on the MSL (mean sea level) trend estimates.
Further analysis has allowed us to include several evolutions in the processing which correct for other anomalies that currently impact the operational processing. The main impact is obviously on the MSL trend but some regional impacts are also noticed. This is illustrated on the below figure.
To apply the correction, users should simply use the delta__ptr_time_delay_Ku correction value whose datation corresponds to that of the GDR. This correction should be removed from all altimeter ranges (Ku-band ocean range,18 Hz Ku-band ocean ranges, …). For example, the sea surface height should be computed as follow:
Users are also advised that:
Related (Key) Documentation
Related Software Tools