CryoSat/SIRAL Cal1 Calibration Orbits

Marco Fornari (ESA/ESTEC, Netherlands)

CoAuthors

Michele Scagliola (ARESYS, Italy); Tommaso Parrinello (ESA/ESRIN, Italy); Jerome Bouffard (ESA/ESRIN, Italy)

Event: 2017 Ocean Surface Topography Science Team Meeting

Session: Instrument Processing: Measurement and Retracking

Presentation type: Type Poster

The main payload of CryoSat is a Ku band pulse-limited radar altimeter, called SIRAL, that transmits phase coherent pulses at a high Pulse Repetition Frequency allowing SAR processing to improve along-track resolution. Being a phase coherent altimeter, SIRAL calibration includes not only corrections for transfer function, gain and instrument path delay (as in previous altimeters), but also corrections for phase (SAR/SARIn) and phase difference between the two receiving chains (SARIN only).
Due to CryoSat non-sun-synchronous orbit, SIRAL temperature slightly changes along the orbit with a period of about 480 days. By analysis of the CAL1 data, it has been verified that SIRAL calibration is affected by the instrument thermal status, leading to calibration measurements (i.e. the instrument behavior) slightly varying along the orbit.
In order to quantify such variation along the orbit, a continuous sequence of CAL1 has been performed over a few orbits. Moreover, the analysis of the CAL1 calibration corrections produced along the Calibration orbits allowed us verifying whether the current calibration plan provides sufficiently accurate corrections at any latitude.
The CryoSat/SIRAL Cal1 Calibration Orbits have been performed twice in 2016, on the 20th of July and on the 24th of November, requiring coordination among many operation teams (Mission Planning, FOS, PDS and Quality).
In this abstract, the Calibration Orbits will be presented together with the calibration corrections generated during this activity. By analysis of such calibrations data, it was possible to derive a model for the calibration corrections as function of the instrument temperature. Comparing the modeled corrections with the actual ones (used in CryoSat operations) it was possible to estimate the accuracy of the current calibration plan. Preliminary results will be shown that confirm that the effectiveness of the CryoSat calibration strategy.

 

Poster show times:

RoomStart DateEnd Date
Concerto Ballroom Thu, Oct 26 2017,14:00 Thu, Oct 26 2017,18:00
Marco Fornari
ESA/ESTEC
Netherlands
marco.fornari@esa.int