How Sentinel-3 tandem phase contributes to Sentinel-3 error budget

Sylvie Labroue (CLS, France)

CoAuthors

Matthias Raynal (CLS, France); Pierre Féménias (ESA, Italy); François Boy (CNES, France); Franck Borde (ESA/ESTEC, The Netherlands)

Event: 2018 Ocean Surface Topography Science Team Meeting

Session: Quantifying Errors and Uncertainties in Altimetry data

Presentation type: Type Poster

The ESA (European Space Agency) mission Sentinel-3A was successfully launched in February 2016 and recently followed by its twin Sentinel-S3B launched on 25 April 2018. Sentinel-3 satellites are a multi-instrument mission to measure sea-surface topography, sea- and land-surface temperature, ocean colour and land colour with high-end accuracy and reliability.
During the S3B commissioning phase, a special configuration is performed where both satellites fly the same ground tracks separated by 30 seconds. This tandem phase was decided following the success of the Jason tandem phase performed for all Jason missions.
In this paper, we will show how such configuration allows accessing to small magnitude signal in the altimetry error budget. On the one hand, the difference is dominated by large scale errors such as residual global bias between both payloads (either coming from SRAL processing, MWR calibration or orbit calculation), large scale differences due to orbit signals, SRAL processing or residual SSB features. On the other hand, the difference of the high frequency content is analysed to check the assumption of decorrelated white noise between both altimeters. This topic is of high interest, especially given the SARM sensitivity to swell.
The SRAL (Sentinel Radar Altimeter) sensor on board Sentinel-3 differs from previous conventional pulse limited altimeters by providing observations with the Synthetic Aperture Radar mode (SARM). Along with this processing, an LRM like processing can be applied to retrieve the geophysical parameters as for LRM but with a higher noise (the so-called P-LRM processing).
While first objective of the tandem phase is to insure an accurate validation of Sentinel-3B mission and a seamless transition between both satellites, it also offers opportunity to further refine the assessment of the different signal processing. The Sentinel tandem phase lasts 4 months during which several configurations are experienced by changing the S3-B altimeter acquisition mode (LRM, SARM Open Loop and SARM Closed Loop). This is of specific interest to understand different topics: the sensibility of the SARM processing to the SRAL acquisition mode, the comparison of the perfomances between LRM and SARM observations and between LRM and P-LRM observations that are for the first time available on a collocated data set.

 

Poster show times:

Room Start Date End Date
Foyer, Salao Nobre & tent Thu, Sep 27 2018,18:00 Thu, Sep 27 2018,20:00
Foyer, Salao Nobre & tent Fri, Sep 28 2018,14:00 Fri, Sep 28 2018,15:00
Sylvie Labroue
CLS
France
sylvie.labroue@cls.fr