Performance comparison of Sentinel-3 and CryoSat-2 Delay-Doppler (SAR) processing baselines over Open Ocean and Coastal zones

Eduard Makhoul (isardSAT, United Kingdom)

CoAuthors

Garcia Albert (isardSAT, United Kingdom); Escolà Roger (isardSAT, United Kingdom); Moyano Gorka (isardSAT, United Kingdom); Mònica Roca (isardSAT, United Kingdom); Garcia Pablo (isardSAT, Spain); David Cotton (Satellite Oceanographic Consultants, United Kingdom); Restano Marco (SERCO/ESRIN, Italy); Ambrózio Américo (DEIMOS/ESRIN, Italy); Jérôme Benveniste (ESA-ESRIN, Italy)

Event: 2016 SAR Altimetry Workshop

Session: SAR mode performances: SAR CALVAL from Cryosat-2 and Sentinel-3

Presentation type: Type Oral

During the last decade the radar altimetry has entered in its golden age as demonstrated by the different number of missions (Jason-3, CryoSat-2, SARAL/Altika, Sentinel-3) currently operating and the forthcoming ones (Sentinel-6). The relatively new operational SAR mode in CryoSat-2 and Sentinel-3 missions, opens a new paradigm in the capabilities offered by satellite radar altimeter missions. The delay-Doppler processor (DDP), also known as SAR processor, coherently integrates a series of pulses to provide a series of Doppler beams with an improved along-track resolution (around 300 m) and focused to a specific location, which after being correctly aligned (compensating for the slant-range variation, among others) provide several looks that can be incoherently averaged. In this way, an improvement on the performance of the geophysical retrievals compared to a conventional altimetry operation is expected, whenever an optimised processing baseline is set up.

Within the framework of the SCOOP (SAR Altimetry Coastal and Open Ocean Performance) project funded under the ESA SEOM (Scientific Exploitation of Operational Missions) Programme Element, and in order to characterise the potential performance of Sentinel-3 SRAL SAR mode altimeter products, a comparative study is undertaken in this presentation between the CryoSat-2 and Sentinel-3 SAR processing baselines. Such evaluation is performed over several regions of interest covering both the open-ocean and coastal zones, taking as input the recently released CryoSat-2 Baseline-C FBR data.

This comparative study is based on the validation of the different in-house developed DDP processing approaches through the inversion of the geophysical parameters (SSH, SWH and sigma0), exploiting an in-house implementation of the Chris et al 2015 analytical SAR retracker. This analytical retracker is adapted hand-in-hand to the L1B processing in order to create an L1B waveform modelling as accurate as possible.

The impact of the different processing options is evaluated and characterised across the different processing levels: first, within the L1 processing itself (stack level analysis), at L1B waveform and at L2 (geophysical retrieval). The performance of the geophysical retrievals (RMSE and goodness of fitting, among others) will be exploited comparatively over the different tracks and regions in order to identify the most suitable processing approach. The objective is to define a roadmap identifying potential improved processing options for the Sentinel-3 baseline and if possible to show some preliminary results based on the implementation of some upgrades.
 

Oral presentation show times:

RoomStart DateEnd Date
Auditorium Mon, Oct 31 2016,15:00 Mon, Oct 31 2016,15:15
Eduard Makhoul
isardSAT
United Kingdom
eduard.makhoul@isardsat.co.uk