Application and Evaluation of ACDC Delay-Doppler processing over CryoSat-2 for Open-Ocean zones

Eduard Makhoul (isardSAT, United Kingdom)

CoAuthors

Chris Ray (Saint Mary’s College, United States); Mònica Roca (isardSAT, United Kingdom); Albert Garcia (isardSAT, United Kingdom); Roger Escolà (isardSAT, United Kingdom)

Event: 2016 SAR Altimetry Workshop

Session: Innovative SAR processing methods

Presentation type: Type Poster

During the last decade there has been a tremendous evolution in radar altimetry from both technological and operational standpoints. This has been concreted in the development of the Synthetic Aperture Radar (SAR) altimetry, with CryoSat-2 as the reference mission and the follow-on Sentinel-3 mission for oceanographic purposes. Such framework represents a breakthrough in altimetry, offering the possibility to investigate new processing approaches in order to enhance the quality of the SAR altimetric products (especially in terms of geophysical retrievals).

In this line and from the experience gained within the Sentinel-6 project, this presentation is devoted to show the integration and operation of the ACDC (amplitude compensation and dilation compensation) technique in an in-house developed L1B processor based on the CryoSat-2 as well as Sentinel-3 baselines. Preliminary results on the ACDC performance on real FBR CryoSat-2 data over open ocean zones will be presented.

ACDC was originally proposed by Chris Ray and isardSAT team within the Sentinel-6 project. The basic idea is to perform a two-step compensation once the stacking has been performed and right after geometry corrections application: 1) along-track amplitude compensation to equalise the Doppler-dependent weighting induced by the acquisition geometry in combination with both antenna and surface radiation patterns; and 2) across-track dilation compensation to correct for the waveform widening when moving away from the central beam. In this way, a better alignment of the waveforms within the stack is obtained focusing the spread along-track energy into a single range bin, such that an improved speckle reduction and signal-to-noise ratio (SNR) are expected. This results in a simpler and more computationally efficient analytical retracker over ACDC L1B waveforms when compared to the conventional SAR analytical retracker on L1B waveforms. As proved over simulated Sentinel-6 data, the combination of the ACDC processing within L1B and the implementation of the simpler ACDC retracker provides improved (less noisier) geophysical retrievals.

Taking into account such considerations, the core of this presentation intends to show the potential capabilities of the ACDC method when integrate in the CryoSat-2 and Sentinel-3 processing baselines, comparing the retrieved geophysical parameters with the conventional SAR processing baselines for both missions over FBR CryoSat-2 data on several tracks over open-ocean. Taking into account that under ideal considerations (perfectly known attitude, antenna and surface radiation patterns) a flat response over the ACDC stack is expected. Therefore, deviations on such expected flatness could be potentially linked to wrong attitude information (already presented by Chris Ray in OSTST in 2015) and even related to specific characteristics on the surface backscattering itself (and so to specific geophysical parameters). In this line, this presentation will attempt to show preliminary analysis on these latter aspects as well.

 

Poster show times:

RoomStart DateEnd Date
Grande Halle Mon, Oct 31 2016,18:30 Mon, Oct 31 2016,19:30
Eduard Makhoul
isardSAT
United Kingdom
eduard.makhoul@isardsat.co.uk