ESA’s Sentinel-6 mission incorporates a Fully-Focussed SAR processor © ESA

isardSAT has generated a new cycle of Sentinel-6 Level-1 Fully-Focussed SAR data, processed using a GPU and including algorithm accelerations. This methodology allows to reduce the processing time of a 10 minute granule from days to minutes, so a cycle can be processed in a few days. You can download it here.

Delay-Doppler altimetry is a methodology to process altimetry data, used operationally for the first time in the CryoSat-2 mission (2010). It receives this name because it exploits the Doppler effect caused by the satellite movement.

Fully Focussed SAR: processing altimetry data with an improved along-track resolution

Classic delay-Doppler algorithms process altimeter data with a resolution of 300 m, while the Fully-Focussed (FF-SAR) algorithm (Egido et al., 2017) , allows to achieve along-track resolution close to the theoretical limits, which for typical altimeters such as CryoSat-2, Sentinel-3, and Sentinel-6, is about 0.5 m.

Sentinel-6 © Eumetsat.

At isardSAT, we are designing and implementing ESA’s Sentinel-6 Level-1 Ground Prototype Processor (S6 L1 GPP) for the Poseidon-4 altimeter, which incorporates a FF-SAR Back-Projection processor. This software offers better precision than other FF-SAR algorithms such as FF-SAR Omega-K. Moreover, it provides the maximum theoretical along-track resolution, opening the door to new applications such as swell retrieval, inland waters, or sea-ice leads, among others.

However, the run-time performance of this processor is poor. We can reduce the processing time of a 10 minute granule from days to minutes by introducing two changes:

• Processing the data using a Graphics Processing Unit (GPU).
• Incorporating accelerations in the FF-SAR Back projection algorithm.

For example, while a classic Level-1 FF-SAR back projection, without any algorithm acceleration nor GPU would take 12 days for a 10 minutes input data, with algorithm acceleration and a NVIDIA GPU we it can be reduced up to around 10-20 minutes, depending on the GPU and on the configuration. So a cycle can be processed in days.

Try out our first cycle of FF-SAR data!

You can download here our first cycle of Level-1 Fully-Focussed SAR Back Projection data, processed using a GPU and the algorithm accelerations. You will also find the Level-1 FF-SAR Omega-K data. You can send us your feedback and suggestions at s6_ffsar_data@isardSAT.cat.

More information

Processing Fully-Focussed SAR with GPUs (presented at 30 Years of Progress in Radar Altimetry Symposium. Montpellier, 2-7 September 2024).