S4Pro: Prototype Implementation of Staggered SAR On-Board Processing

In recent years, Synthetic Aperture Radar (SAR) spaceborne systems such as ESA’s Sentinel-1 have evolved to provide unprecedented data availability. This has fostered numerous applications and further increased the interest of the scientific community in SAR, which has matured as an invaluable tool in applications comprising such diverse fields as glaciology, maritime security and forestry, to name a few. High-Resolution Wide-Swath (HRWS) Synthetic Aperture Radar (SAR) is the next chapter in this story, already constituting an important trend for near-future Earth Observation Systems, such as Sentinel-1 Next Generation (S-1 NG) and the expansion of ESA’s Copernicus Program. In this context, Staggered-SAR is an important technique that plays a role in several future mission concepts, such as S-1 NG, Tandem-L and ROSE-L (Radar Observatory System for Europe in L-band), for which it is considered the baseline mode. This class of system allows imaging of very wide swaths up to 400 km with fine azimuth resolution up to 5 m. Nonetheless, it bears significant challenges in terms of the output data rate, also due to the intrinsic azimuth oversampling required by the staggered SAR mode. These prompt the development of high-performance on-board processing solutions for data resampling, filtering and decimation; which allow tackling the data-downlink bottleneck. S4Pro (Smart and Scalable Satellite High-Speed Processing chain) is a Horizon 2020 Project which aims at implementing a hardware demonstrator of a flexible, low- power and high-computation-capacity ARM architecture capable of fulfilling the demanding ROSE-L on-board processing requirements. One of its aims is demonstrating the feasibility of an on-board implementation of the azimuth resampling and decimation filter, bringing it from Technological Readiness Level (TRL) 3 up to 5/6, an important further step in the realization of near-future Staggered SAR Systems. The full version of the paper shall review the motivation for Staggered SAR systems, discuss the on-board implementation architecture and algorithmic details, as well as discuss preliminary results and the way forward for the demonstration of the on-board processing technology. (This work receives funding from the EU’s Horizon 2020 research and innovation programme under grant agreement No 822014) (www.s4pro-h2020.eu)