GRCon21 - Passive bistatic RADAR using spaceborne Sentinel1 non-cooperative source...

Passive bistatic RADAR using spaceborne Sentinel1 non-cooperative source, a B210 and a Raspberry Pi4 presented by Jean-Michel Friedt and Weike Feng at GNU Radio Conference 2021 We have previously demonstrated passive bi-static RADAR using a static emitter and static (passive bistatic RADAR) [1a] or moving (passive bistatic synthetic aperture RADAR) [1b] receiver: range estimate to target is achieved by cross-correlating the reference signal facing the non-cooperative emitter with the surveillance signal facing the target. Azimuth resolution is achieved by moving either receiver or both emitter and receiver [1a, 1b]. We have previously demonstrated the ability to analyze the raw spaceborne Sentinel1 C-band (5.405 GHz) RADAR records [2a,2b] freely provided by the European Space Agency which, beyond providing the raw IQ streams including ground based emissions and echoes, includes telemetry parameters such as pulse shape and pulse repetition interval (PRI). In this presentation we demonstrate experimentally how to receive from ground the signal transmitted by the satellite as it is illuminating a given area of the Earth -- with a repetition of one pass every 12 days for each of the two Sentinel1 satellites -- using an Ettus Research B210 dual channel receiver feeding an 8-GB Raspberry Pi4 running a dedicated UHD-based acquisition software, with the second channel facing targets illuminated by the satellite. We demonstrate how this experimental setup allows for mapping range and azimuth reflector distribution at a range of a few kilometers from the receivers, with the challenge that the spaceborne mobile source is not accurately known as acquisition time is not accurately timestamped. Nevertheless. knowing only the satellite orbital velocity, altitude and PRI is sufficient to recover a quantitative image of reflectors. We believe this demonstration, which can be reproduced worldwide as Sentinel1 is emitting Interferometric Wide (IW) swath signals over most landmasses, is an educational opportunity to introduce with minimal financial investment Synthetic Aperture RADAR processing.