Jean-Michel Friedt built a passive radar system illuminated by the NISAR NASA/ISRO synthetic-aperture radar satellite instead of a terrestrial RF source. Using two GNSS antennas — one pointing at the satellite and one capturing ground reflections — along with an SDR and Raspberry Pi, the setup captures L-band chirp signals during the satellite's brief pass (roughly once every 12 days). Both a high-end Ettus B210 SDR and a cheap MAX2771-based homebrew SDR produced recognizable terrain contour images. The project demonstrates that meaningful passive radar imagery is achievable with low-cost hardware and no transmitter license.
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