Sentinel-1B

Sentinel-1B is the second C-band SAR satellite of ESA's Sentinel-1 constellation under the Copernicus Earth observation programme, completing the two-satellite radar pair alongside Sentinel-1A and achieving a six-day global repeat cycle for monitoring surface deformation, sea ice, and marine environments.

MICROSCOPE, a 300 kg CNES microsatellite sharing the flight, was designed to test the weak equivalence principle - the foundational assumption that inertial and gravitational mass are equal - with precision exceeding any prior ground experiment.