Sentinel-1C

Sentinel-1C is the third satellite in the Copernicus Sentinel-1 C-band SAR constellation, operated by ESA under the EU Copernicus programme [^esa-facts]. It launched on 5 December 2024 aboard a Vega-C rocket (flight VV25) from Europe's Spaceport in Kourou, French Guiana [^esa-press-release]. The satellite was built by Thales Alenia Space as prime contractor, with Airbus Defence and Space delivering the C-SAR radar instrument [^esa-press-release]. Each Sentinel-1 satellite has a launch mass of 2,185 kg [^esa-constellation].

Sentinel-1C occupies a sun-synchronous polar orbit at 693 km altitude, paired with Sentinel-1D (launched November 2025) to constitute the current operational Sentinel-1 constellation [^esa-facts]. Its arrival restored the two-satellite constellation design following the retirement of Sentinel-1B, which suffered a power failure in December 2021 and was decommissioned in 2022 -- a gap of approximately 2.5 years during which only Sentinel-1A operated. Sentinel-1C data became available through the Copernicus Data Space Ecosystem from January 2025 onward [^copernicus-dataspace].

The satellite carries the C-SAR imaging instrument -- a C-band (5.405 GHz) active phased-array SAR with a 12-metre antenna [^esa-instrument], operating in four modes: Interferometric Wide Swath (IW, 250 km swath, 5 x 20 m resolution), Extra Wide Swath (EW, ~400 km, 20 x 40 m), Stripmap (SM, 80 km, 5 x 5 m), and Wave (WV, 20 x 20 km tiles). Sentinel-1C additionally carries an integrated Automatic Identification System (AIS) receiver with four onboard antennas, a capability absent from Sentinel-1A and Sentinel-1B [^esa-instrument], enabling vessel tracking alongside land and ice SAR imaging.

The C-band SAR time series underpinning global forest disturbance alert systems, maritime surveillance, and deformation monitoring continues uninterrupted with the Sentinel-1C/1D operational pair. All Sentinel-1 data are distributed free and openly under the Copernicus Sentinel Data Legal Notice [^copernicus-terms].