Sentinel-1

ESA’s C-band SAR constellation, redistributed by NASA’s ASF DAAC because the Copernicus program publishes data openly to the world. The largest-volume Earth-observation data family in NASA’s archive (~24 PB), even though NASA doesn’t own the satellites.

What it sees

• C-band SAR (5.405 GHz, ~5.5 cm wavelength) — sees through clouds, day and night, sensitive to surface roughness + moisture + dielectric properties.
• Four acquisition modes: Stripmap, Interferometric Wide-Swath (IW, the default for most land), Extra Wide-Swath (EW, polar), Wave (open ocean).
• Dual polarization (VV+VH most common) — enables crude land-cover classification + change detection.

Why it matters

• All-weather, day-and-night imaging — the only such free global dataset at 10–40 m resolution.
• Critical for wetlands, sea ice, flood mapping, deformation/InSAR, ship detection, oil-spill detection — anywhere optical fails.
• The InSAR-able archive enables time-series of mm-scale ground deformation (subsidence, earthquakes, volcanoes, glacier flow).

Where to get the data

• earthaccess Python: short_name="SENTINEL-1_INTERFEROMETRIC_WIDE_GRDH_HIGHRES" or via Vertex search
• ASF Vertex: search.asf.alaska.edu — best UI for finding scenes
• HyP3 (on-demand RTC, InSAR products): hyp3.asf.alaska.edu
• OPERA RTC-S1: cloud-optimized analysis-ready backscatter, lower friction than raw GRD

What it enables

• Flood inundation mapping (real-time emergency response)
• Sea ice classification (NSIDC analyses)
• Volcano + earthquake deformation (InSAR time series)
• Land-subsidence monitoring (urban + agricultural)
• Forest disturbance even under cloud cover (where Landsat fails)

Gotchas

• Sentinel-1B is dead. Failed Dec 2021; replaced by Sentinel-1C only in Dec 2024. The 2022–2024 period has degraded revisit (12 days instead of 6 in most places).
• SAR is not optical. Speckle is noise; you must average / multilook. Bright pixels are not “bright in the visible spectrum”; they’re radar-bright. Layover and shadow in mountainous terrain.
• InSAR requires the SLC product, not GRD. Different file format, different processing chain.
• OPERA RTC-S1 is the analysis-ready path — start there unless you need raw phase information.
• SAFE bundles are bulky (typically 4–8 GB per scene) — not friendly for casual exploration.

Related missions

• NISAR (NASA-ISRO, launched 2025): L-band + S-band SAR, complements Sentinel-1’s C-band with longer wavelength (better forest penetration, longer InSAR coherence).
• Sentinel-1 NextG (ESA, planned ~2028): replacement architecture.
• ALOS-2 / -4 (JAXA): commercial L-band SAR, complementary.

Related datasets