Category: Sensors and missions
Sentinel-1
Sentinel-1 is an ESA SAR mission providing radar observations that work through clouds and at night.
Also known as: S1, Sentinel 1
Expanded definition
Sentinel-1 delivers C-band SAR data with frequent revisit. Because SAR does not depend on sunlight and is not blocked by clouds, Sentinel-1 is widely used for monitoring during cloudy seasons and at high latitudes.
Sentinel-1 backscatter is sensitive to moisture, structure, and geometry, so it complements optical data rather than replacing it. Many operational workflows use Sentinel-1 to maintain continuity when optical observations are missing.
Interpretation requires attention to polarization, incidence angle, speckle reduction, and consistent preprocessing. Small differences in processing can cause apparent shifts in time series.
Related terms
SAR (Synthetic Aperture Radar)
SAR is an active radar sensor that works day or night and can see through clouds, measuring surface scattering rather than reflected sunlight.
Backscatter
Backscatter is the amount of radar signal returned to the sensor, influenced by roughness, moisture, and structure.
Polarization (VV, VH, HH, HV)
Polarization describes the transmit and receive orientation of radar waves; different polarizations respond to different surface properties.
Incidence Angle
Incidence angle is the angle between the radar beam and the surface; it affects SAR backscatter and comparability.