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Sentinel-1 is a C-band radar satellite constellation from the European Space Agency (Copernicus program). SAR (Synthetic Aperture Radar) uses microwave pulses at 5.405 GHz to image the Earth, working through clouds and at night. The constellation includes Sentinel-1A (2014) and Sentinel-1C (2024), providing global coverage.

Sentinel-1 Interferometric Wide (IW) mode provides 5×20m resolution (10m resampled for GRD products). GRD (Ground Range Detected) products are multi-looked for reduced speckle. RTC (Radiometrically Terrain Corrected) products correct for terrain distortion using a DEM. The swath width is 250km.

The two-satellite constellation provides a 6-day exact repeat cycle at the equator. Higher latitudes benefit from orbit overlap with more frequent coverage. Ascending and descending passes offer different viewing geometries.

Yes! C-band radar waves (5.6cm wavelength) penetrate clouds, light rain, and smoke. SAR is also independent of sunlight, making it ideal for monitoring during storms, at night, and in polar winter conditions.

SAR excels at detecting water (floods appear dark due to specular reflection), ships (bright points from metal hulls), oil spills (smooth surfaces), urban structures (corner reflectors), deforestation (texture changes), and ground deformation (using InSAR). It is critical for disaster response when clouds obscure optical sensors.

Sentinel-1 IW mode provides dual polarization: VV (vertical transmit, vertical receive) and VH (vertical transmit, horizontal receive). VV is sensitive to surface roughness, while VH cross-polarization is useful for vegetation analysis and flood mapping.