How it works
Sentinel-2A and 2B orbit together so that, in India, a given field is imaged about every five days. Their bands include visible, red-edge, near-infrared and shortwave-infrared light, from which vegetation and water indices such as NDVI, NDRE and NDWI are computed.
Optical satellites cannot see through cloud. Sentinel-1, a radar satellite in the same programme, can, which is why the two are used together in the monsoon.
Why it matters for Indian farmers
Sentinel-2 makes field-level monitoring possible for every smallholder in India at no data cost. What was missing was turning those images into a short, specific message a farmer can use.
How VarshaKrishi uses it
VarshaKrishi reads Sentinel-2 surface reflectance (Level-2A) for each registered field, fills cloud gaps with NASA HLS, and uses Sentinel-1 radar when the monsoon hides the field. Every message names the source and the date of the image.
Methods and evidence A year of real Sentinel-2 NDVI for one field (open data)
Questions about Sentinel-2
How often does Sentinel-2 see my field?
About every five days, but cloud can hide the field for weeks in the monsoon. The message says when no clear image was available.
Is Sentinel-2 data free?
Yes. It is published openly by the European Space Agency through the Copernicus programme.
Can it see individual plants?
No. Each pixel is 10 m by 10 m, so it sees patches of a field, not single plants or trees.