Calibration information in product metadata

This is not about the SNAP toolbox per se. Please help me out though. I am a novice in this area of SAR data processing. I need to understand the basics to implement a code. I am working on a project concerned with calculating the calibration constant(K). The metadata of a sentinel 1 product(dual-Pol) shows K to be 1.000000e+00. However the values that my code gives are way beyond this value.

  1. Is this the actual calibration constant as shown in metadata or not? If yes, how is this calculated in the first place? Can SNAP itself calculate the absolute calibration constant?
  2. I also have a quad-Pol RADARSAT-2 data but it does not contain K value in the metadata. How do I verify my code for such products.

It would be really helpful if someone could explain the process of finding K in SNAP or any other source(an existing software maybe) so that I can debug and test my code.

For Sentinel-1A, the absolution calibration constant (K) is indeed 1.0 as given in the product meta data. The calculate the radar cross-section of a distributed target or point target, please see the ESA document ‘Radiometric Calibration of S-1 Level-1 Products Generated
by the S-1 IPF’ available at

Thanks a lot! Is there a place where I could get the values of calibration constants of these SAR satellites like S1, RADARSAT-2, etc.

Hi, in general the best place to find calibration constants is in the product meta data (in case they vary with time period for example). This is the case for Sentinel1 A & B.

Dear mdrpanwar,

The calibration constant (K) is not sonething that you can compare from a a mission to another.
In general, K depedends on the imaging system (instrument + processor) configuration which is different for each mission.

In general, you should estimate the RCS over a point target for which the RCS is known. The calibration constant is the difference between the measured - expected value (in the average sense).
Once the calibration constant has been determined for a specific mission, you can calibrate the data to e.g. sigma nought which is intercomparable.