The purpose of CryoSat Calibration and Validation (Cal/Val) activities is to provide confidence in estimates of the uncertainty of CryoSat data products.

Product Calibration aims to test the contents of the data products for correctness (primarily Level 1B products), and to quantify imperfections in the measurement system. Activities generally lead to adjustment of parameters, or perhaps algorithms, used in the processors.

The calibration strategy for SIRAL includes both internal and external calibrations. The instrument performs periodic instrument calibrations; these are processed by the CryoSat IPF1 to obtain calibration corrections, which are subsequently applied to the data. The calibration products have been designed to model a wide range of inconsistencies of the instrument, and can be analysed to monitor changes in the stability of SIRAL over time.

External calibration is performed with the use of a ground transponder, located in Svalbard. Analysis of transponder acquisitions is used to calibrate the instrument for range and datation as well as to calibrate the angle of arrival measured by the interferometer.

Product Validation aims to ensure the correctness, and identify the confidence limit, of the Level 2 products. Activities may involve comparison with independent sources of data or in-situ measurements. Geophysical validation techniques include in-situ measurements using ground-based, airborne and balloon-borne instruments, data assimilation using numerical prediction models and satellite inter-comparison.

Learn more about the airborne CryoSat campaigns that were conducted in support to calibration and validation of SIRAL:

• CryoVEx 2016