The collection of data required to perform calibration of the instrument science data, instrument engineering data, and the spacecraft or platform engineering data. It includes pre-flight and in-flight calibration measurements, calibration equation coefficients derived from calibration software routines, and ground truth data that is to be used in the data calibration processing routine.
Definition from CEOS-WGISS Glossary of Acronyms and Terms, v1.0
https://earthdata.nasa.gov/user-resources/glossary