PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM SPACECRAFT_NAME = GALILEO_ORBITER INSTRUMENT_NAME = "NEAR INFRARED MAPPING SPECTROMETER" INSTRUMENT_ID = NIMS OBJECT = TEXT NOTE = "Description of calibration files provided with the NIMS Cube CD-ROM set" PUBLICATION_DATE = 1998-12-10 END_OBJECT = TEXT END The CALIB directory contains or points to data files required for (non-geometric) processing of NIMS data, such as calibration files and dark files. DARK files (.DRK) are average dark current files derived from "heaven dark" or other special observations at different times during the mission, and from off-limb data taken during ordinary targeted observations. They contain the average dark current values as tables in detector, mirror position and mirror direction, for each of four gain states. Different dark files may be needed for different periods of time during the mission. CALIBRATION files (.CAL) contain NIMS sensitivities for each detector and grating position in each of four gain states. These sensitivities are based on ground calibration data but are corrected to account for changes in the instrument during flight, as shown by periodic NIMS observations of the Photometric Calibration Target (PCT) and Radiometric Calibration Target (RCT), and by special Optical Calibration (OPCAL) and Electronic Calibration (ECAL) observations. Different calibration files may be needed for different periods of time during the mission. Dark and calibration files are used by ISIS and Vicar cube generation programs to convert raw phase 2 data numbers (DNs) to radiances. They will be included in later volumes of this CD-ROM set, or on a separate volume. Provisional versions of these files may be obtained from the NIMS team.