urn:nasa:pds:context:target:calibration_field.cal_target 1.0 1.7.0.0 Product_Context 2016-10-01 1.0 extracted metadata from PDS3 catalog and modified to comply with PDS4 Information Model CAL_TARGET Calibration Field A spectralon calibration target mounted on the inside of the MESSENGER payload adapter ring. The spacecraft may be tilted in order to provide solar illumination of the target. The large range of motion of the pivot assembly enables either the MDIS-NAC or MDIS-WAC to point at the target, permitting an absolute in-flight radiometric calibration and flat-field measurement.