Absolute radiometric calibration accuracy of the Atmospheric Infrared Sounder (AIRS)

Abstract

The Atmospheric Infrared Sounder (AIRS) on the EOS Aqua Spacecraft was launched on May 4, 2002. AIRS has demonstrated in-flight NIST traceability and high radiometric accuracy. This accuracy is achieved in orbit by transferring the calibration from a Large Area Blackbody (LABB) to the On-Board Calibrator (OBC) blackbody during preflight testing. The LABB theoretical emissivity is in excess of 0.9999 and temperature uncertainty is less than 30 mK. The LABB emitted radiance is NIST traceable through precision Platinum Resistance Thermometers (PRTs) located on the internal surfaces. The radiometric accuracy predictions for AIRS based on the OBC, LABB, and pre-flight measurements give an accuracy of 0.2K, 3 sigma. AIRS pre-flight calibration coefficients have not changed in flight, preserving the link between observations and pre-flight calibration and characterization. An update is being considered that will improve accuracy and preserve traceability.