APMIR: airborne polarimetric microwave imaging radiometer

APMIR is a new instrument that is currently under construction at the U.S. Naval Research Laboratory in Washington, D.C. The system will include channels from C- to Ka-band (specifically 6.6, 6.8, 7.2, 10.7 or 10.65, 18.7 or 19.35, 22.23 or 23.8, and 37.0 or 36.5 GHz). Each channel will provide verticallyand horizontally-polarized brightness temperatures, and several (10.7, 18.7, and 37.0 GHz) will be fully polarimetric. This instrument is being built to provide calibration data for two satellite programs, as well as for supporting algorithm development. The first satellite is the Defense Meteorological Satellite Program's SSMIS. The second instrument is the Coriolis WindSat, a joint Navy, NPOESS, and Air Force mission. Additionally, APMIR has many of the same frequency bands as AMSR-E. Though the system has been developed primarily for the calibration effort, a great deal of flexibility has been incorporated, such that other missions can be accommodated. These satellite instruments have extremely tight error budgets, which in turn lead to correspondingly formidable error budgets for the instruments involved in calibration. A new aircraft system, planned and built from the ground up with the design philosophy of controlling the errors that are critical to the calibration of these particular instruments, was thought to be the best way to meet the error budget. An extra degree of care has been exercised in all areas, but particularly antenna pointing determination and control, system environmental control, EMI suppression and power supply stability.