An assessment of the near-field contamination and off-axis leakage effects on earthlimb background measurements from CIRRIS 1A

Efforts to reduce or eliminate contamination and off-axis leakage for the Cryogenic Infrared Radiance Instrument for the Shuttle (CIRRIS) 1A program flown on STS-39 are examined. The question of whether the Space Shuttle is a viable platform for space measurements is addressed. Mission restrictions and system precautions are reviewed. Results obtained are compared to the current models and previous data. The data show how telescope leakage and/or contamination effects can dominate the minimum signal floor and place a limit on the weakest signal that can be measured when these undesired elements are present. The Space Shuttle is found to be an acceptable platform for high-sensitivity earthlimb background and celestial measurements if prudent clean procedures are followed. Acceptable mirror bidirection reflectance distribution function can be monitored over a considerable period of time if the sensor has been pumped for a considerable period of time and careful handling procedures are followed.