Implications of Space Shuttle Flight on the Calibration of Instruments Observing Atmospheric Ozone and the Solar Irradiance

Accurate calibration of remote-sensing instruments has become increasingly more important for studying long-term changes in our environment. Changes in atmospheric ozone are of great concern and have been observed from satellites for over a decade. Despite this record, long-term trends in ozone remain uncertain, primarily due to uncertainties in satellite instrument calibration after launch. In order to overcome this problem a Shuttle-borne Solar Backscatter Ultraviolet (SSBUV) radiometer is being flown almost yearly in conjunction with the series of SBUV-type ozone sounders that are being flown on NASA research and NOAA operational satellites. The SSBUV calibration must be tracked to 1% or better to provide the requisite calibration transfer so that an ozone trend can be derived from the satellite data set. The first flight of the SSBUV occurred in October 1989. Calibration of the instrument was tracked before and after flight to a precision of 1% through laboratory calibrations, field calibration checks, and inflight calibration checks. As a result of the flight, the instrument experienced a 1% to 2% change in sensitivity in the wavelengths used for measuring ozone.