Radiometric calibration of total ozone mapping spectrometer: flight model 5 (TOMS-5) aboard QuickTOMS

12 The Total Ozone Mapping Spectrometer - Flight Model 5 (TOMS- 5), aboard the QuikTOMS spacecraft, is designed to continue the measurement of the total column amount of ozone in the atmosphere in order to monitor the global trend. Since the predicted total ozone change due to man-made sources is very small, an accurate calibration of the measuring instrument is required. Since in the TOMS-5 experiment the total ozone amount is determined from the ratio of the measurement of the solar backscattered ultraviolet Earth radiance to the incident solar irradiance, the accuracy of the calibration of the instrument sensitivity to this ratio measurement is critical. The prelaunch calibration of TOMS-5 was designed to achieve a ratio calibration accuracy of 1% in addition to the uncertainties of the standards used. Multiple calibration techniques were employed to ensure the self- consistency of results of different techniques to eliminate any systematic errors. TOMS-5 prelaunch radiometric calibration was performed twice, one in 1996 and the second in 1999 due to the launch delay. The ratio calibration was reproduced within 0.5% from the tests of 1996 to those of 1999 while the calibration of the individual measurement modes agreed among the various techniques to within 1%.