CALIBRATION AND POSTLAUNCH PERFORMANCE OF THE METEOR 3 TOMS INSTRUMENT/

Prelaunch and postlaunch calibration results for the Meteor 3/TOMS ins trument are presented here. The instrument, launched aboard a Russian spacecraft in 1991, is the second in a series of total ozone mapping s pectrometer (TOMS) instruments designed to provide daily global mappin g of ozone overburden. Ozone amounts are retrieved from measurements o f Earth albedo in the 312- to 380-nm range. The accuracy of albedo mea surements is primarily tied to knowledge of the reflective properties of diffusers used in the calibrations and to the instrument's waveleng th selection. These and other important prelaunch calibrations are pre sented. Their estimated accuracies are within the bounds necessary to determine column ozone to better than 1%. However, postlaunch validati on results indicate some prelaunch calibration uncertainties may be la rger than originally estimated. Instrument calibrations have been main tained postlaunch to within a corresponding 1% error in retrieved ozon e. Onboard calibrations, including wavelength monitoring and a three-d iffuser solar measurement system, are described and specific results a re presented. Other issues, such as the effects of orbital precession on calibration and recent chopper wheel malfunctions, are also discuss ed.