MOPITT sensitivity studies: Computation of instrument parameter dependencies

A detailed radiative transfer model of the MOPITT instrument and the Earth´s atmosphere was developed and validated. This model simulates the various radiometric sources for the instrument (atmosphere, space, onboard and laboratory calibration targets) as well as a number of detailed internal features not considered in the operational MOPITT retrieval algorithm (optical imbalance, chopper emission, etc.). It was employed to establish sensitivity levels of MOPITT to the uncertainty in various instrument parameters. It should also prove useful in the development of successor MOPITT instruments, and related correlation radiometers. The sensitivity studies highlighted several critical parameters including the filter positions, gas cell lengths and pressures, and optical imbalance. MOPITT calibration events are shown to reduce the impact of instrument parameter uncertainties on target gas retrievals, but in-flight validation is likely required for MOPITT to achieve its stated accuracy objectives.