Abstract
This paper describes the goals and performance characteristics of the LIMS radiometer to be flown on the NIMBUS G spacecraft scheduled for launch into a polar orbit in 1978. Radiance measurements are made of gases (03, H2 0, NO2 , HNO3 , and CO2) that are key elements in the nitrogen ozone photochemistry, which is crucial to an understanding of the natural processes controlling the ozone distribution in the atmosphere. The earth limb is scanned and imaged with an optical system designed for compatibility with a two-stage solid-cryogen cooler. Six different bandpass (Hg,Cd)Te detectors are cooled with solid methane to 65 K. The detected outputs are demodulated and low pass filtered before being multiplexed and digitized with a 12-bit A/D converter. The primary LIMS data output is in the form of a highly multiplexed serial digital word at 4 K bps rate. Every LIMS word transmitted from spacecraft to ground control contains data from each radiance channel and pertinent housekeeping functional performance data. Inversion algorithms are used to operate on the CO2 limb radiance profiles which determine the vertical temperature distribution. Along with the measured radiance profiles in the other spectral bands, this inferred temperature profile is used to calculate the vertical distribution of NO2, H2 0, 03 , and HNO3. Profiles are determined with 1 and 2 km resolution over altitudes of 10 km to 80 km.
