An AOTF-based spectrometer for the studies of Mars atmosphere for Mars express ESA mission

The SPICAM Light optical package on the ESA Mars Express mission is dedicated to the nadir and limb observations in the UV between 118 nm and 320 nm, and has originally included an IR solar occultation channel, an inheritance of the IR part of the SPICAM solar occultation instrument for Mars 96. Because of severe mass constrains of the mission this channel has been replaced by a lightweight (0.7 kg) near infrared instrument that employs a new technology acousto-optical tuneable filter (AOTF). This channel is dedicated to the nadir measurements of water vapour column abundance in the near infrared between 1 and 1.7 mum simultaneously with ozone measured in the U-V. In addition to the measurements of water vapour column abundance in the band of 1.38 mum, the NIR nadir spectrometer will measure the CO2 quantity in the bands of 1.43, 1.57-1.6 mum, and, consequently, the surface pressure (with known topography); and will contribute to the studies of atmospheric aerosols and the surface, by spectro-polarimetry measurements. Fully functional model of the instrument has been assembled, has been undergone a number of tests; the spectra of terrestrial atmospheric transmittance have been recorded. The scientific context of the experiment will be discussed along with the instrument's description; current development status and the calibration results will be presented. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.