SOIR operations and archiving Bojan Ristic (bojan.ristic@aeronomie.be) and the SOIR team Belgian Institute for Space Aeronomy (BIRA-IASB)

SOIR Characteristics and Performances Value or range Units Wavelength range 2.2 to 4.3 µm Wavenumber range 2353 to 4310 cm-1 Spectral sampling interval (1 pixel) 0.1 Instrument Line Profile 0.2 Corresponding resolving power [/=/] 23200 to 43100 FOV in spectral direction 2 arc minutes FOV in spatial direction 30 Entrance aperture diameter 20 mm Mass 6.5 kg Size 414 x 254 x210 mm3

http://www. esa. int/esa-mmg/mmg. pl http://www.esa.int/esa-mmg/mmg.pl?b=b&type=A&mission=Venus%20Express&single=y&start=8

Solar Occultation Technique Self calibrated measurements: transmittances obtained by dividing measured spectra by full sun spectra Altitude range probed on Venus: 65km to 160km Orbit 232 – Order 129 From Sun VEX So, SOIR performs solar occultation measurements. It is a self calibrated technique, as transmittances are obtained by dividing a recorded outside atmosphere spectrum by the atmospheric spectrum. It results in a transmittance. The altitude range probed goes from 65km – which is the top of the cloud desk – up to 160km, depending on the studied molecular specie. The right hand side graph show the recorded spectra during orbit 232 for order 129. From an altitude of 100 km and further, several absorption lines appear, which correspond to HCl main and second isotope. The background level decrease is due to the aerosol absorption in the atmosphere. When the altitude probed gets close to 65km, the signal falls to zero, and the occultation is done. Venus Cloud deck Atmosphere

Spatial Coverage of the Measurements