1. SOIR operations and archiving
Bojan Ristic and the SOIR team
Belgian Institute for Space Aeronomy (BIRA-IASB)

2. 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

3. http://www. esa. int/esa-mmg/mmg. pl

4. 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

5. Spatial Coverage of the Measurements