[Ian: This paper concerns VEx/SOIR, but is included here on the NOMAD website because the same algorithm is used to calibrate SO and UVIS occultations]
Applied Optics (2016) Vol. 55, Issue 32, pp. 9275 - 9281 https://doi.org/10.1364/AO.55.009275; http://pdfs.semanticscholar.org/240b/016c68c9d1f4a7b323a253fd4cbc77a18102.pdf
Loic Trompet, Arnaud Mahieux, Bojan Ristic, Séverine Robert, Valérie Wilquet, Ian R. Thomas, Ann Carine Vandaele, and Jean-Loup Bertaux
The Solar Occultation in the InfraRed (SOIR) instrument onboard the ESA Venus Express spacecraft, an infrared spectrometer sensitive from 2.2 to 4.3 μm, probed the atmosphere of Venus from June 2006 until December 2014. During this time, it performed more than 750 solar occultations of the Venus mesosphere and lower thermosphere. A new procedure has been developed for the estimation of the transmittance in order to decrease the number of rejected spectra, to check that the treated spectra are well calibrated, and to improve the quality of the calibrated spectra by reducing the noise and accurately normalizing it to the solar spectrum.