2.5 Dataset
TGO performs an occultation on each
node of the 2-h orbit with one or both of two instruments: ACS and NOMAD
(Nadir and Occultation for Mars Discovery). Because of a subtle
misalignment of the ACS and NOMAD lines-of-sight (LOS), two occultation
observing modes are implemented: ACS MIR-driven and NOMAD-driven. ACS
NIR operates both kinds of pointing, but ACS MIR can be used only with
the ACS pointing. On average, ACS NIR accomplished seven occultations
per sol in both hemispheres (from 1 to 21), except during several
periods of about 15 to 20 days long without occultations due to orbital
plane orientation. ACS NIR provides water vapor in the 1.38 µm band and
temperature measurements in 1.57 µm and 1.43 µm CO2bands, as well as aerosol extinctions at various wavelengths for each
occultation. We analyzed NIR occultation profiles obtained both with ACS
and NOMAD pointings (the latter constituting ~40% of
profiles). From the beginning of the TGO science phase in April 2018
(Ls=163° of MY34) to January 2022 (Ls=170° of MY36), ACS NIR collected
~8 500 profiles (Figure 3).