HF was observed for the first time in the Venus atmosphere by Connes et al. [Connes et al., 1967], who estimated its mixing ratios at the cloud top as being 5 ppb. More recent nightside observations [Bézard et al., 1990] provided measurements of HF below the clouds. These authors reported values of 5±2 ppb respectively, which are similar to the values found by Connes et al. (1967). Preliminary measurements of Bjoraker et al. [Bjoraker et al., 1992] corresponding to altitudes above 72 km yielded a HF mixing ratio of 6.5±0.3 ppb, in agreement with the values found previously.
Vertical profiles of the HF density (left) and volume mixing ratio in ppb (right) obtained during the occultations 357 ( --- : 13/04/2007; distance to the limb at 65 km tangent height: 3325 km; 83 N), 462 ( … : 27/07/2007; distance to the limb: 1864 km; 88 N), and 484 ( - - - : 18/08/2007; distance to the limb: 2670 km; 70 N).
For comparison, the solid line with dots corresponds to a profile of constant vmr (5 ppb). Error bars correspond to the fitting error on the single fitted parameter, i.e. the density (vmr) in the corresponding layer, and does not take into account the errors on the densities (vmr) in the upper layers. Values from the literature are also indicated: Connes et al. (1967) and Bjoraker et al. (1992). (credits BISA)
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