1.5 Measurement characteristics
1.5.1 Vertical coverage and vertical sampling
The altitude coverage of vertical profiles retrieved from GOMOS measurements is generally between 120 km and an altitude level in the upper troposphere. The lower altitude limit actually varies for each occultation, depending on the star characteristics, on the state of the atmosphere and on the illumination condition.
The limb viewing geometry, the point source nature of stars and the short measurement integration time lead to a good vertical resolution of the profiles retrieved from GOMOS measurements. During one occultation GOMOS measures the stellar light in 0.5 s integration time intervals. This corresponds in the worst case (occultation in the orbital plane) to an interval of 1.7 km of altitude projected at the limb. The sampling vertical resolution is therefore 1.7 km in the case of an occultation in the orbital plane and better than 1.7 km for oblique occultations.