Nadir viewing

Satellite instrumentation orbiting the earth view the stratosphere in limb and nadir viewing geometries. In addition both solar, lunar and stellar occulation have also been exploited very successfully. 

Fig. 6.2.10 Representative TES spectra showing dust and water ice features. Spectra dominated by dust features are shown as solid lines, while those dominated by ice features are dashed. Signatures of gaseous CO2 (strongest near 667 cm ), water ice clouds (strongest near 230 and 825 cm ), and dust aerosol (strongest near 1075 cm" ) are apparent (a) Brightness temperature spectra for nadir viewing, (b) Radiance spectra for limb observations. (Pearl et al., 2001.)...

Providing the instrumental field of view can be made sufficiently small, measurements tangential to the planetary limb can produce atmospheric profiles with a vertical resolution higher than that achievable from nadir viewing measurements. In addition, the very long path length with a cold space background permits retrieval of trace gas abundances that could not otherwise be accomplished. This approach has been used extensively to determine thermal structure and trace gas distributions in the Earth s stratosphere and mesosphere. 

Fig. 3.1 Perspective view of part of the caldera of Olympus Mons on Mars. This view was obtained from the digital altitude model derived from the stereo channels, from the nadir channel (vertical perspective) and the colour channels on the Mars Express Orbiter. The photograph was taken on 21 January 2004 from a height of 273 km. The vertical face is about 2.5 km high, i.e., about 700 m higher than the north face of the Eiger mountain (Switzerland). With permission of the DLR...

These poor resolution qualities become worse and worse as we leave the vertical. As a function of the angle of view (nadir angle) ... 

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