Nadir Geometry In Nadir mode the atmospheric volume directly under the instrument (i.e. the spacecraft) is observed. Each scan covers an area on the ground of up to 960 km across track with a maximum resolution of 26 km x 15 km.

Limb Geometry In Limb mode the instrument looks at the edge of the atmosphere. Scans at different tangent altitudes over a range of up to 960 km in horizontal direction are performed with a geometrical vertical resolution of approximately 2.6 km.

Occultation measurements are performed using the same geometry as in Limb mode, but with the sun or the moon in the instrument's field of view. Atmospheric densities are obtained by comparing measurements of the transmitted solar or lunar radiation with the unattenuated source. Solar occultation measurements are performed regularly during sunrise (latitude range 90° N - 65° N). Lunar occultation measurements during moonrise (between 30°S - 90°S) - which are possible for about one week per month - are used for process studies.

Limb / Nadir Matching One of the most important features of SCIAMACHY is the possibility to observe the same atmospheric volume first in limb and then after about 7 minutes in nadir geometry. By using this Limb/Nadir matching three-dimensional information about the atmosphere can be obtained.