Fig 1.3.2.2.4.9.1: Overlapping limb and nadir scans.

The alternation of the two modes is arranged so that the same air volume is finally measured in both modes. The instrument arrives over the same volume that was previously scanned in limb mode approximately 435 s (~7 min) later and now scans it again in nadir mode. The volumes scanned in nadir and limb modes therefore match up after a seven minute time offset.

SCIAMACHY therefore observes the same air volume in two different ways within a period of about seven minutes. This is one of its most important and novel features.