SCIAMACHY near real time products and algorithms

SCIAMACHY, which is part of the ENVISAT-1 scientific payload, is a double grating spectrometer designed to observe the light reflected, transmitted and back-scattered by the Earth's atmosphere. Its broad spectral coverage (240 to 2400 nm) combined with multiple viewing geometries (nadir, limb, solar and lunar occultation) enable the measurement of numerous atmospheric constituents in the stratosphere as well as in the troposphere. The list of trace gases includes O/sub 3/, NO/sub 2/, BrO, SO/sub 2/, OClO, H/sub 2/CO in the UV and visible regions and H/sub 2/O, N/sub 2/O, CO, CH/sub 4/ and CO/sub 2/ in the IR regions. Geolocated engineering calibrated products (level 1b) as well as geolocated geophysical products (level 2) containing the total column amounts for the above species (excluding CO/sub 2/) are produced by a near real time (NRT) processor and are available to users three hours after data acquisition. An enhanced off-line processor additionally produces (several days after acquisition) stratospheric profiles of most of the above molecules as well as O/sub 3/ profiles down to the troposphere. As an Expert Support Laboratory, the DLR-DFD in Oberpfaffenhofen has specified the algorithms required for the NRT processing chain. This paper summarises these NRT algorithms and the resulting level 1b and 2 products distributed to users.