For the validation community, overpass table of their instrument are very important for planning there activities. For the SCIAMACHY instrument as well as for the other atmospheric chemistry instruments, ESA provides overpass tables for a large amount of stations. However, they have the disadvantage of not knowing the actual planning for limb and nadir measurements of SCIAMACHY.
On the webpage of the Sciamachy Operations Support Team (SOST), this information is available as maps and ASCII files (look at Geolocation). On the SCIAVALIG webpage, overpass maps for more than 130 Stations can be browsed. Here, from the ASCII files overpass tables for limb and nadir are generated and can be downloaded.
These columns are given in the overpass tables, generated from the swath visualization ASCII files:
As the time tags provided in the ENVISAT planning files are derived for the reference orbit, it may occur that the actually executed time tags differ by as much as 5-10 sec from the start/stop times in the swath visualization files (shortly before execution the time-tags are updated by Flight Operations to reflect the predicted orbit). Therefore it is recommended to use the Elapsed Time when searching for a particular event along the orbit. The Elapsed Time is the time elapsed since the last ascending node crossing (ANX). ANX time and event time-tags are affected similarly by the time update, i.e. no significant deviations between reference and predicted orbit are expected.
Overpass tables for limb and nadir are generated. Match condition: Station is inside the given ground pixel.
Caution: For limb the ground pixel
ambiguous, because it is defined from the tangent points at start(low) and
stop(high) time of the measurements, whereas the lightpath along the line-of-sight
covers a much wider area. Use the limb lists carefully.
The nadir overpass tables can be used straightforward. For the nominal limb-nadir matching operation, each nadir ground pixel corresponds to a limb measurement. Exceptions are begin and end of the measurements during an orbit.
You can select the SCIAMACHY overpasstable for a single station in the Single station directory or as Archiv in .tar.gz or .zip format. Available are:
|Overpass||Single station||Archiv (tar.gz)||Archiv (zip)|
|SOST NADIR (inside)||->||X||X|
|SOST LIMB (inside)||->||X||X|