Geolocation

SCIAMACHY geolocation files exist for nadir and limb states only. They illustrate the start/stop location of each state in the atmosphere (nadir at the Earth surface, limb with start at limb_low = tangent height altitude of 0 km and stop at limb_high = tangent height altitude of 100 km).

The files presented here are either Earth maps with nadir/limb geolocation (gif) or tabular listings of geographic coordinates at state start/stop (geolocation ASCII). The files are based on the swath template provided by the ESA s/w tool ESOV. 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 geolocation 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.

The sub-satellite orbit track displayed in the maps is based on the reference orbit as well. Different track colours indicate the illuminated part of the orbit (yellow) and the eclipse phase (dark blue). The eclipse phase is defined by the eclipse exit/entry times to be given in the Reference Orbit Event (ROE) file.

The geographic longitude and latitude is given for 6 locations at the ground pixel. These are LEFT_W, LEFT_S, MID, RIGHT_S and RIGHT_W. 'LEFT' refers to the left side of the ground pixel at ANX, 'RIGHT' to its right side at ANX (at DNX both sides are reversed). Wide swath is denoted by the flag 'W' while small swath ('S') is an approximation reflecting a swath of 120 km. The 'MID' position coincides with the ENVISAT ground track.

In the final flight state configuration, coordinates shall be used as follows: