Chapter 4: Instrument Operations

Kurzfassung

SCIAMACHY operations have to be highly autonomous. All instrument activities are stored on-board and activated by time-tagged commands. They execute measurements in all required viewing geometries including the unique limb/nadir matching. Observations of the Sun in occultation over the northern hemisphere and the Moon in occultation over the southern hemisphere occur at regular intervals, ranging from each orbit to each month. They are complemented by sub-solar observations. The lunar measurements need particularly accurate preparation due to the orbital motions of the Moon and ENVISAT around Earth. Both Sun and Moon occultations have to take refraction into account for the period when both targets are viewed through the lower atmosphere. Timing of SCIAMACHY measurement operations is entirely Sun or Moon related. The specified mission scenarios combine nadir, limb and eclipse measurements between Sun or Moon related events along the orbit. The smallest functional sequences are states, controlled via various parameter tables. When combining individual states, timelines are generated. Sets of states and timelines are stored on-board. Each timeline is activated by a single macrocommand. Both states and timelines can be modified from ground. Since SCIAMACHY has been provided by national agencies instrument operations is a shared enterprise between DLR/NIVR and ESA.