Minimize SCIAMACHY Product Handbook

Definition

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Definition

Based on the objectives of each orbital mission scenario and the occurrence of sun and moon fixed events along the orbit, timelines can be built from the set of 70 states. Each timeline corresponds to an orbit interval with start/stop being related to a sun or moon fixed event. Timelines can be assigned to the following orbit intervals:


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SO&C window

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MO&C window

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eclipse

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end of SO&C window to start of eclipse

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end of SO&C window to start of sub-solar window

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end of sub-solar window to start of eclipse

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end of SO&C window to start of MO&C window

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end of sub-solar window to start of MO&C window

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end of MO&C window to start of eclipse


A complete orbital mission scenario is implemented by assembling a sequence of timelines which covers the full orbit and executes those states required in the scenario. This is an efficient building block approach which reduces the command load drastically. The most frequent scenario executes 4 timelines only – a SO&C timeline, followed by a long limb/nadir sequence and two calibration timelines in eclipse. Because the sequence of limb/nadir states generates a ring-like pattern of nadir and limb ground pixels, it has been decided to switch between two limb/nadir sequences in consecutive orbits. At latitudes where nadir ground pixels exist in one orbit, limb ground pixels are thus generated in the following orbit. The result is a chessboard type pattern better suited for global value added data processing.

All timelines starting or ending with the MO&C window have to accommodate the strong temporal variability of lunar events within a monthly visibility period. Therefore several versions of moon related timelines with different lengths do exist for the same segment. Triggered by mission planning, they are exchanged on-board whenever required by lunar position. This is different from timelines allocated to sun related orbit segments which require only single instances due to the moderate seasonal changes. (fig. 2-17)

 

click to enlarge

fig. 2-17:

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Example of the seasonal temporal variability of orbital segments. The time interval between end of SO&C window and start of eclipse varies only slightly over a year (yellow). In the monthly moon visibility periods, the time between end of MO&C window and start of eclipse shows a much higher variation (red curves). The blue segments indicate lunar visibility phases where moonrise occurs on the nightside, i.e. those which can be used for occultation. (Graphics: DLR-IMF)
 

As in the case of states, a final flight configuration exists that reflects the currently agreed and verified set of 63 timelines. Its configuration controlled status can be modified via the OCR procedure.

 

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