XMM Users' Handbook


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Data from the Attitude & Orbit Control Subsystem (AOCS)

The AHF is a file containing processed AOCS telemetry. Clipped to the start/end times of an observation or slew, the relevant portion of the AHF becomes an ODF or SDF component which is delivered to the observer. For ``stable pointing periods'' the data records identify intervals of time during which the spacecraft's boresight did not deviate by more than a configurable limit from the mean boresight during that period. For open loop slews and post-slew attitude trims, the AHF provides the instantaneous boresight at equidistant points in time (typically 10 seconds). It should be noted that attitudes for open loop slews are derived from a ``slew model'' into which the boundary conditions (actual start/end times and attitudes) have been entered, i.e., the intermediate attitudes provided for slews are not based on sensor data telemetered during the slews.



European Space Agency - XMM Science Operations Centre