All of the wall-clock time required for the execution of a specific observation, by means of an Astronomical Observation Request (AOR), will be charged to that particular AOR. This assessment of observing time starts with the beginning of the sequence of events associated with the AOR and continues until the completion of the events in that AOR. Assessed time shall include all science integration time, readout time, internal calibrations, and routine instrument/spacecraft motions embedded within the AOR.
In addition, overhead is assessed with each AOR in order to distribute the time used for necessary Observatory activities among all science observations. Each AOR will be assessed 180 seconds to account for telescope slew time, regardless of the actual time utilized. Moving target AORs are assessed an additional 210 second overhead to account for the additional commands required to schedule moving targets. The algorithm used to calculate observing time, including standard overheads, is integrated into the software time estimators that scientists use in planning observations. Overhead burdens are reevaluated from one observing cycle to another.
Target of Opportunity (ToO) observations requiring activation less than eight weeks prior to execution will be assessed an additional overhead burden (§5.1). This overhead reflects the lost observing time that was allocated to other programs if the observations are executed, and will be factored into the proposal review. Proposals must include these overheads in the total requested observation time.
The total observing time assessed to a program shall consist of the sum of observing times for each of its constituent AORs, including applicable overhead burdens.
Note that Observatory engineering, calibration and telemetry activities are functions of the SSC, and the wall-clock time required to perform these functions is accounted for separately from the science observing time. Any estimates of General Observer time published as part of a Call for Proposals will refer to the science observing time, and will be derived after adequate time for facility activities is reserved.