In calculating the time estimates, we have used all the information available to date about the instruments and flight software performance. We expect that, barring unforeseen circumstances, these estimates will prove now to be good to a few percent of the total 'AOR duration', or 'wall-clock time'. This information has been updated as knowledge of the characterisation of the instruments and telescope has improved and we no longer expect it to show large variations during the rest of the mission, but small changes are still possible. Obviously, this means that the time estimates may change during proposal preparation if new information becomes available. Out of date time estimates are shown in red in the observations table and should be re-calculated before proposal submission.
![[Note]](../../admonitions/note.gif) | Note |
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| Version 5.0 of HSpot incorporates in-flight information on sensitivities that, in some cases, imply important changes in observing time to reach a desired flux level. |
HSpot reports the following when you request an observing time estimate:
AOR Duration: This is the 'wall-clock' time, or total time required to execute the observation, including time on source, internal calibrations, slewing, settling, command execution, and the fixed slew overhead applied to each AOR. In otherwords: this time is your exposure time, plus all the overheads that are required to complete the observation. This is the time you must request in your proposal for this observation.
Slew Time: The time spent on slews internal to the AOR.
Observatory Overhead: A 180 second overhead applied to all AORs to account for the initial slew to source and other observatory overheads. For constrained observations the overhead applied is 600s to compensate for the increased difficulty in and inefficiency of scheduling and thus the hidden overhead implied by constrained observations.
Integration Time(s): Estimated on-source integration time(s) in seconds. HSpot returns observing time estimates from the CUS server for all of the AOTs.
Time estimates are liable to change if observing methods are further optimised in flight. No guarantee can be made that some time estimates will not increase a little with even better knowledge of instrument sensitivity and observatory performance (while other AORs may give better than expected s/n in the time calculated). The amounts of time given to each proposal by HOTAC will not change a posteriori based on in-flight performance. It is expected that after approval of proposals some modification of AORs may be needed to optimise them; this process will be carried out in co-operation with the Herschel Science Centre.