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 to be good to around 10% of the total 'AOR duration', or 'wall-clock time'. This information will be updated as knowledge of the characterisation of the instruments and telescope improves. 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 Out of date time estimates are shown in red in the observations table and should be re-calculated before proposal submission.
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 scheduling and thus 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 after launch as the observatory and the instruments are properly characterised in flight. No guarantee can be made that some time estimates will not increase with better knowledge of instrument sensitivity and observatory performance (while other AORs will 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 launch some modification of AORs may be needed to optimise them; this process will be carried out in co-operation with the Herschel Science Centre.