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Overheads are considered to be the time spent on calibrators and slewing (i.e. any time not spent integrating on the science targets). The percentage of overall requested time can vary based on the length of the schedule block, number of pointings and whether polarisation or other specialised calibration is needed, as described here: Observation overheads
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For example, a proposal requested 8 hours on target, and assumed 25% overheads, leading to a maximum time request of 10 hours. However, once the schedule block is set up and the observation is simulated, the total duration of the block is 9 hours. This does not mean that the time on target should be increased to extend the block to 10 hours, since this is not necessary to achieve the science goal as per the approved project. Conversely, we may have a situation where the observatory has requested the observer to split the observation into shorter blocks in order to expedite scheduling, and the overheads increase to 30% when following the recommended calibration strategy. This would be considered acceptable in the cause of reducing of reducing scheduling idle time.
The OPT
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