Group Scheduling Assumptions

JWST exposure groups with short duration will receive a warning or error based on the estimated minimum duration of the group.

Group links with short durations will receive a warning or error based on the estimated minimum duration of the group, which includes the durations of all of the component Observations’ visits and slews as well as a statistical overhead for required Observatory maintenance activities. Table 5, below, shows the overhead duration and period for these activities:

Table 1. Overheads for minimum group duration

Overhead

Duration(min)

Period(days)

Wavefront Sensing

46

2

Wavefront Control

107

14

Momentum Unloads

180

7

Station Keeping

120

21

 These overheads are used to compute the minimum group duration as follows:

  1. All visit durations, except the last(sequence) or shortest(group) visit are summed, as well as the estimated slews between those visits.
  2. Based upon that summed duration, for each of the overheads in table 5, add floor(summed duration/period) times the overhead duration.

If the requested link duration is less than the duration summed in step 1, an error will be generated. A warning will be generated if the duration is less than the value calculated in step 2.

Change log

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Version 1 (June 6, 2017)

  1. Initial version.