7.8.1 Timing Constraints

The timing constraints determined in §7.4 must now be recorded as part of the IRS AOR. This step cannot be accomplished until after an IRS AOR has been configured and stored in Spot's memory (see §7.7). The process is relatively simple. After completing the IRS AOR, make sure it is highlighted in the AOR Table in the main Spot window, and then select the ``Timing Constraints'' option under the ``Tools'' pull-down menu. This will open the AOR Timing window, which displays the full range of available visibility windows for the target, and includes a table where the start and stop dates for the PA-constrained visibility windows can be entered. The completed timing constraint table is shown in Figure 7.12. Note that the exact start and stop dates for the visibility windows are slightly different than shown in Figure 7.2. This is because Spot refines the visibility windows based on the AOR configuration, to ensure that the desired observations can be completed. Because Spot's knowledge of Spitzer's orbit can change slightly in time, these visibility windows may change slightly in the future. Timing constraints that are made as loose as possible have the best chance of being successfully integrated into Spitzer's observing schedule. If we specify slightly larger timing windows than the visibility windows as now calculated, Spot will let us know that we've done that, but will allow us to do so. The observations, obviously, will not be scheduled when the object is not visible to Spitzer.

Figure 7.12: AOR Timing window showing the completed timing constraints table.