Observer-Imposed Constraints: Tips and Tricks

Make constraints flexible!

• In general, "GROUP-WITHIN" is more likely to be scheduled than a "SEQUENCE" which is more likely to be scheduled than a "CHAIN."
• A "GROUP-WITHIN" that constrains 4 hours of observations to occur in the same week is more likely to be scheduled than a "GROUP-WITHIN" that constrains the same 4 hours of observations to occur within a 12 hour period. A good rule is to have the window of the constraint be at least twice the total duration of the AORs within the constraint.
• A less tightly mandated constraint allows the Scheduling Team more leeway to solve problems and avoid conflicts, as well as produce more efficient schedules. For example, do not use a "SEQUENCE" if a "GROUP-WITHIN" will do.
• Extremely complex constraint structures formulated to save a small amount of observing time may render the observatory LESS efficient rather than more so. Please let our schedulers take care of optimization.
• Narrow timing constraints (less than 1-2 days) are more difficult to schedule than timing constraints with windows of ~ 10 days. And timing constraints with less than a 1 day window can be challenging to impossible to schedule. Use these constraints with care.
• When using shadow constraints, it is easier to schedule observations if your shadow (background) observation comes AFTER the main observation. If it doesn't matter to your science whether your shadow observation comes before or after the object, put it after.

Use simple constraints!

• Constraints may be combined, but do so judiciously.
• The more complex a set of constraints, the lower the probability that it can be scheduled.

Be aware of the operational constraints!

• Spacecraft and instrument-imposed events take place roughly every 12 hours. AOR durations should, in general, not exceed this unless there is a strong science justification (i.e. a long duration exoplanet observation).

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