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Observer-imposed constraints can severely limit the scheduling efficiency
of the telescope. With that in mind, observers should note that
all constraints need to be strongly justified in the telescope
proposal. With scheduling efficiency in mind, the
following constraint tips are offered. For additional insight into
scheduling, see this overview of how scheduling
works.
- Make constraints flexible!
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- 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!
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- 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!
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- 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).
Go back to main Constraints page
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