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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. Due to the 5 +/- 2 years of mission lifetime in which
to accomplish as many observations as possible, efficient observation
scheduling is of high priority. 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 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.
- Timing constraints of any sort can create real headaches. For early in
the mission, ensure that a timing window of at least 2 BIC cycle
(previously 9+8+6=23 days, then 8+13+14=35 days, now 10+12+12=34 days) is
available.
- 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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- A follow-on of IRAC -> MIPS is much more feasible than a follow-on of
MIPS -> IRAC!
- A single IRAC observation of 6 hours is very feasible but a "SEQUENCE"
of several 6 hour observations would be, at best, inefficient and
protracted!
- Spacecraft- and instrument-imposed events take place roughly every 3
(or 6), 8, and 12 hours, and the absolute maximum observation size does not
divide evenly into some of these time blocks. For example, if you have a
series of IRAC or MIPS mapping observations that need to take place within
12 hours, linking them in 2-hour blocks is easier to schedule than
3-hour blocks.
Go back to main Constraints page
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