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Observer-Imposed Constraints: Tips and Tricks


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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!
  • 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!
  • 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!
  • 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.


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This file was last modified on Tue Oct 3 15:55:16 2006.

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