(revised 1 July 1991)
All Principal Investigators (PI) are sent a Scheduling Request Form and an Assignment of Responsibility Form for each approved program at the beginning of the episode. PIs are asked to complete the scheduling form to make each program's scheduling requirements known to the Observatory. The Assignment of Responsibility Form (see Appendix E) must be completed if someone other than the PI is to be authorized to make observing plans or receive the Guest Observer (GO) data.
At the beginning of the episode a scheduling request deadline is established. This date is usually 4-6 weeks after the Project Scientist announces the accepted programs. PIs are requested to send scheduling requirements for the entire episode for each observing program to the Observatory by this date. If a program's scheduling requirements remain as stated in the observing proposal, this fact must also be communicated to the Observatory. These requests are used to establish a draft schedule for the episode. Requests received before the deadline are weighted according to scientific need and are not considered in order of receipt. Requests received after the deadline will be accommodated only to the extent allowed by the earlier requests. In view of increasing constraints on telescope operations GOs are strongly urged to observe the deadline.
The Observatory attempts to honor all reasonable requests for specific observing dates to perform time-critical or coordinated ground-based observations or to satisfy other scientific requirements. It is the GO's responsibility to verify that the target will be at a favorable beta angle on the dates in question. Specific time requests should include information concerning scientific constraints of the observations and specify a range of dates, if appropriate, rather than a single date to permit some flexibility in scheduling. Except for observing dates for collaborative programs, specific observing dates cannot be guaranteed. Collaborative programs are scheduled for the entire year at the beginning of the episode.
Requests should be made for specific dates (or range of dates) to observe solar system objects. It is the GO's responsibility to check the dates for best planet-satellite configuration, if applicable, and to provide an ephemeris specifying UT or local time and including the object's drift rates (in arcseconds per hour) in right ascension and declination prior to the observing run.
Programs will be scheduled, if possible, at a time when high-priority targets are at beta angles where the spacecraft batteries will not discharge, but outside the OBC heating region (see Table 3.1, Section 3.1). In the absence of designated target priorities, programs are scheduled at a time when a majority of their targets will be available. The availability of all targets cannot be assured for those programs with a small number of shifts and/or a long target list. For programs having a small number of targets or all targets in a localized region, possible conflict with the moon will be checked manually. For those programs with large numbers of targets or with changing target priorities and with remaining shifts to be scheduled, GOs should fill out a Scheduling Update form (see Appendix E). A supply of these forms is kept at the GO desk in TOC. Completed forms should be left with the on-duty RA or mailed to the Scheduler.
The monthly NASA IUE observing schedule is finalized three months in advance. Once the schedule for a given month is complete the Observatory will not initiate any revisions without strong scientific justification to do so. If a GO wishes to change the dates of his/her scheduled shifts, we ask that he/she contact the GOs thereby affected to arrange a time trade. The Observatory must be notified of any such arrangements as soon as these trades are finalized.
When major targets of opportunity appear, such as comets or novae, the Project Scientist will consult with the PIs having approved Target of Opportunity programs to determine how much observing time should be allotted to the particular event under discussion. In the case of comets, there is usually sufficient lead time to incorporate them into the normal scheduling process. The sudden appearance of a bright nova or supernova would require last-minute scheduling, possibly preempting previously scheduled observers. Programs thereby affected will be compensated for the lost observing time.
Programs are scheduled for eight-hour low (US1) and high (US2) radiation shifts according to the shift allocations given by the Project Scientist. The Observatory will attempt to honor requests for partial shift scheduling if there is scientific justification. As a rule, observing time will not be scheduled in segments less than four hours duration; partial US1 shifts will be scheduled for highly time-critical observations and special monitoring programs. Observers should note the difficulty in scheduling partial US1 shifts may result in additional time being charged to the program.
Approximately four shifts per month (usually US2) are set aside for calibration and maintenance. At the end of the month the Observatory normally absorbs the two hour loss due to the monthly shift time change.
Conflicts with teaching obligations, AAS meetings, IAU symposia, etc., will not be taken into consideration for scheduling purposes, since many GOs tend to have similar conflicts. Should the observer have other, more compelling reasons for not being scheduled on a given date, these should be presented in writing to the Observatory as soon as possible.