Fred Seward reviewed the September presentation to the Science Working Group, concerning the Users' Committee thoughts about GTO observations. The AXAF Science Working Group members are currently updating their observing programs, and Alan Bunner explained the revised NASA policy about the distribution of GTO time. The Committee discussed the merits of this plan and its effect on potential GO proposals. The Committee considered the plan described below to be conducive to good science and fair to both guaranteed-time and general observers.
The plan has 100% of AXAF time for the first 2 months (after one month of engineering studies and calibration) devoted to GTO observations. 30% of AXAF time from month 3 to month 20 will be GTO time, 15% of time from month 21 to month 60 (or month 36; the committee was almost evenly split between these two numbers) will be GTO time. All remaining time is GO time. GTO observations for the first 20 months will not be subject to competition from GO observations, and no proposals need be written to justify choice of GTO targets, although a brief statement of scientific objective would be needed. Targets will be picked to fill GTO time for months 1-8, before the first NRA. GO observations will then be chosen by peer review to fill the GO time from months 3-8. GTO targets will then be chosen to fill the 30%-time from months 9-20. The second NRA will then solicit proposals for GO targets for the interval 9-20 months.
During the period 1-20 months, members of GTO groups will refrain from proposing as PIs to use GO time. Anyone supported in whole or part with NASA GTO funding will be considered to be part of a GTO group.
After month 20, an explicit policy was not endorsed by the Committee, since several issues need further thought and discussion. Members of GTO groups should probably be allowed to compete as PIs for time outside the 15% allocation, but perhaps general observers should also be allowed to compete for targets specified by GTO groups for the 15% time allocation. Some on the committee thought it would be simpler to remove the GO/GTO distinction after 20 months, while still providing 15% GTO time through the peer review process using an oversubscribed GTO list. It was decided to defer further discussion on 20-month-plus policy until after hearing comments from the Science Working Group on this plan. Steve Kahn also thought that there should be funding available for GOs who would like to work with GTOs on particular targets, but this led to a spirited discussion regarding fairness.
The committee next attempted to define a `conflict' - two proposed observations which are similar enough in character so that only one is chosen to be accomplished. Identical targets, instruments, and observing time is a conflict unless a convincing argument is made for variability (or calibration). What spread in observing time makes the observation `different'? A factor of 4 was proposed with no objections, but no definitive position was established on this issue.
Proprietary data rights for each target will expire 1 year after data goes to the observer. If a long observation is fragmented, it shall be considered `complete' when 80% (or some agreed upon %) of the data are obtained and the proprietary clock will start at that point. It is worth noting that, because of the orbit, fragmentation should be much much less of a problem with AXAF-I than it has been with ROSAT. Projects which involve many targets cannot hang on to the data until 80% of the targets are observed; data rights are considered on a target by target basis.
All `calibration' targets not counted in the allocation of a GTO or GO program will go directly into the public archive. These may indeed be targets (Capella is a stellar example) which are so valuable as calibration sources that calibration should preempt their being chosen for any GTO or GO investigation. The Committee considered it critical to have calibration data accessible early to all observers so that they might use it in their analysis and judge possible errors and uncertainties. It is likely that observers will find something important to bring to the attention of the AXAF calibration team. This suggested approach to calibration targets must also be discussed with the GTO teams (the Science Working Group).