Comments from the TAC

A New TAC Process

(Extracted from NOAO Newsletter No. 45, March 1996)

Several years ago the demand for dark time was largely composed of proposals for observations of faint extragalactic objects, while the bright time was primarily used for galactic objects and stellar evolution programs. Since a separation by lunar phase also separated the overall scientific areas of interest, KPNO convened two committees, the "Bright" TAC and the "Dark" TAC with different areas of scientific expertise to reflect this difference in demand.

The development of infrared arrays changed all this. We are now seeing many proposals in bright time that require expertise in extragalactic astronomy for proper evaluation. Similarly, the advent of wide field CCD detectors gave rise to programs in dark time that addressed problems in stellar populations in our own and nearby galaxies. The composition of the two committees rapidly changed to reflect this new demand, and both committees now have expertise in galactic and extragalactic astronomy. However, the two committees still retain the "Bright" and "Dark" names, and for the larger aperture telescopes the proposals seen by each committee are still sorted by lunar phase. This can cause some problems, particularly when a given program asks for dark time on one telescope and bright time on another. Moreover, having both galactic and extragalactic expertise on both committees means that this expertise must be spread rather thinly if each committee is to be an optimal size.

We have been aware of these problems caused by the evolution of the TAC process and have been exploring options for addressing them. An additional complication arises from the need to consider future demands on the TAC process, such as inclusion of Gemini programs and review of programs that may involve time at private observatories. Discussions on this complex topic have been held at a special AURA workshop last spring, with the combined KPNO/CTIO Users Committees during their fall 1995 meeting, and with each of the standing KPNO TACs. Options discussed ranged from maintaining the status quo to establishing many narrowly focused discipline-specific panels.

The general outcome of these discussions is one of evolutionary change with an eye to future demands. Thus for the fall 1996 semester there will again be two KPNO TACs, but they will be named "Galactic" and "Extragalactic," with expertise concentrated in the appropriate areas. The division between "Galactic" and "Extragalactic" is not always clear. In general "Galactic" will include objects in our galaxy and the Local Group. However, the Galactic committee will have general expertise in stellar evolution and stellar populations, so proposals that explore the evolution of stellar populations in distant galaxies, if done spectroscopically, could go to the "Galactic" TAC. However, stellar population studies at very high redshift that use wideband photometry with multiple bandpasses would probably go to the "Extragalactic" TAC. In order to assist us in sorting the proposals, the proposal form will be revised to allow you to pick the category in which you wish your proposal to reside. This change will not only allow for a better match of expertise to programs for each TAC, it will also allow one TAC to evaluate completely complex programs that require several telescopes at different lunar phases.

After the TAC review, the telescopes will be scheduled as before. We anticipate that the extragalactic programs will still demand most of the dark time, and that this lunar phase will, for most telescopes, be more heavily oversubscribed than bright time. Proposals with the highest TAC grade will be given preference in terms of lunar phase.

We hope this change in the TAC procedure will produce an improved review process. Please send us your comments on any aspect of our proposal review program. We will continue to monitor its performance and will make further changes in response to your comments and to changes in our users' needs.

David De Young

Some Reminders from the TAC

(Extracted from NOAO Newsletter No. 41, 1 March 1995)

During the last series of telescope Time Allocation Committee meetings it became clear that some individuals may have forgotten some of the guidelines that should be followed in submitting observing proposals to KPNO. As the next proposal submission cycle is approaching, now is an appropriate time to point out some of these guidelines.

Long Term Status

The rules under which a proposal may be considered by the TAC for long term status are fairly simple and well defined. In order to qualify for long term status, a proposal must successfully argue that all of the data must be obtained before the basic scientific question being posed can be answered. Simply enlarging a sample for the sake of completeness or better statistics is not sufficient. Put another way, a long term status project is one in which no conclusions will be able to be drawn if, say, only half the observations are made. In its simplest form it is an all or nothing criterion.

Other Facilities

This is often a confusing issue. Having access to other facilities does NOT preclude proposing to KPNO or jeopardize its discussion by the TAC. Many successful KPNO observers also have access to other facilities. What the TAC very much wants to see is the reason why observations are also needed with KPNO telescopes. Such factors could be unique or complementary instrumentation, darker site, coordinated observations involving other sites, etc. Problems arise when it is known that the principal investigators or co-investigators are affiliated with an organization that has access to other facilities and yet there is no explanation given as to why there is also a need to use KPNO telescopes. If such an affiliation exists but is not real, due to internal organizational structure, this should be explained, as the TAC is usually unaware of these internal restrictions.


The guideline for the length of the scientific justification is one page of text plus figures. This criterion is often violated, sometimes flagrantly. Violation of the length guideline may not be beneficial, as it can serve to reduce the degree of benevolence with which a given TAC member may view a proposal. Repeated offenses are often remembered. If a scientific program is well defined and well thought out, a convincing justification can easily be made to fit on one page and within the print size requirements.


Please be sure to use the current proposal submission form; we are still receiving the occasional proposal on obsolete forms. Electronic submission, which is described in an accompanying Newsletter article, works well and is strongly encouraged.

David De Young

Facts and Fiction About the TAC Process

(Extracted from NOAO Newsletter No. 39, 1 September 1994)

The recent KPNO user survey included several questions about the telescope time allocation process. Responses to this section of the survey revealed, in some cases, significant misunderstandings about some aspects of the TAC process. This article is an attempt to clarify these issues.


Some respondents believed that the TACs are composed largely of KPNO scientific staff members. In fact the opposite is the case. Each TAC has only one member from the KPNO staff; the remaining members are all from outside institutions. Although the TAC Chair is filled by a KPNO staff member, the Chair is a non-voting position, and the Chair does not take part in the discussion of the proposals. The term of membership for all voting members is now 5 semesters, with only a minority of the membership changing at any one time in order to retain a "corporate memory" on the committee. Members are chosen primarily on the basis of their scientific expertise, but some familiarity with the KPNO facilities is also desirable. Nominations for replacement members are solicited from the TAC, members of the general astronomical community, and NOAO scientific staff. Candidates are selected by the TAC Chair in consultation with the NOAO and KPNO Directors. Considerable effort is made to balance the committee expertise in stellar, galactic and extragalactic astronomy. Planetary and solar system proposals are sent to two external referees as well as being reviewed by the committee.


It is important to note that every proposal for every telescope is discussed in the TAC meetings. Before the TAC meetings grades are obtained from each TAC member for every proposal to be considered by that TAC. TAC members are then given the average initial grades for each proposal, but they are not given the individual grades submitted by other committee members. After each proposal is discussed, the committee is asked if any member wishes to change her or his grade in light of the discussion. If this occurs, a new average grade is calculated in real time for subsequent use. Because the 4-m and 2.1-m telescopes are the most heavily oversubscribed, every proposal for these telescopes is assigned a "lead reviewer". This person is a TAC member who is responsible for obtaining added background material about the proposal and who is charged with leading the discussion of the proposal during the meeting. The lead reviewer process not only provides focus and direction for the discussion; it also helps ensure that all the relevant issues concerning the proposal will be brought forward.

It is likely that this process will be used for the WIYN telescope as well. After the proposals for a given telescope are discussed and any regrading is done, the TAC is then asked to recommend the number of nights a proposal should be given if it can be scheduled. This number is a recommendation only, and it may be modified as the schedule for that telescope is developed.

Areas of Concern

Historically, the TAC has focussed on a few major areas of concern, virtually independent of changes in committee membership. The first and foremost of these is, of course, scientific merit. Because the committee is rather small and must cover a wide range of astrophysical expertise, it is essential that proposals make very clear just what scientific questions will be addressed by the proposed observations. The committee often wishes to see these goals placed in a larger context; i.e., how these questions relate to major unresolved astrophysical questions. Vague generalities such as "increasing our understanding" are not sufficient; the committee looks for specific questions that will be unambiguously addressed by the observations. Another issue of concern is the description of a clear path from the taking of the data through the reduction and analysis that will permit answers to be obtained. Other questions that often arise are whether or not similar programs have been done or are being done elsewhere, and if previous observing programs have resulted in the data being published in a timely manner.

Conflicts of Interest

This is an extremely important and delicate issue, and great care is exercised to make the TAC discussions as fair and impartial as possible. Lead reviewers are not given proposals where any PI or Co-I is located at their home institution. TAC members are not permitted to grade proposals from their home institution or from any of their collaborators (and, obviously from themselves). TAC members are asked to leave the room during discussion of their proposals and proposals of their collaborators. These procedures are also followed if any TAC member has any other conflict of interest for any reason.

We hope this description will help clarify the TAC process. The TAC procedures are continually being scrutinized and modified in an effort to provide the best system we can devise. We welcome any comments and suggestions you may have concerning the KPNO telescope time allocation process.

David De Young