Table of Content

• How the OPC works
• The OPC and the VLT
• Hints for successful applicants
  • General remarks
  • Scientific justification
  • Points of interest
• Concluding remarks

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How the OPC works

The function of the "Observing Programmes Committee" (OPC) is to review and rank the observing proposals for the use of ESO facilities and, thereby, to advise the Director General on the distribution of observing time.

The OPC consists of members nominated by the respective national Committees and of "members-at-large" nominated by the Director General in consultation with the OPC Chairman. The increase in the capabilities of the ESO facilities over the years has led to a substantial increase in the number of (good) proposals, and the OPC has adapted its structure and working procedures accordingly. An adequate number of discipline-oriented sub-committees (panels) has thus been appointed by the Director General to ensure a proper reviewing of the observing proposals submitted by the community. There are currently seven panels. Each panel consists of one or two OPC representatives and of "expert advisers" selected by the Director General in consultation with the OPC Chairman. The chair of the panels rotates between the OPC representatives only.

The current time-allocation procedure is carried out in three steps. A first ranking is made based on the grades given by three panel members who act as referees. During the panel meeting all proposals are then discussed in detail by all panel members and are ranked for each telescope separately. Third, while strictly respecting the ranking assigned by the various panels, the OPC finally adjusts the time allocated to each panel, i.e. the "cut-off" line, which was defined in a preliminary way taking into account the typical amount of time allocated to the panel during previous periods and various constraints on a particular telescope (test time, key programmes, guaranteed time), which may change from one period to another. First, each panel chair reports on the particular situation in his/her panel and requests a new time allocation for the panel, which may be induced by the large number of high-quality proposals, sometimes triggered by new instrumentation. If a consensus cannot be reached on a modified time allocation per panel, then the scientific merit of the proposals near the cut-off line is specifically discussed and the final decision involves a voting of the full OPC.

The advantage of the panel system clearly is that all proposals are discussed and ranked by experts in the field. Furthermore, the adjustment of the time allocated per panel and per telescope made by the OPC, together with an inter-comparison of the scientific merit of proposals in different panels near the cut-off line, provides the flexibility required by the dynamics of our science, all the more important since the implementation of a new instrument can drastically change the potential of a particular telescope. Finally, to average out the unavoidable effects induced by the individual bias of panel membership, the terms of the panel and OPC members are limited to two and three years, respectively. ESO puts particular emphasis on involving young scientists in the panel work.

The final recommendation for time allocation is prepared by the OPC under the guidance of the OPC Chairman. It should be noted that small adjustments are always dictated by scheduling constraints.

The OPC and the VLT

With the advent of the VLT, the OPC enters a new era. In order to be ready for the unanticipated, a full week has been reserved for the OPC and panel meetings for Period 63. All the OPC members will have read the VLT proposals for all panels. The meeting will start with a full OPC meeting where a first evaluation will be made in order to better define the time allocated to each panel for the VLT-UT1. It is our expectation that the proposed science will be innovative, and it is clear that the first two VLT instruments, FORS1 and ISAAC, do not cover the fields addressed by the different panels in a homogeneous way.

The proposal selection for the VLT will to a large extent be dictated by the innovative and ambitious, even risky, character of the science, i.e. these proposals that exploit in the most intelligent way the capabilities of the instrumentation for exploring new frontiers will be favoured. It is probable that some of these proposals will require substantial amounts of observing time; in this case the capacity of the group or consortium introducing the proposal for handling the huge data flow will be critically assessed.

It is important that the applicants thoroughly read the "VLT Science Policy" document endorsed by the STC and the OPC, and approved by Council.

Hints for successful applicant

The view of observing proposals from the standpoint of panel and/or OPC members is sometimes strikingly different from the point of view of the proposers. In what follows, Professor Frank Verbunt (Utrecht), who served in the OPC during the transition period from the "old" to the "new" (i.e. panel) system, describes aspects of this different perspective, in the hope that this may assist prospective users of ESO telescopes in their preparation of observing proposals.

General remarks

The amount of time requested at ESO is always in excess - often by a large factor - of the time available at the telescopes. This implies that it is not sufficient for an observing proposal to be merely good. To be successful, a proposal must be better than many - often most - other proposals. The author of a proposal should realize this, and try to produce the best possible arguments. The members of the panels must make their decisions in a limited amount of time, and based on a limited amount of information. It is incumbent on the proposer to provide the panel with as much relevant information as possible,