The Committee on Radio Astronomy Frequencies (CRAF) is a committee of
the European Science Foundation (ESF).
1. The process
The general time allocation process for practically all astronomical observing facilities in the world is as follows:
An astronomical observatory is a general and technical services institute for astronomical research done at universities. Astronomers at university institutes submit their requests for observing time to a Program Committee. Such a request contains (a) the scientific case, (b) the specifications for the observation(s) requested, (c) the amount of time needed, (d) how the data are calibrated and processed and (e) when needed an indication of the urgency of the program. The Program Committee is recruited from expert astronomers of university institutes, while often the Director of the observatory involved participates in the meetings as an observer. Is it common practice that the Program Committee is formally appointed by a national research council.
The Program Committee will evaluate the scientific case of the request and (usually in consultation with the observatory on technical issues related to the telescope) allocates an amount of observing time to the request.
The advise of the Program Committee is binding, although in the very strict legal sense the Director of the observatory has the authority to decide what is in fact observed. On the basis of the allocations made by the Program Committee, the observatory schedules the observations. This procedure implies that an observatory itself cannot control the amount of time needed to perform the astronomical observations with some particular observing facility: this is given by the allocation process which is driven the scientific question and guided by time allocation by the Program Committee. Several observatories interpret the time allocation as "the time given to a project to guarantee the astronomer the necessary data quality to proceed with his research" - this may imply that more clock-time is used for a project than allocated to it by the Program Committee.
2. Time scales
A Program Committee usually meets 2 to 4 times per year. Thus at such a time scale the telescope schedule is known. However, since the Universe does not tell us all its secrets in advance, surprises may happen and they do. The Program Committee's time allocation process handles such targets of opportunity by interim allocations which may request observing time even at a time scale of less than a day. Therefore, any timescale between a day and several months for scheduling definition occurs in practice: this is driven by the scientific case only.