When the ATNF is upgraded to 3 mm operation in 2000-2001, we can expect that only about 50% of the observing time will be suitable for millimetre operation. In order to make efficient use of the telescope, we will have to change the way we allocate and schedule observing time. This discussion paper considers some of the options, in order to initiate a discussion over how we should do this.
It should be noted that this same decision is being made for similar reasons at other observatories, and we should follow those discussions closely. We have one constraint which other observatories tend not to have which is that, because Australia is geographically isolated, our desire to encourage observers to visit us is probably greater than that at other observatories.
I assume for the purposes of this document that by
the time the ATCA is operational at millimetre wavelengths, there
will be instruments at Narrabri capable of characterising the
weather conditions, and determining whether they are suitable
for millimetre observing. These might include water vapour radiometers
(either stand-alone or integral to the ATCA receiver package)
and/or a dedicated interferometer continuosly measuring the phase
on a geostationary satellite
This is essentially the way that optical telescopes (e.g. AAT) are allocated at present. In the case of the AT, we might nominate periods in the winter months as being the millimetre observing times, allocate tracks to different observers, and if the weather is not suitable then they just have to re-apply the following year. However, we differ from optical telescopes in that, even if the weather is unsuitable for millimetre observing, it is probably suitable for centimetre observing.
Option 2: Full dynamic queue scheduling
In this option, local staff (or software) make the decision as to which observation to make, in real time, on the basis of current weather conditions. As the schedule is continuously changing, it is impracticable for observers to come to the telescope for their observations, and so all observations have to be done in an absentee observing mode, which in turn implies hiring staff to make the observations.
Option 3: Dynamic queue scheduling for part of the year
This is essentially the same as option 2, but the dynamic scheduling would be operating for only part of the year (e.g. 3-6 winter months). Outside that time, operations would continue as at present.
Option 4: Observers propose backup programs
This is similar to the option exercised by some optical telescopes for projects that need photometric conditions. Each proposal is accompanied by a backup proposal that the observers will switch to if conditions become unsuitable for the prime proposal.
Option 5: Override queue scheduling
This is a compromise between the options above. Observers
would be expected to come for their observations as at present.
However, if the weather became bad then millimetre programs would
be halted and a centimetre project (selected from a backup list
of such projects) observed instead. The millimetre project then
goes on a queue of projects and will be observed by local staff,
the duty astronomer, or other observers, when conditions permit.
The millimetre observer is guaranteed to obtain the observing
time by the end of the term.
When the observations switch to centimetre wavelengths,
a choice has to be made of which centimetre project to observe.
If the millimetre observer chooses to submit a centimetre backup
project, and this is ranked high enough, then this backup project
will be given priority over other centimetre observing projects.
Otherwise, a project will be selected from a list of such projects,
which may include some long-term survey projects chosen expressly
for this purpose. The millimetre observer will be asked to help
make these observations in return for his/her millimetre observations
being handled by someone else.
There are two ways in which the required extra time for the queued millimetre observations could be obtained:
In either case, the millimetre or centimetre observer
would be guaranteed his/her observing time by the end of the term.
The decision as to when to switch from millimetre to centimetre observations (or vice-versa) could be made in one of two ways:
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Last updated: 19 Sept 1997Ray Norris (email@example.com)