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Guidelines for Flexible Observing at the JCMT
Guidelines for Flexible Observing at the JCMT
In order to maximise the productivity of the JCMT,
the ITAC has approved the concept of
flexible scheduling whereby the choice of project observed is
determined
primarily by the weather conditions and then by the TAG-assigned priority.
To facilitate this we identify
the range of weather conditions within which each programme
allocated time should be pursued. The weather categories adopted, in
liason with the Director JCMT, are as follows:
The weather categories adopted at JCMT
| Weather Grade |
Definition |
CSO Tau |
Prime Instrument(s) |
| 1 | very dry | τ < 0.05 | RxW(D), HARP (>360GHz) |
| 2 | dry | 0.05 < τ < 0.08 | HARP |
| 3 | medium | 0.08 < τ < 0.12 | HARP |
| 4 | wet | 0.12 < τ < 0.2 | HARP, RxA3 |
| 5 | very wet | 0.2 < τ | RxA3 |
Each of the queues at the JCMT operates under its own
rules
for observing projects, rules which are dictated by the national TAGs. However,
we are frequently observing across queue boundaries, increasingly so since the onset of
the JCMT Legacy Survey (JLS).
JLS observing happens under the auspices of the JCMT Board and occurs outside of the
national queues. This new variant has demanded a unified, unambiguous code of
conduct for flexible observing:
Default condition
The observer at the telescope has the highest priority to observe his or her own project in accordance
with the
rules
of the appropriate national TAG. These differ for each queue and any ambiguity or
confusion will be resolved by the national queue manager at the JAC.
Moving to the queues
If it is not possible to carry out the scheduled program for whatever reason (e.g. weather
constraints, program completion), then programs from the queue should be selected
according the following scheme:
Unified Guidelines for Flexible Observing
- Choose the highest-ranked project from the scheduled national queue, appropriate for the current
weather conditions.
- As conditions change, new projects must be sought and new MSBs executed.
Judging when to switch projects is left to the
observer and TSS to decide: however, do not abort or interrupt the current observation
unless, for instance, it has just started and will otherwise run for a long
time and the change in weather is dramatic and certain. Changing projects may also mean changing
receivers, which will incur additional overheads for pointing, calibration etc.,
so for these and other reasons it is difficult to prescribe the precise conditions under
which changing the project becomes inevitable.
- If there is no appropriate project available within the scheduled national queue,
then a project may be chosen from a worse weather band (same national queue).
- When S/N or RMS completion criteria
are given in the MSB for that project, then the integration time may be adjusted.
- The exception to this is when observing for the JLS where there is no national
assignment. In this
case, observe the highest-ranked project for the current weather band from the 4 national queues;
effectively the 4 national queues act as one single queue. This is possible since the
priorities assigned by the national TAGs and ITAC are now normalized, enabling cross-queue
comparison of projects.
- If no project is available in the current semester, look for the highest-ranked project within the
scheduled national queue from the previous semester and then the semester before that;
appropriate for the current weather conditions.
- If there is still no project available then a project may be chosen from a
worse weather band within the same national queue from these
previous semesters.
- If there is still no project available, then look to the other national queues, never going back
further than two semesters.
- As an exception to the above rules: if the weather moves into Band 1 then
- look for the highest-ranked Band 1 project from the scheduled national queue.
- Try to be sure (as best as it's possible to be) that the improvement into Band
1 weather is a
genuine one and will remain stable. It is an inefficient use of telescope time to continually
change between projects.
- If nothing is available, then look for the highest-ranked Band 1 project from the other national
queues. For Band 1 projects that are observed from other national queues, all
efforts will be made to pay back that time in kind (to be arranged by the Telescope Scheduler).
- If there is still nothing available, then look to the (two) previous semesters, starting with
the current (scheduled) national queue before moving to the others.
Departures from the guidelines can only be authorized via a formal request to the Telescope
Scheduler, Head of Operations, or the Associate Director (in that order).
Target of Opportunity
Ever so often the TAGs award time to a Target of Opportunity (ToO)
project. If the ToO is triggered (information of which will come from the
relevant queue manager) then it immediately assumes top priority within
the approved weather bands.
At times, ToO projects are approved by the ITAC. In this case, all queues
may be overridden by such projects. Notification of this will come from
the Telescope Scheduler and/or the Head of Operations.
Disabling Old Projects from the Queue
The following guidelines are to prevent the situation where the same targets may be observed multiple times
for the same project (but from different semesters), and to disable old projects.
- Projects which are more than two semesters old will be disabled at the start of the third semester
- For example, at the start of semester 08B, projects that are still active from semester 07A
and earlier will be disabled.
- However, projects which are deliberately carried forward by the TAG (e.g. Canadian thesis
projects, long-term projects) will be disabled two semesters after the last semester into which
they were carried forward.
- Those projects which are disabled can be re-enabled via a formal request from the PI to the
national TAG.
- Any justification for re-enabling a project will be based on scientific grounds and so can only
be authorized by the TAGs.
- Projects which are awarded time in one semester for which the PI subsequently applies for (and is
allocated) more time in a subsequent semester, will have the previous project disabled at the start
of the new semester.
- This is a task which can be tracked by the scheduler and who can then inform the respective
national TAGs and ITAC at their meetings.
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