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Guidelines for Flexible Observing at the JCMT
Guidelines for Flexible Observing at the JCMT
- Introduction & weather bands
- Guidelines for flexible observing in the national queues
- Observing Target of Opportunity (ToO) projects
- Disabling old projects from the queue
- Guidelines for flexible observing in the JLS queue
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,
- the TAG-assigned priority.
To facilitate this we identify
the range of weather conditions within which each programme
allocated time should be pursued as follows:
The weather categories adopted at JCMT
| Weather Grade |
Definition |
CSO Tau |
| 1 | very dry | τ < 0.05 |
| 2 | dry | 0.05 < τ < 0.08 |
| 3 | medium | 0.08 < τ < 0.12 |
| 4 | wet | 0.12 < τ < 0.2 |
| 5 | very wet | 0.2 < τ |
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 has demanded a unified, unambiguous code of
conduct for flexible observing:
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 Telescope Scheduler (IMC) or, in his absence, the Associate Director (ACC).
If it is not possible to carry out the scheduled program for whatever reason (e.g. weather
constraints, program completion, target availability), then programs from the queue should be selected
according the following scheme:
- For reference only, we refer to the "national queues" as those from the UK, CA, NL, and IN. Note: The ITAC has no jurisdiction over the UHawaii observing queue. This means that they are allowed to observe any UH project they wish in any weather band.
- 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.
- Do not abort or interrupt the current observation to change projects
unless, e.g. it has just started and will otherwise run for a long
time, the change in weather is dramatic and certain.
- Changing projects may also mean changing
receivers, which will incur additional overheads for pointing, calibration etc. It is thus preferable to stay with the same instrument if priorities allow.
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.
- If no project is available in the current semester, look for the highest-ranked project available within the
scheduled national queue from the previous semester and then the semester before that (i.e. going back no further than 2 semesters) that is
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 (and Band 1 is not allocated to the observer at the telescope):
- 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 other national queues.
- If there are still no projects available to observe, then observe the highest ranked project from the JLS queue (for the current weather conditions).
Departures from the guidelines can only be authorized via a formal request to the Telescope
Scheduler or, in his absence, the Associate Director.
Ever so often the ITAC awards time to a Target of Opportunity (ToO) project.
- If the ToO is triggered (information of which will come from the
Telescope Scheduler or, at times, directly from the PI) then it immediately assumes top priority within
the approved weather bands.
- ToO projects are approved by the ITAC and only they will stipulate whether all the national queues may be overridden by these projects. Notification of
this will come from
the Telescope Scheduler and/or the Associate Director.
- The ITAC cannot override the
UH queue and so any ToO triggered during a UH observing block will need to be negotiated with the UH observer. If the ToO is observed, the Scheduler will ensure that the UH queue is paid back any time lost due to executing the ToO. The time is to be paid back by the national queue triggering the request.
- The JLS queue can be overridden by ToO requests. Similarly, time will be paid back to the project which was overridden by the national queue triggering the request.
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.
- 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 have to be based on scientific grounds and so can only be authorized by the TAGs.
- Projects that are awarded time in one semester and for which are subsequently awarded more time in a subsequent semester (in a separate proposal), will have the previous project disabled at the start of the new semester.
- This is a task which can be tracked by the Telescope Scheduler and who can inform the respective
national TAGs and ITAC at their meetings.
- The JLS team that is scheduled at the telescope will have the top priority
- If there are no MSBs available for the current JLS project in the current weather conditions:
- Search the JLS queue for another suitable project/MSB, staying within the constraints of the current weather conditions.
- Note that some JLS projects will have MSBs available in a range of weather bands. Needless to say, stay with the current (scheduled) project if possible.
- If there is no JLS project available for the current weather conditions, select the highest ranked project from the national queues.
- Do not try to observe a JLS project in a worse weather band than that allocated.
- At the present time, the advice is to not observe JLS projects in better weather bands (e.g. observing band 4 SASSy MSBs in band 3). This is because the main priority for the JLS projects is uniformity across the whole of data set. Observing strategies are designed with this in mind. As such it is desirable to remain within the weather constraints of the MSBs.
- However, this advice may change in the future.
- Note that project MJLSY03 has special status. It is a very lowly ranked project that should only be attempted if there is nothing available in EITHER the JLS or the national queues. It is an empty queue project.
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