The JCMT OT primer

NOTE: A new version of the JCMTOT was released during semester 08B. Users of the JCMTOT software must update to this version before submitting MSBs. For a more detailed and technical discussion read 'Heterodyne Obsmodes'.

This document is a primer on how to use the JCMT Observing Tool (JCMT OT) to prepare and submit observations (see Why do I have to do this?). It assumes that you have already downloaded and installed the software (see our download page - make sure you have downloaded the latest version!). If you are using a JAC or summit machine, the software is already installed. You will also need the OMP password for your project in order to be able to upload your MSBs to our observing database.

If you are viewing this document through the JCMT-OT Help menu, there may be a more up-to-date version on our web site at http://www.jach.hawaii.edu/software/jcmtot/.

If, after reading this guide you have any questions about preparing your observations, please consult with your "Friend of the Project" (see http://www.jach.hawaii.edu/JCMT/allocations), or email jcmtot@jach.hawaii.edu.

General Information:

This version of the JCMT OT enables users to build their science program for heterodyne observations only. A templates library is provided that covers the observing modes being offered: Samples, Grids, Jiggles, and Rasters. Investigators are urged to carefully inspect the example for a beam-switched observation below and to read the more extensive explanation and instructions presented for each observing mode. While the components will look familiar to experienced JCMT observers, most have changed, sometimes in a fairly subtle manner.

Calibrations

The JCMT observing software needs further development to enable a more flexible inclusion of calibration observations: presently there is no easy way to add calibration observation MSBs. The JCMT telescope operators (TSS) will insert calibrations, pointings, foci, etc. into the observing sequence as appropriate. Without any specific instructions in the science program calibrations will be carried out by observing a 'standard' line in a suitable calibration source.

PIs are strongly advised to, at a minimum, add instructions and wishes regarding calibrations in the Calibration Note to the TSS and observers. A sample note has been included with the library templates. For information on standard sources, lines, and observational setup, see: JCMT Heterodyne Standards. Please be aware that the submm positions for calibrators as used at the JCMT may differ substantially from the the ones in archives such as SIMBAD.

There are several options for calibrations and ways to customize them:

1. No special calibration MSBs are provided in the Science Program: the calibrations will be carried out on a suitable calibration source selected by the TSS at a 'standard' frequency, possibly different from MSB tuning or redshift. For many applications, this is the most appropriate option.
2. A number of separate calibration MSBs on suitable targets are added to the science program, clearly identified as calibrations in their title. Typically the set of calibration MSBs should cover the RA-range of the science observations to ensure that at least one calibration MSB is available at any time. PIs can customize the Het setup but need to take care to pick an appropriate switching-scheme for each calibrator chosen. The TSS will insert the calibration MSBs into the observing queue as needed and per instruction in the science program.
   • The ACSIS library has a set of special template MSBs for a position-switch, beam-switch, or raster calibration. The MSBs start with a series of (optional) pointing and focus observations. The calibration itself is a regular observation that has been marked as a calibration. Configure the Het setup and Target Component to customize the calibration for your project. Typically choose either a position-switch, beam-switch, or raster calibration, depending on the selected calibration target (many of which require a position-switch). Observational details for the calibrators can be found at this location: JCMT Heterodyne Standards. The calibration MSBs should be added to the science program with a high priority (low number) and high repeat counter to ensure that they will come up prominently and repeatedly in the JCMT Query Tool.
3. Calibration observations are part of the science MSBs:
   • Embed the calibration observation of a specific standard source and line in your science MSB by copying and pasting the desired components from the calibration template described above under option 2 (please read those instructions). The MSB should look like:

            -------------------------
            MSB
              ...
              Het setup
              Science Target
     

              Calibration Observation (marked as Calibration)
     

              Science Observation 
            -------------------------
     

     Please be aware of inheritance: in the example above you will need to add another Target Component inside Calibration Observations with the coordinates and offsets of the calibrator! Likewise, if the calibration needs to be done at a different frequency, another Het setup needs to be added inside the Calibration Observation. This will result in the appropriate retune between the calibrator and the science target. This should NOT be done for the manually tuned RxW. WARNING: If you include a calibration observation in this manner, both your target and calibration source must be observable before the MSB can be scheduled, which can severely restrict the night-time available to the project in case of an unfortunate combination of calibration and science targets.

Issues to consider regarding calibrations may be:

• How important is a precise calibration? For many projects it is sufficient to ensure that the telescope and receiver are within spec.
• Can the calibration be done at a 'standard' frequency, possibly different from MSB tuning or redshift? Or should the calibration be done with the Het setup of the science observation and, if not close to a standard frequency, should a line-rich source be selected that will allow for the relative calibration of observations from night-to-night?
• Can the calibration be done using a different bandwidth than the science observation? Is an increase in bandwidth allowed to catch a nearby standard line? Increasing the bandwidth should not affect the calibration, except that the peak of very narrow lines will drop because of the lower resolution.
• Is it important to observe a planet? Can this be done at one of the standard frequencies or should the Het setup from the science MSB be used? Efficiencies derived from isolated observations of the continuum level of planets typically are not very accurate.

Integration times

Note that throughout this document integration times are the "on"-source time only, instead of "on+off" as before.