The JCMT OT primer
The JCMT OT primer
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
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
If, after reading this guide you have any questions about preparing
your observations, please consult with your "Friend of the Project"
or email firstname.lastname@example.org.
This version of the JCMT OT enables users to build
their science program for heterodyne and SCUBA-2 observations. Template libraries are provided
that cover the observing modes being offered: Samples, Grids,
Jiggles, for heterodyne observing and Scans for heterodyne
and SCUBA-2 observing. 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
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:
- 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
- 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 scan 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 scan 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.
- Calibration observations are part of the science MSBs:
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
- 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
- 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
Note that throughout this document integration times are the
"on"-source time only, instead of "on+off" as
Advanced OT Topics
There is a section on Advanced
Topics that observers should read. There you will learn more about
how the Target and Heterodyne components can interact with each other,
and also how to use the AND/OR
folders when you have many MSBs in your programme. Survey containers may significantly
simplify your setup if used properly.
Please be sure to carefully double-check your program and to
validate after high-lighting the top-most entry in the
OT program. The quoted Observing times are approximate and estimates
of overheads are based on limited tests. Check the validation messages
and contact your Friend of the
Project if you need help.
Detailed description of Observing Modes
A detailed description of the various observing modes, rms noise,
and durations is available as a document Heterodyne Obsmodes. Even
though the information is not required in order to set up a science
program, experienced as well as novice JCMT observers are encouraged
to read the document as a general background.
Because the OT is a graphical tool, the initial description of
how to use it will undoubtedly appear long-winded. But if you use
the text and screen shots to give yourself some practice you'll
find that you'll actually be able to prepare your program in a
modest number of steps.
Before we get started, a few words about the OT. The purpose of
the OT is to fully specify the observations you wish to be carried
out at the telescope. It
is quite a powerful tool; here we will simply see how to prepare a
typical observing project and point you to further sources of
information as necessary.
Ok, let's do this. Start the JCMT Observing Tool.
You will see two windows pop up. One has a colour picture of the
telescope - that's the JCMT root window. You can use its menus to
open and save files and fetch programs from our database. The
window with the JCMT line drawing, which pops on top of the root
window, provides a shortcut to some of the most common startup
actions, so we call that the startup screen:
For now, press "Create New Program" on the startup screen. The
startup window will be replaced by an science program window. If
you are using a proxy server to connect to the internet now would
be a good time to configure the OT to use this - see the
("Open Existing Program" lets you open a science program that
you've previously edited and saved in your own computer system. "Fetch
Program" allows you to download a program that that you have
completed and uploaded to our observing database. To download
the program, of course, you will need the project
(e.g. m06bc18) and password.
Look at your blank science program window. It's essentially
divided in four sections:
The bar between the program panel and the editor panel can be
dragged around to enlarge or reduce them.
- the menu and general tool bars at the top
- the program tool bar down the left side
- the program panel in the middle
- the editor panel on the right
Currently, the only thing in your program panel is a "Science Program"
line. We'll add things to it later. For now, take the time to fill in
its details in the Science Program editor on the right. The most
important field here is the Project ID field. You have to get this
right otherwise you will not be able to submit your program to
us. Your project ID is what you were assigned when you submitted
your proposal for telescope time. It is of the form m06b followed by a
country letter and a two digit proposal number (sometimes followed by
a letter). You can also find your country and
proposal number in our web page of time
Also on the panel are estimates of the total time the specified
program will take with and without optional observations, which are currently both 0 since we haven't specified any
Now that we've done something we can save it. Open the File menu
in your Science Program window and choose "Save As...".
You will be prompted for a filename and so on:
The file format is XML, which is a text (not binary) format that
you can read in later with the OT, or email to your
collaborators. If you have a question, you can also email your
file to your "Friend of the Project" (FOP; see allocations web page) along with your question.
You might have noticed that the title of your Science Program
was italics and now that you've saved the file, the title is
normal font. When you edit a component
of your Science Program its title changes font to indicate that
you need to save your work.
Time to step back for a moment. JCMT is a flexibly scheduled
facility. But what is it that we are actually scheduling? The
quantum of scheduling is a Minimum Schedulable Block, or MSB. An
MSB consists of one or more scientifically meaningful observations
as well as any calibrations required to fully reduce the
data. An MSB will always be executed at the telescope in its
entirety. For more information see What makes
a good MSB? but for the moment bear in mind that the most
efficient MSB consists of a 0.5 to 2 hour observation on a single
science target and any necessary calibrations.
Now that you've seen the basics of creating an observing program,
and know what an MSB is, you will want to start creating your
own. We've created a library of MSBs for the most commonly used
observing modes which are currently supported. For a
description of each, and help in creating your own program,
please consult the heterodyne
Once you've created your MSBs and validated that they are correct,
you will need to upload the program to our observing database so
that the observations can be carried out. Check submitting MSBs for
instructions on how to do so.