Checklist for schedule-based observations with XARCOS

Notice that actions take place in three different “locations”:

  • (1) = action to be performed in a terminal on the observing machine (the one with the DISCOS system interface)

  • (2) = action to be performed in a terminal on the project/schedule/data machine

  • (op) = command to be given in the operatorInput panel of DISCOS

Login on both (1) and (2) Connect via VNC to (1) as “observer”, from there use ssh to access (2) with your project-specific account.

Launch the monitors, if necessary (1):

$ discosConsole

Set the project name (op):

> project=[projectID]

Initial setup (op):

> setupKKC      (or other receiver code: CCC, XXP)

Tune the local oscillator, if any (op):

> setLO=[freq]
—> e.g. setLO=22000 - start frequency of the observed band will depend on the backend

Point the antenna to a reference position (op):

> goTo=[Az]d,[El]d
—> e.g. goTo=180d,45d

Always explicitly choose the Total Power backend (XARCOS might have been left active) (op):

> chooseBackend=TotalPower

Measure the cold sky signal level (op):

> getTpi
> setAttenuation=[sect],[att]  (values range from 0 dB to 15 dB, 1-dB step)
—> iteratively adjust attenuations until the level is about 700-900 counts

Get a Tsys (op):

> tsys

Pointing check (op):

> track=name                    (choose a proper calibrator from source catalogue)
> chooseRecorder=MANAGEMENT/CalibrationTool
—> the following command on (1):
        $ calibrationtoolclient  (to display the plots)
> crossScan=HOR,0.2d,00:00:15    (set proper parameters according to your beamsize)
> azelOffsets=0d,0d              (only if wanting to reject the measured offsets!)


  • System offsets, such as the ones measured with a Point acquisition, sum up to the ones indicated inside schedules ONLY if they are expressed in the same coordinate frame.

This means that, if you perform observations using EQ offsets, also the fine-pointing cross-scans must be carried out in the EQ frame. The same holds for HOR scans. If there is a frame mismatch, the system offsets are automatically rejected (bug under fixing).

Choose and set the spectrometer (op):

> chooseBackend=XArcos
> initialize=[code]      (either XC00 or XK00)
If needed, set the spectrometer attenuators
> setAttenuation=[sect],[att]

(values around 19-21 dB have proven to be OK to avoid saturation, but it depends on the signal level)

If needed, create a schedule (2):

Use schedulecreator (see its own guide):
$ basie –c [configfile] [out_directory]

Parse the schedule (2):

$ scheduleChecker [schedulename].scd
—> Move the schedule files to the observing machine

Launch the schedule (op):

> startSchedule=[schedulename].scd,[N]


  • The project ID written inside the .scd schedule file MUST coincide with the one invoked during the observations (and thus with the project-specific path it is stored into).

Data quick-look

Quick-look for XARCOS data is not available at the moment.

Weather conditions and webcam (in a web browser)

Weather: Webcam:

Stop the schedule (op):

> haltSchedule
Copy the data (2)

—> Get the latest subfolders written in the main data folder

Stow the antenna and restore default user (op):

> antennaPark
> project=staff