Mopra antenna control and IF setup is all run from a terminal based program called vlobs. This is similar but not the same as caobs at Narrabri. Some antenna control is done via the simple GUI “attest” (focus, stow, changing attenuation). The VLBI backend consists of two “LBA DAS” which sample and filter the IF and the LBADR recorder which captures the sampled data, formats it in software and writes to local or remote disk (or streams for eVLBI). The DAS setup is controlled via the “DAS GUI” and the recorder via “cdisko2”. These are the same for ATCA, Parkes and Mopra and some documentation is available at: ATNF observing notes
The antenna is controlled via a terminal based program called vlobs on bigrock. If it is not running just type “
vlobs” on a terminal on bigrock. Sometimes vlobs fails to start (usually spews gibberish all over the screen). If it doesn't start, just try again (and again - very occasionally up to 10 times).
To start a schedule type:
> file <SCHEDULENAME> > start
The schedule name will generally be the name of the experiment. When you type “file” check carefully it really loaded the schedule - if you have a typo in the schedule name or the schedule does not exist there is not an obvious error issued. There is no need to “unstow” the antenna.
The useful vlobs commands are:
|file <SCHEDULE>||Load schedule called SCHEDULE.sch|
|stop||Stop the current schedule running|
|start||Starting running the loaded UT schedule|
|lo_disable||Stop vlobs adjusting the frequency (use with caution)|
|lo_enable||Allow vlobs to adjust frequency based on the running schedule|
|set att servo off||Disable vlobs adjusting the IF attenuation. This is the default|
To stow the antenna, stop the running schedule and stow from attest (see below).
Use attest to focus the antenna, stow the antenna and adjust attenuation
Click the “stow” tab on the attest gui. Press “Go”
Click the “atten” tab in attest. Generally you will not have to adjust the coarse attenuation. There are 4 “fine atten” values corresponding to 2 pols and 2 IFs (A1, B1, A2, B2 where A and B are the two polarisations). Note that the value shown in attest are not necessarily the current values. The attest fine value are in steps of 2dB, while the values seen in MoniCA are the actual attenuation in dB. E.g. a fine atten of 3 is actually 6 dB.
Generally automatic attenuation is disabled as it causes various problems. As the observer you need to monitor the power levels and adjust attenuation as necessary. Note the power levels can be a little off nominal so the attenuation does not usually need to be adjusted more that occasionally if at all.
If either GTP/SDO or DAS levels are too high, add some fine attenuation to the appropriate IF. Similarly if the power levels are too low, remove attenuation. Once you have changed the attenuation, click “Go”.
Note it is sometime impossible to get a “good” power level for the GTP/SDO and DAS simultaneously.
You should regularly monitor the following every 10-15 minutes