DAS
The DAS is the LBA Data Acquisition System. At Mt. Pleasant, it refers to both the hardware (contained in beige panels beneath the frequency translator in rack 6) and the computer program that controls it.
Using the DAS Software
The DAS software runs on a Windows PC running in rack 9. You can also access this via VNC at das.phys.utas.edu.au:1 (The password is not the usual one). The desktop should look something like this:
the progrm is controlled through the keyboard. Each page shows the possible commands along the lower edge of the screen, with the relevant key bracketed with < and >. If the DAS program is not running, you can restart it from the shortcut on the desktop (circled in red). If so, you will be asked to select a profile - you must choose VSOP.PRO and confirm that the default settings are ok by pressing Enter.
DAS profiles
The current profile is listed in the upper left corner of the program (COR16000.PRO in the image above). If you need to load a different profile, press P (for the Profile menu). The next screen shows a list of all the possible profiles - press L to load one, and then enter its name. Make sure that you have selected "Load" before typing the profile name - otherwise you can end up overwriting profiles.
Once it is loaded, you need to set up the hardware - press S for setup. A few lines should appear on the screen before it goes back to the man page.
Once you have the correct profile loaded and set up, you need to make sure that the IF power levels are correct.
The red loop shows the IF power level for channel 1 of the DAS and green is channel 2. The highlighted box shows the current power reading and C indicates the current target. In both channels, the IF power level is slightly higher than nominal. To centre the DAS, you should adjust the attenuation on the configurable backend to get the levels centred. Small changes in the power level (of 1-2 divisions on the DAS sliding scale) are normally seen when the telescope goes to different elevations and will be handled correctly by the DAS. The BSB and LSB sliding scales should be ok once the IF power level is correct.
DAS alarms
The DAS monitors itself continuously and if alarms are enabled, it will produce an audible alarm when it detects a problem. The current status of the DAS is listed inthe yellow loop in the image above. If the alarms are listed as ON, there will be a loud alarm chime at Mt Pleasant if there are any detected problems. The usual cause is that the power levels have gone out of range (i.e the highlighted box on the slider has gone to the far end of the scale) or that there's a problem with the electronics - check for any ERRORS in the yellow-looped area.