Check Essential Online Tasks

Certain tasks are essential for operation of the Compact Array. In general, these will already be going when you come to observe, but you should check the most important tasks. Do not close down any of these programs. The following programs are essential to the safe operation of the CA. If XBONES crashes for some reason, you can find the restarting instruction in the Expert's Folder, however, it is advisable to get help from local staff.

CHECK CAOBS is running.

Look for black window with yellow writing in Screen 2 of Pericles. (CAOBS is run on XBONES.)

Figure 5.1: A typical CAOBS screen display.

Unless you have good reason for disabling them, ensure that the attenuators for each antenna are under automatic control by entering:

CAOBS$>$ enable auto

Ensure that the local oscillator phase is being tracked.

	CHECK the LO-tr field reads ON.		Right side of CAOBS window.
	If not, turn it on using:
	CAOBS$>$ set lo_track_on

	CHECK that $tsys$ field reads ON.		Right side of CAOBS window.
	If not, turn it on using:
	CAOBS$>$ enable tsys

Note that sometimes when changing some parameter in CAOBS another page containing that parameter may appear. However, the standard CAOBS page with system parameters will reappear automatically when the next scan begins. Alternatively, you can type:

CAOBS$>$ show status to view the standard page again.

CHECK CACOR is running.

Look for gui, (generally situated next to CAOBS) on PERICLES . A typical CACOR screen is shown below.

Figure 5.2: The CACOR gui display.

	CHECK SPD is running.		Generally on Screen 0 (Leftmost screen) on PERICLES (Runs on CACCC.)
	CHECK ASSISTANCE is running.		Normally in Screen 3 (rightmost screen) on PERICLES. (Runs on XBONES.)
	CHECK VIS is running.		Normally in Screen 1 on PERICLES. (Runs on XBONES.)
	CHECK CAMON is running in several windows.		Normally in Screen 3 on PERICLES. (Runs on XBONES.)

CAMON and ASSISTANCE are monitoring programs that can be run on ordinary terminals, or more usually, on one of the screens on PERICLES. CAMON and ASSISTANCE must run at all times, as these programs may alert you to certain problems that effect the safety of the Compact Array and the quality of your data.

If, for some reason, the CAMON or ASSISTANCE windows are absent on PERICLES screens, create a new xterm to display them in by typing:

XBONES$ xterm

and enter the XBONES:$\sim$$ ASSISTANCE or XBONES:$\sim$$ camon command as appropriate.

Note: A useful command in CAOBS, CAMON, and ASSISTANCE is disable/enable bell when the warning bell indicates problems unnecessarily.

The Correlator Data Display (SPD)
The SPD program displays correlator information. It is usually used to plot correlator data with channel number (or frequency) on the abscissa. While setting up you might look at the correlation function; and while observing, look at spectra. A spectral display provides immediate warning of interference. Use of this program is discussed fully.

The Visibility Display VIS

To specify visibilities to be plotted, enter commands in the VIS window displayed on Screen1. VIS commands are described in detail.

For now it suffices to know that a displays amplitudes, p, phases, and d delays of the visibilities listed at the bottom of the plot To display all three in one display:

VIS$>$ tapd

Two optional numbers can be used to define the vertical range of a plot.

	E.g.,
	VIS$>$ scale a 0 20		Displays with a vertical range of 0 to 20Jy.

If you are unhappy with the choice of visibilities displayed, choose another set by entering:

	E.g.,
	VIS$>$ select 12AA, 13BB		Displays Freq 1 XX and YY polarisations of baselines 1-2 and 1-3.

Up to 15 visibilities (rather than the two described here) can be displayed at once. You can define your own visibility sets, save them with the VIS$>$ save command and retrieve them with the VIS$>$ recall command.

VIS, CAMON and ASSISTANCE can also be run from any XBONES terminal using the following commands:
XBONES:$\sim$$ vis
XBONES:$\sim$$ camon
XBONES:$\sim$$ assistance
This can be useful if you are working in the Observer's Room.

Each of the above online programs and displays is discussed in detail . Note that commands entered into online tasks (CAOBS in particular) do not always take effect immediately. You may need to wait several integration periods (up to one or two minutes) for some commands to be performed and reflected in the monitoring displays.