Online Computers: Overview of Observing System

Output from the correlator modules is sent to CACCC, a Linux machine which controls the correlator blocks (via the BCCs), and the delays (with the Delay Unit Control Computer DUCC), and performs the Fourier transforms. CACCC stores data to disk in RPFITS file format. CACOR running on the main observing display (PERICLES) is a GUI providing an interface to the correlator.

For many years, the clustered VAX computers NOEL and LEON, running VMS, controlled the array and provided the user interface to the array. They have now been replaced by the Linux machines SKULL and XBONES (which in turn replaced ELLEN and NELLE). The main operational tasks run on XBONES. Ask your Duty Astronomer for the password to the atcaobs account. XBONES (and SKULL) are located in the screened computer room, and the interface is displayed through the four screens of PERICLES in the Control Room. Except in the case, of remote observing, control of the array is done from this machine. Likewise, the observer usually monitors the array from here.

The task that controls the observing is called CAOBS and runs on XBONES. This task reads your schedule file and then directs the antennas to track the position you requested. CAOBS also selects appropriate feeds, sends commands to the correlator, interfaces with the monitoring system and presents online calibration data.

The task CAMON displays data obtained from hundreds of monitor points throughout the array, informing the user of the status of the antennas, receivers and all associated subsystems, including the correlator. This array data is written to a common area called obscom. There are a number of tasks that access obscom to give the observer information on the start of their observations. These include ASSISTANCE, CAMON, WINDS, LOMON, all of which can be run on XBONES.

To make the observer's job easier, the monitoring system uses ASSISTANCE to inform you of error conditions that you should know about, while CAMON is available for further investigation of problems.

Visibility data is displayed using the task VIS, also usually run on XBONES. Refer to ection  VIS for an explanation of how to view the incoming data.

SPD displays the correlator output, either in the form of the lag spectrum (ie. cross-correlation function) or the frequency spectrum. SPD is run on CACCC, but can be displayed anywhere by using ssh to XBONES. Refer to the Section SPD.

In addition, there is a new monitoring program, MONICA which is available for much of the ATCA monitoring. MONICA is a Java-based graphical user interface (GUI) program that enables both observers and technical staff to monitor the thousands of data points available at each site, including things such as cryogenic temperatures and pressures, sampler statistics, site weather information, power supply voltages and so on. Currently, MONICA is available on FURIOUS (the second linux workstation in the control room). MONICA only works within the ATNF network. See section 8.7 on page  for more information.

At the end of observing, a CD or DVD of the data is generally created using the TCL/TK script on FURIOUS. A Windows XP workstation called ARCHIVER carries out all the actual archiving and CD-ROM writing. Both FURIOUS and ARCHIVER are located in the control room. For further instructions see to cdrom or exabyte.

If an exabyte is preferred this can be done using the drive attached to HYDRUS in the Observer's Area.

Observations can also be monitored from elsewhere, e.g., a workstation in the observer's area (outside the control room) or on the lodge PC while having dinner, by running ASSISTANCE and CAMON from XBONES windows. To do this, ssh xbones and login as atcaobs. By ensuring the bell is enabled (type >enable bell in ASSISTANCE and CAMON), you will be alerted there also.

WWW documentation is available for most online systems. For more information about using Linux/UNIX (and some historical information about VMS), see Some Useful Linux/UNIX Commands .