Compact Array and Mopra report

LINUX at the Compact Array

Since November 2005, the standard observing system offered to the astronomers on site has been based on the LINUX operating system. The LINUX-based observing system is fully functional. However, when compared to the VMS system which has been in use for 17 years, it is understandable that the new system is somewhat less robust and may contain some bugs. Feedback from observers on the LINUX system is appreciated, particularly when enough detail can be given to help track down the problems. For the time being the VMS system continues to be the one recommended for remote observers.

The change to LINUX has resulted in changes to some CAOBS commands such as the commands used to switch generators on and off. Observers are advised to note that as LINUX is case-sensitive, some care needs to be taken with filenames. The simplest way for observers to avoid case problems is to use lower case names for all their files.

Please see the "Current Issues" web page on the Narrabri site for a summary of changes and issues with the LINUX-based system.

Narrabri control building

Figure 1: A sketch of the southern side (main entrance area) of the new Control Building. The
existing building can be seen on the right edge of the structure (click on image for larger version).

The development of plans for the major refurbishment of the Control Building is progressing steadily. The major design decisions have been made, and the layout of the building is being fine-tuned. During the period when the existing Control Building is being refurbished, the Control Room, Observers Area and the offices of the operations staff will be relocated to the current Receiver Laboratory. This will happen in late 2006 or early 2007. During the construction phase, there will be some inconvenience, but only minor interruptions, to the Compact Array operation.

Broadband fibre at Narrabri

Figure 2: A cable-laying machine burying the broadband fibre near the central area
of the Narrabri Observatory (click on image for larger version). Photo: Peter Mirtschin

Thirty kilometres of broadband fibre was installed in late-December and January, connecting the observatory to the AARNet3 network running down the Newell Highway. The final commissioning of the fibre and network is expected to happen in late February or early March. When completed, this will increase the network speed to the Observatory from 512 kbits/s to 1 Gbit/s. Amongst other improvements, this fibre will usher in new approaches to VLBI and observing data retrieval.

Mopra developments

As with Narrabri, a broadband fibre connection to Mopra and Siding Spring Observatory was installed in early December, with commissioning again expected in late February or early March.

The major development at Mopra in 2006 will be the installation of the MOPS digital filterbank backend. In its initial configuration it will allow observations in four 2.2 GHz windows (at least 2048 channels per window), or in eight 137.5 MHz windows (4096 channels per window). This will give Mopra an impressive multi-line capability. Installation is expected in late May or early June, and will be available to the bulk of observations during the Mopra millimetre season.

Operational statistics

For the period 1 October 2005 to 31 January 2006, the equipment lost time fraction at the Compact Array was 1.7% - close to the long-term average. The weather lost time fraction (1.5%) and fraction of weather overrides (also 1.5%) are somewhat higher than usual: in addition to the usual thundery summer, a wet October disrupted a number of millimetre observations. Mopra similarly had a wet October, with 14.4% of October lost to the weather. The Mopra observing season finished on 6 November.

Explosive events

A noteworthy event happened on 9 December 2005: The main 22 kV transformer within the central area of the Narrabri Observatory failed explosively in the early hours of the morning. The surges that accompanied the failure overwhelmed the Control Building uninterruptible power supply, causing a power loss to the Control Building equipment. The local grid also experienced a brief blackout. Systems were brought back for normal observing by mid-morning - under generator power and with the uninterruptible power supply restarted. By early evening the failed transformer was shipped off for repair, and replaced with a transformer from the north spur. With the site then reconnected to the local power grid, all was back to normal. We are indebted to fast assistance from Country Energy, who moved heavy equipment and several expert technicians here at zero notice. The repaired transformer is expected to be re-installed in late March or April - in time for the millimetre season.

Another even more spectacular event happened at Mopra near midnight on 12 January 2006: Mopra received a major lightning strike. A broad range of Mopra systems were damaged in the event and these are being assessed and repaired. The damage caused some electronics chips to explode while wires fused and the cryogenics systems failed. As of writing the Mopra uninterruptible power supply has yet to be brought back online and receiver health is yet to be tested. At present this event is not expected to have a major impact on VLBI or the start of the millimetre season.

Staff

After four years of tireless service, at all hours of the day and night, Derek Aboltins, the site's senior cryogenics technician, left CSIRO to take up a position at the Melbourne Synchrotron. We wish Derek all the best with this change. To help plug the hole left by Derek, we welcome John Wilson and his family to the Narrabri district.

We were sad to farewell John Giovannis, who left the Observatory at the end of January to work for CSIRO in Melbourne. In addition to keeping Windows and other computing gremlins at bay, John contributed to the life of the Observatory and the community in many ways.

Ravi Subrahmanyan and Lakshmi Saripalli will be moving to India in March to enable Ravi to take on the Directorship of the Raman Research Institute; see separate article. We congratulate them on this very exciting and prestigious move in their lives. Their contributions will be sorely missed.

Maxim Voronkov has accepted a position in Marsfield to work on issues associated with the NTD and so will be moving to Sydney in the near future. At the same time Jürgen Ott has completed his term as Mopra Scientist, and will revert to a full-time Bolton postdoctoral fellow. The process to appoint a successor Mopra Scientist is in progress.

Excellent contributions were made over the summer by vacations students Rachel Poldy and Yadav Padmanaban. Rachel worked on a variety of problems related to RFI, whereas Yadav studied the Compact Array antenna power usage and worked towards understanding the energy budget of SKA-like antenna arrays.

Finally, this is my last report as Officer-in-Charge (OIC) for Narrabri and Mopra. I would like to thank the broad ATNF community for their continuing support of Narrabri and Mopra Observatories and their assistance to me over the last four years. The OIC position has been advertised externally. An outcome from this appointment process is likely in February. In an interim period, Brett Hiscock will be Acting OIC, and Mark Wieringa will be Assistant OIC.

Bob Sault
Officer-in-Charge, Narrabri Observatory
(Bob.Sault@csiro.au)