Compact Array and Mopra report

Operations

Figure 1: ATCA usage for September - December 2003 (2003SEPT)

We had a good September term, with very low lost time and comparatively high astronomical use. Half of the lost time was a result of spring weather: overall the weather was milder than normal (spring is usually the worst term for lost weather time). The new antenna control computers (ACCs) continue to show their value: lost time as a result of ACCs continues to decline to the point where it is no longer a significant contributor. Minor lingering issues continue to be ironed out. Less apparent in the lost-time statistics is the improvement in antenna monitoring and tuning that the new ACCs give us. These are helping us address and resolve long-term "hidden" problems.

One of the highlights of the term was the "christening" of the H214 array and station N14 on 16 October. This marked the completion of the North Spur and new antenna-station upgrade. The term also saw the installation of a new data-archiving workstation in the Control Room. Observers can now choose whether to burn their data onto CDROM or DVD.

Late in the term, a signal compression problem was discovered in the 12-mm systems. This problem has probably been there since June: it has caused a minor loss in sensitivity and has meant that noise diode effective flux-density varies with sky brightness. A temporary solution has been implemented. Following this, the noise diodes in the 12-mm system have been calibrated, and the raw "pseudo-Jansky" scale at 12-mm given by the on-line system is now more closely aligned with the true flux-density scale. A permanent solution to the compression problem awaits a shutdown in June.

With an eye to future pipeline and "virtual observatory" processing of ATCA data, there has been some thought given to understanding what extra data needs to be stored in the RPFITS output file to define the state of the telescope and observing environment at the time of the observation. Some extra data are already being saved (see the separate article on ATCA millimetre data), and more will be saved in the future. Observer suggestions about "what is missing in the RPFITS file" are welcome.

The Observatory's on-line calibrator database is constantly being added to, with better flux and ancillary information, and occasionally with new calibrators. Contributions to this are always appreciated, particularly at 12- and 3-mm wavelengths.

Winter 2004 observing plans

A three-week shutdown of the Compact Array is planned during June to allow for the completion of the 12- and 3-mm upgrade of the ATCA. This upgrade will provide operation from 85 to 105 GHz on five antennas at Narrabri. Noise-diode and paddle calibration will be available on all antennas.

To give some robustness to 3-mm observing, the swap system of scheduling will be in use again this winter. Note that a component of the swap scheduling is that centimetre-wavelength observers can request that their project be considered for use as a swap partner. Note that service observing is offered to the centimetre partner in a swap pair. See the on-line documentation for more information.

Visitors Centre

Landscaping work at the Visitors Centre is nearly complete, with the new plantings taking hold. After a long period of being out-of-action (partly for safety reasons), the so-called People's Telescope is back. This is a single dish operating at 20 cm that visitors can steer by hand, and "see" the strong radio emission when pointed towards the Sun. Thermal emission from nearby objects can also be detected.

A new video for the Visitors Centre is now in preparation.

Observer feedback

I would like to thank all those who have taken the time to complete the web-based observer feedback form. These responses are taken seriously: by completing them, you are helping us understand the issues that are of concern, and helping us to respond. This is not to say that easy or quick solutions can be found to all issues!

Figures 2 and 3 summarize the results from the observer feedback questionnaires for 2003. Figure 2 is for all observers (77 responses), whereas Figure 3 shows the results specifically related to the new 3- and 12-mm systems (25 responses). Observers rate various aspects of the Observatory on a scale of 1 (poor) to 5 (excellent).

Figure 2: Observer feedback for 2003

Figure 3: Observer feedback for millimetre systems for 2003

The "all observers" feedback shows no significant change between 2002 and 2003. The millimetre observers' responses show an approximately half-point improvement in all but one question. The one exception was the weather during the swap slot. This response suffers from luck and small-number statistics, as only two swaps were invoked!

Staff

There have been a number of staff changes since October 2003, with us farewelling some and welcoming others.

Ben Reddall, who has served in the Narrabri Electronics Group for over 11 years, has accepted a position working at Owens Valley in California on the construction of a new cosmic microwave background telescope. Ben's broad "historical" knowledge and experience of the electronics at Narrabri and Mopra will be missed. At about the same time that Ben resigned, Brett Hiscock has been offered and has accepted the position of deputy Officer-in-Charge at Narrabri (see separate article). We are currently working to fill the vacancies within the Electronics Groups that have resulted from Ben's departure and Brett's promotion.

Clive Murphy has resigned to pursue another job opportunity in the Narrabri area. We thank Clive for his work here and wish him the best of luck with this change.

After 15 months on leave at the South Pole, and 15 years of sterling service to the ATNF, Allan Day has resigned to allow him to return to the Pole for another winter. Allan had been the senior cryogenics technician at Narrabri for a number of years, and is well known for his meticulous skills and playful sense of humour. In his place on a short-term contract, we welcome Bruce Tough.

We also welcome Norm Webster, who joined us in November. Norm's primary responsibility is for the mechanics of the antennas and generators and making sure the motors and drive systems continue to operate smoothly.

During November, we hosted Nicholas Ebner for the professional experience component of his degree at RMIT. Nicholas worked with Ravi Subrahmanyan on frequency dependence of the optics at 12 mm.

With us during the summer as vacation scholars are Marija Vlajic and David Jones. Marija is working with Michael Dahlem on the halos of edge-on spirals, whereas David is working with Ravi Subrahmanyan on high-resolution imaging of a class of extended radio galaxies.

Mopra operations

The usage statistics for Mopra for 2003 are given in Figure 4. Total usage increased by 25 days over 2002, with Mopra scheduled for observing for 165 days during 2003. This improvement is almost solely because of an increase in the national facility 3-mm time requested. In all but one case, these requests were from overseas observing teams. The overall usage increase was despite problems with the VSOP spacecraft, which have meant that VSOP observations have virtually ceased.

It is estimated that 25% of scheduled Mopra 3-mm time was lost, with 15% being caused by weather (rain, heavy cloud or wind) and 10% being a result of equipment failure or unscheduled maintenance override. This high weather lost time reflects the more stringent requirements of 3-mm observing and the windier site at Mopra. The seemingly large lost time as a result of equipment failure, etc., reflect the telescope's isolation and a difference in the scheduling and maintenance approach. During the winter virtually no maintenance is scheduled and problems are addressed as required.

Since the end of the 2003 millimetre season, a new ACC has been installed. "First light" was the detection of a methanol line on 27 November. Currently the ACC is undergoing final integration into the observing systems. The new ACC will allow reliable use of short cycle times which will cut down on a number of overheads in the telescope observing system.

Figure 4: Mopra usage for 2003

Mopra is in the early stages of a wideband upgrade specifically aimed at the 3-mm system. A prototype of the new spectrometer will be available during the winter of 2004. The main upgrade, which includes a 4-GHz spectrometer and an ATCA-style 12/3-mm receiver package, will be installed after the end of the 2004 season.

See the time assignment information section for more information on Mopra's capability during the 2004 millimetre season.

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