Installation of a new 3/12-mm receiver at Mopra

The timely installation of a new millimetre-wave capable receiver at Mopra has been achieved. This receiver can truly be described as 3/12-mm because observations at 115 GHz on 22 September have already detected the tell-tale line of carbon monoxide.

With installation scheduled in the week starting 12 September staff from Narrabri and Marsfield converged on Mopra on the Monday. The SIS receiver (see page 8) and its compressor were removed and the new items slotted into their places nicely all within two hours on the Tuesday morning…well not quite that nicely. The rest of Tuesday was spent aligning the new package. This required the repositioning of the L/S feed and package and evening had descended by the time the final location was determined. The cryogenics crew looked after the new compressor and lines while all this was going on.

The cryostat was evacuated overnight and the fridge purged next morning so cooling could commence at about 10 am. By 4 pm we had a cold receiver with all cryostat related electronics, both monitor and control, hooked up and operational.

Thursday was taken up with getting the receiver, local oscillator and conversion system installed and functioning while others worked to complete changes that had begun on Monday to the AT conversion rack. In the background the necessary software modifications had been going on and this allowed the receiver to be configured remotely and noise-temperature measurements to be made after dinner that night. These indicated that all was well. A repeat of the measurements on the Friday confirmed this though the weather had closed in making measurements of the sky temperature less than meaningful. The calibration injection system functioned and workers were able to pack up and return to Narrabri and Sydney…well most of them anyway.

The crew: Derek Aboltins, Graeme Carrad, Michael Laxen, Les Reilly, Brett Hiscock and Russell Bolton. Photo: Bruce Tough

Little had to be done to achieve a decent pointing solution and the beam patterns indicate that no coma lobe problems, seen at Mopra previously, have surfaced so the subreflector won't require significant repositioning.

All in all the installation was as smooth as could be expected with the package having more capability than originally envisioned. Thanks are in order for those who got the bits made on time, for those who put in the preparatory work to have the antenna ready and particularly to those whose "no fuss" attitude made the fit out a pleasurable experience.

Graeme Carrad
(Graeme.Carrad@csiro.au)