The Story So Far
The first part of the work will be the construction of a 200 metre long rail track running in a north/south direction that will intersect the existing 3 km long east/west track near the middle. Preliminary work has begun with cable trenches being excavated. The major excavations started on May 25 after a short delay due mainly to weather and are progressing smoothly. By June 2nd the topsoil had been stripped away and heavier earthmoving machinery is now being employed to take the subsoil down to the base level of the rail ballast.
The end of June has seen the majority of the excavations completed and work is now progressing towards setting up the new stations. The east/west rail track has been cut in two places and sections removed to facilitate th is work. Heavy rain on June 22nd (50mm recorded on site) caused a few problems and large pumps were employed to remove an estimated 1.5 Megalitres of water from the construction area.
Along with these civil works will be the installation of 4 new antenna stations on the east/west track and a system of turntables that will allow the existing 270 tonne antennas to be transferred from the east/west track to the north/south track. See a graphic HERE for details of the track layout.
While the civil works are in progress new receivers are being designed to allow the Telescope to operate at much higher frequencies. The 16 - 25 GHz bandwidth will be accessed by new, state of the art, 12mm receivers and the 85 - 100GHz band will use 3mm receivers. Both sets of receivers are being designed and tested in house by CSIRO.
The original design of the Compact Array's antennas called for the outer reflective panels of the main dish to be perforated. This was done to ensure the antennas would withstand very high wind loads. With the upgrade to higher frequencies, these outer pa nels would not be able to reflect the short wavelength signals to the receivers therefore reducing the effective dish diameter from 22m to 15m. To overcome this effect and to increase the receiving power of the Telescope at the higher frequencies, the ou ter dish panels will be converted from perforated to solid panels. CSIRO developed a process that will ensure these panels are accurate to within a fraction of a millimetre of the perfect shape.
Of course there are many other areas of development in progress and details will be posted as they become available. Also, as the actual work progresses, we will be able to bring you pictures of the changing face of the Narrabri site plus pictures of the items being developed that will usher Australia's radio astronomy effort into the 21st century.
Original: Tim Kennedy (1-Apr-1998)
Modified: Tim Kennedy (2-Jul-1998)