Marsfield Engineering Development Group report
The last few months have been a very busy time for the group with a number of major instruments being installed, or shortly due for installation, at both Narrabri and Parkes.
The completion of the 12-mm system at Narrabri in June was quickly followed by the delivery of a new 8-GHz receiver at Parkes in August. This receiver was built under contract to NASA as part of the upgrade to Parkes for tracking of spacecraft heading for Mars. The final performance of the Parkes telescope turned out to be considerably better than the NASA specifications, due largely to the excellent performance of the receiver.
Figure 1: The 8-GHz analogue correlator
A new wide-band analogue correlator system is being prepared for installation at Narrabri in early October. This will replace the 4-GHz bandwidth single-baseline system used last year with an 8-GHz bandwidth three-baseline-system. The new system makes full use of the maximum bandwidth available from the new 12-mm receivers and should result in a significant increase in sensitivity. An interesting feature of the new system is the use of ATNF designed wide-band analogue multipliers, developed under the Executive Special Projects program. These devices were fabricated using the TRW indium phosphide (InP) hetero-junction bipolar transistor (HBT) process and are the second application of this process in ATNF instruments. The first was the use of fast 2-bit sampler circuits in the Parkes wide-band correlator system. Both of these circuits were developed by Paul Roberts who has also done the design of the 16-lag correlators. Each correlator has 16 InP analogue multiplier chips fed from splitter/delay line circuits to provide measurements of the degree of correlation of the input signals at 16 different delays (Figure 1).
The three-baseline system will use three ATCA antennas spaced at 30-m increments. Like the single-baseline system from last year it will operate in a meridian transit mode, thereby avoiding the difficult problem of providing continuously variable delays on the 8-GHz bandwidth analogue IF signals.
Another major installation comes later in October when the new dual-band 10/50-cm pulsar receiver is due for delivery to Parkes. The new receiver, together with the wide-band pulsar correlator, will provide a 1-GHz bandwidth capability for pulsar observations at 10-cm wavelength.
Other major projects keeping us busy at the moment are the 3-mm upgrade for the ATCA, the 21-cm multibeam receiver for Arecibo and the 8-GHz spectrometer for Mopra. All of these are due for delivery over the next year.
Warwick Wilson
(Warwick.Wilson@csiro.au)