First light with the Mopra Spectrometer (MOPS)


First light for the new Mopra MOPS digital filterbank.

As part of a major upgrade program, a new millimetre receiver system (see the separate page) and backend system have just been installed at Mopra. The backend produces two 8-GHz bandwidth IFs from each polarisation, and is capable of observing several spectral lines simultaneously.

The broadband signal channels are transmitted to the Mopra Spectrometer, MOPS, installed in the Mopra equipment room via broad band analogue fibre optic links. Each 8-GHz IF is then split into four 2.2-GHz bandwidth channels and down converted to the base band.

Every 2.2-GHz base band IF signal is digitised by a 2-bit 4.4 Gsample/sec Indium Phosphide digitiser. The digitisers were developed at ATNF and fabricated at TRW in March 2000, under the CSIRO Special Executive program.

A dual-channel Polyphase Digital Filter Bank spectrometer, capable of processing two 2.2GHz IFs was commissioned at Mopra by ATNF staff from Epping and Narrabri on 14 October. The spectrometer is currently configured to produce two zoom spectra from each IF. The zoom spectra have a bandwidth of 137.5 MHz and 4000 spectral channels. Two spectral separations of 825 MHz and 1650 MHz are offered, per IF.

Commissioning of the first segment of the MOPS system marks a major milestone in the development of ATNF broadband backends. In 2006 the full MOPS system (able to observe 8 spectral lines simultaneously) will be complete, and the broadband upgrade of the Compact Array will be in full swing.

Dual polarisation spectra showing C34S emission at 96.372 GHz (top row) and CS emission at 98.022 GHz (bottom row) from the supergiant star VX Sgr. The spectra were obtained simultaneously using the new MOPS spectrograph.
Credit: Warwick Wilson, ATNF

The first on-the-fly map obtained at the Mopra telescope using the new MOPS spectrometer. The image shows part of a molecular cloud that is being studied in the Delta Quadrant Survey. Here, the grey-scale image shows emissions from CS at 98.022 GHz while the contours show the C34S emission at 96.273 GHz.
Credit: Michael Burton, UNSW
Original: Mark Leach (20-Oct-2005)