The UTMOST: A hybrid digital signal processor transforms the MOST

Abstract

The Molonglo Observatory Synthesis Telescope (MOST) is an 18,000 square meter radio telescope situated some 40 km from the city of Canberra, Australia. Its operating band (820-850 MHz) is now partly allocated to mobile phone communications, making radio astronomy challenging. We describe how the deployment of new digital receivers (RX boxes), Field Programmable Gate Array (FPGA) based filterbanks and server-class computers equipped with 43 GPUs (Graphics Processing Units) has transformed MOST into a versatile new instrument (the UTMOST) for studying the dynamic radio sky on millisecond timescales, ideal for work on pulsars and Fast Radio Bursts (FRBs). The filterbanks, servers and their high-speed, low-latency network form part of a hybrid solution to the observatory's signal processing requirements. The emphasis on software and commodity off-the-shelf hardware has enabled rapid deployment through the re-use of proven 'software backends' for its signal processing. The new receivers have ten times the bandwidth of the original MOST and double the sampling of the line feed, which doubles the field of view. The UTMOST can simultaneously excise interference, make maps, coherently dedisperse pulsars, and perform real-time searches of coherent fan beams for dispersed single pulses. Although system performance is still sub-optimal, a pulsar timing and FRB search programme has commenced and the first UTMOST maps have been made. The telescope operates as a robotic facility, deciding how to efficiently target pulsars and how long to stay on source, via feedback from real-time pulsar folding. The regular timing of over 300 pulsars has resulted in the discovery of 7 pulsar glitches and 3 FRBs. The UTMOST demonstrates that if sufficient signal processing can be applied to the voltage streams it is possible to perform innovative radio science in hostile radio frequency environments.

12 pages, 6 figures

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• The Host Galaxy and Redshift of the Repeating Fast Radio Burst FRB 121102
• DiFX: A software correlator for very long baseline interferometry using multi-processor computing environments
• The Molonglo Galactic Plane Survey (MGPS-2): Compact Source Catalogue
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• The 2018 X-ray and Radio Outburst of Magnetar XTE J1810-197
• Synthesizing the intrinsic FRB population using frbpoppy
• A Survey of the Galactic Plane for Dispersed Pulses with the Australian Square Kilometre Array Pathfinder
• MeerTRAP: Twelve Galactic fast transients detected in a real-time, commensal MeerKAT survey
• Estimating fast transient detection pipeline efficiencies at UTMOST via real-time injection of mock FRBs
• Radio observations of two intermittent pulsars: PSRs J1832+0029 and J1841-0500
• Hunting for radio emission from the intermittent pulsar J1107-5907 at low frequencies
• Systematic upper limits on the size of missing pulsar glitches in the first UTMOST open data release
• The Low Frequency Perspective on Fast Radio Bursts
• Constraints on wide-band radiative changes after a glitch in PSR J1452-6036
• History of Astronomy in Australia: Big-Impact Astronomy from World War II until the Lunar Landing (1945-1969)
• Detection of a Glitch in PSR J0908$-$4913 by UTMOST