In this paper, we have concentrated on the technical description and first application of a new type of pulsar instrument for baseband signal acquisition and processing, the S2 baseband processing system (S2-BPS) employing the S2 recording system. By virtue of its low capital and operations cost and extended recording and playback periods, the S2 has gained widespread acceptance and use in the radio astronomy community. It is currently in use at numerous radio observatories world-wide for VLBI observations. It is also being used for pulsar baseband recording. At the pulsar processing centers, the S2-TCI allows for maximum flexibility in analyzing the pulsar data at the highest theoretical time resolution. A single S2 records 128 Mbits/s and yields 31 ns sample time resolution. Pulsar applications requiring greater bandwidth and higher time resolution can readily use multiple S2's, both during acquisition and processing. Of particular note is the reliability of the S2, which enables tight embedded interaction with the controlling computer, necessary for successful automated, unattended processing of the large data volumes implied by pulsar baseband processing applications. This system has applications in many areas of pulsar research including pulsar timing, pulsar searches, and single pulse studies, and should also find applications in other challenging scientific and instrumentation applications.
Future extensions to the current generation of baseband processing systems, such as the S2-BPS described in this paper, could involve direct interface of tape recorder systems or even radio telescope acquisition systems to super computers, thus eliminate the present bottleneck of the intermediary computer in present implementations. Evolving computer network standards, such as "Gigabit ethernet", will also help in this regard. These systems could implement the next step towards even higher volume and faster processing throughput in the demanding data-intensive applications described here.
The authors wish to thank M. Bailes from the Swinburne University of Technology, and J. Reynolds and W. Wilson from the Australian Telescope National Facility for their assistance in acquiring the 1995 Vela pulsar demonstration data from the Parkes radio telescope.
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