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A real-time coherent dedispersion pipeline for the giant metrewave radio telescope

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Abstract

A fully real-time coherent dedispersion system has been developed for the pulsar back-end at the Giant Metrewave Radio Telescope (GMRT). The dedispersion pipeline uses the single phased array voltage beam produced by the existing GMRT software back-end (GSB) to produce coherently dedispersed intensity output in real time, for the currently operational bandwidths of 16 MHz and 32 MHz. Provision has also been made to coherently dedisperse voltage beam data from observations recorded on disk. We discuss the design and implementation of the real-time coherent dedispersion system, describing the steps carried out to optimise the performance of the pipeline. Presently functioning on an Intel Xeon X5550 CPU equipped with a NVIDIA Tesla C2075 GPU, the pipeline allows dispersion free, high time resolution data to be obtained in real-time. We illustrate the significant improvements over the existing incoherent dedispersion system at the GMRT, and present some preliminary results obtained from studies of pulsars using this system, demonstrating its potential as a useful tool for low frequency pulsar observations. We describe the salient features of our implementation, comparing it with other recently developed real-time coherent dedispersion systems. This implementation of a real-time coherent dedispersion pipeline for a large, low frequency array instrument like the GMRT, will enable long-term observing programs using coherent dedispersion to be carried out routinely at the observatory. We also outline the possible improvements for such a pipeline, including prospects for the upgraded GMRT which will have bandwidths about ten times larger than at present.

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Acknowledgments

We would like to thank the staff members from NCRA who have helped at various stages of this work. We acknowledge the support of the back-end team at the GMRT who have provided support for the computing infrastructure that was required for this work. We would particularly like to thank Mr. S. S. Kudale from the GMRT digital back-end team for useful inputs on the voltage-beam mode of the telescope. The GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research.

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Authors and Affiliations

  1. Indian Institute of Science, Bangalore, 560012, India

    Kishalay De

  2. National Centre for Radio Astrophysics, TIFR, Pune University Campus, Post Bag 3, Pune, 411 007, India

    Yashwant Gupta

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  1. Kishalay De
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Correspondence to Kishalay De.

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The work was carried out as a part of the Student Training Programme of the National Centre for Radio Astrophysics (NCRA), Pune, using equipment and facilities funded by NCRA. Kishalay De was visiting Yashwant Gupta at NCRA, Pune during the working period. Kishalay De’s participation in the project was supported by a fellowship from the Kishore Vaigyanik Protsahan Yojana (KVPY) scheme of the Department of Science and Technology, Government of India, which promotes research careers for undergraduate students.

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De, K., Gupta, Y. A real-time coherent dedispersion pipeline for the giant metrewave radio telescope. Exp Astron 41, 67–93 (2016). https://doi.org/10.1007/s10686-015-9476-8

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