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Published January 1, 2019 | Published
Journal Article Open

The Caltech-NRAO Stripe 82 Survey (CNSS). II. On-the-fly Mosaicking Methodology


Telescope slew and settle time markedly reduce the efficiency of wide-field multi-epoch surveys for sensitive interferometers with small fields of view. The overheads can be mitigated through the use of on-the-fly mosaicking (OTFM), where the the antennas are driven at a non-sidereal rate and visibilities are recorded continuously. Here we introduce the OTFM technique for the Very Large Array (VLA), and describe its implementation for the Caltech-NRAO Stripe 82 Survey (CNSS), a dedicated five-epoch survey for slow transients at the S band (2–4 GHz). We also describe the OTFSim tool for planning dynamically scheduled OTFM observations on the VLA, the latest imaging capabilities for OTFM in CASA, and present a comparison of OTFM observations with pointed observations. Using the subset of our observations from the CNSS pilot and final surveys, we demonstrate that the wide-band and wide-field OTFM observations with the VLA can be imaged accurately, and that this technique offers a more efficient alternative to standard mosaicking for multi-epoch shallow surveys such as the CNSS and the VLA Sky Survey. We envisage that the new OTFM mode will facilitate new synoptic surveys and high-frequency mapping experiments on the VLA.

Additional Information

© 2018. The American Astronomical Society. Received 2018 May 3; revised 2018 October 31; accepted 2018 November 6; published 2018 December 31. The authors would like to thank Urvashi Rau and Sanjay Bhatnagar for developing (and implementing in CASA) the algorithms used extensively in this work. We are also grateful to Barry Clark, Michael Rupen, and other NRAO staff who provided extensive support during the commissioning of the OTFM observing mode. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. K.P.M. is currently a Jansky Fellow of the National Radio Astronomy Observatory.

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Published - Mooley_2019_ApJ_870_25.pdf


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August 22, 2023
August 22, 2023