The Zwicky Transient Facility: Surveys and Scheduler

Creators: Bellm, Eric C.; Kulkarni, Shrinivas R.; Barlow, Tom; Feindt, Ulrich; Graham, Matthew J.; Goobar, Ariel; Kupfer, Thomas; Ngeow, Chow-Choong; Nugent, Peter; Ofek, Eran; Prince, Thomas A.; Riddle, Reed; Walters, Richard; Ye, Quan-Zhi

Abstract

We present a novel algorithm for scheduling the observations of time-domain imaging surveys. Our integer linear programming approach optimizes an observing plan for an entire night by assigning targets to temporal blocks, enabling strict control of the number of exposures obtained per field and minimizing filter changes. A subsequent optimization step minimizes slew times between each observation. Our optimization metric self-consistently weights contributions from time-varying airmass, seeing, and sky brightness to maximize the transient discovery rate. We describe the implementation of this algorithm on the surveys of the Zwicky Transient Facility and present its on-sky performance.

Additional Information

© 2019. The Astronomical Society of the Pacific. Received 2019 January 2; accepted 2019 March 2; published 2019 April 29. E.C.B. thanks Eric Saunders, Ben Shappee, Lynne Jones, and Peter Yoachim for useful conversations. Based on observations obtained with the Samuel Oschin Telescope 48 inch and the 60 inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. Z.T.F. is supported by the National Science Foundation under grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Program of the University System of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. E.C.B. is supported in part by the NSF AAG grant 1812779 and grant #2018-0908 from the Heising-Simons Foundation. E.C.B. also acknowledges support from the Large Synoptic Survey Telescope, which is supported in part by the National Science Foundation through Cooperative Agreement 1258333, managed by the Association of Universities for Research in Astronomy (AURA), and the Department of Energy under Contract No. DE-AC02-76SF00515 with the SLAC National Accelerator Laboratory. Additional LSST funding comes from private donations, grants to universities, and in-kind support from LSSTC Institutional Members. E.C.B. is grateful for further support from the University of Washington College of Arts and Sciences, Department of Astronomy, and the DIRAC Institute. University of Washington's DIRAC Institute is supported through generous gifts from the Charles and Lisa Simonyi Fund for Arts and Sciences, and the Washington Research Foundation. E.O.O. is grateful for support by grants from the Willner Family Leadership Institute, Ilan Gluzman (Secaucus NJ), the Israel Science Foundation, Minerva, BSF, BSF-transformative, Weizmann-UK, and the I-Core program by the Israeli Committee for Planning and Budgeting and the Israel Science Foundation (ISF). Facility: PO:1.2 m. - Software: Astropy (The Astropy Collaboration et al. 2018), Astroplan (Morris et al. 2018b), Numpy (Van Der Walt et al. 2011), Scipy (Jones et al. 2001), pandas (McKinney 2010), Matplotlib (Hunter 2007), Seaborn (Waskom et al. 2018), Scikit-Learn (Pedregosa et al. 2011), xgboost (Chen & Guestrin 2016), Gurobi (Gurobi Optimization 2018), makecite (Price-Whelan et al. 2018).

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