Organized Autotelescopes for Serendipitous Event Survey (OASES): design and performance

Abstract

Organized Autotelescopes for Serendipitous Event Survey (OASES) is an optical observation project that aims to detect and investigate stellar occultation events by kilometer-sized trans-Neptunian objects (TNOs). In this project, multiple low-cost observation systems for wide-field and high-speed photometry were developed in order to detect rare and short-timescale stellar occultation events. The observation system consists of commercial off-the-shelf $0.28\mathrm{m}$ aperture $f/1.58$ optics providing a $2.3\times 1.8$ square-degree field of view. A commercial CMOS camera is coupled to the optics to obtain full-frame imaging with a frame rate greater than $10\mathrm{Hz}$. As of September 2016, this project exploits two observation systems, which are installed on Miyako Island, Okinawa, Japan. Recent improvements in CMOS technology in terms of high-speed imaging and low readout noise mean that the observation systems are capable of monitoring $\sim 2000$ stars in the Galactic plane simultaneously with magnitudes down to $\mathrm{V}\sim 13.0$, providing $\sim 20\%$ photometric precision in light curves with a sampling cadence of $15.4\mathrm{Hz}$. This number of monitored stars is larger than for any other existing instruments for coordinated occultation surveys. In addition, a precise time synchronization method needed for simultaneous occultation detection is developed using faint meteors. The two OASES observation systems are executing coordinated monitoring observations of a dense stellar field in order to detect occultations by kilometer-sized TNOs for the first time.

26 pages, 13 figures, accepted for publication in PASJ

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