Overview of the Tomo-e Gozen project
Tomo-e Gozen is an observation system including the worldfs first astronomical wide-field movie camera and artificial intelligence software, which is developed to explore the universe changing with short timescales (Fig. 1-3). The Tomo-e Gozen camera covers a field-of-view of 20 square degrees on the sky at once, corresponding to a total area of 84 full-moons, by 84 chips of high-sensitivity CMOS image sensors with a total 190 million pixels. This camera produces movie bigdata of the sky of 30 TBytes, corresponding to about 10 thousand cinemas, in a night. The software of Tomo-e Gozen can detect variations of brightness and positions of stellar objects precisely by comparing with data sets taken in past observations in real-time (Fig. 4-10).
(left: Fig. 1) Scientific meaning for studying the changing universe. (right: Fig. 2) Phenomena with timescales shorter than 1 day have not been sufficiently explored. A main purpose of Tomo-e Gozen is to reveal the unexplored universe.
- Movie 1(mp4): M27(planetary nebula) -> Altair (first-magnitude starj -> M11iopen star clusterj
- Movie 2(mp4): Sky areas 53-arcmin apart from (1) in the south direction
- Movie 3(mp4): Meteor and its trail crossing behind thin clouds
These movies are played at five times the real speed. Each movie is taken by a single sensor. Each exposure time of consecutive frames is 0.5 seconds.
The large-format high-sensitivity CMOS image sensors on the Tomo-e Gozen camera are not required to be cooled down like image sensors on other astronomical instruments because low dark current and low readout noise are achieved even at room temperature. This allows us to make a large size camera system (Fig. 11). The 84 chips of CMOS sensors are placed precisely along a spherical focal plane of the Schmidt telescope (Fig. 12). The Tomo-e Gozen camera and the telescope are automatically controlled by software with optimization algorisms on a computing system directly connected to the camera. Observation data is also automatically processed by software with machine learning models (Fig. 13). Since the observation data taken by the Tomo-e Gozen camera is too large, 30 TBytes/night, to keep it for a long time, it is deleted from a data storage in 7 days after the observations. The analysis software of Tomo-e Gozen saves only gattractive informationh to a long-term storage before it is deleted. Astronomers mine information interesting for themselves from the long-term storage by onsite computers. When interesting stellar objects and events are found, alerts for follow-up observations are sent to other observatories in the world quickly. In order to build a quick and smooth alert system, we will connect between an information center at Kiso and a data center at the Kashiwa campus of the University of Tokyo via a high-speed network (Fig. 14). Tomo-e Gozen automatically creates observation plans and executes them based on demands of astronomers, and reoptimizes the running plans according to changing weather conditions and additional astronomical information such as detections of transient events by other telescopes (Fig. 15).
Wide-field movie survey of the sky
Over 100 nights every year, Tomo-e Gozen carries out movie surveys of the sky repeatedly in a night (Fig. 16-18). These survey observations enable us to detect more than 130 thousand events of transient phenomena with short timescales of 1 second to 1 hour by monitoring brightness and positions of about 100 million sources on the observation images (Fig. 19-22). There is no precedent for such wide-field movie survey of the sky.
(left: Fig. 16) Overview of wide-field movie observations of the sky by Tomo-e Gozen. (right: Fig. 17) Scanning pattern. It fills gaps between sensors by moving the telescope slightly in 2x2 or 2x3 patterns.
Movie (mp4): Foot prints of Tomo-e Gozen in a wide-field movie survey.
It is expected that transient events found by Tomo-e Gozen include many scientifically important phenomena such as supernovae just after explosions and asteroids with possibility of collision to the Earth (Fig. 23-24). We have a collaboration plan between Tomo-e Gozen, the gravitational wave observatory KAGRA, and the 3.8-m SEIMEI telescope, which is operated by Kyoto university and NAOJ at Okayama, to reveal origins of gravitational waves (Fig.25). Since bigdata obtained by Tomo-e Gozen every night contains many events appearing on the sky comprehensively, data driven astronomy based on cooperation among multiple fields such as studies on Earthfs upper atmosphere, monitoring of satellites and space debris, and social outreaches with real science data is expected (Fig. 26).
(left: Fig. 25) Multi messenger astronomy by the gravitational wave observatory KAGRA, Tomoe- Gozen, and the 3.8-m SEIMEI telescope. (right: Fig. 26) Utilization of sky bigdata via high-speed networks.
Please credit images and movies on this site to Kiso Observatory, the University of Tokyo. ex) Image credit: Kiso Observatory, the University of Tokyo
- Tomo-e Gozen is a collaboration project with following institutes,
Research Center for the Early Universe, School of Science, the University of Tokyo; Department of Astronomy, School of Science, the University of Tokyo; National Astronomical Observatory of Japan; Japan Aerospace Exploration Agency; the Institute of Statistical Mathematics; Tohoku University; Kyoto University; Kyoto Sangyo University; Konan University; Kobe University; Japan Spaceguard Association; the Nippon Meteor Society
- Tomo-e Gozen is supported by following companies,
Canon Inc.; Interface Inc.; Oki Electric Cable Co., Ltd.; System works Corporation; Kiso Wide Area Information Center
- Tomo-e Gozen is supported by following funding agencies,
Japan Society for the Promotion of Science; Japan Science and Technology Agency; National Astronomical Observatory of Japan