Journal of the Korean Astronomical Society https://doi.org/10.5303/JKAS.2021.54.3.89 54: 89 ∼ 102, 2021 June pISSN: 1225-4614 · eISSN: 2288-890X Published under Creative Commons license CC BY-SA 4.0 http://jkas.kas.org SOMANGNET:SMALL TELESCOPE NETWORK OF KOREA Myungshin Im1,2, Yonggi Kim3,4, Chung-Uk Lee5, Hee-Won Lee6, Soojong Pak7,8, Hyunjin Shim9, Hyun-Il Sung5, Wonseok Kang10, Taewoo Kim10, Jeong-Eun Heo11, Tobias C. Hinse12, Masateru Ishiguro1,2, Gu Lim1,2, Cuc T. K. Ly´12, Gregory S. H. Paek1,2, Jinguk Seo1,2, Joh-na Yoon4, Jong-Hak Woo1,2, Hojae Ahn7, Hojin Cho1,2, Changsu Choi1,2, Jimin Han7, Sungyong Hwang1,2, Tae-Geun Ji7, Seong-Kook J. Lee1,2, Sumin Lee8, Sunwoo Lee7, Changgon Kim7, Dohoon Kim8, Joonho Kim1,2, Sophia Kim1,2, Mankeun Jeong1,2, Bomi Park1,2, Insu Paek1,2, Dohyeong Kim13, and Changbom Park14 1SNU Astronomy Research Center, Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 08826, Korea; [email protected] 2Astronomy Program, Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 08826, Korea 3Dept. of Astronomy & Space Science, Chungbuk National University, Chungdae-ro, Seowon-gu, Cheongju, Cheongbuk 28644, Korea 4Chungbuk National University Observatory, Eunjin-ro 29, Munbaek-Myeon, Jincheon-gun, Cheongbuk 27867, Korea 5Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Korea 6Department of Astronomy and Space Science, Sejong University, 209 Neungdong-ro, Kwangjin-gu, Seoul 05006, Korea 7School of Space Research, Kyung Hee University, 1732 Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 17104, Korea 8Department of Astronomy and Space Science, Kyung Hee University, 1732 Deogyeong-daero, Gigeung-gu, Yongin-si, Gyeonggi-do 17104, Korea 9Department of Earth Science Education, Kyungpook National University, 80 Daehak-rho, Buk-gu, Daegu, 41566, Korea 10National Youth Space Center, Goheung, Jeollanam-do, 59567, Korea 11Gemini Observatory/NSF's National Optical-Infrared Astronomy Research Laboratory, Casilla 603, La Serena, Chile 12Department of Astronomy, Space Science and Geology, Chungnam National University, 99 Daehak-ro, 34134 Daejeon, South Korea 13Department of Earth Sciences, Pusan National University, Busan 46241, Korea 14Korea Institute for Advanced Study, 85 Hoegi-ro, Dongdaemun-gu, Seoul 02455, Korea Received January 29, 2021; accepted April 28, 2021 Abstract: Even in an era where 8-meter class telescopes are common, small telescopes are considered very valuable research facilities since they are available for rapid follow-up or long term monitoring observations. To maximize the usefulness of small telescopes in Korea, we established the SomangNet, a network of 0.4{1.0 m class optical telescopes operated by Korean institutions, in 2020. Here, we give an overview of the project, describing the current participating telescopes, its scientific scope and operation mode, and the prospects for future activities. SomangNet currently includes 10 telescopes that are located in Australia, USA, and Chile as well as in Korea. The operation of many of these telescopes currently relies on operators, and we plan to upgrade them for remote or robotic operation. The latest SomangNet science projects include monitoring and follow-up observational studies of galaxies, supernovae, active galactic nuclei, symbiotic stars, solar system objects, neutrino/gravitational-wave sources, and exoplanets. Key words: telescopes | methods: observational | instrumentation: photometers | instrumentation: spectrographs | surveys 1.I NTRODUCTION future. Indeed, small telescopes played important roles Small telescopes, namely optical telescopes with the in the first identification and the immediate follow-up primary mirror aperture sizes at a range of ∼0.4{1 m, observations of the electromagnetic (EM) counterpart of are still considered valuable research facilities. Despite the gravitational wave (GW) event GW170817 (e.g., Ab- their limited light gathering power in comparison to bott et al. 2017a; Arcavi et al. 2017; Coulter et al. 2017; 4-to-8 meter class telescopes, the small telescopes have Lipunov et al. 2017; Valenti et al. 2017; Im et al. 2017; specific advantages like wide fields of view thanks to Troja et al. 2017). Small telescopes have continued to their short focal lengths, and readily available telescope play important roles in MMA for performing follow-up time that is suitable for intense monitoring observations observations of GW sources (e.g., Agayeva et al. 2020; and follow-up observations of transients. Im et al. 2020) as well as neutrino sources (e.g., Hwang With the advance of time-domain astronomy and et al. 2021; Morokuma et al. 2021). Small telescopes multi-messenger astronomy (MMA), the importance of are also supporting time-critical observations and rapid small telescopes is expected to rise even more in the near transient follow-ups. As a result, there exist a number of networks of small telescopes located worldwide, e.g., Corresponding author: M. Im 89 90 Im et al. (SomangNet Collaboration) Korea 60°N LOAO WIT 30°N SAO, KHAO 0° CBNUO LSGT KCT, RASA36 30°S DOAO 60°S 30°W 0° 30°E 60°E 90°E 120°E 150°E 180° 150°W 120°W 90°W 60°W 30°W Figure 1. The locations of the SomangNet telescopes. SomangNet includes telescopes on several sites across the world. the Las Cumbres Observatory Global Telescope Net- ing of knowledge and pave the way for new syner- work, LCOGT (Brown et al. 2013), the Global Rapid getic projects. Running observatories requires hands-on Advanced Network Devoted to the Multi-messenger Ad- know-how to fix problems encountered during the ob- dicts, GRANDMA (Agayeva et al. 2020), the Optical servatory operation, and a common collaborative frame- and Infrared Synergetic Telescopes for Education and work provides a way to exchange knowledge and tech- Research, OISTER (e.g., Itoh et al. 2013; Ishiguro et nical/scientific resources for mutual benefits. The com- al. 2015), the Burst Observer and Optical Transient Ex- bined capabilities of these telescopes will allow more ploring System, BOOTES (Castro-Tirado et al. 1999), science projects to be carried out than what would be Global Relay of Observatories Watching Transients Hap- possible for a single facility. pen, GROWTH (e.g., Kasliwal et al. 2019), the Mobile With these advantages in mind, we started a project Astronomical System of Telescope-Robots, MASTER to systematically organize Korean-owned small tele- (Lipunov et al. 2004; Gorbovskoy et al. 2013), the All-Sky scopes for astronomical research. The project is named Automated Survey for Supernovae, ASAS-SN (Shappee SomangNet, where the word \Somang" has two mean- et al. 2014; Kochanek et al. 2017), and the Catalina ings in Korean: it is an abbreviation of \small telescope", Real-time Transient Survey, CRTS (Drake et al. 2009). and also means \wish". The project idea was first dis- In Korea, there are dozens of small optical tele- cussed in 2019 within the Optical/IR/UV Astronomy scopes with apertures ∼0.4 m or larger, but most of division of the Korean Astronomical Society, and after them are being used for educational activities, and reg- a short preparation period, the project started in 2020 ular, full night operations of small telescopes are rare. with support from various organizations. Connecting these telescopes together for a common pur- In this paper, we give an overview of the SomangNet. pose can provide a number of advantages. Section2 summarizes the SomangNet telescopes and their capabilities, Section3 describes the way how So- First, it can mitigate the bad weather conditions in mangNet is being run, and Sections4 and5 describe Korea for a more efficient execution of observational pro- the current and future science projects and educational grams. Since various telescopes are located all over the activities of SomangNet. Future prospects and the sum- country, a single observational program can be carried mary of the paper are given in Section6. out at one of the sites that happens to have good weather even if the other sites suffer from bad weather at that 2.S OMANGNET TELESCOPES time. This is especially advantageous for time-critical Currently, there are 10 telescopes participating in So- observation with a stringent time window. mangNet. These telescopes are all operated by Korean Second, mutual collaboration allows researchers to institutions. Many of these are only capable of imaging access telescopes with different capabilities and instru- observations, but a few of them have wide-field imaging ments. Some telescopes can be suited for wide-field (> 1 deg) or spectroscopy capabilities. Some of the surveys, and there can be other telescopes with spec- telescopes are located in the USA, Chile, and Australia, troscopic capabilities. Sharing of these resources opens allowing SomangNet to access the southern sky and access for a wide range of observational programs. time zones that cannot be covered by facilities in Korea. Third, collaborative activities can lead to the shar- The locations of the SomangNet telescopes are shown SomangNet: Small Telescope Network of Korea 91 in Figure1, and the capabilities of these telescopes are pointing based on astrometry (Ji et al. 2021, in prepa- summarized in Table1. We provide short descriptions ration). The script mode of KAOS enables automatic of the SomangNet telescopes below, in order of the ob- observations that follow a preset schedule written in a servatory longitude from the Prime Meridian toward predefined script format. Typical seeing FWHM values east. have been recorded as 200: 0, although sub-arcsec seeing has been reported at rare occasions. The point-source, 2.1. SNU Astronomical Observatory (SAO) 1.0 m 5-σ limiting magnitude is about R ∼ 18 AB mag with Telescope 5 min of single exposure under clear and dark sky with The SAO 1 m telescope saw the first light in March 2018, the typical seeing. and since then has been used regularly for educational activities and research-oriented observations.