Jang-Hyun Park, Korea Astronomy and Space Science Institute; Hong-Suh Yim, Korea Astronomy and Space Science Institute; Young-Jun Choi, Korea Astronomy and Space Science Institute (KASI) / University of Science and Technology (UST); Jung Hyun Jo, Korea Astronomy and Space Science Institute; Hong-Kyu Moon, Korea Astronomy and Space Science Institute; Young-Sik Park, Korea Astronomy and Space Science Institute; Dong-Goo Roh, Korea Astronomy and Space Science Institute; Sungki Cho, Korea Astronomy and Space Science Institute; Eun-Jung Choi, Korea Astronomy and Space Science Institute; Myung-Jin Kim, Korea Astronomy and Space Science Institute; Jin Choi, Korea Astronomy and Space Science Institute (KASI) / University of Science and Technology (UST)
Keywords: Satellite tracking, robotic telescope, optical observation
Abstract:
The OWL-Net (Optical Wide-field patroL Network) is composed of 0.5m wide-field optical telescopes spread over the globe (Mongolia, Morocco, Israel, South Korea, and USA). All the observing stations are identical, operated in a fully robotic style, and controlled by the headquarters located in Daejeon, Korea. The main objective of the OWL-Net is to get orbital information of Korean LEO and GEO satellites using purely optical means and to maintain their orbital elements.
We have developed a telescope system (optical tube assembly, mount, telescope controller) and a station-keeping system (enclosure, dome, environment monitoring system) for robotic observation dedicated to satellite tracking. The aperture size of the mirror is 0.5m with Ritchey-Chretien configuration, and its field of view is 1.1 deg on the CCD sensor. The telescope is equipped with an electric-cooled 4K CCD camera with 9 um pixel size, and its pixel scale is 0.9 arcsec/pixel. A chopper wheel with variable speed is adopted to get multi points in a single exposure. Its rotation speed is accelerated from 0 to a constant value which makes differences in trail lengths and results in identification of the direction of motion. Each chopped trail has time-tagged information with a few milliseconds precision. The CCD camera and all the rotating parts (chopper wheel, de-rotator, and filter wheel) are integrated into one compact component called a wheel station. Each observatory is equipped with heavy duty environment monitoring system including weather sensors, cloud sensors, electric power sensors, security cameras, etc. for robust robotic observation.
The headquarters is composed of an observatory status monitoring system, an automatic scheduler, a network operating system (NOS), an orbit calculation server, and a database server. The NOS controls the headquarters and the whole observatory network. Schedules for observation are generated and updated automatically by the scheduler, and then translated into an observation command file (OCF) which is a pre-defined ASCII file. An OCF is transferred to each site via internet. The site operating system (SOS) receives the OCF, and then sends it to the telescope controller which interprets it and makes observations. Observed data is directly saved into the data storage and immediately reduced into time and coordinates data in an ASCII file. The SOS collects reduced data and environment monitoring data and all the information collected at each site is gathered into the headquarters in quasi real time.
The OWL-Net is a system developed to track LEO satellites at a relatively low cost using currently available technologies for optical observation. It is also designed as a multipurpose system capable of observing GEO satellites as well as LEO satellites and performing astronomical observations. The test phase operation of the whole system started early 2017 although test runs for individual sites started from 2015. The OWL-Net has 7 observation modes for artificial satellites and astronomical objects, but we are concentrating on a few modes for LEO satellites and calibration during the early phase. Some early results and analysis for system performance will be presented, and their implications will be discussed.
Date of Conference: September 11-14, 2018
Track: Optical Systems Instrumentation