Technical Paper J. Astron. Space Sci. 28(4), 319-332 (2011) http://dx.doi.org/10.5140/JASS.2011.28.4.319 Visibility Analysis of Domestic Satellites on Proposed Ground Sites for Optical Surveillance Jae-Hyuk Kim1,2†, Jung Hyun Jo1, Jin Choi1, Hong-Kyu Moon1, Young-Jun Choi1, Hong-Suh Yim1, Jang-Hyun Park1, Eun-Seo Park1, and Jong-Uk Park1 1Korea Astronomy and Space Science Institute, Daejeon 305-348, Korea 2Department of Astronomy, Yonsei University, Seoul 120-749, Korea The objectives of this study are to analyze the satellite visibility at the randomly established ground sites, to determine the five optimal ground sites to perform the optical surveillance and tracking of domestic satellites, and to verify the ac- quisition of the optical observation time sufficient to maintain the precise ephemeris at optimal ground sites that have been already determined. In order to accomplish these objectives, we analyzed the visibility for sun-synchronous orbit satellites, low earth orbit satellites, middle earth orbit satellites and domestic satellites as well as the continuous visibility along with the fictitious satellite ground track, and calculate the effective visibility. For the analysis, we carried out a series of repetitive process using the satellite tool kit simulation software developed by Analytical Graphics Incorporated. The lighting states of the penumbra and direct sun were set as the key constraints of the optical observation. The minimum of the observation satellite elevation angle was set to be 20 degree, whereas the maximum of the sun elevation angle was set to be -10 degree which is within the range of the nautical twilight. To select the candidates for the optimal optical ob- servation, the entire globe was divided into 84 sectors in a constant interval, the visibility characteristics of the individual sectors were analyzed, and 17 ground sites were arbitrarily selected and analyzed further. Finally, five optimal ground sites (Khurel Togoot Observatory, Assy-Turgen Observatory, Tubitak National Observatory, Bisdee Tier Optical Astronomy Observatory, and South Africa Astronomical Observatory) were determined. The total observation period was decided as one year. To examine the seasonal variation, the simulation was performed for the period of three days or less with respect to spring, summer, fall and winter. In conclusion, we decided the optimal ground sites to perform the optical sur- veillance and tracking of domestic satellites and verified that optical observation time sufficient to maintain the precise ephemeris could be acquired at the determined observatories. Keywords: optical surveillance, visibility analysis, dawn-dusk orbit, sun-synchronous orbit, ground track analysis, do- mestic satellites 1. INTRODUCTION orbit tracking are superior to the orbit measurement by means of optical observation in terms of precision and The attempt to determine satellite orbit and maintain accuracy. Among these orbit observation methods, SLR the ephemeris through optical observation has been and GPS orbit tracking require the installation of a laser continuously made since Sputnik I was launched in retro-reflector array (LRRA) or a GPS receiver (Pearlman 1957 (King-Hele 1983). The methods that are generally et al. 2002). The orbit of the objects with which mutual used for orbit observation such as satellite laser ranging communication is impossible, such as space debris or (SLR), radar tracking and global positioning system (GPS) discarded satellites, cannot be determined by these two This is an Open Access article distributed under the terms of the Received Aug 03, 2011 Revised Aug 25, 2011 Accepted Aug 31, 2011 Creative Commons Attribution Non-Commercial License (http://cre- †Corresponding Author ativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, E-mail: [email protected] provided the original work is properly cited. Tel: +82-42-865-2185 Fax: +82-42-861-5610 Copyright © The Korean Space Science Society 319 http://janss.kr pISSN: 2093-5587 eISSN: 2093-1409 J. Astron. Space Sci. 28(4), 319-332 (2011) methods. However, the orbit determination by optical ary and December, 2010. The subject satellite was Korea observation is not dependent on the transmission and multi-purpose satellite-2 (KOMPSAT-2). Table 1 summa- reception of specific observation data. Refer to Kim et al. rizes the specification of KOMPSAT-2. The orbit propa- (1987) for detailed information on optical observation. If gator used for the simulation was the simplified general only the observable optical visibility and sufficient obser- perturbations propagator (SGP4)1 that receives the two- vation time are allowed, the satellite ephemeris can be line elements (TLE) provided by Analytical Graphics In- maintained or improved by estimating the observation corporated (AGI) as the input orbital elements to predict position on the celestial sphere in advance on the basis the orbit. of the orbital elements of a given satellite. The important KOMPSAT-2, a domestic sun-synchronous orbit (SSO) factors for this process are the effective range and possible satellite, was observationally visible only in the high lati- frequency of the optical observation with reference to the tude region (north latitude 34 degrees or higher or south ground. To explain the efficiency of optical observation latitude 30 degrees or higher) as shown in Fig. 2. For about to maintain satellite ephemeris, the optimal ground sites 300 astronomical observatories including ground-based with the higher visibility should be determined first, and astronomical facilities and overseas observatories in the the effective visibility (EV) of each observatory should be analyzed (Jo 2011). Table 1. KOMPSAT-2 satellite and orbit specification.* Satellite information Launch date 20060728 2. VISIBILITY ANALYSIS OF SUN-SYNCHRONOUS Projectile Rokot rocket ORBIT SATELLITES ON SECTORIZED FICTITOUS Launch site Plesetsk, Russia Mass 800 kg GROUND SITES Diameter 200 cm Height 280 cm Basically, for all the simulation process, the maximum Orbital elements of the sun elevation angle was set to be -10 degree which Perigee 656.2999877929688 km is within the range of the nautical twilight. The lighting Apogee 680.9000244140625 km Orbital period 98.5999984741211 min states of the penumbra and direct sun were set as the Inclination 98.0999984741211 deg key constraints. The minimum of the observation satel- Eccentricity 0.0017455226043239236 lite elevation angle was set to be 20 degree, which is the Orbit SSO KOMPSAT-2: Korea multi-purpose satellite-2, SSO: sun-synchronous orbit. consideration of the light pollution and local sites. To an- * http://en.wikipedia.org/wiki/Arirang-2 [cited 2011 Feb 4] alyze the visibility, 84 fictitious ground sites were set in a 30° interval for the earth’s latitude and longitude (Fig. 1). 1http://www.stk.com/resources/help/online/stk/source/stk/vehsat_orbitprop_ The entire simulation period was one year between Janu- choose.htm [cited 2011 Feb 2] Fig. 1. Eighty-four sectorized fictitious ground sites are positioned every 30 deg (30° × 30°), and the text color means same latitude mark, the ground track displayed in the figure is by Korea multi-purpose satellite-2 (KOMPSAT-2). http://dx.doi.org/10.5140/JASS.2011.28.4.319 320 Jae-Hyuk Kim et al. Visibility Analysis for Optical Surveillance list of astronomical observatories2, we checked out the tration-18 (NOAA-18) satellite (Fig. 4) had the widest visi- weather conditions, number of clearly sky days, and pro- bility range which was north latitude 25 degrees or higher vision of the communication and technological support. or south latitude 30 degrees or higher. Excluding the candidate observatories in the countries that are difficult to approach because of international po- litical reasons, 17 candidate observatories were set as in 3. VISIBILITY ANALYSIS OF LOW EARTH ORBIT Table 2. The visibility for the SSO satellites that are gener- AND MIDDLE EARTH ORBIT SATELLITES ON ally known at the determined observatories was verified PROPOSED 17 GROUND SITES as shown in Table 3. The GeoEye satellite (Fig. 3) had the most narrow visibility range which was north latitude 35 Before analyzing the visibility of the low earth orbit degrees or higher or south latitude 40 degrees or higher, (LEO) satellites and middle earth orbit (MEO) satellites, whereas the national oceanic and atmospheric adminis- we verified if it was possible to categorize currently op- erating satellites according to orbital elements, and if the 2http://en.wikipedia.org/wiki/List_of_astronomical_observatories [cited 2011 Feb 7] categorized groups had the visibility characteristics. Fig. 2. Visibility of KOMPSAT-2 on 84 sectorized fictitious ground sites is drawn in topocentric horizon, and the results of same latitude are represented same colors (Kim 2011a). Table 2. Characteristics of proposed 17 ground sites (Moon 2011). Proposed ground sites Latitude (deg) Longitude (deg) Elevation (m) Main telescope Khurel Togoot Observatory 47.865 107.0536111 1,620 0.4 m Indian Astronomical Observatory 32.77944444 78.96416667 4,500 2 m Assy-Turgen Observatory 43.22444444 77.87138889 2,665 1 m RC Tien-Shan Observatory 43.95 76.95 2,800 1 m RC Pamir High-Mountain Observatory 38 74 4,350 0.7 m RC Sanglokh Observatory 38.2 69 2,300 1 m RC Mount Dushak-Erekdag Observatory 37.95583333 57.90583333 2,020 1 m Wide-field Maidanak Observatory 38.6725 66.90083333 2,000 1.5 m Roque de Los Muchachos Observatory 28.76666667 -17.88333333