Design of an Elliptical Orbit for High-Resolution Optical Observation at a Very Low Altitude over the Korean Peninsula

Dongwoo Kim,Taejin Chung The Korean Space Science Society 2023 Journal of Astronomy and Space Sciences Vol.40 No.1

Surveillance and reconnaissance intelligence in the space domain will become increasingly important in future battlefield environments. Moreover, to assimilate the military provocations and trends of hostile countries, imagery intelligence of the highest possible resolution is required. There are many methods for improving the resolution of optical satellites when observing the ground, such as designing satellite optical systems with a larger diameter and lowering the operating altitude. In this paper, we propose a method for improving ground observation resolution by using an optical system for a previously designed low orbit satellite and lowering the operating altitude of the satellite. When the altitude of a satellite is reduced in a circular orbit, a large amount of thrust fuel is required to maintain altitude because the satellite's altitude can decrease rapidly due to atmospheric drag. However, by using the critical inclination, which can fix the position of the perigee in an elliptical orbit to the observation area, the operating altitude of the satellite can be reduced using less fuel compared to a circular orbit. This method makes it possible to obtain a similar observational resolution of a medium-sized satellite with the same weight and volume as a small satellite. In addition, this method has the advantage of reducing development and launch costs to that of a small-sized satellite. As a result, we designed an elliptical orbit. The perigee of the orbit is 300 km, the apogee is 8,366.52 km, and the critical inclination is 116.56°. This orbit remains at its lowest altitude to the Korean peninsula constantly with much less orbit maintenance fuel compared to the 300 km circular orbit.

Minimum-Energy Spacecraft Intercept on Non-coplanar Elliptical Orbits Using Genetic Algorithms

Snyoll Oghim,이창열,이현재 한국항공우주학회 2017 International Journal of Aeronautical and Space Sc Vol.18 No.4

The objective of this study was to optimize minimum-energy impulsive spacecraft intercept using genetic algorithms. A mathematical model was established on two-body system based on f and g solution and universal variable to address spacecraft intercept problem for non-coplanar elliptical orbits. This nonlinear problem includes many local optima due to discontinuity and strong nonlinearity. In addition, since it does not provide a closed-form solution, it must be solved using a numerical method. Therefore, the initial guess is that a very sensitive factor is needed to obtain globally optimal values. Genetic algorithms are effective for solving these kinds of optimization problems due to inherent properties of random search algorithms. The main goal of this paper was to find minimum energy solution for orbit transfer problem. The numerical solution using initial values evaluated by the genetic algorithm matched with results of Hohmann transfer. Such optimal solution for unrestricted arbitrary elliptic orbits using universal variables provides flexibility to solve orbit transfer problems.

Minimum-Energy Spacecraft Intercept on Non-coplanar Elliptical Orbits Using Genetic Algorithms

Oghim, Snyoll,Lee, Chang-Yull,Leeghim, Henzeh The Korean Society for Aeronautical and Space Scie 2017 International Journal of Aeronautical and Space Sc Vol.18 No.4

The objective of this study was to optimize minimum-energy impulsive spacecraft intercept using genetic algorithms. A mathematical model was established on two-body system based on f and g solution and universal variable to address spacecraft intercept problem for non-coplanar elliptical orbits. This nonlinear problem includes many local optima due to discontinuity and strong nonlinearity. In addition, since it does not provide a closed-form solution, it must be solved using a numerical method. Therefore, the initial guess is that a very sensitive factor is needed to obtain globally optimal values. Genetic algorithms are effective for solving these kinds of optimization problems due to inherent properties of random search algorithms. The main goal of this paper was to find minimum energy solution for orbit transfer problem. The numerical solution using initial values evaluated by the genetic algorithm matched with results of Hohmann transfer. Such optimal solution for unrestricted arbitrary elliptic orbits using universal variables provides flexibility to solve orbit transfer problems.

Bézier Curves for Smooth Entry into Elliptic Orbits

Vladimir Shin,Mirzobek Malikov,김윤수 한국항공우주학회 2024 International Journal of Aeronautical and Space Sc Vol.25 No.2

This paper describes a path planning approach for smooth entry of an aerospace vehicle (ASV) into a 3D elliptic orbit. The generated path represents a polynomial Bézier curve connecting a given position of the ASV with the orbital entry point. Recursive and non-recursive analytical formulas for the last k intermediate control points determining Ck smooth Bézier path are derived. To evaluate the performance of the proposed approach, a practical measure of path smoothness such as path length, average curvature, and maximum curvature is introduced to choose the best entry point on the orbit and the corresponding Bézier path. The simulation results demonstrate that minimizing the maximum curvature yields a path that optimizes the proposed smoothness measure.

Linear time-varying model predictive control of magnetically actuated satellites in elliptic orbits

Kim, Jongbum,Jung, Youeyun,Bang, Hyochoong Elsevier 2018 Acta astronautica Vol.151 No.-

<P><B>Abstract</B></P> <P>Three-axis attitude control using only magnetic actuators has been considered a difficult task due to earth's time-varying magnetic field, the inherent under-actuation associated with this task, and constraints on control dipole moments. In this study, a linear time-varying model predictive control approach is applied to magnetically actuated satellites in elliptic low-earth orbits for nadir and inertial pointing. A linear time-varying model predictive control problem is formulated using an augmented state-space model based on small-angle approximations for both nadir and inertial-pointing nonlinear dynamics models. To reduce the on-line computational load, the model predictive control design for an inertial-pointing problem with Laguerre functions is proposed, and exponential data weighting is used to improve the numerically ill-conditioned problem. Nonlinear simulation results demonstrate the effectiveness of the proposed method.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Three-axis attitude control using only magnetorquers is presented. </LI> <LI> A state-space model is formulated for an elliptic orbit. </LI> <LI> The effectiveness of LTV-MPC formulation for nadir pointing is verified. </LI> <LI> The convergence of proposed method for inertial pointing is improved. </LI> </UL> </P>

나로과학위성의 운용 결과

강경인,임철우,신현진,이근우,이준찬,왕희집,김지철 한국항공우주학회 2014 한국항공우주학회 학술발표회 논문집 Vol.2014 No.4

우리나라 발사장에서 우주궤도로 진입한 첫 번째 위성인 나로과학위성은 나로호 발사체의 궤도 투입 성공 여부 확인, 우주환경 관측 및 국내 우주 기술의 우주 검증을 위한 임무를 가진 위성으로 임무 수명 기간 동안 국내 관제 기술로 성공적인 위성 운용을 수행하였다. 나로과학위성은 발사 시 근지점 298km, 원지점 1,504km 의 타원궤도로 하루에 약 14 바퀴씩 돌고 있으며, 임무수명 기간 동안 지상국과는 1,000 여회 교신했다. 그 동안 적외선영상센서의 우주 검증 시험을 위해 한반도 주변의 육지와 해양 등의 관측을 비롯하여 펨토초 레이저 발진기, 반작용 휠, 이온층 관측센서, 우주방사선량 측정센서 등의 탑재체 운용을 수행하였다. 각 탑재체별 임무수명은 기술검증 탑재체가 3 개월, 과학관측 임무가 1 년으로 2013 년 1 월 30 일 발사체의 궤도투입 검증을 시작으로 임무수행을 성공적으로 수행하였다. The STSAT-2C, Naro Science Satellite is a small satellite with 100kg mass, and was launched into an elliptical orbit of 298 ~ 1,504 km by the Korea Satellite Launch Vehicle, KSLV-1 at Naro Space Center in Korea. Missions are to verify the orbit injection of KSLV-1, space environment observation and new-developed space technology verification in orbit. During mission life, the STSAT-2C is communicated around 1,000 times by KAIST ground station. In terms of functional performance, the new developed space technologies are working well in orbit. The STSAT-2C was observed thermal images of lands and oceans by Infra-Red Sensor, tested functional performance of Femto-Second Laser Oscillator, Reaction Wheel and measured the space environments by Langmuir Probe, Space Radiation Dosimeter successfully since Jan. 30, 2013.

최적의 인공위성 인터셉트

이현재,박성용,이상기,방효충 한국항공우주학회 2013 한국항공우주학회 학술발표회 논문집 Vol.2013 No.11

본 연구는 인공위성의 인터셉트 문제를 시간지연을 고려하여, 에너지를 최소화하는 방법을 제안하였다. 대부분의 이와 같은 연구는 원궤도-원궤도, 동일 평면상에서 서술되어지는 것이 기본적이나 본 연구에서는 좀더 일반적인 궤도에 대해서 연구하였다. 기존의 궤도를 표현하기 위하여 새로운 운동 방정식으로 접근을 시도하였다. 본 연구에서는 2 가지 형태에 대해서 논하였다. 먼저 에너지를 최소화하는 방법에 대해서 논하였으며, 또한 시간지연을 고려한 에너지 최적화 문제를 고려하였다 비록 하나의 닫힌 형태의 해를 구할 수는 없었으나, 기초적은 수치방법을 사용하여 성공적으로 해를 도출하였다 마지막으로 수치적인 방법을 적용하여 본 연구의 적용가능성에 대해서 검증을 시도하였다. A new approach to the minimum energy impulse intercept problem for spacecraft in orbit is explored. The types of orbits investigated in this paper are not restricted to a particular one. The constrained optimization technique is formulated with the universal variable, which is used to describe orbit information with sufficient accuracy for general types of orbits. Two optimization problems are posed. First, a problem for minimum velocity change and time of flight for intercept are investigated with the constraint on the final position of two satellites. Next, the so-called wait time is also added as an additional parameter to be determined. Although a closed-form solution is not obtained, the Newton iteration technique is successfully applicable. Finally, by numerically comparing the proposed solution to the Hohmann transfer, the suggested approach is demonstrated to be a feasible technique applicable to a broad class of orbit transfer problems.

Design of an Elliptical Orbit Constellation for High-Resolution Optical Observations over a Specific Area

김동우,정태진 한국항공우주학회 2024 International Journal of Aeronautical and Space Sc Vol.25 No.2

Most military threats originate in a particular area, such as the Korean Peninsula. This study aims to design an elliptical orbit constellation capable of closely monitoring a specific area (the Korean Peninsula). We propose a technique for enhancing ground observation resolution by reducing the operational altitude of the satellite while utilizing a previously constructed optical system for a low Earth orbit (LEO) satellite. First, we create an elliptical orbit for a single LEO satellite capable of achieving high-resolution imagery. The orbit has a perigee of 300 km, an apogee of 8065.62 km, and a critical inclination of 116.56°. Second, a design strategy is implemented for operating these satellites as a constellation. The constellation consists of 40 satellites capable of observing the Korean Peninsula every 36 min. As a result, we provide a satellite constellation with a revisit cycle that can be used as a military reconnaissance satellite on the Korean Peninsula.

Application of DSD Mechanism to Robot Hand

Chiharu Ishii,Yosuke Nishitani,Hiroshi Hashimoto 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8

Recently, the development of a versatile robot hand aiming at the application to an artificial arm or a humanoid robot is in demand. In this paper, omni-directional bending mechanism which is called “double-screw-drive mechanism” was applied to a robot hand. The robot hands with two fingers and three fingers were built. For the robot hand with three fingers, each fingertip was controlled so as to track the elliptical orbit and experiment was carried out.The DSD robot hand succeeded in rotating the cap of the PET bottle and removing the cap from the bottle.

타원 궤도를 운행하는 로봇 장착 인공위성 강체동역학의 임의의 좌표계 표현

최영진(Youngjin Choi),성민창(Minchang Sung),원대희(Daehee Won) 한국항공우주학회 2023 한국항공우주학회 학술발표회 논문집 Vol.2023 No.11