• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2004년도 한국우주과학회보 제13권2호
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• pp.285-289
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• 2004

An optimal interplanetary trajectory is presented for Human Outer Planet Exploration (HOPE) by using an advanced magnetoplasma spacecraft. A detailed optimization approach is formulated to utilize Variable Specific Impulse Magnetoplasma Rocket (VASIMR) engine with capabilities of variable specific impulse, variable engine efficiency, and engine on-off control. To design a round-trip trajectory for the mission, the characteristics of the spacecraft and its trajectories are analyzed. It is mainly illustrated that 30 MW powered spacecraft can make the mission possible in five-year round trip constraint around year 2045. The trajectories obtained in this study can be used for formulating an overall concept for the mission.

• 천문학회보
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• 제37권1호
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• pp.101.1-101.1
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• 2012

Interplanetary dust particles are observable as zodiacal light, which is the sunlight scattered by the interplanetary dust particles. The origins of interplanetary dust particles are still in question because they are eroded by Poynting-Robertson photon drag and mutual collisions among dust particles. The small-scale structures in the zodiacal light provided a clue to specify their origins. Asteroidal debris were detected as band-like structures (dust bands), and the cometary large particles were detected as narrow trails (dust trails). However, little is confirmative about their detailed origins and mineralogical compositions because of the lack of observational data particularly in the optical wavelength. We made a high-resolution optical zodiacal light map based on the CCD observations at Mauna Kea, Hawaii. We analyzed data taken on November 12, 2004. After the data reduction, such as flat fielding and subtraction of airglow emissions, we succeeded in the construction of the zodiacal light map with the spatial resolution of 3' in the solar elongation between 45 degree and 180 degree. This is the highest resolution map in the visible wavelength so far. In this map, we confirmed the dust bands structures near the ecliptic plane. We will discuss about the similarities and the differences between optical and infrared dust bands.

• 천문학논총
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• 제32권1호
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• pp.63-65
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• 2017

The zodiacal light emission is the thermal emission from the interplanetary dust and the dominant diffuse radiation in the mid- to far-infrared wavelength region. Even in the far-infrared, the contribution of the zodiacal emission is not negligible at the region near the ecliptic plane. The AKARI far-infrared all-sky survey covered 97% of the whole sky in four photometric bands with band central wavelengths of 65, 90, 140, and $160{\mu}m$. AKARI detected the small-scale structure of the zodiacal dust cloud, such as the asteroidal dust bands and the circumsolar ring, in far-infrared wavelength region. Although the most part of the zodiacal light structure in the AKARI far-infrared all-sky image can be well reproduced with the DIRBE zodiacal light model, there are discrepancies in the small-scale structures. In particular, the intensity and the ecliptic latitude of the peak position of the asteroidal dust bands cannot be reproduced precisely with the DIRBE models. The AKARI observational data during more than one year has advantages over the 10-month DIRBE data in modeling the full-sky zodiacal dust cloud. The resulting small-scale zodiacal light structure template has been used to subtract the zodiacal light from the AKARI all-sky maps.

• Journal of Information Processing Systems
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• 제15권6호
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• pp.1472-1488
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• 2019

Critical elements in the China's Lunar Exploration reside in that the lunar rover travels over the surrounding undetermined environment and it conducts scientific exploration under the ground control via teleoperation system. Such an interplanetary transportation mission teleoperation system belongs to the ground application system in deep space mission, which performs terrain reconstruction, visual positioning, path planning, and rover motion control by receiving telemetry data. It plays a vital role in the whole lunar exploration operation and its so-called trustworthy evidence must be assessed before and during its implementation. Taking ISO standards and China's national military standards as trustworthy evidence source, the net assessment model and net assessment method of teleoperation system are established in this paper. The multi-dimensional net assessment model covering the life cycle of software is defined by extracting the trustworthy evidences from trustworthy evidence source. The qualitative decisions are converted to quantitative weights through the net assessment method (NAM) combined with fuzzy analytic hierarchy process (FAHP) and entropy weight method (EWM) to determine the weight of the evidence elements in the net assessment model. The paper employs the teleoperation system for interplanetary transportation as a case study. The experimental result drawn shows the validity and rationality of net assessment model and method. In the final part of this paper, the untrustworthy elements of the teleoperation system are discovered and an improvement scheme is established upon the "net result". The work completed in this paper has been applied in the development of the teleoperation system of China's Chang'e-3 (CE-3) "Jade Rabbit-1" and Chang'e-4 (CE-4) "Jade Rabbit-2" rover successfully. Besides, it will be implemented in China's Chang'e-5 (CE-5) mission in 2019. What's more, it will be promoted in the Mars exploration mission in 2020. Therefore it is valuable to the development process improvement of aerospace information system.

• 우주기술과 응용
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• 제1권3호
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• pp.302-318
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• 2021

지구접근 소행성을 목적지로 하는 우주탐사선의 발사 시기를 결정하는 방법에 대하여 기본적인 연구를 수행하였다. 향후, 지구 궤도에 접근하는 소행성을 대상으로 하는 탐사선 임무가 국내에서 진행될 경우에 발사시기를 결정하기 위해서는 전역최적화(global optimization)기법을 적용하여 적절한 해를 구하여야 한다. 이를 위해서는 먼저 각 소행성들의 정확한 궤도 정보가 필요하고. 지구의 공전궤도 정보, 탐사선의 주엔진 성능 정보, 중력보조 기동의 횟수, 최대 비행시간 제한 등의 사전 시나리오가 논의되어야 한다. 또한 최적화의 기준이 우선 결정되어야 한다. 본 논고에서는 이러한 전제 조건과 정보를 바탕으로 PyKEP, EMTG(Evolutionary Mission Trajectory Generator) 등의 오픈소스 경로탐색 프로그램을 사용하여 소행성 탐사선의 발사 시기를 찾는 방안을 연구하였다.

• 한국위성정보통신학회논문지
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• 제12권4호
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• pp.42-49
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• 2017

지연/분열 허용 네트워크는 간헐적인 통신링크 단절, 높은 전송 에러율와 같은 행성 간 통신에서 마주하는 주된 문제점들을 해결할 주된 기술로 여겨진다. 행성 간 통신에서 종단간 연결성이 보장되지 않아 간헐적으로 통신링크가 단절되면 길고 일정하지 않은 시간 지연과 정보 손실이 발생하고, 따라서 종단간 연결성을 요구하는 인터넷 프로토콜은 행성 간 통신에 적합하지 않다. Store-and-forward 메시지 전송 방식을 따르는 지연/분열 허용 네트워크는 행성 간 통신에서 종단간 연결성이 보장되지 않아 발생하는 문제점을 해결할 수 있다. 본 논문에서는 지구 기지국-지구 위성-달궤도선-달탐사체로 구성된 3-hop 릴레이 우주통신 환경에 지연/분열 허용 네트워크 개념을 적용한 통신 모델을 제시하며, ONE 시뮬레이터를 이용한 실제 우주통신환경 모델링 및 성능 분석을 통해, 안정적인 메시지 전송을 보장하는 최적의 메시지 수명, 버퍼 공간 및 메시지 분할 방법을 제시한다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.389-396
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• 2002

In XXI century it is necessary to expect the recommencement and development of activities on mastering the Moon. In the long term it is construction of manned lunar bases with industrial, astrophysical, procuring, repair equipment and services. Interplanetary flights from the Moon demand smaller power expenditures, than from the Earth, therefore it is favourable to use its surface for the construction of space-vehicle launching sites. Flights of devices in libration points in the system 'Earth - Moon' are considered. Experience of engineering system creation for the Moon displays the great complexity in provision of serviceability and reliability of friction units. Open friction units should operate under following conditions on the Moon: pressure of environment (vacuum) $p\;>10\;^{-10}$ Pa; wide range of temperature change $+150^{\circ}C\;...170^{\circ}C$; high evaporability of lubricants; influence of temperature gradients and warping of constructions; sublimation of elements of constructional materials; irradiation of different physical nature; effect of micrometeorites; reduced gravitation; influence of abrasive particles of lunar ground; requirements on minimization of size and weight characteristics of a construction (high tension); undesirability (impossibility) of application of liquid and plastic lubricants; vibration, shock, acoustic loadings during start and landings to the Earth; difficulties in repair-regenerative operations in conditions of the Moon etc. Adhesive interaction of conjugated surfaces is the principal reason of possible failures of rubbed units on the Moon. In the research of the Moon automatic interplanetary stations of 'Luna' (USSR), 'Surveyer', 'Apollo' (USA) series were used. Stations executed functions of flying, landing, artificial satellites of the Moon, moon-rovers and manned spacecrafts such as 'Apollo'. The experimental- theoretical researches carried out in the sixtieth years on tribology for conditions of the Moon appeared to be rather useful to engineering of an outer space exploration and the decision of complex problems for the friction units operating in extreme conditions on the Earth. For the creation of highly loaded friction units for the long service life on the Moon it is required not only to use accumulated experience and designed technologies, but also to carry out wide scientific research.

• Journal of Astronomy and Space Sciences
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• 제41권3호
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• pp.195-208
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• 2024

As human exploration goals shift from missions in low Earth orbit (LEO) to long-duration interplanetary missions, radiation protection remains one of the key technological issues that must be resolved. The low Earth orbit space radiation dosimeter (LEO-DOS) instrument to measure radiation levels and create a global dose map in the LEO on board the the next generation small satellite-2 (NEXTSat-2) was launched successfully on May 25, 2023 using the Nuri KSLV-III in Korea. The NEXTSat-2 orbits the Earth every 100 minutes, in an orbit with an inclination of 97.8° and an altitude of about 550 km above sea level. The LEO-DOS is equipped with a particle dosimeter (PD) and a neutron spectrometer (NS), which enable the measurement of dosimetric quantities such as absorbed dose (D), dose equivalent (H) for charged particles and neutrons. To verify the observations of LEO-DOS, we conducted a radiation dose estimation study based on the initial results of LEO-DOS, measured from June 2023 to September 2023. The study considered four source categories: (i) galactic cosmic ray particles; (ii) the South Atlantic Anomaly region of the inner radiation belt (IRB); (iii) relativistic electrons and/or bremsstrahlung in the outer radiation belt (ORB); and (iv) solar energetic particle (SEP) events.

• Journal of Astronomy and Space Sciences
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• 제21권2호
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• pp.153-166
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• 2004

향후 우리나라의 행성 탐사 임무에 대비하여 행성 근접 통과를 이용한 목성 탐사 임무의 최적 발사 가능 시기에 대한 연구를 수행하였다. 본 연구를 통해서 관련 비행 궤적을 설계할 수 있는 자체적인 프로그램을 개발하였으며 일련의 과정을 통해 그 성능을 검증하였다. 목성까지의 비행 궤적 중 직행 임무(Direct mission), 단일 행성 근접 통과를 이용한 임무(Single planet gravity assist mission) 그리고 복수 행성 근접 통과를 이용한 임무(Multi planet gravity assist mission)에 대한 비행 궤적을 각각 설계하였으며 이에 대한 최적의 발사시기를 선정하였다. 목성 탐사 비행 궤적 중, 지구-화성-지구-목성의 비행 궤적 (Earth-Mars-Earth-Jupiter Gravity Assist, EMEJGA Trajectory)을 갖는 복수 행성 근접 통과 임무가 약 29.231$Km^2$/$S^2$의 발사 에너지($C_3$)값을 필요로 하였으며 이는 직행 임무의 발사 에너지($C_3$)값 75.756$\textrm{km}^2$/s$^2$및 화성 근접 통과만을 고려한 단일 행성 근접 통과 임무의 발사 에너지($C_3$)값 63.590$Km^2$/$S^2$보다 현저하게 낮은 수치이다. 이러한 결과는 행성간 탐사선의 비행 궤적 설계 시 행성 근접 통과를 고려하였을 경우 발사 에너지의 절감 효과 및 한번의 발사로 하나 이상의 행성의 탐사가 가능함으로 임무의 효율성을 증대시킬 수 있다는 사실을 보여 주고 있다. 또한 복수 행성 근접 통과를 이용하였을 경우 요구되는 총 임무 기간은 약 4.6년으로 직행 혹은 단일 행성 근접 통과를 이용하였을 경우(각 약2.98년 및 약2.33년의 총 임무 기간)에 비해 임무 기간이 길어지는 단점이 있음을 확인 시켜 주고 있다.

• 천문학회보
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• 제46권2호
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• pp.58.1-59
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• 2021

Exploration of asteroids' internal structure is essential for understanding their evolutional history. It also provides a fundamental information about the history of coalescence and collision of the solar system. Among several models of the internal structures, the rubble-pile model, confirmed by the near-Earth asteroid (25143) Itokawa by Hayabusa mission [1], is now widely regarded as the most common to asteroids with size ranging from 200 m to 10 km [2]. On the contrary, monolithic and core-mantle structures are also possible for small asteroids [3]. It is, however, still challenging to look through the interior of a target object using remote-sensing devices. In this presentation, we introduce our ongoing research conducted at Seoul National and propose an idea to infer the internal structure of Apophis using available instruments. Itokawa's research provides an important benchmark for Apophis exploration because both asteroids have similar size and composition [4][5]. We have conducted research on Itokawa's evolution in terms of collision and space weathering. Space weathering is the surface alteration process caused by solar wind implantation and micrometeorite bombardment [6]. Meanwhile, resurfacing via a collision acts as a counter-process of space weathering by exposing fresh materials under the matured layer and lower the overall degree of space weathering. Therefore, the balance of these two processes determine the space weathering degrees of the asteroid. We focus on the impact evidence on the boulder surface and found that space weathering progresses in only 100-10,000 years and modifies the surface optical properties (Jin & Ishiguro, KAS 2020 Fall Meeting). It is important to note that the timescale is significantly shorter than the Itokawa's age, suggesting that the asteroid can be totally processed by space weathering. Accordingly, our result triggers a further discussion about why Itokawa indicates a moderately fresh spectrum (Sq-type denotes less matured than S-type). For example, Itokawa's smooth terrains show a weaker degree of space weathering than other S-type asteroids [7]. We conjecture that the global seismic shaking caused by collisions with >1 mm-sized interplanetary dust particles induces granular convection, which hinders the progression of space weathering [8]. Note that the efficiency of seismic wave propagation is strongly dependent on the internal structure of the asteroid. Finally, we consider possible approaches to investigate Apophis's internal structure. The first idea is studying the space weathering age, as conducted for Itokawa. If Apophis indicates a younger age, the internal structure would have more voids [9]. In addition, the 2029 close encounter with Earth provides a rare natural opportunity to witness the contrast between before and after the event. If the asteroid exhibits a slight change in shape and space weathering degree, one can determine the physical structure of the internal materials (e.g., rubble-pile monolithic, thick or thin regolith layer, the cohesion of the materials). We will also consider a possible science using a seismometer.