• 한국환경독성학회:학술대회논문집
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• 한국환경독성학회 2003년도 추계국제학술대회
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• pp.158-158
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• 2003

Bioassays using gametes of sea urchins are widely used in ecotoxicological assessments of marine environments. Since most of sea urchin species in Korean coastal water spawn from spring to autumn, bioassay with them during the winter is impossible. In the course of developing standard methods for bioassays with Korean species, we found a winter-spawning starfish, Asterias amurensis, Since reproductive mode of asteroids is similar to echinoids, the bioassay protocol for sea urchins could be applied similarly to the starfish. Here, we tested and determined several conditions for the acceptability of bioassay with A. amurensis. The least required time for formation of fertilization membrane of fertilized eggs to be easily distinguished from unfertilized ones was 60 min. The threshold of sperm to egg ratio that could make acceptable fertilization rates in controls was 3000. The allowed time for manipulation of sperm after dilution in seawater was at most 3 hr. The optimal exposure time of sperms when the response against toxicant solution was relatively stable was in the range of 20-60 min. The tolerance range of sperms to the salinity of test solution was 26-38 psu. The sensitivity of A. amurensis sperm was intermediate among marine organisms commonly used in aquatic toxicity tests. The sperm bioassay with A. amurensis can be satisfactorily applied to toxicity assessments of marine environments.

• 천문학회보
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• 제39권1호
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• pp.67.1-67.1
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• 2014

Comets are mysterious travelers from outer Solar System. It is considered that comets loose their subsurface ice once they were injected into a snow-line of the solar system, at the same time, develop adiathermic dust layers on the surface in a time scale of ~10,000 years. They eventually become inactive (see also the presentation by Yoonyoung Kim et al.). Optical similarity between comets and asteroids in comet-like orbits suggests the existence of such dormant or inactive comets supporting the evolutionary scenario. However, unforeseen accidents cast a misgiving to modify the stereotype. A periodic comet, 17P/Holmes, is known as comet with very low activity before 2007. However, the comet suddenly exhibited an outburst in 2007 October, which is known as the most energetic cometary outburst since the beginning of modern astronomy. On the other hand, another periodic comet, P/2010 V1, was not known before 2010 November probably because of low activity and discovered while it experienced outburst. We investigated the time-evolution of the magnitudes and the morphological developments based on the dynamical theory of dust grains, and derived the energy per unit mass of ~10,000 J/kg. From these observational evidences, we suggest that crystallization of buried amorphous ice (even in low-activity comets) can be responsible for the dramatic cometary outbursts.

• 천문학회보
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• 제37권2호
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• pp.106.1-106.1
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• 2012

The Gegenschein is a faint glow around the anti-solar point caused by the interplanetary dust particle(IDP)'s back-scattering enhancement. From the previous low resolution observations, the overall morphology of the Gegenschein has been intensively studied. However, sub-degree scale fine structure of the Gegenschein is still not well known, even though the detailed morphology of the Gegenschein within a few degree from the anti-solar point may supply pivotal information about the property of the IDPs. We made optical CCD observations of the Gegenschein between 2003 March and 2006 November. From the observations, we succeeded in making high resolution images of the Gegenschein, with unprecedented 1.'4 resolution. Our results concur with IDP cloud model based on the infrared observations combined with scattering phase function derived from low resolution data. The only exception is the anti-solar point. We found a steep additional brightness enhancement existing at the exact anti-solar point. Plausible explanation of the finding is that the IDPs are significantly larger than observing wavelength, and have irregular morphology or inhomogeneous internal structure. Furthermore, we measured average geometric albedo of the IDPs from the optical brightness of the anti-solar point. The geometric albedo was $0.06{\pm}0.01$, similar to those of comets or C-type asteroids.

• Animal Systematics, Evolution and Diversity
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• 제8권2호
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• pp.243-258
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• 1992

1980년 4월부터 1992년 4월까지 우리나라의 남해연안과 여러 도서 지방의 총 69개 지역에서 채집된 해성류를 동정하였다. 그 결과 5목 8과 23종이 밝혀졌고, 이들 중 Mediaster brachiatus와 Stellaster equestris 2종은 한국 미기록종이었으며 Asterina pecitinifera는 43개 지역에서 채집되어 가장 흔한 종이었다. 대한해협과 제주도 해역에는 각각 15종의 해성류가 있었으며 온대종 15종, 열대종 7종, 한대종 3종이 분포하고 있었다. 현재까지 밝혀진 해성류는 43종이 된다.

• Journal of Astronomy and Space Sciences
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• 제38권2호
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• pp.105-117
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• 2021

In this study, a preliminary trajectory design is conducted for a conceptual spacecraft mission to a near-Earth asteroid (NEA) (99942) Apophis, which is expected to pass by Earth merely 32,000 km from the Earth's surface in 2029. This close approach event will provide us with a unique opportunity to study changes induced in asteroids during close approaches to massive bodies, as well as the general properties of NEAs. The conceptual mission is set to arrive at and rendezvous with Apophis in 2028 for an advanced study of the asteroid, and some near-optimal (in terms of fuel consumption) trajectories under this mission architecture are to be investigated using a global optimization algorithm called monotonic basin hopping. It is shown that trajectories with a single swing-by from Venus or Earth, or even simpler ones without gravity assist, are the most feasible. In addition, launch opportunities in 2029 yield another possible strategy of leaving Earth around the 2029 close approach event and simply following the asteroid thereafter, which may be an alternative fuel-efficient option that can be adopted if advanced studies of Apophis are not required.

• Advances in Computational Design
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• 제4권2호
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• pp.141-153
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• 2019

This research is comprised of virtually simulating behavior while experiencing low gravity effects in advance of real world testing in low gravity aboard Zero Gravity Corporation's (Zero-G) research aircraft (727-200F). The experiment simulated a drill rig penetrating a regolith simulant. Regolith is a layer of loose, heterogeneous superficial deposits covering solid rock on surfaces of the Earth' moon, asteroids and Mars. The behavior and propagation of space debris when drilled in low gravity was tested through simulations and visualization in a leading dynamic simulation software as well as discrete element modeling software and in preparation for comparing to real world results from flying the experiment aboard Zero-G. The study of outer space regolith could lead to deeper scientific knowledge of extra-terrestrial surfaces, which could lead us to breakthroughs with respect to space mining or in-situ resource utilization (ISRU). These studies aimed to test and evaluate the drilling process in low to zero gravity environments and to determine static stress analysis on the drill when tested in low gravity environments. These tests and simulations were conducted by a team from Texas A&M University's Department of Construction Science, the United States Air Force Academy's Department of Astronautical Engineering, and Crow Industries

• 항공우주의학회지
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• 제30권1호
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• pp.18-24
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• 2020

In 2019, the Aerospace Medical Association of Korea celebrated its 30th anniversary. On the other side of the world, it was also the 62nd anniversary of Russian launch Sputnik 1 of the world's first artificial satellite on October 4, 1957. In additionally, the world, especially the United States was shocked, when on November 3, 1957, Sputnik 2 blasted into Earth orbit with a dog named "Laika"; it was the role of veterinarian's activities for aerospace medical research and exploration. Veterinarians (Vets) are responsible for the health of all the animals for aerospace medicine whether on the ground or in space. Vets can enhance animal and public health and this knowledge of Vets and astronauts can extend their mission durations, go to nearby Earth Asteroids, Mars and other heavenly bodies to study their living and non-living characteristics. This review article is the brief history of the original growth of the veterinarian's activities for the aerospace medical research, in order to stimulate future strategies for improvements in the space life sciences and exploration.

• 천문학논총
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• 제38권2호
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• pp.25-36
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• 2023

Since interstellar objects like 1I/'Oumuamua and 2I/Borisov originate from exoplanetary systems, even if we do not visit the exoplanetary systems, flyby, rendezvous, and sample return missions of interstellar objects can provide clues to solve the mysteries of cosmic life phenomena such as the origin of exoplanetary systems, galactic evolution, biosignatures (or even technosignatures), and panspermia. In this paper, we review space missions for interstellar object exploration in the stage of mission design or concept study such as Project Lyra, Bridge, Comet Interceptors, and Lightcraft^TM. We also review space missions, OSIRIS-REx and NEA Scout, designed for Near Earth Asteroids(NEA) explorations, to investigate the current state of basic technologies that can be extended to explore interstellar objects in a velocity of ~ 6AU/year. One of the technologies that needs to be developed for interstellar object exploration is a spacecraft propulsion method such as solar sail, which can catch up with the fast speed of interstellar objects. If this kind of propulsion becomes practical for space explorations, interstellar object explorations will mark a new era and serve as a driving force to provide evidences of cosmic life.

• 천문학회보
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• 제40권1호
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• pp.56.3-57
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• 2015

As of early 2015, more than 12,000 Near-Earth Objects (NEOs) have been catalogued by the Minor Planet Center, however their observational properties such as broadband colors and rotational periods are known only for a small fraction of the population. Thanks to time series observations with the KMTNet, orbits, optical sizes (and albedo), spin states and three dimensional shapes of asteroids and comets including NEOs will be systematically investigated and archived for the first time. Based on SDSS and BVRI colors, their approximate surface mineralogy will also be characterized. This so-called DEEP-South (Deep Ecliptic Patrol of the Southern Sky) project will provide a prompt solution to the demand from the scientific community to bridge the gaps in global sky coverage with a coordinated use of the network of ground-based telescopes in the southern hemisphere. We will soon finish implementing dedicated software subsystem consisted of automated observation scheduler and data pipeline for the sake of increased discovery rate, rapid follow-up, timely phase coverage, and efficient data analysis. We will give a brief introduction to test runs conducted at CTIO with the first KMTNet telescope in February and March 2015 and experimental data processing. Preliminary scientific results will also be presented.

• 항공우주기술
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• 제9권2호
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• pp.14-21
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• 2010

이온추력기는 전기추력기의 일종으로 높은 추력을 내기가 힘든 단점이 있으나 상대적으로 매우 높은 비추력을 낼 수 있는 장점이 있기 때문에 장거리 혹은 장시간의 우주비행이 요구되는 미션을 위해 활용되는 우주추진기관이다. 최근에 들어 우주탐사에 대한 세계 각국의 관심이 높아져 가고 있고 기존의 미국, 러시아, 유럽 이외에도 일본, 중국, 인도 등이 우주탐사에 나서고 있다. 소행성탐사나 외행성탐사와 같은 장거리 임무의 경우에는 화학식 추력기만을 사용하는 경우 과도한 추진제 적재로 인해 발사 중량이 증가하는 단점이 있어 최근에 들어서는 화학식 추력기와 이온추력기를 조합하여 사용하는 것이 세계적인 추세이다. 본 논문에서는 이온추력기 개발을 위해 수행된 이온화 방식 및 제작 기술과 관련된 연구의 수행 내역과 이온추력기 기본 모델의 제작 결과 및 방전 시험 결과를 소개하였다.