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Optical Design of a Reflecting Telescope for CubeSat
진호,임주희,김영주,김상혁 한국광학회 2013 Current Optics and Photonics Vol.17 No.6
Space telescope optics is one of the major parts of any space mission used to observe astronomicaltargets or the Earth. This kind of space mission typically involves bulky and complex opto-mechanicswith a long optical tube, but attempts have been made to observe a target with a small satellite. In thispaper, we describe the optical design of a reflecting telescope for use in a CubeSat mission. For this designwe adopt the off-axis segmented method for astronomical observation techniques based on aRitchey-Chrétien type telescope. The primary mirror shape is a rectangle with dimensions of 8 cm × 8cm, and the secondary mirror has dimensions of 2.4 cm × 4.1 cm. The focal ratio is 3 which can yielda 0.383 degree diagonal angle in a 1280 × 800 CMOS color image sensor with a pixel size of 3 μm× 3 μm. This optical design can capture a ~ 4 km × ~ 2.3 km area of the earth’s surface at 700 kmaltitude operation.
진호,서희종 한국전자통신학회 2012 한국전자통신학회 논문지 Vol.7 No.4
In this paper, we proposed an efficient algorithm based on SPFA(shortest path faster algorithm), which is an improved the Bellman-Ford algorithm. The Bellman-Ford algorithm can be used on graphs with negative edge weights unlike Dijkstra's algorithm. And SPFA algorithm used a queue to store the nodes, to avoid redundancy, though the Bellman-Ford algorithm takes a long time to update the nodes table. In this improved algorithm, an adjacency list is also used to store each vertex of the graph, applying dynamic optimal approach. And a queue is used to store the data. The improved algorithm can find the optimal path by continuous relaxation operation to the new node. Simulations to compare the efficiencies for Dijkstra's algorithm, SPFA algorithm and improved Bellman-Ford were taken. The result shows that Dijkstra's algorithm, SPFA algorithm have almost same efficiency on the random graphs, the improved algorithm, although the improved algorithm is not desirable, on grid maps the proposed algorithm is very efficient. The proposed algorithm has reduced two-third times processing time than SPFA algorithm. 이 논문에서 SPFA(shortest path faster algorithm)을 사용해서 기존의 벨만-포드(Bellman-Ford)을 개선한효율적인 알고리듬을 제안한다. 벨만-포드 알고리듬은 딕스트라(Dijkstra) 알고리듬과 다르게 부(-)인 가중치를갖는 그래프에서 사용할 수 있다. SPFA 알고리듬은 한 대기열을 이용하여 노드를 저장한다. 그래서 중북을피할 수 있다. 벨만-포드 알고리듬은 시간을 더 사용하여 노드 표를 업데이트를 시킨다. 이 개산 알고리듬에서는 인접 리스트를 이용하여 표의 각 노드를 저장한다. 한 대기열을 통하여 데이트를 저장한다. 개선 방법에서는 새로운 점에 계속 relaxation을 통하여 최적 패스를 얻을 수 있다. 딕스트라 알고리듬과 SPFA 알고리듬과개선된 알고리듬의 성능을 비교하기 위해서 시뮬레이션을 하였다. 실험 결과에서 랜덤(random) 그래프에서 개선된 알고리듬, SPFA 알고리듬과 딕스트라 알고리듬은 효율이 비슷했었는데, 격자형 지도에서 개선 알고리듬의 효율이 더 높았었다. 처리시간에서 개선된 알고리듬은 SPFA 알고리듬 보다 3분의 2를 감소시켰다.
CCD를 이용한 경희대학교 천문대 관측시스템 소프트웨어개발
진호,김갑성,Jin, Ho,Kim, Gap-Seong 한국천문학회 1994 天文學論叢 Vol.9 No.1
We have investigated intensively an optical telescope with 76cm diameter and CCD camera system in astronomical observatory of Kyung Hee university, in order to maximize instrumental functions of our observational equipments and to construct a more reliable photometric system. And computer softwares AUTO DOME, KH CCD and KH PHO for astronomical image observations and their automatic photometries with high accuracy have been made for observers w use our observational system conveniently and efficiently. Throughout careful examinations of these programs, it has been proved that the observing time by our program is shorter than that by manual operations, so that, fast and accurate observations can be executed with ease. For open cluster NGC 7063 observed with S/N value of 350 or more by KH PHO, we have found the magnitude measurements of 11 object stars would show 0.007 magnitude difference, comparing with magnitude data from IRAF/APPHOT. From automatic photometry of eclipsing binary, AB And observed by our software, total 220 data points with good quality have been acquired during 8 hours and so we could make a better light curve than that obtained from any observational results by domestic photoelectric photometry system.