• Title/Summary/Keyword: Small satellite

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Functional Verification of Engineering Model of Non-explosive Shockless Holding and Release Mechanism Using Heating Wire Cutting Method (열선 절단 방식을 적용한 비폭발식 무충격 구속분리장치 EM의 기능검증)

  • Oh, Hyun-Ung;Jeon, Su-Hyeon
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.23 no.5
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    • pp.401-406
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    • 2013
  • Non-explosive shockless holding and release mechanism for a nano class small satellite application has been proposed and investigated. The great advantages of the mechanism are a much lower shock level and larger constraint force than the conventional mechanism using pyro and the heating wire cutting mechanism which has been generally applied to the cube satellite program. To investigate the effectiveness of the mechanism design, EM mechanism was developed and tested to verify the basic function of the mechanism. The test results indicate that the proposed mechanism is well functioning as the mechanism design intends.

A Design of Solar Array Regulator for LEO Satellites (저궤도 인공위성용 태양전력 조절기 설계)

  • Park, Heesung;Cha, Hanju
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.64 no.10
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    • pp.1432-1439
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    • 2015
  • The solar array regulator supplies the electric power to the battery and the other units of a satellite by controlling the operating point of a solar array. In this paper, the solar array regulator composed with analog circuits is proposed. The solar array regulator has three modes. The first is a maximum power point tracking mode for harvesting the maximum photovoltaic power generation. The second is a power limitation mode which is designed for optimizing the volume and weight of the solar array regulator by preventing the excessive power conversion. The last constant voltage mode is proposed to keep the Li-Ion battery is not over-charge. The small signal model of the solar array regulator which has the reversed input and output variables in comparison with conventional converter is established and the stability is analysed. Finally, the proposed design of the solar array regulator is verified by experiments.

The Generation of True Orthophotos from High Resolution Satellites Images

  • Chen, Liang-Chien;Wen, Jen-Yu;Teo, Tee-Ann
    • Proceedings of the KSRS Conference
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    • 2003.11a
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    • pp.885-887
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    • 2003
  • The purpose of this investigation is to generate true orthophotos from high resolution satellite images. The major works of this research include 4 parts: (1) determination of orientation parameters, (2) generating traditional orthophotos using terrain model, (3) relief correction for buildings, and (4) process for hidden areas. To determine the position of satellites, we correct the onboard orientation parameters to fine tune the orbit. In the generation of traditional orthophotos, we employ orientation parameters and digital terrain model(DTM) to rectify tilt displacements and relief displacements for terrain. We, then, compute relief displacements for buildings with digital building model (DBM). To avoid double mapping, we detect hidden areas. Due to the satellite’s small field of view, an efficient method for the detection of hidden areas and building rectification will be proposed in this paper. Test areas cover the city of Kaohsiung in southern Taiwan. Test images are from the QuickBird satellite.

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Determination of Flood Hydrograph by Remote Sensing Techniques in a Small Watershed (원격탐사 기법에 의한 소유역의 홍수 수문곡선 결정)

  • 남현옥;박경윤;조성익
    • Korean Journal of Remote Sensing
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    • v.5 no.1
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    • pp.13-27
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    • 1989
  • In recent years satellite data have been increasingly used for the analysis of floodprone areas. This study was carried out to demonstrate the usefulness of repetitive satellite imagery in monitoring flood levels of the Pyungchang watershed. Runoff characteristics parameters were analyzed by Soil Conservation Service(SCS) Runoff Curve Number(RCN) based on Landsat imagery and Digital Terrain Model data. The RCN average within the watershed was calculated from RCN estimates for all the pixels(picture elements) and adjusted by antecedent precipitation conditions. The direct runoff hydrograph was derived from the unit hydrograph using SCS dimensionless unit hydrograph and effective rainfalls estimated by the SCS method. In comparsion of the direct runoff hydrograph with the measured rating curve their peak times differ by one hour and peak discharges differ by 5.9 percents of the discharge from each other. It was shown that repetitive satellite image could be very useful in timely estimating watershed runoffs and evaluating ever-changing surface conditions of a river basin.

Application of QuickBird Satellite Image to Storm Runoff Modeling

  • Kim, Sang-Ho;Lee, Mi-Seon;Park, Geun-Ae;Kim, Seong-Joon
    • Korean Journal of Remote Sensing
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    • v.23 no.1
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    • pp.15-20
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    • 2007
  • This study is to apply QuickBird satellite image for the simulation of storm runoff in a small rural watershed. For a $1.05km^2$ watershed located in Goesan-Gun of Chungbuk Province, the land use from the QuickBird image was produced by on-screening digitising after ortho-rectifying using 2 m DEM. For 3 cases of land use, soil and elevation scale (1:5,000, 1:25,000 and 1:50,000), SCS-CN and the watershed physical parameters were prepared for the storm runoff model, HEC-HMS (Hydrologic Modelling System). The model was evaluated for each case and compared the simulated results with couple of selected storm events.

Development of a Vertical polarized Leaky-wave Waveguide Slot Array Antenna for Receiving the Ku-band Direct Broadcasting Satellite Signals

  • Lim, Gye-Jae
    • Journal of Satellite, Information and Communications
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    • v.2 no.2
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    • pp.10-15
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    • 2007
  • Small size and low profile antenna for mobile vehicular-top-mounted is needed in satellite communication services such as DBS, Satellite Internet and VSAT. In middle latitudes, the development of an array antenna which has the conformal, low profile and 45 degree beam tilted configuration, and has the high gain with sharp beamwidth, low sidelobe and low loss is required for Ku-band satellite communication. In this paper, in order to meet with these performances, an array antenna consisting of the vertical polarized waveguide longitudinal slots based on the leaky-wave mode of traveling wave antenna is proposed. An array antenna consisting of 16 leaky-wave elements is showing 30 dBi of gain, 4.9 degree of beamwidth, below than -20 dB of sidelobe level, 45 degree of beam tilt angle in center frequency. Feed network designed by waveguide cooperated feed shows good performance of wideband and low loss.

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Analysis of Pseudolite Augmentation for Vessel Berthing

  • Cho, Deuk-Jae;Park, Sang-Hyun;Suh, Sang-Hyun
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • v.1
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    • pp.15-19
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    • 2006
  • GPS has been increasingly exploited to provide positioning and navigation solutions for a variety of applications. In vessel berthing application, however, there are stringent requirements in terms of positioning accuracy, availability and integrity that cannot be satisfied by GPS alone. This is because the performance of satellite-based positioning and navigation systems are heavily dependent on both the number and the geometric distribution of satellite tracked by receivers. Due to the limited number of GPS satellites, a sufficient number of ‘visible’ satellites cannot be sometimes guaranteed. This paper discusses some issues associated with the implementation of ground-based pseudolite augmentation for vessel berthing. Pseudolite means small transmitter that transmits GPS-like signals in local area. Actually, pseudolite can play three different roles in GPS augmentation scheme, depending on the operational conditions. Firstly, in the case of kinematic GPS operation where there are no signal blockages, and more than five satellites are available, additional pseudolites strengthen the GPS satellite-pseudolite geometry, and more accurate and reliable positioning solution can be achieved. Secondly, in the case when there are adverse GPS operational environments in which the number of tracked satellites is less than four, pseudolites can complement the GPS signals. In the third case, GPS signals are completely unavailable, such as when operated indoor. In such cases the pseudolites can replace the satellite constellation. However, the first role will be considered in this paper, since more than four satellite signals can usually be tracked in most marine applications. This paper presents that the pseudolite-augmented precise positioning system can provides continuous centimeter-level positioning accuracy through comparison analysis of RDOP simulation result of the GPS satellite constellation and the pseudolite-augmented GPS satellite constellation.

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Coverage Evaluation of mmWave Small Cell in Outdoor Environment (실외환경에서 밀리미터파 소형 셀의 커버리지 측정)

  • Nguyen, Thanh Ngoc;Jeon, Taehyun
    • Journal of Satellite, Information and Communications
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    • v.12 no.4
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    • pp.162-165
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    • 2017
  • In an effort to compensate the rising of the data throughput demand nowadays, there have been many research works to optimize the radio resource and increase the capacity of the network. At the present, small cell network, mmWave band and beamforming technology are leading the trend and becoming the core solutions of the fifth generation (5G) cellular networks. Since the propagation characteristics of radio wave in the mmWave band is quite different from the conventional bands, the communication systems which work in these bands have to be redesigned. In this paper, a 3D simulation model is discussed for cellular network at 60 GHz in outdoor environments. Coverage analysis and system performance is carried out for a small cell system in the typical urban environment including street canyon simulation scenario. In addition, the beamforming technique is considered to evaluate the throughput improvement. Simulation results show that the mmWave small cell systems is expected to be one of the major candidate technologies to satisfy the requirements of 5G in terms of data rate.

A Design of Mode-Coupler with a Pair of Slots for Ka Band Multi-Mode Monopulse Tracking System (Ka 대역 다중모드 모노펄스 추적 시스템을 위한 한 쌍의 슬롯(Slot)을 갖는 모드커플러 설계)

  • Kwon, Kun-Sup;Heo, Jong-Wan;Hwang, Ki-Min
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.26 no.2
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    • pp.158-164
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    • 2015
  • The main mission of OTM(On-The-Move) satellite communication system is to provide satellite communication service while moving on a vehicle. So it should have a capability to maintain a reliable communication channel when it travels at high speeds or in a severe fluctuation region. This paper presents a small-sized multi-mode monopulse structure applicable to OTM satellite communication system which has only single mode-coupler with a pair of slot using a feature of circular polarized received signal. And tracking error signal is defined using fundamental and high-order modes.

Road Centerline Tracking From High Resolution Satellite Imagery By Least Squares Templates Matching

  • Park, Seung-Ran;Kim, Tae-Jung;Jeong, Soo;Kim, Kyung-Ok
    • Proceedings of the KSRS Conference
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    • 2002.10a
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    • pp.34-39
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    • 2002
  • Road information is very important for topographic mapping, transportation application, urban planning and other related application fields. Therefore, automatic detection of road networks from spatial imagery, such as aerial photos and satellite imagery can play a central role in road information acquisition. In this paper, we use least squares correlation matching alone for road center tracking and show that it works. We assumed that (bright) road centerlines would be visible in the image. We further assumed that within a same road segment, there would be only small differences in brightness values. This algorithm works by defining a template around a user-given input point, which shall lie on a road centerline, and then by matching the template against the image along the orientation of the road under consideration. Once matching succeeds, new match proceeds by shifting a matched target window further along road orientation at the target window. By repeating the process above, we obtain a series of points, which lie on a road centerline successively. A 1m resolution IKONOS images over Seoul and Daejeon were used for tests. The results showed that this algorithm could extract road centerlines in any orientation and help in fast and exact he ad-up digitization/vectorization of cartographic images.

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