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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Astronomy and Space Sciences
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The Korean Space Science Society
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Volume 13, Issue 2 - Jun 1996
Volume 13, Issue 1 - Jun 1996
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OVERVIEW OF KITSAT-1/2 MICROSATELLITE SYSTEMS
Journal of Astronomy and Space Sciences, volume 13, issue 2, 1996, Pages 1~19
Satellite Technology Research Center(SaTReC) of Korean Advanced Institute of Science and Technology(KAIST) has started a collaborative research, development, and training program in the field of space technology. As the result of that, SaTReC has successfully developed and operated the KISTAT-1, which is the first Korean satellite system. From the experience gained. SaTReC has developed the KITSAT-2 with its own technology and man-power and acquired the capability to design and to manufacture small satellite systems. In this paper, an overview of KITSAT-1/2 microsatellite systems and operational results are introduced.
POWER MANAGEMENT ANALYSIS FOR KITSAT-1
Journal of Astronomy and Space Sciences, volume 13, issue 2, 1996, Pages 20~29
Provision of the electrical power generated from solar array is one of the most fundamental requirements for the spacecraft payloads. Power subsystem collects, regulates and distributes power to the experiment payloads and to the various spacecraft subsystem. In this paper, the analysis result of the KITSAT-1 WOD shows that the in-orbit operation of whole power system has been in good condition.
TELEMETRY AND TELECOMMAND SYSTEM OF LOW-EARTH-ORBIT MICROSATELLITE, KITSAT-1 AND 2
Journal of Astronomy and Space Sciences, volume 13, issue 2, 1996, Pages 30~40
The telecommand system of KITSAT micorsatellite receives commands from ground stations or on-board computers. It decodes, validates and delivers commands to sub-system. The telemetry system is to collect, process and format satellite housekeeping and mission data for use by on-board computer and ground station. It is crucial for the telemetry and telecommand system to have high reliability since the spacecraft operation is mostly based on the function of this system. The telemetry and telecommand(TTC) systems for KITSAT-1 and 2 had been developed under the consideratin of the space environment of Low-Earth-Orbit and the limited mass, volume and power of micorsatellite. Since both satellites were launched in August 1992 and September 1993 respectively, the have shown to be working successfully as well as the TTC systems on-board both satellites.
ON-BOARD COMPUTER SYSTEM FOR KITSAT-1 AND 2
Journal of Astronomy and Space Sciences, volume 13, issue 2, 1996, Pages 41~51
KITSAT-1 and 2 are microsatellites weighting 50kg and all the on-board data are processed by the on-board computer system. Hence, these on-board computers require to be highly reliable and be designed with tight power consumption, mass and size constraints. On-board computer(OBC) systems for KITSAT-1 and 2 are also designed with a simple flexible hardware for reliability and software takes more responsibility than hardware. KITSAT-1 and 2 on-board computer system consist of OBC 186 as the primary OBC and OBC80 as its backup. OBC186 runs spacecraft operating system (SCOS) which has real-time multi-tasking capability. Since their launch, OBC186 and OBC80 have been operating successfully until today. In this paper, we describe the development of OBC186 hardware and software and analyze its in-orbit operation performance.
DESIGN AND IMPLEMENTATION OF THE SMALL SATELLITE ON-BOARD COMPUTER SYSTEM : KASCOM
Journal of Astronomy and Space Sciences, volume 13, issue 2, 1996, Pages 52~66
In this paper, we present the design methodology of KASCOM(KAIST satellite computer), the experimental on-board computer system of KITSAT-2. The design of the on-board computer system should consider the following constraints: operational throughput, fault tolerant input-output, low power, size, weight, and radiation hardness. KASCOM is designed to satisfy these constraints. This paper also presents the implementation and testing details of KASCOM. Finally, the in-orbit operational results are presented. The results show that about 2 SEU errors occur for the program memory(1Mbit SRAM) in a day, while 3.7 SEU errors occur for the data memory(4Mbit SRAM). This implies that high-integrated memories are more susceptible to the radiation environment than low-integrated memories.
ATTITUDE DETERMINATION AND CONTROL SYSTEM OF KITSAT-1
Journal of Astronomy and Space Sciences, volume 13, issue 2, 1996, Pages 67~81
The attitude dynamics of KITSAT-1 are modeled including the gravity gradient stabilization method. We define the operation scenario during the initial attitude stabilization period by means of a magnetorquering control algorithm. The required constraints for the gravity gradient boom deployment are also examined. Attitude dynamics model and control laws are verified by analyzing in-orbit attitude sensor telemetry data.
KITSAT-1/2 COMMUNICATION SYSTEM
Journal of Astronomy and Space Sciences, volume 13, issue 2, 1996, Pages 82~93
The paper discusses the design and construction of KITSAT-1/2 communication systems. Several requirements for the communication system have been analyzed and the specifications for KITSAT-1/2 communication systems have been summarized. Also the design and performance of KITSAT-1/2 communication system is described.
DEVELOPMENT OF KITSAT-1 AND 2 MECHANICAL SYSTEM AND RESULTS OF ENVIRONMENT TEST
Journal of Astronomy and Space Sciences, volume 13, issue 2, 1996, Pages 94~104
The satellite experiences the launch environment such as vibration, acceleration, shock induced by rocket and the orbit environment such as high vacuum, no gravity, high temperature and cryogenic. Therefore, the satellite should be designed and manufactured to endure such environments. Also, special care must be taken on the assembly of parts and subsystem. Finally, we describe the environment test of microsatellite to ensure the reliable operation during launch period as well as in-orbit operation.
DEVELOPMENT OF THE THERMAL MODEL FOR KITSAT-1/2 MICROSATELLITES AND ITS VERIFICATION USING IN-ORBIT TELEMETRIES
Journal of Astronomy and Space Sciences, volume 13, issue 2, 1996, Pages 105~116
This study is based upon the thermal modeling, analysis and operational results of KITSAT-1 and KITSAT-2 microsatellites launched on August 11, 1992 and Septermber 26, 1993, respectively. As KITSAT-1/2 was designed to be launched as an auxiliary payload of ARIANE launcher, the constraints on volume, power consumption, and mass were required to adopt passive thermal control method controlling absorptivity, emissivity, and conductivities among adjacent modules. The main of KITSAT was to take Earth images using CCD cameras positioned at the bottom of spacecraft, in which the cameras were always pointing to the center of Earth. This study is concerned with orbital analysis, thermal modeling, simulation results, and its verification by utilizing in-orbit telemetry data of KITSAT-2. The results of telemetry analysis show that the thermal modeling is matched to actual temperature data within 10 degrees of error range in average.
STORED-AND-FORWARD PACKET COMMUNICATION PAYLOAD OF KITSAT 1/2 MICROSATELLITES
Journal of Astronomy and Space Sciences, volume 13, issue 2, 1996, Pages 117~133
In this paper, we describe the architecture and protoccl of stored-and-forward packet communication payload of KITSAT 1/2 microsatellites and then analyze this payload in terms of the probabilities of login success and login refusal, and maximum throughput as quality of service parmaeters.
MODELLING AND VERIFICATION OF KITSAT PACKET COMMUNICATION PROTOCOLS
Journal of Astronomy and Space Sciences, volume 13, issue 2, 1996, Pages 134~148
In this paper, in order to verify KITSAT 1/2 packet communication protocols, we model the AX.25 protocol and PACSAT protocol by using an extended Petri net and then verify the correctness, boundedness, liveness and deadlock freeness of packet protocols by utilizing reachability trees.
SPACE RADIATION ENVIRONMENT MONITORED BY KITSAT-1 AND KITSAT-2
Journal of Astronomy and Space Sciences, volume 13, issue 2, 1996, Pages 149~162
The results of space radiation experiments carried out on board the first two Korean technology demonstration microsatellites are presented in this paper. The first satellite, KITSAT-1, launched in August 1992, carries a radiation monitoring payload called cosmic ray experiment(CRE) for characterizing the low-earth orbit(LEO) radiation environment. The CRE consists of two sub-systems: the cosmic particle experiment (CPE) and the total dose experiment(TDE). In addition, single event upset(SEU)rates of the program memory and the RAM disk are also monitored. The second satellite, KITSAT-2, launched in September 1993, carries a newly developed 32-bit on-board computer(OBC), KASCOM(KAIST satellite computer in addition to OBC186. SEUs ocurred in the KASCOM, as well as in the program memory and RAM disk memory, have been monitored since the beginning of the satellite operation. These two satellites, which are very similar in structures but different in orbits, provide a unique opportunity to study the effects of the radiation environment characterized by the orbit.
DIGITAL SIGNAL PROCESSING EXPERIMENT OF KITSAT-1 AND KITSAT-2
Journal of Astronomy and Space Sciences, volume 13, issue 2, 1996, Pages 163~172
The objective of this paper is to show how digital signal processing experiment(DSPE) was designed and to present its experimental results in orbit and on the ground. The multi-missional and flexible DSPE was designed in a reliable manner. Among several experiments executed in orbit and on the ground, a high-speed(19.2kbps) software modulator experiment was discussed in this paper. A 32bit floating-type TMS320C30, which was developed for commercial purposes, was used on LEO micro-satellites, KITSAT-1 and KITSAT-2. This digital signal processor(DSP) can be applied to the various payloads of the next generation satellites.
KITSAT-1/2 ANALOG SUN SENSORS-IN-ORBIT RESULTS
Journal of Astronomy and Space Sciences, volume 13, issue 2, 1996, Pages 173~180
This paper briefly describes the KITSAT-1 and KITSAT-2 spacecrafts and presents the functions, calibration procedures and in-orbit results of the KITSAT-2 analog sun sensors have been flown as an experimental payload for the future mission. We have two constraints in their design: small size and very low power consumption due to the tight mass and power budget of the spacecraft. Two one-dimensional analog sun sensors are mounted on the top facet of the KITSAT-2 spaceraft. Each has
60 degrees of view angle and they cover 210 degree field of view in total as the 30 degree view angles are overlapped. Only the relative sun angle around the Z-axis (yaw-axis) and the spin rate of the spacecraft can be achieved as the one dimensional sun sensors are used and they are aligned with the Z-axis. The calibration formulae are obtained using the fifth order line fitting algorithm for each sun sensor on the ground and they are applied to the obtained in-orbit data. ASS-1 with silicon solar cells has maximum error of 1.5 degree and ASS-2 with silicon photocells manufactured at KAIST has maximum error of 0.5 degree except near 0 degree of sun ray incident anagle where random reflection of incident sun ray is maximum in orbit. The results are presented in chapter 4. The performance of each sun sensor and the possible mounting errors are stated in chapter 5.
우리별 1호 CCD 지구 관측 영상의 전처리
Journal of Astronomy and Space Sciences, volume 13, issue 2, 1996, Pages 181~197
Thc CCD earth image experiment(CEIE) is one of the main payload of the KITSAT-1. Since it was launched on Age. 11, 1992, the CEIE has taken more than 500 images on the earth surface world-wide so far. An image from the space is very different from a feature on the real Earth surface due to various radiometric and geometric distortions. Preprocessing to remove those distortions has to take place before the image data are processed and analyzed further for various applications. This paper summarizes the result of the operation of the CEIE and describes the procedure to perform preprocessing including radiometric and geometric correction.
REMOTELY SENSEDC IMAGE COMPRESSION BASED ON WAVELET TRANSFORM
Journal of Astronomy and Space Sciences, volume 13, issue 2, 1996, Pages 198~209
In this paper, we present an image compression algorithm that is capable of significantly reducing the vast mount of information contained in multispectral images. The developed algorithm exploits the spectral and spatial correlations found in multispectral images. The scheme encodes the difference between images after contrast/brightness equalization to remove the spectral redundancy, and utilizes a two-dimensional wavelet trans-form to remove the spatial redundancy. The transformed images are than encoded by hilbert-curve scanning and run-length-encoding, followed by huffman coding. We also present the performance of the proposed algorithm with KITSAT-1 image as well as the LANDSAT MultiSpectral Scanner data. The loss of information is evaluated by peak signal to noise ratio (PSNR) and classification capability.