• Current Industrial and Technological Trends in Aerospace
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• v.8 no.2
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• pp.31-38
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• 2010

Environment and climate changes affect all aspects of our society. The enhanced remote sensing technology made the satellite to be widely used in the environment monitoring applications. Geostationary environmental monitoring is also actively researched due to the increased needs for the monitoring of diurnal environmental changes, troposhperic pollution and its origin. In this paper, recent development trends of geostationary environment monitoring payloads are introduced. GEO-CAFE and GIFTS missions are researched by the leading of the NASA and Sentinel-4 by the ESA. Those missions are in the state of detailed conceptual design and hardware development preparing with the launch plan in the late 2010s. By considering these development trends, domestic environment monitoring payloads shall be developed with careful analysis on the mission and data application.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.12
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• pp.1128-1139
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• 2013

KOMPSAT-5(KOrea Multi-Purpose SATellite-5) has a benefit of continuously conducting its mission in all weather and even night by loading SAR(Synthetic Aperture Radar) payload, which is different from optical sensor of KOMPSAT-2 satellite. During IOT(In-Orbit Test) periods, SAR image calibration should be conducted through ground target of which location and RCS is pre-determined. Differently from the conventional corner reflector, active transponder has a capability to change its internal transfer gain and delay, which allows active transponder to be shown in a pixel of SAR image with very high radiance and virtual location. In this paper, the development of active transponder is presented from design to I&T(Integration and Test).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.1
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• pp.56-62
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• 2011

A Satellite transponder is mounted on the Satellite and performs radio communications with the ground station. A Digital transponder compared to The analog transponder is made easy and accurate performance prediction. Also Modulation Scheme, Data Rate, Loop Bandwidth, Modulation Index and etc. can be changed on orbit, by implementing FPGA can reduce the weight and volume. The core technology of digital transponder is Carrier Recovery loop. Dynamic Range, Frequency Tracking Range, Frequency Tracking Rate and Coherent performance are determined by the performance of the Carrier Recovery loop. In this paper, we proposed the structure of Carrier Recovery loop for the Satellite digital transponder, then tested and verified the structure.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.12
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• pp.1279-1286
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• 2009

This paper addresses the analysis of the interference produced between the LEO(Low Earth Orbit) satellite constellation and FS(Fixed Service) system operating in the same frequency and area. At first, we calculates the interference of FS system from the LEO satellite constellation depending on the number of LEO satellite antenna beams. Simulation results show that the amount of interference that was calculated from each region. This result can be used to define the carrier level for protecting FS system from total interference by LEO satellite constellation. In the second scenario, we calculates the interference of LEO satellite system earth station by the FS link depending on radius of protection area. The presented results can be used to design FS systems minimizing interference to earth station.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.7
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• pp.583-591
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• 2018

In this paper, we propose a new deployment test equipment that is characterized for the deployment test of single large solar panel with tape spring hinge. To perform the deployment test on ground, a device that takes gravity compensation into account should be used to create a zero gravity environment similar to that in orbit. We analyzed the advantages and disadvantages of the most commonly used deployment test equipment in the past through simple conceptual design, analysis, and tests to judge whether it is applicable to the deployment of the solar panel to be tested. A dummy frame was proposed to reduce the air drag effect during on-ground test and a self-aligning ball bearing and adjusting screws were applied to the deployment test equipment to solve the alignment problem with the gravity axis. And a horizontal bearing for radial movement applied to compensate for the change of the axis of the tape spring hinge. From these, we solved the problems of the conventional deployment test equipment by developing and verifying the new deployment test equipment characterized for the solar panel to be deployed in this paper.

• Journal of Astronomy and Space Sciences
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• v.28 no.2
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• pp.133-141
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• 2011

A satellite power system should generate and supply sufficient electric power to perform the satellite mission successfully during the satellite mission period, and it should be developed to be strong to the failure caused by the severe space environment. A satellite power system must have a high reliability with respect to failure. Since it cannot be repaired after launching, different from a ground system, the failures that may happen in space as well as the effect of the failures on the system should be considered in advance. However, it is difficult to use all the hardware to test the performance of the satellite power system to be developed in order to consider the failure mechanism of the electrical power system. Therefore, it is necessary to develop an accurate model for the main components of a power system and, based on that, to develop an accurate model for the entire power system. Through the power system modeling, the overall effect of failure on the main components of the power system can be considered and the protective design can be devised against the failure. In this study, to analyze the failure mode of the power system and the effects of the failure on the power system, we carried out modeling of the main power system components including the solar array regulator, and constituted the entire power system based on the modeling. Additionally, we investigated the effects of representative failures in the solar array regulator on the power system using the power system model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.8
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• pp.695-701
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• 2016

Spacecraft propulsion system is a kind of rocket engine that has been developed from the end of 1950s for attitude control and orbit maintenance of satellite. Since the spacecraft propulsion system has to be used for a relatively long time, therefore, stability of propellant and life of thruster could be very important factor for propulsion system design. Recently, green propellant propulsion and all electrical propulsion system have became very important issue, and we also need a development according to well organized plan. In this paper, we will introduce the development status, key technologies and development prospect of spacecraft propulsion system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.7
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• pp.647-654
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• 2007

A Discrete continuation Method/homotopy approaches are studied for energy/fuel optimal low thrust Earth escape trajectory by solving a two point boundary value problem(TPBVP). Recently, maneuvers using low thrust propulsion system have been identified as emerging technologies. The low thruster is considered as the main actuator for orbit maneuvers. The cost function consists of a energy/fuel consumption function, and constraints are position and velocity vectors at the terminal escape point. Solving the minimum energy/fuel problem directly is not an easy task, so we adopt the homotopy analysis. Using a solution of the minimum energy, which is solved by discrete continuation method, we obtain the solution of the minimum fuel problem.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.4
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• pp.40-46
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• 2006

A 30-tonf-class fullscale thrust chamber for the application to a Low-Earth-Orbit Space Launch Vehicle has been combustion tested over the wide ranges of a mixture ratio and a chamber pressure. The thrust chamber designed for a pump-fed open cycle engine was tested with an ablative chamber instead of a regenerative one for the initial evaluation of its performance and function. The test results revealed stable combustion characteristics. The hardware survived the harsh environment and showed very sound functional characteristics. The measured combustion efficiency turned out to be 95% and a specific impulse at sea level was estimated as 254sec, which are comparable to or above the predetermined design values.

• Journal of Astronomy and Space Sciences
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• v.18 no.2
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• pp.163-173
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• 2001

In this paper, space radiation environment and single event effect(SEE) have been analyzed for the KOMPSAT-2 operational orbit. As spacecraft external and internal space environment, trapped proton, SEP(solar energetic particle) and GCR(galactic cosmic ray) high energy Protons and heavy ions spectrums are analyzed. Finally, SEU and SEL rate prediction has been performed for the Intel 80386 microprocessor CPU that is planned to be used in the KOMPSAT-2. As the estimation results, under nominal operational condition, it is predicted that trapped proton and high energetic proton induced SBU effect will not occur. But, it is predicted that heavy ion induced SEU can occur several times during KOMPSAT-2 3-year mission operation. KOMPSAT-2 has been implementing system level design to mitigate SEU occurrence using processor CPU error detection function of the on-board flight software.