• Advances in aircraft and spacecraft science
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• v.4 no.5
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• pp.543-553
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• 2017

Vibration is a source of performance degradation in all optical imaging systems. Performance of high resolution remote sensing payloads is often limited due to satellite platform vibrations. Effects of Linear and high frequency sinusoidal vibrations on the system MTF are known exactly in closed form but the low frequency vibration effects is a random process and must be considered statistically. Usually the vibration MTF budget is defined based on the mission requirements and the overall MTF limitations. For analyzing low frequency effects, designer must know all the systems specifications and parameters. With a good understanding of harmful vibration frequencies and amplitudes in the system preliminary design phase, their effects could be removed totally or partially. This procedure is cost effective and let the designer to eliminate just harmful vibrations and avoids over-designing. In this paper we have analyzed the effects of low-frequency platform vibrations on the payload's modulation transfer function. We have used a statistical analysis to find the probability of imaging with a MTF equal or greater than a pre-defined budget for different missions. The worst and average cases have been discussed and finally we have proposed "look-up figures". Using these look-up figures, designer can choose the electro-optical parameters in such a way that vibration effects be less than its pre-defined budget. Furthermore, using the results, we can propose a damping profile based on which vibration frequencies and amplitudes must be eliminated to stabilize the payload system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.8
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• pp.710-717
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• 2016

Satellite payload can be classified as electro-optical payload, SAR, microwave radiometer, communication payload, navigation payload and so on in accordance with the mission objective. The technology of satellite payload was tried to be obtained through development of KOMPSAT series, COMS and STSAT in Korea. In this paper, the required technology for the development and world market trend of satellite payload were studied and described. Since KOMPSAT program has been started in 1994, technology status and future prospects of satellite payload in Korea are studied and analyzed.

• Journal of Satellite, Information and Communications
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• v.11 no.3
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• pp.86-91
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• 2016

KARI(Korea Aerospace Research Institute) has been developing the KPLO(Korea Pathfinder Lunar Orbiter) for Korean first lunar exploration, and analysing various subjects for the mission success. Especially the performance of the communication is one of important factors, because massive scientific and technical data acquired by multiple payloads might be transferred to ground stations on the Earth. In this paper, we explained the study on the 1-day average downlink capacity based on the visibility analysis between ground stations and KPLO, and described its results.

• Journal of the Korean Society of Safety
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• v.30 no.5
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• pp.92-99
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• 2015

The diameter of a new wheel in EMUs is 860mm and it can be used up to 773mm. To obtain an predefined acceleration despite wheel diameter changes, the tractive efforts of the vehicles must be properly controlled. In the commencement of this study, acceleration tests were performed for empty EMUs when the wheel diameter was changed to 860mm, 820mm and 780mm, respectively. In order to deal with more complicated running conditions, we developed dynamic simulation models of the EMUs using VI-Rail, and simulated the models in empty and full passenger loads, respectively. Using the simulation results, we analyzed the gradient of time-velocity graphs by considering the changes of the total weight vehicles and moment of inertia of the wheelsets as well as tractive effort according to the wheel diameter changes. As the results, it was found that there are significant differences in acceleration performances according to the wheel diameters and the payloads of EMUs. In case of 860mm which is the maximum wheel diameter, the test & simulation results show that the vehicle couldn't reach the predefined acceleration, 3.0km/h/s, due to lack of tractive effort.

• The KIPS Transactions:PartC
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• v.12C no.1 s.97
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• pp.11-18
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• 2005

This paper proposes a packet header collector, based on a network processor with multi-processor and multi-threads, that shows a high throughput on gigabit network. The proposed collector has an architecture to separate packets coming from gigabit network into headers and payloads, and distribute them to multiple 100Mbit MAC ports. The architecture hiring a unique buffer management method and load distribution strategy among multiple processors is evaluated empirically in depth.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.336-339
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• 2004

Communication, Ocean and Meteorological Satellite (COMS) has been developed by Korean Aerospace Research Institute (KARI) since 2003. Ocean Color Imager (OCI) is the one of COMS payloads, which will monitor the marine environment around Korean peninsula routinely with the intermediate resolution. But considering COMS is to be located in the geostationary orbit, required geographical coverage is not positioned in the nadir direction of COMS but in specific location with horizontal and vertical offsets from the nadir. In this study, coverage by OCI Field Of View (FOV) is analyzed. First of all, OCI is modeled as the sensor which is a $2,500{\times}2,500$ sized 2-D CCD and the pixel resolution is about 500m. And then, OCI is simulated to be controlled to target the required coverage accurately. As a result of it, coverage by OCI FOV is determined. Finally, all coverages by OCI FOV are mapped.

• Proceedings of the KSRS Conference
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• v.1
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• pp.56-59
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• 2006

In this paper, Korea's first geostationary Communication, Ocean and Meteorological Satellte(COMS) program is introduced. COMS program is one of the Korea National Space Programs to develop and operate a pure civilian satellite of practical-use for the compound missions of meteorological observation and ocean monitoring, and space test of experimentally developed communication payload on the geostationary orbit. The target launch of COMS is scheduled at the end of 2008. COMS program is international cooperation program between KARI and ASTRIUM SAS and funded by Korean Government. COMS satellite is a hybrid satellite in the geostationary orbit, which accommodates multiple payloads of MI(Meteorological Imager), GOCI(Geostationary Ocean Color Imager), and the Ka band Satellite Communication Payload into a single spacecraft platform. The MI mission is to continuously extract meteorological products with high resolution and multi-spectral imager, to detect special weather such as storm, flood, yellow sand, and to extract data on long-term change of sea surface temperature and cloud. The GOCI mission aims at monitoring of marine environments around Korean peninsula, production of fishery information (Chlorophyll, etc.), and monitoring of long-term/short-term change of marine ecosystem. The goals of the Ka band satellite communication mission are to in-orbit verify the performances of advanced communication technologies and to experiment wide-band multi-media communication service mandatory.

• Proceedings of the KSRS Conference
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• v.1
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• pp.271-273
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• 2006

In this paper, we describe the MI2U ORB function which is a part of the flight software executed on SCU and controls MI2U/MI which is one of three payloads on COMS. The MI2U ORB function manages MI2U/MI redundancy and reconfiguration, monitors MI2U/MI equipment, performs FDIR, and provides the routing service of commands from Ground/IP (Interpreted Program) through the current used 1553 channel. The MI2U hardware achieves the interface between the SCU and the MI. The MI2U is connected to SCU through MIL-STD-1553B system bus. The MI2U has the internal redundancy but is used in cold redundancy. The MI2U ORB function considers that they are not expected to be simultaneously switched on. The connection combination between MI2U and MI is electrically cross-strapped. However the MI2U ORB function considers only two combinations (MI2U A + MI 1, MI2U B + MI 2). Other combinations can be manually achieved by ground in case of the emergency case.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.4
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• pp.389-394
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• 2010

This paper describes the conceptual design of mass memory unit for high speed data processing and mass memory management in the STSAT-3 compared to that of STSAT-2. The FPGA directly controls the data receiving from two payloads with the maximum 100Mbps speed and 32Gb mass memory management to satisfy these requirements. We used SRAM-based FPGA from XILINX having fast operating speed and large logic cells. Therefore, the Triple Modular Redundancy(TMR) and configuration memory scrubbing techniques will also be used to protect FPGA from Single Event Upset(SEU) in space.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.185-188
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• 2008

This paper introduces the Bootstrap method for statistical analysis of noise and vibration spectrum in aeronautic and space fields. Generally, all components of a launch vehicle and its payloads are subjected to high intensive noise and vibration environment during the lift-off phase and the ascent phase through Mach =1 and Max Q. In order to verify their survivabilities against these severe vibroacoustic environments during qualification tests and acceptance tests, it is most important to estimate the proper upper limits of the environmental condition. Although NASA has typically utilized the Normal Tolerance Limit method in deriving these levels, the reference[1] says that the Bootstrap can be also an alternative method to estimate the maximum expected environments. In this paper, a general procedure of the Bootstrap method is summarized, and it is applied to analyze acceleration power spectral density functions, which were measured during acoustic test on the upper stage of KSLV-I.