• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.12
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• pp.877-888
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• 2022

Recently, as the CAPSTONE, a precursor mission for Lunar Gateway, was launched on a small launch vehicle for the purpose of demonstrating communications and navigation technology in the NRHO, large attention was brought to this event that enabled high-impact deep space mission using dedicated small launch vehicle and small spacecraft. In this study, we introduced the concept of a dual launch operation and examined the capability of the new concept in the exploration of the Moon, Mars and asteroid. It turned out a single launch is sufficient for the lunar low orbit mission up to around 247 kg, and the dual launch option can transport 215 kg and 183 kg to nearby destinations as such as Mars and astroid Apophis respectively.

• Journal of the Korea Society of Computer and Information
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• v.21 no.10
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• pp.125-133
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• 2016

In this paper, we propose a real-time fault monitoring and dual system design of the countdown time-generating system, which is the main component of the mission control system. The countdown time-generating system produces a countdown signal that is distributed to mission control system devices. The stability of the countdown signal is essential for the main launch-related devices because they perform reserved functions based on the countdown time information received from the countdown time-generating system. Therefore, a reliable and fault-tolerant design is required for the countdown time-generating system. To ensure system reliability, component devices should be redundant and faults should be monitored in real time to manage the device changeover from Active mode to Standby mode upon fault detection. In addition, designing different methods for mode changeover based on fault classification is necessary for appropriate changeover. This study presents a real-time fault monitoring and changeover system, which is based on the dual system design of countdown time-generating devices, as well as experiment on real-time fault monitoring and changeover based on fault inputs.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.5
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• pp.423-433
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• 2016

In this paper, we consider the cybersecurity issue of ship information system (SIS) from a new perspective which is called opacity. For a SIS, its confidential information (named as "secret") may be leaked through the working behaviors of each Distributed Control Unit (DCU) from an outside observer called an "intruder" which is able to determine ship's mission state by detecting the source of each data flow from the corresponding DCUs in SIS. Therefore we proposed a dual layer mechanism to enforce opacity by activating non-essential DCU during secret mission. This mechanism is calculated by two types of insertion functions: Safety-assured insertion function ($f_{IS}$) and Admissibility-assured insertion function ($f_{IA}$). Due to different objectives, $f_{IS}$ is designed to confuse intruder by constructing a non-secret behaviors from a unsafe one, and the division of $f_{IA}$ is to polish the modified output behaviors back to normal. We define the property of "$I_2$-Enforceability" that dual layer insertion functions has the ability to enforce opacity. By a given mission map of SIS and the marked secret missions, we propose an algorithm to select $f_{IS}$ and compute its matchable $f_{IA}$ and then the DCUs which should be activated to release non-essential data flow in each step is calculable.

• Journal of Astronomy and Space Sciences
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• v.27 no.4
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• pp.345-352
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• 2010

Korea multi-purpose satellite-5 (KOMPSAT-5) is a low earth orbit (LEO) satellite scheduled to be launched in 2010. To satisfy the precision orbit determination (POD) requirement for a high resolution synthetic aperture radar image of KOMPSAT-5, KOMPSAT-5 has atmosphere occultation POD (AOPOD) system which consists of a space-borne dual frequency global positioning system (GPS) receiver and a laser retro reflector array. A space-borne dual frequency GPS receiver on a LEO satellite provides position data for the POD and radio occultation data for scientific applications. This paper describes an overview of AOPOD system and operation concepts of the radio occultation mission in KOMPSAT-5. We showed AOPOD system satisfies the requirements of KOMPSAT-5 in performance and stability.

• Proceedings of the KSRS Conference
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• v.2
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• pp.784-787
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• 2006

Dual-polarized transmission is one of the effective methods to transmit such a high speed data thanks to two independent channel leads to the orthogonal feature between RHCP (Right-Hand Circular Polarization) and LHCP (Left-Hand Circular Polarization). However, in practical case, the transmitted signal by RHCP polarized antenna in satellite can be occurred at the output port of LHCP polarized antenna in ground station, vice versa. XPD (Cross-Polarization Discrimination) is the ratio of the signal level at the output of a receiving antenna that is nominally co-polarized to the transmitting antenna to the output of a receiving antenna of the same gain but nominally orthogonally polarized to the transmitting antenna. In this paper, the detailed estimation of XPD within the interface between satellite and ground station is written and the influence of XPD to link performance is also described.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.3
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• pp.342-348
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• 2018

The important issue of equipment installed in maritime weapon system is shock survivability against underwater explosion(UNDEX). If the shock survivability of equipment should not be guaranteed, the successful mission also could not be achieved. For that reason, the shock-resistance of each equipment under UNDEX environment should be demonstrated before deployment at combat field. However, the actual UNDEX test on the ocean is too expensive to conduct. Also, it has diverse dangerous factors. The main characteristic of UNDEX is a dual-pulse shock. The vertical shock test machine able to simulate dual pulse shock signal on the ground will be introduced in this paper. The dual-pulse shock signal presented in certain shock standard was achieved with this shock-test machine on the ground. The analytical procedure to set a test condition was verified by comparing simulation result with experiment result.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.31.4-32
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• 2008

The microwave instruments are used many areas of the space remote sensing and space science applications. The imaging radar of synthetic aperture radar (SAR) is well known microwave radar sensor for earth surface and ocean research. Unlike radar, microwave radiometer is passive instrument and it measures the emission energy of target, i.e. brightness temperature BT, from earth surface and atmosphere. From measured BT, the geophysical data like cloud liquid water, water vapor, sea surface temperature, surface permittivity can be retrieved. In this paper, the radiometer characteristics, system configuration and principle of BT measurement are described. Also the radiometer instruments TRMM, GPM, SMOS for earth climate, and ocean salinity research are introduce. As first korean microwave payload on STSAT-2, the DREAM (Dual-channels Radiometer for Earth and Atmosphere Monitoring) is described the mission, system configuration and operation plan for life time of two years. The main issues of DREAM unlike other spaceborne radiometers, will be addressed. The calibration is the one of main issues of DREAM mission and how it contribute on the space borne radiometer. In conclusion, the radiometer instrument to space science application will be considered.

• Aerospace Engineering and Technology
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• v.4 no.2
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• pp.60-64
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• 2005

STSAT-2 will demonstrate the scientific mission(acquisition of brightness temperature of the earth at 23.8 GHz and 37 GHz) and spacecraft technologies(laser ranging, frame-type satellite structure, Dual-head star tracker, CCD sun sensor, pulsed plasma thruster, etc.). In this paper STSAT-2 satellite system is described. It includes the definition of the system and the overview of payloads and BUS.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.493-495
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• 2007

Future sub-meter resolution LEO missions require simultaneous dual-polarization downlink and/or multiple channel downlinks in single polarization. Especially, dual-polarization is needed to cope with bandwidth limitation due to high speed data transmission. Current KARI 13m X-Band antenna system needs to be upgraded to cope with such downlink schemes. This paper describes brief discussions on engineering work regarding how to meet the new requirements with minimum impact on current system as well as C&M (Control and Monitoring) software.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.1 no.2
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• pp.13-20
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• 2008

Reliability is absolutely necessary in most recent mission critical systems which usually utilize the Ethernet based computer networks. A typical way to increase system reliability is to equip the fault tolerant Ethernet. In this paper we try to formulate the fault tolerant dual Ethernet concept and presents a comparison of its implementation approaches. Two types of dual Ethernet configuration are analyzed; the divided and the connected. Then the characteristics of three current implementation approaches which are the hardware based, the software based, and the recently proposed hybrid approach are compared. The results show that the hardware based or the hybrid approaches can be a better solution for the real time mission critical systems. Also for the systems which require the use of Commercial-Off-The-Shelf (COTS) hardware for fault tolerant Ethernet the possible choice is the software based or the hybrid approach.