• Journal of Positioning, Navigation, and Timing
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• v.12 no.4
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• pp.437-445
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• 2023

A space system refers to a network of sensors, ground systems, and space-craft operating in space. The security of space systems relies on information systems and networks that support the design, launch, and operation of space missions. Characteristics of space operations, including command and control (C2) between space-craft (including satellites) and ground communication, also depend on wireless frequency and communication channels. Attackers can potentially engage in malicious activities such as destruction, disruption, and degradation of systems, networks, communication channels, and space operations. These malicious cyber activities include sensor spoofing, system damage, denial of service attacks, jamming of unauthorized commands, and injection of malicious code. Such activities ultimately lead to a decrease in the lifespan and functionality of space systems, and may result in damage to space-craft and, lead to loss of control. The Cybersecurity Adversarial Tactics, Techniques, and Common Knowledge (ATT&CK) matrix, proposed by Massachusetts Institute of Technology Research and Engineering (MITRE), consists of the following stages: Reconnaissance, Resource Development, Initial Access, Execution, Persistence, Privilege Escalation, Defense Evasion, Credential Access, Discovery, Lateral Movement, Collection, Command & Control, Exfiltration, and Impact. This paper identifies cybersecurity activities in space systems and satellite navigation systems through the National Institute of Standards and Technology (NIST)'s standard documents, former U.S. President Trump's executive orders, and presents risk management activities. This paper also explores cybersecurity's tactics attack techniques within the context of space systems (space-craft) by referencing the Sparta ATT&CK Matrix. In this paper, security threats in space systems analyzed, focusing on the cybersecurity attack tactics, techniques, and countermeasures of space-craft presented by Space Attack Research and Tactic Analysis (SPARTA). Through this study, cybersecurity attack tactics, techniques, and countermeasures existing in space-craft are identified, and an understanding of the direction of application in the design and implementation of safe small satellites is provided.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.3
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• pp.245-255
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• 2023

Time comparison techniques are necessary for generating and keeping Coordinated Universal Time (UTC) and distributing standard time clocks. Global Navigation Satellite System (GNSS) Common View, GNSS All-in-View, Two-Way Satellite Time and Frequency Transfer (TWSTFT), Very Long Baseline Interferometry (VLBI), optical fiber, and Network Time Protocol (NTP) based methods have been used for time comparison. In these methods, GNSS based time comparison techniques are widely used for time synchronization in critical national infrastructures and in common areas of application such as finance, military, and wireless communication. However, GNSS-based time comparison techniques are vulnerable to jamming or interference environments and it is difficult to respond to GNSS signal disconnection according to the international situation. In response, in this paper, Code-Division Multiple Access (CDMA) based All-to-All TWSTFT operation method is proposed. A software-based simulation platform also was designed for performance analysis in multi-TWSTFT signal environments. Furthermore, code and carrier measurement jitters were calculated in multi-signal environments using the designed simulation platform. By using the technique proposed in this paper, it is anticipated that the TWSTFT-based time comparison method will be used in various fields and satisfy high-performance requirements such as those of a GNSS master station and power plant network reference station.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.41 no.1
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• pp.1-8
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• 2004

The INS(Inertial Navigation System) provides high rate position, velocity and attitude data with good short-term stability while the GPS(Global Position System) provides position and velocity data with long-term stability. By integrating the INS with GPS, a navigation system can be achieved to Provide highly accurate navigation Performance. For the best performance, time synchronization of GPS and INS data is very important in GPS/INS integrated system But, it is impossible to synchronize them exactly due to the communication and computation time-delay. In this paper, to reduce the error caused by the measurement time-delay in GPS/INS integrated systems, error compensation methods using separate bias Kalman filter are suggested for both the loosely-coupled and the tightly-coupled GPS/INS integration systems. Linearized error models for the position and velocity matching GPS/INS integrated systems are Int derived by linearizing with respect to its time-delay and augmenting the delay-state into the conventional state equations for each case. And then separate bias Kalman Inter is introduced to estimate the time-delay during only initial navigation stage. The simulation results show that the present method is effective enough resulting in considerably less position error.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4828-4834
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• 2015

From the moment that a firing pin triggers the detonator to the moment that a grenade leaves a barrel is called Action Time. Since a loading and percussion of 40mm grenade happens simultaneously, action time should be within a certain time in order to prevent a Jamming malfunction. Previously, unreliable action time device of 40mm grenade made it difficult to improve quality assurance of K4 Grenade Machine Gun. Here, various sensors were compared and a special device was designed to seek an accurate measurement on action time. In this device, the gap between a signal from an optical sensor in Firing Pin and that from Eddy current probe in the barrel was recorded and data were sent to a computer in real time. Confirming if action time is within the criteria, it is expected that action time plays an important role in quality assurance on 40mm grenade.

• Fire Science and Engineering
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• v.29 no.3
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• pp.59-64
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• 2015

This study analyzed results of the causes of failure in 1,022 fire trucks currently being used in South Korea (aerial ladder, aerial platform, pumper, and chemical fire trucks). The results show that 46% of aerial ladder trucks have defective in the elevator brake systems, 29% of aerial platform trucks have contamination in the hydraulic oil, 37% of pumpers have defective in the pneumatic cylinders of the air supply system, and 39% of chemical fire trucks have defective in the powder fire extinguishing systems. The principal reasons for malfunctions are deterioration of the apparatuses, and accumulated fatigue from repetitive use of certain components, such as pneumatic cylinders in the air supply system and wire rope jamming in rollers in the ladder apparatus. These manufacturing defects should be improved upon in the manufacturing process. As a result, the fire trucks, which are used for 5 years or more, need precise inspections in accordance with the Regulation on Fire Apparatus Maintenance. Fire apparatuses have a service life of 10 to 12 years or more. They need to be replaced or require life extension, and they should be kept in top shape with the best maintenance for public safety.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.32 no.1
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• pp.63-73
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• 2014

Recently, researches on DBRN(DataBase Referenced Navigation) system are being carried out to replace GNSS(Global Navigation Satellite System), as weaknesses of GNSS were found that are caused by the intentional interference and the jamming of the satellite signal. This paper describes the gravity gradient modeling and the construction of EKF(Extended Kalman Filter) based GGRN(Gravity Gradient Referenced Navigation). To analyze the performance of GGRN, fourteen flight trajectories were made for simulations over whole South Korea. During the simulations, we considered the errors in both DB(DataBase) and sensor as well as the flight altitudes. Accurate performances were found, when errors in the DB and the sensor are small and they located at lower altitude. For comparative evaluation, the traditional TRN(Terrain Referenced Navigation) was also developed and performances were analyzed relative to those from the GGRN. In fact, most of GGRN performed better in low altitude, but both of precise gravity gradient DB and gradiometer were required to obtain similar level of precisions at the high altitude. In the future, additional tests and evaluations on the GGRN need to be performed to investigate on more factors such as DB resolution, flight speed, and the update rate.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.4 no.2
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• pp.1-8
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• 2005

In this paper, n system did research about effect that interference effect with neighborhood single equipment or group equipment gets in DMB service. For this, 2.6425 GHz SDMB(Satellite Digital Multimedia Broadcasting) that a special of electric wave interference is near frequency-band including interference of signal by unnecessary radiation level that is radiated in UWB system, and degree of 3.4125GHz broadcasting relay net that is In-band frequency-band and interference effect that get in service analyzed comparison ud, modulation of broadcasting relay net and interference measurement equipment used Impulse and OFDM methods. Impulse method was $BER=1{\times}10^4$ that broadcasting signal receiption is possible at 1.4m point because interference effect happens from 2m point in SDMB system, and it was $BER=1^{\times}10-4$ that OFDM method receives interference effect from 0.8m point and broadcasting signal receiption is possible at 0.5m point. Also, about gap-filler center frequency, in case of space interval more than 0.01m, there was no interference effect. Therefore, for the electric wave of W system that is small output applies to system without interference effect in DMB service, confirmed that UWB system of OFDM method is less interference effect than UWB system of impulse method.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.5
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• pp.44-50
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• 2014

Chaos communication system is one of the security algorithms that is applied to improve the security. Chaos signal is non-linear, and it is generated randomly according to the initial conditions. Also, chaos communication system has characteristics such as non-periodic, wide-band, non-predictability of signals and easy implementation. So, security of chaos communication system is superior, and it has low interception probability and good anti-jamming characteristic. However, BER performance is worse than digital communication system, because it has many self interference signal in case of CDSK system. To improve these disadvantages, we analyze the PDF trend which can improve the BER performance in existing study, and we proposed a chaos map. And, proposed chaos map was defined as the 'Boss map'. Generally, BER performance is changed according to initial values, parameters and spreading factors. Therefore, in this paper, we will introduce PDF trends which can improve the BER performance, and will describe about Boss map. Also, characteristics of Boss map is analyzed by evaluating the BER performance of Boss map according to initial values, parameters and spreading factors. As a result, while maintaining the similar BER performance, initial value of Boss map can be selected from 0 to 1.2, and BER performance is best when parameter alpha is 2.5. Also, BER performance is best when spreading factor is 50.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.7 no.1
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• pp.23-31
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• 2007

In this paper, UWB system did research about effect that interference effect with neighborhood single equipment or group equipment gets in broadcasting communication service. For this, 2.6425GHz SDMB(Satellite Digital Multimedia Broadcasting) that a special of electric wave interference is near frequency-band including interference of signal by unnecessary radiation level that is radiated in UWB system, and degree of 3.4125GHz broadcasting relay net that is In-band frequency-band and interference effect that get in service analyzed comparison and, modulation of broadcasting relay net and interference measurement equipment used Impulse and OFDM methods. Impulse method was $BER\;=\;1{\times}\;10^{-4}$ that broadcasting signal receiption is possible at 1.4m point because interference effect happens from 2m point in SDMB system, and it was $BER\;=\;1{\times}\;10^{-4}$ that OFDM method receives interference effect from 0.8m point and broadcasting signal receiption is possible at 0.5m point. Also, about Gap-Filler center frequency, In case of space interval more than 0.01m, there was no interference effect. Therefore, for the electric wave of UWB system that is small output applies to system without interference effect in broadcasting communication service, confirmed that UWB system of OFDM method is less interference effect than UWB system of Impulse method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.7
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• pp.365-371
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• 2014

Chaos communication system is possible to improve the system security by using chaos signal. Further, it is possible to reduce the possibility of eavesdropping, and have strong characteristics from interference signal and jamming signal. However, BER(Bit Error Rate) performance of chaos system is worse than digital communication system. By this reason, researches in order to improve the BER performance of chaos communication system are being actively studied. In previous studies, we proposed a novel chaos map for BER performance improvement, and called it 'Boss map'. Also, we proposed a novel chaos transceiver for BER performance improvement. However, BER performance is evaluated differently according to delay time in transceiver. Therefore, in order to use Boss map effectively, we should find the optimal delay time in proposed chaos transceiver. In this paper, when Boss map is used, we evaluate BER performance of CDSK(Correlation Delay Shift Keying) system and novel chaos transceiver according to delay time. After evaluation of BER performance according to delay time, we find a delay time that is possible to have best BER performance in CDSK system and novel chaos transceiver.