• Journal of Space Technology and Applications
• /
• v.3 no.2
• /
• pp.144-153
• /
• 2023

The existing military satellite communication system was based on geostationary satellites equipped with special communication payloads against enemy's jamming and signal reception. With the advent of new weapon systems such as unmanned systems, the need for low-orbit satellite-based communication system is increasing. This paper introduces various waveform technologies suitable for cube satellite-based communication system and the operational concept of a future military nanosatellite communication system.

• Bulletin of the Korean Space Science Society
• /
• 2011.04a
• /
• pp.22.4-22.4
• /
• 2011

위성항법시스템에서 위성 신호의 이상 발생 시 신속하게 위성시계의 고장 유무를 판단할 수 있도록 실시간 위성 시계 이상감지 시스템을 구축하였다. 위성 시계는 시스템 성능에 직접적인 영향을 미치는 핵심 요소로서 고장이나 이상 발생 시 측정치에 매우 큰 영향을 미칠 수 있다. 특정 위성 시계에 고장이나 이상이 발생한 경우 사용자들이 해당 위성의 측정치를 사용하지 않도록 가능한 빨리 이를 감지하고 공지할 수 있어야 한다. 현재 GPS의 경우 시스템 자체만으로는 위성 상태 정보가 적절한 시간 내에 제공되지 못하므로, 사용자가 직접 위성 신호의 사용 유무를 판단할 수 있는 위성 상태 감시 기능이 필요하다. 이 논문에서는 위성 시계 이상 발생 시 이를 실시간으로 감지할 수 있도록 한국항공우주연구에서 구축한 실시간 위성 시계 이상 감지 시스템에 대해 소개하고자 한다. 시스템 구현을 위해 적용한 방법은 크게 세 단계로 나뉠 수 있다. 첫 번째, 실시간으로 수신한 GPS 이중 주파수 측정치로부터 반송파 스무딩 필터를 적용하여 위성 시계 바이어스를 추정한다. 두 번째, 위성 위치 및 시계 정보의 실시간 적용을 위해 항법력보다 성능이 뛰어난 IGS Ultra-rapid 예측 정보를 활용한다. 마지막으로 위성시계 바이어스 추정치와 예측치를 비교하여 시계 이상 유무를 판별한다. 실제 위성 시계 이상이 발생한 위성의 측정치를 적용하여 시스템에 대한 검증시험을 수행하였고, 10 나노 초 수준의 위성 시계도약 현상이 발생한 위성의 감지를 통해 시스템의 성능을 확인하였다. 이는 항공항법분야와 같이 고성능의 위치 정보를 요구하는 응용분야에 신뢰성 있는 위성 정보 제공을 위해 활용될 수 있다.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.11
• /
• pp.919-931
• /
• 2021

In the recent New Space era, Nanosatellites are being used to carry out space business and practical missions by private space companies, government agencies and military reconnaissance organizations, away from satellite system education tools. In Korea, the development of nanosatellite satellites, which started with universities at the center, is gradually being attempted by various subjects, including private industries. However, it is not easy to find relevant information to share the experience and prepare for the space environment test, test results, and the various problems that may arise in the process, which can increase the chances of mission success for nanosatellites. In this paper, we expect that the subjects who want to develop the nanosatellite(SNIPE) will be used as useful references for reducing trial and error and increasing the possibility of mission success by organizing the 6U-class space environment test, test process, test results and problems.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.12
• /
• pp.83-91
• /
• 2005

Air-Launching is an effective method that can launch the 'Nanosat' with low launching cost. In this study, system and subsystem design of the air launching rocket for nanosats which perform a simple mission, have been performed. For this purpose, the WBS of the MIRINAEⅡ, and the subsystem schematics have been defined first. Based on these results, detailed configuration and DMU have been developed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2005.11a
• /
• pp.293-298
• /
• 2005

Air-Launching is an effective method that can launch the 'Nanosat' with low launching cost. In this study, system and subsystem design of the air launching rocket for nanosats which perform a simple mission, have been performed. Foe this purpose, the WBS of the Air-launching Rocket System, and the subsystem schematics have been defined first. Based on these results, detailed configuration and DMU have been developed.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.12 no.1
• /
• pp.64-70
• /
• 2008

Thanks to the breakthroughs in micro fabrication technology, numerous concepts of micro aerospace systems including micro aerial vehicle, nano satellite and micro robot have been proposed. In order to activate these mobile micro systems, high density power in a small scale power source is required. However, we still do not have micro power source that has energy density that can support these systems. In the present article, status of micro power sources are described and alternatives that have been derived from the past experience are proposed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2007.04a
• /
• pp.175-178
• /
• 2007

The mode transition from cone-jet to dripping in colloid thruster operation has been analytically investigated. The transition has been predicted by the dynamic behavior of a liquid drop at the tip of the cone-jet. Conservation laws are applied to determine the upward motion of the drop, and an instability model of electrified jets is used to determine the jet breakup. Finally, for the first time, the analysis enables prediction of the transition in terms of the Weber number and electric Bond number. The predictions are in good agreement with experimental data.

• Korean Journal of Optics and Photonics
• /
• v.32 no.1
• /
• pp.9-14
• /
• 2021

In this paper we have studied an optical system according to the aperture position of an off-axis TMA telescope for satellites. An off-axis TMA telescope should have high resolution and wide field of view (FOV). In addition, the optical system should have a wide tolerance range, because it is structurally located off-axis and is difficult to assemble. However, there are differences in performance and sensitivity according to the aperture-stop position, so it is important to select a suitable aperture-stop position. Therefore, in this paper we have designed each off-axis TMA telescope according to the aperture-stop position, and have analyzed the performance and sensitivity to suggest a suitable aperture-stop position.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.17 no.6
• /
• pp.1312-1317
• /
• 2013

Pseudolite is a contraction of the term "pseudo-satellite", used to refer to something that is not a satellite which performs a function commonly in the domain of satellites. Pseudolite are most often small transceivers that are used to create a local, ground-based GPS alternative. Pseudo-range measurement of pseudolite has around 300m range error, when time synchronization error of $1{\mu}sec$ occurs. Therefore the time synchronization methods play an important part in navigation augmentation using pseudolite. This paper proposes three clock synchronization methods that are installation method of pseudolite station, method using KRISS-UTC and method using PRN code phase difference for pseudolite. The simulation platform structure is presented for evaluating proposed clock synchronization performance.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.11
• /
• pp.106-114
• /
• 2005

This study addresses space simulation test results and thermal modelling verification of HAUSAT-2 nanosatellite STM (Structural-Thermal Model). The thermal modelling of the HAUSAT-2 has been modified in accordance with test results. Thermal analysis results were repeatedly compared with test results for modified thermal modelling. It is verified that the analysis results for modified thermal modelling agree well with test results. Some surface heaters were implemented to simulate solar illumination for HAUSAT-2 Thermal Vacuum/Balance Test. A low-cost and effective thermal test methodology, which is applicable to ultra-small satellite system, was proposed and verified by test results in this study.