• Journal of Positioning, Navigation, and Timing
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• v.8 no.3
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• pp.119-127
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• 2019

COsmicheskaya Sisteyama Poiska Avariynich Sudov Search and Rescue Satellite-Aided Tracking (COSPAS-SARSAT) is an international communication support program to perform search and rescue (SAR) operations in emergency situations by using satellite signals relayed from a beacon. The legacy COSPAS-SARSAT was originally composed of low altitude and geostationary Earth orbit satellites; thus, a limited number of directional dish antennas was sufficient to cover the limited number of visible satellites at the local user terminal. However, the second generation COSPAS-SARSAT newly added the medium Earth orbit satellites, e.g., Global Navigation Satellite Systems (GNSS) to the existing system, so that the number of visible satellites increase dramatically, and the system upgrade to cover all the visible satellites is foreseen. The additional use of planned Korea Positioning System (KPS) to existing GNSS is envisaged to provide a better performance of their SAR service. This paper presents the benefits of the additional use of KPS together with the phased array antennas at the local user terminal of the COSPAS-SARSAT. This is to effectively response to the increase of the number of visible satellites. Numerical simulation is included to evaluate the performance improvement of COSPAS-SARSAT in terms of the number of visible satellites, geometry between satellites and user, and position estimation accuracy.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.4
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• pp.484-490
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• 2012

This paper is devoted to investigate the feasibility of using a medium power ground-based laser to produce a torque on LEO satellites of various shapes. The laser intensity delivered to a satellite is calculated using a simple model of laser propagation in which a standard atmospheric condition and linear atmospheric interaction mechanism is assumed. The laser force is formulated using a geocentric equatorial system in which the Earth is an oblate spheroid. The torque is formulated for a cylindrical satellite, spherical satellites and for satellites of complex shape. The torque algorithm is implemented for some sun synchronous low Earth orbit cubesats. Based on satellites perigee height, the results demonstrate that laser torque affecting on a cubesat has a maximum value in the order of $10^{-9}$ which is comparable with that of solar radiation. However, it has a minimum value in the order of $10^{-10}$ which is comparable with that of gravity gradient. Moreover, the results clarify the dependency of the laser torque on the orbital eccentricity. As the orbit becomes more circular it will experience less torque. So, we can conclude that the ground based laser torque has a significant contribution on the low Earth orbit cubesats. It can be adjusted to obtain the required control torque and it can be used as an active attitude control system for cubesats.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.1
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• pp.98-106
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• 2018

With the advancement in technology, miniaturization, integration, and weight reduction of satellite components have become possible. In this regard, existing medium and large satellites have been replaced by small satellites. As the demand for small satellites increases, the need for micro-thrusters has emerged for precise attitude and position control. A laser ablation micro-thruster, which generates thrust by using ablation jets that offer a wide range of thrusts and low-impulse thrusts, is considered as an alternative for micro-thrusters in small satellites. The objective of the present study is to introduce configurations of the laser ablation micro-thruster and its research trend.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.753-756
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• 2017

With the advancement of technology, miniaturization, integration, and weight reduction have become possible, and the existing medium and large satellites have been replaced by small satellites, and the need for a micro thruster has emerged. Laser ablation micro-thruster is a new type thruster using laser ablation. It is emerging as a new candidate in micro-thrusters with wide thrust range and low single impulse thrust. The objective of present study is to introduces the structure, propellant, and research trends of the laser ablation micro-thruster.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.8
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• pp.605-612
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• 2013

When developing medium satellites or large satellites, coupled load analysis(CLA) is performed in order to verify satellite design as a final assessment under launch environment. Maximum acceleration, gap between adjacent parts, internal loads obtained from CLA are used to assess the safety of satellite design by comparing them with the allowable loads of every component. To achieve reliable CLA results, satellite FE model have to be properly updated to match with the sine vibration test results. In this paper, the validation procedure of satellite FE model and its results are discussed.

• Proceedings of the KSRS Conference
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• v.2
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• pp.1001-1002
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• 2006

Special problem emphasized by specialists in the field of analyzing the heat interchanges in the system ocean-atmosphere (SOA) is a necessity of determination of the near-surface atmospheric temperature, which can be only indirectly connected with characteristics of the SOA natural microwave radiation measured from satellites. That is why, the following dilemma is not obvious, but interesting and promised: what is better - to use the satellite methods for retrieving the partial parameters of the SOA or for analysis its state as a whole. To our opinion, this task is similar to the idea recognized by specialists engaged in the heat infrared region (8-12 mcm) of electromagnetic spectrum and its applications, where an intensity of natural infrared radiation (effective radiation) is used as the inherent property (the attribute) of the SOA heat balance. Here we studied important aspects of this problem: a) what medium initiates a heat transfer in the SOA and disturbs its heat balance - the ocean or the atmosphere b) what SOA parameters directly influence on its natural microwave radiation intensity (brightness temperature) measured from satellites? We relate these processes mainly to the synoptic range of time scales enriched by various events in the SOA interface such as the mid-latitude and tropical cyclones.

• Journal of Aerospace System Engineering
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• v.13 no.3
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• pp.23-31
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• 2019

The design requirements of modern satellites vary depending on the purpose of operation. Like conventional medium and large-scale satellites, small satellites which operate on low orbit may also serve military purposes. As a result, there is increased demand for high-resolution photos and videos and multi-target observation becomes important. The most important design parameter for multi-target observation is the satellites' maneuverability. For increased maneuverability, the miniaturization is required to increase the stiffness of the satellite as this decreases the mass moment of inertia of the satellite. In the case of a solar panel having relatively low stiffness compared to the satellites' body, vibrations are generated when the attitude maneuver is performed, which greatly influences the image acquisition. For verification of such vibrational characteristics, the satellites is modeled as a reduced model, and experimental zig for simulating attitude maneuver is introduced. A rigidity simulator for simulating the stiffness of the satellite is also proposed. Additionally, the objective of the experimental method is to simulate the maneuvering angle of the satellite based on the winding length of the wire using a step motor, and to experimentally verify the vibration characteristics of the satellite body and the solar panel generated during the maneuvering test.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.134-135
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• 2003

Medium-sized Aperture Camera (MAC)는 근적도궤도(Near Equatorial Orbit) 지구관측위성 MACSAT의 주탑재체로, 우리나라의 (주)쎄트렉아이와 말레이시아의 ATSB社와 오는 2004년 발사를 목표로 공동 개발되고 있다. MAC은 push-broom 방식의 전자광학 탑재체로, 지상해상도 2.5 m를 가지는 PAN band 1개, 지상해상도 5 m를 가지는 Multi-Spectral band 4 개를 가지고, 지상의 swath width는 20 km를 가진다. (중략)

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.136-137
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• 2003

Medium-sized Aperture Camera (MAC)는 근적도궤도(Near Equatorial Orbit) 지구관측위성 MACSAT의 주탑재체로, 우리나라의 (주)쎄트렉아이와 말레이시아의 ATSB社와 오는 2004년 발사를 목표로 공동 개발되고 있다. MAC은 push-broom 방식의 전자광학 탑재체로, 지상해상도 2.5 m를 가지는 PAN band 1개, 지상해상도 5 m를 가지는 Multi-Spectral band 4 개를 가지고, 지상의 swath width는 20 km를 가진다. (중략)

• Journal of Advanced Navigation Technology
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• v.10 no.4
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• pp.377-384
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• 2006

In this paper the detection time of the distress signal for the satellite-based search and rescue (SAR) system is evaluated. Present LEOSAR system in operation employs a few Low-altitude Earth Orbit (LEO) satellites and hence provides poor and local coverage availability. This results in a considerably long waiting time for a distress beacon to be detected by a rescue mission control center. One can expect that the detection time of the distress signal will be significantly reduced if the proposed MEOSAR system, which is based on the Medium-altitude Earth Orbit (MEO) satellites, is implemented. Taking into account the influence of the obstacles on the beacon signal, simulations are carried out to evaluate the detection time of distress signals for the LEOSAR and MEOSAR systems and the corresponding results are analyzed.