• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.3
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• pp.483-488
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• 2019

The propagation prediction model of the earth-space communication link used as an international standard was used to calculate and analyze the total losses on the communication path. The standard definition and scope of ITU-R Rec. were analyzed for each parameter(rain, scintillation, atmospheric gas, clouds) used to calculate the total loss. The total losses were calculated using the standard model for each parameter and the statistical data provided by ITU-R, and the results were analyzed using the validation examples data. The rain losses were calculated using long-term local rainfall attenuation statistics data measured in the region, and compared with the calculation results using a rainfall map in the ITU-R Recommendation. The data of Cheollian satellites for the L-Band and Ka-Band were used to calculate the rainfall attenuation. In the range of 0.01% to 0.1%, it was found to have a greater attenuation slope when using local data than attenuation by the model of ITU-R.

• Journal of Space Technology and Applications
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• v.4 no.1
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• pp.48-61
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• 2024

In this paper, we introduce the concept of the cube satellite Chungnam National University Laser Unity Bus (CLUB), which can provide an integrated infrastructure for various ground-space laser applications. With the advent of the new space era, the rapid expansion of space utilization has begun to reveal the limitations of conventional radio frequencies. As space missions diversify, lasers are garnering attention as a viable alternative. Between ground and space, lasers are applied in various fields including satellite laser ranging (SLR), laser weapons, and laser communication. However, laser used between the ground and space are significantly influenced by the Earth's atmosphere. Consequently, understanding the atmospheric effects on laser propagation is crucial. In particular, atmospheric turbulence, which refracts and distorts laser beams, intensifies closer to the Earth's surface, exerting a greater impact on the uplink than on the downlink. While downlink verification is facilitated by ground detection, verifying the uplink poses challenges due to the necessity of space-based detection. In response to these challenges, we propose the idea of cube satellite as a means to enhance understanding and verification of laser propagation in the uplink. Additionally, we present the results of conceptual design by analyzing requirements, focusing on mission design of the CLUB cube satellite, following the stages of systems engineering for systematic cube satellite development.

• Journal of Satellite, Information and Communications
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• v.12 no.4
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• pp.42-49
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• 2017

Delay- and Disruption-Tolerant Network (DTN) has been considered as a key technology to overcome main challenges in interplanetary communications such as an intermittent connectivity and high bit error rates. The lack of end-to-end connectivity between source and destination results in long and variable delays and data loss, hence the Internet Protocols cannot operate properly in such environments because it requires an end-to-end connectivity. The DTN, which utilizes 'store-and-forward' message passing scheme between nodes, can overcome the lack of end-to-end connectivity in Interplanetary Network (IPN). In this paper, DTN is applied to 3-hop relay IPN, where messages are transmitted from Earth ground station to Lunar lander through Earth satellite and Lunar orbiter. ONE simulator is used to reflect the real environment of IPN and an efficient resource management method are analyzed to guarantee the message delivery by optimizing a message TTL (Time to Live), buffer size and message fragmentation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.3
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• pp.254-260
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• 2011

Telemetry link is dynamic communication link that antenna gain and polarization are varying with the movement of the airplane. In this paper we calculated the antenna gain, polarization mismatch using the flight trajectory, motion of the airplane and 3D antenna pattern. And we modeled the multipath environment to the 2-Ray spherical earth reflection geometry, estimated the received signal strength when the narrow beam antenna received the RF signal transmitted from the airplane. Also we performed the flight test and after comparing measured value with the estimated value, we confirmed to almost coincide with each other.

• 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 for Aeronautical & Space Sciences
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• v.35 no.2
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• pp.171-176
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• 2007

The tracking antenna must always point to track moving vehicle for data link. In this paper, we determine pointing angle from the geometric relationship of antenna and UAV(Unmaned Aerial Vehicle) to let an antenna be toward a moving vehicle. The pointing angle of antenna is set through GPS measurement data installed in antenna and UAV. We verify the performance of this system from the fixing a camcoder on the antenna.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.6
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• pp.489-496
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• 2021

The X-band frequencies for transmitting the data from earth observation satellites are limited, so a number of satellites share the frequency bands. In order for multiple satellites to utilize same or adjacent frequency bands, International Telecommunication Union - Radiocommunication (ITU-R) limits power flux density (PFD), which overcomes the interferences among multiple satellites. However, even under the regulation, the interference effect needs to be analyzed when multiple satellites are connected to communicate with multiple ground stations (GSs) located close to each other. In this paper, the interference effect is analyzed based on signal to interference plus noise ratio (SINR) when two low earth orbit (LEO) satellites operating in different orbits are connected to communicate with randomly located two GSs in Korean peninsula. From the analysis results, it is confirmed that there can be interferences during 365 days operation even if the satellites meet PFD requirement, but the periods under interference effects are short and the interference can be foreseen.

• Journal of Space Technology and Applications
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• v.2 no.2
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• pp.121-136
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• 2022

Automatic Identification System used in ship communication is required for marine control way, including monitoring of vessel operation in coastal and exchanging of information for safety navigation between them. But, it uses a very high frequency band of approximately 160 MHz, and at the same time, due to the curvature of Earth, there is a limit to the communication distance. Several demonstrations were made successfully over satellite, but not much work has been done yet through cube-satellite which has low-orbit at 500 km altitude. Here, we demonstrate a reception test of AIS (automatic identification system) receiver for a cube-satellites using software-defined radio (SDR). We collected AIS data from ship at port of Busan, Korea, using R8202T2 SDR and established to transmit them using Adam-Pluto and Matlab Simulink. The process of weakening the signal strength to a satellite was constructed using attenuator. Through above process, we demonstrated whether AIS data was successfully received from the AIS payload.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.2
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• pp.309-316
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• 2013

Since the solar activity, one of the factors influencing on lunar communication systems, is to reach its maximum occurring at 11-year solar cycle in autumn 2013, the solar burst frequency and strength are expected to increase. The solar burst has an effect on earth magnetosphere and causes malfunction, loss of communication, and breakdown of various types of satellites and probes. These problems give rise to huge economic and physical loss. Therefore, we should analyze the effect of solar burst on lunar communications and minimize the expected loss. In this paper, we perform the analysis of the link model and link performance between a land station and a lunar orbiter under the solar burst for orbiter's survivability and stable communication channel operations.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.187-196
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• 2009

Synthetic Aperture Radar(SAR) satellite system for broad-area imaging has RF systems including SAR radiating a high power, data link system transmitting the acquired image data from the SAR, TC&R(Telemetry, Command, and Ranging) to communicate with a ground segment to control a satellite. Each system transmits RF signal having various frequencies and radiates a high power, RS(Radiated Susceptibility) specification should be verified at an electronic unit mounted in satellite. RF interference can be happened because of non-linearity of a RF system. Therefore, we manufactured a structure model installed antennas which have a similar pattern with a real antenna, the effect by RF interference is analyzed and verified.