• Journal of Satellite, Information and Communications
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• v.1 no.2
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• pp.76-82
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• 2006

The Mission Control System for KOMPSAT-2 was developed by ETRI and is being operated at Satellite Control Center at KARI to monitor and control KOMPSAT-2 (KOrea Multi-Purpose Satellite) which was launched in July 28th, 2006. MCE provides the functions such as telemetry reception and processing, telecommand generation and transmission, satellite tracking and ranging, orbit prediction and determination, attitude maneuver planning, satellite simulation, etc. KOMPSAT-2 is the successor of KOMPSAT-1 which is an earth-observation satellite. KOMPSAT-2 has higher resolution image taking ability due to MSC (Multi Spectral Camera) payload in the satellite and precise orbit and attitude determination by Mission Control System. It can produce one meter resolution image compared to six meter resolution image by KOMPSAT-1.

• Journal of Advanced Navigation Technology
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• v.20 no.1
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• pp.8-14
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• 2016

High-level conceptual design analysis results of satellite communication system for Korea augmentation satellite system (KASS) satellite communication system, which is a part of KASS and consisted of KASS uplink Stations and two leased GEO is presented in this paper. We present major functions such as receiving correction and integrity message from central processing system, taking forward error correction for the message, modulating and up converting signal and conceptual design analysis for concepts for design process, GEO precise orbit determination for GEO ranging that is additional function, and clock steering for synchronization of clocks between GEO and GPS satellites. In addition to these, KASS requires 2.2 MHz for SBAS Augmentation service and 18.5 MHz for Geo-ranging service as minimum bandwidths as a results of service performance analysis of GEO ranging with respect to navigation payload(transponder) RF bandwidth is presented. These analysis results will be fed into KASS communication system design by carrying out final analysis after determining two GEOs and sites of KASS uplink stations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.5
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• pp.472-478
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• 2015

This paper describes the design of the active optical compensation movements(at focal plane, secondary mirror) for the image stabilization of a small satellite camera. The movements can correct optical misalignment on-line and directly compensate vibration disturbances in the focal plane. Since the devices are installed inside the space camera, it has an remarkable advantage to deal with the structural deformation of a space camera effectively. In this paper, the requirements of the active optical compensation movements for 1m GSD small satellite camera have been analyzed. Based on the established requirements, the design of the active compensation movements have been conducted. The designed active optical compensation system can control 5 axes movements independently to compensate micro-vibration disturbances in the focal plane and to refocus the optical misaligned satellite camera.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.8
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• pp.695-701
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• 2016

Spacecraft propulsion system is a kind of rocket engine that has been developed from the end of 1950s for attitude control and orbit maintenance of satellite. Since the spacecraft propulsion system has to be used for a relatively long time, therefore, stability of propellant and life of thruster could be very important factor for propulsion system design. Recently, green propellant propulsion and all electrical propulsion system have became very important issue, and we also need a development according to well organized plan. In this paper, we will introduce the development status, key technologies and development prospect of spacecraft propulsion system.

• Aerospace Engineering and Technology
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• v.13 no.2
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• pp.142-149
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• 2014

After launch of Low Earth Orbit(LEO) satellite, Initial Activation Checkout(IAC) and Calibration and Validation(Cal & Val) procedure are performed prior to enter normal operation phase. During normal operation phase, most of the time is allocated for mission operation except following up measures to anomaly and orbit maintenance. Since mission operation capability is key indicator for success of LEO satellite program and consistent with promotion purpose of LEO satellite program, reliability should be ensured by conducting through test. In order to ensure reliability by examining the role of LEO satellite and ground station during ground test phase, realistic test scenario that is similar to actual operation conditions should be created, and test that aims to verify full mission cycle should be performed by transmitting created command and receiving image and telemetry data. This paper describes the test design and result. Consideration items for test design are described in detail and result of designed test items are summarized.

• Journal of Astronomy and Space Sciences
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• v.14 no.2
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• pp.347-354
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• 1997

We developed a GPS phase data processing S/W system which calculates baseline vectors and distances between two points located in the surface of the Earth. For this development a Double-Difference mothod and L1 carrier phase data from GPS(Global positioning System) were used. This S/W system consists of four main parts: satellite position calculation, Single-Difference equation, Double-Difference equation, and correlation. To verify our S/W, we fixed KAO($N36^{circ}.37,E127^{circ}.37,H77.61m$), one of the International GPS Services for Geodynamics, which is located at Tae-Jon, and we measured baseline vectors and relative distances with data from observations at approximate baseline distances of 2.7, 42.1, 81.1, 146.6km. Then we compared the vectors and distances with the data which we obtained from the GPSurvey S/W system, with the L1/L2 ION-Free method and broadcast ephemeris. From the comparison of the vectors and distances with the data from the GPSurvey S/W system, we found baseline vectors X, Y, Z and baseline distances matched well within the extent of 50cm and 10cm, respectively.

• Journal of Astronomy and Space Sciences
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• v.24 no.4
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• pp.297-308
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• 2007

The AOPOD (Atmosphere Occultation and Precision Orbit Determination) system, the secondary payload of KOMPSAT (KOrea Multi-Purpose SATellite)-5 scheduled to be launched in 2010, shall provide GPS radio occultation data. In this paper, we simulated the GPS radio occultation characteristic of KOMPSAT-5 and retrieved electron density profiles using KROPS (KASI Radio Occultation Processing Software). The electron density retrieved from CHAMP (CHAllenging Minisatellite Payload) GPS radio occultation data on June 20, 2004 was compared with IRI (International Reference Ionosphere) - 2001, PLP (Planar Langmuir Probe), and ionosonde measurements. When the result was compared with ionosonde measurements, the discrepancies were 5 km on the $F_2$ peak height ($hmF_2$) and $3{\times}10^{10}el/m^3$ on the electron density of the $F_2$ peak height ($NmF_2$). By comparing with the Laugmuir Probe measurements of CHAMP satellite (PLP), both agrees with $1.6{\times}10^{11}el/m^3$ at the height of 365.6 km.

• Journal of Astronomy and Space Sciences
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• v.25 no.1
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• pp.43-52
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• 2008

As the next generation of global satellite navigation system, the Galileo project is about to witness an initial orbit validation stage as the successful test of navigation message transmission from Giove-A in 2007. The Space Geodesy division ana the Radio Astronomy division of the Korea Astronomy & Space Science Institute had collaborated on the field survey for the Galileo Sensor Station (GSS) RF environment of the proposed site near Jeju Tamla University from August 3rd to August 5th, 2006. The power spectrums were measured in full-band $(800{\sim}2000MHz)$ and in-band (E5, E6 and L1 band) in frequency domain for 24 hours respectively. Finally, we performed a time domain analysis to characterize strong in-band interference source based on the result of the previous step.

• Journal of Cadastre & Land InformatiX
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• v.50 no.1
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• pp.107-123
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• 2020

With stabilization of the recent multi-GNSS infrastructure, and as multi-GNSS has been proven to be effective in improving the accuracy of the positioning performance in various industrial sectors. In this study, in view that SF(Single frequency) GNSS receivers are widely used due to the low costs, evaluate effectiveness of SF Real Time Point Positioning(SF-RT-PP) based on four multi-GNSS surveying methods with RTCM-SSR correction streams in static and kinematic modes, and also derive response challenges. Results of applying SSR correction streams, CNES presented good results compared to other SSR streams in 2D coordinate. Looking at the results of the SF-RT-PP surveying using SF signals from multi-GNSS, were able to identify the common cause of large deviations in the altitude components, as well as confirm the importance of signal bias correction according to combinations of different types of satellite signals and ionospheric delay compensation algorithm using undifferenced and uncombined observations. In addition, confirmed that the improvement of the infrastructure of Multi-GNSS allows SF-RT-SPP surveying with only one of the four GNSS satellites. In particular, in the case of code-based SF-RT-SPP measurements using SF signals from GPS satellites only, the difference in the application effect between broadcast ephemeris and SSR correction for satellite orbits/clocks was small, but in the case of ionospheric delay compensation, the use of SBAS correction information provided more than twice the accuracy compared to result of the Klobuchar model. With GPS and GLONASS, both the BDS and GALILEO constellations will be fully deployed in the end of 2020, and the greater benefits from the multi-GNSS integration can be expected. Specially, If RT-ionospheric correction services reflecting regional characteristics and SSR correction information reflecting atmospheric characteristics are carried out in real-time, expected that the utilization of SF-RT-PPP survey technology by multi-GNSS and various demands will be created in various industrial sectors.