• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.6
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• pp.642-650
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• 2010

In this paper, we study a TT&C link to obtain a required specifications of TT&C(Telemetry Tracking and Command system) antenna for an LEO(Low Earth Orbit) satellite. The premised mission orbit is the sun-synchronized and circular orbit and it performs earth-space observations. We design minimum TT&C link-budget to obtain required antenna beamwidth and gain. The proposed turnstile antenna provides wide beamwidth and circular polarization. We suggested the attaching position that shows the most effective results by confirming the variation of antenna performance when the proposed antenna is adapted to satellite's various positions. Also we proved the proposed antenna's ability while it is performing the mission through the orbit simulation based on the electrical performance of the proposed turnstile antenna.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.1 s.104
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• pp.24-38
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• 2006

In this paper, we investigate the design and fabrication of a conical spiral antenna suitable for satellite TT&C applications. The shape of the spiral is optimized using a commercial electromagnetic software for good gain and axial ratio performances over $2.0{\sim}2.3\;GHz$ frequencies. A coaxial infinite balun feeding the spiral is designed using experimental methods. A method for precision fabrication of the spiral is presented. Measurements of the fabricated antenna show satisfactory performances over $2.0{\sim}2.3\;GHz$ such as a reflection coefficient less than -18 dB, a maximum gain greater than 4 dB, a gain greater than 0 dB over angles ${\pm}75^{\circ}$ from the antenna boresight, an axial ratio less than 5 dB over angles ${\pm}90^{\circ}$ from the antenna boresight, a front-back ratio greater than 15 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.7
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• pp.842-849
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• 2010

This paper deals with a TT&C circularly polarized turnstile antenna for LEO satellites. The turnstile antenna consists of radiator for radiating power to free-space and power divider for generating circularly polarized wave. we presents a radiator to tolerate in space environments and a power divider to provide flat phase difference at wide bandwidth. The bandwidth of the proposed antenna covers the frequency bands of up- and down-link. The antenna shows wide beamwidth and enhanced axial ratio for unfavorable space environments.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.467-470
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• 2004

In early 2004, KARI developed 5ft S-Band TT&C antenna for especially KOMPSAT-2 operation in LEOP phase. This paper shows system features of 5ft S-Band antenna and its test result with KOMPSAT-l. Tracking test, command uplink test and telemetry downlink test were performed. Through tests, 5ft antenna was verified to be operational in uplink and downlink with KOMPSAT series. Due to its inherent wide 3dB beam-width of about 7deg at S-Band, this antenna system can be used very effectively even though orbital information is less accurate like LEOP and spacecraft safe mode.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.914-923
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• 2009

Helix antennas have been widely applied to satellite TT&C, data communication and GPS receiver systems onboard military, remote sensing and communication purpose satellites. The helix antennas are known to be convenient to control impedance and radiation coverage characteristics with a maximum directivity in satellite z-axis. Waveguide horn is commonly used for radar system that needs ultra-wideband pulse for exploration ground radar and electromagnetic disability measurement etc. It has high efficiency and low reflection characteristics provided by the low-profile shape and suppressed radiation distortion. In this paper, a waveguide horn structure incorporated with helix antenna design is proposed for satellite applications that require ultra-wideband pulse radar and high rate RF data communication link to ground station over wide coverage area. The main design concern is to synthesize variable beam forming pattern based on modified horn-helix combination helicone structure such that multi-mission antenna is implemented applicable for TT&C, earth observation, high data rate transmission. Waveguide horn helps to reduce the overall antenna structure size by introduction fold type reflector connected to the tapered helix antenna. The next generation KOMPSAT satellite currently under development requires high-performance precision attitude control system. We present an initial design of a hybrid hern-helix antenna structure suitable for efficient RF communication module design of multi-purpose satellite systems.

• Journal of Astronomy and Space Sciences
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• v.14 no.1
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• pp.158-165
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• 1997

The Sun interference event predictions for the KOMPSAT TT&C station were performed to analyze the frequency of the event and the impact on the TT&C link. The KOMPSAT orbit was propagated including only J2 geopotential term for maintaining the Sun-synchronism and no other perturbations were included. Local time of ascending node of the KOMPSAT satellite was set to 10h50m00s. The TT&C station was assumed to locate in Taejon and have 9 meter antenna for S-band link. One year of simulation from 1999/07/01 were performed out of 3 year of mission lifetime of KOMPSAT satellite. Total four times of Sun interference events were occurred during 1 year of simulation and those lasted about 50 seconds altogether. The C/N degradation of the TT&C system was calculated about 4dB. The Sun interference event of 50 seconds of year are 0.0076 percents of the S-band contact time when the 30 minute of contact time is assumed in a day.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.36.2-36.2
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• 2008

This paper presents the impact of Japanese radio source on the S-Band communication between KOMPSAT-2 satellite and TT&C ground system. Major specifications such as transmitting EIRP (Effective Isotropic Radiated Power) and location of Japanese terrestrial station were informed from Radio Research Laboratory in Korea Communication Commission. To estimate path loss in S-Band, the distance between Japanese station and TT&C ground system was obtained by using COTS (Commercial Off-The-Shelf) software. After that the signal strength of Japanese radio source placed at the TT&C ground system was calculated from link parameters such as transmitting EIRP, path loss, and receiving antenna gain. Consequently, this paper shows that the degradation caused by Japanese radio source is acceptable to TT&C ground system for satellite operation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.12
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• pp.1359-1369
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• 2007

This paper describes the technique of satellite direction finding and main beam steering of the adaptive array antenna system which is used for mobile TT&C(Tracking Telemetry&Command) system. To be able to control the satellite on mobile vehicle while moving, the relative directional information of the satellite to the mobile vehicle is necessary to make main beam to the direction of satellite. To do this MUSIC, which is one of the super-resolution algorithm of wave direction finding, is used and then the performance analysis and quantization problem of phase shifter are addressed. This paper is valuable in the respect of showing feasibility of designing the moble TT&C using adative array antenna system.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.464-466
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• 2004

Ranging and 2-way Doppler measurements are very essential source for orbit determination in LEOP (Launch and Early Operation). This paper shows ranging system features of 13M TT &C antenna and test results recently acquired with KOMPSAT-l. Ranging and 2-way Doppler measurements were compared with KOMPSAT-I GPS telemetry data. Through comparison, it was found that constant and accurate ranging measurements are available with 13M antenna system. Ranging and Doppler measurement function is expected to be used for KOMPSAT-1 and KOMPSAT-2.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.11 s.114
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• pp.1082-1088
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• 2006

A turnstile antenna using the parasitic monopole has been developed for STSAT-2 TT&C application. The antenna consists of two radiating elements; a bow-tie dipole and a parasitic monopole. The bow-tie dipole is main radiating element, used a bow-tie structure for bandwidth improvement and size reduction. The parasitic monopole improved beamwidth and axial ratio. The input impedance of the antenna is about 50 ohm without a matching circuit. The proposed antenna has beamwidth of $>140^{\circ}$, axial ratio of < 3 dB and VSWR of < 1.5 in the band of $2.075{\sim}2.282GHz$.