• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.4
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• pp.347-352
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• 2007

This paper describes the design and implementation of PFM(Proto Flight Model, PFM) of DRE(Data Receiving Equipment, DRE) for Science and Technology Satellite 2(STSAT-2) and the results of integration performance test. DRE components are X-band receiver, DCE(Data Combine Equipment, DCE) and RAC(Receiving and Archiving Computer, RAC). DCE consists of I&Q data combiner and ECL signal distributor. RAC consists of DRC(Data Receiving Card) and ST2RAS(STSAT-2 Receiving and Archinving Software). X-band receiver receives 10Mbps QPSK I, Q satellite data and sends the data to DCE. DRC stores the I&Q combine data from DCE to RAID. The pre-processing program sorts and stores to satellite status data and payload data. The performance of DRE in the functional and space environments test satisfies the requirements of STSAT-2.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.5
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• pp.93-98
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• 2005

An Engineering Model(EM) of the Telemetry-Command Unit(TCU) for STSAT-2 was developed. The TCU of STSAT-2 has some improved features compared with that of STSAT-1. To reduce weight and size of TCU all logics are implemented in FPGA without CPU. EM I&T(Integration and Test) was successfully performed with no errors.

• Bulletin of the Korean Space Science Society
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• 2003.05b
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• pp.37-37
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• 2003

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.5
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• pp.507-517
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• 2010

The KOREAN AIR - R&D Center has developed a solar array for STSAT-2 Flight Model, SaTReC-KAIST, using a fully localized technology and has verified the performance through a launch vibration test, orbit environment test and electrical performance test. The solar array will be launched at NARO Space Center by KSLV-I which is the first Korean launch vehicle, in May 2010. In this paper, a current-voltage curve that shows the power characteristics of solar arrays was derived by applying elements that affects the power performance of STSAT-2's solar arrays to the solar cell equivalent models. The result was compared to LAPSS test results, and accuracy of the solar cell equivalent model and the power performance simulation has been analyzed.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.526-529
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• 2005

Dual-channel Radiometers for Earth and Atmosphere Monitoring (DREAM) is the Korean first spaceborne microwave radiometer which is the main payload of Science and Technology SATellite-2 (STSAT-2). STSAT-2 will be launched by Korea Space Launch Vehicle-l (KSL V-I) at NARO Space Center in Korea in 2007. DREAM is a two-channel, total power microwave radiometer with the center frequencies of 23.8 GHz and 37 GHz. The spaceborne radiometer is composed of an antenna unit, a receiver unit, and a data acquisition/processing unit. The bandwidths of radiometer are 600 MHz at 23.8 GHz and 1000 MHz at 37 GHz. The integration time of two channels is 200 rns. The sensitivity of DREAM is less than 0.5 K. This paper presents the required performance and system design of DREAM in detail.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.31.4-32
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• 2008

The microwave instruments are used many areas of the space remote sensing and space science applications. The imaging radar of synthetic aperture radar (SAR) is well known microwave radar sensor for earth surface and ocean research. Unlike radar, microwave radiometer is passive instrument and it measures the emission energy of target, i.e. brightness temperature BT, from earth surface and atmosphere. From measured BT, the geophysical data like cloud liquid water, water vapor, sea surface temperature, surface permittivity can be retrieved. In this paper, the radiometer characteristics, system configuration and principle of BT measurement are described. Also the radiometer instruments TRMM, GPM, SMOS for earth climate, and ocean salinity research are introduce. As first korean microwave payload on STSAT-2, the DREAM (Dual-channels Radiometer for Earth and Atmosphere Monitoring) is described the mission, system configuration and operation plan for life time of two years. The main issues of DREAM unlike other spaceborne radiometers, will be addressed. The calibration is the one of main issues of DREAM mission and how it contribute on the space borne radiometer. In conclusion, the radiometer instrument to space science application will be considered.

• International Journal of Aeronautical and Space Sciences
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• v.4 no.2
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• pp.17-25
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• 2003

Simple methods are developed to predict temperatures of a satellite box during launch stage. The box is mounted on outer surface of satellite and directly exposed to space thermal environment for the time period from fairing jettison to separation. These simple methods are to solve a 1st order ordinary differential equation (ODE) which is simplified from the governing equation after applying several assumptions. The existence of analytical solution for the 1st order ODE is determined depending on treatment of time-dependent molecular heating term. Even for the case that the analytical solution is not available due to the time dependent term, the 1st order ODE can be solved by relatively simple numerical techniques. The temperature difference between two different approaches (analytical and numerical solutions) is relatively small (Jess than $1^{\circ}C$ along the time line) when they are applied to STSAT-I launch scenario. The present methods can be generally used as tools to quickly check whether a satellite box is safe against space environment during the launch stage for the case that the detailed thermal analysis is not available.

• Bulletin of the Korean Space Science Society
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• 2007.10a
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• pp.93.2-93.2
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• 2007

• Korean Journal of Optics and Photonics
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• v.23 no.4
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• pp.167-171
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• 2012

This paper reports on the stray light analysis results of a compact imaging spectrometer (COMIS) for a microsatellite STSAT-3. COMIS images Earth's surface and atmosphere with ground sampling distances of 27 m at the 18~62 spectral bands (0.4 ~ 1.05 ${\mu}m$) for the nadir looking at an altitude of 700 km. COMIS has an imaging telescope and an imaging spectrometer box into which three electronics PCBs are embedded. The telescope images a $27m{\times}28km$ area of Earth surface onto a slit of dimensions $11.8{\mu}m{\times}12.1mm$. This corresponds to a ground sampling distance of 27 m and a swath width of 28 km for nadir looking posture at an altitude of 700 km. Then the optics relays and disperses the slit image onto the detector thereby producing a monochrome image of the entrance slit formed on each row of detector elements. The spectrum of each point in the row is imaged along a detector column. The optical mounts and housing structures are designed in order to prevent stray light from arriving onto the image and so deteriorating the signal to noise ratio (SNR). The stray light analysis, performed by a non-sequential ray tracing software (LightTools) with three dimensional housing and lens modeling, confirms that the ghost and stray light arriving at the detector plane has the relative intensity of ${\sim}10^{-5}$ and furthermore it locates outside the concerned image size i.e. the field of view of the optics.

• Korean Journal of Optics and Photonics
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• v.22 no.4
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• pp.184-190
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• 2011

A compact imaging spectrometer (COMIS) was developed for a microsatellite STSAT-3. The satellite is now rescheduled to be launched into a low sun-synchronous Earth orbit (~700 km) by the end of 2012. Its main operational goal is the imaging of the Earth's surface and atmosphere with ground sampling distance of 27 m and 2 - 15 nm spectral resolution over visible and near infrared spectrum (0.4 - 1.05 ${\mu}m$). A flight model of COMIS was developed following an engineering model that had successfully demonstrated hyperspectral imaging capability and structural rigidity. In this paper we report the environmental test results of the flight model. The mechanical stiffness of the model was confirmed by a small shift of the natural frequency i.e., < 1% over 10 gRMS random vibration test. Electrical functions of the model were also tested without showing any anomalies during and after vacuum thermal cycling test with < $10^{-5}$ torr and $-30^{\circ}C\;-\;35^{\circ}C$. The imaging capability of the model, represented by a modulation transfer function (MTF) value at the Nyquist frequency, was also kept unvaried after all those environmental tests.