• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.540-543
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• 2007

The modulation transfer function (MTF) in a camera system is a measurement of how well the system will faithfully reproduce the original scene. The electro-optical camera system consists of optics, an array of pixels, and an electronics which is related to the image signal chain. The system MTF can be cascaded with each element's MTF in the frequency domain. That is to say, the electronics MTF including the detector MTF can be recalculated easily by the acquired system MTF if the well-known test optics is used in the measuring process. A Time-Delay and Integration (TDI) detector can make a signal increase by taking multiple exposures of the same object and adding them. It can be considered the various methods to measure the MTF of the TDI camera system. This paper shows the actual and practical MTF measuring methods for the detector and electronics in the TDI camera. The several methods are described according to the scan direction as well as the TDI stages such as the single line mode and the multiple-lines mode. The measuring is performed in the in the static condition or dynamic condition to get the point spread function (PSF) or the line spread function (LSF). Especially, the dynamic test bench is used to simulate on track velocity to synchronize with TDI read out frequency for the dynamic movement.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1734-1735
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• 2011

In case of inspection on aluminum castings, traditional RT (Radiographic Testing) method have been utilized for its advantages in interpretation, cost and perpetual storage. But it has disadvantages like time consumption in film processing, low efficiency in storage and environmental pollution. In this thesis, a DRS (Digital Radiography System) utilizing X-Ray TDI Camera (Time Delay and Integration Camera) is developed. Inspections on aluminum castings are performed using the developed Digital Radiography System, DRS and reviewed if newly developed system can substitute for the traditional method.

• Bulletin of the Korean Space Science Society
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• 2003.10a
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• pp.104-104
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• 2003

본 포스터에서는 다목적 위성 2호의 주 탑재체인 MSC(Multi-Spectral Camera)가 TDI(Time Delayed Integration) 방식을 채택함에 따라, TDI에 의해 MSC 영상 자료가 어떻게 영향을 받게 되는 지를 연구한 내용을 설명한다. MSC는 지상 해상도가 1m인 고해상도에서 영상을 촬영하기 때문에 상대적으로 입사 광량이 부족한 문제를 안고 있음에 따라 32 line의 TDI 방식을 사용한다. TDI 방식을 사용하여 MSC에서 직하방향으로 영상을 촬영할 경우, 영상의 가운데 pixel에서 멀어질수록 TDI에 의해 영상의 MTF 값이 떨어지는 결과가 발생한다. 또한, 다목적 위성 2호는 Roll 축을 중심으로 $\pm$30도 Pitch 축을 중심으로 $\pm$30도 tilt를 하여 영상을 촬영하도록 운영될 예정이기 때문에 더더욱 TDI에 의채 영상의 MTF 값이 떨어지는 결과가 발생하게 된다. 이외에도 TDI는 다목적 위성 2호의 고도가 감소하거나, Yaw 축의 변화, Jitter 등에 의해서도 영상의 MTF 값이 감소하게 된다. 물론 MSC CCD pixel의 sampling rate인 Line Rate 값을 각각의 경우에 따라 적절한 값을 부여함으로써 TDI에 의한 MTF 값의 감소를 많은 부분은 수습할 수 있으나 완벽한 보정은 힘든 상황이다.

• Proceedings of the KSRS Conference
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• v.2
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• pp.797-799
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• 2006

The Electro-optical camera subsystem as a payload of a satellite system consists of OM (optical module) and CEU(camera electronics unit), and most performances of the camera subsystem depend a lot on the CEU in which TDI CCDs(Time Delayed Integration Charge Coupled Device) take the main role of imaging by converting the light intensity into measurable voltage signal. Therefore it is required to specify and design the CEU very carefully at the early stage of development with overall specifications, design considerations, calibration definition, test methods for key performance parameters. This paper describes the overview of CEU development. It lists key requirement characteristics of CEU hardware and design considerations. It also describes what kinds of calibration are required for the CEU and defines the test and evaluation conditions in verifying requirement specifications of the CEU, which are used during acceptance test, considering the fact that CEU performance results change a lot depending on test and evaluation conditions such as operational line rate, TDI level, and light intensity level, so on.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.101-101
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• 2000

MSC(Multispectral Camera), which will be a unique payload on KOMPSAT-II, is designed to collect panchromatic and multi-spectral imagery with a ground sample distance of 1m and a swath width of 15km at 685km altitude in sun-synchronous orbit. The instrument is designed to have an orbit operation duty cycle of 20% over the mission life time of 3 years. MSC electronics consists of three main subsystems; PMU(Payload Management Unit), CEU(Camera Electronics Unit) and PDTS(Payload Data Transmission Subsystem). PMU performs all the interface between spacecraft and MSC, and manages all the other subsystems by sending commands to them and receiving telemetry from them with software protocol through RS-422 interface. CEU controls FPA(Focal Plane Assembly) which contains TDI(Timc Delay Integration) CCD(Charge Coupled Device) and its clock drivers. PMU provides a Master Clock to synchronize panchromatic and multispectral camera. PDTS performs compression, storage and encryption of image data and transmits them to the ground station through x-band.

• Korean Journal of Remote Sensing
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• v.31 no.2
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• pp.85-99
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• 2015

TDI CCD sensors are being used for most of the electro-optical camera mounted on the low earth orbit satellite to meet high performance requirements such as SNR and MTF. However, the CMOS sensors which have a lot of implementation advantages over the CCD, are being upgraded to have the TDI function. A few methods for improving the issue of motion blur which is apparent in the CMOS sensor than the CCD sensor, are being introduced. Each pixel can be divided into a few sub-pixels to be read more than once as is the same case with three or four phased CCDs. The fill factor can be reduced intentionally or even a kind of mask can also be implemented at the edge of pixels to reduce the blur. The motion blur can also be reduced in the TDI CMOS sensor by reducing the integration time from the full line scan time. Because the integration time can be controlled easily by the versatile control electronics, one of two performance parameters, MTF and SNR, can be concentrated dynamically depending on the aim of target imaging. MATLAB simulation has been performed and the results are presented in this paper. The goal of the simulation is to compare dynamic MTFs affected by the different methods for reducing the motion blur in the TDI CMOS sensor.

• Aerospace Engineering and Technology
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• v.3 no.2
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• pp.160-169
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• 2004

In order to get the high resolution satellite image, MSC has TDI function in the KOMPSAT-2. So it is required to control the yaw angle of the attitude as operation concepts of KOMPSAT-2. This study was to explain the TDI function, to set up the geometric equation to satisfy the condition, and finally to determine the equation of yaw angle. The calculating program was developed and simulated with orbit and imaging attitude as input data, and the results were compared with the yaw steering values calculated in the on-board computer.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.825-827
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• 2003

Multi-Spectral Camera(MSC) is a payload on the KOMPSAT-2 satellite to perform the earth remote sensing. The instrument images the earth using a push-broom motion with a swath width of 15 km and a ground sample distance (GSD) of 1 m over the entire field of view (FOV) at altitude 685 Km. The instrument is designed to have an on-orbit operation duty cycle of 20% over the mission lifetime of 3 years with the functions of programmable gain/ offset and on-board image data compression/storage. The MSC instrument has one(1) channel for panchromatic imaging and four(4) channel for multi-spectral imaging covering the spectral range from 450nm to 900nm using TDI CCD Focal Plane Array (FPA). In this paper, the architecture and function of MSC hardware including electrical interface and the operation concept which have been established based on the mission requirements are described. And the design and the preparation of MSC system operation are analyzed and discussed.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.633-636
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• 2005

An electro-optical camera system consists of many subsystems such as the optics, the detector, and the electronics and so on. They may create variations in the processed image that were not present original scene. The performance analysis of the electro-optical camera system is a mathematical construct that provides an optimum design through appropriate trade off analysis. The SNR(Signal to Noise Ratio) is one of the most important performance for the electro-optical camera system. The SNR analysis shown in this paper is performed based on the practical high resolution satellite camera design. For the purpose of the practical camera design, the analysis assumes that the defined radiance, which is calculated for the Korean peninsula, reached directly to the telescope entrance. In addition, the actual operation concept such as integration time and the normal operation altitude is assumed. This paper compares the SNR analysis results according to the various camera characteristics such as the optics, the detector, and the camera electronics. In detail, the optical characteristics can be split into the focal length, F#, transmittance, and so on. And the system responsivity, the quantum efficiency, the TDI stages, the quantization noise and the analogue noise can be used for the detector and the camera electronics characteristics. Finally this paper suggests the optimum design to apply the practical electro-optical system.

• Korean Journal of Remote Sensing
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• v.18 no.1
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• pp.53-59
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• 2002

The MSC is a payload on the KOMPSAT-2 satellite to perform the earth remote sensing. The instrument images the earth using a push-broom motion with a swath width of 15 km and a GSD(Ground Sample Distance) of 1 m over the entire FOV(Field Of View) at altitude 685 km. The instrument is designed to haute an on-orbit operation duty cycle of 20% over the mission lifetime of 3 years with the functions of programmable gain/offset and on-board image data compression/storage. The MSC instrument has one channel for panchromatic imaging and four channel for multi-spectral imaging covering the spectral range from 450nm to 900nm using TDI(Time Belayed Integration) CCD(Charge Coupled Device) FPA(Focal Plane Assembly). The MSC hardware consists of three subsystem, EOS(Electro Optic camera Subsystem), PMU(Payload Management Unit) and PDTS(Payload Data Transmission Subsystem) and each subsystems are currently under development and will be integrated and verified through functional and space environment tests. Final verified MSC will be delivered to spacecraft bus for AIT(Assembly, Integration and Test) and then COMSAT-2 satellite will be launched after verification process through IST(Integrated Satellite Test). In this paper, the introduction of MSC, the configuration of MSC electronics including electrical interlace and design of CEU(Camera Electronic Unit) in EOS are described. MSC Operation parameters induced from the operation concept are discussed and analyzed to find the influence of system for on-orbit operation in future.