• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2002년도 가을 학술발표회 논문집
• /
• pp.475-482
• /
• 2002

Optical fibre sensors have shown a potential to serve real time health monitoring of Slope and structure. They can be easily embedded or attached to the structures and are not affected by the electro-magnetic field. Furthermore, they have the flexibility of the sensor size and very highly sensitive. In this study, we conducted several laboratory on slope and field tests using a novel optical sensor based on Brillouin scattering and PVC pipe. One of the advantages of this technique is that the bare fibre itself acts as sensing element without any special fibre processing or preparation. Test results have shown that BOTDR can be a great solution for sensor systems of Slope.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
• /
• pp.452-455
• /
• 2004

MSC (Multi-Spectral Camera) system is a remote sensing instrument to obtain high resolution ground image. EOS (Electro-Optic System) for MSC mainly consists of PMA (Primary Mirror Assembly), SMA (Secondary Mirror Assembly), HSTS (High Stability Telescope Structure) and DFPA (Detector Focal Plane Assembly). High performance of EOS makes it possible for MSC system to provide high resolution and high quality ground images. Temperature of the EOS needs to be controlled to be in a specific range in order not to have any thermal distortion which can cause performance degradation. It is controlled by full redundant CPU based electronics. The validity of thermistor readings can be checked because a few thermistors are installed on each control point on EOS. Various kinds of thermal control logics are used to prevent 'Single Point Failure'. Control logic has a few set of database in order not to be corrupted by SEU (Single Event Upset). Even though the thermal control logic is working automatically, it can also be monitored and controlled by ground-station operator. In this paper, various ways of thermal control logic for EOS in MSC will be presented, which include thermal control mode and logic, redundancy design and status monitoring and reporting scheme.

• 대한원격탐사학회지
• /
• 제33권2호
• /
• pp.159-169
• /
• 2017

위성용 전자광학탑재체는 제한된 소모전력 및 우주방사선과 같은 사용 환경에 의해 설계부터 특별한 요구사항을 가지고 있으며, 획득 영상의 품질은 주로 GSD (Ground Sampled Distance), 신호대잡음비(SNR, Signal to Noise Ratio), MTF (Modulation Transfer Function)에 따라 좌우된다. 영상센서의 출력신호에 포함된 잡음 감소를 통한 신호대잡음비 개선을 위하여, 센서에 추가된 프리픽셀(Pre-pixel) 및 다크픽셀(Dark-pixel)을 사용하여 CDS (Corrective Double Sampling) 방식을 통해 영상센서의 잡음 성분을 포함한 오프셋 신호(Offset Signal)를 제거하는 아날로그 신호처리(ASP, Analog Signal Processor) 방법을 제안한다. 또한 센서 제어시스템에서는 영상의 불균일성 처리를 위해 제어시스템의 출력 포트별 게인(Gain), 오프셋, 및 센서의 화소별 특성을 반영한 다양한 방식에 의한 보정 방법이 적용된다. 본 논문에서는 이상 설명한 여러 가지 잡음 개선방법을 시스템 설계 및 운영에 적용하여 위성탑재용 전자광학카메라의 신호대잡음비 향상 방법을 제안하고, 실험을 통해 검증한다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2013년도 추계학술대회 논문집
• /
• pp.763-764
• /
• 2013

A three-dimensional image capturing device and its signal processing algorithm and apparatus are presented. Three dimensional information is one of emerging differentiators that provides consumers with more realistic and immersive experiences in user interface, game, 3D-virtual reality, and 3D display. It has the depth information of a scene together with conventional color image so that full-information of real life that human eyes experience can be captured, recorded and reproduced. 20 Mega-Hertz-switching high speed image shutter device for 3D image capturing and its application to system prototype are presented[1,2]. For 3D image capturing, the system utilizes Time-of-Flight (TOF) principle by means of 20MHz high-speed micro-optical image modulator, so called 'optical resonator'. The high speed image modulation is obtained using the electro-optic operation of the multi-layer stacked structure having diffractive mirrors and optical resonance cavity which maximizes the magnitude of optical modulation[3,4]. The optical resonator is specially designed and fabricated realizing low resistance-capacitance cell structures having small RC-time constant. The optical shutter is positioned in front of a standard high resolution CMOS image sensor and modulates the IR image reflected from the object to capture a depth image (Figure 1). Suggested novel optical resonator enables capturing of a full HD depth image with depth accuracy of mm-scale, which is the largest depth image resolution among the-state-of-the-arts, which have been limited up to VGA. The 3D camera prototype realizes color/depth concurrent sensing optical architecture to capture 14Mp color and full HD depth images, simultaneously (Figure 2,3). The resulting high definition color/depth image and its capturing device have crucial impact on 3D business eco-system in IT industry especially as 3D image sensing means in the fields of 3D camera, gesture recognition, user interface, and 3D display. This paper presents MEMS-based optical resonator design, fabrication, 3D camera system prototype and signal processing algorithms.

• 대한원격탐사학회지
• /
• 제18권1호
• /
• pp.53-59
• /
• 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.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
• /
• pp.372-375
• /
• 2006

The MSC is a high resolution multi-spectral camera system which is mounted on the KOMPSAT-II satellite. The electro-optic camera system has a refocusing mechanism which can be used in-orbit by ground commands. By adjusting locations of some elements in optics, the system can be focused precisely. The focus mechanism in MSC is implemented with stepper motor and potentiometer. By reading the value of the potentiometer, rough position of the motor can be understood. The exact location of the motor can not be acquired because the information from the potentiometer can not be so accurate. However, before and after certain events of the satellite, like a satellite launch, the direction of the movement or order of the magnitude of the movement can be understood. In this paper, the trend analysis of the focus motor position during the ground test phase is introduced. This result can be used as basic information for the focus calibration after launch. By studying the long term trend, deviation from the best focal point can be understood. The positions of the focus motors after launch are also compared.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
• /
• pp.1406-1408
• /
• 2003

KOMPSAT-1 (KOrea Multi-Purpose SATellite ? 1) EOC (Electro Optic Camera) raw images are radiometrically corrected on ground based on the characteristics of EOC. They consist of each CCD (Charge?Coupled Device) pixel’s calibration slope which was measured on ground, electrical gains which are applied to amplify for increasing output pixel counts. Currently, radio-metrically corrected EOC images with calibration slope have still shown defective features by residual stripes. So, it should be compensated by adjusting the calibration slope. In this paper, the adjustment of current calibration slope for de-striping EOC images is addressed and test results are shown.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
• /
• pp.229-234
• /
• 2002

Under the hostile influence of the extreme space environmental conditions due to the deep space and direct solar flux, the thermal control in space applications is especially of major importance. There are tight temperature range restrictions for electro-optical elements while on the other hand there are low power consumption requirements due to the limited energy sources on the spacecraft. So, we usually have strong requirement of thermal and power control module in space applications. In this paper, the design concept of a thermal and power control module in the MSC(Multi-Spectral Camera) system which will be a payload on KOMPSATII is described in terms of H/W & S/W. This thermal and power control module, called THTM(Thermal and Telemetry Module) in MSC, resides inside the PMU(Payload Management Unit) which is responsible for the proper management of the MSC payload for controlling and monitoring the temperature insides the EOS(Electro-Optic System) and gathering all the analog telemetry from all the MSC sub-units, etc. Particularly, the designed heater controller has the special mode of "duty cycle" in addition to normal closed loop control mode as usual. THTM controls heaters in open loop according to on/off set time designed through analysis in duty cycle mode in case of all thermistor failure whereas it controls heaters by comparing the thermistor value to temperature based on closed loop in normal mode. And a designed THTM provides a checking and protection method against the failure in thermal control command using the test pulse in command itself.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
• /
• pp.593-596
• /
• 2005

The MSC is a remote sensing instrument with very high performance that is to be installed on KOMPSAT2 satellite. The MSC consists of EOS (Electro-Optic Subsystem), PMU (Payload Management Unit) and PDTS (Payload Data Transmission Subsystem). PMU controls and monitors all the other payload units by sending commands and collecting telemetry. PMU is in charge of interfacing between payload system and satellite bus system. PMU gets commands from ground-station via OBC (On-Board Computer) that is a main controller of the satellite bus system and sends telemetry to the ground-station via OBC. There is a processor module, called SBC (Single Board Computer) in the PMU. The SBC is a main controller of the MSC system. The main roles of the SBC are payload mission management, command validation and execution, telemetry collection and monitoring, ancillary data handling, event reporting, power control of payload sub-units and communication with these units. Intel's 80486DX2 processor has been used for the SBC. Due to the fact that the SBC plays important roles for imaging mission execution and handles a lot of control data that is required for payload operation, it is required to make analysis of the CPU load when it is in maximum operation mode. In this paper, the analysis and measurement results of the SBC throughput in the maximum operation mode.

• Smart Structures and Systems
• /
• 제6권5_6호
• /
• pp.641-659
• /
• 2010

Structural Health Monitoring (SHM) gradually becomes a technique for ensuring the health and safety of civil infrastructures and is also an important approach for the research of the damage accumulation and disaster evolving characteristics of civil infrastructures. It is attracting prodigious research interests and the active development interests of scientists and engineers because a great number of civil infrastructures are planned and built every year in mainland China. In a SHM system the sheer number of accompanying wires, fiber optic cables, and other physical transmission medium is usually prohibitive, particularly for such structures as offshore platforms and long-span structures. Fortunately, with recent advances in technologies in sensing, wireless communication, and micro electro mechanical systems (MEMS), wireless sensor technique has been developing rapidly and is being used gradually in the SHM of civil engineering structures. In this paper, some recent advances in the research, development, and implementation of wireless sensors for the SHM of civil infrastructures in mainland China, especially in Dalian University of Technology (DUT) and Harbin Institute of Technology (HIT), are introduced. Firstly, a kind of wireless digital acceleration sensors for structural global monitoring is designed and validated in an offshore structure model. Secondly, wireless inclination sensor systems based on Frequency-hopping techniques are developed and applied successfully to swing monitoring of large-scale hook structures. Thirdly, wireless acquisition systems integrating with different sensing materials, such as Polyvinylidene Fluoride(PVDF), strain gauge, piezoresistive stress/strain sensors fabricated by using the nickel powder-filled cement-based composite, are proposed for structural local monitoring, and validating the characteristics of the above materials. Finally, solutions to the key problem of finite energy for wireless sensors networks are discussed, with future works also being introduced, for example, the wireless sensor networks powered by corrosion signal for corrosion monitoring and rapid diagnosis for large structures.