System Trade-Off Study and Opto-Thermo Analysis of a Sunshield on the MSC of the KOMPSAT-2

The Multi-Spectral Camera (MSC) is the payload of KOMPSAT-2 which is designed for earth imaging in optical and near-infrared region on a sun-synchronous orbit. The telescope in the MSC is a Ritchey-Chretien type with large aperture. The telescope structure should be well stabilized and the optical alignment should be kept steady so that best images can be achieved. However, the MSC is exposed to adverse thermal environment on the orbit which can give impacts on optical performance. Solar incidence can bring non-uniform temperature rise on the telescope tube which entails unfavorable thermal distortion. Three ways of preventing the solar radiation were proposed, which were installing external mechanical shield, internal shield, and maneuvering the spacecraft. After trade-off study, internal sun shield was selected as a practical and optimal solution to minimize the effect of the solar radiation. In addition, detailed designs of the structure and sunshield were produced and analyses have been performed. The results were assessed to verify their impacts to the image quality. It was confirmed that the internal sunshield complies with the requirements and would improve image quality

Performance Enhancement of Spaceborne Cooler Passive Launch and On-Orbit Vibration Isolation System

A spaceborne cryogenic cooler induces undesirable microvibration disturbances during its on-orbit operation, which is one of the main sources that degrades the image quality of submeter-level high-resolution observation satellites. Several types of vibration isolation systems based on passive approaches have been developed for reducing the microvibration of the cooler. A coil-spring-type passive vibration isolation system developed in a previous study has shown excellent performance in both launch vibration and on-orbit microvibration isolation. To improve the capability of the conventional cooler isolator, including the position sensitivity and launch vibration reduction, we propose a new version of a dual coil-spring-type passive vibration isolator system. The effectiveness of the newly proposed design was validated through a microjitter measurement test, position sensitivity test, and qualification-level launch vibration test of the isolator

Organic Electrochemical Transistor Based Immunosensor For Prostate Specific Antigen (Psa) Detection Using Gold Nanoparticles For Signal Amplification

We demonstrated a highly sensitive organic electrochemical transistor (OECT) based immunosensor with a low detection limit for prostate specific antigen/α1-antichymotrypsin (PSA-ACT) complex. The poly(styrenesulfonate) doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) based OECT with secondary antibody conjugated gold nanoparticles (AuNPs) provided a detection limit of the PSA-ACT complex as low as 1. pg/ml, as well as improved sensitivity and a dynamic range, due to the role of AuNPs in the signal amplification. The sensor performances were particularly improved in the lower concentration range where the detection is clinically important for the preoperative diagnosis and screening of prostate cancer. This result shows that the OECT-based immunosensor can be used as a transducer platform acceptable to the point-of-care (POC) diagnostic systems and demonstrates adaptability of organic electronics to clinical applications. © 2010 Elsevier B.V

Temperature control of micro heater using Pt thin film temperature sensor embedded in micro gas sensor

Abstract Pt thin film temperature sensors (Pt T sensors) are embedded in micro gas sensors to measure and control the working temperature. We characterized electrical resistances of Pt T sensors and micro heaters with temperature changing in the oven and by Joule heating. In order to enhance the accuracy of temperature measurement by the Pt T sensors, we investigated the correlation among the Pt T sensor, micro heater, and the working temperature, which was linear proportional relation expressed as the equation: T2 = 6.466R1–642.8, where T2 = temperature of the Pt micro heater and R1 = the electrical resistance of the Pt T sensor. As the error by physically separated gap between Pt T sensor and micro heater calibrated, measuring and controlling temperature of micro heater in micro gas sensors were possible through the Pt T sensors. For the practical use of Pt T sensor in micro gas sensor, the gas sensing properties of fabricated micro gas sensors to 25 ppm CO and 1 ppm HCHO gases were characterized