Korea Multi-Purpose Satellite Research Articles

A new geometrical correction method for inaccessible area imagery

The geometric correction of a satellite imagery is performed by making a systematic correction with satellite ephemerides and attitude angles followed by employing the Ground Control Points (GCPs) or Digital Elevation Models (DEMs). In a remote area or an inaccessible area, however, GCPs are unavailable to be surveyed and thus they can be obtained only by reading maps, which is not accurate in reality. In this study, we performed the systematic correction process to the inaccessible area and the precise geometric correction process to the adjacent accessible area by using GCPs. Then we analyzed the correlation between the two geo-referenced Korea Multipurpose Satellite (KOMPSAT-1 EOC) images. A new geometrical correction for the inaccessible area imagery is achieved by applying the correlation to the inaccessible imagery. By employing this new method, the accuracy of the inaccessible area imagery is significantly improved absolutely and relatively.

IONOSPHERIC OBSERVATION USING KOREAN SATELLITES

We report the results of the ionospheric measurement obtained from the instruments on board the Korea Multi-Purpose Satellite - 1 (KOMPSAT-l). We observed a deep electron density trough in the nighttime equatorial ionosphere during the great magnetic storm on 15 July 2000. We attribute the phenomena to the up-lifted F-layer caused by the enhanced eastward electric field, while the spacecraft passed underneath the layer. We also present the results of our statistical study on the equatorial plasma bubble formation. We confirm the previous results regarding its seasonal and longitudinal dependence. In addition, we obtain new statistical results of the bubble temperature variations. The whole data set of measurement for more than a year is compared with the International Reference Ionosphere (IRI). It is seen that the features of the electron density and temperature along the magnetic equator are more prominent in the KOMPSAT-l observations than in the IRI model.

Estimation of urban runoff and water quality using remote sensing and artificial intelligence

Water quality and quantity of runoff are strongly dependent on the landuse and landcover (LULC) criteria. In this study, we developed a more improved parameter estimation procedure for the environmental model using remote sensing (RS) and artificial intelligence (AI) techniques. Landsat TM multi-band (7bands) and Korea Multi-Purpose Satellite (KOMPSAT) panchromatic data were selected for input data processing. We employed two kinds of artificial intelligence techniques, RBF-NN (radial-basis-function neural network) and ANN (artificial neural network), to classify LULC of the study area. A bootstrap resampling method, a statistical technique, was employed to generate the confidence intervals and distribution of the unit load. SWMM was used to simulate the urban runoff and water quality and applied to the study watershed. The condition of urban flow and non-point contaminations was simulated with rainfall-runoff and measured water quality data. The estimated total runoff, peak time, and pollutant generation varied considerably according to the classification accuracy and percentile unit load applied. The proposed procedure would efficiently be applied to water quality and runoff simulation in a rapidly changing urban area.

ELECTRICAL GROUND SUPPORT EQUIPMENT (EGSE) DESIGN FOR SMALL SATELLITE

This paper describes EGSE design for the small satellite such like KOMPSAT-2 satellite. Recent design trend of small satellite and EGSE is to take short development time and less cost. For this purpose, the design for KOMPSAT-2 satellite and EGSE are not much modified from KOMPSAT-1 heritage. It means that it is able to be accommodated the verified hardware and software modules used in KOMPSAT-1 satellite program if possible. The objective of EGSE is to provide hardware and software for efficient electrical testing of integrated KOMPSAT-2 satellite in three general categories. (1) Simulators for ground testing (e.g. solar-simulation power, earth scenes, horizons and sun sensor). (2) Ground station type satellite data acquisition and processing test sets. (3) Overall control of satellite using hardline datum. In KOMPSAT (KOrea Multi-Purpose SATellite) program, KOMPSAT-2 EGSE was developed to support satellite integration and test activities. The KOMPSAT-2 EGSE was designed in parallel with satellite design. Consequently, the KOMPSAT-2 EGSE was based on the KOMPSAT-1 heritage since the spacecraft design followed the heritage. The KOMPSAT-2 baseline was elaborated by taking advantage of experience from KOMPSAT-1 program. The EGSE of KOMPSAT-2 design concept is generic modular design with preference in part selection with commercial off-the-shelf which were proven from KOMPSAT-1 programs, flexible/user friendly operational environment (graphical interface preferred), minimized new design and self test capability.

Large density depletions in the nighttime upper ionosphere during the magnetic storm of July 15, 2000

We measured electron density and temperature of the nighttime upper ionosphere for the several key intervals during the progress of the magnetic storm on 15 July 2000 with the Langmuir probe on Korea Multipurpose Satellite‐1 (KOMPSAT‐1). During the main phase of the storm KOMPSAT‐1 detected near 0°E a very deep and extensive trough of electron density centered around the geomagnetic equator. The electron density dropped sharply from ∼4 × 105cm−3 to less than 2 × 104cm−3, with the trough region extended over 1400 km along the satellite track. Later in the recovery phase, KOMPSAT‐1 observed severe distortion still persisted near 230°E, with enhanced density in the southern hemisphere. Together with DMSP observations, we estimate the size of the observed trough to be at least 5500 km in the longitudinal direction. DMSP data indicates that the trough was caused by the enhanced eastward electric field which lifted the equatorial F‐region ionosphere upward.

Worst Case를 고려한 위성체 접속회로의 최적설계

The electrical characteristics of solid state devices such as BJT(Bipolar Junction Transistor) and MOSFET, etc, are altered by impinging nuclear radiation and temperature in the space environment. This phenomenon is well known and has been studied extensively since the early 1960's when satellites were first being designed and used in the United States. However, the studies and the developments of radiation hardening technologies for the electronic components at the industrial fields in our country has not been popular so far. The worst case design technology in the electrical circuit is required for the appropriate operation of solid state devices in the space environment. In this paper, the interface circuit used in KOMPSAT(Korea Multipurpose Satellite), which is now being operated since the one was launched in 1999, is optimally designed to accomodate the worst case design and radiation effect.

Study on the First On-Orbit Solar Calibration Measurement of Ocean Scanning Multi-spectral Imager (OSMI)

The ocean Scanning Multi-spectral Imager (OSMI) is a payload on the KOrea Multi-Purpose SATellite (KOMPSAT) to perform worldwide ocean color monitoring f the study of biological oceanography. OSMI performs solar and dark calibrations for on-orbit instrument calibration. The purpose of the solar calibration is to monitor the degradation of imaging performance for each pixel of 6 spectral bands and to correct the degradation effect on OSMI image during the ground station date processing. The design, the operation concept, and the radiometric characteristics of the solar calibration are investigated. A linear model of image response and a solar calibration radiance model are proposed to study the instrument characteristics using the solar calibration data. The performance of spectral responsivity and spatial response uniformity. The first solar calibration data and the analysis results are important references for further study on the on-orbit stability of OSMI response during its lifetime.

Thermal distortion analysis of orbiting solar array including degradation effects of composite materials

In this study, transient analyzes were conducted to predict the thermal distortion of the Korea Multi-Purpose Satellite (KOMPSAT) solar array during its orbital motion. The solar array consists of five honeycomb sandwich panels with aluminum facesheets. To enable future improvements, the solar arrays were also analyzed with composite facesheets for the temperature distribution and thermal distortion. In order to evaluate the degradation effects of the material properties of the composite facesheets in low earth orbit environment, the composite materials were exposed to simulate low earth orbit environmental conditions including ultraviolet (UV) radiation, high vacuum and thermal cycling. The values of the degraded properties were used in the thermal distortion analysis. The results show that the solar arrays with composite facesheets are beneficial with regard to weight savings, temperature distribution and thermal distortion during the mission when compared to those with aluminum facesheets, even though the composite materials are degraded due to low earth orbit environmental factors.

Parameter Robust Risk-Sensitive Control Synthesis for a Satellite with Structured Parameter Uncertainties

The parameter robust Risk-Sensitive control synthesis is newly developed to deal with the parameter uncertainties of a system. In this synthesis the parameter uncertainties are decomposed into three parts and are reflected in the cost function and the noise models. This new method improves the tolerance of a controller to parameter uncertainties in a system. A nonlinear attitude model of a satellite with thrusters, magnetic torquers and reaction wheels is developed. Then the linearized version of the satellite attitude model is derived for the attitude hold mode. To determine the performance of the parameter robust Risk-Sensitive control method, the steady-state mean square histories of the state and input variables are calculated by finding the covariance matrices. Moreover, the performance and stability robustness of parameter robust Risk-Sensitive control are compared with the classical linear quadratic Guassian control. Finally, as an application of this parameter robust Risk-Sensitive control, we use the Korea Multi-Purpose Satellite model equipped with reaction wheels and thrusters as the attitude control devices. The numerical simulations show that the parameter robust Risk-Sensitive control method has better performance and stability characteristics than the classical linear quadratic Guassian control method, especially when the parameter uncertainties are large.

Spacecraft Attitude Maneuver Planning for the Mission Support

The first KOrea Multi Purpose SATellite(KOMPSAT) will be launched in July 1999 into low earth orbit(LEO) sun synchronous circular orbit at 685 km altitude. To support the KOMPSAT mission, a mission planning support software has been developed to observe the Earth landmark. It computes the required parameters such as the timing of the commands and the required pointing angle to accomplish various task of Earth observations and generates timeline events for spacecraft maneuver planning. This work can be easily applied to the spacecraft's maneuvers planning that are controlled relative to the non-inertial reference frame and inertial frame, such as high precision land mark observations, planet observation, target tracking. This papers examines the Science mode planning of the KOMPSAT for the earth observation as a basis for the discussion.