Gwang-Rae Cho

Observation of secondary ozone peaks near the tropopause over the Korean peninsula associated with stratosphere‐troposphere exchange

[1] Vertical profiles of ozone partial pressure and temperature were obtained from ozonesonde measurements for 10 years from 1995 to 2004, over the midlatitude area at Pohang, Korea (36.02°N, 129.23°E), where stratosphere to troposphere exchange (STE) is very active. Secondary ozone peaks were observed in the upper troposphere/lower stratosphere at altitudes of about 14 km mostly in winter and spring. The 450 ozonesonde profiles were analyzed for this study together with satellite measurements from Halogen Occultation Experiment (HALOE) onboard the Upper Atmosphere Research Satellite (UARS). To compare with the satellite data sets, 188 HALOE data sets were archived over the period of 1993-2004 with extended locations for latitudes 32°N-40°N and longitudes of 120°E-135°E, which cover the Korean Peninsula region. The occurrence of secondary maxima in the upper troposphere is highly correlated with zonal wind speed and temperature enhancements. Most of these secondary peaks also were associated with stratosphere-troposphere exchange processes. The backward trajectory model, Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) from National Oceanic and Atmospheric Administration (NOAA) was used to examine these transport events further. The frequency of the secondary ozone peak appearance was found to increase at a rate of 1.4% yr -1 and 2.5% yr -1 for the past 10 years in this region on the basis of the ozonesonde and HALOE observations, respectively.

Design of an Initial Fine Alignment Algorithm for Satellite Launch Vehicles

In this paper, an initial fine alignment algorithm, which is developed for the strap-down inertial navigation systems of satellite launch vehicles, is considered. For fast and accurate alignment, a simple closed-loop estimation algorithm using a proportionalintegral controller is introduced. Through computer simulation for the sway condition in the launch pad, it is shown that a simple filter structure can guarantee fast computational speed that is adequate for real-time implementation as well as the required alignment accuracy and robustness. In addition, its implementation results are presented for the Naro-1 flight test.

Development of a GPS Receiver System for Satellite Launch Vehicles

This paper deals with electromagnetic tests of the GPS receiver system that should be developed to satisfy emission and susceptibility requirements for a satellite launch vehicle. Performance of the GPS receiver system against electromagnetic environment that is improved through several tests satisfies all requirements about electromagnetic tests. The outline of the electromagnetic tests and emission test results of CE102, CE106 and RE102 on MIL-STD-461E are described in Part Ⅰ.

Day-to-Day Repeatability of the Navigation Solution and SNR from the GPS Receiver installed on KSLV-I

This paper deals with quantitative analysis about the characteristics of GNSS(Global Navigation Satellite System) signals contaminated with multipath signals and day-to-day repeatability of the navigation solution and SNR(Signal to Noise Ratio) caused by multipath signals using the collected data from GPS receiver installed on KSLV-I which was on standby on the launch pad at Naro Space Center. Since the GPS antennas, surrounding environments and GPS satellite orbits were very slightly changed with respect to the day, the repeating pattern of the solution and SNR caused by the multipath signals was verified from the collected data. Analytic result of the multipath effects and day-to-day repeatability of the navigation solution and SNR observed at the launch pad would be used for obtaining more stable performance of the GPS receiver when the satellite launch vehicles are on standby.

Operation of the GPS Receiver System for KSLV-I on the Launch Site at Naro Space Center

This paper describes the operation results of the GPS receiver system for KSLV (Korea Space Launch Vehicle)-I on the launch site at Naro Space Center that is the first spaceport of South Korea located at Goheung. All equipments of KSLV-I including the GPS receiver system should be monitored and controlled through hard-wired interface during KSLV-I is on standby at the launch pad. The GPS receiver for KSLV-I is connected to triple almost omni-directional patch antennas mounted on the cylindrical surface of KSLV-I that should be erected vertically on the launch pad until lift-off. Signal interference and multipath effects observed in the GPS receiver on the launch site are analyzed in this paper based on the GPS signals received from each GPS antenna.

Error analysis of the ground based navigation test using extended kalman filtering

This paper considers the error analysis of the ground based navigation test of the strapdown type inertial navigation system. Using an extended Kalman filter, the biases in the inertial sensor are estimated in the static condition of the laboratory environment and the dynamic condition by the test car where another highly accurate instrument is carried to provide target states. The results show that the gyro bias estimates of the filter are within 0.2 deg/hr and the accelerometer biases are within 0.1 mg.

Attitude Controller Design and Test of Korea Space Launch Vehicle-I Upper Stage

This paper introduces the upper stage attitude control system of KSLV-I, which is the first space launch vehicle in Korea. The KSLV-I upper stage attitude control system consists of two electro-hydraulic actuators and a reaction control system using cold nitrogen gas. A proportional, derivative, and integral controller is designed for the electro-hydraulic thrust vectoring system, and Schmidt trigger ON/OFF controllers are designed for the reaction control system. Each attitude controller is designed to have enough stability margins. The stability and performance of KSLV-I upper stage attitude control system is verified via hardware in the loop tests. Hardware in the loop tests are accomplished for perturbed flight conditions as well as nominal flight condition. The test results show that the attitude control loop of KSLV-I upper stage is very stable and the attitude controllers perform well for all flight conditions. Attitude controllers designed in this paper have been successfully applied to the first flight of KSLV-I on August 25, 2009. The flight test results show that all attitude controllers of the KSLV-I upper stage performed well and satisfied the accuracy specifications even during abnormal flight conditions.

Development of 30-Ton f LOx/Kerosene Rocket Engine Combustion Devices(II) - Gas Generator

The development process of a gas generator for a 30-tonf pump-fed space liquid rocket engine is described. Starting from the development of an injector, followed by subscale and full-scale test specimens, the development of LOx/kerosene fuel-rich gas generator has been concluded successfully. Various analytical methods have been utilized in the course of design and the performance requirements have been verified experimentally through ignition tests, combustion performance and stability assessment tests and duration tests. The gas generator has proven its workability and stability within a defined operation window of varying chamber pressure and mixture ratio and demonstrated compliance to the performance and life time requirements.

Comparative Performance Analyses of GPS Receivers under High-Dynamic Conditions

The KSLV-I GPSR that is the first GPS receiver utilized on a satellite launch vehicle developed by KARI should operate normally under harsh environments such as extremely high vibration and shock, wide operating temperature range as well as high-dynamic conditions. Several extensive terrestrial tests have been already done in order to verify performance of the KSLV-I GPSR before flight. This paper deals with comparative performance analyses between the KSLV-I GPSR and other two GPS receivers without velocity and altitude restrictions under high-dynamic conditions. The tracking capability and accuracy of the GPS receivers are compared using a GPS signal simulator with various scenarios like a centrifuge, a satellite launch vehicle, and a spacecraft.

RF Link Analysis of Improvement in Tracking Range for KSLV-I's Tracking System

This paper presents the RF link prediction results for tracking system of KSLV(Korea space launch vehicle)-I especially, these are compared in terms of both the feeding methods of two onboard antennas and the antenna polarization of ground radar. According to dynamic link results considering the trajectory and attitude of launcher, onboard switching technique and radar circular polarization improve link stability and margin, and furthermore increase maximum tracking range.