Simulation And Analysis For Dynamic Target Observation Of Geostationary Interferometric Microwave Sounder

The Geostationary Earth Orbit has an altitude of about 36000 km.It needs to develop a reflector antenna with large aperture and high precision for microwave atmospheric sounding in GEO orbit using the traditional radiometer,thus has great technical difficulties.By far it still lacks passive microwave technology application in GEO meteorological satellite.Geostationary Interferometric Microwave Sounder(GIMS)uses inteferometric measurement from sparsely distributed antenna array to replace the large antenna needed for traditional radiometer.So it can overcome the difficulties for traditional radiometer in spaceborne application and has better spatial resolution performance with multi-frequency sounding capability.Therefore,GIMS has promising application prospect in GEO microwave sounding.GIMS is aimed to atmospheric temperature and humidity sounding.Since microwave can penetrate most clouds and precipitation,offering three dimensional internal structure of clouds,combining with optical and infrared sensor currently equipped on GEO orbit,GIMS can detect vertical distribution of temperature and humidity inside clouds as well as precipitation.GEO satellite appears motionless to ground observers,so it can constantly monitor a fixed area,acquiring extremely high temporal resolution on wide range earth observation.Therefore,GIMS can effectively monitor weather condition and is especially capable of continuously observing disastrous weather condition such as tropical cyclone and heavy rainfall that happen suddenly and with short duration,hence making forecast and timely alert in such condition.Currently,no GEO microwave measurement can be obtained due to the lack of passive microwave sensors in GEO orbit.GIMS is still in need for system requirement analysis against its observation target's brightness temperature variation regularities.Simulation system and data processing procedure for GIMS are expected to be established to evaluate the sensor's imaging performance in viewing specific observation target.Therefore,this research is proposed to build simulation system for GIMS and its observation target,make analysis for brightness temperature variation regularities of observation target and evaluate GIMS' imaging performance in viewing near real observation target based on the simulation,and improve data processing method to reduce imaging error for GIMS.A detailed discussion is as follows:(1)An observation target modeling method utilizing National Center for Environmental Prediction Final Operational Global Analysis data,Weather Research and Forecasting Model and Radiative Transfer for Tiros Operational Vertical Sounder has been built.The simulation results have been compared with measurements from polar orbit satellite to validate the modeling method.Based on the modeling method,a set of brightness temperature maps with continuous-time variation for seven frequencies in 50~56GHz has been obtained.Choosing one of the primary observation target for GIMS,tropical cyclone,as research object,the brightness temperature temporal variation and spatial distribution characteristic for tropical cyclone have been discussed from both typical case and statistical aspect to make requirement analysis for GIMS' temporal and spatial resolution of each frequency.(2)Based on inteferometric measurement fundamentals,GIMS' observing process that rotate sparsely distributed circular antenna array to realize time-sharing sampling has been simulated to obtain visibility measurements.Together with measurement processing and image retrieval procedure,a brightness temperature level end-to-end simulation system for GIMS has been built,which is then validated by viewing a static brightness temperature map.Through the simulation system,GIMS' imaging performance for different frequency has been assessed,and a difference inversion method using flat target and iterative retrieval brightness temperature has been proposed to improve imaging quality.(3)Combining dynamic observation target obtained by target modeling method and GIMS simulation system,and adjusting value of imaging period,GIMS imaging performance in viewing dynamic target can be assessed for different configured imaging period.To reduce imaging error introduced by viewing dynamic target,an algorithm utilizing Kalman filter and cubic spline interpolation has been proposed.In addition,imaging performance of synthetic aperture system and traditional real aperture system in viewing dynamic target has been evaluated respectively before and after the proposed error-reducing algorithm.From the evaluation,suitability of the two systems in viewing dynamic target have been discussed.