Research On Key Technologies Of Interferometric Calibration For Microwave Interferometric Surveying And Mapping Satellites

Distributed microwave interferometric surveying and mapping satellites are based on multiple satellites that meet a certain formation configuration,with synthetic aperture radar and high-precision inter-satellite relative state measurement equipment as payloads,and have all weather and day acquisition of radar interference image data,have abilities of rapidly surveying global digital surface models,digital radar orthophotos and other surveying and mapping products.They can also be called distributed In SAR surveying and mapping satellites.Interference calibration is an important part of the ground system.Its task is to use appropriate algorithms to calculate the deviation between the key parameters that affect the positioning precision of the system and its true value with the support of the ground calibration field control information,so as to gain the purpose of eliminate system errors and improve data product precision.This paper has conducted an in-depth research of the key technologies involved in the interferometric calibration of microwave interferometric surveying and mapping satellites,focusing on the calculation of the baseline calibration field range,the solution of ground point to image point coordinates,atmospheric delay calculation,channel delay calibration,and single-scene data baseline calibration model,near-far beam position joint baseline calibration model,control points layout(selection)strategy and other issues have been studied,and an engineered interference calibration software has been developed.The main work and innovations of the thesis are as follows:1.This paper introduces the technical system and main performance design indicators of TH-2,confirms the calibration parameters by analyzing the main error sources and error properties of interferometric calibration,discusses the principle of interferometric calibration,interferometric phase acquisition method,In SAR positioning model,interference calibration process and scaler design.The design scheme of the calibration field is studied,the basic requirements of the baseline calibration field are clarified,and the calculation method of the baseline calibration field range based on the satellite orbit and radar parameters is proposed,which is used for the site selection of the baseline calibration field for the microwave interferometric surveying and mapping satellite.2.A solution model for ground point to image point coordinates in dual-base imaging mode is proposed.The ground point to image point solution precision of the master image is better than 1 pixel,and the precision of the slave image ground point to image point solution is better than 2 pixels.The solution precision is high,and it is suitable for solving the ground point to the image point in different terrain types.3.The proposed atmospheric delay calculation model combined of mapping method and the ray tracing method,using the tropospheric sounding data and ionospheric vertical sensing data from four regional stations in China for the model precision better than 0.62 m.After the slant-range correction,the precision of the predicted image point coordinates(from the object side to the image side)of the ground point and the precision of the system ground positioning(from the image side to the object side)are verified,and the expected results are achieved.This model is suitable for calculating the atmospheric delay value of spaceborne SAR/In SAR systems.4.A single-scene data baseline calibration model based on the slave radar range modification equation and doppler equation is proposed.The model is based on ground control points and uses least squares iteration to calculate the axis errors of the baseline,and its calibration precision reaches millimeters level,which is suitable for baseline calibration when the area of the calibration field is small(the area covered by one scene data).5.An improved near-far beam position joint baseline calibration model is proposed.By establishing the local master radar antenna phase center coordinate system,the model calculation process is simplified,and the control point layout strategy is used at the near and far beam positions.Control points are arranged at the near range of near beam position and far range of far beam position to improve calibration precision.The calibration precision of this model is higher than that of the single-scene data calibration model,and it is suitable for baseline calibration when the calibration field is large(larger than or equal to the coverage area of the near and far beam position).6.A control point layout(selection)strategy is proposed.According to the fact that baseline calibration actually uses multiple ground control points to intersect the baseline vector,and the principle that increasing the intersection angle can improve the intersection precision,the control points layout strategy is given.That is,the method of arranging control points on both sides of the near and far ends can significantly improve the precision and robustness of calibration compared with the method of evenly distributed control points.In order to solve the problem of interferometric calibration of the TH-2 satellite,relevant technical research is carried out and directly used for the construction of the satellite's ground system,which also lay the foundation for the subsequent interferometric calibration of microwave interferometric surveying and mapping satellites.