Three-dimensional Imaging Radar Altimeter Interferometry Technology And Its Error Analysis

The radar altimeter can measure the sea surface height centimeter by transmitting a narrow pulse signal to the nadir point of satellite.The traditional altimeter can only measure the nadir point along the ground track of the satellite,and its pulse limited footprint is only 6~7km.There are a lot of gaps(200~300km)in the intersections and the spatial resolution is very low.The new three-dimensional imaging radar altimeter is proposed for the traditional altimeter can only measure the height of the nadir point of satellite,the spatial resolution is limited by the limitations of its footprint,it applies interferometry in the synthetic aperture altimeter can be all-weather,wide slash,high-precision three-dimensional imaging of the sea surface.In this paper,the basic principles of the altimeter-based altimetry,aperture synthesis and interferometry are introduced respectively.Based on these basic principles,the system composition of three-dimensional imaging radar altimeter and the role of each subsystem and submodule are analyzed.On the basis of synthetic aperture interferometry,the specific process of interferometric measurement data processing for altimeter of three-dimensional imaging radar is introduced.The two images are accurately registered,and the phase of phase is removed by using interferometric phase spectrum migration.The circular period mean filter and the weighted circular period mean filter.The phase unwrapping is performed using the branch cut method,and finally the phase value to height value conversion is completed.The error distribution scheme of the interferometric measurement module for the three-dimensional imaging altimeter near the nadir was analyzed.The main factors affecting the slant range measurement are atmospheric path delays,atmospheric path delays including dry,wet neutral path delays,and ionospheric delays,taking into account the influence of atmospheric path delays at small incident angles.Simultaneously,the influences of slant length,baseline length,baseline inclination,phase measurement and orbit height error on the height error were simulated and analyzed.The simulation results sat-isfied the technical specifications of the three-dimensional imaging altimeter ocean working mode.Finally,an interferometric imaging experiment was performed using 3D imaging altimeter data.Interferometric phase maps and relative digital elevation maps of the target region were successfully generated,and Sentinel-1 satellite were used to intervene in the same region with the single-look complex product data in the wide-interval mode.Imaging processing,analysis and comparison of the difference between the two elevation maps,verify the correctness of the interferometric data processing flow of the three-dimensional imaging radar altimeter.