Landsat7 ETM + Data Processing Technology

Landsat7, a resource satellite launched by NASA in 1999, has played an important role in remote sensing and exploring of earth because of its plentiful and high-quality images. Many researchers are attracted to focus on it, especially radiometric calibration and geometric calibration in its ground processing system. The characteristic of its focal plate arrays and bi-directional scan make the calibration complex and challenging.The paper studies the pre-processing system , the systematically calibration algorithms and imaging evaluating system, completing the first integrated ground processing system of Landsat7 in China.The pre-process is the first step of imaging process as well as the basis of the research of this paper. According to wideband mission data protocol, the paper finishs such work as identifying synchronization codes , inverting pseudo randomizer, unwrapping data packages. Then , According to ETM+ mission data formats, imaging data and parameters used in calibration are extracted, and inputed into files. So far, 0 level product are generated, during which several problems are resolved such as droped synchronization codes of downlink data , errors of codes , droped synchronization codes and ends codes of imaging major frames , droped synchronization codes and ends codes of parameter major frames.The study on systematically radiometric calibration is summarizing radiometric problems and performance parameters, performing systematically radiometric calibration using these parameters. The output of the procedure is 1R level product. The parameters contain impulse noise, memory effect, scan correlated shift, coherent noise, random noise, dropped lines, inoperable detectors, saturated detectors, MTF, system resolution. The paper analyzes each radiometric problem in detail, and introduces methods of parameter measuring and radiometric calibration.The procedure of systematically geometric calibration is analyzing geometric model and bi-direction scan character at first, introducing calibration method, performing the method, generating 1G level product. The coordinate systems and time systems are described in detail at first, then the paper presents the whole algorithm containing line of sight generation and projection attitude data combination scanmirror calibration , find corresponding grid cell, resample. At the same time, scan gaps and detector delays are analyzed in detail.In order to save time and reduce computational complexity in geometric calibration, a new idea is introduced, a new method on basis of it is presented. The image distortions are decomposed into nominal distortions, caused by nominal scan mirror and spacecraft motion, and seven perturbations, caused by deviations from the nominal motion. The paper analyzes each perturbation, build up a new equation to solve line of sight.The final work of the paper is evaluating image quality. As for images after radiometric calibration, 3-dimention noise analyzing method is introduced. For image after geometric calibration, three performance parameter are used to evaluate the images, and algorithm of the paper is validated.