Research On Image Simulation Of Satellite Three-line-array TDI CCD Camera

As our first commercial high-resolution three-dimensional mapping satellite being carried out. Our remote sensing satellite will stride an important step from "experimental" to "applied". Our satellite has a big gap int the geometric accuracy and image quality compared with advanced countries. One of the important reasons that weaken the ability of our satellite development is lack of a quantitative analysis of image quality. Satellite imaging simulation technology is an important part in satellite project because it is the primary means of quality assessment. This paper absorbed the existing satellite imaging simulation and related technologies, was proposed the TDI CCD camera imaging simulation technology according to the camera's imaging characteristics, technical indicators and imaging environment. It conducted research on input modeling, signal transmission link, technical methods of relevant areas and the core simulation algorithm in detail. It was proposed for an imaging simulation method for domestic TDI CCD camera for mapping. It conducted preliminary research on factors affecting geometric resolution, geometric accuracy and directional model accuracy. The main contribution and innovation points are as follows.1. It analyzed the radiative transfer and imaging mechanism of remote sensing TDI CCD camera from theoretical and experimental sides. It interpreted the imaging process from physical principles, and laided the foundation for the design of remote sensing camera imaging simulation algorithm. At the same time, it presented its own point of view on the construction of input digital model for imaging simulation. And it summarized factors affecting the accuracy of sub-models in simulation link.2. It was proposed a specific Monte-Carlo ray tracing method for TDI CCD camera imaging simulation. In this method, the main line is the transmition process of rays, and it linked the complex characteristics such as the distortion of the optical system, geometric errors of CCD installation, motion of the satellite platform, atmospheric refraction, and block of the light source, block of observation and the band characteristics and direction characteristics of reflection orderly. Then, it got the "continuous" energy distribution on the image surface.3. According to the characteristics of TDI CCD camera, it was proposed the dynamic integration imaging simulation model based on Monte-Carlo ray tracing. It combined the optical PSF and rectangular filter PSF of CCD, and constructed an equivalent PSF called static PSF. It could get the mean energy in a CCD once, and expressed it by average apparent radiance. And it got the average apparent radiance equivalent the radiance in sense of laboratory calibration. But the "average apparent radiance" is just for one CCD column. It was proposed the radiation response simulation method of TDI CCD camera on the basis of access the average pupil radiance. Including the simulation of the overall response function, radiation-resolution, and nonuniformity of CCD response and system noise of camera.4. It was proposed the high-dimentional sampling method for optical remote sensing camera on the basis of conclusion of existing sampling method. The sampling spaces include the two-dimensional space of TDI CCD, the time of ray, the imaging band and the solid angle of imaging beam. It estimates the base sampling density according to the resolution and terrain of the input signal to avoid missing signal. And it uses Jitter sampling as the basic sampling strategy and decides whether or not to increase the sampling density according to the radiometric resolution. It will obtain higher simulation accuracy using rays as little as possible.5. This paper analyzed and summarized the PSF in all radiative transfer stages. This paper summarized the mechanism of PSFs and the calculation of MTF in all stages. In the SNR analysis of remote sensing camera, it not only considered the typical CCD noises and circuit noises, but was proposed the generalized noise concept. In this concept, it handles the radiation attenuation caused by atmospheric transmittance and optical transmittance, signal general uplift caused by atmospheric haze light and circuit dark signal, stray radiation of optical system, radiometric resolution and inconsistency of CCD response as "noise". And it was proposed the MTF-SNR integrated simulation flow of remote sensing camera. At last, it analyzed the impact on geometric resolution of MTF and SNR factors in imaging links.6. Dynamic imaging and multi-level integration are key factors affecting imaging geometric quality. This paper summarized dynamic imaging factors of TDI CCD camera and established the mathematical model.It did research on the factors affecting accuracy of three-line-array TDI CCD camera imaging model. And obtain high-precision control points by setting targets. On this basis, it did research on description of "tight" imaging model and factors affecting accuracy, factors affecting accuracy RPC model and quasi-epipolar model.In summary, this paper is aiming at doing research on simulation method of three-line-array TDI CCD camera. And it focused on the key technologies of imaging simulation. Including radiation signal transmission and imaging mechanism, modeling of terrestrial digital signal field, estimation of the camera apparent radiance by numerical integration algorithm, MTF and SNR modeling and simulation algorithm, modeling and simulation algorithm of dynamic imaging factors, research on factors affecting geometric accuracy, directional model accuracy and geometric resolution. By summarizing ideas and methods dealing with related issues in the existing research and with specific issues, it was proposed computer simulation methods for remote sensing TDI CCD camera. So, it lay a good basis for evaluate imaging capability correctly.