Research On Underwater Photogrammetry For Surface Measurement Of Satellite Antenna In Simulated Zero-Gravity Conditions

With the exigent requirement for precision measurement of the satellite antenna surface, the technology of underwater photogrammetry was introduced with the zero-gravity conditions. The simulated zero-gravity conditions were achieved with the gravity compensation by the flotage of water. Serial theory researches and technical tests were done on the close range underwater photogrammetry. The theory and technology for underwater photogrammetry were validated through the surface measurement of satellite antenna in water.Primary coverage of this dissertation and innovation were as following:1. The geometry model was analyzed and discussed among three couples of datum marks and planes in one optical system. The optical imaging system mainly depended on its datum marks and planes. The conclusion had been verified that the camera lens system depended on not only its structure but also the refractive indexes of object space and image space.2. The collinearity theory with three points was interpreted with the optical rays through the nodal points for one-media photogrammetry. The relation of position were analyzed among object, image and the principal distance f 0 of camera in one-media photogrammetry.3.Based on the variable projection center and principal distance of camera, the collinearity theory with three points was advanced of underwater photogrammetry. The conclusion had been drawn that the principal distance of underwater camera was magnified with a factor of water refractive index by the one in air. All those were validated by one test of underwater photogrammetry.4.The characteristics of underwater rays transmission and the effects on imaging were analyzed. Some methods and steps were recommended to improve underwater imaging quality. An equipment was designed and manufactured in order to protect camera from watering in underwater photogrammetry shallowly. And the equipment was performed successfully to take underwater photos.5.The common methods of underwater camera calibration and its characteristics were analyzed. One optimal scheme of underwater camera calibration was put forward. Experiment results have shown that this scheme was effective and successful.6.The error factors of underwater close-rang photogrammetry were analyzed. The influence on measurement precision was discussed, including the equipment of protecting camera, underwater environment and measurement network. The practical ways were taken out to reduce the influence of these factors. Three types of precision measurement tests were carried out. The results have shown that measurement network was more prominent than the others for precision. And the measurement precision for camera with protection equipment was accordant between underwater and on-top water of photogrammetry.7.The technical scheme and the method were presented for the underwater surface measurement of a 1.3m caliber Spring-Back antenna. The experiment was implemented successfully. The experiment results have shown that the flotage of water could proportionally compensate the gravity and the antenna surface in water was slightly distorted comparing with that in air.