Study On Technique Of Daytime Detection And Design Of Telescope

Telescope is widely used in astronomy observation, natural resources research,outer space explore. And the developing trend of it is larger and larger aperture,higher and higher resolution, and further and further detecting distance.Because of impact of the strong sky background and stray light, majority of thetelescopes can only work in the night, which will lose the observation opportunity ofsome objects in the space as well as lower the observation efficiency of the telescope.So, this paper carried on research on techniques of daytime detection of space objectsand designed a daytime detection telescope based on the spectrum filtering technique.The main content is as follows:1. For expanding the operating time of telescope, this paper combined thedetecting principle and theory, the limiting daytime detecting capability of telescopesystem was analyzed and calculated. With developing the limiting capability of thetelescope system as the goal, the differences of spectrum filtering to the limitingcapability, the spectrum filtering principle, the selective basis and method of filter,and the impact of the filter to detecting signal-to-noise was analyzed. Also, the impactof focal length, aperture and field of optical system to the detecting capability wasstudied. Besides, the influence of the stray light to the imaging quality was analyzed.Meanwhile, the technique of stray light suppression was researched.2. In this paper, shape of the main mirror and its supporting structure wasdesigned and the supporting rigidity and the distortion of the main reflecting surfacewere analyzed using the FEA software. The analysis result illustrates that when theoptical axis is vertical and under the action of gravity, the maximum deformation ofthe supporting mount is1.1μm and the surface distortion of the main mirrorPV=48.1nm，RMS=14nm. When the optical axis is vertical and under the action ofboth gravity and28℃ambient temperature difference, the surface distortion of themain mirror PV=49.2nm，RMS=15.4nm. When the optical axis is horizontal andunder the action of gravity, the maximum deformation of the supporting mount is0.4um and the surface distortion of the main mirror PV=16.5nm，RMS=4.2nm. Whenthe optical axis is horizontal and under the action of both gravity and28℃ambienttemperature difference, the surface distortion of the main mirror PV=55.2nm，RMS=11.6nm. The modal analysis result indicates that the first order resonance frequency of the supporting mount is363Hz, which is further bigger than thevibrating frequency of outside loads. It’s known from the above analysis that the mainmirror and its supporting structure have high rigidity and stability, and the surfacedistortion of the main mirror satisfies the design request（PV<λ/6, RMS<λ/30,λ=632.8nm）.3. In this paper, supporting structure of the secondary mirror was designed andanalyzed. The analysis result illustrates that when the optical axis is vertical and underthe action of gravity, the maximum deformation of the supporting mounts is1.33um.When the optical axis is horizontal and under the action of gravity, the maximumdeformation of the supporting mounts is0.41um. The modal analysis indicates thatthe first order resonance frequency of the supporting mount is272Hz, which is furtherbigger than the vibrating frequency of outside loads. It’s known from the aboveanalysis that the secondary mirror’s supporting structure has high rigidity and stabilitywhich meets the needs of design. Meanwhile, in order to adjust the design request, thesupporting structure is adjustable at5degrees of freedom.4. In this paper, baffle of the telescope was designed and the stray lightsuppression effect was analyzed. The analysis result indicates that when off-angle ofthe stray light source is bigger than40°, the PST(Point Source Transmission) of theopto-mechanical system is smaller than210-8, which meets the stray lightsuppression target and displays a well suppression effect.5. In this paper, the limiting detecting magnitude of the designed telescopesystem was calculated. The result indicates that the actual limiting detectingmagnitude is6.7mvusing the0.925to1.675μm band-pass filter, which meets thedesign request.