Research On Thermal And Stray Light Techniques Of Space Solar Magnetic Field Telescope

With the abilities of all day and all climate observation,space solar observation is an important method to study the solar magnetic field.Our country proposed the Deep Space Solar Observatory(DSO)science program in 2011.The main load Magnetic Field Telescope(MFT)attempts to achieve 0.1?~0.15? high space resolution imaging among 393nm~656nm on L1 point Halo Orbit in Sun-Earth System,which is the difficulty of science research and technology.In this paper,the optical system design,stray light suppression,and thermal simulation of MFT are studied.And the specific research methods and achievements are as follows:(1)Several commonly used solar telescope structure and their application characteristics are analyzed.And the Reflect-Refractor Structure(RRS)and Gregorian Structure have been chosen combined with MFT requirements.The optical design of these two structure types is carried out using the confocal design scheme.Results show that the collimate lens could achieve apochromatic in the 393 nm to 656 nm spectrum with large relative aperture and long focal length,and the optical system of MFT is close to a diffraction-limited system over the whole spectral region.Differential thermal analysis results show that the working temperature of diffraction-limited imaging of the two structure types is 20±1? and 20±6? respectively.(2)Considering the difference between MFT and other astronomical telescopes in stray light suppression,a method of eliminating MFT stray light by increasing the size of the primary mirror is put forward.The difficulty of system thermal control in this method is reduced by ensuring that the non-optical surface is non-illuminated.Corresponding to the two kinds of structure the optical system,including the lens cone,light barrier,field diaphragm and heat extraction is completed respectively.And then the stray light performance of the two optical systems is simulated and analyzed.Results show that the main source of system stray light is the surface scattering of reflector.(3)To meet the stray light requirements a novel optical surface roughness control method is proposed based on total integrated scattering theory(TIS)and bidirectional scattering distribution function(BSDF).This method adopts the band-limited root mean square roughness to represent surface polishing accuracy,which can accurately illustrate the relationship between surface scattering and the performance of stray light.Aiming at the stray light suppression index,requirements on the reflector surface roughness are determined.(4)Commonly used thermal analysis software considers the sun as a hot spot source.However under this assumption the solar heating function is not applicable to MFT thermal simulation.According to the characteristic of MFT,this paper proposes to regard the illuminance distribution obtained by optical analysis software as the thermal load in the thermal analysis model,which avoids rebuilding the solar simulation source.Thermal analysis of MFT is carried out using this scheme and thereby relationship between the temperature distribution of the main optical element and the radiation characteristics of the surrounding components is obtained.(5)The tolerances of the two types of MFT collimators are analyzed.Due to the tolerance of Reflect-Refractor Structure is out of the manufacture limitation,only the Gregorian structure collimator has been manufactured.The imaging performance and temperature sensitivity are tested experimentally.And the test results are in good agreement with the design.