Research On Key Technologies Of Imaging System In Astronomy

With the development of science and technology and the improvement of the comprehensive national strength of our country,more and more attention has been paid to the development of ground-based large optical telescopes and telescopes in the Antarctic.Astronomical imaging system is an important equipment for astronomical research,whose functions and structure are various from different systems because of their different environment and the characteristics of the observed objects.Thus,the development and implementation of the astronomical imaging system are the research and solution of related key technologies.In this paper,the temperature control technology in the extreme temperature and the weak signal detection technology for the near infrared skylight are mainly researched.And the related technologies are been studied deeply.For the astronomy imaging system,it is very important to ensure the steady of the optical system in the Antarctic.In the extreme cold environment,the temperature control for the temperature sensitive optical component can guarantee the steady of the optical system.For the brightness star survey telescope in the Antarctic,the component needed to be controlled temperature is the shutter.However,because of the narrow space to mount the thermal insulator and the short distance from the window glass of the CCD camera,there are many new challenges to control of temperature and design of thermal insulation structure,the electronic circuit and the algorithm.Based on the heat transfer theory,the demands of the temperature control are analyzed,and the structure,the temperature control circuit and the control algorithm are deeply researched.The relevant detail are also introduced.In addition,the effect of some electronic components on the performance drift and its solution are analyzed and researched.The temperature control system had been tested in the-86 ?environment for long time and steadily working until now in the Zhongshan Station of China in the Antarctic.Near infrared skylight intensity is one of the most important parameters in developing infrared astronomical telescopes in China.In near infrared band,the skylight intensity of J,H and K band of the atmosphere windows are the band needed to measure.However,our country has been lack of independent designed near infrared sky measurement system at present.The measurement of the near infrared skylight requires the system which has the ability of weak signal detection and automatic observation.So,the pre-amplifier for near infrared detector,the sampling module of ADC and data,the vacuum and refrigeration and data processing algorithm are deeply researched.In order to reduce noise,the detector should been cool down to 77K.The pre-amplifier which adopts the Trans-impedance amplifier method should have low noise.The electromechanical device are also needed to realize the automatic observation.In order to match the dynamic range of the skylight,high accuracy ADC and its data sampling module are designed.In the aspect of SNR improvement,the wave modulation coupled with the orthogonal vector type digital phase lock amplifying algorithm is adopted to extract the detector's signal.At present,the near infrared skylight measurement system is accomplished,and has been test by the black body with different temperature.In this paper,the temperature control for the shutter of the brightness star survey telescope and the near infrared skylight measurement system are realized and some research results have been obtained.The innovations of this paper are as follows:(1)The research method of the combination of insulating cavity structure and electronics are used,which realize the temperature control for the shutter in the brightness sky survey telescope in-86 ?.The temperature control system can steadily work in-86 ? without any warming components.High accuracy temperature control has been achieved,and the insecurity of temperature control in the environment has been erased.(2)The vacuum,low temperature,optical electromechanical integration system has been designed.Via a cold chain and thermal isolation for the detector and optical system,the deep refrigeration to 61.4K for the detector has been achieved.Different from the foreign method,the optical system keeps in room temperature to reduce the thermal load with little contribution to the inner noise.(3)The noise from the InSb detector has been reduced by the deep refrigeration.In order to avoid the interference of 1/f noise,a high precision chopper is used to modulate the effective signal to higher frequency.What's more,coupled with the orthogonal vector lock-in amplifier and relative reading out circuit,the prototype system of the near infrared sky background measurement instrument is completed.