The Fizeau type interferometric telescope forms an array of several sub telescopes for direct imaging on the image plane based on the principle of optical interferometry. Compared to the optical long baseline interferometer, this kind of telescope can be used for real time imaging of celestial body due to some excellent characteristics such as sufficient spatial frequencies coverage, single mounting avoiding outer optical delay lines and so on. We have built an interferometric imaging telescope with four apertures. Although each aperture size is 100mm, but this telescope can reach the higher angular resolution which is equivalent to a monolithic telescope of 280mm aperture size through optimal array configuration. Some novel opto-mechanical structure design and error control methods have been applied to this telescope successfully. For example, in order to enhance the rigidity of mechanical system, a unique C-shape structure to replace the traditional azimuth axis is adapted. Piston, tip/tilt errors between all apertures can be detected at the same time by extracting signals from Modulation Transfer Function (MTF), so some classical beam splitters can be removed which will reduce light loss significantly. At present, we have finished the final assembly, co-phasing calibration and verifying of dynamic co-phasing close-loop methods at laboratory. The FWHM of far field image spot is 0.43 arcsecond which is consistent with theoretical values. The out-door astronomical observation will be carried out soon.
In this paper we report on the laboratory experiment we settled in the Shanghai Astronomical Observatory (SHAO) to investigate the pyramid wave-front sensor (WFS) ability to measure the differential piston on a sparse aperture. The ultimate goal is to verify the ability of the pyramid WFS work in close loop to perform the phasing of the primary mirrors of a sparse Fizeau imaging telescope. In the experiment we installed on the optical bench we performed various test checking the ability to flat the wave-front using a deformable mirror and to measure the signal of the differential piston on a two pupils setup. These steps represent the background from which we start to perform full close loop operation on multiple apertures. These steps were also useful to characterize the achromatic double pyramids (double prisms) manufactured in the SHAO optical workshop.
SLR (Satellite Laser Ranging) is the common satellite observation technology with the highest single shot precision. The 532nm wavelength laser signal derived from 1064nm wavelength laser system is generally adopted to laser measurement to satellites. The 1064nm wavelength laser signal has better performances than 532nm ones in atmospheric attenuation, photon number, laser power, development and price, and so on, which is beneficial to enhance the detection ability of measuring system, and carry out the goal of weak signal detection. In this paper, the relevant techniques are presented in building up SLR system with 1064nm wavelength, and the corresponding solutions are put forward. With these techniques, the 1064nm wavelength high precise SLR measurement was successfully carried out by using si-detector for the first time in Shanghai Astronomical Observatory (SHAO) and the experimental foundations have been laid for the further development and applications in the field of far distance and weak signal space targets observation.
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