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5 August 2015 Preliminary results of centroiding experiment for the STEP mission
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Search for Terrestrial Exo-Planet (STEP)[1] was originally proposed in 2013 by the National Space Science Center, Chinese Academy of Sciences, which is currently being under background engineering study phase in China. The STEP mission is a space astrometry telescope working at visible light wavelengths. The STEP aims at the nearby terrestrial planets detection through micro-arcsecond-level astrometry. Determination of the separation between star images on a detector with high precision is very important for astrometric exoplanets detection through the observation of star wobbles due to planets. The requirement of centroiding accuracy for STEP is 1e-5 pixel. A centroiding experiment have been carried out on a metrology testbed in open laboratory. In this paper, we present the preliminary results of determining the separations between star images. Without calibration of pixel positions and intra-pixel response, we have demonstrated that the standard deviation of differential centroiding is below 7.4e-3 pixel by the algorithm of linear corrected photon weighted means(LCPWM)[2,3]. For comparison, the photon weighted means(PWM) and Gauss fitting are also used in the data reduction. These results pave the way for the geometrical calibration and the intra-pixel quantum efficiency(QE) calibration of detector array equipment for micro-pixel accuracy centroiding.
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Haitao Li, Baoquan Li, Yang Cao, Ding Chen, and Ligang Li "Preliminary results of centroiding experiment for the STEP mission", Proc. SPIE 9622, 2015 International Conference on Optical Instruments and Technology: Optoelectronic Imaging and Processing Technology, 96221A (5 August 2015);

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