Analysis of Error Sources in STEP Astrometrytwo |
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| Authors: | Liu Shu-yu Liu Jia-cheng Zhu Zi |
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| Institution: | School of Astronomy and Space Science, Nanjing University, Nanjing 210093 |
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| Abstract: | The space telescope Search for Terrestrial Exo-Planets (STEP) employed a method of sub-pixel technology which ensures that the astrometric accuracy of the telescope on the focal plane is at the order of 1 μas. This kind of astrometric precision is promising to detect the earth-like planets beyond the solar system. In this paper, we analyze the influence of some key factors, including the errors in the stellar proper motion, parallax, the optical center of the system, and the velocity and position of the satellite, on the detection of exoplanets. We propose a relative angular distance method to evaluate the non-linear terms in the variation of star-pair's angular distance caused by the possibly existing exoplanet. This method could avoid the direct influence of measuring errors of the position and proper motion of the reference stars. Supposing that there are eight reference stars and a target star with a planet system in the same field of view, we simulate their five-year observational data, and use the least square method to get the parameters of the planet orbit. Our results show that the method is robust to detect terrestrial planets based on the 1 μas precision of STEP. |
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| Keywords: | Astrometry Telescopes planets and satellites: terrestrial planets methods: analytical |
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