近地小行星Apophis的天体测量试验观测

Preliminarily Astrometric Observations of NEO Apophis

Apophis是一颗对地球具有高潜在威胁的小行星（Potentially Hazardous Asteroid，PHA）．对其开展高精度定位观测可为精确计算其轨道提供基本数据。2013年2月4～7日，使用云南天文台2．4m望远镜云南暗弱天体光谱及成像仪（YunnanFaint-Obiect Spectrograph and Cainera．YFOSC）对Apophis进行观测，采用天体测量软件Astrometrica处理原始CCD图像，获得了一批定位结果，并与JPL历表和IMCCE历表进行了外部比较，结果表明，当与JPL历表比较时，赤经、赤纬两个方向的观测位置减去计算位置（0一C）不大于O．1arcsec，每个方向单次测量精度约为0．1arcsec。

The Near-Earth Asteroid Apophis is a potentially hazardous asteroid( PHA),thus it is crucial to develop high precision astrometry that can provide basic data for the accurate calculation of its orbit. The original CCD frames were taken by the YFOSC( the Yunnan Faint Object Spectrograph and Camera) attached to the 2. 4m telescope at Yunnan Observatories during February 4- 7,2013. After we used the astrometry image reduction software 'Astrometrica'to process the CCD frames,76 observational positions of Apophis were obtained. When compared with JPL and IMCCE ephemerides,the absolute mean difference between our results and that of JPL is less than 0. 1 arcsec in both right ascension and declination. This is consistent with what is expected.