Helene的Cassini ISS图像的天体测量  

Astrometric reduction of Cassini ISS images of Helene

作　　者：张庆丰[1,2] 熊语桃 彭青玉[1,2] 孟小华[1,2] 李展[1,2] 王娜[1,2] ZHANG QingFeng;XIONG YuTao;PENG QingYu;MENG XiaoHua;LI Zhan;WANG Na(Department of Computer Science,Jinan University,Guangzhou 510632,China;Sino-French Joint Laboratory for Astrometry,Dynamics and Space Science,Jinan University,Guangzhou 510632,China)

机构地区：[1]暨南大学计算机科学系,广州510632 [2]暨南大学天体测量动力学和空间科学中法联合实验室,广州510632

出　　处：《中国科学：物理学、力学、天文学》2019年第1期92-99,共8页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家自然科学基金委员会-中国科学院天文联合基金重点项目(编号:U1431227);国家自然科学基金项目(编号:11873026;11403008;11703008);广东省自然科学基金项目(编号:2016A030313092;2014A030313374);广东省教育厅高等学校科技创新项目(编号:2013KJCX0020);中央高校基本科研业务费专项资金;中山大学广东省计算科学重点实验室开放基金资助

摘　　要：Helene是土星的一颗小卫星,因其暗弱和靠近土星环,而致地面难以观测,历史上观测数据非常少.Cassini ISS在2004–2017年间观测了大量Helene的图像,本文对这些观测图像进行了天体测量工作.具体地说,我们先使用参考星对ISS相机的指向进行校正,然后使用二维高斯法对Helene的量度坐标进行测量,最后将该位置归算到Cassini为原点的国际天球参考架下的赤经、赤纬坐标.并与JPL的历表SAT393进行了比较,计算了位置残差.我们对总计890幅图像进行了有效测量.测量结果显示:和SAT393相比,赤经、赤纬方向的残差均差分别为0.23和-0.63 km,标准差分别为3.48和2.23 km.这个精度远超地面观测的精度,显示了空间观测的优势.Helene is a small irregular Saturnian satellite. It is difficult to observe Helene by ground-based telescopes because of its weak lightness(18.5 mag) and proximity to Saturn's rings. The number of historical observations of the satellite is small,but a large number of images of Helene were obtained between 2004 and 2017 using the Imaging Science Subsystem(ISS)in Cassini Spacecraft. In this paper, astrometry reduction was performed based on these observations. Specifically, we first corrected the initial pointing of the Narrow Angle Camera in ISS using the referencing Gaia DR2, and then measured the Helene's center position in image coordinates using the two-dimensional Gaussian fitting method. Finally the position was transformed to the Right Ascension(α) and Declination(δ) in International Celestial Reference Frame(ICRF) centered at Cassini. The result was compared with JPL SAT393 ephemerides, and the position residual was calculated. Totally 890 images were effectively measured. The results showed that compared with SAT393, the mean values of all residuals in α*cos(δ) and δ directions were 0.23 and-0.63 km, respectively, and the standard deviations were 3.48 and 2.23 km,respectively. This precision was much higher than that of ground observations, indicating the advantage of space-based observations.

关 键 词：Helene 天体测量 卡西尼 光学成像系统 历表 

分 类 号：P12[天文地球—天体测量]