小行星掩星的今天和明天：走向GAIA时代
Asteroid occultations today and tomorrow: toward the GAIA era
摘要：
背景：观测掩星是确定小行星形状和大小的有力工具。这是研究小行星带演变和校准间接确定大小方法（如用于分析热红外观测的模型）所必需的关键信息。到目前为止，小行星掩星的观测基本上是由配备小型便携式设备的业余天文学家进行的。然而，现有星历表的准确性妨碍了对小于~100公里的天体的掩星事件的准确预测。目的：我们调查目前的限制，在可预测性和可观测性的小行星掩星，我们研究它们可能的演变在未来，当高精度的小行星轨道和恒星位置（如预期从任务盖亚的欧洲航天局）将可用。研究方法：我们使用一个简单的模型，小行星星历的不确定性和数值算法估计的仪器所施加的限制，假设现实的CCD性能和小行星的大小分布，估计预期的掩星率在不同的条件下。结果如下：我们表明，高精度星历，这将是在未来将扩展到小得多的小行星观测小行星掩星的可能性，大大增加了事件和对象的数量。如果有一个小型的地面1米望远镜网络专门用于掩星研究，几年内就可以获得一套完整的尺寸测量结果，测量范围可低至约10公里的主带小行星。
英文摘要：
Context: Observation of star occultations is a powerful tool to determine shapes and sizes of asteroids. This is key information necessary for studying the evolution of the asteroid belt and to calibrate indirect methods of size determination, such as the models used to analyze thermal infrared observations. Up to now, the observation of asteroid occultations is an activity essentially secured by amateur astronomers equipped with small, portable equipments. However, the accuracy of the available ephemeris prevents accurate predictions of the occultation events for objects smaller than ~100 km. Aims: We investigate current limits in predictability and observability of asteroid occultations, and we study their possible evolution in the future, when high accuracy asteroid orbits and star positions (such as those expected from the mission Gaia of the European Space Agency) will be available. Methods: We use a simple model for asteroid ephemeris uncertainties and numerical algorithms for estimating the limits imposed by the instruments, assuming realistic CCD performances and asteroid size distribution, to estimate the expected occultation rate under different conditions. Results: We show that high accuracy ephemerides which will be available in the future will extend toward much smaller asteroids the possibility of observing asteroid occultations, greatly increasing the number of events and objects involved. A complete set of size measurements down to ~10 km main belt asteroids could be obtained in a few years, provided that a small network of ground-based 1m telescopes are devoted to occultation studies.
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