“下一代大型空间天文望远镜”(NGST)、空间干涉测量飞行任务”(SIM)和 “天体物理 的全天球天体测量干涉仪”(GAIA)是21世纪初的大型空间天文望远镜的计划。 NGST和SIM是 NASA“起源计划”的关键项目，可用于探索在宇宙最早期形成的第 一批星系、星团。NGST是大孔径被动制冷望远镜，口径4~ 8m,是哈勃空间望 远镜(HST)和红外 空间望远镜(SIRTF)的后续项目。它强大的观测能力特别体现在光学、近红外和中红外的大 视场、衍射限成图能力上。将运行在近地轨道上的SIM采用迈克尔干涉方案，提 供4 µ as精度的恒星的精密绝对 定位测量，由此导出高精度视差和自行，同时它具有综合成图能力，能产生10mas 分辨率的图像。SIM可用于搜索其他的太阳系，研究恒星和太阳系的形成的过程； 利用精密全天球天体测量，研 究恒星和星团的动力学；校准宇宙距离尺度的距离和年龄指示器；探测活动星系演化的动力学。 GAIA可对银河系的总体几何结构及其运动学做全面而彻底的普查，在此基础上开辟广阔的天体 物理研究领域。GAIA采用Fizeau干涉方案，视场1°。GAIA和SIM在很大程度上是互相补充的飞 行，使得两者的天文观测能力互相得到加强。
The new space telescopes were initially planned some five years ago. There are NGST (Next Generation Space Telescope), SIM (Space Interferometry Mission) and GAIA (Global Astrometric Interferometry for Astrophysics) among them. NGST and SIM are two key programs from NASA's Origins program for exploration of galaxies and clusters formed extremely early in the history of the universe. The NGST will be a large aperture, passively cooled telescope of 4~ 8m effective aperture to follow HST and SIRTF. It will have an enormous scientific impact relative to other facilities, particularly for wide-field, diffraction-limited imaging in the optical, near-IR, and mid-IR. SIM will use a Michelson interferometer in a low-Earth orbit to provide 4 µ as precision absolute position measurements of stars and the derived high-precision paralaxes and proper motions. It can use the technique of Rotational Synthesis Imaging to produce images with 10 milliarcsecond resolution. It will be used to search for other solar systems and study the processing of star and solar system formation, the dynamics of stars and star clusters in our galaxy using precision global astrometry, calibrate distance and age indicator used for the cosmic distance scale, and probe the dynamics and evolution of active galaxies. GAIA is aimed at a comprehensive survey of the overall geometric structure and its kinematics of our Galaxy which lead to broad research into astrophysics. It uses Fizeau type interferometer with a degree field of view. GAIA and SIM are largely complementary missions and can greatly enhance each other capabilities and the scientific progress in the field of astrometry.