空间VLBI卫星VSOP/HALCA是日本宇航科学研究所(ISAS)的飞行任务(mission)， 已经在1997年2月升空。它拥有8m直径的射电望远镜，远地点达22000 km。和地面的射 电望远镜联合观测(干涉观测)，其最高分辨率比地面VLBI提高了3倍。该项空间VLBI 观测由NASA的地面跟踪站支持。第一批VLBI图像已经在因特网上发表。RadioAstron 项目由俄罗斯科学院列别捷夫物理研究所天文空间中心(ASC)启动，除卫星主要由俄 罗斯研制外，其科学仪器有10多个国家参加研制。它也用NASA的地面跟踪站对卫 星进行跟踪。 RadioAstron具有10m射电望远镜，其远地点高度达70000 km，最高分辨率可达30 µas。其升空时间被安排在俄罗斯的高能卫星Spectrum X-Gamma和Spectrum UV之后。 ARISE是第二代空间VLBI卫星，正在论证和研制当中。与VSOP和RadioAstron不同，其 最高频段达86GHz，天线直径25~30m，并采用“吸附制冷”新技术，使总系 统温度可达10~ 20K，而且寿命长。预计ARISE卫星有可能在2008年发射升空。

The VSOP (VLBI Space Observatory Programme) mission is led by the Institute of Space and Astronautical science, in collaboration with the National Observatory of Japan. It was launched on February 12, 1997. The VSOP satellite , renamed HALCA after its successful launch, carries a radio telescope with 8m in diameter, and moves in an elliptical Earth orbit, with an apogee height of 21000 km. The resolution is three times better than that with ground VLBI array. The Space VLBI is supported by NASA ground tracking stations. First images have been shown on Internet. The RadioAstron program was initiated by Astro Space Center (ASC) of Lebedev Physical Institute of Russian Academy of Sciences, and has expanded into a broad international collaboration. RadioAstorn will be supported by NASA tracking stations also. It has a 10 m radio telescope, and its orbit has an apogee height about 70000km, providing an angular resolution as high as 30 microarcsecond. Particular scientific goal of the mission is the study of radio galaxies and quasar with unprecedented angular resolution approaching angular size of accretion discs around massive black holes. The launch of the mission is scheduled after the high energy satellites Spectrum X-Gamma and Spectrum UV. ARISE is a next-generation space VLBI satellite under development. The differences between ARISE and VSOP-RadioAstron are: the operating frequency as high as 86GHz, antenna diameter 25~30 meter, new technology ``sorption cooler"permitting system temperature on the order of 10~20 K with long lifetime. This enables investigation on the nature of the innermost relativistic jets in gamma ray blazars, and the physics associated with extragalactic H₂O megamaser. The launch of the satellite will probably be in 2008.