VO Crawler: A Crawling System for Virtual Observatory Services

We report on the development of VU Crawler under the Japanese Virtual Observatory (JVO) project. VU Crawler accesses Virtual Observatory (VO) Services around the world, and caches data over the whole sky. As all the data are managed in a single system, it is able to do a quick search among the huge amount of data and to display the footprint where observation data exist on a sky map. We are developing applications which utilize data stored by the VU Crawler: JVO Sky which displays the stored data on a sky map, Whole Sky Search system which finds objects from multi-band data on the whole sky, and My Catalog Builder which assists one to build custom-made catalogs from the stored data.