NAVO: NASA Data in the Virtual Observatory

NASA archives curate many of the most important datasets used in astronomical research. This paper describes a recent NASA initiative, the NASA Astronomical Virtual Observatories or NAVO, to ensure that these data are fully accessible through the standardized protocols that being developed through the International Virtual Observatory Alliance. It describes the archives involved, the major data holdings, the initial approach that has been used to provide access to data, and how astronomers and other users can get to NASA holdings.