NSF AST (NSF Astronomical Sciences Division or just AST) is the division of the US National Science Foundation (NSF) dedicated to supporting research in astronomy/astrophysics. Support includes funding individual's research projects, funding the development of instruments, and development and continuing funding of observatories. As such, it is always faced with tradeoffs, e.g., continuing to support existing observatories versus providing funds for new ones.
Among the programs is MSIP, Mid-scale Innovations Program, aiming at projects and ongoing research at a level below the most expensive. Funding includes conditions aimed at making the results useful, e.g., providing a certain amount of freely-available results-data and some access to proposed research efforts.