Astronomers have to fight for every expenditure for things like space telescopes. In 2011 the NRO (National Reconnaissance Office) revealed that they had two space telescopes that they did not need and offered them to NASA. They also happened to be twice a big as the space telescope being planned at the time. NASA still has to build the cameras but they at least have the large mirror already built.
(The Great Courses – The Search for Exoplanets)