ASTOR is Airborne Stand-off Radar - battlefield surveillance - the equivalent of the US JSTARS Boeings. 5 Squadron will be getting 5 of them - eventually. They were all due to be in service by September 2005, but the last one, currently being fitted out by Raytheon at Broughton, won't be up and running until December this year.
Well, you did ask!
Rod