Spiny Norman said:
Well I never knew that either.
One thing I’m pretty sure of is that the main mirror in the Hubble is that same diameter as that in the early American KH-11 spy satellites (KH short for keyhole). The camera equipment is different. The total length of the KH-11s is said to be shorter and the lens cap is in two pieces as against one piece for Hubble.
“In January 2011 NRO offered NASA two space optical systems with 2.4 m diameter primary mirrors, similar to the Hubble Space Telescope, yet with steerable secondary mirrors and shorter focal length resulting in a wider field of view. These would be spare hardware from the KH-11 program”. “The National Reconnaissance Office (NRO) is one of the 17 U.S. intelligence agencies and considered, along with the Central Intelligence Agency (CIA), …”
I’ve heard it said that the whole original purpose of the Space Shuttle was to put the KH-11 space telescopes in orbit. But the space shuttle only operated from 1981 to 2011, which leaves open the question of how the KH-11 was launched outside those years, particularly the one that went up on 28 Aug 2013. I see, went up on a Delta IV rocket from Vandenberg Air Force Base. I thought the Delta IV had retired, I see, it was only retired from civilian use, in 2003, but remains in military use.
The KH-11 space telescopes haven’t yet been declassified, unlike its predecessor the KH-9 space telescopes with a 0.51 m main mirror and Schmidt-like optics, that were declassified in September 2011.