This answer links to Space.com's NASA May Launch Donated Spy Satellite Telescope to Mars which emphasized textsays:
An unexpected gift
The two donated telescopes were apparently built for a National Reconnaissance Office program called Future Imagery Architecture, which was terminated in 2005.
NASA announced in June 2012 that it had acquired the instruments, which are designed to have a much wider field of view than Hubble, despite sporting Hubble-like 8-foot-wide (2.4 meters) main mirrors.
In November, the space agency asked scientists to suggest potential uses for the NRO scopes, which are basically just primary and secondary mirrors, with no instruments attached. More than 60 serious proposals came flooding in, 33 of which — including MOST — were presented in early February at the Study on Applications of Large Space Optics (SALSO) workshop in Huntsville, Ala.
I don't understand the use of "despite" there, but my question is:
- What exactly gives a larger field of view to the donated "spy" telescopes that NASA may send to Mars? I'm assuming that are Cassegrain-like telescopes. It's possible that sources might be available from Was Hubble really related to spy satellites?
- How much larger are we talking about here; 50%? a factor of ten?