[nerfbatplz]

Considering Hubble was an old NRO design that they donated, I bet there are more backup parts than are publically known to be available.

[MontyCarloHall]

Just to clarify: Hubble was not an NRO donation, although it bears some similarity to the KH-11, an NRO satellite from the 70s. It is not confirmed whether the two actually share parts, as the KH-11 is still classified.

The NRO did donate two unlaunched telescopes to NASA in 2012 (with optics present but sans electronics), which still have not yet been retrofitted and launched.

[hatsunearu]

If you read up on it, the NRO gave a shell for a Keyhole something to do NASA. It had no optics and no sensor AFAIK, that was on NASA to build.