Certainly not optical spying, it's not big enough because of diffraction limits. The old NRO telescopes are basically Hubbles that point down, so they have a mirror about 2 metres across and probably a resolution somewhat better than Hubble (30cm on the surface).

They even donated the chassis of some[1] to NASA once they were thoroughly obsolete. Imagine what the new ones can do if a Hubble-alike was such old hat it didn't even need to be secret.

Also imagine if we'd been able to put a fleet of Hubbles out there rather than just one!

[1] https://en.wikipedia.org/wiki/2012_National_Reconnaissance_O...