It’s interesting how it appears to have a finite DOF despite being at optical infinity. Of course, it wasn’t imaged optically.
I don’t see any mention of DoF in that linked article. The do mention a resolution of 5m (The theoretical resolution for the frequency they use would be on the order of cm)
That’s why I said “appears”, just from a visual viewpoint. It looks as if the near edge is sharper than the far.
the GBT’s enhanced radar system will deliver data at higher resolutions and wavelengths than were previously impossible
What does it mean the data will be of higher wavelengths than previously impossible?
I suspect they had a mix up between “than previously possible” and “that were previously impossible”.
Disregarding the fact that “higher wavelengths” is an odd way of putting it - higher frequencies (i.e. shorter wavelengths) would seem more likely…
[grumble]
I saw this thread before, but hadn’t followed the link. It is quite interesting. 13.9GHz. Hmmm…
I’ve dabbled with 10GHz 
in the form of some little Doppler radar modules. With some very simple external circuitry you can transmit voice using wideband FM (frequency modulation). With an old satellite dish jury-rigged at one end I got about 90m of range. 