I'm having a hard time finding details online.
Do you know an approximate FOV and resolution for a MIR unit?
Another thing that we need to look at is how easily (where easily is a relative term) a sensor can be space qualified.
On the other hand we are very power limited which would make an impulse/low power technique very appealing.
Also while I have not used an MIR before, I have found radar to have very noisy data which gets in the way of high resolution scans.
The Livermore website is pretty vague on details, but they provide a technical contact, so you should probably ask directly. My guess is that FOV, range and resolution are very much a function of antenna design, and that it's not unusual to employ this technology in phased arrays. The nice thing about RF is that it is not so difficult to harden against environment in comparison with other technologies.
Micropower pulsed radar imaging is not a new technology - just do some searches on low power radar, and you'll probably turn up a lot more information. Along those lines, here was an interesting link - http://spie.org/x8537.xml