ABMA was about missile development, not missile defense. Reagan-era organizations that were about missile defense have been kept, since, from doing anything much to actually implement it in any robust fashion, though the largely useless organizations have been kept around because our ruling statists have a very difficult time closing down any government organization.

Ares V was a huge, insanely expensive, completely disposable rocket with a pathetic potential production rate – just like SLS, which is, in essence, Ares V with a different coat of paint. As such, it would have had no useful role to play in anything defense-related just as has proven repeatedly true of SLS.

Useful SARsats don’t have to be enormous and are not. As their name says, they rely on a synthetic aperture that is created by their motion relative to the ground being scanned. The whole point of SAR is that one can get the data one needs without launching gigantic satellites with actual giant apertures. Thus, SARsats are a perfect fit for the sort of proliferated and distributed LEO satellite architecture the USSF is now rushing into service.

Are there space advocates in the USSF? Yes. Lots of them. What there are not in the USSF are nostalgiasts and ardent admirers of useless and obsolete bad ideas from the past.

As for space based radar
https://en.m.wikipedia.org/wiki/Discoverer_II

Early on, I had hoped what was then called Ares V would be flying with DoD forced to use it:
https://phys.org/news/2007-06-big-space-telescopes.amp

The 150 meter dish that could be used for radio astronomy—that and large space based radars could be lofted by Starship…but I wonder if some of the folks in USSF are plants…all I read about is smallsat this and smallsat that.

Are space advocates really in power at USSF?

But, in order to track such objects in real-time, one needs a constellation of SARsats large enough to keep continuous watch on enemy territory 24/7/365. The U.S., so far as I know, does not yet have such capability though we finally seem to be moving in that direction. Whether any of the commercial SAR imagery companies have satellite constellations large enough to allow such unblinking-eye coverage I do not know. I’m not even sure if the DoD could cobble together such a capability by buying continuous data streams from all such imagery vendors in combination.

We have no such capability because, up until five years ago, our military space stuff was all under the control of the morons at USAF – the sons and daughters of the USAF fools who wanted nothing to do with GPS back in the 80s because it was a Navy program. As the late Gen. Curtis LeMay once famously said, “You have to understand that the Soviet Union is our opponent. Our enemy is the U.S. Navy.”

So we have no Argus-eyed SAR coverage for the same reason we have no VLEO interceptor platforms capable of shooting down any rockets rising from enemy territory – the idiots at USAF, and the even bigger idiots that have run this country as a bi-partisan oligarchy for a century or more think that building such things would be “provocative” and “de-stabilizing.” Weakness, dithering and idiocy are provocative and destabilizing and we’ve had more than our fill of all three for far too long.