Planetary defense actually is one of the critical survival-drivers for the long-term future, but
public discussion of the subject today is mostly so far from reality that I tend to avoid the subject. If folks still can't tie their shoes with a simple thing like RLV... planetary defense is 'way beyond what they can be expected to handle, so why create more heat than light by discussions which miss all the key points?
But yes, imaging space beyond earth is one of the key technologies in that arena, not as important as low cost RLV, but important enough, of growing importance.
One of the things which screws up progress in that arena is the usual combination in DC of iron triangle politics/organization and the striving of a network which I sometimes call Magog. (Not a great name for it, but it's a complicated political network and there is no proper term. Let me just say that Shelby and Lamar Smith tend to be reliable nodes in Magog.) Those two do overlap a lot anyway.
In the iron triangle politics, people strive to display firm loyalty to the idea that the purpose of all streams of information flowing to Congress and the public is to maximize flows of money to existing activities without anything going to new things and without any problems being allowed to surface. Strong antibodies are in place to enforce this more and more at all levels. And so, since the official home for observation of space is at NASA Ames, team players like Al Globus at NSS will push hard for the goal of expanding those classical
programs which cross Ames and JPL. "We have known for centuries what the right technologies are and we should not be distracted from the need to crusade for more money for them." (The maxim "we will only fund proven technology" is something I have heard from the key people in Capitol Hill itself.)
And yet, our long-term position in planetary defense depends critically on whether we do or do not take advantage of opportunities to do a few orders of magnitude better, sooner or later. I am still aghast at the creatures in DC who do not comprehend that a few orders of magnitude in what you can buy per billion dollars actually might affect whether our capabilities ever amount to anything real. Sometimes spending billions upon billions of dollars at a price thousands of times too high buys you so little it would be better not to do it at all.
Years ago, at NSF, I funded a project by Professor Hyland at Texas A&M (who had long experience working with high levels of the Air Force in technology to observe the earth), who developed a new variation of Hanbury-Twiss quantum interferometry which, in constellation optics, offers an order of magnitude improvement in resolution for a given price. You can find his paper on exoplanets via
scholar.google.com, an essential resource. NSF did have a few folks like Globus even then, before Lamar Smith truncated things, but in the old NSF I could go ahead and start this work without getting approval from a bureaucratic committee reporting to staffers. When Hyland was funded, it was the start of a very difficult new road along a new paradigm, but in time he overcame the obstacles and found connections to the advanced groups at JPL, and he was included in the Terrestrial PLanet Finder (TPF) next generation effort.
I still have photos of the things he built, that worked, fielded in constellation tests on the ground in Texas. But then came Magog to NASA.
Still, some of the folks who stayed at JPL even after the Magog purges remembered about constellation optics, and folks I know at google made a few connections through the private sector, a sector which MOSTLY screws up too but which becomes very effective due to what it offers the minority of people who don't screw up as much. If you study the web page of Planetary Resources, and probe hard, you can see
that their supposed "way out asteroid mining" is actually a very solid and progressive business plan, rooted in stuff way ahead what Ames allows itself to understand. It is amusing how folks who defend new space
and spaceX furiously when they see benefits to Ames (which a lot of them rely on for
good old fashioned historic technology to support RLV) can be equally furious in objecting to more use of private sector folks like Planetary Resources for things like planetary defense.
In the meantime... while the best next generation "A team" imaging would come from a proper synthesis of what Planetary Resources and Hyland offer... a rational policy would also make way for a bit of
exploration of advanced team B stuff. (Let me make an analogy here. For imaging, the usual planetary defense stuff is like the SLS, what gets the big money form Magog and produces nothing. Really nothing.
The Planetary Resources to Hyland cluster of technologies is like the Chase/Snead RLV Big Next Step
I would give total priority to now. But sometimes I talk about "team B", NOT as an inferior team, but as
a kind of more advanced thing to try to add to the pipeline, as a backup to the A team and as something to move in in the future, if it does as well as we hope. Air breathing and use of plasma effects are important "B team" areas for RLV, and now I discuss a B team for imaging space. Space ladders are a team C, even further in the future, because they demand a lot of mass in space, not feasible until teams A or B
enable that. Guys like Mankins or Chase would say "hey, you are reinventing TRL." OK. A and B and C represent waves of future generations.)
For imaging space and for planetary defense in a broader sense, there are principles in quantum optics which allow things 'way beyond what the Planetary Resources and Hyland technologies allow. I do wish there could be room to advance that, even as the earlier work is supported for the sake of its more immediate applications. In my view, the next critical step forward to enable that B team imaging
is to perform a specific experiment I have proposed, reviewed in detail in my paper in Quantum Information Processing 2016 -- easy to find at scholar.google.com, but available to the general public on the web only viawww.werbos.com/physics.htm. (Springer allows posting on one's own web page but not at places like arxiv, at least for a year; I need to check the copyright agreement.) I said a little bit more, in common English, on the future possibilities for triphoton quantum ghost imaging at NATO workshop last week, one of the presentations posted at:
The US had the lead and initiated all these capabilities, but, thanks to Magog, only Austria and China actually have the capability still alive to do the first step. There is also some worry that the cybersecurity applications of the technology might persuade China to do the critical experiment, and some of the follow-on technologies (of which imaging space is only one), without even bothering to let us know what universe we are in, encouraging us to continue to waste money on .. stuff like what Magog cheerfully wastes money on.
A few other points might be worth mentioning. Of course, China does not know of many of the follow-on technologies, which are hinted at and logically implicit in our QIP paper, but not as visible as the ghost imaging and so on. If they do not go pubic with the results, maybe human societies will never know. And of course, one of the reasons I did not discuss ghost imaging of the future in the QIP paper is that science prefers that we go one step at a time, and limit discussion of further steps until after step one is publicly replicated and so on.
Also, I forgot to mention Criswell's proposal for a large-scale phased array system, also relevant to long-term future imaging and directed beam options. A complementary C team.