I have been exploring opportunities to apply knowledge and skills to The heavily funded Ionospheric/Tomography research that has been underway for some time now. Perfect fit for experienced Amateur Radio operators who pursue Long range HF communications, with DX. Been doing that for 60 years or so. Even though being a late arrival to this DARPA funding offer, on this Tomography stuff, I discovered there are vast levels and layers [call them F1, F2, and D and E layers] :-) of R and D research on going to model he ionosphere which is dynamic, and complex. So far I have found pretty much ALL the commercial HF broadcasting sites around the world... [where HF RHOMBICS 1000 feet or more long are found or may be constructed.] Finding opportunities, is like finding and using a paper road map to Paris-- from Berlin. I discovered this NTA site that can offer some navigation assistance, "to Paris".
Look up NTA.ORG and if you learn anything, a hot lead, that you can share, please do. -- PJB