If you have a stuck Hawk, here is the fix....

[Vhayne]

I had this problem with Testing Ground 1. I brought the Hawk down, but didn't realize I needed it to open the door (because when it's down, the cameras are down) to the testing ground. So I left and did the main mission for a while, hoping that when I got back out, the Hawk would be repaired and I could access the cameras again.

Nope. Still stuck on the ground, all cameras in the area down. I searched all over, trying to find the solution. Found lots of people who were having the same problem, specifically with the Hawk at TG1.

Here is what I did: Again, this was after quite some time, another testing ground, and a big main mission (VDNH). I went back, and began destroying Pchelyas? (the drone things). And all of a sudden, while I was killing them, the cameras all began popping back up. It's like they got stuck or something?

As soon as the cameras that would access TG1 were up, I immediately opened the door and ran inside. The Hawk was still on the ground at that moment. So, it's still bugged I suppose.

Anyway, hope that helps someone. Kill "some" of the drones.

[Wis]

This worked for me!
Had to shoot a couple of repair droids stuck in the sky, shot a couple of cameras (not the one I needed) and suddenly after connecting to a node they were available for hacking.
Hawk n.1 is still down, but at least I could grant myself access to the first testing ground.
Thanks!