I think it is more likely than not that Freeman did the trip. Range security isn't all that great at the periphery of the range, especially at the
NTS. There has been talk of installing ground surveillance radar on the NTS. It wouldn't surprise me if the USAF was looking into the same gear. I
believe the device I saw being tested at Base Camp was ground surveillance radar. But the technology isn't all that great. From what I have read,
they use the radar to determine where to point a camera for visual inspection.
Detecting a person on foot over such a wide area can't be done cheaply, plus really there is no need to detect persons on the range unless they are
near infrastructure, and that you can protect electronically. Think about it. If you walked 5 miles past the front gate of Groom Lake, you still
wouldn't see the base.
I suppose the bombing ranges are an exception to the rule, but then again, a person on a bombing range could be a temporary problem. If they don't
get bombed or shot, there is unexploded ordnance and toxic DU.
The NTS isn't all that radioactive, though I wouldn't have gone through plutonium valley There are spot on the range where the set off nukes but the
crater never formed, but potentially the ground could collapse. But there are warning signs.
Most secure facilities have microwave beams, kind of like the beam of light you break when entering some stores. But they are close to the area to be
protected. I've seen the gear at Edwards South Base.