[aerohead]

I've been reading about both of them.
They carried a suite of eleven ( 11) instruments aboard their scanning platforms.
The charged particle and cosmic particle sensors would have broadcast a change in intensity to JPL as the space probe exited the Heliopause and into unprotected space.
Evidently, there is no facility with which to 'image' the geometry of the Heliopause 'surface,' just to detect a change in exposure to cosmic radiation beyond its limit, at a single point in space.
I still don't understand what 'downstream' means in connection with the Heliopause.
I have no idea how NASA, JPL, CalTech could 'know' about the 'shape' of the Heliopause, and where is 'thinness' would occur, only to make educated guesses, as geologists do about Earth's interior based upon seismic studies.
I'm sure I'm 'wrong' about this. Many here will tell you.
My analyst with FOX network did encourage me to quantify my stupidity though, so we'd both know how hopeless my situation actually is. My medication regimen is contingent upon this sort of intelligence gathering. Any additional data would be welcome. Thanks in advance.