>The answer is, when your orbit is elliptical,
>you will both gain and lose altitude during a full orbit. eventually your orbit will be low enough to catch enough atmosphere that you will be unable to regain altitude.
true, but totally unrelated to what is being observed. it's "skipping" off the atmosphere. what you describe does NOT produce sudden jumps in altitude in the span of frations of 1˚ of orbit.
there's NOTHING more dangerous than a little bit of knowledge. QED.