[orbital-decay]

> It is, of course, actually an aircraft, like all satellites, to some degree, at least in the layman's definition of the word.

Aircraft use the surrounding air as support to counter the gravity. While lift has been measured for GOCE at different angles of attack, it never used it to stay at its altitude; the "wings" were just solar panels to feed the power-hungry engine and stabilize the attitude. At GOCE operating altitudes, the air is sparse, Knudsen number is high, and the aerodynamics differ quite a bit. It wasn't an aircraft, it was a "satelloid", an old idea that got implemented.