An astronaut on a circular orbit around Earth tosses three small pieces of trash, each with speed $u$ relative to themselves, where $u$ is much smaller than the orbital speed $v$. Piece I is thrown in the direction of orbital motion (prograde), piece II opposite to orbital motion (retrograde), and piece III radially outward (away from Earth). After exactly one orbital period of the astronaut, which piece(s) collide with the astronaut?