In his excellent answer to the question of how we make a round trip journey to Mars, @MarkAdler mentions that aerocapture would be used to get into orbit around Mars, saving fuel and therefore weight. This sounds like a nice idea in principal.
However, if the spacecraft comes in too near the planet there is a risk of slowing too much and crashing into the surface. On the flip side, coming in too far away from the planet risks not being captured and flying off into deep space. My question is: Given a normal amount of fuel for such a mission; how narrow is this altitude window in which the spacecraft is captured but doesn't crash or get lost in space?