This, as I understand it, being the closest approach to our orbit, not our atmosphere or so. To put this in perspective, the Earth is some 6.4 Mm in radius, so

This, as I understand it, being the closest approach to our orbit, not our atmosphere or so. To put this in perspective, the Earth is some 6.4 Mm in radius, so that's 40-6.4 = 33.6 Mm above the surface.