Post portal orbits sometimes don't work out

From #169:

I am not sure whether it is a related problem, but even if the jump succeeds, there is a good chance to be on an orbit quite far from the target portal (and incompatible with appearing close to a portal with wrong speed).

After going thru a portal, you are supposed to be placed in orbit around the portal on the other side, but sometimes it places you far away. I suspect this might have something to do with a bug in the quadrant calculation.