The rate of change of their relative positions is what matters. At 5400km distance this is likely slowish so that tracking is not a big issue as long as positio

The rate of change of their relative positions is what matters. At 5400km distance this is likely slowish so that tracking is not a big issue as long as position is well known, which it is. Re. Link quality: laser, line of sight, most of the trip is in vacuum and the rest in very sparse atmosphere. So interferences are likely quite low.