Are certain altitudes above Earth reserved (or commonly selected) to limit possibility of collision between objects travelling in prograde, retrograde and polar orbits? Like a one way street, if everything at a certain altitude is travelling in the same direction, the possibility of collisions would be greatly reduced.

Or is space so large and debris so small, that this is not a major concern?


I had used the word 'elevation' rather than 'altitude' in the original version of the question.

  • $\begingroup$ Space debris collision is a legitimate concern in LEO and GEO, see Kessler syndrome $\endgroup$
    – Dragongeek
    Mar 4, 2018 at 20:34
  • $\begingroup$ @Dragongeek Ah, that helps. I didn't know the technical name for the debris concern. $\endgroup$ Mar 4, 2018 at 20:56
  • $\begingroup$ That is such a good point I wonder if I should replace elevation in the question... $\endgroup$ Mar 5, 2018 at 2:59
  • $\begingroup$ Just the Geostationary orbit, and even there its not so much to avoid collision but the very nature of the orbit itself. $\endgroup$ Aug 27, 2021 at 7:51

1 Answer 1


Orbits are not reserved. Orbits are on a first-come-first-serve basis. Orbits are managed, though.

Space debris is a major problem. Sure, space is huge but it is quite populated with debris. Famously, a speck of paint bore a hole in the ISS (not all the way through.) This problem is known as the Kessler Syndrome, and it is a huge problem.

Space debris is tracked by NASA and the Department of Defense. Tracking space debris is a huge must. Being blind to space debris leaves the ISS susceptible to "pecking."

Agencies announce launches to let people know that the rocket that the agency is launching does not have a warhead and let other agencies be aware of the satellite. No agency is going to launch a satellite in the ISS's orbit (disregarding rendezvous.) No-one wants to lose a one-billion satellite nor four astronauts.

Orbits are not reserved per se, but they are managed to avoid collisions. Agencies spend a lot of time tracking spacecraft. Without this managing, we would have lost quite a few satellites. Agencies sometimes fail to track all of them, resulting in collisions. One such example is when a French reconnaissance satellite smashed into Ariane rocket debris. You can see more collisions here.

  • $\begingroup$ Kessler syndrome isn't just debris hitting a satellite, it's the cascading effect when one satellite gets hit and the debris produced hits two satellites, etc. $\endgroup$
    – djr
    Mar 5, 2018 at 22:37
  • $\begingroup$ As I understand it unfortunately there is a range of debris sizes that is big enough to do major damage, but not big enough to effectively track. $\endgroup$ May 20, 2019 at 17:51

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