The comment:

In a similar vein, it would be interesting to know if going around the moon rather than to the ISS removes any legal hurdles. Do we have any questions covering the legal ramifications (if any) of breaching the ISS's Keep Out Sphere for instance?

under the question Does SpaceX have any significant additional legal hurdles for flying private citizens around the moon? has inspired me to ask What is the "ISS's Keep Out Sphere" and what is its radius?

I have found some references in this blog but I am not sure I understand it completely.


1 Answer 1


NASA has made a list of requirements for spacecraft approaching the ISS.

SSP 50808 is an ITAR controlled document that identifies the requirements for rendezvous, proximity operations, and physically meeting the ISS interface.

An excerpt is available online:

  • Trajectories must be designed such that ISS safety is preserved ...
  • Safe trajectories must be defined for each region near the ISS
  • Baselined regions defined in concept documents:
  • Approach Ellipsoid (AE): 4x2x2 km (SSP 50011)
  • Keep out Sphere (KOS): 200 m radius (SSP 50011)
  • Omni directional communications disk: 3x1½ km (SSP 50235)

Safety regions around the ISS

Spacecraft approaching the ISS must comply with requirements set in SSP 50808 before they're allowed into a safety region, each region has its own requirements.

  • $\begingroup$ Note that because SSP 50808 is ITAR-controlled, specific details of the operations cannot be discussed in a public forum. $\endgroup$ Commented Mar 25, 2017 at 20:14
  • $\begingroup$ The link to the excerpt seems to be broken. This comment says that there is another copy here: dokumen.tips/documents/… $\endgroup$
    – uhoh
    Commented Jul 8, 2020 at 13:26

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