The ISS' SATCAT ID is 1998-067A. The CubeSats and other objects released from the space station are considered its sub-units, thus using different suffixes: 1998-067C, etc. The same principle applies to satellites which break up in orbit.

Apparently, the suffix might be up to 3 letters long, thus giving us 17576 sub-units per one launch.

What happens when that space gets exhausted? How are IDs assigned to the objects outside of that range?

  • $\begingroup$ 17576 units per launch is a factor 200 more than the current record, so there's room to play. Presumably when they run out of space, United States Space Command assigns a programmer to increase the field length by 1 character, and they're good up to 26^4 objects per launch. It's not that complicated. $\endgroup$
    – Hobbes
    Oct 6 '17 at 16:14
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    $\begingroup$ @Hobbes That wouldn't fit in a TLE though... (When are we going to finally abandon that ancient standard?) $\endgroup$
    – Mark
    Oct 6 '17 at 16:38
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    $\begingroup$ Seems like a good excuse to update TLE. That'll have to be done sometime before 2057 anyway, because TLE only reserves 2 digits for the launch year. $\endgroup$
    – Hobbes
    Oct 6 '17 at 17:01
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    $\begingroup$ Assuming 1U cubesats each take up 15x15x15cm of space in a deploy mechanism in a F9 fairing, that's over 30,000. So while it is certainly unlikely to ever happen, a larger fairing on a larger rocket might hold more than 17,576 3U's which are big enough to be potentially economically useful (e.g. Planet Labs). So the scenario is not absolutely impossible. However I'm not sure an authoritative answer can be formulated. $\endgroup$
    – uhoh
    Oct 7 '17 at 1:18
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    $\begingroup$ I'm more interested in what happens when the number of launches exceeds 1000, which in my mind is more likely to happen then the 3 letter code running out... $\endgroup$
    – PearsonArtPhoto
    Oct 7 '17 at 15:00

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