In this AP/WISN news item Air leak at International Space Station temporarily plugged by a thumb they show a file photo of German astronaut Alexander Gerst at the Baikonur cosmodrome, making what looks like a gesture with his two hands, possibly forming the letter "K".

Question: What does it mean? Are there many hand signals used on the ISS? Is there a standard reference for such?

Member of the International Space Station (ISS) expedition 56/57, German astronaut Alexander Gerst gestures as his space suit is tested in the Russian-leased Baikonur cosmodrome on June 6, 2018. SOURCE: Vyacheslav Oseledko/AFP/Getty Images

German astronaut Alexander Gerst

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    $\begingroup$ From another angle it might look like an A or triangle. Maybe, he's just in the middle of gesticulating $\endgroup$
    – Dragongeek
    Sep 3, 2018 at 0:34
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    $\begingroup$ @Dragongeek I'm thinking "K" for OK perhaps"? $\endgroup$
    – uhoh
    Sep 3, 2018 at 1:17
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    $\begingroup$ Well I can tell you what it's not: A common German gesture or American one. I don't think it's standard sign language either and all other photos I can find of Gerst gesturing are easy to identify and none are similar to this. Maybe it's K for Kosmonaut? $\endgroup$
    – Dragongeek
    Sep 3, 2018 at 22:26
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    $\begingroup$ I am unaware of any ISS specific sign language. I can think of some gestures that could be used, for example, when someone takes the last piece of fresh fruit from a shipment. $\endgroup$ Mar 11, 2019 at 12:21
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    $\begingroup$ There would be significant downsides to using two hands for any common signal gesture, so unless he happens to be signing, I suspect he's illustrating something. It looks to me like he's demonstrating a particular spatial attitude with his left hand with respect to two orthonormal reference axes indicated with his right hand, e.g., "so if this is our up and left, we're oriented like this..." $\endgroup$ Feb 22, 2021 at 5:26

1 Answer 1


K might be short for Klaar ("Clear" in German) but:

It's the wrong way round from his perspective;

It's unlikely that the crew he is working with knows German - they are more likely to communicate in English than in Russian, but both are more likely than his mother-tongue.

If we had this as a video clip, I believe we would see him make an O shape immediatly beforehand.

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    $\begingroup$ Is this answer based on anything other than speculation? $\endgroup$ Mar 11, 2019 at 17:04
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    $\begingroup$ "Clear" in German is "klar", but "OK" is much more commonly used in such a situation. But without a video of the context and the full gesture, this answer is just speculation. $\endgroup$
    – DK2AX
    May 20, 2019 at 11:35
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    $\begingroup$ Being the wrong way round from his perspective merely means he's signing to someone else. I've certainly worked in places where 'OK' was indicated by 'K' in chats etc. $\endgroup$
    – user21103
    Oct 25, 2020 at 13:10
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    $\begingroup$ The common signal for 'OK' is just a circle formed by thumb and index finger (i.e. the 'O' part) - originally used by divers but now virtually universal. I don't see why he would go out of his way to make a 'K' as well (or instead of). $\endgroup$
    – GordonD
    Jun 22, 2021 at 8:39
  • $\begingroup$ in the video he is sat at the back from the glass, at this point awaiting his leak-check. He is at great distance form the glass, and so can only communicate to family with hand signals. Clearly his mother is on the other side of the glass and perhaps his sister. Everyone else is either for the other crew or press. $\endgroup$ Jun 23, 2021 at 8:31

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