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.
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