CAPE CANAVERAL, Fla. (AP) — A NASA astronaut said Tuesday that he pulled out of a spacewalk this week because of a pinched nerve in his neck.

NASA canceled Tuesday’s spacewalk at the International Space Station less than 24 hours in advance, citing “a minor medical issue” with Mark Vande Hei but didn’t elaborate.

The retired Army colonel, who’s 54, is one-third of the way through an anticipated yearlong mission. He said he’s grateful for all the concern and tweeted: “Today just wasn’t the right day” for a spacewalk.

NASA said it will reschedule Vande Hei’s excursion — which will be conducted alongside Japanese astronaut Akihiko Hoshide — after an upcoming SpaceX cargo delivery and pair of Russian spacewalks. There is no urgency attached to their outdoor work, which involves installing a bracket for new solar panels due to arrive next year.

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