Astronaut Chris Cassidy lost grip of the mirror on his way for a spacewalk from the International Space Station, and to work on batteries.
According to the U.S. spaceflightnow.com outlet, Cassidy, while coming out of the airlock to begin works on the ISS outer surface, reported that the small mirror had somehow come off the sleeve of his spacesuit and floated into space at a speed of about a mile per hour.
The lost item did not pose any risk to the spacewalk or the ISS. Cassidy inspected his spacesuit sleeve later in sunlight but didn't see any clues that might explain how the mirror came off.
Their spacewalk is expected to last up to seven hours, and they'll go for round two - which will also be broadcast live - on Wednesday.
Once these six new lithium-ion batteries have completed installation, the orbiting lab must be good for the remaining time of its operation life, NASA said in the report.
There are more batteries that Benhken and Cassidy will plugin before the job is done.
The battery replacements began in 2017, with previous crews putting in 18 lithium-ion batteries, half as many as the old ones replaced.
Throughout July, before Benkhen travels back to Earth in August, the spacewalks will continue.
This was the seventh spacewalk for both men. The space walk lasted 6 hours and 7 minutes.
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