Live coverage: Cygnus rendezvous and arrival journal and webcast

What began as a concept scribbled on a cocktail napkin in a Tucson bar 12 years ago — sending a spacecraft to an asteroid and retrieving a pristine sample to bring back to Earth for study — becomes reality Thursday with the launch of NASA’s OSIRIS-REx mission.

The launch of a Japanese H-2B rocket was called off Tuesday after a fire broke out on the launch pad a few hours before liftoff. A new target launch date has not been confirmed. The mission will carry an HTV cargo ship into orbit on a resupply run to the International Space Station.

An apparent exterior coolant leak from a Russian laboratory module at the International Space Station has been reported by the crew. It follows similar leaks that struck a Russian Soyuz crew ferry craft and a Progress cargo ship within the past year.