WASHINGTON - NASA is set to launch four astronauts to the International Space Station on Friday, replacing a crew that was evacuated early due to a medical issue.
The US space agency is targeting February 13 for the lift-off of Crew-12's mission aboard a SpaceX Falcon 9 rocket, with a window opening at 5.15am local time.
The pre-dawn launch was delayed by two days over adverse weather forecasts across the US East Coast, including high winds that could have complicated any potential emergency manoeuvres.
If Friday morning's launch goes as planned, the astronauts should arrive at the orbiting ISS by approximately 3:15 pm on Saturday.
Crew-12 is composed of Americans Jessica Meir and Jack Hathaway, along with French astronaut Sophie Adenot and Russian cosmonaut Andrey Fedyaev.
They have been in quarantine at NASA's Kennedy Space Center in Florida as they await blast-off.
The travellers will replace Crew-11, which returned to Earth in January a month earlier than planned in the first medical evacuation in the space station's history.
The ISS, a scientific laboratory orbiting 400 kilometres above Earth, has since been staffed by a skeleton crew of three.
NASA declined to disclose any details about the health issue that cut the mission short.
Once the astronauts finally arrive, they will be one of the last crews to live aboard the football field-sized space station.
Continuously inhabited for the last quarter century, the ageing ISS is scheduled to be pushed into Earth's orbit before crashing into an isolated spot in the Pacific Ocean in 2030.