NASA delays return of Starliner astronauts from space station

June 14 (UPI) -- Starliner's return to Earth is now delayed to June 22 or later, NASA announced Friday.

NASA astronauts Butch Wilmore and Suni Williams, who embarked on the long-awaited Boeing Starliner mission June 5 and docked at the International Space Station the following day, will have to spend a little more time in orbit than originally planned.

Both astronauts were originally set to complete a full assessment of the Starliner on board the ISS in just under a week, but the mission was lengthened due to a need to collect more information about the spacecraft.

"We are continuing to understand the capabilities of Starliner to prepare for the long-term goal of having it perform a six-month docked mission at the space station," NASA Commercial Crew Program Manager Steve Stich said in a blog post.

This is the second delay in Starliner's return to Earth, following an announcement this week that the spacecraft would disembark from the ISS on June 18.

The return mission originally was pushed forward to give ISS astronauts more time to perform a space walk originally planned for Thursday 13, but that mission was scrubbed an hour before it started because of what astronauts said was "spacesuit discomfort."

In the meantime, Wilmore and Williams will perform tests of the spacecraft's aft thrusters and review its hatch operations. They also will perform "safe haven" drills to prepare the capsule for an emergency situation.

The crew also will work to better understand some of the anomalies Starliner experienced on its journey into low-Earth orbit, including a helium leak that led to a May 6 launch scrub.

Since then, four other helium leaks have been discovered, as well as a valve in the capsule's service module that was not properly closed.

Since arriving at the ISS, Wilmore and Williams have contributed to the station upkeep and assisted with space walks and scientific research.

NASA and Boeing officials will provide more information on the Starliner mission's progress during a press briefing at noon EDT Tuesday.

The primary and backup landing sites for the capsule's return in the southwestern United States are yet to be determined.