Arizona Tribune - Boeing's Starliner faces one more challenge as it returns to Earth

The spaceship is scheduled to autonomously undock at 2:36 pm Eastern Time (1836 GMT) and touch down in New Mexico just over four hours later, at 2249 GMT, wrapping up a six-day mission crucial to restoring Boeing's reputation after past failures.

Orbital Flight Test-2 (OFT-2) is the last hurdle for Starliner to clear before it carries humans in another test flight that could take place by the end of this year.

Starliner rendezvoused with the ISS on Friday, a day after blasting off from the Kennedy Space Center in Florida.

Over the weekend, astronauts living aboard the research platform opened the hatch and "greeted" the capsule's sole passenger: Rosie the Rocketeer, a mannequin equipped with sensors to understand what human crew would have experienced in the journey.

The mission hasn't been without its hiccups. These include propulsion problems early on Starliner's journey that saw two thrusters responsible for placing it in a stable orbit failing, though officials insisted there was plenty of redundancy built into the system.

On the day of docking, the vessel missed its scheduled contact time by more than an hour, after a ring responsible for latching on to the station failed to deploy correctly. Engineers had to retract the ring then pop it out again before it worked the second time.

Still, the glitches are little compared to the troubles Starliner saw during its first test launch, back in 2019, when one software bug caused it to burn too much fuel to reach its destination, and another almost meant that the vehicle was destroyed during re-entry.

The second error was caught in time to upload a patch, and the vessel was able to achieve a gentle landing, slowed by its enormous parachutes, at White Sands Space Harbor -- the same spaceport where Space Shuttles once launched, and where Starliner is once more expected for touchdown.

Boeing and NASA also tried to launch Starliner in August 2021, but the capsule was rolled back from the launchpad to address sticky valves that weren't opening as they should and the ship was eventually sent back to the factory for fixes.

NASA is looking to certify Starliner as a second "taxi" service for its astronauts to the space station -- a role that Elon Musk's SpaceX has provided since succeeding in a test mission for its Dragon capsule in 2020.

A.O.Scott--AT