NASA – the US National Aeronautics and Space Administration – and Boeing aim to launch the first crewed Starliner mission to the International Space Station (ISS) this Saturday, starting at 5:25 pm (Lisbon time). If the first crewed flight of the Boeing Starliner spacecraft, part of the agency's Commercial Crew Program, does not depart on that date, other launch opportunities will be available on Sunday, June 2, Wednesday, June 5, and Thursday, June 6.

After a series of postponements, the CTF (short for Crewed Test Flight) mission was able to see the “green light” on Saturday: the vehicle, with the capsule already attached, was transported to the launch pad last Thursday. This was the second time the Starliner-Atlas V constellation had traveled this route in less than a month. The first was on May 4, before the launch two days later. But this attempt was foiled about two hours before liftoff, when team members noticed bad behavior in the valve in the rocket's upper stage.

ULA decided to replace the valve, which required returning the vehicle to a nearby assembly facility, a process that delayed the launch until May 17. The date was changed again, after a small helium leak was discovered in one of the reaction control engines in the Starliner service module.

You can follow the launch live here.

The Starliner will dock at the front door of the station's Harmony Unit at approximately 6:50pm on Sunday.

During a flight test readiness review last Wednesday at NASA's Kennedy Space Center in Florida, NASA, Boeing and United Launch Alliance (ULA) leaders confirmed launch readiness, including all systems, facilities and teams supporting the test flight.

The flight test will take NASA astronauts Butch Wilmore and Sonny Williams to the International Space Station. The duo are the first to be launched aboard a Boeing Starliner to the space station as part of the agency's Commercial Crew Program, where the astronauts will spend about a week in the orbiting laboratory before returning to Earth, according to NASA. The Starliner spacecraft is reusable and has the capacity to carry seven people, but the crewed missions NASA has ordered from Boeing expect four or five astronauts.