ISS astronauts splash down off Florida on SpaceX craft

The crew reported they were feeling well after their arrival back on Earth following a nearly six-month mission aboard the International Space Station, NASA said.

A SpaceX Crew Dragon capsule carrying four astronauts back to Earth splashed down off Florida early Sunday, a NASA livestream showed.

Support teams work around the SpaceX Crew Dragon Resilience spacecraft shortly after it landed with NASA astronauts. (AP)

The crew reported they were feeling well after their arrival back on Earth following a nearly six-month mission aboard the International Space Station, NASA said.

The capsule splashed down at 2:56 am (0656 GMT) in the dark in the Gulf of Mexico off Panama City after a six-and-a-half hour flight from the ISS, night-vision images relayed by NASA's WB-57 high-altitude research aircraft showed.

Teams aboard the Go Navigator recovery ship retrieved the capsule and hoisted it on to the deck about half an hour later. It was the first nighttime splashdown for NASA since the crew of Apollo 8 arrived in the Pacific Ocean on December 27, 1968.

Commander Michael Hopkins was the first to emerge after the hatch was opened, doing a little jig as he set foot on deck, followed shortly after by fellow NASA astronaut Victor Glover.

"On behalf of Crew-1 and our families, we just want to say thank you ... It's amazing what can be accomplished when people come together. Y'all are changing the world. Congratulations. It's great to be back," Hopkins said in a NASA tweet.

The four went to space last November as the crew on the first fully operational mission to the ISS aboard a vehicle made by Elon Musk's SpaceX, which has become NASA's favored commercial transportation partner.

The four crew will now be taken out of the spacecraft and receive medical checks before being flown by helicopter to Pensacola to board a plane for Houston to be reunited with their friends and family, NASA said.

Seven astronauts remained on the ISS including a new crew of four who arrived on a different SpaceX craft last week.

"Thanks for your hospitality," Hopkins said earlier as the capsule undocked from the space station for its return journey. "We'll see you back on Earth."

Prior to that, two American astronauts made a test mission to the ISS in May and stayed for two months.

That was the first launch to the ISS from US soil since the end of the Space Shuttle program in 2011. It was also the first crewed mission run by a private company, as opposed to NASA.

Until then US astronauts had caught rides to the ISS aboard Russian spacecraft.