Four astronauts, part of the NASA-SpaceX Crew-2 mission, have safely returned to Earth after setting a record for the longest spaceflight by a US crewed spacecraft.

The international crew -- NASA astronauts Shane Kimbrough and Megan McArthur, Japan Aerospace Exploration Agency astronaut Akihiko Hoshide, and European Space Agency astronaut Thomas Pesquet returned to Earth in a parachute-assisted splashdown at 10.33 p.m. EST Monday (9.03 a.m. on Tuesday) off the coast of Pensacola, Florida.

SpaceX-NASA crew-1 astronauts return safely from space station
SpaceX-NASA crew-1 astronauts return safely from space stationIANS

The astronauts spent 199 days in orbit

"NASA's SpaceX Crew-2 astronauts have safely splashed down in the Gulf of Mexico off the coast of Florida aboard the Crew Dragon Endeavour spacecraft," NASA said in a statement.

The astronauts spent 199 days in orbit, surpassing the 168 days set by NASA's SpaceX Crew-1 mission earlier this year.

"We're happy to have Shane, Megan, Aki, and Thomas safely back on Earth after another successful, record-setting long-duration mission to the International Space Station," said NASA administrator Bill Nelson, in the statement.

"Congratulations to the teams at NASA and SpaceX who worked so hard to ensure their successful splashdown. NASA's Commercial Crew Programme continues to demonstrate safe, reliable transportation to conduct important science and maintenance on the space station," he added.

The Crew-2 mission launched April 23 on a Falcon 9 rocket from NASA's Kennedy Space Center in Florida. Crew Dragon Endeavour docked to the Harmony module's forward port of the space station on April 24, nearly 24-hours after liftoff.

Kimbrough, McArthur, Hoshide, and Pesquet travelled 84,653,119 statute miles during their mission, stayed 198 days aboard the space station, and completed 3,194 orbits around Earth.

spaceX starship representational
spaceX starship representational

What did they study?

Throughout their mission, the Crew-2 astronauts contributed to a host of science and maintenance activities, scientific investigations, and technology demonstrations. In addition, they conducted four spacewalks and multiple public engagement events while aboard the orbiting laboratory.

They studied how gaseous flames behave in microgravity, grew hatch green chiles in the station's Plant Habitat Facility, installed free-flying robotic assistants, and even donned virtual reality goggles to test new methods of exercising in space, among many other scientific activities.

The astronauts took hundreds of pictures of Earth as part of the Crew Earth Observation investigation, one of the longest-running investigations aboard the space station, which contributes to tracking of natural disasters and changes to our home planet.

On July 21, all four Crew-2 astronauts boarded Endeavour for a port relocation manoeuvre, moving their spacecraft from the forward-facing port to the space-facing port on the station's Harmony module.

The return of Crew-2 comes just before the launch of NASA's SpaceX Crew-3 mission, currently scheduled for no earlier than November 10, on another long-duration mission of approximately six months.

The next NASA and SpaceX crew rotation mission Crew-4 is currently targeted for launch in April 2022.