New Delhi: Indian astronaut Shubhanshu Shukla and three other crew members of the Axiom-4 mission boarded the Dragon Grace spacecraft on Monday, preparing to return to Earth after an 18-day stay aboard the International Space Station (ISS).

The crew Shukla, mission pilot; commander Peggy Whitson; and mission specialists Slawosz Uznanski-Wisniewski of Poland and Tibor Kapu of Hungary entered the capsule and suited up for their 22.5-hour journey home.

The hatch connecting Dragon Grace to the ISS was sealed at 2.37 pm IST, and the crew began final checks ahead of undocking, which was scheduled for 4.35 pm IST. NASA streamed the undocking procedures live from the space station.

The return of Dragon Grace is fully automated. After separation, the spacecraft will carry out a series of engine burns to distance itself from the ISS and begin re-entry.

In preparation for atmospheric entry, the capsule will jettison its trunk section and orient its heat shield, designed to withstand temperatures up to 1,600°C.

During descent, parachutes will deploy in two stages: stabilising chutes at around 5.7 km altitude, followed by the main parachutes at approximately 2 km above sea level.

Splashdown is expected off the California coast at 3.01 pm IST on Tuesday, roughly 22.5 hours after undocking. A recovery team aboard a specialised vessel will retrieve the spacecraft from the Pacific.

The Axiom-4 mission had lifted off on June 25, with the Dragon capsule launched atop a Falcon 9 rocket from Florida’s Kennedy Space Center, marking yet another milestone in commercial spaceflight.