Shubhanshu Shukla's Axiom-4 mission to splash down off San Diego at 3:01 pm

New Delhi: Astronaut Shubhanshu Shukla and three others of the commercial Axiom-4 mission are on track to return to Earth with a splash down off San Diego in California on Tuesday, capping a 22.5-hour journey after an 18-day stay at the International Space Station.

The Dragon 'Grace' spacecraft carrying Shukla, commander Peggy Whitson, and mission specialists Slawosz Uznanski-Wisniewski of Poland and Tibor Kapu of Hungary, undocked from the space station at 4:45 pm IST on Monday.

"Dragon and the @Axiom_Space Ax-4 crew are on track to reenter Earth's atmosphere and splash down off the coast of San Diego at ~2:31 am PT tomorrow (3:01 pm IST, Tuesday)," SpaceX, the transporter for the Axiom-4 mission, said in a post on X.

It said the spacecraft will also announce its arrival with a brief sonic boom prior to splashing down in the Pacific Ocean.

The de-orbit burn is expected to take place at 2:07 pm IST over the Pacific Ocean as the spacecraft re-enters the Earth's atmosphere.

Final preparations include detaching the capsule's trunk (at 2:26 pm IST) and orienting the heat shield ahead of atmospheric entry, which will expose the spacecraft to temperatures nearing 1,600 degrees Celsius.

Parachutes will deploy in two stages -- first stabilising chutes at about 5.7 km altitude at 2:57 pm IST, followed by the main parachutes at roughly two km before splash down.

The spacecraft will be hauled up on a special recovery ship where the astronauts will be brought out from the capsule.

The Axiom-4 crew will undergo a series of medical checks on board the ship before boarding a helicopter for a ride back to the shore.

The four astronauts are expected to spend seven days in rehabilitation as they adjust back to life on Earth under the influence of gravity, unlike the weightlessness experienced in orbit.

After hugs and handshakes, the four astronauts entered the Dragon spacecraft on Monday, donned their spacesuits and closed the hatch connecting the spacecraft to the ISS at 2:37 pm IST.

"Jaldi hi dharti pe mulaqat karte hai (we will meet on Earth soon)," Shukla, who became the second Indian astronaut to travel to space after Rakesh Sharma's 1984 odyssey, said at the farewell ceremony onboard the ISS on Sunday.

The Axiom-4 mission marked the return to space for India, Poland and Hungary after over four decades.

On Sunday, Shukla recalled the time when his icon Rakesh Sharma had travelled to space 41 years ago and described how India looked from there.

"We all are still curious to know how India looks today from above. Aaj ka Bharat mahatvakanshi dikhta hai. Aaj ka Bharat nidar dikhta hai, Aaj ka Bharat confident dikhta hai. Aaj ka Bharat garv se purn dikhta hai. (Today's India looks full of ambition, fearless, confident and full of pride)," Shukla said.

"It is because of all these reasons, I can say it once again that today's India still looks 'saare jahan se accha'," he said.

"I didn't imagine all of this when I started on the Falcon-9 on June 25. I think it has been incredible because of the people involved. People standing behind me (the Expedition 73 crew) have made it really special for us. It was an incredible joy to be here and work alongside professionals like you," Shukla said.

It has been a historic trip for Shukla, who became the first Indian to travel to the ISS and only the second to travel to space after Sharma's pathbreaking spaceflight as part of the then Soviet Union's mission to Salyut-7 space station in 1984.

ISRO paid approximately Rs 550 crore for Shukla's travel to the ISS, an experience that will help the space agency in the planning and execution of its human spaceflight programme, Gaganyaan, set to take to orbit in 2027.