New Delhi, 13 July

After 18 days of intense science experiments at the International Space Station, it is time for farewells and feasts for Shubhanshu Shukla and three other astronauts of the Axiom-4 mission who are set to begin their return journey to Earth on Monday.

The Axiom 4 (Ax-4) crew — Commander Peggy Whitson, Pilot Shubhanshu "Shux" Shukla, and Mission Specialists Slawosz "Suave" Uznanski-Wisniewski and Tibor Kapu — are nearing the completion of their research and preparing to undock.

"Arrival back to earth.... splash down scheduled for 15 July at 3pm IST," Science and Technology Minister Jitendra Singh said on X.

As the Axiom-4 mission drew to a close, astronauts on board the ISS gathered for a feast with a diverse menu from the six nations they represent.

Currently, there are 11 astronauts on the ISS, seven of Expedition 73 and four of the Axiom-4 commercial mission.

"One of the most unforgettable evenings I've experienced on this mission was sharing a meal with new friends, Ax-4, aboard the International @Space_Station," US astronaut Jonny Kim said on X last week.

"We swapped stories and marvelled at how people from diverse backgrounds and nations came together to represent humanity in space," he said.

For appetisers, the astronauts made rehydrated shrimp cocktails and crackers and the main course featured savoury chicken and beef fajitas. The cosmonauts capped the night with a delicious cake made from sweet bread, condensed milk, and walnuts, Kim said.

Shukla had got aam ras and carrot halwa for the feast, while Polish astronaut Slawosz had brought his native dish, pierogi with cabbage and mushrooms, to the ISS.

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 Rakesh Sharma's pathbreaking spaceflight as part of the then Soviet Russia's mission to Salyut-7 space station in 1984.

So far, Shukla has spent 18 days in space, witnessing 16 sunrises and sunsets every day as the ISS travels at a speed of 28,000 km per hour in an orbit about 400 km above the Earth.

According to ISRO, post splashdown, Shukla will undergo a rehabilitation programme (about 7 days) under the supervision of a flight surgeon to adapt back to Earth's gravity.

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.

Shukla and the three other astronauts are expected to board the spacecraft at 2.25 pm IST, wear their space suits and carry out the necessary tests before they begin their journey to the Earth.

The ISS is orbiting the Earth at a speed of 28,000km per hour, and the Dragon spacecraft will initiate the autonomous undocking process to gradually slow down and re-enter the planet's atmosphere for a splashdown off the coast of California.

"The Dragon spacecraft will return with more than 580 pounds of cargo, including NASA hardware and data from over 60 experiments conducted throughout the mission," NASA said.

During his stay at the ISS, Shukla worked on the microalgae experiment, deploying and stowing samples that could one day provide food, oxygen and biofuels for deep-space missions, Axiom Space said in a statement.

The crew also continued the Voyager Displays study, which examines how spaceflight affects eye movement and coordination.

The crew collected data for a study to explore how astronauts perceive and interact with their environment in orbit, which is critical for designing mentally supportive habitats for long-duration missions.

Another study focused on cerebral blood flow, investigating how microgravity and elevated carbon dioxide levels affect cardiovascular function, which could later benefit both astronauts and patients on Earth.

Radiation exposure was monitored using the compact Rad Nano Dosimeter, a tool to assess astronaut safety.