On the eve of his 70th birthday, Don Pettit, NASA’s oldest active-duty astronaut, and two cosmonaut crewmates undocked from the International Space Station Saturday and geared up for a fiery overnight plunge back to Earth to close out a 220-day expedition.
Pettit, Soyuz MS-26/72S commander Alexey Ovchinin and flight engineer Ivan Vagner undocked from the Russian Rassvet docking port at 5:57 p.m. Eastern Time, setting up a parachute-assisted landing on the steppe of Kazakhstan near the town of Dzhezkazgan at 9:20 p.m. local time, or 6:20 a.m. Eastern Time Sunday, Pettit’s birthday.
NASA
Russian recovery crews and NASA personnel were deployed nearby to help the returning crew out of the Soyuz descent module with initial medical checks and satellite phone calls to family and friends as they begin their readjustment to gravity after seven months in weightlessness.
Assuming an on-time landing, mission duration will stand at 220 days and nearly nine hours, spanning 3,520 orbits and 93.3 million miles since launch last Sept. 11 from the Baikonur Cosmodrome in Kazakhstan.
At touchdown, Ovchinin will have logged 595 days in space over four flights, followed closely by Pettit, whose total will stand at 590 days over four flights of his own. Vagner’s total will be 416 days aloft during two space station visits.
The world record for most cumulative time in space is held by cosmonaut Oleg Kononenko, who spent nearly 1,111 days in orbit over five missions. The U.S. record is held by astronaut Peggy Whitson. She spent 675 days in space over four flights.
NASA 
As for Pettit’s age, John Glenn, the first American in orbit, was 77 when he flew aboard the space shuttle in 1998 as a NASA spaceflight participant. He holds the record as the oldest person to fly in orbit.
From Kazakhstan, Ovchinin and Vagner will head back to Star City near Moscow while Pettit will be flown to the Johnson Space Center in Houston for more detailed tests and begin his physical rehabilitation.
The trio’s return to Earth marked the final chapter in an extended crew rotation that began with launch of SpaceX Crew 10 commander Anne McClain, Nichole Ayers, Japanese astronaut Takuya Onishi and cosmonaut Kirill Peskov on March 14.
Crew 10’s arrival at the station cleared the way for Crew 9 commander Nick Hague, cosmonaut Alexander Gorbunov, Starliner commander Barry “Butch” Wilmore and pilot Sunita Williams to return to Earth four days later.
The Russians then launched replacements for Pettit’s crew — Soyuz commander Sergey Ryzhikov, Alexey Zubritsky and NASA’s Jonny Kim — on April 8, clearing the way for Ovchinin, Vagner and Pettit to return to Earth Saturday.
NASA 
In a brief ceremony Friday, Ovchinin turned command of the station over to Onishi.
“It’s a great honor for me to accept the command of the ISS,” Onishi said. “I feel so special that I am taking over the command from you because it’s been almost nine years since we met here in 2016 during Expedition 48. At that time, both of us were rookies and here we are two veterans who are ISS commanders.”
“Human space flight is not easy. Only continuous dedication from generation to generation made it possible for human beings to get here. Now today, we have four rookies (on board). I’m sure one day they will come back and become commanders … that’s how we will continue to develop human space flight,” Onishi said.
The ISS has been continuously staffed by rotating crews since Nov. 2, 2000. Scheduled for retirement in five years, the lab is facing problems on multiple fronts, ranging from air leaks in the Russian segment to uncertain funding, spare parts shortages and resupply delays.
“Spaceflight is difficult and very risky,” Rich Williams, a member of NASA’s independent Aerospace Safety Advisory Panel, told the group in a public meeting Thursday. “The ISS has entered the riskiest period of its existence.”
“The ISS management, crew and support personnel always make spaceflight look easy. Spaceflight is anything but easy, and the increasing risks attending the ISS program are making it harder,” Williams said.
The air leaks in the Zvezda module’s aft docking compartment are presumably the results of metal fatigue and repeated pressure cycles as visiting Soyuz crew ships and Progress cargo freighters come and go.
NASA 
“Primary risk mitigation activities at this point include application and patching materials to known cracks and limiting … pressurization cycles to try to limit stress and fatigue,” Williams said. “The ISS program is monitoring this closely, and the panel considers this one of our highest concerns.”
NASA has hired SpaceX to build a U.S. deorbit vehicle, or USDV, to drive the million-pound space station back into the atmosphere in 2030 to ensure it breaks up over the southern Pacific Ocean, far from shipping lanes and populated areas. The USDV is expected to arrive at the lab in 2029.
“Delivering and utilizing this USDV capability is critical to ensuring that the deorbit debris risk meets the established government public safety standards,” Williams said. “If there is a deorbit of the ISS before the USDV is delivered, the risk to the public from ISS breakup debris will increase by orders of magnitude.”
He said NASA and Russian space officials are working “to address the challenges associated with achieving a safe deorbit capability, both for end-of-life as well as a risk-managed deorbit for contingencies.”
The major problem facing the ISS is what Williams called “a large ISS budget shortfall.” NASA’s fiscal 2024 budget included nearly $1 billion for station operations and maintenance with another $1.6 billion earmarked for crew launches and resupply missions.
“It is critical to maintain adequate budget and resources until the vehicle has safely re-entered, not only to assure safety of day-to-day operations in a high-risk environment, but also to ensure controlled, safe deorbit within debris footprint requirements for the sake of public safety,” Williams said.
In summary, he said, “the panel appreciates the demonstrated operational excellence of the ISS program, but remains deeply concerned about the increasing and cascading risks attending the program over the next several years.”