WASHINGTON — A Soyuz rocket successfully launched a new crew to the International Space Station April 9 on a mission that overcame complications from a global pandemic and a change in crew members.

A Soyuz-2.1a rocket lifted off from the Baikonur Cosmodrome in Kazakhstan at 4:05 a.m. Eastern and placed the Soyuz MS-16 spacecraft into orbit nine minutes later. The spacecraft, making a four-orbit approach to the ISS, is scheduled to dock with the ISS at approximately 10:15 a.m. Eastern.

On board the Soyuz spacecraft are Russian cosmonauts Anatoly Ivanishin and Ivan Vagner and American astronaut Chris Cassidy. They will remain on the station for six months as the Expedition 63 crew.

This Soyuz mission faced some unusual challenges. In February, Roscosmos announced it was replacing the two Russian cosmonauts who had been assigned to the mission, Nikolai Tikhonov and Andrei Babkin, with their backups, Ivanishin and Vagner. Both Russian and American officials would only say that a medical issue led to their replacement, although Russian media reported that Tikhonov suffered an injury in training.

NASA and Roscosmos downplayed the effect of the crew swap on the mission. In an interview in early March, Kirk Shireman, ISS program manager at NASA, said that Cassidy had been training with Ivanishin and Vagner for a time before the crew swap, and that the Russian cosmonauts had robotics and spacewalk training should a spacewalk be required during the mission.

“Of course, it was a surprise,” Ivanishin, speaking through an interpreter, said in a prelaunch interview broadcast on NASA TV. But, he added, “any backup crew is ready to become prime.”

A second issue is the ongoing coronavirus pandemic that has led to travel restrictions and stay-at-home orders in countries around the world. While Soyuz crews normally go into a quarantine a couple weeks before launch, there were additional restrictions before this launch, including reduced staffing at the launch site and a prohibition on guests.

“I knew I was going to be in quarantine these two weeks, but what’s really different is everybody else around us is in quarantine, too,” Cassidy said in a prelaunch interview on NASA TV. “It’ll be a really, really skeletal crew in the Baikonur Cosmodrome, which will be quite different.”

“No virus is stronger than the human desire to explore,” NASA Administrator Jim Bridenstine tweeted after the Soyuz spacecraft reached orbit. “I’m grateful to the entire NASA and Roscosmos teams for their dedication to making this launch a success.”

Cassidy, Ivanishin and Vagner will join the current ISS crew of NASA astronauts Jessica Meir and Andrew Morgan and Roscosmos cosmonaut Oleg Skripochka. Those three will return to Earth on the Soyuz MS-15 spacecraft April 17.

Two NASA astronauts are scheduled to fly to the station later this spring on the SpaceX Crew Dragon Demo-2 test flight. Bob Behnken and Doug Hurley could remain on the station until as late as August in order to provide additional crew time for maintenance and science work.

Cassidy is, for now, the last NASA astronaut planned to fly on a Soyuz spacecraft. NASA officials have previously discussed buying one or more additional Soyuz seats as a hedge against further commercial crew delays, but have yet to announce a deal.

NASA has also proposed swapping seats between Soyuz and commercial crew vehicles on a no-cost basis, with Russian cosmonauts flying on Crew Dragon and Boeing’s CST-100 Starliner in exchange for astronauts flying on Soyuz missions. Such “mixed crew” missions would ensure there is at least one American and one Russian crew member on the station even if either the Soyuz or commercial crew vehicles are unavailable.

Roscosmos officials, though, told their NASA counterparts at a joint meeting in December that they would not assign cosmonauts to commercial crew missions until those vehicles are flight proven. The four-person crew for the first operational Crew Dragon mission, announced by NASA March 31, features three NASA astronauts and one from the Japanese space agency JAXA.