At the Baikonur Cosmodrome in Kazakhstan, Expedition 63 crewmember Chris Cassidy of NASA suits up March 25, 2020, for pre-launch training activities. Cassidy and Anatoly Ivanishin and Ivan Vagner of Roscosmos will launch April 9 on the Soyuz MS-16 spacecraft from Baikonur for a six-and-a-half month mission on the International Space Station. Credit: Courtesy of Andrey Shelepin of the Gagarin Cosmonaut Training Center via NASA

A York High School graduate who served as the nation’s top astronaut is returning to outer space for the third time.

Astronaut Christopher Cassidy, 50, will join Russian cosmonauts Anatoly Ivanishin and Ivan Vagner aboard the Soyuz MS-16 at the Baikonur Cosmodrome Kazakhstan, where they will blast off Thursday morning for their journey to the International Space Station, according to NASA.

The spaceflight, scheduled for 4:05 a.m. Eastern Daylight Time, will be Cassidy’s third.

Cassidy, who was born in Salem, Massachusetts, considers York his hometown. He graduated from York High School, where he played basketball. In 2013, Cassidy told a crowd of middle schoolers at Husson University’s Gracie Theatre that he had dreamed when he was young not of joining NASA, but the NBA.

“I really feel I’m just another Maine guy who’s had some really cool experiences in life,” Cassidy said in 2013.

After graduating from York High School, Cassidy went on to study at the Naval Academy Preparatory School in Newport, Rhode Island, where he graduated with a bachelor’s degree in mathematics in 1989. He then moved on to the Massachusetts Institute of Technology, earning a master’s degree in ocean engineering in 2000.

Cassidy spent 11 years as a U.S. Navy SEAL, and he was deployed to Afghanistan two weeks after the Sept. 11 terrorist attacks. He became a captain in 2014 and remains on active duty, according to NASA.

His career as an astronaut began in 2004 after he met fellow Navy SEAL and astronaut Bill Shepherd, who was commander of the first space station crew, according to the BDN archive. Cassidy was one of 11 people selected to join NASA’s 19th class of astronauts.

Cassidy’s first spaceflight was in 2009, when he left Earth aboard the space shuttle Endeavour for a 16-day mission and became the 500th person to enter space, according to NASA. His next spaceflight came in 2013, when he spent 182 days aboard the International Space Station. During his astronaut career, Cassidy has logged six spacewalks for a total of 31 hours and 14 minutes in the vacuum of space.

In 2015, Cassidy was named the nation’s chief astronaut, succeeding Robert L. Behnken. Cassidy held that post until June 2017, when he was replaced by Patrick G. Forrester and returned to normal flight status.

Cassidy has compared being an astronaut to the legacy of those explorers who have pushed “the frontiers of where humans are.” That will one day include, he said in 2013, living on Mars.

“[Space exploration] is essential to the growth of mankind and I honestly believe that eventually — maybe it won’t be in my kids’ lifetimes and it might not even be in my grandkids’ lifetimes — there will be people living on Mars and probably on the moon and, right now, we are setting the groundwork for that to happen,” Cassidy told students gathered at Husson in 2013.

Ahead of Thursday’s launch, Cassidy has been living in quarantine in Kazakhstan because of the coronavirus pandemic. Cassidy told the Associated Press last month that he won’t have any guests accompany him to the launch and his wife returned to the U.S. three weeks sooner than planned.

When he arrives at the International Space Station on Thursday, Cassidy won’t be the only Maine native aboard. He will join Caribou native Jessica Meir, who has been at the space station since Sept. 25, 2019, when she became the first Maine woman to fly into space.

But there will be two Maine natives in space only briefly. Meir is scheduled to return to Earth after completing her mission on April 16.