The space shuttle commander who led the final mission to fix the Hubble Space Telescope is leaving NASA, as is a two-time spacewalker, the space agency announced Tuesday.

Veteran shuttle commander Scott Altman and astronaut Linda Godwin, both of whom flew on four shuttle missions, are leaving to pursue other interests, NASA officials said. Godwin will retire and Altman will take a job in the private sector. [Photos of Altman and Godwin.]

They are the latest astronauts to announce their departure from NASA as the agency's shuttle program nears its end. NASA plans to fly two final shuttle missions to complete the International Space Station. Those missions are scheduled for November and February, though the possible addition of a third shuttle flight for the summer of 2011 is under discussion in Congress.

Once NASA's shuttle fleet retires, the space agency plans to rely on Russian, Japanese and European spacecraft to fly astronauts and supplies to the space station until U.S. commercial spacecraft become available.

With the departures, NASA's pool of astronauts stands at about 85, with nine more set to join them in a year.

Long spaceflight careers

Altman, 51, is a retired Navy captain who joined NASA in 1995. He logged more than 51 days in space. He served as shuttle pilot for two missions, STS-90 in 1998 and STS-106 in 2000, and he commanded the final two missions to the Hubble Space Telescope, STS-109 in 2002 and STS-125 in 2009.

Altman graduated from the Navy Test Pilot School and logged more than 5,000 hours in more than 40 different types of aircraft.

"Scott has been a tremendous contribution to the astronaut corps and this agency," NASA chief astronaut Peggy Whitson said in a statement. "In his 15 years with NASA, he has performed flawlessly and demonstrated leadership in every position he's served. He will be greatly missed."

Godwin, 58, joined NASA in 1980 and became an astronaut in July 1986. Her four shuttle missions took place from 1991 to 2001. She served as payload commander of Endeavour's mission in 1994.

She logged more than 38 days in space and went on two spacewalks, totaling more than 10 hours.

Godwin, who holds a Ph.D. in physics, also supported numerous technical assignments within NASA's Astronaut Office.

"Linda's 30-year career at NASA was filled with contributions to the human spaceflight mission," said astronaut Brent Jett, director of flight crew operations at NASA's Johnson Space Center in Houston. "She should be proud of her service to the agency and the country."

New astronauts waiting in the wings

Last summer, NASA selected nine more Americans for its rigorous, two-year astronaut training program, from a pool of more than 3,500 applicants. The agency also accepted five international candidates — two Canadians and three Japanese — to round out what it calls the astronaut class of 2009, based on the year of their acceptance. This class is the 20th in NASA history and the first since 2004.

The 14 trainees are getting scientific and technical briefings in a number of fields, including robotics, according to NASA officials. They are learning how the International Space Station works, as well as how to perform spacewalks and fly T-38 Talon supersonic jets, with which astronauts have trained since the 1960s.

The new class is also getting intense physiological training, including instruction in water and wilderness survival, NASA officials have said.