"We look forward to gathering applications and then being able to select from the largest pool possible," said Ellen Ochoa, NASA's chief of flight crew operations at the Johnson Space Center in Houston. "Continuing our impressive record in successfully carrying out challenging human spaceflight missions depends on maintaining a talented and diverse astronaut corps."

Applicants must hold a bachelor's degree in engineering, science or mathematics and have three years of relevant professional experience. Typically, NASA said, successful applicants have significant qualifications in engineering or science, or extensive experience flying high-performance jet aircraft.

Teaching experience, including work at the kindergarten through 12th grade levels, is also considered qualifying. Educators with the appropriate background are encouraged to apply, officials said.

After six-months of evaluation and interviews, NASA will announce final selections in early 2009. Candidates will report for basic training during the summer of 2009.

NASA will accept applications through July 1, 2008. To apply visit http://www.usajobs.gov or contact NASA's Astronaut Selection Office at 281-483-5907. More information is available at http://www.nasa.gov/astronauts/recruit.html.