CAPE CANAVERAL, FLA., SEPT. 26 -- Sally K. Ride, America's first woman in space, today ended a 10-year NASA career that included two space shuttle flights and a role in the investigation of the Challenger disaster.

Ride, who is 36 and has a doctorate in physics, announced in May that she planned to return to her home state of California to work as an arms-control scholar at the independent Stanford University Center for International Security and Arms Control in Palo Alto.

Today was her last day on the payroll with the National Aeronautics and Space Administration, according to NASA spokesman Edward Campion in Washington.

One of NASA's most visible figures, Ride and five other women were accepted as astronauts in 1978. Her launch aboard the shuttle Challenger five years later formally opened up what had been a male fraternity of rocket pilots.

"When I was growing up, I didn't have the opportunity to have an astronaut as a role model," she told the National Press Club after her first flight in 1983. "It had honestly never occurred to me that I could be an astronaut.

"I think it's very important for . . . young women to profit by my experience and have a role model they can live up to."