The nation's space agency will be led for the first time by "a hero of its own making," President Bush said in announcing he will nominate astronaut Richard Truly as administrator of the National Aeronautics and Space Administration.

The nomination, which had been expected, must be confirmed by the Senate.Truly, 50, has been an astronaut since 1969, was pilot of the second shuttle flight in 1981 and commander of the eighth in 1983 and has been associate NASA administrator for space flight since 1986.

Truly succeeds James C. Fletcher, a former NASA administrator who resumed the position after the Challenger disaster in January 1986. Fletcher retired this month.

"This marks the first time in its distinguished history that NASA will be led by a hero of its own making, an astronaut who has been to space," Bush told members of Congress and others in the Roosevelt Room of the White House Wednesday.

Bush also announced that he plans to nominate James R. Thompson Jr., director of NASA's Marshall Space Flight Center in Huntsville, Ala., to succeed Dale D. Myers as deputy administrator.

Before his space flights, Truly was pilot for one of the two-man crews that conducted landing tests with the space shuttle Enterprise when it was hauled aloft on the back of a 747 jumbo jet.

After the Challenger disaster Jan. 28, 1986, Truly was in charge of the recovery team and of redesigning the shuttle's boosters and overhauling the shuttle safety program.