President Bush's choice for NASA administrator is Sean O'Keefe, the deputy director of the agency that oversees the budget, the Office of Management and Budget. He will replace Daniel Goldin, who recently announced that he would step down later this month after nearly 10 years at NASA's helm.

Mr. O'Keefe, a former civilian head of the U.S. Navy, will take over an agency whose biggest program, the space station, is under intense scrutiny because of steep, unanticipated cost increases.

NASA revealed earlier this year that the project was $4 billion over budget, an expense the Bush administration is requiring it to absorb from other programs instead of providing extra funding. As a result, NASA cannot afford to build a crew dormitory and emergency escape vehicle for seven astronauts that would allow the outpost to expand from its present three crewmembers. NASA has been talking with station partners Russia and Italy about whether they can supply comparable equipment.

Space policy expert John Logsdon of George Washington University says Mr. O'Keefe's appointment is a message to NASA. "O'Keefe is, I think, being sent to NASA to put cost and management discipline into the program," he says. "I think it will be intriguing to see how someone coming from what is viewed by NASA as the enemy, that is, the Office of Management and Budget, establishes his bona fides [credibility] as a leader of the organization."

Earlier this month, an independent panel of experts said NASA would have to reduce the number of space shuttle flights to the station and cut other costs if it wanted to complete the outpost as the full time orbiting research laboratory with seven crewmembers it envisions.

In his budget office role, Mr. O'Keefe has estimated that station costs could nearly double to $30 billion by 2006 over its original estimate of $17 billion. He told the House of Representatives Science Committee last week that he was worried about the escalation. "From a technical, scientific, and engineering standpoint, this is a solid effort. From a cost standpoint, I'm doubtful," he says. "I'm not sure we've seen the end of this, and that's what scares me more than anything else."

Mr. O'Keefe called for major changes in the design and management of the space station and NASA's human spaceflight program.