In wooded seclusion, holed up in a former hotel near Thomas Jefferson's old stomping grounds, some of the top federal executives are locked in debate over whether to tell the president there may be intelligent life in outer space.

The scenario being discussed at the Federal Executive Institute (FEI) is make-believe. But the exercise is meant to be a real test of the participants' abilities to reason, persuade, balance options and assemble new and rapidly changing information, all important skills for career government executives accustomed to grappling with more earthly concerns.

Since opening its classrooms in late 1968, FEI has served as a kind of bureaucratic "think tank" for more than 5,000 civil servants, all drawn from the ranks of managerial employes who are GS15s or higher. They come, 500 to 600 a year for three to seven weeks, for a crash course in management and the chance to "get away from it all" while exploring a wide range of government issues.

"When the train's been running for so long, you need to take it off the track and take a look at it," said Gene Lucero, a regional official of the Environmental Protection Agency and one of 65 executives in a recent three-week program.

But those days of academic and social reflection may be numbered. From Washington comes the news that the Office of Personnel Management, which runs FEI, may shut down the facility by 1983 to accommodate President Reagan's budget cuts. Although the final word on FEI's fate isn't expected until January, the institute's biggest boosters are pessimistic and see the threatened closure as the latest slap at career executives.

"Management is too important to leave it to chance," argues Robert Matson, FEI's acting director. "Government needs to be concerned about the health and vitality of its executive corps--it's the biggest corporation in the world."

Matson said FEI alumni "are our best support system, and there's been a lot of phone calling and stirrings over this. But when the defense budget is being cut and food stamps are being cut, it's hard to argue that we're that vital."

FEI's $2.5 million-a-year budget is actually a revolving fund, reimbursed by agencies that reserve places at a room-board-tuition rate of $840 to $980 a week, depending on the stay. So the question of its continued operation has less to do with appropriations than with personnel ceilings and whether the federal government ought to have its own career development facilities when private institutions--Harvard, Stanford and the Brookings Institution, for example--operate somewhat similar programs.

OPM also operates three training centers for GS13s through GS15s, which are not threatened at this time.

Those who have gone through FEI say it is not the usual academic graduate school. It is, instead, a place where they can learn from their peers and recharge batteries drained by seemingly non-stop criticism and a four-year-long pay cap. They look upon attending the institute as reward for a job well done, as well as a nice addition to their resumes.

"So many of us are point people that it's easy to get depressed; it's nice to come here and meet a lot of able, dedicated people," said Lucero. At 34, he's one of the youngest in an FEI class that includes representatives from virtually every department, as well as the Central Intelligence Agency.

For instance, William Lindahl, director of manpower analysis in the secretary of the Navy's office, and Eugene Haberman, chief of propulsion analysis at Edwards Air Force Base in California, swapped views on the respective problems of headquarters vs. field operations.

"It's a change of pace that allows you to relax and be somewhat introspective," said Lindahl, 35. "I didn't even know about some of the agencies represented here." Gene Hassell, 50, a top official with the Forest Service in Albuquerque, N.M., especially enjoyed the seminar on relations with Latin America. "You know, out in the trees you don't get a real chance to get in touch with other ideas and people."

Guy Rankin, 41, director of administration for the Federal Labor Relations Authority and a candidate for the Senior Executive Service, only went to work for the federal government in January. FEI is giving him exposure to government organization and contacts.

And Carolyn Lieberman, 35, assistant general counsel for litigation at the Housing and Urban Development Department, said she picked the FEI program because "it had a good reputation, and I was looking for a course that would teach me how to do a better job of running meetings."

Since so many future government executives climb the career ladder as specialists rather than generalists, FEI supporters argue the institute helps these specialists-turned-managers gain the skills they need to assume their new jobs.

Most of the time, the executive "students" are in the classroom, attending seminars and workshops on economics, strategic planning, foreign policy, stress management and organizational change. Their FEI day begins at 7:30 a.m. in the dining room for breakfast and ends at 9 p.m. when evening classes adjourn for homework.

Participants also undergo some simple psychological tests to help them gain insight into their personalities and are even encouraged to set aside two hours after lunch each day for physical fitness.

Associate director Patrick Conklin said the idea behind FEI is to help executives "get information about themselves--how do you get 'closure' after endless meetings, how do you reach decisions or keep people from coming to a decision too soon? "

Sal Culosi, acting director for logistics, program, budget and analysis at the Department of Defense, learned, for example, that "I'm a little bit impetuous after I've received all the information. Sometimes you have to nurture a solution, baby it and do a better job of presenting it."