Top brass at the space agency will be called on the Senate carpet to explain why they have given special treatment to high-ranking military retirees who are allowed, by special exemption, to draw combined federal pay and military pension of up to $78,000 a year.

Sen. William Proxmire (D-Wis.), whose Senate subcommittee controls the budget of the National Aeronautics and Space Administration, and Sen. Adlai Stevenson (D-Ill.), who heads the subcommittee dealing with NASA spending authorizations, want to find out why and to what extent NASA has exempted retired admirals and generals on its payroll from the law limiting pensions of retired regular military officers who take federal jobs.

On Feb. 8 and 9, this column reported that NASA has at least 17 high-ranking military retirees on the payroll whose combined pay and pension runs from $55,000 to $78,000. Some of the retired generals and admirals get $47,500, the top career civilian federal salary, in addition to pensions exceeding $30,000.

Proxmire has asked NASA for a list of all retired regulars who are benefiting from exemptions to the DUal Compensation Act, and also for lists of retired reserve officers holding top jobs with NASA.

Under the Dual Compensation Act, retired regular officers must take a pension reduction when they take regular civil service jobs. That offset gives them only the first $4,219 of their retired pay, plus half the remainder.

Retired reserve officers and retired enlisted personnel, are allowed to keep all their military pension and their full civilian federal salaries. There are at least 141,000 military retirees in government.

But under a special exemption to the Dual Compensation Act, NASA and other agencies can allow retired regulars to draw full pension and full pay for "special or emergency" employment. The idea is that nobody else could do the job, and that NASA could not get the top retired military talent unless it waived the rule and allowed them both full pay and pension.

Stevenson's hearings in April before his Science, Technology and Space Subcommittee could have top NASA brass squirming for answers. He plans to ask NASA to justify the exemptions, and explain why it could not get the retired military men on the same financial basis that other retired regular officers take federal employment.

Stevenson also is concerned about the "militarization" of the civilian space agency. On Jan. 23, he wrote NASA Administrator Robert A. Frosch about the appointment of Kenneth Chapman, retired Air Force major general, to be associate administrator for external affairs. Stevenson said h saw nothing in the press release concerning Chapman's appointment to indicate experience "that prepared him for this important appointment . . ."

Stevenson said many career NASA employees were passed over for the job, and he wants to know why.

Meantime, NASA insiders say that some officials of the agency have been engaged in a "witchhunt" to find out which employes "leaked" the salary data to this column. Although the information is public, under the Freedom of Information Act, NASA apparently wants to shove an uncomfortable gag in employe's mouths anyhow.

The hunt for the whistle-blowers, who simply obeyed the law of the land, has centered on ANSA's personnel and public affairs offices. Both Proxmire and Stevenson are aware of the situation, and might have some interesting questions for NASA on that score, too.

The 17 officers who are drawing full pay and pension include four retired Air Force generals, one admiral, six retired Navy captains and several retired Air Force colonels.