A trade association has asked the Federal Communications Commission to give aerospace manufacturers more time to move to other parts of the radio spectrum to make room for a new satellite television service.

The FCC had authorized a direct satellite-to-home television service (DBS) a few years ago that would reach antenna dishes mounted on roofs in sparsely populated areas that do not receive conventional television or cable programming.

The agency notified users of private microwave radio networks they would have to make room on the airwaves by 1988 for what was to be a burgeoning new entertainment business. Manufacturers, who use the spectrum to transmit data and for ground-to-air communications, must vacate the frequencies on an as-needed basis. But that means they also will have to invest in new equipment to operate on higher frequencies, say industry sources.

Other businesses that could be affected by the FCC action include railroads, petroleum companies, utilities and newspapers using the private microwave systems for communication purposes.

In recent months, several companies, including CBS Inc., Western Union Telegraph Co., and Communications Satellite Corp., have drastically curtailed or abandoned plans for the DBS service because of high costs and a firmly entrenched cable TV industry. As a result, businesses using private microwave networks are questioning why they should give up their place in the spectrum.

"Given the recent events that have affected the prospects and outlook for DBS, we think it totally inappropriate to require microwave licensees to junk perfectly serviceable equipment based on the mere supposition that DBS may be viable by September 1988," said Ken Keane, an attorney representing the Aerospace and Flight Test Radio Coordinating Council (AFTRCC).

The council represents aerospace manufacturers who use the microwave networks for data communications in connection with flight testing of high-performance jet aircraft.

"While we don't object to DBS, we think that since the market has not evolved the way the commission planned, we ought to be able to stay in those frequencies that were to revert to DBS broadcasters for at least five years past 1988," said Kathleen Criner, director of telecommunications affairs for the American Newspaper Publishers Association.

FCC officials, who have rejected previous petitions from AFTRCC as well as the American Petroleum Institute, maintain the DBS service will be viable. "There is still interest, DBS is not dead," said Stuart Bedell, chief of the FCC distribution services branch. "Some companies have pulled, out but others seem eager."

Bedell said Hughes Galaxy Communications, Direct Broadcast Satellite Corp., Dominion Video Satellite Inc. and United States Satellite Broadcasting Co. had demonstrated interest and the agency had granted a number of permits to proceed with the service.

Nevertheless, Jerome Lucas, president of TeleStrategies, a McLean telecommunications consulting firm, said "there is no viable business concept using DBS in the entertainment field right now because of the very high penetration of cable -- the DBS window is closed."