The National Aeronautics and Space Administration wants to bring a new portable radio telephone service to rural America via satellite.

The new service is called cellular radio, and hundreds of companies are competing to offer the service in the nation's biggest cities, beginning in 1984. New technology permits a computerized switching of calls between vehicles and local telephone networks.

But the system, as now proposed, is land-based. That makes it extremely difficult and costly to install in widely spaced rural areas, interspersed with mountains and other frequency barriers.

NASA believes cellular radio and other mobile telephone services could offer as much to rural communities as they do to the cities. So NASA officials went before the Federal Communications Commission yesterday in effect to ask the FCC to set the stage for a market test.

NASA wants the FCC to reserve frequencies that could be used by commercial companies to establish "a land mobile satellite service." The space agency says such a service would complement cellular radio mobile systems currently in planning, and other mobile systems already in use.

"We're simply asking the FCC not to destroy the option for future commercial land mobile satellite services," said Jerry Freibaum, a NASA program director. He said NASA has spent the last five years conducting experiments that have proved the "feasibility of using satellites" to augment land-based mobile telephone systems.

"We know it's feasible. But there's a great deal of reservation about a potential market. We happen to think that there's a great demand for this use of satellites," Freibaum said.

The FCC, acting mostly on reservations about market potential, denied a similar NASA request last year. FCC officials declined comment yesterday, on the ground they have not had a chance to review NASA's latest filing.

NASA officials say their primary purpose in pushing for the market test is that other countries "are moving forward to develop mobile satellite services" under frequency allowances made by 1979 World Administrative Radio Conference (WARC). "Unless the commission acts promptly to provide [frequencies] for such services, the United States' leadership role in satellite communications and in mobile communications equipment will be jeopardized," NASA said in its filing yesterday.

The space agency would not be involved in building the communications satellites. But Freibaum said NASA, using shuttlecraft such as the Columbia, could deliver the satellites to space stations for commercial users.

The NASA filing said mobile telecommunications systems in the United States "have historically been available only through terrestrial facilities, and thus have been limited in range" and restricted to use in mostly urban areas. A satellite-augmented system could pull in up to 288,000 rural subscribers by 1990, NASA said.