Dana Milner believes the future of trucking is installed in the cab of his 18-wheeler.

Along with his CB radio, radar detector and several pine-tree shaped air fresheners, Milner rides with a computer device linking him via satellite to his home base in Ontario."It's a pretty handy gizmo," said Milner, 27, a leased driver for Frederick Transport Ltd. of Dundas, Ontario. "It's what trucking of tomorrow is all about."

Milner no longer must call General Motors Corp. every four hours to give the progress of his three weekly trips from Ontario to Baltimore with roof supports for GM vans.

A Geostar Corp. satellite orbiting 22,000 miles above Earth automatically tracks Milner's progress and relays the information through a ground station to a Frederick Transport dispatcher.

Milner also can send messages with a keyboard if he is stuck in traffic, has engine trouble or needs emergency help.

"I'd say five years from now, you're going to see every major trucker in the United States and Canada using it," said Milner, who has been a truck driver for the past six years.

A U.S. Commerce Department report issued in May estimated annual mobile satellite services revenues could reach $150 million to $200 million worldwide by 1992 and $1 billion or more by 1995.

In the United States, more than 135,000 units could be in operation by the end of 1990, according to the report, "Space Commerce: An Industry Assessment."

Costs for the units, now more than $3,000, are expected to drop below $500 apiece in coming years.

The just-in-time delivery system now favored by the automotive and other industries has broadened he need for improved communication between dispatchers and truckers, said Edward K. Morlok, a University of Pennsylvania professor of transportation.

Under just-in-time delivery, manufacturers get parts when they are needed for assembly instead of constantly keeping large parts inventories.

Most dispatchers now must wait for a driver to call in before they can reroute a truck or learn if it's delayed, Morlok said. Drivers, in turn, must find a telephone and often wait on hold for the dispatcher, he said.

A 1985 survey published in Motor Carrier Computer News showed 85 percent of trucking companies used telephones to communicate with their drivers. Most of the remaining U.S. companies among the 1,134 surveyed by The Marketing Research Bureau Inc. used two-way radio.

Geostar, one of only two companies offering satellite communications, began its tracking service in May 1987, added one-way data communication in June and plans to have two-way communication in January.

The publicly held, Washington-based company, has 55 clients with 1,025 satellite transponders and orders for 7,500 more, said Geostar spokeswoman Joanne C. DeVincent. Sales are expected to reach $12 million this year, she said.

Most companies purchasing the $3,300 to $3,450 units made by Sony or Hughes are in the long-haul trucking business, but Geostar also has sold its service to track planes, trains and ships, Ms. DeVincent said.

In 1992, Geostar plans to launch a satellite designed to calculate a vehicle's relative distance to another vehicle to within 5 meters for use as a collision avoidance system.

QualComm Inc., a privately held, San Diego-based company, in June began offering a satellite tracking and two-way data communication system called OmniTRACS, said Richard Beyer, the system's marketing and sales vice president.

QualComm has sold the system to 17 trucking companies, and some 43 other companies have expressed interest in the $4,100 units, which QualComm manufactures.

QualComm's anticipated annual sales are $70 million for the fiscal year ending Sept. 30, 1989, Beyer said.

Morlok said satellites also can track the progress of valuable or hazardous cargo, monitor the temperature of a refrigerated truck and send electronic signals from the engine.

American Mobile Satellite Consortium, an eight-company consortium organized in May, wants to give truckers and their dispatchers voice communication as well.

The consortium plans in the next five years to launch a satellite capable of transmitting voice communication anywhere in the country.