Globalstar rolled out its satellite-based cell phone service last October when it had 40 satellites in orbit, enough to offer uninterupted service to customers. Eight more satellites were launched by the end of November, completing the planned constellation of 48 satellites.

On Tuesday, Globalstar sent four more satellites into orbit atop a commercial Boeing Delta 2 rocket. After a two- to three-week check out and testing period, Globalstar controllers will rearrange their constellation of satellites so that 48 are considered operational and four others are in place as spares.

With the business of launching the satellites behind them, Globalstar officials say they will now concentrate on rolling out service in as many nations as they can, with Mexico, Brazil, China and Russia topping the list of prospective customers, Klineberg said.

"The major importance for us is rolling out the service where there really is no alternative, and there are a lot of areas in the world that are like that," Klineberg said.

Klineberg noted that although there is respectful interest in the Globalstar cell phone service in the United States and Europe, most users from those nations only sporadically use the service.

For example, many North American customers only dial up Globalstar on the weekend when recreational activities such as camping or boating take people far from the nearest telephone or traditional ground-based cell phone tower, Klineberg said.

"We want people to use the phone," he said.

The reason: Globalstar gets paid by the minute, acting as a wholesaler of the service to regional and local cell phone service companies.

Here's how it is supposed to work: You buy a Globalstar-equipped cell phone from a company like Qualcomm, Telit, or Ericcson and sign up for the service with an authorized service provider. Once you get the phone you just swing the small antenna straight up, dial your number and hit send.

The signal travels to one or more of the 48 satellites flying overhead at the time and then is bounced back to a gateway station on Earth, where the signal is transferred into the normal telephone system and relayed on to the person you are calling.

Globalstar began launching its satellites two years ago, flying seven Delta 2 rockets and six Russian Soyuz rockets, each loaded with four satellites each. A September 1998 mission on a Ukrainian Zenit 2 rocket was the only failure, costing Globalstar 12 satellites in a single flight.

Tuesday's launch placed the final four in space, lifting off from pad 17B at Cape Canaveral at 4:24 p.m. Eastern Standard Time. Some 70 minutes later the four satellites were literally sprung away from the rocket into their orbit two at a time, successfully completing the mission.

Although there is no need for any spares just yet, Globalstar managers say they want to be prepared to move quickly should one of the satellites fail.

"The satellites have been working very, very well," Klineberg said, noting that they are designed to last at least 10 years in low Earth orbit, but exposure to radiation and atomic oxygen molecules in space will eventually damage the satellites.

Eight more satellites will be manufactured during the next year or so and launched, four at a time, on two Delta 2 rockets already procured from Boeing, Klineberg said.

The next launch from Florida's Space Coast is scheduled for Friday at 12:30 p.m. EST when NASA's space shuttle Endeavour is to lift off on an 11-day radar mapping mission of planet Earth.