Rocket Men Iridium marks deployment milestone for space-based PCS By Loring Wirbel, EETimes Tempe, Ariz. -- Its critics have dismissed its concept of space-based personal communications as too costly. But Iridium LLC, a coalition of companies led by Motorola Inc. and Lockheed-Martin Corp., is well on its way to silencing the skeptics. Late last month, a Delta II rocket carrying five Iridium satellites was launched from Vandenberg Air Force Base into low Earth orbit (LEO), bringing the coalition's total number of deployed satellites to 34. More than half of the program's planned 66 fully operational satellites (there also will be six spares) are now in orbit. And they're not out there alone. Satellites riding Delta II, Russian Proton and Chinese Long March rockets have lifted off launch pads around the world over the past year as Iridium, Globalstar (Iridium's closest competitor) and several other "big LEO" and "little LEO" coalitions have scrambled to put voice and data networks online. The systems all rely on constellations of satellites that orbit within a few hundred miles of the earth. Such networks are qualitatively different from the geosynchronous- and polar-orbiting systems that rely on large, bulky satellite terminals to enable both the relay of terrestrial phone calls and the placement of direct earth-to-space calls. The point behind Iridium, Globalstar and other networks is to allow PCS services from any point on the surface of the planet, in Iridium's case using a space-based time-division multiple-access (TDMA) system that interfaces with the public switched telephone network and with global cellular networks operating at both 800 MHz and 1.9 GHz. Calls are either handled through a ground-based gateway to the space-based PCS or carried out directly from handset to orbiting satellite. Andrew Croughan, director of the gateway-technology office at Iridium North America, said Iridium holds an advantage over competitors because it offers a "switching matrix in the sky," meaning that calls can be handed off directly from one satellite to another in space. Other systems allow only space-to-ground links, complicating call transfers, he said. The race to complete gateways--the worldwide ground stations for managing the space constellations--is as heated as the launch contests. Iridium North America is responsible for managing the beta-site gateway in Tempe, where many of the initial operational tests for the satellites are run. Iridium LLC and its partners are building a total of 11 gateways worldwide. Globalstar, a coalition led by Qualcomm Inc. and Loral Space & Communications, has a bigger task to accomplish for its code-division multiple-access (CDMA)-based PCS system, because calls cannot be switched between satellites. Consequently, Globalstar is building 35 gateways worldwide (though there will be 48 satellites in its constellation, compared with Iridium's 66). On the same day the Delta II went up with five new Iridium satellites, Globalstar partners held a groundbreaking ceremony in Smiths Falls, Ont., Canada, marking the start of construction on the first of two planned gateways in Canada. Hitting the halfway point in system buildout is especially important for Iridium, whose skeptics have claimed that both the upfront investment costs and the unavailability of launch platforms could ground the coalition's plans for space-based PCS. The explosion of a Delta II carrying a Global Positioning System satellite in January seemed to validate the critics' assertions. Despite the loss of that rocket, however, Iridium has been able to keep to its deployment schedule this year, and it expects to have a fully operational constellation in place, as scheduled, by third quarter 1998. (Next article) (c) 1997 CMP Media, Inc [This article comes from EE Times in a joint cooperative effort with the Motley Fool. For more articles like it, please look at Fool's Gold every weekend or simply go to the Fool's Gold Mine and page through our back issues, which all have clever and cool EE Times articles in them.]

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