By J.R. Wilson
The first constellation of global personal communications satellites is now in place and final systems checks of satellites, Earth stations, and handsets is heading toward an anticipated public operational start date of 23 September. It has been a long road - more than 10 years - of advancing technology, creating global partnerships and bowing to global political realities.
Originally designated Iridium because its constellation of 77 satellites equaled the number of electrons in the iridium atom, technological advances soon broke that connection. The constellation now consists of 66 active satellites and six on-orbit spares that will enable anyone anywhere on Earth to place a call directly to anyone else - Iridium to Iridium, Iridium to cellular or landline, cellular or landline to Iridium. The last five spares are scheduled for launch aboard a Delta II rocket this summer.
"We will maintain the six spares on orbit, one per plane, but the total number we have to build over the years may be fewer than we originally had in our business plan," says Bary Bertiger, senior vice president and general manager of Motorola`s satellite communications group, which pioneered the $5 billion Iridium project.
The satellites, which were designed to last for five years, carry sufficient fuel and radiation-tolerant electronics to last eight years. "We continue to use those numbers and probably will wind up launching a new generation of satellites before they run out of life," Bertiger says.
The six spares fly below the mission orbit. If an operational satellite fails, the spare maneuvers to its location. If two went out in the same plane, the rest of the constellation would cover the resulting "hole" until two new satellites - one operational and one replacement spare - could be launched, which Motorola officials predict could happen within 30 to 45 days.
Iridium also launched the most satellites by a commercial venture, the most for a single application, the most successful consecutive launches (putting up the entire constellation in 15 launches), and the most within a 12-month period, from the first launch in May 1997 to completion of the constellation in May 1998. It also was the first program to use a combination of U.S. Boeing (nee McDonnell Douglas) Delta, Russian Proton, and Chinese Long March rockets.
Because Motorola experts believe they will need no more than one or two replacement satellites at any one time, they plan to launch future spares for the current constellation on Long March, which carries only two of the satellites at a time, compared to five on the Delta and seven on the Proton.
Rad-hard electronics
"We designed the satellites for a particular radiation environment and the environment we anticipated is the one we are seeing, so there have been no issues in that area," Bertiger says. "The satellites have demonstrated a higher reliability than our statistics had led us to expect."
The radio spectrum that Iridium uses includes L-band (1616-1626.5 MHz) for voice communication with and between Iridium subscribers, and the Ka-band (19.4-19.6 GHz for downlinks; 29.1-29.3 GHz for uplinks) for gateway and Earth terminal transmissions. This is not a program designed for the high-bandwidth demand of data transmissions, which other systems will address.
Among those is Teledesic, in which Motorola recently took a 26 percent stake and, as prime contractor, will build the entire constellation of 288 low-Earth-orbit satellites operating in the high-frequency Ka-band (28.6 - 29.1 GHz uplink and 18.8 - 19.3 GHz downlink). That will give most users two-way connections as fast as 64 megabits per second on the downlink and as fast as 2 megabits per second on the uplink - some 2,000 times faster than the fastest analog connections currently available.
Motorola joined Boeing and Matra Marconi Space, Europe`s leading satellite manufacturer, in the $9 billion "Internet-in-the-sky" venture. This project also has drawn large investments from Microsoft chairman Bill Gates, Saudi Prince Alwaleed Bin Tala, and the family of Teledesic chairman Craig McCaw, who was chairman of McCaw Cellular Communications Inc. until he sold to AT&T in 1994.
Iridium LLC has no role in Teledesic, but Motorola`s position as prime contractor and satellite manufacturer for both is likely to result in a substantial exchange of technology advances.
As for Iridium, the 1,500-pound satellites orbit 420 nautical miles above the Earth, with each spacecraft covering a tightly focused segment of the planet below. The satellites act essentially like giant cellular towers. By being in low Earth orbit rather than the more traditional geostationary orbit (22,300 nautical miles) of most communications satellites, Iridium spacecraft communicate directly with small handsets, making global personal communications possible. Intersatellite crosslinks make it possible for Iridium satellites to hand off calls between satellites in the same or adjacent orbiting planes, thus enabling a customer to continue a conversation even if the satellite through which a connection originally was made is no longer in line-of-sight.
For Iridium, Motorola became the first to apply Henry Ford`s assembly line concept to the construction of satellites. Partly this was possible - and necessary - because of the large number of satellites required within so short a period of time. Bertiger says the process has become standard at Motorola for most future satellites.
"Normally, you leave a satellite in place and technicians come in and add a piece, then another does the same when that one is finished," Bertiger says. "We developed a production line somewhat like an automobile. In our factory, it takes 4.3 days rather than several months to build a satellite, so we are substantially faster than standard production. Our satellites also are substantially less expensive than one of equal functionality produced the old way.
"It is in large measure because of the numbers, but not entirely. No one has really been willing to break the old mold until we did it with Iridium," Bertiger continues. "The processes we use are not specific to large-run satellites. Even for as few as three or four satellites, the processes we use could be used."
That assembly line will be back in business building the second generation of Iridium satellites much more quickly than most people may have imagined.
"We`re in the process of discussing the next generation with our customer (Iridium LLC) right now. When we start launching is a function of how quickly the market accepts the service. We`ll probably start launching sometime around the turn of the century or shortly thereafter," Bertiger says, adding they are looking at increased functionality in the satellites and better connection with the phones, which are expected to advance even more quickly.
Part of the speed with which the entire system evolves comes from a heavy investment in virtual prototyping and simulation, he adds. "We do an awful lot of simulation here and the way we get the kind of success we have in terms of reliability is we are very careful to model what we do in very detailed and exacting tests. Before we build anything, we know how it is going to perform via its models."
As with modern cellular phones, the Iridium handset (somewhat larger than a cellphone, although that is expected to change by the end of next year) uses a Subscriber Identity Module (SIM) card to identify the user to the system. Unlike most cellphones, however, this credit card-sized device can be removed and placed in another handset. The most common circumstance for that will be aboard commercial airliners, where the use of a standard handset would be banned due to potential interference with the aircraft`s electronic systems.
"There will be equipment on airliners allowing you to plug your SIM card in, so your seat becomes your phone. No one calling you will even know you`re on an airplane," Bertiger explained. "Keep the card in your wallet - or in your phone - but plug it into the airplane seat phone. You don`t have to worry about changing phone numbers or billing or anything because, with the SIM card in place, that seat becomes your phone and phone number."
The removable SIM card also is seen as added security, because without it the handset is neutral and, if stolen, cannot be used to charge calls to the owner. And the owner will be able to upgrade to the next generation of handset by simply moving his SIM card. SIM cards will have far more memory and capability than required by Iridium handsets, however, and also may become universal smartcards, replacing credit cards, providing medical information, perhaps even replacing drivers licenses, passports, and visas.
But within Iridium, the concept is to provide one phone, one phone number and one bill, all traveling with the user whenever and wherever on Earth that person may go.
The initial target market will be business travelers who often may be outside the range of standard cellular systems (a dual-use phone, which will connect to the satellites only if a land-based cellular system is not available, also is offered). Plans also are underway for solar-powered Iridium phone booths in remote areas of the world that currently have no telephone service. The handsets also could be used at sea or anywhere on Earth where telephones or cellular systems are not in service.
Military utility
Because communications are the first target in any military conflict, Iridium phones could change the face of 21st century warfare. It is possible to selectively terminate satellite access within a fairly tightly defined area - be that a city or a nation - but the problem for Iridium LLC will be determining who makes that decision, which side gets cut off.
That is but one of the difficult geopolitical problems that program officials have had to contemplate. The system now has 12 gateways - Earth stations that link landlines and cellular systems to the satellites - far more than needed by technology alone. But they also constitute political and financial concessions to host nations.
"I don`t think this project would have gotten off the ground if we had not recognized political realities and the local issues and environment and having the locals be part of the whole decision-making process," notes Keith Bubb, director of gateway business operations at Motorola, which also builds the gateways for Iridium.
However, he adds there also were technological realities to be considered: "The growth of cellular was not seen as nearly as capable when Iridium was conceived as it has become. That`s why we decided a couple of years ago to include a significant partnering element with cellular. And I think that change will have a significant impact on how Iridium services are received and used all over the world."
Having so many gateways may mean some cost advantages to users, as well, says John Rasmussen, manager of government market development for Iridium LLC, "Having multiple gateways spread across different regions significantly reduces long distance charges once those calls (from Iridium to non-Iridium) hit the ground. Part of our cost structure is how much it costs to get from your phone to the Iridium circuit. If you`re going Iridium phone to Iridium phone, it never touches a gateway."
Not in a required technical mode, that is. Each country in the world has been assigned to a gateway. When an Iridium handset is turned on, the system knows when and where that happens and if it is authorized for use in that country. Thus, program officials admit, the concept of borders and allowing or disallowing calls into or out of a specific country does exist, even if the attempted call is Iridium to Iridium.
"The system has the capability to manage calls from any country, so there are certain things a local government can do to manage calls," Rasmussen acknowledged. "We have the ability to manage the access to the system by ID numbers. But we also give the local government a piece of the action every time someone makes a call, even if they don`t have any actual contact with the call."
What Iridium eventually hopes to do is give the world the kind of convenience and ease in personal communications they have watched for 30 years on Star Trek.
"I think you`ll probably see something even closer to Star Trek communicators with the next generation of satellites and handsets, which will be even more closely integrated into the terrestrial wireless networks," says Craig Bond, vice president of market development for Iridium LLC. "That is the direction all satellite providers are going - bandwidth on demand, global footprint, completely passive from the customers` perspective. They don`t know what technology they are using; they just know they can make and receive phone calls.
"The only problem today is if I make a call on a satellite and walk into a building, the call will drop, which is a problem," Bond says. "But the next generation of satellites in five or six years will more closely interwork with the terrestrial networks and that problem will disappear."
