Creating the Global Hot Spot

[apcmiller]

LONDON -- Telecom giant Inmarsat is weeks away from launching the second in a series of two super-satellites -- designed to be among the most powerful commercial communications spacecraft in orbit -- that will beam broadband data and voice services to almost any location on the planet.

The I-4 satellites will serve as switchboards in the sky for Inmarsat's Broadband Global Area Network, or BGAN, service, scheduled for rollout in 2006. Instead of cruising for a Starbucks, BGAN subscribers can hit the road with a portable terminal as small as their laptop computer and surf the web -- or connect with the office LAN -- at broadband speeds of up to 492 Kbps.

"The network will cover 88 percent of the globe's landmass," said Chris McLaughlin, vice president of corporate communications for Inmarsat in London.

Satellite broadband plans have crashed and burned before, notably with the multibillion-dollar bust of wireless pioneer Craig McCaw's Iridium venture. But dreams of blanketing the globe with ubiquitous high-speed connectivity die hard, and satellite communications providers are once again lining up to provide commercial broadband services to consumers and businesses.

Denver's WildBlue Communications launched a consumer satellite broadband service in June, offering rural customers a 512-Kbps downstream connection for about $50 a month.

After an earlier false start, satellite giant Hughes Network Systems is preparing to launch a broadband service in North America called Spaceway by 2006, promising downstream speeds of up to 30 Mbps in certain locations.

In this resurgent field, Inmarsat's $1.5 billion project could be one of the first to deliver broadband data and voice simultaneously -- with truly toteable hardware -- using what the company claims are the most powerful and sophisticated commercial communications satellites ever launched.

The BGAN service will be somewhat of a holy grail for customers like media organizations, sales professionals and construction personnel who often need web or phone access in isolated areas. Bulky equipment, spotty reception and tooth-grinding bit rates are the common problems that plague current mobile broadband gear. Inmarsat says it will change all that.

"The portable satellite terminals will be available in a wide variety of bit rates, up to half a meg," McLaughlin said. "The Hughes terminal will offer the highest speed, and will accept Wi-Fi connections for up to five users."

Assembled in France by EADS Astrium, the satellites will eliminate the chunky, dish-dependent designs of other broadband networks with precise spot beams. Within its footprint, each spacecraft will blanket one-third of the Earth's surface with a single global beam -- plus 19 wide-spot beams and 228 narrow-spot beams -- emitted from an array of high-efficiency helix feed elements.

Those spot beams beneath the satellite are cone-shaped, so a large beam could cover several cities and a narrow beam could focus on an individual city. The smaller beams provide a more compact, more powerful broadcast signal to a smaller area.

The spot beams can be manipulated in response to instructions from the Satellite Command Center in London and refocused on any region in the satellite footprint to accommodate evolving network bandwidth demand. For example, if the number of subscribers logging on in a given area should suddenly spike, the smaller spot beams can be trained on that area to provide a stronger signal to meet the increased demand. The spot beams also allow many subscribers to use the same frequency without interfering with each other.

One of the most advanced digital signal processors ever built for a satellite will serve as the heart of the I-4 satellites' communication system. The DSP will switch uplink and downlink signals between the various spot beams -- assigning bandwidth allocations for the best possible bit rates -- and amplify weak incoming signals.

In addition to the I-4 satellites' flexibility, the spacecraft have a lot of output-power muscle. Each has ample downlink broadcast strength of 12 kilowatts, more than enough to provide an excellent signal to the terrestrial terminals.

To capitalize on power and multiply uplink sensitivity, each I-4 wields a piece of hardware resembling a circular, oversized trampoline. This giant mesh reflector has been engineered to concentrate and focus inbound and outbound signals to the satellite's antenna array, similar to the way a parabolic mirror reflects and concentrates light rays.

Each AstroMesh reflector -- built by a subsidiary of Northrop Grumman -- occupies about as much space as a kitchen refrigerator when it is stowed prior to launch. Once the I-4 is perched in orbit, the reflector unfurls on carbon-fiber rods like a giant umbrella, occupying 80 square meters.

Weighing in at a scale-tipping 13,000 pounds, and approaching the size of a double-decker bus, the I-4 is a silicon brute. To get it into the sky, Inmarsat has enlisted the help of Sea Launch, of Long Beach, California. The satellite will get a fiery ride atop a Zenit 3SL rocket from the middle of the Pacific at the equator, to provide the shortest route to orbit.

"This is our first launch for Inmarsat, and we're excited to be helping them get started," said Paula Korn, communications director for Sea Launch.

The I-4 satellite and rocket will be ushered out to sea aboard Odyssey, Sea Launch's tricked-out ocean drilling platform launch-pad conversion. The Sea Launch Commander, a ship housing the launch systems and personnel, will accompany Odyssey on the 11-day journey.

At 154 degrees west longitude, Odyssey will be precisely positioned at the correct point in the Pacific for launch and prevented from deviating from this position during the launch.

"Once it gets to the launch site, we ballast it down to 65 feet, which gives it tremendous stability," said Korn. The Odyssey platform has compartments, much like a submarine's, that can be flooded with water. When the compartments are flooded, the weight of the extra water acts like the ballast in a hot air balloon. The weight of the water in the compartments causes the platform to sink until its surface is only 65 feet above the water.

"On Odyssey, we use azimuth thrusters linked to GPS, and a dynamic positioning system," Korn said.

Following liftoff, the three-stage Zenit 3SL rocket will propel the I-4 satellite to an apogee of 55,926 miles. At approximately 1 hour and 25 minutes into the mission, the satellite will be inserted into an elliptical geostationary transfer orbit, and separation from the final Block DM stage of the rocket will take place.

About four days following orbital insertion, Inmarsat satellite controllers will begin the weeklong series of short burns of the I-4's on-board thrusters to establish a circular geostationary orbit. The satellite is equipped with a plasma propulsion subsystem and chemical thrusters for in-orbit adjustments and station keeping.

In its final geostationary orbit, the I-4 will appear to be motionless at 53 degrees west over the Atlantic Ocean, where it will travel at 6,875 mph to match the Earth's rotation.

The satellite will harvest power from the sun by deploying massive solar panels that almost span the width of a football field. The panels will also act as solar sails, using the pressure of particles from the sun to provide additional propulsion in orbit.

While Sea Launch wouldn't disclose the exact launch date for the satellite, Korn offered a time frame. "It'll be early November," she said. "We'll be announcing it on our website."

Early adopters will be watching.

Wired News

[nsane]

that's sweet, only thing now is hoping it doesn't cost an arm and a leg when it first comes out :P