Delta 4 rocket soars on Defense Department mission
BY JUSTIN RAY
Posted: January 20, 2012
A new Air Force satellite headed for service over the Middle East to route essential communications to U.S. military forces and improve data links to unmanned aerial drones was successfully launched from Cape Canaveral last night.
Liftoff occurred at the opening minute of a launch window set months in advance.
Valued at $464 million, the 6.5-ton satellite will enhance military communications over a turbulent portion of the globe when it commences broadcasting duties in a few months.
Dropped off into a highly-elliptical, preliminary orbit by the Delta 4 rocket, the satellite's conventional bi-propellant chemical main engine will execute four apogee and four perigee firings through early February before beginning 40 days of final orbit circularization maneuvers with its xenon-ion propulsion thrusters to reach geosynchronous perch 22,300 miles above Earth in March.
Once its appendages are fully unfurled in space, the craft's solar-power wings will span 134 feet.
In-orbit testing with the military's Camp Roberts facility in California will occur from mid-March through mid-April. Boeing will control the craft's initial flying until handover to the Air Force at the end of April.
From there, the spacecraft will drift to the operational location over the Indian Ocean to receive final acceptance into the WGS constellation and enter service this summer.
The Air Force says it plans to put this WGS 4 spacecraft's coverage footprint over the Middle East and Southeast Asia for use by U.S. Central Command and U.S. Pacific Command.
"WGS provides critical operation and situational awareness information to the warfighter," said Dave Madden, director of the Military Satellite Communications Systems Directorate at the Air Force's Space and Missile Systems Center. "I want to thank Boeing and the work they have done to give us a first-class quality satellite that's going to be a critical add to our constellation."
WGS 4 starts an enhanced "block" of satellites with improved bandwidth for communications to the military's remote-controlled drones known for their stealthy and undercover operations in global hotspots. The vehicles can carry cameras, radar sensors and detectors to sniff out uranium and radioactive material.
"The UAVs and moving large amounts of data around is a major requirement that drove us to do the upgrade, which is giving us the significantly more bandwidth and capacity," said Madden.
Once slid into its orbital home high above the Indian Ocean, the satellite will join the expanding fleet of Wideband Global SATCOM communications satellites that form the Pentagon's worldwide communications backbone across all branches of the military.
"WGS is the DOD's highest capacity communications satellite system. These satellites provide tremendous operational flexibility to deliver the needed capacity, coverage and connectivity in support of demanding operational scenarios," said Mark Spiwak, the WGS program director for satellite-builder Boeing.
"It does that by using a channelizer, which is kind of the heart of the satellite which is able to convert the frequencies from X-to-Ka or X-to-X or Ka-to-Ka, and that provides a certain bandwidth availability and a number of channels associated with that," Spiwak said.
But the new Block 2 satellites, beginning with WGS 4, come with a bypass feature for unmanned aerial drone communications to skip the crossbanding path and use two uplink and two downlink channels that offer three times the bandwidth as the normal channels, opening up a much bigger pipeline for data to flow.
That increased capacity will directly help the military's remotely-controlled unmanned drone programs, which are used for surveillance, intelligence-gathering and offensive operations.
"So why is that good? That's good because as the Global Hawks, the Reapers, the Predators, all of the AISR platforms, as they are converting to their different terminals, obviously the more bandwidth is good for them, and you can lock on to one or several Global Hawks, multiple Reapers and Predators, and the more bandwidth allows the operators to pump more data through. You've got that wider pipe on two uplink and two downlink channels," Spiwak said.
"That's kind of the main change (for Block 2). It still has all of the X-band flexibility, Ka-band flexibility that the first three have, but this has these extra, larger pipes that you can really pump a lot of data through."
WGS 1 was launched in October 2007 to cover the vast U.S. Pacific Command that stretches from the U.S. western coast all the way to Southeast Asia.
WGS 2 satellite followed with an April 2009 launch to serve U.S. Central Command and the forces in Afghanistan, Iraq and other parts of Southwest Asia.
WGS 3 went up in December 2009 to cover U.S. European Command and U.S. Africa Command, plus lend additional support over the Middle East.
"Three Block 1 satellites are currently on-orbit, providing critical communication links to DOD and allied forces worldwide," said Spiwak.
For over four decades, the Defense Satellite Communications System was the foundation for flowing secure information to military forces around the globe. But that heritage system is being phased out as the aging craft retire and the new WGS satellites ascend to orbit to take advantage of new technology.
The final DSCS craft was launched by a Delta 4 rocket in 2003. (Our launch story)
There's still 8 DSCS satellites in service today.
"We will use 'em up till the very last minute because the DSCS's are still providing significant capability as well," said Madden.
Each WGS bird possesses 10 times the capacity of a single DSCS satellite and offers 19 coverage areas with its steerable antennas versus 8 under the heritage craft.
The X-band communications through DSCS and WGS allow data, photos and video to be relayed to troops on the battlefield. But WGS also brings Ka-band to the table for high-volume broadcasting to user terminals across the reception area.
A key advancement that WGS brings is an internal box called a digital channelizer that enables a user with a Ka-band terminal to seamlessly connect to someone with an X-band terminal, or vice versa.
The data transmission rates range from 2.1 to 3.6 Gbps.
"Everyday WGS helps save and improve the lives of users worldwide. This launch (is) another important step in advancing these capabilities," said Spiwak.
The 217-foot-tall Delta 4 carrying WGS 4 flew in the Medium+(5,4) configuration, which is the most powerful of the Medium-version rockets and below only the triple-core Heavy in the modular family's lineup.
WGS is one of the satellite programs that's interchangeable between ULA's Atlas and Delta rocket families. The first two WGS satellites went up on Atlas, and now the subsequent two have flown on Delta.
"Our ability to integrate and launch satellites successfully and efficiently on two launch systems to provide operational flexibility was a primary reason that ULA was formed."
The Medium+(5,4) features a five-meter-diameter upper stage loaded with more cryogenic propellants than the optional four-meter motor used for other launches, such as GPS missions. The rocket also has a full set of four solid-fuel boosters strapped to the first stage, double the number used for GPS and other lower-weight payloads.
The first stage is powered by the RS-68 hydrogen-fed main engine and the upper stage has the RL10B-2 engine, the powerplants used on all 18 Delta 4 missions to date.
It was the first rocket launch from Cape Canaveral of the new year and begins the Delta 4 rocket's 2012 that is dedicated to military service with as many as five flights scheduled from both Florida and Vandenberg Air Force Base in California to deploy WGS, GPS and classified National Reconnaissance Office spacecraft.
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