Next month, the Centennial, Colo.-based United Launch Alliance (ULA) will hit a milestone by launching its 75th mission since the company was formed in December 2006. Already deep into processing, the Atlas V vehicle for the scheduled late September mission will deliver the U.S. Air Force’s third Advanced Extremely High Frequency (AEHF-3) satellite into supersynchronous transfer orbit. A successful launch will establish AEHF-3 as the latest member of a “constellation” of high-powered satellites providing fast and secure communications to link civilian leadership with military assets, anywhere in the world.
For only the third time in its operational history, the storied Atlas V will fly in its so-called “531” configuration, boasting a 17.7-foot (5.4-meter) payload fairing, three strap-on solid-fueled boosters, and a single-engine Centaur upper stage. It has the potential to deliver a payload weighing up to 34,330 pounds into low-Earth orbit or up to 16,480 pounds into geostationary transfer orbit. Stacking of the Atlas V 531 at Cape Canaveral Air Force Station, Fla., got underway on 2 August in the Vertical Integration Facility, when the Common Booster Core (CBC)—the central component of the rocket’s first stage—was rotated into position on its mobile launch platform. Over the following days the three Aerojet-built boosters were affixed to their mounting points on the first stage, and on 13 August the Centaur upper stage was hoisted atop the stack.
Next steps include the completion of checkout of AEHF-3 itself, which arrived at the Cape on 10 July from prime contractor Lockheed Martin’s facility in Sunnyvale, Calif. At the time of writing, the 13,600-pound spacecraft was undergoing clean room testing and loading of maneuvering propellants. It will shortly be encapsulated within its two-piece (“bisector”) payload fairing and mounted atop the Atlas V for flight. Liftoff from Space Launch Complex (SLC)-41 at the Cape is scheduled to take place on 25 September.
Built by Lockheed Martin, the AEHF system replaces the outdated Milstar network. The AEHF-1 mission was launched in August 2010, followed by AEHF-2 in May 2012. After the launch of AEHF-3, a total of three more satellites in the network are scheduled to fly. The satellites operate at extreme high frequencies (44 GHz uplink) and super high frequencies (20 GHz downlink) and can relay communications directly without passing through ground stations. Their phased array antennas help to eliminate possible sources of radio jamming, and each AEHF spacecraft can support data rates as high as 8.192 Mbits/sec. By the time the sixth and final member of the constellation reaches operational service, AEHF will provide full surface coverage between 65 degrees North and 65 degrees South latitude.
As United Launch Alliance’s 75th mission since the company was formed in December 2006, the AEHF-3 launch will also mark the 40th flight of the Atlas V itself, which first flew back in August 2002. Although it is still less than a decade old, ULA’s vehicles have delivered an array of remarkable missions into space: some devoted to national security and thus shrouded in secrecy, others for commercial and scientific purposes.
ULA currently operates three vehicles—the Atlas V, the Delta IV, and the Delta II—and has established for itself an impressive success record. Despite a Centaur glitch in June 2007, which produced a lower than intended thrust for its classified payload, the Atlas V has performed virtually without a blemish. The Delta IV, too, has only once seriously underperformed: on the maiden voyage of its Heavy configuration, back in December 2004, the vehicle suffered a premature engine shutdown during ascent. More recently, it also endured and recovered well during a problematic launch last October. As for the Delta II, it is one of the most reliable U.S. launch vehicles currently in active operational service. Although it has not flown since October 2011, it is slated to loft NASA’s Orbiting Carbon Observatory (OCO)-2 in July 2014.
Aboard the Atlas V, key missions have included the latest Landsat, the Lunar Reconnaissance Orbiter (LRO) and Lunar Crater Observation and Sensing Satellite (LCROSS), and NASA’s Juno spacecraft to Jupiter. Aboard the Delta IV, large missile warning satellites, reconnaissance satellites, weather satellites, and military communications satellites—most recently, last week’s launch of the sixth Wideband Global Satcom (WGS-6)—have ensured that the United States’ military assets retain the high ground in space. And Delta II vehicles have lofted NASA’s Phoenix mission to Mars, the Dawn asteroid exploration spacecraft, and the Kepler observatory.
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