Just two days after space shuttle Discovery's spectacular launch, a United Launch Alliance Atlas V rocket is scheduled to liftoff tonight with the second Wideband Global Satellite communications satellite from Cape Canaveral Air Force Station in Florida. Launch is currently set for 9:24 p.m. EDT from Launch Complex 41. The weather forecast is generally positive, with a 70% chance of acceptable conditions during tonights 37-minute launch window.
READ: WGS-2 MISSION BOOKLET READ: LAUNCH WEATHER FORECAST READ: LAUNCH HAZARD ADVISORY READ: RESTRICTED AIRSPACE MAP VIDEO: ATLAS V AND WGS-2 ROLL TO THE LAUNCH PAD MONDAY MORNING "We are extremely proud to be a part of the team that will launch the second Wideband Global SATCOM satellite," said Brig. Gen. Edward L. Bolton Jr., 45th Space Wing commander. "The launch of this satellite will provide our military with the capacity, connectivity, and flexibility to successfully complete its mission." These WGS satellites are designed to provide high-capacity communications for the United States Department of Defense. They will augment and eventually replace the aging Defense Satellite Communication System (DSCS), which has been the Department of Defense's backbone for satellite communications over the last two decades. The WGS satellite provides a giant leap in communications bandwidth and technology. The launch vehicle for the mission is the reliable Atlas V 421 consists of a single Atlas V booster stage, the Centaur upper stage, and two solid rocket boosters (SRB). The Atlas V booster is 12.5 ft in diameter and 106.5 ft long. The booster’s tanks are structurally rigid, and constructed of isogrid aluminum barrels, spun-formed aluminum domes, and intertank skirts. Atlas booster propulsion is provided by the RD-180 engine system (a single engine with two thrust chambers). The RD-180 burns RP-1, which is highly purified kerosene, and liquid oxygen, and delivers 860,200 lb of thrust at sea level. The SRBs are 61.28 in. in diameter, 67 ft long, and are constructed of a graphite-epoxy composite. The SRBs burn for 90 seconds and are then jettisoned. The Centaur upper stage is 10 ft in diameter and 41.5 ft long. The propellant tanks are constructed of pressure-stabilized corrosion-resistant stainless steel. Centaur is a cryogenic liquid hydrogen/liquid oxygen-fueled vehicle. It uses a single RL10A-4-2 engine that produces 22,300 lb of thrust. The Atlas V booster is controlled by the Centaur avionics system, which provides guidance, flight control, and vehicle sequencing functions during booster and Centaur phases of flight. The WGS-2 spacecraft is an approximately 13,200-lb communications satellite. The spacecraft is mated to the Centaur upperstage by the space vehicle contractor-provided spacecraft launch vehicle adapter, separation system, and electrical harness, and a ULA-provided, mission-unique C22 launch vehicle adapter. WGS supports communications links in the 500 MHz range of the X-band and 1 GHz range of the Ka-band spectra. WGS can filter and route up to 4.875 GHz of instantaneous bandwidth. Depending on the mix of ground terminals, data rates, and modulation schemes employed, a WGS satellite can support data transmission rates between 2.4 and 3.6 Gbps. Four Army Wideband Satellite Operations Centers (WSOC) provide command and Control of WGS. Each Global SATCOM Configuration and Control Element (GSCCE) has the capability to control up to three satellites at a time, using X-band or Ka-band telemetry and command links. Spacecraft platform control is accomplished by the 3rd Space Operations Squadron at Schriever Air Force Base in Colorado Springs, CO using WGS mission-unique software and databases. Support technologies for WGS include the xenon-ion propulsion system (XIPS), which is 10 times more efficient than conventional bipropellant systems; highly efficient triple-junction gallium arsenide solar cells; and deployable radiators with flexible heat pipes. Four 25-cm XIPS thrusters remove orbit eccentricity during transfer orbit operations. The thrusters are also used to perform orbit maintenance and any required station-change maneuvers during the mission’s life. First launched in 2007, WGS will consist of a constellation of five satellites that will supply service for military commanders to command and control their tactical forces. After the launch of WGS-2, WGS-3 will round out the remainder of the first phase of satellites. The WGS-3 satellite has completed its test programs and is slated for launch later this year. (The Spacearium / Space Media Corporation)
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