On January 20 between 0038 and 0211 UTC, a Delta 4 rocket will liftoff from the Cape with the next Wideband Global Satellite Communications (WGS) satellite.This WGS mission is the fourth installment of the Wideband Global SATCOM (WGS) system. The WGS satellites are an important element of a new highcapacity satellite communications system providing enhanced communications capabilities to our troops in the field for the next decade and beyond. WGS enables more robust and flexible execution of Command and Control, Communications, Computers, Intelligence, Surveillance and Reconnaissance (C4lSR), as well as battle management and combat support information functions. WGS-4 augments the existing service available through the UHF Follow-on, WGS-1, WGS-2 and WGS-3 satellites by providing enhanced information broadcast capabilities.
WGS-4 SATELLITE | Overview
The WGS-4 satellite is an approximately 13,200-lb communications satellite. 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. WGS-4, the first Block II satellite, includes a high-bandwidth RF bypass capability in addition to the previous capabilities provided by the Block I satellites. 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. WGS has 19 independent coverage areas that can be positioned throughout its field of view. This includes eight steerable/shapeable X-band beams formed by separate transmit/receive phased arrays; 10 Ka-band beams served by independently steerable diplexed antennas (three with selectable RF polarization); and transmit/receive X-band Earth-coverage beams. WGS can tailor coverage areas and connect X-band and Ka-band users anywhere within its field of view. 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 (XlPS), 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 XlPS thrusters remove orbit eccentricity during transfer orbit operations. The thrusters also used to perform orbit maintenance and any required station-change maneuvers during the mission’s life. The triple-junction gallium arsenide solar cells provide on-orbit electrical power for the spacecraft. The deployable radiators’ flexible heat pipes provide increased radiator area, resulting in a
cooler, more stable thermal environment for the spacecraft.
