Wideband Global SATCOM

The Wideband Global SATCOM system (sometimes called the Wideband Gapfiller Satellite system) is a satellite communications system planned for use in partnership by the United States Department of Defense (DoD) and the Australian Department of Defence. The system is composed of the Space Segment satellites, the Terminal Segment users and the Control Segment operators. DoD wideband satellite communication services are currently provided by a combination of the existing Defense Satellite Communications System (DSCS) and Global Broadcast Service (GBS) satellites. According to United Launch Alliance, quoted on Spaceflight Now, "A single WGS spacecraft has as much bandwidth as the entire existing DSCS constellation."

Mission

The Wideband Global SATCOM (WGS) satellites are key elements of a system that increases the communications capabilities of the U.S. and Australia. WGS supports the U.S. and Aus Department of Defense's warfighting information exchange requirements, enabling execution of tactical command and control, communications, and computers; intelligence, surveillance, and reconnaissance (C4ISR); battle management; and combat support information. WGS also augments the current Ka-band Global Broadcast Service (on UHF F/O satellites) by providing additional information broadcast capabilities. The combination of the Wideband Global Satellites, DSCS satellites, GBS payloads, wideband payload and platform control assets, and earth terminals operating with them has been referred to as the Interim Wideband System (IWS). It provides services to the US and Aus. Department of Defence. The IWS System supports continuous 24 hour per day wideband satellite services to tactical users and some fixed infrastructure users. Limited protected services will be provided under conditions of stress to selected users employing terrestrial modems capable of providing protection against jamming. The combined wideband satellite communications system consists of space vehicles of multiple types, control terminals and facilities, and user terminals.

Capabilities

The new Wideband Global SATCOM (WGS) satellites will complement the DSCS III Service Life Enhancement Program (SLEP) and GBS payloads, and offset the eventual decline in DSCS III capability. WGS will offer 4.875 GHz of instantaneous switchable bandwidth, thus each WGS can supply more than 10 times the capacity of a DSCS III Service Life Enhancement Program (SLEP) satellite. Together these assets will provide wideband services during the transition period between today's systems and the advent of the Objective X/Ka wideband system or Advanced Wideband System (AWS), which has merged with Transformational Communications System (TCS), in 2008-2009. The DSCS system will be replaced by six fully operational WGS satellites, each of which will be able to downlink 2.4 Gbit/s of data to tactical users. The very first WGS satellite in orbit will provide greater capability and bandwidth than all the DSCS satellites combined.

File:Payload Block Diagram.jpg Diagram illustrating the payload subsystem of a WGS satellite

Space segment

The primary contractor for the satellites is Boeing Satellite Systems, which will build them around the Boeing 702 satellite platform. Originally five satellites were planned. On 3 October 2007 the Australian Defence Ministry announced Australia would join in partnership and fund a sixth satellite in the constellation. Once in their orbits at an altitude of 22,300 mi (35,900 km), each will weigh approximately 7,600 lb (3,400 kg). The program intends to use both the Delta IV and the Atlas V as launch vehicles. The Air Force Space Command estimates each satellite will cost approximately US$300 million.

The first three WGS satellites form Block I of the space segment. WGS satellites 4, 5, and 6 make up Block II.

WGS-1

The first launch (WGS-1) was conducted by United Launch Alliance (ULA) on 10 October 2007. The satellite was carried by an Atlas V (421) lifting off from LC-41 at Cape Canaveral Air Force Station (CCAFS). After launch, the WGS-1 satellite was given the US military designation USA-195. Its coverage area stretches from the U.S. western coast to Southeast Asia.

WGS-2

Launch of the second satellite (WGS-2) was also conducted by ULA, at 01:31 GMT on 4 April 2009, using an Atlas V 421. A ULA Delta IV flying from LC-37B at CCAFS launched the third spacecraft on 6 December 2009. The WGS-2 satellite was positioned over the equator around 60° East longitude (over the Indian Ocean) for use by U.S. Central Command in Afghanistan, Iraq and other parts of Southwest Asia. Originally, the second spacecraft was to fly on the Delta, and the third on the Atlas, but they were switched for an undisclosed reason.

WGS-3

SATCOM3, launched on 6 December 2009, covers the eastern Atlantic Ocean. The satellite was launched by a Delta IV "Medium+ (5,4)" rocket (originally Atlas V but switched with WGS-2; see above).

WGS-4, 5, and 6

WGS 4, 5 and 6 are under construction by Boeing for deployment in the coming years. These satellites represent the Block II WGS satellites. Like WGS-3, launch of WGS-4 is planned for a Delta IV Medium+ (5,4). The target date for the launch is between December 2011 and February 2012.

WGS-7

On Aug. 23, 2010, Boeing was awarded an Air Force contract worth $182 million to begin work on the seventh WGS satellite. The new spacecraft is being procured under the WGS Block II follow-on contract. The contract will ultimately include options for production of up to six WGS satellites.

Terminal segment

The Terminal segment describes the "users" or "customers" of the communication services provided by the WGS. Users include the Australian Defence Force and U.S. Army ground mobile terminals, U.S. Navy ships and submarines, national command authorities for the nuclear forces, and various national security/allied national forces. Additionally the Air Force Satellite Control Network will also use the WGS in a similar manner as the DSCS III constellation is used to route ATM packets through the DISA "cloud" to establish command and control streams with various satellite constellations. One of the emerging applications is SATCOM-ON-The-Move which is now being extensively used on the military tactical vehicles for Blue Force Tracking and C3 missions.

Control segment

The Control segment refers to the satellite operators in charge of commanding and monitoring the satellite's bus and payload systems as well as managing the network operating over the satellite. Currently, as with the legacy DSCS constellation, bus commanding will be handled by the 3rd Space Operations Squadron out of Schriever AFB, Colorado. Payload commanding and network control will be handled by the Army 53rd Signal Battalion headquarterd at Peterson AFB, Colorado with subordinate elements A Co. at Ft. Detrick, Maryland, B Co. at Ft. Meade, Maryland, E Co. at Ft. Buckner ,Okinawa Japan, C Co. Landstuhl Germany, and , D Co. Wahiawa Hawaii.