Wideband Global SATCOM (WGS) Satellite, United States of America

The wideband global SATCOM (WGS) system, previously known as the wideband gapfiller satellite system, is a high-capacity communication satellite.

It is principally designed and developed for the US Department of Defence (DoD). The WGS systems feature digitally channelised transponded satellites that provide communication capacity, connectivity and flexibility to the US military forces.

These satellites operate in the programmed X and Ka-band frequency spectrum.

A team led by Boeing Integrated Defence Systems was awarded a contract to develop the WGS system in 2001. The contract was worth $160.3m, and is extendible up to $1.3bn. Under the contract, Boeing's team will supply the satellites, spacecraft, payload control equipment, logistics, training and sustained engineering support.

The WGS system enhances the DoD's communication services currently provided by the defence satellite communications system (DSCS) satellites and the global broadcast system (GBS) operating at ultra high frequency (UHF).

The system provides two-way X-band and Ka-band communications, as well as Ka-band broadcast services to US armed forces and other allied forces worldwide. The X-band satellites transfer data, photos and videos to troops on the battlefield. In January 2011, Boeing conducted ground test for a Ka-band SATCOM antenna system for installation in the spacecraft.

The WGS satellite communication system has six satellites divided into two blocks. Block I contains WGS-1, WGS-2 and WGS-3 satellites, while block II satellites include WGS-4, WGS-5 and WGS-6.

Under an MoU signed with the DoD in 2007, the Australian Government will provide A$927m (US$822.7m) in funding for ground infrastructure of the sixth WGS satellite. In return, the Australian Defence Ministry will be given access to the data sent by the sixth satellite. The sixth WGS satellite is being developed to increase the bandwidth capacity of US forces.

HX System (for mobiles and airborne / maritime communications) of Hughes Network Systems has obtained Wideband Global SATCOM (WGS) certification by the US Strategic Command in November 2010.

Wideband Global Satcom (WGS) satellites

The WGS system comprises three main segments: space, terminal and control.

The space segment refers to satellites in orbit. The WGS-1 was launched into orbit on 10 October 2007 on the United Launch Alliance (ULA) Atlas V launch vehicle. After the launch, the military designated the WGS-1 as USA-195. It entered service in April 2008. The WGS-1 satellite operates over the Pacific region.

In April 2009, Boeing successfully launched the WGS-2 into geostationary orbit on the Atlas V. The WGS-2 satellite was designated as USA-204. It entered into service in August 2009. The satellite operates in the Indian Ocean region and provides high-capacity communication links to the US troops in Iraq and Afghanistan.

Both satellites were launched from Space Launch Complex 41 of Cape Canaveral Air Force Base.

The WGS-3 satellite was delivered to Cape Canaveral Air Force Station, Florida, on 28 September 2009. It was launched successfully in December 2009 on a ULA Delta IV launch vehicle from Space Launch Complex 41. It is positioned over the Eastern Atlantic at an orbital slot of 12°> West longitude to operate in the Atlantic region.

The block II satellites WGS-4, WGS-5 and WGS-6 were scheduled to be launched in 2011, 2012 and 2013. Launch of WGS-4 has been postponed to 2012. They are being developed to meet the bandwidth requirements of warfighters thereby providing information exchange, enabling execution of tactical command and control, communications and computers, intelligence, surveillance, reconnaissance (C4ISR), battle management and combat support information.

Boeing received a $182m order from the US Air Force in August 2010 for the seventh wideband satellite under WGS Block II programme.

In September 2011, the US Air Force extended the order value to $1.09bn for production, launch and on-orbit activation of the seventh satellite and also to procure the long lead materials for an eighth WGS satellite.

Block II satellites will have a radio frequency bypass capability design to support airborne intelligence, surveillance and reconnaissance platforms that require ultra-high bandwidth and data rates demanded by unmanned aerial vehicles.

The terminal segment refers to the users of the communication services provided by the WGS system. The users of the WGS system include the Australian Defence Force and the US Army ground mobile terminals, the US Navy ships and submarines, national command authorities for the nuclear forces and various national security / allied national forces.

The satellite operators come under the control segment. The 3rd Space Operations Squadron (SOPS) located at Schriever AFB, Colorado, manages bus commanding of the DSCS constellation.

Payload commanding and network control are managed by the army's 53rd Signal Battalion at Peterson AFB, Colorado, with subordinate elements at seven locations. WGS-2 is operated by 3rd SOPS at 50th Space Wing, Schriever AFB, under the operational command of JFCC SPACE at Vandenberg.

Capacity of WGS satellites

WGS system provides 4.875GHz instantaneous switchable bandwidth. Around 500MHz of X-band and 1GHz Ka-band spectrum is allocated to WGS. Based on the mix of ground terminals, data rates and modulation schemes employed, each satellite of WGS system provides 2.1Gbps to 3.6Gbps of data transmission rates. Each WGS system has the capacity to supply ten times faster data transmission rates compared to DSCS service life enhancement programme (SLEP) satellites.

Connectivity of the US satellites

The breakage of uplink bandwidth into approximately 1,900 independently routable 2.6MHz subchannels by a digital channeliser has increased the connectivity between uplink and downlink coverage area.

The X and Ka bands are interconnected through a digital channeliser and provide better connectivity in WGS. The digital channeliser also offers multicast and broadcast services to support the network protocol.

The WGS satellites were built on a Boeing 702 spacecraft with 13kW of power and flexible coverage areas. The Boeing 702 uses advanced technologies in propulsion, power generation and thermal control. The spacecraft has the ability to connect X-band and Ka-band users within the coverage field of view through reconfigurable antennas and a digital channeliser.

Rocket launcher and orbital launch vehicles used

The Atlas V is equipped with 4m-diameter payload fairing, two solid rocket motors and a single-engine Centaur upper stage attached to a single common core booster (CCB) powered by a RD-180 engine.

The Delta IV is an orbital launch vehicle equipped with 5m diameter payload fairing, three CCBs powered by a Rocketdyne RS-68 engine. It is available in different medium models & ndash; medium+ (4,2), medium+ (5,2) and medium+ (5,4) and heavy. The models are differentiated depending on the specific payload size and weight ranges.

Ground station for the US Wideband Global Satcom (WGS) satellites

The satellites launched into orbit are controlled through four army wideband satellite operations centres (WSOCs) on the ground, using ground equipment hardware and software developed by Boeing, ITT Industries and Raytheon.

Three satellites operating in X-band and Ka-band can be controlled and tracked by a global satellite configuration and control element (GSCCE) using telemetry tracking and command links (TT&C) system.

The telemetry tracking and command system is a technology primarily used to track and control the satellite from deviating its orbit.

The third SOPS controls the spacecraft platform using unique software and databases designed by Boeing, and fitted on the command and control segment consolidated (CCS-C) systems supplied by Integral Systems.

Boeing's team of contractors includes Harris Corporation, ITT Industries, Logicon and SAIC.

Harris provides satellite communications ground terminals and terminal and payload interfaces, and ITT Industries supplies communications network and control systems. Logicon provides communications software and SAIC extends engineering and communications architectures.