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By Adam Baddeley, Deputy Editor, BATTLESPACE

Military Satellite Communications (MILSATCOM) represents a sine qua non for deployed forces. The US is transforming its satellite communications capabilities in parallel with its other military capabilities. They are addressing the need for both satellites and the terminals to meet requirements ranging from routine logistics and administrative traffic right up to secure communications capable of operating under a nuclear attack. Improvements also need to encompass the growing requirement for Satcom On the Move (SOTM) and Satcom On the Pause (SOTP). Other countries are equipping themselves with similar but much smaller scale capabilities and in the area of EHF are working with the US to leverage their future capacity.

Changing of the guard

The US provides MILSATCOM in three main areas – Narrow Band UHF, Protected EHF and Wideband SHF. Each is having its own significant upgrade of capability to provide transformational communications to the warfighter on land, sea –above and beneath – and air.

Today’s protected EHF communications provide secure survivable communications for the strategic mission and protected comms. For tactical users their role is dubbed the ‘Fed Ex’ of the satcom mission by the program office. The five current Milstar I/II satellites each provide up to 40Mbps throughput. These will be replaced by the Advanced EHF (AEHF) satellites each with 250Mbps throughput and backwards compatible with the Milstar Legacy. In basic terms, a Tomahawk Tasking Order of 0.03Mb takes 100 seconds using the Low Data Rate capability of Milstar 1 satellites with AEHF XDR (Extended Data Rate) throughput of an 8Mbps channel: this will be reduced to 0.03 seconds.

Initial Operating Capability is due in 2009 with the first of three funded ‘birds’ to be launched in 2006. With the AEHF programme, unlike its predecessor the US envisages international co-operation will enable allies to make use of it. The AEHF programme is being developed by the National Team of Lockheed Martin Space Systems and TRW Space & Electronics and is valued at $3.2billion.

Wideband satellite communications in the US today rely on the DSCS (Defense Satellite Communications System) III and the Raytheon Global Broadcast System (GBS) package aboard UFO (UHF Follow On) narrow band satellites. The former provides X-band only, anti-jam communications for tactical users around the world with five satellite and coverage areas supported by a further five satellites in residual orbit. GBS provides a one-way Ka band broadcast capability with three coverage beams. Raytheon is currently migrating the GBS architecture to IP/DVB along with automatic sharing and reallocation of bandwidth and has reduced the size, weight and cost of the Ground Receive Suite by half since it entered service.

In the next few years the Wideband Gapfiller Satellite (WGS) will provide a high capacity link with huge boosts to Army, Navy and Air Force users. With each satellite providing throughput of 2.4Gbps, Boeing – the prime contractor- has delivered twice the threshold requirements. This represents a twelve-fold increase over the 200Mbps from the DSCS II constellation. In its MDR (Medium Data Rate), the EHF Milstar II can provide a satcom throughput of 1.5Mbps.

A further key difference between the WGS and its predecessors is its ability to support airborne Intelligence Surveillance and Reconnaissance (ISR). The WGS will for the first time be able to provide single data rate links of 137Mbps to up to six Global Hawk UAVs – something not possible with Milstar, DCSC or AEHF satellites. It is worth noting that the DoD has concerns regarding balancing the AEHF satellites’ strategic and tactical roles.

The Airforce has a requirement for three satellites with options for three more. The first satellite is to be launched in 2004. WGS has a fourteen-year design life and is expected to have an 11.8-year mean mission du

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