Defence

Chief Information Officer

Tracking SATCOM

By SQNLDR Steve Warr & Kev Perks

Satellite Communications (SATCOM) is a capability used by the Australian Defence Force (ADF) to enable fast, efficient communication from locations that do not have stable communications infrastructure. ADF elements utilise satellite communications both at home and in combat.

How does SATCOM work and why is it an essential capability for the ADF?

The basic satellite system consists of a space segment and a ground segment. The space segment consists of the satellites plus control stations to maintain the satellites in orbit. Control stations are necessary to keep satellites operating in space. They provide constant checking of a satellites' status and, by sending commands, ensure that satellites stay in good health and in the correct orbit. The ground segment of the satellite system consists of all of the communications earth stations that access the operational satellite. These communications earth stations may include ships, aircraft and land forces.

Communications satellites are essentially radio relay stations orbiting the Earth that receive, amplify and re-transmit radio transmissions. Most communications satellites are placed in an orbit of approximately 36,000 kilometres above the equator known as the geostationary orbit. At this height the satellite is travelling at the same speed and direction as the Earth's rotation and will generally appear to be at a fixed location in the sky. A satellite at this height can view approximately one third of the Earth's surface; therefore, three satellites positioned equally around the geostationary orbit can view the majority of the Earth's populated areas.

The principle characteristic of military satellite communications is its flexible nature - it needs to be able to cope with a wide range of users and scenarios. It encompasses both high capacity links, which are fixed for strategic applications, and lower capacity links for mobile or tactical applications. In contrast to its civil counterparts, many parts of the system may be required to operate in hostile environments and are designed to withstand these.

Satellite communications is particularly attractive for military applications in that it provides a highly reliable, high capacity service over a wide coverage area. This service is available at short notice in virtually any part of the world without reliance on any national communications infrastructure. Communications can therefore be established in an environment with little or no communications infrastructure or in conditions where the local infrastructure is denied or deemed unreliable.

The ADF has been using satellites for communications for over 15 years. The use of satellites for telecommunications has distinct advantages over ground based alternatives. Satellite communication allows military users to operate in remote locations, sending and receiving large amounts of information. For the reasons stated, satellite communications has been especially useful for the ADF while operating in East Timor, the Gulf region and during the tsunami relief missions.

The ADF currently accesses a wide range of satellites to achieve substantial earth coverage. However, within the Asia Pacific region the OPTUS C1 satellite, launched and operationally accepted in 2003, underpins Defence's SATCOM capability. OPTUS C1 is a joint military and commercial satellite owned by Defence and SINGTEL OPTUS, which incorporates separate communications payloads for the civilian and military applications.

The unique features of satellite communications offer the ADF great flexibility and independence in responding rapidly to situations in a way that cannot be provided by other means of communication. This has ensured that the use of satellite communications is now embedded in to the ADF military doctrine and is considered to be a critical element of the defence infrastructure. The ADF has already made significant investment into securing satellite communications infrastructure for this decade. However, it is recognised that in a changing operational environment, Defence faces significant challenges in the immediate future if it is to retain the use of this essential service.

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