AIR POWER DEVELOPMENT CENTRE BULLETIN

Jindalee—Bending RadaR Waves to its Will

The 2013 Defence White Paper outlines four principle tasks for the Australian Defence Force (ADF), the first of these being to deter and defeat armed attacks on Australia. The White Paper acknowledges that Australia’s geographic characteristics require a predominantly maritime strategy as a fundamental requirement to assure the security of its sovereign territories and national interests. The air-sea gap to the north of Australia covers millions of square kilometres and poses significant challenges for the ADF in maintaining situational awareness across this massive area. Australia’s Over-the-Horizon Radar (OTHR) network provides the ADF with the means to establish and maintain surveillance across Australia’s northern and western approaches. The three OTHRs that lie at the heart of the Jindalee Operational Radar Network (JORN) provide a layered surveillance system that covers the vital northern approaches. The effects delivered through JORN provide a clear demonstration of the air power characteristics of perspective, reach, penetration, responsiveness, flexibility, concurrent operations, concentration of force, and persistence.

Unlike conventional microwave radar, OTHR is not limited in range to the visual horizon. OTHR utilises the unique properties of a segment of the atmosphere known as the Ionosphere to ‘bounce’ emitting radio waves beyond visual ranges. The Ionosphere allows for the refraction of High Frequency (HF) electromagnetic emissions, or HF waves, back towards the surface of the Earth. When these refracted HF waves hit a metallic surface of sufficient size, either in the airborne or maritime environment, some of the energy is reflected back along

the transmission path to the OTHR receiver. The use of refracted HF beams negates the traditional limitations of line-of-sight caused by curvature of the earth, and allows OTHR to detect and track targets between 1000 and 3000 kilometres from the radar site. This perspective makes it difficult for ships or low-flying aircraft to operate in the air-sea gap undetected.

Reach and penetration are also important characteristics of OTHR. The reach of an airborne platform is characterised by the ability to project military power over long distances largely unconstrained by

physical barriers. OTHR’s unique operating method means that it is not constrained by limitations of aircraft, such as fuel, or by terrain and other physical barriers. From bases in Longreach, Alice Springs, Laverton and Adelaide, JORN can surveil the air-sea gap to Australia’s north without any restrictions.

OTHR does not ‘sweep’ its area of coverage in a manner similar to conventional radars; rather it focuses emitted energy

onto a particular area (or ‘tile’) through the utilisation of electronic beam steering. The tiles can be selected on the basis of long-term tasking requests, or can be moved quickly in response to intelligence queuing or a changing operating environment. The placement of each of these tiles requires a thorough understanding of the operating environment—the best results being achieved when JORN works cooperatively with intelligence agencies. JORN has a close relationship to intelligence for its optimised employment and is able to respond rapidly to changing operational requirements.

Tiles can be located across a very large geographic area, supporting multiple operations and searching for several

JORN Transmit Array

Issue 199, May 2013

We have developed in Australia the world’s most advanced long range radar, the Jindalee Over–the–Horizon Radar. A system of up to three new stations is being planned to allow around the clock surveillance of Australia’s vast northern approaches.

—Defence White Paper 1987.

target types. JORN has the capacity to detect vessels the size of Armidale Class patrol boats in the Torres Strait, then switch, within minutes, to tracking aircraft overflying oil rigs along the north-west shelf, or to supporting search and rescue activities near Darwin. No other surveillance capability within the ADF offers this level of responsiveness and flexibility. The capabilities of the three radars can also be concentrated to support high priority operations, with multiple, overlapping tiles providing high quality surveillance of a smaller area of interest.

Effective use of OTHR radar can create persistent effects by generating a knowledge base of activities across Australia’s northern approaches. This situational awareness allows the Australian Government and the ADF to maintain a level of information and decision superiority. Such an application of air power allows the achievement of a persistent effect in both the physical and virtual domains. OTHR’s physical persistence is broadly known, and widespread awareness of the RAAF’s JORN capability may shape the decision-making processes of those wishing to operate in Australia’s northern approaches. This persistent effect could influence the actions of potential adversaries if they are aware that their maritime and air activities across the north and west of Australia can be detected and tracked by the ADF at will.

OTHR does have limitations, and these must be taken into account when integrating its product into operational plans. OTHR is designed to detect vessels down to an Armidale Class patrol boat sized vessel, and air targets of a similar size to a BAE Hawk-127 aircraft. Targets of smaller size may not offer a sufficient radar cross-section to reflect HF energy back to the receiver. Additionally, the Ionosphere is a highly dynamic component of the atmosphere and presents additional difficulties. Diurnal

(day/night) and seasonal changes as well as solar activity such as solar flares result in Ionosphere inconsistencies, which can significantly impact the detection probability and characteristics of OTHR.

JORN’s embodiment of air power characteristics such as perspective, reach and penetration combine to give the ADF the capability to conduct surveillance across a wide geographic area. JORN provides the ADF with the ability to conduct persistent surveillance across Australia’s northern approaches and to respond rapidly to changing situations. The system’s flexibility allows surveillance efforts to be diverted quickly and effectively from one target or object to another, or from one area to another, in response to shifting priorities. Alternately, surveillance operations can be focused on a single area of high interest. JORN’s unique design and operating method make it integral to the delivery of air power to contribute to Australia’s national security.

Key Points

• The effects delivered through JORN exemplify the key air power characteristics of perspective, reach, penetration, responsiveness, flexibility, concurrent operations, concentration of force and persistence.

• The use of refracted HF beams negates traditional limitations of conventional radar systems caused by the curvature of the earth, and allows OTHR to detect and track targets between 1000 and 3000 kilometres from the radar site.

• JORN provides the ADF with the ability to conduct persistent surveillance across Australia’s northern approaches and to respond rapidly to changing situations.

Air Power Development CentreF3-GF, PO Box 7932, Department of Defence

CANBERRA BC ACT 2610Ph: 02 6128 7041 Fax: 02 6128 7053

Email: airpower@defence.gov.auWeb: www.airforce.gov.au/airpower

Disclaimer: The views in this Pathfinder are not necessarily those of the RAAF

OTHR focuses emitted energy on to selected footprints