Jindalee Operational Radar Network

The roots of the JORN can be traced back to post World War II experiments in the United States and a series of Australian experiments at DSTO Edinburgh, South Australia[3] beginning in the early 1950s.

In 1969, The Technical Cooperation Program membership and papers by John Strath prompted development of a core "Over the Horizon" radar project.[3]

From July 1970 a study was undertaken; this resulted in a proposal for a program to be carried out, in three phases, to develop an over-the-horizon-radar system.[4][5]

The JORN project (JP2025) has had 5 phases,[15] and has cost approximately A$1.8 billion. The ANAO Audit report of June 1996 estimated an overall project cost for Phase 3 of $1.1 billion.[16] Phase 5 costs have been estimated at $70 million.[15] Phase 6 costs expect to be $1.2 billion.[14]

JORN consists of:

• three active radar stations: one near Longreach, Queensland (Radar 1), a second near Laverton, Western Australia (Radar 2), and a third near Alice Springs, Northern Territory (Radar 3);
• a control centre at RAAF Base Edinburgh in South Australia (JCC);
• seven transponders; and
• twelve vertical ionosondes distributed around Australia and its territories.[2]

DSTO previously used the radar station near Alice Springs, Northern Territory (known as Jindalee Facility Alice Springs) for research and development[17] and also has its own network of vertical/oblique ionosondes for research purposes.[2][18][19] The Alice Springs radar was fully integrated into the JORN during Phase 5 to provide a third active radar station.[17]

Each radar station consists of a transmitter site and a receiver site, separated by a large distance to prevent the transmitter from interfering with the receiver. The JORN transmitter and receiver sites are:

• the Queensland transmitter at Longreach,[20] with 90-degree coverage (23.658047°S 144.145432°E / -23.658047; 144.145432, also on OzGeoRFMap),
• the Queensland receiver at Stonehenge,[20] with 90-degree coverage (24.291095°S 143.195286°E / -24.291095; 143.195286, also on OzGeoRFMap),
• the Western Australian transmitter at Leonora,[20] with 180-degree coverage (28.317378°S 122.843456°E / -28.317378; 122.843456, also on OzGeoRFMap), and
• the Western Australian receiver at Laverton, with 180-degree coverage (28.326747°S 122.005234°E / -28.326747; 122.005234, also on OzGeoRFMap).

• the Alice Springs transmitter at Harts Range,[20][21] with 90-degree coverage (22.967561°S 134.447937°E / -22.967561; 134.447937, also on OzGeoRFMap), and
• the Alice Springs receiver at Mount Everard,[20][21] with 90-degree coverage (23.521497°S 133.677521°E / -23.521497; 133.677521, also on OzGeoRFMap).

The Alice Springs radar was the original 'Jindalee Stage B' test bed on which the design of the other two stations was based. It continues to act as a research and development testbed in addition to its operational role.

The Mount Everard receiver site contains the remains of the first, smaller, 'Jindalee Stage A' receiver. It is visible in aerial photos, behind the stage B receiver (23.530074°S 133.68782°E / -23.530074; 133.68782). The stage A transmitter was rebuilt to become the stage B transmitter.[5]

The high frequency radio transmitter arrays at Longreach and Laverton have 28 elements, each driven by a 20-kilowatt power amplifier giving a total power of 560 kW.[2] Stage B transmitted 20 kW per amplifier.[2] The signal is bounced off the ionosphere, landing in the "illuminated" area of target interest. Much incident radiation is reflected forward in the original direction of travel, but a small proportion "backscatters" and returns along the original, reciprocal transmission path. These returns again reflect from the ionosphere, finally being received at the Longreach and Laverton stations. Signal attenuation, from transmit antenna to target and finally back to receive antenna, is substantial, and its performance in such a context marks this system as leading-edge science. The receiver stations use KEL Aerospace KFR35 series receivers.[17] JORN uses radio frequencies between 5 and 30 MHz,[22][23][24] which is far lower than most other civilian and military radars that operate in the microwave frequency band. Also, unlike most microwave radars, JORN does not use pulsed transmission, nor does it use movable antennas. Transmission is Frequency-Modulated Continuous Wave (FMCW), and the transmitted beam is aimed by the interaction between its "beam-steering" electronics and antenna characteristics in the transmit systems. Radar returns are distinguished in range by the offset between the instantaneous radiated signal frequency and the returning signal frequency. Returns are distinguished in azimuth by measuring phase offsets of individual returns incident across the kilometres-plus length of the multi-element receiving antenna array. Intensive computational work is necessary to JORN's operation, and refinement of the software suite offers the most cost-effective path for improvements.

The JORN ionosonde network is made up of vertical ionosondes, providing a real time map of the ionosphere. Each vertical incidence sounder (VIS) is a standardized Single-Receiver "Digisonde" Portable Sounder built by Lowell for the JORN. A new ionospheric map is generated every 225 seconds.[19] In a clockwise direction around Australia, the locations of the twelve (11 active and one test) JORN ionosondes are below.

JORN Ionosondes[18][19]

The DSTO ionosonde network is not part of the JORN, but is used to further DSTO's research goals.[19] DSTO uses Four-Receiver Digisonde Portable Sounders (DPS-4), also built by Lowell.[2][18] During 2004 DSTO had ionosondes at the following locations.

DSTO Ionosondes[18]

From west to east, the seven JORN transponders are located at

• Christmas Island[2][17] (OzGeoRFMap),
• Broome, WA[2][25] (OzGeoRFMap),
• Kalumburu, WA[20] (OzGeoRFMap),
• Darwin, NT[2] (OzGeoRFMap),
• Nhulunbuy, NT[2][20] (OzGeoRFMap),
• Normanton, Qld[2][20] (OzGeoRFMap), and
• Horn island, Qld[2][20] (OzGeoRFMap).

All of the above sites (and many more that likely form part of the network) can be found precisely on the RadioFrequency Map,[26] which also lists the frequencies in use at each site.

The JORN network is operated by No. 1 Remote Sensor Unit (1RSU). Data from the JORN sites is fed to the JORN Coordination Centre at RAAF Base Edinburgh where it is passed on to other agencies and military units. Officially the system allows the Australian Defence Force to observe air and sea activity north of Australia to distances up to 4000 km.[27] This encompasses all of Java, Irian Jaya, Papua New Guinea and the Solomon Islands, and may include Singapore.[28] However, in 1997, the prototype was able to detect missile launches by China[29] over 5,500 kilometres (3,400 mi) away.

JORN is so sensitive it is able to track planes as small as a Cessna 172 taking off and landing in East Timor 2600 km away. Current research is anticipated to increase its sensitivity by a factor of ten beyond this level.

It is also reportedly able to detect stealth aircraft, as typically these are designed only to avoid detection by microwave radar.[9] Project DUNDEE[30] was a cooperative research project, with American missile defence research, into using JORN to detect missiles.[31] The JORN was anticipated to play a role in future Missile Defense Agency initiatives, detecting and tracking missile launches in Asia.[32]

As JORN is reliant on the interaction of signals with the ionosphere ('bouncing'), disturbances in the ionosphere adversely affect performance. The most significant factor influencing this is solar changes, which include sunrise, sunset and solar disturbances. The effectiveness of JORN is also reduced by extreme weather, including lightning and rough seas.[33]

As JORN uses the Doppler principle to detect objects, it cannot detect objects moving at a tangent to the system, or objects moving at a similar speed to their surroundings.[33]

JORN received an Engineering Heritage International Marker from Engineers Australia as part of its Engineering Heritage Recognition Program.[34]

• Cobra Mist
• Duga radar, a similar Russian system
• Imaging radar