Conventional radar cannot see past the horizon, because the Earth curves away and the planet's bulge hides everything beyond. The Jindalee Operational Radar Network refuses to accept that limit. From a quiet patch of grazing country near Longreach, it fires high-frequency radio waves up at the ionosphere and lets them ricochet back down, reaching over the horizon to detect aircraft and ships thousands of kilometres away. One of its three transmitter sites sits out here in central-west Queensland, antennas stretched across the plain, listening to a sky that begins, in effect, somewhere over Indonesia.
Most military radars send out sharp microwave pulses and sweep with moving dishes. JORN does almost the opposite. It operates in the high-frequency band, uses no pulses and no moving antennas, and transmits a frequency-modulated continuous wave whose beam is steered electronically. The waves climb to the ionosphere, the electrically charged layer of the upper atmosphere, and bend back toward the surface far beyond the curve of the Earth. Distance is read from the frequency offset between the outgoing and returning signal; direction is read from tiny phase differences measured across a receiving antenna array kilometres long. The whole thing is less a searchlight than a vast, patient mathematical instrument, and refining its software remains the most cost-effective way to make it sharper.
JORN is not a single radar but a network, operated by the Royal Australian Air Force. Three active transmitter stations anchor it: Radar 1 near Longreach in Queensland, Radar 2 near Laverton in Western Australia, and Radar 3 near Alice Springs in the Northern Territory. The Queensland receiver sits at Stonehenge, south of here, with 90-degree coverage. Everything feeds back to the JORN Coordination Centre at RAAF Base Edinburgh in South Australia, run by No. 1 Remote Sensor Unit. Because the system reads the ionosphere itself, it carries its own web of vertical ionosondes scattered around the country, each redrawing a real-time map of the upper atmosphere roughly every four minutes so the radar knows exactly how the sky above it is behaving.
The numbers are startling. JORN monitors air and sea movements across some 37,000 square kilometres, with a normal operating range of 1,000 to 3,000 kilometres, enough to watch activity well to Australia's north. Officially it can observe out to about 4,000 km, taking in Java, New Guinea and the Solomon Islands. The system is sensitive enough to track an aircraft as small as a Cessna 172 taking off and landing in East Timor, 2,600 km away. In 1997 the prototype detected missile launches by China more than 5,500 km distant. Because stealth aircraft are shaped mainly to defeat microwave radar, JORN's high-frequency approach reportedly gives it a chance of seeing them too.
JORN's roots reach back to post-war experiments and a series of Australian ionospheric studies in the early 1950s, followed by Project Geebung and the decision to build the full network in October 1986. The road was rough. Telstra, with GEC-Marconi, signed a fixed-price contract in 1991 but ran into technical trouble and cost overruns, and the project passed to Lockheed Martin and Tenix, who delivered an operational system in April 2003. Later phases upgraded the radars and folded in Alice Springs, and in March 2018 BAE Systems Australia took on a further $1.2 billion, decade-long upgrade. All told, the program has cost on the order of $1.8 billion, an Australian-invented sentinel watching the northern approaches from the middle of the outback.
For all its reach, JORN is not omniscient. It depends entirely on the ionosphere, so anything that disturbs that layer disturbs the radar. Sunrise, sunset and solar storms all change how the signals bounce, and the system's performance shifts with them. Heavy weather hurts too: lightning and rough seas degrade what it can resolve. And because it relies on the Doppler principle, picking targets out by their motion toward or away from the array, it struggles to see objects moving crossways to the beam, or moving at the same pace as their surroundings. It is a remarkable instrument, but one married to the moods of the sky above Longreach.
The Longreach JORN transmitter site is near 23.66°S, 144.15°E, on flat plains roughly 25 km west of Longreach township; the associated receiver lies near Stonehenge to the south. This is an active Australian Defence Force facility, so treat the area as sensitive and avoid loitering or low passes over the antenna fields. From altitude, the long, regular antenna arrays are visible as linear cuttings across otherwise empty grazing land. Recommended transit altitude is normal cruise; the nearest sealed airport is Longreach (ICAO YLRE), about 12 nm east. Terrain is dead flat with sparse obstacles, but check NOTAMs and any restricted airspace before operating nearby, and expect strong summer heat haze over the plain.