Defence Update

The project to develop an OTHR network is being led by Air Commodore Joe Owens as Director General and directly responsible to the General Manager of the Defence Communications Systems Division, Mr Ian Maggs.

New contracts were negotiated late in 1986 with AWA to upgrade the existing facilities to operational status and enable them to provide a research and development test bed which will lead to the expansion of Jindalee into an integrated network providing a wide coverage capable of detecting any intruder in Australia’s air and sea space regions of interest. The surveillance net will range from central Western Australia across the northern part of the continent and beyond and out from central Queensland. The current OTHR will operate as an operational training facility, run by an Air Force unit with RAAF operators. Squadron Leader Peter Gamgee is the site manager at Alice Springs. The R&D aspect will mostly fall to the Defence Science and Technology Organization, whose scientists and engineers over many years gradually developed the outstanding Jindalee system.

While the upgrading (expected to cost about $57 million) has occupied top priority through late 1987, some clear idea of the possible new locations of the three additional OTHRs could be known in the first half of 1987, even if negotiations for purchase of sites takes somewhat longer. In rough terms, each site is expected to require an area about five kilometres long by three kilometres wide.

One new site is expected to be near the West Australian coast in the virinity of Geraldton, some 450km north of Perth. On the east coast or not far from it, another site appears to be required around the Rockhampton region, give or take 100km or so. The idea is to have the OTHR stations spaced east to west so as to minimise the effect of what is known as the dawn terminator Around dawn the ionosphere, from which the radar waves are bounced to gain over the horizon detection, can become unstable and disrupted. With only one OTHR blind spot can occur before the system gets back to normal as the ionosphere settles down after dawn. The spacing is designed to overcome this problem because the planned network will provide overlapping coverage. At present the Jindalee system at Alice Springs points north west to the major commercial air traffic routes out of Singapore and Malaysia.

There is one other planned new OTHR location that we have yet to mention. This is expected to be in the northwest, somewhere between the Kimberleys and Darwin. The systems will be able to triangulate and point their detecting equipment in different directions. Thus the three systems, other than the one in the east, will provide a heavy concentration in a sweep well out into the Indian Ocean and through the north west to the north and the north west where the Alice Springs station will overlap with the one in the central Queensland area.

In his announcement, Mr Beazley said an operational OTHR network would give Australia the capability to monitor activity over wide areas far in excess of that obtainable for the same cost from other systems. However, he said the decision to acquire an OTHR network in no way pre-empted future decisions on AEW&C systems for the Defence Force.

“The Government considers broad area surveillance of our northern approaches to be of the highest priority,” Beazley said. “The Dibb Review of Australia’s Defence Capabilities also noted the potential contribution of OTHR to this surveillance need and strongly recommended that further. Development proceed as soon as possible. This new development will, for the first time, enable us to monitor effectively aircraft and shipping movements in the remote northern approaches. ”

Because of the high priority attached by the Government, the Minister said a number of development phases would be undertaken concurrently. The experimental Jindalee radar at Alice Springs would be upgraded to provide a test bed for scientific, engineering and operational development over 5½ years. This was estimated to cost $57. 5 million. (The results of a special strategic study by former RAAF Air Commodore Tex Watson into all forms of surveillance and the formulation of a complete air defence plan are part of the OTHR requirement. Other radar systems Watson has examined included AEW, normal microwave ground radars and balloon-borne radars. )

The upgrading was necessary to enable the testing of important new features planned for incorporation into the new radars including new specialised transmitters, greater computing capacity and further development of the complex computer software. It would also enable Service operators to gain valuable operational experience on an OTHR in preparation for the new network.

“Concurrently studies will be undertaken to determine the number of new radars required, site locations, characteristics and equipment specifications,” Beazley noted. “While the sites for the operational radars have yet to be identified, current planning is for one or two radars to be sited in the north east and one in the west or southwest. This is a major undertaking. The first new operational radar is expected to enter service around the mid 1990s. ”

Beazley paid tribute to the Defence scientists and engineers of the Electronics Research Laboratory at Salisbury who had paved the way for the OTHR network development through their commitment and effort they had put into the Jindalee radar. “Jindalee is a unique Australian development which has placed Australia at the forefront of this type of technology,” he said. “A recent Defence Department review of the OTHR programme has found that the characteristics and potential capabilities of an Australian system are better suited to Australia’s strategic requirements than are systems based on American designs. ” But Beazley acknowledged the part played by the US in the development of the Jindalee system.

Stressing that the decision to build up an OTHR network did not in any way pre-empt future decisions on AEW&C systems, he said OTHA was needed irrespective of future decisions on AEW&C systems. “Proposals from aerospace industries for AEW&C systems have recently been submitted to the Department and these are now being evaluated,” Beazley said. ”This evaluation, a study into air defence systems currently being conducted within Defence (the Watson study) and ongoing experience with OTHR would guide future decisions on additional surveillance and control systems,” he added.

In a recent presentation, the Chief Defence Scientist, Professor Tom Fink (who retired in January 1987 to return to his academic career in Sydney), outlined that adequate surveillance of Australia’s region of direct military interest required covering thousands of kilometres in search of ship and air targets only a few metres long. Doing that by conventional radars or other means was beyond Australia’s financial resources, he said. But Over the Horizon Radars was a way out of the dilemma.

Professor Fink said the influence of the ionosphere on high frequency radio performance had been known for weir over 50 years. In the 1960s the possibility of its use for long-range radar for Australia was stimulated by observations made at Woomera SA of ionization effects associated with ballistic missile transit into and out of the atmosphere. In the early 1970s Australian defence scientists set up Project Geebung as a preliminary project involving ionospheric propagation of radio waves between Woomera and Broome WA. This enabled them to assess the feasibility of OTHRs.

Jindalee Stage A, a pilot OTHR, was set up at Alice Springs in 1974 to project a pencil beam towards Derby to obtain basic performance data. As Professor Fink explained, this was used against many targets, including civil air traffic to and from Singapore, to develop techniques and particularly, to check the reliability of ionospheric propagation. A successful Stage A resulted in Stage B starting at Alice Springs in 1979. It involved a major extension to test operation precepts. A facility was provided for swinging two beams within a quadrant relative to a north-westward-looking bore site. The scientists used a 2. 8km long receiving aerial to pick up the very weak return signals.

Professor Fink outlined that the Jindalee OTHR represented more than 15 years of R&D work by defence scientists and engineers at Salisbury SA. It incorporated advances made in response to Australia’s own surveillance requirements and also reflected the benefit of extensive contacts with OTHR specialists in the USA which were established through earlier collaborative activities. Fink said Australia was ahead of the USA in some important aspects, but not so far down the development road in others. For example, the US Air Force was well advanced with their first sectors of the continental air defence coverage. The US Navy was developing a separate system for naval operations, especially for use in the North Pacific.

He also explained the scientific background to Jindalee.

Conventional, so-called microwave, radars with wavelengths of centimetres had the same line of sight limitation as the eye; eg. they could not detect an aircraft intruding at 500ft until it was within 43km – or three minutes warning. Shining a microwave beam up to the ionosphere was useless because, like light, it would go straight through: Only the much longer radio wavelengths (tens of metres long) would be bent by the layers of the ionosphere; that is by layers of particles electrically charged by the energy of the sun. So outside the evident skip zone, typical ranges of illumination of targets, at all heights down to the earth’s surface, reach from 1000-1300km for a single bounce.

The next thing to look at was what was returned by way of reflected radiation. This is mostly- unwanted radar energy scattered back from the earth’s surface – as well as very weak target signals. The way around this was to cut out returns from all stationary objects and to pick up moving targets from the socalled ‘Doppler shift’ of frequency produced by target motion. (Fink explained this by saying that everyone knew about the change of sound when cars or trains passed by. This was the ‘Doppler shift’ of frequency). Signal processing skills of the highest order, together with powerful computers, then are needed to convert the minute radar returns into, say, aircraft tracks on a screen.

Because the doppler shift was produced by velocity components towards or away from the receiver, there were problems with aircraft flying precisely along tangents to all circles drawn from the receiver site. However other techniques were used to cope with that problem. A positive feature was that because OTHR used long wave lengths, stealth aircraft could not avoid detection.

Fink said as regards ship detection, the much slower speed of ships allowed them to be illuminated for longer, thus generating better data. The clutter returns from the moving sea – including its own dopplers – made ship detection more difficult. But DSTO scientists had made major breakthroughs in this area and had observed hundreds of vessels in recent years. This was a very promising area of development, the Chief Defence Scientist said. But he did issue a word of caution about the reliability of the ionosphere. What the sun gave, could also be taken away, at least in part. The sun subjected the ionosphere to variations with night and day, from season to season and of course to the eleven year sunspot cycle.

But Fink said Australia’s research in Stage B of Jindalee had demonstrated that the Australian ionospheric environment would support OTHA operations ‘quite reliably’. Australian scientists and engineers also had learnt how to develop the very complicated software required to give practical results.

“So Australia can now capitalise on years of investment in Over The Horizon Radar research,” he optimistically concluded.