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{{cite video|url=https://www.youtube.com/watch?v=LI8zmnls-aM |archive-url=https://ghostarchive.org/varchive/youtube/20211213/LI8zmnls-aM |archive-date=2021-12-13 |url-status=live|title=DST |work= Jindalee Operational Radar Network (JORN)|quote=1950s: Early research into high frequency RADAR at DSTO Edinburgh reveals potential for over the horizon surveillance.}}{{cbignore}} 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.

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.[http://www3.austlii.edu.au/au/other/dfat/treaties/1997/29.html "Project Arrangement between the Government of Australia and the Government of the United States of America on Data Fusion for Over-the-Horizon Radar ATS 29 of 1997"] {{Webarchive|url=https://web.archive.org/web/20170416125818/http://www3.austlii.edu.au/au/other/dfat/treaties/1997/29.html |date=16 April 2017 }}. Australasian Legal Information Institute, Australian Treaties Library. Retrieved on 15 April 2017.{{citation |url= http://trove.nla.gov.au/work/19292409?selectedversion=NBD6206931 |title= The Development of Over-the-Horizon Radar in Australia |author= D.H. Sinnott |volume= 90 |pages= 16099 |publisher= Defence Science and Technology Organisation, Australian Department of Defence |date= 1988 |work= DSTO Bicentennial History Series |isbn= 0-642-13561-4|bibcode= 1989STIN...9016099S }}

Phase 1, Project Geebung, aimed to define operational requirements for an OHR and study applicable technologies and techniques. The project carried out a series of ionospheric soundings evaluating the suitability of the ionosphere for the operation of an OTHR.

Phase 2, Project Jindalee, aimed at proving the feasibility and costing of OHR. This second phase was carried out by the Radar Division, (later, the High Frequency Radar Division), of the Defence Science and Technology Organisation (DSTO). Project Jindalee came into being during the period 1972–1974 and was divided into three stages.

Stage 'A' commenced in April 1974. It involved the construction of a prototype radar receiver at Mount Everard, (near Alice Springs), a transmitter (at Harts Range, {{convert|160|km|disp=or}} away) and a beacon in Derby. When completed (in October 1976) the Stage A radar ran for two years, closing in December 1978. Stage A formally ended in February 1979, having achieved its mission of proving the feasibility of OTHR. The success of stage A resulted in the construction of a larger stage 'B' radar, drawing on the knowledge gained from stage A.

Stage 'B' commenced on 6 July 1978. The new radar was constructed next to the stage A radar. Developments during stage B included real time signal processing, custom built processors, larger antenna arrays, and higher power transmitters, which resulted in a more sensitive and capable radar.

• The first data was received by stage B in the period April–May 1982,
• the first ship was detected in January 1983, and
• an aircraft was automatically tracked in February 1984.

Trials were carried out with the Royal Australian Air Force during April 1984, substantially fulfilling the mission of stage B, to demonstrate an OHR operating in Australia. Another two years of trials were carried out before the Jindalee project officially finished in December 1985.

Stage 'C' became the conversion of the stage B radar to an operational radar. This stage saw substantial upgrades to the stage B equipment followed by the establishment of No. 1 Radar Surveillance Unit RAAF (1RSU) and the handover of the radar to 1RSU. The aim was to provide the Australian Defence Force with operational experience of OHR.{{cite conference |first= Samuel B.(Bren) |last= Colegrove |title= Project Jindalee: From Bare Bones To Operational OTHR |book-title= IEEE International Radar Conference - Proceedings |pages= 825–830 |publisher= IEEE |year= 2000 |doi= 10.1109/RADAR.2000.851942 }}

Phase 3 of the OTHR program was the design and construction of the JORN. The decision to build the JORN was announced in October 1986. Telstra, in association with GEC-Marconi, became the prime contractor and a fixed price contract for the construction of the JORN was signed on 11 June 1991. The JORN was to be completed by 13 June 1997.

Telstra was responsible for software development and systems integration, areas in which it had no previous experience. GEC-Marconi was responsible for the HF Radar and related software aspects of the project, areas in which it had no previous experience.{{cite web |title= Jindalee Over-the-Horizon Project (JORN) : Extract from a Channel 9 television program broadcast on 23rd March 1997 |date= 23 March 1997 |publisher= ourcivilisation.com |access-date= 20 March 2014 |url= http://www.ourcivilisation.com/decline/jindalee.htm }} Other unsuccessful tenderers for the project included experienced Australian software development and systems integration company, BHP IT, and experienced Australian defence contractor AWA Defence Industries. Both of these companies are no longer in business.{{cite web |title= BHP IT purchase propels CSC to No. 2 |date= 5 June 2000 |author= Natasha David |publisher= Computerworld|access-date= 20 March 2013 |url= http://www.ourcivilisation.com/decline/jindalee.htm }}

By 1996, the project was experiencing technical difficulties and cost overruns.{{cite web|first=Ray |last=McNally |title=Jindalee Operational Radar Network: Department of Defence |work=The Auditor-General Performance Audit Audit Report No.28 1995–96 |publisher=Australian National Audit Office|date=18 August 1996 |url=http://www.anao.gov.au/WebSite.nsf/Publications/4A256AE90015F69B4A25690A002479D2/$file/rpt28-96.pdf |access-date=2006-11-17 |archive-url=https://web.archive.org/web/20060917204646/http://anao.gov.au/WebSite.nsf/Publications/4A256AE90015F69B4A25690A002479D2/%24file/rpt28-96.pdf |archive-date=17 September 2006 |url-status=dead}} Telstra reported a {{AUD|609-million|link=yes}} loss and announced that it could not guarantee a delivery date.{{cite web |url= http://defence-data.com/features/fpage37.htm |title= JORN assures early warning for Australia |access-date=2006-11-15 |last=Sinclair-Jones |first=Michael |date=29 February 2000 |work=Defence Systems Daily |publisher=Defence Data Ltd. |url-status= usurped |archive-url = https://web.archive.org/web/20071116065249/http://defence-data.com/features/fpage37.htm |archive-date = 2007-11-16}}

The failed Telstra contract prompted the project to enter a fourth phase.

Phase 4 involved the completion of the JORN and its subsequent maintenance using a new contractor. In February 1997 Lockheed Martin and Tenix received a contract to deliver and manage the JORN. Subsequently, during June 1997 Lockheed and Tenix formed the company RLM Group to handle the joint venture.{{cite web|url=http://www.rlmgroup.com.au |title=RLM Group web site |url-status=dead |archive-url=https://web.archive.org/web/20060823233508/http://www.rlmgroup.com.au/ |archive-date=23 August 2006 }} An operational radar system was delivered in April 2003, with maintenance contracted to continue until February 2007.{{cite web |url=http://www.defence.gov.au/dmo/esd/jp2025/jp2025.cfm |title=Projects: JP 2025 - Jindalee Operational Radar Network (JORN) |access-date=2006-11-15 |last=Thurston |first=Robin |date=21 June 2006 |work=Defence Materiel Organisation Website |publisher=Department of Defence |url-status=dead |archive-url=https://web.archive.org/web/20061003193001/http://www.defence.gov.au/dmo/esd/jp2025/jp2025.cfm |archive-date=3 October 2006}}

In August 2008, Lockheed Martin acquired Tenix Group's interest in RLM Holdings.{{cite web |url=https://www.lockheedmartin.com.au/au/news/press-releases/2008-releases/0825-rlm.html |title=Lockheed Martin Completes Acquisition of Tenix Group's Interest in Australia-Based RLM Holdings|website=Lockheed Martin|access-date=2018-04-01}}

As a consequence of the duration of its construction, the JORN delivered in 2003 was designed to a specification developed in the early 1990s. During this period the Alice Springs radar had evolved significantly under the guidance of the Defence Science & Technology Organisation. In February 2004 a fifth phase of the JORN project was approved.

Phase 5 aimed to upgrade the Laverton and Longreach radars to reflect over a decade of OTHR research and development. It was scheduled to run until approximately the year 2011, but was completed around 2013/2014 due to skills shortage. All three stations are now similar, and use updated electronics.[http://aviationweek.com/technology/australia-s-jindalee-radar-system-gets-performance-boost Australia’s Jindalee Radar System Gets Performance Boost] Aviation Week & Space Technology, 22 September 2014. Accessed: 24 September 2014. [https://web.archive.org/web/20140924211311/http://aviationweek.com/technology/australia-s-jindalee-radar-system-gets-performance-boost Archived] on 24 September 2014

In March 2018 it was announced that BAE Systems Australia would undertake the $1.2{{nbsp}}billion upgrade to Australia’s Jindalee Operational Radar Network, which was expected to take 10 years to complete.{{Cite news|url=https://www.pyneonline.com.au/media-centre/media-releases/boon-for-australian-defence-industry-as-our-jorn-gets-an-upgrade|title=Boon for Australian defence industry as our JORN gets an upgrade|last=Pyne|first=Christopher|authorlink=Christopher Pyne|work=pyneonline.com.au|access-date=2018-05-15|language=en}}{{Update inline|date=April 2024}}

The JORN project (JP2025) has had 5 phases,{{cite web |title= JP 2025 - Jindalee Operational Radar Network (JORN) |work= Projects |publisher= Defence Materiel Organisation, Australian Department of Defence |date= 15 July 2009 |first= Gary |last= Saun |access-date= 19 March 2014 |url= http://www.defence.gov.au/dmo/esd/jp2025/jp2025.cfm |url-status= dead |archive-url= https://web.archive.org/web/20061003193001/http://www.defence.gov.au/dmo/esd/jp2025/jp2025.cfm |archive-date= 3 October 2006}} and has cost approximately $1.8{{nbsp}}billion.{{citation needed|date=March 2014}} The ANAO Audit report of June 1996 estimated an overall project cost for Phase 3 of $1.1{{nbsp}}billion.{{cite web |title= Department of Defence : Jindalee Operational Radar Network : Performance Audit |work= Audit Report No. 28 1995–96 : Summary |publisher= Australian National Audit Office (ANAO) |date= 18 June 1996 |access-date= 19 March 2014 |url= http://www.anao.gov.au/~/media/Uploads/Documents/audit%20rep%2028%2095%2096%20summ.doc |url-status= dead |archive-url= https://web.archive.org/web/20140212181215/http://www.anao.gov.au/~/media/Uploads/Documents/audit%20rep%2028%2095%2096%20summ.doc |archive-date= 12 February 2014}} Phase 5 costs have been estimated at $70{{nbsp}}million. Phase 6 costs expect to be $1.2{{nbsp}}billion.

On 18 March 2025, Canadian prime minister Mark Carney announced the AU$6.5 billion purchase of JORN radar technology by Canada, for deployment over the Arctic.{{cite web|url=https://www.abc.net.au/news/2025-03-19/canada-snuck-past-trump-buy-jorn-defence-radar/105069292|date=19 March 2025|author=Andrew Greene|title=Australia's 'biggest defence export' was meant to go to the US first, but Canada snuck past Donald Trump|website=Australian Broadcasting Corporation}}

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.

DSTO previously used the radar station near Alice Springs, Northern Territory (known as Jindalee Facility Alice Springs) for research and development{{cite journal |last=Wise |first=John C. |title=Summary of recent Australian radar developments |journal=IEEE Aerospace and Electronic Systems Magazine |volume=19 |issue=4 |pages=8–10 |publisher=IEEE |date=December 2004 |doi=10.1109/MAES.2004.1374061 |s2cid=25857760 }} and also has its own network of vertical/oblique ionosondes for research purposes.{{cite web |url=http://ulcar.uml.edu/slist.htm |title=Digisonde Station List |access-date=2006-11-29 |date=February 2004 |publisher=University of Massachusetts Lowell, Center for Atmospheric Research}}{{cite conference |first=R.S. |last=Gardiner-Garden |title=Ionospheric variability in sounding data from JORN |book-title=Workshop on the Applications of Radio Science (WARS) |date=February 2006 |location=Leura, NSW |url=http://www.ips.gov.au/IPSHosted/NCRS/wars/wars2006/proceedings/poster/gardiner_garden_p.ppt |access-date=2006-11-29 |archive-date=27 August 2006 |archive-url=https://web.archive.org/web/20060827173010/http://www.ips.gov.au/IPSHosted/NCRS/wars/wars2006/proceedings/poster/gardiner_garden_p.ppt |url-status=dead }}

The Alice Springs radar was fully integrated into the JORN during Phase 5 to provide a third active radar station.

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,{{cite journal |last=Hill |first=Senator Robert |title=Defence: Properties (Question No. 2685) |journal=Senate Official Hansard |volume=6, 2004 |issue=Fortieth Parliament, First Session–Eighth Period |pages=23144 |publisher=Commonwealth of Australia |date=12 May 2004 |url=http://www.aph.gov.au/hansard/senate/dailys/ds120504.pdf |access-date=2006-11-28 |url-status=dead |archive-url=https://web.archive.org/web/20060902220438/http://www.aph.gov.au/hansard/senate/dailys/ds120504.pdf |archive-date=2 September 2006}} with 90-degree coverage ({{coord |23.658047|S |144.145432|E |region:AU_scale:25000 |display=inline}}),
• the Queensland receiver at Stonehenge, with 90-degree coverage ({{coord |24.291095|S| 143.195286|E |region:AU_scale:25000 |display=inline}}),
• the Western Australian transmitter at Leonora, with 180-degree coverage ({{coord |28.317378|S |122.843456|E |region:AU_scale:25000 |display=inline}}), and
• the Western Australian receiver at Laverton, with 180-degree coverage ({{coord |28.326747|S |122.005234|E |region:AU_scale:25000 |display=inline}}).
• the Alice Springs transmitter at Harts Range,Erwin Chlanda, [http://www.alicespringsnews.com.au/1113.html Nowhere To Hide When Alice's Radar Zeroes In], [http://www.alicespringsnews.com.au/ Alice Springs News], 28 April 2004 with 90-degree coverage ({{coord |22.967561|S |134.447937|E |region:AU_scale:25000 |display=inline}}), and
• the Alice Springs receiver at Mount Everard, with 90-degree coverage ({{coord |23.521497 |S|133.677521|E |region:AU_scale:25000 |display=inline}}).

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 ({{coord |23.530074|S |133.68782|E|region:AU_scale:10000 |display=inline}}). The stage A transmitter was rebuilt to become the stage B transmitter.

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. Stage B transmitted 20 kW per amplifier. 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 [https://web.archive.org/web/20061208194846/http://www.kel.com.au/ KEL Aerospace] KFR35 series receivers. JORN uses radio frequencies between 5 and 30 MHz,{{cite web|url=http://www.kel.com.au/products/kpr35c1.htm|title=Specification: KPR35C1 HF Radar Receiver|access-date=2006-11-29|work=KEL Aerospace website|publisher=KEL Aerospace|quote=RF Input Frequency Range: 5 to 30 MHz}}{{cite web|url=http://www.kel.com.au/products/kpr35c2.htm|title=Specification: KPR35C2 HF Radar Receiver|access-date=2006-11-29|work=KEL Aerospace website|publisher=KEL Aerospace|quote=RF Input Frequency Range: 5 to 30 MHz}}{{cite web|url=http://www.kel.com.au/products/kpr35c3.htm|title=Specification: KPR35C3 HF Radar Receiver|access-date=2006-11-29|work=KEL Aerospace website|publisher=KEL Aerospace|quote=RF Input Frequency Range: 5 to 30 MHz}} 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,{{cite web |title=Background to Ionospheric Sounding |website=University of Massachusetts Lowell Space Science Lab |url=https://ulcar.uml.edu/digisonde_dps.html |access-date=2024-07-22}} built by University of Massachusetts Lowell for the JORN. A new ionospheric map is generated every 225 seconds. In a clockwise direction around Australia, the locations of the twelve (11 active and one test) JORN ionosondes are below.

;JORN Ionosondes

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

;DSTO Ionosondes

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

• Christmas Island ([http://maps.spench.net/rf/#pos=-10.4406252,105.675143&zoom=12&type=hybrid&auto_fetch=true&clustering=true&cluster_level=16&site=68332 OzGeoRFMap]),
• Broome, WA{{cite conference|first=Ben A.|last=Johnson|author2=Dr. Yuri Abramovich|title=Detection-estimation of Gaussian sources for under-sampled training conditions: Practical HF OTHR application results|book-title=Adaptive Sensor Array Processing (ASAP) Workshop|pages=24|publisher=Massachusetts Institute of Technology Lincoln Laboratory|date=6–7 June 2006|location=Lexington, Massachusetts|url=http://www.ll.mit.edu/asap/asap_06/pdf/Presentations/04_Johnson-P.pdf|access-date=2006-11-29|archive-date=3 June 2011|archive-url=https://web.archive.org/web/20110603231423/http://www.ll.mit.edu/asap/asap_06/pdf/Presentations/04_Johnson-P.pdf|url-status=dead}} ([http://maps.spench.net/rf/#pos=-17.8983354,122.2590636&zoom=11&type=hybrid&auto_fetch=true&clustering=true&cluster_level=16&site=49931 OzGeoRFMap]),
• Kalumburu, WA ([http://maps.spench.net/rf/#pos=-14.2912545,126.6452112&zoom=16&type=hybrid&auto_fetch=true&clustering=true&cluster_level=16&site=44767 OzGeoRFMap]),
• Darwin, NT ([http://maps.spench.net/rf/#pos=-12.4419079,130.9596515&zoom=17&type=hybrid&auto_fetch=true&clustering=true&cluster_level=16&site=28451&filter=%5B%7B%22freq%22%3A25000000%2C%22freq_range%22%3A25000000%7D%5D&q=0-50mhz OzGeoRFMap]),
• Nhulunbuy, NT ([http://maps.spench.net/rf/#pos=-12.164382,136.7764342&zoom=13&type=hybrid&auto_fetch=true&clustering=true&cluster_level=16&site=54255 OzGeoRFMap]),
• Normanton, Qld ([http://maps.spench.net/rf/#pos=-17.6957147,141.0750269&zoom=16&type=hybrid&auto_fetch=true&clustering=true&cluster_level=16&site=39330 OzGeoRFMap]), and
• Horn island, Qld ([http://maps.spench.net/rf/#pos=-10.5909833,142.2914219&zoom=10&type=hybrid&auto_fetch=true&clustering=true&cluster_level=16&site=55610 OzGeoRFMap]).

All of the above sites (and many more that likely form part of the network) can be found precisely on the RadioFrequency Map,[http://wiki.spench.net/wiki/JORN Australian Geographical RadioFrequency Map] 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 {{convert|4000|km}}.{{cite web|url=http://www2.rfsworld.com/StayConnected/pdf/Stay2_98.pdf |title=JORN HF Antenna Arrays Project Completed |access-date=2006-11-21 |last=Styles |first=Barry |date=1998 |issue=2 |work=Stay Connected: The Radio Frequency Systems Bulletin |publisher=Radio Frequency Systems (RFS) |pages=11–12 |quote=RFS Australia proudly completes the USD25M Antenna Arrays for the Jindalee Operational Radar Network on time, on budget and within specification. Jindalee Over the Horizon Radar Network (JORN) is a High Frequency network that is designed to and sea radar coverage of up to 4,000 km from a large part of the Australian coastline. |url-status=dead |archive-url=https://web.archive.org/web/20120206003705/http://www2.rfsworld.com/StayConnected/pdf/Stay2_98.pdf |archive-date=6 February 2012 }} This encompasses all of Java, New Guinea and the Solomon Islands, and may include Singapore.{{cite news|url=http://www.abc.net.au/worldtoday/content/2010/s3094895.htm|title=Rough seas could have impeded boat detection: Analyst|publisher=ABC The World Today|date=16 December 2010|quote=There's two layers if you like of radar surveillance. One is what's called the JORN system, which is a very, very long range strategic early warning system, that's capable of detecting targets as far away as, we think, Singapore.}}

However, in 1997, the prototype was able to detect missile launches by China{{cite web|url=http://www.strategypage.com/htmw/htecm/articles/20041031.aspx|title=Electronic Weapons|access-date=2006-11-21|date=2004-10-31|work=Strategy Page|publisher=StrategyWorld.com|quote=In 1997, the prototype JORN system demonstrated the ability to detect and monitor missile launches by Chinese off the cost of Taiwan, and to pass that information onto U.S. Navy commanders.}} over {{convert|5500|km}} away.

JORN is so sensitive it is able to track planes as small as a Cessna 172 taking off and landing in East Timor {{convert|2600|km}} away.{{Citation needed|date=December 2014}} Current research is anticipated to increase its sensitivity by a factor of ten beyond this level.{{Citation needed|date=December 2014}}

It is also reportedly able to detect stealth aircraft, as typically these are designed only to avoid detection by microwave radar. Project DUNDEE{{cite web|url=http://missilethreat.com/systems/project_dundee_.html |archive-url=https://web.archive.org/web/20051223112826/http://missilethreat.com/systems/project_dundee_.html |url-status=dead |archive-date=23 December 2005 |title=Project DUNDEE |access-date=2006-11-21 |date=1 August 2004 |work=MISSILETHREAT.com |publisher=The Claremont Institute }} was a cooperative research project, with American missile defence research, into using JORN to detect missiles.[https://web.archive.org/web/20090714020131/http://www.mda.mil/mdalink/html/dndenews.html U.S. And Australia Cooperate In Missile Detection], [http://www.mda.mil/ Missile Defense Agency] {{webarchive|url=https://web.archive.org/web/20060301165436/http://www.mda.mil/ |date=1 March 2006 }} The JORN was anticipated to play a role in future Missile Defense Agency initiatives, detecting and tracking missile launches in Asia.{{cite news|first=Brendan|last=Nicholson|title=Australia's key role in missile shield|url=http://www.theage.com.au/news/national/australias-key-role-in-missile-shield/2006/01/06/1136387625745.html|work=The Age|publisher=Fairfax|date=7 January 2006|access-date=2006-11-18}}

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.{{cite web |title= Fact Sheet: Jindalee Operational Radar Network |publisher= Royal Australian Air Force |url= https://www.airforce.gov.au/docs/JORN_Fact_Sheet.pdf |access-date= 1 January 2015 |archive-url= https://web.archive.org/web/20121016084041/https://www.airforce.gov.au/docs/JORN_Fact_Sheet.pdf |archive-date= 16 October 2012 |url-status= live }}

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.

JORN received an Engineering Heritage International Marker from Engineers Australia as part of its Engineering Heritage Recognition Program.{{cite web

| url = https://portal.engineersaustralia.org.au/heritage/jindalee-over-horizon-radar

| title = Jindalee Over-the-horizon Radar

| publisher = Engineers Australia

| access-date = 2020-05-02

}}

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

{{reflist}}

Category:Military equipment of the Royal Australian Air Force

Category:Defence Science and Technology Organisation

Category:Over-the-horizon radars

Category:Recipients of Engineers Australia engineering heritage markers

Category:Australian inventions

Category:Air defence radar networks