• The PETRA module built at Daronmont's Mawson Lakes facility. Credit: Daronmont Technologies
    The PETRA module built at Daronmont's Mawson Lakes facility. Credit: Daronmont Technologies
  • The interior of the PETRA module, which is fully transportable, has multiple configurations. Credit: Daronmont Technologies
    The interior of the PETRA module, which is fully transportable, has multiple configurations. Credit: Daronmont Technologies

Passive radar has come a long way in a short space of time thanks to improvement in technology and an increased interest in applying this technology to military applications. Daronmont Technologies and DST Group are working together to produce a useful operational capability in this space for the ADF.

Unlike conventional radar systems that incorporate a transmission system to illuminate targets in the environment, passive radar systems utilise non-cooperative Radio Frequency transmitters in the environment such as commercial broadcasts and communications signals as the illumination source for target detection. Signals from these transmission sources are scattered by objects in the environment and received by a sophisticated receiving and signal processing system that detects and tracks targets in the environment.

DST Group’s National Security and ISR Division (NISD) have been actively developing an indigenous Passive Radar experimental capability over the last 10 years. Australia is not alone in seeking to develop this technology and academic institutions, defence researchers and commercial organisations in a number of countries, including the US, Germany and the UK are undertaking research.

Passive Radar is a form of bi-static radar where the system does not have its own transmitter and external transmitters (non-cooperative transmitters) in the environment are used for illumination of targets of interest.
“DST Group’s been working on passive radar technology for about 10 years and for the past six years we’ve been supporting them above the line with engineering resources to implement a real-time test bed for this technology,” Daronmont’s business development manager Lee Stanley explained to ADM.

The concepts of Passive Radar have been known since the 1930s, however the realisation of practical systems has only recently become viable. The wide spread introduction of digital broadcast and communications systems has provided sources that provide for superior performance when compared to older analogue transmission systems. Advances in computing now permit the necessary signal processing to be performed in real-time. These two developments have allowed the development of Passive Radar systems that provide real-time situational awareness of the air, land and maritime environments.

Broad application
“We can use television broadcast signals, commercial radio signals, mobile phone signals, we can essentially capture the reflections from those signals off targets and receive them to create a situational awareness picture like any other active radar does but without giving away the position of our receiver,” Stanley explained.

The primary role of Passive Radar is the generation of surveillance data to support situational awareness. The performance of Passive Radar does not support the generation of targeting information. However, it may be used to cue sensors (such as a Giraffe radar) that support targeting. Passive radars can sit in the background while targeting radars can ‘pop up’ as needed to complete the kill chain.

The interior of the PETRA module, which is fully transportable, has multiple configurations. Credit: Daronmont Technologies
The interior of the PETRA module, which is fully transportable, has multiple configurations. Credit: Daronmont Technologies

Daronmont have just signed a commercialisation agreement with DST Group that will see passive radar progressed for further testing and evaluation. Current trials systems started life in round 19 of the Capability Technology Demonstrator program and have grown well beyond the initial scope of work.

Daronmont has just delivered a Passive Experimental Transportable Radar (PETRA) system to DST Group. PETRA improves DST Group’s ability to deploy Passive Radar research systems, providing an advanced Passive Radar in a containerised solution that facilitates classified operations and enables multiple receive site integration and fusion experimentation. The radar system is housed in a lightweight, secure shelter that enables the system to be deployed for trials and experimentation to remote locations around Australia on land or sea, and abroad. PETRA is designed to be transportable by air (C-17, C-130), road or sea.

Benefits of Passive radar

Current interest in Passive Radar technology stems from the following benefits:
• Surveillance is covert, the location of the sensor is not revealed by RF transmissions
• Difficult to defeat with Electronic Attack due to inherent resistance to jamming
• Frequencies used may be more effective than conventional radar against low observable platforms that are optimised for signature reduction in the microwave band
• Can be used to detect targets that are not transmitting, conventional EW sensors rely on detecting the RF/EO emissions of the target
• Systems can operate when access to the RF spectrum for transmission is not available which may be a result of RADHAZ concerns or lack of bandwidth/licencing
• Continuous 360o surveillance permits higher track update rates to be achieved as there is no need to scan for targets as conventional radars do with rotating antenna and electronically steered beams.
• Alternately, the system can be configured for slower track update rate and longer integration time to increase the probability of detection of targets with small signatures.
• Relatively low cost, with no rotating elements, no transmitter, and low power requirements.

Daronmont’s latest generation lightweight air transportable shelter design forms the basis for the PETRA Operation Shelter. The shelter complies with the ISO 20’ shipping footprint and can be transported by road, air and maritime transport. To maintain TEMPEST control the shelter is designed to provide shielding effectiveness in excess of 60dB from 400kHz to 10GHz.

To simplify transportation the shelter has been specifically designed so that all peripheral equipment, e.g. air conditioners, antennas, masts and the generator, can be securely stowed in the shelter during transit.
The new Commercialisation Agreement in place with DST Group will allow both parties to mature the capability in partnership with users, such as the Army’s 16th Air Land Regiment, the Army's only ground-based air defence unit.

Air 6500
Passive Radar has been identified as one of the technologies of interest to projects like Air 6500. PETRA provides an ideal basis for considering possible architectures going forward. At a minimum the system would include the VHF and UHF radars that are currently included in PETRA.

Mobility has been identified as one of the principle design drivers for the Air 6500 solution elements. Daronmont’s experience with PETRA is that the Passive Radar electronic equipment does not require significant rack space and the existing implementation can be miniaturised. Active antennas can be used to reduce the physical size of the VHF and UHF antennas.
Additionally, advances in technology between now and the acquisition of Air 6500 will provide opportunities to reduce the volume of equipment even further with greater enhancements to mobility made possible.

Passive Radar signal processing software will continue to be enhanced by DST Group as further field trials and research are conducted. Daronmont’s commercialisation agreement with DST Group provides for the ongoing transfer of algorithm updates from DST Group into Daronmont’s product development activities.

ADM will continue to keep on eye on this technology and its possible applications in adjacent programs.

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