Silent guardians: portable passive sensors close tactical gap in electronic warfare

Detecting and analysing radar and communication signals is one of the most important tasks of today's armed forces. High-tech equipment is needed across all domains to gather as much information as possible about enemy activities and potential threats. A high level of situational awareness and a clear picture of the situation are the basis for making the right strategic and tactical decisions and ultimately protecting as many lives as possible. The rapid pace of technological change is a major challenge here. More and more signals are being produced and more and more technology is trying to hide, detect or deliberately manipulate these signals. The fact is: Only those who can quietly collect as much data as possible and classify or analyse it in a very short time will be ahead of the enemy.

A central problem in the procurement of data is one's own visibility. "Anyone who uses radars to detect targets also reveals their own location. With passive sensors, on the other hand, you can observe the enemy’s signals without becoming an emitter yourself. And it is precisely this capability that is becoming increasingly relevant in electronic warfare," explains Mathew Willmot, Sales Director for Sirius Compact at the Swedish defence company Saab. For decades, the company has been developing and producing complex systems of passive sensors for ships, vehicles and aircraft. Today, Saab is regarded as a one of the market leaders in the field of Signals Intelligence (SIGINT) and Electronic Support Measures (ESM). So, it's no wonder that the latest achievement in the field of passive sensors also comes from Saab: Sirius Compact is the name of the modular and scalable, lightweight passive Electronic Warfare (EW) sensor that has been on the market for just under two years and is already in series production. The sensor is an answer to the increasing challenges of surveillance at all levels of tactical operations and can be used stand-alone, in a sensor network or as a supplement to existing sensors. Compared to larger static solutions, Sirius Compact can be placed anywhere by an operator and its range is scalable depending on the situation.

A lightweight contender with a 360° view

Sirius Compact is available in a number of configurations depending on the application, the smallest variant is just 35 cm high, has a diameter of 15 cm and weighs no more than three kilograms. The system therefore fits in any backpack and is easy to transport. The system has an integrated IMU/GNSS sensor to provide the positional data and has a power requirement of less than 60 W - it is powered by batteries carried by the soldier; or via the host platform. Mounted on a tripod, Sirius Compact can be positioned virtually anywhere on the ground, but the sensor can also be integrated on drones, vehicles or smaller boats such as Saab's Combat Boat 90 (CB90) or an Unmanned Surface Vessel (USV).

Sirius Compact provides individuals and small units with instant situational awareness - where and when you need it. "The move towards portable systems that are intuitive to use and do not require years of specialist training is a response to the need for mobile and flexible real-time intelligence-gathering capabilities and new possibilities in tactical electronic warfare," explains Willmot. The existing expertise from more complex systems has been incorporated into the development of Sirius Compact. With 360° azimuth coverage, radar and data link emissions in the 1-18 GHz frequency range can be instantaneously detected from any direction. The platform and data link independence is also particularly relevant for armed forces - the sensor can therefore be easily integrated into existing networks and platforms.

Magic triangle enables precise geolocation

Even a single sensor improves the situational awareness of troops - with three or more sensors, precise geolocation through triangulation is possible with a bearing accuracy of less than 2° rms (root mean square). It is important that the sensors are positioned at an appropriate distance and that height differences in the terrain are also taken into account. Since the product came onto the market almost two years ago, Saab has carried out a large number of tests and customer demonstrations that show the impressive performance of the compact sensors - even in extreme wind and weather conditions. For example, an aircraft taking off 200 kilometres away could be detected at a distance of 190 kilometres - as soon as it appeared over the radio horizon with very accurate Direction Finding (DF). During the entire detection and analysis process, the potentially hostile aircraft did not receive a single signal from the sensor - so the enemy does not know that it has been detected.

Sirius Compact was also shown to perform reliably on a fast-maneuvering combat boat in challenging weather conditions. The performance as well as the ease of use of the TRS Lite (Tasking & Reporting System) software have not only been confirmed by Saab itself. The sensors were put through their paces in an independent test by major military organisations. After a brief introduction, the infantry troops were able to set up the sensor themselves in just a few minutes and were impressed by its immediate operational capability and simple operation. "The product naturally benefits from our expertise in the field of signals intelligence. The challenge is not only to make highly technological devices as small and mobile as possible, but also to ensure that the performance is not limited," explains Mathew Willmot, Sales Director for Sirius Compact.

Managing the threat situation

Detecting signals is the first step in obtaining situational awareness. In a second step, the identified signals must be analysed and classified. The threat libraries of armed forces contain enormous amounts of data, which are constantly being contributed to sensors such as Sirius Compact. A wealth of knowledge that must be protected accordingly. Saab therefore does not store any sensitive data from the threat library in the sensor but forwards the signals directly. If you want to use the sensor on a drone for an intelligence-gathering flight without being detected, the sensor can be operated without a network connection as well. Although the data is then temporarily stored in the sensor, it is useless without the software and an associated threat library. Sirius Compact is controlled by the TRS Lite software. With it, the sensors can be controlled via a tablet and therefore supports tactical operability. Up to five sensors can be easily managed per soldier. These five sensors can in turn be grouped and controlled as bundles in the more complex version called TRS 9EW. "Using these associated software systems, users can automatically generate reports, assign tasks to other sensors or even record new signals and thus expand their own threat library," explains Mathew Willmot.

The perfect addition to any network

Portable passive sensors are suitable for a wide range of applications and are an ideal electronic support measures asset. They complement more complex systems and act in particular as an early warning system, for example for ground-based air defence (GBAD). Due to its size, the sensor can be mounted almost anywhere - even on civilian infra-structure. These sensors also bring advantages for alliance partners such as NATO, as the information obtained can be shared within the framework of Cooperative Electronic Support Measures Operations (CESMO) and thus benefits all coalition partners. The uniform DNA of all products from Saab's Sirius family also ensures high precision and expertise from decades of research and development in the new, compact model. The entire product range is constantly being further developed. 

Precise early warning system indispensable

The increasingly complex requirements and threats facing armed forces require efficient and precise early warning systems. While radars are looking, passive sensors are listening and are therefore the ears of tomorrow's modern battlefield. They provide a detailed picture of enemy activities without making an appearance themselves. Mobile systems are more than just a technological achievement; they are a strategic necessity in modern warfare, says Mathew Willmot. "Sirius Compact is a clear product of our time. More than ever, critical information needs to be provided without compromising one's position. In a world where electronic warfare and information dominance increasingly determine the outcome of conflicts, these systems are indispensable." Passive sensors such as Sirius Compact enable a new dimension of tactical planning and decision-making. They are the silent guardians and protectors of our armed forces and will increasingly play a key role in the cat and mouse game of electronic warfare.

Silent Power – Where you want it. When you want it.

Sirius Compact is a modular and scalable passive Electronic Warfare (EW) sensor network, providing a true force-multiplier by enhancing situational awareness through silent detection, classification and prioritisation of radar and datalink emissions.

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