Rethinking the Battlefield: The Quiet Might of Passive Surveillance

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In modern warfare, the ability to gather critical intelligence while remaining hidden is crucial. New portable surveillance technologies are disruptive. Replacing static devices, they are deployable on the ground, in the air and on the water surface. This significantly enhances discreet, versatile, and rapid intelligence-gathering capabilities.

Today’s armed forces rely heavily on detecting and analyzing radar and communication signals, using advanced technology across domains to confirm enemy actions and identify threats. This high-tech surveillance is crucial for informed decision-making and safeguarding lives. As technology evolves rapidly, the ability to discreetly gather and swiftly analyze extensive data becomes key in maintaining a strategic advantage over adversaries.

Digital upgrades to systems such as surveillance, tracking, and fire control radars, along with weapon seeker heads and communication networks, have enabled the implementation of countermeasures against electronic warfare. Visibility is a major concern when gathering data. Using radar to locate targets inevitably discloses one’s position. However, with passive sensors, it’s possible to monitor enemy signals without emitting any yourself. Countries like Germany and India are exploring passive radar systems to boost their air defenses and improve target detection and tracking capabilities. In late 2023, the sensor solution provider Hensoldt announced its strategic partnership with air traffic control developer ERA to jointly offer the Passive Surveillance System VERA-NG to the German Airforce Luftwaffe.

Saab’s newest development, Sirius Compact, is a versatile and passive sensor and thus well suited for tactical operations. Available for nearly two years and already in series production, it offers a scalable solution that can operate independently, within a network, or alongside existing systems. Unlike bulkier setups, it can be deployed flexibly by operators in various scenarios.

Drones can carry Sirius Compact. (IMAGE: Saab)

360° Coverage in a Portable Package

Saab’s Sirius Compact is a small and lightweight device that can be deployed quickly by individual soldiers or integrated onto platforms such as drones, vehicles, ships and unmanned installations offering flexibility unseen in earlier, static and larger equipment. Weighing around 3.5 kilograms and boasting a compact form factor (35 cm in height and 15 cm in diameter) in its lightest configuration, it underscores a design philosophy that prioritizes portability and ease of use without compromising on capability.

The Sirius Compact delivers immediate situational awareness to individuals and small military units, adaptable for on-demand use. “This shift to intuitive, man-portable systems minimizes the burden of specialist training while meeting the demand for agile, real-time situational awareness and intelligence gathering in modern electronic warfare,” stated Mathew Willmot, Sales Director for Sirius Compact at Saab, a leader in Signals Intelligence (SIGINT) and Electronic Support Measures (ESM). Evolved from technologies stemming from Saab’s broader Sirius multi-domain SIGINT family, Sirius Compact features 360° azimuth coverage, instantaneously detecting radar and data link emissions in the 1-18 GHz frequency span. Its compatibility with existing platforms and independence from specific datalinks make it particularly valuable for seamless integration into military networks.

Stridsbåt 90 (Combat Boat 90) of the Swedish Navy.

Geolocational Precision Through Triangulation

Sirius Compact significantly enhances troop situational awareness, enabling accurate emitter geolocation through triangulation when using a minimum of two or more sensors, considering terrain height differences and sensor placement. Since its launch nearly two years ago, Saab has extensively tested and demonstrated the sensor’s robust performance under severe conditions. For example, a target fighter aircraft taking off 200 kilometers away could be detected at 190 kilometers – as soon as it appeared over the radio horizon with Direction Finding (DF) performance in the order of 2° rms. Target aircraft at high altitudes have also been detected and geolocated at significantly longer ranges, due to the unobstructed Line Of Sight (LOS). The passive nature of the sensors ensures the enemy remains unaware of its activation due to its silent operation.

Additionally, Sirius Compact has proven effective on fast-moving combat boats and Unmanned Surface Vessels (USV) in difficult weather. Independent military evaluations have confirmed that soldiers can deploy the sensor swiftly with minimal training, benefiting from its compact design and powerful capabilities.

Small and lightweight devices can be deployed quickly by individual soldiers. (IMAGE: Saab)

Optimizing Tactical Responses to Security Threats

Signal detection is the initial step toward gaining situational awareness, followed by the critical automatic analysis and classification of these signals. The extensive threat libraries maintained by armed forces feed emitter data into systems like the Sirius Compact, emphasizing the importance of safeguarding this information. Saab ensures security by not storing sensitive threat information within the sensor itself but instead forwarding signals directly for real-time processing. The sensor can also operate autonomously without a network connection, making it ideal for covert operations on drones or remote installations, although any data stored temporarily remains encrypted and inaccessible without the requisite authorization. The Sirius Compact is managed through Saab’s TRS Lite software, which allows control via a tablet further enhancing tactical flexibility. Each soldier can typically control up to five sensors, with the capability to group and oversee them collectively through the more advanced TRS 9EW system. This setup enables users to generate reports, assign tasks and even capture new signals, thereby enriching the operational threat library.

Enhancing Security with Precise Early Alerts

The growing complexity of the electromagnetic spectrum demands efficient and precise early warning systems for modern armed forces. While radars actively search, passive sensors quietly monitor, serving as the unseen ears of the battlefield. These systems capture detailed insights into enemy activities without revealing their presence, making them not just technological advancements but strategic essentials in contemporary military operations.

The overarching theme across these developments is the transition towards more integrated, networked, and autonomous defence systems whilst remaining tactically mobile. Such systems are designed not only to enhance detection and response capabilities but also to ensure a strategic upper hand in an increasingly complex and technology-driven battlefield.

This shift is not just about technological advancement but also about the strategic integration of these technologies into comprehensive defense frameworks that span Multi-Domain Operations (MDO) realms.

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