The ability of nations to defend their territorial airspace is a cornerstone upon which their sovereignty rests. Governments therefore invest tremendous resources to establish and maintain effective Air Defence capabilities. In many instances it is the country's Air Force which is entrusted with this important task. The ultimate effectiveness of Air Defence systems depends on their ability to create an accurate and up-to-date air situation picture.

The capability to quickly identify and classify aerial vehicles and to distinguish between actual threats and innocent targets is essential for air defence operators to operate effectively. However, this capability has been challenged in recent years by a number of factors. Foremost is the continuing growth in worldwide aviation (notwithstanding the current pandemic crisis), which has resulted in a denser national aerospace, making the identification and classification of penetrating targets more difficult. Another factor is the proliferation of platforms with a small Radar Cross-Section (RCS). The increasing use of small, slow, low-flying platforms, and the spread of stealth technologies, are testing the ability of radar systems to detect, track and classify these threats.

Recently, technological breakthroughs in the SIGINT domain, in conjunction with the application of advanced data processing, have enabled ELTA to make substantial inroads in addressing these challenges. In fact, ELTA's SIGINT systems have become an important component of air surveillance and defence systems.

ELTA Systems Ltd. was founded in 1967 as a subsidiary of Israel Aerospace Industries, Israel's largest aerospace and defence concern. ELTA specializes in the design and manufacture of defence electronics, including radar, SIGINT and EW systems. ELTA has achieved considerable advances in the design of Electronic Signal Intelligence (ELINT) sensors, improving their sensitivity, and thereby enabling the detection of targets at longer ranges, while at the same time sustaining tracking continuity by exploiting target side lobes. ELTA's expertise in high-sensitivity and wide-bandwidth scanning offers significant improvements in the ability to cope with targets equipped with advanced low probability-of-intercept radar systems. This innovative scanning capability enables ELTA's ELINT system to perform simultaneous scanning of an extensive bandwidth, successfully tracking targets that employ sophisticated radars equipped with advanced frequency agility and frequency selection systems.

To further bolster ELINT system performance, ELTA has developed unique, advanced algorithms that enable maneuvering targets to be tracked with data from even a single sensor. The tracking data is analyzed based on signal parameters and geospatial information. The system supports the association of ELINT tracks with radar tracks, creating a common integrated track. Advanced capabilities based on a combination of Big Data analytics, Machine Learning processes, and Artificial Intelligence (AI) technology allow the system to adapt rapidly to new environments or threats, and to classify and identify each signal received in the system and update the database according to the target's behavior over time.

ELTA designed its ELINT system for air surveillance and defence missions to be flexible and robust, and to support a wide range of deployments and modes of operation – from independent, standalone deployment as a fully passive system, to co-deployment with a radar sensor. This enables multi-sensor integration, combining active radar with an array of passive SIGINT and Electro-Optical sensors to achieve a multi-disciplinary air situation picture via a single multi-sensor platform.

Furthermore, the integration of passive ELINT sensors with ELTA's advanced radars provides optimal synergy both in terms of operational performance and cost effectiveness. For example, integrating ELTA's Passive Coherent Location (PCL) multi-static radar systems alongside its SIGINT systems complements the ability to generate the passive air situation picture and achieve timely detection and classification. Moreover, the all-ELTA solution facilitates reduced acquisition costs and simplified maintenance logistics, reducing lifecycle cost.

The synergistic integration of data from both passive and active sensors presents considerable challenges. It requires advanced, sophisticated data extraction and transformation techniques. ELTA's passive sensor integration system, Acapella, creates a unified and centrally managed air situational awareness picture.

The ability of passive sensors to classify and identify aerial targets with unchallenged reliability has a direct impact on air defence performance. The quick and unambiguous identification of threats facilitates faster activation of air defence capabilities, creating more opportunities for target interception by both ground-based air defence systems and air superiority aircraft. Furthermore, the use of passive sensors supports advanced Concept-of-Operations (CONOPS) with more conservative radar transmission protocols for enhanced survivability and improved efficacy.

ELTA's passive air surveillance and defence systems make a significant contribution to the Ground-Based Air Defense (GBAD) mission:

Better awareness - Dramatically improve classification and identification to support the critical air situation picture. Enable long-range detection, continuous tracking, and the ability to discriminate between targets based on their SIGINT signature.

Better efficiency - Enable more efficient weapons system operation, reducing classification and identification time and providing more interception opportunities.

Better survivability – Passive systems are compact, do not emit RF, and facilitate careful use of radar transmissions.

In summary, ELTA's SIGINT systems break out of the intelligence-gathering domain and become a significant force multiplier for the air surveillance and defence mission.

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