Successful sea trials for ECA GROUP’s UMISAS sonar

As part of the programme to replace the naval Mine Countermeasures capability of the Belgian and Royal Netherlands navies, which includes the supply of twelve minehunters equipped with unmanned systems (Toolbox), ECA GROUP announces the completion of sea trials of its UMISAS sonar for both the AUVs and Towed Sonars of the rMCM programme. The next step is the on-going production of the UMISAS sonars for their integration in the A18-M and T18-M adapted to the rMCM programme. This integration will take place between October 2021 and March 2022.

UMISAS 120 VHF sonar image of S.S. Ferrando collected off the coast of Hyères, France.
Image size: 40 m x 135 m, Image resolution 3 cm x 3 cm

ECA GROUP decided to develop its own range of Synthetic Aperture Sonars in 2014 and launched an internal programme. SAS sonars proposed by partners did not fulfil ECA GROUP’s internal requirements:

• Their weight, size or power consumption would have led to a too big and too heavy AUV whereas ECA GROUP’s MCM AUV was targeting the size of an A18-M medium-size AUV;
• Impossibility to precisely synchronize the SAS and the inertial navigation of the AUV in order to fully exploit the benefits of a new technique protected by an ECA GROUP patent for both SAS imagery and AUV navigation.

The A18-M AUV and T18-M Towed Sonar have the best performance when fitted with UMISAS sonars. Thus, these drones are exclusively commercialized with UMISAS sonars.

UMISAS: A NEW GENERATION OF SYNTHETIC APERTURE SONARS

ECA GROUP’s research and development in the field of sonars started back in 2014 together with its development of new generation Autonomous Underwater Vehicles in the A18 range. Driven by operational needs of Navies requesting high performance and more compact unmanned solutions for mine detection missions, ECA GROUP brings on the market their own sonar technology to be fitted on its naval drones and fully integrated into its unmanned systems.

The UMISAS sonars are interferometric synthetic aperture sonars (InSAS) used for mine detection missions as part of Mine Countermeasures operations at sea. The UMISAS sonars aim to obtain a spatial resolution of about 3 cm x 3 cm to optimally classify small and irregularly shaped objects on the seabed.

The positioning of the platform required to form the synthetic antennas is an integral part of the UMISAS processing chain. UMISAS directly uses the data from the A18-M or T18-M navigation grade inertial unit to perform SAS processing, thus eliminating the use of low cost navigation sensors used by some commercial SAS systems on the market which perform only the short term navigation required to produce focused SAS imagery, but do not allow for geo-referencing of the SAS images or improved positioning of the AUV by exploiting the SAS and, above all, are much less reliable.

UMISAS SONAR JOINS THE ECA GROUP DRONE FAMILY

The UMIS^TM Toolbox developed by ECA GROUP is a comprehensive solution for stand-off and autonomous mine clearance missions at sea to be operated from the ship or from the shore. It contains: a USV INSPECTOR125 surface drone , AUV A18-M underwater drones and T18-M towed sonars for mine detection, SEASCAN and K-STER C MIDS (Mine Identification and Disposal System) for mine identification and neutralization as well as UMISOFT, a comprehensive software suite for mission planning, drone control and data management.

UMIS^TM drones perform accurate navigation and positioning, obstacle detection and avoidance with a high level of performance, and one of the key elements, which will guarantee the expected high level of performance of the system, is the quality of imagery provided by these drones, which the ECA GROUP’s UMISAS Synthetic Aperture Sonar can offer.

UMISAS PROVIDES SUPERIOR COVERAGE RATE– DETECTING & CLASSIFYING STEALTHY MINES

UMISAS, an Interferometric Synthetic Aperture Sonar (InSAS), is an innovative underwater imaging technology that considerably improves seabed surveys by providing ultra-high resolution imagery at superior coverage rates, i.e. 4 times greater in terms of coverage and between 5 and 10 times greater in terms of resolution compared to  conventional side scan sonars. Combining several dozens of acoustic pings to form an image with a much higher resolution, UMISAS processes raw data into 3 cm X 3 cm resolution images, constant with range, together with high area coverage rates (i.e. 1 square nm per hour for the UMISAS 240 fitted on the T18-M).

”This combination of resolution, area coverage and accurate positioning is what makes UMISAS unique. It allows for a high detection and classification probability, even of stealthy mines, which are a challenge for other sonars.”

Marc Pinto, Naval Robotics Scientific Advisor at ECA GROUP

DRONES + SONAR = DUAL EXPERTISE FOR BETTER MISSION PERFORMANCE

ECA GROUP is one of the few manufacturers capable of developing the drones as well as the InSAS sensor, optimising both in an integrated system approach ensuring a seamless integration and successful mine detection and classification operations. This integration expertise is a real asset to the global performance of the system:

• Close collaboration between trajectory control, navigation and positioning, sonar signal processing systems, allowing system tradeoffs to be made at the right place;
• Greatly facilitated electrical and mechanical integration of the InSAS sensor into the drone as both were designed together;
• Optimized Size-Weight-Power and Cost.

AI DRIVEN REAL-TIME PROCESSING INCREASES AUTONOMY

In addition, ECA GROUP engineers have focused on real-time InSAS processing on Graphical Processing Units leveraging significant progress in COTS computer hardware driven by AI applications:

• Thus, the real-time InSAS processor is very compact and has a low and optimized power consumption, inferior to 30W, which increases mission duration.

UMISAS’ systems operate on 2 frequency bands: High Frequency & Very High Frequency:

• Permitting a superior signal to noise ratio and thus a high contrast imagery at long range, even in harsh environments, including multi-pathing in shallow waters and high absorption in warm waters.

PROVIDING HI RES BATHYMETRY IMAGES

Finally, UMISAS has a pair of vertically superposed arrays for reception on each side of the platform for interferometric processing, allowing for high resolution of the bathymetry which is co-registered with the imagery for improved environmental assessment.

A18-M AUV fitted with UMISAS 120 system - transmitter and receiver arrays visible on port side