Fraunhofer Institute for High Frequency Physics and Radar Techniques FHRAvalanche Monitoring with Passive Radar
To ensure safety in mountainous regions, reliable avalanche monitoring is essential. A feasibility study by Fraunhofer FHR highlights the advantages of passive radar over existing monitoring methods. The new satellite mega-constellations play a key role in this development.
When snow falls heavily from the sky or temperatures rise rapidly, certain areas face a familiar warning: avalanche danger! To reduce the risk to people and infrastructure, controlled explosions are sometimes used—causing the snow masses to thunder down the mountain in a predicted and planned path. But was the avalanche triggered as intended? Confirmation is required for that. Monitoring is also crucial for naturally occurring avalanches to ensure public safety. Radar technologies are often used for this purpose, enabling continuous remote monitoring in all weather conditions. The challenge, however, is that avalanches typically occur in remote areas where no terrestrial infrastructure is available.
Starlink and Co. as Signal Providers
Passive radar is ideally suited for avalanche detection. Unlike traditional radar, this system doesn’t emit electromagnetic energy itself but instead uses signals from broadcast or mobile networks. The advantages include good availability, low cost, easy installation, no need for transmission licenses, and the ability to create a bistatic radar with synthetic aperture (SAR) using just a stationary receiver, thanks to the movement of satellites. However, a drawback is that broadcast signals are often unavailable in remote mountainous regions. In the SLIDE project, short for "FSS-constellations for avalanche detection with passive radar," Fraunhofer FHR leverages satellite-based illumination systems, such as the mega-constellations Starlink and OneWeb with fixed satellite services (FSS). Multiple satellites illuminate the mountainous areas simultaneously from various observation angles, enabling effective detection.
But can these satellite constellations be used for avalanche detection? This question was explored by researchers at Fraunhofer FHR on behalf of ESA-ESTEC in a feasibility study. “Using the topographic data of a mountain, we developed a simulation environment to model avalanches and analyze whether they can be detected with Starlink signals,” explains Dr. Diego Cristallini, Group Leader of Passive Radar in the Signal Processing & Imaging Radar department. To practically verify the promising simulation results, the researchers also used their passive radar system to detect small controlled landslides in a former mining site on the Rhine near Remagen. The site is set to be refilled with soil, and the avalanches occur when an excavator dumps its load into the still open pit. “Both the simulations and the practical test demonstrate,” Cristallini summarizes, “that passive radar with signals from satellite mega-constellations is well-suited for avalanche detection.“