Space-based tech for locating missing boats

Waipapa Taumata Rau, University of Auckland Earth observation scientist Dr Tom Dowling and engineer Ella Fasciana are developing the passive radar reflector in collaboration with the New Zealand Defence Force. The project is known as SAR4SaR – Synthetic Aperture Radar for Search and Rescue.

The concept is simple: a lightweight object that can be carried on a small vessel and, in an emergency, popped open and dropped into the water. From there, it floats upright and reflects radar signals back to satellites orbiting overhead, enabling rescuers to spot the vessel’s location even in stormy or low visibility conditions.

“The aim is integration into real-world search and rescue systems, particularly those serving the seafaring cultures of the Pacific,” says Dowling. “Affordability, reliability and independence from electronic infrastructure are essential.”

The project is in collaboration with Defence, Science and Technology, the science arm of the New Zealand Defence Force.

Many communities in the Pacific Islands depend on small boats for fishing and transport, often without high-end navigation or emergency gear. If a vessel breaks down or drifts off course, the consequences can quickly become life threatening. Emergency beacons and radios are expensive, require batteries and maintenance, and have a shelf life. For many, they are simply out of reach.

“This is a different approach,” says Dowling. “If we can make something that just works – that you don’t have to charge, you don’t have to activate, and it tells satellites where you are – that could be a real breakthrough.”

The reflector they are developing is designed to be folded flat and stored under a seat or in a compartment on a small boat. Unlike electronic devices, the reflector is completely passive. It doesn’t transmit a signal or require power. Instead, it focuses and reflects the energy of radar signals sent from satellites – like how a mirror reflects light – making it visible in the radar images.

Synthetic aperture radar, the satellite-based technology, is “synthetic” because it simulates the results from an unfeasibly large antenna by combining the data from sequences of radar readings recorded as the satellite moves across the sky.

This process allows it to generate detailed images of the Earth’s surface, even through cloud, rain, darkness or smoke.

“Synthetic aperture radar has been around since the 1970s and NASA did some early research into using it for search and rescue,” says Dowling. “But recent advances in low Earth orbit satellites – smaller, cheaper satellites flying much closer to Earth – have made it feasible to use this technology for something like search and rescue for a wider range of actors.”

An artificial intelligence tool will scan the radar imagery for the distinctive signature of the reflector so authorities can be alerted to the distress signal.

Working in the fabrication space at Te Pūnaha Ātea – Auckland Space Institute, the pair began by experimenting with origami-like concertina designs. They used computer modelling to test different shapes and materials for the strength of the signal returned, then constructed dozens of prototypes using items such as corflute, gaffer tape, aluminium foil and tarpaulins from local hardware stores.

Early tests took place at the University’s Ardmore field station in South Auckland, where the team worked out whether satellites could even detect the reflectors from orbit. Encouraged by the results, they moved to water trials, testing stability and radar visibility in real-world sea conditions.

One of the most demanding tests was conducted with the Royal New Zealand Navy from the HMNZS Canterbury near subantarctic Campbell Island. In conditions that included 50-knot winds – over 90km/h – the reflector stayed afloat and visible to satellites.

“We were very nervous to begin with but got more confident as the test progressed and are absolutely thrilled at the results,” Dowling told a reporter.

More recently, in July 2025, the team completed a week-long experiment at Omaha, north of Auckland. With support from the University’s Leigh Institute of Marine Science and the research vessel Te Kaihōpara, the reflectors were put through a series of trials that confirmed their detectability, durability and ease of deployment.

For Ella Fasciana, who will dedicate her PhD research to the project, the work combines her knowledge from engineering and environmental science degrees with a passion for practical solutions.

Designing the device has involved balancing several tough requirements: it must be light enough to carry and store, strong enough to survive a storm, and cheap enough for widespread use. Different configurations – diamond, cube, wedge – have been tested to find the most effective shape.

Bobbing on the ocean’s surface, the geometry of aluminium-surface plates inside the device focuses radar energy back toward the satellite.

The goal is to manufacture a device that could retail for $50 to $60. The team has filed a patent and, pending further testing, hopes to move towards production-ready prototypes. One remaining challenge is filtering out potential false positives from ice and some waves.

The University and the Defence Force have jointly contributed some $40,000 to the project so far, while the scientists have donated time and the Defence Force has provided logistical support. “It’s been a highly cost-efficient and collaborative project,” says Dowling.

The reflectors would not replace emergency beacons or radios but could complement them or serve as substitute for vessels without access to high-tech gear.

Any tool that shortens the time it takes to find a missing boat could also reduce the enormous cost of search and rescue operations. In New Zealand, this often involves long-range maritime patrol aircraft such as the Royal New Zealand Air Force’s P-8 Poseidon, which are essential but resource-intensive to operate.

New Zealand’s Rescue Coordination Centre is responsible for maritime search and rescue across one of the largest search and rescue regions in the world – 30 million square kilometres, from the mid-Tasman Sea to halfway across the Pacific Ocean, and from the South Pole almost to the Equator.

“When you’re searching for a missing boat in the Pacific, it really is like looking for a needle in a haystack,” says Dowling. “This kind of technology could give you the one clue you need to start narrowing things down.”

A simple device that increases the chances of being spotted – and doesn’t rely on electronics, batteries or someone remembering to switch it on – could make all the difference.

“Sometimes it’s the simplest things that save lives,” says Dowling.