New InSAR instrument may give researchers bird’s-eye view of dynamic Earth systems

NASA's ALTUS II UAV platform for Earth observation. A new InSAR instrument may use HALE aircraft like ALTUS to observe fast-changing Earth systems at the millimeter scale. (Image Credit: NASA)

NASA’s ALTUS II UAV platform for Earth observation. A new InSAR instrument may use HALE aircraft like ALTUS to observe fast-changing Earth systems at the millimeter scale. (Image Credit: NASA)

10/3/2023 – A new radar instrument could make it easier for researchers to study earthquakes, volcanic eruptions, and other fast-changing Earth systems.

The instrument, “HALE InSAR,” is a compact Interferometric Synthetic Aperture Radar System (InSAR) for High Altitude, Longer Endurance (HALE) aircraft – such as balloons, airships, and drones. Featuring a novel electronically steered antenna and a cutting-edge navigation system, HALE InSAR would be one of the smallest and most precise InSAR instruments yet developed for science missions.

InSAR instruments are active sensors that emit radio signals to measure subtle deformations in Earth’s surface. These sensors can measure surface changes as small as a millimeter, making them extremely useful for observing everything from glacial melt to sea level rise to earthquakes.

No precision InSAR instruments are currently light enough and compact enough to gather data from HALE platforms, which are designed to fly as high as 21 kilometers above Earth’s surface for months at a time, but HALE InSAR would change that.

Weighing only seven kilograms and consuming less than 300 watts of power, about as much power as it takes to run a small electric bike, HALE InSAR would be ideal not only for HALE aircraft but also, eventually, small, low-orbiting satellites.

Lauren Wye, CEO of Aloft Sensing, Inc., and Principal Investigator for HALE InSAR, explained that developing an effective radar system so compact was no small task.

“All of these stratospheric vehicles are extremely mass conscious. The heavier the radar is, the bigger the vehicle needs to be, the more expensive it is to launch, the more solar power is needed to stay aloft, and the less time there is available for the radar to operate,” said Wye.

She and her team, which includes researchers from NASA, the Unites States Geological Survey (USGS), and a coalition of private companies, pioneered several novel technologies to try and reduce the mass of their InSAR instrument without compromising operational flexibility.

These include a flat, electronically steered antenna that gives their HALE InSAR a wider field of regard and makes it more aerodynamic compared to traditional antennas, as well as a novel radar-based positioning system.

“We have a patent-pending positioning technique that uses the radar itself to know where it is precisely, better than any GPS level of accuracy. And it can do so in a self-contained fashion without any additional hardware support,” said Wye. Ultimately, it is this positioning technique that enables the high degree of measurement sensitivity provided by HALE InSAR.

Wye and her team are finishing a laboratory-based prototype of their instrument, which they will ultimately fly onboard a medley of HALE systems, including fixed wing aircraft and airships, all of which are unmanned and piloted remotely.

After validating their instrument with airborne testing, Wye intends to send HALE InSAR to the stars, adapting it to function aboard a small satellite in low-Earth orbit.

NASA’s Instrument Incubation Program – a part of NASA’s Earth Science Technology Office – funded this project, providing Wye and her team with the support they needed to create their instrument prototype.

“It was a door opening opportunity to have this funding and the trust that comes with it from the NASA ESTO program managers, to say we believe that you know what you’re doing, we believe in your vision, and we believe that you can go out there and achieve it,” said Wye.

Gage TaylorNASA Earth Science Technology Office