Airborne Visible/Infrared Imaging Spectrometer-5, or AVIRIS-5, is a new high-precision spectrograph developed by NASA. It is planned to be used to search for valuable minerals on Earth. To do this, it will be installed on a balloon that will rise 18 km into the sky.
Sensor for finding minerals
Located in the nose of a high-altitude research aircraft, NASA’s new sensor took to the skies to help geoscientists map rocks containing lithium and other important minerals on the Earth’s surface approximately 18,300 meters below. In collaboration with the US Geological Survey (USGS), these flights are part of the largest aviation campaign of its kind in the country’s history.
But this is just one of many tasks on the horizon for AVIRIS-5, short for Airborne Visible/Infrared Imaging Spectrometer-5, which has much in common with sensors used to study other planets.
About the size of a microwave oven, AVIRIS-5 detects spectral “fingerprints” of minerals and other compounds in reflected sunlight. Like its “relatives” flying in space, the sensor exploits the fact that all types of molecules, from rare earth elements to flower pigments, have unique chemical structures that absorb and reflect different wavelengths of light.
The technology was first developed at NASA’s Jet Propulsion Laboratory in Southern California in the late 1970s. Over the decades, imaging spectrometers have visited every major rocky body in the Solar System, from Mercury to Pluto. They have studied the surface of Mars in detail, discovered lakes on Titan, and tracked mineral-rich dust in the Sahara and other deserts. One of them is heading to Europa, Jupiter’s ocean-covered moon, to search for the chemical components necessary to sustain life.
Improvements in spectrometer technology
Although imaging spectrometers vary depending on their mission, they share certain common equipment—including mirrors, detector arrays, and electron-beam gratings designed to capture light reflected from a surface and then separate it into its constituent colors, as a prism does.
Many of the best flying image spectrometers have been made possible by components invented at NASA JPL’s Microdevices Laboratory. There, instrument makers combine advances in physics, chemistry, and materials science with the classic properties of light discovered by physicist Isaac Newton in the 17th century. Newton’s experiments with a prism showed that visible light consists of a rainbow of colors.
Today, NASA JPL engineers are working with advanced materials such as black silicon—one of the darkest substances ever made—to improve efficiency. Under a powerful microscope, black silicon looks like a forest of prickly needles. Etched by lasers or chemicals, these nanoscale structures block the passage of extraneous light, trapping it in their spikes.
Hunting for minerals from the height of an airplane
The optical methods used in the Microdevices Laboratory have been continuously refined since the first AVIRIS instrument was launched in 1986. Four generations of these sensors have already been used to analyze volcanic eruptions, diseased crops, debris in downtown New York City, and forest fires in Alabama, among many other applications. The latest model, AVIRIS-5, has twice the spatial resolution of the previous model and can explore areas ranging from less than one foot (30 centimeters) to approximately 30 feet (10 meters).
This year, aircraft flew more than 200 hours at high altitudes over Nevada, California, and other western states as part of a project called GEMx (Geological Earth Mapping Experiment). The flights are conducted using a NASA ER-2 aircraft operated from the Armstrong Flight Research Center in Edwards, California. This work is the aerial component of a larger USGS initiative called the Earth Mapping Resources Initiative (Earth MRI), which aims to modernize the mapping of the nation’s surface and subsurface resources.
Since 2023, a team from NASA and the USGS has been collecting data from more than 950,000 square kilometers of the American West, where dry, treeless areas are well suited for mineral spectroscopy.
One exciting early discovery is a lithium-bearing clay called hectorite, found among the tailings of an abandoned mine in California, as well as in other locations. Lithium is one of approximately 50 minerals whose supply is vulnerable to disruption and which the USGS has identified as critical to national security and the economy.
Range of application of the AVIRIS-5 sensor
Helping communities derive new value from old and abandoned deposits is one of GEMx’s long-term goals, said Dana Chadwick, an Earth systems scientist at NASA JPL. This also applies to identifying sources of acidic mine water, which can form when rock waste is exposed to weathering and enters the environment.
“The breadth of different questions you can take on with this technology is really exciting, from land management to snowpack water resources to wildfire risk,” Chadwick said. “Critical minerals are just the beginning for AVIRIS-5.”
According to phys.org
