NASA’s CASALS Instrument Bridges Gaps in 3D Maps of Earth’s Surface.
Researchers at NASA's Goddard Space Flight Center built CASALS, a lidar instrument that steers laser pulses by wavelength to map Earth's surface in continuous 3D swaths instead of single lines.
Space-based lidar instruments today measure Earth's forests and terrain along narrow lines, according to NASA. The areas between those lines, which include millions of acres, are never directly measured. A team at NASA's Goddard Space Flight Center has developed an instrument meant to close those gaps.
The instrument is called the Concurrent Artificially-intelligent Spectrometry Lidar System, or CASALS. It was built with support from NASA's Earth Science Technology Office. Instead of aiming a laser with moving mirrors, CASALS steers light by changing its wavelength. A fast-pulsing, tunable seed laser centered at 1040 nanometers cycles through 256 wavelengths and sends the pulses through a transmission grating, an optical component with a microscopic pattern of ridges. Because light bends at slightly different angles depending on wavelength, each of the 256 pulses lands in a different position across the flight path.
NASA says this produces a continuous 3D swath of ground rather than isolated tracks. Removing moving parts also cuts the instrument's size, weight and power needs and makes it more reliable in space, the agency says. The detector array has a quantum efficiency of 80%, meaning it converts most returning photons into an electrical signal. NASA says this lets CASALS pick up weaker returns from darker surfaces or through denser vegetation.
An airborne prototype flew on NASA's B200 King Air aircraft in November 2024 and produced science-quality datasets on its first campaign, exceeding the team's expectations. From about five kilometers up, it achieved a horizontal resolution of 22 centimeters and could distinguish individual tree branches and subtle changes in ground elevation. "We're able to see really fine details of vegetation structure and changes in the topography of the surface," said John Yorks, the principal investigator.
More work remains before a space version exists. The team plans to widen the swath and add onboard data processing software, and it aims to fly CASALS again in the ASCENT campaign scheduled for summer 2027. NASA says that if development succeeds, CASALS could become the first spaceborne lidar to map forests and terrain as continuous 3D swaths.
At a Glance
- CASALS cycles a 1040-nanometer seed laser through 256 wavelengths, steering pulses with a transmission grating instead of moving mirrors.
- The detector array operates at 80% quantum efficiency, allowing measurements from darker surfaces and through denser vegetation.
- An airborne prototype flew on NASA's B200 King Air in November 2024 and reached 22-centimeter horizontal resolution from about five kilometers.
- The next planned flight is the ASCENT campaign, scheduled for summer 2027.
Sources
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