NASA’s CASALS lidar prototype steers laser pulses by changing their wavelength, allowing it to measure a continuous strip of terrain without scanning mirrors. An October 21, 2026 technology update describes the optical design, airborne results, and planned improvements before development of a space-ready version.
Lidar measures distance using laser light returned from a surface. As New Space Economy’s explanation of satellite data analytics describes, its value includes measuring vertical structure, such as forest height and terrain. Conventional spaceborne lidar measurements follow narrow tracks, leaving areas between those tracks unmeasured.
The Concurrent Artificially-intelligent Spectrometry Lidar System, or CASALS, addresses that sampling problem by directing successive pulses to different positions across the flight path. Its tunable seed laser operates around 1040 nanometers and cycles through 256 wavelengths.
The pulses pass through a transmission grating, an optical element with a fine repeating structure. Diffraction sends different wavelengths in slightly different directions. Changing the wavelength changes where the pulse goes, so the instrument scans across the ground without turning a mirror.
The resulting measurements form a swath, a strip of coverage with width across the direction of travel. This geometry is useful for observing the arrangement of vegetation and terrain between individual flight tracks.
NASA reports a detector quantum efficiency of 80%, describing how effectively incoming photons produce an electrical response. Detecting a larger fraction of returning light helps the instrument measure weaker signals, including returns from darker surfaces.
The technology has flown on an aircraft. A prototype operated aboard NASA’s B200 King Air in November 2024, including a flight over Delaware’s Great Cypress Swamp. NASA reports 22-centimeter horizontal resolution from an altitude of roughly five kilometers, sufficient to distinguish fine vegetation structure and small terrain features under those flight conditions.
These are airborne measurements, not results from an orbiting CASALS instrument. The team, led by John Yorks at Goddard Space Flight Center, plans to widen the swath and add onboard processing before building a space-ready prototype.
Another flight opportunity is planned for summer 2027 through the Airborne Surface, Cryosphere, Ecosystem, and Nearshore Topography campaign. That work will continue testing how wavelength-steered lidar can collect detailed surface measurements over continuous areas.
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