How NASA’s CASALS Instrument Bridges Gaps in Earth Surface Maps With Laser Science

Mapping between lidar tracks

Space-based laser instruments measure forests and terrain along narrow lines, leaving large areas between tracks unmeasured. NASA’s Concurrent Artificially-intelligent Spectrometry Lidar System, or CASALS, is intended to create continuous three-dimensional views of the ground.

Developed by researchers at NASA’s Goddard Space Flight Center with support from NASA’s Earth Science Technology Office, the system uses machine learning and a compact lidar instrument. It steers light through wavelength changes rather than mechanical mirrors, producing a broad ground swath.

Wavelengths steer the laser

CASALS sends rapid pulses from a tunable seed laser centered at 1040 nanometers. The laser cycles through 256 wavelengths, which pass through a transmission grating with a microscopic pattern of ridges.

Diffraction bends each wavelength at a slightly different angle, directing the pulses to separate positions across the flight path. By avoiding motorized mirrors, the design reduces size, weight and power needs while removing a potential source of mechanical failure.

Detector captures faint returns

The instrument’s detector array has a quantum efficiency of 80 percent, indicating how effectively it converts incoming photons into electrical signals. That efficiency helps CASALS detect weaker returns, including signals from darker surfaces and through denser vegetation.

In November 2024, an airborne prototype flew on NASA’s B200 King Air aircraft and produced science-quality datasets during its first campaign. At an altitude of about five kilometers, it resolved details such as individual tree branches and small changes in elevation, with 22-centimeter horizontal resolution.

John Yorks, the CASALS principal investigator and a physical research scientist at Goddard, praised the team’s performance on the first flight. He said the instrument showed fine detail in vegetation structure and surface topography.

Preparing for future flights

The team aims to fly CASALS again during the Airborne Surface, Cryosphere, Ecosystem, and Nearshore Topography campaign, scheduled for summer 2027. Before developing a space-ready prototype, researchers plan to widen the instrument’s swath and add onboard data-processing software.

Moving from an airborne prototype to a space mission remains a challenge. The team is funded to optimize the technology and improve its performance.