Plate Nº 96 · recorded October 21, 2026
Space & AstronomyReported finding
NASA's CASALS Lidar Steers Light With Wavelength, Not Mirrors
NASA's CASALS lidar uses 256 laser wavelengths and diffraction instead of mirrors to map terrain in continuous 3D — resolving tree branches from 5 km up on its first flight.
By Nathan Brooks4 min read705 words
In brief
- In November 2024, an airborne CASALS prototype produced science-quality data on its first flight over Delaware's Great Cypress Swamp.
- CASALS cycles through 256 laser wavelengths to steer its beam by diffraction, with no moving mirrors.
- The instrument's detector runs at 80% Quantum Efficiency, capturing almost all returning light.
- Flying at about 5 km altitude, CASALS achieved 22-centimeter horizontal resolution, distinguishing individual tree branches.
- A second flight campaign, ASCENT, is scheduled for summer 2027, ahead of a planned space-ready prototype.
NASA's new lidar instrument resolved individual tree branches from an altitude of five kilometers — about the cruising height of a small airliner — during its very first test flight. The instrument, called CASALS, could become the first spaceborne laser sensor to map Earth's terrain as continuous 3D swaths instead of isolated lines with millions of unmapped acres in between.
A team at NASA's Goddard Space Flight Center (GSFC) built CASALS — the Concurrent Artificially-intelligent Spectrometry Lidar System — with support from NASA's Earth Science Technology Office. Today's space-based laser instruments measure the planet one narrow track at a time. Between those tracks sit enormous gaps, including millions of acres of land scientists never directly measure. CASALS aims to close them.
How do you steer a laser without moving parts?
Legacy lidars swivel their beams with motorized mirrors — hardware that adds weight and can fail in space. CASALS takes a different route. It uses a fast-pulsing, tunable "seed" laser centered at 1040 nanometers that rapidly cycles through 256 unique wavelengths.
Each pulse passes through a transmission grating, an optical component with a microscopic pattern of ridges. Here diffraction does the work: light bends at slightly different angles depending on its exact wavelength, so the grating naturally steers each of the 256 pulses to a distinct position across the flight path.
The result is a continuous, 3D swath of the ground below — no gaps between tracks, no motorized mirrors. Stripping out the moving parts also cuts the instrument's size, weight and power demands, which makes it more reliable in the harsh environment of space.
Why 80% quantum efficiency matters
CASALS carries a second innovation in its detector array: a Quantum Efficiency (QE) of 80%. QE measures how effectively a detector converts incoming photons into an electrical signal. At 80%, CASALS wastes almost none of the light that returns to the sensor.
That sensitivity lets the instrument detect much weaker return signals, so it can collect useful measurements from darker surfaces or through denser vegetation.
What did the flight tests show?
In November 2024, an airborne CASALS prototype flew over the Great Cypress Swamp in Delaware aboard NASA's B200 King Air aircraft. It produced science-quality datasets on the first campaign, exceeding the team's expectations. The flight video shows tree canopy tops in green, the ground in purple and near-ground vegetation in blue.
"I'm very impressed with Guang Yang, Jeffrey Chen, and all our engineers, and how well CASALS performed. This worked really well from the first time we flew it, which is pretty impressive," said John Yorks, a physical research scientist at GSFC and the project's principal investigator.
At its roughly five-kilometer flight altitude, the instrument's 22-centimeter horizontal resolution — finer than a yoga mat laid end to end is wide — picks out individual branches and subtle shifts in ground elevation.
"We're able to see really fine details of vegetation structure and changes in the topography of the surface," Yorks said.
What comes next?
The team plans to fly CASALS again during the Airborne Surface, Cryosphere, Ecosystem, and Nearshore Topography (ASCENT) campaign, scheduled for summer 2027.
Before building a space-ready prototype, engineers will widen the instrument's swath and add onboard data processing software. Moving from a successful airborne prototype to a full space mission remains a real challenge, and the results so far come from a single test campaign — a caveat the team itself acknowledges.
"The team's really done a great job of sticking together and keeping on task and on schedule. We are being funded to optimize and improve the performance, and we're also then looking at ways to take the technologies used in the airborne instrument and mature them and prepare them for a spaceborne version in the future," Yorks said.
If it works, CASALS would hand scientists a dramatically more complete picture of Earth's forests and terrain — continuous 3D maps of a changing planet rather than thin, isolated profiles.
The project is led by John Yorks at GSFC, with sponsorship from NASA's Decadal Survey Incubation program, NASA's Instrument Incubation Program, GSFC, UC Santa Barbara and Virginia Tech. Details are available on NASA TechPort.
via techport.nasa.gov (Original)
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