NASA’s Goddard Space Flight Center has built a laser mapping instrument called CASALS that is designed to fill the gaps between the narrow tracks that today’s space lidars leave behind. In an airborne test in November 2024, a prototype produced science-quality data and resolved detail as fine as 22 centimeters from about 5 kilometers up. This article on CASALS lidar summarizes NASA’s description of how it works, what it achieved and what comes next.
What is CASALS?
CASALS stands for Concurrent Artificially-intelligent Spectrometry Lidar System. It is a NASA Goddard instrument supported by NASA’s Earth Science Technology Office. Lidar is a technology that measures distance by timing laser pulses that bounce off a surface. NASA says existing spaceborne lidars measure Earth’s surface one narrow line at a time, which leaves large unmapped gaps. CASALS is designed to fill those gaps with a continuous three-dimensional swath.
How does it scan without moving mirrors?
NASA says CASALS uses no moving mirrors. A tunable seed laser centered at 1040 nanometers cycles through 256 wavelengths, and a transmission grating steers each pulse to a different position across the flight path. Because the direction of each pulse depends on its wavelength, the instrument can sweep across the ground without mechanical scanning. A transmission grating is an optical component that splits light into directions based on wavelength. That definition is general and is not a quotation from NASA.
How sensitive is the detector?
NASA says the detector operates at 80% quantum efficiency, which allows it to detect weaker returns from darker surfaces or through dense vegetation. Quantum efficiency is the share of arriving light particles that a detector actually registers. A higher figure means the instrument can work with less light, which matters when a laser pulse has to travel from orbit to the ground and back.
What did the airborne test show?
In November 2024, a prototype flew on NASA’s B200 King Air aircraft and produced science-quality data on its first campaign. One flight covered the Great Cypress Swamp in Delaware on November 12, 2024. At an altitude of roughly 5 kilometers, NASA says the instrument has a 22-centimeter horizontal resolution, enough to distinguish individual tree branches and small changes in ground elevation.
What comes next?
The team plans to fly CASALS again during the ASCENT campaign, scheduled for summer 2027. Before a space-ready version, they plan to widen the swath and add onboard data processing software. The work is funded through NASA’s Decadal Survey Incubation program and Instrument Incubation Program, with partners at NASA Goddard, the University of California, Santa Barbara and Virginia Tech. John Yorks is the principal investigator.
How to read the numbers
By our own arithmetic, a 22-centimeter resolution from 5 kilometers is about one part in 23,000, since 5,000 meters divided by 0.22 meter is roughly 22,700. The 256 wavelengths mean 256 distinct pointing directions across the swath, if each wavelength maps to a separate position as NASA’s description implies. The resolution applies to aircraft altitude, not orbit, so a space version would likely have coarser detail unless the design changes. That last point is our general inference and is not stated by NASA.
Why does a continuous map matter?
Scientists use lidar to measure forest height, ice thickness and terrain. With line-by-line sampling, researchers must estimate what lies between lines. A continuous swath would remove that guesswork. NASA’s page describes the gap problem but does not list specific science uses, so we mention these only as general examples of what 3D surface maps are used for.
What are the limits of the report?
The instrument is a prototype tested from an aircraft. NASA describes the next steps as widening the swath and adding onboard processing, which means those capabilities are not yet built. There is no launch date or space mission for CASALS in the page we used. Readers should treat it as technology development and not as an approved satellite.
What does artificially intelligent mean here?
The name includes the phrase artificially-intelligent, and NASA’s plan to add onboard data processing software points to the same idea: handle some of the data on the spacecraft so that less raw data must be sent to the ground. The page excerpt does not describe the software, so we cannot say what methods it will use. The point for readers is that a continuous swath produces much more data than a line-by-line instrument, and processing on board is one way to manage that volume.
What should readers watch for next?
The next milestone is the ASCENT campaign in summer 2027, where the team plans to fly CASALS again. Results from that campaign, and any move to widen the swath, will show whether the design scales up. A path to space would need further funding and approval that the page does not mention.
How does it connect to other coverage?
CASALS is an example of Earth-observing technology. Our article on NASA’s AWE experiment covers an instrument that watched the atmosphere from the space station, and our report on the Mars helicopter blade design covers another NASA engineering study. Our summary of the NASA ISAM State of Play covers technologies for working on spacecraft in orbit. Instrument development often takes years of such steps before flight.
Related reading: Supercooled Large Droplet Icing: How NASA Is Testing Drop-Size Probes.
Glossary
- Lidar: a laser-based method of measuring distance and shape
- Swath: the strip of ground an instrument views as it moves
- Quantum efficiency: the fraction of incoming light a detector registers
- Transmission grating: an optical part that sends different wavelengths in different directions
- Horizontal resolution: the smallest ground distance an instrument can separate
These definitions are general explanations and are not quoted from NASA.
What is not covered here?
NASA’s page does not give the pulse rate, power, mass or cost of CASALS, and it does not compare it with a specific existing satellite. We have not added any of these.
Key facts at a glance
- Instrument: CASALS lidar from NASA Goddard
- Scan method: 256 wavelengths around 1040 nanometers, no moving mirrors
- Detector: 80% quantum efficiency
- Test: November 2024 on a B200 King Air, 22-centimeter resolution at about 5 kilometers
- Next flight: ASCENT campaign, summer 2027
Frequently asked questions
Is CASALS on a satellite?
No. It has only flown on an aircraft so far.
What can it see?
NASA says it can distinguish individual tree branches and small changes in ground elevation.
Who leads it?
John Yorks is the principal investigator.
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