Navigation Doppler Lidar for Precise Velocity and Range Sensing (NDL)

IM-1 · landed · NASA payload

A lidar landing sensor: an electronics chassis and an optical head with three small telescopes. It measures the lander's velocity and its range to the ground with high precision during descent. On IM-1 it was a demonstration, meant at most as a secondary velocity sensor.

PI: Farzin Amzajerdian (NASA Langley); chief engineer Glenn Hines
Built by: NASA Langley Research Center (NASA center)

Technology	landing sensor (Doppler lidar)
Moon Base need	#1101 (The study's reading: NASA's gap #1101 and the guide's landing challenge do not name NDL. The fit is direct: the challenge asks for landing systems that take accurate range and velocity measurements, which is what NDL does.)
Route onto CLPS	NPLP; NASA-Provided Lunar Payloads, SMD's 2019 request to NASA centers: on the 21 February 2019 list. In January 2020 NASA assigned NDL to both of the first two deliveries, Astrobotic's Peregrine and Intuitive Machines' IM-1. On Peregrine it flew as part of the lander, not as a NASA payload (see open questions).; 2019-02-21
Timeline	first funding 2005 (Langley proof of concept); first flight test 2008-08 (helicopter, NASA Dryden); selected 2019-02-21 (NPLP); assigned to IM-1 and Peregrine in January 2020; launch 2024-02-15; landing 2024-02-22
On the Moon	operated as planned
FO	tested

Flights before the Moon

• aircraft (not FO): Helicopter, NASA Dryden (now Armstrong) Flight Research Center, ALHAT project, 2008-08. Early NDL prototype: real-time altitude and velocity against GPS and inertial navigation.

"helicopter flight test campaigns in August 2008 at NASA Dryden (now Armstrong) Flight Research Center"
— NTRS 20250010290, page 9

• aircraft (not FO): Helicopter, NASA Kennedy Space Center, ALHAT project, 2012-12. NDL sensing in flight, compared with GPS and inertial navigation.

"and in December 2012 at NASA Kennedy Space Center (KSC)"
— NTRS 20250010290, page 9

• NASA test vehicle: Morpheus rocket-powered test lander, Kennedy Space Center, ALHAT project, 2014. Second-generation NDL on six flights: three open-loop, three with NDL in the closed-loop navigation. FO's NDL page dates the Morpheus flight 2012; NASA's 2025 memo says 2014.

"The ALHAT project conducted six flight tests of the NDL sensor on the rocket powered Morpheus test vehicle at KSC in 2014"
— NTRS 20250010290, page 9

"the second generation NDL flew aboard the prototype Morpheus lander vehicle at NASA's Kennedy Space Center in Florida"
— Moon Mission for Flight-Tested Navigation Doppler Lidar

• FO: Masten (now Astrobotic) Xodiac rocket-powered lander, Mojave, California, in NASA's COBALT payload, 2017-04-06 and 2017-04-13. The third-generation NDL (60% smaller and three times faster than the Morpheus unit), open-loop, on a 500 m climb and 300 m divert: the effect of real landing-vehicle dynamics on NDL.

"Masten completed two flight campaigns for Flight Opportunities in FY2017, both on its Xodiac VTVL platform. Among the payloads demonstrated were the Navigation Doppler Lidar Sensor Demonstration for Precision Landing on Solar System Bodies"
— nasa.gov: flightopportunities-2017-annualreport-508-highres.pdf, FY2017 report

Data: date: Apr 6 and Apr 13, 2017
— FO annual report, FY2017, flights of TechPort project 91351 (flight table, pp. 48-49)

"The third-generation NDL model"
— Moon Mission for Flight-Tested Navigation Doppler Lidar

• FO: Blue Origin New Shepard (Van Horn, Texas), in NASA's SPLICE payload (FO technology T0269, TechPort 106705; flight under NASA's Deorbit, Descent and Landing Tipping Point with Blue Origin), 2020-10-13. An NDL engineering test unit (ETU #2, a sister of the IM-1 unit) in SPLICE's descent-and-landing package. NASA says the helium environment of the rocket hurt NDL operation and gave limited measurements.

Data: date: Oct. 13, 2020
— FO annual report, FY2021, flights of TechPort project 106705 (p. 8)

"The SPLICE project flew NDL sensors on the Blue Origin New Shepard suborbital rocket on two flights in 2020 and 2021"
— NTRS 20250010290, page 9

"Suborbital flight test on Blue Origin New Shepard vehicle (2020,2021)"
— NTRS 20230008771, page 10, ETU #2

"The DLC system includes a high-performance computer, camera, navigation Doppler LIDAR, and an IMU"
— NTRS 20210024223, section III

"The NASA/Blue Origin 2018 De-orbit Descent and Landing (DDL) Tipping Point includes two flights on the New Shepard launch vehicle"
— NTRS 20210024223, section II

• FO: Blue Origin New Shepard (Van Horn, Texas), in NASA's SPLICE payload (FO technology T0269), 2021-08-26. The same NDL engineering test unit, second SPLICE flight. Fixes for the rocket's helium environment did not work, and NDL performance could not be evaluated.

Data: date: Aug. 26, 2021
— FO annual report, FY2021, flights of TechPort project 106705 (p. 9)

"The NDL operation was adversely affected by the helium environment of the New Shepard rocket during these flights and provided limited measurements."
— NTRS 20250010290, pages 9-10

• aircraft (not FO): Aircraft flight tests (type not stated), NDL ETU #1, 2021-2023. A sister engineering test unit in aircraft flight tests and integrated tests with other avionics.

"Aircraft flight tests (2021 - 2023)"
— NTRS 20230008771, page 10, ETU #1

• Earth orbit or deep space: Astrobotic Peregrine Mission One (NDL ETU #4, part of the lander, not a CLPS payload), 2024-01-08. A sister unit operated in space for 6.5 hours, five weeks before IM-1. Peregrine had a propulsion failure and did not land.

"NDL operated nominally for 6.5 hours"
— NTRS 20240016238, slide 11

"Astrobotic: NDL was the primary navigation sensor Not a CLPS payload"
— NTRS 20240016238, slide 10

• aircraft (not FO): Erickson Air-Crane helicopter, California (ALHAT second field test), c. 2010 (the paper is dated April 2011; the exact date is not in the source). Improved NDL hardware and signal-processing algorithms in an instrumentation pod, on landing-approach profiles up to about 1,700 m altitude and 58 m/s, against a GPS/inertial reference. The Langley 2016 paper counts three helicopter campaigns; the record has the 2008 and December 2012 ones only.

"The NDL was mounted in an instrumentation pod aboard an Erickson Air-Crane helicopter and flown over vegetation free terrain."
— NTRS 20120003317

"This second field test was a very challenging campaign to equipment and personnel, due to the high summer temperatures in the California dessert, and the extreme vibration environment of the Erickson Air-Crane helicopter."
— NTRS 20120003317

"a moving truck, and three helicopter flight test campaigns"
— NTRS 20160011576

Heritage hardware

• design heritage (engineering test unit line): The IM-1 sensor is ETU #3 of four NDL engineering test units of one design. ETU #1 flew aircraft tests, ETU #2 flew on New Shepard, ETU #4 flew on Peregrine. Lessons from the 2017 Xodiac flights went into the ETU design. Ground tests also included a high-speed rocket-sled test at China Lake.

"Four NDL ETUs have been built and tested"
— NTRS 20240016238, slide 9

"Lunar Landing Demonstration onboard Intuitive Machines lander (2024)"
— NTRS 20240016238, slide 9, ETU #3

"The lessons learned from this testing were critical in design, build, and testing of an NDL Engineering Test Unit"
— Moon Mission for Flight-Tested Navigation Doppler Lidar

Funding before the lunar flight

• Langley seed money for a proof of concept (2005), then funding to build and test a helicopter prototype (2007) (NASA Langley; 2005-2007): amount not in public sources

"In 2005, he and his team received funding from Langley to put together a proof of concept."
— NASA’s Laser Navigation Tech Enables Commercial Lunar Exploration - NASA

• ALHAT and Morpheus (second-generation NDL), then 'Lander Technology: ALHAT capabilities including NDL' (TechPort 10686, 2011-2014; TechPort 93112, 2017-2020) (STMD and HEOMD projects; TechPort program MCO; 2011-2020): amount not in public sources

"In 2012, under the STMD's Autonomous Landing Hazard Avoidance Technology (ALHAT) project, the second generation NDL flew aboard the prototype Morpheus lander vehicle"
— Moon Mission for Flight-Tested Navigation Doppler Lidar

"Lander Technology: ALHAT capabilities including Navigation Doppler Lidar (NDL)"
— TechPort project 93112, batch summary, MCO, 2017-10-01 to 2020-09-01

• COBALT (third-generation NDL, 2016-2017) and SPLICE (NDL engineering test units, 2017-2026), both STMD Game Changing Development (TechPort 93913, 94114) (STMD GCD; 2013-2026): amount not in public sources

"from 2013 through 2017, NDL was part of the Cooperative Blending of Autonomous Landing Technologies (COBALT) project"
— Moon Mission for Flight-Tested Navigation Doppler Lidar

"NASA's Space Technology Mission Directorate (STMD) further matured the NDL technology as part of the Safe and Precise Landing"
— Moon Mission for Flight-Tested Navigation Doppler Lidar

• Several NASA offices, by NASA's own account: STMD, SMD's Exploration Program Office, CLPS, and Langley offices. STMD's own count: FO, Technology Transfer, SBIR/STTR and GCD contributed. (STMD, SMD, CLPS, Langley; not in public sources): amount not in public sources

"The NDL sensor development was supported by multiple NASA program offices including the Space Technology Mission Directorate"
— NTRS 20250010290, page 4, Acknowledgments

"Four programs within STMD contributed to NDL's development"
— NASA’s Laser Navigation Tech Enables Commercial Lunar Exploration - NASA

• NDL parts purchased by NASA in 2019, the period of the engineering-test-unit builds: FPGAs from Avnet. Linked by the award description, which names NDL. The sources do not say which of the four units used them. (NASA purchase order 80NSSC19P1892; 2019-08-20 to 2019-10-24): $180,000

"FPGAS FOR NAVIGATION DOPPLER LIDAR (NDL)"
— USAspending.gov, award 80NSSC19P1892, description; amount 180000.0

• NDL parts, 2019: analog-to-digital converters from Avnet. Linked by the award description. (NASA purchase order 80NSSC19P1354; 2019-06-24 to 2019-07-24): $45,897

"ADCS FOR NAVIGATION DOPPLER LIDAR (NDL)"
— USAspending.gov, award 80NSSC19P1354, description; amount 45897.12

• NDL parts, 2019: switching converters from Avnet. Linked by the award description. (NASA purchase order 80NSSC19P1738; 2019-08-06 to 2019-10-29): $31,937

"SWITCHING CONVERTERS FOR NAVIGATION DOPPLER LIDAR"
— USAspending.gov, award 80NSSC19P1738, description; amount 31937.0

• NDL parts, 2019: NAND flash memory from 3D Plus. Linked by the award description. (NASA purchase order 80NSSC19P1111; 2019-05-17 to 2019-09-23): $21,050

"EDAC NAND FLASH FOR NAVIGATION DOPPLER LIDAR (NDL)"
— USAspending.gov, award 80NSSC19P1111, description; amount 21050.0

• Earlier NDL purchases: Avnet (2017), Aldec switching converters (2017-2018), Nuphoton laser fiber amplifier for evaluation (2016-2017). Linked by the award descriptions; these predate the engineering test units. (NASA purchase orders 80LARC17P0016, 80NSSC17P1780, NNL16AE18P; 2016-2018): amount not in public sources

"LASER FIBER AMPLIFIER FOR EVALUATION AND TESTING AS AN INTEGRATED COMPONENT OF THE NAVIGATION DOPPLER LIDAR"
— USAspending.gov, award NNL16AE18P, description; amount 62500.0

"IGF::OT::IGFSWITCHING CONVERTERS FOR NAVIGATION DOPPLER LIDAR"
— USAspending.gov, award 80NSSC17P1780, description; amount 20985.0

How it got onto CLPS

"The Navigation Doppler Lidar for Precise Velocity and Range Sensing payload will make precise velocity and ranging measurements during the descent"
— NASA Selects Experiments for Possible Lunar Flights in 2019 - NASA

"Two of the payloads will be integrated onto both the Astrobotic lander and the Intuitive Machines lander."
— First Commercial Moon Delivery Assignments to Advance Artemis - NASA, 22 Jan 2020

"In January 2020, NASA selected Langley's navigation Doppler lidar (NDL) technology as a payload on two future CLPS missions."
— nasa.gov: dr-fop-pub-anr-20-03-fop-accomp-report-online.pdf, FY2020 report p. 5

On the Moon

NDL worked through descent and gave valid range and velocity data from about 10 km to the surface; one beam measured ranges of more than 20 km, beyond the expected 5 km. Hours before landing, Intuitive Machines found its own laser rangefinders could not be turned on and tried a software patch to use NDL data. NASA's 2025 memo says the patch did not work and the landing used no NDL data. The data still allowed a full reconstruction of the descent.

"NDL provided 100% valid measurements from 10 km to the Moon's surface"
— Moon Mission for Flight-Tested Navigation Doppler Lidar

"Beam A, pointing nearly nadir, was able to measure ranges of more than 20 km, in excess of the expected 5 km performance."
— NTRS 20250010290, page 14

"the attempt proved to be unsuccessful and the vehicle conducted its landing without the use of any NDL data"
— NTRS 20250010290, page 11

FO's role

Grade: tested. Grade unchanged (tested); the evidence is stronger than the earlier traceback's. The 2017 Xodiac flights gave 'a unique environment for examining the effect of landing vehicle dynamics on the NDL operation', and the lessons 'were critical in design, build, and testing of an NDL Engineering Test Unit' (FO's NDL page). Added by this study: FO's FY2021 report lists SPLICE (FO technology T0269) on two FO-supported New Shepard flights, and NASA says SPLICE flew NDL ETU #2, a sister of the IM-1 unit, on those flights. The rocket's helium environment limited the NDL data, so those flights tested the flight environment more than NDL's performance. FO's NDL pages do not mention the New Shepard flights. NDL also flew outside FO: helicopters, Morpheus, aircraft and Peregrine.

FO flights: 4. FO bought the flights (two Xodiac flight days in 2017 and two New Shepard flights in 2020-2021, the latter shared with other payloads); their cost per payload is in FO records, not in public sources. The New Shepard flights were also part of NASA's Tipping Point with Blue Origin; how the cost was split is not public. Psionic's NASA SBIR awards fund Psionic's own NDL versions, not this unit.

"The rocket-powered Xodiac vehicle provided a unique environment for examining the effect of landing vehicle dynamics on the NDL operation."
— Moon Mission for Flight-Tested Navigation Doppler Lidar

"This flight testing with Masten Space Systems (now Astrobotic) was instrumental in bridging the gap in technology maturation toward spaceflight."
— Moon Mission for Flight-Tested Navigation Doppler Lidar

"Safe and Precise Landing Integrated Capabilities Evolution (SPLICE)"
— nasa.gov: dr-fop-pub-anr-21-02-fop-2021-accomp-report-2022-online.pdf, FY2021 report, flight tables pp. 8-9 (1160)

"SPLICE (Safe & Precise Landing Integrated Capabilities Evolution)"
— TechPort project 106705, title (FO program, Johnson, 2020-2023)

Who built it

"Payload Principal Investigator: Dr. Farzin Amzajerdian, NASA Langley Research Center"
— NASA press kit, Commercial Lunar Payload Services Intuitive Machines IM-1 Mission

"developed by NASA's Langley Research Center in Hampton, Virginia, under the agency's Space Technology Mission Directorate (STMD)"
— NASA’s Laser Navigation Tech Enables Commercial Lunar Exploration - NASA

Moon Base need

"Develop precision landing systems capable of taking highly accurate range and velocity measurements over low-visibility terrain"
— Moon to Mars knowledge base: Moon Base technology and knowledge challenges, Headline challenge 1, technology challenge

"technologies should enable safe and accurate landings in all visibility conditions"
— Moon to Mars knowledge base: ESDMD #1101: Lunar Precision Landing and Hazard Avoidance for Human Exploration, Description

Open questions

• Did the IM-1 landing use NDL data? NASA's 2025 memo (NTRS 20250010290) says no; Wikipedia's IM-1 article (revision of 26 Sep 2026) says NDL was used operationally. This study follows NASA.
• Morpheus: FO's NDL page says the second-generation NDL flew in 2012; NASA's 2025 memo says the NDL flights on Morpheus were in 2014.
• Which NDL unit flew on each New Shepard flight? Langley slides say ETU #2 flew on New Shepard in 2020 and 2021 (NTRS 20230008771) or in 2021 only (NTRS 20240016238).
• What FO paid for the 2017 Xodiac and 2020-2021 New Shepard flights, and how the New Shepard cost was split with the Tipping Point: FO records.
• The cost of the IM-1 NDL unit (ETU #3): not in public sources. USAspending shows only parts orders that name NDL.