Laser Retroreflector Array (LRA)¶
IM-4 · manifested · NASA payload
A passive optical marker: eight small glass corner-cube prisms in a dome-shaped aluminum frame on the lander deck. Laser altimeters on orbiters or approaching landers can range to it from most directions, so it marks the lander's position on the Moon for decades. It needs no power.
PI: Xiaoli Sun (NASA Goddard)
Built by: NASA Goddard Space Flight Center (NASA center)
| Technology | passive navigation marker (laser retroreflector) |
| Moon Base need | #0101, #1101 (The study's reading, as for the IM-1 and IM-2 arrays. No NASA gap names the LRA; the knowledge base files it as a navigation aid. NASA says LRAs could later guide landings in the dark near the South Pole (#1101) and build a growing network of fixed markers for positioning (#0101); in June 2026 it called the LRA 'flight-proven' and its data critical to safe human exploration. The IM-4 array will sit at Mons Mouton near the South Pole, where IM-2's array already lies on a tipped lander. IM-4's 2027 date falls in Phase 1 ('Now through 2028'), the study's reading.) |
| Route onto CLPS | other NASA; No payload call. The LRA was developed under NASA's CLPS program itself and goes on most US landers. The CLPS office listed an LRA for CP-22 by 2023; NASA named it in the IM-4 award of 29 August 2024. When this unit was assigned is not public.; 2024-08-29 |
| Timeline | first funding not in public sources (the design was space-qualified at Goddard in 2018); first flight test 2019-02-21 (the design, on Beresheet); selected 2024-08-29 (named in the IM-4 award; listed for CP-22 by the CLPS office in 2023); launch 2027 (NASA); landing not in public sources |
| On the Moon | not yet flown |
| FO | none |
Flights before the Moon¶
- earlier lunar mission: SpaceIL's Beresheet lander (same Goddard design), 2019-02-21. The first flight of the design, integrated in November 2018; the first NASA instrument on a non-governmental mission to the Moon. How Beresheet ended is not in these sources.
"LRALL was integrated with the SpaceIL Beresheet spacecraft prior to its February 21, 2019 launch and became the first NASA instrument to fly on a non-governmental mission to the Moon."
— NTRS 20205001993
- earlier lunar mission: ISRO's Chandrayaan-2 Vikram lander (an uncoated version), 2019. A space-qualified uncoated version, integrated in April 2019. The landing attempt is not described in these sources.
"one of which was integrated in April, 2019 with the Indian Space Research Organization (ISRO) Vikram lander, a part of the Chandrayaan-2 mission"
— NTRS 20205001993
- earlier lunar mission: ISRO's Chandrayaan-3 Vikram lander (NASA LRA), 2023-08-23. The design on the surface. LRO's laser altimeter ranged to it from 12 December 2023, the first ranging to a small array from orbit; by December 2025 LOLA's success rate to it was 32% by day and 9% by night.
"ISRO's (Indian Space Research Organization) Vikram lander, with a NASA retroreflector on it, touched down on the Moon on Aug. 23, 2023."
— Laser Instrument on NASA’s LRO Successfully ‘Pings’ Indian Moon Lander - NASA Science"At 3 p.m. EST on Dec. 12, 2023, NASA’s LRO"
— Laser Instrument on NASA’s LRO Successfully ‘Pings’ Indian Moon Lander - NASA Science"32% daytime and 9% nighttime for CH3"
— hou.usra.edu: 1707.pdf
- earlier lunar mission: JAXA's SLIM lander (a NASA retroreflector), 2024-01. A NASA LRA on the surface. LRO ranged to it, though rarely, because SLIM rests in an off-nominal attitude.
"including one on JAXA's (Japan Aerospace Exploration Agency) SLIM lander, due to land on the Moon on Jan. 19, 2024"
— Laser Instrument on NASA’s LRO Successfully ‘Pings’ Indian Moon Lander - NASA Science"opportunities and success rate to SLIM were low given"
— hou.usra.edu: 1707.pdf
- Earth orbit or deep space: Astrobotic's Peregrine Mission One (its NASA LRA), 2024-01-08. Nothing: the LRA is passive and works only on the surface, and Peregrine did not land.
"As NASA’s LRA (Laser Retroreflector Array) instrument is a passive experiment, and operations could only take place"
— NASA Science, Astrobotic Peregrine Mission One Concludes - NASA
- earlier lunar mission: Intuitive Machines' IM-1 (Odysseus), the same LRA on the same lander family, 2024-02-22. The design on a Nova-C lander. Odysseus tipped over and its LRA sits on a solar panel facing nearly the horizon; LRO had no returns from it as of December 2025.
"It landed on February 22, 2024."
— Commercial Lunar Payload Services (CLPS) Deliveries - NASA Science"So far, no returns have"
— hou.usra.edu: 1707.pdf, continues: 'been received from IM-1'
- earlier lunar mission: Intuitive Machines' IM-2 (Athena) at Mons Mouton, the same LRA on the same lander family, 2025-03-06. The design at IM-4's own target region. Athena landed on its side; the array stays fixed to its top deck. No ranging to it is reported in these sources.
"IM-2 touched down at approximately 11:30 a.m. March 6"
— NASA Receives Some Data Before Intuitive Machines Ends Lunar Mission - NASA"will remain affixed to the top deck of the lander"
— NASA Receives Some Data Before Intuitive Machines Ends Lunar Mission - NASA
Heritage hardware¶
- design heritage and batch build: Similar small arrays flew on the ExoMars and InSight Mars landers. Goddard had optically tested 13 LRALL units by 2021; whether the IM-4 unit is one of them is not stated.
"Similar small LRAs were placed on the ExoMars and InSight landers"
— NTRS 20205001993"All 13 LRALL units tested met the design specification"
— NTRS 20210010915, LPSC 2021 poster
Funding before the lunar flight¶
- NASA's CLPS program (with a NASA Postdoctoral Program fellowship for the optical tests). No amount public for the program or this unit; no SBIR or USAspending award names it. (NASA CLPS; not in public sources): amount not in public sources
"Funding National Aeronautics and Space Administration (NASA) Commercial Lunar Payload Services (CLPS)"
— NTRS 20205001993, Funding
How it got onto CLPS¶
"Laser Retroreflector Arrays for Lunar Landers (LRALL) developed under the Commercial Lunar Payload Services (CLPS) program"
— NTRS 20210010915, LPSC 2021 poster"Surface Exosphere Alterations by Landers (SEAL), and LRA"
— NTRS 20230010539, CLPS office overview, LEAG 2023 (CP-22 payloads)"The Laser Retroreflector Array is a collection of eight retroreflectors"
— NASA Awards Intuitive Machines Lunar South Pole Research Delivery - NASA, 29 Aug 2024
On the Moon¶
Manifested on IM-4. NASA has also put the same LRA on Blue Moon Pathfinder Mission 1, Blue Ghost Mission 4 and four late-2028 landings (see the study's manifest).
"Laser Retroreflector Array (LRA): Reflects laser beams transmitted by Moon orbiters or landing spacecraft"
— NASA Awards More Moon Base Science, Previews New Opportunities - NASA
FO's role¶
Grade: none. No FO project, flight or report mentions the LRA or its Goddard team. A passive marker had no need of a suborbital test; its proof came from earlier landers and LRO ranging. The study's earlier traceback grade (none found) stands.
"No FO record or report names SCALPSS, ROLSES, LN-1, the retroreflectors,"
— earlier finding of this study (not a public source)"Nothing in the FO sources. Not in the CLPS office's CP-22 paragraph; named in NASA's award release."
— earlier finding of this study (not a public source)
Who built it¶
"PI: Dr. Xiaoli Sun, GSFC"
— CLPS CP-22 Science - NASA Science"The retroflector array is managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland."
— NASA Awards Intuitive Machines Lunar South Pole Research Delivery - NASA
Moon Base need¶
"Navigation aid, not a data gap's subject."
— Moon to Mars knowledge base: Architecture data gaps: all 25, LRA row"LRAs can eventually be used to help spacecraft land in otherwise pitch-dark places close to permanently shadowed regions near the lunar South Pole"
— How NASA Uses Simple Technology to Track Lunar Missions - NASA"this growing network will allow scientists to gauge the location of key landers and other points of interest more and more accurately"
— How NASA Uses Simple Technology to Track Lunar Missions - NASA"These three payloads are flight-proven and their data is critical to supporting safe human explo"
— NASA Awards More Moon Base Science, Previews New Opportunities - NASA, 30 Jun 2026"box with a date range: Phase 1 "Now through 2028""
— Moon to Mars knowledge base: Moon Base phases
Open questions¶
- The LRA program's cost and the cost per array: not in public sources.
- Lessons from the tipped IM-1 and IM-2 arrays (mounting location, tilt): has the IM-4 mounting changed? Not in public sources.
- Which of the 13 tested units flies on IM-4: not in public sources.