Laser Retroreflector Array (LRA)¶

IM-2 · landed · NASA payload

A passive optical marker: eight small glass corner-cube prisms in a gold-painted aluminum dome on the lander's top deck. Laser altimeters on orbiters or landers can range to it, 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 array. 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 network of fixed markers for positioning (#0101). The IM-2 array sits at Mons Mouton, near the South Pole, where Moon Base sites are.)
Route onto CLPS	other NASA; No payload call named. The LRA was developed under NASA's CLPS program itself and is added to most CLPS landers. NASA's page lists the same LRA for TO2-IM, TO2-AB, VIPER's task order and PRIME-1; the IM-2 unit rode under the PRIME-1 task order, awarded in October 2020. When this unit was assigned is not in public sources.
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 not in public sources (rode under the PRIME-1 task order of 2020-10-16); launch 2025-02-26; landing 2025-03-06
On the Moon	not in public sources
FO	none

Flights before the Moon¶

earlier lunar mission: SpaceIL's Beresheet lander (same Goddard LRA design), 2019-02-21. The first flight of this array 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 of the design), 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. On 12 December 2023 LRO's laser altimeter ranged to it from orbit, the first such ranging to a small array.

"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

earlier lunar mission: JAXA's SLIM lander (a NASA retroreflector), 2024-01. A NASA LRA landed in January 2024. LRO has 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

"The number of opportunities and success rate to SLIM were low given the off-nominal lander attitude."
— 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 type, 2024-02-22. The same design on a Nova-C lander. Odysseus tipped over, and LRO had no returns from its LRA as of December 2025.

"It landed on February 22, 2024."
— Commercial Lunar Payload Services (CLPS) Deliveries - NASA Science

"So far, no returns have been received from IM-1"
— hou.usra.edu: 1707.pdf

Heritage hardware¶

design heritage: Similar small arrays flew on the ExoMars and InSight landers. The design is smaller than the Apollo arrays and dome-shaped, so orbiters, not Earth stations, can range to it from most directions. Small retroreflectors are also docking markers on the ISS.

"Similar small LRAs were placed on the ExoMars and InSight landers"
— NTRS 20205001993

"Laser ranging is also used for docking spacecraft"
— How NASA Uses Simple Technology to Track Lunar Missions - NASA

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. (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

"They will be attached to most of the landers from United States companies"
— How NASA Uses Simple Technology to Track Lunar Missions - NASA

"Task Order: CLPS TO2-IM (2/20C/OP), TO2-AB, TO20A-VIPER, and PRIME-1"
— TO2-IM Science Payloads - NASA Science

On the Moon¶

The array landed on the top deck of a lander lying on its side in a crater. NASA says it stays fixed to the deck; no source reports any laser ranging to it. A Goddard LPSC 2026 abstract lists the small arrays on the Moon as of late 2025 (Chandrayaan-3, IM-1, SLIM, Chang'e-6) and does not mention IM-2's. The array is passive, so it could still be found later.

"NASA’s Laser Retroreflector Array, a passive instrument meant to provide a reference point on the lunar surface and does not power on, will remain affixed to the top deck of the lander."
— NASA Receives Some Data Before Intuitive Machines Ends Lunar Mission - NASA

"lunar landers. As of late 2025 these include the"
— hou.usra.edu: 1707.pdf, the list follows: CH3, IM-1, SLIM, CE6

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)

Who built it¶

"Lead Development Organization: NASA Goddard Space Flight Center"
— NASA press kit, Commercial Lunar Payload Services IM-2 (Intuitive Machines-2) Lunar Mission

"Task Order: CLPS TO2-IM (2/20C/OP), TO2-AB, TO20A-VIPER, and PRIME-1"
— TO2-IM Science Payloads - NASA Science

"Payload PI: Dr. Xiaoli Sun"
— TO2-IM Science Payloads - NASA Science

Moon Base need¶

"Navigation aid, not a data gap's subject."
— Moon to Mars knowledge base: Architecture data gaps: all 25, Moon Base science awards table, 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

Open questions¶

Has LRO tried to range to the IM-2 array, and with what result? Not in public sources; the LPSC 2026 abstract does not list it.
Which way does the array face now that Athena lies on its side? Not in public sources.
The LRA program's cost and the cost per array: not in public sources.