First use of laser ranging to surface retroreflectors for orbit determination: LRO at the Moon
Gael Cascioli
This work presents the first successful spacecraft-based lunar laser ranging (LLR) measurements, using the Lunar Reconnaissance Orbiter (LRO) to obtain ranges to laser retroreflector arrays (LRAs) on the Moon's surface.
Between February 2023 and December 2024, we successfully ranged to four different targets: the Apollo 11 and Apollo 14 retroreflector arrays deployed during the historic lunar missions, as well as two modern miniature LRAs carried by the Chandrayaan-3 and Chang'E-6 missions.
The dataset includes ranging measurements spanning 42 orbital arcs over nearly two years of operations. Our ranging attempts targeted LRAs during favorable geometric conditions when LRO's orbital position provided optimal viewing angles and distances. The successful measurements demonstrate range accuracies of approximately 1.7 meters and angular accuracies of about 0.023 degrees (~400 microradians), representing the first time such measurements have been obtained from a spacecraft rather than Earth-based observatories.
We integrated these LRA measurements with traditional Doppler tracking data in LRO's orbit determination process, solving simultaneously for spacecraft trajectory parameters and LRA coordinates in the lunar body-fixed reference frame. The analysis shows good agreement between our derived LRA positions and independent estimates from Lunar Reconnaissance Orbiter Camera (LROC) observations and historical lunar laser ranging data, with coordinate differences typically within expected uncertainties.
We provide the raw dataset we used in the analysis. Data collection occurred across various lunar lighting conditions and orbital geometries, offering a comprehensive view of the measurement capabilities under different circumstances.
This demonstration proves the feasibility of using orbiting spacecraft for lunar laser ranging, complementing traditional Earth-based LLR operations. The technique could enhance navigation accuracy for future lunar missions by establishing geodetic reference networks on the lunar surface. The miniature LRAs, in particular, represent a practical approach for future landers to contribute to such networks with minimal mass and power requirements.
The LOLA data used in this work is archived here in CSV format. The CSV contains only the LOLA observations of successful LRA returns during the period February 5 2023 – December 13 2024.
The data contained in the csv file is a subset of the data that can be obtained by the LOLA raw data (RDR products). The full and updated archive of LOLA RDRs can be found on the PDS Geosciences (link, doi:10.17189/1520652).
The CSV file can be downloaded here.
Data description
Below a description of the data contained in the csv and a scheme showing the data selection logic (for more details on the data selection logic see the accompanying manuscript, section 3.2).| Column name | Unit | Description |
|---|---|---|
| RDR filename | - | Name of the original LOLA RDR file the data was extracted from. |
| Target site | - | Name of the targeted LRA. |
| Day/night | - | Indicates if the observation was taken on the day or night side. |
| TDT transmit | s | Laser pulse transmit time. Time system Terrestrial Dynamical Time (TDT), seconds past 01-JAN-2000 12:00. |
| Orbit time | s | Time since ascending node. |
| Return time | ms | Receive time of the laser pulse expressed in ms in the Mission Elapsed Time (MET) time system. |
| Off-nadir angle | degree | LOLA pointing angle off-nadir. |
| Channel number | - | The LOLA spot (channel) number of this record/row. |
| Latitude | degree | Geolocated latitude of the laser pulse hit point (with respect to a spherical moon with radius 1737400 m). |
| Latitude | degree | Geolocated longitude of the laser pulse hit point (with respect to a spherical moon with radius 1737400 m). |
| Raw range | km | Uncalibrated one-way range (time of flight). |
| Pulse Width Corr. Range | km | One-way range calibrated by subtracting half the pulse width |
| Radius | m | Hit point radial location with respect to a spherical moon (1737400 m). |
| Delta Radius | m | Difference with respect to a priori location of the LRA. |
| Distance to LRA | m | Distance to the a priori location of the LRA on the surface of the moon. |
| Noise rate | Hz | Estimated noise rate of the laser pulse (noise counts per second). |
| Pulse width | ns | Width of the emitted laser pulse. |
| Energy | fJ | Received energy. |
| Threshold | mV | Receiver threshold. |
| Range_Valid | True/False | Flag indicating if the range measurement has been considered valid (see selection logic below). |
| Angle_Valid | True/False | Flag indicating if the angle measurement has been considered valid (see selection logic below). |
| Angle sigma | - | Scale factor on the measurement noise for the angle measurement (if valid, see below) |
| Range sigma | - | Scale factor on the measurement noise for the range measurement (if valid, see below) |
The decision logic for measurement selection and relative weighting (see Section 3.2 in the accompanying manuscript).
Data Usage Policy
Please cite the following reference when using any of the products described above:Manuscript: Cascioli, G. et al. (2025), First use of laser ranging to surface retroreflectors for orbit determination: LRO at the Moon, The Planetary Science Journal, doi:10.3847/psj/ae0e0b.
Dataset: Cascioli, G. et al. (2025), First use of laser ranging to surface retroreflectors for orbit determination: LRO at the Moon [Data set]. NASA Goddard Space Flight Center Planetary Geodesy Data Archive. doi:10.60903/GSFCPGDA-LOLA-LRA.