# GRACE-FO Laser Ranging Interferometer (LRI)
*sensor . products*

Laser inter-satellite ranging technology demonstration on GRACE-FO.

## Specifications
- **manufacturer**: nasa-jpl
- **product status**: demonstration
- **deployment context**: orbital
- **sensor**: {"instrument_family":"gravimeter","gravimeter_principle":"sst-ll","intersatellite_distance_km":220,"notes":"Laser interferometric inter-satellite ranging demonstration on GRACE-FO, operated alongside the microwave ranging system."}
- **entity type**: sensor
- **last verified date**: 2026-06-08
- **verified by**: agency-doc
- **claim status**: agency-sourced
- **provider**: nasa-jpl
- **attributes**: {"kind":"sensor","manufacturer":"nasa-jpl","product_status":"demonstration","deployment_context":"orbital","description":"Laser inter-satellite ranging technology demonstration on GRACE-FO.","sensor":"{\"instrument_family\":\"gravimeter\",\"gravimeter_principle\":\"sst-ll\",\"intersatellite_distance_km\":220,\"notes\":\"Laser interferometric inter-satellite ranging demonstration on GRACE-FO, operated alongside the microwave ranging system.\"}"}
- **relevance**: in-scope

## Editorial
GRACE-FO Laser Ranging Interferometer (LRI) is the laser inter-satellite ranging instrument flown on the GRACE-FO twin spacecraft. It measures fluctuations in the distance between the satellites by laser interferometry rather than microwave ranging [^gracefo-spacecraft]. The instrument was switched on after launch in 2018 and produced laser-ranging measurements across the roughly 220 km spacecraft separation [^lri-first-light]. LRI is a technology demonstration for future gravity missions while GRACE-FO continues the K/Ka-band microwave ranging record [^gracefo-spacecraft].

## Compositional position
- grace-fo (missions) --[mission_payloads]--> GRACE-FO Laser Ranging Interferometer (LRI)

## Sources
- [gracefo-spacecraft] | GRACE-FO spacecraft and instruments, NASA JPL | https://www.jpl.nasa.gov/news/press_kits/grace-fo/mission/spacecraft/ | tier=agency-doc | accessed=2026-06-08
- [lri-first-light] | First Laser Light for GRACE Follow-On, NASA JPL | https://gracefo.jpl.nasa.gov/news/138/first-laser-light-for-grace-follow-on/ | tier=operator-press | accessed=2026-06-08 | published=2018-07-02
- [gfz-gracefo] | GRACE-FO project, GFZ | https://www.gfz.de/en/section/global-geomonitoring-and-gravity-field/projects/grace-fo | tier=agency-doc | accessed=2026-06-08

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Source: https://eo-atlas.org/products/sensor/lri
Maintainer: SpectraWorks B.V. (CC-BY 4.0)