# Satellite gravimetry
*sensing . methodologies*

Retrieves time-variable gravity-field and mass-change signals by tracking changes in distance between two co-orbiting satellites, as in GRACE and GRACE-FO.

## Specifications
- **family**: Gravimetry
- **requirements envelope**: {"kind":"temporal","cadence_max_days":31,"time_series_length_min":12}
- **entity type**: methodology
- **last verified date**: 2026-06-08
- **verified by**: agency-doc
- **claim status**: agency-sourced
- **subtype**: sensing
- **attributes**: {"family":"Gravimetry","summary":"Retrieves time-variable gravity-field and mass-change signals by tracking changes in distance between two co-orbiting satellites, as in GRACE and GRACE-FO.","requirements_envelope":"{\"kind\":\"temporal\",\"cadence_max_days\":31,\"time_series_length_min\":12}","kind":"sensing"}
- **technology**: gravimetry
- **relevance**: in-scope

## Editorial
Satellite gravimetry is the method used when the target is mass redistribution rather than surface appearance. A pair of satellites follows the same orbit; changes in the pull of Earth's gravity alter their separation, and precision inter-satellite ranging turns those distance changes into monthly gravity-field and equivalent-water-height maps. It resolves basin-to-global mass signals such as ice-sheet mass, groundwater and terrestrial water storage, and ocean-mass sea-level components. It is weak for local detail: spatial resolution is coarse, leakage corrections matter near coasts and small basins, and the retrieval depends on geophysical background corrections.

## Sources
- [grace-fo-overview] | GRACE-FO Mission Overview, NASA/JPL | https://gracefo.jpl.nasa.gov/mission/overview/ | tier=agency-doc | accessed=2026-06-08
  Describes paired GRACE-FO satellites, approximately 220 km separation, precise microwave ranging, accelerometers, and monthly gravity-field maps showing mass movement.
- [grace-jpl] | Gravity Recovery and Climate Experiment (GRACE), NASA/JPL | https://www.jpl.nasa.gov/missions/gravity-recovery-and-climate-experiment-grace/ | tier=agency-doc | accessed=2026-06-08
  Mission overview: GRACE measured gravity changes with twin spacecraft and supported ice mass, sea level, groundwater, drought, and solid-Earth applications.
- [grace-review] | Applications and Challenges of GRACE and GRACE Follow-On Satellite Gravimetry | https://pmc.ncbi.nlm.nih.gov/articles/PMC9050784/ | tier=peer-reviewed | accessed=2026-06-08
  Review of GRACE/GRACE-FO satellite gravimetry applications and limitations for cryosphere, hydrology, oceans, and solid Earth.

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Source: https://eo-atlas.org/methodologies/satellite-gravimetry
Maintainer: SpectraWorks B.V. (CC-BY 4.0)