# Gravity Recovery and Climate Experiment

> joint mission of NASA and the German Aerospace Center

**Wikidata**: [Q704319](https://www.wikidata.org/wiki/Q704319)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/GRACE_and_GRACE-FO)  
**Source**: https://4ort.xyz/entity/gravity-recovery-and-climate-experiment

## Summary
The Gravity Recovery and Climate Experiment (GRACE) was a joint mission between NASA and the German Aerospace Center (DLR) designed to measure Earth's gravity field and its variations over time. Launched in 2002, the mission used twin satellites (GRACE-1 and GRACE-2) to track changes in water distribution, ice mass, and other climate-related phenomena by detecting minute shifts in gravitational pull.

## Key Facts
- **Joint mission** between NASA (United States) and the German Aerospace Center (Germany).
- **Launched on March 17, 2002**, from Plesetsk Cosmodrome Site 133 using a Rokot launch vehicle.
- **Consisted of two satellites**: GRACE-1 and GRACE-2, which orbited Earth in tandem.
- **Operational period**: 2002–2017 (retired on October 27, 2017).
- **Primary objective**: Measure Earth's gravity field to study climate-related changes, such as water distribution, ice melt, and ocean currents.
- **Manufacturers**: Space Systems (general contractor) and Lanteris Space Systems (subcontractor).
- **Follow-on mission**: Gravity Recovery and Climate Experiment Follow-On (GRACE-FO), which continued the original mission's goals.

## FAQs
### Q: What was the purpose of the GRACE mission?
A: The GRACE mission aimed to map Earth's gravity field with unprecedented precision, enabling scientists to track changes in water storage, ice sheets, and ocean currents—key indicators of climate change.

### Q: How did GRACE measure gravity?
A: The twin satellites (GRACE-1 and GRACE-2) flew in formation, using microwave ranging to detect tiny distance changes caused by variations in Earth's gravitational pull, which reflect mass distribution below.

### Q: When did GRACE end, and what replaced it?
A: GRACE retired on October 27, 2017, after 15 years of operation. It was succeeded by GRACE-FO (Follow-On), launched in 2018, which continues the same scientific objectives.

### Q: Who operated the GRACE mission?
A: The mission was a collaboration between NASA (U.S.) and the German Aerospace Center (DLR), with contributions from research institutions like the University of Texas and GFZ Potsdam.

### Q: What were the key discoveries of GRACE?
A: GRACE provided critical data on ice loss in Greenland and Antarctica, groundwater depletion, and ocean circulation patterns, significantly advancing climate science.

## Why It Matters
The Gravity Recovery and Climate Experiment revolutionized our understanding of Earth's dynamic systems by providing the first comprehensive, high-resolution maps of the planet's gravity field. By tracking subtle changes in mass distribution—such as melting glaciers, shifting water tables, and ocean currents—GRACE offered direct evidence of climate change's impact on Earth's physical systems. Its data has been instrumental in improving climate models, water resource management, and disaster preparedness. The mission's success also paved the way for GRACE-FO, ensuring continuity in monitoring these critical environmental variables. For scientists, policymakers, and the public, GRACE underscored the interconnectedness of Earth's systems and the urgency of addressing climate-related challenges.

## Notable For
- **First mission to map Earth's gravity field** with high temporal and spatial resolution.
- **Pioneered twin-satellite formation flying** for gravitational measurements, a technique later adopted by GRACE-FO.
- **Provided direct evidence of ice sheet loss** in Greenland and Antarctica, quantifying their contribution to sea-level rise.
- **Revealed groundwater depletion** in major aquifers worldwide, highlighting unsustainable water use.
- **Enabled breakthroughs in oceanography** by tracking deep ocean currents and their role in climate regulation.

## Body
### Mission Overview
The Gravity Recovery and Climate Experiment (GRACE) was a collaborative space mission between NASA and the German Aerospace Center (DLR). Its primary goal was to create detailed maps of Earth's gravity field and its variations over time, which are influenced by the redistribution of mass—such as water, ice, and air—across the planet.

### Satellite Design and Operation
- **Twin Satellites**: GRACE-1 and GRACE-2 orbited Earth in a near-polar orbit at an altitude of approximately 500 km, separated by about 220 km.
- **Measurement Technique**: The satellites used a microwave ranging system to measure minute changes in their separation distance (as small as a few micrometers) caused by gravitational anomalies.
- **Data Collection**: Over 15 years, GRACE collected monthly gravity field maps, enabling scientists to monitor long-term trends and seasonal variations.

### Launch and Lifespan
- **Launch Date**: March 17, 2002, at 09:21:27 UTC from Plesetsk Cosmodrome, Russia.
- **Launch Vehicle**: Rokot (a modified Russian SS-19 intercontinental ballistic missile).
- **Mission Duration**: Operated from 2002 to 2017, far exceeding its original 5-year design lifetime.
- **End of Mission**: GRACE-2's battery failure led to the mission's retirement on October 27, 2017.

### Scientific Contributions
- **Ice Sheet Monitoring**: GRACE data showed accelerated ice loss in Greenland and Antarctica, contributing to global sea-level rise.
- **Groundwater Studies**: Identified critical groundwater depletion in regions like California's Central Valley and the Indian subcontinent.
- **Oceanography**: Improved understanding of ocean bottom pressure and deep currents, which influence climate patterns like El Niño.
- **Earthquake and Tsunami Research**: Detected mass redistributions associated with major seismic events, such as the 2004 Sumatra-Andaman earthquake.

### Follow-On Mission
GRACE was succeeded by **GRACE-FO** (Follow-On), launched in May 2018. The new mission uses similar twin-satellite technology but incorporates laser ranging for even higher precision. GRACE-FO continues to monitor Earth's gravity field, ensuring uninterrupted data for climate research.

### Key Institutions Involved
- **NASA**: Primary operator and data distributor (via the Jet Propulsion Laboratory).
- **German Aerospace Center (DLR)**: Co-operator and funder, with contributions from GFZ Potsdam.
- **University of Texas at Austin**: Hosted the Center for Space Research, a major data processing hub.
- **Space Systems/Loral**: Manufactured the satellites as the general contractor.

## Schema Markup
```json
{
  "@context": "https://schema.org",
  "@type": "Thing",
  "name": "Gravity Recovery and Climate Experiment",
  "description": "A joint mission of NASA and the German Aerospace Center to measure Earth's gravity field and its variations over time.",
  "url": "https://grace.jpl.nasa.gov/",
  "sameAs": [
    "https://www.wikidata.org/wiki/Q6272367",
    "https://en.wikipedia.org/wiki/GRACE_and_GRACE-FO"
  ],
  "additionalType": "SpaceMission"
}

## References

1. [Source](https://space.skyrocket.de/doc_sdat/grace.htm)
2. Jonathan's Space Report
3. Freebase Data Dumps. 2013
4. [Source](https://www.jpl.nasa.gov/news/news.php?feature=6984)