Overview
- GRACE ( Gravity Recovery and Climate Experiment) was a joint satellite mission of NASA and the German Aerospace Center (DLR).
- Launched in 2002, it operated till 2017.
- Objective was to map Earth’s gravity field and track its changes over time.
Scientific Principle
- GRACE consisted of two identical satellites flying about 220 km apart in the same orbit.
- Variations in Earth’s gravity caused slight changes in the distance between the satellites.
- These distance changes were measured with micron-level precision, allowing scientists to infer mass redistribution on Earth.
What GRACE Measured
- Changes in groundwater storage
- Melting of glaciers and ice sheets
- Variations in soil moisture
- Changes in sea level and ocean mass
- Mass shifts due to droughts, floods, and earthquakes
Key Contributions
- Provided the first direct satellite-based measurement of groundwater depletion.
- Confirmed rapid ice mass loss in Greenland and Antarctica.
- Enabled monitoring of large river basins such as the Ganga, Indus, Amazon, and Mississippi.
- Helped quantify the contribution of land ice melt to global sea-level rise.
Importance for India
- GRACE data showed significant groundwater depletion in northwestern India, especially in Punjab, Haryana, Rajasthan, and parts of Uttar Pradesh.
- Highlighted the unsustainable extraction of groundwater due to intensive agriculture and urban demand.
- Strengthened evidence-based policymaking on water security and climate adaptation.
Successor Mission: GRACE-FO
- GRACE Follow-On (GRACE-FO) launched in 2018.
- Continues the original mission with improved technology, including laser interferometry for even higher precision.
- Ensures continuity of long-term gravity and climate data.
Why GRACE Matters
- Enabled a shift from indirect estimates to direct observation of Earth’s water balance.
- Plays a critical role in climate change studies, disaster assessment, and sustainable resource management.
- Considered one of the most impactful Earth-observation missions for hydrology and climate science.
