GRACE: Tracking Water from Space

The GRACE twin satellites, launched 17 March 2002, are making detailed measurements of Earth's gravity field and revolutionizing investigations about Earth's water reservoirs, over land and ice...and over the oceans.GRACE TELLUS
  
GRACE Orbital Configuration (plots updated daily)
Educational Material

Orbiting Twins - The GRACE satellites

Why GRACE Tellus ? . Tellus was the Roman Goddess of the planet Earth, and in English it offers a wordplay, so we can ask 'What can GRACE, and time changes in gravitational acceleration TELL US about our changing planet'?

GRACE (Gravity Recovery and Climate Experiment) is a NASA mission that uses a pair of satellites to measure Earth's gravitational field. By regularly measuring changes in the gravitational field, scientists can indirectly track the motions of large masses of water. The GRACE satellites began orbiting in March 2002. They orbit once every 90 minutes, taking 30 days to cover the entire Earth. Since the movement of water can be detected on this time scale, GRACE's ever-growing data set is revealing long-term changes in Earth's water and its relationship to changing climate.

GRACE Gravity Recovery and Climate Experiment 
Scientists have been using small variations in the Earth's gravity to identify trouble spots around the globe where people are making unsustainable demands on groundwater, one of the planet's main sources of fresh water.

Gravity Recovery and Climate Experiment, known as Grace, relies on the interplay of two nine-year-old twin satellites that monitor each other while orbiting the Earth, thereby producing some of the most precise data ever on the planet's gravitational variations. The results are redefining the field of hydrology, which itself has grown more critical as climate change and population growth draw down the world's fresh water supplies.