On March 17, 2002, NASA launched the GRACE twins, two Gravity Recovery and Climate Experiment satellites. They flew about 220 km ( 137 mi ) apart in a polar orbit at 485 km (300 mi) above Earth, measuring regional areas of its gravity field, working together as a single instrument.
This pair of satellites made up a phenomenal science cool tool. By measuring gravity periodically, GRACE reported on how much water storage in underground aquifers changed over time. Or in its ice sheets. This is because Earth’s gravitational field strength changes with minor surface changes – more water, less water, running water, rainstorm and flooding water – that affect the distribution of Earth’s mass. The twins took precise gravity measurements so they detected water differences from one data recording to another.
As the GRACE twins revealed freshwater storage, freshwater trends, and freshwater reserves around the world, we learned more about this priceless resource and how much international planning and cooperation we required to preserve it for life on our planet.
Today, the next generation of these twins – GRACE-FO (GRACE-Follow On) continues the work to track those gravitational changes in sea levels, ice sheets, glaciers, along with large lake and river water levels and moisture in soils. The new GRACE-FO twins additionally create a minimum of 200 daily profiles of our planet’s atmospheric temperature distribution and water vapour content.
B Bondar / Real World Content Advantage