Science

GRACE-FO 1

Earth Gravity Field Science Satellite (Water & Ice Monitoring) · NASA / DLR (Germany)

GRACE-FO 1, one of a pair of identical satellites flying 137 miles apart, so precisely tracking the tiny changes in distance between them — down to less than the width of a human hair — that scientists can map how Earth's gravity itself shifts as water moves around the planet. When a drought drains an aquifer or an ice sheet loses mass, gravity there weakens by a barely perceptible amount, and GRACE-FO catches it. Launched in 2018 as a joint NASA-German Aerospace Center mission continuing the original GRACE satellites' work, it also carries an experimental laser ranging interferometer accurate to a single nanometer — technology now considered foundational to LISA, the future space-based gravitational wave observatory.