In 1964, NASA bounced a laser off a satellite; today, it helps track melting ice

Goddard physicist Henry Plotkin inspects the retroreflector array destined for the 1964 Beacon Explorer A satellite, PC: Henry Plotkin/ Nasa On October 29, 1964, a team at NASA's Goddard Space Flight Centre in Greenbelt, Maryland, recorded the first successful laser returns from an artificial satellite. The target was Beacon Explorer B, also known as Explorer 22, a satellite fitted with a laser retroreflector array designed to bounce a beam of light back toward its source. NASA publicised the results on November 13, 1964, describing the system as GODLAS, short for Goddard laser. The technique, now known as satellite laser ranging, measures the distance between a ground station and an orbiting satellite by timing how long a laser pulse takes to travel to the spacecraft and return. What began as a single experiment in Maryland eventually became a highly precise way to study Earth's shape, gravity and motion. Related laser technology now helps scientists measure changes in ice sheets, monitor glaciers from orbit and determine how melting ice contributes to rising seas around the world.How satellite laser ranging beat radar tracking by 25 times the precisionAccording to Nasa's history ...