Before our Global Positioning System (GPS) navigation devices can inform us where we are, the satellites that form the GPS need to know precisely where they themselves are. For that, they rely on a network of sites that serve as “you are here” signs planted throughout the world. The catch is, the sites don’t sit still because they’re on a planet that isn’t at rest, yet modern measurements require more and more accuracy in pinpointing where “here” is. To meet this need, NASA is helping to lead an international effort to upgrade the four systems that supply this crucial location information. Read More
