In time for Earth Day, NASA ran an online contest to let Earthlings pick the top 10 biggest accomplishments in the agency's five decades of observing the planet.
The candidates were picked from a National Academy of Sciences study in 2008. The winners were announced Tuesday, on the eve of Earth Day.
First place: GPS.
According to NASA, the power behind the Global Positioning System is a large body of scientific data about the Earth. "Precise navigation with GPS satellites would be impossible without ultra-precise knowledge of Earth's shape and how it rotates. NASA pioneered much of this work with a global network of laser ranging satellites and super-charged GPS receivers to monitor daily changes in Earth's surface," the agency says.
This is NASA's Laser Geodynamics Satellite, Lageos I, launched in 1976.
