The audio of this story, as was the case in a previous Web introduction, incorrectly says that the spacecraft's orbit was half a million miles from the sun. It's actually half a billion miles.
Joe Palca is a science correspondent for NPR. Since joining NPR in 1992, Palca has covered a range of science topics — everything from biomedical research to astronomy. He is currently focused on the eponymous series, "Joe's Big Idea." Stories in the series explore the minds and motivations of scientists and inventors. Palca is also the founder of NPR Scicommers – A science communication collective.