Radio readings from an array of antennas in Chile are helping the scientists behind NASA's New Horizons mission to Pluto determine the dwarf planet's precise position — so that the spacecraft can zero in properly during next July's flyby. Pluto is 40 times farther away from the sun than Earth, and it's been tracked for only 84 years' worth of its 248-year orbit. “With these limited observational data, our knowledge of Pluto’s position could be wrong by several thousand kilometers," New Horizons project scientist Hal Weaver explained in a news release from the National Radio Astronomy Observatory.
Scientists are cutting that uncertainty in half by picking up faint radio emissions from Pluto and its largest moon, Charon, using the Atacama Large Millimeter/Submillimeter Array (better known as ALMA). Those emissions, plus newly analyzed visible-light measurements, were compared with radio readings from a cosmic reference point — a distant quasar known as J1911-2006. New Horizons' principal investigator, Alan Stern, said the results should "help us better target our historic exploration of the Pluto system."
— Alan Boyle, NBC News