"New Horizons on Approach: 22 AU Down, Just 10 to Go
Few spacecraft travel 10 astronomical units during their entire mission. But with New Horizons already logging more than twice that distance on its way to Pluto, coming to within 10 AU of its main target is akin to entering the home stretch.
An astronomical unit is the average distance between Earth and the sun, about 93 million miles or 149 million kilometers. At around 4:55 Universal Time on Feb. 11 (or late tonight in the U.S.), New Horizons crosses to within 10 AU of the Pluto system. To the team that has guided the piano-sized probe since its launch in January 2006, that means approach distances that used to be marked in billions of miles can be counted in millions, and astronomical units to go are listed in single digits.
