ALMA Pinpoints Pluto to Guide New Horizons Mission to Distant Planet

Pluto may just be the guiding "star" that NASA's spacecraft needs. Astronomers are using the Atacama Large Millimeter/submillimeter Array (ALMA) to make high-precision measurements of Pluto's location and orbit in order to help guide the New Horizons spacecraft to its target.

Although scientists have examined Pluto and its five known moons for decades, they're still trying to pin down its exact position and path around our solar system. This uncertainty is mostly due to its extreme distance from the sun-about 40 times farther out than Earth. In addition, it's only been studied for about one-third of its orbit; it takes Pluto 248 years to complete one revolution.

"With these limited observational data, our knowledge of Pluto's position could be wrong by several thousand kilometers, which compromises our ability to calculate efficient targeting maneuvers for the New Horizons spacecraft," said Hal Weaver, New Horizons Project scientist, in a news release.

The researchers used ALMA positioning data along with newly analyzed visible light measurements in order to figure out how to perform the first scheduled course correction for New Horizons. This maneuver, called a Trajectory Correction Maneuver (TCM), helps ensure that the spacecraft uses the minimum amount of fuel to reach Pluto.

The most distant, and apparently stable, objects in the universe are called quasars. These are galaxies that are more than 10 billion light years away. In this case, ALMA used a bright quasar named J1911-2006 in order to cut in half the uncertainty of Pluto's position.

"We are very excited about the state-of-the-art capabilities that ALMA brings to bear to help us better target our historic exploration of the Pluto system," said Alan Stern, New Horizons Principal Investigator.

Currently, New Horizons is slated to wind up near Pluto before continuing its journey to a possible extended mission to explore Kuiper Belt objects.