The Hubble Space Telescope has joined the hunt for a target beyond Pluto for NASA’s New Horizons robotic spacecraft.

Three years of searching for a suitable Kuiper Belt Object, or KBO, with ground-based telescopes proved fruitless and scientists are running out of time.  A close encounter with a KBO is a major part of New Horizons’ science goals to investigate outer bodies in the solar system. The spacecraft, which was launched in 2006, is slated to fly by Pluto on July 14, 2015.

Scientists on Monday began a two-week observation campaign with Hubble in an effort to find at least one KBO that will be in range of New Horizons following its Pluto encounter.

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The spacecraft must fire its maneuvering engine to put itself on track for a KBO flyby by December 2015.

"Hubble can knock this out in a couple of weeks with a 95 percent probability of success," lead scientist Alan Stern, with the Southwest Research Institute in Boulder, Colo., told Discovery News.

If the two-week pilot search with Hubble is successful, scientists will get another 160 orbits' worth of telescope time to flesh out details of the target's orbit and perhaps find more than one KBO that will be within New Horizons' range.

"My fondest hope is we could find a couple or three KBOs and then be in the happy position of having to choose between them," Stern said.

Pluto, an icy dwarf planet about 4.7 billion miles from Earth, has never been visited by a spacecraft. New Horizons is designed to not only explore Pluto and its constellation of satellites, but also at least one smaller body in the pristine, frigid Kuiper Belt region of the solar system.

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Scientists believe KBOs are untouched remnants of the solar system's formation some 4.6 billion years ago. Pluto, which is now known as a "dwarf planet," has undergone tremendous changes since its formation, including a massive collision that scientists believe created its large partner moon, Charon.

Pluto also may generate enough internal heat to maintain an underground ocean.

New Horizons' science observations of Pluto are due to begin in January. By May, its view of Pluto should be better than Hubble's, Stern said.

Image: Hubble view of Pluto, the best pictures of the dwarf planet until New Horizons’ approach. Credit: NASA/ESA/M.Buie, Southwest Research Institute