The planet Pluto—or “dwarf planet” as the members of the International Astronomical Union prefer to classify it today—is a very long way from Earth. If viewed from the icy surface of Pluto, our Sun would appear as an especially bright and large star.
At its closest approach to us in its highly eccentric and inclined orbit, Pluto is 4.2 billion km (2.6 billion miles) away, while at its farthest distance from us is 7.5 billion km (4.6 billion miles) away.
The idea of sending a nuclear-powered robot spacecraft to Pluto began in 1990 when a 29-cent U.S. stamp was released captioning speculative artwork of the gauzy planet Pluto as “Not Yet Explored.”
Origins of New Horizons
A small, but determined “Pluto Underground”—with most of its members being space enthusiasts, amateur astronomers, and academic researchers—began writing letters addressed to NASA and U.S. legislators to consider a bold, new planetary mission to the distant world, discovered by astronomer Clyde Tombaugh in 1930.
After several premature efforts, including the stillborn Pluto Fast Flyby and Pluto Kuiper Express missions, the U.S. space agency’s New Horizons mission plan to explore Pluto and the Kuiper Belt ignited the imaginations of key space scientists, D.C. legislators, and bureaucrats.
Thus, New Horizons emerged from the ashes of the Pluto Fast Flyby and Pluto Kuiper Express efforts.
New Horizons: Survivor in Deep Space
On Jan. 19, 2006, the New Horizons spacecraft began its nine-year voyage to Pluto after being lofted into space by an Atlas 5 rocket from Cape Canaveral, Florida.
The compact robot is expected to reach Pluto space in July 2015.
In the intervening years, between its Bush-era launch and today, this little-known NASA mission has endured the news media’s short-attention span, a new White House’s lack of passion for space exploration, even the political brinksmanship of a government shutdown.
As of November 2013, the RTG, or radioisotope thermal generator, powered spacecraft (traveling at 58,000 kph or 36,000 mph) is 11 billion km (6.8 billion miles) from Earth. For an idea of just far away New Horizons is, radio signals from Earth take nearly 4 hours to reach it (with another 4 hours to receive a return signal).
On its long trek to Pluto, the rugged spacecraft has already gathered impressive data sets about an asteroid, the geophysics of interplanetary space beyond Mars, and the super-charged space around the gas giant Jupiter and its retinue of moons, both large and small.
A few months after launch, New Horizons zipped by the asteroid 132524 APL beyond the orbit Mars. The spacecraft’s spectral instrument revealed for the first time that the object is an S-type asteroid—stony and composed of iron and magnesium silicates.
Then, in 2007, when New Horizons began its flyby of Jupiter, it collected the best data yet on the Jovian magnetosphere.
The robot radioed back to Earth, via NASA’s Deep Space Network, detailed data and images of Jupiter’s long-lasting Little Red Spot cyclonic storm, the northern aurora, the planet’s ring system, the moon Io’s erupting volcanoes (the onboard imager captured a stop-motion sequence of a giant volcanic plume spewing molten sulfur into space), as well as images of the other Galilean moons.
Voyage to Pluto
After leaving Jupiter, and bypassing Saturn, New Horizons was
intentionally placed in hibernation in order to conserve onboard
systems for the remaining leg of its long, cold interplanetary voyage.
In March 2011, the robot crossed the orbit of the planet Uranus with
plans to cross the orbit of even more distant Neptune on Aug. 25, 2015
– 25 years from the moment Voyager 2 passed the planet.
A New Day of Robot Space Exploration Dawns
The spacecraft will remain slumbering in anticipation of the big day—arrival at Pluto, and still a little over year and a half away. Then, a new day of robot space exploration will have dawned at the far end of the solar system.
NASA. About New Horizon. (2013). Accessed December 3, 2013.
The International Astronomical Union. Home. (2013). Accessed December 3, 2013.
*Editorial Note: This article originally included an error in the *Voyage to Pluto* – the author has corrected the issue.*