New Horizons: First Mission to the Last Planet
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: January 14, 2006
KENNEDY SPACE CENTER, Fla. (CBS) - Imagine the sun the size of a quarter - one inch across - on the goal line of the Rose Bowl.
The Earth, just 0.009 inches across, would be positioned around the three-yard line. Mighty Jupiter, just one tenth of an inch across, would be "orbiting" inside the red zone at the 15-and-a-half yard line and ringed Saturn would be just inside the 30. The outer gas giants, Uranus and Neptune, would be orbiting on the opponent's side of the field, 57 and 90 yards from the sun.
And what of frigid Pluto, circling the sun in a lopsided orbit at an average distance of 3.7 billion miles? The icy dwarf would be an invisible speck one thousandth-of-an-inch across 18 yards beyond the opponent's goal line. At that scale, light would move at two-tenths of an inch per second and it would take radio signals more than five hours, on average, to cross the field and reach the ninth planet. The nearest star would be some 460 miles from Pasadena.*
Now imagine sending a spacecraft from Earth, on the three-yard line, to Pluto more than 100 yards away. That's exactly what NASA plans to do Jan. 17 when it launches the nuclear-powered New Horizons probe on a $700 million mission to the only one of the solar system's nine traditional planets that has never been visited.
Given the mind-boggling distances involved, NASA is launching the small, 1,054-pound New Horizons probe atop one of the most powerful unmanned rockets in the U.S. inventory, a 20-story-tall, 1.2-million-pound Lockheed Martin Atlas 5 equipped with five strap-on boosters. Departing Earth at a record 36,000 mph, the spacecraft will cross the moon's orbit just nine hours after liftoff. It will cross the orbit of Mars, race through the asteroid belt and get to Jupiter in just 13 months for a velocity boosting gravity assist flyby that also will give the science team an opportunity to thoroughly test the probe's half-dozen instruments.
Even though its velocity will be 100 times faster than a jetliner throughout its long voyage, it will still take New Horizons, the fastest thing ever built by the people of planet Earth, more than eight additional years to reach Pluto and its moon Charon. Kids in the first grade today will be in high school, dating and learning to drive by the time the spacecraft reaches its target. Their parents will have voted in two presidential elections and Vince Young, the University of Texas quarterback who starred in this year's Rose Bowl game, will be facing the twilight of his professional football career.
"This is, in a very real sense, the capstone of the initial reconnaissance of the planets that the United States has led for the world since the 1960s," said Alan Stern, New Horizons principal investigator at the Southwest Research Institute in Boulder, Colo.
"We're going farther to reach our target and we're travelling faster than any spacecraft ever has. This is a little bit about leadership, a little bit about re-writing the textbooks about the outer planets. But I also want to point out it's also about inspiring the next generation of scientists and explorers, who we hope will take us to even greater heights."
Equipped with powerful cameras to map the sunlit side of the planet, spectrometers to characterize its space environment, the planet's tenuous atmosphere and surface composition and a student-built dust collector, New Horizons will race past Pluto in July 2015, streaking within 5,500 miles of the surface at a velocity of more than 31,000 mph.
After rapid-fire observations of Pluto, Charon and at least two other recently discovered moons, New Horizons will sail on into the Kuiper Belt, a vast realm of icy dwarf worlds that serves as a reservoir of short-period comets and home to at least one, and presumably more, planets larger than Pluto, the zone's most famous member.
If all goes well, New Horizons, built by the Applied Physics Laboratory at Johns Hopkins University, will fly past at least one other Kuiper Belt world before the mission's funding runs out. After that, the spacecraft will continue on into interstellar space, joining NASA's twin Voyagers and Pioneers as the fifth human artifact to depart the solar system.
"New Horizons is the first mission to the last planet," said project scientist Hal Weaver. "It's going to perform a detailed reconnaissance of Pluto and its companion, Charon. We're actually not going to stop there. We're going to continue to fly past Pluto deep into the Kuiper Belt. New Horizons is going to be going where no other mission has ever been, so it truly is a mission of exploration and discovery.
"Why are we doing this? Science is the driver. Science is the reason new Horizons is making this journey to the outskirts of the solar system. We think the study of Pluto, Charon and the Kuiper Belt objects are key to understanding the origin and evolution of the solar system."
It is remarkable to remember that astronomer Clyde Tombaugh discovered Pluto in 1930 and that in a single generation - 76 years - technology has progressed from propeller-driven aircraft and steamships to spacecraft capable of reaching that distant world.
"Pluto was discovered in 1930," Weaver said. "In 1978, its moon, Charon, was discovered. It has only been in the past 10 years that we've known about this third zone, a torus-shaped region surrounding the sun that we now call the Kuiper Belt. It's only been in really the last 10 years that we've recognized that Pluto and Charon actually are more similar to these small icy worlds in the Kuiper Belt than they are to the other planets.
"All of those objects - Pluto, Charon and the Kuiper Belt objects - have been kept in a deep freeze on the outskirts of the solar system since the time of its formation 4.6 billion years ago," Weaver said. "And for that reason, it's preserved that original material from which the solar system formed and that's one of the important reasons for going there. It's really the frontier of planetary science, it's a region we have never been before."
With the discovery of other sizeable bodies in the Kuiper Belt, including one even bigger than Pluto, the ninth planet's status has been called into question in recent years. Singer Christine Lavin even wrote a song about the debate called "Planet X."
"St. Christopher is looking down on all thisBut to Stern, frozen Pluto will always be a planet.
"We've really gone through a revolution, a paradigm shift in planetary science," he said. "We really just didn't realize the diversity of planetary types in our solar system. Pluto looked like a misfit because it was the only one we saw. And just as a Chihuahua is still a dog, these ice dwarfs are still planetary bodies. They're large enough to make themselves round by self gravity and they surely pass the test of planethood.
"So it's really quite an opportunity to first, find that you're notions were wrong, it's almost like a Copernican revolution. The misfit becomes the average. ... The opportunity is to go now and have a chance to study this most common type of planetary body in the solar system for the first time."
* The scale model used in this story was put together using the Build a Solar System web page.
MISSION STATUS CENTER