The would use a gravity assist from Jupiter, then slip by Uranus en route to multiple Kuiper Belt Objects (KBOs), said Alan Stern, Principal Investigator for New Horizons at the Southwest Research Institute here.
"We have an opportunity to study building a New Horizons II. The science looks very good and a second mission would yield a much larger sample of KBOs," Stern told SPACE.com.
The New Horizons 2 idea will be showcased June 21, Stern said, at a Uranus System Encounter with New Horizons II Workshop, prior to a Forum on Outer Planetary Exploration being held in Pasadena, Calif. that begins June 22.
Stern said conducting a second New Horizons mission is the same concept used for numerous other dual missions over the last three decades, such as Voyager, Pioneer, and the twin Mars rovers now busy at work on the red planet.
"When youre a long way from homeyou bring two. Its risk reduction," Stern said.
Encounter mode
For the New Horizons probe already on the books, its Earth departure for Pluto by way of Jupiter occurs in January 2006. After launch, the spacecraft is to arrive at Jupiter just over a year later. New Horizons would pass through the Jupiter system at 50,000 mph, ending up on a path that could get the spacecraft to Pluto and Charon as early as 2015.
After passing Pluto and Charon, the nuclear-powered spacecraft has enough fuel to retarget itself and study one or more of the icy mini-worlds in that vast region. In encounter mode with a KBO, the probe would map the object, study its composition, and scrutinize the celestial body for an atmosphere.
The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland manages the New Horizons mission.
Uranus for free
Consider this. Around four dozen missions have been sent to study eight planets from Mercury to Neptune.
Stern said that the Kuiper Belt is loaded with more than 100,000 large objects. "I think it could stand a second mission for the science." And a ballistic bonus for a New Horizons II is essentially getting Uranus tossed in for free.
"If you fly in 2008 or in 2009, Uranus just happens to be in the way. We can revisit that planet with modern instrumentation," Stern explained. Voyager 2 zipped by distant Uranus in January 1986.
A New Horizons II would zip by Uranus at a very special time, Stern said, at equinox when the planet, all of its satellites and ring systems, as well as magnetosphere, could be observed in unprecedented fashion.
"That only happens every 42 years. If New Horizons II doesnt do it, no mission could do it until 40 years later in the middle of the century. Im looking forward to being 100 years old, but you know, thats a long way off," Stern pointed out.
One-two punch
Given a Uranus flyby with New Horizons II in 2015, that same year the earlier launched New Horizons I encounters Pluto.
Heading past Uranus, a New Horizons II trajectory could take it to large binary KBO -- 1999 TC36 a large KBO circled by a smaller satellite. "Its like a little compact miniature of the Pluto-Charon systemexactly the same thing," Stern said.
As an outer planet spacecraft, a New Horizons II would present less risk in its fabrication and be less-costly -- by drawing upon the earlier probes development.
"It really opens up the deep outer solar system in a way that the first New Horizons can only begin to do, not that the first spacecraft wont revolutionize things. But the one-two punch just looks mouthwatering," Stern said.
Embryos of planets
Due to the variety of KBOs within the Kuiper Belt, the opportunity to sample other large KBOs makes an enormous amount of sense, said Jeff Moore, a planetary geologist at the NASA Ames Research Center, near San Francisco, California. He is also head of the imaging team for New Horizons.
"There are several different classes of KBOs out there," Moore said. "We are just starting to appreciate that there are swarms of these objects that are different from one another," he added.
KBOs represent the frozen leftovers, the bodies remaining from the solar system's formation, Moore noted. "That makes them very important objects that we want to understand."
People debate whether the KBOs are planets or not, Stern said. "They are really embryos of planets. They are very much the same relationship to full-grown planets that a biologist would call a fetus," he explained.
There is scientific conjecture that a satellite of Saturn, Phoebe, might be a captured KBO. Up-close imagery by the Cassini spacecraft just taken of Phoebe reveals it to be a surprising world.
While still very much in the idea stage, Stern concluded, a New Horizons II helps respond to the growing scientific interest in the menagerie of Kuiper Belt Objects that exist on the ragged edge of our solar system.
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