“When I went to graduate school and I learned about astronomy, the Solar System had a very different architecture,” says Stern, who is 55. “What I now call the middle Solar System used to be called the outer Solar System, and the entire geography of the Kuiper Belt and all the small planets there was not even known, with the exception of Pluto.”
The public is likely to be most taken with early data returning from the spacecraft's cameras, which will be imaging Pluto and its moons beginning in January 2015. Five of them are known. The largest of them, Charon, was discovered in 1978. The smallest, named Styx, turned up last year, and no one will be surprised if more are spotted as New Horizons approaches.
“We've planned particular observations to look for small satellites, many of them going deep, deep imaging with the panchromatic camera,” says Young. “We even took one of our color scans of Pluto and Charon and extended the duration of it to cover the entire system. So, even if we discover an object in the data a year and a half after encounter, we can go back and say there ought to have been a moon there.”
It is also possible that the probe will discover planetary rings, and researchers have long been planning how they will study the tenuous atmosphere they expect to find, and how it interacts with the solar wind.
New Horizons carries three imagers. Lorri is a simple 20.8-cm (8.2-in.) telescope that will generate images with a resolution as fine as 100 meters (330 ft.) on the planet's surface at closest approach. Also onboard are visible/infrared and ultraviolet imager/spectrometers dubbed Ralph and Alice, respectively. Ralph will generate color maps and data on composition and temperatures; Alice will study atmospheres at Pluto and perhaps Charon.
The Radio Science Experiment (Rex) is a passive radiometer that will measure the composition and temperatures of atmospheres it encounters at Pluto and perhaps elsewhere. The Solar Wind Around Pluto instrument will measure atmospheric escape at the dwarf planet, and its interaction with the solar wind, while the Pluto Energetic Particle Spectrometer Science Investigation will study plasma leaving the atmosphere.
The Venetia Burney Student Dust Counter, built as an education project by students at the University of Colorado and elsewhere, has been at work since the probe was launched on Jan. 19, 2006, measuring the interplanetary dust along the trajectory.
The science team has just started polling astronomers who use telescopes on and in orbit around Earth to mount an observation campaign that will collect data in parallel with New Horizons' passage through the Pluto system. In addition to more moons, scientists hope to identify at least one Kuiper Belt object beyond Pluto and retarget the probe for a flyby of that object.
The job will be “like looking for somebody sending Morse code signals from a New York City apartment building,” Young says, because the center of the Milky Way galaxy lies behind the target region. But observations from Hawaii have enjoyed “good seeing,” she says, and the team is hopeful the campaign will discover a good Kuiper Belt target.