"Pluto is a frontier world that has never been explored by spacecraft, and NASA's planned Pluto-Kuiper Express (PKE) mission is exploration at its greatest," says Dr. Alan Stern. Dr. Stern is the director of SwRI's Department of Space Studies and the Principal Investigator of a SwRI-led proposal to put a miniaturized package of imagers and spectrometers aboard the PKE mission.
"The instrument package is called the Pluto Express Remote Sensing Investigation, but we call it PERSI for short, in honor of Percival Lowell, the astronomer who launched the successful search for Pluto," says Stern. PERSI's team of outer solar system experts and space instrument builders includes scientists and engineers from two NASA centers, the CalTech/NASA Jet Propulsion Laboratory (JPL), SwRI, Ball Aerospace, the Johns-Hopkins Applied Physics Laboratory, and several major research universities. "We have a spectacularly talented and dedicated team of men and women, and a fantastically capable instrument suite. I hope NASA decides to fly PERSI to Pluto," adds Stern.
NASA's Pluto-Kuiper Express mission will be managed by JPL. PKE will feature a single, advanced flyby reconnaissance spacecraft that will be launched from Earth in 2003 or 2004, fly past Jupiter to gain speed, and then head directly for its Pluto flyby in 2011 or 2012. Pluto lies over 30 times as far from the Sun as Earth does, so PKE will have to cross almost 8 billion kilometers (5 billion miles) of cold vacuum to reach its main target. By the time PKE reaches Pluto, the sunlight falling on it will be so weak that spacecraft's outer skin temperature will hover near 60 degrees above absolute zero. "That's about 200 degrees centigrade colder than the coldest antarctic night," says PERSI Co-Investigator Dr. John Spencer of Lowell Observatory. PERSI Co-Investigator William McKinnon of Washington University adds, "Pluto and Charon truly constitute a double planet, given their relatives sizes and masses. So in a very real sense we will get two flyby encounters for the price of one! And because we think Charon was made in a giant impact much the way we think the Earth-Moon system was formed, we expect to learn more about giant impacts and the way our own moon formed."
After an eye-popping flyby of the Pluto system made at almost 65,000 km/hr (40,000 miles/hr), PKE will speed off to explore one or more of the myriad Kansas-sized icy Kuiper Belt objects orbiting far beyond Pluto. Astronomers have discovered that Kuiper Belt Objects are relics of planetary formation in the outer solar system. "These objects are like time capsules, containing a nearly unchanged chemical record of the building blocks from which the planets formed," says PERSI Co-Investigator Dr. Richard Binzel of the Massachusetts Institute of Technology.
The proposed PERSI instrument package was developed and lab tested over a period of six years, primarily with NASA "Advanced Technology Insertion" funds specifically targeted at the advanced sensor and miniaturization needs of a Pluto mission.
PERSI consists of a set of 6 cameras, along with both infrared and ultraviolet spectrometers, all packed into a single, integrated package that weighs less than 10 kilos (22 pounds) and draws less than 7 watts of power (less than many nightlights!). PERSI will be assembled at Ball Aerospace in Boulder Colorado, with major components being contributed by Ball, SwRI, and NASA's Goddard Space Flight Center.
"I've spent most of my professional career studying Pluto and the Kuiper Belt, beginning with my graduate work that began in 1980," says PI Stern "Over those 20 years we've seen an explosion of knowledge about Pluto and its moon, Charon, but despite all that we've learned, we know from past planetary exploration that there really is no substitute for what close up measurements can reveal-- that's why we need PKE."
In the early 1990s Dr. Stern led the group of young planetary astronomers who rallied NASA to consider a Pluto mission. NASA then appointed him to chair its Outer Planets Science Working Group (OPSWG) in order to flesh out the scientific goals and the implementation strategy of such a mission. Stern reminisces: "Despite the limitations of any mission this hard, and traveling this far away, we were able to hammer out a set of critical goals for the first reconnaissance of Pluto, the farthest of the planets. Those goals include mapping its surface, measuring the composition and structure of its atmosphere, and mapping its surface composition. Similar observations will be obtained of Pluto's satellite, Charon, and a search will be made for other, as yet undiscovered satellites in the Pluto system." PERSI Co-Investigator Dale Cruikshank of NASA's Ames Research Center adds, "When PKE makes flybys of Kuiper Belt Objects we'll map them and obtain more high quality spectra, just as we will at Pluto."
"It's a good feeling to have completed the PERSI proposal and turned it in to NASA," remarks says PERSI project manager John Scherrer. "We worked hard to satisfy NASA's scientific objectives for PKE without overly complicating the instrument, and we resisted the temptation to add extra `bells and whistles' that could introduce risk." PERSI Co-Investigator Harold Reitsema, a leader of the Ball Aerospace team that will assemble PERSI agreed, "We took a conservative design approach that gives us plenty of room to fit within NASA's tight mass and power constraints. We also have developed a detailed project schedule and cost plan that will help us avoid problems as we build the instrument."
Principal Investigator Stern summed up his feelings recently by saying, "The road to open up Pluto for exploration has been a long one, and the journey is far from complete. The competition to put instruments aboard PKE will be fierce. We all feel that the exploration of Pluto will be a lifelong achievement, and an exciting kind of planetary exploration that hearkens back to the days of Apollo, Viking, and Voyager, when spacecraft first explored the closer planets."
More information on the PERSI instrument proposed for Pluto Kuiper Express can be found at www.boulder.swri.edu/PERSI.html. Information on NASA's PKE mission itself can be found at www.jpl.nasa.gov/ice_fire/.