NASA needs a mix of mission sizes, the SSES notes: Cheaper, better, and faster probes that conduct focused research are necessary. Larger, more capable spacecraft for certain classes of modestly expensive missions are also needed. These fall into NASA's new category of probes called New Frontiers.
But top-of-the-line "Flagship" craft are vital for sample return or heavy-duty studies of some select targets. A Flagship effort -- like the Saturn-bound Cassini mission -- are pricey affairs that can cost in the billion dollars and beyond range. This class of mission should be flown once per decade.
Some future endeavors are vast in scope and too tough to do alone. In these cases, the SSES encourages NASA to continue pursuing cooperative programs with other nations.
Kuiper Belt first, Pluto and Charon second
Specially convened SSES study groups cast their respective nets widely. Hauled in is a hoped-for broad consensus of opinion from the scientific community.
Sending a probe to the Kuiper Belt and its largest member, Pluto, should be NASA's first priority in solar system exploration, said SSES chair, Michael Belton of Belton Space Exploration Initiatives, based in Tucson, Arizona. A large, more comprehensive mission to Europa within the decade was also given high priority as a NASA Flagship mission.
Belton said in a press meeting today that the current New Horizons mission to the Pluto Kuiper-Belt could be altered to focus more on the diversity of Kuiper-Belt Objects. However, if full-funding for New Horizons is not attained, "modest changes" - such as adding solar electric propulsion - could be made to the spacecraft design. This would permit the spacecraft to survey the Kuiper-Belt and Pluto within the decade scoped out by the SSES.
The SSES disagrees with NASA's view that a Pluto mission should wait for nuclear electric propulsion, Belton said. "It seems to us that nuclear propulsion is not appropriate for reconnaissance missions," he added.
Nuclear electric propulsion, however, is highly desirable for future orbiters that could circle Saturn and Neptune, as example. "It's an excellent thing to do, but not quite right now. You need to get the basic engineering done before you start to include them into your suite of missions," said Joseph Burns, a member of the SSES Steering Group.
"We are excited and gratified that the Decadal Survey has recognized that a Pluto-Kuiper Belt mission should be at the top of the priority list for planetary exploration. We on New Horizons are working hard every day to see this mission take place as soon as possible. We are on schedule and running under cost, and we are looking forward to carrying out this exciting scientific mission to some truly new frontiers," said Alan Stern, principal investigator for the mission, and director of the Southwest Research Institute's Department of Space Studies in Boulder, Colorado.
Conceptual missions
A roster of exciting and relevant "conceptual missions" were identified by the SSES, Belton said.
Space missions on the books, now en route, and those advocated in the SSES report, Belton said, can answer some of the most profound questions, such as: Are we alone? From where did we come? What is our destiny? Answers to these cosmic queries "may be within our grasp," he said.
The SSES report offers a top-priority list of suggested spacecraft projects for the decade 2003-2013, including:
- Kuiper Belt-Pluto Explorer (KBP): First eyeing Pluto and its moon, Charon, the KBP Explorer will then investigate several Kuiper Belt objects. KBP would be the first spacecraft dispatched for scientific measurements within the remote, entirely unexplored outer half of the solar system. Mission intent is to study what should be the home for the most primitive material in the solar system. KBP Explorer would reveal the significance of this material in the evolution of objects in other parts of the solar system.
- Europa Geophysical Explorer (EGE): A Flagship mission to investigate the probable subsurface ocean of this moon. As one of Jupiter's moon's, enigmatic Europa sports an overlying ice shell. The EGE is geared to define the properties of any interior ocean and identify the makeup of Europa's icy face. Before orbiting Europa, this craft also scrutinizes Ganymede and Callisto - both believed to have subsurface oceans. The reconnaissance of Europa by EGE will gain insight as to the moon's astrobiological potential, paving the way for future landings on the intriguing object.
- South Pole-Aitken Basin Sample Return (SPA-SR): NASA should make a robotic return to the Moon to help unravel the story of early impacts within the inner solar system, as well as better grasp the history of the Earth-Moon system. The South Pole-Aitken Basin is the largest impact structure known in the solar system. The SPA-SR can discern more about the nature of the Moon's upper mantle. Learning how to return bits of the Moon can spur technology useful for other sample missions in the future.
Also on the SSES need-to-do list for the 2003-2013 time frame is a Jupiter Polar Orbiter with Probes (JPOP); a Venus In Situ Explorer (VISE); and a Comet Surface Sample Return (CSSR).
Belton told SPACE.com that the SSES looked at some 27-candidate missions. Falling off the table for now were such things as a Europa Lander mission, a Titan exploration probe, and a Neptune spacecraft. "They are all very exciting missions, but we felt it was time to do those after the prime set that we've identified," he said.
Mars sample return within reach
Further exploration of Mars is also addressed in the SSES report.
The study backs NASA's current science-driven strategy to study the Red Planet, but underscores the need for eventual return to Earth of Mars samples. The survey group recommends that NASA begin its planning for Mars sample return (MSR) missions to be carried out early in the decade 2013-2023.
"Current studies of simplified Mars sample-return missions indicate that such missions are now within technological reach. Early on, NASA should engage prospective international partners in the planning and implementation of MSR," the report states.
Advocated by the SSES is establishment of a Mars Long-Lived Lander Network. This grid of Mars science stations would run for at least one Martian year from spots around the planet. The armada of stations would complement a suite of planned French NetLander packages, a system limited in number and spaced across Mars's equatorial region.
Additionally, a Mars upper Atmosphere Orbiter is promoted by the SSES. This small, dedicated mission can help reconstruct the evolution of the Red Planet's atmosphere.
DSN: definite support needed
In peppering the Solar System routinely with probes there is a data pipeline problem.
The express lane flow of spacecraft data hurtling back to Earth and then distributed to the broad research community "must be systematically improved," the SSES study urges. There is insufficient downlink communications capacity through NASA's Deep Space Network (DSN) of radio receiving dishes.
"The DSN needs to be continually upgraded as new technologies become available and system demands increase," recommends the study.
Furthermore, the survey report stresses that, as missions increase in number, more funds to distribute, interpret and archive incoming data is needed.
In its work, the SSES also requests that NASA partner with the National Science Foundation to build and operate the Large-Aperture Synoptic Survey Telescope. That ground-based hardware can be tapped to detect near-Earth approaching comets and asteroids, as well as observe distant objects in the Kuiper Belt.
Belton said that NASA officials were briefed early this week as to the SSES findings and recommendations. "It was quite well received. This report is considered exceedingly valuable to them," he said
"We think we have a document that not only will do excellent science and excite our community, but a document that will push a program of great interest to the American public," Burns said.
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