Solar System Report Sets 10-Year Exploration Priorities
DOI: 10.1063/1.1522205
In a comprehensive, 417-page report designed to serve as a roadmap for the next decade of solar system exploration, a committee of planetary scientists is urging NASA to launch a reoriented Pluto–Kuiper Belt (PKB) mission and is advocating a return to costly, once-a-decade flagship missions in the $650 million to $1 billion range. The National Research Council (NRC) report, entitled New Frontiers in the Solar System: An Integrated Exploration Strategy, was compiled at NASA’s request and is modeled after the decadal reports in astronomy and astrophysics.
After reviewing 27 missions proposed by six panels, a 15-member steering committee, chaired by astronomer Michael Belton, president of Belton Space Exploration Initiatives in Tucson, Arizona, recommended that NASA conduct 12 missions. Dimitri Papanastassiou, a committee member and cosmochemist with the Jet Propulsion Laboratory in Pasadena, California, said NASA asked the committee to “identify and prioritize potential missions, separately for the Solar System and for Mars. The steering group was keenly aware of the need to reach a consensus and I believe we did so.” He added, “The final decisions were based on scientific merit, technical readiness, and cost.”
The recommended missions are intended to answer scientific questions that stem from four crosscutting themes: the first billion years of Solar System history, the volatile and organic materials that make up “the stuff of life,” the origin and evolution of habitable worlds, and the processes that reveal “how planets work.” Committee members developed 12 scientific questions based on the four themes, then measured the proposed missions against their ability to answer the questions.
Underlying premise
The report’s underlying premise is that “it is crucial to maintain a mix of mission sizes and complexities in order to balance available resources against potential schemes for implementation.” To achieve that proper mix, the committee recommended that NASA establish three classes of planetary missions.
Small missions would launch once every 18 months and would cost less than $325 million. This class of missions would essentially be a continuation of NASA’s Discovery program, which has sent spacecraft to asteroids, comets, Mars, Mercury, and the Moon. These missions could be developed quickly in response to discoveries during the decade, the report says. “We see them as an essential component because they allow the ability to follow up on new science discoveries and allow individual scientists to propose highly creative and new concept missions,” Belton said in a press conference following the report’s release.
Medium-sized missions, approximately on the scale of the New Frontiers exploration program NASA created earlier this year, would consist of flights costing from $325 million up to $650 million. The report recommends that during the next decade, in order of priority, NASA fly a PKB mission, a lunar South Pole sample return mission, the Jupiter Polar Orbiter with probes, the Venus In-Situ Explorer mission, and a comet surface sample return mission.
Large flagship missions that exceed $650 million are recommended at the rate of one per decade. These costly missions were abandoned in the early 1990s under the “faster, better, cheaper” approach of Dan Goldin, who stepped down as NASA’s administrator a few months ago. “Experience has shown that large missions, which enable detailed, extended, and scientifically multifaceted observations, are an essential element of the mission mix,” the report says. Placing a spacecraft in orbit around Jupiter’s moon Europa is recommended as the highest priority large mission. Belton said NASA’s projected budget should allow one flagship mission per decade, but NASA’s Colleen Hartman, head of the Solar System Exploration office, says there isn’t enough money in the budget for Europa-scale missions.
The report also recommends that NASA continue with its Mars Exploration program, including two small-mission programs, two medium-sized missions involving several landers, and plans for flagship-level Mars sample return missions that can begin “early in the decade 2013–2023.” The Mars subcommittee recommended that a sample return mission be undertaken in 2011; however, it would cost at least $2 billion, the steering committee bumped the program into the next decade and recommended that NASA seek international partners.
Problematic recommendations
Most problematic for NASA are the report’s recommendations that high priority be given to a PKB mission and the Europa orbiter, both of which the space agency canceled earlier this year for budgetary reasons. The report says that the Pluto mission that has been under development for several years is important but should be reoriented to focus on visiting two or three Kuiper Belt objects. Pluto and its moon, Charon, would get a flyby wave from the spacecraft, but would not be the mission’s primary goal.
For the past two years, NASA has zeroed out the budget for the Pluto mission, but Congress, led by Senator Barbara Mikulski (D-Md.), has continued to fund the project. Mikulski put $30 million in NASA’s budget last year for the mission. This past May, Ed Weiler, NASA’s associate administrator for space science, told Congress that a “Pluto–Kuiper Belt mission should not be pursued at this time” given the cost, the technical challenges, and the need to launch by 2006. The launch date is important for the spacecraft to get a velocity boost from Jupiter and reach Pluto before 2020, when the planet’s atmosphere is expected to collapse as its orbit carries it farther away from the Sun. In the wake of the NRC report, NASA officials have indicated that the agency’s position on the PKB mission is being reviewed, and that $122 million will be required in the budget for fiscal year 2003 if the flight is to meet the 2006 launch date.
The mission to put an orbiter around Europa to study the ocean suspected to exist under the layer of ice that covers the moon would mark the return to very expensive missions, something NASA has been reluctant to do. Weiler told Congress in May that the Europa mission, whose price tag had doubled from $500 million to $1 billion, had been canceled. The money already allocated for the mission was reallocated to the medium-sized missions in the agency’s New Frontiers program.
In recommending reinstatement of the Europa orbiter, the report says, “The first step in understanding the potential for icy satellites as abodes for life is a Europa mission with the goal of confirming the presence of an interior ocean, characterizing the satellite’s ice shell, and understanding its geological history. Europa is important for addressing the issue of how far organic chemistry goes toward life in environments….”
Joseph Burns, a member of the steering committee and astronomer from Cornell University, said NASA’s Weiler and Hartman considered the report “exceedingly valuable” when they were briefed on the recommendations.” We’ve proposed an ambitious program,” Burns said. “They have to sit back and think about it. We have to give [NASA officials] time to see how they can fit it together.”
More about the Authors
Paul Guinnessy. pguinnes@aip.org
