Solar System Exploration Subcommittee (SSES) Findings and Recommendations 31 Mar 2002

Status Report From: NASA Advisory Council
Posted: Wednesday, April 3, 2002

March 31, 2002
Colleen Hartman, Director, Solar System Exploration Division
Orlando Figueroa, Director, Mars Exploration Program
Code S
NASA Headquarters
Washington, D.C. 20546
Dear Colleen and Orlando:

The Solar System Exploration Subcommittee (SSES) of the Space Science Advisory Committee (SScAC) met from February 27 to March 1 in Washington, D. C. The purpose of this letter is to summarize the findings and recommendations of that meeting.

The SSES was gratified by the degree of cooperation and integration between the Mars Program and the Solar System Exploration Division, both in technology development and Mars science. The SSES commends Directors Orlando Figueroa and Colleen Hartman for developing this healthy, synergistic relationship.

Office of Space Science

Ed Weiler briefed the SSES on the current state of the Office of Space Science Program by telecon. The budget for the Office of Space Science proposed by the Office of Management and Budget (OMB) increases dramatically (by $682M) by FY 07. The Deep Space Network is proposed to transfer to Office of Space Science control. A Nuclear Systems Initiative (NSI) is proposed. A new planetary program called New Frontiers, capped at $650M per fully competed mission with a launch every three years is proposed. The SSES commends NASA on achieving this budget request.

On the negative side, the Europa Orbiter mission and the New Horizons competitively selected mission to Pluto and the Kuiper Belt are cancelled. We comment explicitly about these actions later in this letter.

All Mars missions after FY 09 are cancelled pending a review of the program for the ensuing decade.

The SSES strongly supports the NASA budget request, especially the nuclear initiative that will enable long duration surface activities on planets, complex maneuvering orbital mission, and faster trip times to the outer solar system. However, the SSES also endorses augmentation of New Frontiers with New Horizons as first mission, as discussed later in this letter.

The SSES endorses a coordinated education and public outreach approach for communication with the public, media, educators, students, legislators and governmental bodies about the development and use of power systems outlined in the Nuclear Systems Initiative. Public engagement and grade-level appropriate educational materials would be developed for long-term use in a variety of venues to educate and inform the public well in advance of the deployment of such systems for solar system exploration.

Colleen Hartman and Orlando Figueroa - 2

Solar System Exploration Program

Colleen Hartman noted that the OMB characterization of the Solar System Exploration Program, including Mars was:

Discovery Program - Effective
Mars Program - Moderately Effective
Outer Planets Program (not including Galileo and Cassini) - Ineffective

In addition to providing more detail on the Nuclear Systems Initiative and the New Frontiers Program, Hartman pointed out that the Solar System Exploration Program budget is projected to increase by 73% between FY02 and FY07. Research and Analysis funding will increase by about 3.5% from FY02 to FY03, significantly above inflation, with the Astrobiology Science and Technology for the Exploration of Planets (ASTEP) program increasing by 30%. A new program titled "New Frontiers", capped at $650M per mission, was proposed. Discovery Program missions 9 and 10, DAWN and KEPLER, were selected.

The SSES commends NASA on its vision in increasing Research and Analysis, introducing the Nuclear Systems Initiative, and securing OMB approval for the New Frontiers line. These are significant accomplishments. The continued success of the competed Discovery Program is noted.

The Nuclear Systems Initiative currently includes three elements; an advanced RTG power source which will see first use on the 2009 Mars Mobile Laboratory, Nuclear Fission Power, and Nuclear Fission Propulsion. These systems will enable complex surface operations over extended periods of time, and allow for complex spacecraft maneuvering. For distant planets it will also lead to reduced travel times. It will not, however, be useful for the New Horizons mission to Pluto and the Kuiper Belt.

Given this generous budget, it is perhaps surprising that there are high priority missions that cannot be flown. Although supportive of the New Frontiers program as proposed in the FY03 budget, the SSES discussed several of the highest priority scientific objectives (as articulated by SSES and COMPLEX in the past) that are unlikely to be able to be accomplished for $M 650 or less. These include, but are not limited to, further exploration of Europa including characterization of its ocean, return of a pristine sample from a nucleus of a comet, and in-situ exploration of the Titan atmosphere and surface. Technological advances may lower the costs of accomplishing these objectives in the future, and budget estimates are not absolutely certain. Nonetheless, it seems clear, based on the briefing by Torrence Johnson on the hard look taken at the cost of the previously proposed Europa Orbiter as well as comparison of the relative complexity of the Europa Orbiter and possible missions to Titan (for example), that very high priority science objectives will remain unmet unless missions costing on the order of 1 G$ can be flown.

The issue of whether life arose elsewhere remains an important focus of solar system exploration. Yet missions capped at $650M are unlikely to allow orbital missions around high value targets like Europa, and are far below the budget level needed for Mars Sample Return.

The SSES strongly supports the Presidentís budget request while noting the above-referenced and other deficiencies. The SSES strongly urges NASA to explore the avenues whereby such missions might be added into future budgets, either as a program of larger-scale missions, or on a case-by-case basis.

Colleen Hartman and Orlando Figueroa - 3

Pluto and the Kuiper Belt

The proposed budget also does not include funds for the New Horizons mission to Pluto and the Kuiper Belt. This mission remains the highest outer planets priority of the SSES. It is also urgent. We lose about 2% of the planet per year at present, or something approaching 170,000 square kilometers. While this loss rate is non-linear, by 2029 most of one hemisphere of Pluto (and Charon as well) will be in "winter night" lasting decades. [Pluto moves from equator facing the Sun to latitude 60 degrees facing the Sun. A ten-year mission arrival delay corresponds to losing about 20% of the observable surface.] Terrain in darkness cannot be imaged or studied by infrared spectral instruments. The atmosphere of Pluto will probably have snowed out by 2020, precluding atmospheric measurements and possibly obscuring albedo contrasts on the surface. Going to Pluto later than the New Horizons time line means less of Pluto and less of Charon to study. This point is a simple matter of celestial mechanics.

New Horizons was competitively selected in response to a NASA AO, and as such represents the most cost-effective way to explore Pluto-Charon and the Kuiper Belt. It also provides an excellent model for how the proposed New Frontiers program should be implemented. We note that the proposed outyear budgets for New Frontiers are sufficient to support New Horizons toward a 2006 launch; it is only in FY03 where the budget shortfall is severe.

For the above reasons, augmenting of the New Frontiers budget line to $122M in the FY03 budget and designation of New Horizons as the first New Frontiers mission is strongly encouraged. However, the SSES specifically opposes transferring funds from other parts of the OSS budget to support New Horizons. Such a short-term gain would be achieved at the expense of the long-term health of planetary exploration.

Europa Missions

A mission to Europa remains the highest SSES priority in the outer solar system after a mission to Pluto and the Kuiper Belt. Nevertheless, the SSES examined the specific case of Europa Orbiter. The science goals of the proposed Europa Orbiter continue to be of the highest priority, as previously stated. However, two factors suggest that reexamination is appropriate for this mission.

First, the evidence is now very strong for a subsurface water ocean on Europa. This evidence was not available at the time the Europa Orbiter level one science requirements were established. Thus one of the primary goals for a Europa orbiter mission may have already been met. The evidence for an ocean comes from the magnetometer data collected by Galileo (PI, Kivelson at UCLA) showing that Europa behaves like a conducting body. This evidence has been consistent for several flybys. The only plausible explanation for this conductivity is a salty ocean. Other evidence collected by Galileo is consistent with this interpretation. This development strengthens the case for a mission to Europa but the form and goals of that mission should be reconsidered, as previously formulated Europa Orbiter level one science requirements no longer fully reflect current understanding.

Second, current estimates for a Europa orbiter now exceed $1B. The lowest cost missions that are conceivable for Europa, including multiple flybys or very short-lived orbiters, may significantly enhance our knowledge, but are less likely to lead to a quantum leap in our understanding, such as would occur by determining ice thickness and its regional variation. Ambitious missions that would do so may not fit within the current budgetary constraints and the need for a balanced program.

Colleen Hartman and Orlando Figueroa - 4

We recognize the importance of a balanced and sustained program. This means that the highest priority science goals may not be achieved first if they involve missions that are particularly challenging or expensive. In this respect "priority" does not equal "order of launching or arrival". Balance means scientific balance, consideration of science per dollar, and balance among missions of different size. We cannot preserve balance within current budgetary constraints with a Europa mission of over $1B. The high priority Europa science goals may require a mission that involves new concepts and a different budgetary environment. It is incumbent on the scientific community to develop the case for a $1B+ mission to Europa, or find a cheaper way to accomplish high priority Europa science.

We note further that it is desirable to consider other missions in the outer solar system as part of a balanced and sustained program. In all these considerations, we affirm the essential need for technology development and mission concept development including the capability of advanced power and propulsion systems.

Mars Program

Orlando Figueroa and James Garvin briefed the SSES on the current state of the Mars Program. Mars Surveyor has been extended to allow further scientific measurements of high value. Mars Odyssey is returning exciting results, particularly about the presence of subsurface water ice polewards of 60 degrees south latitude. Mars Exploration Rovers remain on track, although budget and schedule are of concern to the SSES. Mars Reconnaissance Orbiter is progressing on schedule, as is the Mars Scout selection and Mars Mobile Laboratory. The Mars Fundamental Research Program is scheduled to rise to about 1.7% of the Mars budget by FY04.

There are several areas of concern, however. All missions after FY09 have been cancelled, pending review of the various paths forward in the second decade. Orlando Figueroa outlined a plan for missions in that decade capped at $700M (FY02) per launch opportunity. Major missions costing in excess of $700M would require a compelling scientific rationale. The earliest sample return opportunity is now delayed until 2016 and would consume at least two launch opportunities, at least four years of budget, or at least $1.4B. The SSES notes that Mars Exploration Rovers and the 2009 Mars Mobile Laboratory all exceed the $700M cost cap, and Mars Sample Return missions are estimated to cost $1.6B-$2.8B. The $700M target cost cap raises serious questions about the viability of a vital Mars Program after 2009.

The SSES notes that public support for the Mars Program appears predicated on the promise of searching for possible current or past life on Mars. SSES is concerned that any pathway chosen for the second decade may not adequately address this question, leading to an erosion of public support. The SSES notes that return of samples to Earth is the only known way to unequivocally address the life question, although incremental progress towards that goal can be made by orbital and landed missions

. Another area of concern is the international Mars Express/Beagle 2 mission, which needs additional communications and navigation assistance. There are implications for use of Odyssey and the Deep Space Network. The SSES requests a briefing on the Deep Space Network at its June, 2002, meeting.


A report on the Technology Workshop was presented. The SSES commends Colleen Hartman and Orlando Figueroa for working together on technology, pooling resources for the common good of both Programs. The SSES emphasizes the importance of scientists, technologists, and mission planners meeting together in order to effectively advocate our technology needs to code R. The SSES notes that code R technologies need to be specifically aligned with code S needs.

Colleen Hartman and Orlando Figueroa - 5

Based on briefing to the committee, it is apparent that continued technology development is concentrated on concepts that are relatively advanced (Technology Readiness Levels [TRL] 4 and above). Although exploration of the outer planets is being reorganized and reconceptualized, it is important that early technology development (TRL 1-3) not be abandoned, even if future missions are (as yet) unspecified. This is especially true for the proposed New Frontiers program, which will need to draw on existing technologies in each competitive cycle. SSES urges NASA and its responsible field centers to create a mechanism whereby appropriate long-lead-time technologies can be selected and nurtured, well in advance of mission opportunities. We also anticipate that the independent instrument development by Astrobiology for Mars exploration will also provide cross-over opportunities for possible future in-situ Europa or Titan exploration.


Chas Beichman gave a presentation by telecon on the status of the Astrobiology Task Force (ABTF). The ABTF previously had been reporting directly to SScAC. However, because of the transfer of astrobiology programmatically to the Solar System Exploration Division and with the increased maturity of the astrobiology program, it was felt both that the ABTF should report directly to SSES and that the ABTF should exercise its sunset clause and that future oversight of astrobiology should come directly from the SSES.

While no immediate concerns were raised regarding astrobiology, several issues on the table for the next year were highlighted, with the expectation that the SSES would exercise appropriate oversight. These included the following issues, raised either by the ABTF or by the SSES:

(i) The NASA Astrobiology Institute (NAI) currently is in a state of transition, with the current Director (Dr. Baruch Blumberg) having announced his resignation and with a search in progress to select a new Director.

(ii) The NASA Chief Scientist and the astrobiology program/discipline scientist had previously taken steps to initiate a formal visiting committee to evaluate the status, direction, and maturity of the NAI. It is important that this visiting committee not fall through the cracks during the current state of transition (with both the NASA CS and the NAI Director positions changing hands).

(iii) There is concern over the relative sizes of the components of the astrobiology program, in particular the amount of funds going to the NAI compared to those going to the more-traditional exobiology R& A program. This issue should be considered on an ongoing basis by the SSES.

(iv) A review of the two NSCORT programs also has been initiated, with issues on the table including their continuation, whether they should be somehow folded into the NAI, and what the implications would be for the NAI and for the overall astrobiology program. Again, it is important that the review be carried to completion and that the SSES consider the issues in the near future.

The SSES requests formal presentation at its June, 2002, meeting regarding the astrobiology program in general, the status of the several component programs, the status of the NAI Director search, the status of the NAI visiting committee, and the status of the NSCORT evaluations.

Colleen Hartman and Orlando Figueroa -6


Several reports summarizing progress on the Solar System Exploration Roadmap were presented. The broad themes of the Roadmap are Planetary Origins, Planetary Evolution, and Planetary Habitability. Within this conceptual framework, Roger Phillips is responsible for the inner solar system ( including Mars and asteroids, with input from MEPAG), Bill McKinnon for the outer solar system (including comets), Bruce Jakosky for astrobiology (with input from Mike Meyer and Carl Pilcher), Andy Cheng and Mike Zolensky for international partnerships, Bill Jeffrey for technology, Jim Kasting, Mike Zolensky, and David Stevenson for Research and Analysis, and Sheri Klug for Education and Public Outreach.

Next Meeting

The date of the next meeting is June 3-5, 2002 in Washington, D.C.


Michael J. Drake, Chair
Solar System Exploration Subcommittee

c. Dr. Ed Weiler, Associate Administrator for Space Science
Dr. Andrew Christensen, Chair, Space Science Advisory Committee
Dr. Jay Bergstralh, Associate Director, Solar System Exploration Division
Dr. Gunter Riegler, Executive Director for Science, Office of Space Science
Dr. Jim Garvin, Lead Scientist for Mars, Office of Space Science
Solar System Exploration Subcommittee

From: Office of the Head and Director
Department of Planetary Sciences
Lunar and Planetary Laboratory
University of Arizona
PO Box 210092
Tucson Arizona 85721-0092
Tel: (520) 621-6962
Fax (520)
626-6647 email:

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