Status Report

Solar System Exploration Subcommittee (SSES) Minutes 28 Feb – 1 Mar 2001

By SpaceRef Editor
March 1, 2001
Filed under ,


Pasadena, California
February 28 – March 1, 2001

Letter to Solar System Exploration Acting Director Dr. Jay Bergstralh, Outer Planets Program Director Dr. Colleen Hartman, and Mars Program Director Mr. Scott Hubbard from Dr. Michael Drake, Chair of SSES

Dear Jay, Colleen, and Scott:

The Solar System Exploration Subcommittee (SSES) of the Space Science Advisory Committee (SScAC) met from February 28 to March 1, 2001 in Washington, D.C.Ê The purpose of this letter is to summarize the findings and recommendations of that meeting.

A general briefing on the state of the Planetary Program was given by Dr. Bergstralh and on the state of the Space Science Program by Dr. Weiler.Ê In addition, the President’s preliminary budget was released at noon on February 29.


The SSES notes that the cost cap on the Discovery Program has not been adjusted in recent years for inflation, increase in launch vehicle cost for technical reasons, and increased costs associated with the re-evaluation of the acceptable degree of risk.Ê ÊThe SSES endorses raising the cost cap to an appropriate level.

Research and Analysis

Dr. Gunter Riegler briefed the SSES on the state of the Research and Analysis Program.Ê Severe understaffing at NASA Headquarters, compounded by the need to respond very rapidly to the recommendation of the SSES to compete the Pluto-Kuiper mission through an AO, drained personnel from grant processing.Ê This reassignment of personnel led to serious delays in awarding of grants.Ê The SSES commends Dr. Riegler for recognizing this problem of slow processing of grants and has confidence in his stated plans to solve the problem rapidly and prevent its recurrence.

The SSES strongly urges the hiring of more civil servants and IPAs at NASA Headquarters.Ê The current personnel are clearly spread too thin.

Near-Earth Objects (NEOs)

The SSES is concerned that some proposals to study NEOs are “falling through the cracks” for programmatic reasons. Specifically, there appears to be a lack of balance between discovery of NEOs and their physical characterization.Ê The SSES notes that the study of NEOs is mandated by Congress and that their physical characterization is clearly directed in the baseline recommendation of the National Research Council’s 1998 report on NEOs [ref. 1].Ê Further, satisfying the congressional requirement for the discovery of 1 km NEOs requires physical characterization to transform magnitudes into physical sizes, i.e., if you don’t know the albedo, you cannot estimate a mean size.

The SSES recommends restoring balance to the study of NEOs, either by supporting physical studies within the NEO program or by ensuring that the Planetary Astronomy Program considers physical studies as part of its peer-reviewed science program.

[1]Ê “The Exploration of Near-Earth Objects”.Ê Space Studies Board, National Research Council.Ê National Academy Press, Washington, D.C. (1998).

Outer Planets

The current status of the Outer Planets Program was reviewed by Dr. Colleen Hartmann.Ê It was reiterated that OMB and the Congress had not approved an Outer Planets Program, even though both OMB and the relevant congressional committees had supported the release of the Pluto AO.Ê Even the Europa Orbiter mission is far from assured, given technical challenges and budget constraints.

During the meeting, the President’s FY02 “mini-budget” was announced.Ê It cancelled the Pluto AO.Ê By the end of the SSES meeting, majority and minority members of the Senate Appropriations Subcommittee had made clear that they expected the Pluto AO to go forward, with a funding decision to be made by Congress as part of the FY02 budget process, and NASA agreed to comply.Ê The situation with respect to outer planets missions remains uncertain.Ê A major task of the SSES is to articulate a compelling Outer Planets Initiative that is intellectually sound and publicly appealing.Ê See below.

Further, the SSES strongly recommends that outer solar system advanced mission studies be tightly focussed to respond to the specific recommendations of the SSES.


Bob Mitchell, Cassini Project Manager, provided an update on the Cassini mission. The failure to account adequately for the Doppler shift between Cassini and the Huygens probe was discussed. Final decisions must await the Huygens Recovery Task Force report at the end of June.Ê It appears, however, that there are solutions related to mission operations that can compensate for this oversight. In particular, delaying deployment of the probe for a few orbits seems plausible.Ê The SSES recommends that any solution maximizes overall mission science return, even if it involves delaying deployment of the Huygens probe.

The SSES expresses concern that science is underfunded by ~50%.Ê The SSES recommends that all efforts be made to find adequate science funding by examining the balance between mission operations and data analysis.

Mars Exploration

The SSES received reports from Scott Hubbard and Jim Garvin.Ê The Mars Program appears to be in good health, although concern about the pace of the Program persists.Ê During the SSES meeting, the President’s “mini budget” demonstrated support of a “robust” Mars Program.Ê This position, if adopted by Congress, indicates the Mars Program is on track for a more aggressive course.

The SSES noted the need to define the scope of the Mars Scout program, specifically the inclusion or exclusion of missions primarily focussed on the Martian moons Phobos and Deimos.

The SSES is also concerned about the tight development schedule for the 2007 Scout mission under the current plan of holding a “San Juan Capistrano-style” Workshop, followed by a two step approach to final mission selection involving extensive phase A studies of several mission options.Ê The SSES recommends simplifying the 2007 Scout mission selection by reducing steps and increasing development time for the selected mission.

Extended Missions

The Solar System Exploration Program does not budget for extended missions.Ê Yet terminating an expensive, viable spacecraft that still has high quality peer-evaluated science to conduct is an unconscionable squandering of the Nation’s resources.Ê Every planetary mission in recent memory has conducted one or more extended missions, stretching the Solar System Exploration Program severely as the Director reprograms funds.Ê Recent examples of the investment of small amounts of money compared to the overall cost of the missions in which new high-quality data of great scientific importance have been or will be returned are Galileo, Mars Global Surveyor, and NEAR-Shoemaker.

The SSES has three recommendations.

1.ÊÊÊÊÊÊÊ Fund a final extended Galileo mission that will return high quality Io data ending with an inevitable Jupiter impact.

2.ÊÊÊÊÊÊÊ Develop a plan to fund extended mission(s) for the Cassini spacecraft.Ê It would be irresponsible to turn off a functioning $3B spacecraft if peer-reviewed science remains to be done.

3.Ê For all future missions, plan in advance for MO&DA funds for extended missions.

Roadmap Planning

The SSES began preparing for the next Road Mapping exercise.Ê The Road Map tasks will be split into two parts.Ê

1The Committee on Planetary and Lunar Exploration (COMPLEX) of the National Academy of Sciences has agreed to writean introduction covering the “big picture” – a holistic and global framework for future planetary exploration.

2.The SSES will work on the implementation of the COMPLEX introduction.Ê Specifically, those elements of the last Road Map that have been successful will be retained.Ê Those areas that were unsuccessful – “The Outer Planets Program” and “To Build a Planet” will be revisited.Ê

Two SSES subcommittees were chartered.Ê

The first subcommittee, chaired by Bill McKinnon and consisting of Jakosky, Stevenson, Cuzzi, and Zolensky, will focus on the outer solar system.Ê It is suggested that “Exploring Organic-Rich Environments” remains a useful intellectual theme, although the mission set will probably be different from the last Road Map.Ê Europa Orbiter is the approved mission, with the view of ultimately seeking if life started on Europa.Ê Pluto/Kuiper is of high priority, as witnessed by the Senate Appropriations Subcommittee directing that the Pluto AO remain open and OMB proposing technology funds for advanced propulsion in support of a “sprint” to Pluto by 2020.Ê Pluto is also unique in that its orbital elements lead inexorably to the conclusion that a mission must be flown in the next few years or else we will wait for a quarter of a millennium.Ê Cassini/Huygens will produce (unknowable, in advance) new knowledge about Titan.Ê Studying prebiotic chemistry at Titan is a essential element to unraveling the origin of life, and is a likely third mission option.Ê Studying cometary nucleus material formed in the region of the outer planets gives us insight into the fundamental building blocks, organic and inorganic, that may have led to life on Europa and to possible prebiotic chemistry on Titan.Ê Comet nucleus sample return, informed by the results of the Stardust mission, is a likely fourth mission in this mission set, which could be titled “Exploring Organic Rich Environments”.

The second subcommittee, chaired by Ellen Stofan and consisting of Grinspoon, Jakosky, and Leshin will focus on the inner planets.Ê The SSES notes that Venus, while a compelling target of scientific enquiry, is “orphaned” at present.Ê A possible strategy for the exploration of Venus might be to address the question, why have Venus, Earth, and Mars, so similar in many respects, arrived at such different evolutionary states 4.55 Ga after their formation.Ê A possible mission set might fall under the title, “Evolution of a Habitable Planet”.

With kindest regards.


Michael J. Drake
Solar System Exploration Subcommittee

SpaceRef staff editor.