Solar System Exploration Subcommittee Findings and Reccommendations

Office of the Head and Director

Department of Planetary Sciences

Lunar and Planetary Laboratory

University of Arizona

PO Box 210092

Tucson Arizona 85721-0092

drake@lpl.arizona.edu

Tel: (520) 621-6962

Fax: (520) 626-6647

November 27, 2000

Dr. Jay Bergstralh

Code S

NASA Headquarters

Washington, D.C. 20546

Dear Jay:

The Solar System Exploration Subcommittee (SSES) of the Space Science
Advisory Committee (SScAC) met on October 30 and 31, 2000 in
Pasadena, California. The purpose of this letter is to summarize the
findings and recommendations of that meeting.

Mars Exploration

The SSES received reports from Scott Hubbard, Jim Garvin, and Farouz
Naderi. It is clear to the SSES that NASA has put its “A Team” in charge
of the Mars Exploration Program, and overwhelmingly endorses the
missions set laboriously constructed after consultations with a wide range
of constituencies. Given budget constraints, the team has done an
excellent job. A minority view felt the plan was “timid” in that it did not
obviously engage enough public support and may be inconsistent with a
possible future decision to send humans to Mars in the next decade.

Antarctic Meteorites

The SSES noted that one way to increase access to Martian samples for
fairly low cost is to increase the recovery rate of Martian Meteorites.
Currently, Martian Meteorites from Antarctica account for approximately 1
in 2000 Antarctic meteorite specimens, or a recovery rate of about 1 every
4 years. For an investment of ~$400K – $450K per year (or 0.02% of the
currently projected cost of a Mars sample return mission), predominantly
for field logistics and curation support, the rate of Antarctic meteorite
recovery could be approximately doubled. This would be accomplished by
putting a second field team on the ice each season, either in a
reconnaissance mode (investigating new regions to assess their suitability
for future collecting seasons) or collecting mode (systematic searching for
meteorites in one or more areas). The consensus of the SSES is that this
moderate investment from the Mars Program budget could go a long waay
to preparing us to handle and analyze returned Martian samples, but should
not be construed as a substitute for returning a scientifically selected suite
of samples from Mars in the near future. The SSES recommends that
investment in increasing the recovery rate of Martian
meteorites be made.

Outer Planets

The highest priority outer planet missions, Pluto-Kuiper Express (PKE)
and Europa Orbiter (EO), have received strong endorsements in previous
considerations by COMPLEX and SSES. Recent developments in our
understanding of the solar system have strengthened the case for both of
these missions as a compelling and essential part of NASA’s planetary
program. This is documented below. There is no compelling scientific
basis for a program that places EO ahead of PKE in importance. An
orderly and timely program that accomplishes these missions takes
advantage of the 2004 launch opportunity for PKE. The likely delay in EO
that is implied by this choice is unfortunate but vastly preferable to the
alternative of a long delay and possible associated degraded science of
PKE. Given the difficulty in solving EO engineering problems before
2006 at the earliest, it is logical to consider flying PKE first. EO would
still return data first.

PKE is a pioneering mission. It takes us to examples of an important and
little understood class of bodies, the small icy objects that populate the
Kuiper Belt. In our developing understanding of these
bodies, we have come to recognize that they are essential to our
understanding of how planets form and what materials go into habitable
planets, including Earth. The giant planets define the architecture of our
solar system, define the inner edge of the Kuiper belt, and probably
determined the delivery of much of the most volatile materials including
water to planet Earth. In the Kuiper belt bodies, the largest known example
of which is the planet Pluto, we have repositories of volatile and organic
matter and information on the mass and distribution of materials dating
back to solar system
origin. We need to learn about compositions, and about the population of
bodies expressed through impact cratering of the surfaces of these bodies.
These goals are central aspects of NASA’s Origins Program.

We must go there. The information needed is mostly unobtainable from
telescopic observations, even allowing for future improvements. Though
small, Pluto has an atmosphere and is expected to have internal dynamic
processes. The Pluto-Charon binary planet system has no other solar
system analog in its tidal evolution except possibly Earth and our
companion the Moon. The images from the Pluto encounter, collected over
an extended period, are likely to fascinate the public. From our perspective
close in to the Sun, this is a mission to the frontier of the solar system, an
appealing aspect to both scientists and the public.

The scientific justification for EO remains strong. Galileo results have
strengthened the case for a water ocean but have led to no consensus about
ice thickness or the conditions beneath the thin,
outermost brittle layer of very cold ice. A well-instrumented EO should be
designed to answer with certainty the issue of whether there is an ocean
and identify some aspects of the nature of this subsurface environment that
might support life. An orderly approach to Europa exploration calls for an
orbiter before a lander. However, there is no aspect of our developing
view of Europa that would compel us to place its importance above that of
the science addressed by PKE.

The SSES received a presentation from Lockheed-Martin which suggested
that different PKE concepts could possibly achieve scientific objectives at
lower cost than the current PKE baseline mission.

The consensus of the SSES is that JPL should be given until
approximately the end of November 2000 to formulate a plan
that achieves Europa Orbiter and Pluto-Kuiper Express within
the current budget. If they are unable to come up with a
solution PKE and, possibly, Europa Orbiter should be put out
for competitive bidding through an appropriate process.

If such a plan is followed and JPL is unable to come with a viable plan, the
recommended boundary conditions are:

c. NASA announce selections of the PKE and EO science payloads by
January 2001 from those that have been proposed in response
to the September 10, 1999 AO (AO-99-OSS-04).

d. AO solicitation be issued by NASA on or before 1/15/01,
requesting proposals that include the totality of the OP
program, a la Discovery, and accommodate the NASA-selected
science payloads. Responses should be requested by 4/15, with
intended NASA selection by 6/1/01.

e. Simultaneously with the issuance of the AO, NASA should proceed
to begin manufacture of an appropriately-sized RTG (e.g.
RTG9), with currently existing hardware. Also, NASA should
initiate processes for regulatory approval of a PKE launch no
earlier than December 2004.

The above recommendations will accomplish a number of Outer Planets
science and programmatic objectives. These include: timely launch of a
PKE mission to take advantage of the unprecedented opportunity in the
2004 launch window, within a possibly affordable budget; continued
development of EO technology for a launch in the 2005-2010 timeframe
that will result in returned science data from Europa long before the PKE
flyby of the Pluto-Charon system; and likely implementation of the
program within NASA budgetary guidelines, with appropriate
adjustments.

Attached Payloads

The SSES considered the problem of the suborbital/attached payloads
program that has found itself fitted within the Planetary Atmospheres
program as an unfunded mandate. For FY00 that amount is $300K out of
the $8M Planetary Atmospheres budget. It was widely agreed that level
of funding is far below any reasonable support level for the program and
that the mandate must necessarily grow to 450K in FY01 and 600K in
FY02. The consensus of the SSES is that if that program support remains
within Planetary Atmospheres, it should continue to be separated by a
firewall from the rest of Planetary Atmospheres. The two programs are
distinctly different in terms of their average grant size (about a factor of
two) and in their objectives (basic investigator science vs. flight missions,
technology development, space hardware training). The SSES sees as the
most important objective to find a natural home for the planetary
suborbital/attached payloads program, perhaps as a new, free standing
Research and Analysis Program for suborbital/attached payloads that cuts
across themes. This would allow SSE proposals to compete more directly
with their naturally complementary counterparts from other themes. The
financial support at the current or projected level from the SSE suborbital
grants would be contributed to this program. This kind of cross-theme
program is not unprecedented. Such a program currently exists in the
Flight Information Systems area. The SSES recommends that the
SScAC review the suborbital/attached payloads issue to
advise on the possibility of creating a cross-theme program.
The availability of the Space Shuttle and the International Space Station
should not be overlooked by the Solar System Exploration Program.

Cassini

The failure to account adequately for the Doppler shift between Cassini and
the Huygens probe was discussed. It appears that there are solutions
related to mission operations that can compensate for this oversight. The
SSES recommends that any solution maximizes overall
mission science return, even if it involves delaying
deployment of the Huygens probe.

Deep Space Network (DSN)

The SSES received a briefing which points to a significant overload of
DSN capabilities in 2004 and beyond, but that measures are being
followed to mitigate this problem. The Solar System Exploration Division
should nevertheless remain concerned that an adequate solution is
achieved.

Planetary Data System (PDS)

It appears the PDS is underfunded by about $2M per year. The Solar
System Exploration Program needs to address this issue.

MUSES-CN

MUSES-CN is a Japanese mission to an asteroid to carry out in situ
science and return samples to Earth. The SSES concurs in NASA’s
decision to terminate its involvement in the rover program. It is critical,
however, that NASA assures access to samples for U.S.
scientists.

With kindest regards.

Sincerely,

Michael J. Drake, Chair

Solar System Exploration Subcommittee

c. Dr. Jay Bergstralh, Director, Solar System Exploration

Dr. Scott Hubbard, Mars Program Office

Dr. Ed Weiler, Associate Administrator for Space Science

Dr. Steve Squyres, Chair, Space Science Advisory Committee

Solar System Exploration Subcommittee