Subject: New Missions Selected to Study Earth's Forests and Gravity Field
----------------------------Original message----------------------------
Douglas Isbell
Headquarters, Washington, DC March 18, 1997
(Phone: 202/358-1547)
RELEASE: 97-46
NEW MISSIONS SELECTED TO STUDY EARTH'S
FORESTS AND GRAVITY FIELD VARIABILITY
Small, lower-cost spacecraft to study the distribution of
Earth's forests and the variability of its gravity field have
been competitively selected by NASA for development under a
new Office of Mission to Planet Earth program called Earth
System Science Pathfinders (ESSP).
The Vegetation Canopy Lidar (VCL) mission, led by Dr.
Ralph Dubayah of the University of Maryland, College Park,
seeks to provide the first global inventory of the vertical
structure of forests across Earth using a multibeam laser-
ranging device. VCL will enable direct measurement of tree
heights, forest canopy structure, and derived parameters such
as global biomass with at least ten times better accuracy
than existing assessments.
The Gravity Recovery and Climate Experiment (GRACE), led
by Dr. Byron Tapley of the University of Texas at Austin,
employs a satellite-to-satellite microwave tracking system
between two spacecraft to measure the Earth's gravity field
and its time variability over five years. Such measurements
are directly coupled to long-wavelength ocean circulation
processes and to the transport of ocean heat to Earth's
poles. GRACE includes major international cooperation
through Dr. C. Reigber as Co-Principal Investigator from
GeoForschungsZentrum (GFZ) in Potsdam, Germany.
A proposed mission to better understand how atmospheric
circulation controls the evolution of key trace gases,
aerosols and pollutants over time has been selected as an
alternate, should one of the selected missions encounter
serious cost, schedule or technical problems in their early
development phases. Called the Chemistry and Circulation
Occultation Spectroscopy Mission (CCOSM), the mission would
be led by Dr. Michael Prather of the University of California at
Irvine.
"These exciting missions will deliver their first
science results in a little over three years, remarkably fast
for such capable spacecraft," said William Townsend, acting
Associate Administrator for Mission to Planet Earth at NASA
Headquarters, Washington, DC. "At the
same time, they will cost-effectively complement NASA's Earth
Observing System (EOS) program by addressing emerging
research questions that will further expand our scientific
knowledge of the Earth.
"Science value per dollar was the top criteria in this
selection," Townsend added. "We also spent a great deal of
effort validating the realism of the proposers' cost
estimates and their technical readiness. For all of these
reasons, the alternate mission should be considered a very
real option should one of the selected missions unexpectedly
encounter major difficulties."
"It also is important to note that the three selected
missions collectively address all four major science research
priorities of the U.S. Global Change Research program: land
cover change, atmospheric chemistry, and both seasonal and
long-term climate change," said Dr. Ghassem Asrar, Earth
Observing System chief scientist at NASA Headquarters.
The ESSP selections were made from a group of 12
proposals that were evaluated in the second phase of a
rigorous, two-phased selection process that began less than
eight months ago with a July 1996 Announcement of
Opportunity. This original announcement generated 44
proposals, which were initially reviewed for scientific
merit. This review resulted in 12 proposals that met the
requirements for the second phase of the ESSP evaluation.
As with NASA's Discovery program of small, focused space
science-oriented spacecraft, the underlying philosophy of
ESSP is to achieve maximum science value while complementing
existing or planned flight missions. In the Principal
Investigator (PI) mode for implementing ESSP, the single PI
and their team are ultimately responsible for developing the
flight mission hardware from selection to a launch-ready
condition in 36 months, with minimal direct NASA oversight.
The PI and their mission team are responsible for
accomplishing the stated scientific objectives and delivering
the proposed measurements to the broader Earth science
community and general public as expediently as possible.
The laser mapping technique to be used by VCL, which was
pioneered by NASA in aircraft experiments several years ago,
should help resolve a major uncertainty in the scientific
understanding of the global carbon cycle, particularly the
role of terrestrial ecosystems in sequestering the
atmospheric carbon dioxide produced by industrial activities
and automobile exhausts. At the same time, the multibeam VCL
lidar instrument will generate a vast array of reference
points for future surveys of land topography, including the
planned NASA-Department of Defense Shuttle Radar Topography
Mission in 1999-2000. VCL measurements should also have
practical commercial applications in forestry management.
The total mission lifecycle cost to NASA of VCL is $59.8
million, including the launch vehicle. VCL will be launched
in spring 2000 on a Pegasus launch vehicle. Industrial
partners in VCL include CTA Space Systems, McLean,VA;
Fibertek Inc., Herndon, VA; and Omitron Inc., Greenbelt, MD,
with participation by scientists at NASA's Goddard Space
Flight Center, Greenbelt, MD, and several U.S. universities.
GRACE will provide a framework for studying the
gravitational signatures of gigantic continent-sized
underground water reservoirs, or aquifers. It also will
provide a never-before-available perspective on global ocean
circulation and the time variability of Earth's overall
external shape, or geoid. This fundamental dataset could
enable great improvements in existing ocean radar altimetry
datasets, and retrospective improvements of seasonal to
interannual climate change estimates.
Through an innovative teaming arrangement, GRACE's German
partner GFZ will provide mission operations and a Russian
booster for a spring 2001 launch, greatly reducing the direct
total cost to NASA, which is $85.9 million. Other partners
include Loral Space Systems, Palo Alto, CA; the Jet
Propulsion Laboratory, Pasadena, CA, and Dornier of Germany
to build the spacecraft.
CCOSM would make at least 18 months of measurements of
the vertical distribution of more than 30 diagnostic trace
gases and aerosol properties. Such data will provide never-
before-available chemical and physical boundary conditions
from which to model the behavior of the chemistry of Earth's
atmosphere, such as the mixing of pollutants in the lower
atmosphere. Measurements to be acquired by CCOSM will be
used in conjunction with general atmospheric circulation
models to assess the effectiveness of the Montreal Protocol
(i.e., the banning of chlorofluorocarbons and other
potentially harmful gases) on controlling the depletion of
atmospheric ozone.
Partners in CCOSM include Lockheed-Martin Infrared
Imaging Systems, Lexington, MA; Spectrum Astro Inc., Gilbert,
AZ; and the Jet Propulsion Laboratory.
In addition to the funding support for the science team
associated with each mission, NASA has set aside ten percent
of the annual budget for the ESSP Program to support
innovative use and analysis of the observations resulting
from the ESSP missions. The intent is to utilize these funds
to support science data analysis and research investigations
through an open solicitation and peer review process once
data from the ESSP missions become available. NASA intends
to solicit another set of ESSP missions in the fall of 1998.
The ESSP program is a new element of NASA's Office of
Mission to Planet Earth, a long-term, coordinated research
enterprise designed to study the Earth as a global
environmental system.
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