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Introduction
NASA's Earth Observing System (EOS) has been designed to build
on 30 years of scientific and technical experience in remote sensing from
space. As the technology has matured from the early weather satellites,
the Earth science community has had the opportunity to integrate remote
sensing techniques and data products into its research. The new data
have answered many questions but raised more. The existence of global
measurement techniques and modern computational capabilities has led to
significant advances in the conceptual approach to the study of a natural
environment from a disciplinary to an interdisciplinary focus and from
a local or regional to a global perspective. Over the past decade, these
developments have contributed to the emergence of a new field of scien-
tific inquiry, Earth system science, and to international research activities
such as the World Climate Research Program (WCRP) and the Interna-
tional Geosphere-Biosphere Program (IGBP), and to the initiation of the
U.S. Global Change Research Program (USGCRP). Satellite measurement
programs are a key element of Earth system science.
In the EOS program, NASA proposes a major step in the evolution
of the science and technology of global remote sensing and microwave
imagers that provide detailed images of the Earth's surface; tropospheric
and stratospheric sounders that provide vertical profiles of parameters
such as temperature, trace gas concentration, and humidity; and accurate
positioning instruments. EOS will carry two classes of instruments: facility
and principal investigator (PI) instruments. The facility class instruments
are those that NASA will supply in response to the general mission; the
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PI class instruments were selected through a competition and are aimed at
the specific focused research interests of the selected investigators.
The objective of EOS is to integrate a number of related, but previ-
ously unavailable or disparate, space-based measurements into one contin-
uing system and thereby to enhance research capabilities significantly. It
will also provide a test bed for the development of the next generation
of operational, Earth-observing instruments and measurement techniques.
EOS is designed to yield a long-term, continuous set of high-priority mea-
surements on a global basis that are consistent with the needs of the U.S.
Global Change Research Program (USGCRP). The measurements will be
combined with complementary data obtained from space, suborbital, and
surface-based sources into the EOS Data and Information System (EOS-
DIS). The comprehensive contents of EOSDIS are intended to enable
the scientific community to document, monitor, and model environmental
change, to broaden its understanding of the entire Earth system, and to
improve predictive capabilities. Both the EOS space-based measurements
and EOSDIS are planned as interdisciplinary, interagency, international
endeavors, all of which are essential features of the USGCRP.
While EOS as proposed would provide extensive capabilities in remote
sensing and data management, it is best understood in the larger context
of NASAs Mission to Planet Earth and the even broader context of the
programs and plans for remote sensing of other agencies and nations. The
framework of the Mission to Planet Earth includes a number of near-
term smaller satellite missions (Earth Probes) to provide essential data and
added flexibility to the overall program. Both EOS and Earth Probes are
included in the FY 1991 USGCRP. Geostationary platforms for continuous
synoptic observations are being considered for later flight.
This report is based on a review of the most recent NASA documen-
tation on the current status of the proposed EOS, including the 1990 EOS
Reference Handbook (published by NASA), several briefing reports, and
oral briefings. In particular, we, the panel, had access to the draft report
of the Space Studies Board's Committee on Earth Studies (SSB/CES),
which examines the EOS initiative in a broader context. That report will
be issued after this one. We also received a copy of a review of EOS by
the American Geophysical Union, draft letters on instrument selection and
data simultaneity from the Chairman of the EOS Payload Advisory Panel
to NASAs Associate Administrator for Space Science and Applications,
and the latest information on plans for the USGCRP.
Currently EOS is at the point in the NASA process where instruments
have been selected for development, but not yet selected for flight. Thus
the information we had for this review was a "snapshot" in time of an
ongoing process of development. All details of the mission have not yet
been established, and even some of the major decisions have not yet been
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made. Mindful of this situation, we dealt with the information as part of
a changing process, so that what we have provided here is an assessment
that should itself be viewed as a snapshot of a developing program.
Because of the limited time available, we were not able to review
many aspects of this complex program in detail. Moreover, as noted below,
much of the documentation for the program is fragmentary and informal.
In spite of this limitation, we believe that our general conclusions are
sound. Because of the importance of this program to Earth scientists and
to the U.S. Global Change Research Program in general, we recommend
that a continuing ovemew by independent nongovernmental scientists and
engineers be maintained.
We were charged to address four questions. They appear verbatim at
the openings of Chapters 5 through 8 below and are followed in each case
by our responses and recommendations.
Representative terms from entire chapter:
planet earth
