Assessment of Mission Size Trade-offs for NASA's Earth and Space Science Missions (2000) / Chapter Skim
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2 Science Priorities and NASA Mission Plans
2 Science Priorities and NASA Mission Plans
Pages 31-51
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From page 31... ...
also included questions on such factors as the impact of new technology and international cooperation to ascertain the range of mission sizes that scientists consider appropriate for their discipline area and its high-priority scientific objectives. The ad hoc committee drew on the discipline committees' contributions (Appendix E)
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From page 32... ...
The cross-cutting themes include issues such as portfolio balance, science objectives and larger missions, spacecraft and instrument availability, long-term planning, international partnerships, and the trade-off between more frequent flights for scientific spacecraft and the risk that science objectives will not be met. The second part of the chapter addresses the history, requirements, and programmatic directions of the various disciplines as those factors influence the mission size mix in the disciplines (Earth science, planetary science, solar and space physics, and astronomy and astrophysics)
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From page 33... ...
In contrast to the quantitative assessment in Appendix E, which shows many larger missions, a qualitative assessment of new starts in NASA's Earth science portfolio would show more medium and smaller missions. Some Important Science Objectives Require Larger Missions Inserting smaller missions into the Earth and space science programs promises greater flexibility and more timely science.
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From page 34... ...
They would address scientific objectives that require difficult orbits for example, an orbit needed to make in situ measurements of interstellar space or would involve studies of planetary environments requiring long-duration travel and significant power and fuel resources. In Earth sciences, large platforms often have been used for measurements that require instruments with large aperture sizes.
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From page 35... ...
If a mission like this is designed to meet a complex series of scientific objectives, it is highly unlikely that a specific payload instrument can be found among existing commercial or government sources that meets those objectives. The first order of business in traditional missions is development of the scientific instruments required to meet the ambitious scientific objectives.
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This section discusses how such cooperation can contribute to the mix of mission sizes in NASA's portfolio of Earth and space science missions. Cooperative international programs are a clear example of how flexibility in mission planning has produced excellent science at low costs.
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From page 37... ...
Thus far as long as the problems with STEDI and TIMED do not recur missions aimed at providing more frequent science cannot be judged to have introduced significant risk into the solar and space physics program. In the planetary science program, however, the recent loss of the Mars Climate Observer and the Mars Polar Lander exemplified the potential risks that the FBC approach poses for the strategic plan.
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From page 38... ...
Earth Sciences Earth science includes diverse scientific disciplines such as oceanography, land processes, atmospheric sciences, meteorology, climate, and geodesy, all of which utilize observations and measurements from space. For more than 30 years these disciplines have relied heavily on observations from meteorological satellites that now include NOAA's polar-orbiting operational environmental satellites (POES)
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project that also has extensive participation from Germany.5 Space Studies Board, National Research Council, and European Science Foundation, U.S.-European Collaboration in Space Science, National Academy Press, Washington, D.C., 1998, pp.
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24NASA, Earth Science Enterprise Technology Development Plan, 1999. 25Space Studies Board, National Research Council, An Integrated Strategy for the Planetary Sciences: 1995-2010, National Academy Press, Washington, D.C., 1994.
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From page 41... ...
While the five instruments on Lunar Prospector have provided useful information about the composition of the lunar surface and gravity field, the potential scientific accomplishments of Cassini could not be achieved with a series of multiple missions of the Lunar Prospector class. Thus, solar system exploration is optimized by a mixed portfolio of mission sizes, which includes occasional large missions for major objectives (particularly necessary in the outer solar system)
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From page 42... ...
. Its scientific objectives are to conduct the following observations: · Orbital remote sensing of Saturn's atmosphere, icy satellites, and rings; · In situ orbital measurements of charged particles, dust particles, and magnetic fields; and · Detailed measurements with six instruments on the Huygens probe during descent through Titan's dense nitrogen atmosphere to the surface.1 These science objectives respond directly to the NRC scientific strategy, which calls for the exploration of the outer planets, including an intensive study of Saturn the planet, satellites, rings, and magnetosphere as one its highest priorities.
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Esposito to Lennard A Fisk, associate administrator for NASA's Office of Space Science and Applications, August 10, 1990; Space Studies Board, "On the CRAF/Cassini Mission," letter from Space Studies Board Chair Louis J
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Squeezing Large Science Objectives onto Medium-Size Missions Important scientific objectives such as sample returns, surface landers, and flights to the outer solar system cannot be achieved without larger missions. Nevertheless, as noted previously, a number of important scientific goals best addressed by large missions are being implemented as medium-sized (or nearly so)
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From page 45... ...
Mission Mix and NASA Plans The slate of recommended missions in the new SEC Roadmap34 builds on, and is generally consistent with, the OSS Strategic Plan of 1997 and with the Committee on Solar and Space Physics' assessment of that plan.35 Thus, each STP and Frontier Probe contributes significantly to one or more of the scientific objectives of the OSS Strategic Plan. The OSS Strategic Plan of 1997 does not specifically address mission cost or cost caps, but it does support the FBC approach, as discussed in the plan' s appendix on metrics.36 The new SEC Roadmap incorporates a strategy to implement the plan's science objectives primarily using STP missions (less than $250 million)
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From page 46... ...
Certain focused scientific objectives can often be accomplished with small or medium-size missions, which could be conducted through the Explorer or STP programs. Other scientifically more challenging and complex objectives would require far greater financial resources and large missions to be successful.
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From page 47... ...
The 1,850-kg spacecraft is equipped with 12 instruments, including helioseismology instruments to study the structure and dynamics of the solar interior from the deep core to the outermost layers and remote-sensing instruments, including extreme ultraviolet and ultraviolet imagers, spectrographs, and coronagraphs to view the outer solar atmosphere and corona. Since SOHO began its 3-year mission in 1995, the observatory has provided the first image of the convection zone of a star; the first tracing of the slow-speed solar wind near the equatorial current sheet; the first detection of elements and isotopes in the solar wind; and the first observations of coronal mass ejections (CM Es)
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From page 48... ...
These observations are taken from a single, high-resolution telescope.7 The images and observations made from TRACE provide insight into the three-dimensional magnetic structure emanating from the Sun and help define the geometry and dynamics of the upper solar atmosphere, known as the transition region and corona. In addition, the telescope is acquiring solar images taken through filters that select different spectral features.
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See also Space Studies Board, "On ESA's FIRST and Planck Missions," letter to Wesley T Huntress, Jr., NASA Associate Administrator for Space Science, from Claude R
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. The general outcome is that the Hubble Space Telescope has had the greatest impact of any observatory-type facility available in space.2~3 Submillimeter Wave Astronomy Satellite The Submillimeter Wave Astronomy Satellite (SWAS)
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The thematic approach to AOs allowed the science community to respond to certain scientific goals in NASA's strategic plans, while the new approach, although it has yielded excellent scientific proposals, does not define scientific areas and therefore cannot be incorporated into long-term plans.
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