Assessment of Mission Size Trade-offs for NASA's Earth and Space Science Missions (2000) / Chapter Skim
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1 Issues and Considerations in the Assessment of Mission Size Trade-offs in the Earth and Space Sciences
1 Issues and Considerations in the Assessment of Mission Size Trade-offs in the Earth and Space Sciences
Pages 6-30
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, Mars Climate Observer, and Mars Polar Lander. 1For example, the SSB commented on the value of small missions in its report Planetary Exploration 1968-1975, which stressed the importance of a "series of relatively small and inexpensive spacecraft" to provide for a broad and flexible program in planetary exploration.
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FUNDAMENTAL SCIENCE LIMITS Because the Earth and space sciences that utilize observations from space encompass diverse scientific disciplines, the goals for space missions are diverse as well. The scientific goals may call, for instance, for substantially different mission time horizons, orbit requirements, and size and complexity of instrumentation, and the measurements may exploit different segments of the electromagnetic spectrum.
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In general, greater distances mean higher costs. Deep space missions require more launch and spacecraft capability than low-Earthorbit missions, all else being equal.
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Solar irradiance exhibits cyclic variations every 11 years or so. 7See SSB, The Role of Small Satellites in NASA and NOAA Earth Observation Programs, 2000, p.
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elegantly describe the motion of a body subject to gravitational forces and thus describe a satellite in orbit about the Sun, a moon, or a planet. For a satellite in near-circular Earth orbit, the time required to complete one revolution is determined primarily by its altitude.ll A satellite in Sun-synchronous Earth orbit tuned to cross the equator always at the same local timemay be required if the science objectives for a mission require a constant angle of solar illumination, for example.
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describe the behavior of electromagnetic waves as they propagate. Portions of the electromagnetic spectrum are used by all space missions.
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In all cases, however, the final design for the communication channel must satlsly the fundamental data rate limits. Summary Science objectives, seen through their attributes of where, when, what, and how, establish the data requirements.
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CREDITS: Raghvendra Sahai and John Trauger (Jet Propulsion Laboratory) , the Wide Field and Planetary Camera Science Team 2, and NASA for the Hourglass Nebula (MyCnl8)
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Instrument costs can become unreasonable if the amount of data they produce is very large, as has been proven more than once.21 Once there is agreement on science objectives, a cost-effective system should evolve through a thoughtful mission design process. Since legitimate science objectives vary widely, well-designed science missions likewise vary in size and complexity.
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21; SSB, The Role of Small Satellites in NASA and NOAA Earth Observation Programs, 2000. 26For example, the National Oceanic and Atmospheric Administration (NOAA)
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IMPLEMENTATION This section discusses some aspects of program implementation, including how space missions are managed, the extent of international cooperation, and the educational components of the missions. Management The move to apply FBC principles to NASA's Earth and space science missions has encouraged important changes in the ways NASA missions are managed.
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ISSUES AND CONSIDERATIONS IN THE ASSESSMENT OF MISSION SIZE TRADE-OFFS , ~ Science < ~ > Results obJective Do Lta requirements Feasibility r ~ ~d ~ ~ design ~ ~~ 1 ~~ ~~ / \ '- -' / / System \, . / /Sensor requirements ~,' data , my/ Science r~rodllets 17 / ~ Original mission goals Formal education Serendipitous discoveries Informal outreach Archival value · Comparison with other databases · Popular publications FIGURE 1.3 The raw data from a mission can have a broader impact than the originally proposed science goals.
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mission, which offers the chance of monitoring the application of such principles to larger missions. In addition, pursuing efficient contractor practices, low-overhead management techniques, concurrent engineering, integrated product development teams, and fewer formal reviews as well as coordinating with rather than overseeing the contractor, can enhance management effectiveness.35 The foregoing suggests that FBC principles applied wisely are beneficial for all management approaches and implementation modes.
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The effectiveness of the PI mode may change when new instruments must be conceived, developed, and tested.39 International Collaboration and FBC Principles The mission portfolios of NASA's Earth science and space science programs can benefit substantially when opportunities for international collaboration are taken advantage of. This section discusses the selection and planning processes for international cooperative missions, the risks in conducting such missions, and opportunities to facilitate them.
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, are providing, for the first time, an opportunity to determine the composition of material ejected from the cores of massive stars.3 1 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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Education NASA science missions provide opportunities for a wide variety of educational activities. These activities take forms that range from formal education at schools and colleges to informal life-long learning, through the 41SSB arid ESF, U.S.-European Collaboration, 1998, p.
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Previous Space Studies Board reports raised expectations that the FBC approach would enhance the educational role of NASA science missions because small missions need not be done exclusively at large contractors or government facilities: "Small missions provide a variety of opportunities for education at K-12 levels. The involvement of universities in small missions is also an excellent chance to excite and inspire students in various disciplines at both undergraduate and graduate levels and to provide technical, scientific, and managerial experiences that might be extremely valuable for a wide variety of careers.
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Funded by NASA and managed by the Universities Space Research Association (USRA) , the program aims to demonstrate the potential for university-led teams to successfully carry out high-quality space science and technology missions at a relatively low cost on a time scale of 2 years from go-ahead to ready-for-launch.2 The three missions selected were (1 )
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The observatory has "revolutionized observation astronomy by providing crisp images of objects ranging from protoplanetary disks and exploding stars to images of the most distant galaxies ever observed."8 ~ Space Studies Board, Board on Atmospheric Science and Climate, National Research Council, An Assessment of the Solar and Space Physics Aspects of NASA's Space Science Enterprise Strategic Plan, National Academy Press, Washington, D.C., 1997, p.
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Two Approaches to Infusing New Technology The process of infusing new technology into Earth and space science missions has changed dramatically over the course of the space program. In the rush to establish the U.S.
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The U.S. budget for NASA and the Department of Defense space activities in the late 1980s was considerably larger than a decade before, and new technologies were developed for a wide variety of space applications.48 The confluence of long technology development times, increasing complexity, and growing costs of space systems led to an interest in cutting the time elapsed between the ground qualification of a new technology and its subsequent integration into space missions.
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government payloads to be launched on vehicles manufactured in the United States.50 Moreover, U.S. commercial spacecraft requirements are driving the market towards larger launch vehicles, and there is little industry interest in providing opportunities for science missions to fly as secondary payloads on large commercial launchers.
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4. Risk in mission operations The large number of current and planned science missions is not well matched to the declining financial support for the Deep Space Network and thus imposes risk on mission operations.52 PROBLEMS WITH PAST MISSIONS While the committee has noted several benefits of the FBC approach and linked improvements to this approach, not all missions using it have been successful.
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This occurred as the spacecraft was about to go into orbit around the planet. The Mars Climate Observer Mishap Investigation Board concluded that "the root cause for the loss of the MCO spacecraft was the failure to use metric units in the coding of a ground software file."55 This problem caused the orbiter to fire its thrusters at levels that put it on an inaccurate trajectory toward the planet.
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It will provide further insight into and analysis of FBC principles and will show where the paradigm needs to be modified. The failures of some missions conducted under the FBC approach can be countered by the successes of others, so it will be important to strengthen effective practices while carefully making corrections, where necessary, in how the approach is administered.
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