Extending Science NASA's Space Science Mission Extensions and the Senior Review Process (2016) / Chapter Skim
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2 The Scientific Benefits of Mission Extensions
2 The Scientific Benefits of Mission Extensions
Pages 15-35
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From page 15... ...
ASTROPHYSICS DISCOVERIES DURING EXTENDED MISSIONS The Astrophysics Science Division conducts a broad program of research in astronomy, astrophysics, and fundamental physics. Investigations address issues such as the nature of dark matter and dark energy, discovery of exoplanets and analysis of which planets could harbor life, and the nature of space, time, and matter at the edges of black holes.
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In this way, the servicing missions "reset the clock," as updated technology and hardware repairs extended Hubble's lifetime as well as the time it spent in its prime phase. The final prime mission phase, post-SM4, began with the 2009 servicing mission and ended in 2014, when Hubble entered its extended-mission phase.
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Spitzer Space Together with Hubble Space Telescope identified very distant galaxy GNz-11, finding that star formation Telescope proceeds much more rapidly than previously known in the early universe (Oesch et al, 2016)
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. TDEs are a unique probe of dormant supermassive black holes in galaxies that are too distant for resolved kinematic studies.
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In turn, such revisions would affect estimates of the stellar initial mass function in galaxies and of star formation through cosmic time, which rely on the predictions of stellar evolution models. EARTH SCIENCE DISCOVERIES DURING EXTENDED MISSIONS Earth is a complex, dynamic system and to fully understand it requires understanding Earth's atmosphere, lithosphere, hydrosphere, cryosphere, and biosphere as a single interconnected system.
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The monthly measurements also contribute to assessing ground water storage in aquifers, ocean mass change from melting of glaciers, measuring the change in mass distribution of polar ice and the episodic mass change associated with large earthquakes. GRACE entered extended mission phase in 2008 and has been extended several times since then.
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By enabling GRACE to continue operating until GRACE Follow-On is operational, scientists can remove any bias in the data caused by transferring from the current sensor to the next sensor, even though the two sensors theoretically have the same specification. Such cross-calibration has been important for other Earth science missions, such as missions for measuring solar irradiance (e.g., Acrimsat)
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mission launched in December 1999, whose prime mission ran through September 30, 2005. It has been extended through the Earth Science Senior Reviews in 2005, 2007, 2009, 2011, 2013, and 2015, and all five instruments are still operating nearly as well as at launch, with the exception of the 1999 failure of the shortwave-infrared instrument on ASTER (Advanced Spacebourne Thermal Emission and Reflection Radiometer, a contribution from the Japanese Ministry of Economy, Trade, and Industry)
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Thus, even a spacecraft that has been operating for many years and no longer represents the state of the art can be used in new and sophisticated ways. HELIOPHYSICS DISCOVERIES DURING EXTENDED MISSIONS Heliophysics is the study of the Sun, the heliosphere, and the interactions of the Sun and the solar wind with planetary environments.
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Even today, the in situ measurements of plasma and magnetic TABLE 2.3 Examples of Science Results Made Possible by Extended Missions in Heliophysics Mission Science Results ACE Continuous observation of solar wind conditions for studies of energy, mass, and momentum flow through the geospace system (Gopalswamy et al., 2005)
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spacecraft in Earth orbit continue to provide information about the farthest reaches of the heliosphere; the new data challenge our scientific preconceptions and are generating new understanding. From the large scale and the outer reaches of the solar system to the smallest scale in our own backyard, important scientific discoveries have been made and are continuing to be made using data from extended missions.
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extended missions were operating and were able to monitor the state of the Sun and the solar wind. The deep solar minimum was felt throughout the system; for example, data from the TIMED (Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics)
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For planetary science missions, a number of major science results have been possible only because of extended missions (see Table 2.4 for examples from some current extended missions)
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. NOTE: LRO, Lunar Reconnaissance Orbiter; MER, Mars Exploration Rovers, MRO, Mars Reconnaissance Orbiter, NEOWISE, Near-Earth Object Wide-field Infrared Survey Explorer.
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The decision to operate the WISE spacecraft beyond its original lifetime has provided a first glimpse into this unique and rare population of small bodies. What the planetary science extension examples demonstrate is that sometimes new scientific discoveries are only possible after a spacecraft moves into a new orbit or to a new location that could not be achieved during the prime mission, such as Cassini making multiple orbits around Saturn enabling it to make more and better planned observations of Enceladus, or a Mars rover reaching a new location far from its landing site.
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SOURCE: NASA Jet Propulsion Laboratory, "Encroaching Shadow," accessed June 27, 2016, http://www.jpl.nasa.gov/spaceimages/ details.php? id=PIA17184; courtesy of NASA/ JPL-Caltech/Space Science Institute.
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CONCLUSIONS Extended missions in all four divisions of NASA's Science Mission Directorate have made major scientific contributions at low cost relative to the initial investments for the prime missions. Finding: Extended science missions are valuable assets in NASA's portfolio because they provide excellent science at low incremental cost.
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From page 32... ...
Examples include GRACE leading to GRACE-Follow On, Mars discoveries leading to new landing sites and future orbiter science priorities, and discovery of subsurface oceans leading to new missions such as the Europa multiple flyby mission and a new Ocean Worlds program. Finding: NASA's extended missions are an important part of both achieving science objectives of the decadal surveys (see Appendix D)
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Geophysical Research Letters 32(12)
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2015. NASA Earth Science Senior Review 2015.
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Geophysical Research Letters 38(12)
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