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The Scientific Context for Exploration of the Moon 4 Implementation The science concepts discussed in Chapter 3 encompass broad and multicomponent science issues and most of the concepts require a diversity of approaches along with integrated analysis. Table 4.1 tabulates implementation options for each of the eight concepts. Each column of the table provides examples of different types of endeavors that can be achieved for a specific choice of implementation options (information extraction; orbital measurements; sample return; landed experiments, instruments, and rovers; and human fieldwork, or human-tended surface experiments). Science objectives requiring a permanent human presence or large structures are more aligned with the long-term Vision for Space Exploration (VSE) activities on the Moon and are beyond the scope of this report. Such science opportunities and their requirements should nevertheless be continually evaluated as the VSE is implemented. As discussed in Chapter 7, NASA’s VSE program builds on considerable strength if science is fully integrated in operations planning. Exploration of the Moon is no longer in the reconnaissance phase. As a result of Apollo, we understand that the Moon is a differentiated planetary body, it contains few volatiles, its rocks are old, and its history is closely tied to that of Earth. As discussed throughout the preceding chapters, we now pose far more sophisticated questions about how planets work. Answers to such questions, however, are not simple, nor are they necessarily easy to obtain. As has been the case for the exploration of Mars over the past decade, multiple avenues of implementation for lunar science will be the hallmark of a visionary and progressive science program. IMPLEMENTATION OPTIONS Guidelines on how the lunar science concepts might be addressed with different possible elements of the VSE are provided in Table 4.1. Since four sophisticated orbital remote sensing missions are scheduled to return data before the end of 2008 (SELENE [Selenological and Engineering Explorer], Chang’e, Chandrayaan-1, LRO [Lunar Reconnaissance Orbiter]—see below), column (a) of Table 4.1 identifies information and knowledge that can and should be harvested from this rich bounty of orbital data. Assuming that all four of these missions and their host of modern sensors are successful, plans for information extraction must be made in order to benefit from the deluge of raw data returned. Column (b) identifies science return that would result from additional orbital measurements beyond those planned in the four missions already under way. It should be noted that if an instrument or mission fails to return
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The Scientific Context for Exploration of the Moon TABLE 4.1 Implementation Options for Principal Science Concepts Science Concepts Implementation (a) Information Extraction (b) Orbital Measurements (c) Sample Return (d) Landed Experiments, Instruments, and Rovers (e) Human Fieldwork The science goals for each concept are discussed in detail in the text (see Chapter 3). An enabling new frame work for lunar exploration will be provided by data from SMART-1, SELENE, Chang’e, Chandrayaan-1, and LRO. The assumption is that all missions and key instruments will be successful. Orbital measurements are not included in the complement of missions planned for launch by 2008. The assumption is that the four missions planned will return appropriate data as planned; if not, new measurements that provide similar high-priority compositional and geophysical data need to be acquired. The types of returned samples and of science analyses required are identified. These include science measurements for/from landed sites; category also encompasses penetrators/impactors. Science areas that specifically benefit from human capabilities are identified. 1. The bombardment history of the inner solar system is uniquely revealed on the Moon. Crater counts of benchmark terrain using high-resolution images. Targeted higher-resolution images of specific terrains. Sample return from the impact-melt sheet of SPA, from young basalt flows, and frombenchmark craters (e.g., Copernicus and Tycho). Development of insitu instrumentation for dating. Field observations provide critical geologic context; human interaction improves chances of obtaining best/most appropriate samples. 2.The structure andcomposition of the lunar interior provide fundamental information on the evolution of a differentiated planetary body. Farside gravity. High-quality topographic information. Possible information on heat flow and magnetic sounding results. Relay orbiter for farside stations (e.g., relay of seismic data). Samples from the interior are important constraints on lunar geochemistry and geophysics (e.g., remanent magnetism). Simultaneous, globally distributed seismic and heat flow network. Expanded retroreflector network. Although some landed experiments can beemplaced autonomously, it is assumed that more capable sensors are possible with human guidance/assistance. 3. Key planetary pro-cesses are manifested in the diversity of lunar crustal rocks. Detailed global elemental and mineralogical information in a spatial context. Search for and documentation of a diversity of rock types using returned samples and lunar meteorites. Perform high-resolution mapping of lunar crustal magnetic fields. Higher-spatial-resolution compositionaldata are desirable from priority targets. Relay orbiter for farside stations (e.g., relay of seismic data). Magnetic survey from 10 km orbit. Return samples from priority targets. Every return mission should include a bulk soil and a sieved sample with geologic documentation. Strategic site selection. Conduct in situ analyses and mineralogical and elemental characterization of the rocks and provide a thorough description of the geologic context. Determine thevertical structure using an active regional seismic network. Field observations provide critical geologic context; human interaction improves chances of obtaining best/most appropriate samples.
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The Scientific Context for Exploration of the Moon 4.The lunar poles arespecial environments that may bear witness to the volatile flux over the latter part of solar system history Primary understanding of polar environment (photometry, morphology, topography, temperature, and distribution and inventory of volatiles). High-spatial-resolution distribution of volatiles on and in the regolith poleward of 70 degrees. Cryogenically preserved sample return to determine the complexity of the polar deposits. Understand physical properties of polar regolith. Determinethe localized character and lateral and vertical distribution of polar deposits. Measure chemical and isotopic composition and physical and mineralogical characteristics. Human-assisted robotic exploration of regolith. 5. Lunar volcanism provides a window into the thermal and compositional evolution of the Moon. Detailed global elemental and mineralogical information in a spatial context. Improved age-dating for basalts through crater counting. Stratigraphy of specific basalt flows (subsurface sounding). High-spatial-resolution compositional data desirable. Sample the youngest and oldest basalt flows. Need samples from unsampled benchmark lava flows and pyroclastic deposits. Strategic site selection. Conduct in situ analyses and mineralogical and elemental characterization of the rocks and provide a thorough description of the geologic context. Strategic site selection, core drilling, and active subsurface sounding to determine layering and volume. Sample a complete sequence of flows to determine the evolution of basalt composition. 6. The Moon is an accessible laboratory for studying the impact process on planetary scales. Detailed geologic mapping of compositionally diverse craters and basins. Evaluation of upper-surface stratigraphy (sounding). Determination of the shape of craters and the distribution of ejecta. Sample returns from benchmark craters and basins. In situ compositional and structural analyses of craters and basins (via traverses). Core samples from impact-melt sheets. Traverses across ejecta blankets. 7. The Moon is anatural laboratory for regolith processes andweathering on anhydrous airless bodies. Maps of regolith maturity and derivation of the temporal progression of space weathering. Identification of regions that contain ancient regolith. Evaluation of upper-surface stratigraphy (sounding). Regolith from unsampled terrain of diverse composition and age. Understand the evolution of the regolith. Sample old regolith where it is stratigraphically preserved. Characterization of returned sample environment. Obtain paleoregolith samples (exposed in selected outcrops or through deep drilling). 8. Processes involved with the atmosphere and dust environment of the Moon are accessible for scientific study while the environment remains in a pristine state. Characterize surface electric field; dust grain size, charge, and spatial distribution, and effects of human activity on dust environment. Variation in mass with time and compositional inventory (“with time” refers to the lunar diurnal and Earth-orbital/solar cycles). Not applicable. Sample return not currently feasible. Variation of mass withtime and identification of dominant species. Environmental monitoring near human activity. Measure electric field and dust environment. Not applicable. Human presence will alter atmospheric characteristics. NOTE: Acronyms are defined in Appendix B.
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The Scientific Context for Exploration of the Moon the quality of data anticipated, reflight of comparable instruments is required in order to acquire data that will address items in column (a). Column (c) provides examples of the type of materials that would specifically benefit the different science concepts through sample return and analyses in Earth-based laboratories. Analytical capabilities improve with each technology advancement, continually expanding the value of the sample-return investment. Column (d) highlights an array of landed experiments, instruments, and rovers that will contribute substantially to exploration of the Moon in specific terrains. In situ activities are fundamental to detailed scientific understanding. Initial human activities on the Moon fall within the timeframe of this report, and column (e) provides examples of human fieldwork to be undertaken for each science concept. These are activities that specifically benefit from the abilities of humans present to carry out integrated or challenging tasks. Well-designed human-robotic partnership will be central to the success of the activities. The actual implementation of individual options within NASA’s VSE requires an integrated partnership between universities, NASA and government centers, industry, and the private sector. If the United States wishes to take a leadership role in this activity, then sustained commitment must be made to involve each of these partners in the effort and to maintain and build on strength and experience developed in the U.S. science and engineering communities. In addition, it is clear that an expanding group of space-faring countries will continue to play a central role in exploration of the Moon, and ultimately in how lunar resources are used in human society. Developing the appropriate balance and interaction between U.S. participants and foreign partners/collaborators will be a challenge as well as an opportunity. INTERNATIONAL CONTEXT The lunar exploration activities of the recent past and the near future are pervasively international in scope. The European Space Agency (ESA) launched Small Missions for Advanced Research in Technology (SMART)-1 to the Moon in September 2003 on a technology-demonstration mission to validate solar-electric propulsion systems. After a long journey, SMART-1 entered orbit around the Moon and began limited studies of the lunar surface with a suite of small, innovative instruments. SMART-1 scheduled a successful end-of-mission impact on the lunar nearside along with coordinated observations during the fall of 2006. A new image mosaic from the farside of the Moon obtained by SMART-1 is shown in Figure 4.1. The Japanese Aerospace Exploration Agency has planned two missions for near-term implementation, Lunar A and SELENE. Lunar A is designed to study the lunar interior using seismometers and heat flow probes deployed by penetrators, but technical difficulties during testing put the mission on hold and it was later cancelled. SELENE, however, is a mature orbiter prepared for launch in 2007 for a 1-year nominal mission. The goals of SELENE are to study lunar origin and evolution and to develop technology for future lunar exploration. It carries an array of modern remote sensing instruments for the global assessment of surface morphology and composition. SELENE also carries two subsatellites that will enable the gravitational field of the farside to be measured accurately. The Chinese National Space Administration formally announced its Chang’e lunar program in March 2003. Chang’e 1, a lunar orbiter with a broad complement of modern instruments, is prepared for launch in 2007. Chang’e 1 carries several remote sensing instruments to study surface topography and composition as well as the particle environment near the Moon. In addition, Chang’e 1 carries a four-wavelength microwave sounder to probe the regolith structure. Future elements being planned for the Chang’e program include a lander/rover and a sample-return mission as precursors to human exploration. The Indian Space Research Organization will launch its Chandrayaan-1 spacecraft in 2008 on a 2-year orbital mission to perform simultaneous composition and terrain mapping using high-resolution remote sensing observations at visible, near-infrared, x-ray, and low-energy gamma-ray wavelengths. This spacecraft will carry two sophisticated instruments from the United States to characterize and map mineralogy using near-infrared spectroscopy and to map the shadowed polar regions by radar. It will also carry three ESA instruments, two of which were prototypes on SMART-1. In addition to the remote sensing experiments, the Chandrayaan-1 spacecraft will also carry an instrumented probe that will be released and targeted for a hard surface landing.
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The Scientific Context for Exploration of the Moon FIGURE 4.1 Image mosaic across the northwest part of South Pole-Aitken Basin obtained by the Advanced Moon Micro-Imager Experiment camera onboard the SMART-1 spacecraft. The subdued 76 km crater Oresme is of Nectarian age. The small, sharp, kilometer-scale features to the northwest that are oriented in several directions are of unknown origin. SOURCE: Courtesy of the European Space Agency/SMART-1 and the Space Exploration Institute. NASA’s Lunar Reconnaissance Orbiter is scheduled for launch in the fall of 2008. LRO’s goals are to improve the lunar geodetic network,1 evaluate the polar areas, and study the lunar radiation environment. A secondary payload, Lunar Crater Observation and Sensing Satellite (LCROSS), launched with LRO, will result in an impact into a polar region target with coordinated analysis. After the first year of measurements, the LRO instruments will be operated to maximize the science return. NASA’s plans for the next step of robotic exploration are currently not specified. The group of four missions described above, having highly sophisticated sensors, will produce an unprecedented array of exceptionally valuable data for the Moon. There are several unique instruments on each spacecraft that give each mission its own flavor and scientific emphasis. There are also a number of similar instruments on different spacecraft that provide an excellent opportunity for cross calibration and validation between missions. All of these international participants in lunar exploration have expressed their intention of publicly releasing data returned (typically 1 year later) in a compatible format that will allow fruitful comparisons and the planning of international lunar exploration. As we embark on this new era of detailed lunar exploration, several other nations have expressed a serious intent to participate with additional orbital spacecraft sent to the Moon in the near future: Russia, Germany, Italy, and perhaps Great Britain and Ukraine. After the initial orbital missions of Japan, China, and India, the intended next steps by these nations have been publicly stated to be landed in situ experiments or sample return. 1 Establishing a precision geodetic coordinate system is essential for the cartographic needs of both exploration and science. With the tremendous amounts of data expected to begin arriving with LRO (over 350 terabytes), setting a uniform standard for lunar data sets is essential and urgent, given the LRO launch date.
Representative terms from entire chapter: