Lunar and Planetary Science XXXVIII (2007) 2292.pdf

SCIENTIFIC EXPLORATION OF NEAR-EARTH OBJECTS VIA THE CREW EXPLORATION 1,* 2 3 4 5 6 7 VEHICLE. P. A. Abell , D. J. Korsmeyer , R. R. Landis , E. Lu , D. Adamo , T. Jones , L. Lemke , A. Gonza- les7, B. Gershman8, D. Morrison7, T. Sweetser8 and L. Johnson9, 1Planetary Astronomy Group, Astromaterials Re- search and Exploration Science, NASA Johnson Space Center, Houston, TX 77058, paul.a.abell1@jsc.nasa.gov. 2Intelligent Systems Division, NASA Ames Research Center, Moffett Field, CA 94035. 3Mission Operations, NASA Johnson Space Center, Houston, TX 77058. 4Astronaut Office, NASA Johnson Space Center, Houston, TX 77058. 5Houston, TX 77058. 6Oakton, VA 20153. 7NASA Ames Research Center, Moffett Field, CA 94035. 8Jet Propulsion Laboratory, Pasadena, CA 91109. 9NASA Headquarters, Washington, DC 20546.*NASA Postdoctoral Fellow.

Introduction: The concept of a crewed mission to etc. Such missions to NEOs are vital from a scientific a Near-Earth Object (NEO) has been analyzed in depth perspective for understanding the evolution and ther- in 1989 as part of the Space Exploration Initiative [1]. mal histories of these bodies during the formation of Since that time two other studies have investigated the the early solar system, and to identify potential source possibility of sending similar missions to NEOs [2,3]. regions from which these NEOs originated. A more recent study has been sponsored by the Ad- NEO exploration missions will also have practical vanced Programs Office within NASA’s Constellation applications such as resource utilization and planetary Program. This study team has representatives from defense; two issues that will be relevant in the not-too- across NASA and is currently examining the feasibility distant future as humanity begins to explore, under- of sending a Crew Exploration Vehicle (CEV) to a stand, and utilize the solar system. A significant por- near-Earth object (NEO). The ideal mission profile tion of the NEO population may contain water, an at- would involve a crew of 2 or 3 astronauts on a 90 to tractive source of life support and fuel for future deep 120 day flight, which would include a 7 to 14 day stay space missions. The subject of planetary defense from for proximity operations at the target NEO. impacting asteroids has garnered much public and One of the significant advantages of this type of Congressional interest recently because of the increas- mission is that it strengthens and validates the founda- ing discovery rate of asteroids with a small, but non- tional infrastructure for the Vision for Space Explora- zero probability of striking Earth. NASA has already tion (VSE) and Exploration Systems Architecture been directed by Congress in the 2005 Authorization Study (ESAS) in the run up to the lunar sorties at the Bill to report on options for deflecting a threatening end of the next decade (~2020). Sending a human ex- asteroid should one be found. Many proposed deflec- pedition to a NEO, within the context of the VSE and tion schemes depend critically on asteroid characteris- ESAS, demonstrates the broad utility of the Constella- tics such as density, internal structure, and material tion Program’s Orion (CEV) crew capsule and Ares (CLV) launch systems. This mission would be the first properties – precisely the parameters that a crewed human expedition to an interplanetary body outside of mission to a NEO could measure. the cislunar system. Also, it will help NASA regain Precursor Missions: A robotic mission would be crucial operational experience conducting human ex- required in order to maximize crew safety and effi- ploration missions outside of low Earth orbit – which ciency of mission operations at any candidate NEO. humanity has not attempted in nearly 40 years. Such an in depth reconnaissance by small robotic Scientific and Practical Rationale: Piloted mis- spacecraft would help to identify the general character- sions using the CEV to NEOs will not only provide a istics of potential NEOs selected for study, and pro- great deal of technical and engineering data on space- vide an important synergy between the robotic scien- craft operations for future human space exploration, tific programs of the Science Mission Directorate but have the capability to conduct an in-depth scien- (SMD) and the human exploration program of the Ex- tific investigation of these objects. Essential physical ploration Systems Mission Directorate (ESMD). and geochemical properties of NEOs can best be de- Knowledge of such things as the gravitational field, termined from dedicated spacecraft missions. Al- shape, surface topography, and general composition though ground-based observations can provide general would aid in planning for later CEV proximity opera- information about the physical properties (rotation tions. Precursor missions would also be useful to iden- rates, taxonomic class, size estimates, general compo- tify potential hazards to the CEV (and any of its de- sition, etc.) of NEOs, spacecraft missions to NEOs are ployable assets) such as the presence of satellites, or needed to obtain detailed characterizations of surface non-benign surface morphologies, which may not be morphology, internal structure, mineral composition, detectable from ground-based observations. The pre- topography, collisional history, density, particle size, cursor spacecraft should ideally have a visible camera for surface feature characterization, and a spectrometer Lunar and Planetary Science XXXVIII (2007) 2292.pdf

capable of obtaining surface spectra in both visible and packages that may be deployed could be in-situ ex- infrared wavelengths for compositional investigation. periments designed to test such technologies as surface Other instruments such as a laser altimeter for surface anchors/tethers, drills/excavation equipment, or mate- topography may also be useful for constraining addi- rial extraction equipment. The CEV could also deploy tional characteristics of the NEO. It should be noted a transponder to the surface of the object for a long- that the data from all of the instruments on the precur- term study of the NEO’s orbital motion. This could be sor spacecraft would add to the current body of knowl- particularly useful for monitoring such objects that edge of NEOs in addition to characterizing potential have the potential for a possible future Earth impact. mission targets for the CEV. The crew has the added advantage of EVA for sam- CEV Science Capabilities: A CEV-type mission ple collection during close proximity operations. The will have a much greater capability for science and ability for the crew to traverse and collect one or more exploration of NEOs than robotic spacecraft. The main macroscopic samples from specific terrains on the sur- advantage of having piloted missions to a NEO is the face of an NEO is the most important scientific aspect flexibility of the crew to perform tasks and to adapt to of this type of mission. Having a human being interact- situations in real time. Robotic spacecraft have only ing in real-time with the NEO surface material and limited capability for scientific exploration, and may sampling various locales in context would bring a wealth of scientific information on such things as par- not be able to adapt as readily to certain conditions ticle size, potential space weathering effects, impact encountered at a particular NEO. The Hayabusa history, material properties, and near-surface densities spacecraft encountered certain situations that were a of the NEO. challenge for both it and its ground controllers during Conclusions: To date, the planetary science com- close proximity operations at Itokawa. A human crew munity has based much of its interpretation of the for- is able to perform tasks and react quickly in a micro- mation of asteroids and comets (i.e., parent bodies of gravity environment, faster than any robotic spacecraft the NEO population) on data from meteorite and inter- could (rapid yet delicate maneuvering has been a hall- planetary dust particles recovered on Earth. These ma- mark of Apollo, Skylab, and shuttle operations). In terials are known to come from such objects, but the addition, a crewed vehicle is able to test several differ- exact location of the specific parent bodies within the ent sample collection techniques, and to target specific solar system is not generally known. Unfortunately areas of interest via extra-vehicular activities (EVAs) direct connections of these samples to specific objects much more capably than a robotic spacecraft. Such cannot be made with any degree of certainty, which capabilities greatly enhance any scientific return from limits the ability of scientists to put their findings in a these types of missions to NEOs. larger context. However, with pristine samples from In terms of remote sensing capability, the CEV known locations within the solar system, scientists can should have a high-resolution camera for detailed sur- start to “map outcrops” and glean new insights into the face characterization and optical navigation. A light compositions and formation history of these NEOs. detection and ranging (LIDAR) system would be es- While such knowledge will aid in a better understand- sential for hazard avoidance (during close proximity ing of our solar system, it also has the potential for operations) and detailed topography measurements. In more practical applications such as resource utilization addition, the CEV should be outfitted with a radar (water, precious metals, oxygen, etc.) and NEO hazard transmitter to perform tomography, enabling a detailed mitigation (material properties, internal structures, look at the interior structure of the NEO. Given that macro-porosities, etc.). These scientific, commercial, several NEOs appear to have a high degree of porosity and hazard mitigation benefits, along with the pro- (e.g., Itokawa is estimated to be 40% void space by grammatic and operational benefits of a human venture volume), it is important to measure this characteristic into deep space, make a mission to a NEO using Con- of the target NEO. Such information on its internal stellation systems a compelling prospect. structure not only has implications for the formation References: [1]Davis, D. R. et al. (1990) The Role and impact history of the NEO, but also may have im- of Near-Earth Asteroids in the Space Exploration Ini- plications for future hazard mitigation techniques. tiative. SAIC-90/1464, Study No. 1-120-232-S28. Another advantage of the CEV is the capability to [2]Jones, T. D. et al. (1994) Human Exploration of place precisely and re-deploy relatively small scientific Near-Earth Asteroids. In Hazards Due to Comets and packages on the surface of the NEO. Such packages as Asteroids, 683-708, Univ. of Arizona Press, Tucson, remotely operated (or autonomous) rovers with one or AZ. [3]Jones, T. D. et al. (2002) The Next Giant Leap: two instruments could greatly enhance the amount of Human Exploration and Utilization of Near-Earth Ob- data obtained from the surface, and fine-tune the site jects. In The Future of Solar System Exploration, selection for subsequent sample collection. Other 2003-2013 ASP Conference Series, 272,141-154.