Paul A. Abell

Near-Infrared Spectral Results of Asteroid Itokawa from the Hayabusa Spacecraft

The near-infrared spectrometer on board the Japanese Hayabusa spacecraft found a variation of more than 10% in albedo and absorption band depth in the surface reflectance of asteroid 25143 Itokawa. Spectral shape over the 1-micrometer absorption band indicates that the surface of this body has an olivine-rich mineral assemblage potentially similar to that of LL5 or LL6 chondrites. Diversity in the physical condition of Itokawas surface appears to be larger than for other S-type asteroids previously explored by spacecraft, such as 433 Eros.

Scientific exploration of near-Earth objects via the Orion Crew Exploration Vehicle

A study in late 2006 was sponsored by the Advanced Projects Office within NASAs Constellation Program to examine the feasibility of sending the Orion Crew Exploration Vehicle (CEV) to a near-Earth object (NEO). The ideal mission profile would involve two or three astronauts on a 90 to 180 day flight, which would include a 7 to 14 day stay for proximity operations at the target NEO. This mission would be the first human expedition to an interplanetary body beyond the Earth-Moon system and would prove useful for testing technologies required for human missions to Mars and other solar system destinations. Piloted missions to NEOs using the CEV would undoubtedly provide a great deal of technical and engineering data on spacecraft operations for future human space exploration while conducting in-depth scientific investigations of these primitive objects. The main scientific advantage of sending piloted missions to NEOs would be the flexibility of the crew to perform tasks and to adapt to situations in real time. A crewed vehicle would be able to test several different sample collection techniques and target specific areas of interest via extra-vehicular activities (EVAs) more efficiently than robotic spacecraft. Such capabilities greatly enhance the scientific return from these missions to NEOs, destinations vital to understanding the evolution and thermal histories of primitive bodies during the formation of the early solar system. Data collected from these missions would help constrain the suite of materials possibly delivered to the early Earth, and would identify potential source regions from which NEOs originate. In addition, the resulting scientific investigations would refine designs for future extraterrestrial resource extraction and utilization, and assist in the development of hazard mitigation techniques for planetary defense.

Rotational characterization of Hayabusa II target Asteroid (162173) 1999 JU3

Abstract The Japanese Space Agency’s Hayabusa II mission is scheduled to rendezvous with and return a sample from the near-Earth Asteroid (162173) 1999 JU3. Previous visible-wavelength spectra of this object show significant variability across multiple epochs which has been attributed to a compositionally heterogeneous surface. We present new visible and near-infrared spectra to demonstrate that thermally altered carbonaceous chondrites are plausible compositional analogs, however this is a tentative association due to a lack of prominent absorption features in our data. We have also conducted a series of high signal-to-noise visible-wavelength observations to investigate the reported surface heterogeneity. Our time series of visible spectra do not show variability at a precision level of a few percent. This result suggests two most likely possibilities. One, that the surface of 1999 JU3 is homogenous and that unaccounted for systematic effects are causing spectral variation across epochs. Or two, that the surface of 1999 JU3 is regionally heterogenous, in which case existing shape models suggest that any heterogeneity must be limited to terrains smaller than approximately 5% of the total surface area. These new observations represent the last opportunity before both the launch and return of the Hayabusa II spacecraft to perform ground-based characterization of this asteroid. Ultimately, these predictions for composition and surface properties will be tested upon completion of the mission.

Composition of near-Earth Asteroid (4179) Toutatis

Abstract Surface composition of near-Earth Asteroid (4179) Toutatis is consistent with an undifferentiated L-chondrite composition. This is inconsistent with early observations that suggested high pyroxene iron content and a differentiated body.

Asteroid Destinations Accessible for Human Exploration: A Preliminary Survey in Mid-2009

Theflexible path is one of several space exploration strategy options developed by theReview ofU.S.HumanSpace Flight Plans Committee in 2009. Among proposed flexible path destinations are near-Earth objects, those asteroids and comets having perihelions of less than 1.3 astronomical units and periods of less than 200 years. Heliocentricorbit element criteria have been developed with the objective of rapidly identifying the near-Earth object subset potentially accessible for human exploration capabilities. When these criteria were applied to the Jet Propulsion Laboratory’s small-body database in June 2009, the accessible subset was found to contain 36 near-Earth objects. Opportunities to visit these destinations have been obtained and assessed over the interval from 2020 through 2050. With the number of cataloged near-Earth objects expected to grow by more than an order of magnitude in the next 20 years, the number and frequency of human near-Earth object exploration opportunities will likewise increase.

A Piloted Orion Flight to a Near-Earth Object: A Feasibility Study

This viewgraph presentation examines flight hardware elements of the Constellation Program (CxP) and the utilization of the Crew Exploration Vehicle (CEV), Evolvable Expendable Launch Vehicles (EELVs) and Ares launch vehicles for NEO missions.

Observing Near-Earth Objects with the James Webb Space Telescope

The James Webb Space Telescope (JWST) has the potential to enhance our understanding of near-Earth objects (NEOs). We present results of investigations into the observability of NEOs given the nominal observing requirements of JWST on elongation (85°–135°) and non-sidereal rates (<30 mas s−1). We find that approximately 75% of NEOs can be observed in a given year. However, observers will need to wait for appropriate observing windows. We find that JWST can easily execute photometric observations of meter-sized NEOs that will enhance our understanding of the small NEO population.

Between the Moon and Mars: Piloted and surface operations at a NEO

In late 2006, NASAs Constellation Program (CxP) sponsored a study to examine the feasibility of sending a piloted Orion spacecraft to a near-Earth object (NEO — in the broadest definition these are small, primitive bodies that cross Earths orbit; the most likely and suitable targets for the Orion are those NEOs in heliocentric orbits similar to Earths). One of the significant advantages of this type of mission is that it strengthens and validates the foundational infrastructure of the United States Space Exploration Policy and is highly complementary to the already-planned lunar sorties and outpost build-up circa 2020. Sending a human expedition to a NEO not only underlines the broad utility of the CxPs Orion vehicle and Ares launch systems. Such a mission would also be the first human expedition to an interplanetary body beyond the Earth-Moon system. For the onboard crew and systems, as well as the mission control team, these deep space operations will present unique challenges not present in lunar missions. While our Phase 1 study focused solely on the practicality of using the lunar architecture and systems to mount NEO missions, it did not delve into potential radiation issues (and effective mitigation strategies) nor did it explore human operations in proximity to and on the surface of NEOs. Executing several such piloted NEO missions will enable NASA to gain crucial long-duration, deep space operational experience, a necessary prerequisite for future human missions to Mars, its moons, Phobos and Deimos, or even the Main Belt or Trojan asteroids.