HED Meteorites and Their Relationship to the Geology of Vesta and the Dawn Mission

Howardite-eucrite-diogenite (HED) meteorites, thought to be derived from 4 Vesta, provide the best sampling available for any differentiated asteroid. However, deviations in oxygen isotopic composition from a common mass-fractionation line suggest that a few eucrite-like meteorites are from other bodies, or that Vesta was not completely homogenized during differentiation. The petrology and geochemistry of HEDs provide insights into igneous processes that produced a crust composed of basalts, gabbros, and ultramafic cumulate rocks. Although most HED magmas were fractionated, it is unresolved whether some eucrites may have been primary melts. The geochemistry of HEDs indicates that bulk Vesta is depleted in volatile elements and is relatively reduced, but has chondritic refractory element abundances. The compositions of HEDs may favor a magma ocean model, but inconsistencies remain. Geochronology indicates that Vesta accreted and differentiated within the first several million years of solar system history, that magmatism continued over a span of ??10 Myr, and that its thermal history extended for perhaps 100 Myr. The protracted cooling history is probably responsible for thermal metamorphism of most HEDs. Impact chronology indicates that Vesta experienced many significant collisions, including during the late heavy bombardment. The age of the huge south pole crater is controversial, but it probably ejected Vestoids and many HEDs. Continued impacts produced a regolith composed of eucrite and diogenite fragments containing only minor exotic materials. HED meteorites serve as ground truth for orbital spectroscopic and chemical analyses by the Dawn spacecraft, and their properties are critical for instrument calibration and interpretation of Vesta??s geologic history.     

Advanced materials for next generation NiMH portable, HEV and EVbatteries

While Ovonic NiMH batteries are already in high volume commercial production for portable applications, advances in materials technology have enabled performance improvements in specific energy (100 Wh/kg), specific power (600-1000 W/kg), high temperature operation, charge retention, and voltage stability. Concurrent with technology advances, Ovonic NiMH batteries have established performance and commercial milestones in electric vehicles, hybrid electric vehicles, as well as scooter, motorcycle and bicycle applications. As important as these advances, significant manufacturing cost reductions have also occurred which allow continued growth of NiMH technology. In this paper, advances in performance, applications and cost reduction are discussed with particular emphasis on the improved proprietary metal hydride and nickel hydroxide materials that make such advances possible     

Probing the first stars and black holes in the early Universe with the Dark Ages Radio Explorer (DARE)

A concept for a new space-based cosmology mission called the Dark Ages Radio Explorer (DARE) is presented in this paper. DARE’s science objectives include: (1) When did the first stars form? (2) When did the first accreting black holes form? (3) When did Reionization begin? (4) What surprises does the end of the Dark Ages hold (e.g., Dark Matter decay)? DARE will use the highly-redshifted hyperfine 21-cm transition from neutral hydrogen to track the formation of the first luminous objects by their impact on the intergalactic medium during the end of the Dark Ages and during Cosmic Dawn (redshifts z = 11–35). It will measure the sky-averaged spin temperature of neutral hydrogen at the unexplored epoch 80–420 million years after the Big Bang, providing the first evidence of the earliest stars and galaxies to illuminate the cosmos and testing our models of galaxy formation. DARE’s approach is to measure the expected spectral features in the sky-averaged, redshifted 21-cm signal over a radio bandpass of 40–120 MHz. DARE orbits the Moon for a mission lifetime of 3 years and takes data above the lunar farside, the only location in the inner solar system proven to be free of human-generated radio frequency interference and any significant ionosphere. The science instrument is composed of a low frequency radiometer, including electrically-short, tapered, bi-conical dipole antennas, a receiver, and a digital spectrometer. The smooth frequency response of the antennas and the differential spectral calibration approach using a Markov Chain Monte Carlo technique will be applied to detect the weak cosmic 21-cm signal in the presence of the intense solar system and Galactic foreground emissions.     

Structural health management technologies for inflatable/deployable structures: Integrating sensing and self-healing

Inflatable/deployable structures are under consideration as habitats for future Lunar surface science operations. The use of non-traditional structural materials combined with the need to maintain a safe working environment for extended periods in a harsh environment has led to the consideration of an integrated structural health management system for future habitats, to ensure their integrity. This article describes recent efforts to develop prototype sensing technologies and new self-healing materials that address the unique requirements of habitats comprised mainly of soft goods. A new approach to detecting impact damage is discussed, using addressable flexible capacitive sensing elements and thin film electronics in a matrixed array. Also, the use of passive wireless sensor tags for distributed sensing is discussed, wherein the need for on-board power through batteries or hardwired interconnects is eliminated. Finally, the development of a novel, microencapuslated self-healing elastomer with applications for inflatable/deployable habitats is reviewed.     

Analysis of nonlinear deformation and stability of reinforced elliptic cylindrical shells under bending with internal pressure

A finite element statement of solving problems on stability of reinforced elliptic cylindrical shells taking into account momentness and nonlinearity of their subcritical stress strain state is presented. The explicit expressions for displacements of noncircular cylindrical shell elements as rigid bodies are determined by integrating the equations obtained by equating the components of linear strains to zero. These expressions were used to construct the form functions for an efficient quadrilateral finite element of natural curvature. An efficient numerical algorithm of nonlinear deformation and stability of shells was developed. The stability of reinforced elliptic cylindrical shells under combined loading by bending moment, transverse boundary force and internal pressure is analyzed. We also examine how the critical loads are affected by the strain nonlinearity and ellipticity of shell deformation at the subcritical stage.     

DORIS geodesy: A dynamic determination of geocentre location

Geoscience Australia contributed a multi-satellite, multi-year weekly time series to the International DORIS Service combined submission for the construction of International Terrestrial Reference Frame 2008 (ITRF2008). This contributing solution was extended to a study of the capability of DORIS to dynamically estimate the variation in the geocentre location. Two solutions, comprising different constraint configurations of the tracking network, were undertaken. The respective DORIS satellite orbit solutions (SPOT-2, SPOT-4, SPOT-5 and Envisat) were verified and validated by comparison with those produced at the Goddard Space Flight Center (GSFC), DORIS Analysis Centre, for computational consistency and standards. In addition, in the case of Envisat, the trajectories from the GA determined SLR and DORIS orbits were compared. The results for weekly dynamic geocentre estimates from the two constraint configurations were benchmarked against the geometric geocentre estimates from the IDS-2 combined solution. This established that DORIS is capable of determining the dynamic geocentre variation by estimating the degree one spherical harmonic coefficients of the Earth’s gravity potential. It was established that constrained configurations produced similar results for the geocentre location and consequently similar annual amplitudes. For the minimally constrained configuration Greenbelt–Kitab, the mean of the uncertainties of the geocentre location were 2.3, 2.3 and 7.6 mm and RMS of the mean uncertainties were 1.9, 1.2 and 3.5 mm for the X, Y and Z components, respectively. For GA_IDS-2_Datum constrained configuration, the mean of the uncertainties of the geocentre location were 1.7, 1.7 and 6.2 mm and RMS of the mean uncertainties were 0.9, 0.7 and 2.9 mm for the X, Y and Z components, respectively. The mean of the differences of the two DORIS dynamic geocentre solutions with respect to the IDS-2 combination were 1.6, 4.0 and 5.1 mm with an RMS of the mean 21.2, 14.0 and 31.5 mm for the Greenbelt–Kitab configuration and 4.1, 3.9 and 4.3 mm with an RMS 8.1, 9.0 and 28.6 mm for the GA_IDS-2_Datum constraint configuration. The annual amplitudes for each component were estimated to be 5.3, 10.8 and 11.0 mm for the Greenbelt–Kitab configuration and 5.3, 9.3 and 9.4 mm for the GA_IDS-2_Datum constraint configuration. The two DORIS determined dynamic geocentre solutions were compared to the SLR determined dynamic solution (which was determined from the same process of the GA contribution to the ITRF2008 ILRS combination) gave mean differences of 3.3, −4.7 and 2.5 mm with an RMS of 20.7, 17.5 and 28.0 mm for the X, Y and Z components, respectively for the Greenbelt–Kitab configuration and 1.1, −5.4 and 4.4 mm with an RMS of 9.7, 13.3 and 24.9 mm for the GA_IDS-2_Datum configuration. The larger variability is reflected in the respective amplitudes. As a comparison, the annual amplitudes of the SLR determined dynamic geocentre are 0.9, 1.0 and 6.8 mm in the X, Y and Z components. The results from this study indicate that there is potential to achieve precise dynamically determined geocentre from DORIS.     

Testing for Year 2000 readiness: technical and management issues

The approach of the Year 2000 (Y2K) has called into question the condition of readiness of computer systems upon which organizations depend. Will these systems operate reliably after midnight, January 1, 2000, or will problems associated with date calculations cause failures that adversely affect users? This question has caused organizations to identify their critical systems, test these systems for Y2K problems, and take corrective action where necessary to ensure Y2K readiness. This paper examines various technical and management issues that Southwest Research Institute has dealt with in solving these problems