Time filter

Source Type

Pasadena, CA, United States

Cianciolo A.D.,NASA | Cantor B.,Malin Space Science Systems | Barnes J.,Oregon State University | Tyler Jr. D.,Oregon State University | And 5 more authors.
Advances in the Astronautical Sciences

On August 6, 2012, the Mars Science Laboratory rover, Curiosity, successfully landed on the surface of Mars. The Entry, Descent and Landing (EDL) sequence was designed using atmospheric conditions estimated from mesoscale numerical models. The models, developed by two independent organizations (Oregon State University and the Southwest Research Institute), were validated against observations at Mars from three prior years. In the weeks and days before entry, the MSL "Council of Atmospheres" (CoA), a group of atmospheric scientists and modelers, instrument experts and EDL simulation engineers, evaluated the latest Mars data from orbiting assets including the Mars Reconnaissance Orbiter's Mars Color Imager (MARCI) and Mars Climate Sounder (MCS), as well as Mars Odyssey's Thermal Emission Imaging System (THEMIS). The observations were compared to the mesoscale models developed for EDL performance simulation to determine if a spacecraft parameter update was necessary prior to entry. This paper summarizes the daily atmosphere observations and comparison to the performance simulation atmosphere models. Options to modify the atmosphere model in the simulation to compensate for atmosphere effects are also presented. Finally, a summary of the CoA decisions and recommendations to the MSL project in the days leading up to EDL is provided. Source

Rott H.,University of Innsbruck | Cline D.W.,National Oceanic and Atmospheric Administration | Duguay C.,University of Waterloo | Essery R.,University of Edinburgh | And 7 more authors.
International Geoscience and Remote Sensing Symposium (IGARSS)

(CoReH2O) satellite mission was selected for detailed scientific and technical studies within the Earth Explorer Programme of ESA. The sensor is a dual frequency SAR, operating at 17.2 GHz and 9.6 GHz, VV and VH polarizations The mission will deliver spatially distributed snow and ice observations to improve the representation of the croysphere in hydrological and climate models. Primary parameters are the extent and water equivalent (SWE) of the snow pack and snow accumulation on glaciers. Scientific preparations of the mission include the development and testing of algorithms for retrieval of snow parameters, studies on synergy of CoReH2O-type snow products with passive microwave measurements, the assimilation of satellite snow data in process models, and field experiments. Performance of retrievals for snow extent and SWE was tested with simulated and experimental data, including Ku- and X-band SAR images of the airborne SnowSAR system. © 2012 IEEE. Source

Su K.Y.L.,University of Arizona | Rieke G.H.,University of Arizona | Malhotra R.,University of Arizona | Stapelfeldt K.R.,NASA | And 7 more authors.
Astrophysical Journal

Vega and Fomalhaut are similar in terms of mass, ages, and global debris disk properties; therefore, they are often referred to as "debris disk twins." We present Spitzer 10-35 μm spectroscopic data centered at both stars and identify warm, unresolved excess emission in the close vicinity of Vega for the first time. The properties of the warm excess in Vega are further characterized with ancillary photometry in the mid-infrared and resolved images in the far-infrared and submillimeter wavelengths. The Vega warm excess shares many similar properties with the one found around Fomalhaut. The emission shortward of 30 μm from both warm components is well described as a blackbody emission of 170 K. Interestingly, two other systems, ε Eri and HR 8799, also show such an unresolved warm dust using the same approach. These warm components may be analogous to the solar system's zodiacal dust cloud, but of far greater mass (fractional luminosity of 10-5 to 10-6 compared to 10-8 to 10-7). The dust temperature and tentative detections in the submillimeter suggest that the warm excess arises from dust associated with a planetesimal ring located near the water-frost line and presumably created by processes occurring at similar locations in other debris systems as well. We also review the properties of the 2 μm hot excess around Vega and Fomalhaut, showing that the dust responsible for the hot excess is not spatially associated with the dust we detected in the warm belt. We suggest it may arise from hot nano grains trapped in the magnetic field of the star. Finally, the separation between the warm and cold belt is rather large with an orbital ratio ≳10 in all four systems. In light of the current upper limits on the masses of planetary objects and the large gap, we discuss the possible implications for their underlying planetary architecture and suggest that multiple, low-mass planets likely reside between the two belts in Vega and Fomalhaut. © 2013. The American Astronomical Society. All rights reserved. Source

Beavan J.,Institute of Geological & Nuclear Sciences | Motagh M.,German Research Center for Geosciences | Fielding E.J.,JPL CalTech | Donnelly N.,Land Information New Zealand | Collett D.,Land Information New Zealand
New Zealand Journal of Geology and Geophysics

We present source models derived from geodetic data for the four major Canterbury earthquakes of 2010-2011. The September 2010 Darfield earthquake was largely right-lateral, but with several other fault segments active. The February 2011 Christchurch earthquake was mixed right-lateral and reverse with a left-stepping offset interrupting an ENE-striking rupture. The June 2011 earthquake included left-lateral slip on a NNW-striking fault. The December 2011 earthquakes were characterised by offshore reverse slip on an ENE-striking plane. Displacements of GPS sites define small but clearly detectable postseismic deformation east of the September 2010 earthquake, near the February 2011 earthquake and following the June 2011 earthquake. There has been no major moment release in a 15-km-long region between the eastern end of the September 2010 faulting and the western end of the February 2011 faulting. We recommend careful monitoring of this region for the next several years. © 2012 The Royal Society of New Zealand. Source

Hussmann H.,German Aerospace Center | Lainey V.,French National Center for Scientific Research | Matson D.L.,JPL 183 335 | McKinnon W.B.,Washington University in St. Louis | And 5 more authors.
Space Science Reviews

Evolutionary scenarios for the major satellites of Jupiter, Saturn, Neptune, and Pluto-Charon are discussed. In the Jovian system the challenge is to understand how the present Laplace resonance of Io, Europa, and Ganymede was established and to determine whether the heat being radiated by Io is in balance with the present tidal dissipation in the moon. In the Saturnian system, Enceladus and Titan are the centers of attention. Tidal heating is the likely source of activity at the south pole of Enceladus, although the details of how the heating occurs are not understood. An evolutionary scenario based on accretion and internal differentiation is presented for Titan, whose present substantial orbital eccentricity is not associated with any dynamical resonance. The source and maintenance of methane in Titan's present atmosphere remain uncertain. Though most attention on the Saturnian moons focuses on Titan and Enceladus, the mid-size satellites Iapetus, Rhea, Tethys, and the irregular satellite Phoebe also draw our interest. An evolutionary scenario for Iapetus is presented in which spin down from an early rapidly rotating state is called upon to explain the satellite's present oblate shape. The prominent equatorial ridge on Iapetus is unexplained by the spin down scenario. A buckling instability provides another possible explanation for the oblateness and equatorial ridge of Iapetus. Rhea is the only medium-size Saturnian satellite for which there are gravity data at present. The interpretation of these data are uncertain, however, since it is not known if Rhea is in hydrostatic equilibrium. Pluto and Charon are representative of the icy dwarf planets of the Kuiper belt. Did they differentiate as they evolved, and do either of them have a subsurface liquid water ocean? New Horizons might provide some answers when it arrives at these bodies. © 2010 The Author(s). Source

Discover hidden collaborations