JPL CalTech

Pasadena, CA, United States

JPL CalTech

Pasadena, CA, United States
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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) | Year: 2012

(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.

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 | Year: 2012

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.

Kaiser A.,Institute of Geological & Nuclear Sciences | Holden C.,Institute of Geological & Nuclear Sciences | Beavan J.,Institute of Geological & Nuclear Sciences | Beetham D.,Institute of Geological & Nuclear Sciences | And 20 more authors.
New Zealand Journal of Geology and Geophysics | Year: 2012

A moment magnitude (Mw) 6.2 earthquake struck beneath the outer suburbs of Christchurch, New Zealand's second largest city, on 22 February 2011 local time. The Christchurch earthquake was the deadliest in New Zealand since the 1931 Mw 7.8 Hawkes Bay earthquake and the most expensive in New Zealand's recorded history. The effects of the earthquake on the region's population and infrastructure were severe including 181 fatalities, widespread building damage, liquefaction and landslides. The Christchurch earthquake was an aftershock of the Mw 7.1 Darfield Earthquake of September 2010, occurring towards the eastern edge of the aftershock zone. This was a low recurrence earthquake for New Zealand and occurred on a fault unrecognised prior to the Darfield event. Geodetic and seismological source models show that oblique-reverse slip occurred along a northeast-southwest-striking fault dipping southeast at c. 69°, with maximum slip at 3-4 km depth. Ground motions during the earthquake were unusually large at near-source distances for an earthquake of its size, registering up to 2.2 g (vertical) and 1.7 g (horizontal) near the epicentre and up to 0.8 g (vertical) and 0.7 g (horizontal) in the city centre. Acceleration response spectra exceeded 2500 yr building design codes and estimates based on standard New Zealand models. The earthquake was associated with high apparent stress indicative of a strong fault. Furthermore, rupture in an updip direction towards Christchurch likely led to strong directivity effects in the city. Site effects including long period amplification and near-surface effects also contributed to the severity of ground motions. © 2012 The Royal Society of New Zealand.

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 | Year: 2010

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).

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 | Year: 2013

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.

Dash P.,National Oceanic and Atmospheric Administration | Dash P.,Colorado State University | Ignatov A.,National Oceanic and Atmospheric Administration | Martin M.,UK Met Office | And 25 more authors.
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2012

There are a growing number of level 4 (L4; gap-free gridded) sea surface temperature (SST) products generated by blending SST data from various sources which are available for use in a wide variety of operational and scientific applications. In most cases, each product has been developed for a specific user community with specific requirements guiding the design of the product. Consequently differences between products are implicit. In addition, anomalous atmospheric conditions, satellite operations and production anomalies may occur which can introduce additional differences. This paper describes a new web-based system called the L4 SST Quality Monitor (L4-SQUAM) developed to monitor the quality of L4 SST products.L4-SQUAM intercompares thirteen L4 products with 1-day latency in an operational environment serving the needs of both L4 SST product users and producers. Relative differences between products are computed and visualized using maps, histograms, time series plots and Hovmöller diagrams, for all combinations of products. In addition, products are compared to quality controlled in situ SST data (available from the in situ SST Quality Monitor, iQUAM, companion system) in a consistent manner. A full history of products statistics is retained in L4-SQUAM for time series analysis. L4-SQUAM complements the two other Group for High Resolution SST (GHRSST) tools, the GHRSST Multi Product Ensemble (GMPE) and the High Resolution Diagnostic Data Set (HRDDS) systems, documented in part 1 of this paper and elsewhere, respectively.Our results reveal significant differences between SST products in coastal and open ocean areas. Differences of >2. °C are often observed at high latitudes partly due to different treatment of the sea-ice transition zone. Thus when an ice flag is available, the intercomparisons are performed in two ways: including and excluding ice-flagged grid points. Such differences are significant and call for a community effort to understand their root cause and ensure consistency between SST products. Future work focuses on including the remaining daily L4 SST products, accommodating for newer L4 SSTs which resolve the diurnal variability and evaluating retrospectively regenerated L4 SSTs to support satellite data reprocessing efforts aimed at generating improved SST Climate Data Records. © 2012 Elsevier Ltd.

Freeman A.,Jet Propulsion Laboratory | Zlotnicki V.,JPL CalTech | Liu T.,JPL CalTech | Holt B.,JPL CalTech | And 5 more authors.
Oceanography | Year: 2010

Seasat, launched by the US National Aeronautics and Space Administration (NASA) in 1977, was the first dedicated ocean-viewing satellite. Since then, in addition to NASA, the space agencies of Europe, France, Canada, Germany, India, Japan, and China have all launched ocean-viewing sensors or dedicated ocean-viewing satellites. Properties currently measured from space are sea surface temperature; topography (height); salinity; significant wave height and wave spectra; surface wind speed and vectors; ocean color; continental and sea ice extent, flow, deformation, thickness; ocean mass; and to a lesser extent, surface currents. By 2025, one additional measurement may become available-total surface currents-but the largest foreseen improvements are increased spatial and temporal resolution and increased accuracy for all the currently measured properties.

Spry J.,JPL Caltech | Conley C.A.,NASA
43rd International Conference on Environmental Systems | Year: 2013

Planetary protection is the discipline of protecting solar system objects from harmful contamination resulting from the activities of interplanetary spacecraft, and of similarly protecting the Earth from uncontrolled release of a putative extra-terrestrial organism from returned extra-terrestrial samples. Planetary protection requirements for Mars are becoming further refined as more is understood about the nature of the Martian environment as a potential habitat. Likewise, increased understanding of the limits of life on Earth is informing planetary protection policy. This presentation will discuss recent technology developments, ongoing work and future challenges of implementing planetary protection for the proposed future mission set.

Parness A.,JPL Caltech
Proceedings of the International Astronautical Congress, IAC | Year: 2015

It is well established that space debris poses a significant threat to operational assets, exemplified by the catastrophic satellite collision in 2009 and the several-Times per year events when the International Space Station must alter its orbit to ensure the safety of the crew. Large pieces of debris, like dead satellites and rocket bodies, pose a unique threat in their ability to obliterate any active system in the event of a collision and also in the challenges they present for grappling and control. The most dangerous of these large pieces of debris are often tumbling and have limited hard points for grappling, exceeding the proven capabilities of rendezvous and docking technologies or cooperative grappling systems being developed for satellite servicing. This paper presents a grappling technology and a mission concept for mitigating the threat of the largest of these debris objects. The grappling tool relies on synthetic gecko-Adhesives, which use microscopic angled hairs to selectively stick to a wide range of surfaces. The adhesion can be turned ON and OFF by reversing the load direction tangential to the surface. Prior work demonstrated over 30,000 adhesion cycles, more than a 1-year lifetime, adhesion in vacuum and at cold temperatures, and function on over 30 common spacecraft surfaces. This paper will present the maturation of the gripper mechanism technology to include both flat and curved surfaces as well as an increase in adhesive capability of over 4-fold. Results from a zero-gravity experiment, the integration onto a robotic arm, and gripper/arm system test results from the flat floor facility at JPL will be presented. Using adhesive grappling significantly reduces the requirements that arc levied on other subsystems like perception and spacecraft control (as well as the robotic arm) because large areas on the debris can be targeted, like solar panels and fuel tanks. Current grappling systems and rendezvous and docking technologies require extremely precise motions to grapple the Marman ring or other hard points on a target, driving the overall cost and complexity of the mission. Copyright © (2015) by International Astronautical Federation All rights reserved.

Garcia-Llama E.,NASA | Ivanov M.C.,JPL Caltech. | Winski R.G.,NASA | Grover M.R.,JPL Caltech. | And 2 more authors.
IEEE Aerospace Conference Proceedings | Year: 2012

In 2011, the Mars Science Laboratory (MSL) was launched in a mission to deliver the largest and most capable rover to date to the surface of Mars. A follow on MSL-derived mission, referred to as Mars 2018, is being proposed to launch in 2018. Mars 2018 is investigating performance enhancements of the Entry, Descent and Landing (EDL) system over that of its predecessor MSL mission of 2011. This paper will discuss the main elements of the proposed Mars 2018 EDL preliminary design that are being considered to increase performance on the entry phase of the mission. In particular, these elements are discussed with the goals of increasing the parachute deploy altitude to allow for more time margin during the subsequent descent and landing phases, increasing the entry mass, and reducing the delivery ellipse size at parachute deploy, through modifications in the entry reference trajectory design, vehicle's lift to drag ratio, parachute deploy trigger logic design, and the effect of additional navigation hardware. © 2012 IEEE.

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