Jet Propulsion Laboratory

About: Jet Propulsion Laboratory is a facility organization based out in La Cañada Flintridge, California, United States. It is known for research contribution in the topics: Mars Exploration Program & Telescope. The organization has 8801 authors who have published 14333 publications receiving 548163 citations. The organization is also known as: JPL & NASA JPL.

Ultraclean two-stage aerosol reactor for production of oxide-passivated silicon nanoparticles for novel memory devices

Abstract: Silicon nanoparticle-based floating gate metal oxide semiconductor field effect devices are attractive candidates for terabit cm^–2 density nonvolatile memory applications. We have designed an ultraclean two-stage aerosol process reactor and 200 mm wafer deposition chamber in order to integrate Si/SiO2 nanoparticles into memory devices. In the first stage, silicon nanoparticles are synthesized by thermal decomposition of silane gas in a reactor that has been optimized to produce nonagglomerated nanoparticles at rates sufficient for layer deposition. In the second stage, the silicon particles are passivated with thermal oxide that partly consumes the particle. This two-stage aerosol reactor has been integrated to a 200 mm silicon wafer deposition chamber that is contained within a class 100 cleanroom environment. This entire reactor system conforms to rigorous cleanliness specifications such that we can control transition metal contamination to as good as 10^10 atoms cm^–2. The deposition chamber has been designed to produce a controllable particle density profile along a 200 mm wafer where particles are thermophoretically deposited uniformly over three-quarters of the wafer. Thus, we now have the capability to deposit controlled densities of oxide-passivated silicon nanoparticles onto 200 mm silicon wafers for production of silicon nanoparticle memory devices.

Near-Infrared Mapping and Physical Properties of the Dwarf-Planet Ceres

Abstract: Aims. We study the physical characteristics (shape, dimensions, spin axis direction, albedo maps, mineralogy) of the dwarf-planet Ceres based on high-angular resolution near-infrared observations. Methods. We analyze adaptive optics J/H/K imaging observations of Ceres performed at Keck II Observatory in September 2002 with an equivalent spatial resolution of∼50 km. The spectral behavior of the main geological features present on Ceres is compared with laboratory samples. Results. Ceres’ shape can be described by an oblate spheroid ( a = b = 479.7± 2.3 km, c = 444.4± 2.1 km) with EQJ2000.0 spin vector coordinatesα0 = 288 ◦ ± 5 ◦ andδ0 = +66 ◦ ± 5 ◦ . Ceres sidereal period is measured to be 9.074 10 +0.000 10 −0.000 14 h. We image surface features with diameters in the 50-180 km range and an albedo contrast of∼6% with respect to the average Ceres albedo. The spectral behavior of the brightest regions on Ceres is consistent wit h phyllosilicates and carbonate compounds. Darker isolated regions could be related to the presence of frost.

Thermal Stability of Volatiles in the North Polar Region of Mercury

Abstract: Thermal models for the north polar region of Mercury, calculated from topographic measurements made by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, show that the spatial distribution of regions of high radar backscatter is well matched by the predicted distribution of thermally stable water ice. MESSENGER measurements of near-infrared surface reflectance indicate bright surfaces in the coldest areas where water ice is predicted to be stable at the surface, and dark surfaces within and surrounding warmer areas where water ice is predicted to be stable only in the near subsurface. We propose that the dark surface layer is a sublimation lag deposit that may be rich in impact-derived organic material.

Lithium Plating Behavior in Lithium-Ion Cells

Abstract: A Li-ion cell does not contain metallic lithium under normal conditions of operation. Under strenuous charge conditions, however, metallic lithium may deposit on the carbon anode in preference to lithium intercalation and may cause problems in terms of performance, reliability and safety of the cell. Factors that affect the anode polarization and also Li intercalation kinetics play a crucial role in determining the propensity for such lithium deposition. Such factors include the nature of electrolyte, anode/cathode capacity ration, which have been studied with specific examples here. Further, various prototype cells from different manufacturers have been examined for their susceptibility towards lithium plating from a set of systematic charge/discharge tests at different charge rates and temperatures.

MISR stereoscopic image matchers: techniques and results

Abstract: The Multi-angle Imaging SpectroRadiometer (MISR) instrument, launched in December 1999 on the NASA EOS Terra satellite, produces images in the red band at 275-m resolution, over a swath width of 360 km, for the nine camera angles 70.5/spl deg/, 60/spl deg/, 45.6/spl deg/, and 26.1/spl deg/ forward, nadir, and 26.1/spl deg/, 45.6/spl deg/, 60/spl deg/, and 70.5/spl deg/ aft. A set of accurate and fast algorithms was developed for automated stereo matching of cloud features to obtain cloud-top height and motion over the nominal six-year lifetime of the mission. Accuracy and speed requirements necessitated the use of a combination of area-based and feature-based stereo-matchers with only pixel-level acuity. Feature-based techniques are used for cloud motion retrieval with the off-nadir MISR camera views, and the motion is then used to provide a correction to the disparities used to measure cloud-top heights which are derived from the innermost three cameras. Intercomparison with a previously developed "superstereo" matcher shows that the results are very comparable in accuracy with much greater coverage and at ten times the speed. Intercomparison of feature-based and area-based techniques shows that the feature-based techniques are comparable in accuracy at a factor of eight times the speed. An assessment of the accuracy of the area-based matcher for cloud-free scenes demonstrates the accuracy and completeness of the stereo-matcher. This trade-off has resulted in the loss of a reliable quality metric to predict accuracy and a slightly high blunder rate. Examples are shown of the application of the MISR stereo-matchers on several difficult scenes which demonstrate the efficacy of the matching approach.