Application of pushbroom altimetry from space using large space antennas

The capabilities of multibeam altimetry are discussed and an interferometric multibeam technique for doing precision altimetry is described. The antenna feed horn arrangement and the resulting footprint lube pattern are illustrated. Plans for a shuttle multibeam altimetry mission are also discussed

Applications of active microwave imagery

The following topics were discussed in reference to active microwave applications: (1) Use of imaging radar to improve the data collection/analysis process; (2) Data collection tasks for radar that other systems will not perform; (3) Data reduction concepts; and (4) System and vehicle parameters: aircraft and spacecraft

EDGE: a code to calculate diffusion of cosmic-ray electrons and their gamma-ray emission

The positron excess measured by PAMELA and AMS can only be explained if there is one or several sources injecting them. Moreover, at the highest energies, it requires the presence of nearby ($\sim$hundreds of parsecs) and middle age (maximum of $\sim$hundreds of kyr) source. Pulsars, as factories of electrons and positrons, are one of the proposed candidates to explain the origin of this excess. To calculate the contribution of these sources to the electron and positron flux at the Earth, we developed EDGE (Electron Diffusion and Gamma rays to the Earth), a code to treat diffusion of electrons and compute their diffusion from a central source with a flexible injection spectrum. We can derive the source's gamma-ray spectrum, spatial extension, the all-electron density in space and the electron and positron flux reaching the Earth. We present in this contribution the fundamentals of the code and study how different parameters affect the gamma-ray spectrum of a source and the electron flux measured at the Earth.Comment: Presented at the 35th International Cosmic Ray Conference (ICRC2017), Bexco, Busan, Kore

Relaxation of strained silicon on Si0.5Ge0.5 virtual substrates

Strain relaxation has been studied in tensile strained silicon layers grown on Si0.5Ge0.5 virtual substrates, for layers many times the critical thickness, using high resolution x-ray diffraction. Layers up to 30 nm thick were found to relax less than 2% by the glide of preexisting 60° dislocations. Relaxation is limited because many of these dislocations dissociate into extended stacking faults that impede the dislocation glide. For thicker layers, nucleated microtwins were observed, which significantly increased relaxation to 14%. All these tensile strained layers are found to be much more stable than layers with comparable compressive strain

Evidence from satellite altimetry for small-scale convection in the mantle

Small scale convection can be defined as that part of the mantle circulation in which upwellings and downwellings can occur beneath the lithosphere within the interiors of plates, in contrast to the large scale flow associated with plate motions where upwellings and downwellings occur at ridges and trenches. The two scales of convection will interact so that the form of the small scale convection will depend on how it arises within the large scale flow. Observations based on GEOS-3 and SEASAT altimetry suggest that small scale convection occurs in at least two different ways

Boulder Bands on Lobate Debris Aprons: Does Spatial Clustering Reveal Accumulation History for Martian Glaciations?

Glacial landforms such as lobate debris aprons (LDA) and Concentric Crater Fill (CCF) are the dominant debris-covered glacial landforms on Mars. These landforms represent a volumetrically significant component of the Amazonian water ice budget, however, because small craters (diameter D 0.5-1 km) are poorly retained glacial brain terrain surfaces, and, since the glacial landforms are geologically young, it is challenging to reliably constrain either individual glacial deposit ages or formational sequences in order to determine how quickly the glaciers accumulated. A fundamental question remaining is whether ice deposition and flow that formed LDA occurred episodically during a few, short instances, or whether glacial flow was quasi-continuous over a long period (~108 yr). Because glaciation is thought to be controlled largely by obliquity excursions, a larger question is whether glacial deposits on Mars exhibit regional to global characteristics that can be used to infer synchronicity of flow or degradation

Quantitative measurements of the thermopower of Andreev interferometers

Using a new second derivative technique and thermometers which enable us to determine the local electron temperature in a mesoscopic metallic sample, we have obtained quantitative measurements of the low temperature field and temperature dependent thermopower of Andreev interferometers. As in previous experiments, the thermopower is found to oscillate as a function of magnetic field. The temperature dependence of the thermopower is nonmonotonic, with a minimum at a temperature of $\simeq0.5$ K. These results are discussed from the perspective of Andreev reflection at the normal-metal/superconductor interface.Comment: 6 pages, 4 figure