Cryogenic Storage of Helium for Propellant Tank Pressurization

This paper has been prepared in response to many inquiries regarding the application of cryogenic helium storage to propellant tank pressurization systems. The high weight penalties associated with conventional helium storage systems have prompted the development of a Supercritical Helium Storage and Supply System for this application

Estimation of inertial platform errors

Equations for inertial platform error mode

Holt v. Grange Mutual Casualty Co.: Children Not Insureds under Policy Are Entitled to Death Benefits

The automobile insurance industry is up in arms after a decade of consumer friendly Ohio Supreme Court decisions. The insurance industry and commentators have noted the trend of judicial activism in interpreting insurance contracts. These decisions have been overwhelmingly in favor of consumers and against insurance companies. The Ohio Supreme Court decision of Holt v. Grange Mutual Casualty Co., is another consumer friendly decision and represents both an equitable and sound interpretation and application of Ohio law to consumer insurance contracts. This note walks through the Holt case, starting at the trial court level and working up through the Ohio Supreme Court decision. The authors conclude that the Ohio Supreme Court has taken a significant and laudable step to support the public policy considerations embodied in the uninsured/underinsured insurance statute and wrongful death statute at the expense of the narrowly drafted language imposed upon consumers in contracts crafted by insurance companies

Titan solar occultation observations reveal transit spectra of a hazy world

High altitude clouds and hazes are integral to understanding exoplanet observations, and are proposed to explain observed featureless transit spectra. However, it is difficult to make inferences from these data because of the need to disentangle effects of gas absorption from haze extinction. Here, we turn to the quintessential hazy world -- Titan -- to clarify how high altitude hazes influence transit spectra. We use solar occultation observations of Titan's atmosphere from the Visual and Infrared Mapping Spectrometer (VIMS) aboard NASA's Cassini spacecraft to generate transit spectra. Data span 0.88-5 microns at a resolution of 12-18 nm, with uncertainties typically smaller than 1%. Our approach exploits symmetry between occultations and transits, producing transit radius spectra that inherently include the effects of haze multiple scattering, refraction, and gas absorption. We use a simple model of haze extinction to explore how Titan's haze affects its transit spectrum. Our spectra show strong methane absorption features, and weaker features due to other gases. Most importantly, the data demonstrate that high altitude hazes can severely limit the atmospheric depths probed by transit spectra, bounding observations to pressures smaller than 0.1-10 mbar, depending on wavelength. Unlike the usual assumption made when modeling and interpreting transit observations of potentially hazy worlds, the slope set by haze in our spectra is not flat, and creates a variation in transit height whose magnitude is comparable to those from the strongest gaseous absorption features. These findings have important consequences for interpreting future exoplanet observations, including those from NASA's James Webb Space Telescope.Comment: Updated journal reference; data available via http://sites.google.com/site/tdrobinsonscience/science/tita

Probing Light Atoms at Sub-nanometer Resolution: Realization of Scanning Transmission Electron Microscope Holography

Atomic resolution imaging in transmission electron microscopy (TEM) and scanning TEM (STEM) of light elements in electron-transparent materials has long been a challenge. Biomolecular materials, for example, are rapidly altered when illuminated with electrons. These issues have driven the development of TEM and STEM techniques that enable the structural analysis of electron beam-sensitive and weakly scattering nano-materials. Here, we demonstrate such a technique, STEM holography, capable of absolute phase and amplitude object wave measurement with respect to a vacuum reference wave. We use an amplitude-dividing nanofabricated grating to prepare multiple spatially separated electron diffraction probe beams focused at the sample plane, such that one beam transmits through the specimen while the others pass through vacuum. We raster-scan the diffracted probes over the region of interest. We configure the post specimen imaging system of the microscope to diffraction mode, overlapping the probes to form an interference pattern at the detector. Using a fast-readout, direct electron detector, we record and analyze the interference fringes at each position in a 2D raster scan to reconstruct the complex transfer function of the specimen, t(x). We apply this technique to image a standard target specimen consisting of gold nanoparticles on a thin amorphous carbon substrate, and demonstrate 2.4 angstrom resolution phase images. We find that STEM holography offers higher phase-contrast of the amorphous material while maintaining Au atomic lattice resolution when compared with high angle annular dark field STEM.Comment: 9 pages, 5 figures in main text, 1 supplemental figure in the appendi