Physics Commons^™

First Temperature Observations With The Usu Very Large Rayleigh Lidar: An Examination Of Mesopause Temperatures, Leda Sox, Vincent B. Wickwar, Joshua P. Herron, Marcus J. Bingham, Lance W. Petersen, Matthew T. Emerick

Posters

As the impetus for extended observational measurements throughout the middle atmosphere has increased1 , the limits of previous instrumentation need to be pushed. The Rayleigh lidar group at the Atmospheric Lidar Observatory (ALO) at Utah State University has pushed such limits on existing Rayleigh scatter lidar technology and, through major upgrades to the previous lidar system, has been able to gather temperature measurements in the upper mesosphere and lower thermosphere from approximately 70P109 km. A data campaign with the new system was conducted around the annual temperature minimum, centered on late June 2012, in this region. The temperatures from this …

Defect-Driven Dynamic Model Of Electrostatic Discharge And Endurance Time Measurements Of Polymeric Spacecraft Materials, Charles Sim, Alec Sim, Jr Dennison, Matthew Stormo

Posters

Charge buildup on insulating materials in the space environment can produce long exposure to electric fields, which can lead to Electrostatic Discharge (ESD). Charge buildup is the leading cause of spacecraft failure due to space environment interactions. ESD can be thought of as the point at which the buildup of charge in localized defects, found in polymeric insulating materials, leads to a catastrophic change in electrical conductivity, which can cause the materials to structurally breakdown. Defects produced by radiation, or prolonged exposure to electric fields, significantly alter the endurance time, the time it takes to produce enough defects to generate …

Muon Contribution To Cathodoluminescence Tests?, Justin Dekany, Allen Anderson, Jr Dennison

Posters

Tests of composites incorporating highly disordered insulating materials that were bombarded with low-flux keV electron beams exhibited three distinct forms of light emission: short-duration (<<1 s), high intensity luminous electrostatic discharges between the insulator and ground--termed “arcs”; intermediate-duration (10-100 s), intense surface emissions—termed “flares”; and lower intensity, continuous surface cathodoluminescent “glow”. During long-duration experiments at temperatures <150 K, relatively intense flare events occurred at rates of ~2 per min. Rapid increase in photon emission and electron displacement current were observed, with long exponential decay times >1 min. We propose that the source of the flares is the interactions of high energy muons—of cosmic ray origin—with the highly-charged insulating components of the composite materials, which trigger avalanche electrostatic discharge and subsequent recharging along with concomitant light emission. We review evidence from the insulator conductivity at low temperatures, the rates and magnitude of surface charging, the flare frequency, and the magnitude and time-dependence of currents and light emission with regard to this …

Charging Effects Of Multilayered Dielectric Spacecraft Materials: Surface Voltage, Discharge And Arcing, Gregory Wilson, Amberly Evans, Justin Dekany, Jr Dennison

Posters

Charging of thin-film, multilayer dielectric materials subject to electron bombardment was found to evolve with time. The charging behavior was also highly dependent on the incident energy of the monoenergetic electron beams; this is driven by energy dependant processes including the electron penetration depth, electron emission, and material conductivity. The electron penetration depth is the average range to which incident electrons at a given incident energy penetrate into the material, thus defining the mean depth of an embedded charge layer. The secondary electron yield is the ratio of electrons emitted from the surface to the number of incident electrons; this …

Electron Transport Models And Precision Measurements In A Constant Voltage Chamber, Justin Dekany, Alec Sim, Jerilyn Brunson, Jr Dennison

Posters

The conductivity of the material is a key transport parameter in spacecraft charging that determines how deposited charge will redistribute throughout the system, how rapidly charge imbalances will dissipate, and what equilibrium potential will be established under given environmental conditions. As the requirements for space missions extend to new regions of space and more stringent requirements are placed on spacecraft performance, it becomes necessary to better understand the underlying conduction mechanisms that determine the dynamic response of insulators to temperature, electric field dose rate, and sample conditioning and history. This study performed detailed measurements of the transient conductivity of representative …

Ultrahigh Vacuum Cryostat System For Extended Low Temperature Space Environment Testing, Justin Dekany, Robert H. Johnson, Gregory Wilson, Amberly Evans, Jr Dennison

Posters

The range of temperature measurements have been significantly extended for an existing space environment simulation test chamber used in the study of electron emission, sample charging and discharge, electrostatic discharge and arcing, electron transport, and luminescence of spacecraft materials. This was accomplished by incorporating a new cryostat system and sample mount, which maintained compatibility with an existing ultrahigh vacuum chamber (base pressure

The new two-stage, closed-cycle helium cryostat has an extended sample temperature range from450 K, with long-term controlled stability of

The new capabilities in this chamber have been employed to study the temperature dependence of materials properties critical to …

The Dynamic Interplay Between Spacecraft Charging, Space Environment Interactions And Evolving Materials, Jr Dennison

Posters

The charge on spacecraft is constantly changing as a result of the dynamic nature of the space environment, the spacecraft orbit, the interactions between environment and spacecraft, and even the evolving spacecraft materials. While the effects on spacecraft charging from varying environmental conditions and from the selection of different construction materials have been studied extensively, the modification of material properties by the space plasma environment can also have profound effects on spacecraft charging. Given the increasingly demanding nature of space missions, there is clearly a need to extend our understanding of the dynamic nature of material properties that affect spacecraft …

Low Temperature Cathodoluminescence Of Space Observatory Materials, Amberly Evans, Gregory Wilson, Justin Dekany, Alec Sim, Jr Dennison

Posters

In recent charging studies, a discernable glow was detected emanating from sample surfaces undergoing electron beam bombardment that resulted from a luminescent effect termed cathodoluminescence. This suggests that some of the materials used as optical elements, structural components, and thermal control surfaces in the construction of space-based observatories might luminesce when exposed to sufficiently energetic charged particle fluxes from the space plasma environment. If these visible, infrared and ultraviolet emissions are intense enough, they can potentially produce optical contamination detrimental to the performance of the observatory optical elements and sensors, and act to limit their sensitivity and performance windows. As …

Defect-Driven Dynamic Model Of Electrostatic Discharge And Endurance Time Measurements Of Polymeric Spacecraft Materials, Charles Sim, Alec Sim, Jr Dennison, Matthew Stromo

Posters

Measurements of the electrostatic field strength of thin film insulating materials due to interactions with the space plasma environment are one of the most important concepts to understand for the effective design of spacecraft. It is therefore critical to understand how electrostatic field strength (FESD) of spacecraft materials varies due to environmental conditions such as temperature, duration of applied electric field, rate of field changes, and history of exposure to high fields. This research STUDY emphasizes experimental and theoretical investigations on the FESD of polymeric insulators as a function of temperature, applied field, and time to breakdown. It suggests that …

Small Scale Simulation Chamber For Space Environment Survivability Testing, Robert H. Johnson, Lisa D. Montierth, Jr Dennison, James S. Dyer, Alex Chanson

Posters

A versatile vacuum system for long duration testing of materials modifications due to exposure to simulated space environment conditions has been designed and built. The chamber is particularly well suited for cost-effective tests of multiple small scale materials samples over prolonged exposure. Critical environmental components simulated include neutral gas [ultrahigh vacuum (10-7 Pa) to ambient], FUV/UV/VIS/NIR solar spectrum, electron plasma fluxes, and temperature. The UV/VIS/NIR solar spectrum is simulated using an external, normally incidence and collimated class AAA Solar Simulator source, with standard Air Mass Zero (AM0) filters to shape the incident radiation spectrum. This Xe arc discharge tube source …

The Effects Of Space Environment On Wireless Communication Devices' Performance, Hillyard Landon, Jr Dennison

Posters

This project evaluates the effects of the space environment on small radio hardware devices called Bluetooth (a proprietary open wireless technology standard for exchanging data over short distances) chips (hoovers). When electronics are exposed to the harsh environment outside the Earth's atmosphere, they sometimes do not perform as expected. The USU Getaway Away Special (GAS) team is now in the design stages of launching a CubeSat (a 10 cm cubed autonomous satellite to fly in Low Earth Orbit). In order to conduct experiments proposed for the USU GAS Cubesat, Bluetooth wireless communication will be used. By testing commercially available hardware …