390 research outputs found
Charge Analyzer Responsive Local Oscillations
The first transatlantic radio transmission, demonstrated by Marconi in December of 1901, revealed the essential role of the ionosphere for radio communications. This ionized layer of the upper atmosphere controls the amount of radio power transmitted through, reflected off of, and absorbed by the atmospheric medium. Low-frequency radio signals can propagate long distances around the globe via repeated reflections off of the ionosphere and the Earth's surface. Higher frequency radio signals can punch through the ionosphere to be received at orbiting satellites. However, any turbulence in the ionosphere can distort these signals, compromising the performance or even availability of space-based communication and navigations systems. The physics associated with this distortion effect is analogous to the situation when underwater images are distorted by convecting air bubbles. In fact, these ionospheric features are often called 'plasma bubbles' since they exhibit some of the similar behavior as underwater air bubbles. These events, instigated by solar and geomagnetic storms, can cause communication and navigation outages that last for hours. To help understand and predict these outages, a world-wide community of space scientists and technologists are devoted to researching this topic. One aspect of this research is to develop instruments capable of measuring the ionospheric plasma bubbles. Figure 1 shows a photo of the Charge Analyzer Responsive to Local Oscillations (CARLO), a new instrument under development at NASA Marshall Space Flight Center (MSFC). It is a frequency-domain ion spectrum analyzer designed to measure the distributions of ionospheric turbulence from 1 Hz to 10 kHz (i.e., spatial scales from a few kilometers down to a few centimeters). This frequency range is important since it focuses on turbulence scales that affect VHF/UHF satellite communications, GPS systems, and over-the-horizon radar systems. CARLO is based on the flight-proven Plasma Local Anomalous Noise Environment (PLANE) instrument, previously flown on a U.S. Air Force low-Earth orbiting satellite, which successfully measured ion turbulence in five frequency decades from 0.1 Hz to 10 kHz (fig 2)
Linkages Between the Phenologies of Jack Pine \u3ci\u3e(Pinus Banksiana)\u3c/i\u3e Foliage and Jack Pine Budworm (Lepidoptera: Tortricidae)
A field study conducted in 2001 and 2002 in the Michigan Upper Peninsula investigated seasonal associations between the development of jack pine, Pinus banksiana Lamb., and larvae of the jack pine budworm Choristoneura pinus Freeman (Lepidoptera: Tortricidae). There was almost no active relationship between post-diapause emerging second instars and elongation of vegetative shoots. Early instars were not closely synchronized with the flushing of current-year needle fascicles, which is required to optimize larval feeding. How- ever, there were close feeding and shelter relationships between early instars and year-2 pollen cone development. Associations with, and larval damage to, year-2 seed cones were dependent upon larval population size and posed only minimal and periodic threats to jack pine seed production. As a consequence, early instar jack pine budworm relied almost exclusively on pollen cones for survival. Third to fifth instars vacated pollen cones as soon as they became desiccated. Only then did these larvae start close associations with vegetative shoots. First, they excised partially emerged needles at their base, and when the needle-pairs completely escaped their fascicle sheath, the larvae fed routinely on the complete needle lamina. Late instars, pupae and adults were associated with previous years’ and current-year foliage without any apparent bias. This study has shown that it might be more practical to time insecticide strategies, which are intended to manage jack pine budworm larvae, to the tree’s phenology rather than jack pine budworm larval indices
ISS Local Environment Spectrometers (ISLES)
In order to study the complex interactions between the space environment surrounding the ISS and the ISS surface materials, we propose to use lowcost, high-TRL plasma sensors on the ISS robotic arm to probe the ISS space environment. During many years of ISS operation, we have been able to condut effective (but not perfect) extravehicular activities (both human and robotic) within the perturbed local ISS space environment. Because of the complexity of the interaction between the ISS and the LEO space environment, there remain important questions, such as differential charging at solar panel junctions (the so-called "triple point" between conductor, dielectric, and space plasma), increased chemical contamination due to ISS surface charging and/or thruster activation, water dumps, etc, and "bootstrap" charging of insulating surfaces. Some compelling questions could synergistically draw upon a common sensor suite, which also leverages previous and current MSFC investments. Specific questions address ISS surface charging, plasma contactor plume expansion in a magnetized drifting plasma, and possible localized contamination effects across the ISS
Target of Opportunity Multipoint in Situ Measurements with Falconsat-2
This paper describes the FalconSAT-2 mission objectives to take advantage of targets of opportunity to make multipoint in situ measurements of ionospheric plasma depletions simultaneously with other spacecraft. Because these plasma depletions are known to interfere with radio transmissions over a broad range of frequencies, including 100-1000 MHz, the international space weather community is investigating the instigation, temporal evolution, and spatial propagation of these structures in the hopes that a prediction tool may be developed to warn operators of outages in communications or navigation. FalconSAT-2 will be launched into a low altitude (360 km), medium inclination (52 degrees) orbit with sensors designed to measure in situ suprathermal plasma spectra at a rate of 10 samples per second. The primary mission objectives are to 1) investigate F region ionospheric plasma depletion morphology relative to geomagnetic activity, and 2) demonstrate the utility of the Miniature Electrostatic Analyzer (MESA) in measuring energy-resolved spectra of ionospheric electrons over a dynamic range such that plasma density depletions down to 0.1% of the background may be resolved at a rate of 10 Hz. Simultaneous in situ multipoint observations of ionospheric plasma depletions are designated as a secondary objective since FalconSAT-2 consists of a single spacecraft, and opportunities to make these simultaneous measurements with other spacecraft in compatible orbits are not in our control. Both deep and shallow bubbles, frequently observed in the pre- and post-midnight sectors, respectively [Singh at al., 1997], are known to exhibit magnetic field-aligned behavior [Fagundes et al., 1997]; thus, there is the expectation (to first order) that multiple spacecraft entering a magnetic flux tube simultaneously have the opportunity to observe a depletion structure at different points within the structure. This observation would provide insight into the plasma depletion extent along the field line. Other conjunction types, such as non-simultaneous intersection of a flux tube or crossing of orbital paths simultaneously in different magnetic flux tubes, provide insight into other aspects of depletion structure, such as constraining the plasma depletion extent and propagation speed along the magnetic field line, or plasma depletion vertical extent. With this paper, a statistical analysis of the probability that FalconSAT-2 will intersect a magnetic flux tube during eclipse simultaneously with other spacecraft capable of measuring thermal electrons is presented
Employee benefit plans : best practices in presentation and disclosure; Accounting Trends & Techniques
https://egrove.olemiss.edu/aicpa_att/1097/thumbnail.jp
Eigenanalysis of Space Weather Climate Data: Discovering Structure within Large Multivariate Data Sets
No abstract availabl
Determinants of tetanus, pneumococcal and influenza vaccination in the elderly: a representative cross-sectional study on knowledge, attitude and practice (KAP)
Severity and incidence of vaccine-preventable infections with influenza viruses, s. pneumoniae and c. tetani increase with age. Furthermore, vaccine coverage in the elderly is often insufficient. The aim of this study is to identify socio-economic and knowledge-, attitude- and practice- (KAP)-related determinants of vaccination against influenza, pneumococcal disease and tetanus in the older German population
Progress toward Miniature Space Weather Stations
Responding to a growing need to specify (nowcast) and predict (forecast) hazardous space weather events and their deleterious effects on space systems, the authors have developed a prototype suite of instruments that would serve as a key component of a miniature space weather station. Space environment data have been gathered over several solar cycles, and though these data assist space operators in predicting hazards to space systems based upon derived climatology, no true forecasting ability yet exists. (As an analogy, consider for example the difference between tropospheric weather reports based on data-driven forecast models versus a prediction based upon the average temperature for a given city on a given date over the last hundred years.) True space weather forecasting models require assimilation of space-based in situ data into physics-based models. Data collection of fundamental characteristics, such as plasma density and temperature, neutral wind and bulk ion velocity, and electric and magnetic field strengths is required at multiple grid points, similar to tropospheric weather stations that measure temperature, wind speed, humidity, etc. Recent breakthroughs in fabrication techniques have enabled the development of a suite of instruments that is comprised of 16 individual analyzers, each of which is capable of providing a unique measurement of a partially ionized space environment. The suite is designed to measure ion spectra differential in energy and angle, bulk ion velocities, bulk neutral velocities, and ion and neutral mass spectra. Preliminary functional testing has indicated the ability to resolve He, O, O2, and Ar; separation of O2 and N2 has proved elusive to date. In the prototype suite, the instrument assembly that houses the 16 analyzers is stacked to a conventional Printed Circuit Board (PCB) with anodes and circuit components and an electronics enclosure containing a high voltage power supply, amplifier Application Specific Integrated Circuits (ASICs), and a Rad Hard microcontroller. The suite configuration, including all aforementioned components, has a total volume of 7 cm ´ 7 cm ´ 4 cm = 196 cm3, a mass of 400 g, and a peak power requirement of 1.5 W (for neutral measurements). Challenges inherent to miniaturization of spacecraft capable of providing real utility are identified and addressed
Eclipse 2017: Partnering with NASA MSFC to Inspire Students
NASA's Marshall Space Flight Center (MSFC) is partnering with the U.S. Space and Rocket Center (USSRC), and Austin Peay State University (APSU) to engage citizen scientists, engineers, and students in science investigations during the 2017 American Solar Eclipse. Investigations will support the Citizen Continental America Telescopic Eclipse (CATE), Ham Radio Science Citizen Investigation(HamSCI), and Interactive NASA Space Physics Ionosphere Radio Experiments (INSPIRE). All planned activities will engage Space Campers and local high school students in the application of the scientific method as they seek to explore a wide range of observations during the eclipse. Where planned experiments touch on current scientific questions, the camper/students will be acting as citizen scientists, participating with researchers from APSU and MSFC. Participants will test their expectations and after the eclipse, share their results, experiences, and conclusions to younger Space Campers at the US Space & Rocket Center
- …