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NASA NTRS2010

Research Plans for Improving Understanding of Effects of Very Low-Frequency Noise of Heavy Lift Rotorcraft

This report reviews the English-language technical literature on infrasonic and low-frequency noise effects; identifies the most salient effects of noise produced by a future large civil tiltrotor aircraft on crew, passengers, and communities near landing areas; and recommends research needed to improve understanding of the effects of such noise on passengers, crew, and residents of areas near landing pads.

Fidell, Sanford↗

NASA NTRS2010

Adaptive Planning: Understanding Organizational Workload to Capability/ Capacity through Modeling and Simulation

In August 2003, the Secretary of Defense (SECDEF) established the Adaptive Planning (AP) initiative [1] with an objective of reducing the time necessary to develop and revise Combatant Commander (COCOM) contingency plans and increase SECDEF plan visibility. In addition to reducing the traditional plan development timeline from twenty-four months to less than twelve months (with a goal of six months)[2], AP increased plan visibility to Department of Defense (DoD) leadership through In-Progress Reviews (IPRs). The IPR process, as well as the increased number of campaign and contingency plans COCOMs had to develop, increased the workload while the number of planners remained fixed. Several efforts from collaborative planning tools to streamlined processes were initiated to compensate for the increased workload enabling COCOMS to better meet shorter planning timelines. This paper examines the Joint Strategic Capabilities Plan (JSCP) directed contingency planning and staffing requirements assigned to a combatant commander staff through the lens of modeling and simulation. The dynamics of developing a COCOM plan are captured with an ExtendSim [3] simulation. The resulting analysis provides a quantifiable means by which to measure a combatant commander staffs workload associated with development and staffing JSCP [4] directed contingency plans with COCOM capability/capacity. Modeling and simulation bring significant opportunities in measuring the sensitivity of key variables in the assessment of workload to capability/capacity analysis. Gaining an understanding of the relationship between plan complexity, number of plans, planning processes, and number of planners with time required for plan development provides valuable information to DoD leadership. Through modeling and simulation AP leadership can gain greater insight in making key decisions on knowing where to best allocate scarce resources in an effort to meet DoD planning objectives.

Hase, Chris↗

NASA NTRS2010

NASA's Advancements in Space-Based Spectrometry Lead to Improvements in Weather Prediction and Understanding of Climate Processes

AIRS is a precision state of the art High Spectral Resolution Multi-detector IR grating array spectrometer that was launched into a polar orbit on EOS Aqua in 2002. AIRS measures most of the infra-red spectrum with very low noise from 650/cm to 2660/cm with a resolving power of 2400 at a spatial resolution of 13 km. The objectives of AIRS were to perform accurate determination of atmospheric temperature and moisture profiles in up to 90% partial cloud cover conditions for the purpose of improving numerical weather prediction and understanding climate processes. AIRS data has also been used to determine accurate trace gas profiles. A brief overview of the retrieval methodology used to analyze AIRS observations under partial cloud cover will be presented and sample results will be shown from the weather and climate perspectives.

Susskind, Joel↗

NASA NTRS2010

Understanding Solar Eruptions with SDO/HMI Measuring Photospheric Flows, Testing Models, and Steps Towards Forecasting Solar Eruptions

The Solar Dynamics Observatory (SDO) is carrying the first full-disk imaging vector magnetograph, the Helioseismic and Magnetic Imager (HMI), into an inclined geosynchronous orbit. This magnetograph will provide nearly continuous measurements of photospheric vector magnetic fields at cadences of 90 seconds to 12 minutes with 1" resolution, precise pointing, and unfettered by atmospheric seeing. The enormous data stream of 1.5 Terabytes per day from SAO will provide an unprecedented opportunity to understand the mysteries of solar eruptions. These ground-breaking observations will permit the application of a new technique, the differential affine velocity estimator for vector magnetograms (DAVE4VM), to measure photospheric plasma flows in active regions. These measurements will permit, for the first time, accurate assessments of the coronal free energy available for driving CMEs and flares. The details of photospheric plasma flows, particularly along magnetic neutral-lines, are critical to testing models for initiating coronal mass ejections (CMEs) and flares. Assimilating flows and fields into state-of-the art 3D MHD simulations that model the highly stratified solar atmosphere from the convection zone to the corona represents the next step towards achieving NASA's Living with a Star forecasting goals of predicting "when a solar eruption leading to a CME will occur." Our presentation will describe these major science and predictive advances that will be delivered by SDO/HMI.

Schuck, Peter W.↗

NASA NTRS2010

Dynamics of the Earth's Inner Magnetosphere and its Connection to the Ionosphere: Current Understanding and Challenges

The Earth's inner magnetosphere, a vast volume in space spanning from 1.5 Re (Earth radii) to 10 Re, is a host to a variety of plasma populations (with energy from 1 eV to few MeV) and physical processes where most of which involve plasma and field coupling. As a gigantic particle accelerator, the inner magnetosphere includes three overlapping regions: the plasmasphere, the ring current, and the Van Allen radiation belt. The complex structures and dynamics of these regions are externally driven by solar activities and internally modulated by intricate interactions and coupling. As a major constituent of Space Weather, the inner magnetosphere is both scientifically intriguing and practically important to our society. In this presentation, I will discuss our recent results from the Comprehensive Ring Current Model, in the context of our current understanding of the inner magnetosphere in general and challenges ahead in making further progresses.

Zheng, Yihua↗

NASA NTRS2005

Chemical Loss of Polar Ozone: Present Understanding and Remaining Uncertainties

Not long after the discovery of the Antarctic ozone hole, it was established that halogen compounds, supplied to the atmosphere mainly by anthropogenic activities, are the primary driver of polar ozone loss. We will briefly review the chemical mechanisms that cause polar ozone loss and the early evidence showing the key role played by anthropogenic halogens. Recently, stratospheric halogen loading has leveled off, due to adherence to the Montreal Protocol and its amendments that has essentially banned CFCs (chlorofluorocarbons) and other halocarbons. We will describe recent reports of the first stage of recovery of the Antarctic ozone hole (e.g., a statistically significant slowing of the downward trend), associated with the leveling off of stratospheric halogens. Despite this degree of understanding, we will discuss the tendency of photochemical models to underestimate the observed rate of polar ozone loss and a hypothesis that has recently been put forth that might resolve this discrepancy. Finally, we will briefly discuss chemical loss of Arctic ozone, which

climate change↗

NASA NTRS2010

Understanding Solar Eruptions with SDO/HMI Measuring Photospheric Flows, Testing Models, and Steps Towards Forecasting Solar Eruptions

The imminent launch of Solar Dynamics Observatory (SDO) will carry the first full-disk imaging vector magnetograph, the Helioseismic and Magnetic Imager (HMI), into an inclined geosynchronous orbit. This magnetograph will provide nearly continuous measurements of photospheric vector magnetic fields at cadences of 90 seconds to 12 minutes with I" resolution, precise pointing, and unfettered by atmospheric seeing. The enormous data stream of ~1.5 Terabytes per day from SDO will provide an unprecedented opportunity to understand the mysteries of solar eruptions. These ground-breaking observations will permit the application of a new technique, the differential affine velocity estimator for vector magnetograms (DAVE4VM), to measure photospheric plasma flows in active regions. These measurements will permit, for the first time, accurate assessments of the coronal free energy available for driving CMEs and flares. The details of photospheric plasma flows, particularly along magnetic neutral-lines, are critical to testing models for initiating coronal mass ejections (CMEs) and flares. Assimilating flows and fields into state-of-the art 3D MHD simulations that model the highly stratified solar atmosphere from the convection zone to the corona represents the next step towards achieving NASA's Living with a Star forecasting goals of predicting "when a solar eruption leading to a CME will occur." This talk will describe these major science and predictive advances that will be delivered by SDO /HMI.

Schuck, Peter W.↗

NASA NTRS2011

Dynamics of the Earth's Inner Magnetosphere and Its Connection to the Ionosphere: Current Understanding and Challenges

Zheng, Yihua↗

NASA NTRS2011

Experimental Investigation and Fundamental Understanding of a Slowed UH-60A Rotor at High Advance Ratios

This paper describes and analyzes the measurements from a full-scale, slowed RPM, UH-60A rotor tested at the National Full-Scale Aerodynamics Complex 40- by 80- ft wind tunnel up to an advance ratio of 1.0. A comprehensive set of measurements, that includes performance, blade loads, hub loads and pressures/airloads makes this data set unique. The measurements reveal new and rich aeromechanical phenomena that are special to this exotic regime. These include reverse chord dynamic stall, retreating side impulse in pitch-link load, large inboard-outboard elastic twist differential, supersonic flow at low subsonic advancing tip Mach numbers, diminishing rotor forces yet dramatic build up of blade loads, and dramatic blade loads yet benign levels of vibratory hub loads. The objective of this research is the fundamental understanding of these unique aeromechanical phenomena. The intent is to provide useful knowledge for the design of high speed, high efficiency, slowed RPM rotors of the future and a challenging database for advanced analyses validation.

Datta, Anubhav↗

NASA NTRS2011

Understanding Effective Diameter and Its Application to Terrestrial Radiation in Ice Clouds

The cloud property known as "effective diameter" or "effective radius", which in essence is the cloud particle size distribution (PSD) volume at bulk density divided by its projected area, is used extensively in atmospheric radiation transfer, climate modeling and remote sensing. This derives from the assumption that PSD optical properties can be uniquely described in terms of their effective diameter, D(sub e), and their cloud water content (CWC), henceforth referred to as the D(sub e)-CWC assumption. This study challenges this assumption, showing that while the D(sub e)-CWC assumption appears generally valid for liquid water clouds, it appears less valid for ice clouds in regions where (1) absorption is not primarily a function of either the PSD ice water content (IWC) or the PSD projected area, and (2) where wave resonance (i.e. photon tunneling) contributes significantly to absorption. These two regions often strongly coincide at terrestrial wavelengths when De less than ~60 m, which is where this D(sub e)-CWC assumption appears poorest. Treating optical properties solely in terms of D(sub e) and IWC may lead to errors up to 24%, 26% and 20% for terrestrial radiation in the window region regarding the absorption and extinction coefficients and the single scattering albedo, respectively. Outside the window region, errors may reach 33% and 42% regarding absorption and extinction. The magnitude and sign of these errors can change rapidly with wavelength, which may produce significant errors in climate modeling, remote sensing and other applications concerned with the wavelength dependence of radiation. Where the D(sub e)-CWC assumption breaks down, ice cloud optical properties appear to depend on D(sub e), IWC and the PSD shape. Optical property parameterizations in climate models and remote sensing algorithms based on historical PSD measurements may exhibit errors due to previously unknown PSD errors (i.e. the presence of ice artifacts due to the shattering of larger ice particles on the probe inlet tube during sampling). More recently developed cloud probes are designed to mitigate this shattering problem. Using realistic PSD shapes for a given temperature (and/or IWC) and cloud type may minimize errors associated with PSD shape in ice optics parameterizations and remote sensing algorithms. While this topic was investigated using two ice optics schemes (the Yang et al., 2005 database and the modified anomalous diffraction approximation, or MADA), a physical understanding of the limitations of the D(sub e)-IWC assumption was made possible by using MADA. MADA allows one to approximate the contribution of photon tunneling to absorption relative to other optical processes, which reveals that part of the error regarding the D(sub e)-IWC assumption can be associated with tunneling. By relating the remaining error to the radiation penetration depth in bulk ice (DELTA L) due to absorption, the domain where the D(sub e)-IWC assumption is weakest was described in terms of D(sub e) and DELTA L.

Mitchell, D. L.↗

NASA NTRS2011

Next-Generation Satellite Precipitation Products for Understanding Global and Regional Water Variability

A major challenge in understanding the space-time variability of continental water fluxes is the lack of accurate precipitation estimates over complex terrains. While satellite precipitation observations can be used to complement ground-based data to obtain improved estimates, space-based and ground-based estimates come with their own sets of uncertainties, which must be understood and characterized. Quantitative estimation of uncertainties in these products also provides a necessary foundation for merging satellite and ground-based precipitation measurements within a rigorous statistical framework. Global Precipitation Measurement (GPM) is an international satellite mission that will provide next-generation global precipitation data products for research and applications. It consists of a constellation of microwave sensors provided by NASA, JAXA, CNES, ISRO, EUMETSAT, DOD, NOAA, NPP, and JPSS. At the heart of the mission is the GPM Core Observatory provided by NASA and JAXA to be launched in 2013. The GPM Core, which will carry the first space-borne dual-frequency radar and a state-of-the-art multi-frequency radiometer, is designed to set new reference standards for precipitation measurements from space, which can then be used to unify and refine precipitation retrievals from all constellation sensors. The next-generation constellation-based satellite precipitation estimates will be characterized by intercalibrated radiometric measurements and physical-based retrievals using a common observation-derived hydrometeor database. For pre-launch algorithm development and post-launch product evaluation, NASA supports an extensive ground validation (GV) program in cooperation with domestic and international partners to improve (1) physics of remote-sensing algorithms through a series of focused field campaigns, (2) characterization of uncertainties in satellite and ground-based precipitation products over selected GV testbeds, and (3) modeling of atmospheric processes and land surface hydrology through simulation, downscaling, and data assimilation. An overview of the GPM mission, science status, and synergies with HyMex activities will be presented

Hou, Arthur Y.↗

NASA NTRS2011

Debris Disks in Aggregate: Using Hubble Space Telescope Coronagraphic Imagery to Understand the Scattered-Light Disk Detection Rate

Despite more than a decade of coronagraphic imaging of debris disk candidate stars, only 16 have been imaged in scattered light. Since imaged disks provide our best insight into processes which sculpt disks, and can provide signposts of the presence of giant planets at distances which would elude radial velocity and transit surveys, we need to understand under what conditions we detect the disks in scattered light, how these disks differ from the majority of debris disks, and how to increase the yield of disks which are imaged with 0.1" angular resolution. In this talk, I will review what we have learned from a shallow HSTINICMOS NIR survey of debris disks, and present first results from our on-going HST /STIS optical imaging of bright scattered-light disks.

Grady, Carol A.↗

NASA NTRS2011

Understanding Space Weather: The Sun as a Variable Star

The Sun is a complex system of systems and until recently, less than half of its surface was observable at any given time and then only from afar. New observational techniques and modeling capabilities are giving us a fresh perspective of the solar interior and how our Sun works as a variable star. This revolution in solar observations and modeling provides us with the exciting prospect of being able to use a vastly increased stream of solar data taken simultaneously from several different vantage points to produce more reliable and prompt space weather forecasts. Solar variations that cause identifiable space weather effects do not happen only on solar-cycle timescales from decades to centuries; there are also many shorter-term events that have their own unique space weather effects and a different set of challenges to understand and predict, such as flares, coronal mass ejections, and solar wind variations

Strong, Keith↗

NASA NTRS2012

Understanding Differences in the Response to Composition Change as Simulated by CCMVal Models

Chemistry climate models (CCMs) have a common conceptual basis. Differences in implementation lead to differences in the stratospheric ozone response to changes in composition and climate. Although evaluation by CCMVal-2 identified strengths and weaknesses of participant models, the evaluation results were not used to discriminate among projections for future ozone evolution, at least in part because the overall diagnostic evaluation did not cleanly relate to the differences in CCM response. Here we use a subset of CCMVal diagnostics and additional analysis to understand the differences in response. In the upper stratosphere, differences in simulated temperature and total odd nitrogen prior to increases in chlorine loading explain the large differences in CCM sensitivity. In the lower atmosphere, there are two principle contributions to differences in CCM sensitivity to chlorine and climate change. First, differences in the lower stratospheric ClO affect simulated sensitivity to chlorine. CCMs with best transport performance match NDACC column HCl measurements at a broad range of latitudes. Other CCMs disagree with observations due to differences in total inorganic chlorine, partitioning between HCl and ClONO2, or both. Differences in ClONO2 are directly related to differences in simulated ClO. Second, although all CCMs predict increased tropical upwelling, the rate of increase varies and contributes to differences in tropical ozone and the 60N-60S column average.

Douglass, Anne R.↗

NASA NTRS2011

An Overview of the Current Understanding of Gamma-Ray Bursts in the Fermi Era

Gamma-ray bursts are the most luminous explosions in the Universe, and their origin as well as mechanism are the focus of intense research and debate. More than three decades since their serendipitous discovery, followed by several breakthroughs from space-borne and ground-based observations, they remain one of the most interesting astrophysical phenomena yet to be completely understood. Since the launch of Fermi with its unprecedented energy band width spanning seven decades, the study of gamma-ray burst research has entered a new phase. Here we review the current theoretical understanding and observational highlights of gamma-ray burst astronomy and point out some of the potential promises of multi-wavelength observations in view of the upcoming ground based observational facilities .

Bhat, P. N.↗

NASA NTRS2011

Contribution of Satellite Gravimetry to Understanding Seismic Source Processes of the 2011 Tohoku-Oki Earthquake

The 2011 great Tohoku-Oki earthquake, apart from shaking the ground, perturbed the motions of satellites orbiting some hundreds km away above the ground, such as GRACE, due to coseismic change in the gravity field. Significant changes in inter-satellite distance were observed after the earthquake. These unconventional satellite measurements were inverted to examine the earthquake source processes from a radically different perspective that complements the analyses of seismic and geodetic ground recordings. We found the average slip located up-dip of the hypocenter but within the lower crust, as characterized by a limited range of bulk and shear moduli. The GRACE data constrained a group of earthquake source parameters that yield increasing dip (7-16 degrees plus or minus 2 degrees) and, simultaneously, decreasing moment magnitude (9.17-9.02 plus or minus 0.04) with increasing source depth (15-24 kilometers). The GRACE solution includes the cumulative moment released over a month and demonstrates a unique view of the long-wavelength gravimetric response to all mass redistribution processes associated with the dynamic rupture and short-term postseismic mechanisms to improve our understanding of the physics of megathrusts.

Han, Shin-Chan↗

NASA NTRS2012

Understanding Prebiotic Chemistry Through the Analysis of Extraterrestrial Amino Acids and Nucleobases in Meteorites

The discoveries of amino acids of extraterrestrial origin in many meteorites over the last 50 years have revolutionized the Astrobiology field. A variety of non-terrestrial amino acids similar to those found in life on Earth have been detected in meteorites. A few amino acids have even been found with chiral excesses, suggesting that meteorites could have contributed to the origin of homochirality in life on Earth. In addition to amino acids, which have been productively studied for years, sugar-like molecules, activated phosphates, and nucleobases have also been determined to be indigenous to numerous meteorites. Because these molecules are essential for life as we know it, and meteorites have been delivering them to the Earth since accretion, it is plausible that the origines) of life on Earth were aided by extrataterrestrially-synthesized molecules. Understanding the origins of life on Earth guides our search for life elsewhere, helping to answer the question of whether biology is unique to Earth. This tutorial focuses on meteoritic amino acids and nucleobases, exploring modern analytical methods and possible formation mechanisms. We will also discuss the unique window that meteorites provide into the chemistry that preceded life on Earth, a chemical record we do not have access to on Earth due to geologic recycling of rocks and the pervasiveness of biology across the planet. Finally. we will address the future of meteorite research, including asteroid sample return missions.

Burton, Aaron S.↗

NASA NTRS2012

The Radiation Belt Storm Probes Mission: Advancing Our Understanding of the Earth's Radiation Belts

We describe NASA's Radiation Belt Storm Probe (RBSP) mission, whose primary science objective is to understand, ideally to the point of predictability, the dynamics of relativistic electrons and penetrating ions in the Earth's radiation belts resulting from variable solar activity. The overarching scientific questions addressed include: 1. the physical processes that produce radiation belt enhancement events, 2. the dominant mechanisms for relativistic electron loss, and 3. how the ring current and other geomagnetic processes affect radiation belt behavior. The RBSP mission comprises two spacecraft which will be launched during Fall 2012 into low inclination lapping equatorial orbits. The orbit periods are about 9 hours, with perigee altitudes and apogee radial distances of 600 km and 5.8 RE respectively. During the two-year primary mission, the spacecraft orbits precess once around the Earth and lap each other twice in each local time quadrant. The spacecraft are each equipped with identical comprehensive instrumentation packages to measure, electrons, ions and wave electric and magnetic fields. We provide an overview of the RBSP mission, onboard instrumentation and science prospects and invite scientific collaboration.

Sibeck, David↗