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All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Prospects for annihilating Dark Matter towards Milky Way's dwarf galaxies by the Cherenkov Telescope Array

We derive the Cherenkov Telescope Array (CTA) sensitivity to dark matter (DM) annihilation in several primary channels, over a broad range of DM masses. These sensitivities are estimated when CTA is pointed towards a large sample of Milky Way's dwarf spheroidal galaxies (dSphs) with promising J -factors and small statistical uncertainties. This analysis neglects systematic uncertainties, which we estimate at the level of at least 1 dex. We also present sensitivities on the annihilation cross section from a combined analysis of 4 dSphs. We assess the CTA sensitivity by: i ) using, for each dSph, a recent determination of the J -factor and its statistical error; ii ) considering the most up-to-date cosmic ray background; and iii ) including both spatial and spectral terms in the likelihood analysis. We find that a joint spectral and spatial analysis improves the CTA sensitivity, in particular for primary channels with sharp features in the γ-ray energy spectrum and for dSphs with steep J -factor profiles, as deduced from the internal kinematics. The greatest sensitivities are obtained for observations of Ursa Minor among the classical dSphs and of Ursa Major II for ultra-faint dSphs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

High-Resolution Characterization of Comingled Contaminants in the Deep Vadose Zone, Hanford Site, Washington - 17387

The contaminated deep vadose zone in the Central Plateau of the Hanford Site in Washington state presents a unique challenge to remediation. The Comprehensive Environmental Response, Compensation, and Liability Act, commonly known as the CERCLA project responsible for addressing these deep contaminants is designated as the 200-Deep Vadose Zone Operable Unit (DV-1 project). The vadose zone is 55-82 meters (180-270 feet) thick and is contaminated with both radiological and chemical contaminants from multiple historical waste streams. The mobile contaminants from this waste are still present in the deep vadose zone and pose a potential threat to the groundwater. Characterizing the nature and extent of the comingled mobile contaminants is an important step before assessing possible remedial alternatives. One factor controlling the migration and distribution of subsurface contaminants is the lithologic heterogeneity of the vadose zone sediments. A sampling plan for the DV-1 project includes continuous sediment core collection and analysis to identify key lithologic factors (i.e., small-scale bedding and structural features) that act as barriers, preferential pathways or conduits for mobile contaminants migrating through the vadose zone. Over six hundred meters (2,000 feet) of intact sediment core from 26 boreholes were collected in 1.5 meters (5 feet) long, 10 centimeter (4-inch) diameter segments. These intact sediment samples provide significant improvement in the level of detail and understanding of mechanisms and features controlling contaminant distribution that is not possible with traditional homogenized drill cuttings or conventional split-spoon samples. Detailed geological descriptions and photographs of the intact core are correlated to high-resolution geophysical logs which aid in the development of a comprehensive contaminant distribution profile of the borehole. These lithologic interpretations are used to define specific depth intervals for sampling based on changes in moisture, lithology, and elevated gamma radiation. The selected samples are analyzed for contaminants of concern, geochemical parameters, and hydraulic properties. Significant lithologic features observed in the intact cores include sharp contact boundaries to graded bedding, iron-oxide and carbonate cementation, silty laminations, clastic dike intrusions, and soft sediment deformation. Preliminary geologic logs integrated with the sample analysis indicate features that correlate to the variable distribution of contaminants both laterally and vertically. Integration of measured hydraulic parameters to lithologic units in individual borehole profiles provide key inputs for more precise geo-framework and vadose zone flux models supporting the DV-1 project. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Prototype Design, Analysis, and Results for a Liquid Radiological Waste Control Room

Human factors researchers at Idaho National Laboratory are collaborating with a utility partner to address human factors in the modernization of their radiological waste control room. The collaborating utility, Palo Verde, plans to remove all control boards associated with the liquid radiological waste system, which include controls, indicators, and alarm systems, and replace them with modernized digital instrumentation and controls and displays. To be sure the new system either supports current operational performance or enhances it, researchers have carried out three planning and analysis activities: expert operator review, function allocation analysis, and human factor principles and design applications. Researchers utilized access to expert operators to gain information about the system. Operators were asked to detail a procedure exemplifying typical interactions with the liquid radiological waste system and provide it to Idaho National Laboratory with a list of functionalities to incorporate (Section 4.1). Later, operators were asked to provide additional feedback to inform a prototype with adequate realism to support sound analysis of the system design (Section 4.2). Other operators not associated with the utility partner were also involved in experiment design and prototype evaluation (Section 4.2). Due to the extent of the upgrade, care was given to measure the change in the operator’s role (Section 7). As part of the modernization, some plant systems are expected to be equipped with automation or sensors that send information directly to the control where previously operators were required to enter controlled areas to find the information. Such updates made slight changes to operator role requirements, but the impact was negligible. The way the system is operated will remain largely the same, but operator convenience and safety is expected to increase. Additionally, to map operator tasks during the selected procedure, an Operational Sequence Diagram was created (Section 7.1). The diagram helped to account for every interaction and piece of equipment needed to create the prototype design. Alternatively, the diagram can be created following the final design to identify any function reallocations due to redesign. Human factors principles were also applied to the design. An ergonomic assessment was performed on the workspace resulting in various recommendations for placing and designing the new workstation (Section 6). A 3 D mockup of the control room was created to depict the options available with in-depth descriptions of each. Furthermore the prototype design incorporates well known human factors principles. However, to be sure the principles are sound in the control room context, the researches have designed an experiment to measure the impact design decision has on operator performance. The experiment is described in detail in Section 5. Lastly, a tool emerged as this effort began called the NUREG 0711 Crosswalk (Section 8). The tool has multiple uses, but it was primarily intended to communicate how the researcher’s action directly mapped to specific results suggested in the Nuclear Regulatory Commission review guideline. The tool also maps how current results impact future decisions in the modernization process.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Secure environment establishment for FPGA-based safety-critical systems: quality management system context - 159

The paper discusses importance of secure development and operational environment establishment process, its particular stages, including security-oriented analysis and assessment of safety-critical instrumentation and control (I and C) systems. Two particular aspects are covered - security assessment and security assurance related to processes established by Quality Management System (QMS). One of the underlying ideas for the security assessment approach is in performance of gap analysis. Such analysis considers influence of all different factors within I and C system development process, and further application of Intrusion Modes and Effect Criticality Analysis (IMECA) technique. It makes the approach applicable to various safety-critical systems, considering underlying technologies (for example, Field-Programmable Gate Arrays (FPGA). Nowadays FPGA technology is often used in wide spectrum of hardware devices - from personal devices to complex I and C systems for Nuclear Power Plants (NPPs). The problem of cyber security assessment and assurance for FPGA technology in general and its application in safety-critical I and C systems in particular is not completely solved due to several reasons that cover regulations, QMS processes, implementation of development and verification activities, etc. The paper overviews existing regulations, which cover various aspects of NPP I and C systems development and operation, FPGA technology implementation, and secure development and operational environment establishment and assurance. The paper also emphasizes that complex approach should be used to identify and mitigate all specific vulnerabilities thorough the whole life cycle on the basis on Intrusion Modes, Effect and Criticality Analysis technique. The paper also proposes approach to the development of safety-critical I and C systems in the scope of cyber security assurance process at developer site. Secure development environment is described as a key factor during the development process and the paper also discusses establishment and maintenance of such environment as a part of company's Nuclear Quality Assurance's QMS. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1978

Cargo Logistics Airlift Systems Study (CLASS). Volume 1: Analysis of current air cargo system

The material presented in this volume is classified into the following sections; (1) analysis of current routes; (2) air eligibility criteria; (3) current direct support infrastructure; (4) comparative mode analysis; (5) political and economic factors; and (6) future potential market areas. An effort was made to keep the observations and findings relating to the current systems as objective as possible in order not to bias the analysis of future air cargo operations reported in Volume 3 of the CLASS final report.

Burby, R. J.↗
DOE OSTI2023

Image Characterization of Reactions Generated by an Aeroengine Micromixing Injector for Lean Direct Injection of Hydrogen and Hydrogen/Natural Gas Blend

An aeroengine micromixing injector, originally designed for lean direct injection of jet fuel, was adapted to work with hydrogen, natural gas, and any blend in between. The ultimate goal of the design was to achieve low NOx emissions when operated on pure hydrogen; to better characterize its performance, flame imaging diagnostics was implemented. Three types of cameras mounted parallel to the injector base and pointing towards the quartz combustor cylinder with the same angle were operated simultaneously: Nikon D90, Dynacolor FB-N9-U, and Phantom v7.1, to capture the visible spectrum, OH* chemiluminescence, and dynamic behavior of the flames, respectively. The current work also includes the overlapping of visible spectrum and OH* chemiluminescence, as an effort to qualitatively define the heat release over the flame area, i.e., UV over visible domain. Additionally, a z-type schlieren configuration was employed to reinforce the presence of some small-scale details occurring near the injector outlet ports. Using the airbox pressure drop, preheat temperature, fuel composition and flame temperature as the factors of study, a Box Behnken model was designed yielding into a 16-points matrix for the operability region, at atmospheric pressure. The main responses were extracted from the OH* images, because of its correlation with the flame heat release, these being the flame area and its average brightness, the heat release area and its center of gravity and leading edge. To assess the importance of the main factors and their interactions, an analysis of variance (ANOVA) was performed for each response, considering as significant each contributor with a p-value below 0.05. For these five responses it was found that all four main factors need to be included into the model (most of them because its own significance, others to ensure the model hierarchy), as well as some common interactions as the preheat and flame temperatures or pressure drop and fuel composition, and quadratic terms from fuel composition or flame temperature. Three of the five models presented R2 and coefficient of variance (C.V.) indicators around 0.97 and 5%, respectively; the leading edge ANOVA yielded into R2=0.78 and C.V.=18.88%; and the heat release area showed R2=0.91 and C.V.=24.13%. Lastly, the confinement ratio effect of the combustor over the flame structure was quantified, for three different conditions: the original 80 mm inner diameter and 200 mm length cylinder was compared against a shorter 150 mm tube (same inner diameter) and a narrower 47 mm inner diameter one (same 200 mm length). The length had a smaller effect than the inner diameter, even though both factors were not strong enough to make a significant deviation on most of the flame parameters: the difference was within the repeatability margin of error for the brightness, flame area, and center of gravity and leading edge of the heat release area.

Imaging diagnostics, flame characterization, OH* c↗
DOE OSTI2025

Understanding and Modeling Pooled Rideshare Acceptance: Influential Factors, Preferred User Experiences, and Implications

Ridesharing allows people to share a vehicle with others traveling in the same direction, which can reduce costs and traffic congestion. Pooled rideshare (PR) services, such as UberX Share and Lyft Shared, offer an economical and environmentally friendly alternative by matching passengers traveling similar routes. However, despite these benefits, PR adoption remains low due to concerns about safety, privacy, and convenience. This research explores the factors influencing PR adoption and provides recommendations to improve user acceptance. A nationwide survey of 5,385 participants across the U.S. was conducted to understand why people choose or avoid PR. The study identified five key factors influencing PR consideration: safety, service experience, privacy, traffic/environment, and time/cost. Additional research examined ways to optimize PR experiences by identifying four critical factors: comfort/ease of use, convenience, vehicle technology/accessibility, and passenger safety. To measure the impact of these factors, a statistical model called the Pooled Rideshare Acceptance Model (PRAM) was developed, providing insights into how each element influences PR adoption. Further analysis using the Pooled Rideshare Acceptance Model Multigroup Analyses (PRAMMA) revealed how demographic characteristics such as age, gender, income, and past rideshare experience shape PR perceptions. Some key findings from the multigroup analyses showed that younger users valued technological features and environmental benefits, while older users prioritized reliability and service transparency. Additionally, privacy concerns were more significant for female users, while convenience was critical for higher-income groups. These results emphasize that a 'onesize-fits-all' approach to PR service design is not effective, highlighting the need for tailored strategies to address different user segments. Further, workshops were conducted with researchers and students to translate the findings into real-world solutions. These workshops and 3 all the statistical analyses led to the development of 95 actionable recommendations. The recommendations focus on key areas such as safety, service reliability, user education, and accessibility, offering tangible improvements to PR services. The insights from this study provide valuable guidance for policymakers, transportation network companies (TNCs), and researchers aiming to make PR services safer, more accessible, and widely accepted. By addressing user concerns, PR can become a more viable transportation option, supporting sustainable urban mobility and reducing reliance on private vehicles. Additionally, these findings emphasize the importance of user-centric service design in encouraging broader PR adoption. Future research should explore evolving trends in PR preferences, technological advancements, and policy changes to ensure continued improvements. By implementing these recommendations, PR services can better align with user expectations, enhance trust in shared mobility, and contribute to a more efficient transportation ecosystem.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2019

Effect of Temperature and Hydrophilic Ratio on the Structure of Poly( N -vinylcaprolactam)- block -poly(dimethylsiloxane)- block -poly( N -vinylcaprolactam) Polymersomes

Nanosized polymeric vesicles (polymersomes) assembled from ABA triblock copolymers of poly(N-vinylcaprolactam)-poly(dimethylsiloxane)-poly(N-vinylcaprolactam) (PVCL–PDMS–PVCL) are a promising platform for biomedical applications, as the temperature-responsiveness of the PVCL blocks enables reversible vesicle shrinkage and permeability of the polymersome shell at elevated temperatures. Herein, we explore the effects of molecular weight, polymer block weight ratios, and temperature on the structure of these polymersomes via electron microscopy, dynamic light scattering, small angle neutron scattering (SANS), and all-atom molecular dynamics methods. We show that the shell structure and overall size of the polymersome can be tuned by varying the hydrophilic (PVCL) weight fraction of the polymer: at room temperature, polymers of smaller hydrophilic ratios form larger vesicles that have thinner shells, whereas polymers with higher PVCL content exhibit interchain aggregation of PVCL blocks within the polymersome shell above 50 °C. Model fitting and model-free analysis of the SANS data reveals that increasing the mass ratio of PVCL to the total copolymer weight from 0.3 to 0.56 reduces the temperature-induced change in vesicle diameter by a factor of 3, while simultaneously increasing the change in shell thickness by a factor of 1.5. Finally, by analysis of the shell structures and overall size of polymersomes with various PVCL weight ratios and those without temperature-dependent polymer components, we bring into focus the mechanism of temperature-triggered drug release reported in a previous study. This work provides new fundamental perspectives on temperature-responsive polymersomes and elucidates important structure–property relationships of their constituent polymers.

36 MATERIALS SCIENCE↗
NASA NTRS1945

An analysis of life expectancy of airplane wings in normal cruising flight

In order to provide a basis for judging the relative importance of wing failure by fatigue and by single intense gusts, an analysis of wing life for normal cruising flight was made based on data on the frequency of atmospheric gusts. The independent variables considered in the analysis included stress-concentration factor, stress-load relation, wing loading, design and cruising speeds, design gust velocity, and airplane size. Several methods for estimating fatigue life from gust frequencies are discussed. The procedure selected for the analysis is believed to be simple and reasonably accurate, though slightly conservative.

Putnam, Abbott A↗
DOE OSTI2024

Improved Statistical Analysis for the Neutrinoless Double-Beta Decay Matrix Element of 136Xe

Neutrinoless double beta decay nuclear matrix element (M0ν) for 136Xe was recently analyzed using a statistical approach (Phys. Rev. C 107, 045501 (2023)). In the analysis, three initial shell model effective Hamiltonians were randomly altered, and their results for 23 measured observables were used to infer credibility for the M0ν nuclear matrix element (NME) based on a Bayesian Model Averaging approach. In that analysis, a reasonable Gamow-Teller quenching factor of 0.7 was assumed for each starting effective Hamiltonian. Given that the result of the statistical analysis was sensible to this choice, we are here improving that analysis by assuming that the Gamow-Teller quenching factor is also randomly chosen within reasonabe limits for all three starting Hamiltonians. The outcomes are slightly higher expectation values and uncertainties for the M0ν NME.

Astronomy & Astrophysics↗
DOE OSTI2025

A Comparison Between Industrial Energy Efficiency Measures in Guatemala and the United States

Energy auditing has been cited as a key tool in closing the gap between the actual energy consumption in industrial facilities and what should be at an environmentally sustainable level. Several factors affect the likelihood that energy audits will be effective in closing that gap, and more analysis is needed to understand these factors, especially for developing nations. This study compares three energy efficiency measures (EEMs) frequently recommended in both the United States and Guatemala, namely, installing solar panels to generate electricity, installing higher-efficiency lighting, and upgrading to premium efficiency motors. The implementation of each of these EEMs contributes to more sustainable energy consumption, and each of these EEM’s payback periods is affected by capital costs, energy costs, and other local factors analyzed in this study. Projected payback periods for each EEM based on Guatemalan and U.S. capital cost and energy cost ranges are assessed via EEM-specific payback period calculations and compared to the energy audit data from each country. While lower capital costs incentivize EEM implementation and reduce payback periods, there is an interplay between energy cost and capital cost that impacts the trends in the U.S. and Guatemala. As in the case of the solar panel installation EEM, though Guatemalan companies pay ~110% more for electricity than U.S. companies, when Guatemalan capital costs are lower, payback periods are lower than in the U.S. Conversely, in cases where Guatemalan capital costs are higher—as for higher-efficiency lighting and motor installation—Guatemalan payback periods are roughly the same as those in the U.S. because of the higher Guatemalan energy costs.

Khosla, Radhika↗
NASA NTRS2000

Finite Element Analysis of Reverberation Chambers

The primary motivating factor behind the initiation of this work was to provide a deterministic means of establishing the validity of the statistical methods that are recommended for the determination of fields that interact in -an avionics system. The application of finite element analysis to reverberation chambers is the initial step required to establish a reasonable course of inquiry in this particularly data-intensive study. The use of computational electromagnetics provides a high degree of control of the "experimental" parameters that can be utilized in a simulation of reverberating structures. As the work evolved there were four primary focus areas they are: 1. The eigenvalue problem for the source free problem. 2. The development of a complex efficient eigensolver. 3. The application of a source for the TE and TM fields for statistical characterization. 4. The examination of shielding effectiveness in a reverberating environment. One early purpose of this work was to establish the utility of finite element techniques in the development of an extended low frequency statistical model for reverberation phenomena. By employing finite element techniques, structures of arbitrary complexity can be analyzed due to the use of triangular shape functions in the spatial discretization. The effects of both frequency stirring and mechanical stirring are presented. It is suggested that for the low frequency operation the typical tuner size is inadequate to provide a sufficiently random field and that frequency stirring should be used. The results of the finite element analysis of the reverberation chamber illustrate io-W the potential utility of a 2D representation for enhancing the basic statistical characteristics of the chamber when operating in a low frequency regime. The basic field statistics are verified for frequency stirring over a wide range of frequencies. Mechanical stirring is shown to provide an effective frequency deviation.

Bunting, Charles F.↗
DOE OSTI2015

Dynamic heterogeneity of DNA methylation and hydroxymethylation in embryonic stem cell populations captured by single-cell 3D high-content analysis

Cell-surface markers and transcription factors are being used in the assessment of stem cell fate and therapeutic safety, but display significant variability in stem cell cultures. We assessed nuclear patterns of 5-hydroxymethylcytosine (5hmC, associated with pluripotency), a second important epigenetic mark, and its combination with 5-methylcytosine (5mC, associated with differentiation), also in comparison to more established markers of pluripotency (Oct-4) and endodermal differentiation (FoxA2, Sox17) in mouse embryonic stem cells (mESC) over a 10-day differentiation course in vitro: by means of confocal and super-resolution imaging together with 3D high-content analysis, an essential tool in single-cell screening. In summary: 1) We did not measure any significant correlation of putative markers with global 5mC or 5hmC. 2) While average Oct-4 levels stagnated on a cell-population base (0.015 lnIU/day), Sox17 and FoxA2 increased 22-fold and 3-fold faster, respectively (Sox17: 0.343 lnIU/day; FoxA2: 0.046 lnIU/day). In comparison, global DNA methylation levels increased 4-fold faster (0.068 lnIU/day), and global hydroxymethylation declined at 0.046 lnIU/day, both with a better explanation of the temporal profile. 3) This progression was concomitant with the occurrence of distinct nuclear codistribution patterns that represented a heterogeneous spectrum of states in differentiation; converging to three major coexisting 5mC/5hmC phenotypes by day 10: 5hmC{sup +}/5mC{sup −}, 5hmC{sup +}/5mC{sup +}, and 5hmC{sup −}/5mC{sup +} cells. 4) Using optical nanoscopy we could delineate the respective topologies of 5mC/5hmC colocalization in subregions of nuclear DNA: in the majority of 5hmC{sup +}/5mC{sup +} cells 5hmC and 5mC predominantly occupied mutually exclusive territories resembling euchromatic and heterochromatic regions, respectively. Simultaneously, in a smaller subset of cells we observed a tighter colocalization of the two cytosine variants, presumably delineating chromatin domains in remodeling. We conclude that 1) 5mC emerges as the most differential marker in our model system. 2) However, the combined enrollment of the two DNA modifications provided higher-definition screening and lead to the identification of cell subpopulations based on differential 5hmC/5mC phenotypes corresponding to different 5hmC/5mC ratios. The results encourage: a) assessing the regenerative potential of early-endodermal cells enriched for the three DNA methylation/hydroxymethylation categories, and b) exploring the universality of this type of epigenetic phenotyping across other lineage-specific differentiations. - Highlights: • First reported single-molecule super-resolution 3D-visualization of 5mC/5hmC sites in cells. • Identification of cells with differential 5mC/5hmC nuclear codistribution phenotypes. • Application of principle component and robust regression analyses for evaluation of 3D high-content-screening data. • Global 5mC constitutes a highly differential spatiotemporal in situ marker in early endodermal cell differentiation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

23.4% monolithic epitaxial GaAsP/Si tandem solar cells and quantification of losses from threading dislocations

A 2-terminal, dual-junction, epitaxially integrated, GaAsP/Si tandem solar cell with an 3rd party certified efficiency of 23.4 % was fabricated via MOCVD growth on an ex-situ produced Si sub cell. The drastic efficiency improvement over the authors previous peer-reviewed demonstration of such a device architecture is examined. Critical advancements in top cell design to maximize short wavelength response were critical in enabling improved top cell response. An in-depth analysis of this champion tandem cell has identified key loss mechanisms which elucidate the pathway for further efficiency gains. First, voltage dependent collection efficiency in the GaAsP top cell is the primary cause of fill factor losses currently limiting efficiency. Analysis of spectrally resolved I–V measurements and analytical device modeling and indicate poor diffusion length due to elevated dislocation densities as the likely cause for the voltage dependent collection efficiency. Second, modeling for the GaAs 0.75 P 0.25 top cell, using experimental data at multiple dislocation densities, provides quantitative understanding of the current and voltage losses associated with threading dislocations providing a clear efficiency pathway with reduction in dislocation density. Finally, Si subcell modeling identifies the pathway for further Si subcell advances over the present, simplistic design, which has yet to employ the known benefits of rear surface texture or dielectric passivation.

14 SOLAR ENERGY↗
DOE OSTI2017

Market-driven automotive industry compliance with fuel economy and greenhouse gas standards: Analysis based on consumer choice

This paper explored factors that affect market-driven compliance with both Corporate Average Fuel Economy (CAFE) and greenhouse gas (GHG) standards (together called the National Program) in the United States for phase I 2012–2016 and phase II 2017–2025. We considered a consumer-choice-based simulation approach, using the MA3T model, to estimate the market acceptance of fuel efficiency (FE) technologies and alternative fuel technologies as reflected by new sales of light-duty vehicle (LDV). Because both full and extremely low FE valuations are common in the literature, we use a moderate assumption of a 10-year perceived vehicle lifetime at a 7% annual discount rate in the baseline and include both extreme views (5 years and 15 years) in the sensitivity analysis. The study focuses on market-driven compliance and therefore excludes manufacturers’ cross-subsidization. The model results suggest that the LDV industry is able to comply with both standards even without cross-subsidization and with projected high technology cost, mainly thanks to the multiple credit programs and technology advancements. The compliance robustness, while encouraging, however is based on moderate market assumptions, such as Annual Energy Outlook 2016 Reference oil price projection and moderate FE consumer valuation. Finally, sensitivity analysis results reveal two significant risk factors for compliance: low oil prices and consumers’ FE undervaluation.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1994

OARE flight maneuvers and calibration measurements on STS-58

The Orbital Acceleration Research Experiment (OARE), which has flown on STS-40, STS-50, and STS-58, contains a three axis accelerometer with a single, nonpendulous, electrostatically suspended proofmass which can resolve accelerations to the nano-g level. The experiment also contains a full calibration station to permit in situ bias and scale factor calibration. This on-orbit calibration capability eliminates the large uncertainty of ground-based calibrations encountered with accelerometers flown in the past on the orbiter, thus providing absolute acceleration measurement accuracy heretofore unachievable. This is the first time accelerometer scale factor measurements have been performed on orbit. A detailed analysis of the calibration process is given along with results of the calibration factors from the on-orbit OARE flight measurements on STS-58. In addition, the analysis of OARE flight maneuver data used to validate the scale factor measurements in the sensor's most sensitive range is also presented. Estimates on calibration uncertainties are discussed. This provides bounds on the STS-58 absolute acceleration measurements for future applications.

Blanchard, Robert C.↗
DOE OSTI2022

Surface analysis insight note: Synthetic line shapes, integration regions and relative sensitivity factors

Here, methods for estimating photoemission intensity from X-ray photoelectron spectroscopy data are examined. The role played by “synthetic” bell-shaped curves, integration intervals, background curves, and the use of relative sensitivity factors (RSFs) in reporting percentage atomic concentration for a sample is presented. In particular, photoemission lines with differing energy distributions obtained from the NaCl sample surface are used to demonstrate how a comparison of photoemission intensities is dependent on the line shapes, background curves, and appropriate use of RSFs.

42 ENGINEERING↗