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Results for “sensitivity estimation”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Residual acceleration data on IML-1: Development of a data reduction and dissemination plan

A residual acceleration data analysis plan is developed that will allow principal investigators of low-gravity experiments to efficiently process their experimental results in conjunction with accelerometer data. The basic approach consisted of the following program of research: (1) identification of sensitive experiments and sensitivity ranges by order of magnitude estimates, numerical modelling, and investigator input; (2) research and development towards reduction, supplementation, and dissemination of residual acceleration data; and (3) implementation of the plan on existing acceleration data bases.

Rogers, Melissa J. B.↗
NASA NTRS1992

TOPEX/Poseidon orbit acquisition maneuver design

The current baseline injection orbit for the jointly sponsored NASA/CNES TOPEX/Poseidon mission is near-circular, approximately 30 km below the desired operational orbit altitude and at the operational orbit inclination. A baseline maneuver sequence to retarget from this injection orbit to the desired operational orbit has been designed based upon the expected worst-case 3-sigma injection and maneuver execution errors. The sequence requires seven maneuvers, including an initial calibration burn, and achieves the operational orbit with the desired ground track pattern in 30 days. A delay sensitivity analysis has been conducted to estimate the allowable operational delay for each maneuver without increasing the total orbit acquisition period. The baseline sequence provides back-ups for a one-revolution delay for each maneuver and one-day delay for most maneuvers. It is also shown that a higher injection orbit allows the maneuver sequence to achieve the operational orbit in 26 days under a worst-case scenario.

Bhat, Ramachandra S.↗
NASA NTRS1992

The solution of coupled Schroedinger equations using an extrapolation method

In this paper, extrapolation to the limit in a finite-difference method is applied to solve a system of coupled Schroedinger equations. This combination results in a method that only requires knowledge of the potential energy functions for the system. This numerical procedure has several distinct advantages over the more conventional methods. Namely, initial guesses for the term values are not needed; assumptions need be made about the behavior of the wavefunctions, such as the slope or magnitude in the nonclassical region; and the algorithm is easy to implement, has a firm mathematical foundation, and provides error estimates. Moreover, the method is less sensitive to round-off error than other methods since a small number of mesh points is used and it can be implemented on small computers. A comparison of the method with another numerical method shows results agreeing within 1 part in 10 exp 4.

Goorvitch, D.↗
NASA NTRS1993

Residual acceleration data on IML-1: Development of a data reduction and dissemination plan

The research performed consisted of three stages: (1) identification of sensitive IML-1 experiments and sensitivity ranges by order of magnitude estimates, numerical modeling, and investigator input; (2) research and development towards reduction, supplementation, and dissemination of residual acceleration data; and (3) implementation of the plan on existing acceleration databases.

Rogers, Melissa J. B.↗
NASA NTRS1992

Gamma-ray monitoring of AGN and galactic black hole candidates by the Gamma-Ray Observatory

The Burst and Transient Spectroscopy Experiment (BATSE) on the Compton Gamma-Ray Observatory has a powerful capability to provide nearly uninterrupted monitoring in the 25 keV-10 MeV range of both AGN and Galactic black hole candidates such as Cygnus X-1, using the occultation of cosmic sources by the Earth. Progress in background modeling indicates that the data accept region, or fit window tau, around the occultation step can be substantially increased over that conservatively assumed in earlier estimates of BATSE's Earth occultation sensitivity. We show samples of large-tau fits to background and source edges. As a result we expect to be able to perform long-term monitoring of Cygnus X-1 and many of the brighter AGN for the duration of the CGRO mission.

Wheaton, Wm. A.↗
NASA NTRS1993

Global variations of zonal mean ozone during stratospheric warming events

Eight years of Solar Backscatter Ultraviolet (SBUV) ozone data are examined to study zonal mean variations associated with stratospheric planetary wave (warming) events. These fluctuations are found to be nearly global in extent, with relatively large variations in the tropics, and coherent signatures reaching up to 50 deg in the opposite (summer) hemisphere. These ozone variations are a manifestation of the global circulation cells associated with stratospheric warming events; the ozone responds dynamically in the lower stratosphere to transport, and photochemically in the upper stratosphere to the circulation-induced temperature changes. The observed ozone variations in the tropics are of particular interest because transport is dominated by zonal-mean vertical motions (eddy flux divergences and mean meridional transports are negligible), and hence, substantial simplifications to the governing equations occur. The response of the atmosphere to these impulsive circulation changes provides a situation for robust estimates of the ozone-temperature sensitivity in the upper stratosphere.

Randel, William J.↗
NASA NTRS1997

The polarimetric capabilities of NICMOS

The polarimetric capabilities of Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) are demonstrated from data obtained during the Early Release Observations of IRC+10216 and CRL 2688 (the Egg Nebula). Preflight Thermal Vacuum tests revealed that each polarizer has a unique polarizing efficiency, and that the position angle offsets differ from the nominal positions of O deg, 120 deg and 240 deg. Therefore an algorithm different from that of an ideal polarizer is required for proper reduction of astronomical polarimetry data. We discuss this new algorithm and the results of its application to NICMOS data. We also present preliminary estimates of the Instrumental Polarization, the sensitivity of the grisms to polarized light, and the accuracy of NICMOS imaging polarimetry for faint and low polarization objects. Finally, we suggest strategies for maximizing the success of NICMOS polarimetry observations.

Hines, D. C.↗
NASA NTRS1995

An Extended Ab Initio and Theoretical Thermodynamics Studies of the Bergman Reaction and the Energy Splitting of the Singlet Ortho-, Meta-, and Para-Benzynes

The autoaromatization of (Z)-hex-3-ene-1,5-diyne to the singlet biradical para-benzyne has been reinvestigated by state of the art ab initio methods. Previous CCSD(T)/6-31G(d,p) and CASPT2[0]/ANO[C(5s4p2d1f)/H(3s2p)] calculations estimated the the reaction heat at 298 K to be 8-10 and 4.9 plus or minus 3.2 kcal/mol, respectively. Recent NO- and oxygen-dependent trapping experiments and collision-induced dissociation threshold energy experiments estimate the heat of reaction to be 8.5 plus or minus 1.0 at 470 K (recomputed to 9.5 plus or minus 1.0 at 298 K) and 8.4 plus or minus 3.0 kcal/mol at 298 K, respectively. New theoretical estimates at 298 K predict the values at the basis set limit for the CCSD(T) and CASPT2(g1) methods to be 12.7 plus or minus 2.0 and 5.4 plus or minus 2.0 kcal/mol, respectively. The experimentally predicted electronic contribution to the heat of activation is 28.6 kcal/mol. This can be compared with 25.5 and 29.8 kcal/mol from the CASPT2[g1] and the CCSD(T) methods, respectively. The new study has in particular improved on the one-particle basis set for the CCSD(T) method as compared to earlier studies. For the CASPT2 investigation the better suited CASPT2[g1] approximation is utilized. The original CASPT2 method, CASPT2[0], systematically favors open shell systems relative to closed shell systems. This was previously corrected empirically. The study shows that the energy difference between CCSD(T) and CASPT2[g1] at the basis set limit is estimated to be 7 plus or minus 2 kcal/mol. The study also demonstrates that the estimated heat of reaction is very sensitive to the quality of the basis set.

Lindh, Roland↗
NASA NTRS2001

Yb fiber laser pumped mid-IR source based on difference frequency generation and its application to ammonia detection

A Yb fiber laser pumped cw narrow-linewidth tunable mid-IR source based on a difference frequency generation (DFG) in a periodically poled LiNbO3 (PPLN) crystal for trace gas detection was demonstrated. A high power Yb fiber laser and a distributed feedback (DFB) laser diode were used as DFG pump sources. This source generated mid-IR at 3 microns with a powers of ~2.5 microW and a spectral linewidth of less than 30 MHz. A frequency tuning range of 300 GHz (10 cm-1) was obtained by varying the current and temperature of the DFB laser diode. A high-resolution NH3 absorption Doppler-broadened spectrum at 3295.4 cm-1 (3.0345 microns) was obtained at a cell pressure of 27 Pa from which a detection sensitivity of 24 ppm m was estimated.

NASA Discipline Environmental Health↗
NASA NTRS2006

Using SCIAMACHY and Ground-based FTS Measurements to Test the OCO X(sub CO2) Retrieval and Validation Approach

Global, space-based observations of atmospheric CO2 with precision, resolution, and coverage needed to monitor sources and sinks: a) Spectra of reflected/scattered sunlight in NIR CO2 and O2 bands used to estimate X(sub CO2) with large sensitivity to surface; b) A-train orbit (1:15 PM polar sun sync); c) 16 day repeat cycle samples seasonal cycle on semi-monthly intervals; and d) NASA ESSP (Earth Space System Pathfinder) scheduled for Sept 2008 launch; 2 yrs lifetime. Initial comparison of SCIAMACHY and FTS retrievals for Park Falls: a) Positive bias in X(sub CO2) of approx. 10 ppm; and b) Negative bias in surface pressure After correction of spectral artifacts in O2A band: a) Largely improved agreement between SCIAMACHY and FTS X(sub CO2) (without clear bias) and in surface pressure; and b) Standard deviation of SCIAMACHY X(sub CO2 approx. 6 ppm. Good qualitative agreement with GEOS-CHEM, with GEOS-CHEM underestimating seasonal cycle. OCO is a dedicated CO2 instrument and will achieve much higher accuracy and precision: a) much higher spectral resolution (by factor of 20); and b) smaller ground pixels (by factor of 600).

CO2 measurements↗
NASA NTRS2007

Impacts of Center of Mass Shifts on Messenger Spacecraft Operations

The MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) has successfully completed its first three years of flight operations following launch on August 3, 2004. As part of NASA s Discovery Program, MESSENGER will observe Mercury during flybys in 2008 and 2009, as well as from orbit beginning in March 2011. This paper discusses the impact that center of mass (CM) location changes have had on many mission activities, particularly angular momentum management and maneuver execution. Momentum trends were altered significantly following the first deep-space maneuver, and these changes were related to a change in the CM. The CM location also impacts maneuver execution, and uncertainties in its location led to the significant direction errors experienced at trajectory correction maneuver 11. Because of the spacecraft sensitivity to CM location, efforts to estimate its position are important to momentum and maneuver prediction. This paper summarizes efforts to estimate the CM from flight data, as well as the operational strategy to handle CM uncertainties and their impact on momentum trends and maneuver execution accuracy.

O'Shaughnessy, D. J.↗
NASA NTRS2008

Assimilation of Aura Ozone Data and Comparisons with In Situ Observations

Ozone data from the Ozone Monitoring Instrument (OMI) and the Microwave Limb Sounder (MLS) onboard EOS Aura satellite were assimilated into the Goddard Earth Observing System Version 4 (GEOS-4) ozone assimilation system. Comparison of assimilated ozone with ozone sonde and MOZAIC data indicate an agreement within 10% in the lower stratosphere, where dynamical processes dominate. Assimilation of OMI and MLS data improves tropospheric column estimates in the Atlantic region, but leads to an overestimation in the tropical Pacific in comparison with SHADOZ sondes. Transport and data biases are considered in order to understand these discrepancies. Comparisons of assimilated tropospheric ozone columns with ozone sonde data reveal root-mean-square (RMS) differences of 2.9 to 7.2 DU, which are typically smaller than the model-sonde RMS differences. Four different definitions of the tropopause using temperature lapse rate, potential vorticity (PV) and isentropic surfaces or ozone isosurfaces are compared with respect to their global impact on the estimated tropospheric ozone column. The largest sensitivity in the tropospheric ozone column is found near the subtropical jet, where the ozone or PV determined tropopause typically lies below the lapse rate tropopause.

Stajner, Ivanka↗
NASA NTRS2009

NASA Tech Briefs, October 2009

Topics covered include: Light-Driven Polymeric Bimorph Actuators; Guaranteeing Failsafe Operation of Extended-Scene Shack-Hartmann Wavefront Sensor Algorithm; Cloud Water Content Sensor for Sounding Balloons and Small UAVs; Pixelized Device Control Actuators for Large Adaptive Optics; T-Slide Linear Actuators; G4FET Implementations of Some Logic Circuits; Electrically Variable or Programmable Nonvolatile Capacitors; System for Automated Calibration of Vector Modulators; Complementary Paired G4FETs as Voltage-Controlled NDR Device; Three MMIC Amplifiers for the 120-to-200 GHz Frequency Band; Low-Noise MMIC Amplifiers for 120 to 180 GHz; Using Ozone To Clean and Passivate Oxygen-Handling Hardware; Metal Standards for Waveguide Characterization of Materials; Two-Piece Screens for Decontaminating Granular Material; Mercuric Iodide Anticoincidence Shield for Gamma-Ray Spectrometer; Improved Method of Design for Folding Inflatable Shells; Ultra-Large Solar Sail; Cooperative Three-Robot System for Traversing Steep Slopes; Assemblies of Conformal Tanks; Microfluidic Pumps Containing Teflon[Trademark] AF Diaphragms; Transparent Conveyor of Dielectric Liquids or Particles; Multi-Cone Model for Estimating GPS Ionospheric Delays; High-Sensitivity GaN Microchemical Sensors; On the Divergence of the Velocity Vector in Real-Gas Flow; Progress Toward a Compact, Highly Stable Ion Clock; Instruments for Imaging from Far to Near; Reflectors Made from Membranes Stretched Between Beams; Integrated Risk and Knowledge Management Program -- IRKM-P; LDPC Codes with Minimum Distance Proportional to Block Size; Constructing LDPC Codes from Loop-Free Encoding Modules; MMICs with Radial Probe Transitions to Waveguides; Tests of Low-Noise MMIC Amplifier Module at 290 to 340 GHz; and Extending Newtonian Dynamics to Include Stochastic Processes.

Source record↗
NASA NTRS2017

New-Generation NASA Aura Ozone Monitoring Instrument (OMI) Volcanic SO2 Dataset: Algorithm Description, Initial Results, and Continuation with the Suomi-NPP Ozone Mapping and Profiler Suite (OMPS)

Since the fall of 2004, the Ozone Monitoring Instrument (OMI) has been providing global monitoring of volcanic SO2 emissions, helping to understand their climate impacts and to mitigate aviation hazards. Here we introduce a new-generation OMI volcanic SO2 dataset based on a principal component analysis (PCA) retrieval technique. To reduce retrieval noise and artifacts as seen in the current operational linear fit (LF) algorithm, the new algorithm, OMSO2VOLCANO, uses characteristic features extracted directly from OMI radiances in the spectral fitting, thereby helping to minimize interferences from various geophysical processes (e.g., O3 absorption) and measurement details (e.g., wavelength shift). To solve the problem of low bias for large SO2 total columns in the LF product, the OMSO2VOLCANO algorithm employs a table lookup approach to estimate SO2 Jacobians (i.e., the instrument sensitivity to a perturbation in the SO2 column amount) and iteratively adjusts the spectral fitting window to exclude shorter wavelengths where the SO2 absorption signals are saturated. To first order, the effects of clouds and aerosols are accounted for using a simple Lambertian equivalent reflectivity approach. As with the LF algorithm, OMSO2VOLCANO provides total column retrievals based on a set of predefined SO2 profiles from the lower troposphere to the lower stratosphere, including a new profile peaked at 13 km for plumes in the upper troposphere. Examples given in this study indicate that the new dataset shows significant improvement over the LF product, with at least 50% reduction in retrieval noise over the remote Pacific. For large eruptions such as Kasatochi in 2008 (approximately 1700 kt total SO2/ and Sierra Negra in 2005 (greater than 1100DU maximum SO2), OMSO2VOLCANO generally agrees well with other algorithms that also utilize the full spectral content of satellite measurements, while the LF algorithm tends to underestimate SO2. We also demonstrate that, despite the coarser spatial and spectral resolution of the Suomi National Polar-orbiting Partnership (Suomi-NPP) Ozone Mapping and Profiler Suite (OMPS) instrument, application of the new PCA algorithm to OMPS data produces highly consistent retrievals between OMI and OMPS. The new PCA algorithm is therefore capable of continuing the volcanic SO2 data record well into the future using current and future hyperspectral UV satellite instruments.

OMI↗
NASA NTRS2023

Accounting for Dose Uncertainty in Dose-Response Curve Estimation Using Hierarchical Bayes Models

As part of their development of the technology for low-boom supersonic flight, the National Aeronautics and Space Administration (NASA) is planning to conduct a set of supersonic aircraft annoyance surveys in select communities in the United States, to measure public perception of the reduced sonic boom. The relationship between a noise exposure level of a supersonic flight event and the probability of an individual being highly annoyed by the event is quantified by a dose-response curve, which is usually based on logistic regression modeling. Unavoidable amounts of estimation error are expected in the upcoming noise measurements, which can bias the results of the logistic regression if ignored. Hence, the development of an estimation approach that accounts for such error when estimating the dose-response curve is imperative. In this paper, an evaluation study is conducted to assess the impact of measurement error on dose-response curve estimation. For this, hierarchical Bayes models using different specifications are fit to data collected by NASA in 2018, as part of a risk-reduction study of supersonic flights affecting Galveston, Texas. It is observed that the estimated dose-response curve appears sensitive to uncertainty in dose measurements, being subject to attenuation bias.

community response↗
NASA NTRSDate not supplied

Joint Assimilation of CO, O3, NO2, SO2, PM, AOD, NH4, PAN, and HNO3 in Support of the Tropospheric Regional Atmospheric Composition and Emissions Reanalysis (2005 - 2024) (TRACER-I)

NASA Ames Research Center is collaborating with the NOAA Chemical Systems Laboratory (NOAA/CSL), the NASA Jet Propulsion Laboratory (JPL), the NASA Goddard Modeling and Assimilation Office, and the National Center for Atmospheric Research to prepare a 20-year Tropospheric Regional Atmospheric Composition and Emissions Reanalysis (2005 – 2024) (TRACER-I) for the continental United States during the summer ozone (O3) and wildfire seasons (April to October). TRACER-I will be a regional complement to JPL’s global Tropospheric Chemistry Reanalyses II and III. We will use WRF-Chem/DART with NOAA/CSL’s WRF-Chem setup at 12 km x 12 km horizontal resolution, 51 vertical levels, and 30 ensemble members. We will assimilate: (i) conventional meteorological observations; (ii) EPA’s Air Quality System in situ measurements of carbon monoxide (CO), O3, nitrogen dioxide (NO2), sulfur dioxide (SO2), particulate matter (PM) with diameters less than 10 µm (PM10), and PM with diameters less than 2.5 µm (PM2.5); and (iii) MOPITT, MODIS, OMI, TROPOMI, GOME-2a, MLS, TES, SCIAMACHY, CrIS, and TEMPO total/partial column and/or profile retrievals of CO, O3, NO2, SO2, aerosol optical depth (AOD), formaldehyde (HCHO), ammonia (NH4), peroxyacetyl nitrate (PAN), and/or nitric acid (HNO3) with 3-hr cycling. We will present an overview of this project, its status, and available results (likely the analysis of sensitivity experiment results from the assimilation/emissions estimation system).

data assimilation↗
NASA NTRSDate not supplied

Evaluating Combined Lidar and Polarimeter Measurements of Cloud Top Parameters (Extinction, Scattering Cross Sections, and Droplet Number Density, Liquid Water Content)

We present a new method to derive profiles of extinction from a lidar which is then combined with polarimeter measurements to derive cloud droplet number density (CDNC) in the tops of warm clouds. The method employs polarization-sensitive elastic backscatter lidar measurements to estimate attenuation of the lidar signal within the cloud and polarimeter estimates of cloud droplet size distributions. The measurements used for this demonstration are from NASA Langley Research Center’s High Spectral Resolution Lidar – Generation 2 (HSRL-2) and NASA GISS’s Research Scanning Polarimeter (RSP). The measurements were acquired on NASA’s ACTIVATE mission, during which the instruments were deployed in a down-looking mode from a high-altitude aircraft, which flew in coordination with a low-flying aircraft acquiring coincident in situ measurements of cloud droplet size and number. The high vertical (1.25 m) and horizontal (~50 m) sampling resolution of the HSRL-2 data enabled retrievals of single-scattering extinction profiles to within ~2.5 optical depths of cloud top. Another key feature of the method was the well-calibrated measurement of backscatter at cloud top due to using the HSRL technique. The RSP retrievals of cloud droplet effective radius and variance were accomplished using the “cloud-bow” technique. Overall, the technique provides extinction profile estimates for the top 2.5 optical depths of water clouds that can be used to estimate the cloud droplet number density in various types of warm clouds. The mean extinction values at cloud top (0-1 optical depth) are compared against cloud drop size and number concentration acquired from wing-mounted probes (e.g., DMT Cloud Droplet Probe - CDP, SPEC Fast Cloud Droplet Probe FCDP, and SPEC 2D Stereo Probe - 2DS) that were deployed on the low-flying aircraft. Comparisons between the effective radius and variance from the polarimeter, lidar ratio (extinction to backscatter) from the lidar and polarimeter, and LWC are also presented. All measurements were acquired over the Western North Atlantic over 3 years from 2020 to 2022.

lidar↗
NASA NTRSDate not supplied

Artemis I Space Launch System Base Heat Shield Thermal Protection System Performance

The Space Launch System (SLS) Core Stage base heat shield experienced the highest external heating environments on the entire launch vehicle during Artemis I ascent flight. This result was consistent with design predictions. The base heat shield experiences P50 cork combustion dynamics at low altitudes, plume-induced recirculation at moderate altitudes and then in-space base flow physics out to Main Engine Cut-Off (MECO). The base heat shield thermal protection system (TPS) is composed of a P50 cork ablator which is bonded to a substrate. The heat shield protects the gimbal actuation system, RS-25 turbomachinery systems and other aft section sensitive components during ascent. This paper estimates the base heat shield TPS performance from Artemis I using flight data from the NASA Langley Research Center’s Scientifically Calibrated In-Flight Imagery (SCIFLI) Airborne Multispectral Imager (SAMI), development flight instrumentation (DFI) and other TPS recession flight measurements. Predictions from computational and ground test-derived engineering ablation models and observations are also applied. Since no base heat shield substrate thermocouple data were obtained for Artemis I, an estimate of the TPS performance data is derived here. This data assesses thermal margin of the SLS Core Stage base heat shield and best informs the Artemis II Crewed mission to the moon.

aerothermodynamics↗