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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 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Spectral Characterization of Suspected Acid Deposition Damage in Red Spruce (picea Rubens) Stands from Vermont

In an attempt to demonstrate the utility of remote sensing systems to monitor sites of suspected acid rain deposition damage, intensive field activities, coupled with aircraft overflights, were centered on red spruce stands in Vermont during August and September of 1984. Remote sensing data were acquired using the Airborne Imaging Spectrometer, Thematic Mapper Simulator, Barnes Model 12 to 1000 Modular Multiband Radiometer and Spectron Engineering Spectrometer (the former two flown on the NASA C-130; the latter two on A Bell UH-1B Iroquois Helicopter). Field spectral data were acquired during the week of the August overflights using a high spectral resolution spectrometer and two broad-band radiometers. Preliminary analyses of these data indicate a number of spectral differences in vegetation between high and low damage sites. Some of these differences are subtle, and are observable only with high spectral resolution sensors; others are less subtle and are observable using broad-band sensors.

Vogelmann, J. E.↗
NASA NTRS1986

Laser Docking System Radar flight experiment

Flight experiments to verify the Laser Docking System Radar are discussed. The docking requirements are summarized, and the breadboarded hardware is described, emphasizing the two major scanning concepts being utilized: a mechanical scanning technique employing galvanometer beamsteerers and an electronic scanning technique using an image dissector. The software simulations used to apply hardware solutions to the docking requirements are briefly discussed, the tracking test bed is described, and the objectives of the flight experiment are reviewed.

Erwin, Harry O.↗
NASA NTRS1993

Advanced ballistic range technology

Optical images, such as experimental interferograms, schlieren, and shadowgraphs, are routinely used to identify and locate features in experimental flow fields and for validating computational fluid dynamics (CFD) codes. Interferograms can also be used for comparing experimental and computed integrated densities. By constructing these optical images from flow-field simulations, one-to-one comparisons of computation and experiment are possible. During the period from February 1, 1992, to November 30, 1992, work has continued on the development of CISS (Constructed Interferograms, Schlieren, and Shadowgraphs), a code that constructs images from ideal- and real-gas flow-field simulations. In addition, research connected with the automated film-reading system and the proposed reactivation of the radiation facility has continued.

Yates, Leslie A.↗
NASA NTRS1992

HST PSF simulation using Tiny Tim

Tiny Tim is a program which simulates Hubble Space Telescope imaging camera PSF's. It is portable (written and distributed in C) and is reasonably fast. It can model the WFPC, WFPC 2, FOC, and COSTAR corrected FOC cameras. In addition to aberrations such as defocus and spherical, it also includes WFPC obscuration shifting, mirror zonal error maps, and jitter. The program has been used at a number of sites for deconvolving HST images. Tiny Tim is available via anonymous ftp on stsci.edu in the directory software/tinytim.

Krist, J. E.↗
NASA NTRS1995

CAE for thermal management of aerospace electronic boards using the BETAsoft program

Aerospace electronic boards require special attention to thermal management due to constraints such as their need to be light, small, and maintain high power densities. Also, cooling is mainly through conductive and radiative modes with minor or negligible convective cooling. Due to these particular requirements, thermal design has become an integrated part of the electronic design process in order to avoid expensive repeat prototyping and to ensure high reliability. To achieve high speed simulations, the BETAsoft code uses semi-empirical formulations and an advanced finite difference scheme that incorporates local adaptive grids. Detailed conduction, convection and radiation heat transfer is considered. Various benchmark verifications of the software simulation compared to infrared images typically prove to be within 10% of each other. The thermal analysis of a sample avionic card in a natural convection environment is shown. Then, the individual effects of attaching metal screws to the casing, increasing radiative emissivities of the casing, increasing the conductance of the wedge lock, adding an aluminum core to the board, adding metal strips in board layers, inserting conduction pads under components, and adding heat sinks to components are demonstrated.

Bobish, Kimberly↗
NASA NTRS1997

Endothelial Cell Morphology and Migration are Altered by Changes in Gravitational Fields

Endothelial cell migration is important to vascular wall regeneration following injury or stress. However, the mechanism(s) governing this response is not well understood. The microgravity environment of space may complicate the response of these cells to injury. To date, there are no reports in this area. We examined how bovine aortic (BAEC) and pulmonary (BPEC) endothelial cells respond to denudation injury under hypergravity (HGrav) and simulated microgravity (MGrav), using image analysis. In 10% FBS, the migration of confluent BAEC and BPEC into the denuded area was not affected by HGrav or MGrav. However, in low FBS (0.5%), signficantly retarded migration under MGrav, and increased migration under HGrav was found. MGrav also decreased the migration of postconfluent BPEC while HGrav showed no difference. Both MGrav and HGrav strongly decreased the migration of postconfluent BAEC. Also, both cell lines showed significant morphological changes by scanning electron microscopy. These studies indicate that endothelial cell function is affected by changes in gravity.

Melhado, Caroline↗
NASA NTRS1999

Hyperspectral Remote Sensing and Ecological Modeling Research and Education at Mid America Remote Sensing Center (MARC): Field and Laboratory Enhancement

The purpose of this project was to establish a new hyperspectral remote sensing laboratory at the Mid-America Remote sensing Center (MARC), dedicated to in situ and laboratory measurements of environmental samples and to the manipulation, analysis, and storage of remotely sensed data for environmental monitoring and research in ecological modeling using hyperspectral remote sensing at MARC, one of three research facilities of the Center of Reservoir Research at Murray State University (MSU), a Kentucky Commonwealth Center of Excellence. The equipment purchased, a FieldSpec FR portable spectroradiometer and peripherals, and ENVI hyperspectral data processing software, allowed MARC to provide hands-on experience, education, and training for the students of the Department of Geosciences in quantitative remote sensing using hyperspectral data, Geographic Information System (GIS), digital image processing (DIP), computer, geological and geophysical mapping; to provide field support to the researchers and students collecting in situ and laboratory measurements of environmental data; to create a spectral library of the cover types and to establish a World Wide Web server to provide the spectral library to other academic, state and Federal institutions. Much of the research will soon be published in scientific journals. A World Wide Web page has been created at the web site of MARC. Results of this project are grouped in two categories, education and research accomplishments. The Principal Investigator (PI) modified remote sensing and DIP courses to introduce students to ii situ field spectra and laboratory remote sensing studies for environmental monitoring in the region by using the new equipment in the courses. The PI collected in situ measurements using the spectroradiometer for the ER-2 mission to Puerto Rico project for the Moderate Resolution Imaging Spectrometer (MODIS) Airborne Simulator (MAS). Currently MARC is mapping water quality in Kentucky Lake and vegetation in the Land-Between-the Lakes (LBL) using Landsat-TM data. A Landsat-TM scene of the same day was obtained to relate ground measurements to the satellite data. A spectral library has been created for overstory species in LBL. Some of the methods, such as NPDF and IDFD techniques for spectral unmixing and reduction of effects of shadows in classifications- comparison of hyperspectral classification techniques, and spectral nonlinear and linear unmixing techniques, are being tested using the laboratory.

Cetin, Haluk↗
NASA NTRS1999

Effects on Training Using Illumination in Virtual Environments

Camera based tasks are commonly performed during orbital operations, and orbital lighting conditions, such as high contrast shadowing and glare, are a factor in performance. Computer based training using virtual environments is a common tool used to make and keep CTW members proficient. If computer based training included some of these harsh lighting conditions, would the crew increase their proficiency? The project goal was to determine whether computer based training increases proficiency if one trains for a camera based task using computer generated virtual environments with enhanced lighting conditions such as shadows and glare rather than color shaded computer images normally used in simulators. Previous experiments were conducted using a two degree of freedom docking system. Test subjects had to align a boresight camera using a hand controller with one axis of rotation and one axis of rotation. Two sets of subjects were trained on two computer simulations using computer generated virtual environments, one with lighting, and one without. Results revealed that when subjects were constrained by time and accuracy, those who trained with simulated lighting conditions performed significantly better than those who did not. To reinforce these results for speed and accuracy, the task complexity was increased.

Maida, James C.↗
NASA NTRS2004

Orbit Optimization and Scattering Coefficient Analysis for the Proposed GLORIA System

This paper investigates the optimization of an orbit for a Low-Earth Orbiting (LEO) satellite for coastal coverage over Antarctic and United States shorelines as part of the Geostationary/Low-Earth Orbiting Radar Image Acquisition (GLORIA) System. Simulations over a range of orbital parameters are performed to determine the optimal orbit. Scattering coefficients are computed for the optimal orbit throughout the day and characterized to compare various scenarios for which link budget comparisons could then be made.

Welch, Bryan↗
NASA NTRS2017

Surface-Height Determination of Crevassed Glaciers-Mathematical Principles of an Autoadaptive Density-Dimension Algorithm and Validation Using ICESat-2 Simulator (SIMPL) Data

Glacial acceleration is a main source of uncertainty in sea-level-change assessment. Measurement of ice-surface heights with a spatial and temporal resolution that not only allows elevation-change calculation, but also captures ice-surface morphology and its changes is required to aid in investigations of the geophysical processes associated with glacial acceleration.The Advanced Topographic Laser Altimeter System aboard NASAs future ICESat-2 Mission (launch 2017) will implement multibeam micropulse photon-counting lidar altimetry aimed at measuring ice-surface heights at 0.7-m along-track spacing. The instrument is designed to resolve spatial and temporal variability of rapidly changing glaciers and ice sheets and the Arctic sea ice. The new technology requires the development of a new mathematical algorithm for the retrieval of height information.We introduce the density-dimension algorithm (DDA) that utilizes the radial basis function to calculate a weighted density as a form of data aggregation in the photon cloud and considers density an additional dimension as an aid in auto-adaptive threshold determination. The auto-adaptive capability of the algorithm is necessary to separate returns from noise and signal photons under changing environmental conditions. The algorithm is evaluated using data collected with an ICESat-2 simulator instrument, the Slope Imaging Multi-polarization Photon-counting Lidar, over the heavily crevassed Giesecke Braer in Northwestern Greenland in summer 2015. Results demonstrate that ICESat-2 may be expected to provide ice-surface height measurements over crevassed glaciers and other complex ice surfaces. The DDA is generally applicable for the analysis of airborne and spaceborne micropulse photon-counting lidar data over complex and simple surfaces.

Herzfeld, Ute C.↗
NASA NTRS2017

Characteristic of a Digital Correlation Radiometer Back-End with Finite Wordlength

Performance of a radiometer DBE is analyzed. The particular design corresponds to the DBE of the airborne Hurricane Imaging Radiometer. A computer simulator is developed to analyze effect of input power on various DBE output products. 2nd moment non-linearity is found to be negligible in the expected input signal dynamic range. Observed scaling between I and Q channels and the scaling among cross-correlation signals are verified by the simulator. Kurtosis sensitivity can be improved by lowering the input power - predicted by the simulator and verified in the lab.

radiometry↗
NASA NTRS2019

A Robust Vision-Based Algorithm for Detecting and Classifying Small Orbital Debris Using On-Board Optical Cameras

This study develops a vision-based detection and classification algorithm to address the challenges of in-situ small orbital debris environment classification including debris observability and instrument requirements for small debris observation. The algorithm operates in near real time and is robust under difficult tasks in moving objects classification such as multiple moving objects, objects with various movement trajectories and speeds, very small or faint objects, and substantial background motion. The performance of the algorithm is optimized and validated using space image data available through simulated environments generated using NASA Marshall Space Flight Centers Dynamic Star Field Simulator of on-board optical sensors and cameras.

Zamani, Yasin↗
NASA NTRS2020

Bioinspired multilayered cellular composites with enhanced energy absorption and shape recovery

Inspired by the multiscale configuration of the microstructure of cork, the paper describes the design, 3D printing, and evaluation of a new type of multilayered cellular composite (MCC) structure composed of hard brittle and soft flexible phases. The mechanical behavior of 3D printed MCC structures have been investigated both experimentally and numerically. The experiments show that the MCC structure absorbs four times the amount of energy of a conventional cellular configuration under compressive strains up to 70%. Finite element simulations and 2D digital image correlation (DIC) also show that the multilayered architecture provides a more uniform strain distribution and higher stress transfer efficiency, with a resulting progressive failure mode rather than a catastrophic one. Cyclic loading tests demonstrate that the MCC structure also possesses exceptional shape recoverability under compressive deformations up to 40%. These remarkable performance characteristics result from synergies between the properties of the two constituent materials and the chosen multilayered cellular microstructure. The soft phase, in particular, plays a pivotal role in absorbing elastic energy during loading and then releasing the stored energy while unloading. The volume fraction of the soft phase is also essential to control energy absorption and the transition of failure modes. The deformation mechanisms demonstrated here are robust and applicable to other architected cellular materials across multiple length scales and suggest new ways to design lightweight and high-resilience structural materials.

bioinspired composites↗
NASA NTRS2005

An optical vortex coronagraph

In this manuscript, I will discuss the aberration sensitivity of an optical vortex coronagraph and the key advantages it may hold over other coronagraph architectures. I will also provide numerical simulations demonstrating high contrast imaging in the presence of low-order static aberrations.

Palacios, David M.↗
NASA NTRSDate not supplied

Development of a Terrain Mapping/Crater Evolution Measurement using Diffractive Optical Elements

When landing on the moon, understanding the interaction of the engine exhaust plume with the lunar surface is critical for the success of the descent and landing flight phases. Two evaluation tools currently used are computational simulations and ground test measurements. Computational simulations require experimental measurements for comparison/validation, but ground test measurements cannot accurately emulate all aspects of an actual lunar landing; flight tests remain the only method of obtaining fully representative data. A terrain mapping/crater evolution measurement system was developed for potential inclusion on a future lander mission. This system uses two stereo cameras viewing a laser dot grid pattern projected on the ground, where the grid is created by shining a laser through one or two diffractive optical elements. CAD simulations of the stereo imaging system are first used to validate the proposed design. Laboratory testing of the system using both a large-scale fixed-geometry crater and a small-scale evolving-geometry crater validate the use of the system for terrain mapping measurements, and for its potential inclusion on a future lander mission.

Joshua M Weisberger↗
NASA NTRSDate not supplied

Development of a Terrain Mapping/Crater Evolution Measurement using Diffractive Optical Elements

When landing on the moon, understanding the interaction of the engine exhaust plume with the lunar surface is critical for the success of the descent and landing flight phases. Two evaluation tools currently used are computational simulations and ground test measurements. Computational simulations require experimental measurements for comparison/validation, but ground test measurements cannot accurately emulate all aspects of an actual lunar landing; flight tests remain the only method of obtaining fully representative data. A terrain mapping/crater evolution measurement system was developed for potential inclusion on a future lander mission. This system uses two stereo cameras viewing a laser dot grid pattern projected on the ground, where the grid is created by shining a laser through one or two diffractive optical elements. CAD simulations of the stereo imaging system are first used to validate the proposed design. Laboratory testing of the system using both a large-scale fixed-geometry crater and a small-scale evolving-geometry crater validate the use of the system for terrain mapping measurements. High-speed, front-illumination shadow particle tracking of particles ejected from the evolving geometry crater is also performed, demonstrating another diagnostic that can be used to further the understanding of plume-surface interactions.

Joshua M Weisberger↗
NASA NTRS2022

SKYSURF: Constraints on Zodiacal Light and Extragalactic Background Light through Panchromatic HST All-sky Surface-brightness Measurements. I. Survey Overview and Methods

We give an overview and describe the rationale, methods, and testing of the Hubble Space Telescope (HST) Archival Legacy project "SKYSURF." SKYSURF uses HST's unique capability as an absolute photometer to measure the ∼0.2–1.7 μm sky-surface brightness (sky-SB) from 249,861 WFPC2, ACS, and WFC3 exposures in ∼1400 independent HST fields. SKYSURF's panchromatic data set is designed to constrain the discrete and diffuse UV to near-IR sky components: Zodiacal Light (ZL), Kuiper Belt Objects (KBOs), Diffuse Galactic Light (DGL), and the discrete plus diffuse Extragalactic Background Light (EBL). We outline SKYSURF's methods to: (1) measure sky-SB levels between detected objects; (2) measure the discrete EBL, most of which comes from AB≃17–22 mag galaxies; and (3) estimate how much truly diffuse light may exist. Simulations of HST WFC3/IR images with known sky values and gradients, realistic cosmic ray (CR) distributions, and star plus galaxy counts were processed with nine different algorithms to measure the "Lowest Estimated Sky-SB" (LES) in each image between the discrete objects. The best algorithms recover the LES values within 0.2% when there are no image gradients, and within 0.2%–0.4% when there are 5%–10% gradients. We provide a proof of concept of our methods from the WFC3/IR F125W images, where any residual diffuse light that HST sees in excess of zodiacal model predictions does not depend on the total object flux that each image contains. This enables us to present our first SKYSURF results on diffuse light in Carleton et al.

Hubble Space Telescope↗