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NASA NTRS1998

Elementary Theoretical Forms for the Spatial Power Spectrum of Earth's Crustal Magnetic Field

The magnetic field produced by magnetization in Earth's crust and lithosphere can be distinguished from the field produced by electric currents in Earth's core because the spatial magnetic power spectrum of the crustal field differs from that of the core field. Theoretical forms for the spectrum of the crustal field are derived by treating each magnetic domain in the crust as the point source of a dipole field. The geologic null-hypothesis that such moments are uncorrelated is used to obtain the magnetic spectrum expected from a randomly magnetized, or unstructured, spherical crust of negligible thickness. This simplest spectral form is modified to allow for uniform crustal thickness, ellipsoidality, and the polarization of domains by an periodically reversing, geocentric axial dipole field from Earth's core. Such spectra are intended to describe the background crustal field. Magnetic anomalies due to correlated magnetization within coherent geologic structures may well be superimposed upon this background; yet representing each such anomaly with a single point dipole may lead to similar spectral forms. Results from attempts to fit these forms to observational spectra, determined via spherical harmonic analysis of MAGSAT data, are summarized in terms of amplitude, source depth, and misfit. Each theoretical spectrum reduces to a source factor multiplied by the usual exponential function of spherical harmonic degree n due to geometric attenuation with attitude above the source layer. The source factors always vary with n and are approximately proportional to n(exp 3) for degrees 12 through 120. The theoretical spectra are therefore not directly proportional to an exponential function of spherical harmonic degree n. There is no radius at which these spectra are flat, level, or otherwise independent of n.

Voorhies, C.↗

NASA NTRS1999

Capella: Structure and Abundances

This grant covers the analysis of EUVE spectra of the cool star binary system Capella. This project has also required the analysis of simultaneous Advanced Satellite for Cosmology and Astrophysics (ASCA) data. The ASCA spectrum of Capella could not be fit with standard models; by imposing models based on strong lines observed with EUVE, a problem wavelength region was identified. Correcting the problem required calculations of atomic collision strengths of higher principal quantum number than had ever been calculated. With these new models applied to the ASCA spectrum, better fits were obtained. Findings are that: (1) ASCA and EUVE spectra are both dominated by a region at 6 x 10(exp 6) K. (2) The high energy cut-off of the ASCA spectrum is consistent with emission from the highest ionization stages of EUVE, namely Fe XXIV. (3) EUVE requires a continuous emission measure distribution with more than two temperatures. (4) The ASCA spectra are of such high statistical significance that systematic uncertainties dominate, including atomic physics issues and calibration issues. (5) While the ASCA spectral fits achieve lower Chi(exp 2 with two-temperature fits, the EUVE-derived emission measure distribution models are also consistent with the spectra. (6) The Fe/H ratio obtained from the ASCA fit is within 20 % of the Fe/H abundance obtained from the summed spectra of Capella over 5 EUVE pointings, as well as the 1996 EUVE data. This result confirms our claims that quasi-continua composed of weak emission lines in the short wavelength spectrometer of EUVE are not major contributors to the measured Capella continuum. Other abundance ratios are also determined from the ASCA data, using models derived with EUVE. Si, Si, and Mg appear to be close to solar photospheric values, while the ratio of Ne/Fe is three to four times lower than solar photospheric values. Whether there is a general First Ionization Potential (FIP) effect or a specific neon anomaly cannot be determined from these data. (8) EUVE line ratios indicating low optical depth place limits on the extent to which the X-ray lines are optically, thick. While the brightest lines may be marginally thick, the ASCA spectrum is not of sufficient resolution to determine the optical depth in these lines.

Brickhouse, Nancy S.↗

NASA NTRS2003

Satellite and Surface Data Synergy for Developing a 3D Cloud Structure and Properties Characterization Over the ARM SGP. Stage 1: Cloud Amounts, Optical Depths, and Cloud Heights Reconciliation

One of the primary Atmospheric Radiation Measurement (ARM) Program objectives is to obtain measurements applicable to the development of models for better understanding of radiative processes in the atmosphere. We address this goal by building a three-dimensional (3D) characterization of the cloud structure and properties over the ARM Southern Great Plains (SGP). We take the approach of juxtaposing the cloud properties as retrieved from independent satellite and ground-based retrievals, and looking at the statistics of the cloud field properties. Once these retrievals are well understood, they will be used to populate the 3D characterization database. As a first step we determine the relationship between surface fractional sky cover and satellite viewing angle dependent cloud fraction (CF). We elaborate on the agreement intercomparing optical depth (OD) datasets from satellite and ground using available retrieval algorithms with relation to the CF, cloud height, multi-layer cloud presence, and solar zenith angle (SZA). For the SGP Central Facility, where output from the active remote sensing cloud layer (ARSCL) valueadded product (VAP) is available, we study the uncertainty of satellite estimated cloud heights and evaluate the impact of this uncertainty for radiative studies.

Genkova, I.↗

NASA NTRS2007

Satellite to Ground-based LIDAR Comparisons using MPLNET Data Products

The Micro-Pulse Lidar Network (MPLNET) is a network of ground-based lidar systems that provide continuous long-term observations of aerosol and cloud properties at approximately 10 different locations around the globe. Each site in the network uses an elastic scattering lidar co-located with a sunphotometer to provide data products of aerosol optical physical properties. Data products from sites are available on a next-day basis from the MPLNET website. Expansion of the network is based on partnering with research groups interested in joining MPLNET. Results have contributed to a variety of studies including aerosol transport studies and satellite calibration and validation efforts. One of the key motivations for MPLNET is to contribute towards the calibration and validation of satellite-based lidars such as GLAS/ICESAT and CALIPSO. MPLNET is able to provide comparison to several of the key aerosol and cloud CALIPSO data products including: layer height and thickness, optical depth, backscatter and extinction profiles, and the extinction-to-backscatter ratio.

Berkoff, T.A.↗

NASA NTRS2011

Orion Parachute Riser Cutter Development

This paper presents the tests and analytical approach used on the development of a steel riser cutter for the CEV Parachute Assembly System (CPAS) used on the Orion crew module. Figure 1 shows the riser cutter and the steel riser bundle which consists of six individual cables. Due to the highly compressed schedule, initial unavailability of the riser material and the Orion Forward Bay mechanical constraints, JSC primarily relied on a combination of internal ballistics analysis and LS-DYNA simulation for this project. Various one dimensional internal ballistics codes that use standard equation of state and conservation of energy have commonly used in the development of CAD devices for initial first order estimates and as an enhancement to the test program. While these codes are very accurate for propellant performance prediction, they usually lack a fully defined kinematic model for dynamic predictions. A simple piston device can easily and accurately be modeled using an equation of motion. However, the accuracy of analytical models is greatly reduced on more complicated devices with complex external loads, nonlinear trajectories or unique unlocking features. A 3D finite element model of CAD device with all critical features included can vastly improve the analytical ballistic predictions when it is used as a supplement to the ballistic code. During this project, LS-DYNA structural 3D model was used to predict the riser resisting load that was needed for the ballistic code. A Lagrangian model with eroding elements shown in Figure 2 was used for the blade, steel riser and the anvil. The riser material failure strain was fine tuned by matching the dent depth on the anvil with the actual test data. LS-DYNA model was also utilized to optimize the blade tip design for the most efficient cut. In parallel, the propellant type and the amount were determined by using CADPROG internal ballistics code. Initial test results showed a good match with LS-DYNA and CADPROG simulations. Final paper will present a detailed roadmap from initial ballistic modeling and LS-DYNA simulation to the performance testing. Blade shape optimization study will also be presented.

Oguz, Sirri↗

NASA NTRS2003

Automated Serial Sectioning for 3D Reconstruction

Some aspects of an apparatus and method for automated serial sectioning of a specimen of a solder, aluminum, or other relatively soft opaque material are discussed. The apparatus includes a small milling machine (micromiller) that takes precise, shallow cuts (increments of depth as small as 1 micron) to expose successive sections. A microscope equipped with an electronic camera, mounted in a fixed position on the micromiller, takes pictures of the newly exposed specimen surface at each increment of depth. The images are digitized, and the resulting data are subsequently processed to reconstruct three-dimensional (3D) features of the specimen.

Alkemper, Jen↗

NASA NTRS2013

Mars Science Laboratory Heatshield Aerothermodynamics: Design and Reconstruction

The Mars Science Laboratory heatshield was designed to withstand a fully turbulent heat pulse based on test results and computational analysis on a pre-flight design trajectory. Instrumentation on the flight heatshield measured in-depth temperatures in the thermal protection system. The data indicate that boundary layer transition occurred at 5 of 7 thermocouple locations prior to peak heating. Data oscillations at 3 pressure measurement locations may also indicate transition. This paper presents the heatshield temperature and pressure data, possible explanations for the timing of boundary layer transition, and a qualitative comparison of reconstructed and computational heating on the as-flown trajectory. Boundary layer Reynolds numbers that are typically used to predict transition are compared to observed transition at various heatshield locations. A uniform smooth-wall transition Reynolds number does not explain the timing of boundary layer transition observed during flight. A roughness-based Reynolds number supports the possibility of transition due to discrete or distributed roughness elements on the heatshield. However, the distributed roughness height would have needed to be larger than the pre-flight assumption. The instrumentation confirmed the predicted location of maximum turbulent heat flux near the leeside shoulder. The reconstructed heat flux at that location is bounded by smooth-wall turbulent calculations on the reconstructed trajectory, indicating that augmentation due to surface roughness probably did not occur. Turbulent heating on the downstream side of the heatshield nose exceeded smooth-wall computations, indicating that roughness may have augmented heating. The stagnation region also experienced heating that exceeded computational levels, but shock layer radiation does not fully explain the differences.

Edquist, Karl T.↗

NASA NTRS2014

Revisiting AVHRR Tropospheric Aerosol Trends Using Principal Component Analysis

The advanced very high resolution radiometer (AVHRR) satellite instruments provide a nearly 25 year continuous record of global aerosol properties over the ocean. It offers valuable insights into the long-term change in global aerosol loading. However, the AVHRR data record is heavily influenced by two volcanic eruptions, El Chichon on March 1982 and Mount Pinatubo on June 1991. The gradual decay of volcanic aerosols may last years after the eruption, which potentially masks the estimation of aerosol trends in the lower troposphere, especially those of anthropogenic origin. In this study, we show that a principal component analysis approach effectively captures the bulk of the spatial and temporal variability of volcanic aerosols into a single mode. The spatial pattern and time series of this mode provide a good match to the global distribution and decay of volcanic aerosols. We further reconstruct the data set by removing the volcanic aerosol component and reestimate the global and regional aerosol trends. Globally, the reconstructed data set reveals an increase of aerosol optical depth from 1985 to 1990 and decreasing trend from 1994 to 2006. Regionally, in the 1980s, positive trends are observed over the North Atlantic and North Arabian Sea, while negative tendencies are present off the West African coast and North Pacific. During the 1994 to 2006 period, the Gulf of Mexico, North Atlantic close to Europe, and North Africa exhibit negative trends, while the coastal regions of East and South Asia, the Sahel region, and South America show positive trends.

volcanoes↗

NASA NTRS2021

TOI-1518b: A Misaligned Ultra-hot Jupiter with Iron in Its Atmosphere

We present the discovery of TOI-1518b—an ultra-hot Jupiter orbiting a bright star (V = 8.95). The transiting planet is confirmed using high-resolution optical transmission spectra from EXPRES. It is inflated, with Rp = 1.875 ± 0.053 RJ, and exhibits several interesting properties, including a misaligned orbit (240.34 (+0.93, -0.98) degrees) and nearly grazing transit (b=0.9036 (+0.0061, -0.0053)). The planet orbits a fast-rotating F0 host star (Teff ≃ 7300 K) in 1.9 days and experiences intense irradiation. Notably, the TESS data show a clear secondary eclipse with a depth of 364 ± 28 ppm and a significant phase-curve signal, from which we obtain a relative day–night planetary flux difference of roughly 320 ppm and a 5.2σ detection of ellipsoidal distortion on the host star. Prompted by recent detections of atomic and ionized species in ultra-hot Jupiter atmospheres, we conduct an atmospheric cross-correlation analysis. We detect neutral iron (5.2σ), at K(p) = 157 (+68, -44) km/s and V(sys) = -16 (+2, -4), adding another object to the small sample of highly irradiated gas-giant planets with Fe detections in transmission. Detections so far favor particularly inflated gas giants with radii ≳1.78 R(J), which may be due to observational bias. With an equilibrium temperature of T(eq) = 2492 ± 38 K and a measured dayside brightness temperature of 3237 ± 59 K (assuming zero geometric albedo), TOI-1518b is a promising candidate for future emission spectroscopy to probe for a thermal inversion.

Samuel H. C. Cabot↗

NASA NTRS2022

Design of a Low-Cost, Submersible, Digital Holographic Microscope for in Situ Microbial Imaging

The methodologies for studying marine microbiology typically consist of utilizing instrumentation within a laboratory. This typically requires extracting a sample from its place of origin prior to examination, which may be days after collection. Oftentimes, the solution is to bring the lab to the ocean, which may be costly and provide further limitations for a sterile and stable laboratory environment. Here we present a low-cost, submersible, digital holographic microscope (DHM) designed to image marine microorganisms (such as bacteria and plankton) in their natural underwater environment. Our instrument eliminates the need to transport samples and allows for instantaneous data collection of microbes in-situ. The DHM achieves sub-micron spatial resolution and is paired with artificial intelligence for the detection and tracking of specimens to reduce the overall collected data. This instrument also aims to reduce the cost of manufacturing and field expenses relative to marine microbiological research. “Off the shelf” components were selected in the design process of this instrument which allows us to achieve precise results without sacrificing data quality. The DHM itself costs under one thousand dollars and features a low-cost high-resolution camera, the Arducam MT9J001. Included in the design were five main subsystems: optical, mechanical, electrical, power, and machine learning. Our on board computer and artificial intelligence consist of a Raspberry Pi 4 (8 Gb) and Google Coral USB Tensorflow accelerator. Instrument testing has successfully proven our abilities of data acquisition for at least two hours in depths of at least forty meters below sea level. Additionally, our artificial intelligence system is currently capable of tracking up to ten areas of interest in a fraction of a second with over ninety percent confidence via the neural net driven by the tensor cores on the Google Coral. Furthermore, we have demonstrated the versatility of our instrument by mounting it on an ocean-going ROV, the BlueRov2 by BlueRobotics. Our tests on the BlueRov2 exemplified the cost-effective nature of a submersible and reusable instrument that can be implemented in moderate environments and on most vessels.

Wallace, James Kent↗

NASA NTRSDate not supplied

Space Launch System Base Aerothermodynamics Post-Flight Reconstruction for Artemis I

Artemis I was the first uncrewed integrated test flight of the NASA heavy-lift, human-rated, exploration-class launch vehicle, Space Launch System (SLS), and Orion spacecraft. Artemis I successfully launched from Pad39B at NASA Kennedy Space Center on November 16th, 2023. The integrated test flight is composed of launch and ascent of the SLS vehicle from lift-off to RS-25 main engine cut-off (MECO), interim cryogenic propulsion stage (ICPS) in-space flight and Orion’s trajectory around the moon and landing in the Pacific Ocean which occurred on December 11th, 2023. The SLS total thrust of 8,800,000 lbf is powered by four LOX/LH2 RS-25 engines and two 5-segment solid rocket boosters. As a result, base flow environments for this vehicle are highly complex and extreme. SLS base aerothermodynamics covers rocket plume-induced convection and radiation of the vehicle’s aft region during powered flight from lift-off to MECO. This work discusses the SLS base flow physics observed during Artemis I and comparisons of post-flight reconstruction with pre-flight models and Space Shuttle data. This is the first time in-depth base heating flight reconstruction has been investigated for an exploration-class launch vehicle since the Saturn V Program.

aerothermodynamics↗

NASA NTRSDate not supplied

Space Launch System Base Aerodynamics Post-Flight Reconstruction for Artemis I

Artemis I was the first uncrewed integrated test flight of the NASA heavy-lift, human-rated, exploration-class launch vehicle, Space Launch System (SLS), and Orion spacecraft. Artemis I successfully launched from Pad39B at NASA Kennedy Space Center on November 16th, 2022. The integrated test flight was composed of launch and ascent of SLS vehicle from lift-off to RS-25 main engine cut-off (MECO), interim cryogenic propulsion stage (ICPS) in-space flight and Orion’s trajectory around the moon and landing in the Pacific Ocean which occurred on December 11th, 2022. The SLS total thrust of 8,800,000 lbf was powered by four LOX/LH2 RS-25 engines and two 5-segment solid rocket boosters. As a result, the base flow field had highly complex phenomena and regimes. SLS base aerodynamics covers vehicle base pressure and integrated axial force during powered flight from lift-off to MECO. This work discusses the SLS base flow physics observed during Artemis I and comparisons of post-flight reconstruction with pre-flight models and Space Shuttle data. This was the first time in-depth base aerodynamics flight reconstruction has been investigated for an exploration-class launch vehicle since the Saturn V Program.

aerothermodynamics↗

NASA NTRSDate not supplied

Space Launch System Base Aerothermodynamics Post-Flight Reconstruction for Artemis I

aerothermodynamics↗

NASA NTRSDate not supplied

Base Aerodynamics Post-Flight Reconstruction for Artemis I

Artemis I was the first uncrewed integrated test flight of the NASA heavy-lift, human-rated, exploration-class launch vehicle, Space Launch System (SLS), and Orion spacecraft. Artemis I successfully launched from Pad39B at NASA Kennedy Space Center on November 16th, 2022. The integrated test flight was composed of launch and ascent of SLS vehicle from lift-off to RS-25 main engine cut-off (MECO), interim cryogenic propulsion stage (ICPS) in-space flight and Orion’s trajectory around the moon and landing in the Pacific Ocean which occurred on December 11th, 2022. The SLS total thrust of 8,800,000 lbf was powered by four LOX/LH2 RS-25 engines and two 5-segment solid rocket boosters. As a result, the base flow field had highly complex phenomena and regimes. SLS base aerodynamics covers vehicle base pressure and integrated axial force during powered flight from lift-off to MECO. This work discusses the SLS base flow physics observed during Artemis I and comparisons of post-flight reconstruction with pre-flight models and Space Shuttle data. This was the first time in-depth base aerodynamics flight reconstruction has been investigated for an exploration-class launch vehicle since the Saturn V Program.

aerothermodynamics↗

NASA NTRSDate not supplied

Space Launch System Liftoff and Separation Dynamics Analysis Tool Chain

A flexible, hierarchical tool chain that is being applied to NASA’s Space Launch System (SLS) for critical dynamics phenomena is described. This tool chain, called CLVTOPS, is used to investigate lateral liftoff movement of the vehicle as it departs and clears the mobile launch tower and separation of the two solid rocket boosters without collision with the core stage and payload. The toolset’s architecture was configured to take advantage of a modern software-engineering approach for maximum flexibility and utilization of open-source simulations and associated tools. As opposed to a “monolithic” approach, scripting languages were used to “bind” together a tool chain to configure and organize input data, execute and produce analysis results, and post-process these results to facilitate a rapid iterative analysis process to quickly address issues and pursue alternatives with emphasis on analysis automation. Key capabilities in the tool chain include processing and mining of very large data sets, a wide range of graphical depictions, and high-fidelity, physics-based simulations. The paper begins with a problem description and the motivation for liftoff and separation dynamics analysis followed by a historical survey of dynamics analyses for previous NASA human-rated launch vehicles. Details of the tool chain and its components are then introduced divided, first, into description of the scripting language architecture used to “bind” the simulation tools, programs, and scripts together and, second, the physics models and simulations. Representative analyses and data products are shown for liftoff and booster separation dynamics that provide in-depth insight to the tool chain’s capabilities. Supporting activities such as simulation tool chain verification, version archiving and data management, and training are addressed. The paper concludes with case examples on how the tool chain can be tailored to related aerospace dynamics analyses, both large and small. These patterns and techniques for SLS dynamics tool construction can be applied for other aerospace simulations.

6DOF↗

NASA NTRS1987

Thematic mapper research in the earth sciences: Small scale patches of suspended matter and phytoplankton in the Elbe River Estuary, German Bight and Tidal Flats

A Thematic Mapper (TM) field experiment was followed by a data analysis to determine TM capabilities for analysis of suspended matter and phytoplankton. Factor analysis showed that suspended matter concentration, atmospheric scattering, and sea surface temperature can be retrieved as independent factors which determine the variation in the TM data over water areas. Spectral channels in the near infrared open the possibility of determining the Angstrom exponent better than for the coastal zone color scanner. The suspended matter distribution may then be calculated by the absolute radiance of channel 2 or 3 or the ratio of both. There is no indication of whether separation of chlorophyll is possible. The distribution of suspended matter and sea surface temperature can be observed with the expected fine structure. A good correlation between water depth and suspended matter distribution as found from ship data can now be analyzed for an entire area by the synoptic view of the TM scenes.

Grassl, H.↗

NASA NTRS1986

Voyager 2 photopolarimeter experiment - Evidence for tenuous outer ring material at Saturn

Voyager 2 photopolarimeter data are employed to characterize two regions of optically thin material outside the Saturn F ring. The study consists of a statistical analysis of optical depth value fluctuations caused by occultations of starlight from Delta Sco as viewed through the material. One the optically thin regions surrounds the orbital semimajor axis of the outer F ring shepherd satellite Pandora and the other thin region lies 144,090 km farther outward. The first region, with an optical depth of 0.008-0.016, is about 200 km in radius and the second, with an optical depth of 0.005-0.013, is about 1000 km in radial width. The data had a resolution of 0.5 km.

Graps, A. L.↗

NASA NTRS1975

NiCd battery reliability for shuttle serviced spacecraft

Data from life-cycle testing of 22-cell NiCd batteries designed for shuttle-service spacecrafts are analyzed, first by averaging battery cycle lives as a function of temperature and depth of discharge, and then by calculating single cell failure and survival probabilities as a function of temperature, depth of discharge, and number of operating cycles. The single cell data are used to calculate battery survival probabilities. A mathematical failure model which is a function of the quantity of charge through the battery and the temperature is characterized, suggesting a predictive capability for accurate estimation of energy storage subsystem life and performance of accelerated tests. The failure mechanism described is apparently independent of most charge-discharge parameters and common to most cell sizes.

Eliason, J.↗