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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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

An Approach to Reliability Testing of Microcircuits at Cryogenic Conditions

This viewgraph presentation reviews an approach to testing microcircuits at cryogenic temperatures. Standard testing procedures are not adequate to test microcircuits that are to operate at cryogenic temperatures. It is therefore necessary to perform analysis of operation conditions and reliability conditions for planning qualification testing of microcircuits at cryogenic temperatures. The major degradations for microcircuits operating at low temperatures depend on the number of switching cycles rather than on the duration of part operation. Therefore instead of accelerating degradation of the parts by increasing the level of stress, the possibility of which is very limited at cryogenic temperatures, the reliability testing can be based on the number of switching cycles.

Teverovsky, Alexander↗
NASA NTRS2015

Development of Long-Lifetime Pulsed Gas Valves for Pulsed Electric Thrusters

It is advantageous for gas-fed pulsed electric thrusters to employ pulsed valves so propellant is only flowing to the device during operation. The propellant utilization of the thruster will be maximized when all the gas injected into the thruster is acted upon by the fields produced by the electrical pulse. Gas that is injected too early will diffuse away from the thruster before the electrical pulse can act to accelerate the propellant. Gas that is injected too late will miss being accelerated by the already-completed electrical pulse. As a consequence, the valve must open quickly and close equally quickly, only remaining open for a short duration. In addition, the valve must have only a small amount of volume between the sealing body and the thruster so the front and back ends of the pulse are as coincident as possible with the valve cycling, with very little latent propellant remaining in the feed lines after the valve is closed. For a real mission of interest, a pulsed thruster can be expected to pulse at least 10(exp 10) - 10(exp 11) times, setting the range for the number of times a valve must open and close. The valves described in this paper have been fabricated and tested for operation in an inductive pulsed plasma thruster (IPPT) for in-space propulsion. In general, an IPPT is an electrodeless space propulsion device where a capacitor is charged to an initial voltage and then discharged, producing a high-current pulse through a coil. The field produced by this pulse ionizes propellant, inductively driving current in a plasma located near the face of the coil. Once the plasma is formed, it can be accelerated and expelled at a high exhaust velocity by the electromagnetic Lorentz body force arising from the interaction of the induced plasma current and the magnetic field produced by the current in the coil. The valve characteristics needed for the IPPT application require a fast-acting valve capable of a minimum of 10(exp 10) valve actuation cycles. Since even 10(exp 9) cycles is well above anything demonstrated, this lower value was selected as the design point for the present work. The valve seal must remain leak-tight throughout operation, and the body must maintain a low internal leakage at relatively high operating temperatures. The full set of design requirements used for this program are summarized in Table 1. In this work, we describe two pulsed gas valves that have been fabricated to have long lifetime and demonstrate the characteristics listed above. The first is a miniaturized, conventional electromagnet-based valve while the second is a piezoelectric-based valve design. The conventional valve, shown in Fig. 1, is opened by use of a solenoid electromagnetic actuator. When current is applied to the solenoid coil, magnetic forces pull the plunger away from the valve seat, allowing fluid to flow through the valve. Removal of electrical current permits the spring and fluid pressure to seat the plunger, halting the flow of fluid. The valve body is fabricated from 304L corrosion resistant steel (CRES) and while the parts that form the magnetic circuit are fabricated from 430 CRES. This material does not have optimum magnetic properties, but its corrosion resistance permits incorporation into a design without requiring an additional plating process. A viton O-ring compound (Parker V0884-75), selected for its mechanical strength at elevated temperatures, was used for the valve seat seal. The design was based solely on the use of analytical sizing calculations, as opposed to a more rigorous finite element analysis. While this valve is small and relatively lightweight, it does not represent a design that is optimized for mass and/or a given volume envelope. The piezoelectric valve is a "puller" valve design. Applying a voltage to the piezo crystal causes it to elongate and pull a pintle off the seat, opening the valve. The valve seal consists of the pintle with an external, spherically-formed tip fabricated from Inconel 625 and the seat fabricated from Inconel 718 and possessing a spherical surface that permits the pintle to align with the valve body centerline after each cycle, maintaining the circumferential metal-on-metal seal. The contact stress on the valve pintle is expected in the worst case to be 96.5 MPa (14 ksi), which is well below the work hardening value of 413.7 MPa (60 ksi) for Inconel 615. Results presented in this work will compare the performance of each valve, both to each other and to the valve design requirements given in Table 1. In general, both valves meet all the performance envelope requirements, but the piezoelectric valve consumes considerably less power and has a faster response time over the conventional solenoid-driven valves.

Burkhardt, Wendel M.↗
NASA NTRS2020

Challenges of Testing EB Coated CMC under SPLCF Conditions in Steam Environment at High Temperatures

Environmental barrier (EB) coated monolithic SiC (Hexoloy) and 3D woven SiC/SiC composite specimens were tested under sustained peak low cycle fatigue (SPLCF) conditions at 1204°C at 69 MPa (maximum stress) in steam environment up to 200hrs. Both types of specimens were coated with a multilayer EB coating (Mullite + rare earth disilicate (RED) bond coat and RED top coat) by slurry method. The coated Hexoloy specimen survived 200hrs testing of testing, but the coating showed through-the-thickness cracks and delamination. In contrast, the coated 3D woven SiC/SiC composite specimens failed between 48 and 160 hrs and showed extensive damage in the coating as well as within the CMC substrate.

R T Bhatt↗
NASA NTRS2022

Irrigation and Warming Drive the Decreases in Surface Albedo Over High Mountain Asia

Human and climate induced land surface changes resulting from irrigation, snow cover decreases, and greening impact the surface albedo over High Mountain Asia (HMA). Here we use a partial information decomposition approach and remote sensing data to quantify the effects of the changes in leaf area index, soil moisture, and snow cover on the surface albedo in HMA, home to over a billion people, from 2003 to 2020. The study establishes strong evidence of anthropogenic agricultural water use over irrigated lands (e.g., Ganges-Brahmaputra) which causes the highest surface albedo decreases (≤1%/year). Greening and decreased snow cover from warming also drive changes in visible and near-infrared surface albedo in different areas of HMA. The significant role of irrigation and greening in influencing albedo suggests the potential of a positive feedback cycle where albedo decreases lead to increased evaporative demand and increased stress on water resources.

Climate sciences↗
DOE OSTI2015

Four key areas for training the next-generation of global change researchers

Anthropogenic activities are changing the global environment in numerous ways, including increasing concentration of atmospheric carbon dioxide, alteration of biogeochemical cycles and changing land-cover types. These changes are increasing stresses on ecosystem goods and services, driving climate change and thus creating a few grand challenges for sustainability of the human society. Improving our understanding of these profound changes and grand challenges will help us in developing better predictive capabilities for the future. As these changes are expected to be long-lasting and we still do not have a complete understanding of their causes and consequences, the next generation of scientists needs to be properly trained in knowledge, methods and techniques in order to meet the research needs to tackle future challenges in global change ecology research. This guest editorial discusses the challenges and opportunities in preparing the next-generation global change researchers according to four key aspects of training.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Modeling low cycle fatigue (LCF) of additively manufactured Hastelloy X using An accelerated crystal plasticity fatigue damage model

This paper presents a microstructure-based model for low cycle fatigue (LCF) behavior and life of Nickel-based alloy Hastelloy X manufactured using laser-powder bed fusion (L-PBF) additive manufacturing (AM). AM Hastelloy X, a solution-strengthened alloy, is tested at elevated temperature under fully reversed LCF conditions at different strain levels. A generalized plane strain finite element model is generated from electron backscatter diffraction (EBSD) characterization. The constitutive behavior of the material under fatigue is modeled using crystal plasticity and calibrated with both monotonic tensile and cyclic stress–strain data. The fatigue micro-crack initiation and propagation in the microstructure is modeled using a modified Chaboche fatigue damage model. An embedded boundary condition with a homogenous medium is used to apply the cyclic deformation and prevent numerically introduced over-constraints during fatigue simulation. A ‘cycle-jump’ method is used to accelerate the fatigue simulation and reduce the computational cost. The simulation results are compared to LCF experiments, showing satisfactory matches in cyclic stress behavior and number of cycles to macro-crack initiation for all applied strain ranges. In addition, the model illustrates the potential for quantifying microscale fatigue life impacting factors such as microstructure and surface roughness, which is needed to accurately quantify the reliability of AM components in service.

36 MATERIALS SCIENCE↗
NASA NTRS2021

Topical: Stem Cell-Based Tissue Regenerative Health in Space

The maintenance of healthy adult tissues in mammals requires a complex homeostasis of molecular, cellular, tissue, and metabolic processes which are fundamentally different from the development and aging processes that bookend life. Cellular homeostasis in the adult requires molecular maintenance and repair of non-dividing cells such as cardiomyocytes and neurons, but also stem cell-based tissue regeneration via direct replacement of cell loss, such as in the blood, immune system, bone, skin, liver, intestine, and other tissues. Because stem cell-based tissue regenerative health requires constant proliferation and differentiation of stem cell progenitors in the bone marrow, and other adult stem cell niches, it is uniquely sensitive to the stresses of spaceflight including exposure to space radiation and mechanical unloading in microgravity. A key central hypothesis in this field is that those spaceflight stress factors can have profound negative effects on long-term tissue regenerative health mediated by adult stem cells, and that unmitigated, they may lead to premature tissue aging and functional failure. Specifically, it is thought that mechanical unloading due to lack of weight-bearing in space reduces mitogenic mechanotransduction necessary to promote adult stem cell proliferation and differentiation, and that space radiation can also lead to activation of cell cycle arrest mechanisms, further reducing adult stem cell proliferation. These hypotheses are being tested in low earth orbit(LEO)using a variety of cellular and whole organism tissue model systems, suggesting that spaceflight consistently interferes with stem cell tissue regenerative processes such as in mammalian embryoid bodies, regenerating newt tails, and mouse bone marrow hematopoietic and osteoprogenitor cells. Furthermore, potential molecular mechanisms integrating both space radiation and mechanical disuse via oxidative stress and the cell cycle inhibitor Cdkn1aare now under study using single cell (scRNAseq) expressome analysis of bone marrow osteoprogenitors, both under stretch loading, and spaceflight conditions including in various mouse transgenic null backgrounds relevant to these mechanisms. Future work in the area of tissue regenerative health in space for the coming decade should seek to understand the responses the various tissue regenerative stem cell niches in humans and relevant model organisms, and how they respond to long-term exposure to the space environment. Special emphases of future work should be on how regenerative deficits in whole-organism stem cell niches may lead to tissue degeneration and premature aging, and on the long-term proliferation and differentiation of stem cell derived tissue organoid models in the deep space environment outside of LEO.

Eduardo A C Almeida↗
DOE OSTI2013

Selenoprotein P Inhibits Radiation-Induced Late Reactive Oxygen Species Accumulation and Normal Cell Injury

Purpose: Radiation is a common mode of cancer therapy whose outcome is often limited because of normal tissue toxicity. We have shown previously that the accumulation of radiation-induced late reactive oxygen species (ROS) precedes cell death, suggesting that metabolic oxidative stress could regulate cellular radiation response. The purpose of this study was to investigate whether selenoprotein P (SEPP1), a major supplier of selenium to tissues and an antioxidant, regulates late ROS accumulation and toxicity in irradiated normal human fibroblasts (NHFs). Methods and Materials: Flow cytometry analysis of cell viability, cell cycle phase distribution, and dihydroethidium oxidation, along with clonogenic assays, were used to measure oxidative stress and toxicity. Human antioxidant mechanisms array and quantitative real-time polymerase chain reaction assays were used to measure gene expression during late ROS accumulation in irradiated NHFs. Sodium selenite addition and SEPP1 overexpression were used to determine the causality of SEPP1 regulating late ROS accumulation and toxicity in irradiated NHFs. Results: Irradiated NHFs showed late ROS accumulation (4.5-fold increase from control; P<.05) that occurs after activation of the cell cycle checkpoint pathways and precedes cell death. The mRNA levels of CuZn- and Mn-superoxide dismutase, catalase, peroxiredoxin 3, and thioredoxin reductase 1 increased approximately 2- to 3-fold, whereas mRNA levels of cold shock domain containing E1 and SEPP1 increased more than 6-fold (P<.05). The addition of sodium selenite before the radiation treatment suppressed toxicity (45%; P<.05). SEPP1 overexpression suppressed radiation-induced late ROS accumulation (35%; P<.05) and protected NHFs from radiation-induced toxicity (58%; P<.05). Conclusion: SEPP1 mitigates radiation-induced late ROS accumulation and normal cell injury.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

The effect of contact severity on micropitting: Simulation and experiments

In this work, a numerical contact fatigue model combining the effects of rolling contact fatigue and wear has been developed based on mixed elastohydrodynamic lubrication (EHL) theory, continuum damage mechanics (CDM) and the Archard's wear law. A series of benchtop tests were conducted using a triple-contact test rig to study the influence of surface roughness, speed and load on micropitting. The proposed surface damage model was used to simulate the rolling-sliding line contact of surfaces having different surface topography. The film thickness, contact pressure and sub-surface stress were determined by solving the generalized Reynolds equation and using the well-developed discrete convolute and fast Fourier transformation (DC-FFT) method. The jump-in-cycle was assumed to evaluate the accumulated damage based on the tested fatigue life and sub-surface stress histories. Surface topography was updated by calculating the wear height with the Archard's wear equation. Results reveal that micropitting occurs under the combined effect of wear and contact fatigue. The micropitting rate increased then turn to decreased as the lambda ratio (lambda) increased. The contact pressure significantly affected the contact fatigue life and the micropitting rate.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Final Report: Characterization of Canister Mockup Weld Residual Stresses

Stress corrosion cracking (SCC) of interim storage containers has been indicated as a high priority data gap by the Department of Energy (DOE) (Hanson et al., 2012), the Electric Power Research Institute (EPRI, 2011), the Nuclear Waste Technical Review Board (NWTRB, 2010a), and the Nuclear Regulatory Commission (NRC, 2012a, 2012b). Uncertainties exist in terms of the environmental conditions that prevail on the surface of the storage containers, the stress state within the container walls associated both with weldments as well as within the base metal itself, and the electrochemical properties of the storage containers themselves. The goal of the work described in this document is to determine the stress states that exists at various locations within a typical storage canister by evaluating the properties of a full-diameter cylindrical mockup of an interim storage canister. This mockup has been produced using the same manufacturing procedures as the majority of the fielded spent nuclear fuel interim storage canisters. This document describes the design and procurement of the mockup and the characterization of the stress state associated with various portions of the container. It also describes the cutting of the mockup into sections for further analyses, and a discussion of the potential impact of the results from the stress characterization effort.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Experimental and numerical investigation into rapid cooling of rock salt related to high frequency cycling of storage caverns

High frequency cycling of salt caverns is becoming common practice to meet the needs of energy markets and to foster underground energy storage. In the case of rapid cooling, tensile stresses and thermally-induced fractures can appear in the surrounding rock, with potential detrimental consequences to the integrity of the storage project. To further investigate the effects of rapid cycles on the integrity of rock salt, a thermo-mechanical test was performed in a salt mine. It consisted in cooling rapidly several times a salt surface of 10 m 2 (Δ T =-20 °C in about 8 h). Extensive monitoring allowed tracking the thermo-mechanical response of the rock, including possible fracture creation and propagation. Although more research is needed, the test demonstrated that tensile fracturing due to rapid cooling is possible. Furthermore thermo-mechanical modeling allowed reproducing fairly well the location, orientation and timing of the first fracture; indeed, fractures should be avoided to ensure cavern integrity, and therefore knowledge about the critical zones where fractures could appear is sufficient at the design stage.

58 GEOSCIENCES↗
NASA NTRS1983

Tensile and Compressive Constitutive Response of 316 Stainless Steel at Elevated Temperatures

Creep rate in compression is lower by factors of 2 to 10 than in tension if the microstructure of the two specimens is the same and are tested at equal temperatures and equal but opposite stresses. Such behavior is characteristic for monotonic creep and conditions involving cyclic creep. In the latter case creep rate in both tension and compression progressively increases from cycle to cycle, rendering questionable the possibility of expressing a time stabilized constitutive relationship. The difference in creep rates in tension and compression is considerably reduced if the tension specimen is first subjected to cycles of tensile creep (reversed by compressive plasticity), while the compression specimen is first subjected to cycles of compressive creep (reversed by tensile plasticity). In both cases, the test temperature is the same and the stresses are equal and opposite. Such reduction is a reflection of differences in microstructure of the specimens resulting from different prior mechanical history.

Manson, S. S.↗
DOE OSTI2022

Stress-Controlled Creep–Fatigue of an Advanced Austenitic Stainless Steel at Elevated Temperatures

Creep–fatigue interaction occurs in many structural components of high-temperature systems operating under cyclic and steady-state service conditions, such as in nuclear power plants, aerospace, naval, and other industrial applications. Thus, understanding micromechanisms governing high-temperature creep–fatigue behavior is essential for safety and design considerations. In this work, stress-controlled creep–fatigue tests of advanced austenitic stainless steel (Alloy 709) were performed at a 400 MPa stress range and 750 °C with tensile hold times of 0, 60, 600, 1800, and 3600 s, followed by microstructural examinations. The creep–fatigue lifetime of the Alloy 709 was found to decrease with increasing hold time until reaching a saturation level where the number of cycles to failure did not exhibit a significant decrease. Softening behavior was observed at the beginning of the test, possibly due to the recovery of entangled dislocations and de-twining. In addition, hysteresis loops showed ratcheting behavior, although the mean stress was zero during creep–fatigue cycling, which was attributed to activity of partial dislocations. Microstructural examination of the fracture surfaces showed that fatigue failure dominated at small hold times where the cracks initiated at the surface of the sample. Larger creep cracks were found for longer hold times with a lower probability of dimpled cavities, indicating the dominance of creep deformation. The results were compared with other commonly used stainless steels, and plausible reasons for the observed responses were described.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Casein kinase 2 promotes interaction between Rad17 and the 9-1-1 complex through constitutive phosphorylation of the C-terminal tail of human Rad17

Highlights: • Rad17-S667 in the C-terminal tail is constitutively phosphorylated in vivo. • Rad17-S667 phosphorylation is dependent on casein kinase 2 (CK2) activity. • CK2-dependent Rad17-S667 phosphorylation is important for the 9-1-1 interaction. • The Rad17-S667 phosphorylation is the only role of CK2 in the 9-1-1 interaction. An interaction between the Rad17-RFC2-5 and 9-1-1 complexes is essential for ATR-Chk1 signaling, which is one of the major DNA damage checkpoints. Recently, we showed that the polyanionic C-terminal tail of human Rad17 and the embedded conserved sequence iVERGE are important for the interaction with 9-1-1 complex. Here, we show that Rad17-S667 in the C-terminal tail is constitutively phosphorylated in vivo in a casein kinase 2-dependent manner, and the phosphorylation is important for 9-1-1 interaction. The serine phosphorylation of Rad17 could be seen in the absence of exogenous genotoxic stress, and was mostly abolished by S667A substitution. Rad17-S667 was also phosphorylated when the C-terminal tail was fused with EGFP, but the phosphorylation was inhibited by two casein kinase 2 inhibitors. Furthermore, interaction between Rad17 and the 9-1-1 complex was inhibited by the casein kinase 2 inhibitor CX-4945/Silmitasertib, and the effect was dependent on the Rad17-S667 residue, indicating that S667 phosphorylation is the only role of casein kinase 2 in the 9-1-1 interaction. Our data raise the possibility that the C-terminal tail of vertebrate Rad17 regulates ATR-Chk1 signaling through multi-site phosphorylation in the iVERGE.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Thermal Stress Modeling and Analysis of Packed-bed Thermocline Energy Storage Tank for INL Thermal Energy Distribution System (TEDS)

The Thermal Energy Distribution System (TEDS) at Idaho National Laboratory (INL) is a thermal-hydraulic flow loop to support the integration of co-located multiple experimental systems, where a packed-bed thermal energy storage (TES) is installed as a thermal buffer and storage unit for TEDS. The packed-bed TES is adopted in TEDS because of its benefit as a low-cost single-tank storage option compared to the traditional two-tank storage. However, thermal ratcheting is one potential design concern which is caused by the rearrangement of granular filler inside a packed-bed tank during continuous thermal cycling operation of the packed-bed TES tank. If the thermally induced stress exceeds yield strength of the tank wall, it may cause catastrophic consequences like rupture of the thermal storage tank. Thus, it is crucial to understand the phenomenon to ensure the robust operation. Based on the temperature boundary conditions given by transient thermal analyses with computational fluid dynamics (CFD) simulations, the thermal ratcheting analysis is then conducted to evaluate the hoop stress and resultant thermal ratcheting potential of the TES tanks with two different modeling approaches: (1) infinite rigidity model and (2) Drucker-Prager (DP) model. The validity of each modeling method was examined by comparing the numerical simulation with the experimental data obtained from the packed-bed TES tank for Solar One Plant and evaluate the thermal ratcheting potential of the TEDS TES tank.

25 ENERGY STORAGE↗
NASA NTRS1982

Tensile and compressive constitutive response of 316 stainless steel at elevated temperatures

It is demonstrated that creep rate of 316 SS is lower by factors of 2 to 10 in compression than in tension if the microstructure is the same and tests are conducted at identical temperatures and equal but opposite stresses. Such behavior was observed for both monotonic creep and conditions involving cyclic creep. In the latter case creep rate in both tension and compression progressively increases from cycle to cycle, rendering questionable the possibility of expressing a time-stabilized constitutive relationship. The difference in creep rates in tension and compression is considerably reduced if the tension specimen is first subjected to cycles of tensile creep (reversed by compressive plasticity), while the compression specimen is first subjected to cycles of compressive creep (reversed by tensile plasticity). In both cases, the test temperature is the same and the stresses are equal and opposite. Such reduction is a reflection of differences in microstructure of the specimens resulting from different prior mechanical history.

Manson, S. S.↗
NASA NTRSDate not supplied

Auroral ovals versus flare ribbons: Optical footprints of explosive magnetic field reconfiguration in Earth’s magnetosphere and the Sun’s corona

Despite drastically different plasma conditions in the two systems, eruptive energy release events in solar active regions and in Earth’s magnetosphere have a lot in common. Both solar active region eruptions and the substorm activity in the nightside magnetosphere are known to be associated with an abrupt large-scale reorganization of the supporting magnetic systems enabling the conversion and dissipation of the stored free magnetic energy. The rate of energy accumulation in either system tends to be by orders of magnitude slower than the energy release rate, leading to the formation of an impulsive loading-unloading cycle involving a relatively long pre-reconnection phase (substorm growth phase, pre-flare stressing of an active region magnetic field), a short and explosive reconnection phase (substorm breakup and expansion, eruptive flares and CMEs), and a prolonged post-reconnection phase (substorm recovery phase and the post-flare active region reconfiguration). In Earth’s magnetosphere, this loading-unloading cycle is diagnosed by monitoring characteristic changes in the particle precipitation pattern in the northern and southern auroral ovals marking the boundary between the open and close magnetic flux. The position, shape, structure, and dynamics of the auroral borealis were shown to communicate critically important information about an upcoming substorm, the location and timing of the initial reconnection onset, and the subsequent return of the magnetosphere to a lower-energy state. On the Sun, a similar role is played by the chromospheric flare ribbons which enable a detailed diagnostics of the overlying reconnecting magnetic field. In this talk, we’ll discuss similarities and differences in using auroral and flare ribbon observations for monitoring eruptive energy release in respectively Earth’s magnetosphere and solar corona. Special emphasis will be placed on the quantitative interpretation of the two types of optical signatures for empirical diagnostics of the underlying reconnection activity and for constraining its theoretical models. We’ll also compare forecasting capabilities of the two types of optical signatures in the context of space weather prediction objectives.

V. M. Uritskiy↗
DOE OSTI2018

Using imaging spectroscopy to detect variation in terrestrial ecosystem productivity across a water-stressed landscape

A central challenge to understanding how climate anomalies, such as drought and heatwaves, impact the terrestrial carbon cycle, is quantification and scaling of spatial and temporal variation in ecosystem gross primary productivity (GPP). Existing empirical and model-based satellite broadband spectra-based products have been shown to miss critical variation in GPP. We evaluate the potential of high spectral resolution (10 nm) shortwave (400–2,500 nm) imagery to better detect spatial and temporal variations in GPP across a range of ecosystems, including forests, grassland-savannas, wetlands, and shrublands in a water-stressed region. Estimates of GPP from eddy covariance observations were compared against airborne hyperspectral imagery, collected across California during the 2013–2014 HyspIRI airborne preparatory campaign. Observations from 19 flux towers across 23 flight campaigns (102 total image-flux tower pairs) showed GPP to be strongly correlated to a suite of spectral wavelengths and band ratios associated with foliar physiology and chemistry. A partial least squares regression (PLSR) modeling approach was then used to predict GPP with higher validation accuracy (adjusted R 2 = 0.71) and low bias (0.04) compared to existing broadband approaches (e.g., adjusted R 2 = 0.68 and bias = -5.71 with the Sims et al. model). Significant wavelengths contributing to the PLSR include those previously shown to coincide with Rubisco (wavelengths 1,680, 1,740, and 2,290 nm) and V cmax (wavelengths 1,680, 1,722, 1,732, 1,760, and 2,300 nm). These results provide strong evidence that advances in satellite spectral resolution offer significant promise for improved satellite-based monitoring of GPP variability across a diverse range of terrestrial ecosystems.

47 OTHER INSTRUMENTATION↗