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NASA NTRS2020

TOI 564 b and TOI 905 b: Grazing and Fully Transiting Hot Jupiters Discovered by TESS

We report the discovery and confirmation of two new hot Jupiters discovered by the Transiting Exoplanet Survey Satellite(TESS): TOI 564 b and TOI 905 b. The transits of these two planets were initially observed by TESS with orbital periods of 1.651 and 3.739 days, respectively. We conducted follow-up observations of each system from the ground, including photometry in multiple filters, speckle interferometry, and radial velocity measurements. For TOI 564 b, our global fitting revealed a classical hot Jupiter with a mass of-+1.4630.0960.10MJand a radius of-+1.020.290.71RJ. Also a classical hot Jupiter, TOI 905 b has a mass of-+0.6670.0410.042MJand radius of-+1.1710.0510.053RJ. Both planets orbit Sun-like, moderately bright, mid-G dwarf stars with V11. While TOI 905 b fully transits its star, we found that TOI 564 b has a very high transit impact parameter of-+0.9940.0490.083, making it one of only∼20 known systems to exhibit a grazing transit and one of the brightest host stars among them. Therefore, TOI 564 b is one of the most attractive systems to search for additional nontransiting, smaller planets by exploiting the sensitivity of grazing transits to small changes in inclination and transit duration over a timescale of several years.

Exoplanet astronomy↗
NASA NTRS2020

Cluster Difference Imaging Photometric Survey. II. TOI 837: A Young Validated Planet in IC 2602

We report the discovery of TOI 837b and its validation as a transiting planet. We characterize the system using data from the NASA Transiting Exoplanet Survey Satellite mission, the ESA Gaia mission, ground-based photometry from El Sauce and ASTEP400, and spectroscopy from CHIRON, FEROS, and Veloce. We find that TOI 837 is a T = 9.9 mag G0/F9 dwarf in the southern open cluster IC 2602. The star and planet are therefore 35(sup +11)(sub -5) million years old. Combining the transit photometry with a prior on the stellar parameters derived from the cluster color–magnitude diagram, we find that the planet has an orbital period of 8.3 days and is slightly smaller than Jupiter (R(sub p) = 0.77(sup + 0.09)(sub -0.07) R(sub Jup)). From radial velocity monitoring, we limit M(sub p) sin i to less than 1.20 M(sub Jup) (3σ). The transits either graze or nearly graze the stellar limb. Grazing transits are a cause for concern, as they are often indicative of astrophysical false-positive scenarios. Our follow-up data show that such scenarios are unlikely. Our combined multicolor photometry, high-resolution imaging, and radial velocities rule out hierarchical eclipsing binary scenarios. Background eclipsing binary scenarios, though limited by speckle imaging, remain a 0.2% possibility. TOI 837b is therefore a validated adolescent exoplanet. The planetary nature of the system can be confirmed or refuted through observations of the stellar obliquity and the planetary mass. Such observations may also improve our understanding of how the physical and orbital properties of exoplanets change in time.

Exoplanets↗
NASA NTRS2021

TIC 168789840: A Sextuply Eclipsing Sextuple Star System

We report the discovery of a sextuply eclipsing sextuple star system from TESS data, TIC 168789840, also known as TYC 7037-89-1, the first known sextuple system consisting of three eclipsing binaries. The target was observed in Sectors 4 and 5 during Cycle 1, with light curves extracted from TESS Full Frame Image data. It was also previously observed by the WASP survey and ASAS-SN. The system consists of three gravitationally bound eclipsing binaries in a hierarchical structure of an inner quadruple system with an outer binary subsystem. Follow up observations from several different observatories were conducted as a means of determining additional parameters. The system was resolved by speckle interferometry with a 0 42 separation between the inner quadruple and outer binary, inferring an estimated outer period of ∼2 kyr. It was determined that the fainter of the two resolved components is an 8.217 day eclipsing binary, which orbits the inner quadruple that contains two eclipsing binaries with periods of 1.570 days and 1.306 days. Markov Chain Monte Carlo (MCMC) analysis of the stellar parameters has shown that the three binaries of TIC 168789840 are “triplets,” as each binary is quite similar to the others in terms of mass, radius, and Teff. As a consequence of its rare composition, structure, and orientation, this object can provide important new insight into the formation, dynamics, and evolution of multiple star systems. Future observations could reveal if the intermediate and outer orbital planes are all aligned with the planes of the three inner eclipsing binaries.

Brian P. Powell↗
NASA NTRS2021

Generating Flood Probability Map Based on Combined Use of Synthetic Aperture Radar and Optical Imagery

Despite a lot of efforts to respond flood hazards with remote sensing data, it is still difficult to generate an accurate flood map using solely optical or radar imagery. While optical data is relatively high-resolution and does not suffer from speckle noise compared to radar data, it is very likely to be impacted by cloud and shadow. On the other hand, radar imagery can be used in all weather conditions due to its capability of penetrating clouds. Although a significant improvement of flood monitoring capability is achieved by using radar data, it is still challenging to map urban floods because of strong backscattering by man-made structures. Therefore, complementary use of optical and radar imagery in flood response is required, particularly in urban areas. In this study, we have adopted the Bayesian Joint Probability function to combine two different flood products generated from SAR and optical imagery. Flood detection with SAR data relies on the difference of backscatter signals between standing water and rougher land surface, while a Normalized Difference Water Index (NDWI) approach is used for optical data. Specifically, Planet Dove data with its 3m spatial resolution is used with higher weight values to detect flood extent in urban areas.

floods↗
NASA NTRSDate not supplied

Multi-Star Wavefront Control with SCExAO Instrument: Demonstration with an Internal Source

Although only a small fraction of currently known exoplanets was found in binary and multiple systems, studies show that such stars do form planets, with an efficiency that is smaller, but within an order of magnitude of single stars. However, binaries are rarely considered as targets for exoplanet imaging space missions because of challenges of removing light from the second binary component. In our previous works it was shown how to solve two main issues that make exoplanet imaging in multiple systems impossible, namely, the mutual incoherence of speckles created by different binary components, and inability of a deformable mirror (DM) to control the starlight beyond the DM outer working angle/Nyquist limit. Feasibility of the developed Multi-Star Wavefront Control (MSWC) and Super-Nyquist Wavefront Control(SNWC) algorithms was demonstrated at the Ames Coronagraph Experiment (ACE) laboratory using a simple imaging system with a DM and no coronagraph. In this paper, we report the results our MSWC experiments using the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument that is part of our technology development effort. The main goal of these experiments is to validate MSWC on a real coronagraphic system by using an internal source to simulate at least one real representative binary target. In our demonstration narrow-band contrast of 4.1×10−6has been reached by using MSWC in a 12×6λ/D dark zone separated from the primary component of the simulated binary star (STF 3121 AB) by 4λ/D. This contrast is better by a factor of 13.2 than the contrast floor reached by standard single-star wavefront control (SSWC). We also discuss the main limiting factors that affect the MSWC performance in our experiments.

Binary stars↗
NASA NTRS2021

Exploring Sentinel-1 and Sentinel-2 diversity for Flood inundation mapping using deep learning

Identification of flood water extent from satellite images has historically relied on either synthetic aperture radar (SAR) or multi-spectral (MS) imagery. MS sensors are limited to cloud free conditions, whereas SAR imagery is plagued by noise-like speckle. Prior studies that use combinations of MS and SAR data to overcome individual limitations of these sensors have not fully examined sensitivity of flood mapping performance to different combinations of SAR and MS derived spectral indices or band transformations in color space. This study explores the use of diverse bands of Sentinel 2 (S2) through well-established water indices and Sentinel 1 (S1) derived SAR imagery along with their combinations to assess their capability for generating accurate flood inundation maps. The robustness in performance of S-1 and S-2 band combinations was evaluated using 446 hand labeled flood inundation images spanning across 11 flood events from Sen1Floods11 dataset which are highly diverse in terms of land cover as well as location. A modified K-fold cross validation approach is used to evaluate the performance of 32 combinations of S1 and S2 bands using a fully connected deep convolutional neural network known as U-Net. Our results indicated that usage of elevation information has improved the capability of S1 imagery to produce more accurate flood inundation maps. Compared to a median F1 score of 0.62 when using only S1 bands, the combined use of S1 and elevation information led to an improved median F1 score of 0.73. Water extraction indices based on S2 bands have a statistically significant superior performance in comparison to S1. Among all the band combinations, HSV (Hue, Saturation, Value) transformation of S2 bands provides a median F1 score of 0.9, outperforming the commonly used water spectral indices owing to HSV’s transformation’s superior contrast distinguishing abilities. Additionally, U-Net algorithm was able to learn the relationship between raw S2 based water extraction indices and their corresponding raw S2 bands, but not of HSV owing to relatively complex computation involved in the latter. Results of the paper establishes important benchmarks for the extension of S1 and S2 data-based flood inundation mapping efforts over large spatial extents.

Goutam Konapala↗
NASA NTRS2021

Spin State and Moment of Inertia of Venus

Fundamental properties of the planet Venus, such as its internal mass dis-tribution and variations in length of day, have remained unknown. We usedEarth-based observations of radar speckles tied to the rotation of Venus ob-tained in 2006–2020 to measure its spin axis orientation, spin precession rate,moment of inertia, and length-of-day variations. Venus is tilted by 2.6392±0.0008 degrees (1σ) with respect to its orbital plane. The spin axis precessesat a rate of 44.58±3.3 arcseconds per year (1σ), which gives a normalized mo-ment of inertia of 0.337±0.024 and yields a rough estimate of the size of thecore. The average sidereal day on Venus in the 2006–2020 interval is 243.0226±0.0013 Earth days (1σ). The spin period of the solid planet exhibits variationsof 61 ppm (∼20 minutes) with a possible diurnal or semidiurnal forcing. Thelength-of-day variations imply that changes in atmospheric angular momentumof at least∼4% are transferred to the solid planet.

Jean-Luc Margot↗
NASA NTRS2022

Precision Thermal Control Technology to Enable Thermally Stable Telescopes

Abstract. The precision thermal control (PTC) project was a multiyear effort initiated in fiscal year 2017 to mature the technology readiness level (TRL) of technologies required to enable ultra-thermally stable ultraviolet/optical/infrared space telescope primary-mirror assemblies for ultra-high-contrast observations of exoplanets. PTC had three objectives: (1) validate thermal optical performance models, (2) derive thermal system stability specifications, and (3) demonstrate multi-zonal active thermal control. PTC successfully achieved its objectives and matured active thermal control technology to at least TRL-5. PTC’s key accomplishments are a demonstration of better than 2-mK root-mean-square stable thermal control of the 1.5-m ultra-low expansion (ULE®) Advanced Mirror Technology Development-2 (AMTD-2) mirror when exposed to thermal disturbances in a relevant thermal/vacuum environment, and the ability to shape the 1.5-m AMTD-2 mirror to picometer precision. Additionally, an analysis approach is demonstrated for quantifying thermally induced mid-spatial frequency error which can cause speckle noise in the coronagraph dark hole.

thermal control↗
NASA NTRSDate not supplied

Laboratory Demonstration of High Contrast with the PIAACMC Coronagraph on an Obstructed and Segmented Aperture

Coronagraphs (together with starshades) are an important tool to directly image and characterize exoplanets, and enable the search for biomarkers in reflected light on potentially habitable worlds. Their performance and efficiency has steadily been improving over the past several decades, but has not yet reached performance limits. In particular, the expected exoplanet yield for missions such as the Astro2020-recommended “IR/O/UV Flagship” can still be improved by factors of at least 2-3, simply by continued improvements in coronagraph performance, before they plateau due to physics limits. One possible architecture that can enable at least a part of this improvement is the Phase-Induced Amplitude Apodization Complex Mask Coronagraph (PIAACMC). Itoffersthe advantages of high throughput, small inner working angle (IWA),and almost noloss inPSF sharpness, and natively supports obstructed and segmented apertures, which is essential to the Astro2020 “IR/O/UV Flagship”mission. Historically, key disadvantages of PIAA have been poor tolerance to stellar angular sizes and maturity, but latest designs and demonstrations have made significant strides in this respect.In this paper, we present the current status and overview of our program to mature the PIAACMC technology. We first review PIAACMC designs for LUVOIR-A and B, which resultedin improved expected yield of Exo-Earths relative tothe baselines for both mission concepts. In particular, for LUVOIR-B, the yield improves from 28 to 42due to improvedtolerance to stellar angular size in our design. The improvement in yield is marginal for LUVOIR-A, but our design enables detecting planets around smaller diameter stars (nearby K-dwarfs and/or farther FG stars). We also describe our modeling and vacuum demonstrationsfor the LUVOIR-A aperture(which is more challengingthan LUVOIR-B due to the central obstruction).The demonstration included a LUVOUR-A pupil mask, an on-axis PIAA set of 2 mirrors with central holes, a Boston Micromachines DM, a patterned CMC mask, Lyot stop, and supporting masks and optics. Demonstrations were conducted at JPL’s High Contrast Imaging Testbed (HCIT) using several characterization andwavefront control techniques (primarily standard EFC, several experimental techniques were attempted, as well as speckle nulling). So far, our results include 1.9e-8 raw contrast in 10% broadband light between 3.5 and 8 l/D; 4.1e-8 and 1.6e-9 coherent contrasts in monochromatic light between 2-4 and 4-8 l/D, respectively. We also present measurements and analysis of sensitivity to tip/tilt jitter and stellar angular size. Finally, we compare our test results to models, present an analysis of our limiting factors, and explorefuture prospectsfor improvement based on validated models.

Coronagraph↗
NASA NTRSDate not supplied

Initial Test Results for NASA Goddard’s Low-Cost Optical Terminal Adaptive Optics System

This presentation presents the testing approach and initial laboratory test results of the Adaptive Optics (AO) Subassembly (AOS) for the Low-Cost Optical Terminal (LCOT), a low-cost and flexible optical communications ground terminal. Leveraging commercial components and subassemblies wherever possible, LCOT is being developed by the NASA Goddard Space Flight Center (GSFC) Advanced Communications Capabilities for Exploration and Science Systems (ACCESS) project. An economical ground terminal allows NASA to create a global optical terminal network and enables the expansion of direct-to-Earth (DTE) optical communications. Located at the Goddard Geophysical and Astronomical Observatory (GGAO), LCOT is in the development phase and will receive first light during initial testing beginning in 2023. This new optical terminal includes a 700 mm Ritchey-Chretien commercial telescope, able to track Low Earth Orbit (LEO) spacecraft, receive instruments specified from 1500 - 1600 nm, and an uplink transmit optical system. Demodulation of optical coherent modulation formats requires downlink signal coupling into single-mode fiber. Due to atmospheric turbulence, signals experience wavefront distortions creating speckle patterns larger than the fiber core and high jitter requiring precise beam steering. AO is necessary to correct atmospheric turbulence effects and allow efficient coupling of received signals. In 2020, GSFC contracted with General Atomics to provide the LCOT AO system. This system has been delivered to GSFC in September 2021 and has been tested in laboratory to evaluate performance. This paper describes the laboratory testing approach, turbulence phase plate design, test results, and the AO field testing plan when installed on the LCOT telescope.

Adaptive Optics↗
NASA NTRS2022

Simulating Reflected Light Coronagraphy of Earth-like Exoplanets with a Large IR/O/UV Space Telescope: Impact and Calibration of Smooth Exozodiacal Dust

Observing Earth-like exoplanets orbiting within the habitable zone of Sun-like stars and studying their atmospheres in reflected starlight requires contrasts of ∼1e–10 in the visible. At such high contrast, starlight reflected by exozodiacal dust is expected to be a significant source of contamination. Here, we present high-fidelity simulations of coronagraphic observations of a synthetic solar system located at a distance of 10 pc and observed with a 12 m and an 8 m circumscribed aperture diameter space telescope operating at 500 nm wavelength. We explore different techniques to subtract the exozodi and stellar speckles from the simulated images in the face-on, the 30 deg inclined, and the 60 deg inclined case and quantify the remaining systematic noise as a function of the exozodiacal dust level of the system. We find that in the face-on case, the exozodi can be subtracted down to the photon noise limit for exozodi levels up to ∼1000 zodi using a simple toy model for the exozodiacal disk, whereas in the 60 deg inclined case this only works up to ∼50 zodi. We also investigate the impact of larger wave front errors and larger system distance, finding that while the former has no significant impact, the latter has a strong (negative) impact. Ultimately, we derive a penalty factor as a function of the exozodi level and system inclination that should be considered in exoplanet yield studies as a realistic estimate for the excess systematic noise from the exozodi.

Exoplanet detection methods↗
NASA NTRS2021

Enabling High-Contrast Imaging of Binary Stars With the Roman Space Telescope Coronagraph Instrument

A large fraction of Sun-like stars is contained in binary systems, in fact within 10 pc there are 67 FGK stars, out of which 42 belong to a multi-star system, and 28 have companion leak that is greater than 1e-9 contrast, assuming typical Hubble-quality space optics. Currently, those binary stars are not included in the Roman Space Telescope Coronagraph Instrument target list, but they could be observed if high-contrast imaging around binary star systems using Roman was possible. The Multi-Star Wavefront Control (MSWC) algorithm can be used to suppress companion star leakage. If the targets have angular separations larger than the Nyquist controllable region of the Deformable Mirror, MSWC must operate in its Super-Nyquist (SN) mode. This mode requires a target star replica within the SN region in order to provide the ability to null speckles at SN angular separations. For the case of Roman, more than half of the targets that can be observed using MSWC, including Alpha Centauri, have angular separations larger than the Nyquist controllable region of the 48x48 actuator Deformable Mirror (DM) to be used. In this paper, we describe how super-Nyquist MSWC can be implemented in Roman CGI adding a mild grating on a replica of the Wide-field Shaped Pupil mask, which would use a spare space in the Shaped Pupil Active Mechanism. We present the feasibility analysis, simulation results, and discuss the latest results on MSWC experiment from three different laboratories at NASA Ames, the Jet Propulsion Laboratory, and the Subaru telescope.

Prada, Camilo Mejia↗
NASA NTRSDate not supplied

A New Integral Field Spectrograph for Broadband Coronagraph Demonstrations at the High Contrast Imaging Testbed Facility

An integral field spectrograph (IFS) camera may help fulfill the exoplanet characterization goals of a future Habitable Worlds Observatory. During the Nancy Grace Roman Space Telescope mission formulation phase, the Coronagraph Instrument Project established the laboratory performance baseline of a combined coronagraph and IFS system with the Prototype Imaging Spectrograph for Coronagraphic Exoplanet Studies (PISCES; 1E-8 contrast over an 18% bandpass; 3--9 lambda/D bowtie-shaped control region). New laboratory demonstrations are needed to expand on this milestone in terms of contrast, bandpass, and field of view towards the requirements of a future mission capable of characterizing the atmospheres of Earth-like exoplanets. Here we present the design of a successor to PISCES that can observe a 20 lambda/D-diameter field of view with an instantaneous bandpass up to 30%, at a resolving power R > 70 at visible wavelengths. This instrument will interface with the existing coronagraph layout in the High Contrast Imaging Facility DST-2 vacuum chamber. The addition of a spectroscopic imaging camera at HCIT will benefit the wider coronagraph technology community by enabling other NASA-supported investigators to automatically obtain multi-wavelength measurements of speckles both inside and outside of their control region, and the instrument will support community-led demonstrations of high-order wavefront sensing and control techniques such as dark hole maintenance and linear dark field control.

coronagraph↗
NASA NTRSDate not supplied

Maize Rough Endosperm6 (rgh6) Encodes A Predicted Dead-Box RNA Helicase and Affects Mirna Processing in Endosperm Development

Maize rough endosperm (rgh) mutants have defective kernels with a rough, etched, or pitted endosperm surface. Molecular genetic analysis of this mutant class has identified multiple RNA processing proteins critical to endosperm development. Here, we report on the developmental and molecular function of the rgh6 locus. The rgh6 mutant was isolated from the UniformMu transposon tagging population. Mutant kernels have reduced endosperm size and defective embryos that develop in a more apical position than typical for defective embryos. TB translocation crosses revealed that rgh6 mutant endosperm inhibits normal embryo development. Positional cloning of the rgh6 locus found that it encodes a predicted DEAD-box RNA helicase. Consistent with a predicted function for RNA processing, transient expression of a RGH6-GFP fusion protein is localized to nucleolus and nuclear speckles in Nicotiana benthamiana leaves. Rgh6 transcripts are highly expressed in endosperm epidermal cell types such as the aleurone, basal endosperm cell layer, embryo surrounding region, and endosperm adjacent to scutellum. Markers of these cell types show increased levels in rgh6 mutant kernels. Mutant endosperm tissues have increased precursor microRNA (pre-miRNA) and decreased mature miRNA relative to normal sibling endosperm, indicating that rgh6 is required for miRNA processing. The transcript levels for most miRNA target genes accumulate to a higher level in rgh6 mutant tissue. These results suggest that miRNA processing and regulation of miRNA target genes are required for normal endosperm development.

Plant Sciences↗
NASA NTRSDate not supplied

Applications and Development Work for Digital Image Correlation Using High Speed Cameras

NASA, Army, and industry partners are working to advance optical measurement techniques used in highly dynamic rocket engine and missile test environments. This allows for direct component data collection during test and flight environments, significantly reduced analysis time, and associated cost savings. Digital Image Correlation (DIC) uses calibrated stereo cameras to collect three-dimensional (3-D) displacements, strains, and acceleration data by referencing a stochastic speckle pattern applied to the test object. These optical measurement techniques provide significantly improved data resulting in better performance predictions, model validation, and information about components during hot-fire tests and test flights.

Rachel Paden↗
NASA NTRSDate not supplied

High-Speed Self-Aligned Focusing Schlieren and Background-Oriented Schlieren with Pulsed Laser Illumination

Laser light sources are commonly used in schlieren-based flow visualization techniques that are in development at NASA Langley Research Center. Of particular interest are high-intensity, low coherence sources that allow for high signal-to-noise schlieren imagery to be acquired without the laser speckle that typically occurs as a result of interference. Results from a self-aligned focusing schlieren system developed at NASA Langley and a background-oriented schlieren system are presented to highlight the effectiveness of these sources.

Schlieren↗
NASA NTRS2023

A Hunting Expedition For High-Order Hierarchies

Stellar hierarchical systems of high order containing more than three stars are rare and fascinating objects; their disco v ery and study highlight still unknown aspects of star formation and early evolution. We matched eclipsing binaries disco v ered by Transiting Exoplanet Surv e y Satellite with a Gaia catalogue of wide binaries and selected candidate quadruple (or higher order) systems based on e xcessiv e astrometric noise. A subset of 192 southern candidates located within 500 pc was observed by speckle interferometry, and we resolved for the first time 50 close pairs, confirming their high-order (from four to five components) multiplicity. These observations are reported, and some remarkable hierarchical systems are discussed.

Brian P Powell↗
NASA NTRSDate not supplied

In-Situ Scanning Electron Microscope Experiments for Microscale Mechanical Testing and Validated Modeling of Fiber Reinforced Thermoplastics

A novel, in-situ, scanning electron microscope (SEM) mechanical testing capability for materials at the microscale which provides experimental validation to a machine learning (ML) toolset for full-field validation of physics-based micromechanics models is being developed by researchers at NASA Glenn Research Center. These are enabling technologies for the integration of multiscale digital twins for materials into system level models which will result in the improved performance, material discovery, reduced production cost and time, rapid characterization, and prognostic structural health monitoring (SHM) for materials and structures for extreme environments in support of NASA space exploration missions. In order to bridge the material structure-to-system gap for digital twins, physics-based models must be experimentally validated at multiple length scales. Seminal microscale experiments, conducted at the Air Force Research Laboratory (AFRL), were limited to transverse compression of single-layer, unidirectional thermoset polymer matrix composite (PMC) micropillar specimens [1]. The early phases of the current project followed those initial results and setup to reproduce the compression testing of PMC material on the custom-built piezoelectric actuated micromechanical testing rig built by MicroTesting Solutions LLC. In this work, samples of thermoplastic PMC material were first machined into 3 mm cubes, and then further machining and final milling was done using a Focused Ion Beam (FIB). The initial experiment was done on a pillar roughly 20 µm x 20 µm x 40 µm tall. Additional pillars were milled with final sizes ranging from 20 µm x 20 µm x 40 µm tall to 40 µm x 40 µm x 65 µm tall. A speckle pattern for in-situ full-field measurements using Digital Image Correlation (DIC) was applied with platinum, which was coated on the surface, and then the FIB was used to mill away some of the coating to produce an irregular pattern of Pt on the pillar surface. The samples were loaded into the custom testing rig and placed into the SEM and loaded under compression until failure. Images were collected in the SEM during testing. Post-processing of the images was conducted using DIC to obtain full-field displacement and strain measurements elucidating the role of the matrix as well as fiber-fiber interaction at the microscale within the composite subjected to compression loading well into the non-linear regime of the material. Moreover, the evolution of fiber-matrix debonding and matrix cracking is observed in-situ at the microscale. This data, along with images segmented with a newly developed ML toolset [2], was used to create and validate physics-based micromechanics models. An image of the failed micropillar is shown in Figure 1. The techniques developed in the initial compression experiment was tailored to the validation needs of the models and expanded to include different sized samples as well as possibly tension and fatigue.

Laura Wilson↗