cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.48577/jpl.8wy24l
title: In Search of Subsurface Oceans within the Uranian Moons

description: The Galileo mission to Jupiter discovered magnetic signatures associated with hidden sub-surface oceans at the moons Europa and Callisto using the phenomenon of magnetic induction. These induced magnetic fields originate from electrically conductive layers within these moons and are driven by Jupiter’s strong time-varying magnetic field. The ice giants and their moons are also ideal laboratories for magnetic induction studies as both Uranus and Neptune have a strongly tilted magnetic axis with respect to their spin axis, creating a dynamic and strongly variable magnetic field environment at the orbits of their major moons. Although Voyager 2 visited the ice giants in the 1980s, it did not pass close enough to any of the major moons to detect magnetic induction signatures. However, the Voyager flyby revealed that some of these ice giant moons exhibit surface features that hint at geologically recent activity and the possibility that these objects may harbor sub-surface oceans. Future missions to the ice giants may therefore be capable of discovering hidden sub-surface oceans, thereby adding to the family of known “ocean worlds” in our solar system. Here, we assess magnetic induction as a technique for investigating sub-surface oceans within the major moons of Uranus. Furthermore, we establish the ability to distinguish induction responses created by different interior characteristics that tie into the induction response: ocean thickness, conductivity, and depth, as well as ionospheric conductance. The results reported here demonstrate the possibility of single-pass ocean detection and characterization at the moons Miranda, Ariel, and Umbriel, and provide guidance to required magnetometer performance and trajectory design for future missions to Uranus.
DOI: 10.48577/jpl.lmctk3
title: Disequilibrium Chemistry in Exoplanet Atmospheres observed with the Hubble Space Telescope

description: Literature on the theory of exoplanet atmospheric disequilibrium chemistry is rich, although its ob- servational counterpart has yet to emerge beyond the hints provided by a few targets in dedicated studies. We report results from an uniform data reduction and analysis for a catalog of 62 Hubble Space Telescope exoplanet transit spectra where we assess the atmospheric model preference for dise- quilibrium chemistry (i.e. water vapor is not the dominant absorption spectral signature) over Thermal Equilibrium Chemistry in a comparative planetology context. Where model preference assessment is possible, we find that disequilibrium occurs in about half of the atmospheres, indicating that disequi- librium processes play an important role in the composition of exoplanet atmospheres. While very hot atmospheres, over 1800K, prefer equilibrium chemistry, we find a clustering of preference for disequi- librium in the 1200K - 1800K temperature range. We suggest that UV-augmented thermochemistry may play a significant role for those atmospheres.
DOI: 10.48577/jpl.olx5qv
title: The Aligned Orbit of the Warm Jupiter K2-232 b

description: Measuring the obliquity distribution of stars hosting warm Jupiters may help us to understand theformation of close-orbiting gas giants. Few such measurements have been performed due to practicaldifficulties in scheduling observations of the relatively infrequent and long-duration transits of warmJupiters. Here, we report a measurement of the Rossiter-McLaughlin effect for K2-232b, a warmJupiter on an 11.17-day orbit with an eccentricity of 0.26. The data were obtained with the Automated Planet Finder during two separate transits. The planet’s orbit appears to be well-aligned with the spin axis of the host star, with a projected spin-orbit angle of λ = −11.1 ± 6.6 . Combined with the other available data, we find that high obliquities are almost exclusively associated with planets that either have an orbital separation greater than 10 stellar radii or orbit stars with effective temperatures hotter than 6,000K. This pattern suggests that the obliquities of the closest-orbiting giant planets around cooler stars have been damped by tidal effects.
DOI: 10.48577/jpl.disy7d
title: Tree Canopies Reflect Mycorrhizal Composition

description: Mycorrhizae alter global patterns of CO2 fertilization, carbon storage, and elemental cycling, yet knowledge of their global distributions is currently limited by the availability of forest inventory data. Here, we show that maps of tree-mycorrhizal associations (hereafter “mycorrhizal maps”) can be improved by the novel technology of imaging spectroscopy because mycorrhizal signatures propagate up from plant roots to impact forest canopy chemistry. We analyzed measurements from 143 airborne imaging spectroscopy surveys over 112,975 individual trees collected across 13 years. Results show remarkable accuracy in capturing ground truth observations of mycorrhizal associations from canopy signals across disparate landscapes (R2 = 0.92, p &lt; 0.01). Upcoming imaging spectroscopy satellite missions can reveal new insights into landscape-scale variations in water, nitrogen, phosphorus, carotenoid/anthocyanin, and cellulose/lignin composition. Applied globally, this approach could improve the spatial precision of mycorrhizal distributions by a factor of roughly 104 and facilitate the incorporation of dynamic shifts in forest composition into Earth System models.
DOI: 10.48577/jpl.mdonbo
title: Atmospheric Impacts on Approach Operations and EDL Targeting for the InSight Mission

description: Early in operational testing for the InSight mission to Mars, it was discovered that the final maneuver to target the entry-interface point was unexpectedly sensitive to planned atmosphere updates that would be based on real-time measurements of the Martian atmosphere by Mars Reconnaissance Orbiter. Upon investigation, the team realized the Phoenix mission also discovered this sensitivity during operational testing. Further investigation identified that the sensitivity was a result of the fact that both the entry flight path angle and ground target were being held fixed in the maneuver design process, constraining the maneuver in a way that forced the entry time to change to compensate for changes to the nominal trajectory from updating the atmosphere model. The final maneuver was planned for 22 hours prior to entry, at which point it is very expensive to change entry time. The study also revealed that any unguided Mars entry, descent, and landing mission would be impacted by this sensitivity if it used real-time atmosphere observations to model the nominal expected atmosphere used for maneuver targeting of the entry-interface point. This paper discusses the results of that investigation and presents a number of mitigations as well as the consequences of ignoring the sensitivity.
DOI: 10.48577/jpl.r1ncfj
title: Broadband Dichromatic Variational Measurement

description: Quantum back action imposes fundamental sensitivity limits to the majority of quantum measurements. The effect results from the unavoidable contamination of the measured parameter with the quantum noise of a meter. Back action evading measurements take advantage of the quantum correlations introduced by the system under study to the meter and allow overcoming the fundamental limitations. The measurements are frequently restricted in their bandwidth due to a finite response time of the system components. Here we show that probing a mechanical oscillator with a dichromatic field with frequencies separated by the oscillator frequency enables independent detection and complete subtraction of the measurement noise associated with the quantum back action.
DOI: 10.48577/jpl.cyfxy5
title: The Atmospheric Carbon and Transport (ACT) – America Mission

description: The Atmospheric Carbon and Transport (ACT) – America NASA Earth VentureSuborbital Mission set out to improve regional atmospheric greenhouse gas (GHG)inversions by exploring the intersection of the strong GHG fluxes and vigorous atmospheric transport that occurs within the midlatitudes. Two research aircraft instrumented with remoteand in situ sensors to measure GHG mole fractions, associated trace gases, and atmospheric state variables collected 1140.7 flight hours of research data, distributed across 305 individual aircraft sorties, coordinated within 121 research flight days, and spanning five, six-weekseasonal flight campaigns in the central and eastern United States. Flights sampled 31 synoptic sequences, including fair weather and frontal conditions, at altitudes ranging from the atmospheric boundary layer to the upper free troposphere. The observations were complemented with global and regional GHG flux and transport model ensembles. We found that midlatitude weather systems contain large spatial gradients in GHG mole fractions, in patterns that were consistent as a function of season and altitude. We attribute these patterns to a combination of regional terrestrial fluxes and inflow from the continental boundaries. These observations, when segregated according to altitude and air mass, provide a variety of quantitative insights into the realism of regional CO2 and CH4 fluxes and atmospheric GHG transport realizations. The ACT-America data set and ensemble modeling methods provide benchmarks for the development of atmospheric inversion systems. As global and regional atmospheric inversions incorporate ACT-America’s findings and methods, we anticipate these systems will produce increasingly accurate and precise sub-continental GHG flux estimates.
DOI: 10.48577/jpl.jvhmol
title: The spectral nature of Earth's reflected radiation: measurement and science applications

description: Abstract: This paper introduces the aerosol, clouds, convection and precipitation (ACCP) program that is currently in the process of defining a number of measurement objectives for NASA that are to be implemented toward the end of the current decade. Since a (solar) visible-shortwave infrared (VSWIR) spectrometer is being considered as part of the ACCP architecture, illustrations of the different ways these measurements will contribute to this program and how these measurements can be expected to advance the science objectives of ACCP are highlighted. These contributions range from 1) constraining cloud radiative process and related estimates of radiative fluxes, 2)scene discrimination, 3) providing aerosol and cloud optical properties, and 4) providing other enhanced information such as the phase of water in clouds, and total column water vapor. The spectral measurements also offer new capabilities that will further enhance the ACCP science such as the discrimination of dust aerosol and the potential for the vertical profiling cloud droplet size in shallow clouds. The areas where the maturity of approaches is lacking is also highlighted as a way of emphasizing research topics to be a focus in the coming years.
DOI: 10.48577/jpl.cb6296
title: A Deep-Ultraviolet Raman and Fluorescence Spectral Library of 62 Minerals for the SHERLOC instrument onboard Mars 2020

description: We report deep-ultraviolet (DUV) Raman spectra as measured by a SHERLOC analog instrument (248.6 nm excitation) for 92 samples representing 62 distinct minerals, including borates, carbonates, sulfates, phosphates, halides, metal oxides & hydroxides, silicates & phyllosilicates. We found that DUV Raman is capable of detecting the majority of these minerals, with major mineral peaks occurring at ~500, ~850, 950–1200, and ~3600 cm−1, and that detection thresholds will be better for the SHERLOC flight instrument than the analog used in this study. Minerals can be classified (e.g., sulfate vs carbonate, or pyroxene vs olivine) based on the number of major peaks and their general positions. Identification of specific mineral phases is possible based on precise Raman peak positions, provided the difference between spectrally similar minerals exceeds 10 cm−1. A number of silicate minerals did not produce measurable Raman signal, and iron-rich minerals tend to be more difficult to detect due to significant UV absorption. Many Mars-relevant minerals expected to occur in Jezero crater should be detectable to SHERLOC even during short-exposure survey scans. This library will help inform the detection and identification of mineral phases in Martian samples using the SHERLOC instrument onboard the Mars 2020 Perseverance rover.
DOI: 10.48577/jpl.hodvff
title: Reduced Nonlinear Model for Orbit Uncertainty Propagation and Estimation

description: This paper presents a novelmethod for nonlinear uncertainty propagation and estimation in orbital dynamics.The proposed technique relies on a Taylor series expansion of the integral flow to model the dynamics around the reference solution and introduces an approximation of the high-order variational equations that reduces the complexity of evaluating the series. In particular, the high-order state-transition tensors (STTs) are approximated by capturing the dominant secular terms. Simple expressions to compute them are provided. The approximation stems from confining the Lyapunov instability of the motion to the time domain. The result is a time-explicit approximation of the STTs that can be used to predict the evolution of the uncertainty distribution accounting for nonlinear effects with minimal overhead. Finally, a high-order version of the extended Kalman filter is developed by implementing the approximation of the nonlinear terms of the Taylor series into an estimation scheme. The performance of the algorithm is evaluated with several practical examples.
DOI: 10.48577/jpl.j0xepg
title: Formation of rims around chondrules via porous aggregate accretion

description: Chondrules are often surrounded by fine-grained rims or igneous rims. The properties of these 19 rims reflect their formation histories. While the formation of fine-grained rims is modeled by 20 the accretion of dust grains onto chondrules, the accretion should be followed by the growth of 21 dust grains due to the shorter growth timescale than the accretion. In this paper, we investigate 22 the formation of rims, taking into account the growth of porous dust aggregates. We estimate the 23 rim thickness as a function of the chondrule fraction at a time when dust aggregate accretion onto 24 chondrules is switched to collisions between these chondrules. Our estimations are consistent 25 with the measured thicknesses of fine-grained rims in ordinary chondrites. However, those of 26 igneous rims are thicker than our estimations. The thickness of igneous rims would be enlarged 27 in remelting events.
DOI: 10.48577/jpl.nflu24
title: Resonances of the InSight Seismometer on Mars

description: The InSight seismometer was deployed to the surface of Mars in December 2018 - February 2019. We present here the resonances known to be present in the sensor assembly in order to aid interpretation of the seismic signals observed on Mars. Briefly, there are resonances in the sensor assembly at about 2.9, 5.3, 9.5, 12, 14, 23-28, and 51 Hz. We present various methods that were used to characterize these resonances, evidence for some of them in data collected on Mars, and a transfer function for a similar setup on Earth.
DOI: 10.48577/jpl.o1bsgz
title: Limitations of bin and bulk microphysics in reproducing the observed spatial structure of light precipitation

description: Coarse-gridded atmospheric models often account for subgrid-scale variability by specifying probability distribution functions (PDFs) of process rate inputs such as cloud and rain water mixing ratios ($q_c$ and $q_r$, respectively). PDF parameters can be obtained from numerous sources: in situ observations, ground- or space-based remote sensing, or fine-scale modeling such as large eddy simulation (LES). LES is appealing to constrain PDFs because it generates large sample sizes, can simulate a variety of cloud regimes/case studies, and is not subject to the ambiguities of observations. However, despite the appeal of using model output for parameterization development, it has not been demonstrated that LES satisfactorily reproduces the observed spatial structure of microphysical fields. In this study, the structure of observed and modeled microphysical fields are compared by applying bifractal analysis, an approach that quantifies variability across spatial scales, to simulations of a drizzling stratocumulus field that span a range of domain sizes, drop concentrations (a proxy for mesoscale organization), and microphysics schemes (bulk and bin). Simulated $q_c$ closely matches observed estimates of bifractal parameters that measure smoothness and intermittency. There are major discrepancies between observed and simulated $q_r$ properties, though, with bulk simulated $q_r$ consistently displaying the bifractal properties of observed clouds (smooth, minimally intermittent) rather than rain while bin simulations produce $q_r$ that is appropriately intermittent but too smooth. These results suggest fundamental limitations of bulk and bin schemes to realistically represent higher-order statistics of the observed rain structure.
DOI: 10.48577/jpl.lqsgkr
title: InSAR Phase Unwrapping Error Correction for Rapid Repeat Measurements of Water Level Change in Wetlands

description: Here we present an enhanced algorithm to correct InSAR phase unwrapping errors by incorporating iterative spatial bridging between islands and phase closure among interferograms. We use rapid repeat airborne Synthetic Aperture Radar acquisitions from NASA’s airborne UAVSAR instrument to estimate short-term changes in water level within coastal wetlands from a stack of consecutive interferograms acquired with very short temporal separation (~30 min.). The algorithm is applied to six consecutive UAVSAR images collected in tidal wetlands of the Wax Lake Delta, Louisiana, USA. Validation of our water level change retrievals with in situ field observations were conclusive with high correlation and an RMSE generally smaller than 3cm. Comparison of our algorithm with other phase unwrapping error correction methods shows significant improvement (30% to 35% increase in number of correctly unwrapped pixels) when applied to rapid changes in water level. The set of corrections presented in this work enables measurement of water level change in deltas and other areas where tides drive highly dynamic flooding of inland vegetated areas. Although demonstrated for water level change, the method is applicable to other InSAR data sets with large spatial gradients or observed discontinuities between coherent but spatially isolated areas.
DOI: 10.48577/jpl.mt4wjc
title: An Empirical Algorithm for Mitigating the Sea Ice Effect in SMAP Radiometer for Sea Surface Salinity Retrieval in the Arctic Seas

description: The L-band radiometer onboard the Soil MoistureActive Passive (SMAP) mission is used to retrieve sea surfacesalinity (SSS) over global ocean. In the Arctic seas, one of themajor challenges of SSS remote sensing is the presence of sea ice.This paper proposes a data-driven ice correction (IC) algorithmwhich extracts emission from the water portion of measuredbrightness temperature (TB) in scenes mixed with water and ice.Emission of the ice portion was removed based on estimationaccording to the ice fraction (fice) in the satellite footprint and icesignature derived from surrounding pixels. The IC algorithm isapplied to SMAP TB data to obtain TB with ice correction (TBIC),which are used for SSS retrieval using the standard JPL SMAPCAP processing system. We show that the algorithm is mosteffective near the ice edge, thereby increasing the fice threshold forpossible SSS retrieval to 15% from the current 3% without IC.SMAP SSS are validated using in situ salinity collected duringNASA’s Ocean Melting Greenland (OMG) mission from 2016 to2020 along the Greenland coast. The number of collocationsbetween OMG and SMAP daily gridded salinity increased bymore than 30% with IC. The statistical analysis shows a similarretrieval accuracy with or without IC, with the standard deviationof the difference between OMG and SMAP of 1.41 psu (with IC)and 1.42 psu (without IC). The bias adjusted SMAP SSS depictssalinity patterns and gradients around Greenland consistent withOMG measurements.
DOI: 10.48577/jpl.ygokuc
title: Detecting dark matter subhalos with the Nancy Grace Roman Space Telescope

description: Dark matter substructure is a promising way of distinguishing between dark matter models. While cold dark matter predicts halos down to quite small scales, other models typically predict a cut-off in the subhalo mass function. If these subhalos existed in the Milky Way, they would produce weak lensing signatures on background stars. These signatures would produce correlated apparent velocity and acceleration signatures, which could be observable given sufficient astrometric resolution and cadence. The Nancy Grace Roman Space Telescope's Exoplanet Microlensing Survey will be perfectly suited to looking for the acceleration signatures of these halos. Here we forward model these acceleration signatures and explore the Roman Space Telescope future constraints on lens profiles and populations. In particular, we find that the Roman Space Telescope will place strong limits on both small and large point-source halos, as well as constraints on very concentrated diffuse halos. We also discuss possible systematic effects that could hinder these efforts and methods for improving these constraints.
DOI: 10.48577/jpl.5ozre3
title: New Candidate Extreme T Subdwarfs from the Backyard Worlds: Planet 9 Citizen Science Project

description: Schneider et al. (2020) presented the discovery of WISEA J041451.67−585456.7 and WISEA J181006.18−101000.5, which appear to be the first examples of extreme T-type subdwarfs (esdTs; metallicity ≤ −1 dex, Teff &lt;~1400 K). Here we present new discoveries and follow-up of three T-type subdwarf candidates, with an eye toward expanding the sample of such objects with very low metallicity and extraordinarily high kinematics, properties that suggest membership in the Galactic halo. Keck/NIRES near-infrared spectroscopy of WISEA J155349.96+693355.2, a fast-moving object discovered by the Backyard Worlds: Planet 9 citizen science project, confirms that it is a mid-T subdwarf. With HW2 = 22.3 mag, WISEA J155349.96+693355.2 has the largest W2 reduced proper motion among all spectroscopically confirmed L and T subdwarfs, suggesting that it may be kinematically extreme. Nevertheless, our modeling of the WISEA J155349.96+693355.2 near-infrared spectrum indicates that its metallicity is only mildly subsolar. In analyzing the J155349.96+693355.2 spectrum, we present a new grid of low-temperature, low-metallicity model atmosphere spectra. We also present the discoveries of two new esdT candidates, CWISE J073844.52−664334.6 and CWISE J221706.28−145437.6, based on their large motions and colors similar to those of the two known esdT objects. Finding more esdT examples is a critical step toward mapping out the spectral sequence and observational properties of this newly identified population.