cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.48577/jpl.yjljfd
title: Growth of the Modified Two-stream Instability in the Plume of a Magnetically Shielded Hall Thruster

description: The electrostatic dispersion relation of the Modified Two-Stream Instability has been solved numerically in the near-plume of a magnetically shielded Hall thruster. The plasma conditions have been obtained by 2-D (r-z) multifluid-PIC simulations. The maximum growth rate γ_max is found to be &gt; 0 in most regions of the domain, with the fastest growth approaching the fluid-limit value of ω_LH/2, at angles ≳ π/6 relative to the z-axis and near the magnetic poles where ω_pe/ω_ce ~1. In this region the relative drift between beam ions perpendicular to B and magnetized electrons is u/u_Ti≳3, while that between counter-streaming beam and cathode ions is ≳4. The latter suggests that the ion-ion cross-field lower hybrid instability may also be active here. The presence of these instabilities can lead to anomalous heating of ions striking nearby surfaces.
DOI: 10.48577/jpl.bxolcg
title: Recoverability of known near-Earth asteroids

description: This paper analyzes the current population of known near-Earth asteroids (NEAs) and presents statistics on the recoverability of NEAs with both targeted observation campaigns and all-sky surveys. For an asteroid to be observable at a future apparition, given the right geometry, the plane-of-sky uncertainty must be small enough to be covered by a telescope's eld of view and the asteroid must be brighter than the detector's limiting magnitude. Since recoverability is a telescope-dependent property, we select two representative instruments that span a wide range of capability and availability: the 1.0- meter I52 telescope of the Catalina Sky Survey and the Hyper Suprime-Cam of the 8.2-meter Subaru telescope. Based on this choice, we classify asteroids as recoverable, potentially recoverable, and not recoverable depending on whether they could be detected with an I52-class telescope, only with a Subaru-class telescope, or with neither, respectively. Using these denitions, we nd that the majority (90%) of NEAs with H &lt; 22 and most (93%) potentially-hazardous asteroids (PHAs) are recoverable or potentially recoverable in the next 50 years. When considering fainter asteroids down to H 28, about two thirds of the NEA population and half of the low-MOID asteroids (MOID 0:05 au) are either recoverable or potentially recoverable. As of 2019-Oct-13, the Sentry risk list includes 193 objects with an impact probability greater than 10􀀀6 that are not recoverable. The fraction of NEAs and low-MOID NEAs that are not recoverable can be reduced by up to 47% and 43%, respectively, when incorporating statistical estimates of serendipitous recoveries by all-sky surveys.
DOI: 10.48577/jpl.z5eoee
title: Formation of Tridymite and Evidence for a Hydrothermal History at Gale Crater, Mars

description: Mineralogical and chemical results from the Curiosity Mars rover in Gale crater are consistent with hydrothermal activity occurring after sediment deposition. Chemical similarities between tridymite-bearing regions of the Murray formation and silica-rich alteration halos crosscutting the Stimson formation suggest that the detected tridymite is authigenic. A previous model for the occurrence of tridymite suggests detrital sedimentation from silicic volcanic sources but does not account for chemical similarities with the high-silica alteration halos. Elemental chemistry and mineral phases identified by the Curiosity rover support hydrothermal activity at various temperatures along the traverse through Gale crater.
DOI: 10.48577/jpl.ezi6t4
title: Quantum diffusion of microcavity solitons

description: Coherently-pumped (Kerr) solitons in an ideal optical microcavity are expected to undergo random quantum motion that determines fundamental performance limits in applications of the soli-ton microcombs. Here, this random walk and its impact on Kerr soliton timing jitter is studied experimentally. The quantum limit is discerned by measuring relative position of counter-propagating solitons. Their relative motion features weak interactions and also presents excellent common mode suppression of technical noisetypically hiding the quantum fluctuations. This is in strong contrast to co-propagating solitons which are found to have relative timing jitter well below the quantum limit of a single soliton on account of strong mutual motion correlation. Good agreement is found between theory and experiment. The results establish the fundamental limits to timing jitter in soliton microcombs and provide new insights on multi-soliton physics.
DOI: 10.48577/jpl.ga9tig
title: Compression Algorithms for High Data Volume Instruments on Planetary Missions: a Case Study for the Cassini Mission

description: We investigated data compression algorithms to boost science data return from high data volume instrumentson planetary missions, particularly outer solar system missions where every bit of data represents an engineeringtriumph of over severe constraints on mass (limiting antenna size) and power (limiting signal strength). We developeda methodology to (1) investigate algorithms to improve compression, and (2) to work with the science teams to evaluatethe effects on the science.Our algorithm for compressing the Cassini RPWS (Radio Plasma Wave Science) data achieved a factor of 5 improvementin data compression (relative to what the RPWS team was using), and our algorithm for the Cassini UVIS(Ultraviolet Imaging Spectrograph) Saturn data set achieved a much higher factor (70). In both cases, the investigatorson the science teams who evaluated our results reported that the science goals were not compromised. Ourcompression algorithm for ISS (Imaging Science Subsystem) images achieved on average a factor of 1:7 improvementin lossless compression compared to the original algorithm. We also evaluated the compression effectiveness ofJPL’s Fast Lossless EXtended (FLEX) hyperspectral/multispectral image compressor on Cassini’s VIMS (Visible andInfrared Mapping Spectrometer) data. FLEX lossless compression provides a factor 2 improvement over the originalcompression. We also explore a different range of lossy compression which can achieve an additional factor 2 to 5depending on the fidelity required.Our findings have implications for the design of future space missions, particularly with respect to antenna size andoverall Size, Weight, and Power (SWaP) budgets, by demonstrating strategies to implement better data compression.In addition to improved algorithms, we show that an iterative process involving real-time science team evaluation andfeedback to update the on-board compression algorithm is both essential and feasible. We make the case that a spacecraftfacility compressor hosting a toolbox of compression algorithms, available to all of the science instruments andsupported by a team of compression experts, conveys significant benefits. Beyond the obvious benefits of increasedscience return and faster playback, better data compression enables design trades between antenna size and number ofscience instruments on the payload.
DOI: 10.48577/jpl.bpdvlf
title: Validation of PSF Models for HST and Other Space-Based Observations

description: Forthcoming space-based observations will require high-quality point-spread function (PSF) models for weak gravitational lensing measurements. One approach to gener- ating these models is using a wavefront model based on the known telescope optics. We present an empirical framework for validating such models to conrm that they match the actual PSF to within requirements by comparing the models to the ob- served light distributions of isolated stars. We apply this framework to Tiny Tim, the standard tool for generating model PSFs for the Hubble Space Telescope (HST), test- ing its models against images taken by HST's Advanced Camera for Surveys in the Wide Field Channel. We show that Tiny Tim's models, in the default conguration, dier signicantly from the observed PSFs, most notably in their sizes. We nd that the quality of Tiny Tim PSFs can be improved through tting the full set of Zernike polynomial coecients which characterise the optics, to the point where the practical signicance of the dierence between model and observed PSFs is negligible for most use cases, resulting in additive and multiplicative biases both of order 410􀀀4. We also show that most of this improvement can be retained through using an updated set of Zernike coefficients, which we provide.
DOI: 10.48577/jpl.kod5ry
title: Cage occupancy of methane clathrate hydrates in the ternary H2O-NH3-CH4 system

description: The incorporation of ammonia inside methane clathrate hydrate is of great interest to the hydrate chemistry community. We investigated the phase behavior of methane clathrate formed from aqueous ammonia solution. Ammonia’s presence decreases methane occupancy in the large cages, without Raman spectroscopic evidence for its incorporation inside the structure.
DOI: 10.48577/jpl.tlmlkr
title: Estimating Nitrous Oxide (N2O) Emissions for the Los Angeles Megacity using mountaintop remote sensing observations

description: Nitrous oxide (N2O) is an important greenhouse gas contributing both to global radiative forcing and ozone depletion. Though N2O emissions are largely derived from agricultural activities, urban sources of N2O also contribute significantly to anthropogenic emissions, but are not well understood and difficult to quantify. This study employs a top-down approach to derive urban N2O emissions for the Los Angeles megacity using a unique dataset from a mountaintop remote sensing instrument, which has been observing greenhouse gas mixing ratios in LA since 2011. Maps of N2O mixing ratios above background levels (XN2Oxs) highlight the coastal region of LA as having consistently elevated XN2Oxs compared to the interior basin and indicate a diurnal cycle in which XN2Oxs increases throughout the day. Time series of XN2Oxs show a seasonal cycle with a peak-to-peak amplitude of 10±3 ppb, where greater XN2Oxs values are observed during the winter/spring and a minimum occurs in late summer/ early fall. A tracer-tracer correlation method applied using XN2Oxs and XCO2,xs observations to estimate top-down N2O emissions for the LA basin during 2013-2018 yields a mean annual emissions value of 171 ±17 Gg N2O per year. This top-down estimate is roughly 3 times the official statewide bottom-up inventory for the same time period, but consistent considering uncertainties with other top-down estimates for the LA basin. The discrepancy between top-down emission estimates and the statewide bottom-up inventory highlights the difficulty in using bottom-up methods to constrain N2O emissions, especially for an urban environment.
DOI: 10.48577/jpl.h1bybg
title: Correcting model biases of CO in East Asia: impact on oxidant distributions during KORUS-AQ

description: Global coupled chemistry-climate models underestimate carbon monoxide (CO) in theNorthern Hemisphere, exhibiting a pervasive, negative bias against measurements peaking in late40 winter and early spring. While this bias has been commonly attributed to underestimation of directanthropogenic and biomass burning emissions, chemical production and loss via OH reaction fromemissions of anthropogenic and biogenic VOCs play an important role. Here we investigate thereasons for this underestimation using aircraft measurements taken in May and June 2016 fromthe Korea United States Air Quality (KORUS-AQ) experiment in South Korea and the Air45 chemistry Research In Asia (ARIAs) in the North China Plain (NCP). For reference, multispectralCO retrievals (V8J) from the Measurements of Pollution in the Troposphere (MOPITT) are jointlyassimilated with meteorological observations using an Ensemble Adjustment Kalman Filter(EAKF) within the global Community Atmosphere Model with Chemistry (CAM-chem) and the2Data Assimilation Research Testbed (DART). With regard to KORUS-AQ data, CO isunderestimated by 42 % in the Control-Run and by 12 % with the MOPITT 50 assimilation run. Theinversion suggests an underestimation of anthropogenic CO sources in many regions, by up to 80% for Northern China, with large increments over the Liaoning province and the North ChinaPlains (NCP). Yet, an often-overlooked aspect of these inversions is that correcting theunderestimation in anthropogenic CO emissions also improves the comparison with observational55 O3 datasets, and observationally constrained box model simulations of OH and HO2. Running aCAM-chem simulation with the updated emissions of anthropogenic CO reduces the bias by 29 %for CO, 18 % for ozone, 11 % for HO2 and 27 % for OH. Longer lived anthropogenic VOCs whosemodel errors are correlated with CO are also improved while short-lived VOCs, includingformaldehyde, are difficult to constrain solely by assimilating satellite retrievals of CO. During an60 anticyclonic episode, better simulation of O3, with an average underestimation of 5.5 ppbv and areduction in the bias of surface formaldehyde and oxygenated VOCs can be achieved by separatelyincreasing by a factor of two the modeled biogenic emissions for the plant functional types foundin Korea. Results also suggest that controlling VOC and CO emissions, in addition to wide spreadNOx controls, can improve ozone pollution over East Asia.
DOI: 10.48577/jpl.lddjmt
title: Observing transiting exoplanets with the MicroObservatory: 43 new transit light curves of the hot Jupiter HAT-P-32b

description: Observations of 43 complete transits of the hot Jupiter exoplanet HAT-P-32b using the MicroObservatory 0.15-m robotic telescope network covering a period of 7 years are presented. Compared with the most recent ephemeris for the system, the precision of the mid-transit times yielded a root-mean-square value from the predicted model of 3.0 min. The estimated system parameters based on EXOFAST modelling are broadly consistent with those of the default parameter values listed in the NASA Exoplanet Archive. An updated orbital period of 2.15000815 ± 0.00000013 d and ephemeris of 2458881.71392 ± 0.00027 BJDTDB is consistent with recent studies of the system using larger telescopes. Using this updated ephemeris, the predicted mid-transit time for a notional observation of HAT-P-32b by the NASA JWST mission in mid-2021 is improved by 1.4 min compared with the discovery ephemeris and is ~8 times more precise. Likewise, the mid-transit time for an observation by the ESA ARIEL mission in 2020 is improved by 1.7 min. Thus, observations of transiting exoplanets by MicroObservatory and other users of small telescopes can contribute to the maintenance of the ephemerides of targets for future space-based telescope missions. We also note that one of the HAT-P-32 field stars is a δ Scuti pulsating variable and that characterization using the same observations as this study further demonstrates the utility of MicroObservatory for the observation of stellar variability, whilst simultaneously observing transiting exoplanets for ephemeris maintenance.
DOI: 10.48577/jpl.tz5h8q
title: Simulation of Early Earth Hydrothermal Chimneys in a Thermal Gradient Environment

description: Deep sea hydrothermal vents are self-organizing precipitates generated from geochemical disequilibria and have been proposed as a possible setting for the emergence of life. The growth of hydrothermal chimneys in a thermal gradient environment within an early Earth vent system was successfully simulated by using different hydrothermal simulants, such as sodium sulfide, which were injected into an early Earth ocean simulant containing dissolved ferrous iron. Moreover, an apparatus was developed to sufficiently cool the ocean simulant to near 0 °C in a condenser vessel immersed in a cold water bath while injecting a sulfide solution at hot to room temperatures, effectively creating an artificial chimney structure in a temperature gradient environment over a period of a few hours. Such experiments with different chemistries and variable temperature gradients resulted in a variety of morphologies in the chimney structure. The use of ocean and hydrothermal fluid simulants at room temperature resulted in vertical chimneys, whereas the combination of a hot hydrothermal fluid and cold ocean simulant inhibited the formation of robust chimney structures. The customizable 3D printed condenser created for this study acts as a jacketed reaction vessel that can be easily modified and used by different researchers. It will allow the careful control of injection rate and chemical composition of vent and ocean simulants, which should help accurately simulate prebiotic reactions in chimney systems with thermal gradients similar to those of natural systems.
DOI: 10.48577/jpl.gjmidd
title: The impact and recovery of asteroid 2018 LA

description: Abstract – The June 2, 2018, impact of asteroid 2018 LA over Botswana is only the second asteroid detected in space prior to impacting over land. Here, we report on the successful recovery of meteorites. Additional astrometric data refine the approach orbit and define the spin period and shape of the asteroid. Video observations of the fireball constrain the asteroid's position in its orbit and were used to triangulate the location of the fireball's main flare over the Central Kalahari Game Reserve. 23 meteorites were recovered. A consortium study of eight of these classifies Motopi Pan as a HED polymict breccia derived from howardite, cumulate and basaltic eucrite, and diogenite lithologies. Before impact, 2018 LA was a solid rock of ~156 cm diameter with high bulk density ~2.85 g/cm3, a relatively low albedo pV ~ 0.25, no significant opposition effect on the asteroid brightness, and an impact kinetic energy of ~0.2 kt. The orbit of 2018 LA is consistent with an origin at Vesta (or its Vestoids) and delivery into an Earth-impacting orbit via the 6 resonance. The impact that ejected 2018 LA in an orbit towards Earth occurred 22.8 ± 3.8 Ma ago. Zircons record a concordant U-Pb age of 4563 ± 11 Ma and a consistent 207Pb/206Pb age of 4563 ± 6 Ma. A much younger Pb-Pb phosphate resetting age of 4234 ± 41 Ma was found. From this impact chronology, we discuss what is the possible source crater of Motopi Pan and the age of Vesta's Veneneia impact basin.
DOI: 10.48577/jpl.xn6o1c
title: Radio Observations of HD 80606 Near Planetary Periastron II. LOFAR Low Band Antenna Observations

description: All of the giant planets in the solar system generate radio emission via the electron cyclotron maser instability, most notably giving rise to Jupiter's decametric emissions. HD 80606b is a giant planet and it is highly eccentric, leading to predictions that its radio emission may be enhanced substantially near periastron.This paper reports observations with the Low Frequency Array (LOFAR) of HD 80606b near its periastron in an effort to detect radio emissions generated by an electron cyclotron maser instability in the planet's magnetosphere. The reported observations are at frequencies between 30~MHz and 78~MHz, and they are distinguished from previous radio observations of extrasolar planets generally by two factors: (i) They are at frequencies near 50 MHz, much closer to the frequencies at which Jupiter emits (\nu &lt; 40 MHz) and lower than most previously reported observations of extrasolar planets; and (ii) Sensitivities of approximately a few millijanskys have been achieved, an order of magnitude or more below nearly all previous extrasolar planet observations below 100~MHz. We do not detect any radio emissions from HD 80606b and use these observations to place new constraints on its radio luminosity. We also revisit whether the observations were conducted at a time when it was super-Alfvenic relative to the host star's stellar wind, a necessary condition for generating electron cyclotron maser emission. We find that it is, updating previous estimates.
DOI: 10.48577/jpl.k22uns
title: Mars Sample Return Campaign Concept Status

description: This paper will provide an overview of current options and specific concepts for a potential Mars Sample Return(MSR) architecture being jointly studied by NASA and ESA. Overall objectives and mission options will bedescribed, including the architecture's constraints and notional timelines. The paper will highlight architectureleveltrade studies, including specific elements and their status. The overall Sample Retrieval Lander (SRL)mission concept, including vehicle options will be described, including the Mars Ascent Vehicle (MAV), SampleFetch Rover (being studied by ESA), Orbiting Sample container (OS), and tube transfer robotics systems. Theconcept and status of the Earth Return Orbiter (ERO) mission, being studied by ESA, and the Capture/Containment and Return System (CCRS) which would be the payload on the ERO, will be discussed.The information provided about possible Mars sample return architectures and concepts is for planning anddiscussion purposes only. NASA and ESA have made no official decisions to implement Mars Sample Return.
DOI: 10.48577/jpl.lm7z9u
title: Reconstructing EUV spectra of star forming regions from millimeter recombination lines of HI, HeI, and HeII

description: The extreme ultraviolet (EUV) spectra of distant star-forming regions cannot be probed directly using either ground- or space-based telescopes due to the high cross- section for interaction of EUV photons with the interstellar medium. This makes EUV spectra poorly constrained. The mm/submm recombination lines of H and He, which can be observed from the ground can serve as a reliable probe of the EUV. These lines are weekly impacted by dust absorption, their fluxes are independent of metallicity, and depend linearly on the number of EUV continuum photons. Here we present a study based on Atacama Large Millimeter/submillimeter Array observations of three Galactic ultra-compact HII regions and the starburst region Sgr B2(M), in which we reconstruct the key parameters of the EUV spectra of these sources using mm recombination lines of HI, HeI and HeII. We find that the EUV spectra between 13.6 and 54.4 eV of the objects studied here have similar frequency dependence: Lν ∝ ν−4.5±0.4. We compare the inferred values of the EUV spectral slopes with the values expected for a purely single stellar evolution model (Starburst99) and the Binary Population and Spectral Synthesis code (BPASS v2.1). We find that the observed spectral slope γ ≃ 4.5 ± 0.4 differs from the model predictions. For an instantaneous starburst model with age &lt; 5 Myrs the observed spectral slopes are consistently steeper than predictions of either of the models. For an instantaneous starburst with age &gt; 5 Myrs the observed spectral slope is in-between the values predicted by the two models. This may imply that the fraction of interacting binaries in HII regions is substantially lower than assumed in BPASS v2.1. The technique demonstrated here allows one to deduce the EUV spectra of star forming regions providing critical insight into photon production rates at λ ≤ 912 ̊A and can serve as calibration to starburst synthesis models, improving our understanding of star formation in distant universe and the properties of ionizing flux during reionization.
DOI: 10.48577/jpl.xaxbyo
title: Sensitivity estimation for calculated phase equilibria

description: The development of a consistent framework for Calphad model sensitivity is necessary for the rational reduction of uncertainty via new models and experiments. A sensitivity theory for Calphad was developed, and a closed-form expression for the log-likelihood gradient and Hessian of a phase coexistence measurement was presented. The inherent locality of the defined sensitivity metric was mitigated through the use of Monte Carlo averaging. A case study of the Cr-Ni system was used to demonstrate visualizations and analyses enabled by the developed theory. Criteria based on the classical Cramér–Rao bound were shown to be a useful diagnostic in assessing the accuracy of parameter covariance estimates from Markov Chain Monte Carlo. The developed sensitivity framework was applied to estimate the statistical value of phase equilibria measurements in comparison with thermochemical measurements, with implications for Calphad uncertainty reduction.