cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.48577/jpl.vrg767
title: Large and projected strengthening moisture limitation on end-of-season photosynthesis

description: Terrestrial photosynthesis is regulated by plant phenology and environmental conditions, both of which experienced substantial changes in recent decades. Unlike early-season photosynthesis, which is mostly driven by temperature or wet-season onset, late-season photosynthesis can be limited by several factors and the underlying mechanisms are less understood. Here, we analyze the temperature and water limitations on the ending date of photosynthesis (EOP), using data from both remote-sensing and flux tower-based measurements. We find a contrasting spatial pattern of temperature and water limitations on EOP. The threshold separating these is determined by the balance between energy availability and soil water supply. This coordinated temperature and moisture regulation can be explained by “law of minimum,” i.e., as temperature limitation diminishes, higher soil water is needed to support increased vegetation activity, especially during the late growing season. Models project future warming and drying, especially during late season, both of which should further expand the water-limited regions, causing large variations and potential decreases in photosynthesis.
DOI: 10.48577/jpl.zk5uh7
title: In search of radio emission from exoplanets: GMRT observations of the binary system HD 41004

description: This paper reports Giant Metrewave Radio Telescope (GMRT) observations of the binary HD 41004 that are among the deepest images ever obtained at 150 MHz and 400 MHz in the search for radio emission from exoplanets. The HD 41004 system consists of a K1 primary and an M2 secondary; both stars are host to massive planets / brown dwarfs. Analogous to planets in our solar system that emit at radio wavelengths due to their strong magnetic fields, one or both of the planets in the HD 41004 binary might emit at radio wavelengths and various models predict that HD 41004Bb might have one of the largest expected flux densities at 150 MHz. Our observations at 150 MHz cover the entire orbital period of HD 41004Bb. We do not detect radio emission, setting limits of 1.8 mJy (3σ) at 150 MHz and 0.12 mJy (3σ) at 400 MHz. Both limits are factors of a few to more than an order of magnitude below various predictions. We attribute the lack of detection either to a low conversion efficiency of input power to planetary magnetospheres (&lt;~ 10%) or strong beaming, with the Earth lying outside of the beaming cone.
DOI: 10.48577/jpl.1p8y2e
title: Climate impact of cloud water inhomogeneity through microphysical processes in a global climate model

description: This study investigates how sub-grid cloud water inhomogeneity within a grid spacing of a General Circulation Model (GCM) links to the global climate through precipitation processes. The effect of the cloud inhomogeneity on autoconversion rate is incorporated into the GCM as an enhancement factor using a prognostic cloud water probability density function (PDF), which is assumed to be a truncated skewed-triangle distribution based on the total water PDF originally implemented. The PDF assumption and the factor are evaluated against those obtained by global satellite observations and simulated by a global cloud-system resolving model (GCRM). Results show that the factor implemented exerts latitudinal variations, with higher values at low latitudes, qualitatively consistent with satellite observations and the GCRM. The GCM thus validated for the sub-grid cloud inhomogeneity is then used to investigate how the characteristics of the enhancement factor affect global climate through sensitivity experiments with and without the factor incorporated. The latitudinal variation of the factor is found to have a systematic impact that reduce the cloud water and the solar reflection at low latitudes in the manner that helps mitigate the too-reflective cloud bias common among GCMs over the tropical oceans. Due to the limitation of the factor arising from the PDF assumption, however, no significant impact is found in the warm rain formation process. Finally, it is shown that the functional form for the PDF in a GCM is crucial to properly characterize the observed cloud water inhomogeneity and its relationship with precipitation.
DOI: 10.48577/jpl.bsynhh
title: Value of InSAR for Monitoring Land Subsidence to Support Water Management in the San Joaquin Valley, California

description: Land subsidence because of groundwater extraction in California’s San Joaquin Valley has been occurring for at least nine decades. Historically, in-situ monitoring of subsidence has been limited; the most comprehensive studies and monitoring were associated with construction and operation of large-scale water conveyance infrastructure. Long-term cumulative land subsidence has substantially reduced the conveyance capacity of sections of major canals. The California Department of Water Resources sought NASA’s assistance for remotely sensed satellite- and aircraft-based monitoring of subsidence during the 2012-16 drought. Use of Synthetic Aperture Radar interferometry (InSAR) was highly successful in providing first-ever synoptic measurement of land subsidence over the entire San Joaquin Valley, and in doing so cost-effectively. A key focus of the monitoring was on screening or hotspot detection of impact areas affecting critical water infrastructure. The monitoring revealed that subsidence rates observed during the drought equaled maximum historically observed rates and identified new rapidly emerging hotspots adjacent to critical water infrastructure.
DOI: 10.48577/jpl.vnql6j
title: Mapping Vegetation Health Around the World

description: One of the largest sources of uncertainty in projections of Earth’s future climate and of theMapping Vegetation Health Around the World - Eos https://eos.org/science-updates/mapping-vegetation-health-around-...1 of 9 9/28/20, 9:15 AMeffects of climate change is the cycle of feedbacks (https://eos.org/features/the-future-of-the-carbon-cyclein-a-changing-climate) between climate and responses of the terrestrial biosphere, particularlyEarth’s plant life. These feedbacks can both mediate and contribute to rising levels of carbondioxide (CO2) in the atmosphere [e.g., Cox et al. (https://doi.org/10.1038/nature11882), 2013], whichcan result in different types of responses within ecosystems at different timescales.
DOI: 10.48577/jpl.qsism2
title: A Candidate Electromagnetic Counterpart to the Binary Black Hole Merger Gravitational Wave Event GW190521g

description: We report the first plausible candidate electromagnetic (EM) counterpart to a binary black hole (BBH) merger. The EM flare is consistent with expectations for a kicked BBH merger in the accretion disk of an active galactic nucleus (AGN) [1], and is unlikely (&lt; O(0.01%)) due to intrinsic variability of this source. The lack of color evolution implies that it is not a supernovae and instead is strongly suggestive of a constant temperature shock. Other false-positive events, such as micro- lensing or a tidal disruption event, are ruled out or constrained to be &lt; O(0.1%). If the flare is associated with GW190521g, we find plausible combined values of: total mass MBBH ∼ 100M⊙, kick velocity vk ∼ 200kms−1 at θ ∼ 60◦ in a disk with aspect ratio H/a ∼ 0.01 and gas density ρ ∼ 10−10 gcm−3. The merger could have occurred at a disk migration trap (a ∼ 700rg). The timing of our spectroscopy prevents useful constraints on broad-line asymmetry due to an off- center flare. We predict a repeat flare in this source due to a re-encountering with the disk in ∼ 1.6yr(MSMBH/108M⊙)(a/103rg)3/2.
DOI: 10.48577/jpl.3bw4a7
title: Origin of Interannual Variability in Global Mean Sea Level

description: The two dominant drivers of the GMSL variability at interannual to decadal timescales are steric changes due to changes in ocean heat content and barystatic changes due to the exchange of water mass between land and ocean. With GRACE satellites and Argo profiling floats, it has been possible to measure the relative steric and barystatic contributions to GMSL since 2004. While efforts to “close the budget” with satellite altimetry have been largely successful with regards to trends, the short time period covered by these records prohibits a full understanding of the drivers of interannual to decadal variability in GMSL. One particular area of focus is the link between variations in the El Nino-Southern Oscillation (ENSO) and GMSL, with recent literature disagreeing on the relative importance of steric and barystatic contributions to interannual to decadal variability in GMSL. Here, we use a novel multivariate data analysis technique to estimate variability in barystatic and steric contributions to GMSL back to 1982. These independent estimates explain the observed interannual and decadal variability in satellite altimeter-measured GMSL. Both processes, which are highly correlated with ENSO variations, contribute about equally to observed interannual and decadal GMSL variability. A theoretical scaling analysis corroborates the observational results. The improved understanding of the origins of interannual to decadal variability in GMSL established here has important implications for our understanding of long-term trends in sea level, the hydrological cycle, and the planet’s radiation imbalance.
DOI: 10.48577/jpl.f2kg7u
title: JPL Small Satellite Dynamics Testbed Planar Air Bearing Propulsion System Characterization

description: The Small Satellite Dynamics Testbed (SSDT) at JPL offers infrastructure that supports SmallSat guidance and control algorithm testing in a relevant dynamics environment while constrained by Earth’s gravitational effects. One of the SSDT’s testing environments is its planar air-bearing platform, which has two lateral and one rotational degree of freedom. This paper details the planar air-bearing test platform’s new position-control system, which uses an array of compressed-gas thrusters, and it characterizes the pertinent design and performance parameters related to the platform and propulsion system. The addition of this capability required a hardware and software redesign from the previous uncontrolled platform. A detailed description of the changes in the platform’s hardware and software systems is provided, including interface circuit and thruster control software architecture. Testing shows the reconfigured system has a maximum float time of 13.5 minutes, an average maximum thrust per thruster of 0.51 N, a tank pressure drop of 6.85 PSI/sec, and minimum impulse bit of 40 ms. The paper further presents results necessary for designing position controllers for use on this system, such as the relationship between number of thrusters firing and output force, and the timing latency in the thruster firing control system. We describe the effect of firing multiple thrusters simultaneously on the per-thruster force, and show that the embedded computer used in this platform exhibits timing delays of approximately 34 ms. The implications of these results on control system design are discussed in the conclusions.
DOI: 10.48577/jpl.6d5izy
title: Europa Clipper Planetary Protection Probabilistic Risk Assessment Summary

description: Protecting Jupiter's Icy Moons from terrestrial contamination is a key consideration for the Europa Clipper mission, whose goal is to explore Jupiter's moon, Europa, and investigate its habitability. The mission must satisfy NASA's Planetary Protection (PP) requirements specified in the NASA Procedural Requirement (NPR) 8020.12D, stating: “The probability of inadvertent contamination of an ocean or other liquid water body must be less than 1x10^-4 per mission.” The NPR further defines contamination as “the introduction of a single viable terrestrial microorganism into a liquid-water environment". The probabilistic nature of the requirement demands a probabilistic response. Europa Clipper developed an end-to-end probabilistic risk assessment (PRA) to ensure requirement compliance and to inform resulting design considerations. The methodology offered in the PRA conservatively quantifies the unanticipated events required to place the Europa Clipper mission in the state of concern: contamination of an icy body. This requires a model of spacecraft failure scenarios and the potential for a resulting icy body impact, expected geological resurfacing timescales that may introduce terrestrial biology to interstitial liquid water, and an assessment of biological mortality throughout the journey from Earth over a 1000-year period. Motivation for this PRA follows from the desire to ensure the proper amount of bioburden reduction is performed pre-launch such that the required PP risk threshold is met, while minimizing programmatic and mission risk. The goal is to effectively 'solve for' the not-to-exceed bioburden at launch, and to allow this solution to inform microbial reduction planning and hardware selection. This is a feature previous mathematical approaches have failed to offer, resulting in over or under-specified cleaning protocols and greater risk either to the exploration target or to the mission. If one solely considers sterilizing spacecraft hardware to meet NASA’s PP requirement, the initial results are unintuitive: a 12-log bioburden reduction prelaunch, or virtual sterility, would be required in order for Europa Clipper hardware to be sterile in the event of an inadvertent impact. This is an untenable solution; sensitive spaceflight hardware cannot endure such cleaning protocols. The Project therefore seeks to show compliance with the requirement by demonstrating the probability that Clipper inadvertently impacts Europa and subsequently introduces hardware into the Europa subsurface ocean is sufficiently small, not that the spacecraft hardware would be sterile upon impact. The end-to-end model and findings are explored at a summary level in the following paper.
DOI: 10.48577/jpl.dvz7p7
title: μ TAU: A 60 MYR-OLD ASSOCIATION AT 150 pc FROM THE SUN

description: We present an analysis of the newly identified μ Tau association of young stars at ∼150pc from the Sun and in the vicinity of the Taurus star-forming region although it is likely not related to it. We identify more than 500 candidate members using Gaia DR2 data and the BANYAN Σ Bayesian membership determination tool (Gagn ́e et al. 2018) and we determine an age of 62 ± 7 Myr for the association based on an empirical comparison of its color-magnitude diagram sequence with those of other nearby young associations. As part of this analysis, we introduce an iterative method based on spectral templates to perform an accurate correction of interstellar extinction of Gaia DR2 photometry, which is needed because of its wide photometric bandpasses. We show that members of μ Tau display an expected increased rate of stellar activity and faster rotation rates compared to older stars, and that its present-day mass function is consistent with other known nearby young associations. This relatively large collection of co-moving young stars near the Sun indicates that more work is required to unveil the full kinematic structure of the immediate Solar neighborhood.
DOI: 10.48577/jpl.xarxdl
title: Sea Surface Salinity estimates from Spaceborne L-band radiometers: an overview of the first decade of observation (2010-2019)

description: Operated since the end of 2009, the European Space Agency (ESA) Soil Moisture and Ocean Salinity (SMOS) satellite mission is the first orbiting radiometer that collects regular and global observations from space of two Essential Climate Variables of the Global Climate Observing System: Sea Surface Salinity (SSS) and Soil Moisture. The National Aeronautics and Space Administration (NASA) Aquarius mission, with the primary objective to provide global SSS measurements from space operated from mid-2011 to mid-2015. NASA’s Soil Moisture Active-Passive (SMAP) mission, primarily dedicated to soil moisture measurements, but also monitoring SSS, has been operating since early 2015. The primary sensors onboard these three missions are passive microwave radiometers operating at 1.4 GHz (L-band). SSS is retrieved from radiometer measurements of the sea surface brightness temperature (TB). In this paper, we first provide a historical review of SSS remote sensing with passive L-band radiometry beginning with the discussions of measurement principles, technology, sensing characteristics and complementarities of the three aforementioned missions. The assessment of satellite SSS products is then presented in terms of individual mission characteristics, common algorithms, and measurement uncertainties, including the validation versus in situ data, and, the consideration of sampling differences between satellite SSS and in situ salinity measurements. We next review the major scientific achievements of the combined first 10 years of satellite SSS data, including the insights enabled by these measurements regarding the linkages of SSS with the global water cycle, climate variability, and ocean biochemistry. We also highlight the new ability provided by satellites to monitor mesoscale and synoptic-scale SSS features and to advance our understanding of SSS’ role in air-sea interactions, constraining ocean models, and improving seasonal predictions. An overview of satellite SSS observation highlights during this first decade and upcoming challenges are then presented
DOI: 10.48577/jpl.5yg749
title: Diffraction losses of a Fabry-Perot cavity with nonidentical non-spherical mirrors

description: Optical cavities with both optimized resonant conditions and high quality factors are important metrological tools. In particular, they are used for laser gravitational wave (GW) detectors. In order to have high cavity powers in GW detectors, it is necessary to suppress the parametric instability and to reduce the loss in the arm caused by point absorbers by damping the resonant conditions of harmful higher order optical modes (HOOM). This can be achieved effectively by using non spherical mirrors in symmetric Fabry-Perot (FP) cavities by increasing roundtrip losses of HOOMs [1, 2]. Fabry-Perot cavities in most of the GW detectors have non-identical mirrors to optimize clipping losses and reduce thermal noise by reducing the beam size on one side of the cavity facing to the beam splitter and recycling cavities. We here present a general method to design non spherical non-identical mirrors in non-symmetric FP cavities to damp HOOMs. The proposed design allows to the suppress the loss of the arm power caused by point absorbers on test masses.
DOI: 10.48577/jpl.gop20u
title: Angular Dependence and Spatial Distribution of Jupiter’s Centimeter-Wave Thermal Emission from Juno’s Microwave Radiometer

description: NASA’s Juno spacecraft has been monitoring Jupiter in 53-day orbits since 2016. Its six-frequency microwave radiometer (MWR) is designed to measure black body emission from Jupiter over a range of pressures from a few tenths of a bar to several kilobars in order to retrieve details of the planet’s atmospheric composition, in particular its ammonia and water abundances. A key step toward achieving this goal is the determination of the latitudinal dependendence of the nadir brightness temperature and limb darkening of Jupiter’s thermal emission through a deconvolution of the measured antenna temperatures. We present a formulation of the deconvolution as an optimal estimation problem. It is demonstrated that a quadratic expression is sufficient to model the angular dependence of thethermal emission for the data set used to perform the deconvolution. Validation of themodel and results from a subset of orbits favorable for MWR measurements are presented over a range of latitudes that cover up to 60° from the equator. A heuristic algorithm to mitigate the effects of nonthermal emission is also described.
DOI: 10.48577/jpl.xmhrgc
title: Global Trends in Evapotranspiration Dominated by Increases Across Large Cropland Regions

description: Irrigated croplands require large annual water inputs and are critical to global food production. Actual evapotranspiration (AET) is a main index of water use in croplands, and several remote-sensing products have been developed to quantify AET at the global scale. In this study, we estimate global trends in actual AET, potential ET (PET), and precipitation rate (PP) utilizing the MODIS Evapotranspiration product (2001-2018) within the Google Earth Engine cloud-computing environment. We then introduce a new index based on a combination of AET, PET, and PP estimates—the evapotranspiration warning index (ETWI)—which we use to evaluate the sustainability of observed AET trends. We show that while AET has not considerably changed across global natural lands, it has significantly increased across global croplands (+14% +/- 5%). The average ETWI for global croplands is -0.40 +/- 0.25, which is largely driven by an extreme trend in AET, exceeding both PET and PP trends. Furthermore, the trends in water and energy limited areas demonstrate, on a global scale, while AET and PET do not have significant trends in both water and energy limited areas, the increasing trend of PP in energy-limited areas is more than water-limited areas. Averaging cropland ETWI trends at the country level further revealed nonsustainable trends in cropland water consumptions in Thailand, Brazil, and China. These regions were also found to experiencing some of the largest increases in net primary production (NPP) and solar-induced fluorescence (SIF), suggesting that recent increases in food production may be dependent on unsustainable water inputs. Globally, irrigated maize was found to be associated with nonsustainable AET trends relative to other crop types. We present an online open access application designed to enable near real-time monitoring and improve the understanding of global water consumption and availability.
DOI: 10.48577/jpl.huusqo
title: SCOTI: Science Captioning of Terrain Images for Data Prioritization and Local Image Search

description: Planetary exploration is full of challenges. Data bandwidth is very limited between planetary rovers and ground-based data system. What's worse, even though NASA has accumulated over 34 million images from various missions, it requires significant effort and is hardly possible for any scientist to go through all of them. In order to improve the degree of automation and the efficiency of these processes, we propose a system leveraging machine learning for planetary rovers to actively look for scientifically interesting and valuable features according to text instructions from scientists and prioritize the images captured onboard with those features for downlink. Such an image prioritization mechanism can also be naturally applied to content-based image search through text description in any local planetary image data server, allowing scientists to search for images with desired features without going through them one by one. Besides theoretical and engineering details of our proposed approach, we also present both quantitative and qualitative evaluation of the system along with some concrete examples.