cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.48577/jpl.dtjjs5
title: Implementing Low-Density Parity-Check Codes in the Mars Relay Network

description: This paper describes the implementation of Low- Density Parity-Check (LDPC) channel codes in the Mars Relay Network; specifically in the NASA MAVEN orbiter and the ESA ExoMars Trace Gas Orbiter. LDPC codes, also known as Gallager codes, were invented in the early 1960s. At the time, available computational hardware was not powerful enough to implement these codes, so they became “forgotten.” They were later “rediscovered” in the 1990s, whereupon it was demonstrated that practical LDPC decoders performed substantially better than standard convolutional codes. This spurred research and development of LDPC codes at JPL, which culminated in the implementation of a rate ½ LDPC decoder and encoder in the Electra proximity radio delivered to MAVEN in 2012 and subsequently to other Mars spacecraft. The paper starts with a brief history of LDPC code development and then goes on to describe the development and validation of recent firmware and software updates to facilitate LDPC code operation with adaptive data rate control. The LDPC codes developed for Electra were verified to produce approximately 3 dB coding gain relative to NASA’s standard convolutional code, increasing data return by up to a factor of two. The paper concludes with an assessment of in-flight performance of LDPC-enabled relay passes between MAVEN and the Mars 2020 rover.
DOI: 10.48577/jpl.tvo5ut
title: Thin THz QCL active regions for improved continuous-wave operating temperature

description: We compare the performance of 10 μm and 5 μm thick metal-metal waveguide terahertz quantum-cascade laser ridges operating around 2.7 THz and based on a 4-well phonon depopulation active region design. Thanks to reduced heat dissipation and lower thermal resistance, the 5 μm thick material shows an 18 K increase in continuous wave operating temperature compared to the 10 μm material, despite a lower maximum pulsed-mode operating temperature and a larger input power density. A maximum continuous wave operating temperature of 129 K is demonstrated using the 5 μm thick material and a 15 μm wide ridge waveguide that lased up to 155 K in pulsed mode. The use of thin active regions is likely to become increasingly important to address the increasing input power density of emerging 2- and 3-well active region designs that show the highest pulsed operating temperatures.
DOI: 10.48577/jpl.3iepsq
title: Triton's Variable Interaction with Neptune's Magnetospheric Plasma

description: The tilt between Neptune's magnetic and rotational axes, along with Triton's orbital obliquity, causes a strong time variability of the moon's local electromagnetic environment. To constrain Triton's interaction with the ambient magnetospheric plasma, we apply a hybrid (kinetic ions, fluid electrons) model including the moon's ionosphere and induced. To represent the extremes in the changes to the local electromagnetic field over a synodic rotation, we consider two orientations between the ambient magnetic field and flow velocity. For each, we first investigate the (analytical) magnetic signatures associated with the superposition of Triton's induced field and the magnetospheric field in the absence of any plasma interaction effects. To constrain the effect of Triton's ionosphere on the currents, we model the interaction between the ionospheric and magnetospheric plasma in isolation from the moon's inductive response, before combining these effects to investigate the complex scenario of plasma interaction and induction. Finally, we explore the sensitivity of the plasma interaction to changes in the ambient plasma density and the strength of Triton's inductive response. Despite plasma interaction signatures that dominate the plasma perturbations far from the moon (beyond 3 Triton radii), we illustrate that the induced field is clearly discernible within 3 Triton radii, regard37 less of the moon's location within Neptune's magnetosphere. We find that the orientation of the magnetospheric field and velocity vectors strongly affects Triton's plasma in interaction; at times, resembling those of Jupiter's or Saturn's moons, while at others, revealing unprecedented signatures that are likely unique to moons of the ice giants.
DOI: 10.48577/jpl.jaqmhh
title: Performance of Earth Troposphere Calibration Measurements with the Advanced Water Vapor Radiometer for the Juno Gravity Science Investigation

description: The performance of an atmospheric water vapor radio path delay measurement and correction is reported using observations of the Juno Spacecraft during gravity field mapping of Jupiter. The Juno Gravity Science instrument measures the Doppler shift on the radio signals between the Juno spacecraft and the Earth-based observing stations of NASA’s Deep Space Network (DSN) during times of closest approach to Jupiter in order to map Jupiter’s gravity field. These Doppler measurements are affected by noise sources between the spacecraft and DSN which include charged particles plasma and Earth’s troposphere. A pair of redundant Advanced Water Vapor Radiometers (AWVR) co-located at the DSN’s DSS-25 antenna in Goldstone, CA measure the brightness temperatures at the 22.2, 23.8 and 31.4 GHz spectral lines for water vapor content in Earth’s atmosphere. The measurements of water vapor content are reduced into a measurement of radio path delay, which provides high-precision calibrations of tropospheric noise on the radio links. Analyses of AWVR measurements show that spacecraft tracking errors, after removing other measurable errors from charged particles, are reduced by 46% on average and by as much as 70%, depending on local weather conditions near the Goldstone site.
DOI: 10.48577/jpl.p2p07m
title: Semantic Mapping in Unstructured Environments: Toward Autonomous Localization of Planetary Robotic Explorers

description: Highly accurate autonomous global localization of planetary robotic explorers is crucial for robust, efficient, and safe exploration of planetary bodies. Satellite-based radio-navigation systems (i.e., Global Positioning System) are unavailable in planetary applications. Thus, global localization can be achieved by relying on registration of orbital and ground imagery, using X-band Doppler radio transmissions, or direct observation of the robotic explorers in satellite imagery. While these methods have proven to be effective, they are not automated for real-time onboard use, and require significant human intervention by the ground team. This paper addresses the problem of autonomous visual global localization of planetary robotic explorers by using a trained convolutional neural network (CNN) to obtain saliency maps from semantic segmentation of ground imagery. These saliency maps are then registered to projected views of the terrain elevation maps in the rover's general region of operation, to find the optimal match that places tight constraints on the pose of the robot in a Mars body-fixed coordinate system. We provide details on the use of the DeepLab V3+ framework for semantic image segmentation of Martian landscape imagery, including fine-tune training of existing models on domain specific data. We present that the proposed method can be used for global position estimation of autonomous robots in extreme and GPS-denied environments, and provide localization performance and sensitivity analysis on a Martian landscape dataset obtained by NASA's Perseverance rover, and discuss the limitations of the method and future research directions.
DOI: 10.48577/jpl.3sbr5c
title: Safe and Accurate Landing Enables Perseverance to Advance Scientific Investigations on Mars

description: :unav
DOI: 10.48577/jpl.1ouy7t
title: Keeping Time with Quasars

description: Keeping a standard time is an essential component of the functioning of society and daily life. It is nearly impossible to communicate, travel, land spacecraft, perform precise scientific experiments, or maintain an international economy without a consistent time that can be agreed upon by all people regardless of their region on Earth. It is taken for granted that we all experience the sun overhead at noon, sleep when it is dark, and have a reliable means of coordinating time between our respective time zones. However, the process of keeping an accurate and precise time is complex; it relies on hundreds of terrestrial and celestial factors that must be accounted for in order to produce the value known as Universal Time.
DOI: 10.48577/jpl.2neb1q
title: Erosion of Penitentes Under Experimental Conditions1Relevant to Ice-Covered Airless Worlds

description: The submeter-scale surface morphology of ice-covered worlds is poorly constrained by observations, but is important for understanding their physics and chemistry. In this experiment, we exposed pre-formed snow structures to temperature, pressure, and solar irradiance conditions similar to those on Europa and Enceladus. The sample consisted of 2-D sinusoidal penitente-like ridges, 2.5 cm tall with 1.25 cm spacing. Over one month at 165-175 K, and 10-4 Pa, the ridges decreased in height by 20% and became more triangular and less sinusoidal, evolving toward a more at surface. This despite the fact that the troughs appear brighter than the peaks, indicating focusing of light into the troughs. This suggests that penitentes are unlikely to be stable on airless worlds with free-molecular flow conditions, which is signicant for understanding the spectral and thermal properties of these worlds, and for understanding risks for future landed spacecraft.
DOI: 10.48577/jpl.vqqji8
title: On the relationship between CYGNSS surface heat fluxes and the lifecycle of low-latitude ocean extratropical cyclones

description: Surface latent and sensible heat fluxes are important for extratropical cyclone evolution and intensification. Because extratropical cyclone genesis often occurs at low-latitude, CYGNSS surface latent and sensible heat flux retrievals are composited to provide a mean picture of their spatial distribution in low-latitude oceanic extratropical cyclones. CYGNSS heat fluxes are not affected by heavy precipitation and offer observations of storms with frequent revisit times. Consistent with prior results obtained for cyclones in the Gulf Stream region, the fluxes are strongest in the wake of the cold fronts, and weakest to negative in the warm sector in advance of the cold fronts. As cyclone strength increases, or mean precipitable water decreases, the maximum in surface heat fluxes increases while the minimum decreases. This impacts the changes in fluxes during cyclone intensification: the post-cold frontal surface heat flux maximum increases due to the increase in near surface winds. During cyclone dissipation, the fluxes in this sector decrease, due to the decrease in winds and in temperature and humidity contrast. The warm sector minimum decreases throughout the entire cyclone lifetime and is mostly driven by sea-air temperature and humidity contrast changes. However, during cyclone dissipation, the surface heat fluxes increase along the cold front in a narrow band to the east, independently from changes in the cyclone characteristics. This suggests that, during cyclone dissipation, energy transfers from the ocean to the atmosphere are linked to frontal in addition to synoptic-scale processes.
DOI: 10.48577/jpl.bicrsi
title: Moments of Sunlight Pathlength in Water and Aerosol Clouds from O$_2$ Spectroscopy: Exploitable Parameter Sensitivities

description: According to the latest IPCC assessment, clouds and aerosolsremain a major challenge in future climate prediction using Global ClimateModels (GCMs). Consequently, NASA's 2017 Decadal Survey has made them,along with convection and precipitation, a high priority by calling them outas Designated Observables for future coordinated missions under the "ACCP"banner, now known as the Atmospheric Observing System. Atmosphericscience is now more than ever driving a renewal in remote sensing techniquesthat can probe clouds and aerosols more accurately and with improvedsampling. Herein, we bring new theoretical results that support a special formof Differential Optical Absorption Spectroscopy (DOAS) that uses oxygenabsorption features in the visible/near-IR (VNIR) spectrum where there isan abundance of sunlight. Having known concentration and cross-section,the remaining unknown in O2 DOAS (DO2AS) is the path that the light hasfollowed through the absorbing gas. In the presence of scattering by cloudand aerosol particles, that path is broken at each interaction. Cumulativepathlength through the well-mixed O2 gas thus becomes a continuous randomvariable, and its probability distribution function (PDF) will contain desirableinformation about the clouds and aerosols such as top and bottom altitudesof the layer they occupy as well as its optical thickness. In this study, webuild on previous work to compute statistical moments of the pathlengthPDF. Specifically, we show that mean and variance of the pathlength insidethe scattering particulate medium convey different pieces of information,namely, size and opacity of the optical medium, hence geometric and opticalthicknesses in the case of plane-parallel layers. We also extend, with denseaerosol plumes in mind (e.g., wildfire smoke, volcanic ash, elevated dust),the mean pathlength's close connection between geometric thickness andmean pathlength in the presence of absorption by the scattering particlesthemselves. In summary, we view pathlength moments as intermediate DO2ASproducts that can be obtained from O2 spectroscopic data, and we describe apreliminary algorithm to do just that. In turn, these moments yield cloudor aerosol profile parameters of high interest: layer geometric and opticalthicknesses. One normally thinks about active sensors, radars and lidars, todo such atmospheric profiling. In this case, the profle is parameterized andrepresentative of some kind of horizontal average determined by the multiplescattering. However, there is a clear advantage in using passive over activeinstrumentation, starting with the possibility of imaging over a large swath.
DOI: 10.48577/jpl.vfpddc
title: Using ECOSTRESS to Observe Diurnal Variability in Water Temperature Conditions in the San Francisco Estuary

description: Abstract—The San Francisco Estuary and Sacramento-SanJoaquin River Delta (Bay Delta) is a highly sensitive and criticalhabitat for the Delta Smelt, an endangered endemic fish, withwater temperature being a key determinant of habitat suitability.This study investigates the relationship between open watersurface and subsurface conditions from spaceborne thermal measurements(ECOSTRESS and Landsat-8) and in situ sensor datafrom the California Data Exchange Center (CDEC), respectively,to produce estimates of spatially continuous bulk temperaturein the Bay Delta. We found that ECOSTRESS and Landsat-8 surface temperature measurements are well-correlated withbulk water temperatures (N = 236, r = 0.907 and N = 226, r= 0.976, respectively). For the ECOSTRESS-in situ comparison,accounting for time of day improved the correlation betweensurface and subsurface conditions (r = 0.946, 0.881, and 0.944for morning, midday and evening, respectively). We found thatECOSTRESS surface temperatures were warmer than bulktemperatures in the midday period (2 C peak, at 2PM) andcooler in the morning and evening periods (-1 C peak, at6AM). We also found that a simple harmonic regression modelcan capture the diurnal variability of the skin effect to predictbulk water temperature (RMSE = 0.809 C). With ECOSTRESS,we found that across the Bay Delta, including open waters andpelagic bays, temperature conditions causing stress and mortalityfor the Delta Smelt were persistent throughout the day duringsummer months. ECOSTRESS is a unique dataset capable ofinforming conservation efforts in the Bay Delta.
DOI: 10.48577/jpl.xik6kf
title: Introduction: Mars InSight Entry, Descent and Landing Flight Reconstruction

description: The Journal of Spacecraft and Rockets Mars InSight Entry, Descent and Landing Flight Reconstruction Virtual Collection is a collection of papers documenting the EDL system performance and EDL operations activities of the InSight landing. A list of the papers included in the collection is provided in Table 1. Like the Phoenix EDL system, the InSight EDL system was designed as a ballistic entry system with no expected angle of attack. However, like Phoenix, InSight did generate a small angle of attack that resulted in the vehicle flying a generally lift down trajectory, which resulted in higher-than expected deceleration load, and shorter-than-expected time from entry to landing. The possible reasons for the trim behavior are discussed in the Virtual Collection. Additionally, the collection contains predicted and reconstructed flight dynamics performance of the EDL system. A significant development for InSight was the creation of a landing approach operations plan that could react and adapt to a changing atmosphere, critical for landing during dust storm season, which is described in the collection. Together, the papers in the collection document approach operations, predicted flight performance, and flight reconstruction of InSight’s successful landing on Mars.
DOI: 10.48577/jpl.v4ckh3
title: TESS Hunt for Young and Maturing Exoplanets (THYME) VI: an 11 Myr giant planet transiting a very low-mass star in Lower Centaurus Crux

description: Mature super-Earths and sub-Neptunes are predicted to be ≃Jovian radius when younger than 10 Myr. Thus, we expect to find 5–15R⊕ planets around young stars even if their older counterparts harbor none. We report the discovery and validation of TOI 1227 b, a 0.85 ± 0.05 RJ (9.5R⊕) planet transiting a very low-mass star (0.170 ± 0.015 M⊙ ) every 27.4 days. TOI 1227’s kinematics and strong lithium absorption confirm it is a member of a previously discovered sub-group in the Lower Centaurus Crux OB association, which we designate the Musca group. We derive an age of 11±2 Myr for Musca, based on lithium, rotation, and the color-magnitude diagram of Musca members. The TESS data and ground-based followup show a deep (2.5%) transit. We use multiwavelength transit observations and radial velocities from the IGRINS spectrograph to validate the signal as planetary in nature, and we obtain an upper limit on the planet mass of ≃0.5MJ. Because such large planets are exceptionally rare around mature low-mass stars, we suggest that TOI 1227 b is still contracting and will eventually turn into one of the more common &lt; 5R⊕ planets.
DOI: 10.48577/jpl.vnrizc
title: A recipe for estimating the frequency of asteroid close approaches to Earth

description: We present a simple recipe for estimating the frequency of asteroid close approaches to Earth as a function of theasteroid's absolute magnitude H and the close approach distance r from the geocenter. This formulation can be usefulin assessing how rare a close approach is compared to the background rate from the asteroid population, similarly tohow the Palermo scale (Chesley et al. 2002) is used to rank the risk posed by virtual impactors (Milani et al. 2005).
DOI: 10.48577/jpl.uihsbx
title: A wide-orbit giant planet in the high-mass b Centauri binary system

description: Planet formation occurs around a wide range of stellar masses and stellar systemarchitectures . An improved understanding of the formation process can beachieved by studying it across the full extent of parameter space, particularlytoward the extremes. Earlier studies of planets in close-in orbits around high-massstars have revealed an increase in giant planet frequency with increasing stellarmass until a turnover point at 1.9 solar masses, above which the frequency rapidly decreases . This could potentially imply that planet formation is impeded aroundmore massive stars, and that giant planets around stars exceeding 3 solar massesmay be rare or non-existent. However, the indirect methods used to detect planetsin small orbits are insensitive to planets in wide orbits, causing ambiguity in theinterpretation of planetary frequencies. Here we demonstrate the existence of aplanet at 556 times the Sun-Earth distance from the 6—10 solar mass binary b26 Centauri through direct imaging. The planet-to-star mass ratio of 0.0010—0.0017 is similar to the Jupiter-Sun ratio, but the orbital separation of the detected planet is approximately 100 times wider than that of Jupiter. Our results show that planetscan reside in much more massive stellar systems than what would be expected fromextrapolation of previous results for close-in planets. The planet is unlikely to haveformed in-situ through the conventional core accretion mechanism4, but might haveformed elsewhere and arrived to its present location through dynamicalinteractions, or might have formed via gravitational instability.
DOI: 10.48577/jpl.ypj3di
title: Z CMa: A Likely Flyby Event Caught in Action

description: Close encounters between young stellar objects in star forming clusters are expected to dramatically perturb circumstellar disks. Such events are witnessed in numerical simulations of star formation1–3,but few direct observations of ongoing encounters have been made. Here we report sub-000:1 resolution Atacama Large Millimeter Array (ALMA) and Jansky Very Large Array (JVLA) observationstowards the million year old binary protostar Z CMa in dust continuum and molecular line emission. A point source 4700 au from the binary has been discovered at both millimeter and centimeterwavelengths. It is located along the extension of a 2000 au streamer structure previously found inscattered light imaging, whose counterpart in dust and gas thermal emission is also newly identified.Comparison with simulations shows strong evidence of a rare flyby event in action. Z CMa is a doubleburster, as both binary components undergo accretion outbursts4. Such a scenario may be triggered by perturbations to the host disk by flybys5–7. Our results support this hypothesis.
DOI: 10.48577/jpl.p5r2d2
title: Two Stage Artificial Intelligence Algorithm for Calculating Moisture-Tracking Atmospheric Motion Vectors

description: Much of the errors of Atmospheric Motion Vectors (AMV) may be a consequence of algorithms not incorporating dynamical information. A physics-informed, artificial intelligence algorithm was developed that corrects errors of moisture tracking AMV (from the movement of water vapor) using Numerical Weather Prediction (NWP) fields. The University of Arizona algorithm (UA) uses a variational method as a first step (fsUA), the second step then filters the first-stage AMVs using a Random Forest model that learns the error correction from NWP fields. The UA algorithm is compared with a traditional image feature tracking algorithm (JPL) using a global nature run as the “ground truth”. Experiments use global all sky humidity fields at 500 hPa and 850 hPa,and for January 1-3, 2006, and July 1-3, 2006. UA outputs AMVs with Root Mean Square VectorDifferences (RMSVDs) of 2 m/s for the tropics and ∼ 2 - 3 m/s for mid-latitudes and the poles, whereas JPL outputs much higher RMSVDs of ∼ 3 m/s for the tropics and ∼ 3 - 9 m/s for the mid-latitudes and poles. Although the algorithm fsUA produces approximately the same global RMSVDs as the JPL algorithm, fsUA has a higher resolution since it outputs an AMV per pixel, whereas the JPL algorithm uses a target box that effectively smooths the vectors. Furthermore, UA’s RMSVDs are lower than the intrinsic error (calculated from the differences between two reanalysis datasets). Even for error-prone regions with low moisture gradients and where winds are oriented along moisture isolines, UA’s absolute speed difference with “truth” stays within ∼ 3 m/s.