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NASA NTRS2019

Cold Survivable Distributed Motor Controller (CSDMC)

This paper presents the results of NASA’s COLDTECH development entitled “Cold Survivable Distributed Motor Controller (CSDMC)”. This work addresses the need to lower the mass, power and volume of the motor control electronics and its associated cabling. Landed payload mass of ocean world missions typically requires a spacecraft launch mass of 7-10x the landed mass due to the required propellant to get the payload to the surface. Reduction of landed mass leads to cheaper, more frequent missions and/or increased science return. This work addresses this need by developing a distributed electronics architecture, which places control and power electronics near or at actuators and instruments. The outcome of this effort will result in a 10X reduction in harness mass, enabling a significant increase in science payload which then enables more capable sample acquisition, delivery and analysis systems on these missions. Placing the control and power conversion electronics at or near the actuators or instruments is the cornerstone of our distributed architecture. To do this, we developed the technology necessary to distribute the electronics and place them on a shared interface and power bus. This enables a significant reduction in cable mass along with its associated complexity. This allows spacecraft designers to take advantage of volume at the extremities that would normally not be utilized. In this paper we discuss the technologies and system design to achieve these goals in support of ocean world missions. These technologies include the development of our motor control modules, a point of load regulator and isolated converter modules along with the packaging technology necessary to allow our electronics to survive the extreme temperatures.

Stell, Chris↗

NASA NTRS2017

Distributed Spatiotemporal Motion Planning for Spacecraft Swarms in Cluttered Environments

This paper focuses on trajectory planning for spacecraft swarms in cluttered environments, like debris ﬁelds or the asteroid belt. Our objective is to reconﬁgure the spacecraft swarm to a desired formation in a distributed manner while minimizing fuel and avoiding collisions among themselves and with the obstacles. In our prior work we proposed a novel distributed guidance algorithm for spacecraft swarms in static environments.1 In this paper, we present the Multi-Agent Moving-Obstacles Spherical Expansion and Sequential Convex Programming (MAMO SE–SCP) algorithm that extends our prior work to include spatiotemporal constraints such as time-varying, moving obstacles and desired time-varying terminal positions. In the MAMO SE–SCP algorithm, each agent uses a spherical-expansion-based sampling algorithm to cooperatively explore the time-varying environment, a distributed assignment algorithm to agree on the terminal position for each agent, and a sequential-convex-programming-based optimization step to compute the locally-optimal trajectories from the current location to the assigned time-varying terminal position while avoiding collision with other agent and the moving obstacles. Simulations results demonstrate that the proposed distributed algorithm can be used by a spacecraft swarm to achieve a time-varying, desired formation around an object of interest in a dynamic environment with many moving and tumbling obstacles.

Hadaegh, Fred Y.↗

NASA NTRS2021

Speckle Observations of TESS Exoplanet Host Stars: Understanding the Binary Exoplanet Host Star Orbital Period Distribution

We present high-resolution speckle interferometric imaging observations of TESS exoplanet host stars using the NN-EXPLORE Exoplanet and Stellar Speckle Imager instrument at the 3.5 m WIYN telescope. Eight TESS objects of interest that were originally discovered by Kepler were previously observed using the Differential Speckle Survey Instrument. Speckle observations of 186 TESS stars were carried out, and 45 (24%) likely bound companions were detected. This is approximately the number of companions we would expect to observe given the established 46% binarity rate in exoplanet host stars. For the detected binaries, the distribution of stellar mass ratio is consistent with that of the standard Raghavan distribution and may show a decrease in high-q systems as the binary separation increases. The distribution of binary orbital periods, however, is not consistent with the standard Ragahavan model, and our observations support the premise that exoplanet-hosting stars with binary companions have, in general, wider orbital separations than field binaries. We find that exoplanet-hosting binary star systems show a distribution peaking near 100 au, higher than the 40–50 au peak that is observed for field binaries. This fact led to earlier suggestions that planet formation is suppressed in close binaries.

Stellar Speckle Imager↗

NASA NTRS2022

An Evaluation of Biomass Burning Aerosol Mass, Extinction, and Size Distribution in Geos Using Observations From Camp2EX

Biomass burning aerosol impacts aspects of the atmosphere and Earth system through radiative forcing, serving as cloud condensation nuclei, and air quality. Despite its importance, the representation of biomass burning aerosol is not always accurate in numerical weather prediction and climate models or reanalysis products. Using observations collected as part of the Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP2Ex) in August through October of 2019, aerosol concentration and optical properties are evaluated within the Goddard Earth Observing System (GEOS) and its underlying aerosol module, GOCART. In the operational configuration, GEOS assimilates aerosol optical depth observations at 550 nm to constrain aerosol fields. Particularly for biomass burning aerosol, without the assimilation of aerosol optical depth, aerosol extinction is underestimated compared to observations collected in the Philippines region during the CAMP2Ex campaign. The assimilation process adds excessive amounts of carbon to account for the underestimated extinction, resulting in positive biases in the mass of black and organic carbon, especially within the boundary layer, relative to in situ observations from the Langley Aerosol Research Group Experiment. Counteracting this, GEOS is deficient in sulphate and nitrate aerosol just above the boundary layer. Aside from aerosol mass, extinction within GEOS is a function of ambient relative humidity and an assumed particle size distribution. The relationship between dry and ambient extinction in GEOS reveals that hygroscopic growth is too aggressive within the model for biomass burning aerosol. An additional concern lies in the assumed particle size distribution for GEOS, which has a mode radius that is too small for organic carbon. Variability in the observed particle size distribution for biomass burning aerosol within a single flight also illuminates the fact that a single assumed particle size distribution is not sufficient and that for a proper representation, a more advanced aerosol module with GEOS may be necessary.

Aerosol Mass↗

NASA NTRS2023

Experimental Investigation of Distributed Sand-Grain Roughness Effects on Transition Onset and Turbulent Heating at Mach 6

An experimental investigation of distributed sand-grain surface roughness effects on hypersonic boundary-layer transition and turbulent heating has been performed. Two representative entry vehicle geometries, a sphere-cone aeroshell and a spherical-cap aeroshell, were considered. Cast ceramic models of each geometry were fabricated with distributed sand-grain roughness patterns of different heights that simulated an ablated thermal protection system. Wind tunnel testing was performed at Mach 6 over a range of Reynolds numbers sufficient to produce laminar, transitional, and turbulent flow. Aeroheating and boundary-layer transition onset data were obtained using global phosphor thermography. The experimental heating data are presented herein, as are comparisons to laminar and turbulent smooth-wall heat transfer distributions from computational flow field simulations. The boundary-layer transition data were found to correlate with a functional representation developed in prior roughness studies, although the data scatter was greater owing to the height variability of distributed sand-grain roughness.

Brian R Hollis↗

NASA NTRS2023

An Overview of Distributed Spacecraft Autonomy at NASA Ames

Autonomous decision-making significantly increases mission effectiveness by mitigating the effects of communication constraints, like latency and bandwidth, and mission complexity on multi-spacecraft operations. To advance the state of the art in autonomous Distributed Space Systems (DSS), the Distributed Spacecraft Autonomy (DSA) team at NASA's Ames Research Center is developing within five relevant technical areas: distributed resource and task management, reactive operations, system modeling and simulation, human-swarm interaction, and ad hoc network communications. DSA is maturing these technologies - critical for future large autonomous DSS - from concept to launch via simulation studies and orbital deployments. A 100-node heterogenous Processor-in-the-Loop (PiL) testbed aids distributed autonomy capability development and verification of multi-spacecraft missions. The DSA software payload deployed to the D-Orbit SCV-004 spacecraft demonstrates multi-agent reconfigurability and reliability as part of an ESA-sponsored in-orbit technology demonstration. Finally, DSA's primary flight mission showcases collaborative resource allocation for multipoint science data collection with four small spacecraft as a payload on NASA's Starling 1.0 satellites.

Caleb Ashmore Adams↗

NASA NTRS2023

Spatial distributions of Tribrachidium, Rugoconites, and Obamus from the Ediacara Member (Rawnsley Quartzite), South Australia

The spatial distribution of in situ sessile organisms, including those from the fossil record, provides information about life histories, such as possible dispersal and/or settlement mechanisms, and how taxa interact with one another and their local environments. At Nilpena Ediacara National Park (NENP), South Australia, the exquisite preservation and excavation of 33 fossiliferous bedding planes from the Ediacara Member of the Rawnsley Quartzite reveals in situ communities of the Ediacara Biota. Here, the spatial distributions of three relatively common taxa, Tribrachidium, Rugoconites, and Obamus, occurring on excavated surfaces were analyzed using spatial point pattern analysis. Tribrachidium have a variable spatial distribution, implying that settlement or post-settlement conditions/preferences had an effect on populations. Rugoconites display aggregation, possibly related to their reproductive methods in combination with settlement location availability at the time of dispersal and/or settlement. Additionally, post-settlement environmental controls could have affected Rugoconites on other surfaces, resulting in lower populations and densities. Both Tribrachidium and Rugoconites also commonly occur as individuals or in low numbers on a number of beds, thus constraining possible reproductive strategies and environmental/substrate preferences. The distribution of Obamus is consistent with selective settlement, aggregating near conspecifics and on substrates of mature microbial mat. This dispersal process is the first example of substrate-selective dispersal among the Ediacara Biota, thus making Obamus similar to numerous modern sessile invertebrates with similar dispersal and settlement strategies. Resumen La distribución espacial de los organismos sésiles in situ, incluyendo los del registro fósil, brinda información sobre las historias de vida, tal como los posibles mecanismos de dispersión y/o asentamiento, y sobre cómo los taxones interactúan entre sí y entre sus entornos locales. En el Parque Nacional Nilpena Ediacara (NENP), Australia Meridional, la excelente preservación y excavación de 33 planos de lecho fosilífero del Miembro Ediacara de la Cuarcita Rawnsley revela comunidades in situ de la biota ediacárica. En este estudio analizamos las distribuciones espaciales de tres taxones relativamente comunes, Tribrachidium, Rugoconites y Obamus, que se encuentran en superficies excavadas mediante el análisis de patrones de puntos espaciales. Tribrachidium tiene una distribución espacial variable, lo que implica que las condiciones/preferencias durante o después del asentamiento tuvieron un efecto en las poblaciones. Rugoconites muestran agregación, posiblemente relacionado con sus métodos reproductivos en combinación con la disponibilidad de lugares de asentamiento en el momento de la dispersión y/o asentamiento. Además, los controles ambientales posteriormente al asentamiento podrían estar afectando a Rugoconites en otras superficies, lo que resultaría en poblaciones y densidades más bajas. Tanto Tribrachidium como Rugoconites ocurren como individuos en varios lechos, restringiendo las posibles estrategias reproductivas y las preferencias ambientales/de sustrato. La distribución de Obamus es consistente con un asentamiento selectivo, agregando cerca de sus congéneres y sobre sustratos de tapete microbiano maduro. Este proceso de dispersión es el primer ejemplo de dispersión selectiva de sustrato entre la biota ediacárica, lo que hace que Obamus sea similar a numerosos invertebrados sésiles modernos con estrategias similares de dispersión y asentamiento.

Phillip C. Boan↗

NASA NTRSDate not supplied

Advancing Autonomy in Distributed Space Systems: Insights From on-Orbit Testing with the Starling 1.0 Mission

Autonomous decision-making is crucial for enhancing mission effectiveness in Distributed Space Systems (DSS), particularly in multi-spacecraft operations where communication constraints and mission complexity pose challenges. The Distributed Spacecraft Autonomy (DSA) team at NASA’s Ames Research Center is advancing autonomy in DSS through five key technical areas: distributed resource and task management, reactive operations, system modeling and simulation, human-swarm interaction, and ad hoc network communications. The DSA experiment onboard the Starling 1.0 Mission showcases collaborative resource allocation for multi-point science data collection with four small spacecraft. Autonomy in decision-making is highlighted as a crucial factor for multi-spacecraft missions, enabling spacecraft to operate independently, reducing reliance on ground control. This capability is particularly significant for future deep-space missions, where communication delays and limited data transmission capacity make traditional command and control approaches impractical. This demonstration focuses on a GPS Channel Selection Experiment, leveraging emergent capabilities like "shared sampling" and "simultaneous sampling" to optimize channel selection across the spacecraft swarm. The experiment aims to capture ionospheric phenomena such as the Equatorial Ionization Anomaly and Polar Patches. The DSA system's autonomous reconfiguration ability is showcased, emphasizing its adaptability to natural phenomena without significant integration efforts. The GPS Channel Selection Experiment utilizes a dual-band GPS receiver to estimate plasma density in the ionosphere. Explorative and exploitative channel selections are employed based on the nature of observed phenomena. The performance of DSA algorithms is evaluated in terms of optimal channel allocations and responsiveness to changes in observed features. The DSA Flight Software utilizes the Core Flight System (cFS) framework, ensuring compatibility with the Starling 1.0 flight mission software. DSA showcases results from RTI’s Connext DDS Micro communication middleware, enabling message routing over the Ad-Hoc Network of Starling 1.0. This paper provides a comprehensive overview of the DSA experiment's initial results, emphasizing the advancements in autonomy for Distributed Space Systems and the successful collaboration with the Starling 1.0 mission.

Caleb Ashmore Adams↗

NASA NTRS2024

Variability and Distribution of Nighttime Equatorial to Mid Latitude Ionospheric Irregularities and Vertical Plasma Drift Observed by FORMOSAT-5 Advanced Ionospheric Probe In-Situ Measurements from 2017 – 2020

Irregularities in ionospheric plasma distribution can result in severe scintillation and disruption to the radio frequencies utilized for satellite communications and navigation. In the low and mid latitudes, these irregularities can include Equatorial Plasma Bubbles (EPBs) and Travelling Ionospheric Disturbances (TIDs). EPBs are irregularities manifesting in low latitude nighttime ionosphere plasma density that can extend along magnetic field lines with zonal scales on the order of 100 km or less, while TIDs are propagating wave disturbances. High frequency in-situ measurements of ionospheric plasma aboard spacecraft in Low Earth Orbit (LEO) are a direct measurement of irregularities in plasma density and are therefore valuable for resolving EPB and TID occurrences, variability, and relation to other ionospheric parameters that are believed to play a driving role in the formation of such irregularities. In this study, we utilize observations taken over a three-year period between 2017 and 2020 by the Advanced Ionospheric Probe (AIP) carried aboard the FORMOSAT-5 satellite to examine the spatial, seasonal, and interannual variability of equatorial to mid latitude ionospheric irregularities and vertical ion drift during this time. AIP provides in-situ measurements of ion density and vertical ion drift in the equatorial to mid latitude ionosphere at approximately 720 km altitude with local times between 22:00 – 23:00 local time. Our global scale results resolve distinct and inter-annually recurrent seasonal patterns in the distribution of nighttime ionospheric irregularities and vertical plasma drift during this time. Elevated occurrences of ion density irregularities are resolved along the Equatorial Ionization Anomaly (EIA) latitudes, while notable occurrences with variability consistent with EPBs also observed along the low and equatorial magnetic latitudes. Zonal variability of equatorial irregularities consistent with the signatures of nonmigrating atmospheric tides are observed. It is also notable that the occurrences and geographic distribution of ion density irregularities showed a considerable level of interannual variability, especially at mid latitudes over the South Atlantic and Southern African sectors, which showed much higher levels of irregularities in 2017–––2018, compared to 2019 and 2020. In comparison, the spatial and interannual variation of the co-located vertical ion drifts were much more consistent during the years examined, indicating that the driver for the observed interannual variability in ion density irregularities cannot be attributed to the vertical ion drift at the same time and location of the observations. This highlights the need for in-situ instruments distributed across multiple satellites in different local time zones.

ionosphere↗

NASA NTRS1925

Pressure Distribution on Joukowski Wings and Graphic Construction of Joukowski Wings

In the first article, in connection with a lecture on the hydrodynamic basis of flight and the potential flow about a Joukowski wing, the pressure distribution on several wings is computed and plotted. The diagrams of the pressure distributions are presented accompanied with a qualitative discussion of the pressure distribution. In the second article, the the cross-sectional outline (or profile) a Joukowski wing are plotted.

PRESSURE DISTRIBUTION - AIRFOILS - JOUKOWSKI↗

NASA NTRSDate not supplied

Flight Test Configuration of the Sensor Payload and the Ground Nodes in Distributed Sensing Frameworks

The realization of the Urban Air Mobility (UAM) vision, entailing the deployment of high-density autonomous flights over urban areas, necessitates methodologies transcending contemporary airborne sensing techniques. An instrumental innovation in this realm is the advent of distributed sensing. In this paradigm, environmental sensors function as active agents, engaging in the triad of sensing, processing, and communication either amongst themselves, with ground stations, or both. This concerted effort creates a dynamic and responsive "smart space," facilitating real-time autonomous control. NASA Ames Research Center is actively engaged in a series of comprehensive indoor and outdoor flight tests to garner requisite data and insights essential for the actualization of this ambitious vision. This paper delineates the holistic configuration of the flight payload and the distributed ground nodes pivotal to the NASA flight test campaign. Furthermore, it expounds upon the intricacies of the sensor node communication framework. The narrative extends to provide a detailed overview of the strategic placement of distributed sensors and a comprehensive account of the varied indoor and outdoor flight tests orchestrated in pursuit of UAM objectives.

urban air mobility↗

NASA NTRSDate not supplied

Flight Test Configuration of the Sensor Payload and the Ground Nodes in Distributed Sensing Frameworks

urban air mobility↗

NASA NTRS1988

Frequency distribution histograms for the rapid analysis of data

The mean and standard error are good representations for the response of a population to an experimental parameter and are frequently used for this purpose. Frequency distribution histograms show, in addition, responses of individuals in the population. Both the statistics and a visual display of the distribution of the responses can be obtained easily using a microcomputer and available programs. The type of distribution shown by the histogram may suggest different mechanisms to be tested.

NASA Discipline Plant Biology↗

NASA NTRS2006

Distributed Computing Framework for Synthetic Radar Application

We are developing an extensible software framework, in response to Air Force and NASA needs for distributed computing facilities for a variety of radar applications. The objective of this work is to develop a Python based software framework, that is the framework elements of the middleware that allows developers to control processing flow on a grid in a distributed computing environment. Framework architectures to date allow developers to connect processing functions together as interchangeable objects, thereby allowing a data flow graph to be devised for a specific problem to be solved. The Pyre framework, developed at the California Institute of Technology (Caltech), and now being used as the basis for next-generation radar processing at JPL, is a Python-based software framework. We have extended the Pyre framework to include new facilities to deploy processing components as services, including components that monitor and assess the state of the distributed network for eventual real-time control of grid resources.

synthetic aperture radar (SAR)↗

NASA NTRS2008

Observability and Estimation of Distributed Space Systems via Local Information-Exchange Networks

In this work, we develop an approach to formation estimation by explicitly characterizing formation's system-theoretic attributes in terms of the underlying inter-spacecraft information-exchange network. In particular, we approach the formation observer/estimator design by relaxing the accessibility to the global state information by a centralized observer/estimator- and in turn- providing an analysis and synthesis framework for formation observers/estimators that rely on local measurements. The noveltyof our approach hinges upon the explicit examination of the underlying distributed spacecraft network in the realm of guidance, navigation, and control algorithmic analysis and design. The overarching goal of our general research program, some of whose results are reported in this paper, is the development of distributed spacecraft estimation algorithms that are scalable, modular, and robust to variations inthe topology and link characteristics of the formation information exchange network. In this work, we consider the observability of a spacecraft formation from a single observation node and utilize the agreement protocol as a mechanism for observing formation states from local measurements. Specifically, we show how the symmetry structure of the network, characterized in terms of its automorphism group, directly relates to the observability of the corresponding multi-agent system The ramification of this notion of observability over networks is then explored in the context of distributed formation estimation.

observability↗

NASA NTRS2013

The Radial Distribution of Star Formation in Galaxies at z~1 From The 3D-HST Survey

The assembly of galaxies can be described by the distribution of their star formation as a function of cosmic time.Thanks to the WFC3 grism on the Hubble Space Telescope (HST) it is now possible to measure this beyond thelocal Universe. Here we present the spatial distribution of H emission for a sample of 54 strongly star-forming-galaxies at z~1 in the 3D-HST Treasury survey. By stacking the Halpha emission, we find that star formation occurredin approximately exponential distributions at z~1, with a median Sersic index of n=1.0 plus or minus 0.2. The stacks areelongated with median axis ratios of b/a 0.58 plus or minus 0.09 in Halpha consistent with (possibly thick) disks at randomorientation angles. Keck spectra obtained for a subset of eight of the galaxies show clear evidence for rotation, withinclination corrected velocities of 90-330 km per second. The most straightforward interpretation of our results is that starformation in strongly star-forming galaxies at z~1 generally occurred in disks. The disks appear to be scaled-upversions of nearby spiral galaxies: they have EW(Halpha)~100 Angstroms out to the solar orbit and they have star formation surface densities above the threshold for driving galactic scale winds.

Radial↗

NASA NTRS2012

Origin, Transport, and Vertical Distribution of Atmospheric Polluntants over the Northern Sourth China Sea During the 7-SEAS-Dongsha Experiment

During the spring of 2010, comprehensive in situ measurements were made for the first time on a small atoll (Dongsha Island) in the northern South China Sea (SCS), a key region of the 7-SEAS (the Seven South East Asian Studies) program. This paper focuses on characterizing the source origins, transport processes, and vertical distributions of the Asian continental outflows over the region, using measurements including mass concentration, optical properties, hygroscopicity, and vertical distribution of the aerosol particles, as well as the trace gas composition. Cluster analysis of backward trajectories classified 52% of the air masses arriving at ground level of Dongsha Island as having a continental origin, mainly from northern China to the northern SCS, passing the coastal area and being confined in the marine boundary layer (0-0.5 km). Compared to aerosols of oceanic origin, the fine mode continental aerosols have a higher concentration, extinction coefficient, and single-scattering albedo at 550 nm (i.e., 19 vs. 14 microg per cubic meter in PM(sub 2.5); 77 vs. 59 M per meter in beta(sub e); and 0.94 vs. 0.90 in omega, respectively). These aerosols have a higher hygroscopicity (f at 85% RH = 2.1) than those in the upwind inland regions, suggesting that the aerosols transported to the northern SCS were modified by the marine environment. In addition to the near-surface aerosol transport, a significant upper-layer (3-4 km) transport of biomass-burning aerosols was observed. Our results suggest that emissions from both China and Southeast Asia could have a significant impact on the aerosol loading and other aerosol properties over the SCS. Furthermore, the complex vertical distribution of aerosols-coinciding-with-clouds has implications for remote-sensing observations and aerosol-cloud-radiation interactions.

pollutants↗

NASA NTRS2014

Developing an Integration Infrastructure for Distributed Engine Control Technologies

Turbine engine control technology is poised to make the first revolutionary leap forward since the advent of full authority digital engine control in the mid-1980s. This change aims squarely at overcoming the physical constraints that have historically limited control system hardware on aero-engines to a federated architecture. Distributed control architecture allows complex analog interfaces existing between system elements and the control unit to be replaced by standardized digital interfaces. Embedded processing, enabled by high temperature electronics, provides for digitization of signals at the source and network communications resulting in a modular system at the hardware level. While this scheme simplifies the physical integration of the system, its complexity appears in other ways. In fact, integration now becomes a shared responsibility among suppliers and system integrators. While these are the most obvious changes, there are additional concerns about performance, reliability, and failure modes due to distributed architecture that warrant detailed study. This paper describes the development of a new facility intended to address the many challenges of the underlying technologies of distributed control. The facility is capable of performing both simulation and hardware studies ranging from component to system level complexity. Its modular and hierarchical structure allows the user to focus their interaction on specific areas of interest.

distributed control↗