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NASA NTRS2018

Three Years of Atmospheric Characterization at Ka/Q-band with the NASA/POLIMI Alphasat Receiver in Milan, Italy

Since June of 2014, NASA Glenn Research Center (GRC) and the Politecnico di Milano (POLIMI) have jointly conducted a propagation campaign within the framework of the Alphasat propagation experiment through a propagation terminal at the POLIMI campus in Milan, Italy. The terminal utilizes the 20 GHz and 40 GHz beacons broadcast by the Aldo Paraboni Technology Demonstration Payload (TDP #5), and consists of dual coherent Ka- and Q-band beacon receivers. These provide a direct measurement of the signal attenuation and scintillation and are complemented by concurrent weather instrumentation that provides measurements of the atmospheric conditions at the receiver. The primary goal of these measurements is to improve model predictions of communication system performance at 40 GHz. Over three years of concurrent measurements have now been collected from the terminal, and herein we present a statistical analysis of the results thus far, as well as a summary of recent hardware upgrades to the receivers that were made in September 2017.

Radio Transmission↗

NASA NTRS2018

Three Years of Atmospheric Characterization at Ka/Q-band with the NASA/POLIMI Alphasat Receiver in Milan, Italy

Radio Transmission↗

NASA NTRS2019

Sea Surface Salinity Distribution in the Southern Ocean as Observed from Space

Large-scale spatial and temporal variabilities of sea surface salinity (SSS) in the Southern Ocean from 2011 to 2017 were studied using products derived from microwave sensors on board Aquarius, Soil Moisture and Ocean Salinity (SMOS), and Soil Moisture Active and Passive (SMAP) satellites. Four products, three from Aquarius and one from SMOS, were evaluated and shown to be generally consistent within 0.3 to 0.6 psu and agree favorably with in situ measurements. However, although the Aquarius products show consistent seasonality of SSS with high values of 34.45 psu in October and low values of 33.40 psu in May, theSMOS and SMAP products lack such seasonal variations. This may be caused by larger uncertainties in the SMOS and SMAP data due in part to the lack of concurrent scatterometer measurements that is used to correct for roughness effects. The four products provide similar spatial distributions of SSS with root mean square difference from 0.25 to 0.58 psu. Differences among Aquarius products are mainly due to varying salinity retrieval algorithms, smoothing, and masking of sea ice, while the SMOS product showed the highest SSS deviation that is likely due to the bias adjustment done on the data set. Our analyses show that SSS in the Southern Ocean region has significant meridional variations with the lowest SSS near the ice edge and highest at lower latitudes. The SSS is also lowest in summer indicating the predominant influence of sea ice and glacial melt, but it stays low near ice edges even during the growth season. Salinity together with temperature is the key parameters that control the state and circulation of the World's oceans. The large‐scale distribution of the sea surface salinity of the Southern Ocean is quantified for the first time using Aquarius, Soil Moisture and Ocean Salinity, and Soil Moisture Active and Passive satellite microwave data. Seasonal and interannual changes in the distribution as affected by the sea ice cover, surface temperature, and precipitation are evaluated. Comparative studies were done, using four different products that are publicly available, in conjunction with in situ observations to gain insights into the true nature of the distribution and how consistently the sea surface salinity is depicted by the different products. There are general consistencies in the products, and discrepancies are attributed to different algorithms, smoothing techniques, and sea ice masking. Aquarius data are shown to have higher accuracy than Soil Moisture and Ocean Salinity and Soil Moisture Active and Passive products in part because of having concurrent scatterometer that provides accurate correction to roughness effects.

Garcia-Eidell, Cynthia↗

NASA NTRS2019

NASA Station Explorer for X-Ray Timing and Navigation Technology (SEXTANT) Mission Operations Architecture

"The Station Explorer for X-Ray Timing and Navigation (SEXTANT) mission is a technology demonstrationenhancement to the Neutron Star Interior Composition Explorer (NICER) mission, a NASA AstrophysicsExplorer Mission of Opportunity to the International Space Station (ISS) that was launched in June of 2017.The NICER instrument is a precision pointing X-ray telescope that provides measurements of neutron stars,which the SEXTANT mission uses to perform autonomous onboard X-ray Pulsar Navigation (XNAV) by usingmilli-second pulsars (MSPs), a category of neutron stars, as timing sources for navigation. By comparing thedetected time of arrival of X-ray photons to a reference of expected pulsar lightcurve timing models, one caninfer a range and range rate measurement based on light time delay. Since both timing and orientationinformation comes from a celestial source, this technology could provide a GPS-like navigation capabilityavailable throughout our Solar System and beyond. Applications that XNAV can support include outer planetand interstellar missions, manned missions, libration orbit missions, and current infrastructure such as the DeepSpace Network (DSN). The SEXTANT team successfully completed a rst demonstration of in-space andautonomous XNAV in November 2017. NICER and SEXTANT have separate teams, with NICER being theprimary team with its own science objectives. Operational modes for both missions must have concurrent andindependent components as well as an integrated ground system. Within this joint mission pro le, SEXTANToperations requires an infrastructure and cadence that is exible to handle concurrent science operations fromthe NICER team, independent autonomous navigation demonstrations, and events within the extensive ISSoperations environment. This paper rst details the infrastructure implemented and its concept of operations.It then describes the operations for the SEXTANT demonstration and lessons learned."

Yu, Wayne H.↗

NASA NTRS2019

The Missing Economic Risks in Assessments of Climate Change Impacts

Economic assessments of the potential future risks of climate change have been omitting or grossly underestimating many of the most serious consequences for lives and livelihoods because these risks are difficult to quantify precisely and lie outside of human experience. Political and business leaders need to understand the scale of these ‘missing risks’ because they could have drastic and potentially catastrophic impacts on citizens, communities and companies. Scientists are growing in confidence about the evidence for the largest potential impacts of climate change and the rising probability that major thresholds in the Earth’s climate system will be breached as global mean surface temperature rises, particularly if warming exceeds 2°C above the pre-industrial level. These impacts include: (1) Destabilisation of ice sheets and glaciers and consequent sea level rise. (2) Stronger tropical cyclones. (3) Extreme heat impacts. (4) More frequent and intense floods and droughts. (5) Disruptions to oceanic and atmospheric circulation. (6) Destruction of biodiversity and collapse of ecosystems. Many of these impacts will grow and occur concurrently across the world as global temperature climbs. Some of these impacts involve thresholds in the climate system beyond which major impacts accelerate, or become irreversible and unstoppable. When a threshold is breached, it might cause one or more other thresholds to be exceeded as well, leading to a cascade of impacts. Many of these impacts could exceed the capacity of human populations to adapt, and would significantly affect and disrupt the lives and livelihoods of hundreds of millions, if not billions, of people worldwide. These impacts would also undermine economic growth and development, exacerbate poverty and destabilise communities. Economic assessments fail to take account of the potential for large concurrent impacts across the world that would cause mass migration, displacement and conflict, with huge loss of life. Economic assessments that are expressed solely in terms of effects on output (e.g. gross domestic product), or that only extrapolate from past experience, or that use inappropriate discounting, do not provide a clear indication of the potential risks to lives and livelihoods. It is likely that there are additional risks that we are not yet anticipating simply because scientists have not yet detected their possibility, as we have entered a period of climate change that is unprecedented in human history. Some advances are being made in improving economic assessments of climate change impacts but much more progress is required if assessments are to offer reliable guidance for political and business leaders on the biggest risks. The lack of firm quantifications is not a reason to ignore these risks, and when the missing risks are taken into account, the case for strong and urgent action to reduce greenhouse gas emissions becomes even more compelling.

DeFries, Ruth↗

NASA NTRS2019

Parallel Anisotropic Unstructured Grid Adaptation

Computational Fluid Dynamics (CFD) has become critical to the design and analysis of aerospace vehicles. Parallel grid adaptation that resolves multiple scales with anisotropy is identified as one of the challenges in the CFD Vision 2030 Study to increase the capacity and capability of CFD simulation. The Study also cautions that computer architectures are undergoing a radical change and dramatic increases in algorithm concurrency will be required to exploit full performance. This paper reviews four different methods to parallel anisotropic grid generation. They cover both ends of the spectrum: (i) using existing state-of-the-art software optimized for a single core and modifying it for parallel platforms and (ii) designing and implementing scalable software with incomplete, but rapidly maturating functionality. A brief overview for each grid adaptation system is presented in the context of a telescopic approach for multilevel concurrency. These methods employ different approaches to enable parallel execution, which provides a unique opportunity to illustrate the relative behavior of each approach. Qualitative and quantitative metric evaluations are used to draw lessons for future developments in this critical area for parallel CFD simulation.

Tsolakis, Christos↗

NASA NTRSDate not supplied

Plasmaspheric Plume Turbulence: Signature of an Electrostatic Corotation Convection Shear-Layer Instability

As demonstrated by IMAGE-EUV observations, plasmaspheric drainage plumes are a common feature emanating from the plasmasphere during periods of enhanced convection. Concurrent IMAGE-EUV and LANL-MPA observations reveal that plasmaspheric plumes are not a uniform density structure that extends out to geosynchronous orbit and beyond. Instead, in–situ observations reveal a large spatial-scale structure populated by small-scale density structures suggestive of the presence of a turbulent process. Here, we investigate the occurrence and nature of plasmaspheric drainage plumes as observed by concurrent EUV-MPA observations, as well as explore the possibility that the in–situ observed small-scale density structures are the signature of an instability produced by the sheared velocity found within the plasmaspheric layers separating the corotation of the main plasmasphere from the convection-driven flow generating the plume. Particle-in-cell simulations indicate that the generation of shear-flow driven instabilities is possible under plasmaspheric plasma conditions. The initial results of these simulations indicate that the plasmaspheric instabilities generated are electrostatic in nature, consist with in–situ plume observations.

Mark L Adrian↗

NASA NTRSDate not supplied

The Effect of Reduced Pressure on the Characteristics of Spreading Flames

Flame spread over solid fuels is a canonical problem in fire science, due to its direct implications on material flammability and importance in fire development. In a microgravity environment, such as onboard a spacecraft, flames can behave very differently than on Earth. This is concerning for spaceflight life safety, especially in higher-oxygen environments. Due to the difficulties associated with microgravity testing, low-pressure environments have been proposed as an alternative to approximately replicate the burning behavior of solid fuels observed in reduced gravity conditions because of similar diffusion and heat transfer mechanisms. However, the roles played by gravity and pressure on flame length, standoff distance, and flame spread rate vary with the burning configuration. In concurrent flame spread, the buoyant flow enhances the spread rate by bringing the flame closer to the fuel surface and increasing the heating of the solid fuel. In opposed flame spread, the sample is preheated by the flame ahead of the flame leading edge, which is strongly affected by the surrounding flow field. In this work, we consider flames spreading over thin cotton samples in both downward (opposed) and upward (concurrent) configurations to investigate the effect of pressure (30-100 kPa) on flame characteristics, such as spread rate and standoff distance. A small forced flow is induced upward so that the flames are exposed to a mixed (forced and free) flow. By reducing pressure, flames become less bright, their standoff distance increases, and their spread rates decrease similar to what is observed in low-gravity environments. These results could in help understanding the differences between flames spreading at low pressure and low gravity environments for these similar, yet very different, spreading configurations. They could also provide more information about potential Earth-based flammability testing of materials for spacecraft applications.

fire safety↗

NASA NTRSDate not supplied

The effect of reduced pressure on the characteristics of spreading flames

fire safety↗

NASA NTRS2020

A Robotically Assembled and Serviced Science Station for Earth Observations

In this paper we present the overall architecture of a ”Science Station”, a robotically assembled and serviced persistent platform that can host multiple payloads for Earth observations. Recent decadal survey findings motivate the need to have spatial and temporal concurrency in measurements from multiple instruments. We have architected the science station to simultaneously host up to twelve Earth Venture class instruments at a time. These instruments can be replaced by newer instruments periodically to take advantage of evolving science needs and technology capabilities. The Science Station can also concurrently host science, commercial, defense and other national interest payloads. The Science Station may provide a cost-effective paradigm by mitigating some of the risks and costs associated with multiple free-flyers that may otherwise be needed for the various instruments. It leverages emergent and existent technologies in robotic assembly and servicing, lower cost commercial launch vehicles, secondary launch vehicles, and rendezvous and proximity operations. In this paper, we report the findings of a survey we conducted on the desired performance of the Science Station from various instrument hosting perspectives. We report the various trade studies that we conducted to developed a feasible architecture that meets the goals of the Science Station while also meeting the constraints of a space system. We also report the various considerations in the configuration, thermal system, pointing system, overall concept of operations, and the robotic system of the Science Station architecture. The paper then describes a testbed activity we are undertaking to evaluate the supervised autonomy robotics needed for the Science Station as well as to conduct a riskreduction demonstration of the end-to-end robotics behaviors.

Mukherjee, Rudranarayan↗

NASA NTRS2020

In Silico Methods for Space System Analysis: Optical Link Coding Performance and Lunar Terrain Masks

As deep space links migrate toward higher frequency bands like 𝐾𝑎 and optical, thor- ough trade-space exploration becomes increasingly valuable for designing reliable and efficient communications systems. In this contribution, we leveraged high-performance, concurrent simulations when the run-time complexity of simulation software overwhelms capabilities of ordinary desktop machines. The first part of this manuscript describes how to run error correcting code simulations concurrently on a high-performance supercomputer. The second part of this study describes a framework to produce azimuth and elevation terrain masks from imagery of the Lunar South Pole.

Michels, Dominik L↗

NASA NTRS2022

Responses of Compound Daytime and Nighttime Warm-Dry and Warm-H Events to Individual Anthropogenic Forcings

Daytime heat is often associated with reduced soil moisture and cloud cover, while nighttime heat is connected to high humidity and increased cloud cover. Due to these differing mechanisms, compound daytime and nighttime heat events may respond differently to major anthropogenic forcings (greenhouse gases, anthropogenic aerosols, land-use and land-cover change). Here, we use GISS ModelE2.1-G historical single-forcing runs from 1955 to 2014 to examine how individual anthropogenic forcings affect compound heat events—specifically warm daytime and nighttime temperatures compounded with dry precipitation or high humidity conditions. We show that greenhouse gases alone amplify the natural frequency of warm-dry events by 1.5–5 times and warm-humid events by 2–9 times in tropical and extratropical latitudes. Conversely, aerosols and land-use/land-cover change reduce the frequency of these events, resulting in more modest increases and in some regions, declines, in the historical 'all-forcings' scenario. Individually, aerosol effects are stronger and more widespread compared to land-use, oftentimes reducing the natural frequency of these events by 60%–100%. The responses of these compound events are primarily driven by changes in daytime and nighttime temperatures through large-scale warming via greenhouse gases and cooling from aerosols and land-use/land-cover change. However, changes in warm-dry events are amplified in regions with concurrent precipitation declines (e.g. Central America, Mediterranean regions) and warm-humid events are amplified by global concurrent humidity increases. Additionally, we find differences between daytime and nighttime compound responses in the historical experiment that can be traced back to the individual forcings. In particular, aerosols produce a greater cooling effect on daytime relative to nighttime temperatures, which notably results in a historical reduction of Northern Hemisphere daytime warm-dry events relative to natural conditions. Our analysis provides a more comprehensive understanding of the significant impacts of different anthropogenic climate forcings on daytime and nighttime warm-dry and warm-humid events, informing future risk and impact assessments.

Anthropogenic forcings↗

NASA NTRS2023

Technical Basis Related to the Posture of NASA’s Office of Safety and Mission Assurance for the Launch of Radioactive Material Other than Space Nuclear Systems: Volume 1–Overview of Analysis and Results

NASA has launched and reentered payloads containing radioactive material for over 50 years. The isotopes, their quantity, and their form have varied significantly. The handling of this material prior to its integration into the spacecraft at the launch Center (and after its return to Earth after flight, if applicable) falls under the purview of the Office of the Chief Health and Medical Officer, while after the radioactive material is integrated into the spacecraft at the launch Center, it falls under the purview of the Office of Safety and Mission Assurance’s (OSMA) Nuclear Flight Safety Program. Historically, OSMA concurrence was required for any launch or reentry involving radioactive material. However, OSMA recently revisited this posture due to changes in the Federal policy in this area, and the significant accrued experience. The current report represents the more quantitative study envisioned in the recent change in posture. More specifically, this document addresses the potential risks and other considerations associated with launching small quantities of radioactive material (below the level requiring the Federally-mandated process in National Security Presidential Memorandum- (NSPM-) 20, “Presidential Memorandum on Launch of Spacecraft Containing Space Nuclear Systems” (USG, 2019) to provide the technical basis for when such activities require OSMA concurrence versus notification, as it relates to nuclear flight safety.

Don Helton↗

NASA NTRS2022

Quasi-Periodic Whistler Mode Emission in the Plasmasphere as Observed By the DSX Spacecraft

We describe the quasi-periodic (QP) whistler-mode emissions found in the plasmasphere as detected by electric and magnetic instrumentation onboard the Demonstration and Science Experiments (DSX) spacecraft in medium Earth orbit. Over the course of the nearly 2-year mission, at least 45 episodes of whistler mode QP emissions were detected by the Broad Band Receiver (BBR) onboard DSX. Episodes of QP emissions were identified by discrete events having a clear unambiguous periodic nature as detected by both the electric antennae and search coil magnetic sensor in the BBR survey data at 30 second temporal resolution. Most of the QP episodes occurred in a frequency range between 1- 4 kHz, in a band previously identified by Van Allen Probes and Cluster investigators. However, episodes were also detected by DSX at higher frequencies - events in these episodes extending all the way to 15 kHz. We present our findings on these unusual high frequency events in the presentation herein. Specifically, these high frequency QP episodes tended to be observed near dawn/dusk when the spacecraft was at relatively high magnetic latitudes and on magnetic L-shells between 3-5. Another unusual feature of these episodes is that individual up-drifting events making up the episode were found to sometimes occur concurrently in time: The high frequency portion of one up-drifting ‘polliwog-shaped’ event overlapped in time with the low frequency portion of the subsequent event. This behavior of the QP emissions has not been previously emphasized and we consider how this temporal concurrence relates to the source processes.

Quasi-periodic↗

NASA NTRS2023

Warming Overwhelms the Efficacy of Wet Conditions to Moderate Extreme Heat and Atmospheric Aridity Across the Central Plains

While the relationships between dry land surface conditions, heat, and aridity have been well-established, few studies have addressed whether global warming will affect the ability of wet conditions to moderate high temperatures and atmospheric aridity. Using Coupled Model Intercomparison Project Phase 6 models, we demonstrate that absolute changes in the monthly maximum temperature distribution during Central North American summers strongly outweigh the historical cooling effect of high precipitation and soil moisture conditions. Although wet conditions nearly always prevent concurrent extreme temperatures in the baseline period, these conditions are 40%–48% and 96%–98% less effective at 1 and 2° of global warming, respectively. However, high precipitation and soil moisture partially retain the ability to constrain concurrent high vapor pressure deficit conditions below historical thresholds at 1–2° of warming. Our results highlight the growing vulnerability of Central North America to warmer temperatures and drier atmospheric conditions, even during periods of high precipitation and soil moisture.

global warming↗

NASA NTRS2024

Moon: Handle With Care

The exploration of the Moon involves multiple and complex competing interests, including those of nation states and commercial entities. The goal of this paper is to identify science questions with answers that may be obscured by human activities unless precautions are taken. We aim to encourage follow-on work to produce environmental impact assessments for various lunar activities in order to understand the degree of contamination generated by different processes. We also encourage the preservation of scientifically important regions, as proposed by others (e.g., Committee on Planetary Protection, 2020; Farrell et al., 2021; Krolikowski, 2023). In the following sections, we discuss what measurements are necessary to determine how and where science investigations and exploration (commercial or otherwise) can be carried out concurrently. We advocate a strategy of concurrent exploration and science where possible, and for a science-first approach in cases where exploration may obscure scientific evidence that is uniquely preserved on the Moon.

Rosemary M Killen↗

NASA NTRSDate not supplied

Advancing Open Science in Atmospheric Research: Integrating Data Usability and Machine Learning

In the dynamic realm of atmospheric sciences, the convergence of data science methodologies and open data marks a transformative era, driving research advancements and nurturing aspiring scientists. This abstract highlights two pivotal projects that epitomize open science principles, aligning seamlessly with the session's objective of interdisciplinary synergy and the cultivation of emerging talent. As a NASA-certified data center, our foremost endeavor focuses on enhancing the visibility and traceability of NASA datasets within atmospheric science research. This initiative not only elevates these datasets' prominence but also establishes a robust framework ensuring their credibility in scholarly discourse. By bridging the gap between data sources and research publications, this project serves as an educational catalyst, nurturing a new generation of scholars in open collaboration and dataset authenticity. Concurrently, our second project pioneers an early warning system for flooding events, utilizing machine learning algorithms to predict flooded fractions. Through multi-source data fusion and predictive modeling, this initiative goes beyond forecasting; it embodies the core of open science by enabling proactive risk mitigation strategies. This project not only advances atmospheric sciences but also fosters an environment where young scholars engage in practical, data-driven solutions. These intertwined projects exemplify the fusion of data science with open data solutions, ensuring both the usability of quality datasets and the cultivation of scientific knowledge among emerging scholars. By spotlighting these impactful use cases, our aim is to foster discussions emphasizing the importance of open collaboration, data integrity, and the nurturing of scientific talent in atmospheric sciences." "In the dynamic realm of atmospheric sciences, the convergence of data science methodologies and open data marks a transformative era, driving research advancements and nurturing aspiring scientists. This abstract highlights two pivotal projects that epitomize open science principles, aligning seamlessly with the session's objective of interdisciplinary synergy and the cultivation of emerging talent. As a NASA-certified data center, our foremost endeavor focuses on enhancing the visibility and traceability of NASA datasets within atmospheric science research. This initiative not only elevates these datasets' prominence but also establishes a robust framework ensuring their credibility in scholarly discourse. By bridging the gap between data sources and research publications, this project serves as an educational catalyst, nurturing a new generation of scholars in open collaboration and dataset authenticity. Concurrently, our second project pioneers an early warning system for flooding events, utilizing machine learning algorithms to predict flooded fractions. Through multi-source data fusion and predictive modeling, this initiative goes beyond forecasting; it embodies the core of open science by enabling proactive risk mitigation strategies. This project not only advances atmospheric sciences but also fosters an environment where young scholars engage in practical, data-driven solutions. These intertwined projects exemplify the fusion of data science with open data solutions, ensuring both the usability of quality datasets and the cultivation of scientific knowledge among emerging scholars. By spotlighting these impactful use cases, our aim is to foster discussions emphasizing the importance of open collaboration, data integrity, and the nurturing of scientific talent in atmospheric sciences.

Jennifer Wei↗

NASA NTRS1994

Reengineering the Project Design Process

In response to NASA's goal of working faster, better and cheaper, JPL has developed extensive plans to minimize cost, maximize customer and employee satisfaction, and implement small- and moderate-size missions. These plans include improved management structures and processes, enhanced technical design processes, the incorporation of new technology, and the development of more economical space- and ground-system designs. The Laboratory's new Flight Projects Implementation Office has been chartered to oversee these innovations and the reengineering of JPL's project design process, including establishment of the Project Design Center and the Flight System Testbed. Reengineering at JPL implies a cultural change whereby the character of its design process will change from sequential to concurrent and from hierarchical to parallel. The Project Design Center will support missions offering high science return, design to cost, demonstrations of new technology, and rapid development. Its computer-supported environment will foster high-fidelity project life-cycle development and cost estimating.

Jet Propulsion Laboratory JPL project design concu↗