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A critical assessment by approximately 70 community representatives from NASA, academia, industry, research institutions, and international organizations of candidate activities on the lunar surface and its vicinity that may feed forward to support affordable and sustainable human missions to the surface of Mars in 2030s.
Numerical simulations of acoustic waves in a shear layer and in an idealized combustion chamber using high resolution Total Variation Diminishing (TVD) schemes has been carried out to study the effects of inherent scheme dissipation and dispersion errors of this class of problems. The numerical results are compared against available exact solutions to quantify these errors. Several popular TVD limiters widely used in the Computational Fluid Dynamics (CFD) community have been assessed. Osher-Chakravarthy limiters are modified so that they can be used in explicit schemes. Among all the limiters investigated, Osher-Chakravarthy third-order limiter is identified as having performed the best. It is also found that all TVD schemes have exceptionally small dispersive errors.
The Lower Mekong region is one of the most landslide-prone areas of the world. Despite the need for dynamic characterization of landslide hazard zones within the region, it is largely understudied for several reasons. Dynamic and integrated understanding of landslide processes requires landslide inventories across the region, which have not been available previously. Computational limitations also hamper regional landslide hazard assessment, including accessing and processing remotely sensed information. Finally, open-source software and modelling packages are required to address regional landslide hazard analysis. Leveraging an open-source data-driven global Landslide Hazard Assessment for Situational Awareness model framework, this study develops a region-specific dynamic landslide hazard system leveraging satellite-based Earth observation data to assess landslide hazards across the lower Mekong region. A set of landslide inventories were prepared from high-resolution optical imagery using advanced image-processing techniques. Several static and dynamic explanatory variables (i.e., rainfall, soil moisture, slope, relief, distance to roads, distance to faults, distance to rivers) were considered during the model development phase. An extreme gradient boosting decision tree model was trained for the monsoon period of 2015–2019 and the model was evaluated with independent inventory information for the 2020 monsoon period. The model performance demonstrated considerable skill using receiver operating characteristic curve statistics, with Area Under the Curve values exceeding 0.95. The model architecture was designed to use near-real-time data, and it can be implemented in a cloud computing environment (i.e., Google Cloud Platform) for the routine assessment of landslide hazards in the Lower Mekong region. This work was developed in collaboration with scientists at the Asian Disaster Preparedness Center as part of the NASA SERVIR Program’s Mekong hub. The goal of this work is to develop a suite of tools and services on accessible open-source platforms that support and enable stakeholder communities to better assess landslide hazard and exposure at local to regional scales for decision making and planning.
Radiometric calibration of commercial imaging satellite products is required to ensure that science and application communities can place confidence in the imagery they use and can fully understand its properties. Inaccurate radiometric calibrations can lead to erroneous decisions and invalid conclusions and can limit intercomparisons with other system. In addition, the user community has little or no insight into the design and operation of commercial sensors or into the methods involved in generating commercial products. To address this calibration need, the NASA Stennis Space Center (SSC) Earth Science Applications (ESA) Directorate established a commercial satellite imaging radiometric calibration team consisting of three independent groups: NASA, SSC,ESA, the University of Arizona Remote Sensing Group, and South Dacota State University. Each group determined the absolute radiometric calibration coefficients of the Space Imaging IKONOS 4-band, 4 m multispectral product covering the visible through near-infrared spectral region. For a three year period beginning in 2000, each team employed some variant of a reflectance-based vicarious calibration approach, requiring ground-based measurements coincident with IKONOS image acquisitions and radiative transfer calculations. Several study sites throughout the United States were employed that covered nearly the entire dynamic range of the IKONOS sensor. IKONOS at-sensor radiance values were compared to those estimated by each independent group to determine the IKONOS sensor's radiometric accuracy and stability. Over 10 individual vicariously determined at-sensor radiance estimates were used each year. When combined, these estimates provided a high-precision radiometric gain calibration coefficient. No significant calibration offset was observed. The results of this evaluation provide the scientific community with an independent assessment of the IKONOS sensor's absolute calibration and temporal stability over the 3-year period. While the techniques and method described in this paper reflect those developed at the NASA SSC, the results of the entire team are included.
International and United States Federal regulations evaluate helicopter acoustic emissions for certification purposes as well as community noise impact assessments. The Sound Exposure Level (SEL) is a commonly used metric that represents the loudness of a single event, with a penalty for duration. For example, a flyover lasting ten seconds can have the same SEL as a five-second duration flyover that is 3 dB higher in peak level. Ten helicopters spanning the light and medium weight classes were modeled using flight test data. They were then virtually flown using the Advanced Acoustic Model at multiple speeds and altitudes. SEL and A-weighted SEL (SELA) were calculated at ground-based observer locations for each condition. Scaling laws with altitude are determined, and cruising airspeeds which result in the minimum SEL are found. Implications for future land-use planning will be discussed, and the relationships are reduced to general or vehicle-specific operational guidance for pilots.
Feedback from engineers and scientists in the academic and industrial community provided an assessment of the usage and perceived quality of NASA Langley generated STI and the familiarity and usage of selected NASA publications and services and identified ways to increase the accessibility of Langley STI. The questionnaire utilized both open and closed ended questions and was pretested for finalization. The questions were organized around the seven objectives for Phase IV. From a contact list of nearly 1,200 active industrial and academic researchers, approximately 600 addresses were verified. The 497 persons who agreed to participate were mailed questionnaires. The 381 completed questionnaires received by the cutoff date were analyzed. Based on the survey findings, recommendations were made for increasing the familiarity with and use of NASA and Langley STI and selected NASA publications and services. In addition, recommendations were made for increasing the accessibility of Langley STI.
We now have several decades of experience in deriving vertical ozone profiles from the measurements of diffuse ultraviolet radiation by both ground and satellite-based instruments using Umkehr and BUV techniques. Continuing technological advances are pushing the state-of-the-art of these measurements to high spectral resolution and broader wavelength coverage. These modern instruments include the ground-based Brewer and satellite-based Global Ozone Monitoring Experiment (GOME) instruments, as well as advanced instruments being developed by ESA(SCIAMACHY), Netherlands(OMI) and Japan(ODUS). However, one of the issues that remains unresolved is the 0-30 km ozone profile information retrievable from these measurements. Though it is commonly believed that both the Umkehr and the satellite-based BUV techniques have very limited profile information below 30 km, there are those who argue that the data from these instruments should continue to be reported in this altitude range for they compare well with ozonesondes and hence there is useful scientific information. Others claim that the limitations of the Umkehr and BUV techniques are largely due to their low spectral resolution, and that the profile information below 30 km can be greatly improved by going to high spectral resolution instruments, such as Brewer and GOME. The purpose of this paper is to provide a critical evaluation of the 0-30 km ozone profile information in the various UV remote sensing techniques. We use a database of individual ozone profiles created using ozonesondes and SAGE and 4D ozone fields generated by data assimilation techniques to simulate radiances measured by the various techniques. We then apply a common inversion approach to all the methods to systematically examine how much profile information is available simply from the knowledge of total ozone, how much additional profile information is added by the traditional Dobson Umkehr and satellite buv techniques, and how much better one can do by adding additional wavelengths and by going to higher spectral resolution. An open and honest discussion of these issues is critical to provide the ozone science community a realistic assessment of the quality of data in the lower stratosphere and troposphere expected from both past and future instruments.
A primary objective of the International Space Station is to provide a premier facility for microgravity research. There are many disturbances on board the Station that can disturb the quality of the microgravity environment, including disturbances caused by both system and payload hardware. Disturbances within experiments themselves can also affect the quality of their own environment. The primary functions of the Bridgman Unidirectional Dendrites in Liquids Experiment (BUNDLE) are to melt, directionally solidify, and perform in-situ quench of metallic alloys, providing data to aid in understanding the effects of the microgravity environment on the characteristics of these processed metals. Quenching of the samples in the BUNDLE furnace is accomplished by rapidly introducing high pressure helium into the furnace chamber. This type of quench will induce sample vibrations which may be large enough to adversely affect sample quality. The primary objective of the test described in this presentation was to determine the acceleration imparted on the BUNDLE sample during helium quench. From this information, the science community can better assess whether this method of quench will allow them to obtain the data they need. Utilizing breadboard hardware, the sample quench sequence was conducted. Data was collected from accelerometers located on the breadboard hardware and inside the sample cartridge. The test data indicated that the maximum acceleration achieved by the sample was 0.325 g, which is much higher than the desired microgravity (10(exp -6) g) environment. However, this acceleration level occurred over a time period of less than 0.1 second. Because this time period is so short, there should be no detrimental effects to dendrite growth. This result was consistent with the observations of the experiment scientists, who are satisfied with the results of previous dendrite growth in this breadboard unit.
The Materials Science Research Facility (MSRF) is a multi-user, multi-purpose facility for materials science research. One experiment within the MSRF will be the Quench Module Insert (QMI), a high-temperature furnace with unique capabilities for processing different classes of materials. The primary functions of the QMI furnace are to melt, directionally solidify, and quench metallic samples, providing data to aid in understanding the effects of the microgravity environment on the characteristics of these processed metals. The QMI houses sealed individual sample ampoules containing material to be processed. Quenching of the samples in the QMI furnace is accomplished by releasing low-melting-point metallic shoes into contact with the outside of the sample ampoule, dissipating heat and cooling the sample inside. The impact from this method of quench will induce sample vibrations which could be large enough to adversely affect sample quality. Utilizing breadboard hardware, the sample quench sequence, releasing the shoes, was conducted. Data was collected from accelerometers located on the breadboard sample cartridge, indicating the maximum acceleration achieved by the sample. The primary objective of the test described in this presentation was to determine the acceleration imparted on the sample by the shoe contact. From this information, the science community can better assess whether this method of quench will allow them to obtain the data they need.
The Moderate Resolution Imaging Spectroradiometer (MODIS) was sent into orbit on the Earth Observing System (EOS) Terra spacecraft in December 1999. The MODIS began taking observations on February 24, 2000. Instrument checkout and characterization progressed to the point in the Fall of 2000 along with the checkout of algorithms so that approximately 40 products for land, ocean and atmosphere studies on global and regional scales were and are now being produced systematically. These products are now designated "beta", products indicating that they are still being examined and validated, but in most cases are amenable to examination by the scientific and applications community to further assess their utility and provide feedback to the validation process and the MODIS Science Team. It is expected that many products will progress to "provisionally useful" or fully "validated" status by mid-year 2001. one goal is to produce a systematically processed data set by the end of 2001 from MODIS extends from November 2000 through October 2001. Overall the MODIS instrument and the associated data processing systems are performing well. The many examples of MODIS observations indicate that the prospect for highly useful and exciting studies of the Earth-atmosphere system using MODIS data looks very good.
The Ice, Cloud, and land Elevation Satellite (ICESat) mission used laser altimetry measurements to determine changes in elevations of glaciers and ice sheets, as well as sea ice thickness distribution. These measurements have provided important information on the response of the cryosphere (Earths frozen surfaces) to changes in atmosphere and ocean condition. ICESat operated from 2003-2009 and provided repeat altimetry measurements not only to the cryosphere scientific community but also to the ocean, terrestrial and atmospheric scientific communities. The conclusive assessment of significant ongoing rapid changes in the Earths ice cover, in part supported by ICESat observations, has strengthened the need for sustained, high accuracy, repeat observations similar to what was provided by the ICESat mission. Following recommendations from the National Research Council for an ICESat follow-on mission, the ICESat-2 mission is now under development for planned launch in 2018. The primary scientific aims of the ICESat-2 mission are to continue measurements of sea ice freeboard and ice sheet elevation to determine their changes at scales from outlet glaciers to the entire ice sheet, and from 10s of meters to the entire polar oceans for sea ice freeboard. ICESat carried a single beam profiling laser altimeter that produced approximately 70 m diameter footprints on the surface of the Earth at approximately 150 m along-track intervals. In contrast, ICESat-2 will operate with three pairs of beams, each pair separated by about 3 km across-track with a pair spacing of 90 m. Each of the beams will have a nominal 17 m diameter footprint with an along-track sampling interval of 0.7 m. The differences in the ICESat-2 measurement concept are a result of overcoming some limitations associated with the approach used in the ICESat mission. The beam pair configuration of ICESat-2 allows for the determination of local cross-track slope, a significant factor in measuring elevation change for the outlet glaciers surrounding the Greenland and Antarctica coasts. The multiple beam pairs also provide improved spatial coverage. The dense spatial sampling eliminates along-track measurement gaps, and the small footprint diameter is especially useful for sea surface height measurements in the often narrow leads needed for sea ice freeboard and ice thickness retrievals. The ICESat-2 instrumentation concept uses a low energy 532 nm (green) laser in conjunction with single-photon sensitive detectors to measure range. Combining ICESat-2 data with altimetry data collected since the start of the ICESat mission in 2003, such as Operation IceBridge and ESAs CryoSat-2, will yield a 15+ year record of changes in ice sheet elevation and sea ice thickness. ICESat-2 will also provide information of mountain glacier and ice cap elevations changes, land and vegetation heights, inland water elevations, sea surface heights, and cloud layering and optical thickness.
HabEx Architecture A is a 4m unobscured telescope mission concept optimized for direct imaging and spectroscopy of potentially habitable exoplanets, and also enables a wide range of general astrophysics science. The exoplanet detection and characterization drives the enabling core technologies. A hybrid starlight suppression approach of a starshade and coronagraph diversifies technology maturation risk. In this paper we assess these exoplanet-driven technologies, including elements of coronagraphs, starshades, mirrors, jitter mitigation, wavefront control, and detectors. By utilizing high technology readiness solutions where feasible, and identifying required technology development that can begin early, HabEx will be well positioned for assessment by the community in 2020 Astrophysics Decadal Survey.
This presentation described the RMS effort for infrastructure development aspect of Advanced Air Mobility. In particular, it addresses the Vertiport Location Assessment from a community perspective.
This presentation described the RMS effort for infrastructure development aspect of Advanced Air Mobility. In particular, it addresses the Vertiport Location Assessment from a community perspective.
In its mission to expand knowledge and improve aviation, NASA conducts research to address sonic boom noise, the prime barrier to overland supersonic flight. NASA is currently preparing for a community survey campaign to assess response to noise from the new X-59 aircraft. During each community survey, a substantial number of observations must be collected over a limited timeframe to generate a dose response relationship. A sample of residents will be recruited in advance to fill out a brief survey each time X-59 flies over, approximately 80 times throughout a month. In preparation NASA conducted a month-long test of survey methods in 2023. A sample of 800 residents was recruited from a simulated fly-over area. Because there were no actual X-59 fly-overs, respondents were asked about their reactions to noise from normal aircraft operations. The respondents chose whether to fill out the survey on the web or via a smartphone application. Evaluating response rates and how they evolved over time was a specific focus of the test. Also, a graduated incentive structure was implemented to keep respondents engaged. Finally, location data was collected from respondents since it will be needed to estimate individual noise exposure from X-59. The results of this survey test will help determine the design of the community survey campaign.
Radiation-transport codes or radiation-analysis tools are used in the spacecraft-design community to define and assess the local radiation levels. Among various radiation-transport/analysis tools available, SHIELDOSE-2 is commonly used in the early spacecraft-design phases because it has been established that it provides reasonably reliable results with relatively rapid computation time. The NASA Engineering and Safety Center initiated a two-phased study: (1) to better understand and document the SHIELDOSE-2 code capabilities and limitations, and (2) to recommend alternative tools to use for cases where SHIELDOSE-2 is not applicable. This report provides a summary of the Phase 1 study.
Radiation-transport codes or radiation-analysis tools are used in the spacecraft-design community to define and assess the local radiation levels. Among various radiation-transport/analysis tools available, SHIELDOSE-2 is commonly used in the early spacecraft-design phases because it has been established that it provides reasonably reliable results with relatively rapid computation time. The NASA Engineering and Safety Center initiated a two-phased study: (1) to better understand and document the SHIELDOSE-2 code capabilities and limitations, and (2) to identify alternative tools to use for cases where SHIELDOSE-2 is not applicable. This report provides a summary of the Phase 2 study.
Sustainable long-term space travel will require astronauts to live in built environments cohabited by microbes. Though much of space biology research has focused on microbial monocultures, microbes naturally live in multispecies communities in which they compete and cooperate. Understanding how communities experience spaceflight over generations can influence sanitation measures and the design of synthetic communities for applications in spaceflight. In this study, we investigated the evolutionary stability of mutualism in multispecies communities in microgravity using a model system of cooperating microbes. Our model consisted of bioengineered strains of mutually dependent E. coli and S. enterica. E. coli metabolized lactose and produced a carbon source for S. enterica, which secreted methionine for E. coli. By introducing a noncooperative ("cheater") strain of S. enterica, we tested the dynamic stability of mutualism. Using a rotating wall vessel, we simulated microgravity, specifically a low-shear, diffusion-limited environment where metabolite transfer is limited compared to 1g conditions. Fluorescent motile and non-motile strains were used to assess how motility affects the microbial experience of microgravity. We hypothesized that mutualism in non-motile cocultures would be favored in microgravity due to the diffusion-limited spatial structure, while motile strains would show less difference between simulated microgravity and other conditions. We cultured communities for approximately 20 generations and assessed community composition over time using flow cytometry. We compared simulated microgravity to cultures grown in agar plates as spatially structured controls, shaken flasks as well-mixed controls, and still flasks representing the convective mixing of 1g. A high, sustained cooperator-to-cheater ratio represented stable mutualism within the community. Our results show that microbial communities may better maintain mutualism in microgravity compared to their counterparts in 1g conditions and that the motility of a community’s constituents influences how the community experiences microgravity on generational timescales.