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NASA NTRS2010

Optical and Microphysical Retrievals of Marine Stratocumulus Clouds off the Coast of Namibia from Satellite and Aircraft

Though the emphasis of the Southern Africa Regional Science Initiative 2000 (SAFARI-2000) dry season campaign was largely on emission sources and transport, the assemblage of aircraft (including the high altitude NASA ER-2 remote sensing platform and the University of Washington CV-580, UK MRF C-130, and South African Weather Bureau JRA in situ aircrafts) provided a unique opportunity for cloud studies. Therefore, as part of the SAFARI initiative, investigations were undertaken to assess regional aerosol-cloud interactions and cloud remote sensing algorithms. In particular, the latter part of the experiment concentrated on marine boundary layer stratocumulus clouds off the southwest coast of Africa. Associated with cold water upwelling along the Benguela current, the Namibian stratocumulus regime has received limited attention but appears to be unique for several reasons. During the dry season, outflow of continental fires and industrial pollution over this area can be extreme. From below, upwelling provides a rich nutrient source for phytoplankton (a source of atmospheric sulfur through DMS production as well as from decay processes). The impact of these natural and anthropogenic sources on the microphysical and optical properties of the stratocumulus is unknown. Continental and Indian Ocean cloud systems of opportunity were also studied during the campaign. SAFARI 2000 aircraft flights off the coast of Namibia were coordinated with NASA Terra Satellite overpasses for synergy with the Moderate Resolution Imaging Spectroradiometer (MODIS) and other Terra instruments. MODIS was developed by NASA and launched onboard the Terra spacecraft on December 18, 1999 (and Aqua spacecraft on May 4, 2002). Among the remote sensing algorithms developed and applied to this sensor are cloud optical and microphysical properties that include cloud thermodynamic phase, optical thickness, and effective particle radius of both liquid water and ice clouds. The archived products from these algorithms have applications in climate change studies, climate modeling, numerical weather prediction, and fundamental atmospheric research. The archived MODIS Collection 5 cloud products processing stream will be used to analyze low water cloud scenes off the Namibian and Angolan coasts during SAFARI 2000 time period, as well as other years. Pixel-level Terra and Aqua MODIS retrievals (l. km spatial resolution at nadir) and gridded (1' uniform grid) statistics of cloud optical thickness and effective particle radius will be presented, including joint probability distributions between the two quantities. In addition, perspectives from the MODIS Airborne Simulator, which flew on the ER-2 during SAFARI 2000 providing high spatial resolution retrievals (50 m at nadir), will be presented as appropriate. The H-SAF Program requires an experimental operational European-centric Satellite Precipitation Algorithm System (E-SPAS) that produces medium spatial resolution and high temporal resolution surface rainfall and snowfall estimates over the Greater European Region including the Greater Mediterranean Basin. Currently, there are various types of experimental operational algorithm methods of differing spatiotemporal resolutions that generate global precipitation estimates. This address will first assess the current status of these methods and then recommend a methodology for the H-SAF Program that deviates somewhat from the current approach under development but one that takes advantage of existing techniques and existing software developed for the TRMM Project and available through the public domain.

Platnick, Steven E.↗

NASA NTRS2023

Satellite Data Reveals a Recent Increase in Shifting Cultivation and Associated Carbon Emissions in Laos

Although shifting cultivation is the major land use type in Laos, the spatial-temporal patterns and the associated carbon emissions of shifting cultivation in Laos are largely unknown. This study provides a nationwide analysis of the spatial-temporal patterns of shifting cultivation and estimations of the associated carbon emissions in Laos over the last three decades. This study found that shifting cultivation has been expanding and intensifying in Laos, especially in the last five years. The newly cultivated land from 2016-2020 accounted for 4.5% (±1.2%) of the total land area of Laos. Furthermore, the length of fallow periods has been continuously declining, indicating that shifting cultivation is becoming increasingly intensive. Combining biomass derived from GEDI (Global Ecosystem Dynamics Investigation) and shifting cultivation maps and area estimates, we found that the net carbon emissions from shifting cultivation declined in 2001-2015 but increased in 2016-2020. The largest carbon source is conversion from intact forests to shifting cultivation, which contributed to 89% of the total emissions from 2001 to 2020. In addition, there were increased emissions from intensified use of fallow land. This research provides useful information for policymakers in Laos to understand the changes in shifting cultivation and improve land use management. This study not only supports REDD+ (Reducing Emissions from Deforestation and forest Degradation) reporting for Laos but also provides a methodology for tracking carbon emissions and removals of shifting cultivation.

Shifting cultivation↗

NASA NTRS2005

Interpreting the International Space Station Microgravity Environment

The International Space Station (ISS) serves as a platform for microgravity research for the foreseeable future. A microgravity environment is one in which the effects of gravity are drastically reduced which then allows physical experiments to be conducted without the overpowering effects of gravity. A physical environment with very low-levels of acceleration and vibration has been accomplished by both the free fall associated with orbital flight and the design of the International Space Station. The International Space Station design has been driven by a long-standing, high-level requirement for a microgravity mode of operation. The Space Acceleration Measurement System has been in operation for nearly four years on the ISS measuring the microgravity environment in support of principal investigators and to characterize the ISS microgravity environment. The Principal Investigator Microgravity Services project functions as a detective to ascertain the source of disturbances seen in the ISS microgravity environment to allow correlation between that environment and experimental data. Payload developers need to predict the microgravity environment that will be imposed upon an experiment and ensure that the science and engineering requirements will be met. The Principal Investigator Microgravity Services project is developing n interactive tool to predict the microgravity environment at science payloads based on user defined operational scenarios. These operations (predictions and post-analyses) allow a researcher to examine the microgravity acceleration levels expected to exist when their experiment is operated and then receive an analysis of the environment which existed during their experiment operations. Presented in this paper will be descriptions of the environment predictive tool and an investigation into a previously unknown disturbance in the ISS microgravity environment.

DeLombard, Richard↗

NASA NTRS2022

Science Objectives for Flagship-Class Mission Concepts for the Search for Evidence of Life at Enceladus

Cassini revealed that Saturn's Moon Enceladus hosts a subsurface ocean that meets the accepted criteria for habitability with bio-essential elements and compounds, liquid water, and energy sources available in the environment. Whether these conditions are sufficiently abundant and collocated to support life remains unknown and cannot be determined from Cassini data. However, thanks to the plume of oceanic material emanating from Enceladus’ south pole, a new mission to Enceladus could search for evidence of life without having to descend through kilometers of ice. In this article, we outline the science motivations for such a successor to Cassini, choosing the primary science goal to be determining whether Enceladus is inhabited and assuming a resource level equivalent to NASA's Flagship-class missions. We selected a set of potential biosignature measurements that are complementary and orthogonal to build a robust case for any life detection result. This result would be further informed by quantifications of the habitability of the environment through geochemical and geophysical investigations into the ocean and ice shell crust. This study demonstrates that Enceladus’ plume offers an unparalleled opportunity for in situ exploration of an Ocean World and that the planetary science and astrobiology community is well equipped to take full advantage of it in the coming decades.

Enceladus↗

NASA NTRS2011

Environmental Signatures for Habitability: What to Measure and How to Rank the Habitability Potential of Mars

The environmental signatures for habitability are not necessarily biosignatures, even though on Earth, they are definitive proof of habitability. It is the constant overprint of the chemical signatures of life that makes it difficult to recognize the chemical and physical properties of a potentially habitable environment as distinct from an inhabited one. Mars Science Laboratory (MSL) will soon embark on a mission to Mars to assess its past or present habitability, so it is useful to examine how we measure habitability on Earth and prepare for how that approach may differ for Mars. This exercise includes: (a) articulation of fundamental assumptions about habitability, (b) an inventory of factors that affect habitability, (c) development of metrics, measurement approach and implementation, and (d) a new classification scheme for planetary habitability that goes beyond the binary "yes" or "no." There may be dozens of factors that affect habitability and they can be weighted as a function of specific environment. However a robotic, in situ investigation even on Earth has constraints that prevent the measurement of every environmental factor, so metrics must be reduced to the most relevant subset, given available time, cost, technical feasibility and scientific importance. Many of the factors could be measured with a combination of orbital data and the MSL payload. We propose that, at a minimum, a designation of high habitability potential requires the following conditions be met: (a) thermally stable with respect to extremes and frequency of fluctuation, (b) has more than one energy source, (c) sufficient chemical diversity to make compounds with covalent and hydrogen bonding, (d) can moderate ionizing radiation enough to allow a stable or evolving pool of organic molecules, (e) must have water or other high quality polar solvent, (f) must be able to renew chemical resources (e.g., plate tectonics, volcanism or something else we haven't envisioned). A measurement approach we have taken to measure habitability on Earth is : 1. Study remote sensing data, maps, etc. 2. Decide how big an area to measure. 3. Determine the spatial sampling rate. 4. Determine the temporal sampling rate. 5. Determine the order of measurements 6. Decide where to begin measurements 7. Select locations at field site and proceed While science drives each of the steps, there are additional constraints, e.g., technical, time, cost, safety (risk). This approach is also executable on Mars. Measurement of past habitability is more challenging both for Earth and Mars where access to the past means subsurface access and confrontation with unknowns about preservation of the martian past. Some environments preserve evidence of past habitability better than others, and this is where selection of the landing site to maximize the preservation potential of habitability indicators will be key. Mars presents an opportunity to discover transitional states between habitable or not, and we offer a ranking scale for planetary habitability with Mars as the second test subject: CLASS ONE Uninhabitable and likely has never been so CLASS TWO Has a high potential but no confirmed observation of life (as defined above) CLASS THREE Inhabited (we find life) 3-A Globally inhabited 3-B Primitive life; early in its evolution, but not yet globally established 3-C Exists only in refugia -- planet heading toward class four CLASS FOUR Post-habitable (there once was life, but now it's gone) MSL provides an opportunity to carefully investigate the habitability of at least one site on Mars and it will reveal much about the possible states of planetary habitability

Conrad, Pamela G.↗

NASA NTRS1981

CTB80 - A galactic radio source with directed jets

Recent investigations of the galactic radio source CTB 80 reveal several jet-like structures which can be traced outward to over 30 pc from a point less than 0.1 pc within a central core. If the object is associated with a supernova of 1408, then the jets must move out at a velocity of 0.2 C and can only be about 572 years old. The morphology of the whole source, however, suggests a significant, proper east to west motion of the central object, and indicates a much older age. In this case, continuous ejection into the jets would have occurred for tens of thousands of years. A quantitative explanation is presented in which the supernova explosion ejects several massive path-cutting fragments. It thus appears that the extended jets in CTB 80 do emanate from a small core which is energized by a compact object, but the source of this continuous ejection process still remains unknown

Dickel, J. R.↗

NASA NTRS1994

Episodic nitrous oxide soil emissions in Brazilian savanna (cerrado) fire-scars

The seasonally burned cerrados of Brazil are the largest savanna-type ecosystem of South America and their contribution to the global atmospheric nitrous oxide (N20) budget is unknown. Four types of fire-scarred cerrado along a vegetation gradient from grassland to forest were investigated during the wet season of 1992/93. The effect of fire and subsequent water additions on epiodic emissions of N2O and the associated profile dynamic of soil/gas phase N2O concentrations were studied for several months. Additionally, the effect on episodic emissions of N2O of nitrate and glucose additions to a cerrado soil after fire and the associated profile dynamic of soil/gas phase N2O mixing ratios were determined. Finally, N2O episodic emissions in cerrado converted to corn, soybean, and pasture fields were investigated during one growing/wet season. Results showed N2O consumption/emission for the four fire-scared savanna ecosystems, for nitrogen and carbon fertilization, and for agriculture/pasture ranging from -0.3 to +0.7, 1.8 to 9.1, and 0.5 to 3.7 g N2O-N ha(exp -1) d(exp -1), respectively. During the wet season the cerrado biome does not appear to be a major source of N2O to the troposphere, even following fire events. However, the results of this study suggest that conversion of the cerrado to high input agriculture, with liming and fertilization, can increase N2O emissions more than ten fold.

Nobre, A. D.↗

NASA NTRS1991

Neural mechanisms of kinesthesia

Our primary interest is in where the signals for position and movement of the limbs originate and how the information is encoded. Humans can independently sense the positions and movements of their limbs in the absence of vision, and their senses are derived from mechanoreceptors located in the limbs. Receptors in muscles, skin and joints are potential sources of position and movement signals, but how (and whether) each of these groups contributes to kinesthesia remains uncertain. Recent evidence indicates that a sense of static-position derives from length receptors in muscle, whereas receptors in the skin, and possibly though not likely the joints, can signal movement of a limb but not its static position. At present, we are examining the consequences of not having a static-position sense at the fingers apart from an inability to detect very slow displacements. Using a more demanding test, we have found no substantial difference in the accuracy of reproducing target positions passively imposed on the MCP joint and the proximal interphalangeal (PIP) joint of the index finger. Our working hypothesis is that subjects normally use movement sense mechanisms to detect displacements, probably because they are faster, but how (or whether) subjects manage to obtain an absolute position reference with only a movement sense available remains unknown and is an issue under investigation.

Clark, Francis J.↗

NASA NTRS1994

Archean geochemistry of formaldehyde and cyanide and the oligomerization of cyanohydrin

The sources and speciation of reduced carbon and nitrogen inferred for the early Archean are reviewed in terms of current observations and models, and known chemical reactions. Within this framework hydrogen cyanide and cyanide ion in significant concentration would have been eliminated by reaction with excess formaldehyde to form cyanohydrin (glycolonitrile), and with ferrous ion to formferrocyanide. Natural reactions of these molecules would under such conditions deserve special consideration in modeling of primordial organochemical processes. As a step in this direction, transformation reactions have been investigated involving glycolonitrile in the presence of water. We find that glycolonitrile, formed from formaldehyde and hydrogen cyanide or cyanide ion, spontaneously cyclodimerizes to 4-amino-2-hydroxymethyloxazole. The crystalline dimer is the major product at low temperatue (approximately 0 C); the yield diminishes with increasing temperature at the expense of polymerization and hydrolysis products. Hydrolysis of glycolamide and of oxazole yields a number of simpler organic molecules, including ammonia and glycolamide. The spontaneous polymerization of glycolonitrile and its dimer gives rise to soluble, cationic oligomers of as yet unknown structure, and, unless arrested, to a viscous liquid, insoluble in water. A loss of cyanide by reaction with formaldehyde, inferred for the early terrestrial hydrosphere and cryosphere would present a dilemma for hypotheses invoking cyanide and related compounds as concentrated reactants capable of forming biomolecular precursor species. Attempts to escape from its horns may take advantage of the efficient concentration and separation of cyanide as solid ferriferrocyanide, and most directly of reactions of glycolonitrile and its derivatives.

Arrhenius, T.↗

NASA NTRS2005

Overview of Results from the Cassini Magnetospheric Imaging Instrument (MIMI) During the First Year of Operations

The MIMI investigation comprises three sensors covering the indicated energy ranges: the Ion and Neutral Camera (INCA) -- 7 keV/nuc 3 Mev) and protons (1.6 < E < 160 Mev) from the back end of the dual field-of-view telescope. The Saturn observation sequences began in January, 2004 and culminated in Saturn Orbit Insertion on July 1, 2004. The MIMI sensors observed substantial activity in interplanetary space for several months prior to SOI, including several interplanetary shocks associated with corotating interaction regions, numerous increases most likely originating from particle streams in the vicinity of the Saturnian bow shock and energetic neutral atoms (ENA) emanating from Saturn s magnetosphere. Results following SOI revealed: a dynamical magnetosphere with a day-night asymmetry and an 11-hour periodicity; several water-product ions (O+, OH+, H2O+), but little N+; inferred quantities of neutral gas sufficient to cause major losses in the trapped ions and electrons in the middle and inner magnetosphere; a Titan exosphere that is a copious source of ENA; INCA imaging through ENA has also revealed a previously unknown radiation belt residing inward of the D-ring that is most likely the result of double charge-exchange between the main radiation belt and the upper layers of Saturn s exosphere. Finally, there is ample evidence for the presence of substorm-like injections of plasma that subsequently corotates for a number of days before dissipating on the night-side magnetotail. The observations will be presented and discussed in the context of current theoretical models.

Krimigis, S. M.↗

NASA NTRSDate not supplied

Acquisition of and Access to Research Omics Data

Omics data are essential for understanding the myriad and complex effects of space environments on humans. To assure maximum benefit from these kinds of data, the NASA Human Research Program Data Management Plan stipulates that human omics data should be archived within and accessed through the NASA Life Sciences Portal (NLSP). The NLSP has the capability to acquire and provision access to omics (and other kinds of) research results for individual and ad-hoc groups of subjects at the direction of institutional review boards, or other authorizing bodies or individuals, per institutional, program and investigation-specific policies and procedures. However, because some single-subject omics data, like CT scans and other kinds of large, complex biomedical data, could be used to identify heretofore unknown risks to the subject’s health, or, in certain cases, be used to identify a subject, NASA Policy Directive 7170.1 describes various policies regarding the management of and access to “research genetic testing” data, which includes many kinds of omics data. For example, NPD 7170.1 prohibits access to human research genetic data by NASA personnel who make employment decisions for the subjects from whom the data were obtained. To meet the objective of acquiring research omics data for NLSP in compliance with the policies in NPD 7170.1 and other applicable NASA policies, we designed NOMADS (the NLSP Omics Multimodal Acquisition of Data System), a new component that supports the transfer of large research data files, including research genetic testing data, using one of several different transfer mechanisms. The choice of mechanism is made by the submitter of the data, with guiding information from the system, and is likely to often be determined in large part by the nature and source location of the data. For example, for small files where the source data files are not already stored in a cloud storage system, users are likely to prefer to transfer their data to the NLSP via a web browser. Conversely, for large sets of files already organized and stored in a cloud storage system, users may opt for NOMAD’s cloud-to-cloud transfer method. All omics datasets targeted for the NASA Life Sciences Data Archive must pass a variety of quality checks to ensure data integrity and adherence to the standards defined by the LSDA Data Submission Guidelines (DSG) (see https://nlsp.nasa.gov/explore/lsdahome/datasubmit). These include requirements that data are consistent with open standards established by the omics community. Non-compliant data will not be accepted however archivists are available to advise submitters on how to revise data submissions and re-submit until compliance is achieved. Following compliance with the LSDA DSG, omics data next undergo a variety of additional quality checks to ensure the data meet omics community standards. Domain specific Omics data quality control tools and techniques are continually evolving and linked to the advancements in omics assays utilized and thus, the tools and techniques utilized by the LSDA for data quality control and validation will need to be sustained accordingly. All human omics data will be access controlled according to the policies described above, and requiring IRB approval for any additional access grants once the data are acquired (including access for analysis using the NLSP workspace tools).

Omics↗

NASA NTRS2024

Acquisition of and Access to Research Omics Data

Omics↗

NASA NTRS2011

Discovery of Brownleeite: a New Manganese Silicide Mineral in an Interplanetary Dust Particle

The Earth accretes approximately 40,000 tons of cosmic dust annually, originating mainly from the disintegration of comets and collisions among asteroids. This cosmic dust, also known as interplanetary dust particles (IDPs), is a subject of intense interest since it is made of the original building blocks of our Solar System. Although the specific parent bodies of IDPs are unknown, the anhydrous chondritic-porous IDPs (CP-IDPs) subset has been potentially linked to a cometary source. The CP-IDPs are extremely primitive materials based on their unequilibrated mineralogy, C-rich chemistry, and anomalous isotopic signatures. In particular, some CP-IDPs escaped the thermal, aqueous and impact shock processing that has modified or destroyed the original mineralogy of meteorites. Thus, the CP-IDPs represent some of the most primitive solar system materials available for laboratory study. Most CP-IDPs are comprised of minerals that are common on Earth. However, in the course of an examination of one of the CP-IDPs, we encountered three sub-micrometer sized grains of manganese silicide (MnSi), a phase that has heretofore not been found in nature. In the seminar, we would like to focus on IDP studies and this manganese silicide phase that has been approved as the first new mineral identified from a comet by the International Mineralogical Association (IMA) in 2008. The mineral is named in honour of Donald E. Brownlee, an American astronomer and a founder of the field of cosmic dust research who is the principal investigator of the NASA Stardust Mission that collected dust samples from Comet 81P/Wild-2 and returned them to Earth. Much of our current view and understanding of the early solar system would not exist without the pioneering work of professor Don Brownlee in the study of IDPs.

Keller, Lindsay P.↗

NASA NTRS2013

Evaluating Light Rain Drop Size Estimates from Multiwavelength Micropulse Lidar Network Profiling

This paper investigates multiwavelength retrievals of median equivolumetric drop diameter D(sub 0) suitable for drizzle and light rain, through collocated 355-/527-nm Micropulse Lidar Network (MPLNET) observations collected during precipitation occurring 9 May 2012 at the Goddard Space Flight Center (GSFC) project site. By applying a previously developed retrieval technique for infrared bands, the method exploits the differential backscatter by liquid water at 355 and 527 nm for water drops larger than approximately 50 micrometers. In the absence of molecular and aerosol scattering and neglecting any transmission losses, the ratio of the backscattering profiles at the two wavelengths (355 and 527 nm), measured from light rain below the cloud melting layer, can be described as a color ratio, which is directly related to D(sub 0). The uncertainty associated with this method is related to the unknown shape of the drop size spectrum and to the measurement error. Molecular and aerosol scattering contributions and relative transmission losses due to the various atmospheric constituents should be evaluated to derive D(sub 0) from the observed color ratio profiles. This process is responsible for increasing the uncertainty in the retrieval. Multiple scattering, especially for UV lidar, is another source of error, but it exhibits lower overall uncertainty with respect to other identified error sources. It is found that the total error upper limit on D(sub 0) approaches 50%. The impact of this retrieval for long-term MPLNET monitoring and its global data archive is discussed.

light-rain drop size estimates↗

NASA NTRS1991

The interactions of atmospheric cosmogenic radionuclides with spacecraft surfaces

The discovery of the cosmogenic radionuclide Be-7 on the front surface (and the front surface only) of the Long Duration Exposure Facility (LDEF) spacecraft has opened opportunities to investigate new phenomena in several disciplines of space science. The experiments performed for this work show that the Be-7 results only if the source of the isotope is the atmosphere through which the spacecraft passed. We should expect that the uptake of beryllium in such circumstances will depend on the chemical form of the Be and the chemical nature of the substrate. It was found that the observed concentration of Be-7 does, in fact, differ between metal surfaces and organic surfaces such as PTFE (teflon). It is noted, however, that: (1) organic surfaces, even PTFE, are etched by the atomic oxygen found under these orbital conditions, and (2) the relative velocity of the species is 8 km(exp -1)s relative to the surface and the interaction chemistry and physics may differ from the norm. The Be-7 is formed by spallation of O and N nuclei under cosmic ray proton bombardment. The principal source region is at altitudes of 12-15 km. While very small quantities are produced above 300 km, the amount measured on the LDEF was 3 to 4 orders of magnitude higher than expected from production at orbital attitude. The most reasonable explanation is that Be-7 is rapidly transported from low altitudes by some unknown mechanism. The process must take place on a time scale similar to the half-life of the isotope (53 days). Many other isotopes are produced by cosmic ray reactions, and some of these are suited to measurement by the extremely sensitive methods of accelerator mass spectrometry. A program was initiated to search for these isotopes and it is hoped that such studies will provide new methods for studying mixing in the upper atmosphere.

Gregory, John C.↗

NASA NTRS1992

The interactions of atmospheric cosmogenic radionuclides with spacecraft surfaces

The discovery of the cosmogenic radionuclide Be-7 on the front surface of the Long Duration Exposure Facility (LDEF) spacecraft has opened opportunities to investigate new phenomena in several disciplines of space science. The experiments performed for this work show that the Be-7 results only if the source of the isotope is the atmosphere through which the spacecraft passed. We should expect that the uptake of beryllium in such circumstances will depend on the chemical form of the Be and the chemical nature of the substrate. It was found that the observed concentration of Be-7 does, in fact, differ between metal surfaces and organic surfaces such as PTFE (teflon). It is noted, however, that: (1) organic surfaces, even PTFE, are etched by the atomic oxygen found under these orbital conditions, and (2) the relative velocity of the species is 8 km(exp -1)s relative to the surface and the interaction chemistry and physics may differ from the norm. The Be-7 is formed by spallation of O and N nuclei under cosmic ray proton bombardment. The principal source region is at altitudes of 12-15 km. While very small quantities are produced above 300 km, the amount measured on the LDEF was 3 to 4 orders of magnitude higher than expected from production at orbital altitude. The most reasonable explanation is that Be-7 is rapidly transported from low altitudes by some unknown mechanism. The process must take place on a time scale similar to the half-life of the isotope (53 days). Many other isotopes are produced by cosmic ray reactions, and some of these are suited to measurement by the extremely sensitive methods of accelerator mass spectrometry. A program was initiated to search for these isotopes and it is hoped that such studies will provide new methods for studying mixing in the upper atmosphere.

Gregory, J. C.↗

NASA NTRSDate not supplied

Investigation of the Potential for Lidar & Polarimeter Combined Aerosol Retrievals Using Various Instrument Combinations

As a scientific community, we are motivated to achieve better observational capabilities for aerosols, to reduce uncertainties about aerosol’s role in climate. Encouraged by the National Academies Decadal Survey, many are looking to the synergy of lidar and polarimeter as a means of achieving improved measurements. Polarimetric observations of total-column radiances have excellent sensitivity to aerosol size distribution and absorption properties. Active lidar measurements have fewer wavelengths and view angles and therefore more limited sensitivity to aerosol microphysical properties such as complex refractive index. Yet the advantage of vertically resolved profiles is game-changing, especially given that models contain significant uncertainty about the vertical distribution of aerosol and that polarimeter and other passive retrievals must make assumptions about vertical distribution which can impact performance. To optimize the synergy, a joint polarimeter + lidar mission requires a joint retrieval. However, the exact instruments that will be launched on a future satellite are unknown, and the capabilities of polarimeters and lidars cover a large range. In this study, we perform information content analysis for a range of nominal instrument combinations. The methodology is ideal for assessing the impact of measurements and a priori information (assumptions and constraints) with respect to the desired retrieval products, and for comparing measurement systems. It has advantages that make it useful in advance of or in parallel with retrieval development, such as producing quantitatively useful comparisons even for retrieval scenarios that are significantly underdetermined and therefore impossible to retrieve without significant assumptions, and it is not impacted by retrieval-specific sources of error such as incomplete or incorrect convergence which can complicate the interpretation of a retrieval performance analysis. Here, we will derive the expected uncertainty in retrieved aerosol concentration, effective radius, fine mode fraction and single scattering albedo, for a combination of a polarimeter with various grades of lidar, from an elastic backscatter lidar, similar to the pathfinder CALIOP on the CALIPSO satellite, to a multi-wavelength high spectral resolution lidar.

Sharon P Burton↗

NASA NTRS1996

Report on Alternative Devices to Pyrotechnics on Spacecraft

Pyrotechnics accomplish many functions on today's spacecraft, possessing minimum volume/weight, providing instantaneous operation on demand, and requiring little input energy. However, functional shock, safety, and overall system cost issues, combined with emergence and availability of new technologies question their continued use on space missions. Upon request from the National Aeronautics and Space Administration's (NASA) Program Management Council (PMC), Langley Research Center (LaRC) conducted a survey to identify and evaluate state-of-the-art non-explosively actuated (NEA) alternatives to pyrotechnics, identify NEA devices planned for NASA use, and investigate potential interagency cooperative efforts. In this study, over 135 organizations were contacted, including NASA field centers, Department of Defense (DOD) and other government laboratories, universities, and American and European industrial sources resulting in further detailed discussions with over half, and 18 face-to-face briefings. Unlike their single use pyrotechnic predecessors, NEA mechanisms are typically reusable or refurbishable, allowing flight of actual tested units. NEAs surveyed include spool-based devices, thermal knife, Fast Acting Shockless Separation Nut (FASSN), paraffin actuators, and shape memory alloy (SMA) devices (e.g., Frangibolt). The electro-mechanical spool, paraffin actuator and thermal knife are mature, flight proven technologies, while SMA devices have a limited flight history. There is a relationship between shock, input energy requirements, and mechanism functioning rate. Some devices (e.g., Frangibolt and spool based mechanisms) produce significant levels of functional shock. Paraffin, thermal knife, and SMA devices can provide gentle, shock-free release but cannot perform critically timed, simultaneous functions. The FASSN flywheel-nut release device possesses significant potential for reducing functional shock while activating nearly instantaneously. Specific study recommendations include: (1) development of NEA standards, specifically in areas of material characterization, functioning rates, and test methods; (2) a systems level approach to assure successful NEA technology application; and (3) further investigations into user needs, along with industry/government system-level real spacecraft cost benefit trade studies to determine NEA application foci and performance requirements. Additional survey observations reveal an industry and government desire to establish partnerships to investigate remaining unknowns and formulate NEA standards, specifically those driven by SMAs. Finally, there is increased interest and need to investigate alternative devices for such functions as stage/shroud separation and high pressure valving. This paper summarizes results of the NASA-LaRC survey of pyrotechnic alternatives. State of-the-art devices with their associated weight and cost savings are presented. Additionally, a comparison of functional shock characteristics of several devices are shown, and potentially related technology developments are highlighted.

Lucy, M. H.↗