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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Experimental Study of Unsupported Nonane fuel Droplet Combustion in Microgravity

Soot formation in droplet flames is the basic component of the particulate emission process that occurs in spray combustion. The complexity of soot formation motivates a one-dimensional transport condition which has obvious advantages in modeling. Recent models of spherically symmetric droplet combustion have made this assumption when incorporating such aspects as detailed chemistry and radiation. Interestingly, spherical symmetry does not necessarily restrict the results because it has been observed that the properties of carbon formed in flames are not strongly affected by the nature of the fuel or flaming configuration. What is affected, however, are the forces acting on the soot aggregates and where they are trapped by a balance of drag and thermophoretic forces. The distribution of these forces depends on the transport conditions of the flame. Prior studies of spherical droplet flames have examined the droplet burning history of alkanes, alcohols and aromatics. Data are typically the evolution of droplet, flame, extinction, and soot shell diameters. These data are only now just beginning to find their way into comprehensive numerical models of droplet combustion to test proposed oxidation schemes for fuels such as methanol and heptane. In the present study, we report new measurements on the burning history of unsupported nonane droplets in a convection-free environment to promote spherical symmetry. The far-field gas is atmospheric pressure air at room temperature. The evolution of droplet diameter was measured using high speed cine photography of a spark-ignited, droplet within a confined volume in a drop tower. The initial droplet diameters varied between 0.5 mm and 0.6 mm. The challenge of unsupported droplets is to form, deploy and ignite them with minimal disturbance, and then to keep them in the camera field of view. Because of the difficulty of this undertaking, more sophisticated diagnostics for studying soot than photographic were not used. Supporting the test droplet by a fiber fixes the droplet position but the fiber can perturb the burning process especially for a sooting fuel. Prior studies on heptane showed little evidence for soot formation due to g-droplets of similar size the relationship between sooting and droplet diameter. For nonane droplets we expect increased sooting due to the greater number of carbon atoms. As a sooting droplet burns and its diameter decreases, proportionally less soot should form. This reduced soot, as well as the influence of soot formed earlier in the burning process which collects in a 'shell', on heat transport to the flame offers the potential for a time-varying burning rate. Such an effect was investigated and revealed in results reported here. Speculation is offered for the cause of this effect and its possible relation to soot formation.

Callahan, B. J.↗
NASA NTRS1981

Potential effects of the introduction of the discrete address beacon system data link on air/ground information transfer problems

This study of Aviation Safety Reporting System reports suggests that benefits should accure from implementation of discrete address beacon system data link. The phase enhanced terminal information system service is expected to provide better terminal information than present systems by improving currency and accuracy. In the exchange of air traffic control messages, discrete address insures that only the intended recipient receives and acts on a specific message. Visual displays and printer copy of messages should mitigate many of the reported problems associated with voice communications. The problems that remain unaffected include error in addressing the intended recipient and messages whose content is wrong but are otherwise correct as to format and reasonableness.

Grayson, R. L.↗
NASA NTRS1994

Synthetic aperture radar target detection, feature extraction, and image formation techniques

This report presents new algorithms for target detection, feature extraction, and image formation with the synthetic aperture radar (SAR) technology. For target detection, we consider target detection with SAR and coherent subtraction. We also study how the image false alarm rates are related to the target template false alarm rates when target templates are used for target detection. For feature extraction from SAR images, we present a computationally efficient eigenstructure-based 2D-MODE algorithm for two-dimensional frequency estimation. For SAR image formation, we present a robust parametric data model for estimating high resolution range signatures of radar targets and for forming high resolution SAR images.

Li, Jian↗
NASA NTRS2014

CEO Sites Mission Management System (SMMS)

Late in fiscal year 2011, the Crew Earth Observations (CEO) team was tasked to upgrade its science site database management tool, which at the time was integrated with the Automated Mission Planning System (AMPS) originally developed for Earth Observations mission planning in the 1980s. Although AMPS had been adapted and was reliably used by CEO for International Space Station (ISS) payload operations support, the database structure was dated, and the compiler required for modifications would not be supported in the Windows 7 64-bit operating system scheduled for implementation the following year. The Sites Mission Management System (SMMS) is now the tool used by CEO to manage a heritage Structured Query Language (SQL) database of more than 2,000 records for Earth science sites. SMMS is a carefully designed and crafted in-house software package with complete and detailed help files available for the user and meticulous internal documentation for future modifications. It was delivered in February 2012 for test and evaluation. Following acceptance, it was implemented for CEO mission operations support in April 2012. The database spans the period from the earliest systematic requests for astronaut photography during the shuttle era to current ISS mission support of the CEO science payload. Besides logging basic image information (site names, locations, broad application categories, and mission requests), the upgraded database management tool now tracks dates of creation, modification, and activation; imagery acquired in response to requests; the status and location of ancillary site information; and affiliations with studies, their sponsors, and collaborators. SMMS was designed to facilitate overall mission planning in terms of site selection and activation and provide the necessary site parameters for the Satellite Tool Kit (STK) Integrated Message Production List Editor (SIMPLE), which is used by CEO operations to perform daily ISS mission planning. The CEO team uses the SMMS for three general functions - database queries of content and status, individual site creation and updates, and mission planning. The CEO administrator of the science site database is able to create or modify the content of sites and activate or deactivate them based on the requirements of the sponsors. The administrator supports and implements ISS mission planning by assembling, reporting, and activating mission-specific site selections for management; deactivating sites as requirements are met; and creating new sites, such as International Charter sites for disasters, as circumstances warrant. In addition to the above CEO internal uses, when site planning for a specific ISS mission is complete and approved, the SMMS can produce and export those essential site database elements for the mission into XML format for use by onboard Earth-location systems, such as Worldmap. The design, development, and implementation of the SMMS resulted in a superior database management system for CEO science sites by focusing on the functions and applications of the database alone instead of integrating the database with the multipurpose configuration of the AMPS. Unlike the AMPS, it can function and be modified within the existing Windows 7 environment. The functions and applications of the SMMS were expanded to accommodate more database elements, report products, and a streamlined interface for data entry and review. A particularly elegant enhancement in data entry was the integration of the Google Earth application for the visual display and definition of site coordinates for site areas defined by multiple coordinates. Transfer between the SMMS and Google Earth is accomplished with a Keyhole Markup Language (KML) expression of geographic data (see figures 3 and 4). Site coordinates may be entered into the SMMS panel directly for display in Google Earth, or the coordinates may be defined on the Google Earth display as a mouse-controlled polygonal definition and transferred back into the SMMS as KML input. This significantly reduces the possibility of errors in coordinate entries and provides visualization of the scale of the site being defined. CEO now has a powerful tool for managing and defining sites on the Earth's surface for both targets of astronaut photography or other onboard remote sensing systems. It can also record and track results by sponsor, collaborator, or type of study.

Trenchard, Mike↗
NASA NTRSDate not supplied

BRAINSTACK – A Platform for Artificial Intelligence & Machine Learning Collaborative Experiments on a Nano-Satellite

As space missions continue to become more ambitious, complex, and distant to Earth, the need for advanced on-board intelligent decision making to guide everything from mission operations to fault detection and recovery has become a major front of space research. While the prevalence of research on such Artificial Intelligence / Machine Learning (AI/ML) modules has exploded, the capacity to experimentally validate such modules in space in a rapid and inexpensive format has not. To this end, the Nano Orbital Workshop (NOW) group at NASA Ames Research Center has been at the forefront of performing initial flight evaluation tests of ‘commercially’ available AI/ML computational platforms via the TechEdSat (TES-n) flight series as part of what is programmatically referred to as the BRAINSTACK. BRAINSTACK will provide an orbital AI/ML evaluation laboratory where computational experiments are pre-loaded into memory prior to launch, and then executed as desired during the mission, with results reported back and program tweaks or new data sets uploaded as needed. Processors selected as part of the BRAINSTACK are of ideal size, packaging, and power consumption for easy integration into a cube satellite structure. These experiments have included the evaluation of small, high-performance GPUs and more recently, neuromorphic processors in LEO operations. Neuromorphic processors are of particular interest due to their superior computational power efficiency over GPUs. The first TES-n flight test of an Intel first-generation Loihi neuromorphic processor launched on January 13, 2022 and continues to operate in orbit despite almost no space environment modifications. The Intel Loihi Gen-1 is characterized by a 14nm 128-core Spiking Neural Network (SNN) able to support on-chip training. This experiment utilized a Loihi packaged in the ‘Kapoho Bay’ USB module, providing a relatively straight-forward interface to the bus avionics system. The Kapoho Bay was in turn managed by a host Intel Pentium single-board computer to handle scheduling of the AI/ML application payloads, and communications with the satellite vehicle manager. The recently released Intel Loihi Gen-2, able to support integer-valued spike payloads and produced using 7nm process, will form part of the basis of the evolving BRAINSTACK in the upcoming three TES-n/NOW flights. Additionally, it is planned to measure the radiation environment these processors experience to understand any degradation or computational artifacts caused by long term space radiation exposure on these novel architectures. This evolving flexible and collaborative environment involving various research teams across NASA and other organizations is intended to be a convenient orbital test platform from which many anticipated future space AI/ML applications may be initially tested.

Artificial Intelligence↗
NASA NTRSDate not supplied

BRAINSTACK – A Platform for Artificial Intelligence & Machine Learning Collaborative Experiments on a Nano-Satellite

As space missions continue to become more ambitious, complex, and distant to Earth, the need for advanced on-board intelligent decision making to guide everything from mission operations to fault detection and recovery has become a major front of space research. While the prevalence of research on such Artificial Intelligence / Machine Learning (AI/ML) modules has exploded, the capacity to experimentally validate such modules in space in a rapid and inexpensive format has not. To this end, the Nano Orbital Workshop (NOW) group at NASA Ames Research Center has been at the forefront of performing initial flight evaluation tests of ‘commercially’ available AI/ML computational platforms via the TechEdSat (TES-n) flight series as part of what is programmatically referred to as the BRAINSTACK. BRAINSTACK will provide an orbital AI/ML evaluation laboratory where computational experiments are pre-loaded into memory prior to launch, and then executed as desired during the mission, with results reported back and program tweaks or new data sets uploaded as needed. Processors selected as part of the BRAINSTACK are of ideal size, packaging, and power consumption for easy integration into a cube satellite structure. These experiments have included the evaluation of small, high-performance GPUs and more recently, neuromorphic processors in LEO operations. Neuromorphic processors are of particular interest due to their superior computational power efficiency over GPUs. The first TES-n flight test of an Intel first-generation Loihi neuromorphic processor launched on January 13, 2022 and continues to operate in orbit despite almost no space environment modifications. The Intel Loihi Gen-1 is characterized by a 14nm 128-core Spiking Neural Network (SNN) able to support on-chip training. This experiment utilized a Loihi packaged in the ‘Kapoho Bay’ USB module, providing a relatively straight-forward interface to the bus avionics system. The Kapoho Bay was in turn managed by a host Intel Pentium single-board computer to handle scheduling of the AI/ML application payloads, and communications with the satellite vehicle manager. The recently released Intel Loihi Gen-2, able to support integer-valued spike payloads and produced using 7nm process, will form part of the basis of the evolving BRAINSTACK in the upcoming three TES-n/NOW flights. Additionally, it is planned to measure the radiation environment these processors experience to understand any degradation or computational artifacts caused by long term space radiation exposure on these novel architectures. This evolving flexible and collaborative environment involving various research teams across NASA and other organizations is intended to be a convenient orbital test platform from which many anticipated future space AI/ML applications may be initially tested.

Artificial Intelligence↗
NASA NTRS2003

ISO Key Project: Exploring the Full Range of Quasar/Agn Properties

While most of the work on this program has been completed, as previously reported, the portion of the program dealing with the subtopic of ISO LWS data analysis and reduction for the LWS Extragalactic Science Team and its leader, Dr. Howard Smith, is still active. This program in fact continues to generate results, and newly available computer modeling has extended the value of the datasets. As a result the team requests a one-year no-cost extension to this program, through 31 December 2004. The essence of the proposal is to perform ISO spectroscopic studies, including data analysis and modeling, of star-formation regions using an ensemble of archival space-based data from the Infrared Space Observatory's Long Wavelength Spectrometer and Short Wavelength Spectrometer, but including as well some other spectroscopic databases. Four kinds of regions are considered in the studies: (1) disks around more evolved objects; (2) young, low or high mass pre-main sequence stars in star-formation regions; (3) star formation in external, bright IR galaxies; and (4) the galactic center. One prime focus of the program is the OH lines in the far infrared. The program has the following goals: 1) Refine the data analysis of ISO observations to obtain deeper and better SNR results on selected sources. The ISO data itself underwent 'pipeline 10' reductions in early 2001, and additional 'hands-on data reduction packages' were supplied by the ISO teams in 2001. The Fabry-Perot database is particularly sensitive to noise and slight calibration errors; 2) Model the atomic and molecular line shapes, in particular the OH lines, using revised Monte-Carlo techniques developed by the SWAS team at the Center for Astrophysics; 3) Attend scientific meetings and workshops; 4) Perform E&PO activities related to infrared astrophysics and/or spectroscopy.

Wilkes, Belinda↗
NASA NTRS2007

Dynamic Evolution in the Symbiotic R Aquarii

We report on multiple Chandra observations spanning a period of 5 years as well as a more recent XMM observation of the nearby symbiotic binary R Aqr. Spectral analysis of these four observations reveals considerable variability in hardness ratios and in the strength and ionization levels of emission lines which provides insight into white dwarf accretion processes as well as continuum and line formation mechanisms. Chandra imaging of the central source also shows the formation and evolution of a new south west jet. This growing body of high-resolution X-ray data of R Aqr provides a unique glimpse into white dwarf wind-accretion processes and jet formation.

DePasquale, J. M.↗
NASA NTRS2020

Microscopic, Multipoint Characterization of Foreshock Bubbles With Magnetosphere Multiscale (MMS)

This work presents the first detailed analysis of foreshock bubbles (FBs) using high‐resolution Magnetospheric Multiscale (MMS) data. Between October 2017 and January 2019, MMS captured 10 foreshock transient events with burst resolution data that we show are consistent with FBs. One “textbook” event is examined and described in detail. Employing the multipoint nature of MMS, we demonstrate how the size and orientation, expansion speed, and distance since formation can be estimated. From all 10 events, FB sizes ranged from 1.1 to 9.9 RE (average of 4.4 RE), and expansion speeds ranged from 139 to 377 km/s (average of 257 km/s). FBs formed under a usual range of solar wind conditions between 3 and 20 RE upstream of Earth's bow shock. We also report on new features of FBs: deep and localized magnetic “holes” within the cores of FBs, where the total field strength drops to <1 nT.

D. L. Turner↗
NASA NTRS1973

ERIM progress report on use of ERTS-1 data: Summary report of work on ten tasks

The author has identified the following significant results. Several of the tasks have produced significant results which are summarized: (1) Absolute water depth can be calculated from a ratio of signals from bands MSS 4 and MSS 5. (2) A 13 category terrain feature classification map of Yellowstone National Park has been produced using supervised pattern recognition techniques. (3) ERTS-1 data has been shown to provide a detection and monitoring capability for a number of water quality problems associated with off-shore ocean dumping sites and inland lakes. (4) A corrected ratio of bands MSS-5 and MSS-7 signals has been formed. (5) A concise format has been devised for storing the ratio signatures of geologic rock and mineral materials determined from laboratory reflectance spectra. (6) Results of work in information extraction demonstrate: signal variability exists among ERTS-1 detectors in any one spectral band that will impact users doing quantitative analysis on successive ERTS-1 images; a newly developed computer-aided procedure for correlating ERTS-1 pixels to ground features; the strong influence of atmospheric effects in ERTS-1 data; and area estimation accuracies are better using the ERIM proportion estimation algorithm than for conventional recognition techniques.

Thomson, F. J.↗
NASA NTRS1993

Classical novae and recurrent novae: General properties

We describe the observable characteristics of classical novae and recurrent novae obtained by different techniques (photometry, spectroscopy, and imaging) in all the available spectral ranges. We consider the three stages in the life of a nova: quiescence (pre- and post-outburst), outburst, final decline and nebular phase. We describe the photometric properties during the quiescent phase. We describe the photometric properties during outburst, the classification according the rate of decline (magnitudes per day), which permits us to define very fast, fast, intermediate, slow, and very slow novae and the correlation between luminosity and speed class. We report the scanty data on the spectra of the few known prenovae and those on the spectra of old novae and those of dwarf novae and nova-like, which, however, are almost undistinguishable. We describe the typical spectra appearing from the beginning of the outburst, just before maximum, up to the nebular phase and the correlation between spectral type at maximum, expansional velocity, and speed class of the nova. We report the existing infrared observations, which permit us to explain some of the characteristics of the outburst light curve, and give evidence of the formation of a dust shell in slow and intermediate novae (with the important exception of the very slow nova HR Del 1967) and its absence or quasi-absence in fast novae. The ultraviolet and X-ray observations are described. The X ray observations of novae, mainly from the two satellites EINSTEIN and EXOSAT, are reported. Observations of the final decline and of the envelopes appearing several months after outburst are also reported.

Hack, Margherita↗
NASA NTRS1995

A new process and equipment for waste minimization: Conversion of NO(x) scrubber liquor to fertilizer

A new emissions control system for the oxidizer scrubbers that eliminates the current oxidizer liquor waste and lowers the NO(x) emissions is described. Since fueling and deservicing spacecraft constitute the primary operations in which environmental emissions occur, this will eliminate the second largest waste stream at KSC. This effort is in accord with Executive Order No. 12856 (Federal Compliance with Right-to-Know Laws and Pollution Prevention Requirements, data 6 Aug. 1993) and Executive Order No. 12873 (Federal Acquisition, Recycling, and Waste Prevention, dated 20 Oct. 1993). A recent study found that the efficiencies of the oxidizer scrubbers during normal operations ranged from 70 percent to 99 percent. The new scrubber liquor starts with 1% hydrogen peroxide at a pH of 7 and the process control system adds hydrogen peroxide and potassium hydroxide to the scrubber liquor to maintain those initial conditions. The result is the formation of a solution of potassium nitrate, which is sold as a fertilizer. This report describes the equipment and procedures used to monitor and control the conversion of the scrubber liquor to fertilizer, while reducing the scrubber emissions.

Parrish, Clyde F.↗
NASA NTRS2004

Global Land Ice Measurements from Space

The NSIDC at the University of Colorado has successfully completed the tasks outlined in its proposal 0999.08.1216B, the 'Global Land Ice Measurements from Space' grant funded by NASA under NAG5-9722. The Global Land Ice Measurements from Space (GLIMS) grant reported on here is one of the first completed elements of the overall GLIMS project that continues with separate funding from NASA, the United States Geological Survey (USGS), and internationally by many national agencies and universities. The primary goals of GLIMS are to survey significant numbers of the world's 160,000 glaciers with data collected by the ASTER (Advanced Spaceborne Thermal Emission and reflection Radiometer) instrument aboard the EOS Terra spacecraft, and Landsat ETM+ (Enhanced Thematic Mapper Plus) and to make these data available to users in a common and easily usable format. GLIMS participants include: NSIDC as developer of the GLIMS database, USGS Flagstaff as the GLIMS Coordination Center, USGS EROS Data Center (EDC) as the archive for satellite imagery used in GLIMS analyses (NASA funding for GLIMS also includes the Flagstaff group and EDC through the related ASTER Science Team and Land Processes Distributed Active Archive Center [LP DAAC] activities), and approximately twenty two Regional Centers (RCs). RCs are funded by the national agencies of participating countries to analyze satellite imagery for a specified set of glaciological parameters and provide the results to NSIDC for archive and distribution to the public.

Scharfen, Gregory R.↗
NASA NTRS2016

Restoration of Apollo Data by the Lunar Data Project/PDS Lunar Data Node: An Update

The Apollo 11, 12, and 14 through 17 missions orbited and landed on the Moon, carrying scientific instruments that returned data from all phases of the missions, included long-lived Apollo Lunar Surface Experiments Packages (ALSEPs) deployed by the astronauts on the lunar surface. Much of these data were never archived, and some of the archived data were on media and in formats that are outmoded, or were deposited with little or no useful documentation to aid outside users. This is particularly true of the ALSEP data returned autonomously for many years after the Apollo missions ended. The purpose of the Lunar Data Project and the Planetary Data System (PDS) Lunar Data Node is to take data collections already archived at the NASA Space Science Data Coordinated Archive (NSSDCA) and prepare them for archiving through PDS, and to locate lunar data that were never archived, bring them into NSSDCA, and then archive them through PDS. Preparing these data for archiving involves reading the data from the original media, be it magnetic tape, microfilm, microfiche, or hard-copy document, converting the outmoded, often binary, formats when necessary, putting them into a standard digital form accepted by PDS, collecting the necessary ancillary data and documentation (metadata) to ensure that the data are usable and well-described, summarizing the metadata in documentation to be included in the data set, adding other information such as references, mission and instrument descriptions, contact information, and related documentation, and packaging the results in a PDS-compliant data set. The data set is then validated and reviewed by a group of external scientists as part of the PDS final archive process. We present a status report on some of the data sets that we are processing.

Lunar↗
NASA NTRS1997

Kinetics and Thermochemistry of the Cl((sup 2)P(sub J)) + C2Cl4 Association Reaction

A laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the Cl(sup 2)P(sub j) + C2Cl4 association reaction as a function of temperature (231-390 K) and pressure (3-700 Torr) in nitrogen buffer gas. The reaction is found to be in the falloff regime between third and second order over the range of conditions investigated, although the second-order limit is approached at the highest pressures and lowest temperatures. At temperatures below 300 K, the association reaction is found to be irreversible on the experimental time scale of approximately 20 m-s. The kinetic data at T is less than 300 K have been employed to obtain falloff parameters in a convenient format for atmospheric modeling. At temperatures above 330 K, reversible addition is observed, thus allowing equilibrium constants for C2Cl5 formation and dissociation to be determined. Second- and third-law analyses of the equilibrium data lead to the following thermochemical parameters for the association reaction: Delta-H(298) = -18.1 +/- 1.3 kcal/mol, Delta-H(0) = -17.6 +/- 1.3 kcal/mol, and Delta-S(298) = -27.7 +/- 3.0 cal/mol.K. In conjunction with the well-known heats of formation of Cl((sup 2)P(sub j)) and C2Cl4 the above Delta-H values lead to the following heats of formation for C2Cl5, at 298 and 0 K: Delta-H(f,298) = 8.0 +/- 1.3 kcal/mol and Delta-H(f,0) = 8.1 +/- 1.5 kcal/mol. The kinetic and thermochemical parameters reported above are compared with other reported values, and the significance of reported association rate coefficients for understanding tropospheric chlorine chemistry is discussed.

Nicovich, J. M.↗
NASA NTRS2000

NASA Goddard Space Flight Center

The NASA SLR Operational Center is responsible for: 1) NASA SLR network control, sustaining engineering, and logistics; 2) ILRS mission operations; and 3) ILRS and NASA SLR data operations. NASA SLR network control and sustaining engineering tasks include technical support, daily system performance monitoring, system scheduling, operator training, station status reporting, system relocation, logistics and support of the ILRS Networks and Engineering Working Group. These activities ensure the NASA SLR systems are meeting ILRS and NASA mission support requirements. ILRS mission operations tasks include mission planning, mission analysis, mission coordination, development of mission support plans, and support of the ILRS Missions Working Group. These activities ensure than new mission and campaign requirements are coordinated with the ILRS. Global Normal Points (NP) data, NASA SLR FullRate (FR) data, and satellite predictions are managed as part of data operations. Part of this operation includes supporting the ILRS Data Formats and Procedures Working Group. Global NP data operations consist of receipt, format and data integrity verification, archiving and merging. This activity culminates in the daily electronic transmission of NP files to the CDDIS. Currently of all these functions are automated. However, to ensure the timely and accurate flow of data, regular monitoring and maintenance of the operational software systems, computer systems and computer networking are performed. Tracking statistics between the stations and the data centers are compared periodically to eliminate lost data. Future activities in this area include sub-daily (i.e., hourly) NP data management, more stringent data integrity tests, and automatic station notification of format and data integrity issues.

Carter, David↗
NASA NTRS2009

Distribution of Chromosome Breakpoints in Human Epithelial Cells Exposed to Low- and High-LET Radiations

The advantage of the multicolor banding in situ hybridization (mBAND) technique is not only its ability to identify simultaneously both inter- and intrachromosome exchanges, but also the ability to measure the breakpoint location along the length of the chromosome in a precision that is unmatched with other traditional banding techniques. Breakpoints on specific regions of a chromosome have been known to associate with specific cancers. The breakpoint distribution in cells after low- and high-LET radiation exposures will also provide the data for biophysical modeling of the chromatin structure, as well as the data for the modeling the formation of radiation-induced chromosome aberrations. In a series of experiments, we studied low- and high-LET radiation-induced chromosome aberrations using the mBAND technique with chromosome 3 painted in 23 different colored bands. Human epithelial cells (CH1 84B5F5/M10) were exposed in vitro to Cs- 137 rays at both low and high dose rates, secondary neutrons with a broad energy spectrum at a low dose rate and 600 MeV/u Fe ions at a high dose rate. The data of both inter- and intrachromosome aberrations involving the painted chromosome have been reported previously. Here we present data of the location of the chromosome breaks along the length of chromosome 3 in the cells after exposures to each of the four radiation scenarios. In comparison to the expected breakpoint distribution based on the length of the bands, the observed distribution appeared to be non-random for both the low- and high-LET radiations. In particular, hot spots towards both ends of the chromosome were found after low-LET irradiations of either low or high dose rates. For both high-LET radiation types (Fe ions and neutrons), the breakpoint distributions were similar, and were much smoother than that for low-LET radiation. The dependence of the breakpoint distribution on the radiation quality requires further investigations.

Hada, Megumi↗
NASA NTRS2020

Determination of the Complex Refractive Indices of Aerosol Analogs Formed at Low Temperatures with the NASA Ames Optical Constants Facility (OCF)

The NASA Ames COsmic SImulation Chamber (COSmIC) [1] is a unique experimental facility that allows: 1) cooling a gas mixture to low temperature (150 K) in a jet expansion before inducing chemistry by plasma; and 2) controlling the extent of the chemical reactions by employing a pulsed plasma discharge. This enables the study of the early stages of aerosol production, as well as specific chemical pathways in planetary environments (e.g. Titan’s and Pluto’s atmospheres). Both the gas and solid products can be studied. For a decade COSmIC has been used to simulate Titan’s atmospheric chemistry at low, Titan-like temperature [2]. New developments on the COSmIC facility are investigating formation of aerosols in tenuous, or transitory, atmospheres of other icy bodies [3-5], as well as cool exoplanets atmospheres having a hydrocarbon component, that results in formation of hazes and/or surface deposits of refractory materials. The new Ames Optical Constants Facility enables determination of the aerosol analogs' complex refractive indices, n and k, from 0.59 to 200 μm [2]. Here we report efforts of determining n and k from ex-situ transmission measurements of solid samples produced from binary N-CH and Ar-CH, and tertiary N-CH-CH and Ar-CH-CHgas mixtures in COSmIC, and deposited onto various substrates. A computational technique [6] that addresses interference fringes observed in the laboratory transmission data, particularly at wavelengths < 3 μm, has been implemented and applied to determine n and k for the samples. At visible and near-infrared wavelengths(0.4-1.6 μm) the deposit thickness, and its variation, as well as n and k were determined by a commercial entity. These data provide the ability to compare results, from independent methods, in the region of overlap between the two approaches.

Ella M Sciamma-O'Brien↗