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NASA NTRS2023

Unusually Long Path Length for a Nearly Scatter-Free Solar Particle Event Observed By Solar Orbiter at 0.43 au

Context. After their acceleration and release at the Sun, solar energetic particles (SEPs) are injected into the interplanetary medium and are bound to the interplanetary magnetic field (IMF) by the Lorentz force. The expansion of the IMF close to the Sun focuses the particle pitch-angle distribution, and scattering counteracts this focusing. Solar Orbiter observed an unusual solar particle event on 9 April 2022 when it was at 0.43 astronomical units (au) from the Sun. Aims. We show that the inferred IMF along which the SEPs traveled was about three times longer than the nominal length of the Parker spiral and provide an explanation for this apparently long path. Methods. We used velocity dispersion analysis (VDA) information to infer the spiral length along which the electrons and ions traveled and infer their solar release times and arrival direction. Results. The path length inferred from VDA is approximately three times longer than the nominal Parker spiral. Nevertheless, the pitch-angle distribution of the particles of this event is highly anisotropic, and the electrons and ions appear to be streaming along the same IMF structures. The angular width of the streaming population is estimated to be approximately 30 degrees. The highly anisotropic ion beam was observed for more than 12 h. This may be due to the low level of fluctuations in the IMF, which in turn is very probably due to this event being inside an interplanetary coronal mass ejection The slow and small rotation in the IMF suggests a flux-rope structure. Small flux dropouts are associated with very small changes in pitch angle, which may be explained by different flux tubes connecting to different locations in the flare region. Conclusions. The unusually long path length along which the electrons and ions have propagated virtually scatter-free together with the short-term flux dropouts offer excellent opportunities to study the transport of SEPs within interplanetary structures. The 9 April 2022 solar particle event offers an especially rich number of unique observations that can be used to limit SEP transport models.

Robert F. Wimmer-Schweingruber↗
NASA NTRS1994

A Yohkoh search for `black-light flares'

Calculations which predict that a phenomenon analogous to stellar negative pre-flares could also exist on the Sun were published by Henoux et al. (1990), and Aboudarham et al., (1990), who showed at the beginning of a solar white-light flare (WLF) event an electron beam can cause a transient darkening before the WLF emission starts, under certain conditions. They named this event a `black light flare' (BLF). Such a BLF event should appear as diffuse dark patches lasting for about 20 seconds preceding the WLF emission, which would coincide with intense and impulsive hard X-ray bursts. The BLF location would be at (or in the vicinity of ) the forthcoming bright patches. Their predicted contrast depends on the position of the flare on the solar disk and on the wavelength band of the observation. The Yohkoh satellite provided white-light data from the aspect camera of the Soft X-ray Telescope (SXT) instrument (Tsuneta et al., 1991), at 431 nm and with a typical image interval of 10 - 12 s. We have studied nine white-light flares observed with this instrument, with X-ray class larger than M6. We have found a few interesting episodes, but no unambiguous example of the predicted BLF event. This study, although the best survey to date, was not ideal from the observational point of view. We therefore encourage further searches. Successful observations of this phenomenon on the Sun would greatly strengthen our knowledge of the lower solar atmosphere and its effects on solar luminosity variations.

Van Driel-Gesztelyi, Lidia↗
NASA NTRS2021

Wilson Corners SWMU 001 2019-2020 Annual Long-Term Monitoring Report Kennedy Space Center, Florida

This report presents a summary of the long-term monitoring (LTM) activities that occurred in 2019 and 2020 at Wilson Corners, Solid Waste Management Unit 001, at the John F. Kennedy Space Center (KSC), Florida. The site is monitored under KSC’s Resource Conservation and Recovery Act Corrective Action Program. Adaptive site management is being utilized through ongoing assessment, design, and interim measures. This approach also meets the requirements of Chapter 62-780, Florida Administrative Code. The goal of LTM at this site is threefold: to determine groundwater flow characteristics, monitor the downgradient concentration trends, and monitor select locations internal to the groundwater plume. Every 5 years, upgradient and side-gradient monitoring wells are sampled to verify delineation. The last time this was performed was in 2015. Sampling of these wells in 2020 was replaced with the direct push technology investigations in October 2020 and April 2021. The activities presented in this report include three field events: (1) December 2019 -groundwater gauging of 38 monitoring wells and sampling of 36 monitoring wells; (2) May 2020 - groundwater sampling of 7 monitoring wells; and (3) December 2020 - groundwater gauging of 49 monitoring wells and sampling of 43 monitoring wells. During the December 2019 and May 2020 events, monitoring wells were sampled using passive diffusion bags and were analyzed for a “full list” of volatile organic compounds (VOCs), including Freon 113. During the December 2020 event, the low flow sampling method was used, and samples were analyzed for a “select list” of VOCs, including Freon 113. The following conclusions can be made based on the 2019 and 2020 LTM results: •In December 2019 and December 2020, groundwater flow for the site was generally to the west with the individual zones only varying by occasional northerly and southerly components. This is generally consistent with historical observations at the site. •The GCTL plume continues to extend both horizontally and vertically beyond our current monitoring well network. •The vertical extent of VOCs was historically generally delineated by monitoring wells screened greater than 48 feet bls. The results from the two vertical extent monitoring wells WILC-MW0078 and WILC-MW0130 that were sampled during the 2019 and 2020 LTM indicate that groundwater VOC concentrations in both wells were greater than the GCTL. •Freon 113 was not detected above GCTLs during the 2019 and 2020 LTM events. Based on groundwater sampling activities performed during this reporting period, including recent DPT groundwater sampling conducted for the implementation of an air sparge system, the following recommendations are provided: •Install 10 new monitoring wells, which will be sampled along with 49 existing monitoring wells, to assist with delineation of the low concentration plume. The wells are listed inTable 4-1, and the proposed locations are presented on Figures4 -1 through 4-5. (Figures 4-1, 4-2, 4-3, and 4-5 also show updated plumes and proposed performance monitoring well locations. This information will be discussed and presented under a separate cover.) •Modify the annual LTM sampling plan as presented inTable 4-1. •Sampling for future events at the site will be conducted using low flow pumping methods. The next annual LTM sampling event is currently planned for December 2021. Please note the 10 new monitoring wells will not be installed before this event but will be installed as part of the upcoming IM construction and will be sampled during baseline sampling, along with the 49 existing monitoring wells. Following this sampling event, it is recommended that the Annual LTM be combined with the performance monitoring under the IM implementation, and LTM be temporarily discontinued. Objectives of the 2021 LTM are to: (i) evaluate groundwater gradient and flow direction by collecting depth to water measurements from LTM wells; (ii) continue monitoring the peripheral VOC trends in the northern, southern, and western portions of the site by monitoring existing wells and installing and monitoring new wells as recommended; and (iii) monitor select internal plume wells.

Jennifer Lynn Joyal↗
NASA NTRS2016

Evaluation of NASA's MERRA Precipitation Product in Reproducing the Observed Trend and Distribution of Extreme Precipitation Events in the United States

This study evaluates the performance of NASA's Modern-Era Retrospective Analysis for Research and Applications (MERRA) precipitation product in reproducing the trend and distribution of extreme precipitation events. Utilizing the extreme value theory, time-invariant and time-variant extreme value distributions are developed to model the trends and changes in the patterns of extreme precipitation events over the contiguous United States during 1979-2010. The Climate Prediction Center (CPC) U.S.Unified gridded observation data are used as the observational dataset. The CPC analysis shows that the eastern and western parts of the United States are experiencing positive and negative trends in annual maxima, respectively. The continental-scale patterns of change found in MERRA seem to reasonably mirror the observed patterns of change found in CPC. This is not previously expected, given the difficulty in constraining precipitation in reanalysis products. MERRA tends to overestimate the frequency at which the 99th percentile of precipitation is exceeded because this threshold tends to be lower in MERRA, making it easier to be exceeded. This feature is dominant during the summer months. MERRA tends to reproduce spatial patterns of the scale and location parameters of the generalized extreme value and generalized Pareto distributions. However, MERRA underestimates these parameters, particularly over the Gulf Coast states, leading to lower magnitudes in extreme precipitation events. Two issues in MERRA are identified: 1) MERRA shows a spurious negative trend in Nebraska and Kansas, which is most likely related to the changes in the satellite observing system over time that has apparently affected the water cycle in the central United States, and 2) the patterns of positive trend over the Gulf Coast states and along the East Coast seem to be correlated with the tropical cyclones in these regions. The analysis of the trends in the seasonal precipitation extremes indicates that the hurricane and winter seasons are contributing the most to these trend patterns in the southeastern United States. In addition, the increasing annual trend simulated by MERRA in the Gulf Coast region is due to an incorrect trend in winter precipitation extremes.

MERRA↗
NASA NTRS1974

Observation of a cosmic gamma-ray burst on Apollo 16. II - X-ray time profile and source location

A burst of X-rays was detected during the trans-earth coast phase of Apollo 16 on Apr. 27, 1972 at 10:68 UT, simultaneously with the observation of a transient event by a gamma-ray spectrometer aboard the same spacecraft. The two instruments provide a broad energy range of more than three orders of magnitude for describing the spectral distribution of this event. The conclusion that the incident flux was X-rays and not charged particles is based on the fact that the particle flux detectors in the Apollo gamma ray spectrometer and on the Vela 6A, which also observed the event, did not respond. The time variation of the total count rate in the X-ray range before and after corrections for detector geometry and the analysis for source direction is presented.

Trombka, J. I.↗
NASA NTRS2001

Large Solar Flares and Sheared Magnetic Field Configuration

This Comment gives additional information about the nature of flaring locations on the Sun described in the article "Sun unleashes Halloween storm", by R. E. Lopez, et al. What causes the large explosions from solar active regions that unleash huge magnetic storms and adverse space weather? It is now beyond doubt that the magnetic field in solar active regions harbors free energy that is released during these events. Direct measurements of the longitudinal and transverse components of active region magnetic fields with the vector magnetograph at NASA Marshall Space Flight Center (MSFC), taken on a regular basis for the last 30 years, have found key signatures of the locations of powerful flares. A vector magnetograph detects and measures the magnetic shear, which is the deviation of the observed transverse magnetic field direction from the potential field. The sheared locations possess abundant free magnetic energy for solar flares. In addition to active region NOAA 10486, the one that produced the largest flares last October, the NASA/MSFC vector magnetograph has observed several other such complex super active regions, including NOAA 6555 and 6659.

Choudhary, Debi Prasad↗
NASA NTRS2008

Total Lightning Observations of Extreme Weather Events over the Contiguous United States

The overall objective is to investigate total lightning characteristics of extreme weather events over the contiguous United States (CONUS) using TRMM (Tropical Rainfall Measuring Mission) LIS (Lightning Image Sensor) and OTD (Optical Transient Detector) satellite observations. A large LIS (10+ years) and OTD (5 years) data base is available to study the instantaneous total or cloud-to-ground (CG) plus intracloud (IC) lightning characteristics of extreme weather events. More specifically, the LIS and OTD data are combined with National Lightning Detection Network (NLDN) observations to examine the total and CG lightning flash rate and density, the IC:CG ratio, and positive CG percentage. These instantaneous lightning characteristics can be used for basic science studies to better understand the physical and dynamical linkages between lightning and precipitation and their environmental controls. They can also provide a first-look of extreme weather events leading up to future satellite observations (e.g., NOAA GOES-R Geostationary Lightning Mapper [GLM]) for use in climate studies and the short-term prediction and warning process. Extreme weather events are defined by the NOAA Storm Data reports of tornadoes, large hail (at least 0.75 inch) and strong straight-line winds (at least 50 kts). Over CONUS, there are over 70,000 severe storm reports in the TRMM spatial domain (< 35 N) from 1998-2007 and over 100,000 storm reports in the OTD spatial domain (5/1995-4/2000). Temporal co-location is on the order of 1% (i.e., 1000 s of coincident overpasses), providing a statistically significant sample of instantaneous total lightning properties. This instantaneous behavior of lightning in extreme weather is then compared to that of typical thunderstorm events, or randomly sampled LIS/OTD events in which the extreme events have been eliminated from the population. Results describing the instantaneous behavior of total lightning within a large sample of extreme and typical thunderstorms over CONUS will be presented. When possible, coincident VHF lightning observations from the ground-based Northern Alabama Lightning Mapping Array (LMA) are compared to the LIS/OTD optical lightning signatures, providing a validation source for instantaneous space-based optical lightning properties and a means to extend lightning inferences over the life-cycle of extreme weather.

Carey, Lawrence D.↗
NASA NTRS1987

Short-term forecasting of lightning based on the surface wind field at Kennedy Space Center

Cloud-to-ground lightning is related in time and space to surface convergence for 244 days during the summer over a 790 sqkm network. The method uses surface convergence, particularly the average over the area, to identify the potential for new, local thunderstorm growth, and can be used to specify the likely time and location of lightning during the life cycle of the convection. A threshold of 0.0000075/sec change in divergence is used to define a convergence event, and a separation of 30 min between flashes defines a lightning event. Time intervals are found to be on the order of 1 hr from beginning convergence to first flash, and (CH110) 2 hr from beginning convergence to the end of lightning. Major differences between the convergence-lightning relationships based on low-level mean onshore and offshore flow are noted.

Watson, Andrew I.↗
NASA NTRS1993

Impact damage resistance of composite fuselage structure, part 2

The strength of laminated composite materials may be significantly reduced by foreign object impact induced damage. An understanding of the damage state is required in order to predict the behavior of structure under operational loads or to optimize the structural configuration. Types of damage typically induced in laminated materials during an impact event include transverse matrix cracking, delamination, and/or fiber breakage. The details of the damage state and its influence on structural behavior depend on the location of the impact. Damage in the skin may act as a soft inclusion or affect panel stability, while damage occurring over a stiffener may include debonding of the stiffener flange from the skin. An experiment to characterize impact damage resistance of fuselage structure as a function of structural configuration and impact threat was performed. A wide range of variables associated with aircraft fuselage structure such as material type and stiffener geometry (termed, intrinsic variables) and variables related to the operating environment such as impactor mass and diameter (termed, extrinsic variables) were studied using a statistically based design-of-experiments technique. The experimental design resulted in thirty-two different 3-stiffener panels. These configured panels were impacted in various locations with a number of impactor configurations, weights, and energies. The results obtained from an examination of impacts in the skin midbay and hail simulation impacts are documented. The current discussion is a continuation of that work with a focus on nondiscrete characterization of the midbay hail simulation impacts and discrete characterization of impact damage for impacts over the stiffener.

Dost, Ernest F.↗
NASA NTRS1996

Computational modeling of magnetically actuated propellant orientation

Unlike terrestrial applications where gravity positions liquid at the 'bottom' of the tank, the location of liquid propellant in spacecraft tanks is uncertain unless specific actions are taken or special features are built into the tank. Some mission events require knowledge of liquid position prior to a particular action: liquid must be positioned over the tank outlet prior to starting the main engines and must be moved away from the tank vent before vapor can be released overboard to reduce pressure. It may also be desirable to positively position liquid to improve propulsion system performance: moving liquid away from the tank walls will dramatically decrease the rate of heat transfer to the propellant, suppressing the boil-off rate, thereby reducing overall mission propellant requirements. The process of moving propellant to a desired position is referred to as propellant orientation or reorientation. Several techniques have been developed to positively position propellant in spacecraft tanks and each technique imposes additional requirements on vehicle design. Propulsive reorientation relies on small auxiliary thrusters to accelerate the tank. The inertia of the liquid causes it to collect in the aft-end of the tank if the acceleration is forward. This technique requires that additional thrusters be added to the vehicle, that additional propellant be carried in the vehicle, and that an additional operational maneuver be executed. Another technique uses Liquid Acquisition Devices (LAD's) to positively position propellants. These devices rely on surface tension to hold the liquid within special geometries (i.e. vanes, wire-mesh channels, start-baskets). While avoiding some of the penalties of propulsive orientation, this technique requires the addition of complicated hardware inside the propellant tank and performance for long duration missions is uncertain. The subject of the present research is an alternate technique for positively positioning liquid within spacecraft propellant tanks: magnetic fields.

Hochstein, John I.↗
NASA NTRS1994

NASA Shuttle Lightning Research: Observations of Nocturnal Thunderstorms and Lightning Displays as Seen During Recent Space Shuttle Missions

A number of interesting lightning events have been observed using the low light level TV camera of the space shuttle during nighttime observations of thunderstorms near the limb of the Earth. Some of the vertical type lightning events that have been observed will be presented. Using TV cameras for observing lightning near the Earth's limb allows one to determine the location of the lightning and other characteristics by using the star field data and the shuttle's orbital position to reconstruct the geometry of the scene being viewed by the shuttle's TV cameras which are located in the payload bay of the shuttle.

Vaughan, Otha H., Jr.↗
NASA NTRS1997

Comparison Between Predictions & Observations of Induced Radioactive Background in Interplanetary Missions

Radioactivity induced in detector materials and their immediate surroundings is the major source of discrete-line, gamma-ray background and an important source of continuum background in the performance of remote-sensing, gamma-ray spectroscopy of planetary bodies. In interplanetary space the dominant sources of particles are cosmic rays and their secondaries arising from interactions with the spacecraft and the surface of the target body. In addition, certain future gamma-ray astronomy missions, such as INTEGRAL, are to be located so as to perform their observations in interplanetary space rather than in the traditional low earth orbits. Such location removes contributions from the earth's atmosphere and inner radiation belt at the expense of increased exposure to cosmic rays and solar particle events. Accurate prediction of the activation of key materials by cosmic rays is of the utmost importance for detector design and data interpretation.

Dyer, Clivea↗
NASA NTRS1996

Computational Modeling of Magnetically Actuated Propellant Orientation

Unlike terrestrial applications where gravity positions liquid at the "bottom" of the tank, the location of liquid propellant in spacecraft tanks is uncertain unless specific actions are taken or special features are built into the tank. Some mission events require knowledge of liquid position prior to a particular action: liquid must be positioned over the tank outlet prior to starting the main engines and must be moved away from the tank vent before vapor can be released overboard to reduce pressure. It may also be desirable to positively position liquid to improve propulsion system performance: moving liquid away from the tank walls will dramatically decrease the rate of heat transfer to the propellant, suppressing the boil-off rate, thereby reducing overall mission propellant requirements. The process of moving propellant to a desired position is referred to as propellant orientation or reorientation. Propulsive reorientation relies on small auxiliary thrusters to accelerate the tank. The inertia of the liquid causes it to collect in the aft-end of the tank if the acceleration is forward. Liquid Acquisition Devices (LAD's) rely on surface tension to hold the liquid within special geometries, (i.e. vanes, wire-mesh channels, start-baskets), to positively position propellants. Both of these technologies add significant weight and complexity to the spacecraft and can be limiting systems for long duration missions. The subject of the present research is an alternate technique for positively positioning liquid within spacecraft propellant tanks: magnetic fields. LOX is paramagnetic (attracted toward a magnet) and LH2 is diamagnetic (repelled from a magnet). Order-of-magnitude analyses, performed in the 1960's to determine required magnet size, concluded that the magnets would be prohibitively massive and this option has remained dormant during the intervening years. Recent advances in high-temperature superconducting materials hold the promise of electromagnets with sufficient performance to support cryogenic propellant management tasks. In late 1992, NASA MSFC began a new investigation in this technology commencing with the design of the Magnetically-Actuated Propellant Orientation (MAPO) experiment. A mixture of ferrofluid and water is used to simulate the paramagnetic properties of LOX and the experiment is being flown on the KC-135 aircraft to provide a reduced gravity environment. The influence of a 0.4 Tesla ring magnet on flow into and out of a subscale Plexiglas tank is being recorded on video tape. The most efficient approach to evaluating the feasibility of MAPO is to compliment the experimental program with development of a computational tool to model the process of interest. The goal of the present research is to develop such a tool. Once confidence in its fidelity is established by comparison to data from the MAPO experiment, it can be used to assist in the design of future experiments and to study the parameter space of the process. Ultimately, it is hoped that the computational model can serve as a design tool for full-scale spacecraft applications.

Hochstein, John I.↗
NASA NTRS1997

IAUC 6530: GRO J1744-28; C/1995 01

We have recorded a series of outbursts starting on 1996 Dec. 2 that are consistent with the position of GRO J1744-28, the bursting pulsar. The bursts are detected between 20 and 100 keV, and on Dec. 2 they came in variable rates ranging from every 300 to every 500 s, with a preliminary total number estimated between 80 and 1 00 events. After Dec. 3, the burst rate dropped to 15-20 bursts/day, where it has remained. The current average error radius of the burst locations is about 4 deg. The burst fluence is currently about 2 x 10E-7 erg cmE-2. This indicates that the source is in outburst again. Although the source location is currently very close to the sun, we encourage observations in other wavelengths whenever possible. Persistent, hard x-ray emission from GRO J1744-28 (IAUC 6272, 6284, 6285) is currently being detected through both pulsation and earth occultation. Pulsations with a period near 0.467 s became detectable on Dec. 17, rising to a 20- to 40-keV-rms-pulsed flux of 1.3(1) x 10E-9 erg cmE-1 sE-1 (170 mCrab) by 1997 Jan. 3. On Jan. 1.0, the intrinsic pulse frequency was 2.1408983(4) Hz, and the spin-up rate was 2.8(5) x l0E-12 HzsE-1. This assumes the following circular orbit parameters: P = 11.83665(14) days; epoch of longitude 90 deg = JD 2450126.9977(4) TDB; a sin i = 2.6371(5) light-s (determined using data from the 1995 Dec.-l996 Apr. outburst). Earth-occultation monitoring of flux from GRO J1744-28 shows its intensity increasing by a factor of about two during 1996 Dec. 25-1997 Jan. 6. Although source confusion prevents a precise flux estimate, subtracting a 25-percent background for unresolved galactic-center sources yields a persistent flux for Jan. 3-6 in the energy bands 20-30, 30-40, and 40-50 keV of 590, 470, and 290 mcrab, respectively."

Kouveliotou, Chryssa↗
NASA NTRS1995

Evidence on Sizes and Fragmentation of the Nuclei of Comet Shoemaker-Levy 9 from Hubble Space Telescope Images

Central regions on the digital maps of 13 nuclear condensations of Comet Shoemaker-Levy 9, obtained with the Planetary Camera of the Hubble Space Telescope on January 24-25, March 28-30, and July 4, 1994, have been analyzed with the aim to identify the presence of distinct, major fragments in each condensation, to deconvolve their contributions to the signal that also includes the contribution from a surrounding cloud of dust (modeled as an extended source, using two different laws), to estimate the dimensions of the fragments and to study their temporal variations, and to determine the spatial distributions of the fragments as projected onto the plane of the sky. The deconvolution method applied is described and the results of the analysis are summarized, including the finding that sizable fragments die survive until the time of atmospheric entry. This result does not contradict evidence of the comet's continuing, apparently spontaneous fragmentation, which still went on long after the extremely close approach to Jupiter in July 1992 and which, because of the jovian tidal effects, may even have intensified in the final days before the crash on Jupiter. On plausible assumptions, the largest fragments are found to have had effect diameters of 4 km as late as March and event early July 1994. In most condensations, several sizable companions ( 1 km or more across) have been detected within 1000 km of the projected location of the brightest fragment and the surrounding dust cloud has been found to be centered on a point that is shifted in the general direction of the tail, probably due to effects of solar radiation pressure. Since the developed approach is based on certain premises and involves approximations, the results should be viewed as preliminary and the problem should be a subject of further investigation.

Comet Shoemaker-Levy 9↗
NASA NTRS2008

Processing LiDAR Data to Predict Natural Hazards

ELF-Base and ELF-Hazards (wherein 'ELF' signifies 'Extract LiDAR Features' and 'LiDAR' signifies 'light detection and ranging') are developmental software modules for processing remote-sensing LiDAR data to identify past natural hazards (principally, landslides) and predict future ones. ELF-Base processes raw LiDAR data, including LiDAR intensity data that are often ignored in other software, to create digital terrain models (DTMs) and digital feature models (DFMs) with sub-meter accuracy. ELF-Hazards fuses raw LiDAR data, data from multispectral and hyperspectral optical images, and DTMs and DFMs generated by ELF-Base to generate hazard risk maps. Advanced algorithms in these software modules include line-enhancement and edge-detection algorithms, surface-characterization algorithms, and algorithms that implement innovative data-fusion techniques. The line-extraction and edge-detection algorithms enable users to locate such features as faults and landslide headwall scarps. Also implemented in this software are improved methodologies for identification and mapping of past landslide events by use of (1) accurate, ELF-derived surface characterizations and (2) three LiDAR/optical-data-fusion techniques: post-classification data fusion, maximum-likelihood estimation modeling, and hierarchical within-class discrimination. This software is expected to enable faster, more accurate forecasting of natural hazards than has previously been possible.

Fairweather, Ian↗
NASA NTRS2011

Demonstration of a Particle Impact Monitoring System for Crewed Space Exploration Modules

When micrometeorite or debris impacts occur on a space habitat, crew members need to be quickly informed of the likely extent of damage, and be directed to the impact location for possible repairs. The goal of the Habitat Particle Impact Monitoring System (HIMS) is to develop a fully automated, end-to-end particle impact detection system for crewed space exploration modules, both in space and on the surfaces of Solar System bodies. The HIMS uses multiple thin film piezo-polymer vibration sensors to detect impacts on a surface, and computer processing of the acoustical signals to characterize the impacts. Development and demonstration of the HIMS is proceeding in concert with NASA's Habitat Demonstration Unit (HDU) Project. The HDU Project is designed to develop and test various technologies, configurations, and operational concepts for exploration habitats. This paper describes the HIMS development, initial testing, and HDU integration efforts. Initial tests of the system on the HDU were conducted at NASA?s 2010 Desert Research and Technologies Studies (Desert-RATS). Four sensor locations were assigned near the corners of a rectangular pattern. To study the influence of wall thickness, three sets of four sensors were installed at different layer depths: on the interior of the PEM wall, on the exterior of the same wall, and on the exterior of a layer of foam insulation applied to the exterior wall. Once the system was activated, particle impacts were periodically applied by firing a pneumatic pellet gun at the exterior wall section. Impact signals from the sensors were recognized by a data acquisition system when they occurred, and recorded on a computer for later analysis. Preliminary analysis of the results found that the HIMS system located the point of impact to within 8 cm, provided a measure of the impact energy / damage produced, and was insensitive to other acoustic events. Based on this success, a fully automated version of this system will be completed and demonstrated as part of a crew "Caution/Warning" system at the 2011 Desert-RATS, along with a crew response procedure.

Opiela, J. N.↗
NASA NTRS2014

Comparison of Model Calculations of Biological Damage from Exposure to Heavy Ions with Measurements

The space environment consists of a varying field of radiation particles including high-energy ions, with spacecraft shielding material providing the major protection to astronauts from harmful exposure. Unlike low-LET gamma or X rays, the presence of shielding does not always reduce the radiation risks for energetic charged-particle exposure. Dose delivered by the charged particle increases sharply at the Bragg peak. However, the Bragg curve does not necessarily represent the biological damage along the particle path since biological effects are influenced by the track structures of both primary and secondary particles. Therefore, the ''biological Bragg curve'' is dependent on the energy and the type of the primary particle and may vary for different biological end points. Measurements of the induction of micronuclei (MN) have made across the Bragg curve in human fibroblasts exposed to energetic silicon and iron ions in vitro at two different energies, 300 MeV/nucleon and 1 GeV/nucleon. Although the data did not reveal an increased yield of MN at the location of the Bragg peak, the increased inhibition of cell progression, which is related to cell death, was found at the Bragg peak location. These results are compared to the calculations of biological damage using a stochastic Monte-Carlo track structure model, Galactic Cosmic Ray Event-based Risk Model (GERM) code (Cucinotta, et al., 2011). The GERM code estimates the basic physical properties along the passage of heavy ions in tissue and shielding materials, by which the experimental set-up can be interpreted. The code can also be used to describe the biophysical events of interest in radiobiology, cancer therapy, and space exploration. The calculation has shown that the severely damaged cells at the Bragg peak are more likely to go through reproductive death, the so called "overkill".

Kim, Myung-Hee Y.↗