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NASA NTRS2017

Environmental Effects on Data Retention in Flash Cells

Flash technology is being utilized in fuzed munition applications and, based on the development of digital logic devices in the commercial world, usage of flash technology will increase. Antifuse technology, prevalent in non-volatile field programmable gate arrays (FPGAs), will eventually be phased out as new devices have not been developed for approximately a decade. The reliance on flash technology presents a long-term reliability issue for both DoD and NASA safety- and mission-critical applications. A thorough understanding of the data retention failure modes and statistics associated with Flash data retention is of vital concern to the fuze safety community. A key retention parameter for a flash cell is the threshold voltage (VTH), which is an indirect indicator of the amount of charge stored on the cells floating gate. This paper will present the results of our on-going tests: long-term storage at 150 C for a small population of devices, neutron radiation exposure, electrostatic discharge (ESD) testing, and the trends of large populations (over 300 devices for each condition) exposed to three difference temperatures: 25 C, 125 C, and 150 C.

Flash↗

NASA NTRS1972

Visual light flash phenomenon, part C

The Apollo 16 mission provided the opportunity to obtain additional data on the characteristics and frequency of the light flashes and also provided the first opportunity to obtain a direct physical record of incident cosmic ray particles with the Apollo light flash moving emulsion detector (ALFMED). The ALFMED is an electromechanical device that is worn on the head like a helmet and supports cosmic radiation-sensitive emulsions around the head of the test subject. Two light flash observation sessions were conducted during the mission: one during translunar coast and the second during transearth coast. Characteristics of the light flashes observed and reported by the Apollo crew members were generally similar to those reported on previous missions. Analyses of the ALFMED emulsion plates are proceeding as scheduled, although results are not yet available. The ALFMED results should provide conclusive evidence establishing the correlation, if any, between the incident cosmic ray particles and the perception of light flashes as reported by Apollo crew members.

Richard E. Benson↗

NASA NTRS1982

Atomization and combustion properties of flashing injectors

Flashing injection involves expanding a fluid through an injector until a supersaturated state is reached, causing a portion of the fluid to flash to a vapor. This investigation considered the flow, atomization and spreading properties of flashing injectors flowing liquids containing dissolved gases (Jet A/air) as well as superheated liquids (Freon 11). The use of a two stage expansion process, separated by an expansion chamber, was found to be beneficial for good atomization properties of flashing injection - particularly for dissolved gas systems. Both locally homogeneous and separated flow models provided good predictions of injector flow properties. Conventional correlations for drop sizes from pressure atomized and airblast injectors were successfully modified, using the separated flow model to prescribe injector exit conditions, to correlate drop size measurements. Additional experimental results are provided for spray angle and combustion properties of sprays from flashing injectors.

Solomon, A. S. P.↗

NASA NTRS1985

Flow and atomization in flashing injectors

Flashing injection involves expanding a fluid through an injector until a supersaturated state is reached, causing a portion of the fluid to flash to a vapor. This investigation considered the flow, atomization and spreading properties of flashing injectors with flowing liquids containing dissolved gases (Jet A/air) as well as superheated liquids (Freon-11). The use of a two-stage expansion process, separated by an expansion chamber, was found to be beneficial for good atomization properties of flashing injection - particularly for dissolved gas systems. Both locally homogeneous and separated flow models provided good predictions of injector flow properties. Conventional correlations for drop sizes from pressure and airblast injectors were successfully modified, using the separated flow model to prescribe injector exit conditions, and to correlate drop size measurements. Additional experimental results are provided for spray angles of sprays from flashing injectors.

Solomon, A. S. P.↗

NASA NTRS1987

Optical flash background rates

Flash background rates are measured from August 18-September 5, 1985 using the Lowell 0.61-m telescope at CTIO and the 28-cm f/10 Schmidt-Cassegrain telescope at ESO. During 230.1 hours of observing 40 flash events were detected, and it was observed that the background events were dominated by meteors and satellites passing through the field-of-view. The measured flash rate is compared with that of Pedersen et al. (1984), and it is determined that the background flash rate that is applicable to the data of Pedersen et al. for February 8, 1984 is 0.023 events/hr. The morphology of that flash, which appears to be controlled by a gamma-ray burster, is examined.

Schaefer, B. E.↗

NASA NTRS1987

Cloud-to-ground lightning flash characteristics from June 1984 through May 1985

A magnetic direction-finding network for the detection of lightning cloud-to-ground strikes has been installed along the east coast of the United States. Time, location, flash polarity, stroke count, and peak signal amplitude are recorded in real time. The data were recorded from Maine to North Carolina and as far west as Ohio; analyses were restricted to flashes within 300 km of a direction finder. Measurements of peak signal strength have been obtained from 720,284 first return strokes lowering negative charge. The resulting distribution indicates that few negative strokes have peak currents exceeding 100 kA. Measurements have also been obtained of peak signal strength from 17,694 first return strokes lowering positive charge. These strokes have a median peak current of 45 kA, with some peak currents reaching 300-400 kA. The median peak signal strength and the peak current, double from summer to winter for both negative and positive first return strokes. The polarity of ground flashes is observed to be less than 5 percent positive throughout the summer and early fall, then increases to over 50 percent during the winter, and returns to less than 10 percent in early spring. The percent of positive flashes with one stroke is observed to be approximately 90 percent throughout the year. The percent of negative flashes with one stroke is observed to increase from 40 percent in the summer to approximately 80 percent in January, returning to less than 50 percent in the spring.

Orville, Richard E.↗

NASA NTRS1992

Analysis of lightning flash videos from the Space Shuttle using blob and morphological techniques

Flash rates measured from the Space Shuttle range from 27.8 flashes per minute to 77 flashes per minute. The cloud is an optically thick medium which effectively scatters the energy from a lightning discharge and thereby broadens the risetime and duration of each lightning pulse. Because of the small size, spacecraft sensors with resolutions of 1 km or more are unlikely to detect the individual lightning channels. Instead, the energy from the lightning channel is scattered within the cloud, thereby broadening the apparent area. All of these measurements of lightning flash area and flash rate have involved manual manipulation and analysis of the video or film data. Only a small percentage of the Space Shuttle lightning video has been analyzed. An attempt is made to combine the use of real-time digital disk system and an automated analysis routine in order to overcome this limitation and make processing of a sequence of video frames a much less labor-intensive task.

Pitts, David E.↗

NASA NTRS2001

Flash Mixing on the White-Dwarf Cooling Curve: Understanding Hot Horizontal Branch Anomalies in NGC 2808

We present an ultraviolet color-magnitude diagram (CMD) spanning the hot horizontal branch (HB), blue straggler, and white dwarf populations of the globular cluster NGC 2808. These data, obtained with the Space Telescope Imaging Spectrograph (STIS), demonstrate that NGC 2808 harbors a significant population of hot subluminous HB stars, an anomaly only previously reported for the globular cluster omega Cen. Our theoretical modeling indicates that the location of these subluminous stars in the CMD, as well as the high temperature gap along the HB of NGC 2808, can be explained if these stars underwent a late helium-core flash while descending the white dwarf cooling curve. We show that the convective zone produced by such a late helium flash will penetrate into the hydrogen envelope, thereby mixing hydrogen into the hot helium-burning interior, where it is rapidly consumed. This phenomenon is analogous to the "born again" scenario for producing hydrogen-deficient stars following a late helium-shell flash. The flash mixing of the envelope greatly enhances the envelope helium and carbon abundances that, in turn, leads to a discontinuous increase in the HB effective temperatures. We argue that the hot HB gap is associated with this theoretically predicted dichotomy in the HB properties. Moreover, the changes in the emergent spectral energy distribution caused by these abundance changes are primarily responsible for explaining the hot subluminous HB stars. Although further evidence is needed to confirm that a late helium-core flash can account for the subluminous HB stars and the hot HB gap, we demonstrate that an understanding of these stars requires the use of appropriate theoretical models for their evolution, atmospheres, and spectra.

Brown, Thomas M.↗

NASA NTRS2002

Extreme Lightning Flash Rates as an Early Indicator of Severe Storms

Extreme lightning flash rates are proving to be an early indicator of intensifying storms capable of producing tornadoes, damaging winds and hail. Most of this lightning is in the cloud, where the naked eye can not see it. Recent global observations of thunderstorms from space indicate that giant electrical storms (supercells and convective complexes) with flash rates on the order of 1 flash per second are most common over the land masses of the America sub-tropics and equatorial Congo Basin. Within the United States, the average tornado warning lead time on a national basis is about 11 min. The real-time observation of extreme flash rates and the rapid increase in the in-cloud flash rate, signalling the intensification of the storm updraft, may provide as much as a 50% increase in severe storm warning lead time.

Goodman, Steven J.↗

NASA NTRS2007

Flash Diffusivity Technique Applied to Individual Fibers

A variant of the flash diffusivity technique has been devised for determining the thermal diffusivities, and thus the thermal conductivities, of individual aligned fibers. The technique is intended especially for application to nanocomposite fibers, made from narrower fibers of polyphenylene benzobisthiazole (PBZT) and carbon nanotubes. These highly aligned nanocomposite fibers could exploit the high thermal conductivities of carbon nanotubes for thermal-management applications. In the flash diffusivity technique as practiced heretofore, one or more heat pulse(s) is (are) applied to the front face of a plate or disk material specimen and the resulting time-varying temperature on the rear face is measured. Usually, the heat pulse is generated by use of a xenon flash lamp, and the variation of temperature on the rear face is measured by use of an infrared detector. The flash energy is made large enough to produce a usefully high temperature rise on the rear face, but not so large as to significantly alter the specimen material. Once the measurement has been completed, the thermal diffusivity of the specimen is computed from the thickness of the specimen and the time dependence of the temperature variation on the rear face. Heretofore, the infrared detector used in the flash diffusivity technique has been a single-point detector, which responds to a spatial average of the thermal radiation from the rear specimen surface. Such a detector cannot distinguish among regions of differing diffusivity within the specimen. Moreover, two basic assumptions of the thermaldiffusivity technique as practiced heretofore are that the specimen is homogeneous and that heat flows one-dimensionally from the front to the rear face. These assumptions are not valid for an inhomogeneous (composite) material.

Mayeaux, Brian↗

NASA NTRS2015

Imaging Flash Lidar for Safe Landing on Solar System Bodies and Spacecraft Rendezvous and Docking

NASA has been pursuing flash lidar technology for autonomous, safe landing on solar system bodies and for automated rendezvous and docking. During the final stages of the landing from about 1 kilometer to 500 meters above the ground, the flash lidar can generate 3-Dimensional images of the terrain to identify hazardous features such as craters, rocks, and steep slopes. The onboard flight computer can then use the 3-D map of terrain to guide the vehicle to a safe location. As an automated rendezvous and docking sensor, the flash lidar can provide relative range, velocity, and bearing from an approaching spacecraft to another spacecraft or a space station. NASA Langley Research Center has developed and demonstrated a flash lidar sensor system capable of generating 16,000 pixels range images with 7 centimeters precision, at 20 Hertz frame rate, from a maximum slant range of 1800 m from the target area. This paper describes the lidar instrument and presents the results of recent flight tests onboard a rocket-propelled free-flyer vehicle (Morpheus) built by NASA Johnson Space Center. The flights were conducted at a simulated lunar terrain site, consisting of realistic hazard features and designated landing areas, built at NASA Kennedy Space Center specifically for this demonstration test. This paper also provides an overview of the plan for continued advancement of the flash lidar technology aimed at enhancing its performance to meet both landing and automated rendezvous and docking applications.

Amzajerdian, Farzin↗

NASA NTRS2015

Lunar Impact Flash Locations

A bright impact flash detected by the NASA Lunar Impact Monitoring Program in March 2013 brought into focus the importance of determining the impact flash location. A process for locating the impact flash, and presumably its associated crater, was developed using commercially available software tools. The process was successfully applied to the March 2013 impact flash and put into production on an additional 300 impact flashes. The goal today: provide a description of the geolocation technique developed.

Moser, D. E.↗

NASA NTRS2016

A Comparison of Radiometric Calibration Techniques for Lunar Impact Flashes

Video observations of lunar impact flashes have been made by a number of researchers since the late 1990's and the problem of determination of the impact energies has been approached in different ways (Bellot Rubio, et al., 2000 [1], Bouley, et al., 2012.[2], Suggs, et al. 2014 [3], Rembold and Ryan 2015 [4], Ortiz, et al. 2015 [5]). The wide spectral response of the unfiltered video cameras in use for all published measurements necessitates color correction for the standard filter magnitudes available for the comparison stars. An estimate of the color of the impact flash is also needed to correct it to the chosen passband. Magnitudes corrected to standard filters are then used to determine the luminous energy in the filter passband according to the stellar atmosphere calibrations of Bessell et al., 1998 [6]. Figure 1 illustrates the problem. The camera pass band is the wide black curve and the blue, green, red, and magenta curves show the band passes of the Johnson-Cousins B, V, R, and I filters for which we have calibration star magnitudes. The blackbody curve of an impact flash of temperature 2800K (Nemtchinov, et al., 1998 [7]) is the dashed line. This paper compares the various photometric calibration techniques and how they address the color corrections necessary for the calculation of luminous energy (radiometry) of impact flashes. This issue has significant implications for determination of luminous efficiency, predictions of impact crater sizes for observed flashes, and the flux of meteoroids in the 10s of grams to kilogram size range.

Suggs, R.↗

NASA NTRS2016

Imaging Flash Lidar for Autonomous Safe Landing and Spacecraft Proximity Operation

3-D Imaging flash lidar is recognized as a primary candidate sensor for safe precision landing on solar system bodies (Moon, Mars, Jupiter and Saturn moons, etc.), and autonomous rendezvous proximity operations and docking/capture necessary for asteroid sample return and redirect missions, spacecraft docking, satellite servicing, and space debris removal. During the final stages of landing, from about 1 km to 500 m above the ground, the flash lidar can generate 3-Dimensional images of the terrain to identify hazardous features such as craters, rocks, and steep slopes. The onboard fli1ght computer can then use the 3-D map of terrain to guide the vehicle to a safe location. As an automated rendezvous and docking sensor, the flash lidar can provide relative range, velocity, and bearing from an approaching spacecraft to another spacecraft or a space station from several kilometers distance. NASA Langley Research Center has developed and demonstrated a flash lidar sensor system capable of generating 16k pixels range images with 7 cm precision, at a 20 Hz frame rate, from a maximum slant range of 1800 m from the target area. This paper describes the lidar instrument design and capabilities as demonstrated by the closed-loop flight tests onboard a rocket-propelled free-flyer vehicle (Morpheus). Then a plan for continued advancement of the flash lidar technology will be explained. This proposed plan is aimed at the development of a common sensor that with a modest design adjustment can meet the needs of both landing and proximity operation and docking applications.

Amzajerdian, Farzin↗

NASA NTRS2018

Flash Drought as Captured by MERRA-2: Disentangling the Contributions of Precipitation Deficit and Excess Energy

Flash droughts uncharacteristically rapid dryings of the land system are naturally associated with extreme precipitation deficits. Such precipitation deficits, however, do not tell the whole story. Land surface drying can be exacerbated by anomalously high evapotranspiration (ET) rates driven, for example, by anomalously high temperatures (e.g., during heatwaves) and/or anomalously high incoming radiation (e.g., from reduced cloudiness). In this study the relative contributions of precipitation and ET anomalies to flash drought generation are quantified through the analysis of diagnostic fields contained within the MERRA-2 reanalysis product. Unique to the overall approach is the explicit treatment of soil moisture impacts on ET an ET anomaly that is negative relative to the local long-term climatological mean is still considered positive in terms of its contribution to a flash drought, if it is high for the concurrent value of soil moisture. Maps produced in the analysis show the fraction of flash drought production stemming specifically from ET anomalies and the degree to which these ET anomalies are related to temperature and radiation anomalies. ET is found to have a large impact, for example, on flash drought production in the east-central US and in parts of Russia known from past studies to be prone to heatwave-related drought.

Koster, Randal↗

NASA NTRS2008

Disturb testing in flash memories

Non-volatile memory technology as defined by NAND architecture flash memory continues to lead the process scaling and device shrinking efforts of the entire integrated circuit industry. 45- nm technology nodes are now producing commercial 32Gb devices. These latest 32Gb devices are pioneering new charge trapping memory cell technologies using metal gates and high-k dielectric materials. These cells are called TANOS and consist of tantalum-nitride, aluminum oxide (high k material), nitride, oxide, and silicon. Such high-density memories continue to revolutionize commercial electronics in terms of new high-speed data architectures and significant reductions in overall power and weight consumption. In stark contrast, nearly all science-based interplanetary and earth-orbiting NASA spacecraft are still designing in and around mid-1980s-level non-volatile technology with 1Mb Electrically Erasable Read-Only Memory (EEPROM) devices. NASA has typically shunned the use of modern flash devices because of radiation and reliability concerns due to the commercial-offthe– shelf (COTS) nature of the NAND flash technology. Given the significant potential increases in overall system capability these modern flash devices could bring to NASA missions, it is important to continue to investigate these devices. This report will investigate certain portions of the reliability performance of NAND flash devices, specifically the disturb properties. Understanding the possible limitations such new non-volatile memory technology presents to NASA is the goal of this report.

Freie, Michael↗

NASA NTRS2009

Radiation tests of highly scaled high density commercial nonvolatile NAND flash memories update 2009

Heavy ion single-event measurements on a variety of high density commercial NAND flash memories are reported. Three single event effect (SEE) phenomena are examined: single effect upsets (SEUs), single event functional interrupts (SEFIs), and catastrophic loss of ability to erase and program the device. Also, radiation results of multilevel flash technology are compared with results from single-level flash technology. These commercial high density memories appear to be much less susceptible to SEE and have better TID response compared to older generations of flash memories. The single-level devices are less sensitive to SEUs than multi-level devices. The charge pump in this study survived up to 600 krads. A new high current phenomenon in high density NAND flash memories is also discussed.

Nguyen, Duc N.↗

NASA NTRS2018

Flash Optical Energy from the Geostationary Lightning Mapper

The Geostationary Operational Environmental Satellite -16 (GOES-16) Geostationary Lightning Mapper (GLM) is evaluated for many months during the Post Launch Product Test (PLPT) phase in order to ensure that optimal products are available for both the operational forecasting and broader scientific research communities. The emphasis of the PLPT phase is to validate the GLM performance (i.e., lightning flash detection efficiency, geolocation and time-stamp accuracy) using an extensive network of independent ground-based, in-situ, and space-based reference lightning detection systems. However, another essential aspect of the PLPT phase is to obtain benchmarks of the GLM lightning optical amplitude, so that any long-term degradation in the nadir-staring GLM camera system can be realized and quantitatively assessed. This is accomplished in a straight-forward manner by collecting a very large sample of lightning flashes across many geographical regions in the GLM field-of-view so that statistically meaningful benchmarks of lightning optical amplitude (i.e., optical energy in units of femto-joules per flash) are obtained. The benchmarking is particularly important to follow-on studies that will attempt to incorporate the flash optical energy product into new derived products (e.g., energy-weighted lightning "jump" warning algorithms, and lightning nitrogen oxides production estimates).

Lightning↗