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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

An Indium Gallium Arsenide Visible/SWIR Focal Plane Array for Low Light Level Imaging

PIN photodiodes fabricated from indium gallium arsenide lattice-matched to indium phosphide substrates (In(.53)Ga(.47)As/InP) exhibit low reverse saturation current densities (JD < 10(exp -8) A/sq cm), and high shunt resistance-area products (RoA > 10(exp 6) omega-sq cm) at T=290K. Backside-illuminated, hybrid-integrated InGaAs FPAs are sensitive from 0.9 micrometers to 1.7 micrometers. 290K detectivities, D(*), greater than 10(exp 14) cm-(square root of Hz/W) are demonstrated. This represents the highest room temperature detectivity of any infrared material. The long wavelength cutoff (1.7 micrometers) makes In(.53)Ga(.47)As an idea match to the available airglow that has major peaks at 1.3 micrometers and 1.6 micrometers. The short wavelength 'cut-on' at 0.9 micrometers is due to absorption in the InP substrate. We will report on new InGaAs FPA epitaxial structures and processing techniques. These have resulted in improved performance in the form of a 10 x increase in detectivity and visible response via removal of the InP substrate. The resulting device features visible and SWIR response with greater than 15% quantum efficiency at 0.5 micrometers while maintaining the long wavelength cutoff. Imaging has been demonstrated under overcast starlight/urban glow conditions with cooling provided by a single stage thermoelectric cooler. Details on the material structure and device fabrication, quantitative characterization of spectral response and detectivity, as well as examples of night vision imagery are presented.

Cohen, Marshall J.↗
NASA NTRS1989

Optical multiple object tracking techniques

Two multichannel multiple-object tracking techniques are reviewed. In the diffraction grating technique, the input scene is picked up by a TV camera and imaged onto a liquid-crystal light valve (LCLV), and the output side of the light valve is illuminated with a suitably polarized and collimated coherent laser beam to yield a reflected beam with polarization modulated according to the intensity of the incoherent input. This reflected beam passes through a beam splitter cube and an analyzer, resulting in an intensity modulated coherent image. An array of spectrum islands containing the information of the input appears after crossing a contact screen/lens combination. In the multiple-focus hololens technique, the scene of moving objects is sent into the LCTVSLM through a camera; a collimated laser beam is incident upon the LCTV screen; a low-pass filter is inserted between the LCTVSLM and the hololens for the removal of the high order diffractions due to the grid structure of the LCTV. The feasibility of the LCTVSLM and multiple-focus hololens technique is demonstrated.

Liu, Hua-Kuang↗
NASA NTRS1994

The Infrared Reflection Nebula Around the Protostellar System in S140

We have studied the protostellar system in S140 at 2.2, 3.1 and 3.45 microns using a 128x128 InSb array at the Lick Observatory 3m telescope. Besides the protostellar sources, the data reveal a bright infrared reflection nebula. We have developed a simple model of this region and derived the physical conditions. IRSI is surrounded by a dense dusty disk viewed almost edge-on. Photons leaking out through the poles illuminate almost directly north and south the inner edge of a surrounding shell of molecular gas, Analysis of the observed colors and intensities of the NIR light, using Mie scattering theory, reveal that the dust grains in the molecular cloud are somewhat larger than in the general diffuse interstellar medium. Moreover, the incident light has a "cool" color temperature, approximately equals 800K, and likely originates from a dust photosphere close to the protostar. Finally, we find little H2O ice associated with the dusty disk around IRSI. Most of the 3.1 micron ice extinction arises instead from cool intervening molecular cloud material. We have compared our infrared dust observations with millimeter and radio observations of molecular gas associated with this region. The large scale structure observable in the molecular gas is indicative of the interaction between the protostellar wind and the surrounding molecular cloud rather than the geometry of the protostellar disk. We conclude that S140 is a young blister formed by this outflow on the side of a molecular cloud and viewed edge-on.

Harker, D.↗
NASA NTRS2013

Vision Systems Illuminate Industrial Processes

When NASA designs a spacecraft to undertake a new mission, innovation does not stop after the design phase. In many cases, these spacecraft are firsts of their kind, requiring not only remarkable imagination and expertise in their conception but new technologies and methods for their manufacture. In the realm of manufacturing, NASA has from necessity worked on the cutting-edge, seeking new techniques and materials for creating unprecedented structures, as well as capabilities for reducing the cost and increasing the efficiency of existing manufacturing technologies. From friction stir welding enhancements (Spinoff 2009) to thermoset composites (Spinoff 2011), NASA s innovations in manufacturing have often transferred to the public in ways that enable the expansion of the Nation s industrial productivity. NASA has long pursued ways of improving upon and ensuring quality results from manufacturing processes ranging from arc welding to thermal coating applications. But many of these processes generate blinding light (hence the need for special eyewear during welding) that obscures the process while it is happening, making it difficult to monitor and evaluate. In the 1980s, NASA partnered with a company to develop technology to address this issue. Today, that collaboration has spawned multiple commercial products that not only support effective manufacturing for private industry but also may support NASA in the use of an exciting, rapidly growing field of manufacturing ideal for long-duration space missions.

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NASA NTRS2008

Diagnosing the Structure of the HD 163296 Protoplanetary Disk Via Coronagraphic Imaging Polarimetry

Coronagraphic imaging polarimetry is a high contrast imaging technique which can diagnose both the spatial distribution and size distribution of dust grains which comprise primordial protoplanetary disks. It can therefore be a useful tool to test our understanding of how the structure of young disks evolves through the era of gas giant planet formation. We report our initial analysis of the H-band polarized and total intensity of the nearby Herbig Ae star HD 163296, and characterize the morphology of the scattered light disk in the context of previous optical HST coronagraphic imagery. Our observations were obtained as part of a multi-epoch campaign designed to diagnose and correlate the behavior of the inner and outer regions of select protoplanetary disks. This campaign will help test recent suggestions (Sitko et al. 2008; Wisniewski et al. 2008) that that HD 163296 dis experiences the novel phenomenon of time-variable self-shadowing, whereby occasional changes in the scale height of the inner disk wall induces changes in the illumination of the outer disk.

Kowalski, Adam F.↗
NASA NTRS1993

The quantum efficiency of HgCdTe photodiodes in relation to the direction of illumination and to their geometry

A theoretical study of the effect of the direction of the incident light on the quantum efficiency of homogeneous HgCdTe photodiodes suitable for sensing infrared radiation in the 8-12 microns atmospheric window is presented. The probability of an excess minority carrier to reach the junction is derived as a function of its distance from the edge of the depletion region. Accordingly, the quantum efficiency of photodiodes is presented for two geometries. In the first, the light is introduced directly to the area in which it is absorbed (opaque region), while in the second, the light passes through a transparent region before it reaches the opaque region. Finally, the performance of the two types of diodes is analyzed with the objective of finding the optimal width of the absorption area. The quantum efficiency depends strongly on the way in which the light is introduced. The structure in which the radiation is absorbed following its crossing the transparent region is associated with both higher quantum efficiency and homogeneity. In addition, for absorption region widths higher than a certain minimum, the quantum efficiency in this case is insensitive to the width of the absorption region.

Rosenfeld, D.↗
NASA NTRS2008

NASA Tech Briefs, July 2008

Topics covered include: Torque Sensor Based on Tunnel-Diode Oscillator; Shaft-Angle Sensor Based on Tunnel-Diode Oscillator; Ground Facility for Vicarious Calibration of Skyborne Sensors; Optical Pressure-Temperature Sensor for a Combustion Chamber; Impact-Locator Sensor Panels; Low-Loss Waveguides for Terahertz Frequencies; MEMS/ECD Method for Making Bi(2-x)Sb(x)Te3 Thermoelectric Devices; Low-Temperature Supercapacitors; Making a Back-Illuminated Imager with Back-Side Contact and Alignment Markers; Compact, Single-Stage MMIC InP HEMT Amplifier; Nb(x)Ti(1-x)N Superconducting-Nanowire Single-Photon Detectors; Improved Sand-Compaction Method for Lost-Foam Metal Casting; Improved Probe for Evaluating Compaction of Mold Sand; Polymer-Based Composite Catholytes for Li Thin-Film Cells; Using ALD To Bond CNTs to Substrates and Matrices; Alternating-Composition Layered Ceramic Barrier Coatings; Variable-Structure Control of a Model Glider Airplane; Axial Halbach Magnetic Bearings; Compact, Non-Pneumatic Rock-Powder Samplers; Biochips Containing Arrays of Carbon-Nanotube Electrodes; Nb(x)Ti(1-x)N Superconducting-Nanowire Single-Photon Detectors; Neon as a Buffer Gas for a Mercury-Ion Clock; Miniature Incandescent Lamps as Fiber-Optic Light Sources; Bidirectional Pressure-Regulator System; and Prism Window for Optical Alignment. Single-Grid-Pair Fourier Telescope for Imaging in Hard-X Rays and gamma Rays Range-Gated Metrology with Compact Optical Head Lossless, Multi-Spectral Data Compressor for Improved Compression for Pushbroom-Typetruments.

Source record↗
NASA NTRS1992

Model scattering envelopes of young stellar objects. I - Method and application to circumstellar disks

We describe a Monte Carlo code that accurately treats multiple scattering, absorption, and polarization by dust, and use this code to calculate images of dusty disks around young stellar objects. We present some approximate analytic results that describe the behavior of the Monte Carlo calculations. A geometrically thin disk illuminated by a central T Tauri star scatters very little light at distances of many AU from the star. Viewed at any inclination, the flux scattered by such a disk at the distance to the nearest star-forming region will be overwhelmed by the stellar image. An optically thick disk that has a flaring surface may be observable, especially if viewed nearly edge-on so that the stellar source becomes occulted. An optically thin disk with a finite opening angle, similar to the one surrounding beta Pictoris, is about as observable as the typical flared optically thick disk at a similar distance from the earth. The polarization position angle is perpendicular to the disk plane in all of the models, in contrast to observations of many young stellar objects which have the position angle oriented parallel to the presumed disk plane. We suggest that the scattered light structures observed around many premain-sequence objects are dusty envelopes rather than disks.

Whitney, Barbara A.↗
NASA NTRS1999

Hardware and Methods of the Optical End-to-End Test of the Far Ultraviolet Spectroscopic Explorer (FUSE)

The Far Ultraviolet Spectroscopic Explorer (FUSE), currently being tested and scheduled for a 1999 launch, is an astrophysics satellite designed to provide high spectral resolving power (Lambda/(Delta)Lambda = 24,000-30,000) over the interval 90.5-118.7 nm. The FUSE optical path consists of four co-aligned, normal incidence, off-axis parabolic, primary mirrors which illuminate separate Rowland circle spectrograph channels equipped with holographic gratings and delay line microchannel plate detectors. We describe the hardware and methods used for the optical end-to-end test of the FUSE instrument during satellite integration and test. Cost and schedule constraints forced us to devise a simplified version of the planned optical test which occurred in parallel with satellite thermal-vacuum testing. The optical test employed a collimator assembly which consisted of four co-aligned, 15" Cassegrain telescopes which were positioned above the FUSE instrument, providing a collimated beam for each optical channel. A windowed UV light source, remotely adjustable in three axes, was mounted at the focal plane of each collimator. Problems with the UV light sources, including high F-number and window failures, were the only major difficulties encountered during the test. The test succeeded in uncovering a significant problem with the secondary structure used for the instrument closeout cavity and, furthermore, showed that the mechanical solution was successful. The hardware was also used extensively for simulations of science observations, providing both UV light for spectra and visible light for the fine error sensor camera.

Conard, Steven J.↗
NASA NTRS2011

X-Ray Illumination of the Ejecta of Supernova 1987A

When a massive star explodes as a supernova, substantial amounts of radioactive elements-primarily Ni-56, Ni-57 and Ti-44 are produced. After the initial from shock heating, the light emitted by the supernova is due to the decay of these elements. However, after decades, the energy powering a supernova remnant comes from the shock interaction between the ejecta and the surrounding medium. The transition to this phase has hitherto not been observed: supernovae occur too infrequently in the Milky Way to provide a young example, and extragalactic supernovae are generally too faint and too small. Here we report observations that show this transition in the supernova SN 1987A in the Large Magellan Cloud. From 1994 to 200l, the ejecta faded owing to radioactive decay of Ti-44 as predicted. Then the flux started to increase, more than doubling by the end of 2009. We show that this increase is the result of heat deposited by X-rays produced as the ejecta interacts with the surrounding material. In time, the X-rays will penetrate farther into the ejects, enabling us to analyse the structure and chemistry of the vanished star.

Larsson, J.↗
NASA NTRS2019

Multi-epoch Direct Imaging and Time-variable Scattered Light Morphology of the HD 163296 Protoplanetary Disk

We present H-band polarized scattered light imagery and JHK high-contrast spectroscopy of the protoplanetary disk around HD 163296 observed with the High-Contrast Coronographic Imager for Adaptive Optics (HiCIAO) and Subaru Coronagraphic Extreme Adaptive Optics (SCExAO)/Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) instruments at Subaru Observatory. The polarimetric imagery resolve a broken ring structure surrounding HD 163296 that peaks at a distance along the major axis of 0 65 (66 au) and extends out to 0 98 (100 au) along the major axis. Our 2011 H-band data exhibit clear axisymmetry, with the NW and SE side of the disk exhibiting similar intensities. Our data are clearly different from 2016 epoch H-band observations of the Very Large Telescope (VLT)/Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE), which found a strong 2.7 x asymmetry between the NW and SE side of the disk. Collectively, these results indicate the presence of time-variable, non-azimuthally symmetric illumination of the outer disk. While our SCExAO/CHARIS data are sensitive enough to recover the planet candidate identified from NIRC2 in the thermal infrared (IR), we fail to detect an object with JHK brightness nominally consistent with this object. This suggests that the candidate is either fainter in JHK bands than model predictions, possibly due to extinction from the disk or atmospheric dust/ clouds, or that it is an artifact of the data set/data processing, such as a residual speckle or partially subtracted disk feature. Assuming standard hot-start evolutionary models and a system age of 5Myr, we set new, direct mass limits for the inner (outer) Atacama Large Millimeter/submillimeter Array (ALMA)-predicted protoplanet candidate along the major (minor) disk axis of of 1.5 (2) M(J).

Evan A. Rich↗
NASA NTRS2017

Transparent Conductive Ink for Additive Manufacturing

NASA analyzes, tests, packages, and fabricates electrical, electronic, and electromechanical (EEE) parts. Nanotechnology is listed in NASA's Technology Roadmap as a key area to invest for further development.1 This research project focused on using nanotechnology to improve electroluminescent lighting in terms of additive manufacturing and to increase energy efficiency. Specifically, this project's goal was to produce a conductive but transparent printable ink that can be sprayed on any surface for use as one of the electrodes in electroluminescent device design. This innovative work is known as thick film dielectric electroluminescent (TDEL) technology. TDEL devices are used for "backlighting, illumination, and identification due to their tunable color output, scalability, and efficiency" (I.K. Small, T.D. Rolin, and A.D. Shields, "3D Printed Electroluminescent Light Panels," NASA Fiscal Year 2017 Center Innovation Fund Proposal, unpublished data, 2017). These devices use a 'front-to-back' printing method, where the substrate is the transparent layer, and the dielectric and phosphor are layered on top. This project is a first step in the process of creating a 3D printable 'back-to-front' electroluminescent device. Back-to-front 3D-printed devices are beneficial because they can be printed onto different substrates and embedded in different surfaces, and the substrate is not required to be transparent, all because the light is emitted from the top surface through the transparent conductor. Advances in this area will help further development of printing TDEL devices on an array of different surfaces. Figure 1 demonstrates the layering of the two electrodes that are aligned in a parallel plate capacitor structure (I.K. Small, T.D. Rolin, and A.D. Shields, "3D Printed Electroluminescent Light Panels," NASA Fiscal Year 2017 Center Innovation Fund Proposal, unpublished data, 2017). Voltage is applied across the device, and the subsequent electron excitation results in light emission at the top layer.

Patlan, X. J.↗
NASA NTRS2004

Novel Biomedical Device Utilizing Light-Emitting Nanostructures Developed

Sketches and chemical diagrams of state-of-the-art device and novel proposed device are presented. Current device uses a diode laser that emits into a fluorescent fluid only one wavelength and a photodetector diode that detects only one wavelength. Only one type of bacteria can be detected. The proposed device uses a quantum dot array that emits into a fluorescent fluid multiple wavelengths and an NIR 512 spectrometer that scans 0.8- to 1.7-mm wavelengths. Hundreds of different bacteria and viruses can be detected. A novel biomedical device is being developed at the NASA Glenn Research Center in cooperation with the University of Michigan. This device uses nano-structured quantum dots that emit light in the near-infrared (IR) region. The nanostructured quantum dots are used as a source and excite fluorochrome polymers coupled with antibodies that seek out and attach to specific bacteria and viruses. The fluorochrome polymers/antibodies fluoresce at specific wavelengths in the near-IR spectrum, but these wavelengths are offset from the excitation wavelength and can be detected with a tunable spectrometer. The device will be used to detect the presence of viruses and bacteria in simple fluids and eventually in more complex fluids, such as blood. Current state-of-the-art devices are limited to single bacteria or virus detection and a considerable amount of time and effort is required to prepare samples for analysis. Most importantly, the devices are quite large and cumbersome, which prohibits them from being used on the International Space Station and the space shuttles. This novel device uses nanostructured quantum dots which, through molecular beam epitaxy and highly selective annealing processes, can be developed into an illumination source that could potentially generate hundreds of specific wavelengths. As a result, this device will be able to excite hundreds of antibody/fluorochrome polymer combinations, which in turn could be used to detect hundreds of bacteria and viruses in fluids. A novel sample preparation technique that exploits micromembrane filtration and centrifugation methods has been developed for this device. The technique greatly reduces the time required to prepare the sample and the amount of sample needed to perform an accurate and comprehensive analysis. Last, and probably most important, because of the nano-light-emitting source and the novel sample preparation technique, the overall size of the device could be reduced dramatically. This device will serve as a nanoscale lab-on-a-chip for in situ microorganism detection and will enable tests to be performed on a time scale of minutes rather than days. Thus, it is ideally suited for monitoring the environmental conditions onboard the International Space Station and the space shuttles, thereby enhancing the safety of the astronauts. In addition, the device has important commercial applications, such as detecting the presence of bacteria and viruses in water at food- and beverage-processing centers, water treatment plants, and restaurants. Also, this technology has the potential to be used to detect bacteria and viruses in more complex fluids, such as blood--which in all likelihood would revolutionize blood analysis as it is performed today. This project was made possible through the Director's Discretionary Fund and is ongoing. In addition, this project provides funding to Dr. Rachel Goldman of the University of Michigan for the research and development of nanostructured quantum dots.

Scardelletti, Maximilian C.↗
NASA NTRS2010

Phase-Conjugate Receiver for Gaussian-State Quantum Illumination

An active optical sensor probes a region of free space that is engulfed in bright thermal noise to determine the presence (or absence) of a weakly reflecting target. The returned light (which is just thermal noise if no target is present, and thermal noise plus a weak reflection of the probe beam if a target is present) is measured and processed by a receiver and a decision is made on whether a target is present. It has been shown that generating an entangled pair of photons (which is a highly nonclassical state of light), using one photon as the probe beam and storing the other photon for comparison to the returned light, has superior performance to the traditional classical-light (coherent-state) target detection sensors. An entangled-photon transmitter and optimal receiver combination can yield up to a factor of 4 (i.e., 6 dB) gain in the error-probability exponent over a coherent state transmitter and optimal receiver combination, in a highly lossy and noisy scenario (when both sensors have the same number of transmitted photons). However, the receiver that achieves this advantage is not known. One structured receiver can close half of the 6-dB gap (i.e., a 3-dB improvement). It is based on phase-conjugating the returned light, then performing dual-balanced difference detection with the stored half of the entangled-photon pair. Active optical sensors are of tremendous value to NASA s missions. Although this work focuses on target detection, it can be extended to imaging (2D, 3D, hyperspectral, etc.) scenarios as well, where the image quality can be better than that offered by traditional active sensors. Although the current work is theoretical, NASA s future missions could benefit significantly from developing and demonstrating this capability. This is an optical receiver design whose components are, in principle, all implementable. However, the work is currently entirely theoretical. It is necessary to: 1. Demonstrate a bench-top proof of the theoretical principle, 2. Create an operational prototype off-the-bench, and 3. Build a practical sensor that can fly in a mission.

Erkmen, Baris I.↗
NASA NTRS1994

Use of prismatic films to control light distribution

Piping light for illumination purposes is a concept which has been around for a long time. In fact, it was the subject of an 1881 United States patent which proposed the use of mirrors inside a tube to reflect light from wall to wall down the tube. The use of conventional mirrors for this purpose, however, has not worked because mirrors do not reflect well enough. On the other hand, optical fibers composed of certain glasses or plastics are known to transport light much more efficiently. The light that enters is reflected back and forth within the walls of the fiber until it reaches the other end. This is possible by means of a principle known as 'total internal reflection'. No light escapes through the walls and very little is absorbed in the bulk of the fiber. However, while optical fibers are very efficient in transporting light, they are impractical for transporting large quantities of light. Lorne Whitehead, as a student at the University of British Columbia, recognized that prismatic materials could be used to create a 'prism light guide', a hollow structure that can efficiently transport large quantities of light. This invention is a pipe whose transparent walls are formed on the outside into precise prismatic facets. The facets are efficient total internal reflection mirrors which prevent light travelling down the guide from escaping. Very little light is absorbed by the pipe because light travels primarily in the air space within the hollow guide. And, because the guide is hollow, weight and cost factors are much more favorable than would be the case with very large solid fibers. Recent advances in precision micromachining, polymer processing, and certain other manufacturing technologies have made the development of OLF (Optical Lighting Film) possible. The process is referred to as 'microreplication' and has been found to have broad applicability in a number of diverse product areas.

Kneipp, K. G.↗
NASA NTRS1986

Effects of norflurazon, an inhibitor of carotenogenesis, on abscisic acid and xanthoxin in the caps of gravistimulated maize roots

Maize seeds were germinated in the dark in the presence of the carotenoid synthesis inhibitor norflurazon and the levels of abscisic acid, xanthoxin and total carotenoids were measured in the root cap and in the adjacent 1.5 mm segment. In norflurazon-treated roots abscisic acid levels were markedly reduced, but an increase occurred in the levels of xanthoxin, a compound structurally and physiologically similar to abscisic acid. In the cultivar of maize (Zea mays L. cv. Merit) used for this work, brief illumination of the root is required for gravitropic curving. Following illumination both control and norflurazon-treated roots showed normal gravitropic curvature; however, the rate of curvature was delayed in norflurazon-treated roots. Our data from norflurazon-treated roots are consistent with a role for xanthoxin in maize root gravitropism. The increase in xanthoxin in the presence of an inhibitor of carotenoid synthesis suggests that xanthoxin and abscisic acid originate, at least in part, via different metabolic pathways.

NASA Program Space Biology↗
NASA NTRS2016

Computational Modeling to Limit the Impact Displays and Indicator Lights Have on Habitable Volume Operational Lighting Constraints

The goal of this investigation is to determine design limitations and architectural solutions that limit the impact light from displays and indicator lamps have on the operational environment task lighting and lighting countermeasure spectrum constraints. It is concerning that this innovative architectural lighting system, could be compromised by spectrums from display systems, architectural materials, and structures that are not considered as part a full system design implementation. The introduction of many Commercial Off the Shelf (COTS) products to the spacecraft volume that contain LEDs, without consideration to the human factors and biological constraints, is another problem. Displays and indicators are a necessary part of the spacecraft and it is the goal of this research project to determine constraints and solutions that allow these systems to be integrated while minimizing how the lighting environment is modified by them. Due to the potentially broad scope of this endeavor, the project team developed constraints for the evaluation. The evaluation will be on a set of tasks that required significant exposure in the same environment while having a large chance of impacting the light spectrum the crew is expected to receive from the architectural lighting system. The team plans to use recent HRP research on "Net Habitable Volume" [1] to provide the boundary conditions for volume size. A Zemax ® lighting model was developed of a small enclosure that had high intensity overhead lighting and a standard intensity display with LED indicator arrays. The computer model demonstrated a work surface illuminated at a high level by the overhead light source compared to displays and indicators whose light is parallel to the work plane. The overhead lighting oversaturated spectral contributions from the display and indicator at the task work surface. Interestingly, when the observer looked at the displays and LEDs within the small enclosure, their spectral contribution was significant but could be reduced by reflecting overhead light from the wall(s) to the observer. Direct observation of displays and LEDs are an issue because the user's viewing area is a display, not an illuminated work surface. Since avionics command centers consume significant crew time, the tasks that seemed at higher risk for unwanted spectral contributions as an operational volume with significant quantity of displays and indicators that were either under direct observation of the crew or impacting a volume the crew may be required to sleep in.

Clark, T. E.↗
NASA NTRS2007

New Evidence for the Role of Emerging Flux in a Solar Filament's Slow Rise Preceding its CME-Producing Fast Eruption

We observe the eruption of a large-scale (approx.300,000 km) quiet-region solar filament, leading to an Earth-directed "halo" coronal mass ejection (CME). We use coronal imaging data in EUV from the EUV Imaging Telescope (EIT) on the Solar and Heliospheric Observatory (SOHO) satellite, and in soft X-rays (SXRs) from the Soft X-ray Telescope (SXT) on the Yohkoh satellite. We also use spectroscopic data from the Coronal Diagnostic Spectrometer (CDS), magnetic data from the Michelson Doppler Imager (MDI), and white-light coronal data from the Large Angle and Spectrometric Coronagraph Experiment (LASCO), all on SOHO. Initially the filament shows a slow (approx.1 km/s projected against the solar disk) and approximately constant-velocity rise for about 6 hours, before erupting rapidly, reaching a velocity of approx. 8 km/s over the next approx. 25 min. CDS Doppler data show Earth-directed filament velocities ranging from < 20 km/s (the noise limit) during the slow-rise phase, to approx. 100 km/s-1 early in the eruption. Beginning within 10 hours prior to the start of the slow rise, localized new magnetic flux emerged near one end of the filament. Near the start of and during the slow-rise phase, SXR microflaring occurred repeatedly at the flux-emergence site, in conjunction with the development of a fan of SXR illumination of the magnetic arcade over the filament. The SXR microflares, development of the SXR fan, and motion of the slow-rising filament are all consistent with "tether-weakening" reconnection occurring between the newly-emerging flux and the overlying arcade field containing the filament field. The microflares and fan structure are not prominent in EUV, and would not have been detected without the SXR data. Standard "twin dimmings" occur near the location of the filament, and "remote dimmings" and "brightenings" occur further removed from the filament.

Sterling, Alphonse C.↗