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NASA NTRS1994

The X-ray selected cataclysmic variables H0459 + 246 and H0857 - 242

We report the discovery of two cataclysmic variables located with the assistance of X-ray positions from the HEAO 1 Modulation Collimator and the Large-Area Sky Survey. Each case is distinguished by evidence of two periodic modulations that appear to represent the orbital period and the spin period of the white dwarf, respectively. The first case, H0459 + 246, has been observed optically during faint states (V approximately 16), in which there are spectral features of both an accretion disk and a K star. The light curves in the V and I bands are consistent with ellipsoidal variations in the secondary stars with a binary period of 9.952 hr. X-ray observations with EXOSAT reveal a strong pulsation with a period approximately 62 minutes. This result confirms an 'intermediate polar' classification for H0459 + 246. The pulsation is observed at 63.2 minutes in the optical I band. The long orbital period opens the possibility that H0459 + 246 is a relatively young intermediate polar that might evolve into a polar. The second case, H0857--242, shows radial velocity modulations at 1.78 hr along with photometric variations at a period approximately 49 minutes. The latter are observed only during the decay phase of dwarf nova outbursts (13 less than V less than 17), which apparently recur frequently. Given the lack of X-ray monitoring observations and the absence of proof that the 49 minute periodicity is coherent over long time-scales, we regard H0857--242 as a candidate intermediate polar. Photographic records from th e Harvard Observatory Plate Library further reveal superoutbursts for H0857--242 (V approximately 11). A bright X-ray source that is both an intermediate polar and a continually cycling dwarf nova may provide an effective means of measuring the time delay for the arrival of accreting matter at the white dwarf surface, relative to the onset of optical brightening.

Remillard, R. A.↗

DOE OSTI2022

Photovoltaic fleet degradation insights

Abstract In the PV Fleet Performance Data Initiative, high‐frequency data from commercial and utility‐scale photovoltaic (PV) systems have been collected to examine performance loss rates (PLRs) at a fleet scale. To date, performance data from more than 7.2‐gigawatt (GW) capacity, 1700 sites and 19,000 inverters—approximately equivalent to 6% to 7% of the entire US PV market—have been collected. An overall PLR of −0.75%/year was found, which is in line with historical and recent findings. Tracked silicon (Si) and cadmium telluride (CdTe) performed comparably with all fixed‐tilt systems. Higher PLRs were found for hotter temperature zones; cooler climates exhibit a median −0.48%/year loss, which increases to −0.88%/year in hotter climates. High‐efficiency module technologies showed median PLRs in line with conventional Si technologies but demonstrated markedly different PLR behavior when filtered only for low‐light conditions <600 W/m 2 . Causes for this technology‐dependent behavior are under investigation.

14 SOLAR ENERGY↗

DOE OSTI2020

Spectrally reconfigurable quantum emitters enabled by optimized fast modulation

The ability to shape photon emission facilitates strong photon-mediated interactions between disparate physical systems, thereby enabling applications in quantum information processing, simulation and communication. Spectral control in solid state platforms such as color centers, rare earth ions, and quantum dots is particularly attractive for realizing such applications on-chip. Here we propose the use of frequency-modulated optical transitions for spectral engineering of single photon emission. Using a scattering-matrix formalism, we find that a two-level system, when modulated faster than its optical lifetime, can be treated as a single-photon source with a widely reconfigurable photon spectrum that is amenable to standard numerical optimization techniques. To enable the experimental demonstration of this spectral control scheme, we investigate the Stark tuning properties of the silicon vacancy in silicon carbide, a color center with promise for optical quantum information processing technologies. We find that the silicon vacancy possesses excellent spectral stability and tuning characteristics, allowing us to probe its fast modulation regime, observe the theoretically-predicted two-photon correlations, and demonstrate spectral engineering. Our results suggest that frequency modulation is a powerful technique for the generation of new light states with unprecedented control over the spectral and temporal properties of single photons.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

NASA NTRS1993

Rapid oscillations in cataclysmic variables. IX - BG Canis Minoris (=3A 0729+103)

Results of a 10-yr photometric program on BG Canis Minoris, a novalike variable distinguished by the presence of a strictly coherent 913-s wave in its light curve, are presented. Long-term ephemerides for the orbital clock, which manifests itself through a 3.2-h light modulation, and the 913-s clock, are presented. The light curve exhibits a persistent 0.3 mag modulation at a period consistent with the 3.2-h spectroscopic period. Well-distributed timings of the orbital minima prove that the period is 0.1347486 day. It is inferred from the shape of the waveform and from the existence of X-ray dips with a sharp energy dependence that the modulation is caused by absorption. Power spectra of the nightly light curves show variable secondary features, in addition to the regular 913-s pulse. The 913-s period, presumably the first harmonic of the true white-dwarf spin period, is decreasing by 0.0022 s/yr.

Patterson, Joseph↗

DOE OSTI2023

Recycling the Energy of Indoor Light: Highly Efficient Organic Photovoltaics via a Ternary Strategy

A ternary approach in organic photovoltaics (OPV) is simple and reliable to effectively tune the optical, electrical and morphological properties of the photoactive layer for high efficiency as well as long-term stability under 1 sun. However, there have been few papers reporting spectra and weak illumination compared to outdoor light. In this study, by using two compatible 16 structures, we demonstrate a simultaneous modulation of light absorption and molecular donor polymers (PM7 and PM7 D1) with slightly-different band gaps and similar chemical packing under ambient conditions, which resulted in efficient indoor OPVs exhibiting power conversion efficiency (PCE) over 20% under 1000 lux of warm white light-emitting diode (2900 K). From morphological analysis, we infer that PM7 serves to seed nucleation of PM7 D1 in the ternary blend, templating its crystallization and alignment along the PM7 backbone. Such templating effect leads to increased domain spacing and relative degree of crystallinity (rDoC) compared to those of each binary system. We further show that higher rDoC helps suppress both bimolecular and trap-assisted recombination of photogenerated charges in the ternary devices. As a result, the complementary absorption and synergistic molecular assembly of the two donor polymers enhance the short-circuit current density as to increase the average PCEs from 9.6 to 10.3% under 1 sun and from 18.7 to 20.0% under 1000 lux. We envision that our strategy of incorporating both a planar and a flexible donor polymer with similar chemical structures can be generally applicable to attain a high performance ternary OPV under both 1 sun and indoor light.

14 SOLAR ENERGY↗

NASA NTRS1996

The 0.8 day orbit of the precataclysmic binary EUVE J1016-053

The optical counterpart of the new extreme ultraviolet source EUVE J1016-053 (=RE 1016-053) is known to show intermittent sharp Balmer and HE I emission and traces of an M dwarf associated with a white dwarf optical spectrum. We present extensive optical spectroscopy showing the emission lines vary in velocity and intensity on a period of 0d.78929 +/- 0d.00003. The phase of the emission-line strengths lags that of the velocities by 0.237 +/- 0.013 cycle, consistent with the quarter-cycle offset expected if emission arises from the side of the secondary facing the hot white dwarf. EUVE J1016-053 is another example of an extreme ultraviolet illumination-effect binary, which only recently emerged from a common-envelope phase of binary evolution. Based on spectroscopic measurements and new BVR photometry, we find that the M dwarf secondary's contribution to the combined light is smaller than previously reported, probably because of the difficulty of avoiding contamination from a third star 3".2 distant. The velocity of the weak H II absorption is in antiphase to the emission, suggesting that it originates in the white dwarf photosphere. The mass function implied by the emission-line motion is f(M) = 0.28 +/- 0.08 M solar. Assuming the He II absorption does follow the white dwarf, the mass ratio MWD/MdM is 1.8 +/- 0.5, and the gravitational redshift is 45 +/- 14 km s-1. The modulation of the emission lines suggests the inclination i > 40 degrees, but plausible masses demand this inclination be well above the value.

Non-NASA Center↗

NASA NTRS1974

MSFC Skylab Apollo Telescope Mount thermal control system mission evaluation

The Skylab Saturn Workshop Assembly was designed to expand the knowledge of manned earth orbital operations and accomplish a multitude of scientific experiments. The Apollo Telescope Mount (ATM), a module of the Skylab Saturn Workshop Assembly, was the first manned solar observatory to successfully observe, monitor, and record the structure and behavior of the sun outside the earth's atmosphere. The ATM contained eight solar telescopes that recorded solar phenomena in X-ray, ultraviolet, white light, and hydrogen alpha regions of the electromagnetic spectrum. In addition, the ATM contained the Saturn Workshop Assembly's pointing and attitude control system, a data and communication system, and a solar array/rechargeable battery power system. This document presents the overall ATM thermal design philosophy, premission and mission support activity, and the mission thermal evaluation. Emphasis is placed on premission planning and orbital performance with particular attention on problems encountered during the mission. ATM thermal performance was satisfactory throughout the mission. Although several anomalies occurred, no failure was directly attributable to a deficiency in the thermal design.

Hueter, U.↗

NASA NTRS2004

Design considerations and validation of the MSTAR absolute metrology system

Absolute metrology measures the actual distance between two optical fiducials. A number of methods have been employed, including pulsed time-of-flight, intensity-modulated optical beam, and two-color interferometry. The rms accuracy is currently limited to -5 microns. Resolving the integer number of wavelengths requires a 1-sigma range accuracy of -0.1 microns. Closing this gap has a large pay-off the range (length measurement) accuracy can be increased substantially using the unambiguous optical phase. The MSTAR sensor (Modulation Sideband Technology for Absolute Ranging) is a new system for measuring absolute distance, capable of resolving the integer cycle ambiguity of standard interferometers, and making it possible to measure distance with sub-nanometer accuracy. In this paper, we present recent experiments that use dispersed white light interferometry to independently validate the zero-point of the system. We also describe progress towards reducing the size of optics, and stabilizing the laser wavelength for operation over larger target ranges. MSTAR is a general-purpose tool for conveniently measuring length with much greater accuracy than was previously possible, and has a wide range of possible applications.

Jeganathan, Muthu↗

NASA NTRS1986

Analytical comparison of transient and steady state visual evoked cortical potentials

To better describe the linear-dynamic properties of the human visual-cortical response system, transient and steady state Visual Evoked Response Potentials (VERP) were observed. The stimulus presentation device provided both the evoking stimulus (flickering or pulsing lights) and a video task display. The steady state stimulus was modulated by a complex, ten frequency, sum-of-sines, wave. The transient VERP was the time-locked average of the EEG to a series of narrow light pulses (pulse width of 10 msec). The Fourier transform of the averaged pulses had properties that approximate band limited white noise, i.e., a flat spectrum over the frequency region spanned by the 10 summed sines. The Fourier transform of both the steady state and the transient evoked potentials resulted in transfer that are equivalent and therefore comparable. To investigate the effects of task loading on evoked potentials, a grammatical reasoning task was provided. Results support the relevancy of continued application of a systems engineering approach for describing neurosensory functioning.

Junker, A. M.↗

NASA NTRS1994

Directivity of the radio emission from the K1 dwarf star AB Doradus

We present measurements of the spectrum and polarization of the flaring radio emission from the K1 dwarf star AB Doradus, together with previously reported single frequency measurements (with no polarization information) on 3 other days. On all 4 days spanning a 6 month period, the emission was strong and, when folded with the stellar rotation period, showed similar time variations with two prominant peaks at phase 0.35 and 0.75. These peaks coincide in longitude with two large starspots identified from the stellar optical light curve and have half-powe widths as small as 0.1 rotations and no larger than 0.2 rotations. The modulated emission shows no measurable circular polarization, and its two peaks have different turnover frequencies.

Lim, Jeremy↗

NASA NTRS2015

Advanced Solid State Lighting for AES Deep Space Hab Project

The advanced Solid State Lighting (SSL) assemblies augmented 2nd generation modules under development for the Advanced Exploration Systems Deep Space Habitat in using color therapy to synchronize crew circadian rhythms. Current RGB LED technology does not produce sufficient brightness to adequately address general lighting in addition to color therapy. The intent is to address both through a mix of white and RGB LEDs designing for fully addressable alertness/relaxation levels as well as more dramatic circadian shifts.

Technology Portfolio System↗

NASA NTRS1981

The color of the fast oscillations of AH Herculis

The color of the fast coherent oscillations of AH Herculis is measured by comparing simultaneous records of the photon arrival rate in two wavelength bands, 355 + or - 30 nm and 795 + or - 80 nm. It is found that the color temperature of the coherent oscillation detected in these two wavelength bands is between 28,000 and 73,000 K. The color temperature of the nonoscillating luminosity is much lower. The arrival times of photons in these two bands have also been correlated, and it is found that the time interval between the long-wavelength coherent signal and the ultraviolet coherent signal is 0.26 + or - 0.5 sec. These results suggest that it is the surface of the white dwarf or the hot inner portion of the accretion disk which is emitting the coherent signal. The oscillations become detectably incoherent at the approach to minimum light after the outburst, as would be expected if the oscillating medium becomes more dissipative as it cools, or if there were increased modulation by clouds of obscuring material.

Hildebrand, R. H.↗

NASA NTRS2002

Swiss chard: a salad crop for the space program

Salad greens will be among the first crops grown on lunar or planetary space stations. Swiss chard (Beta vulgaris L.) is an important candidate salad crop because it is high yielding and rich in vitamins and minerals. Five Swiss chard cultivars were grown in the greenhouse under two light levels for 13 weeks to compare cumulative yields from weekly harvests, mineral composition, and to evaluate sensory attributes as a salad green. The varieties Large White Ribbed (LWR) and Lucullus (LUC) were the highest yielding in both light regimes. LWR was the shortest of the cultivars requiring the least vertical space. LWR also received the highest sensory ratings of the five cultivars. LWR Swiss chard should be considered as an initial test variety in food production modules.

NASA Discipline Life Support Systems↗

DOE OSTI2020

Artificial linear brush abrasion of coatings for photovoltaic module first-surfaces

Natural soiling and the subsequent necessary cleaning of photovoltaic (PV) modules result in abrasion damage to the cover glass. The durability of the front glass has important economic consequences, including determining the use of anti-reflective and/or anti-soiling coatings as well as the method and frequency of operational maintenance (cleaning). Artificial linear brush abrasion using Nylon 6/12 bristles was therefore examined to explore the durability of representative PV first-surfaces, i.e., the surface of a module incident to direct solar radiation. Specimens examined include silane surface functionalized-, roughened (etched)-, porous silica-coated-, fluoropolymer-coated-, and ceramic (TiO 2 or ZrO 2 /SiO 2 /ZrO 2 /SiO 2 )-coated-glass, which are compared to monolithic-poly(methyl methacrylate) and -glass coupons. Characterization methods used in this study include: optical microscopy, ultraviolet–visible–near-infrared (UV-VIS-NIR) spectroscopy, sessile drop goniometry, white-light interferometry, atomic force microscopy (AFM), and depth-profiling X-ray photoelectron spectroscopy (XPS). The corresponding characteristics examined include: surface morphology, transmittance (i.e., optical performance), surface energy (water contact angle), surface roughness, scratch width and depth, and chemical composition, respectively. The study here was performed to determine coating failure modes; identify characterization methods that can detect nascent failures; compare the durability of popular contemporary coating materials; identify their corresponding damage characteristics; and compare slurry and dry-dust abrasion. This study will also aid in developing an abrasion standard for the PV industry.

14 SOLAR ENERGY↗

NASA NTRS1980

Nonlinear optical processing with Fabry-Perot interferometers containing phase recording media

New techniques in nonlinear optical processing are explored, based on the operation of intensity level selection as performed by a Fabry-Perot interferometer containing a phase object. The image being processed is recorded on a medium between the mirrors as a spatially varying phase shift less than pi. The interferometer only transmits light through those portions of the object that corresponds to a single value of the phase and hence to a single intensity level in the input. More complicated operations such as thresholding and analog-to-digital conversion are performed by modulating the light source as the different levels are selected. Photoresist and lithium niobate have been used as phase objects, and experimental data for both are presented. Three kinds of Fabry-Perot interferometers have been used to demonstrate nonlinear processing using coherent and incoherent light. Color images have been produced with black and white inputs and white light illumination.

Bartholomew, B. J.↗

NASA NTRS1981

Rapid oscillations in cataclysmic variables. V - H2252-035, a single-sideband X-ray and optical pulsar

Photometric and spectroscopic observations of the optical counterpart of the X-ray source H2252-035 reveal the existence of stable periodicities of 3.59 hr and 14.31 min. Both radial velocity and photometric variations occur at the longer period, suggesting that it is the true orbital period of the underlying cataclysmic binary. The shorter period appears as a 10% modulation in the light curve, superposed on the 3.59 hr variation. The frequency is the lower orbital sideband of the X-ray pulsation frequency, suggesting that the optical pulses arise from reprocessing in the atmosphere of the secondary. Unlike the majority of X-ray pulsars, H2252-035 appears to contain a white dwarf rather than a neutron star.

Patterson, J.↗

NASA NTRS1979

The HEAO-A2 soft X-ray survey of cataclysmic variable stars - EX Hydrae during optical quiescence

Results are reported for HEAO A2 soft X-ray (below 2 keV) scanning observations of the southern dwarf nova EX Hya. An X-ray light curve is presented which shows no apparent orbital modulation. The best-fitting spectral parameters are derived for the source, and the observations are compared with the spectral behavior of the dwarf nova SS Cyg during optical quiescence. The results are discussed in terms of models for X-ray production by accreting white dwarfs.

Cordova, F. A.↗

NASA NTRS1995

Optical Correlation of Images With Signal-Dependent Noise Using Constrained-Modulation Filter Devices

Images with signal-dependent noise present challenges beyond those of images with additive white or colored signal-independent noise in terms of designing the optimal 4-f correlation filter that maximizes correlation-peak signal-to-noise ratio, or combinations of correlation-peak metrics. Determining the proper design becomes more difficult when the filter is to be implemented on a constrained-modulation spatial light modulator device. The design issues involved for updatable optical filters for images with signal-dependent film-grain noise and speckle noise are examined. It is shown that although design of the optimal linear filter in the Fourier domain is impossible for images with signal-dependent noise, proper nonlinear preprocessing of the images allows the application of previously developed design rules for optimal filters to be implemented on constrained-modulation devices. Thus the nonlinear preprocessing becomes necessary for correlation in optical systems with current spatial light modulator technology. These results are illustrated with computer simulations of images with signal-dependent noise correlated with binary-phase-only filters and ternary-phase-amplitude filters.

Downie, John D.↗