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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Variability in Ocean Color Associated with Phytoplankton and Terrigenous Matter: Time Series Measurements and Algorithm Development at the FRONT Site on the New England Continental Shelf

Fronts in the coastal ocean describe areas of strong horizontal gradients in both physical and biological properties associated with tidal mixing and freshwater estuarine output (e.g. Simpson, 1981 and O Donnell, 1993). Related gradients in optically important constituents mean that fronts can be observed from space as changes in ocean color as well as sea surface temperature (e.g., Dupouy et al., 1986). This research program is designed to determine which processes and optically important constituents must be considered to explain ocean color variations associated with coastal fronts on the New England continental shelf, in particular the National Ocean Partnership Program (NOPP) Front Resolving Observational Network with Telemetry (FRONT) site. This site is located at the mouth of Long Island sound and was selected after the analysis of 12 years of AVHRR data showed the region to be an area of strong frontal activity (Ullman and Cornillon, 1999). FRONT consists of a network of modem nodes that link bottom mounted Acoustic Doppler Current Profilers (ADCPs) and profiling arrays. At the center of the network is the Autonomous Vertically Profiling Plankton Observatory (AVPPO) (Thwaites et al. 1998). The AVPPO consists of buoyant sampling vehicle and a trawl-resistant bottom-mounted enclosure, which holds a winch, the vehicle (when not sampling), batteries, and controller. Three sampling systems are present on the vehicle, a video plankton recorder, a CTD with accessory sensors, and a suite of bio-optical sensors including Satlantic OCI-200 and OCR-200 spectral radiometers and a WetLabs ac-9 dual path absorption and attenuation meter. At preprogrammed times the vehicle is released, floats to the surface, and is then winched back into the enclosure with power and data connection maintained through the winch cable. Communication to shore is possible through a bottom cable and nearby surface telemetry buoy, equipped with a mobile modem, giving the capability for near-real time data transmission and interactive sampling control.

Morrison, John R.↗
NASA NTRS2018

Historical and Contemporary Trends in the Size, Drift, and Color of Jupiter's Great Red Spot

Observations of Jupiter's Great Red Spot (GRS) span more than 150 years. This allows for careful measurements of its size and drift rate. High spatial resolution spacecraft data also allow tracking of its spectral characteristics and internal dynamics and structure. The GRS continues to shrink in longitudinal length at an approximately linear rate of 0 deg .194 yr(exp −1) and in latitudinal width at 0 deg .048 yr (exp −1). Its westward drift rate (relative to System III W. longitude) has increased from approx. 0 deg .26/day in the 1980s to approx. 0 deg .36/day currently. Since 2014, the GRS's short wavelength (less than 650 nm) reflectance has continued to decrease, while it has become brighter at 890 nm, indicating a change in clouds/haze at high altitudes. In addition, its north–south color asymmetry has decreased, and the dark core has become smaller. Internal velocities have increased on its east and west edges, and decreased on the north and south, resulting in decreased relative vorticity and circulation. The GRS's color changes from 2014 to 2017 may be explained by changes in stretching vorticity or divergence acting to balance the decrease in relative vorticity.

Simon, Amy A.↗
NASA NTRS1992

Mars: A reassessment of its interest to biology

Of all the planets in the solar system, Mars is certainly the one that has inspired the most speculation concerning extraterrestrial life. Observers had long ago noticed that Mars exhibits changes in its polar caps and alterations in its surface coloration that parallel seasonal changes on Earth. The fascination with Mars and the possibility of life on Mars continued into the spacecraft era and was directly expressed in the Viking Missions. These highly successful missions had the search for life on Mars as one of their principal goals. A review of Viking Missions experiments is presented. Results of these investigations are summarized. While the Viking Missions returned a negative answer to the question of life on Mars, they also showed that many years ago Mars was a very different place and enjoyed conditions that may have been conducive to the origin of life - life that may have long since become extinct. Evidence for the existence of water on Mars in the past is presented. Techniques used to study early life on Earth, which may also be used for similar studies on Mars, are described.

Mckay, Christopher P.↗
NASA NTRS2010

Colorimetric Solid Phase Extraction (CSPE): Using Color to Monitor Spacecraft Water Quality

In August 2009, an experimental water quality monitoring kit based on Colorimetric Solid Phase Extraction (CSPE) technology was delivered to the International Space Station (ISS). The kit, called the Colorimetric Water Quality Monitoring Kit (CWQMK), was launched as a Station Development Test Objective (SDTO) experiment to evaluate the suitability of CSPE technology for routine use monitoring water quality on the ISS. CSPE is a sorption-spectrophotometric technique that combines colorimetric reagents, solid-phase extraction, and diffuse reflectance spectroscopy to quantify trace analytes in water samples. In CSPE, a known volume of sample is metered through a membrane disk that has been impregnated with an analyte-specific colorimetric reagent and any additives required to optimize the formation of the analyte-reagent complex. As the sample flows through the membrane disk, the target analyte is selectively extracted, concentrated, and complexed. Formation of the analyte-reagent complex causes a detectable change in the color of the membrane disk that is proportional to the amount of analyte present in the sample. The analyte is then quantified by measuring the color of the membrane disk surface using a hand-held diffuse reflectance spectrophotometer (DRS). The CWQMK provides the capability to measure the ionic silver (Ag +) and molecular iodine (I2) in water samples on-orbit. These analytes were selected for the evaluation of CSPE technology because they are the biocides used in the potable water storage and distribution systems on the ISS. Biocides are added to the potable water systems on spacecraft to inhibit microbial growth. On the United States (US) segment of the ISS molecular iodine serves as the biocide, while the Russian space agency utilizes silver as a biocide in their systems. In both cases, the biocides must be maintained at a level sufficient to control bacterial growth, but low enough to avoid any negative effects on crew health. For example, the presence of high levels of iodine in water can cause taste and odor issues that result in decreased water consumption by the crew. There are also concerns about potential impacts on thyroid function following exposure to high levels of iodine. With silver, there is a risk of developing argyria, an irreversible blue-gray discoloration of the skin, associated with long term consumption of water containing high concentrations of silver. The need to ensure that safe, effective levels of biocide are maintained in the potable water systems on the ISS provides a perfect platform for evaluating the suitability of CSPE technology for in-flight water quality monitoring. This paper provides an overview of CSPE technology and details on the silver and iodine methods used in the CWQMK. It also reports results obtained during in-flight analyses performed with the CWQMK and briefly discusses other potential applications for CSPE technology in both the spacecraft and terrestrial environments.

Gazda, Daniel B.↗
DOE OSTI2020

Cover Feature: Rational Design of a Uranyl Metal–Organic Framework for the Capture and Colorimetric Detection of Organic Dyes (Chem. Eur. J. 61/2020)

A new uranyl containing metal–organic framework was prepared and the diffraction data reveals the structure consists of interpenetrating 3D nets with a 4,3-connected tbo topology. Furthermore, each net contains large 22.8 Å pores and is constructed from monomeric, hexagonal bipyramidal uranyl nodes that are joined by 1,2,4,5-tetrakis(4-carboxyphenyl)benzene ligands. The crystalline material is stable in aqueous media and due to the large void space (constituting 76% of the unit cell by volume) can sequester organic dyes, the uptake of which induces a visible change to the color of the material.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1972

Lunar dust and radiation darkening of Surveyor 3 surfaces

Measured spectral reflectance, evidence obtained from photographs, scanning electron microscopy, and previous work on Surveyor hardware were used to develop an understanding of the observed discoloration and its meaning to future space and lunar operations. Measured reflectance data were analyzed to separate and understand the effects of lunar dust and radiation damage. It was concluded that organic contamination is not a major contributor to the discoloration. Radiation-induced discoloration on the various surfaces was found to be proportional to the degree of solar illumination. Photobleaching of the radiation damage was observed and was responsible for a gradual change in the color of the camera's surface during the evaluation.

Carroll, W. F.↗
NASA NTRS1973

In situ spectroradiometric quantification of ERTS data

The author has identified the following significant results. A multispectral photo analysis of the Willcox Playa was also made using ERTS imagery on three consecutive overpasses. The results of the analysis showed that a time sequential multispectral color presentation relates color to environmental changes as a function of time, rather than spectral changes for any single date. Since the primary mission of ERTS is to detect changes in the environment, it is believed that this mode of data reduction would be employed further in conjunction with the conventional techniques.

Yost, E.↗
NASA NTRS1976

The Corralitos Observatory program for the detection of lunar transient phenomena

This is a final report on the establishment, observing procedures, and observational results of a survey program for the detection of lunar transient phenomena (LTP's) by electro-optical image conversion means. For survey, a unique detection system with an image orthicon was used as the primary element in conjunction with a 24-in. f/20 Cassegrainian telescope. Observations in three spectral ranges, with 6,466 man-hours of observing, were actually performed during the period from October 27, 1965, to April 26, 1972. Within this entire period, no color or feature change within the detection capabilities of the instrumentation was observed, either independently or in follow up of amateur LTP reports, with the exception of one general bluing and several localized bluings (probably ascribable to the effects of the terrestrial atmosphere) that were observed solely by the Corralitos system. A table is presented indicating amateur and professional reports of LTP's and the results of efforts to confirm these reports through the Corralitos system.

Hynek, J. A.↗
NASA NTRS1975

Differences in visible and near-infrared light reflectance between orange fruit and leaves

The objective was to find the best time during the season (April 26, 1972 to January 8, 1973) to distinguish orange fruit from leaves by spectrophotometrically determining at 10-day intervals when the difference in visible (550- and 650-nm wavelengths) and near-infrared (850-nm wavelength) light reflectance between fruit and nearby leaves was largest. December 5 to January 8 was the best time to distinguish fruit from leaves. During this period the fruit's color was rapidly changing from green to yellow, and the difference in visible light reflectance between fruit and leaves was largest. The difference in near-infrared reflectance between leaves and fruit remained essentially constant during ripening when the difference in visible light reflectance between leaves and fruit was largest.

Gausman, H. W.↗
NASA NTRS1991

Astrometry using the Hubble Space Telescope fine guidance sensors

Plans for the use of the three fine guidance sensors (FGSs) of the NASA Hubble Space Telescope for direct astrometric observations are reviewed. Topics addressed include the optical elements and detectors of the FGSs, the basic and astrometric operating modes of the FGSs, spacecraft pointing control during astrometric observations, and the astrometric data-reduction software provided to HST users. Particular attention is given to the calibration procedures for optical-field angle distortion, the plate scale, filter-wedge errors, lateral color effects, secular changes, velocity aberration, and transfer function. Also discussed are the steps being taken to verify the HST orbit. It is pointed out that the performance of the interferometric FGSs should not be affected by the focusing problems of the main HST instrument.

Duncombe, Raynor L.↗
NASA NTRS1993

Microbiological and corrosion analysis of three urine pretreatment regimes with titanium 6A1-4V

One objective of the water recovery test (WRT) performed at NASA's Marshall Space Flight Center (MSFC) for the environmental control and life support systems (ECLSS) of Space Station Freedom is to determine the ability of the water recovery system to reclaim urine for crew reuse. In the process, raw urine is pretreated using a commercially available oxidant, Oxone (Dupont), and sulfuric acid (to reduce ammonia), and pumped into a urine processing subsystem. A combination of sodium hypochlorite and sulfuric acid were also considered as an alternative pretreatment. The ability of these pretreatments, plus a third pretreatment of ozone, to reduce microbial levels in urine generated during testing of the water recovery system at MSFC was examined. In addition, the corrosion rate of weld and base metal specimens of titanium 6A1-4V, a candidate material for the water system of Space Station Freedom, was monitored in the presence of these pretreatments. Specimen surfaces were examined at completion of the 21-day test using scanning electron microscopy. Change in pH, color, turbidity, and odor were recorded over the course of the test.

Huff, Timothy L.↗
NASA NTRS1992

Ultraviolet Imaging Telescope ultraviolet images - Large-scale structure, H II regions, and extinction in M81

The study employs UV images of M81 obtained by the Ultraviolet Imaging Telescope (UIT) during the December 1990 Astro-1 spacelab mission to determine 2490- and 1520-A fluxes from 46 H II regions and global surface brightness profiles. Comparison photometry in the V band is obtained from a ground-based CCD image. UV radial profiles show bulge and exponential disk components, with a local decrease in disk surface brightness inside the inner Lindblad Resonance about 4 arcmin from the nucleus. The V profile shows typical bulge plus exponential disk structure, with no local maximum in the disk. There is little change of UV color across the disk, although there is a strong gradient in the bulge. Observed m152-V colors of the H II regions are consistent with model spectra for young clusters, after dereddening using Av determined from m249-V and the Galactic extinction curve. The value of Av, so determined, is 0.4 mag greater on the average than Av derived from radio continuum and H-alpha fluxes.

Hill, Jesse K.↗
NASA NTRS1952

Velocity of action of oxygen, hydrogen sulfide, and halogens on metals

This report discusses a method of determining the rate of surface oxidation of a metal by the change in the color of the surface film produced by reactions with oxygen, chlorine, or iodine. The metals studied included iron, nickel, copper, zinc, cadmium, tin, lead, cobalt, and manganese. Tables are given for surface film thickness versus color for various times.

TIN↗
NASA NTRS1993

Microbiological test results using three urine pretreatment regimes with 316L stainless steel

Three urine pretreatments, (1) Oxone (Dupont) and sulfuric acid, (2) sodium hypochlorite and sulfuric acid, (3) and ozone, were studied for their ability to reduce microbial levels in urine and minimize surface attachment to 316L stainless steel coupons. Urine samples inoculated with Bacillus insolitus and a filamentous mold, organisms previously recovered from the vapor compression distillation subsystem of NASA Space Station Freedom water recovery test were tested in glass corrosion cells containing base or weld metal coupons. Microbial levels, changes in pH, color, turbidity, and odor of the fluid were monitored over the course of the 21-day test. Specimen surfaces were examined by scanning electron microscopy at completion of the test for microbial attachment. Ozonated urine samples were less turbid and had lower microbial levels than controls or samples receiving other pretreatments. Base metal coupons receiving pretreatment were relatively free of attached bacteria. However, well-developed biofilms were found in the heat-affected regions of welded coupons receiving Oxone and hypochlorite pretreatments. Few bacteria were observed in the same regions of the ozone pretreatment sample.

Huff, Timothy L.↗
NASA NTRS1997

Mid-IR Spectra Herbig Ae/Be Stars

Herbig Ae/Be stars are intermediate mass pre-main sequence stars, the higher mass analogues to the T Tauri stars. Because of their higher mass, they are expected form more rapidly than the T Tauri stars. Whether the Herbig Ae/Be stars accrete only from collapsing infalling envelopes or whether accrete through geometrically flattened viscous accretion disks is of current debate. When the Herbig Ae/Be stars reach the main sequence they form a class called Vega-like stars which are known from their IR excesses to have debris disks, such as the famous beta Pictoris. The evolutionary scenario between the pre-main sequence Herbig Ae/Be stars and the main sequence Vega-like stars is not yet revealed and it bears on the possibility of the presence of Habitable Zone planets around the A stars. Photometric studies of Herbig Ae/Be stars have revealed that most are variable in the optical, and a subset of stars show non-periodic drops of about 2 magnitudes. These drops in visible light are accompanied by changes in their colors: at first the starlight becomes reddened, and then it becomes bluer, the polarization goes from less than 0.1 % to roughly 1% during these minima. The theory postulated by V. Grinnin is that large cometary bodies on highly eccentric orbits occult the star on their way to being sublimed, for systems that are viewed edge-on. This theory is one of several controversial theories about the nature of Herbig Ae/Be stars. A 5 year mid-IR spectrophotometric monitoring campaign was begun by Wooden and Butner in 1992 to look for correlations between the variations in visible photometry and mid-IR dust emission features. Generally the approximately 20 stars that have been observed by the NASA Ames HIFOGS spectrometer have been steady at 10 microns. There are a handful, however, that have shown variable mid-IR spectra, with 2 showing variations in both the continuum and features anti-correlated with visual photometry, and 3 showing variations in the emission features only while the continuum level remained unchanged. The first 2 stars mentioned probably have reprocessing envelopes. The other 3 stars gives important clues to the controversy over the geometry of the gas and dust around these pre-main sequence stars: the steady underlying 10 microns continuum and variable features indicates that an optically thick continuum probably arising from an accretion disk is decoupled from the optically thin emission features which may arise in a disk atmosphere. Bernadette Rodgers has joined this monitoring campaign in the near-IR using GRIMII with the goal of detecting variations in the hot dust continuum and the gas density in the dense accretion region close to these stars.

Wooden, Diane↗
NASA NTRS2008

Solid-State Lighting Module (SSLM)

The project's goal was to build a light-emitting-diode (LED)-based light fixture that is identical in fit, form, and function to the existing International Space Station (ISS) General Luminaire Assembly (GLA) light fixture and fly it on the ISS in early FY 2008 as a Station Detailed Test Objective (SDTO). Our design offers the following strengths: proven component hardware: Our design uses components flown in other KSC-developed hardware; heat path thermal pad: LED array heat is transferred from the circuit board by silicon pad, negating the need for a cooling fan; variable colorimetry: The output light color can be changed by inserting different LED combinations.

Source record↗
NASA NTRS2012

Electron Beam Induced Luminescence of SiO2 Optical Coatings

Optical coatings of disordered thin film SiO,/SiO, samples undergoing electron beam bombardment exhibited a cathodoluminescence effect. Measurements were made of the absolute illuminance and emission spectra as functions of incident electron energy (0.2 keV to 30 keV). flux (approx. 0.1 nA/sq cm to > 100 nA/sq cm) and power (<50 nW/sq cm to > 3mW/sq cm) for coatings (approx.60 nm to approx.200 nm thick) on reflective metal substrates over a range of sample temperatures (approx.40 K to approx.400 K) and emission wavelengths (approx.260 nm to approx.5000 nm). Illuminance reached a plateau saturation intensity I(sub sat) approx. 10(exp -4)W/sq cm. scaling as [I(sub mc)/(I + I(sub mc)/I(sub sat)] as incident power I(sub mc) approached I(sub sat). Well below I(sub sat), illuminance scaled linearly with incident power for lower-energy non-penetrating radiation that deposited all of its energy in the dielectric film. At higher incident energies (> 1-5 keV) electrons penetrate the dielectric, depositing only a fraction of their energy in the dielectric film, where deposited energy scales as the ratio of film thickness to penetration range. Since electron range exhibits a peak below approx. 1 keV, the illuminance decreased with increasing energy for penetrating radiation. The temperature dependence of the illuminance. in general, increased with decreasing temperature. Changes in apparent color with temperature were also observed. Four bands in the UV/VIS/NIR range from 300 nm to 1000 nm were observed in spectral measurements; no significant luminescence was detected in a range from approx. 1000 nm to approx. 5000 nm. These different bands either increased or decreased in intensity and shifted slightly in energy with decreasing temperature. Our measurements are explained in terms of simple disordered band theory models based on atomic-scale stochastic transport of electrons in highly disordered insulating materials. The theoretical models provide a fundamental basis for understanding the dependence of cathodoluminescence on irradiation time, incident flux and energy. and sample thickness and temperature. The observed luminescence occurs when an incident high energy electron excites a valence band electron into the conduction band. Following the excitation. a complex series of transitions take place between the extended conduction states and the long-lived localized trapped states (or chromophores) associated with structural or compositional defects in the dielectric materials. Thc transport equations and models of thc spatial and energy distribution of the trapped states below the mobility edge, their occupancy, and transitions provide microscopic scale insights into this macroscopic phenomenon. Our observations and theoretical models are also compared with similar previous room temperature studies of similar SiO2 films.

Dennison, J. R.↗