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At least 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Thermal Control Surfaces Experiment (TCSE) materials analysis

Materials on the Thermal Control Surfaces Experiment (TCSE) underwent changes in their properties during the 5.8 years of exposure to the combined space environment. The analysis of these materials is continuing and current results are discussed. Some materials were significantly degraded such as silver Teflon, S13GLO, and Z302; while others such as Z93 and YB71 were stable. Time dependent flight data is provided, along with preflight and postflight measurements. Results are compared with other experiments, demonstrating the atomic oxygen (AO) ram effect. Atomic oxygen texturing of silver Teflon varies with incident angle. Even indirect exposure to atomic oxygen appears to be involved with surface texturing on the interior of the TCSE. Localized contamination occurred at discrete locations both inside and on exterior surfaces. Most of the visible deposits were the result of the classical photo-enhanced contamination deposition. The synergism of combined space environmental effects is demonstrated by the specific localization of contamination caused by photo-enhanced deposition versus AO removal. Optical degradation measurements of these contaminated areas, utilizing a new portable reflectometer, are presented.

Wilkes, Donald R.↗
NASA NTRS1996

Automated Telerobotic Inspection Of Surfaces

Method of automated telerobotic inspection of surfaces undergoing development. Apparatus implementing method includes video camera that scans over surfaces to be inspected, in manner of mine detector. Images of surfaces compared with reference images to detect flaws. Developed for inspecting external structures of Space Station Freedom for damage from micrometeorites and debris from prior artificial satellites. On Earth, applied to inspection for damage, missing parts, contamination, and/or corrosion on interior surfaces of pipes or exterior surfaces of bridges, towers, aircraft, and ships.

Balaram, J.↗
NASA NTRS1993

Proposal for a Universal Particle Detector Experiment

The Universal Particle Detector Experiment (UPDE), which consists of parallel planes of two diode laser beams of different wavelengths and a large surface metal oxide semiconductor (MOS) impact detector, is proposed. It will be used to perform real-time monitoring of contamination particles and meteoroids impacting the spacecraft surface with high resolution of time, position, direction, and velocity. The UPDE will discriminate between contaminants and meteoroids, and will determine their velocity and size distribution around the spacecraft environment. With two different color diode lasers, the contaminant and meteroid composition will also be determined based on laboratory calibration with different materials. Secondary particles dislodged from the top aluminum surface of the MOS detector will also be measured to determine the kinetic energy losses during energetic meteoroid impacts. The velocity range of this instrument is 0.1 m/s to more than 14 km/s, while its size sensitivity is from 0.2 microns to millimeter-sized particles. The particulate measurements in space of the kind proposed will be the first simultaneous multipurpose particulate experiment that includes velocities from very slow to hypervelocities, sizes from submicrometer- to pellet-sized diameters, chemical analysis of the particulate composition, and measurements of the kinetic energy losses after energetic impacts of meteroids. The experiment will provide contamination particles and orbital debris data that are critically needed for our present understanding of the space environment. The data will also be used to validate contamination and orbital debris models for predicting optimal configuration of future space sensors and for understanding their effects on sensitive surfaces such as mirrors, lenses, paints, and thermal blankets.

Lesho, J. C.↗
NASA NTRS1984

Physical Properties of the Uranian Satellites

Recent work on the satellites of Uranus revealed many of their basic physical properties. Radiometric measurements showed that the Ariel, Umbriel, Titania and Oberon have diameters which range from 1630 to 1110 km and albedos which range from 0.30 to 0.18. Spectrophotometric observations of Miranda suggest that it may have the highest albedo of the known Uranian satellites and a diameter of about 500 km. Near-infrared measurements show that Ariel, Titania and Oberon have the largest known opposition surges. All five known satellites of Uranus have surfaces which are composed of water ice contaminated with small amounts of dark material. The dark material on the surfaces of Ariel, Umbriel, Titania and Oberon is spectrally bland and has spectral similarities to carbon black, charcoal, carbonaceous chondritic material and other dark, spectrally neutral materials. Recent density determinations suggest that there may be large density differences among Ariel, Umbriel, Titania and Oberon, with density increasing with distance from Uranus.

Brown, R. H.↗
NASA NTRS1987

Design considerations for long-lived glass mirrors for space

Large mirrors intended for long-term operation in orbital space will have to retain high reflectance in the presence of contamination or destruction by high-energy particles, meteorites, and orbiting debris. These conditions require the use of low-energy outer surfaces that resist the buildup of contamination, the use of small mirror segments that restrict local damage and facilitate replacement, and the use of surface coatings that minimize the effects of atomic oxygen and/or charge buildup. The present recommendations are based on experience accumulated with terrestrial solar-concentrator mirror materials.

Bouquet, Frank L.↗
DOE OSTI2020

Functionalized Magnetic Nanoparticles for Technetium Sequestration from Groundwater

Technetium 99 (Tc) is among the most common environmental contaminants at DOE sites and one of the most common risk drivers in low- and high-level waste disposal sites. The majority of Tc is generated from anthropogenic sources, such as nuclear power plants, global weapons, nuclear storage facilities and medical applications. Through these sources, Tc contamination has been unintentionally introduced in to the environment. The most common chemical form of Tc is Tc(VII)O{sub 4}{sup -}. Due to its high solubility and mobility, Tc can enter the food chain and cause adverse health effects to humans. Currently, ion exchange resins and reduction processes are the most common approaches for Tc immobilization. Although these techniques have shown to be effective, they also possess major drawbacks, such as high cost, low adsorption capacity, and complex creation and maintenance. Therefore, development of more efficient and simple technologies for the remediation of Tc-contaminated systems are needed. Functionalized magnetic nanoparticles have been used to remove organic and inorganic contaminants from water resources. These nanoparticles have attracted extensive attention as an adsorbent material due to their large surface area, high efficiency, low-cost, easy functionalization and separation with a magnet. This study seek to develop functionalized magnetic iron oxide nanoparticles for the efficient removal of Tc and other heavy metal contaminants from water resources under ambient conditions. Objectives: Synthesize magnetic iron oxide nanoparticles and functionalize their surface with Cetyltrimethylammonium Bromide (CTAB) and tetraethyl-orthosilicate (TEOS). Characterize the synthesized nanoparticles using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), Dynamic Light Scattering (DLS) and Zeta PALS. Perform adsorption studies to evaluate their adsorption behavior and capacity for (a) Technetium using Rhenium (ReO{sub 4}{sup -}) as a surrogate and (b) heavy metals, e.g. Cu{sup 2+}. Conclusions: Magnetic iron oxide nanoparticles were successfully functionalized with CTAB and TEOS. The functionalization of the iron oxide nanoparticles affects their surface charge and their hydrodynamic diameter. The addition of CTAB or TEOS decreased the hydrodynamic diameter of the nanoparticles due to repulsive and steric forces. The SEM micrographs show spherical nanoparticles of different sizes. The EDX analysis shows the presence of iron and oxygen from the iron oxide crystalline structure, and the different constituents of the CTAB and TEOS molecules. Proof-of-concept shows the successful adsorption of rhenium (ReO{sub 4}{sup -}) and copper Cu{sup 2+}) onto CTAB-Fe{sub 2}O{sub 3} and TEOS-Fe{sub 2}O{sub 3} respectively.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1986

Report on holographic tests at S-band and K-band on the DSS-63 64 metre antenna

High resolution holographic tests were carried out on DSS-63 at S-band and K-band during May l985. These tests followed a mechanical retrofit which involved the addition of structural bracing to the backing structure. Geosynchronous satellite beacons were used as sources for the tests. At a resolution of 0.4m the S-band and K-band tests revealed rms deviations of the surface to be 2.73mm and 1.53mm, respectively. The difference between these two results is thought to be due mainly to contamination of the S-band surface error map by expected and generally predictable subreflector diffraction effects. The S-band map is also known to be contaminated by diffraction from the subreflector support struts and has a higher noise level than the K-band map. A list of corrections to be applied to the reflector panels is derived from the K-band map. These corrections are predicted to reduce the rms deviation from 1.53mm to 0.86mm at 0.4m resolution. Comparison with results obtained before the mechanical retrofit suggests the major effect of the added structural bracing to be reduction of a third order deformation of the reflector about its axis.

Godwin, M. P.↗
NASA NTRS1985

Evaluation of thermal control surface on-orbit servicing methods for long term missions

Future activities of NASA will include the long-term (10 - 30 years) operation of space vehicles. For this reason, there will be an urgent need to provide the basic technology for space vehicle thermal control surfaces and their functional maintenance for future long-term missions. One of the problems arising in connection with such missions is related to contamination which can degrade operational design parameters of critical and thermal control surfaces. All Space Based Payloads will arrive on orbit with a certain level of contamination from ground handling, and, on orbit, will be subjected to some level of contamination over their mission life. For the extension of mission life, it appears practical to institute surface refurbishment procedures for contaminated and degraded surfaces. Potential resurfacing methods are evaluated, taking into account three potential processes. The most promising of these is a cleaning procedure based on the utilization of atomic oxygen.

Saylor, W.↗
NASA NTRS1989

Space station contamination modeling

Current plans for the operation of Space Station Freedom allow the orbit to decay to approximately an altitude of 200 km before reboosting to approximately 450 km. The Space Station will encounter dramatically increasing ambient and induced environmental effects as the orbit decays. Unfortunately, Shuttle docking, which has been of concern as a high contamination period, will likely occur during the time when the station is in the lowest orbit. The combination of ambient and induced environments along with the presence of the docked Shuttle could cause very severe contamination conditions at the lower orbital altitudes prior to Space Station reboost. The purpose here is to determine the effects on the induced external environment of Space Station Freedom with regard to the proposed changes in altitude. The change in the induced environment will be manifest in several parameters. The ambient density buildup in front of ram facing surfaces will change. The source of such contaminants can be outgassing/offgassing surfaces, leakage from the pressurized modules or experiments, purposeful venting, and thruster firings. The third induced environment parameter with altitude dependence is the glow. In order to determine the altitude dependence of the induced environment parameters, researchers used the integrated Spacecraft Environment Model (ISEM) which was developed for Marshall Space Flight Center. The analysis required numerous ISEM runs. The assumptions and limitations for the ISEM runs are described.

Gordon, T. D.↗
NASA NTRS1972

High resolution measures of polarization and color of selected lunar areas

High resolution observations of intensity, color (UBV) and polarization were obtained with scanning techniques for a number of lunar areas of special interest, including boundaries of some of the brightest and darkest lunar regions, certain Apollo landing sites and prominent craters. Two dimensional raster scans of colors were obtained for Alphonsus, Aristarchus, and Herodotus. The degree of polarization for any given phase angle appears to be roughly indicative of age. The darker younger mare surface are more highly polarized than the lighter and older mare surfaces, which appear to be more contaminated by lighter material from the highlands or by ray material thrown out from fresh craters. All mare surfaces are more highly polarized than the still older and lighter terra regions surrounding the maria. The very oldest craters are either dark-floored and show polarization characteristics similar to those of the mare surfaces, or if located in the highlands, they are less and less distinguishable from the highland background with greater age, and show the general highland polarization characteristics.

Riley, L. A.↗
DOE OSTI2020

Evaluating Remediation Options for a Perched-Water Unit at the Hanford Site - 20378

At the U.S. Department of Energy's Hanford Site, liquid-phase waste was discharged using surface disposal features such as ponds, trenches, and cribs. These practices distributed contaminants in the subsurface, some of which are currently in the vadose zone above the groundwater. At the 200-DV-1 operable unit (OU) at the Hanford Site, a key feature is a perched-water zone. This perched-water zone contains several million liters of water contaminated with high concentrations of uranium, technetium-99 (Tc-99), and nitrate that serves as a continuing source of contamination to the underlying aquifer. Currently, a pumping system is used to remove contaminant mass from the perched-water zone. However, water extraction will become more challenging as the perched unit dewaters. As a result, residual contaminants remaining after pumping is no longer effective needs to be addressed with post-extraction mitigation approaches, appropriate monitoring, and selection of suitable remediation endpoints. Thus, a remedy evaluation needs to include the unique conditions of this perched-water zone. As part of the initial evaluation, a set of technologies have been preliminarily identified as potentially applicable to the perched-water zone, including in situ remediation technologies to sequester uranium and Tc-99 and to degrade nitrate. While there is sufficient information available for direct consideration of some of the reviewed technologies in a feasibility study, five in situ remediation technologies were identified as needing additional information on their effectiveness under the geochemical and contaminant conditions of the perched-water zone. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1985

Elimination of directional wave spectrum contamination from noise in elevation measurements

The Surface Contour Radar (SCR) is a 36-GHz computer-controlled airborne radar which generates a false-color-coded elevation map of the sea surface below the aircraft in real time, and can routinely produce ocean directional wave spectra with post-flight data processing which have much higher angular resolution than pitch-and-roll buoys. The SCR range measurements are not error-free and the resulting errors in the elevations corrupt the directional wave spectrum. This paper presents a technique for eliminating that contamination.

Walsh, E. J.↗
NASA NTRS1992

Qualification of the gritblast assembly and process for the inside diameter of the RSRM forward and aft domes

This gritblast assembly shall be used when refurbishing the Inside Diameter (ID) of RSRM forward and aft domes. Initial blasting is used to remove corrosion and adhesive not removed during the insulation washout. Final blasting is conducted just prior to part finalization in order to remove residual contamination and prepare the ID surface for bonding. The media used in this gritblaster is DuPont Zirclean Blasting Abrasive. It is possible to use other media in this gritblast assembly, however the only facility that has the control capability for this assembly is the Zirclean blast booth. This blast booth can not use other media without the occurrence of contamination. This automated process shall replace the manually controlled gritblasting that is currently in operation. Manual gritblasting does not provide the consistency, control, and safety that an automated process is capable of delivering.

Nolan, Michael J.↗
NASA NTRS2010

Investigating the Performance of the Jason-2/OSTM Radar Altimeter Over Lakes and Reservoirs

Many inland water investigations utilize archival and near-real time radar altimetry data to enable observation of the variation in surface water level. A multi-altimeter approach allows a more global outlook with improved spatial resolution, and combined long-term observations improve statistical analyses. Central to all programs is a performance assessment of each instrument. Here, we focus on data quantity and quality pertaining to the Poseidon-3 radar altimeter onboard the Jason-2/OSTM satellite.Utilizing an interim data set (IGDR), studies show that the new on-board DIODE/median and DIODE/DEM tracking modes are performing well, acquiring and maintaining the majority of lake and reservoir surfaces in varying terrains. The 20-Hz along-track resolution of the data, and particularly the availability of the range output from the ice-retracker algorithm, also improves the number of valid height measurements. Based on test-case lakes and reservoirs, output from the ice-retracker algorithm is also seen to have a clear advantage over the ocean-retracker having better height stability across calm and icy surfaces, a greater ability to gain coastline waters, and less sensitivity to loss of water surface when there is island contamination in the radar echo. Such on-board tracking and postprocessing retracking enables the lake waters to be quickly gained after coastline crossing. Values can range from <0.1 s to 2.5 s, but the majority of measurements are obtained in less than 0.4 s or <2.3 km from the coast. Validation exercises reveal that targets of 150 km2 surface area and 0.8 km width are able to be monitored offering greater potential to acquire lakes in the 100 C300 km2 size-category. Time series of height variations are also found to be accurate to 3 to 33 cm rms depending on target size and the presence of winter ice. These findings are an improvement over the IGDR/GDR results from the predecessor Jason-1 and TOPEX/Poseidon missions and can satisfy the accuracy requirements of both the science-related and operational lake study programs.

Birkett, C. M.↗
DOE OSTI2023

Alteration of the Cesium-137 soil profile by wild boar rooting after the Fukushima Daiichi Nuclear Power Plant accident

Large amounts of Cesium-137 ( 137 Cs, physical half-life ca. 30 years) were released into the environment from the 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in Japan. Initially contaminants from the accident were deposited on the surface soil layers in terrestrial ecosystems, but over time vertical migration of 137 Cs has occurred, with most 137 Cs now distributed a few centimeters below the soil surface. Wild boar (Sus scrofa) rooting likely alters the distribution of contaminants in soil profiles. Such impacts may be particularly pronounced in areas contaminated from the FDNPP accident, given the increase in abundance of wild boar in these areas. Our objective was to determine whether rooting by wild boar alters the distribution of 137 Cs contamination within soil profiles through collection of soil cores from control sites and two different types of rooting samples, “new depressions” and “old depressions” within the difficult-to-return zone surrounding the FDNPP. The 137 Cs ratio [activity concentration of 137 Cs at each depth / the maximum activity concentration of 137 Cs in each core sample] rapidly decreased after reaching a peak at the control sites. However, the 137 Cs ratio at all rooted sites decreased more slowly, and 137 Cs was distributed deeper into the soil layers than control sites, across both new and old rooting sites. Moreover, the 137 Cs soil profiles varied greatly among core samples and sampling sites. Furthermore, these results demonstrate that soil disturbance from wild boar rooting can directly influence the distribution of contaminants within soil profiles. However, the extent to which deeper layers are affected by contamination depends on the unique characteristics (i.e., depth of rooting) of each wild boar rooting disturbance. Further studies are needed to examine the effects of long-term rooting on the alteration of 137 Cs in soil profiles.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
NASA NTRS1984

Development of a new class of chemical and biological ultrasensors: Ribonuclease contamination and control

In order to define ribonuclease contamination, an assay for ribonuclease having picogram level sensitivity was established. In this assay, polycytidylic acid is digested by ribonuclease leading to smaller fragments of poly C that remain soluble after treatment of the sample with perchloric acid and lanthanum acetate. An absorbance measurement at 260 nm of the supernatant from the centrifuged sample measures the ribonuclease. A standard curve is shown. Using this assay procedure, ribonuclease contamination was found to be significant in routine laboratory proteins, in particular, bovine serum albumin, lysozyme, catalase, and cytochrome C. This was confirmed by demonstrating a considerable reduction in this activity in the presence of phosphate buffer since phosphate inhibits ribonuclease. Ribonuclease contamination was not significantly encountered in routine laboratory glassware, plasticware, column surfaces, chromatographic particles, and buffer reagents, including airborne contamination. Some contamination could be introduced by fingerprints, however.

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