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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Ozone Observations by the Gas and Aerosol Measurement Sensor during SOLVE II

The Gas and Aerosol Measurement Sensor (GAMS) was deployed aboard the NASA DC-8 aircraft during the second SAGE III Ozone Loss and Validation Experiment (SOLVE II). GAMS acquired line-of-sight (LOS) direct solar irradiance spectra during the sunlit portions of ten science flights of the DC-8 between 12 January and 4 February 2003. Differential line-of-sight (DLOS) optical depth spectra are produced from the GAMS raw solar irradiance spectra. Then, DLOS ozone number densities are retrieved from the GAMS spectra using a multiple linear regression spectral fitting technique. Both the DLOS optical depth spectra and retrieved ozone data are compared with coincident measurements from two other solar instruments aboard the DC-8 platform to demonstrate the robustness and stability of the GAMS data. The GAMS ozone measurements are then utilized to evaluate the quality of the Wulf band ozone cross sections, a critical component of the SAGE III aerosol, water vapor, and temperature/pressure retrievals. Results suggest the ozone cross section compilation of Shettle and Anderson currently used operationally in SAGE III data processing may be in error by as much as 10-20% in theWulf bands, and their lack of reported temperature dependence is a significant deficiency. A second, more recent, cross section database compiled for the SCIAMACHY satellite mission appears to be of much better quality in the Wulf bands, but still may have errors as large as 5% near the Wulf band absorption peaks, which is slightly larger than their stated uncertainty. Additional laboratory measurements of the Wulf band cross sections should be pursued to further reduce their uncertainty and better quantify their temperature dependence.

Pitts, M. C.↗
NASA NTRS2004

Solar Variability and the Near-Earth Environment: Mining Enhanced Low Dose Rate Sensitivity Data From the Microelectronics and Photonics Test Bed Space Experiment

This effort is a detailed analysis of existing microelectronics and photonics test bed satellite data from one experiment, the bipolar test board, looking to improve our understanding of the enhanced low dose rate sensitivity (ELDRS) phenomenon. Over the past several years, extensive total dose irradiations of bipolar devices have demonstrated that many of these devices exhibited ELDRS. In sensitive bipolar transistors, ELDRS produced enhanced degradation of base current, resulting in enhanced gain degradation at dose rates <0.1 rd(Si)/s compared to similar transistors irradiated at dose rates >1 rd(Si)/s. This Technical Publication provides updated information about the test devices, the in-flight experiment, and both flight-and ground-based observations. Flight data are presented for the past 5 yr of the mission. These data are compared to ground-based data taken on devices from the same date code lots. Information about temperature fluctuations, power shutdowns, and other variables encountered during the space flight are documented.

Turflinger, T.↗
NASA NTRS2004

Reflectance Spectra of CM2 Chondrite Mighei Irradiated with Pulsed Laser and Implications for Low-Albedo Asteroids and Martian Moons

Micrometeoritic bombardment is an important space weathering process modifying surface optical properties of airless solar system bodies. We have used irradiation with a microsecond pulsed laser as an experimental method to simulate such a process on various targets. The experiment discussed here was performed on a powdered sample of CM2 carbonaceous chondrite Mighei. Shingareva et al. report the details of experimental procedure as well as the results of mineralogical and chemical studies of the irradiated material. Here we present reflectance spectra of irradiated Mighei samples and discuss their spectral properties compared to those of non-irradiated meteorite and low-albedo small solar system bodies.

Moroz, L. V.↗
NASA NTRS1990

Solar Irradiance Observed from PVO and Inferred Solar Rotation

Solar irradiance in the extreme ultraviolet flux (EUV) has been monitored for 11 years by the Pioneer Venus Orbiter (PVO). Since the experiment moves around the Sun with the orbital rate of Venus rather than that of Earth, the measurement gives us a second viewing location from which to begin unravelling which irradiance variations are intrinsic to the Sun, and which are merely rotational modulations whose periods depend on the motion of the observer. Researchers confirm an earlier detection, made with only 8.6 years of data, that the EUV irradiance is modulated by rotation rates of two families of global oscillation modes. One family is assumed to be r-modes occupying the convective envelope and sharing its rotation, while the other family (g-modes) lies in the radiative interior which as a slower rotation. Measured power in r-modes of low angular harmonic number indicates that the Sun's envelope rotated about 0.7 percent faster near the last solar maximum (1979 thru 1982) than it did during the next rise to maximum (1986 to 1989). No change was seen in the g-mode family of lines, as would be expected from the much greater rotational inertia of the radiative interior.

Wolff, Charles L.↗
NASA NTRS1990

Preparatory space experiments for development of a CELSS

The goal of Closed Ecological Life Support System (CELSS) studies is to examine the effects of microgravity on yield and quality of plant products and on the interactions between irradiance and crop area. Measuring yield and quality of crops as a function of irradiance in microgravity is virtually unique to the CELSS program, as is the emphasis on canopies rather than individual plants. The first step for space experiments is to develop a relatively stress free environment for plant growth, something that has so far never been achieved. High light levels are essential, and there must be time enough to complete a significant portion of the life cycle. Optimal atmosphere and nutrients must be provided. Such responses as germination, orientation of roots and shoots, photosynthesis and respiration, floral initiation and development, and seed maturation and viability will be studied.

Salisbury, Frank B.↗
NASA NTRS2019

Molecular Identifications in Experiments with Astronomical Ice Analogues: New Data, Old Strategies, and the N2 + Acetone System

A recent publication on the radiation chemistry and IR spectroscopy of N2 plus acetone ices is used to illustrate some of the difficulties encountered in the study of astronomical ice analogues. Concerns and problems are identified and suggestions for their solution are presented, including new infrared (IR) spectra of amorphous ices. The hazards of using peak positions alone for assignments of the IR spectra of irradiated ices are illustrated, and the importance of considering the underlying reaction chemistry is shown. Several experiments are proposed as a way to investigate the behaviour of acetone in cold, extraterrestrial environments. Electronic versions of IR spectra are provided and several new refractive indices of ices are reported.

Hudson, Reggie L.↗
NASA NTRS1989

Handling and analysis of ices in cryostats and glove boxes in view of cometary samples

Comet nucleus sample return mission and other return missions from planets and satellites need equipment for handling and analysis of icy samples at low temperatures under vacuum or protective gas. Two methods are reported which were developed for analysis of small icy samples and which are modified for larger samples in cometary matter simulation experiments (KOSI). A conventional optical cryostat system was modified to allow for transport of samples at 5 K, ion beam irradiation, and measurement in an off-line optical spectrophotometer. The new system consists of a removable window plug containing nozzles for condensation of water and volatiles onto a cold finger. This plug can be removed in a vacuum system, changed against another plug (e.g., with other windows (IR, VIS, VUV) or other nozzles). While open, the samples can be treated under vacuum with cooling by manipulators (cut, removal, sample taking, irradiation with light, photons, or ions). After bringing the plug back, the samples can be moved to another site of analysis. For handling the 30 cm diameter mineral-ice samples from the KOSI experiments an 80x80x80 cm glove box made out of plexiglass was used. The samples were kept in a liquid nitrogen bath, which was filled from the outside. A stream a dry N2 and evaporating gas from the bath purified the glove box from impurity gases and, in particular, H2O, which otherwise would condense onto the samples.

Roessler, K.↗
NASA NTRS2019

TSIS Experiences with ISS Jitter from Inception to On-Orbit Operation

The TSIS instrument has been measuring solar irradiance on a continual basis since January 2018 as an external payload on the ISS. In 2014 when TSIS was directed to fly on the ISS, the jitter environment was highly uncertain, so TSIS designed a robust gimbaled pointing system that showed excellent disturbance attenuation throughout the design, test, and on-orbit phases of the program. This paper discusses how TSIS accounted for this uncertain jitter environment through-out the life of the program.TSIS was able to measure the ISS jitter during commissioning and determined that it was a relatively benign environment less than 4 arcseconds 1σ at low frequencies (<0.5 Hz). More importantly, the measured pointing performance of TSIS was consistently found to be 4 arcseconds 1σ, which easily satisfied the jitter requirement of 60 arcseconds 1σ.

solar irradiance instrument↗
NASA NTRS2015

The Formation of Organic Compounds of Astrobiological Interest by the Irradiation Processing of Astrophysical Ices

Many environments in space contain very low temperature mixed molecular ices that are exposed to ionizing radiation in the form of cosmic rays and high-energy photons. While traditional chemistry would not be expected to occur at the temperatures typical of these ices (T < 50 K), ionizing radiation can break bonds in the original molecules in the ices to form highly reactive ions and radicals. These ions and radicals are subsequently free to react despite the low temperatures of the original ices. Laboratory experiments, many of them carried out at the Astrochemistry Laboratory at NASA-Ames, show that the irradiation of ices made of even simple molecules like H2O, CO, CO2, CH4, NH3, etc. can result in the robust formation of large numbers of far more complex organic compounds. Many of these new products are of direct interest to astrobiology. For example, the irradiation of mixed molecular ices has been shown to produce amino acids, amphiphiles, quinones, sugars, heterocyclic compounds, and nucleobases, all molecular building blocks used by terrestrial life. Insofar as the presence of these materials plays a role in the origin of life on planets, this has profound implications for the potential abundance of life in the universe since these experiments simulate universal conditions that are expected to be found wherever new stars and planets form.

Astrobiology↗
NASA NTRS2003

New Laboratory Methods for Characterizing the Immersion Factors for Irradiance

The experimental determination of the immersion factor, I(sub f)(lambda), of irradiance collectors is a requirement of any in-water radiometer. The eighth SeaWiFS Intercalibration Round-Robin Experiment (SIRREX-8) showed different implementations, at different laboratories, of the same I(sub f)(lambda) measurement protocol. The different implementations make use of different setups, volumes, and water types. Consequently, they exhibit different accuracies and require different execution times for characterizing an irradiance sensor. In view of standardizing the characterization of I(sub f)(lambda) values for in-water radiometers, together with an increase in the accuracy of methods and a decrease in the execution time, alternative methods are presented, and assessed versus the traditional method. The proposed new laboratory methods include: a) the continuous method, in which optical measurements taken with discrete water depths are substituted by continuous profiles created by removing the water from the water vessel at a constant flow rate (which significantly reduces the time required for the characterization of a single radiometer); and b) the Compact Portable Advanced Characterization Tank (ComPACT) method, in which the commonly used large tanks are replaced by a small water vessel, thereby allowing the determination of I(sub f)(lambda) values with a small water volume, and more importantly, permitting I(sub f)(lambda) characterizations with pure water. Intercomparisons between the continuous and the traditional method showed results within the variance of I(sub f) (lambda) determinations. The use of the continuous method, however, showed a much shorter realization time. Intercomparisons between the ComPACT and the traditional method showed generally higher I(sub f)(lambda) values for the former. This is in agreement with the generalized expectations of a reduction in scattering effects, because of the use of pure water with the ComPACT method versus the use of tap water with the traditional method.

Hooker, Stanford B.↗
NASA NTRS1984

User's Guide for ERB 7 Matrix. Volume 1: Experiment Description and Quality Control Report for Year 1

The Nimbus 7 ERB MATRIX Tape is a computer program in which radiances and irradiances are converted into fluxes which are used to compute the basic scientific output parameters, emitted flux, albedo, and net radiation. They are spatially averaged and presented as time averages over one-day, six-day, and monthly periods. MATRIX data for the period November 16, 1978 through October 31, 1979 are presented. Described are the Earth Radiation Budget experiment, the Science Quality Control Report, Items checked by the MATRIX Science Quality Control Program, and Science Quality Control Data Analysis Report. Additional material from the detailed scientific quality control of the tapes which may be very useful to a user of the MATRIX tapes is included. Known errors and data problems and some suggestions on how to use the data for further climatologic and atmospheric physics studies are also discussed.

Tighe, R. J.↗
NASA NTRS1975

The total and spectral solar irradiance and its possible variations

The present status of knowledge of the total and spectral irradiance of the sun is briefly reviewed. Currently accepted values of the solar constant and the extraterrestrial solar spectral irradiance are presented along with a discussion of how they were derived. Data on the variability of the solar constant are shown to be conflicting and inconclusive. Some of the alleged sun-weather relationships are cited in support of the need of knowing more precisely the variations in total and spectral solar irradiance. An overview of a solar monitoring program is discussed, with special emphasis on the Solar Energy Monitor in Space experiment which was proposed for several spacecraft missions. It is a combination of a solar constant detector and a prism monochromator. The determination of absolute values and the possible variations of the total and spectral solar irradiance, from measurements outside of the atmosphere is discussed.

Thekaekara, M. P.↗
NASA NTRS1971

Automated Microbial Metabolism Laboratory

The effect of several environmental parameters on previously developed life detection systems is explored. Initial attempts were made to conduct all the experiments in a moist mode (high soil volume to water volume ratio). However, only labeled release and measurement of ATP were found to be feasible under conditions of low moisture. Therefore, these two life detection experiments were used for most of the environmental effects studies. Three soils, Mojave (California desert), Wyaconda (Maryland, sandy loam) and Victoria Valley (Antarctic desert) were generally used throughout. The environmental conditions studied included: incubation temperature 3 C to 80 C, ultraviolet irradiation of soils, variations in soil/liquid ratio, specific atmospheric gases, various antimetabolites, specific substrates, and variation in pH. An experiment designed to monitor nitrogen metabolism was also investigated.

Source record↗
NASA NTRS1976

A study of satellite remote measurements of stratospheric aerosol and gas parameters using the solar occultation technique

Satellite remote measurements of stratospheric aerosol and ozone profiles using the solar occultation approach were analyzed based on the known properties of the atmospheric parameters. Atmospheric refraction effects which are important in this experiment were determined analytically. Different inversion techniques were developed based on inverting simulated irradiance data. It was shown that aerosol and ozone profiles in the stratosphere can be inverted from the irradiance measurements to an accuracy of better than 10 percent.

Chu, W. P.↗
NASA NTRS1984

Effect of space environment on space-based radar phased-array antenna (A0133)

Kapton polyimide film was selected as the baseline material for the Grumman spce based radar (SBR) concept. To gain the requisite confidence for long-term service durability, it is desirable to subject material specimens as well as a portion of the SBR antenna directly to the combined space environment and compare property degradation to that caused by laboratory simulation. The overall objective of this program is to evauate the effect of the space environment on polymeric materials currently being considered for the Grumman SBR Phased-Array Antenna. Degradation mechanisms caused by thermal cycling, ultraviolet and charged-particle irradiation, applied load, and high-voltage plasma interaction will be evaluated. The experiment occupies a 6-in.-deep end corner tray located on the space end of the Long Duration Exposure Facility and consists of both passive and active parts. The passive part addresses the effect of environment and stress on the dimensional stability spliced and continuous Kapton, both plain and reinforced. The active part will study the interaction of high voltage and low-Earth-orbit plasma.

Delasi, R. J.↗
NASA NTRS1991

Detection of solid methanol toward W33A

A recently detected absorption feature at 3.53 microns in the spectrum of W33A has been assigned to methanol (CH3OH). Its optical depth implies that methanol is the second most abundant molecule (7 percent relative to H2O) in the grain mantles in the line of sight toward W33A observed to date. Laboratory experiments have shown that the implied abundance is difficult to explain by UV irradiation of the dust grains alone. Grain surface reactions or condensation directly out of the gas phase must also play roles, but the relative contributions of the various processes are difficult to estimate. The optical depth of the 3.53-micron feature constrains the contribution of methanol to the 6.8-micron feature in W33A to be 10 percent or less, requiring the contribution of at least one other compound to this feature, while the estimated contribution to the 4.9-micron absorption band is even smaller. Only a small contribution of formaldehyde (H2CO) is consistent with the observed 3.53-micron band profile. In contrast to methanol, formaldehyde can be produced readily by photochemical reactions within the ice mantle.

Grim, R. J. A.↗
NASA NTRS1993

Evaluation of radiation effects in re-oxidized nitrided oxide devices by hot carrier stressing at 77 K

An attempt has been made to understand the mechanisms of radiation induced degradation by using different types of hot carrier (HC) stressing experiments. The degradation of re-oxidized nitrided oxide gate dielectric due to irradiation and hot carriers are reported. The effect of electron and hole traps of the virgin device on radiation induced threshold voltage shift is discussed.

Das, N. C.↗
NASA NTRS1994

Propagation velocities of laser-produced plasmas from copper wire targets and water droplets

Experiments were performed to determine the plasma propagation velocities resulting from KrF laser irradiation of copper wire target (75 microns diameter) and water droplets (75 microns diameter) at irradiance levels ranging from 25 to 150 GW/sq cm. Plasma propagation velocities were measured using a streak camera system oriented orthogonally to the high-energy laser propagation axis. Plasma velocities were studied as a function of position in the focused beam. Results show that both the shape of the plasma formation and material removal from the copper wire are different and depend on whether the targets are focused or slightly defocused (approximately = 0.5 mm movement in the beam axis). Plasma formation and its position relative to the target is an important factor in determining the practical focal point during high-energy laser interaction with materials. At irradiance of 100 GW/sq cm, the air plasma has two weak-velocity components which propagate toward and away from the incident laser while a strong-velocity component propagates away from the laser beam as a detonation wave. Comparison of the measured breakdown velocities (in the range of 2.22-2.27 x 10(exp 5) m/s) for air and the value calculated by the nonlinear breakdown wave theory at irradiance of 100 GW/sq cm showed a quantitative agreement within approximately 50% while the linear theory and Gaussian pulse theory failed. The detonation wave velocities of plasma generated from water droplets and copper wire targets for different focused cases were measured and analyzed theoretically. The propagation velocities of laser-induced plasma liquid droplets obtained by previous research are compared with current work.

Song, Kyo-Dong↗