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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
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NASA NTRS2018

N2 Chemistry in Interstellar and Planetary Ices: Radiation-Driven Oxidation

As part of our work on nitrogen-rich ices, the IR spectra and band strengths used in a recent paper to identify and quantify radiation-induced changes in an N2+H2O ice near 15 K are examined, along with reports of (i) a chemical tracer for N2+H2O ices, (ii) a new IR feature of solid N2, and (iii) a striking 15N isotopic enrichment. Problems are found for each IR band strength used and for each of the three claims made, to the extent that none are supported by the results presented to date. In contrast, new work presented here, combined with several older investigations, strongly supports the formation of di- and triatomic nitrogen oxides in irradiated N2-rich ices. Observations and trends in the chemistry of N2-rich icy solids are described, and conclusions are drawn. A considerable amount of material from previous chemical studies of N2-rich systems, spanning more than a century, is brought together for the first time and used to examine the chemistry of N2-rich ices in extraterrestrial environments. Needs are identified and suggestions made for future studies of N2-rich interstellar and planetary ice analogs

astrobiology – astrochemistry – infrared: ISM – IS↗
NASA NTRS1977

Airborne measurements of solar and planetary near ultraviolet radiation during the NASA/ESA CV-900 spacelab simulation

Results from a comparative study of the feasibility of employing experiment operators on the space shuttle to acquire scientifically worthwhile data are presented. The experiments performed during these tests included spectral observations of the Sun and Venus in the near ultraviolet region. The solar measurements were analyzed to determine ozone abundance in the terrestrial atmosphere. Using a detailed spectral matching technique to compare airborne solar UV measurements with synthetic spectral profiles of sunlight, it is deduced that in winter the total atmospheric ozone abundance is about 0.33 atm/cm at midlatitudes in the northern hemisphere.

Sivjee, G. G.↗
NASA NTRS1986

Studies of radiative transfer in planetary atmospheres

The research emphasis during the period of this report has been on radio observations of comets, related to the International Halley Watch. Observations of the 18 cm lambda-doublet of OH have been carried out monthly. Both of the 1667 and 1665 MHz lines have been repeatedly detected for Comets Halley, Giacobini-Zinner, Thiele, and Hartley-Good. The first astronomical detection of the weak satellite line at 1720 MHz was made for P/Halley. These data promise to supply the highest signal-to-noise-ratio data over an extended period ever obtained for cometary radio observations. Analysis will provide gas production rates as a function of heliocentric distance and allow for detailed comparisons with the OH excitation model involving ultraviolet pumping. In the case of Halley, the lines appear quite symmetric, usually being centered within 0.1 km/s with respect to the nominal nuclear velocity. Line widths have been typically within 10% of 2 km/s. There is thus little evidence for asymmetric emission in the data obtained to date. It seems likely that non-steady-state models of the coma will be required to interpret the data. Evidence for significant departures from the LTE hyperfine ratios was found for Comet Giacobini-Zinner. Smaller, but nonetheless significant, deviations have been found for Comet Halley.

Irvine, W. M.↗
NASA NTRS1986

Studies of radiative transfer in planetary atmospheres

A set of high signal-to-noise spectra of the 18 cm OH emission from the comet P/Halley was obtained. During the course of the Halley OH campaign, high signal-to-noise spectra were also obtained on the comets P/Giacobini-Zinner, C/Thiele, and C/Hartley-Good. The HCN observations of Comet Halley were performed during a total of 56 individual observing sessions between 18 November 1985 and 11 May 1986. These observations represent the largest monitoring program of HCN emission from any comet, and moreover, represent the first time that a cometary parent molecule was so extensively observed. In addition to offering a direct means to monitor the production of a parent molecule from the nucleus, these data also provide fundamental information about the kinematics of parent molecules in the coma. Finally, in addition to monitoring HCN from the comet, attempts were also made to detect other molecues via millimeter-wave spectroscopy. Future plans are descussed.

Irvine, W. M.↗
NASA NTRS1986

Radiative transfer in planetary atmospheres

The research effort was concentrated toward comet P/Halley, although observations of other comets including Giacobini-Zinner, Hartley-Good and Thiele were made as opportunities arise. In preparing for the apparition of P/Halley, detailed predictions for the emission in the 18 cm OH transitions were made in order to assist observers and to indicate what type of data would be particularly valuable. Likewise, since occultations by the comet of background radio sources can provide unique types of information, the tracks of P/Halley and P/Giacobini-Zinner were surveyed with the NRAO Very Large Array, background sources were mapped, and a catalogue of occulted sources published. Beginning in September, 1985, regular observations of the 18 cm OH lines have been made for P/Halley using the 43 m antenna of the NRAO in Greenbank, West Virginia. These data promise to provide the most accurate time sequence for the OH emission for any comet ever obtained at radio wavelengths. From the linewidth and shape, information is obtained on the kinetics of the gas in the cometary coma. An extensive series of observations have been undertaken with 14 m antenna to study emission from the HCN molecule in P/Halley. These data provide the first definitive detection of this component of the cometary ices. Interesting variations in the production of HCN were observed with time scales less than a day. Likewise, there appeared to be variations in the ratio of the hyperfine components of the J = 1-0 transition.

Irvine, W. M.↗
NASA NTRS1988

Radiative transfer in planetary atmospheres

Rheoretical techniques and observations at millimeter wavelengths are combined to study the atmosphere of planets and comets, planetary and satellite regoliths, and planetary rings. Analysis of the very high quality data on the 18 cm OH line observed in recent comets continued. The high spectral resolution and high signal-to-noise make these lines ideal for study of the kinematics in cometary comae. A model of the collisional quenching of the inversion of the lambda doublet responsible for the OH radio emission has been developed by P. Schloerb. For conditions appropriate to Halley's Comet, collisional quenching should lead radio observers to systematically underestimate the OH parent production rate by a factor of approximately 3 relative to its actual value, which is very consistent with differences observed between radio and ultraviolet-derived production rates. Modeling is likewise continuing for the profiles observed in the lowest rotational transition of HCN in Comet Halley in order to better estimate the excitation and hence the abundance of HCN, as well as the kinematics of parent molecules in the coma. A collaborative program to combine data from the 14 m antenna with interferometric data abtained at the Hat Creek Radio Observatory is allowing aperture synthesis mapping of Venus in the CO J=1-0 line.

Irvine, William M.↗
NASA NTRS1991

Radiative transfer in planetary atmospheres

A wide range of topics are covered including the following: (1) the observational study of cometary comae via millimeter and radio spectroscopy; (2) observational and theoretical studies of planetary atmospheres at millimeter wavelengths; and (3) application of theoretical models of the reflection of light from solid surfaces to the study of planetary regoliths and planetary rings.

Schloerb, F. Peter↗
NASA NTRS1991

Radiative transfer in planetary atmospheres: Submillimeter-wave spectroscopy of comets

During 1990, a significant step was made in asertaining the molecular composition of comets by our Planetary Astronomy group at the University of Massachusetts. We obtained several exciting new detections of submillimeter wave spectral lines from molecules in the coma of Comet Levy (1990c) using the 10m telescope of the Caltech Submillimeter Observatory, located on Mauna Kea. The molecules HCN, formaldahyde, and methanol were all detected in abundances that make them important minor constituents of the nucleus. Moreover, the emission was so strong that, for the first time, it was possible to map the distribution of these species in the coma and study their behavior as they flow outwards from the nucleus.

Schloerb, F. Peter↗
NASA NTRS1996

Planetary Atmosphere Dynamics and Radiative Transfer

This research program has dealt with two projects in the field of planetary atmosphere dynamics and radiative energy transfer, one theoretical and one experimental. The first project, in radiative energy transfer, incorporated the capability to isolate and quantify the contribution of individual atmospheric components to the Venus radiative balance and thermal structure to greatly improve the current understanding of the radiative processes occurring within the Venus atmosphere. This is possible by varying the mixing ratios of each gas species, and the location, number density and aerosol size distributions of the clouds. This project was a continuation of the work initiated under a 1992 University Consortium Agreement. Under the just completed grant, work has continued on the use of a convolution-based algorithm that provided the capability to calculate the k coefficients of a gas mixture at different temperatures, pressures and spectral intervals from the separate k-distributions of the individual gas species. The second primary goal of this research dealt with the Doppler wind retrieval for the Successful Galileo Jupiter probe mission in December, 1995. In anticipation of the arrival of Galileo at Jupiter, software development continued to read the radioscience and probe/orbiter trajectory data provided by the Galileo project and required for Jupiter zonal wind measurements. Sample experiment radioscience data records and probe/orbiter trajectory data files provided by the Galileo Radioscience and Navigation teams at the Jet Propulsion Laboratory, respectively, were used for the first phase of the software development. The software to read the necessary data records was completed in 1995. The procedure by which the wind retrieval takes place begins with initial consistency checks of the raw data, preliminary data reductions, wind recoveries, iterative reconstruction of the probe descent profile, and refined wind recoveries. At each stage of the wind recovery consistency is checked and maintained between the orbiter navigational data, the radioscience data, and the probe descent profile derived by the Atmospheric Instrument Team. Preliminary results show that the zonal winds at Jupiter increase with depth to approximately 150 m/s.

Atkinson, David H.↗
NASA NTRS1984

Radiative forcing of stationary planetary waves

To elucidate the role of solar and long-wave transfers in maintaining stationary planetary waves, the potential vorticity equation appropriate to these disturbances in the middle latitudes of the Northern Hemisphere during winter is solved with realistic radiation physics included in the heating term. A series of model experiments demonstrates the roles of the various optically active constituents in maintaining the stationary planetary waves. Clouds and the net radiative heating tend to amplify stationary planetary wavenumber one by increasing the forcing asymmetry, but destructive interference between radiative heating and other diabatic processes and topography causes the net radiative heating to dampen stationary planetary wavenumber two. In the presence of clouds, water vapor and to a lesser extent carbon dioxide damp the waves by reducing cloud-generated forcing asymmetries, particularly at zonal wavenumber one.

Donner, L. J.↗