SEARCH · Search NASA
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
A tunable diode laser spectrometer and the sweep integration technique were used to measure hydrogen-broadened half-widths and nitrogen-broadened half-widths of eight lines between P(1) and P(15) in the CO fundamental at several temperatures between 94 and 298 K. The results are of interest in connection with studies of the atmospheres of earth, Jupiter, Saturn, and Titan.
Explore the source record for details and available documents.
Collision-broadened halfwidths of three lines in the nu3 fundamental band and of four lines in the nu6 fundamental band of (C-12)H3D have been measured at temperatures between 123 and 295 K using the Doppler-limited spectral resolution of a tunable diode laser spectrometer. Temperature dependence of the linewidths has been determined in self-broadening and in broadening by H2, He and N2.
Method for determining temperature-altitude profiles of planetary atmospheres from number density profiles of two inert gases with different molecular weights
Preliminary results of the infrared radiometer experiment on Pioneer Saturn are reported. The instrument made use of two broadband channels centered at 20 and 45 microns which scan at a fixed 75-deg angle with respect to the spacecraft spin axis to acquire 10,000 image pairs of Saturn and its rings in the 2.5 h before closest approach, as well as several observations of Titan. The intensities of radiation observed in both bands indicate an effective temperature of 94.4 + or - 3 K for the planet, implying a total emission greater than twice the absorbed sunlight. Infrared data also indicates a molecular abundance of 0.85 for H2 relative to H2 + He, which can be improved by comparing the derived temperature profiles and radio occultation data. Planetary temperatures are found to range from a minimum of 83 to 140 K at the 1 bar level, with differences of 2.5 K between belts and zones up to the 0.06-bar level, while ring temperatures range from 60 to 70 K on the illuminated side and from less than 60 to 67 K in the planet's shadow and average 55 K on the unilluminated side. Preliminary estimates indicate a 45-micron brightness temperature of 80 + or - 10 K for Titan.
Employing the techniques that were described in several publications for measuring infrared lineshifts, linewidths and line intensities with a tunable diode laser, these parameters were measures for lines in the important infrared bands of several molecules of interest to the planetary astronomer at low temperatures that are relevant to planetary atmospheres using He, Ne, Ar, H2, N2, O2, and air as the perturbers. In addition to obtaining the many original data on the temperature dependence of the intensities and linewidths, it was also the first measurement of the same for the collision-induced lineshift of an infrared line and it showed that it was markedly different from that of the corresponding collision-broadened linewidth.
The recent Magellan images have revealed a broad spatial distribution of surface volcanism on Venus. Previous work in modeling the ascent of magma on both Venus and Earth has indicated that the planetary thermal structure significantly influences the magmatic cooling rates and thus the amount of magma that can be transported to the surface before solidification. In order to understand which aspects of the thermal structure have the greatest influence on the cooling of ascending magma, we have constructed magma cooling curves for both plutonic and crack buoyant ascent mechanisms, and evaluated the curves for variations in the planetary mantle temperature, thermal gradient curvature with depth, surface temperature gradient, and surface temperature. The planetary thermal structure is modeled as T/T(sub 0) = 1-tau(1-Z/Z(sub 0)(exp n), where T is the temperature, T(sub 0) is the source depth temperature, tau = 1-(T(sub s)/T(sub 0)) where T(sub s) is the planetary surface temperature, Z is the depth, Z(sub 0) is the source depth, and n is a constant that controls thermal gradient curvature with depth. The equation is used both for mathematical convenience and flexibility, as well as its fit to the thermal gradients predicted by the cooling half-space models. We assume a constant velocity buoyant ascent, body-averaged magma temperatures and properties, an initially crystal-free magma, and the same liquidus and solidus for both Venus and Earth.
When a planet is in radiative equilibrium, the incoming solar flux balances the outgoing longwave flux. If something were to perturb the system slightly, say the incoming solar flux increased, the planet would respond by radiating at a higher surface temperature. Since any radiation that comes in must go out, if the incoming is increased, the outgoing must also increase, and this increase manifests itself as a warmer equilibrium temperature. The increase in solar flux would correspond to an increase in temperature, which would increase the amount of water vapor in the atmosphere due to increased evaporation. Since water vapor is a greenhouse gas, it would absorb more radiation in the atmosphere leading to a yet warmer equilibrium temperature. The planet would reach radiative equilibrium at this new temperature. There exists a point, however, past which this positive feedback leads to a "runaway" situation. In this case, the planet does not simply evaporate a little more water and eventually come to a slightly higher equilibrium temperature. Instead, the planet keeps evaporating more and more water until all of the planet's available liquid and solid water is in the atmosphere. The reason for this is generally understood. If the planet's temperature increases, evaporation of water increases, and the absorption of radiation increases. This increases the temperature and the feedback continues until all water is in the atmosphere. The resulting equilibrium temperature is very high, much higher than the equilibrium temperature of a point with slightly lower solar flux. One can picture that as solar flux increases, planetary temperature also increases until the runaway point where temperature suddenly "jumps" to a higher value, in response to all the available water now residing in the atmosphere. This new equilibrium is called a "runaway greenhouse" and it has been theorized that this is what happened to the planet Venus, where the surface temperature is more than 700 K (427 C).
A numerical method for calculating the time-average, vertical temperature structure of planetary atmospheres is presented. It is assumed that the atmospheres are in radiative-convective equilibrium, which is a good first approximation to many situations. Numerical tests of the rate of convergence and accuracy of the answer are presented. The method can readily handle molecular sources of opacity. Accurate results can be obtained with a minimum of computer time, because the number of iterations needed (about 4) is small and the number of pressure levels at which the net flux needs to be evaluated (about 10) is small. As an application of this procedure, some model atmospheres of Jupiter are calculated.
Radioisotope power systems have historically been (and still are) the power system of choice from a mass and size perspective for outer planetary missions. High demand for and limited availability of radioisotope fuel has made it necessary to investigate alternatives to this option. Low mass, high efficiency solar power systems have the potential for use at low outer planetary temperatures and illumination levels. This paper documents the impacts of using solar power systems instead of radioisotope power for all or part of the power needs of outer planetary spacecraft and illustrates the potential fuel savings of such an approach.
The Experimental Cloud Lidar Pilot Study (ECLIPS) project has now had two active phases in 1989 and 1991. A number of laboratories around the world have taken part in the study. The observations have yielded new data on cloud height and structure, and have yielded some useful new information on the retrieval of cloud optical properties, together with the uncertainties involved. Clouds have a major impact on the climate of the earth. They have the effect of reducing the mean surface temperature from 30 C for a cloudless planet to a value of about 15 C for present cloud conditions. However, it is not at all certain how clouds would react to a change in the planetary temperature in the event of climate change due to a radiative forcing from greenhouse gases. Clouds both reflect out sunlight (negative feedback) and enhance the greenhouse effect (positive feedback), but the ultimate sign of cloud feedback is unknown. Because of these uncertainties, campaigns to study clouds intensely were initiated. The International Satellite Cloud Climatology (ISCPP) and the FIRE Campaigns (cirrus and stratocumulus) are examples. The ECLIPS was set up similarly to the above experiments to obtain information specifically on cloud base, but also cloud top (where possible), optical properties, and cloud structure. ECLIPS was designed to allow as many laboratories as possible globally to take part to get the largest range of clouds. It involves observations with elastic backscatter lidar, supported by infrared fluxes at the ground and radiosonde data, as basic instrumentation. More complex experiments using beam filter radiometers, solar pyranometers, and satellite data and often associated with other campaigns were also encouraged to join ECLIPS. Two periods for observation were chosen, Sep. - Dec. 1989 and Apr. - Jul. 1992 into which investigators were requested to fit 30 days of observations. These would be either continuous, or arranged to coincide with NOAA satellite overpasses to obtain AVHRR data. The distribution of the ECLIPS international effort as in 1991 is shown. The main gaps in the global distribution are in the tropics and the Southern Hemisphere.
We investigate roles of Alfvénic waves in the weakly ionized atmosphere of hot Jupiters by carrying out non-ideal MHD simulations with ohmic diffusion in one-dimensional magnetic flux tubes. Turbulence at the surface excites Alfvén waves, and they propagate upward to drive hot (≈10{sup 4} K) outflows. The magnetic diffusion plays an important role in the dissipation of the Alfvénic waves in the weakly ionized atmosphere of hot Jupiters. The mass-loss rate of the spontaneously driven planetary wind is considerably reduced, in comparison with that obtained from ideal MHD simulations because the Alfvénic waves are severely damped at low altitudes in the atmosphere, whereas the wave heating is still important in the heating of the upper atmosphere. Dependence on the surface temperature, planetary radius, and velocity dispersion at the surface is also investigated. We find an inversion phenomenon of the transmitted wave energy flux; the energy flux carried by Alfvén waves in the upper atmosphere has a nonmonotonic correlation with the input energy flux from the surface in a certain range of the surface temperature because the resistivity is determined by the global physical properties of the atmosphere in a complicated manner. We also point out that the heating and mass loss are expected only in limited zones if the open magnetic field is confined in the limited regions.
Abstract We investigated the high-pressure behavior of polyethylene (CH 2 ) by probing dynamically-compressed samples with X-ray diffraction. At pressures up to 200 GPa, comparable to those present inside icy giant planets (Uranus, Neptune), shock-compressed polyethylene retains a polymer crystal structure, from which we infer the presence of significant covalent bonding. The A 2 /m structure which we observe has previously been seen at significantly lower pressures, and the equation of state measured agrees with our findings. This result appears to contrast with recent data from shock-compressed polystyrene (CH) at higher temperatures, which demonstrated demixing and recrystallization into a diamond lattice, implying the breaking of the original chemical bonds. As such chemical processes have significant implications for the structure and energy transfer within ice giants, our results highlight the need for a deeper understanding of the chemistry of high pressure hydrocarbons, and the importance of better constraining planetary temperature profiles.
The temperature and cloud structure, relative abundances of H2 and He, and the global climatology of Jupiter's atmosphere have been deduced from Pioneer 10 and 11 infrared radiometer data, along with earth-based observations of the spectrum at 8-14 and 12-24 microns. The H2 and He abundances are near those expected from 'solar' composition. The effective planetary temperature is 125 + or - 3 K. Temperatures at 1.0 bar are near 165 K and drop to 100-110 K at 0.1 bar; an overlying thermal inversion reaches 133-145 K near 0.03 bar. Temperature profiles for various regions of the planet may be quite similar, with differences due to the presence or absence of a thick cloud near 0.7 bar, close to the temperature where NH3 saturation is expected. Remaining problems in the remote sounding of Jupiter's atmosphere are accurate calibration of the global energy balance, sounding in the presence of significant heterogeneity, and temperature recovery of the thermally inverted stratosphere.
Shock temperature measurements have been performed on several materials which have relevance to the modeling of the outer planets. These materials are methane, ammonia and a mixture of water, ammonia, and isopropanol known as synthetic Uranus. Temperatures have been measured in these materials over the pressure range 33-76 GPa for which there also exists measurements of equation of state and electrical conductivity. The temperatures are found to agree well with available calculations, with small discrepancies between data and theory ascribed to energy absorbing processes such as dissociation and molecular ionization.
Statement of the Problem: The earth’s atmosphere experience changes that are caused by pollution from debris streams from exploding stars, nova and supernova. The debris streams also cause global warming. Earth’s sensitivity to the energy added to the biosphere is shown by the areas of major sea ice loss through recent years. Methodology & Theoretical Orientation: By knowing the year of arrival of debris streams at planet earth the longitudinal locations of observations of changing sea ice can be correlated to specific debris stream’s termini. The actual termini points are identified for WZ Sagittae, SN 1006 and SN 1054. Findings: Global warming effects have been correlated with the arrival time of nova and supernova explosions through disappearing sea ice over the past nine years. Conclusion & Significance: The current trend for global warming specialist to blame fossil fuels and CO2 for the increase of planetary temperatures may be incorrect and the true source of our current global warming may be due to debris impact streams from nova WZ Sagittae, SN 1054 and SN 1006. The incentive to inhibit the fossil fuel industry could be changed to design a mechanism or system to stop the incoming particle stream from exploding stars to protect living organisms on our planet. The disappearance of sea ice areas that are correlated with the debris streams being studied is proof of the Supernova and Nova Impact Theory (SNIT).
Analysis of the simulation of seasonal change by the GLAS model of the general circulation reveals deficiencies in the simulation of tropospheric temperature and of convective cloud cover. These interrelated deficiencies are due to a spurious doubling from January to July in the convective cloud cover of the Northern Hemisphere. The spurious doubling, in turn, is due to the oversensitivity of cumulus convection, in the GLAS model, to the specific humidity of the lower atmosphere. The oversensitivity is enhanced by a feedback mechanism which perpetuates the existence of deep, penetrative convective clouds at certain preferred locations. The cumulus parameterization scheme has been modified to more realistically relate the onset of cumulus convection to the relative humidity of the lower atmosphere. The modified parameterization has improved the simulation of tropospheric temperature, planetary albedo and convective cloud cover as well as their seasonal variations. Comparison of this experiment with its control has shown a high degree of interrelation among these fields in the GLAS model and has demonstrated the sensitivity of the atmospheric heat budget to the design of the cumulus parameterization scheme. Also, the modification to the cumulus scheme has demonstrated a plausible mechanism to explain the correlation between convective cloud cover and relative humidity in the real atmosphere.
Ground-based and spacecraft observations of planets, satellites, and asteroids in the thermal infrared have provided a wealth of information on planetary temperatures, dimensions, and surface properties. Internal heat sources have been revealed for Jupiter, Saturn, and Neptune, and active volcanism on Io has been discovered and monitored. The thermophysical properties of Mars have been mapped for nearly all the surface by spacecraft, and ground-based observations have given similar information for the Galilean satellites of Jupiter. Infrared radiometry thus sheds important light on significant problems of dynamics, interiors, and surfaces of solar system bodies.