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NASA NTRS2016

Marli: Mars Lidar for Global Wind Profiles and Aerosol Profiles from Orbit

The Mars Exploration Analysis Group's Next Orbiter Science Analysis Group (NEXSAG) has recently identified atmospheric wind measurements as one of 5 top compelling science objectives for a future Mars orbiter. To date, only isolated lander observations of martian winds exist. Winds are the key variable to understand atmospheric transport and answer fundamental questions about the three primary cycles of the martian climate: CO2, H2O, and dust. However, the direct lack of observations and imprecise and indirect inferences from temperature observations leave many basic questions about the atmospheric circulation unanswered. In addition to addressing high priority science questions, direct wind observations from orbit would help validate 3D general circulation models (GCMs) while also providing key input to atmospheric reanalyses. The dust and CO2 cycles on Mars are partially coupled and their influences on the atmospheric circulation modify the global wind field. Dust absorbs solar infrared radiation and its variable spatial distribution forces changes in the atmospheric temperature and wind fields. Thus it is important to simultaneously measure the height-resolved wind and dust profiles. MARLI provides a unique capability to observe these variables continuously, day and night, from orbit.

Orbit↗
NASA NTRS1980

DIAL with heterodyne detection including speckle noise: Aircraft/shuttle measurements of O3, H2O, and NH3 with pulsed tunable CO2 lasers

Atmospheric trace constituent measurements with higher vertical resolution than attainable with passive radiometers are discussed. Infrared differential absorption lidar (DIAL), which depends on Mie scattering from aerosols, has special advantages for tropospheric and lower stratospheric applications and has great potential importance for measurements from shuttle and aircraft. Differential absorption lidar data reduction involves comparing large amplitude signals which have small differences. The accuracy of the trace constituent concentration inferred from DIAL measurements depends strongly on the errors in determining the amplitude of the signals. Thus, the commonly used SNR expression (signal divided by noise in the absence of signal) is not adequate to describe DIAL measurement accuracy and must be replaced by an expression which includes the random coherent (speckle) noise within the signal. A comprehensive DIAL computer algorithm is modified to include heterodyne detection and speckle noise. Examples for monitoring vertical distributions of O3, H2O, and NH3 using a ground-, aircraft-, or shuttle-based pulsed tunable CO2 laser DIAL system are given.

Brockman, P.↗
NASA NTRS1985

Cosmic rays in the 10(16) to 10(19) eV range from pulsars

The flux is calculated of cosmic rays (CRs) produced by a distribution of pulsars that are: (1) born with rapid rotation rates, (2) slow down as they evolve, and (3) produce energetic nuclei with a characteristic energy proportional to their rotation rates. It is found that, for energy independent escape from the disk of the galaxy, the predicted spectrum will be essentially what is observed between approx 10 to the 16th power to 10 to the 19 power eV if the slow down law as inferred for radio pulsars can be extrapolated to young pulsars with shorter periods.

Wandel, A.↗
NASA NTRS1993

Raman scattering measurements of vibrational and rotational distributions in expanding nitrogen

Vibrational and rotational population distributions in expanding nitrogen in the supersonic nozzle of a reflected shock tunnel were investigated using spontaneous Raman scattering spectroscopy. The experimental data are compared with two multitemperature nonequilibrium calculations, one based on the Landau-Teller model for vibrational relaxation, the other on the solution of the vibrational master equations. Good agreement was found between both the Landau-Teller and the master equation solutions for the vibrational energy mode, but the experimentally inferred rotational temperatures were found to be systematically low, due to collisional narrowing. The dramatic increase in vibrational relaxation rates for a cooling flowfield reported in most previous studies was not reproduced by the present experiments.

Gillespie, Walter D.↗
NASA NTRS1993

Dynamics of the atmospheres of the outer planets - Post-Voyager measurement objectives

Current knowledge about dynamics and thermal structure on the outer planets is reviewed with the aim of identifying important measurements which should be made in the post-Voyager era. The existence of jets and cloud bands is the puzzle that underlies all others. Discussion focuses on the particular case of Jupiter because documentation is most complete. Recent dynamical work has successfully reproduced much of the behavior of jets and spots with simple models that contain few parameters. It is argued that the gross dynamical parameters, such as density stratification and rotation rate, are the keys to their behaviors, rather than the particular specifics of radiative forcing, cloud distributions, thermodynamic transformations. Voyager data have shown that the jet systems decay with height in the region above the visible clouds. Therefore the highest priority must be given to establishing dynamical parameters that characterize levels within and beneath the clouds. These require determination of the deep structure of the jets, of the density stratification, and of the horizontal density contrasts. The deep regions are not easily accessible, and these measurements present challenging opportunities. Indirect inferences about the controlling processes may sometimes be possible by observing waves and other activity in the more easily accessible stratosphere, and some of these issues are also discussed.

Gierasch, Peter J.↗
NASA NTRS1994

The parent magma of xenoliths in shergottite EETA79001: Bulk and trace element composition inferred from magmatic inclusions

The SNC meteorites are samples of the Martian crust, so inferences about their origins and parent magmas are of wide planetologic significance. The EETA79001 shergottite, a basalt, contains xenoliths of pyroxene-olivine cumulate rocks which are possibly related to the ALHA77005 and LEW88516 SNC lherzolites. Olivines in the xenoliths contain magmatic inclusions, relics of magma trapped within the growing crystals. The magmatic inclusions allow a parent magma composition to be retrieved; it is similar to the composition reconstructed from xenolith pyroxenes by element distribution coefficients. The xenolith parent magma is similar but not identical to parent magmas for the shergottite lherzolites.

Treiman, Allan H.↗
NASA NTRS1994

Infrared spectroscopic measurements of the total column abundance of ethan (C2H6) above Lauder, New Zealand

Total vertical column aboundances of atmospheric ethane (C2H6) have been retrieved form more than 350 high-resolution infrared solar spectra recorded on 129 days between December 1992 and March 1994 at the Network for the Detection of Stratospheric Change (NDSC) station in Lauder, New Zealand (latitude 45.04 deg S, 169.68 deg E, 0.37 km altitude). The results are based on nonlinear least squares fits to narrow spectral intervals containing the unresolved C2H6 nu (sub 7) band (P)Q(sub 3) and (R)Q(sub 0) subbranches at 2976.8 and 2986.7/cm. The measured Lauder column abundances show a pronounced seasonal cycle with a maximum value of (8.6 +/- 0.5) x 10(exp 15) molecules/sq cm in September and a minimum value of (3.8 +/- 0.5) x 10 (exp 15) molecules/sq cm in February. Assuming a realistic vertical distribution for C2H6, these values correspond to surface level volume-mixing ratios of 0.52 and 0.23 ppbv (parts per billion by volume), respectively. The phase and relative amplitude of the Lauder C2H6 seasonal cycle are similar to corresponding values determined from infrared measurements at the Jungfraujoch (46.55 deg N, 7.98 deg E, 3.58 km altitude) and Mauna Loa (latitude 19.5 deg N, longitude 155.6 deg W, 3.5 km altitude) NDSC stations, but the inferred absolute magnitudes of the Lauder surface level mixing ratios during the same season are significantly lower. The Lauder C2H6 measurements are also compared with published southern hemisphere surface level sampling measurements and two-dimensional model calculations.

Rinsland, Curtis P.↗
NASA NTRS1996

Seasonal Variations of Water Vapor in the Lower Stratosphere Inferred from ATMOS/ATLAS-3 Measurements of H2O and CH4

Stratospheric measurements of H2O and CH4 by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer on the ATLAS-3 shuttle flight in November 1994 have been examined to investigate the altitude and geographic variability of H2O and the quantity H = (H2O + 2CH4) in the tropics and at mid-latitudes (8 to 49 deg N) in the northern hemisphere. The measurements indicate an average value of 7.24 +/- 0.44 ppmv for H between altitudes of about 18 to 35 km, corresponding to an annual average water vapor mixing ratio of 3.85 +/- 0.29 ppmv entering the stratosphere. The H2O vertical distribution in the tropics exhibits a wave-like structure in the 16- to 25-km altitude range, suggestive of seasonal variations in the water vapor transported from the troposphere to the stratosphere. The hygropause appears to be nearly coincident with the tropopause at the time of observations. This is consistent with the phase of the seasonal cycle of H2O in the lower stratosphere, since the ATMOS observations were made in November when the H2O content of air injected into the stratosphere from the troposphere is decreasing from its seasonal peak in July-August.

Abbas, M. M.↗
NASA NTRS1985

The albedo field and cloud radiative forcing produced by a general circulation model with internally generated cloud optics

A general circulation model (GCM) study is presented in which cloud radiative properties are computed from cloud liquid water content inferred from the GCM hydrological cycle. Model-generated and satellite albedos are in rough agreement. Analysis of the cloud radiative forcing indicates that cloud albedo effects overcome cloud infrared opacity effects in most regions. Both computed and observed albedo of clouds decrease from low to high altitudes. The model with variable cloud optics produces significantly different regional albedos from the same one with fixed cloud optics, especially over the tropics. The cloud droplet size distribution also has a significant impact on the model albedos. The temperature of the tropical upper troposphere is somewhat sensitive to the microphysical characteristics of the model cirrus clouds.

Charlock, T. P.↗
NASA NTRS1990

Application of high stability oscillators to radio science experiments using deep space probes

The microwave telecommunication links between the earth and deep space probes have long been used to conduct radio science experiments which take advantage of the phase coherency and stability of these links. These experiments measure changes in the phase delay of the signals to infer electrical, magnetic and gravitational properties of the solar system environment and beyond through which the spacecraft and radio signals pass. The precision oscillators, from which the phase of the microwave signals are derived, play a key role in the stability of these links and therefore the sensitivity of these measurements. These experiments have become a driving force behind recent and future improvements in the Deep Space Network and spacecraft oscillators and frequency and time distribution systems. Three such experiments which are key to these improvements are briefly discussed and relationship between their sensitivity and the signal phase stability is described. The first is the remote sensing of planetary atmospheres by occultation in which the radio signal passes through the atmosphere and is refracted causing the signal pathlength to change from which the pressure and the temperature of the atmosphere can be derived. The second experiment is determination of the opacity of planetary rings by passage of the radio signals through the rings. The third experiment is the research for very low frequency gravitational radiation. The fractional frequency variation of the signal is comparable to the spatial strain amplitude the system is capable of detecting. A summary of past results and future possibilities for these experiments are presented.

Kursinski, Emil R.↗
NASA NTRS1995

Solar wind ion composition and charge states

The solar wind, a highly tenuous plasma streaming from the Sun into interplanetary space at supersonic speed, is roughly composed of 95% hydrogen and 5% helium by number. All other, heavy elements contribute less than 0.1% by number and thus are truly test particles Nevertheless, these particles provide valuable information not present in the main components. We first discuss the importance of the heavy ions as tracers for processes in the solar atmosphere. Specifically, their relative abundances are found to be different in the solar wind as compared to the photosphere. This fractionation, which is best organized as a function of the first ionization time (FIT) of the elements under solar surface conditions, provides information on the structure of the chromosphere. where it is imparted on the partially ionized material by an atom-ion separation mechanism. Moreover, the charge states of the heavy ions can be used to infer the coronal temperature, since they are frozen-in near the altitude where the expansion time scale overcomes the ionization/recombination time scales. Next, we review the published values of ion abundances in the solar wind, concentrating on the recent results of the SWICS instrument on Ulysses. About 8 elements and more than 20 charge states can be routinely analyzed by this sensor. There is clear evidence that both the composition and the charge state distribution is significantly different in the fast solar wind from the south polar coronal hole, traversed by Ulysses in 1993/94, as compared to the solar wind normally encountered near the ecliptic plane. The fractionation between low- and high-FIT elements is reduced, and the charge states indicate a lower, more uniform coronal temperature in the hole. Finally, we discuss these results in the framework of existing theoretical models of the chromosphere and corona, attempting to identify differences between the low- and high-latitude regions of the solar atmosphere.

vonSteiger, R.↗
NASA NTRS1986

The magnetosphere of Uranus - Hot plasma and radiation environment

Inferences are drawn on the morphology and composition of the Uranus magnetosphere based on low-energy charged particle data collected by Voyager 2. Proton and electron energies in the magnetosphere attained energies of 4 and 1.2 MeV, respectively, although electron intensities surpassed the proton intensities at most energy levels. Protons dominated in the ion energy regime 0.6-1.0 MeV. The ion and electron spectra were Maxwellian below about 200 keV and had a power law distribution at energies over 590 keV. The power law was reduced by a factor of nearly three inside the orbit of Miranda. The proton population is dense enough to polymerize CO and CH4 ice surfaces within 10,000-100,000 yr. The data indicated that the particles are swept out at least to the orbit of Titania by the satellites. The morphology of the magnetosphere closely resembles that around Jupiter, except that plasma sheet distorsion from particle loading is negligible in regions within 15 Uranus radii.

Krimigis, S. M.↗
NASA NTRS1990

The distribution of middle tropospheric carbon monoxide during early October 1984

The measurement of Air Pollution from Satellite experiment measured the distribution of middle-tropospheric CO from the Space Shuttle during October 1984. The data represent average mixing ratios between 57 deg N and 57 deg S. Approximately 75,000 individual CO measurements were obtained during the 9-day mission. The data are presented in maps that show the CO mixing ratios averaged over 5 x 5-deg areas for 6 days of the mission. Comparisons with concurrent direct measurements taken aboard aircraft show that the inferred concentrations are systematically low by 20-40 percent, depending upon which direct measurement calibration standard is used. The data show that there are very large CO sources resulting from biomass burning over South America and southern Africa. Measured mixing ratios were high over northeast Asia and were highly variable over Europe.

Reichle, Henry G., Jr.↗
NASA NTRS1992

Dynamics of the atmospheres of the outer planets

Current knowledge about dynamics and the thermal structure of the outer planets is reviewed with the aim of identifying important measurements which should be made in the post-Voyager era. The existence of jets and cloud bands is the puzzle that underlies all others. The discussion focuses on the particular case of Jupiter because the documentation is the most complete. It is argued that the gross dynamical parameters of the outer planetary atmospheres are the keys to their behaviors, rather than the particular specifics of radiative forcing, cloud distributions, or thermodynamic transformations. Voyager data has shown that the jet systems decay with height in the region above the visible clouds. Therefore, the highest priority must be given to establishing dynamical parameters that characterize levels within and beneath the clouds. These require the determination of the deep structure of the jets, of the density stratification, and of the horizontal density contrasts. The deep regions are not easily accessible and these measurements present challenging opportunities. Indirect inferences about the controlling processes may sometimes be possible by observing waves and other activity in the more easily accessible stratosphere.

Gierasch, Peter J.↗
NASA NTRS1994

The faint end of the galaxy luminosity function

The evolution of the B- and K-band luminosity functions of galaxies is inferred in a relatively model-independent way from deep spectroscopic and photometric surveys. We confirm earlier evidence by Eales for an increase in the amplitude of the B-band galaxy luminosity function at modest redshift (z less than or approx. 0.2). We find in addition that the slope of the faint end of the luminosity function must systematically steepen and progress toward more luminous galaxies with increasing lookback time, assuming that the galaxy redshift distribution may be smoothly extrapolated 2 mag fainter than observed, as suggested by recent gravitational lensing studies. This evolution is shown to be color-dependent, and we predict the near-infrared color distribution of faint galaxies. The luminosity function of blue (B - K less than or approx. 4) galaxies in the range 0.2 less than or approx. z less than or approx. 1 can be represented by a Schechter function with characteristic light density phi(sup *) L(sup *) comparable to that of present-day late-type galaxies, but with a steeper faint end slope alpha approx. 1.4.

Treyer, Marie A.↗
NASA NTRS1996

ASTROP2 Users Manual: A Program for Aeroelastic Stability Analysis of Propfans

This manual describes the input data required for using the second version of the ASTROP2 (Aeroelastic STability and Response Of Propulsion systems - 2 dimensional analysis) computer code. In ASTROP2, version 2.0, the program is divided into two modules: 2DSTRIP, which calculates the structural dynamic information; and 2DASTROP, which calculates the unsteady aerodynamic force coefficients from which the aeroelastic stability can be determined. In the original version of ASTROP2, these two aspects were performed in a single program. The improvements to version 2.0 include an option to account for counter rotation, improved numerical integration, accommodation for non-uniform inflow distribution, and an iterative scheme to flutter frequency convergence. ASTROP2 can be used for flutter analysis of multi-bladed structures such as those found in compressors, turbines, counter rotating propellers or propfans. The analysis combines a two-dimensional, unsteady cascade aerodynamics model and a three dimensional, normal mode structural model using strip theory. The flutter analysis is formulated in the frequency domain resulting in an eigenvalue determinant. The flutter frequency and damping can be inferred from the eigenvalues.

Reddy, T. S. R.↗
NASA NTRS2002

Comet Grains: Their IR Emission and Their Relation to ISM Grains

Comets and the chodritic, porous interplanetary dust particles (CP IDPs) that they shed in their comae are reservoirs of primitive solar nebula materials. The high porosity and fragility of cometary grains and CP IDPs, and anomalously high deuterium contents of highly fragile, pyroxene-rich Cluster IDPs imply these aggregate particles contain significant abundances of grains from the interstellar medium (ISM). IR spectra of comets (3 - 40 micron) reveal the presence of a warm (nearIR) featureless emission modeled by amorphous carbon grains. Broad and narrow resonances near 10 and 20 microns are modeled by warm chondritic (50% Fe and 50% Mg) amorphous silicates and cooler Mg-rich crystalline silicate minerals, respectively. Cometary amorphous silicates resonances are well matched by IR spectra of CP IDPs dominated by GEMS (0.1 micron silicate spherules) that are thought to be the interstellar Fe-bearing amorphous silicates produced in AGB stars. Acid-etched ultramicrotomed CP IDP samples, however, show that both the carbon phase (amorphous and aliphatic) and the Mg-rich amorphous silicate phase in GEMS are not optically absorbing. Rather, it is Fe and FeS nanoparticles embedded in the GEMS that makes the CP IDPs dark. Therefore, CP IDPs suggest significant processing has occurred in the ISM. ISM processing probably includes in He' ion bombardment in supernovae shocks. Laboratory experiments show He+ ion bombardment amorphizes crystalline silicates, increases porosity, and reduces Fe into nanoparticles. Cometary crystalline silicate resonances are well matched by IR spectra of laboratory submicron Mg-rich olivine crystals and pyroxene crystals. Discovery of a Mg-pure olivine crystal in a Cluster IDP with isotopically anomalous oxygen indicates that a small fraction of crystalline silicates may have survived their journey from AGB stars through the ISM to the early solar nebula. The ISM does not have enough crystalline silicates (<5%) , however, to account for the deduced abundance of crystalline silicates in comet dust. An insufficient source of ISM Mg-rich crystals leads to the inference that most Mg-rich crystals in comets are primitive grains processed in the early solar nebula prior to their incorporation into comets. Mg-rich crystals may condense in the hot (approx. 1450 K), inner zones of the early solar nebula and then travel large radial distances out to the comet-forming zone. On the other hand, Mg-rich silicate crystals may be ISM amorphous silicates annealed at approx. 1000 K and radially distributed out to the comet-forming zone or annealed in nebular shocks at approx. 5 - 10 AU. Determining the relative abundance of amorphous and crystalline silicates in comets probes the relative contributions of ISM grains and primitive grains to small, icy bodies in the solar system. The life cycle of dust from its stardust origins through the ISM to its incorporation into comets is discussed.

Wooden, Diane H.↗
NASA NTRS2020

The Impacts of Fossil Fuel Emission Uncertainties and Accounting for 3-D Chemical CO2 Production on Inverse Natural Carbon Flux Estimates from Satellite and In Situ Data

Atmospheric carbon dioxide (CO2) inversions for estimating natural carbon fluxes typically do not allow for adjustment of fossil fuel CO2 emissions, despite significant uncertainties in emission inventories and inadequacies in the specification of international bunker emissions in inversions. Also, most inversions place CO2 release from fossil fuel combustion and biospheric sources entirely at the surface. However, a non-negligible portion of the emissions actually occurs in the form of reduced carbon species, which are eventually oxidized to CO2 downwind. Omission of this ‘chemical pump’ can result in a significant redistribution of the inferred total carbon fluxes among regions. We assess the impacts of different prescriptions of fossil fuel emissions and accounting for the chemical pump on flux estimation, with a novel aspect of conducting both satellite CO2 observation-based and surface in situ-based inversions. We apply 3-D carbon monoxide (CO) loss rates archived from a state-of-the-art GEOS chemistry and climate model simulation in a forward transport model run to simulate the distribution of CO2 originating from oxidation of carbon species. We also subtract amounts from the prior surface CO2 fluxes that are actually emitted in the form of fossil and biospheric CO, methane, and nonmethane volatile organic compounds (VOCs). We find that the posterior large-scale fluxes are generally insensitive to the finer-scale spatial differences between the ODIAC and CDIAC fossil fuel CO2 gridded datasets and assumptions about international bunker emissions. However, accounting for 3-D chemical CO2 production and the surface correction shifts the global carbon sink, e.g., from land to ocean and from the tropics to the north, with a magnitude and even direction that depend on assumptions about the surface correction. A GOSAT satellite-based inversion is more sensitive to the chemical pump than one using in situ observations, exhibiting substantial flux impacts of 0.28, 0.53, and -0.47 Pg C yr(exp -1) over tropical land, global land, and oceans, due to differences in the horizontal and vertical sampling of the wo observation types. Overall, the biases from neglecting the chemical pump appear to be minor relative to the flux estimate uncertainties and the differences between the in situ and GOSAT inversions, but their relative importance will grow in the future as observational coverage further increases and satellite retrieval biases decrease.

James S Wang↗