Generating Synthetic Microphysical Observations Constrained by Satellite & Surface Measurements
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ARTEMIS Observations of Lunar Nightside Surface Potentials in the Magnetotail Lobes: Evidence for Micrometeoroid Impact Charging
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A. R. Poppe↗
Observations on the lunar surface disturbed by the footpads of Surveyor 1.
Mean particle size differences around Surveyor 1 footpads explain albedo differences seen in photographs
Filice, A. L.↗
Vibration detection using lasers
Interference displacement patterns produced when light from a laser illuminates diffusely reflecting, vibrating surface are observed and photographed. Standing wave modes on model surface can be interpreted in order to yield amplitude and frequency of vibrations. Flat, white surfaces yield best interference patterns, even over considerable surface curvature.
Massey, G. A.↗
Nanosecond radar observations of the ocean surface from a stable platform
The measurement of ocean surface waves with a nanosecond radar pulse from a fixed platform at vertical incidence is discussed. By reducing the pulse width of radar until the pulse width resolves the vertical water wave structure, a set of radar returns is available to describe the ocean surface characteristics which differs from returns obtained by conventional radars. A block diagram of the radar and the principles of operation are presented.
Yaplee, B. S.↗
Solar wind observations on the lunar surface with the Apollo-12 ALSEP.
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Neugebauer, M.↗
Microwave radiometric observations of simulated sea surface conditions.
Review of the results of an experimental investigation of various factors affecting the surface properties of the ocean as seen by a passive microwave radiometer operating at 2.66 GHz. The principal uncertainties in the absolute measurements of the thermal emissions from the sea in terms of molecular temperature are shown to stem from (1) surface contaminations, such as oil slicks, (2) spray and foam, (3) salinity variation, and (4) surface waves. The results of a variety of experiments conducted so far indicate that the direct contribution of surface films and spray to the thermal emission from the sea is considerably less significant than that of foam and waves.
Van Melle, M. J.↗
Topographical coordinates from Mariner 9 observations of the Martian surface
Results of Mariner 9 determinations of the coordinates of selected topographical features on Mars. An attempt is made to project uncertainties in such determinations, together with uncertainties in spin-rate and in the inertial orientation of the spin axis of Mars, to some epoch in the distant future, and, to examine the impact of further imaging data from a Mars synchronous orbiter in reducing the uncertainty of the location of any given surface feature on the planet relative to the orbiter. The effect of residual navigational uncertainties, and uncertainties in celestial orientation of the imaging system, on such determinations is discussed.
Mohan, S. N.↗
The radiolysis and radioracemization of amino acids on silica surfaces
Results are presented of experiments on the radioracemization of amino acids in the presence of silica surfaces such as may have been found on the prebiotic earth. L-leucine and a DL-leucine mixture deposited on samples of 1-quartz and an amorphous silica preparation (Syloid 63) was subjected to Co-60 gamma-ray irradiation, then analyzed by gas chromatography to determine the radiolysis and racemization rates. The quartz surface is found to have a marginal efficacy in enhancing radiolysis when compared with a crystalline L-leucine control, although enhancing radioracemization symmetrically by a factor of two. Both the radiolysis and radioracemization of L-leucine and DL-leucine on a Syloid-63 silica surface are observed to increase with increasing radiation dose, and to be substantially greater than in the crystalline controls. Additional experiments with the nonprotein amino acid isovaline deposited on Syloid 63 confirm the greater radiolysis susceptibility of amino acids deposited on silica with respect to the crystalline state, although racemization is not observed. The observations suggest that the presence of a silica surface would have a deleterious effect on any mechanism for the origin of molecular chirality relying on stereoselective beta-radiolysis.
Bonner, W. A.↗
Observations of oceanic surface-wind fields from the Nimbus-7 microwave radiometer
Brightness temperatures from the five-frequency dual-polarized scanning multichannel microwave radiometer (SMMR) on Nimbus 7 have been used to obtain surface wind fields over the ocean. The satellite-derived wind field for 1200Z, Feb. 19, 1979, in the eastern North Pacific has been compared with an operationally generated surface-wind analysis field. Previous point comparisons at selected locations have indicated that satellite winds are accurate to 3 m/sec. The results, although of a preliminary nature, indicate that SMMR-derived winds may be used to determine large-scale wind fields over the ocean, particularly in areas of strong wind gradients such as found in cyclonic systems.
Miller, J. R.↗
Satellite observation of atmosphere and surface interaction parameters
Atmosphere and ocean surface parameters are being derived from weather satellite data acquired by the High Resolution Infrared Sounder and the Microwave Sounding Unit. In this paper, the global distribution and accuracy of the derived parameters are described, and the satellite-derived skin surface temperature is compared with available shelter temperature. Seasonal and interannual changes are examined to study the response time of large-scale atmospheric changes to changes in surface conditions.
Chahine, Moustafa T.↗
Relating the temporal change observed by AIRSAR to surface and canopy properties of mixed conifer and hardwood forests of northern Michigan
The mixed hardwood and conifer forests of northern Michigan were overflown by a 3-frequency airborne imaging radar in Apr. and Jul. 1990. A set of 10 x 10 km test sites near the University of Michigan Biological Station at Douglas Lake and within the Hiawatha National Forest in the upper peninsula of Michigan contained training stands representing the various forest species typical of forest communities across the ecotone between the coniferous boreal forest and mid-latitude hardwood and coniferous forests. The polarimetric radar data were externally calibrated to allow interdate comparisons. The Apr. flight was prior to bud-break of deciduous species and patchy snowcover was present. The Jul. flights occurred during and 2 days after heavy rain showers, and provide a unique opportunity to examine the differences in radar backscatter attributable to intercepted precipitation. Analyses show that there are significant changes in backscattering between biophysically dissimilar forest stands on any given date and also between dates for a given forest stand. These differences in backscattering can be related to moisture properties of the forest floor and the overlying canopy and also to the quantity and organizational structure of the above-ground biomass.
Dobson, M. Craig↗
Venus surface radiothermal emission as observed by Magellan
Radiothermal emission results obtained by the Magellan spacecraft during its first 8-month cycle of data taking, corresponding to one full rotation of Venus, are reported. The new Magellan data confirm the existence of regions with extremely low values of radiothermal emission. Possible mechanisms to explain the anomalous phenomena are an interaction with a single interface between the atmosphere and a high-dielectric permittivity medium versus volume scattering from the interior of a low-loss medium. The discrimination between these mechanisms requires careful observation of the polarized state of the radiothermal emission and that of the radar scattering.
Pettengill, Gordon H.↗
Modeling energy and mass fluxes from prairie canopies
The main emphasis of this research project is on partitioning of mass and energy fluxes between vegetation and soil at the FIFE site, preparation of data from the FIFE Information System for an international thermal data set comparison, and studying the relation between surface temperatures observed from satellites and in situ measurements of surface temperature.
Norman, John M.↗
Springtime microwave emissivity changes in the southern Kara Sea
Springtime microwave brightness temperatures over first-year ice are examined for the southern Kara Sea. Snow emissivity changes are revealed by episodic drops in the 37- to 18-GHz brightness temperature gradient ratio measured by the Nimbus 7 scanning multichannel microwave radiometer. We suggest that the negative gradient ratios in spring 1982 result from increased scatter at 37 GHz due to the formation of a near-surface hoar layer. This interpretation is supported by the results of a surface radiation balance model that shows the melt signature occurring at below freezing temperatures but under clear-sky conditions with increased solar input to the surface. Published observations from the Greenland ice cap show a surface hoar layer forming under similar atmospheric conditions owing to the increased penetration and absorption of solar radiation just below the surface layer. In spring/early summer 1984 similar gradient ratio signatures occur. They appear to be due to several days of freeze-thaw cycling following the movement of a low-pressure system through the region. These changes in surface emissivity represent the transition from winter to summer conditions (as defined by the microwave response) and are shown to be regional in extent and to vary with the synoptic circulations.
Crane, Robert G.↗
Scales of variability of bio-optical properties as observed from near-surface drifters
A drifter equipped with bio-optical sensors and an automated water sampler was deployed in the California Current as part of the coastal transition zone program to study the biological, chemical, and physical dynamics of the meandering filaments. During deployments in 1987 and 1988, measurements were made of fluorescence, downwelling irradiance, upwelling radiance, and beam attenuation using several bio-optical sensors. Samples were collected by an automated sampler for later analysis of nutrients and phytoplankton species compositon. Large-scale spatial and temporal changes in the bio-optical and biological properties of the region were driven by changes in phytoplankton species composition which, in turn, were associated with the meandering circulation. Variance spectra of the bio-optical paramenters revealed fluctuations on both diel and semidiurnal scales, perhaps associated with solar variations and internal tides, respectively. Offshore, inertial-scale fluctuations were apparent in the variance spectra of temperature, fluorescence, and beam attenuation. Although calibration samples can help remove some of these variations, these results suggest that the use of bio-optical data from unattended platforms such as moorings and drifters must be analyzed carefully. Characterization of the scaled of phytoplankton variability must account for the scales of variability in the algorithms used to convert bio-optical measurments into biological quantities.
Abbott, Mark R.↗
Design of a three-layer antireflection coating for high efficiency indium phosphide solar cells using a chemical oxide as first layer
It is well known that the behavior of III-V compound based solar cells is largely controlled by their surface, since the majority of light generated carriers (63% for GaAs and 79% for InP) are created within 0.2 mu m of the surface of the illuminated cell. Consequently, the always observed high surface recombination velocity (SRV) on these cells is a serious limiting factor for their high efficiency performance, especially for those with p-n junction made by either thermal diffusion or ion implantation. A good surface passivation layer, ideally a grown oxide as opposed to a deposited one, will cause a significant reduction in the SRV without adding interface problems, thus improving the performance of III-V compound based solar cells. Another significant benefit to the overall performance of the solar cells can be achieved by a substantial reduction of their large surface optical reflection by the use of a well designed antireflection (AR) coating. In this paper, we demonstrate the effectiveness of using a chemically grown thermally and chemically stable oxide, not only for surface passivation but also as an integral part of a 3-layer AR coating for thermally diffused p+n InP solar cells. A phosphorus-rich interfacial oxide, In(PO3)3, is grown at the surface of the p+ emitter using an etchant based on HNO3, o-H3PO4 and H2O2. This oxide has the unique properties of passivating the surface as well as serving as an efficient antireflective layer yielding a measured record high AMO open-circuit voltage of 890.3 mV on a thermally diffused InP(Cd,S) solar cell. Unlike conventional single layer AR coatings such as ZnS, Sb2O3, SiO or double layer AR coatings such as ZnS/MgF2 deposited by e-beam or resistive evaporation, this oxide preserves the stoichiometry of the InP surface. We show that it is possible to design a three-layer AR coating for a thermally diffused InP solar cell using the In(PO3)3 grown oxide as the first layer and Al2O3 and MgF2 as the second and third layers respectively, so as to yield an overall theoretical reflectance of less than 2%. Since chemical oxides are readily grown on III-V semiconductors materials, the technique of using the grown oxide layer to both passivate the surface as well as serve as the first of a multilayer AR coating should work well for all III-V compound-based solar cells.
Moulot, Jacques↗
TES Observations of the Martian Surface and Atmosphere
The Thermal Emission Spectrometer (TES) instrument is a Fourier transform Michelson interferometer operating with 10 or 5 cm(exp -1) sampling in the thermal infrared spectral region from 1700 to 200 cm(exp -1) (-6 to 50 micrometers) where virtually all minerals have characteristic fundamental vibrational absorption bands. The TES data used in this paper are among the 6 x 10(exp 7) spectra collected during the early mapping phase of the Mars Global Surveyor (MGS) mission from southern hemisphere winter to early summer (aerocentric longitude, L(sub s), 107 deg to 297 deg. The methodology for separating the surface and atmospheric components of the radiance from Mars, which allows detailed analysis and interpretation of surface mineralogy, is described in previous paper. Additional information is contained in original extended abstract.
Christensen, P. R.↗