Water Vapor in the Atmosphere of Venus.

Bottema, Murk J.; Plummer, William T.; Strong, John

doi:10.1086/147841

Cited by 50 publications

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“…With cloudtop pressures of the order of 1 atm [Sagan, 1962], temperatures about 230 o K, and an upper Iimit of 10 .... g cm ..... of water vapor above the clouds [DollfWJ, 1963;Bottema et al, 1964;Spinrad, 1962b], it is clear that water vapor cannot significantly affect the lapse rate above the clouds-approximately one hundred times more water is required. CO. and N. will not condense at the pressures and temperatures of interest.…”

Section: Above the Cloudsmentioning

confidence: 99%

The infrared limb darkening of Venus

Pollack¹,

Sagan²

1965

J. Geophys. Res.

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The observed infrared limb darkening of Venus in the 8‐ to 13‐micron interval and over the observed range in μ, the cosine of the Venus zenith angle, can be expressed as μa, where α ≈ 0.5, according to two independent sets of measurements. Three general categories of models of the atmosphere and clouds of Venus are here proposed to explain the observed limb darkening. For each model, convective and then radiative equilibrium is assumed. In models A, limb darkening is attributed to the temperature gradient in an unknown, approximately gray absorber above the visible cloud deck. Other properties of the absorber, required so that α ≈ 0.5, render these models rather unlikely. In models B, limb darkening is attributed to a combination of the temperature gradient and the angular dependence of the emissivity in approximately gray multiply scattering clouds, initially with isotropic phase functions. In convective model B1, agreement with observation is secured for moderate values of , the albedo for infrared single scattering, if the clouds are diffuse by terrestrial standards; high implies more compact clouds. The temperature range with depth, particle number density, and composition of the clouds are discussed. Moderate variation of the extinction coefficient with depth in the clouds has little effect on the predicted limb darkening over the range in μ reliably observed; but closer to the limb, and for low values of , such variation may significantly influence the limb darkening. In radiative model B2, high values of lead to predictions of the planetary bolometric albedo in conflict with observations. Moderate values of lead to the observed limb‐darkening law if the 8‐ to 13‐μ opacity is about 2.5 times the mean opacity, which is a property of silicate clouds. The preceding models are extended to anisotropic phase functions and to other values of α. An anisotropic phase function of the form (1 + cos θ) increases the contribution of the emissivity to a by about 20%. In models C, the clouds coherently redistribute radiation emitted by the underlying atmosphere. The absence of marked spectral features in 8‐ to 13‐μ Venus spectroscopy leads to the rejection of model C. Methods are described for removing the remaining ambiguity among the models.

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Section: Above the Cloudsmentioning

confidence: 99%

The infrared limb darkening of Venus

Pollack¹,

Sagan²

1965

J. Geophys. Res.

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“…The presence of C0 2 has been known for some time (Adams and Dunham 1932), and the recent measurements by the Veneras 4, 5, and 6 (Avduevsky, Marov, andRozhdestvensky 1968, 1970) and by Mariner V (Fjeldbo, Kliore, and Eshleman 1971) have established the percentage of this gas at between 93 and 97%. Water vapor has been detected spectroscopically by a number of workers (Dollfus 1965;Bottema, Plummer, and Strong 1964;Hunten, Belton, and Spinrad 1967;Connes et al 1967;Owen 1967;Schom et al 1969;Kuiper et al 1969) although the amount and degree of variability of the H 2 0 above the clouds is uncertain (Schom and Young 1971). The direct detection of H 2 0 by the Venera probes has been reported, the percentage of H 2 0 reported to be within the range of 0.4-1.1% by volume (Avduevsky et al 1970).…”

Section: Introductionmentioning

confidence: 99%

Spectral Observations of Venus in the Frequency Interval 18.5-24.0 GHz: 1964 and 1967-68

Jones¹,

Wrathall²,

Meredith³

1972

PASP

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, Venus was observed with a tunable radiometer at eight frequencies in the interval 20.6-24.0 GHz and again at six frequencies in the interval 18.5-24.0 GHz during an eight-month period beginning approximately one month after the inferior conjunction of 1967. Microwave spectra for these frequency intervals were computed using the results from Mariner V and Veneras 4-7 and compared to these data. One block of data suggests a lower percentage of H2O than that reported by the Venera probes, while other blocks may be consistent with the probe data. These data therefore suggest that the distribution of water vapor down to atmospheric levels probed at these frequencies may vary with time or else the Venera probes may have detected localized enhancements in water vapor.

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“…If the hologram is not spatially selective it would not be possible to determine uniquely the source of the pollutant. The use of spatial filters for spectral detection is an old concept [4,5].…”

Section: _)mentioning

confidence: 99%

<title>Model for a novel holographic spectral pattern detector</title>

Bakker

Bykovski

1995

SPIE Proceedings

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The existing technology for detecting chemical species is based on spectral decomposition of light from a multi-species sample. This approach is limited because of line overlapping from different species and is getting increasingly unreliable when the number of species is large. We propose a holographic species analyzer, which decomposes an input in terms of a prespecified set of species. The innovation is to replace a diffraction grating with a holographic memory element designed to recognize the whole light patterns of different species and generate in an output plane a position sensitive map of species present. The holographic element can be optically or computer generated. The proposed technology is shown using computer models to be both highly wavelength and position sensitive.The detection and measurement of individual chemical components in complex samples such as flue gases, tobacco smoke, car exhausts, and complex protein mixtures is a serious problem. The need to accurately determine the presence and concentration of chemical components is an every day concern for many industries. For example, just over a year ago the U.S. Congress passed into law the Clean Air Act Amendments (CAAA) requiring 189 chemical components to be regulated. Implementation of the CAAA presents a real challenge for both companies and government regulatory agencies.The existing technology for optically detecting the presence of chemical species is based on spectral decomposition and developed more than a hundred years ago it is now close to its limit in terms of performance and reliability, especially for complex mixtures. Spectral decomposition measures either the spectral distribution from an excited, fluorescing compound or the optical absorption of a material. The specificity of this approach is due to the quantum electronic transitions that are specific for each atom or molecule and are responsible for the emission or absorption of electromagnetic radiation. Atomic spectra are typically a set of sharp lines of varying intensities, whereas for molecules, particularly large ones, the spectra are complex patterns of sharp lines and continuous bands. When a sample is simple enough spectral analysis is an adequate method, but for complex samples overlap of lines of different species limits the reliability of the method.In short, the present technology is rapidly becoming insufficient to meet the growing regulatory demands. The significance of this problem is based on our urgent need to evaluate and control our environment in a time of intensive use of chemicals. It is our belief that a paradigm shift is necessary. We believe it is possible to design a highly dedicated and selective sensor, sensitive to a specific spectral pattern, rather than to specific lines.We suggest here that smart holographic optical elements can be designed to record the entire chemical signature, or "fingerprint", of a compound. Holographic recording of a spectrum 236 / SPIE Vol. 2570 0-8194-1929-X/95/$6.O0 Downloaded From: http://proceedings.spiedigitalli...

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Water Vapor in the Atmosphere of Venus.

Cited by 50 publications

References 0 publications

The infrared limb darkening of Venus

The infrared limb darkening of Venus

Spectral Observations of Venus in the Frequency Interval 18.5-24.0 GHz: 1964 and 1967-68

<title>Model for a novel holographic spectral pattern detector</title>

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