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1.
Nine plates of the 7883-Å CO2 band were taken between phase angles 7.2 and 10.7° in 1971. A curve-of-growth analysis of 28 rotational lines in the band indicates an average rotational temperature of 236 ± 8°K; the average slope of the curve of growth was 0.63 ± 0.06. The results for this band are compared to those for the 7820-Å band. 相似文献
2.
We present equivalent widths of Venus CO2 scans of the P branch (P8–P32) of the 5ν3 band at 8689 Å, the P16 line of the 5ν3 band, and the P14 line of the ν1 + 5ν3 band at 7820 Å covering phase angles between 5°.1 and 170°. The equivalent widths reach a minimum at 10°, in agreement with a phase function with a backward lobe at 160° which is caused by a single internal reflection within the cloud particles. This is evidence that Venus cloud particles are composed of liquid droplets. Maximum equivalent widths are observed at ～60°, a value which is closer to the maximum of single-layer Mie scattering models than to that of two-layer models. At high phase angles we observe equivalent widths greater than those computed from homogeneous scattering models, indicating that at high altitudes the mixing ratio of scattering particles to CO2 increases with depth. At all phase angles, particularly at large phase angles, the temporal and spatial variations in the observed equivalent widths confuse the phase variation. 相似文献
3.
The shapes of Venus' CO2 profiles are found to vary with solar phase angle. High-resolution spectra of the P16 and P14 lines in the 8689- and 7820-Å bands, respectively, are presented for phase angles ranging from 6 to 158°. The scattering mean free path at 80 mbar, approximately the effective pressure, is 1.7 km. Use of the van de Hulst similarity relations with simple, parametric scattering models is inadequare to separate effects due to the scattering phase function from those due to inhomogeneities in depth when one attempts to determine the atmospheric structure by fitting a family of such models over a wide range of phase angles. 相似文献
4.
To investigate further the Venus inverse phase effect, 12 plates of the 8689 Å CO2 band, taken in 1971, were analyzed for abundances and temperatures using the curve-of-growth method. We found an average rotational temperature of 230 ± 1°K for an average slope of the curve of growth of 0.56 ± 0.03. Day-to-day variations in the equivalent widths of the CO2 lines can be as large as 25%, and long-term changes in the cloud-top temperature are confirmed. On the other hand, the widely accepted “inverse” phase effect of CO2 line equivalent widths near superior conjunction receives no firm support from these results. 相似文献
5.
Forty-seven well exposed photographic plates of Venus which show the spectrum of the carbon dioxide band at 7820Å were obtained at Table Mountain Observatory in September and October 1972. These spectra showed a semiregular four-day variation in the CO2 abundance over the disk of the planet (Young et al., 1974). We also find evidence for temporal variations in the rotational temperature of this band and temperature variations over the disk. The two quantities, CO2 abundance and temperature, do not show any obvious relationship; however, an increase in the temperature usually is accompanied by a decrease in the abundance of CO2. The average temperature, found from a curve-of-growth analysis assuming a constant CO2 line width, is 249±1.4K (one standard deviation). This temperature is noticeably higher than the rotational temperature of 242±2K found for this same band in 1967 (Schorn et al., 1969) and of 242±1.2K in 1968–1969 (Young et al., 1971). 相似文献
6.
Photoelectric spectral scans of the P branch of the 8689 Å CO2 band on Venus were made using the 107-inch coude scanner during seven observing periods in the past 2 years. The relative CO2 line strength was determined for each scan, then normalized to remove the spatial variations leaving only temporal variations.The 4-day periodicity in the relative CO2 line strength noted by Young et al. (1973) is not unique; we do confirm their 4-day periodicity in August 1973. Four other observing periods rule out a 4-day periodicity.A definite North-South asymmetry in the relative CO2 line strength is noted during 1973, in most cases with the same periodicity present in both hemispheres. When the slit positions are referred to the equator of Venus, particularly near inferior conjunction, the large asymmetrics between the slit positions can be explained by a greater CO2 line strength over the polar regions and weaker over the equatorial latitudes. The amplitude of variation of each position on the crescent is much greater near inferior conjunction either because we are sampling a smaller area on the planet or because the upper atmospheric abundance is more sensitive to the mechanism causing the variation in the smaller regions sampled at inferior conjunction.Simultaneous H2O measurementsduring several of the observing runs indicate a lack of correlation in the relative CO2 line strengths and the H2O abundance. 相似文献
7.
Nine plates of the 7820 Å CO2 band were taken in 1971. A curve-of-growth analysis of the CO2 lines indicates a rotational temperature of 241 ± 2°K, with an average slope to the curve of growth of 0.60 ± 0.03. The Venus phase angle ranged from 7.2 to 10.7°. The equivalent widths of the 1971 data fall on a smooth curve fit through the 1969 data for this band; there does not appear to be any discontinuity in the phase curve at small phase angles. 相似文献
8.
By utilizing the known rotational constants for the 7820 and 7883 Å CO2 bands, we are able to derive substantially improved wavelengths for solar lines in the 7780–7925 Å region. 相似文献
9.
Thirty well-exposed photographic plates showing the spectrum of the carbon-dioxide band at 8689 Å in the atmosphere of Venus were obtained during 1968 and 1969. All spectra were obtained at a dispersion of 2 Å/mm for Venus phase angles varying from 10° to 126°. We find rotational temperatures ranging from 236 to 274 K. The average value of the rotational temperature is 246 ± 1 K (one standard deviation); for our 1967 observations, the rotational temperatures ranged from 222 to 248 K, with an average value of 238 ± 4 K. The variation of the equivalent width of the 8689 Å band, with Venus phase angle, was very similar for the two sets of observations (53 plates). The temporal variations, of approximately 30% were comparable with the phase variations over this limited range of phase angle. 相似文献
10.
George W. Kattawar 《Icarus》1979,40(1):60-66
We have introduced a method of partitioning the radiance emerging from a planetary atmosphere in proportion to the average number of scatterings in each atmospheric layer in order to gain a more fundamental understanding of the so-called level of line formation. A realistic model of the Venus atmosphere was used to compute the radiance for a range of phase angles and two planetary colatitudes, namely, 20 and 90°. We computed the core and continuum radiances for the P(16) line of 8689-Å CO2 band and introduced two ways of computing an effective temperature. Both definitions yielded similar results. We found that these effective temperatures varied little with phase angles up to 120°, but fell rather rapidly beyond this point. Also colder effective temperatures were found as we went from equator to pole. The results obtained are all consistent with the spectroscopic temperature determination from CO2 band studies. We have also defined an effective optical depth, τeff, which we feel gives a better understanding of the level of line formation than other definitions used to date. 相似文献
11.
Simultaneous measurements of the upper mesospheric NaD and OH(8,3) band emissions by meridional scanning photometers, and the OI 5577 Å, O2 Atmospheric band at 8645 Å, NaD and OH(8,3) band emissions by multi-channel tilting filter type zenith photometers have been carried out at Cachoeira Paulista (22.7°S, 45.0°W), Brazil. On two nights during the period May–August 1983, the meridional scanning observations showed horizontal intensity gradients and phase propagations. The nocturnal intensity variations on one of these occasions 13–14 June 1983, which was a magnetically disturbed night with 4 ?kp? 8, also showed vertical phase propagation. In this paper, we present these observations and discuss the possible effects of the horizontal wind system and of gravity wave propagation. 相似文献
12.
Photoelectric observations of the strength of the CN band at 3880 Å and of the C2 bands at 5165 Å and 5635 Å were obtained on eight nights from January 13, 1974 to February 21, 1974. Observations were limited to the nucleus and inner coma. 相似文献
13.
N.N. Shefov 《Planetary and Space Science》1983,31(11):1371-1372
Frank-Condon factors for H2O+ bands have been calculated. They are used to estimate the photon scattering coefficient g8.0 for the (8,0) band at 6158 Å. 相似文献
14.
V.G. Teifel 《Icarus》1977,30(1):138-154
Results of photoelectric measurements of the intensity in CH4 5430, 6190, and 7250 Å absorption bands, CH4 absorption lines in the 3ν3 band, and the NH3 6457.1 Å line are examined from the point of view of a model which takes into account the role of multiple scattering inside a homogeneous semi-infinite cloud layer in the formation of absorption components in the Jovian spectrum. Introduced are a number of simple ratios between depths of lines and bands and the parameters which characterize the properties of the cloud layer and the atmosphere above the clouds for occurrence of the Henyey-Greenstein scattering phase function at various degrees of asymmetry in g. The CH4 content inside the cloud layer is determined as an equivalent thickness on the mean free path between scattering events. The latter was found to be equal to AL ? 10 ± 2 m-amagat at g = 0.75 or AL ? 20 ± 3 m-amagat at g = 0.5 along all the above-mentioned CH4 absorption bands. For NH3 it is AL ? 31 ± 4 cm-amagat at g = 0.75 and AL ? 62 ± 8 cm-amagat at g = 0.5.The weakening of the CH4 absorption bands toward the edges of the Jovian disc requires a volume scattering coefficient in the cloud layer of σa ～ 10?6 cm?1. The mean specific abundance of NH3 obtained within the cloud layer does not contradict the calculated abundance of saturated gaseous ammonia. 相似文献
15.
We present eight new 0.8 to 2.4 μm spectral observations of Neptune's satellite Triton, obtained at IRTF/SpeX during 2002 July 15-22 UT. Our objective was to determine how Triton's near-infrared spectrum varies as Triton rotates, and to establish an accurate baseline for comparison with past and future observations. The most striking spectral change detected was in Triton's nitrogen ice absorption band at 2.15 μm; its strength varies by about a factor of two as Triton rotates. Maximum N2 absorption approximately coincides with Triton's Neptune-facing hemisphere, which is also the longitude where the polar cap extends nearest Triton's equator. More subtle rotational variations are reported for Triton's CH4 and H2O ice absorption bands. Unlike the other ices, Triton's CO2 ice absorption bands remain nearly constant as Triton rotates. Triton's H2O ice is shown to be crystalline, rather than amorphous. Triton's N2 ice is confirmed to be the warmer, hexagonal, β N2 phase, and its CH4 is confirmed to be highly diluted in N2 ice. 相似文献
16.
Andrew T. Young 《Icarus》1977,32(1):1-26
A simple radiative-transfer theory that allows for the change in the absorptions of sulfur and carbon dioxide with depth in the atmosphere of Venus can account simultaneously for (1) the spectral reflectance of Venus; (2) the wavelength dependence of contrast in uv cloud features; (3) the CO2 line profile; (4) the change in slope of the curve of growth from the 7820- to the 10488-Å CO2 bands; and (5) the rotational temperature near 246°K found for all CO2 bands. The model cloud consists of 1-μm sulfuric-acid particles, which are well mixed between about 64 km and the 49-km cloud base found by Veneras 9 and 10, plus an overlapping cloud of much larger sulfur particles that extends down to the 35-km cloud base found by Venera 8. The mixing ratios (by number of molecules) below about 64 km are: H2O, 2 × 10?4; H2SO4, 10?5; and sulfur, 10?4. Although the cloud contains an order of magnitude more sulfur than sulfuric acid, the sulfur particles are an order of magnitude larger, and so have only about 1% of the number density of the acid droplets. The “black-white” radiative-transfer model assumes perfectly conservative scattering above the level (which depends on wavelength) where an absorber becomes “black” due to the local temperature and pressure. So-called homogeneous scattering models are inherently self-contradictory, and are inapplicable to planetary atmospheres; the vertical inhomogeneity is an essential feature that must be modeled correctly. The pressure of CO2 line formation is about half the pressure in the region where uv markings occur. 相似文献
17.
The phase function for anisotropic scattering is applied to a homogeneous atmospheric model to ascertain the effects of anisotropy on the near-infrared spectrum of Venus. L. D. G. Young's equivalent widths for the 820 Å CO2 band are analyzed to derive allowed combinations of CO2 specific abundance, continuum albedo, pressure, and degree of anisotropy. From these combinations, values are derived for the photon mean-free path and total optical thickness of the clouds. The Venera 10 measurement of the transmitted flux at 7200 Å is then used in conjunction with spherical albedo requirements to reduce the range of possible solutions to the equivalent-width analysis. Through the application of approximate similarity relations, the “true” (i.e., anisotropic) atmospheric parameters are derived from the isotropic values. For an assumed Mie scatterer with an average anisotropy factor of 〈cos θ〉 = 0.7, the results indicate a total optical thickness of about 55 with a single-scattering albedo of 0.9992 to 0.9995. 相似文献
18.
Edwin S. Barker 《Icarus》1975,25(2):268-281
The Venus water vapor line at 8197.71 Å has been monitored at several positions on the disk of Venus and at phase angles between 21° and 162°. Variations in the abundance have been found with spatial location, phase angle and time. During the 1972–1974 period, the total two-way absorption has varied from less than 1 to 77 μm of water vapor. The dependence on phase angle indicates 20 to 50 μm over the disk between 30° and 110° and small, but detectable amounts present during the rest of the observations. The spatial distribution with respect to the intensity equator is uniform with no location on the disk having systematically a higher or lower abundance. Comparisons made between the water vapor abundandances and the CO2 abundances determined from near-simultaneous observations of CO2 bands at the same positions on the disk of Venus show no correlation for the majority of the samples. 相似文献
19.
Spatially resolved absolute reflectivities of several regions of the Jovian disk in the wavelength region 3000 to 10760 Å are presented. Spectra were obtained of the central meridian and limbs of the Equatorial Region, North Equatorial Belt, and North Tropical Zone. Equivalent widths of several CH4 and NH3 bands are measured. The spatial variations of continuum reflectivity and absorption band profiles are shown in various ratio spectra. 相似文献
20.
Spectrophotometry of Venus from 2170 to about 1950 Å has been obtained by OAO-2 at 10 Å resolution. The new data confirm and extend previous indications that the geometric albedo decreases continuously below 2500 Å. Secular changes in either the amount or distribution, or both, of absorbing constituents in the upper atmosphere are strongly suggested. A narrow absorption feature is found near 2145 Å, confirming an earlier report by Anderson et al. [J. Atmos. Sci.26 (1969), 874–888]. Absorption by trace amounts of nitrogen-bearing molecules, including N2O, HNO3 in aqeous solution, and possibly also NO, together with Rayleigh scattering from CO2, can account for the variation in albedo below 3200 Å, but other explanations are not excluded. For example, H2S may contribute to or be responsible for the decrease in albedo below 2500 Å. 相似文献