Spectrophotometry of comet P/Halley at wavelengths 275—710 nm from Vega 2

Moreels, G.; Clairemidi, J.; Parisot, J. P.; Zucconi, J. M.; Bertaux, Jean-Loup; Blamont, J. É.; Hersé, M.; Krasnopolsky, V. A.; Мороз, В. І.; Krysko, A. A.; Tkachuk, A. Yu.; Gogoshev, M. M.; Gogosheva, Ts.; Werner, R.; Spasov, S.

doi:10.1007/978-3-642-82971-0_99

Cited by 9 publications

(5 citation statements)

References 9 publications

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“…A detailed comparison with these data awaits further information about the observing geometries. While the evidence for the presence of ammonia and methane seems fairly conclusive from HIS ion mass spectra, the value derived for the relative production rates appears large compared to related results from Vega on the column abundances for NH and NH 2 • Moreels et al (1986) report column abundance ratios of NH/OH= 1.410-4 and NH2/0H = 710-4 . Although not directly related to Q(NH 3 )/Q(H2 0), these values are quite small compared to our result of l-210-2 • On the other hand, Moreels et al (1986) report for CH a ratio CH/OH = 0.05, and Wyckoff et al (1986) find from groundbased measurements in the visible spectrum CH+ /H 2 0+ = 0.04.…”

Section: The Ratio M/q = 15/18 and The Inferred Ratio Q(ch4)/q(h2 0)mentioning

confidence: 60%

Evidence for methane and ammonia in the coma of comet P/Halley

Allen

Delitsky

Huntress

et al. 1988

Exploration of Halley’s Comet

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Summary. Methane and ammonia abundances in the coma of Halley are derived from Giotto IMS data using an Eulerian model of chemical and physical processes inside the contact surface to simulate Giotto HIS ion mass spectral data for mass-to-charge ratios (m/q) from 15 to 19. The ratio m/q = 19/18 as a function of distance from the nucleus is not reproduced by a model for a pure water coma. It is necessary to include the presence of NH 3 , and uniquely NH 3 , in coma gases in order to explain the data. A ratio of production rates Q(NH3)/Q(H20) = 0.01-Q.02 results in model values approximating the Giotto data. Methane is identified as the most probable source of the distinct peak at m/q = 15. The observations are fit best with Q(CH4 )/Q(H2 0) = 0.02. The chemical composition of the comet nucleus implied by these production rate ratios is unlike that of the outer planets. On the other hand, there are also significant differences from observations of gas phase interstellar material.

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Section: The Ratio M/q = 15/18 and The Inferred Ratio Q(ch4)/q(h2 0)mentioning

confidence: 60%

Evidence for methane and ammonia in the coma of comet P/Halley

Allen

Delitsky

Huntress

et al. 1988

Exploration of Halley’s Comet

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“…The drawback, as Bertaux pointed out, is that this emission is significant relative to the total OH emission only at distances within ~ 100 km of the nucleus (independent of QH 2 O) a n d i s likely to be attenuated in comets with very high water production due to the absorption of solar Lyman-a radiation by H 2 0 near the nucleus. The latter probably accounts for the lack of detection of "prompt" OH emission by the TKS experiment on Vega-2 (Moreels et al 1987).…”

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confidence: 99%

Ultraviolet Spectroscopy of Cometary Comae

Feldman

1989

International Astronomical Union Colloquium

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During the past decade, vacuum ultraviolet spectra of over 30 comets have been obtained with the International Ultraviolet Explorer (IUE) satellite observatory. With few exceptions, the spectra of these comets appear to be similar, with OH and H produced by the photodissociation of water being the dominant species and emissions of C, O, S, CS and CO+2 usually present. Although signs of variability of many kinds in comet spectra appear, the evidence from the ultraviolet observations suggests that all comets have the same basic chemical composition and that observed differences are due to evolution and ageing processes. The principal exception is S2, which was detected by IUE in comet IRAS-Araki-Alcock (1983 VII), but not in any other comet to date. During the 1985–86 apparition of comet Halley, ultraviolet spectra were also obtained by other spacecraft and by sounding rocket instruments, including a long-slit imaging spectrograph. Further advances await future ultraviolet observations of comets by the Hubble Space Telescope and other planned ultraviolet astronomy missions.

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“…The u-parameter can be determined for each specific spectrum using equation (6) by linear regression on the basis of random number of dust points. The applied regression analysis model is such that the dependent variable y is a random variable and the values of the input variable x are accurately given: lgI() lgI©(?)…”

Section: Calculations Of the Spectral Index Umentioning

confidence: 99%

Investigation of Halley's Comet dust size distribution by Vega-2 interplanetary station visual spectra analysis

et al. 1999

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Spectra in the visible region measured on board the Vega-2 station are analysed to obtain the solar spectrum continuum reflected by the dust particles in the Halley comet coma. It is suggested to determine the continuum level for every individual spectrum. By the time of Vega encounter, the concentration and distribution of particles around the comet had changed. This resulted in a different spectral indices for spectra measured in different time. The cumulative size index has been calculated for each specific spectrum by linear regression on the basis of a random number of dust points. Eleven dust continuum wavelengths are selected. The spectral index shows the mean particle size in the line of sight column around the nucleus (values calculated for 1019 spectra are in the interval of 2.85 -3.48) . Its change with the radial distance to the nucleus is discussed. The continuum spectra are calculated with the obtained values of the spectral index and are normalised to the real spectra on the minimum of interval of pixels in relation to the specific dust intensity, with the help of a linear regression. The continuum spectrum follows well the course of the specific Halley's comet spectrum.

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Spectrophotometry of comet P/Halley at wavelengths 275—710 nm from Vega 2

Cited by 9 publications

References 9 publications

Evidence for methane and ammonia in the coma of comet P/Halley

Evidence for methane and ammonia in the coma of comet P/Halley

Ultraviolet Spectroscopy of Cometary Comae

Investigation of Halley's Comet dust size distribution by Vega-2 interplanetary station visual spectra analysis

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