NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Observations and analysis of O(1D) and NH2 line profiles for the coma of comet P/HalleyA set of high-resolution Fabry-Perot measurements of the coma of comet P/Halley was acquired in the (O I) 6300 A and NH2 6298.62 A emission lines. These high-resolution measurements provide the first optical observations capable of studying directly the photochemical kinetics and dynamic outflow of the coma. The observations were analyzed by a Monte Carlo Particle Trajectory Model. The agreement of the model and observed line profiles was excellent and verified the underlying dynamics, exothermic photodissociative chemistry, and collisional thermalization in the coma. The somewhat wider intrinsic line profile width for the O(1D) emission in 1986 January compared to 1986 May, is, for example, produced by the larger outflow speeds and gas temperatures nearer perihelion in January. The January O(1D) profile, which is wider than the January NH2 profile, is indicative of the photochemical kinetics in the dissociation of the parent molecules H2O and OH in the coma. The absolute calibration of the observations in 1986 January allowed the production rates for H2O and the NH2-parent molecules to be determined. The average daily water production rates derived from the O(1D) emission data for January 16 and 17 are presented. These very large water production rates are consistent with the extrapolated (and 7.6 day time variable) water production rates determined from the analysis of lower spectral resolution observations for O(1D) and H-alpha emissions that covered the time period up to January 13. The large production rates on January 16 and 17 establish that the maximum water production rate for comet Halley accurred pre-perihelion in January. Implications drawn from comparison with 18 cm radio emission data in January suggest that the peak water production rate was even larger. The average production rate for NH3 determined from the NH2 emission data for January 17 was (1.48 +/- 0.10) x 10(exp 28) molecules/s, yielding an NH3/H2O production rate ratio of 0.55%.
Document ID
19950041429
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Smyth, William H.
(Atmospheric and Environmental Research, Inc. Cambridge, MA, United States)
Combi, Michael R.
(Univ. of Michigan, Ann Arbor, MI United States)
Roesler, Fred L.
(Univ. of Wisconsin, Madison, WI United States)
Scherb, Frank
(Univ. of Wisconsin, Madison, WI United States)
Date Acquired
August 16, 2013
Publication Date
February 10, 1995
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 440
Issue: 1
ISSN: 0004-637X
Subject Category
Astronomy
Accession Number
95A73028
Funding Number(s)
CONTRACT_GRANT: NASW-4329
CONTRACT_GRANT: NAGW-695
CONTRACT_GRANT: NAGW-3319
CONTRACT_GRANT: NASW-4496
CONTRACT_GRANT: NAGW-1946
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available