Charge coupled device (CCD) spectroscopy of comets

Tuttle, Stephan-Oterma, Brooks 2, and Bowell

J. R. Johnson, Uwe - Fink, S. M. Larson

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Spectra of the four comets, Tuttle, Stephan-Oterma, Brooks 2, and Bowell, were taken with a prototype space telescope charge coupled device (CCD) camera using a 500 × 500 Texas Instruments chip. The spectra extended from 5600 to 10,400 Å at a resolution of ∼25 A ̊. The spatial coverage along the slit was 180{upwards double arrow}; its resolution was defined by the seeing (2-3{upwards double arrow}). Both absolute flux scales and spectral albedos were determined with the data reduction procedure which included flat fielding and sky subtraction. Comet Tuttle displayed extensive emissions by NH2, the red system of CN, and the C2 Swan bands as well as emissions by the forbidden oxygen lines [OI] 1D at 6300 and 6364 Å, and the ionic species H2O+. A feature at 6851 Å has been tentatively identified as the 3-0 band of CS+. Notable is the absence of the C2 Phillips bands whose transitions are optimally placed in our spectrum. The much dustier comet, Stephan-Oterma showed emissions by CN, NH2, and [OI] while only [OI] could be discerned in the noisier Brooks 2 spectrum. The fresh comet Bowell exhibited an unusually extended coma with an albedo times cross section two orders of magnitude larger than the other comets, a very flat albedo spectrum, and no emission features. For Tuttle and Stephan-Oterma, CN and NH2 column densities using a number of bands were calculated. The CN band intensity ratios show good agreement with theoretical fluorescence models. The spatial profiles for CN and NH2 were compared to two step Haser model decay calculations. The scale lengths most consistent with the data were compared with values previously reported and with values expected for various photodissociation reactions. Production rates were calculated for CN and NH2. These should be less model dependent because of the simultaneous collection of spectral and spatial information. The production rate ratios of the parents of CN and NH2 to the parent of OH are several orders of magnitude smaller than the solar abundance ratios of C/O and N/O.

Original languageEnglish (US)
Pages (from-to)351-372
Number of pages22
JournalIcarus
Volume60
Issue number2
DOIs
StatePublished - 1984

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comets
comet
charge coupled devices
spectroscopy
albedo
Swan bands
coma
data reduction
subtraction
photodissociation
slits
sky
fluorescence
cross section
cameras
chips
prototypes
brook
telescopes
oxygen

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Charge coupled device (CCD) spectroscopy of comets : Tuttle, Stephan-Oterma, Brooks 2, and Bowell. / Johnson, J. R.; Fink, Uwe -; Larson, S. M.

In: Icarus, Vol. 60, No. 2, 1984, p. 351-372.

Research output: Contribution to journalArticle

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abstract = "Spectra of the four comets, Tuttle, Stephan-Oterma, Brooks 2, and Bowell, were taken with a prototype space telescope charge coupled device (CCD) camera using a 500 × 500 Texas Instruments chip. The spectra extended from 5600 to 10,400 {\AA} at a resolution of ∼25 A ̊. The spatial coverage along the slit was 180{upwards double arrow}; its resolution was defined by the seeing (2-3{upwards double arrow}). Both absolute flux scales and spectral albedos were determined with the data reduction procedure which included flat fielding and sky subtraction. Comet Tuttle displayed extensive emissions by NH2, the red system of CN, and the C2 Swan bands as well as emissions by the forbidden oxygen lines [OI] 1D at 6300 and 6364 {\AA}, and the ionic species H2O+. A feature at 6851 {\AA} has been tentatively identified as the 3-0 band of CS+. Notable is the absence of the C2 Phillips bands whose transitions are optimally placed in our spectrum. The much dustier comet, Stephan-Oterma showed emissions by CN, NH2, and [OI] while only [OI] could be discerned in the noisier Brooks 2 spectrum. The fresh comet Bowell exhibited an unusually extended coma with an albedo times cross section two orders of magnitude larger than the other comets, a very flat albedo spectrum, and no emission features. For Tuttle and Stephan-Oterma, CN and NH2 column densities using a number of bands were calculated. The CN band intensity ratios show good agreement with theoretical fluorescence models. The spatial profiles for CN and NH2 were compared to two step Haser model decay calculations. The scale lengths most consistent with the data were compared with values previously reported and with values expected for various photodissociation reactions. Production rates were calculated for CN and NH2. These should be less model dependent because of the simultaneous collection of spectral and spatial information. The production rate ratios of the parents of CN and NH2 to the parent of OH are several orders of magnitude smaller than the solar abundance ratios of C/O and N/O.",
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