A Revised Sensitivity Model for Cassini INMS: Results at Titan

B. D. Teolis, H. B. Niemann, J. H. Waite, D. A. Gell, R. S. Perryman, W. T. Kasprzak, K. E. Mandt, Roger Yelle, A. Y. Lee, F. J. Pelletier, G. P. Miller, D. T. Young, J. M. Bell, B. A. Magee, E. L. Patrick, J. Grimes, G. G. Fletcher, V. Vuitton

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Cassini Ion Neutral Mass Spectrometer (INMS) measurements from roughly a hundred Titan encounters over the Cassini mission yield neutral and ion densities systematically lower, by factors approximately 2 to 3, than estimates from several other spacecraft systems, including the Attitude and Articulation Control System, and Navigation system. In this paper we present a new INMS instrument sensitivity model, obtained by re-analyzing (1) the capture and transmission of neutral gas through the instrument, and (2) the detector gain reduction during pre-launch testing. By correcting for an under-estimation of gas leakage out of the instrument into space by the original calibration model, and adjusting for the gain change, the new model brings INMS densities into much closer agreement with the other Cassini systems. Accordingly, the INMS ion densities are revised upward by a constant detector sensitivity correction factor of 1.55±21 %, while the neutral sensitivities have a complex instrument pointing direction dependence, due (mostly) to the effect of the INMS vent and antechamber-to-closed source tube. In the special case of on-ram pointing the neutral densities are revised upward by a constant factor of 2.2±23 %. The corrected neutral and ion sensitivities given here are applicable to all previously published INMS results at Titan, Enceladus and elsewhere in the Saturn system. The new model gives reliable densities at high ram angles, in some cases above 90 degrees, thereby expanding the list of Titan flybys from which INMS densities may be extracted. We apply the model to obtain accurate densities from several off-ram Titan flybys which gave unusual neutral density vs. altitude profiles, or unreasonably high densities, with the original calibration.

Original languageEnglish (US)
Pages (from-to)47-84
Number of pages38
JournalSpace Science Reviews
Volume190
Issue number1-4
DOIs
StatePublished - Jul 31 2015

Fingerprint

Titan
mass spectrometers
spectrometer
ion
sensitivity
ram
ions
Cassini mission
Enceladus
attitude control
detectors
vents
neutral gases
Saturn
calibration
navigation
encounters
lists
spacecraft
leakage

Keywords

  • Atmospheres
  • Attitude and articulation control
  • Cassini
  • Cassini INMS
  • Enceladus
  • Gas conductance
  • Instrument calibration
  • Instrument sensitivity
  • Ion Neutral Mass Spectrometer
  • Monte Carlo simulations
  • Saturn
  • Spacecraft navigation
  • Thrusters
  • Titan

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Teolis, B. D., Niemann, H. B., Waite, J. H., Gell, D. A., Perryman, R. S., Kasprzak, W. T., ... Vuitton, V. (2015). A Revised Sensitivity Model for Cassini INMS: Results at Titan. Space Science Reviews, 190(1-4), 47-84. https://doi.org/10.1007/s11214-014-0133-8

A Revised Sensitivity Model for Cassini INMS : Results at Titan. / Teolis, B. D.; Niemann, H. B.; Waite, J. H.; Gell, D. A.; Perryman, R. S.; Kasprzak, W. T.; Mandt, K. E.; Yelle, Roger; Lee, A. Y.; Pelletier, F. J.; Miller, G. P.; Young, D. T.; Bell, J. M.; Magee, B. A.; Patrick, E. L.; Grimes, J.; Fletcher, G. G.; Vuitton, V.

In: Space Science Reviews, Vol. 190, No. 1-4, 31.07.2015, p. 47-84.

Research output: Contribution to journalArticle

Teolis, BD, Niemann, HB, Waite, JH, Gell, DA, Perryman, RS, Kasprzak, WT, Mandt, KE, Yelle, R, Lee, AY, Pelletier, FJ, Miller, GP, Young, DT, Bell, JM, Magee, BA, Patrick, EL, Grimes, J, Fletcher, GG & Vuitton, V 2015, 'A Revised Sensitivity Model for Cassini INMS: Results at Titan', Space Science Reviews, vol. 190, no. 1-4, pp. 47-84. https://doi.org/10.1007/s11214-014-0133-8
Teolis BD, Niemann HB, Waite JH, Gell DA, Perryman RS, Kasprzak WT et al. A Revised Sensitivity Model for Cassini INMS: Results at Titan. Space Science Reviews. 2015 Jul 31;190(1-4):47-84. https://doi.org/10.1007/s11214-014-0133-8
Teolis, B. D. ; Niemann, H. B. ; Waite, J. H. ; Gell, D. A. ; Perryman, R. S. ; Kasprzak, W. T. ; Mandt, K. E. ; Yelle, Roger ; Lee, A. Y. ; Pelletier, F. J. ; Miller, G. P. ; Young, D. T. ; Bell, J. M. ; Magee, B. A. ; Patrick, E. L. ; Grimes, J. ; Fletcher, G. G. ; Vuitton, V. / A Revised Sensitivity Model for Cassini INMS : Results at Titan. In: Space Science Reviews. 2015 ; Vol. 190, No. 1-4. pp. 47-84.
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