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Howard Smith

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Space Physicist
  • B.S., Mathematics/Computer Science
    1988, University of Miami
  • M.S., Engineering
    1993, Virginia Tech
  • Ph.D., Engineering Physics
    2006, University of VIrginia

My research focus is on Jupiter, Saturn, Uranus, Neptune and Mercury magnetospheric science and instrumentation. I employ modeling and data analysis to study charged and neutral particle interactions. My experience includes serving as a team member on the NASA Cassini CAPS and MIMI teams, Co-I on the Strofio team (ESA Bepe-Colombo mission), a Co-I on the NASA Europa Mission PIMMS instrument team, Guest Investigator of the JAXA HISAKI mission and Participating Scientist on the NASA Juno mission. Additionally, I lead the John Hopkins University Applied Physics laboratory’s efforts to exploit commercial spacecraft for over eight years with 7 payloads selected for flight under the NASA flight Opportunities Program (successfully completed 6 missions and currently preparing for 9 additional flights).

Notable Awards and Leadership

Year(s) Description
2004 - Present Member, American Geophysical Union (AGU)
2002 - Present Member, American Astronomical Society (AAS)
1988 - Present Member, Phi Beta Kappa Association
1988 - Present Member, Phi Kappa Phi Association

Scholarly Publications

Europa Neutral Torus Confirmation and Characterization Based on Observations and Modeling

The Astrophysical Journal, 2019
, (2019), Europa Neutral Torus Confirmation and Characterization Based on Observations and Modeling, The Astrophysical Journal

Energetic Oxygen and Sulfur Charge States in the Outer Jovian Magnetosphere: Insights From the Cassini Jupiter Flyby

Geophysical Research Letters, 2019
, (2019), Energetic Oxygen and Sulfur Charge States in the Outer Jovian Magnetosphere: Insights From the Cassini Jupiter Flyby, Geophysical Research Letters

Enceladus and Its Influence on Saturn’s Magnetosphere

Enceladus and the Icy Moons of Saturn, 2018
, (2018), Enceladus and Its Influence on Saturn’s Magnetosphere, Enceladus and the Icy Moons of Saturn

Dust grains fall from Saturn’s D-ring into its equatorial upper atmosphere

Science, 2018
, (2018), Dust grains fall from Saturn’s D-ring into its equatorial upper atmosphere, Science

A radiation belt of energetic protons located between Saturn and its rings

Science, 2018
, (2018), A radiation belt of energetic protons located between Saturn and its rings, Science

Spatial Distribution of Io's Neutral Oxygen Cloud Observed by Hisaki

Journal of Geophysical Research: Space Physics, 2018
, (2018), Spatial Distribution of Io's Neutral Oxygen Cloud Observed by Hisaki, Journal of Geophysical Research: Space Physics

Saturn’s Diffuse E Ring and Its Connection with Enceladus

Enceladus and the Icy Moons of Saturn, 2018
, (2018), Saturn’s Diffuse E Ring and Its Connection with Enceladus, Enceladus and the Icy Moons of Saturn

Titan's cold case files - Outstanding questions after Cassini-Huygens

Planetary and Space Science, 2018
, (2018), Titan's cold case files - Outstanding questions after Cassini-Huygens, Planetary and Space Science

The time variation of atomic oxygen emission around Io during a volcanic event observed with Hisaki/EXCEED

Icarus, 2018
, (2018), The time variation of atomic oxygen emission around Io during a volcanic event observed with Hisaki/EXCEED, Icarus

Charge states of energetic oxygen and sulfur ions in Jupiter's magnetosphere

Journal of Geophysical Research: Space Physics, 2016
, (2016), Charge states of energetic oxygen and sulfur ions in Jupiter's magnetosphere, Journal of Geophysical Research: Space Physics

Ion composition in Titan's exosphere via the Cassini Plasma Spectrometer I: T40 encounter

Journal of Geophysical Research-Space Physics, 2015
A. K. Woodson, H. T. Smith, F. J. Crary, R. E. Johnson, (2015), Ion composition in Titan's exosphere via the Cassini Plasma Spectrometer I: T40 encounter, Journal of Geophysical Research-Space Physics, 120, 1, 212-234

Saturn Plasma Sources and Associated Transport Processes

Space Science Reviews, 2015
M. Blanc, D. J. Andrews, A. J. Coates, D. C. Hamilton, C. M. Jackman, X. Jia, A. Kotova, M. Morooka, H. T. Smith, J. H. Westlake, (2015), Saturn Plasma Sources and Associated Transport Processes, Space Science Reviews, 192, 1-4, 237-283

Jupiter’s Magnetosphere: Plasma Sources and Transport

Space Science Reviews, 2015
, (2015), Jupiter’s Magnetosphere: Plasma Sources and Transport, Space Science Reviews

An empirical model for the plasma environment along Titan's orbit based on Cassini plasma observations

Journal of Geophysical Research-Space Physics, 2014
H. Todd Smith, Abigail M. Rymer, (2014), An empirical model for the plasma environment along Titan's orbit based on Cassini plasma observations, Journal of Geophysical Research-Space Physics, 119, 7, 5674-5684

The observed composition of ions outflowing from Titan

Geophysical Research Letters, 2012
, (2012), The observed composition of ions outflowing from Titan, Geophysical Research Letters

Exospheres and Energetic Neutral Atoms of Mars, Venus and Titan

Space Science Reviews, 2011
Yoshifumi Futaana, Jean-Yves Chaufray, H. Todd Smith, Philippe Garnier, Herbert Lichtenegger, Magda Delva, Hannes Groeller, Alessandro Mura, (2011), Exospheres and Energetic Neutral Atoms of Mars, Venus and Titan, Space Science Reviews, 162, 1-4, 213-266

Mapping Magnetospheric Equatorial Regions at Saturn from Cassini Prime Mission Observations

Space Science Reviews, 2011
, (2011), Mapping Magnetospheric Equatorial Regions at Saturn from Cassini Prime Mission Observations, Space Science Reviews

Exospheres and Energetic Neutral Atoms of Mars, Venus and Titan

Space Sciences Series of ISSI, 2011
, (2011), Exospheres and Energetic Neutral Atoms of Mars, Venus and Titan, Space Sciences Series of ISSI

Cassini INMS observations of neutral molecules in Saturn's E-ring

Journal of Geophysical Research-Space Physics, 2010
Mark E. Perry, Ben Teolis, H. Todd Smith, Ralph L. McNutt, Greg Fletcher, Wayne Kasprzak, Brian Magee, Donald G. Mitchell, J. Hunter Waite, (2010), Cassini INMS observations of neutral molecules in Saturn's E-ring, Journal of Geophysical Research-Space Physics, 115

Enceladus plume variability and the neutral gas densities in Saturn's magnetosphere

Journal of Geophysical Research-Space Physics, 2010
H. T. Smith, R. E. Johnson, M. E. Perry, D. G. Mitchell, R. L. McNutt, D. T. Young, (2010), Enceladus plume variability and the neutral gas densities in Saturn's magnetosphere, Journal of Geophysical Research-Space Physics, 115

Neutral Clouds and Their Influence on Pick-up Ions in Saturn's Magnetosphere

Pickup Ions Throughout the Heliosphere and Beyond, 2010
H. T. Smith, JA LeRoux, V Florinski, GP Zank, AJ Coates, (2010), Neutral Clouds and Their Influence on Pick-up Ions in Saturn's Magnetosphere, Pickup Ions Throughout the Heliosphere and Beyond, 1302, 256-262

Cassini evidence for rapid interchange transport at Saturn

Planetary and Space Science, 2009
A. M. Rymer, B. H. Mauk, T. W. Hill, N. Andre, D. G. Mitchell, C. Paranicas, D. T. Young, H. T. Smith, A. M. Persoon, J. D. Menietti, G. B. Hospodarsky, A. J. Coates, M. K. Dougherty, (2009), Cassini evidence for rapid interchange transport at Saturn, Planetary and Space Science, 57, 14-15, 1779-1784

Discrete classification and electron energy spectra of Titan's varied magnetospheric environment

Geophysical Research Letters, 2009
A. M. Rymer, H. T. Smith, A. Wellbrock, A. J. Coates, D. T. Young, (2009), Discrete classification and electron energy spectra of Titan's varied magnetospheric environment, Geophysical Research Letters, 36

Investigation of energetic proton penetration in Titan's atmosphere using the Cassini INCA instrument

Planetary and Space Science, 2009
H. T. Smith, D. G. Mitchell, R. E. Johnson, C. P. Paranicas, (2009), Investigation of energetic proton penetration in Titan's atmosphere using the Cassini INCA instrument, Planetary and Space Science, 57, 13, 1538-1546

Mass Loss Processes in Titan's Upper Atmosphere

Titan From Cassini-Huygens, 2009
R. E. Johnson, O. J. Tucker, M. Michael, E. C. Sittler, H. T. Smith, D. T. Young, J. H. Waite, RH Brown, JP Lebreton, JH Waite, (2009), Mass Loss Processes in Titan's Upper Atmosphere, Titan From Cassini-Huygens, 373-391

THE IMPLANTATION AND INTERACTIONS OF O+ IN TITAN'S ATMOSPHERE: LABORATORY MEASUREMENTS OF COLLISION-INDUCED DISSOCIATION OF N-2 AND MODELING OF POSITIVE ION FORMATION

Astrophysical Journal, 2009
M. B. Shah, C. J. Latimer, E. C. Montenegro, O. J. Tucker, R. E. Johnson, H. T. Smith, (2009), THE IMPLANTATION AND INTERACTIONS OF O+ IN TITAN'S ATMOSPHERE: LABORATORY MEASUREMENTS OF COLLISION-INDUCED DISSOCIATION OF N-2 AND MODELING OF POSITIVE ION FORMATION, Astrophysical Journal, 703, 2, 1947-1954

Cassini detection of water-group pick-up ions in the Enceladus torus

Geophysical Research Letters, 2008
R. L. Tokar, R. J. Wilson, R. E. Johnson, M. G. Henderson, M. F. Thomsen, M. M. Cowee, E. C. Sittler, D. T. Young, F. J. Crary, H. J. McAndrews, H. T. Smith, (2008), Cassini detection of water-group pick-up ions in the Enceladus torus, Geophysical Research Letters, 35, 14

Enceladus: A potential source of ammonia products and molecular nitrogen for Saturn's magnetosphere

Journal of Geophysical Research-Space Physics, 2008
H. T. Smith, M. Shappirio, R. E. Johnson, D. Reisenfeld, E. C. Sittler, F. J. Crary, D. J. McComas, D. T. Young, (2008), Enceladus: A potential source of ammonia products and molecular nitrogen for Saturn's magnetosphere, Journal of Geophysical Research-Space Physics, 113, A11

IDENTIFICATION OF SATURN'S MAGNETOSPHERIC REGIONS AND ASSOCIATED PLASMA PROCESSES: SYNOPSIS OF CASSINI OBSERVATIONS DURING ORBIT INSERTION

Reviews of Geophysics, 2008
N. Andre, M. Blanc, S. Maurice, P. Schippers, E. Pallier, T. I. Gombosi, K. C. Hansen, D. T. Young, F. J. Crary, S. Bolton, E. C. Sittler, H. T. Smith, R. E. Johnson, R. A. Baragiola, A. J. Coates, A. M. Rymer, M. K. Dougherty, N. Achilleos, C. S. Arridge, S. M. Krimigis, D. G. Mitchell, N. Krupp, D. C. Hamilton, I. Dandouras, D. A. Gurnett, W. S. Kurth, P. Louarn, R. Srama, S. Kempf, H. J. Waite, L. W. Esposito, J. T. Clarke, (2008), IDENTIFICATION OF SATURN'S MAGNETOSPHERIC REGIONS AND ASSOCIATED PLASMA PROCESSES: SYNOPSIS OF CASSINI OBSERVATIONS DURING ORBIT INSERTION, Reviews of Geophysics, 46, 4

Ion and neutral sources and sinks within Saturn's inner magnetosphere: Cassini results

Planetary and Space Science, 2008
E. C. Sittler, N. Andre, M. Blanc, M. Burger, R. E. Johnson, A. Coates, A. Rymer, D. Reisenfeld, M. F. Thomsen, A. Persoon, M. Dougherty, H. T. Smith, R. A. Baragiola, R. E. Hartle, D. Chornay, M. D. Shappirio, D. Simpson, D. J. McComas, D. T. Young, (2008), Ion and neutral sources and sinks within Saturn's inner magnetosphere: Cassini results, Planetary and Space Science, 56, 1, 3-18

Observations of molecular oxygen ions in Saturn's inner magnetosphere

Geophysical Research Letters, 2008
Hilary R. Martens, Daniel B. Reisenfeld, John D. Williams, Robert E. Johnson, H. Todd Smith, (2008), Observations of molecular oxygen ions in Saturn's inner magnetosphere, Geophysical Research Letters, 35, 20

Sputtering of ice grains and icy satellites in Saturn's inner magnetosphere

Planetary and Space Science, 2008
R. E. Johnson, M. Fama, M. Liu, R. A. Baragiola, E. C. Sittler, H. T. Smith, (2008), Sputtering of ice grains and icy satellites in Saturn's inner magnetosphere, Planetary and Space Science, 56, 9, 1238-1243

Cassini observations of Saturn's inner plasmasphere: Saturn orbit insertion results (vol 54, pg 1197, 2006)

Planetary and Space Science, 2007
E. C. Sittler, M. Thomsen, R. E. Johnson, R. E. Hartle, M. Burger, D. Chornay, M. D. Shappirio, D. Simpson, H. T. Smith, A. J. Coates, A. M. Rymer, D. J. McComas, D. T. Young, D. Reisenfeld, M. Dougherty, N. Andre, (2007), Cassini observations of Saturn's inner plasmasphere: Saturn orbit insertion results (vol 54, pg 1197, 2006), Planetary and Space Science, 55, 14, 2218-2220

Electron sources in Saturn's magnetosphere

Journal of Geophysical Research-Space Physics, 2007
A. M. Rymer, B. H. Mauk, T. W. Hill, C. Paranicas, N. Andre, E. C. Sittler, D. G. Mitchell, H. T. Smith, R. E. Johnson, A. J. Coates, D. T. Young, S. J. Bolton, M. F. Thomsen, M. K. Dougherty, (2007), Electron sources in Saturn's magnetosphere, Journal of Geophysical Research-Space Physics, 112, A2

Enceladus: The likely dominant nitrogen source in Saturn's magnetosphere

Icarus, 2007
H. T. Smith, R. E. Johnson, E. C. Sittler, M. Shappirio, D. Reisenfeld, O. J. Tucker, M. Burger, F. J. Crary, D. J. McComas, D. T. Young, (2007), Enceladus: The likely dominant nitrogen source in Saturn's magnetosphere, Icarus, 188, 2, 356-366

Understanding the escape of water from Enceladus

Journal of Geophysical Research-Space Physics, 2007
M. H. Burger, E. C. Sittler, R. E. Johnson, H. T. Smith, O. J. Tucker, V. I. Shematovich, (2007), Understanding the escape of water from Enceladus, Journal of Geophysical Research-Space Physics, 112, A6

Cassini observations of Saturn's inner plasmasphere: Saturn orbit insertion results

Planetary and Space Science, 2006
E. C. Sittler, M. Thomsen, R. E. Johnson, R. E. Hartle, M. Burger, D. Chornay, M. D. Shappirio, D. Simpson, H. T. Smith, A. J. Coates, A. M. Rymer, D. J. McComas, D. T. Young, D. Reisenfeld, M. Dougherty, N. Andre, (2006), Cassini observations of Saturn's inner plasmasphere: Saturn orbit insertion results, Planetary and Space Science, 54, 12, 1197-1210

Energetic nitrogen ions within the inner magnetosphere of Saturn

Journal of Geophysical Research-Space Physics, 2006
E. C. Sittler, R. E. Johnson, H. T. Smith, J. D. Richardson, S. Jurac, M. Moore, J. F. Cooper, B. H. Mauk, M. Michael, C. Paranicas, T. P. Armstrong, B. Tsurutani, (2006), Energetic nitrogen ions within the inner magnetosphere of Saturn, Journal of Geophysical Research-Space Physics, 111, A9

Initial interpretation of Titan plasma interaction as observed by the Cassini plasma spectrometer: Comparisons with Voyager 1

Planetary and Space Science, 2006
R. E. Hartle, E. C. Sittler, F. M. Neubauer, R. E. Johnson, H. T. Smith, F. Crary, D. J. McComas, D. T. Young, A. J. Coates, D. Simpson, S. Bolton, D. Reisenfeld, K. Szego, J. J. Berthelier, A. Rymer, J. Vilppola, J. T. Steinberg, N. Andre, (2006), Initial interpretation of Titan plasma interaction as observed by the Cassini plasma spectrometer: Comparisons with Voyager 1, Planetary and Space Science, 54, 12, 1211-1224

Preliminary interpretation of Titan plasma interaction as observed by the Cassini Plasma Spectrometer: Comparisons with Voyager 1

Geophysical Research Letters, 2006
RE Hartle, EC Sittler, FM Neubauer, RE Johnson, HT Smith, F Crary, DJ McComas, DT Young, AJ Coates, D Simpson, S Bolton, D Reisenfeld, K Szego, JJ Berthelier, A Rymer, J Vilppola, JT Steinberg, N Andre, (2006), Preliminary interpretation of Titan plasma interaction as observed by the Cassini Plasma Spectrometer: Comparisons with Voyager 1, Geophysical Research Letters, 33, 8

Production, ionization and redistribution of O-2 in Saturn's ring atmosphere

Icarus, 2006
RE Johnson, JG Luhmann, RL Tokar, M Bouhram, JJ Berthelier, EC Sittler, JF Cooper, TW Hill, HT Smith, M Michael, M Liu, FJ Crary, DT Young, (2006), Production, ionization and redistribution of O-2 in Saturn's ring atmosphere, Icarus, 180, 2, 393-402

The Enceladus and OH tori at Saturn

Astrophysical Journal, 2006
RE Johnson, HT Smith, OJ Tucker, M Liu, MH Burger, EC Sittler, RL Tokar, (2006), The Enceladus and OH tori at Saturn, Astrophysical Journal, 644, 2, L137-L139

Composition and dynamics of plasma in Saturn's magnetosphere

Science, 2005
DT Young, JJ Berthelier, M Blanc, JL Burch, S Bolton, AJ Coates, FJ Crary, R Goldstein, M Grande, TW Hill, RE Johnson, RA Baragiola, V Kelha, DJ McComas, K Mursula, EC Sittler, KR Svenes, K Szego, P Tanskanen, MF Thomsen, S Bakshi, BL Barraclough, Z Bebesi, D Delapp, MW Dunlop, JT Gosling, JD Furman, LK Gilbert, D Glenn, C Holmlund, JM Illiano, GR Lewis, DR Linder, S Maurice, HJ McAndrews, BT Narheim, E Pallier, D Reisenfeld, AM Rymer, HT Smith, RL Tokar, J Vilppola, C Zinsmeyer, (2005), Composition and dynamics of plasma in Saturn's magnetosphere, Science, 307, 5713, 1262-1266

Discovery of nitrogen in Saturn's inner magnetosphere

Geophysical Research Letters, 2005
HT Smith, M Shappirio, EC Sittler, D Reisenfeld, RE Johnson, RA Baragiola, FJ Crary, DJ McComas, DT Young, (2005), Discovery of nitrogen in Saturn's inner magnetosphere, Geophysical Research Letters, 32, 14

Preliminary results on Saturn's inner plasmasphere as observed by Cassini: Comparison with Voyager

Geophysical Research Letters, 2005
EC Sittler, M Thomsen, D Chornay, MD Shappirio, D Simpson, RE Johnson, HT Smith, AJ Coates, AM Rymer, F Crary, DJ McComas, DT Young, D Reisenfeld, M Dougherty, N Andre, (2005), Preliminary results on Saturn's inner plasmasphere as observed by Cassini: Comparison with Voyager, Geophysical Research Letters, 32, 14

The Enceladus satellite as a source of N+ ions in Saturn's magnetosphere.

Comptes Rendus Physique, 2005
M Bouhram, JJ Berthelier, JM Illiano, HT Smith, EC Sittler, FJ Crary, DT Young, (2005), The Enceladus satellite as a source of N+ ions in Saturn's magnetosphere., Comptes Rendus Physique, 6, 10, 1176-1181

The global plasma environment of Titan as observed by Cassini Plasma Spectrometer during the first two close encounters with Titan

Geophysical Research Letters, 2005
K Szego, Z Bebesi, G Erdos, L Foldy, F Crary, DJ McComas, DT Young, S Bolton, AJ Coates, AM Rymer, RE Hartle, EC Sittler, D Reisenfeld, JJ Bethelier, RE Johnson, HT Smith, TW Hill, J Vilppola, J Steinberg, N Andre, (2005), The global plasma environment of Titan as observed by Cassini Plasma Spectrometer during the first two close encounters with Titan, Geophysical Research Letters, 32, 20

Titan interaction with Saturn's magnetosphere: Voyager 1 results revisited

Journal of Geophysical Research-Space Physics, 2005
EC Sittler, RE Hartle, AF Vinas, RE Johnson, HT Smith, I Mueller-Wodarg, (2005), Titan interaction with Saturn's magnetosphere: Voyager 1 results revisited, Journal of Geophysical Research-Space Physics, 110, A9

Titan interaction with Saturn's magnetosphere: mass loading and ionopause location

Proceedings of the International Conference Titan: From Discovery To Encounter, 2004
EC Sittler, RE Hartle, AF Vinas, RE Johnson, HT Smith, I Mueller-Wodard, K Fletcher, (2004), Titan interaction with Saturn's magnetosphere: mass loading and ionopause location, Proceedings of the International Conference Titan: From Discovery To Encounter, 377-394

Titan's atomic and molecular nitrogen tori

Geophysical Research Letters, 2004
HT Smith, RE Johnson, VI Shematovich, (2004), Titan's atomic and molecular nitrogen tori, Geophysical Research Letters, 31, 16