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Science Motivation

Science Motivation. Comparative planetology of the outer planets is key to understanding the origin & evolution of the solar system. Deep, well-mixed atmospheres must be characterized. Abundance of water, thought to be the primary carrier of heavy elements to outer planets, must be determined.

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Science Motivation

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  1. Science Motivation Comparative planetology of the outer planets is key to understanding the origin & evolution of the solar system • Deep, well-mixed atmospheres must be characterized • Abundance of water, thought to be the primary carrier of heavy elements to outer planets, must be determined • Juno seeks to the question of water at Jupiter • Probe missions to other giant planets are also desirable. Cassini has made initial in-roads at Saturn but interior processes remain to be investigated S. Atreya (2006)

  2. Brief Science OverviewHeavy Elemental Abundances of the Giant Planets Relative to H in the atmospheres of the Giant Planets compared to the protosolar values Saturn/Uranus/Neptune: only carbon is measured Do not represent measured data; Instead, it is based on the icy planetesimal model predictions, assuming that they would be similarly enhanced as carbon Represents elemental abundances (ratioed to hydrogen) being the same as in the Sun • Jupiter  data from Galileo Probe Mass Spectrometer (GPMS) • Saturn, Uranus, Neptune  no measurements

  3. Jupiter clouds Equilibrium Hot Spot

  4. Brief Science OverviewCondensible Volatiles in Saturn’s Atmosphere Characterization of heavy elements & dynamics in well-mixed Saturnian atmosphere is essential for the understanding of galaxy evolution / formation Water is the primary carrier of heavy elements to outer planets • Base of water cloud at 25-45 bar (minimum) at Saturn • Liquid water clouds are the lowest-altitude clouds in Saturn's atmosphere; well-mixed heavy elements assumed below 45 bar • Probing to ~100 bar desired to ensure sampling of well-mixed atmosphere Ref: Sushil Atreya, “SATURN PROBES: Why, Where, How?”, International Planetary Probe Workshop, IPPW-4, Pasadena, California, June 2006

  5. Ref: S. Atreya, S. Bolton, T. Owen (similar to FY06 Studies: T. Balint & FY06 Study Team members) Initial Assumptions for a Saturn Multi-probes Study • Required by Science Objectives: • Two (2) shallow probes to 10 bars • Latitude location TBD, preliminary assumption: • Probe 1: equatorial probe, and • Probe 2: mid-latitude probe • Direct-to-Earth or Relay communications • Microwave radiometry (MWR) to ~100 bars • MWR on carrier • Carrier options: Flyby or Orbiter • Required by Programmatics: • New Frontiersclass mission • Cost cap assumptions TBD • Could range from today’s $750M, up to ~$1B • Next NF Opportunity: ~ 2015 (2014-2016/17?) Jupiter MWR Jupiter Ref: SSE Roadmap Team, “Solar System Exploration; This is the Solar System Exploration Roadmap for NASA’s Science Mission Directorate”,NASA SMD PSD, Report #: JPL D-35618, September 15, 2006 Website: solarsystem.nasa.gov Ref: Scott .J. Bolton, Tristan Guillot, Michel Blanc, & the JUNO team, Juno Presentation Juno Presentation to the SSWG to the SSWG, April 20th, 2006, ESA HQ, Paris

  6. Saturn Probe Strawman Payload

  7. Gas Chromatograph Mass Spectrometer (GCMS) • Measurements: • Atmospheric composition • Isotopic ratios • Gaseous disequilibrium • species • Mass: 2.3 kg • Average Power: 15 W • Data Rate: 32 bps assumed for study • Variable bit rate based on desired sampling rate • Dimensions: 18x18x37cm Heritage: Huygens (HassoNiemann, GSFC)

  8. Atmospheric Structure Instrument (ASI) Measurements: • Pressure • Temperature • Density • Accelerometry • Mass: 4.1 kg • Average Power: 6W • Data Rate: 18 bps • Volume: 3100 cm3 Heritage: Galileo (Al Seiff, Ames) Huygens (M. Fulchignoni, Univ. Paris)

  9. Doppler Wind Experiment (DWE) Measurements: • Wind velocity • Probe tracking • Probe dynamics • Mass: 2.1 kg • Average Power: 15 W • Data Rate: • 1.6 bps on probe • 313 bps on probe • Volume: 240 cm3 Heritage: Galileo (D. Atkinson, Univ. Idaho & J. Pollack, Ames) Huygens (M. Bird, Univ. Bonn)

  10. Nephelometer (NEP) Measurements: • Cloud particle number density • Cloud particle size / distribution • Mass: 4.8kg • Average Power: 13.5 W • Data Rate: 10 bps • Dimensions: • Sensor: 50.8x8.9x12.7cm • Electronics: 18.8 dia x16.5cm Heritage: Galileo (B. Ragent, Ames)

  11. Zenith Attenuation Based on Ammonia at 10x Solar Abundances Zenith attenuation of radio signal as a function of probe depth (measured by atmospheric pressure), based on concentrations at 10 times solar abundances, in atmosphere model by Atreya. • Attenuation at 10 bars • UHF (200 MHz): ~0.4 dB • UHF (400 MHz): ~1.2 dB • L-band (1.4 GHz): ~14 dB • S-band (2 GHz): ~31 dB Pre-decisional – for discussion purposes only

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