1. Science Motivation Comparative planetology of the outer planets is key to understanding the origin & evolution of the solar system S. Atreya (2006) –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

2. Brief Science Overview Heavy Elemental Abundances of the Giant Planets Relative to H in the atmospheres of the Giant Planets compared to the protosolar values 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 Saturn/Uranus/Neptune: only carbon is measured Jupiter  data from Galileo Probe Mass Spectrometer (GPMS) Saturn, Uranus, Neptune  no measurements

3. Hot Spot Jupiter clouds Equilibrium

4. Brief Science Overview Condensible Volatiles in Saturn’s Atmosphere 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 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 Ref: Sushil Atreya, “SATURN PROBES: Why, Where, How?”, International Planetary Probe Workshop, IPPW-4, Pasadena, California, June 2006

5. 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 Frontiers class mission – Cost cap assumptions TBD – Could range from today’s $750M, up to ~$1B – Next NF Opportunity: ~ 2015 (2014-2016/17?) Ref: S. Atreya, S. Bolton, T. Owen (similar to FY06 Studies: T. Balint & FY06 Study Team members) 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 Jupiter MWR 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

6. Saturn Probe Strawman Payload

7. 7 Gas Chromatograph Mass Spectrometer (GCMS) 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 Measurements: Atmospheric composition Isotopic ratios Gaseous disequilibrium species Heritage: Huygens (Hasso Niemann, GSFC)

8. 8 Atmospheric Structure Instrument (ASI) Measurements: Pressure Temperature Density Accelerometry Mass: 4.1 kg Average Power: 6W Data Rate: 18 bps Volume: 3100 cm 3 Heritage: Galileo (Al Seiff, Ames) Huygens (M. Fulchignoni, Univ. Paris)

9. 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 cm 3 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. Pre-decisional – for discussion purposes only 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