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AAS National Conference 2008: Candice Hansen
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AAS National Conference 2008: Candice Hansen

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Session 2: Space Science – the Next Decade …

Session 2: Space Science – the Next Decade

18 November 2008, Pasadena California

http://www.astronautical.org/conference/conference-2008

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  • 1. TSSM TSSM JSDT Chairs : J. Lunine, J-P. Lebreton Lead Scientists : A. Coustenis, D. Matson, C. Hansen L. Bruzzone, M-T. Capria, J. Castillo-Rogez, A. Coates, M. Dougherty, A. Ingersoll, R. Jaumann, W. Kurth, M-L. Lara, C. McKay, R. Lopes, R. Lorenz, C. P. McKay, I. M üller-Wodarg, O . Prieto-Ballesteros, F. Raulin, A. Simon-Miller, E. Sittler, J. Soderblom, F. Sohl, C. Sotin, D. Stevenson, E. Stofan, G. Tobie, T. Tokano, P. Tortora, E. Turtle, H. Waite Study managers : Ch. Erd, K. Reh
  • 2. OUTLINE
    • What we know now, from Cassini-Huygens and Voyager missions
    • What we want to learn with TSSM - our new science objectives
    • How we will go about obtaining this new knowledge
      • Instrument payload
      • Spacecraft
      • Mission scenario
  • 3.
    • Titan is Saturn’s largest moon
    • Larger than Mercury, Titan has an atmosphere
    • Like Earth it’s dominantly composed of nitrogen
      • Its atmosphere is very thick and extremely cold
      • Surface pressure: 1.5 x Earth
      • Surface temperature: 94 K ( -290 Fahrenheit)
    • Titan’s atmosphere is rich in hydrocarbons
      • About 3% methane
      • Methane is to Titan as water is to Earth, existing as gas and liquid
      • Cassini-Huygens found clouds, rain, riverbeds, lakes
    • Sunlight converts methane into
      • Ethane, acetelyene, propane, and higher-order H-C-N compounds
      • Smog-like haze of tholin ‘snows’ down onto the surface
    • Titan holds clues to the Solar System’s early chemistry, to the raw ingredients that ultimately led to life
    • To see through this haze Cassini carried a radar and near-infrared imager
    Titan’s Atmosphere Voyager view
  • 4. Aug. 7, 2008 Geology Lakes of ethane Dunes Titan’s surface: Dunes, mountains, lakes Fluvial erosion
  • 5. Titan after Huygens One site well understood from Huygens lander Titan’s surface
  • 6. Titan rivals the earth in complexity Silicate core Internal liquid ocean beneath a water ice crust Cryovolcanism? Lakes, dunes, mountains Thick nitrogen atmosphere with organic haze Clouds and rain
  • 7.  
  • 8. Titan as an object is of keen interest for all areas of planetary science
  • 9. Titan Upper Atmosphere Interaction with Magnetosphere
      • Upper atmosphere (400-950 km) not reached by most measurements
      • Important region for complex organic ion-molecule & aerosol synthesis with relevance for the entire atmosphere and astrobiology: Cassini-Huygens not equipped to study much of Mesosphere/ Thermosphere/Ionosphere chemistry
    • Above 950 km the atmosphere was sensed directly by Cassini’s in situ instruments
  • 10. What Cassini-Huygens Learned 8
    • Saw methane and ethane clouds that varied
    • Imaged fluvial channels, lakes, seas
    • Sniffed evaporating methane/ethane from ground
    • Found evidence for cryovolcanism
    • Detected surface deposits of carbon dioxide
    • Detected unexpectedly complex molecules high up
    • Measured non-synchronous spin: subsurface ocean?
  • 11. ISS Color Mosaic Rev 11 Enceladus Small moon of Saturn (~500 km diameter) Surface composed of water ice Bluish fissures crossing the south pole dubbed “tiger stripes” Water vapor and ice particles spew out of fissures
  • 12. Enceladus: The little moon with active geysers
  • 13. Titan‘s link to Saturn and Enceladus: A rich magnetospheric connection
  • 14. TSSM Science Goals
    • Goal A: How does Titan function as a system; to what extent are there similarities and differences with Earth and other solar system bodies?
    • Goal B: To what level of complexity has prebiotic chemistry evolved in the Titan system?
    • Goal C: What could be learned from Enceladus and Saturn's magnetosphere about the origin and evolution of Titan?
  • 15. Science Objectives define Key Measurement Requirements
    • What are the lakes made of? What’s flowing in the rivers?
      • 1-5 micron spectral images with resolving power 1000
      • Temperatures to 1 K over poles
    • Is there active volcanism? What kinds of tectonics? How thin is the crust?
      • Global imaging to 50 m resolution
      • Global topography to 10 m precision over km spot size
    • How are the polymers made in the atmosphere? What’s the energy source?
      • Identification of species up to 1000 amu with resolving power of 1 amu
    • When and how do the heavy rains occur?
      • Deep atmosphere temperature measurements to 1 K
      • Global imaging to 50 meters resolution
    10
  • 16.
    • Is there a rock/metal core? How thin is the crust?
      • Magnetic measurements sensitive to "sub-Ganymede" fields
      • Global gravity mapping to 0.01 Titan's gravity
      • Global topography to 10 m precision over km spot size
    • Is ammonia present and what is the loss rate of the major gases?
      • Detection of energetic particles from solar wind and magnetosphere
      • 1-5 micron spectral images with resolving power 1000
      • Rotational spectra of molecules in Titan's limb
    • What are the organics at Titan’s surface?
      • 1-5 micron spectral images with resolving power 1000
    Science Objectives define Key Measurement Requirements
  • 17. TSSM Baseline Overview
    • Titan, Saturn System and Enceladus
    • NASA Orbiter with ESA in situ elements
      • Orbiter with Solar Electric Propulsion (SEP)
      • Lake Lander
      • Montgolfière Balloon
      • NASA provided Launch Vehicle and RPS
    • Mission Design
      • 2020 Gravity Assist SEP trajectory
      • 9 years to Saturn arrival
      • SEP stage released ~5 yrs after launch
      • Balloon released on 1 st Titan flyby, Lander on 2 nd Titan flyby
      • ~4 year prime mission: 2 year Saturn tour, 2 mo Titan aerosampling; 20 mo Titan orbit
    • Strawman Payload Complement
      • Orbiter: 6 Instruments + Radio Science
      • Lander: 5 instruments + Radio Science
      • Balloon: 7 instruments + Radio Science
  • 18. In Situ Elements
    • Lake Lander would be targeted to land in a northern polar lake – Kraken Mare
    • Montgolfi ère would be targeted to ~20 deg N. The balloon would circumnavigate Titan at 10 km above the surface
  • 19.  
  • 20. Trace Matrix flows from the three goals to measurements, then instruments For planning and discussion purposes only
  • 21. Planning Payloads
    • Orbiter
    • 1-6 micron hi-res imager and spectrometer (HiRIS)
    • Radar sounder and altimeter (TiPRA)
    • Polymer mass spectrometer (PMS)
    • Microwave spectral sounder (SMS)
    • Thermal Infrared Radiometer and Spectrometer (TIRS)
    • Magnetometer and plasma package (MAPP)
    • Radio science augmented by accelerometry (RSA)
    • Balloon
    • Balloon imaging 1 - 6 micron spectrometer
    • Visible imager
    • Atmospheric structure / meteorology package
    • Electric environment package, magnetometer
    • Radar sounder
    • Chemical analyzer
    For planning and discussion purposes only
    • Lake Lander
    • Chemical analyzer
    • Imager with lamp
    • Atmospheric structure / meteorology package
    • Surface properties and accoustic sounder
  • 22. Orbiter Design Features
    • Telecom
      • 4m X/Ka band HGA with 35W Ka TWTA
      • >140 kbps downlink to 34m DSN station
    • C&DH
      • RAD 750 computer (132 MHz)
      • 32 Gb memory
    • Propulsion
      • Single 890 N gimbaled main engine
      • 16 4.5N RCS thrusters in 8 pods of two each
      • Propellant tanks hold ~2500 kg propellant
    • Power
      • 5 ASRGs + redundant 25 Ahr batteries
      • ~540W at EOM
    • AACS
      • Three-axis stabilized spacecraft
        • 30 arcsec pointing control (3 σ )
        • 0.35 arcsec/sec pointing stability ( 3 σ /axis)
    • Structure
      • Composite and Aluminum for low mass, rigidity
  • 23. Mission Timeline For planning and discussion purposes only
  • 24. 2 Year Saturn Tour Sun For planning and discussion purposes only Four polar flybys at 100 km 300 km flyby at 40º S Two 1,000 km Flybys at 20º N 7 Close Enceladus Flybys Montgolfiere released at first Titan flyby Lake lander released at second Titan flyby
  • 25. Orbiter Science Scenario
    • Saturn Approach
      • Instrument calibration, ops exercises and magnetospheric measurements
    • Saturn Tour - Saturn, Enceladus and Titan Science
      • 7 low-altitude Enceladus flybys (4@100 km, 3 < 1100 km)
        • High resolution imaging; Near & mid IR mapping spectrometry
        • Direct sampling mass spectrometry
        • Subsurface radar measurements
        • Radio Science gravity field measurements
      • 16 Titan Flybys (Altitudes  8 < 1200km, 8 higher)
        • High res. imaging; IR mapping spectrometry; observe Titan/magnetosphere interaction
        • Global imaging; cloud mapping; near & mid IR mapping spectrometry
        • Direct sampling mass spectrometry
        • Limb sounding; IR mapping; cloud imaging
    • Aerobraking - ~200 Titan passes, many at 600–700km altitude
      • High resolution imaging; Near IR mapping spectrometry
      • Direct sampling mass spectrometry
    • Titan Orbit - (next slide)
    • Decommissioning and Disposal
      • Titan data capture and playback until impact
  • 26. ~ 2 Year Titan Orbit Nov 2008 For planning and discussion purposes only View from orbit normal View from Earth 2.5 hr. Variation in LST time of orbit and radio occultations at wide range of latitudes. Saturn’s Gravity Rotates Orbit Plane 2 Months Aerobraking and Aerosampling 20 Months in Circular Polar Orbit In situ sampling of Titan’s entire southern hemisphere below 1,000 km. first orbit Latitude [deg] Altitude [km.] 90S 90N 0 60S 30S 60N 30N 500 1000 1500
  • 27. Titan seasonal cycle: exploration coverage
  • 28. This mission is a giant leap beyond the Cassini-Huygens mission
    • exploration of Titan’s upper atmosphere: (400-900 km)
    • nested 10 meter- and 50 meter scale images across diverse terrains
    • global topographic information and subsurface sounding
    • comprehensive in situ assay from upper atmosphere through to the dissolved components in the lakes
    • test for intrinsic and/or induced magnetic fields
    • high degree gravity mapping of Titan for interior and crustal structure
    • mapping of complex polymers and detailed temperature and composition at Enceladus fissures
    Courtesy of Randy Kirk, USGS
  • 29. The Titan Saturn System Mission
    • Dedicated Titan orbiter with ESA provided in situ elements will provide
    • Enceladus science and Saturn magnetospheric interaction with Titan
    • Advancement in focused understanding of Titan system well beyond the high bar set by the Cassini-Huygens survey
    06 Nov 2008
  • 30. BACKUP For planning and discussion purposes only
  • 31. Phase E Timeline 06 Nov 2008 For planning and discussion purposes only
  • 32.
    • Montgolfiere Data Return
    • Released on approach to first Titan encounter; 6 month prime mission.
    • Data rate (shown below) is a function of range and view period
    • The link can support the relay of up to 1.3 Tb
    • Lander Data Return
    • Released on approach to second Titan encounter; 9 hour prime mission.
    • Data rate (shown below) is a function of range. After 9 hours the orbiter goes over the horizon.
    • The link can support the relay of up to 3.4 Gb
    In situ relay during Saturn Tour Phase
  • 33. Titan: Complex surface, atmosphere and organics detached haze lakes aeolian patterns river channels mountains huge cloud systems wind driven dunes drainage channels chemically complex atmosphere Heavy -ion chemistry Very few craters lakes mid-latitude streaks
  • 34. Baseline Flight System Configuration
    • Configuration is a balance of science, mass, cost & risk
    • Orbiter dry mass 1613 kg including 35% margin
      • 165 kg allocated to orbiter instruments
      • Current in situ mass allocation ~830 kg
        • 600 kg montgolfiere
        • 190 kg lander
        • Remainder for probe support equipment
    • Design incorporates 5 ASRGs
      • 4 for power, one spare
      • ~540 W EOM (4 operating)
    • Total Mission Dose estimated at <15 krad (behind 100 mil Al)
    06 Nov 2008 For planning and discussion purposes only Ox Pressurant Tank Fuel Tank Ox Tank 890 N HiPAT engine ASRG (5) 4-m HGA 4.5 N RCS Thrusters (16 ) In-situ element (montgolfiere) In-situ element (lander) Avionics (3) 15 kW Ultraflex Solar Arrays (two 7.5 kW wings, stowed) NEXT Ion Thrusters (3) Xenon Prop Tanks (3) Launch mass 6203 kg