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Cassini Tour Selection

Cassini Tour Selection. Dr. Kevin R. Grazier IS/SPE With Significant Viewgraph Assistance By: Linda Spilker Cassini Deputy Project Scientist July 26, 2005. History. Tour 89-01 was discussed in the Cassini Announcement of Opportunity (AO)

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Cassini Tour Selection

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  1. Cassini Tour Selection Dr. Kevin R. Grazier IS/SPE With Significant Viewgraph Assistance By: Linda Spilker Cassini Deputy Project Scientist July 26, 2005

  2. History • Tour 89-01 was discussed in the Cassini Announcement of Opportunity (AO) • Discussions about creating a “new tour” began at very first PSG meeting (in December, 1990) • Tour 92-01 was created after Cassini descope. Very Galileo-like in its character. • mostly updated tour 89-01 for new Cassini arrival date - 2 -

  3. Tour 92-01 • Characteristics of 92-01 • 63 Orbits • 33 Titan flybys • 12 inbound, 21 outbound, 10 solar/earth occulations • 4 targeted icy satellite flybys: Enceladus, Dione, Rhea, Iapetus • 12 non-targeted flybys (d<50,000 km) • Saturn/ring occultations: 5 earth and sun during first 2 occultation sequences - 3 -

  4. Tour Trade Study • PSG and Project agreed to a tour design trade study, scheduled between 1993 and 1996 • Discipline Working Groups (Atmospheres, MAPS, Satellites, Rings) developed a list of tour geometry objectives and guidelines • DWG tour priorities generated over several PSG meetings • Finalized by DWGs at ESTEC PSG in May 1995 • Tour design tool (STOCK) provided to teams • With software and excel spreadsheets Cassini scientists could design a Titan-only tour • New orbit rotation technique identified (Titan 180 transfer) - 4 -

  5. Tour Design Considerations • Titan flyby strategy • Tour redesign implications of change in minimum altitude, number of flybys and occultations • Extent of CCW rotation at beginning of tour • Number of moderately inclined (20-50 deg) orbits and location during tour • Extent of CW rotation toward magnetotail • Maximum value of high inclination orbits • Saturn and Rings sun/earth occultation geometry strategy • Icy satellite flyby strategy for given tour rotation/inclination profile • Tour strategy relative to horseshoe/tadpole trapped particle risk regions • Ground system requirements - 5 -

  6. Selecting a Tour • Orbiter workshop held in July, 1995 • 3 IS-led interdisciplinary teams evaluated 8 classes of tours (38 Titan-only tours) • Identified driving requirements and suggested possible compromise tours • At end of tour design trade study, 17 Titan-only tours (T1 – T17) were available for further study - 6 -

  7. Some Tours Looked Rather Familiar - 7 -

  8. Others…. Didn’t - 8 -

  9. Selecting a Tour • At 8/96 PSG, added one class of tour for further study– T18 • Three tours quickly emerged as favored: - 9 -

  10. T2 • Quickly eliminated largely because of low science return. - 10 -

  11. T9 • LOVED by MAPS, Rings, Titan (two 180 transfers; 51 Titan flybys)! • Too difficult operationally (too many consecutive 16-day orbits) - 11 -

  12. The Winner Is: T18 • At 3/99 PSG selected T18-1 as final tour • Less science return than T9-1 • Still difficult operationally, but we decided to “bite the bullet”. • Since T18-1, there have been 4 major revisions and at least 14 minor. - 12 -

  13. Current Reference Tour • 74 Orbits • 45 Titan flybys • 8 targeted icy satellite flybys: Phoebe, Enceladus (3), Dione, Rhea, Hyperion, Iapetus • ~30 non-targeted flybys (d < 100,000 km) • Many Saturn/ring occultation opportunities • Early, middle and late in tour • One Titan 180 transfer • One high inclination sequence at end of tour - 13 -

  14. Our Pre-launch Goals • Scan Platform Working Group: 11/91 • Sequencing process must start early, before launch, if possible • Tour fully designed before SOI (minimizes impact of burnout, divorce, suicide, murder, etc. during tour) - 14 -

  15. Cassini Tour T18-5 • Looking down from Saturn’s North Pole • Outer dotted circle: Orbit of Iapetus • Inner dotted circle: Orbit of Titan • Sun along +X Axis – Plot shows phase Looking in Saturn’s Ring Plane Excursions in inclination different from Galileo All units in Rs - 15 -

  16. CASSINI TOUR T18-5Orbit Insertion and Huygens Mission All units in Rs - 16 -

  17. CASSINI TOUR T18-5Huygens Mission – Rev B Probe Release All units in Rs - 17 -

  18. CASSINI TOUR T18-5Huygens Mission – Rev B Probe Mission All units in Rs - 18 -

  19. CASSINI TOUR T18-52005 FEB 15 to 2005 SEP 07 Mid-Rev 3 to Mid-Rev 14Occultation Sequences All units in Rs - 19 -

  20. CASSINI TOUR T18-52005 FEB 15 to 2005 SEP 07 Mid-Rev 3 to Mid-Rev 14Occultation Sequences All units in Rs - 20 -

  21. CASSINI TOUR T18-52005 SEP 07 to 2006 JUL 22 Mid-Rev 14 to Mid-Rev 26 Magnetotail and Icy Satellites All units in Rs - 21 -

  22. CASSINI TOUR T18-52005 SEP 07 to 2006 JUL 22 Mid-Rev 14 to Mid-Rev 26 Magnetotail and Icy Satellites - 22 -

  23. CASSINI TOUR T18-52006 JUL 22 to 2007 JUN 30 Mid-Rev 26 to Mid-Rev 47 180 Transfer: Rings and MAPS All units in Rs - 23 -

  24. CASSINI TOUR T18-52006 JUL 22 to 2007 JUN 30 Mid-Rev 26 to Mid-Rev 47 180 Transfer: Rings and MAPS - 24 -

  25. CASSINI TOUR T18-52007 JUN 30 to 2007 AUG 31 Mid-Rev 47 to Mid-Rev 49 Iapetus Flyby Preparation/Icy Satellites All units in Rs - 25 -

  26. CASSINI TOUR T18-52007 AUG 09 to 2007 SEP 14Rev 49 Titan Gravity Assist and Iapetus Flyby All units in Rs - 26 -

  27. CASSINI TOUR T18-52007 AUG 09 to 2007 SEP 14Rev 49 Titan Gravity Assist and Iapetus Flyby - 27 -

  28. CASSINI TOUR T18-52007 AUG 31 to 2008 JUL 01 Mid-Rev 49 to EOM High Inclination Revs: Rings and MAPS All units in Rs - 28 -

  29. CASSINI TOUR T18-52007 AUG 31 to 2008 JUL 01 Mid-Rev 49 to EOM High Inclination Revs: Rings and MAPS - 29 -

  30. http://saturn.jpl.nasa.gov http://ciclops.org

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