# Presentation: 359836

## 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)
- 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

- Linda J. Spilker

- 3/3/04

## 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

- Linda J. Spilker

- 3/3/04

## 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)

- Linda J. Spilker

- 3/3/04

## 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

- Linda J. Spilker

- 3/3/04

## 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

- Linda J. Spilker

- 3/3/04

## Some Tours Looked Rather Familiar

- Linda J. Spilker

- 3/3/04

## Others.... Didn’t

- Linda J. Spilker

- 3/3/04

## Selecting a Tour

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

- Linda J. Spilker

- 3/3/04

## T2

- Quickly eliminated largely because of low science return.

- Linda J. Spilker

- 3/3/04

## T9

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

- Linda J. Spilker

- 3/3/04

## 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.

- Linda J. Spilker

- 3/3/04

## 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

- Linda J. Spilker

- 3/3/04

## 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)

- Linda J. Spilker

- 3/3/04

## 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

- Linda J. Spilker

- 3/3/04

## CASSINI TOUR T18-5Orbit Insertion and Huygens Mission

- All units in Rs

- Linda J. Spilker

- 3/3/04

## CASSINI TOUR T18-5 Huygens Mission – Rev B Probe Release

- All units in Rs

- Linda J. Spilker

- 3/3/04

## CASSINI TOUR T18-5 Huygens Mission – Rev B Probe Mission

- All units in Rs

- Linda J. Spilker

- 3/3/04

## CASSINI TOUR T18-52005 FEB 15 to 2005 SEP 07 Mid-Rev 3 to Mid-Rev 14 Occultation Sequences

- All units in Rs

- Linda J. Spilker

- 3/3/04

## CASSINI TOUR T18-52005 FEB 15 to 2005 SEP 07 Mid-Rev 3 to Mid-Rev 14 Occultation Sequences

- All units in Rs

- Linda J. Spilker

- 3/3/04

## CASSINI TOUR T18-52005 SEP 07 to 2006 JUL 22 Mid-Rev 14 to Mid-Rev 26 Magnetotail and Icy Satellites

- All units in Rs

- Linda J. Spilker

- 3/3/04

## CASSINI TOUR T18-52005 SEP 07 to 2006 JUL 22 Mid-Rev 14 to Mid-Rev 26 Magnetotail and Icy Satellites

- Linda J. Spilker

- 3/3/04

## CASSINI TOUR T18-52006 JUL 22 to 2007 JUN 30  Mid-Rev 26 to Mid-Rev 47 180 Transfer: Rings and MAPS 

- All units in Rs

- Linda J. Spilker

- 3/3/04

## CASSINI TOUR T18-52006 JUL 22 to 2007 JUN 30  Mid-Rev 26 to Mid-Rev 47 180 Transfer: Rings and MAPS 

- Linda J. Spilker

- 3/3/04

## CASSINI TOUR T18-52007 JUN 30 to 2007 AUG 31 Mid-Rev 47 to Mid-Rev 49 Iapetus Flyby Preparation/Icy Satellites

- All units in Rs

- Linda J. Spilker

- 3/3/04

## CASSINI TOUR T18-52007 AUG 09 to 2007 SEP 14Rev 49 Titan Gravity Assist and Iapetus Flyby

- All units in Rs

- Linda J. Spilker

- 3/3/04

## CASSINI TOUR T18-52007 AUG 09 to 2007 SEP 14Rev 49 Titan Gravity Assist and Iapetus Flyby

- Linda J. Spilker

- 3/3/04

## CASSINI TOUR T18-52007 AUG 31 to 2008 JUL 01 Mid-Rev 49 to EOM  High Inclination Revs: Rings and MAPS

- All units in Rs

- Linda J. Spilker

- 3/3/04

## CASSINI TOUR T18-52007 AUG 31 to 2008 JUL 01 Mid-Rev 49 to EOM  High Inclination Revs: Rings and MAPS

- Linda J. Spilker

- 3/3/04

## http://saturn.jpl.nasa.gov

- _[http://saturn.jpl.nasa.gov](http://saturn.jpl.nasa.gov/)_
- http://ciclops.org

- Linda J. Spilker

- 3/3/04