Cassini-Huygens Saturn Probe

3.4.1: Cassini.

Object	Orbit Files	Comments
Cassini-Huygens Saturn probe	Cassini JPL home page See also: Exploration Spacecraft of the Outer Solar System by Kevin Butler	Obital positions were obtained from the Horizons Ephemeris System at http://ssd.jpl.nasa.gov/horizons.html, using its telnet interface.
	cassini.zip (140KB, 6Dec2002) Contains the following files: extras/2685.ssc extras/cassini-19980115.ssc extras/cassini-19981201.ssc extras/cassini-19990719.ssc extras/cassini-2000.ssc extras/cassini-2002.ssc extras/cassini-xyz.ssc data/cassini.xyz	This .ZIP archive file includes all of the "elliptical orbit" .SSC files below as well as Chris' cassini.xyz and a .SSC file to invoke it. Note: the xyz file has been updated by Chris to include an appripriate number of samples during the Earth flyby.
		Below are the equivalent elliptical orbits for several segments of the probe's path through the solar system, together showing how the trajectory was modified by using gravity assists at Venus, Earth and Jupiter. This ignores the trajectory adjustments made using the probe's own propulsion system.
	Cassini-19980115.ssc (1KB, 15Oct2002)	for 15-Jan-1998, travelling between Earth and Venus.
	Cassini-19981201.ssc (1KB, 15Oct2002)	for 01-Dec-1998, travelling between Venus and Venus
	Cassini-19990719.ssc (1KB. 15-Oct-02)	for 19-Jul-1999, travelling between Venus and Earth
	Cassini-2000.ssc (1KB, 10-Oct-02)	for 01-Jan-2000, travelling between Mars and Jupiter: near Masursky observation.
	Cassini-2002.ssc (1KB, 10-Oct-02)	for 10-Oct-2002, travelling between Jupiter and Saturn.
	Cassini-ss.ssc (1KB, 4dec02)	for 30June2004 & 1July2004: Saturn insertion, 2 Heliocentric elliptical orbits
	Cassini-s.ssc (1KB, 4dec02)	for 1July2004: just after Saturn orbital insertion, Saturn elliptical orbits.
	cassini-all.zip (150KB 6Dec2002) contains only the files cassini-all.ssc cassini-all.xyz (400KB 2Dec2002)	For the interval 1997-Oct-15 10:30 to 2006-Jan-15 10:30 UDT. This version of Cassini's xyz trajectory contains position samples every two days for most of the trajectory. However it includes much more frequent samples of the spacecraft's path for each of the important encounters: Earth launch, the two Venus gravity assist flybys, the Earth gravity assist flyby, the encounter with asteroid (2685) Masursky, the Jupiter gravity assist flyby, the Phoebe flyby, and the Saturn orbital insertion. Each of those events is sampled 100/day for +/- two days. Several additional samples are included at the time of closest approach to Earth to improve the accuracy of Celestia's display. There may be a problem with the part of the data that describes the Saturn orbital insertion trajectory. This is being investigated.
	cassini-es.ssc (1.5KB 3Dec02)	This .SSC file contains the orbital elements for the time of Cassini's closest approach to the Earth during the Earth gravity assist. If you set Celestia's time to 18-Aug-1999 03:28 UT and follow Cassini, tracking Earth, your field of view will be filled by the South Pacific as you go hurtling by.
Asteroid (2685) Masursky	2685.ssc (1.5K, 16-Oct-02)	NASA Press Release LPL's CICLOPS (Cassini Imaging Central Laboratory for OPerations) description of the encounter. The asteroid has been set to be of Class "moon" to simplify comparisons of its orbit and Cassini's.
Phoebe	phoebe2004-xyz.ssc phoebe2004-xyz.xyz (60KB)	These files specify the Heliocentric cartesian coordinates for Phoebe for slightly more than one of its orbital periods at two day sample intervals. It includes 100 samples/day for +/- 2 days around the time of Cassini's flyby. These coordinates were obtained from Horizons. Using this xyz trajectory, Celestia shows the flyby to be at 2004-Jun-11 19:35 at a distance of about 2,000 km. (Unfortunately, the elliptical orbital elements used by Celestia v1.2.5pre7 place Phoebe 180 degrees away in its orbit.)

Some significant incidents:

Launch: 15-October-1997
- Cassini-19980115.ssc (1KB, 15-Oct-02) for 15-Jan-1998, travelling between Earth and Venus.
  This "EllipticalOrbit" .SSC file includes Beginning and Ending dates, but (as of v1.2.5pre6) Celestia's orbit drawing routines don't yet honor them.
Venus assist: 26-April-1998, altitude=287.2 km
- Cassini-19981201.ssc (1KB, 15-Oct-02) for 01-Dec-1998, travelling between Venus and Venus
Venus assist: 24-June-1999, altitude=600km
- Cassini-19990719.ssc (1KB. 15-Oct-02) for 19-Jul-1999, travelling between Venus and Earth
Earth assist: 18-Aug-1999; closest approach at 03:28 UT, altitude: 1,171km above eastern South Pacific at -23.6 degrees latitude, 231.5 degrees longigude. Ref: http://science.nasa.gov/newhome/headlines/ast18aug99_1.htm
- Cassini-2000.ssc (1KB, 10-Oct-02) for 01-Jan-2000, travelling between Mars and Jupiter.
Asteroid 2685 Masursky observed: 23-Jan-2000, 3:01 UTC
Jupiter assist: 30-Dec-2000, altitude=9,700,000 km
- Cassini-2002.ssc (1KB, 10-Oct-02) for 10-Oct-2002, travelling between Jupiter and Saturn.
Ref: http://www.jpl.nasa.gov/news/fact_sheets/cassini.pdf (Aug, 2001)
passes through E ring
peri-Saturn altitude = 1/6 Saturn diameter (i.e. ~20,000 km)
Huygens release: Dec 25, 2004; H's Titan encounter: Jan 14, 2005
Ref: http://esapub.esrin.esa.it/bulletin/bullet92/b92kohlh.htm (Nov. 1997)
Phoebe Flyby: insertion -19 days 52,000 km
(Celestia shows the flyby to be at 2004-Jun-11 19:35 at a distance of about 2,000 km.)
peri-Saturn: 20,000 km above cloudtops
Ref: http://quest.arc.nasa.gov/saturn/qa/new/Location_of_orbit_injection.txt (as of 12 Jan 2000)
ascending ring crossing between F & G rings
SOI at ring crossing +15 min; 35 min duration; ending at closest approach; out of ring plane by 11 degrees
descending ring crossing 3.76h later between F & G rings
Ref: http://www.spacedaily.com/news/cassini-01e2.html (May 15, 2002)
Planned Saturn Orbital Insertion: 1-July-2004 after passing through rings (period: 148 days)
Titan Flyby 1: Nov 27 2004 (period: 48 days)
Titan Flyby 2: Jan 14 2005 (period: 32 days)
Titan Flyby 3: Feb 15 2005
Enceladus Flyby 1: Mar 9 2005
Enceladus Flyby 2: July 14 2005 1000km
Titan Flyby 6: Aug 22 2005
Titan Flyby: April ? 2006 950 km