Cassini: Ring Plane Crossing Up Ahead

MEDIA RELATIONS
CASSINI IMAGING CENTRAL LABORATORY FOR OPERATIONS
SPACE SCIENCE INSTITUTE
BOULDER, COLORADO 80301

Heidi Finn (720)974-5859


Ring Plane Crossing Up Ahead

In just under four weeks, the Cassini spacecraft will end a seven-year trek
across the solar system when its main engine fires and it slips into orbit
around the planet Saturn. On the evening of June 30, 2004, PDT, just 25
minutes before the main engine ignites, and 52 minutes before the
spacecraft makes its closest approach to the planet, Cassini will pass from
its southerly approach to Saturn into the northern hemisphere by crossing
the planet's ring plane at a distance of about 19,000 km outside the F ring.

Images released today by the Cassini Imaging Team indicate Cassini's
present view of Saturn, in color and looming up ahead, as well as the
position of Cassini's ring plane crossing relative to Saturn's rings and
some of its moons. This location was chosen to minimize any danger to the
spacecraft from orbiting debris.

'After all this time, it's a real thrill to see where Cassini will be in
only a few weeks', said Carolyn Porco, leader of the Cassini imaging team
and director of the Cassini Imaging Central Laboratory for Operations in
Boulder, Colorado.

The spacecraft will fire its main engine for 96 minutes during the critical
Saturn Orbit Insertion (SOI) maneuver. The maneuver will reduce Cassini's
speed, so Saturn can capture it as an orbiting satellite. Cassini will pass
through a gap between the planet's F and G rings, swing close to the
planet, and begin the first of 76 orbits around Saturn's system.

There are risks involved with the SOI maneuver, but mission planners have
prepared for them. There is a backup in case the main engine fails, and the
path through the ring plane was searched for hazards with the best Earth
and space-based telescopes, including the Cassini cameras. Particles too
small to be seen from Earth could be fatal to the spacecraft, so Cassini
will turn to use its high gain antenna as a shield against small objects.

Science planning engineer and associate of the imaging team, Kevin Grazier
of the Jet Propulsion Laboratory said, 'I'm not worried about SOI because
the spacecraft engineers and mission designers have worked it, and worked
it, and re-worked it and as a result, everybody is very confident that by
the end of the burn, we'll be in orbit.'

The Cassini/Huygens mission is a four-year study of Saturn. The 18 highly
sophisticated science instruments will study Saturn's rings, icy satellites,
magnetosphere, and Titan, the planet's largest moon. Hundreds of thousands
of images of Saturn and its rings and moons are expected over the course of
the mission. The highest resolution images of Saturn's rings during the
whole orbital tour will be taken after the orbit insertion burn, when the
spacecraft is less than 16,000 kilometers above the rings.

'Cassini has been functioning so well for so many years now, and so much
effort has been put into making these critical events -- ring plane crossing
and orbit insertion -- as safe as possible', said Porco,`that I have no
trepidations whatsoever about the outcome of events on the evening of June
30. I am far more anxious about keeping up with the flow of events and
images once we're in orbit!'

The Cassini-Huygens mission is a cooperative project of NASA, the European
Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a
division of the California Institute of Technology in Pasadena, manages the
Cassini-Huygens mission for NASA's Office of Space Science, Washington. The
imaging team is based at the Space Science Institute, Boulder, Colo.

The Space Science Institute is a non-profit organization of scientists and
educators engaged in research in the areas of astrophysics, planetary
science and the earth sciences, and in integrating research with education
and public outreach.

The new images can be found at the Imaging Team's website on Thursday, June
3, 2004 at 8:00 a.m. MDT:

http://ciclops.org

Additional information on the Cassini-Huygens mission can be found at:

http://saturn.jpl.nasa.gov