Cassini Mission Status 23 Jul 2002

Now within two years of reaching Saturn, NASA’s Cassini spacecraft took
test images of a star last week that reveal successful results from an extended
warming treatment to remove haze that collected on a camera lens last year.

The quality of the new images is virtually the same as star images taken
before the haze appeared. In the most recent treatment, the camera had been warmed
to 4 degrees Celsius (39 degrees Fahrenheit) for four weeks ending July 9. Four
previous treatments at that temperature for varying lengths of time had already
removed most of the haze. The camera usually operates at minus 90 C (minus 130
F), one of the temperatures at which test images were taken on July 9 of the star
Spica.

“We’re happy with what we’re seeing now,” said Robert Mitchell, Cassini
program manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. The team
will decide in coming weeks whether to proceed with another warming treatment
later this year.

Cassini’s narrow-angle camera worked flawlessly for several months before
and after a December 2000 flyby of Jupiter. Haze appeared when the camera cooled
back to its usual operating temperature after a routine-maintenance heating to 30 C
(86F) in mid-2001. Lens hazing from engine exhaust or other sources is always a
possibility on interplanetary spacecraft. Planners designed heaters for Cassini’s
cameras to cope with just such a situation.

Before treatment, the haze diffused about 70 percent of light coming from a
star, by one method of quantifying the problem. Now, the comparable diffusion is
about 5 percent, Cassini engineers Charles Avis and Vance Haemmerle report.
That’s within one percent of what was seen in images from before the hazing
occurred, possibly within the range of statistical noise in the analysis. Comparison
images are posted at http://www.jpl.nasa.gov/images/cassinicamera_caption.html.

Additional information about Cassini-Huygens is online at
http://saturn.jpl.nasa.gov .

Cassini will begin orbiting Saturn on July 1, 2004, and release its
piggybacked Huygens probe about six months later for descent through the thick
atmosphere of the moon Titan. Cassini-Huygens is a cooperative mission of NASA,
the European Space Agency and the Italian Space Agency. JPL, a division of the
California Institute of Technology in Pasadena, manages the mission for NASA’s
Office of Space Science, Washington, D.C.