Cassini Significant Events for 07/18/02 – 07/24/02

The most recent spacecraft telemetry was acquired from the Goldstone
tracking station on Wednesday, July 24. The Cassini spacecraft is in an
excellent state of health and is operating normally. Information on the
present position and speed of the Cassini spacecraft may be found on the
"Present Position" web page located at
http://saturn.jpl.nasa.gov/cassini/english/where/ .

This week the spacecraft transitioned to the Reaction Control Subsystem
and the use of thrusters for attitude control, and powered off the
Reaction Wheel Assembly. In addition, an autonomous Solid State Recorder
memory load partition repair was performed along with a clearing of the
ACS high water marks.

Instrument activities included a Visual and Infrared Mapping
Spectrometer star characterization, an Ultraviolet Imaging Spectrograph
Hydrogen Deuterium Absorption Cell conditioning activity, a Composite
InfraRed Spectrometer thermal calibration, and calibrations of the Radio
and Plasma Wave Science high frequency receiver.

The Cassini Program released a media report on the Imaging Science
Subsystem haze anomaly in the Narrow Angle Camera (NAC). Analysis of
data obtained over the last few weeks confirms image quality has
returned to virtually the same as prior to when the haze appeared. The
haze was first observed when the NAC cooled back to its usual operating
temperature after a routine maintenance heating to 30 C in mid-2001.
Lens hazing from engine exhaust or other sources is always a possibility
on interplanetary spacecraft and instrument designers incorporate
heaters into the camera assembly to cope with just such a situation.
Four decontamination treatments over varying lengths of time removed
most of the haze. In the latest activity, the camera was warmed to 4
degrees C for four weeks ending July 9. Images were then taken at the
normal operating temperature of minus 90 C, confirming the removal of
the haze. Comparison images are available for viewing at
http://www.jpl.nasa.gov/images/cassinicamera_caption.html .

Uplink Operations offered a course in the use of Cassini’s Pointing
Design Tool to Composite InfraRed Spectrometer instrument team personnel
at the Goddard Spaceflight Center.

A Development tour planning retreat was held to ensure that all
development schedules for achieving tour readiness were consistent and
realistic, dependencies understood and agreed-to, risks identified, and
work prioritized.

Cassini 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, Calif., manages the
Cassini mission for NASA’s Office of Space Science, Washington, D.C.