Cassini Weekly Significant Events for Thursday, 01/20/00 – Wednesday, 01/26/00

The most recent spacecraft telemetry data was acquired from the Goldstone tracking station on Sunday,
01/23. The Cassini spacecraft is in an excellent state of health and is operating normally. The speed of the
spacecraft can be viewed on the “Where is Cassini Now?” web page (
“http://www.jpl.nasa.gov/cassini/today/” )

This week Cassini flew by the asteroid 2685 Masursky, with a closest approach of about 1.5 million km
occurring at 9:58 UTC on January 23. Three of the Remote Sensing instruments (ISS, VIMS, and UVIS) made
observations a few hours before closest approach, when the
sun-spacecraft-earth angle was nearest to 90 degrees. Goals of this activity include determining the asteroid’s
size and dimensions, albedo and photometric measurements; and the first high-resolution spectrum of an
asteroid in the 2.5-5.0 micron region. This event also served as a calibration opportunity, helping to determine
the alignment of the boresights of the three ORS instruments, and determining instrument limitations when
observing a small, barely resolvable object, as will be the case when observing Saturn’s satellites during Tour.

Other on board activities included clearing the AACS High Water Marks, Flight Software Partition Maintenance
and an AACS Active Vector Update.

This week the Mission Planning Team finished updates to the Cassini Mission Plan document that reflect our
plans for the Instrument Checkout – 2 (ICO-2) subphase. The ICO-2 subphase occurs while the Cassini
spacecraft cruises from the outer reaches of the main asteroid belt to Jupiter. It gives the instrument teams
an opportunity to test and calibrate their instruments in preparation for science operations at Saturn,
beginning in 2004, and for science operations during the encounter with Jupiter late this year. Completion of the
Mission Plan updates and supporting documents signals the end of the planning process for ICO-2 and the
start of the implementation process, when the Sequence Team translates the plans into sequences of
commands for the spacecraft.

The Cassini Project Science Group (PSG) met this week. Details will be reported in next week’s status report.

Cassini Outreach

Cassini Mission to Saturn and Titan

Jet Propulsion Laboratory

California Institute of Technology

National Aeronautics and Space Administration