NASA Cassini Significant Events for 06/24/04 – 06/30/04

The most recent spacecraft telemetry was acquired from the Canberra tracking
station on Wednesday, June 30th. 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/operations/present-position.cfm .

During the quiet period leading up to Saturn Orbit Insertion (SOI), members
of the Spacecraft Operations Office (SCO) monitored spacecraft real-time
telemetry on a continuous basis. All operations were nominal and per
predict. Monitoring continued through the pre-SOI critical commanding
period and up until the swap to low gain antenna-1 was commanded. From that
time until a scheduled “call home” after the burn, spacecraft performance
was monitored via the Radio Science Receivers (RSR).

After the antenna swap, the spacecraft was oriented so that the high gain
antenna (HGA) could be used as a shield, protecting Cassini from potential
dust impacts as the spacecraft performed its ascending ring plane crossing
through the gap between the F and G rings.

Traveling at a speed of over 20 km/sec kilometers per second, the spacecraft
was reoriented for a 96-minute main engine burn. This slowed the spacecraft
by 626 meters per second and allowed it to be captured by the gravitational
pull of Saturn. During this time, five science instruments remained on
collecting data that will be unique in the lifetime of the Cassini mission.
Never again will Cassini travel as close to Saturn as it did at 9:03 p.m.
PDT when it reached closest approach of 19,980 kilometers from the cloud
tops.

After completion of the burn, Cassini turned so that the HGA was aimed back
toward Earth for a 20-second burst of telemetry. This “call home” confirmed
for the flight team that the spacecraft was operating normally. Cassini
then turned away and began execution of a science observation sequence.
Science obtained at this time was key, in that the spacecraft was within
15000 kilometers from Saturn’s main rings, ten times closer to the rings
than at any other point in the mission, and in a region of space that had
not been previously observed.

Unique post-SOI science activities included: measurement of the strength and
direction of the magnetic field by the Cassini Magnetometer (MAG), ring
observations by the Optical Remote Sensing Instruments, measurement of the
very sparse neutral molecules in Saturn’s atmosphere by the Ion and Neutral
Mass Spectrometer (INMS), measurement of the charged particles by the
Cassini Plasma Spectrometer (CAPS), and detection of radio emissions emitted
by lightning strokes in Saturn’s atmosphere by the Radio and Plasma Wave
Science instrument (RPWS).

Science data playback began in the early hours of Thursday July 1. Images
are now available for viewing at: http://saturn.jpl.nasa.gov .

A very significant event to occur immediately after SOI was the jettison of
the INMS cover. The cover was left on the instrument since launch until
after the SOI burn was complete. This was to prevent potential
contamination of the instrument by exhaust material from the long burn.
Prior to jettison, INMS was filled with argon to insulate and protect the
interior walls. Team members were able to confirm a successful jettison
when sensors noted the depletion of the argon gas. INMS was powered up at
3:39 SCET and is now taking data for the first time in the mission.

ACS analysis of official port #1 products from Science Operations Plan (SOP)
implementation of tour sequences S31/S32 has been completed. The teams are
working off issues in preparation for preliminary port #2.

Due to SOI activities, the Project Briefing and Waiver Disposition meeting
for the SOP Update process of S04 was canceled. The handoff product will be
generated and delivered to the sequencing team next week.

The Aftermarket decision meeting for S06 was canceled since the number of
changes requested for this sequence was minimal.

System Engineering hosted a Phoebe lessons learned discussion this week.
The Phoebe flyby was the first time an IVP update was required. This
activity will be performed numerous times throughout the mission so the
capturing of information now will assist in future operations. Items on the
agenda included discussion of target motion compensation and live update,
planning and testing for the flyby beginning with the SOP Update process and
including operations readiness tests that were performed for Phoebe,
overview and recommendations for an end-to-end “once the dust settles”
assessment of the process, general lessons learned, and follow ups.