Status Report

Cassini Significant Events for 07/15/04 – 07/21/04

By SpaceRef Editor
July 23, 2004
Filed under , , ,
Cassini Significant Events for 07/15/04 – 07/21/04

The most recent spacecraft telemetry was acquired from the Goldstone
tracking station on Wednesday, July 21. 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

On-board science activities this week included solar wind measurements by
the Magnetospheric and Plasma Science (MAPS) instruments, Ultraviolet
Imaging Spectrograph (UVIS) observations of Saturn’s aurora and inner
magnetosphere, and Imaging Subsystem observations of the southern hemisphere
of Iapetus.

Spacecraft activities included a reaction wheel assembly bias and the
removal of the Saturn Orbit Insertion critical sequence from the SSRs. This
activity involved the uplink of several real-time commands over a period of
three days. The procedure executed normally.

The Cosmic Dust Analyzer discovered a dust particle carrying an electrical
charge of almost 10 fC at a Saturn distance of 26 Rs and -16 degrees
latitude. This is the first such detection in the Saturn environment, and
the first since detection of particle charges in 2000. The charges of
previous interplanetary particles were below 4 fC. The signal detected now
is more than two times stronger and it is well above the detection threshold
of about 1 fC.

Science Operations Plan (SOP) Implementation of tour sequences S31/S32 has
completed and a wrap up meeting is scheduled for next week. Official port#1
for SOP Implementation of S33/S34 occurred with the delivered files merged
and the resulting products delivered to ACS for end-to-end pointing profile
analysis. SOP Implementation for S35/S36 began this week.

SOP update preliminary port#1 for tour sequence S05 occurred this week. The
files were merged and a report identifying problem areas to be worked was
generated and distributed to the team.

The Integration and Test Laboratory has begin retesting the Probe Relay and
Release sequences. This activity will be ongoing for several weeks.

At the final sequence change request and waiver disposition meeting for S03,
it was determined that a re-evaluation of star ID (SID) suspend commanding
built for the sequence was needed. As there was margin remaining in the
development schedule, it was decided to slip delivery of the final products,
receipt of review of final products, delivery of the final package, and the
final approval meeting by two days. ACS analysis subsequently showed no
issues related to SID Suspend commanding. Final sequence products are now
available, and the final Sequence Integration & Validation package has been
distributed to the team. A command approval meeting (CAM) was held to
approve 7 of the 9 instrument expanded block files to be uplinked to the
spacecraft prior to the start of S03. The remaining files will be CAMed
later in the week.

A delivery coordination meeting was held this week for Telemetry, Tracking,
Command & Data Management software v28.2.1. A Software Review /
Certification Requirements meeting was held for Ion and Neutral Mass
Spectrometer 9.0 flight software (FSW). This delivery includes the
functions in an FSW patch that was applied during C44 and S01, as well as
double buffering of the bus interface unit (BIU), use of DTSTART interrupt,
and writing status information to BIU memory. The FSW was accepted for
operational use with one follow-up action item. The software is scheduled
to be uplinked to the spacecraft on September 1.

On July 21, Cassini once again provided an image that was used as Astronomy
Picture of the Day. This spectacular picture of the shadow of Saturn on the
rings, along with all the most recent images may be viewed at and .

Image Advisory: 2004-182
Cassini Exposes Saturn’s Two-Face Moon

The moon with the split personality, Iapetus, presents a perplexing
appearance. One hemisphere of the moon is very dark, while the other is
very bright. Scientists do not yet know the origin of the dark material or
whether or not it is representative of the interior of Iapetus. The most
recent images of this intriguing satellite are available on the Cassini web

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.

SpaceRef staff editor.