Cassini Significant Events — 05/19/05 – 05/25/05

Cassini Significant Events -- 05/19/05 - 05/25/05

May 27, 2005

(Source: Cassini Project)

The most recent spacecraft telemetry was acquired Wednesday from the
Goldstone tracking station. 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 .

Activities this week:

The Radio Science Subsystem team performed the second of eight occultation
experiments this week. Instruments from the Optical Remote Sensing group
participated in joint studies of Enceladus and the rings at 0 deg. phase,
performed a series of stellar occultation activities, observed the apparent
passage of the star CW Leo through the atmosphere of Saturn to obtain
composition and chemistry information at high latitudes, and performed
Far-Infrared hemisphere mapping of Saturn and several radial scans of the
rings to obtain sub-millimeter and temperature measurements. Finally,
instruments from the Magnetospheric and Plasma Science group performed a
high-resolution study of bow shocks and other magnetospheric boundaries.


Thursday, May 19 (DOY 139):

A decision was made by Program Management to go with the new Cassini
adaptation of the Configuration Management system that was demonstrated last
week at the combined Cassini Design Team/Instrument Operations Working Group
Meeting. The system will be ready for Program use in September 2005. A
schedule and plan are being developed to bring the system to operational
readiness. Training is planned for users in the month of August, both at
the Project Science Group Meeting and at JPL.

The Visual and Infrared Mapping Spectrometer (VIMS) was one of the
instruments that performed an occultation observation of star CW Leo as it
passed behind the Saturn limb and one of Omicron Ceti as it passed behind
the rings. Both observations were the first of their kind by VIMS and the
science team reports stunningly successful tracking and data quality.

A Ground Software Monthly Management Review was held to review status for
the June 2005 delivery. All teams reported they are on-track and have no
issues. A recently discovered problem in the Telemetry, Tracking, Command &
Data Management system version 29.1 telemetry software will require a
redelivery with version V29.1.1. Since all Cassini-developed software was
tested on the previous version, we will deploy the June delivery on V28.1.1,
and then upgrade the "core" system when it is delivered and tested.

The first of two S11 live Inertial Vector Propagator updates began execution
very late on Thursday.

Friday, May 20 (DOY 140):

Instrument Operations (IO) reported that the Imaging Science Subsystem (ISS)
has completed a set of reports containing metadata describing the contents
of the first set of archive DVDs being produced by the science team. These
reports are derived from the IO/ Multi-mission Image Processing Laboratory
database.

Saturday, May 21 (DOY 141):

In the wee hours of the morning the first live moveable block in S11 began
execution and ran for about 12 hours. During this time the Radio Science
Subsystem (RSS) measured the properties of Saturn's rings and atmosphere by
performing a diametric radio occultation experiment, and the Cosmic Dust
Analyzer (CDA) measured the dust flux and particle composition during the
Enceladus Orbit Crossing.

There were non-targeted flybys of the Saturnian satellites Atlas,
Prometheus, and Enceladus. A non-targeted flyby is one that occurs without
any maneuvers and observes satellites that just happen to be in a place that
can be seen by Cassini. Typically the altitudes are higher than for
targeted flybys, up to 100,000 km. The altitude will vary as the reference
trajectory changes. Some non-targeted flybys may disappear as the
trajectory changes, and others may suddenly emerge.

Just to complete the picture, a targeted flyby is one that uses maneuvers to
achieve the desired altitude, and the flyby altitude is fixed and does not
change even when the reference trajectory changes. Targeted flybys are
usually less than 3000 km in altitude.

Sunday, May 22 (DOY 142):

Today and for the next two days, Uplink Operations will be sending new
versions of instrument flight software up to the spacecraft for Cassini
Plasma Spectrometer (CAPS), CDA, and ISS.

Monday, May 23 (DOY 143):

Mission Planning posted a report from last week's T5 Titan Atmosphere Model
Working Group meeting to the Cassini Internal web site. The results are
somewhat preliminary but the conclusions are valid for picking a new lowest
Titan safe altitude.

In a press release issued today it was reported that the Cassini spacecraft
has obtained the most detailed look ever at Saturn's rings, including the B
ring, which has eluded previous robotic explorers. Its structure seems
remarkably different from its two neighbors, rings A and C. During the May
2-3 Radio Science Occultation experiment, Cassini mapped this structure with
a clarity never before available.

During a radio occultation, Cassini sends a radio signal from the spacecraft
through the rings to Earth. Scientists then watch how the strength, phase,
and amplitude of the radio signal is affected as the signal passes through
ring material. The denser a ring is, the weaker the signal received. The
experiment helps scientists map the distribution of the amount of ring
material and determine the ring particle sizes.

The Cassini tour was designed specifically to optimize the geometry of the
first radio occultation experiment and seven other occultations scheduled
from May to September 2005. These observations are at the heart of Cassini's
fundamental science objectives of characterizing and understanding Saturn
and its ring system. For more information on this press release go to
http://saturn.jpl.nasa.gov

An image of Saturn's wave maker moon is Astronomy Picture of the Day today.

Tuesday, May 24 (DOY 144):

Cassini Outreach participated in a Career Day at Temple City High School.
NASA stickers and Cassini bookmarks were distributed while members of the
Outreach team spoke to small groups of students.

Cassini Outreach received an amazing thank you card in the mail from Hugo
Reid School in Arcadia, CA this week, in response to a mailing of Cassini
outreach material. Each student in the class wrote a thank you note on one
of 27 paper "students" in a cutout chain. This thank you card, of 27 yellow
students holding hands, is proudly on display in the Cassini outreach
offices.

Wednesday, May 25 (DOY 145):

The S11 leads uplinked checkout exercises for the new CAPS and CDA Flight
Software. The CAPS checkout will execute today, and CDA will perform theirs
on Monday May 30.

A false-color picture of Saturn's rings is Astronomy Picture of the Day
today.

In a second press release this week it was reported that Saturn's moon Titan
shows an unusual bright spot. The 483-kilometer-wide region is
approximately the size and shape of West Virginia, and is located just
southeast of the bright region called Xanadu. Other bright spots have been
seen on Titan, but all have been transient features that move or disappear
within hours, and have different spectral properties than this feature.
This spot is persistent in both its color and location.
For more information link to http://saturn.jpl.nasa.gov


Wrap up:

The most recent spacecraft telemetry was acquired Wednesday from the Goldstone tracking station. The Cassini spacecraft is in an excellent state of health and all subsystems are operating normally. Check out the Cassini web site at http://saturn.jpl.nasa.gov for the latest press releases and images.