Status Report

NASA Cassini Significant Events for 06/17/04 – 06/23/04

By SpaceRef Editor
June 25, 2004
Filed under , , ,
NASA Cassini Significant Events for 06/17/04 – 06/23/04

The most recent spacecraft telemetry was acquired from the Madrid tracking
station on Wednesday, June 23rd. 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 .

After an almost seven year trek to Saturn, the Cassini-Huygens spacecraft is
less than one week away from reaching its goal. On June 30th at 7:36 PM
Pacific Daylight Time, Cassini will execute a 96 minute burn that will
provide a change in speed of 626 m/s, and allow it to be captured by
Saturn’s gravity. The closest approach to Saturn throughout the entire
mission occurs at about 9:00 PM, shortly before burn completion, a mere
20,000 km above the cloud tops. Cassini will pass through the plane of the
rings between the F and G rings, fly directly above the ring plane during
the burn, then cross descending between the F and G rings. This allows for
exciting observations of the mysterious rings after burn completion from a
vantage point ten times closer than at any other time in the mission. After
data collection is complete, the spacecraft will turn to Earth and play back
the data it has collected. Cassini will then encounter Titan, on July 2nd,
only 36 hours after Saturn Orbit Insertion (SOI), for a flyby at an altitude
of 339,000 km. After the playback of data from the Titan flyby, Orbit Trim
Maneuver-001 (OTM) will execute. This maneuver will be used to “clean-up”
the trajectory after SOI. The spacecraft enters Solar Conjunction on July
4th, when Cassini is behind the Sun as seen from Earth. At that time,
communication will be limited for the next eight days.

The spacecraft is programmed to take a number of unique science observations
during SOI. Being so close to the planet allows the Magnetometer Subsystem
(MAG) to measure the strength and direction of the magnetic field. Small
irregularities in the field so close to the planet can reveal clues about
the structure of the very deep interior and core of Saturn, and help to
understand how magnetic fields are generated. Concurrent with these
observations, the Radio and Plasma Wave Science (RPWS) instrument will be
listening for radio wave evidence of lightning from the planet, waves in the
ionosphere, and large meteoroid impacts on the rings. After the burn is
complete, the spacecraft will be oriented in two different directions –
generally not looking straight down – to allow coverage of as much of the
rings as possible in the time available, while simultaneously allowing the
magnetic fields to be measured. Ring properties are known to vary on very
fine scales. Being able to resolve fine scale structure is essential to all
of Cassini’s remote sensing instrument objectives. The instruments will
measure different properties, such as composition, temperature, and
localized clumpy structure.

Several activities occurred during preparation for SOI. A series of
commands was sent to initialize and verify the SOI critical sequence, among
them pointing the spacecraft to the initial attitude, and transition from
reaction wheel to thruster control. The instruments were placed in their
proper configuration for the event.

The SOI critical sequence began executing on Tuesday. This marked the
start of continuous coverage by the Deep Space Network, which will continue
until after the clean-up maneuver on July 3rd.

Other spacecraft activities included the uplink and start of execution of
tour sequence S02, the uplink and verification of Probe Checkout 14, VIMS
ring mosaics, ISS observations of a full rotation of Saturn in three methane
and nearby continuum filters for cloud and haze sounding, ISS data
collection for the creation of movies of the A and C rings while
simultaneously searching for satellites in the ring gaps. Seven of Saturn’s
moons, namely Dione, Enceladus, Hyperion, Iapetus, Mimas, Rhea and Tethys
were also observed this week.

Trajectory Correction Maneuver (TCM)-22 was cancelled due to the excellent
trajectory conditions achieved with TCM-21.

The Navigation team released a new reference trajectory that extends from
now through the four years of the tour. T2004-01 was updated with new
satellite ephemerides, planetary ephemerides, and spacecraft orbit
determination solution. For this trajectory, an Iapetus flyby altitude
constraint was relaxed so that several other constraints could be met,
achieving a better overall trajectory for science purposes.

Sequence development activities are proceeding on schedule. Science
Operations Plan (SOP) Implementation of tour sequences S29 and S30 were
completed and closed with a wrap-up meeting. These products have now been
archived and will be dusted off in December of 2006 for the start of the
Aftermarket process. The official port #1 merged products for S04 as part of
the SOP Update process, and S31/S32 as part of the SOP Implementation
process have been delivered to the ACS team for end-to-end pointing
validation. SOP Implementation for S33/S34 began this week. A waiver
assessment meeting for S03 currently in the Science and Sequence Update
Process was cancelled due to the absence of new waiver requests in the

Scientists met at a workshop in Tucson, Arizona to jointly analyze the
Phoebe data in preparation for Wednesday’s press conference. The press
conference, held at JPL, provided a forum for team members from ISS, VIMS,
UVIS, and CIRS to present their initial findings. Phoebe appears to be a
primordial mixture of ice, rock and carbon-containing compounds similar in
many ways to material seen in Pluto and Neptune’s moon Triton. This
composition indicates Phoebe formed in the outer solar system where it is
cold enough for such compounds to be stable. These findings lend
confirmation to theories that Phoebe could be a Kuiper belt object.

The Cassini K-4 Literacy program is now online both on the home page: and on the NASA Education
Portal page: . K-4 literacy uses the science and technology of
Cassini-Huygens in language arts format to teach science, reading, and
writing skills to our nation’s youngest learners. The program has been
successfully tested with diverse learners in underserved schools. Over 700
teachers have been reached regarding the program through literacy
conferences. The Cassini Mission Literacy Program is now on MERLOT as a
distinguished, high-quality source of learning material. MERLOT
( ) is an online community of faculty who are
collaborating to increase the quantity of high quality web-based,
interactive teaching and learning materials.

Last week’s Phoebe flyby generated the largest web traffic ever to the
Cassini site. The previous “month” high was May 2004 with ~230,000 unique
visitors for the entire month. For 18 days, nearly 600,000 unique visitors
viewed spectacular images of Phoebe. The estimate of the number of unique
visitors is low, since for services like America Online, all patrons from
AOL to the site are seen as 1 visitor.

For the latest Phoebe images go to:

SpaceRef staff editor.