Status Report

NASA Cassini Significant Events for 06/03/04 – 06/09/04

By SpaceRef Editor
June 11, 2004
Filed under , , ,
NASA Cassini Significant Events for 06/03/04 – 06/09/04

The most recent spacecraft telemetry was acquired from the Goldstone
tracking station on Wednesday, June 9. 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 instrument activities this week included continuation of
Ultraviolet Imaging Spectrograph (UVIS) mapping of the Saturn magnetosphere
in neutral and ion photon emissions. The purpose of this activity is to
derive the distribution and density of atomic and molecular species. The
suite of Magnetospheric and Plasma Science (MAPS) instruments continued its
survey of Saturn’s magnetosphere, in particular looking for upstream solar
wind conditions and wave phenomena as we approach Saturn’s bow shock. The
Imaging Science Subsystem (ISS) continued data collection for a Titan movie
that documents evidence of cloud motion that will be used to measure winds.

Additional instrument activities included a Radio and Plasma Wave Science
High Frequency Receiver Calibration, a Cassini Plasma Spectrometer
Power-On-Reset mini-sequence, periodic instrument maintenance of the Radio
Science Subsystem, and Visual and Infrared Mapping Spectrometer (VIMS)
instrument expanded block #3 SSR load, cleanup, verification, and memory
read out.

Spacecraft activities included power cycling of Reaction Wheel Assembly
(RWA)-1, uplink and execution of an RWA bias for Phoebe, and an ACS post
Trajectory Correction Maneuver (TCM)-20 mass properties parameter update.

In support of the upcoming Phoebe flyby, the first “Live Update” process was
executed and the output products uplinked to the spacecraft.

While the knowledge of the spacecraft trajectory and the various bodies in
the Saturnian system are known well enough in advance that science
activities can be planned, in some cases the detailed position knowledge
isn’t known well enough to ensure that the goals of the science teams are
met. In these cases, the Live Update process is used. For this process the
desired activity design is loaded to the spacecraft with “default” timing
and pointing data to ensure basic science return. Then, just before the
encounter the most recent Navigation knowledge is used to update that
default timing and pointing to maximize the science return.

The Live Update process is especially needed with the Phoebe flyby. This
target is so small and faint when viewed from the ground that the only
targeting data available is from Cassini as it approaches closer and closer.
This data provides the navigation team sufficient insight to make accurate
trajectory predictions that meet the science needs.

Closing in on the Phoebe flyby, members of the Cassini Navigation team
worked every day after TCM-20 to collect, reduce, and analyze spacecraft and
Phoebe position data, and to evaluate the remaining position uncertainty
against the pointing knowledge requirements. On Sunday, June 6th, the team
was confident that they had good enough data to commence with the update
process, and the updated trajectory files were released to the project.

The science teams then took those files and assessed the impact to their
activities if the update were to be executed or not. Agreement was reached
at the Live Update Go/No Go meeting that the update was both warranted and
the Navigation knowledge was sufficient to meet the science intent. A “go”
was then given for a continuation of the process and the Sequence Team
executed the update.

There is no DSN track on Friday June 11 when the Phoebe encounter actually
occurs. The flight team is eager with anticipation for the results of the
flyby that will be downlinked over the Madrid and Goldstone DSN complexes on
Saturday June 12.

A NASA News Release, 2004-145 June 9, 2004, entitled “Cassini Spacecraft
Near First Stop in Historic Saturn Tour” giving more information on the
flyby itself can be found at: In addition,
Aviation Week & Space Technology June 7, 2004 has published an article on
Phoebe and the TCMs that are getting us there.

Background sequence products were released as part of the Preliminary
Sequence Integration and Validation (PSIV) 2 cycle for tour sequence S02,
and a final SIV sequence change request and waiver approval meeting was

Preliminary port#2 for Science Operations Plan Implementation of tour
sequences S29 and S30 occurred this week along with preliminary port #1 for
S31 and S32. The products have been merged, checked and any problems
reported to the teams.

As part of the Science Planning aftermarket process, all requested changes
to the S06 sequence were delivered this week. An assessment meeting will be
held on June 14.

In the last week, 500 ISS images were obtained and were distributed along
with 875 VIMS cubes. The total number of ISS images acquired since the
start of Approach Science is now 10219, and the number of VIMS cubes is

As reported at the last Cassini Project Science Group meeting, the Cosmic
Dust Analyzer (CDA) instrument has discovered dust storms from Saturn! The
detected particles are tiny and fast, similar to the dust stream particles
from Jupiter. They appear not only directly from Saturn, but can be detected
as far as 100 degrees off from the direct Saturn-CDA direction.

NASA and European Space Agency (ESA) officials held an arrival press
conference for the Cassini-Huygens Saturn mission this week. The press
conference originated out of NASA Headquarters where panelists discussed an
overview of the Saturn tour, Huygens Probe mission, the Phoebe flyby, and
the challenging maneuver to place the spacecraft in orbit around Saturn.
Panelists included:

  • — Dr. Ed Weiler, NASA’s Associate Administrator for Space Science,Washington.
  • — Orlando Figueroa, Director, Solar System Exploration Division, NASAHeadquarters.
  • — Dr. Charles Elachi, Director, NASA JPL, Team Leader for the Cassini RadarInstrument, Pasadena, Calif.
  • — Robert Mitchell, JPL Cassini Program Manager.
  • — Dr. Jean-Pierre Lebreton, ESA Huygens Probe Project Manager.

The Cassini arrival press kit is available to download from the Cassini
website at:

In conjunction with the press briefing, the Imaging Team released two new
images. One shows a colorful Saturn looming up ahead. The other indicates
the radial position of Cassini’s ring plane crossing relative to the main
rings and some of Saturn’s moons. The images can be found at

From the other side of the globe, the Imperial College of Science,
Technology and Medicine, London, where members of the Magnetometer Subsystem
(MAG) instrument team reside have issued a press release on upcoming Cassini
activities. MAG maps the internal magnetic field of the planet, and will
give a better idea of what the interior of the planet is like, how the
magnetic field is formed, how it is still being generated, and some further
clues about how the solar system was formed. For more information please
link to:

The University of Arizona is hosting a Cassini event on June 19. For maps,
directions, and more information link to:

Outreach participated in ‘Scout Expo,’ an event for Boy Scouts and Cub
Scouts from the San Gabriel Valley Council of the Boy Scouts Association of
America. Over 2,000 scouts attended the one-day event. Cassini staff members
spoke about the flight project, the upcoming Saturn tour, and assisted in
helping ‘Bear Scouts’ complete elective merits in space exploration. The
Cassini Mission to Saturn and Cub Scout pack 482 from Glendora, California
hosted the booth. Scout Expo took place at Santa Anita Race Track in
Arcadia, California.

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.