Cassini Update - May 23, 2008
- From: baalke@xxxxxxxxxxxxx
- Date: Fri, 23 May 2008 13:46:11 -0700 (PDT)
Cassini Significant Events
for 05/14/08 - 05/20/08
The most recent spacecraft telemetry was acquired on Tuesday, May 20,
from the
Goldstone, California tracking complex. The Cassini spacecraft is in
an
excellent state of health and all subsystems are operating normally.
Information on the present position and speed of the Cassini
spacecraft may be
found on the "Present Position" page at:
http://saturn.jpl.nasa.gov/operations/present-position.cfm.
Wednesday, May 14 (DOY 135)
Yesterday at 3:06 PM, part one of the S40 background sequence ended
and part
two began execution. S40 will continue to run until Friday, May 30.Â
Science this week took advantage of auroral crossings that allowed the
Magnetospheric and Plasma Science (MAPS) instruments to observe
energetic
particle interactions in Saturn's polar regions. The Cassini Plasma
Spectrometer (CAPS) and Magnetometer Subsystem (MAG) measured the
vertical
structure and dynamics of the inner magnetosphere. MAG performed
unique
observations of Saturn's internal magnetic field over a unique orbit
track in
latitude and longitude space. Meanwhile, the Radio and Plasma Wave
Science
(RPWS) instrument observed the auroral magnetosphere and Saturn
kilometric
radiation source regions, as well as watching for wideband evidence of
lightning whistlers. These would verify the existence of lightning
already
suspected from Saturn electrostatic discharges, and would provide
information
on the electron density along the field line to the source.Â
Friday, May 16 (DOY 137):
Orbit Trim Maneuver (OTM) #155 was performed today. This is the
cleanup
maneuver after the Titan 43 encounter on May 11. The main engine burn
began at
7:36 PM PDT. Telemetry immediately after the maneuver showed the burn
duration
was 7.1 seconds, giving a delta-V of 1.16 m/s, as planned. All
subsystems
reported nominal performance after the maneuver.
Saturday, May 17 (DOY 138):
Non-targeted flybys of Calypso and Methone occurred today and will be
followed
tomorrow by an Epimetheus flyby.
The Composite Infrared Spectrometer (CIRS) began science activities
today by
leading a joint Optical Remote Sensing (ORS) observation of a Dione
solar
eclipse. The Visual and Infrared Mapping Spectrometer (VIMS) observed
a stellar
occultation by Saturn with Imaging Science (ISS) riding along, and
then
recorded a Saturn polar movie. CIRS also led a joint ORS observation
of Janus.
Cassini Radio Science conducted two special observations today: the
first
North-South Saturn atmospheric occultation, and the second and last
Saturn
gravity experiment in the prime mission. The activities started with
a gravity
inbound experiment, then occultation ingress followed by egress, and
finally,
gravity outbound.
Collectively, the occultations will provide important information
about the
winds in Saturn's atmosphere. They also provide information about the
large
and small scale structure of the atmosphere, the temperature/pressure
profile,
abundance of microwave absorbing species, and the electron number
density
profile in the ionosphere. The gravity field observation was
conducted by
Doppler tracking of the spacecraft during time periods both before and
after
the occultation event. The measured frequency residuals provide key
information about Saturn's gravitational harmonic coefficients and
hence the
interior structure of the planet. Madrid's DSS-55 and DSS-63 and
Goldstone's
DSS-25, DSS-26 and DSS-15 antennas provided support for these events.
The
experiments were completed as planned, and high quality data were
acquired.
Monday, May 19 (DOY 140):
Today the Navigation team released an update to the reference
trajectory.
Trajectory 080520 reflects changes beginning in orbit 68 and
continuing through
to the end of the extended mission in 2010. The primary purpose of
the update
was to change the Enceladus 5 B-plane angle from 70 to 90 degrees, and
to move
three maneuver locations to accommodate Discipline Working Group and
Navigation
Team requests. The maneuvers affected are #162, #168, and #177.
Tuesday, May 20 (DOY 141):
A delivery coordination meeting was held today for the Cassini
Information
Management System (CIMS) Version 3.4. CIMS 3.4 provides many new
features and
updates to align the product with the current Science Planning
process.
The Cassini Imaging Team released the third in its series of atlases
of
Saturn's icy satellites, this one charting the fractured 1125 km wide
moon
Dione. The team has previously released atlases of Enceladus and
Phoebe.
Atlases of other moons will be released as Cassini's mission
continues. Iapetus
and Tethys are next in line. All atlases are simultaneously released
to the
public and to the scientific community via the NASA Planetary Data
System
(PDS).
It is important for planetary scientists to have accurate maps of the
worlds
they study. They serve as the basis for geologic interpretations,
estimates of
the ages of surface regions, and deciphering the processes that formed
the
moons' landscapes. Most importantly, with their accurate reckoning in
latitude
and longitude, these maps make it easy for scientists to find and
refer to
features of interest on the moon's surface.
For links to the full article and the maps go to:
http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=841
http://saturn.jpl.nasa.gov/multimedia/products/detail-cartography.cfm
Wrap up:
Check out the Cassini web site at http://saturn.jpl.nasa.gov for the
latest
press releases and images.
The Cassini-Huygens mission 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,
manages the
Cassini-Huygens mission for NASA's Science Mission Directorate,
Washington,
D.C. JPL designed, developed and assembled the Cassini orbiter.
.
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