Phoebe is wild! Check her out!
http://saturn.jpl.nasa.gov/cgi-bin/gs2.cgi?path=..
/multimedia/images/small-moons/images/PIA06064.jpg&type=image
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(cut-and-paste from a subscription)
Cassini Significant Events
for 06/10/04 - 06/16/04
The most recent spacecraft telemetry was acquired from the Goldstone
tracking station on Wednesday, June 16th. 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 .
On Friday, June 11th, 2004, Cassini made its first encounter with a
member
of the Saturn system. This week's Phoebe encounter, the only flyby of
an
outer Saturnian satellite in the mission, and the first close flyby
ever of
an irregular Saturnian satellite, was spectacularly successful!
Cassini came
within approximately 2,068 kilometers of the dark moon. It has been 23
years
since the Voyager 2 flyby of Phoebe in 1981 at 2.2 million kilometers,
more
than 1,000 times farther away.
Since all of the optical remote sensing instruments were pointing
towards
Phoebe during the flyby, it was not until several hours later that the
spacecraft turned to relay the data back to Earth. The signal was
received
on Saturday, June 12th, through the Deep Space Network antennas in
Madrid,
Spain and Goldstone, California. Five instruments reported taking
significant data: the Composite Infrared Spectrometer (CIRS), Imaging
Science Subsystem (ISS), RADAR, Ultraviolet Imaging Spectrograph
(UVIS), and
the Visible and Infrared Mapping Spectrometer (VIMS).
These instruments returned a wealth of scientific data on this
tortured and
battered moon, thanks to the success of the Live Update process that
enabled
a last minute modification in the pointing of the spacecraft to more
accurately target Phoebe. Further analysis of the data over the next
several weeks will begin to unravel the moon's past and possible age
and
origin, resolve its mass and physical properties, and begin to shed
light on
the moon's composition, surface properties, and topography.
VIMS will provide the first ever resolved spectra of the surface of
Phoebe,
up to 0.5 km/pixel at closest approach, with full range 0.4 to
5-micron
spectra. This data will be used to derive compositional maps of
Phoebe's
surface.
Phoebe is an exceptionally interesting target for CIRS, due to its
unusual
surface composition compared to most of the icy satellites and its
relatively warm temperatures, which will provide high signal to noise
data.
CIRS performed compositional and thermal observations to assist in
identifying Phoebe's origins and surface properties including global
mapping
of composition and both day and night temperature distributions.
UVIS measured Phoebe's ultraviolet surface reflectance, providing the
first
ultraviolet albedo map of this interesting body. The UVIS measurements
will
aid in understanding Phoebe's compositional makeup and distribution of
volatiles.
RADAR team members were excited, as it has been a long time between
observations. The last opportunity was 5 years ago at the time of the
Earth
flyby in June of 1999. RADAR observations of Phoebe penetrated to
between 2
cm and 20 cm, and will constrain the bulk density and/or the relative
ice
cleanliness in the upper layer of regolith. This along with volume
derived
from imaging data will help determine if it is a highly porous 'rubble
pile'
based on its low density, or a more compact body as might be suggested
from
its roughly spherical shape. The density value will also be used to
constrain its composition and indicate the rough proportions of rock
and ice
in its make-up.
ISS will contribute multi-color mapping of almost the entire surface
at 0.3
to 2.1 kilometers per pixel resolution. The first high-resolution
images of
Phoebe show a scarred surface, covered with craters of all sizes and
large
variations of brightness across the surface, giving strong evidence
that the
tiny moon may be rich in ice and covered by a thin layer of darker
material.
Phoebe is a world of dramatic landforms, with landslides and linear
structures such as grooves, ridges and chains of pits.
Although working groups must convene to discuss and refine
conclusions, the
Cassini science community and flight team are extremely pleased and
excitement is running high. This attitude is reflected in the
response of
the general public to this event.
On June 14, a Cassini picture of Phoebe was Astronomy Picture of the
Day.
Also last week the flyby achieved the top science story spot on the
Google
website.
JPL has released multiple press releases and images, and CNN.com, NASA
Ames
Research Center, and ESA published additional articles. Go to
http://saturn.jpl.nasa.gov to access these items. Links to other
sites
referenced in this status report are listed below.
Astronomy Picture of the Day
If "today" for you is no longer June 14, 2004, then go to:
http://antwrp.gsfc.nasa.gov/apod/ap040614.html
Google
http://news.google.com/news/en/us/technology.html
CNN.com - Space probe fly-by of Saturn's moon - Jun 11, 2004
http://www.cnn.com/2004/TECH/space/06/11/saturn.moon/index.html
NASA SCIENTIST HOPES TO EXPLAIN SATURN'S MYSTERIOUS 'BLACK' MOON
June 9, 2004
http://www.arc.nasa.gov/aboutames-pressrelease-print.cfm?id=15000128
Cassini-Huygens looks at Phoebe's distant past
European Space Agency
14 June 2004
http://www.esa.int/esaCP/SEMNL63VQUD_index_0.html
Additional spacecraft activities this week included the successful
execution
of Trajectory Correction Maneuver (TCM) -21. The "quick look"
immediately
after the maneuver showed the burn duration was 38.38 sec, giving a
change
in velocity of 3.68 meters/second.
The SOI critical sequence was also successfully uplinked to the
Command and
Data Subsystem's main memory. The critical sequence is on board and
waiting
for the "activate" command which will be radiated this coming
Thursday, June
17, 2004. Additional on-board instrument activities included a
Radio and
Plasma Wave Science instrument Periodic Instrument Maintenance.
In the last week, 994 ISS images were obtained and were distributed
along
with 1160 VIMS cubes. The total number of ISS images acquired since
the
start of Approach Science is now 11976, and the number of VIMS cubes
is
4085.
Sequence development activities are proceeding on schedule. The
official
port #2 for Science Operations Plan (SOP) Implementation of tour
sequences
S29 and S30 occurred this week, as well as the official port #1 for
tour
sequences S31 and S32. All products have been merged and handed to
the ACS
team for the end-to-end pointing validation.
Preliminary port #1 for SOP Update for tour sequence S04 occurred this
week.
The products were merged and reports delivered to the instrument team.
As
part of the Aftermarket process for S06, an assessment meeting was
held.
Since changes to the sequence were minimal, they were determined to
fit
within the available resources.
The S02 background sequence and Probe Checkout #14 sequence were
approved at
the S02 Sequence Approval meeting. Both files will be uplinked to the
spacecraft next week. S02 begins execution on Saturday June 19. The
Probe
Checkout activity is designed to simulate to release of the probe from
the
orbiter.
In support of SOI activities, a Playback Assessment Meeting has been
scheduled for July 2. The purpose of this meeting is for the
instruments to
report whether or not they found the SOI playback to be sufficient,
based on
pre-determined criteria. This is part of the contingency plan to
ensure
success of the overall orbit insertion activity.
Outreach activities include the formal release of the "Reading,
Writing, and
Rings" lesson set for grades 3 and 4. This release marks the
culmination of
development on Cassini's blended language arts and science lesson sets
for
elementary school classrooms. All materials are now available to
download
from the education section of the Cassini website.
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.
Cassini Outreach
Cassini Mission to Saturn and Titan
Jet Propulsion Laboratory
California Institute of Technology
National Aeronautics and Space Administration
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Received on 2004-06-18 22:42:39