Cassini Update - March 21, 2008
- From: baalke@xxxxxxxxxxxxx
- Date: Fri, 21 Mar 2008 17:06:56 -0700 (PDT)
Cassini Significant Events
for 03/12/08 - 03/18/08
The most recent spacecraft telemetry was acquired on Tuesday, March
18, 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" web page located at
http://saturn.jpl.nasa.gov/operations/present-position.cfm.
Wednesday, March 12 (DOY 072):
Traveling at about 15 kilometers per second and at an altitude of 50
km,
Cassini flew past Enceladus for its fourth encounter with this moon
and its
closest flyby to date with any body, and the deepest penetration yet
of the
Enceladus plumes. The spacecraft passed through the edge of one of
the
plumes at approximately Enceladus Closest Approach (ECA) + 1 minute.
The
reaction wheel (RWA) spin rate changes due to the angular momentum
imparted
on the spacecraft by the plume were -45 rpm, -18 rpm, and -20 rpm, for
RWA-1, -2, and -4, respectively.
The science goals for this flyby were:
(1) Temperature mapping of the north polar region of Enceladus on
approach,
to understand surface physical properties and to look for endogenic
thermal
emission in the northern hemisphere.
(2) Detailed mapping of the warm "tiger stripe" fractures at the south
pole
on departure, in Saturn eclipse, providing the first contiguous
regional
temperature map with spatial resolution sufficient to resolve the
tiger
stripes and locate all the major hot spots.
(3) Long-wavelength mapping of the south polar region to constrain
total
heat flow. Much of the heat radiation may be emitted at long
wavelengths at
which south polar emission was not mapped on the previous Enceladus
flybys.
(4) Observe the warming of Enceladus as it emerges from Saturn's
shadow two
hours after the flyby, to understand surface physical properties.
During Cassini's closest approach, two instruments were prime for
collecting
in-situ plume data--the Cosmic Dust Analyzer (CDA) and the Ion and
Neutral
Mass Spectrometer (INMS). A software hiccup with CDA prevented it from
collecting any data during closest approach, although the instrument
did get
data before and after the closest approach phase. The other four
fields and
particles instruments on the spacecraft, in addition to the INMS,
captured
all of their data, which will complement the overall composition
studies and
elucidate the unique plume environment of Enceladus.
This was the first of four Cassini flybys of Enceladus this year. If
approved, the proposed extended mission will include an additional
seven
flybys, including the three remaining this year. The next Enceladus
flyby
will take place in August of this year.
Link here for the official before and after news releases for the
Enceladus
3 flyby:
http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=822
http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=824
Thursday, March 13 (DOY 073):
The main engine cover, closed during the Enceladus 3 flyby, was opened
Mar.
13, before the Orbit Trim Maneuver #149 prime pass. This was 37th
cycle -
deploy/stow - of the cover since launch.
Orbit Trim Maneuver (OTM) #149 was performed today. This was the
Enceladus
3 cleanup maneuver setting up for the Titan 42 encounter on Mar. 25.
The
main engine burn began at 5:30 PM PDT. Telemetry immediately after the
maneuver showed the burn duration was 16.67 seconds, giving a delta-V
of
2.76 m/sec, as planned. All subsystems reported nominal performance
after
the maneuver.
The Cassini/Enceladus E3 blog has been a hit with the public and the
media,
including several news outlets that linked to the blog. One media
outlet
said: "The best part <about the flyby> is that the team has been
using
blogs.nasa.gov to keep the world posted in a very raw, first-hand
way."
The blog was a venue to convey the emotion and excitement of the flyby
and
to show the personalities of the team.
The blog is at: http://blogs.nasa.gov/cm/blog/Enceladus%20Flyby
Friday, March 14 (DOY 074):
The final delivery of Cassini Information Management System (CIMS)
inputs
for orbits 123-134 occurred today. This is the fourth and final
delivery of
CIMS inputs prior to sequence integration. Orbits 123-134 are
contained
within the S55 through S61 sequences at the end of the proposed
extended
mission.
The Science Operations Plan Update (SOPU) process for S41 completed
today.
Science Planners are in the process of handing off the package to the
sequence leads. S41 is the last sequence in the Cassini Prime
Mission.
Monday, March 17 (DOY 077):
A beautiful picture of Enceladus from ~30,000 km away was Astronomy
Picture
of The Day today, and may be seen at
http://antwrp.gsfc.nasa.gov/apod/ap080317.html
A presentation on "The History of Saturn's Rings" was given today in
Von
Karman auditorium at JPL as part of the Earth and Space Science
Colloquium,
sponsored by the Office of the Chief Scientist & Chief Technologist
and the
Science Division at JPL. The following is an the abstract for the
presentation:
Saturn's rings are made of billions of particles of ice orbiting
Saturn.
They resemble the planet-forming disks surrounding stars. Cassini
observations show Saturn's rings may be ancient, opposite to what has
been
believed since the first Voyager close up views 25 years ago. Cassini
images
and occultations give an unprecedented view of ring structure and
history.
Current ideas suggest that "recycling" can allow the rings to last
indefinitely.
Tuesday, March 18 (DOY 078):
Orbit Trim Maneuver (OTM) #150 was performed today. This was the
apoapsis
maneuver setting up for the Titan 42 encounter on Mar. 25. The
reaction
control subsystem burn began at 12:44 AM PDT. Telemetry immediately
after
the maneuver showed the burn duration was 40.5 seconds, giving a delta-
V of
0.055 m/s. All subsystems reported nominal performance after the
maneuver.
UPCOMING:
JPL's Office of Communications and Education is proud to present the
2008
Theodore von Kármán Lecture Series.
"Enceladus: The Newest Wrinkle from Saturn's Tiger-Striped Moon"
Thursday, March 20th, in the Theodore von Kármán Auditorium at JPL,
and
Friday, March 21st, at Pasadena City College's Vosloh Forum, 1570 East
Colorado Boulevard. Both lectures begin promptly at 7 PM, with
seating
available on a first come, first served basis. For more information
about
the event call the Public Services Office at 818 354-0112, or visit
their
web site at http://www.jpl.nasa.gov/pso/lectures.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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