http://www.jpl.nasa.gov/news/features.cfm?feature=2312
Scientists Discover New Radiation Belt at Saturn
Jet Propulsion Laboratory
September 14, 2009
Scientists using the Cassini spacecraft's Magnetospheric Imaging
instrument have detected a new, temporary radiation belt at Saturn,
located around the orbit of its moon Dione at about 377,000 kilometers
(234,000 miles) from the center of the planet.
The new belt, which has been named "the Dione belt," was detected by the
instrument for only a few weeks on three separate occasions in 2005.
Scientists believe that newly formed charged particles in the Dione belt
were gradually absorbed by Dione itself and another nearby moon, named
Tethys, which lies slightly closer to Saturn at an orbit of 295,000
kilometers (183,304 miles).
The discovery was presented at the European Planetary Science Congress
in Potsdam, Germany on September 14.
For more information about NASA's Cassini mission please visit:
http://saturn.jpl.nasa.gov
Cassini Significant Events
for 09/09/09 - 09/15/09
The most recent spacecraft telemetry was acquired on Sept. 15 from
the Deep Space Network tracking complex at Goldstone, California.
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, Sept. 9 (DOY 252):
The Spacecraft Operations Office (SCO) held an engineering activities
review for the S59 sequence.
This week Imaging Science (ISS) took data for a lit face, high phase
movie in search of ring spokes, and a mosaic of Iapetus. The Visual
and Infrared Mapping Spectrometer (VIMS) observed the rings at phase
angles of 110-130 degrees in an attempt to obtain spoke measurements,
and ISS, the Composite Infrared Spectrometer, and the Ultraviolet
Imaging Spectrograph performed several observations in the Titan
monitoring campaign.
Next week, when the Superior Conjunction separation angle reaches two
degrees, the spacecraft will remain on Earth point for five days
until Sept. 19. As was mentioned in a previous report, Radio Science
will be conducting a daily conjunction experiment from Sept. 6
through the entire conjunction period, ending on Oct. 2. During this
time, the suite of Magnetospheric and Plasma Science instruments will
be gathering as much science data as possible.
Thursday, Sept. 10 (DOY 253):
At the Mission Planning Forum today the team discussed a DSN station
allocation straw man plan for the proposed Extended Extended Mission,
covering what is contained in the plan and when that information will
be propagated to the Cassini Information Management System. The
second topic dealt with implementation of the Y-thruster biasing
activities scheduled to begin with sequence S60.
Friday, Sept. 11 (DOY 254):
The Spacecraft and Uplink Operations teams sent commands to the
spacecraft today to update onboard telemetry (TLM) modes for the
Cassini Plasma Spectrometer (CAPS) and Cosmic Dust Analyzer
instruments. Due to extensive and successful ground testing, it was
decided not to perform a special TLM mode cycling test onboard the
spacecraft. The TLM mode change at the end of today's track provided
the first indication that the update was successful.
Today marked the official start of Superior Conjunction. During this
time the angle between the sun and the spacecraft as seen from Earth
gradually decreases until Sept. 17 when it will reach minimum
separation just under two degrees this year. After the 17th, the
angle begins to increase again with the conjunction period ending on
Sept. 22 when separation reaches four degrees and rising. As is
performed every year, beginning on Sept 15 and for the next 5 days,
SCO will send a series of "empty" commands to the spacecraft to
characterize interference from the Sun during conjunction.
With the expectation that this interference will be prohibitive to
real time commanding, a command moratorium - except in case of
emergency - has been declared for Sept. 15-19. Also with the
expectation that a command loss timer (CLT) update would be unable to
be received by the spacecraft, changes were put into the background
sequence to update the onboard CLT value to 9 days on Sept. 12. This
value will drop approximately one day per day until Sept. 20 when the
timer is returned to the nominal 90-hour value.
Monday, Sept. 14 (DOY 257):
Scientists using the Cassini spacecraft's Magnetospheric Imaging
instrument have detected a new, temporary radiation belt at Saturn,
located around the orbit of its moon Dione at about 377,000
kilometers from the center of the planet. The instrument detected
the new belt, which has been named "the Dione belt," for only a few
weeks on three separate occasions in 2005. Scientists believe that
newly formed charged particles in the Dione belt were gradually
absorbed by Dione itself and another nearby moon, Tethys, which lies
slightly closer to Saturn at an orbit of 295,000 kilometers. The
discovery was presented at the European Planetary Science Congress in
Potsdam, Germany on Sept. 14.
http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20090914/
Tuesday, Sept. 15 (DOY 258):
Saturn's Turbulent 'Storm Alley' Sets Another Record.<br>
The longest continuously observed thunderstorm in the solar system
has been roiling Saturn¬¼s atmosphere since mid-January and is still
churning now, according to a presentation by a Cassini team scientist
at the European Planetary Science Congress in Potsdam, Germany. For
the complete story and images go to:
http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20090915/
Sept. 21, 2009
Dwayne C. Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown@...
Jia-Rui C. Cook
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0850
jia-rui.c.cook@...
RELEASE: 09-217
CASSINI REVEALS NEW RING QUIRKS, SHADOWS DURING SATURN EQUINOX
PASADENA, Calif. -- NASA scientists are marveling over the extent of
ruffles and dust clouds revealed in the rings of Saturn during the
planet's equinox last month. Scientists once thought the rings were
almost completely flat, but new images reveal the heights of some
newly discovered bumps in the rings are as high as the Rocky
Mountains. NASA released the images Monday.
"It's like putting on 3-D glasses and seeing the third dimension for
the first time," said Bob Pappalardo, Cassini project scientist at
NASA's Jet Propulsion Laboratory in Pasadena, Calif. "This is among
the most important events Cassini has shown us."
On Aug. 11, sunlight hit Saturn's rings exactly edge-on, performing a
celestial magic trick that made them all but disappear. The spectacle
occurs twice during each orbit Saturn makes around the sun, which
takes approximately 10,759 Earth days, or about 29.7 Earth years.
Earth experiences a similar equinox phenomenon twice a year; the
autumnal equinox will occur Sept. 22, when the sun will shine
directly over Earth's equator.
For about a week, scientists used the Cassini orbiter to look at puffy
parts of Saturn's rings caught in white glare from the low-angle
lighting. Scientists have known about vertical clumps sticking out of
the rings in a handful of places, but they could not directly measure
the height and breadth of the undulations and ridges until Saturn's
equinox revealed their shadows.
"The biggest surprise was to see so many places of vertical relief
above and below the otherwise paper-thin rings," said Linda Spilker,
deputy project scientist at JPL. "To understand what we are seeing
will take more time, but the images and data will help develop a more
complete understanding of how old the rings might be and how they are
evolving."
The chunks of ice that make up the main rings spread out 85,000 miles
from the center of Saturn, but they had been thought to be only
around 30 feet thick in the main rings, known as A, B, C, and D.
In the new images, particles seemed to pile up in vertical formations
in each of the rings. Rippling corrugations -- previously seen by
Cassini to extend approximately 500 miles in the innermost D ring --
appear to undulate out to a total of 11,000 miles through the
neighboring C ring to the B ring.
The heights of some of the newly discovered bumps are comparable to
the elevations of the Rocky Mountains. One ridge of icy ring
particles, whipped up by the gravitational pull of Saturn's moon
Daphnis as it travels through the plane of the rings, looms as high
as 2.5 miles. It is the tallest vertical wall seen within the rings.
"We thought the plane of the rings was no taller than two stories of a
modern-day building and instead we've come across walls more than two
miles high," said Carolyn Porco, Cassini imaging team leader at the
Space Science Institute in Boulder, Colo. "Isn't that the most
outrageous thing you could imagine? It truly is like something out of
science fiction."
Scientists also were intrigued by bright streaks in two different
rings that appear to be clouds of dust kicked up in collisions
between small space debris and ring particles. Understanding the rate
and locations of impacts will help build better models of
contamination and erosion in the rings and refine estimates of their
age. The collision clouds were easier to see under the low-lighting
conditions of equinox than under normal lighting conditions.
At the same time Cassini was snapping visible-light photographs of
Saturn's rings, the Composite Infrared Spectrometer instrument was
taking the rings' temperatures. During equinox, the rings cooled to
the lowest temperature ever recorded. The A ring dropped down to a
frosty 382 degrees below zero Fahrenheit. Studying ring temperatures
at equinox will help scientists better understand the sizes and other
characteristics of the ring particles.
The Cassini spacecraft has been observing Saturn, its moons and rings
since it entered the planet's orbit in 2004. The spacecraft's
instruments have discovered new rings and moons and have improved our
understanding of Saturn's ring system.
The Cassini-Huygens mission is a cooperative project of NASA and the
European and Italian Space Agencies. JPL manages the mission for the
Science Mission Directorate at NASA Headquarters in Washington. JPL
also designed, developed and assembled the Cassini orbiter and its
two onboard cameras. The imaging team is based at the Space Science
Institute. The Composite Infrared Spectrometer team is based at
NASA's Goddard Space Flight Center in Greenbelt, Md.
To view Cassini images of the equinox and for more information about
the mission, visit:
http://www.nasa.gov/cassini
NASA Television's Video File also will air the images. For downlink,
scheduling information and streaming video, visit:
http://www.nasa.gov/ntv
-end-
Cassini Significant Events
for 09/16/09 - 09/22/09
The most recent spacecraft telemetry was acquired
on Sept. 22 from the Deep Space Network tracking
complex at Goldstone, California. 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, Sept. 16 (DOY 259):
The Cassini Scientist for a Day Fall 2009 Essay
Contest is currently underway. To celebrate the
International Year of Astronomy, this 8th edition
of the contest is open to all nations and
educational organizations. Each country and/or
educational organization is encouraged to run the
contest either following our guidelines or customizing them to fit their
needs.
In the US, students in grades 5-12 may enter with
a fast approaching entry deadline of September
30, 2009, at noon Pacific Time. All essays will
be evaluated by Cassini scientists, flight team
members, and educators. Winning essays will be
selected for each target. Outside the US,
sponsoring organizations are tasked to select a
deadline, collect and judge the essays, and to
send the winning entries to the Cassini Outreach
Team. Winners and their classmates will be
invited to participate in a web-based videoconference with Cassini
scientists.
The actual observation for this contest is
scheduled for October 11. The Science Planning
team designed three possible observation
opportunities. Target number 1 is Saturn and its
rings. Number 2 is Tethys with Saturn's rings,
and number 3 is Titan. For more information link to:
http://saturn.jpl.nasa.gov/education/scientistforaday8thedition/
Thursday, Sept. 17 (DOY 260):
On the Cassini Website, under News & Features,
one can find a link to the Cassini Science
League. Launched in August of this year, the
League endeavors to share with the public more of
the large and diverse volume of science generated
by the scientists on the Cassini mission. Each
Science League entry will highlight a science
paper - or set of interrelated papers - and
provide information on the publication in which the paper appears.
The first two articles "Resolving Rain over
Xanadu" and "Titan and Earth's Future Atmosphere:
Lost to Space" appeared in September and August
respectively. Release #3 is due out before the
end of September. To access the articles link to:
http://saturn.jpl.nasa.gov/news/cassiniscienceleague/
Friday, Sept. 18 (DOY 261):
Non-targeted flybys of Prometheus and Dione occurred today.
Sunday, Sept. 20 (DOY 263):
With the spacecraft and Saturn finally far enough
removed from superior conjunction - a
three-degree separation angle - science data
acquisition and playback activities have resumed.
The final portion of the Rings Equinox campaign
ran from Sunday, Sept. 20, through Sept. 24. The
entire set of ring observations during equinox
were deemed as the highest value rings science of
the Extended Mission. The observations for the
RINGS discipline group in these segments were
designed to look for ring phenomena that
scientists have never had the opportunity to study before.
Monday, Sept. 21 (DOY 264):
Science Planning hosted a presentation on the
science highlights for sequence S58 with a focus
on what is unique and what observations have the
highest priority. This information will help the
flight team as the sequence goes through the
development process, and assist in making trades
should the need arise. The files for the first input port are due Wednesday.
Scientists are marveling over the extent of
ruffles and dust clouds revealed in the rings of
Saturn during the planet's equinox crossing last
month. Once thought to be almost completely flat
- at most 10 meters thick - new images of the
rings reveal some newly discovered "bumps" as
high as the Rocky Mountains. For the full story, link to:
http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20090921/
A slideshow with highlights from Cassini's
five-year tour of Saturn, "The Saturn System: A
Feast for the Eyes," was also released Monday:
http://saturn.jpl.nasa.gov/news/cassinifeatures/thesaturnsystemafeastfortheeyes/
Completing an observation that began on the
previous day, VIMS monitored Saturn's rings
following the equinox. Next came an observation
in the CIRS campaign to monitor the long-term
trends in ring temperatures as the Sun moves
north across the ring plane during the equinox
and illuminates that side of the rings that
hasn't seen direct sunlight in over 14 years. ISS
then turned to study what have come to be known
as "propellers," features that indicate the
presence of ring particles large enough to
disturb the ring particles in their vicinity but
not so large as to be able to open a gap in the rings.
Tuesday, Sept. 22 (DOY 265):
Today Cassini and the equinox images were
mentioned on NBC Nightly News. The piece was
called "NASA Offers a New View of Saturn." The story can be viewed
online at:
http://www.msnbc.msn.com/id/3032619#32975141
After reaching a separation (SEP) angle of 4
degrees, Cassini officially exited superior
conjunction. The minimum SEP angle of 1.95
degrees occurred on Sept. 17. One hundred "NO-OP"
commands were sent on each pass from September 15
through September 19 to test the conjunction command link.
A non-targeted flyby of Titan occurred today.
The Target Working Team (TWT)/ Orbiter Science
Team (OST) integrated products for S59, covering
orbits 129 through 131, from April through May,
2010, were delivered today. The integrated
products are in their final form and no
re-integration is planned. The next step in
sequence development, Science Operations Plan
(SOP) implementation, will kick off on Oct. 7.
Between now and then, the instrument teams will
be working on pointing designs for the sequence.
TWT/OST teams deliver integrated sequence
products for the extended mission about every five weeks.
The DSN schedulers provided a fully negotiated
S55 allocation file at this point in the Science
Operations Plan Process. Because of this, there
was enough time to perform the Sponge Bit
process. This process allowed Science Planning to
give out extra data volume for selected periods
of time where there was SSR and downlink margin.
The process began on the 21st with the
publication of an update to the Solid State
Recorder Management Tool report, and a Sponge
Bits package specifying the amount of data volume
per period that was available. A representative
from each science team then reviewed the package
and discussed with their team members if they
could take advantage of the available data volume
in each period. Based on the inputs received, the
science planner next updated the Sponge Bits
package with a proposed allocation. Then during
the actual Sponge Bits meeting on Tuesday, Sept.
22, the allocation was reviewed and approved.
Bottom line - more data for science!
Cassini Significant Events
for 09/23/09 - 09/29/09
The most recent spacecraft telemetry was acquired
on Sept. 29 from the Deep Space Network tracking
complex at Goldstone, California. 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, Sept. 23 (DOY 266):
Port 1 files for the S58 Science Operations Plan
process were received from all participating
teams today. The files were merged and the
results sent out for review on Sept. 24.
A Simulation Procedure Review meeting was held
today as part of the sequence development process
for S55. Radio Science (RSS) had asked that the
occultation experiments planned for DOY 324 and
344 go through the simulation process. Testing
began on Friday the 25th and completed on Monday, Sept. 28.
A write-up on the Radio Science Solar Conjunction
Experiment is posted to Insider's Cassini. You can find the article at:
http://saturn.jpl.nasa.gov/news/cassiniinsider/insider20090923/
Thursday, Sept. 24 (DOY 267):
The Rings Equinox science segment concluded today
and a Magnetospheric Working Group segment began.
This segment is dedicated to Magnetospheric and
Plasma Science (MAPS) science, with favorable
Cassini Plasma Spectrometer (CAPS) pointing
nearly throughout from Sept. 24 through Oct. 8.
Other than an ISS Iapetus observation on DOY
267/268, the rest of the segment will be mostly
CAPS prime pointing, with a few other
observations in which the secondary axis still allows CAPS to gather data.
Friday, September 25 (DOY 268):
Today ISS performed two observations meant to
track some of Saturn's smaller satellites and
mapped out the lit face of the rings through
eight different filters to determine how the
rings' "color" varies. Such observations can
reveal information about the composition of the
rings, as well as how the ring system evolves
over time and recycles the material within them.
Next the dedicated MAPS campaign began. CAPS
performed an observation designed to allow the
MAPS instruments to study Saturn=B9s magnetospheric
boundary with the solar wind, and the
Magnetospheric Imaging experiment/ Ion and
Neutral Camera (MIMI/INCA) and Radio and Plasma
Wave Science (RPWS) performed studies of the
response of Saturn's magnetosphere.
Tuesday, Sept. 29 (DOY 272)
Although S53 is still executing, a kick off
meeting was held today for the first =AD and only =AD
live update in S54. The update is planned to
execute on DOY 286 with Rhea, Tethys, Mimas, and
Enceladus as the targets. The Go/No Go meeting
for this update is scheduled for this Friday.
Port 3 files for the S56 Science Operations Plan
process were received from all participating teams today.
Beginning yesterday and finishing up today,
Uplink Operations sent Instrument Expanded Block
files necessary for execution of the S54
background sequence to the spacecraft. There were
twelve files sent for the Composite Infrared
Spectrometer, ISS, Visual and Infrared Mapping
Spectrometer, Optical Navigation, UVIS, Ion and
Neutral Mass Spectrometer, and CAPS.
And on Wednesday:
A beautiful image of the rings of Saturn taken
during the recent equinox crossing was Astronomy
Picture of the Day. Check it out at:
http://antwrp.gsfc.nasa.gov/apod/ap090930.html
Visit the JPL Cassini home page for more
information about the Cassini Project:
http://saturn.jpl.nasa.gov/
------------------------
Space Weather News for Oct. 6, 2009
http://spaceweather.com
LUNAR IMPACT: This Friday morning, Oct 9th, at approximately 4:30 am PDT,
NASA's LCROSS spacecraft and its Centaur booster rocket will plunge one
after another into a shadowed crater near the Moon's south pole. The
spectacular double-impact will be shown live on NASA TV from the point of view
of
the LCROSS spacecraft. Meanwhile, impact debris plumes emerging from the
crater may be visible through backyard telescopes. North American sky
watchers west of the Mississippi river are favored with darkness and good views
of the Moon at the time of impact. Visit http://spaceweather.com for
observing tips and full coverage.
New subscribers: To sign up for free space weather alerts, click here:
http://spaceweather.com/services/
HR
...
http://www.jpl.nasa.gov/news/news.cfm?release=2009-150
NASA Space Telescope Discovers Largest Ring Around Saturn
Jet Propulsion Laboratory
October 06, 2009
PASADENA, Calif. -- NASA's Spitzer Space Telescope has discovered an
enormous ring around Saturn -- by far the largest of the giant planet's
many rings.
The new belt lies at the far reaches of the Saturnian system, with an
orbit tilted 27 degrees from the main ring plane. The bulk of its
material starts about six million kilometers (3.7 million miles) away
from the planet and extends outward roughly another 12 million
kilometers (7.4 million miles). One of Saturn's farthest moons, Phoebe,
circles within the newfound ring, and is likely the source of its material.
Saturn's newest halo is thick, too -- its vertical height is about 20
times the diameter of the planet. It would take about one billion Earths
stacked together to fill the ring.
"This is one supersized ring," said Anne Verbiscer, an astronomer at the
University of Virginia, Charlottesville. "If you could see the ring, it
would span the width of two full moons' worth of sky, one on either side
of Saturn." Verbiscer; Douglas Hamilton of the University of Maryland,
College Park; and Michael Skrutskie, of the University of Virginia,
Charlottesville, are authors of a paper about the discovery to be
published online tomorrow by the journal Nature.
The ring itself is tenuous, made up of a thin array of ice and dust
particles. Spitzer's infrared eyes were able to spot the glow of the
band's cool dust. The telescope, launched in 2003, is currently 107
million kilometers (66 million miles) from Earth in orbit around the sun.
The discovery may help solve an age-old riddle of one of Saturn's moons.
Iapetus has a strange appearance -- one side is bright and the other is
really dark, in a pattern that resembles the yin-yang symbol. The
astronomer Giovanni Cassini first spotted the moon in 1671, and years
later figured out it has a dark side, now named Cassini Regio in his
honor. A stunning picture of Iapetus taken by NASA's Cassini spacecraft
is online at http://photojournal.jpl.nasa.gov/catalog/PIA08384 .
Saturn's newest addition could explain how Cassini Regio came to be. The
ring is circling in the same direction as Phoebe, while Iapetus, the
other rings and most of Saturn's moons are all going the opposite way.
According to the scientists, some of the dark and dusty material from
the outer ring moves inward toward Iapetus, slamming the icy moon like
bugs on a windshield.
"Astronomers have long suspected that there is a connection between
Saturn's outer moon Phoebe and the dark material on Iapetus," said
Hamilton. "This new ring provides convincing evidence of that
relationship."
Verbiscer and her colleagues used Spitzer's longer-wavelength infrared
camera, called the multiband imaging photometer, to scan through a patch
of sky far from Saturn and a bit inside Phoebe's orbit. The astronomers
had a hunch that Phoebe might be circling around in a belt of dust
kicked up from its minor collisions with comets -- a process similar to
that around stars with dusty disks of planetary debris. Sure enough,
when the scientists took a first look at their Spitzer data, a band of
dust jumped out.
The ring would be difficult to see with visible-light telescopes. Its
particles are diffuse and may even extend beyond the bulk of the ring
material all the way in to Saturn and all the way out to interplanetary
space. The relatively small numbers of particles in the ring wouldn't
reflect much visible light, especially out at Saturn where sunlight is
weak.
"The particles are so far apart that if you were to stand in the ring,
you wouldn't even know it," said Verbiscer.
Spitzer was able to sense the glow of the cool dust, which is only about
80 Kelvin (minus 316 degrees Fahrenheit). Cool objects shine with
infrared, or thermal radiation; for example, even a cup of ice cream is
blazing with infrared light. "By focusing on the glow of the ring's cool
dust, Spitzer made it easy to find," said Verbiscer.
These observations were made before Spitzer ran out of coolant in May
and began its "warm" mission.
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer
Space Telescope mission for NASA's Science Mission Directorate,
Washington. Science operations are conducted at the Spitzer Science
Center at the California Institute of Technology, also in Pasadena.
Caltech manages JPL for NASA. The multiband imaging photometer for
Spitzer was built by Ball Aerospace Corporation, Boulder, Colo., and the
University of Arizona, Tucson. Its principal investigator is George
Rieke of the University of Arizona.
For additional images relating to the ring discovery and more
information about Spitzer, visit http://www.spitzer.caltech.edu
<http://www.spitzer.caltech.edu/spitzer> and http://www.nasa.gov/spitzer .
Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@...
J.D. Harrington 202-358-5241
NASA Headquarters, Washington
j.d.harrington@...
2009-150
THE FOLLOWING RELEASE WAS RECEIVED FROM THE DIVISION FOR PLANETARY
SCIENCES OF THE AMERICAN ASTRONOMICAL SOCIETY AND IS FORWARDED FOR
YOUR INFORMATION. (FORWARDING DOES NOT IMPLY ENDORSEMENT BY THE PARENT
SOCIETY.) Rick Fienberg, American Astronomical Society:
rick.fienberg@..., 1-202-328-2010 x116.
October 8, 2009
Contacts:
Sanjay S. Limaye
DPS Press Officer
+1 608-262-9541
sanjayl@...
Prof. Richard Greenberg
University of Arizona
greenberg@...
+1 520-904-9457 (cell, through Oct. 9)
+1 520-621-6940 (office)
VERTICAL TRANSPORT THROUGH EUROPA'S CRUST:
IMPLICATIONS FOR OXIDANT DELIVERY AND HABITABILITY
The global ocean on Jupiter's moon Europa contains about twice the
liquid water of all the Earth's oceans combined. New research suggests
that there may be plenty of oxygen available in that ocean to support
life, a hundred times more oxygen than previously estimated.
The chances for life there have been uncertain, because Europa's ocean
lies beneath several miles of ice, which separates it from the
production of oxygen at the surface by energetic charged particles
(similar to cosmic rays). Without oxygen, life could conceivably exist
at hot springs in the ocean floor using exotic metabolic chemistries,
based on sulfur or the production of methane. However, it is not
certain whether the ocean floor actually would provide the conditions
for such life.
Therefore a key question has been whether enough oxygen reaches the
ocean to support the oxygen-based metabolic process that is most
familiar to us. An answer comes from considering the young age of
Europa's surface. Its geology and the paucity of impact craters
suggests that the top of the ice is continually reformed such that the
current surface is only about 50 million years old, roughly 1% of the
age of the solar system.
Richard Greenberg of the University of Arizona has considered three
generic resurfacing processes: gradually laying fresh material on the
surface - opening cracks which fill with fresh ice from below - and
disrupting patches of surface in place and replacing them with fresh
material. Using estimates for the production of oxidizers at the
surface, he finds that the delivery rate into the ocean is so fast
that the oxygen concentration could exceed that of the Earth's oceans
in only a few million years. Greenberg presents his findings tomorrow
at the 41st meeting of the American Astronomical Society's Division
for Planetary Sciences now under way in Fajardo, Puerto Rico
(http://dps.aas.org/press).
Greenberg says that the concentrations of oxygen would be great enough
to support not only microorganisms, but also "macrofauna", that is,
more complex animal-like organisms which have greater oxygen demands.
The continual supply of oxygen could support roughly 3 billion
kilograms of macrofauna, assuming similar oxygen demands to
terrestrial fish.
The good news for the question of the origin of life is that there
would be a delay of a couple of billion years before the first surface
oxygen reached the ocean. Without that delay, the first pre-biotic
chemistry and the first primitive organic structures would be
disrupted by oxidation. Oxidation is a hazard unless organisms have
evolved protection from its damaging effects. A similar delay in the
production of oxygen on Earth was probably essential for allowing life
to get started here.
Richard Greenberg is the author of the recent book "Unmasking Europa:
The Search for Life on Jupiter's Ocean Moon", which offers a
comprehensive picture of Europa for the general reader.
Cassini Significant Events
for 09/30/09 - 10/06/09
The most recent spacecraft telemetry was acquired
on Oct. 6 from the Deep Space Network tracking
complex at Madrid, Spain. 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, Sept. 30 (DOY 273):
An encounter strategy meeting was held today to
cover the period between Oct. 12 and Nov. 7,
Titan flyby T62, Enceladus flyby E7, and maneuvers 218-220.
The final numbers for the U.S. edition of the
Fall 2009 Cassini Scientist for a Day essay contest are in:
U.S. entries: 330 essays
Number of U.S. students: 372
Number of teachers: 41
Number of U.S. states: 19 plus Puerto Rico --
including Idaho, Utah, and Wyoming for the first time
Number of homeschooled students: 8
Most international deadlines are in late October,
so in a month or so Outreach will have a sense of
how many students participated internationally.
Thursday, Oct. 1 (DOY 274):
S54 sequence leads have cancelled the Go/No-go
meeting scheduled for Friday as part of the
development process for the DOY 286 Rhea, Tethys,
Mimas, Enceladus live update. Instrument teams
have agreed that vectors for Rhea, Tethys and
Enceladus need to be updated. The vector files
will be prepared by AACS, with the merged
products released by Monday, Oct. 5. Teams then
have until Oct. 7 to review the products. Uplink
is planned for Friday, Oct 9.
Friday, Oct. 2 (DOY 275):
Today the Titan Orbiter Science Team hosted a
Titan T62-T70 preview. This meeting is a forum
for all instrument teams to present what unique
science will be obtained for each of the flybys
and what observations will be performed.
Monday, Oct. 5 (DOY 278)
The backup inertial reference unit (IRU-B) on
board Cassini was calibrated on Oct. 4. This was
the yearly checkout, with IRU-B made prime for
the duration of the calibration turns. The
results indicated continued proper performance.
The S53 sequence concluded and S54 began
execution today at 2009-278T04:03:00 SCET. The
sequence will run for 39 days and conclude on
November 13. During that time there will be two
targeted encounters, one of Titan, one of
Enceladus, and ten non-targeted flybys - Rhea on
DOY 286, Methone, Atlas, Calypso, Mimas, and
Tethys on DOY 287, Titan on DOY 305, Pallene,
Epimetheus, and Calypso on DOY 306. Six OTMs are
scheduled, numbered 217 through 222.
Science at the top of the sequence begins with a
Magnetospheric segment that will run for almost
seven days and contain some high priority
combined Magnetospheric and Plasma
Science/Optical Remote Sensing auroral
observations, and a Magnetometer calibration
roll on DOY 281.
Tuesday, Oct. 6 (DOY 279)
The Navigation team has completed an in-depth
analysis of the reference trajectory selected at
the June Project Science Group meeting and is
issuing an update. No major design changes or
tweaks have been made - this update is primarily
due to more sophisticated analyses, e.g. mostly
small adjustments to maneuver locations and
updated satellite ephemerides. Timing
differences are expected to be minor.
http://saturn.jpl.nasa.gov/mission/flybys/titan20091012/
Cassini
Titan Flyby
October 12,2009
T-62: Studying Titan's Atmosphere and Retuning to the Plane
Studying Titan's clouds and atmosphere in the south, the Ultraviolet
Imaging Spectrograph (UVIS) and the Visible and Infrared Mapping
Spectrometer (VIMS) observe the sun's light as it passes behind Titan.
This flyby also marks Cassini's return to a more equatorial orbit,
setting up the spacecraft for future close encounters with icy moons.
Titan Flyby
Oct. 12, 2009 (SCET)
*Altitude*
1300 kilometers (808 miles)
*Speed*
6.0 km/sec (13,400 mph)
*Details*
+ Mission Description PDF (535 KB)
<http://saturn.jpl.nasa.gov/files/20091012_titan_mission_description.pdf>
http://www.jpl.nasa.gov/news/features.cfm?feature=2337
Cassini Data Help Redraw Shape of Solar System
Jet Propulsion Laboratory
October 15, 2009
Images from the Ion and Neutral Camera on NASA's Cassini spacecraft
suggest that the heliosphere, the region of the sun's influence, may not
have the comet-like shape predicted by existing models. In a paper
published Oct. 15 in Science Express, researchers from the Johns Hopkins
Applied Physics Laboratory present a new view of the heliosphere, and
the forces that shape it.
"These images have revolutionized what we thought we knew for the past
50 years; the sun travels through the galaxy not like a comet but more
like a big, round bubble," said Stamatios Krimigis of the Applied
Physics Lab, in Laurel, Md., principal investigator for Cassini's
Magnetospheric Imaging Instrument which carries the Ion and Neutral
Camera. "It's amazing how a single new observation can change an entire
concept that most scientists had taken as true for nearly fifty years."
As the solar wind flows from the sun, it carves out a bubble in the
interstellar medium. Models of the boundary region between the
heliosphere and interstellar medium have been based on the assumption
that the relative flow of the interstellar medium and its collision with
the solar wind dominate the interaction. This would create a
foreshortened "nose" in the direction of the solar system's motion, and
an elongated "tail" in the opposite direction.
The Ion and Neutral Camera images suggest that the solar wind's
interaction with the interstellar medium is instead more significantly
controlled by particle pressure and magnetic field energy density.
"The map we've created from the images suggests that pressure from a hot
population of charged particles and interaction with the interstellar
medium's magnetic field strongly influence the shape of the
heliosphere," says Don Mitchell, Magnetospheric Imaging Instrument/Ion
and Neutral Camera co-investigator at the Applied Physics Lab.
Since entering into orbit around Saturn in July of 2004, the Ion and
Neutral Camera has been mapping energetic neutral atoms near the planet,
as well as their dispersal across the entire sky. The energetic neutral
atoms are produced by energetic protons, which are responsible for the
outward pressure of the heliosphere beyond the interface where the solar
wind collides with the interstellar medium, and which interact with the
magnetic field of the interstellar medium.
"Energetic neutral atom imaging has demonstrated its power to reveal the
distribution of energetic ions, first in Earth's own magnetosphere, next
in the giant magnetosphere of Saturn and now throughout vast structures
in space-out to the very edge of our sun's interaction with the
interstellar medium," says Edmond C. Roelof, Magnetospheric Imaging
Instrument co-investigator at the Applied Physics Lab.
The results from Cassini complement and extend findings from NASA's
Interstellar Boundary Explorer, or IBEX, spacecraft. Data from IBEX and
Cassini have made it possible for scientists to construct the first
comprehensive sky map of our solar system and its location in the Milky
Way galaxy.
Researchers from University of Arizona, Tucson; Southwest Research
Institute, San Antonio; and University of Texas at San Antonio
contributed to the article. 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. The Cassini orbiter was
designed, developed and assembled at JPL. The Magnetospheric Imaging
Instrument was developed by the Applied Physics Laboratory.
More information on the Cassini mission is available at:
http://www.nasa.gov/cassini,http://saturn.jpl.nasa.gov
<http://saturn.jpl.nasa.gov> and on the Magnetospheric Imaging
Instrument Web site at http://sd-www.jhuapl.edu/CASSINI/ .
More information on the Interstellar Boundary Explorer is available at:
http://www.nasa.gov/ibex
http://www.jpl.nasa.gov/news/features.cfm?feature=2338
Galileo's Jupiter Journey Began Two Decades Ago
Jet Propulsion Laboratory
October 16, 2009
--Launch: Oct. 18, 1989, from Kennedy Space Center, Fla., on space
shuttle Atlantis on mission STS-34
--Arrival in orbit around Jupiter: Dec. 7, 1995
--VEEGA (Venus-Earth-Earth Gravity Assist) is the acronym mission
planners gave for Galileo's flight path through the inner solar system
--Observed impacts of fragments from comet Shoemaker-Levy 9 into Jupiter
--Approximate number of people (from around the world) who worked on the
Galileo mission: 800
--More than 100 scientists from United States, Great Britain, Germany,
France, Canada and Sweden carried out Galileo's experiments
PASADENA, Calif. - NASA's Galileo spacecraft began what would become a
14-year odyssey of exploration 20 years ago this Sunday, Oct. 18.
Galileo was humanity's first emissary to orbit a planet in the outer
solar system - Jupiter.
Galileo was launched into space aboard the space shuttle Atlantis on
Oct. 18, 1989, from Kennedy Space Center, Florida. The crew of Atlantis
deployed Galileo out of the shuttle's cargo bay only hours after launch.
Then, a little over seven hours after leaving Earth, Galileo was
propelled onto its interplanetary flight path by a two-stage, solid-fuel
motor called an Inertial Upper Stage. Although earlier plans called for
Galileo to use a more powerful upper stage so that it could fly directly
to Jupiter, the final flight took it by other planets first so that it
could gain energy from the gravity of each. Galileo flew past Venus on
Feb. 10, 1990, and then twice past Earth -- once on Dec. 8, 1990, and
again on Dec. 8, 1992.
Even before its arrival at Jupiter in 1995, Galileo was making
groundbreaking discoveries. On Oct. 29, 1991, the spacecraft flew past
asteroid Gaspra - sending back the first close up images of one of these
celestial wanderers. Then on Aug. 28, 1993, Galileo encountered the
15.2-kilometer-wide (9.4-mile) asteroid Ida, where it took the first
images of an asteroid and discovered the first asteroid moon, the
1.6-kilometer-wide (1-mile) Dactyl. During the latter part of its
interplanetary cruise, Galileo was used to observe the collisions of
fragments of Comet Shoemaker-Levy with Jupiter in July 1994.
Galileo arrived at Jupiter on Dec. 7, 1995, entering orbit and dropping
a probe into the giant planet's atmosphere. The probe's velocity as it
entered Jupiter's atmosphere was a blistering 47.6 kilometers per second
(106,500 miles per hour). After the atmospheric drag and a deployed
parachute slowed its descent rate, the probe relayed to Galileo the
first in-place studies of Jupiter's clouds and winds, furthering
scientists' understanding of how the gas giant evolved. The probe also
made composition measurements designed to assess the degree of evolution
of Jupiter compared to the sun.
While the descent of the probe was a highlight of Galileo's mission, it
was hardly the only one. Galileo extensively investigated the geologic
diversity of Jupiter's four largest moons: Ganymede, Callisto, Io and
Europa. It found that Io's extensive volcanic activity is 100 times
greater than that found on Earth. Galileo discovered strong evidence
that Jupiter's moon Europa has a melted saltwater ocean under an ice
layer on its surface. Scientists estimate such an ocean could be up to
100 kilometers (62 miles) deep underneath its frozen surface and contain
about twice as much water as all of Earth's oceans. Data showed moons
Ganymede and Callisto may also have a liquid-saltwater layer. The
biggest discovery surrounding Ganymede was the presence of a magnetic
field. No other moon of any planet is known to have one.
When Galileo turned its instruments towards the giant gas world itself,
the spacecraft made the first observations of ammonia clouds in another
planet's atmosphere. It also observed numerous thunderstorms on Jupiter
many times larger than those on Earth, with lightning strikes up to
1,000 times more powerful than on Earth. It was the first spacecraft to
dwell in a giant planet's magnetosphere long enough to identify its
global structure and to investigate the dynamics of Jupiter's magnetic
field. Galileo determined that Jupiter's ring system is formed by dust
kicked up as interplanetary meteoroids smash into the planet's four
small inner moons. Galileo data showed that Jupiter's outermost ring is
actually two rings, one embedded within the other.
Having traveled approximately 4.6 billion kilometers (about 2.8 billion
miles), the hardy spacecraft endured more than four times the cumulative
dose of harmful Jovian radiation it was designed to withstand -- and
still major systems functioned. But while it was still enjoying
relatively good health, the spacecraft's propellant was low. Without
propellant, Galileo would not be able to point its antenna toward Earth
or adjust its trajectory, so controlling the spacecraft would no longer
be possible. Mission managers at NASA and JPL decided to place their
resilient Jovian explorer on a collision course with Jupiter to
eliminate any chance of an unwanted impact between the spacecraft and
Europa. The possibility of life existing on Europa is so compelling and
has raised so many unanswered questions that it is prompting plans for
future spacecraft to return to the icy moon.
The Galileo spacecraft's 14-year odyssey came to an end on Sunday, Sept.
21, 2003, when the spacecraft passed into Jupiter's shadow, then
disintegrated in the planet's dense atmosphere at 11:57 a.m. Pacific
Daylight Time. Its entry speed was 48.2 kilometers per second (nearly
108,000 miles per hour). That is the equivalent of traveling from Los
Angeles to New York City in 82 seconds.
JPL's Deep Space Network tracking station in Goldstone, Calif., received
the last signal at 12:43:14 PDT, 46 minutes after it was sent. The delay
is due to the time it takes for the signal to travel to Earth. Hundreds
of former Galileo project members and their families were present at JPL
for a celebration to bid the spacecraft goodbye.
Galileo project scientist Torrence Johnson said at the time, "We haven't
lost a spacecraft, we've gained a steppingstone into the future of space
exploration."
JPL, a division of the California Institute of Technology in Pasadena,
managed the Galileo mission for NASA. JPL designed and built the Galileo
orbiter, and operated the mission.
Additional information about the Galileo mission and its discoveries is
available online at: http://www.jpl.nasa.gov/galileo-legacy and
http://galileo.jpl.nasa.gov .
Cassini Significant Events
for 10/07/09 - 10/13/09
The most recent spacecraft telemetry was acquired on Oct. 13 from the
Deep Space Network tracking complex at Madrid, Spain. 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, Oct. 7 (DOY 280):
The Science Operations Plan process for S59 kicked off today. The
first delivery port for this sequence will not occur until Nov. 9,
after the flight team has had a chance to review the results of the
Enceladus 7 flyby, and determine if E9, occurring within S59, will
use reaction wheels or thrusters. In order to prevent a delay in
development, two versions of the flyby sequence have been developed,
one on wheels, and one on thrusters. Only one of these will proceed
past port 1.
Thursday, Oct. 8 (DOY 281):
An Instrument Operations Working Group meeting was held today to
brief instrument personnel on various topics. This particular
presentation was aimed at the Operations Team Leads and engineers
responsible for telemetry processing. In addition, a demonstration
was given on the new MPS editor, the SEQGEN GUI on Solaris 10.
Friday, Oct. 9 (DOY 282):
Orbit Trim Maneuver (OTM) #217 was performed today. This was the
approach maneuver setting up for the Titan 62 encounter on Oct. 12.
The Reaction Control Subsystem burn began at 5:30 AM PDT. Telemetry
immediately after the maneuver showed the burn duration was 130.13
seconds, giving a delta-V of 0.15 m/s. All subsystems reported
nominal performance after the maneuver.
The S54 DOY-286 Live Inertial Vector Propagator update for Rhea,
Tethys, and Enceladus was uplinked on today at 17:27:51 UTC.
Radiation was nominal, and it has been confirmed as registered
onboard.
Saturday, Oct. 10 (DOY 283):
Today the Composite Infrared Spectrometer (CIRS) measured oxygen
compounds, both H2O and CO2, in Saturn's stratosphere as a function
of latitude. Afterwards the Cassini Plasma Spectrometer concluded its
solar wind-aurora campaign with a final 3-hour observation. The day
finished with data collection for the bi-annual Scientist for a Day
outreach activity. The spacecraft obtained images of three possible
targets, Saturn and the rings, Tethys with Saturn's rings, and Titan.
The data will be returned to Earth on the next downlink. After
reviewing essays submitted by participating students, winners will be
selected and the results presented at a live teleconference on Oct.
20.
Monday, Oct. 12 (DOY 285)
Monday was a very busy day for those involved in sequence
development. As part of the ongoing Science Operations Plan (SOP)
processes, a port 3 delivery was due today for S57, and a port 2
delivery for S58. Last Friday Science Planners handed off all
products for S56 to Uplink Operations for the final development
process. Tomorrow a kick off meeting for that process will be held.
The main engine cover was closed/deployed today for dust hazard
avoidance. It will be opened/stowed again on Oct. 14. This is the
51st in-flight cycle for the cover.
On Oct. 12, Cassini flew by Titan at an altitude of 1300 km and a
speed of 6 kilometers per second. Closest approach for T62 occurred
at 3:02 AM PDT, latitude 64 degrees S. This flyby marked Cassini's
return to more nearly equatorial orbits, setting up the spacecraft
for future close encounters with icy moons.
For T62, the Ultraviolet Imaging Spectrograph (UVIS) performed a
self-calibrating solar occultation observation; the information came
from a ratio of signal during occultation to signal of the unocculted
sun or star just before and after occultation.
Solar occultations by Titan are the most valuable Titan observations
for UVIS. They provide detailed vertical profiles of N, N2, and some
hydrocarbons to more than 3000 km altitude. Solar occultation
measurements give a measure of the density profile of the main
constituents of the atmosphere, and the rate of change of the N2
density with altitude gives information on the temperature.
UVIS also conducted Extreme Ultraviolet and Far Ultraviolet
observations during this flyby. These observations give information
on airglow, hydrocarbon absorptions, haze and optical properties
globally, but with lower vertical resolution.
The Visual and Infrared Mapping Spectrometer (VIMS) observed the
formation, evolution, and decay of clouds, particularly mid-latitude
and equatorial clouds. In ride-along mode, a solar occultation
provided information on the vertical structure and composition of
Titan's atmosphere and haze layer. VIMS also obtained a global map of
the western region of Senkyo.
CIRS carried out far-infrared limb sounding at 70 and 75 degrees
latitude South to collect information on the atmospheric temperature,
aerosols, and composition. ISS acquired a full-disk mosaic of
western Senkyo at low phase angles, and rode along with VIMS to
monitor clouds.
T62 was a south polar, post-dusk flyby. Magnetometer (MAG)
measurements provided a description of the draping and the pileup of
the external magnetic field around Titan near the terminator. This
will be a good complement to the data set acquired at T52-T61 and be
used to characterize the background field for a similar local time
with respect to Saturn and different SKR longitudes.
Radio and Plasma Wave Science (RPWS) measured thermal plasmas in
Titan's ionosphere and surrounding environment; searched for
lightning in Titan's atmosphere, and investigated the interaction of
Titan with Saturn's magnetosphere.
Tuesday, Oct. 13 (DOY 286)
A non-targeted flyby of Rhea occurred today.
The topic at the Mission Planning Forum today was Y-thruster bias
plans and strategies. In recent weeks the project has studied the
options and met to review implementing reaction wheel biases using
the Y-facing thrusters with S60 as the target start sequence. These
new biases will be performed after the spacecraft turns to the
delta-momentum vector. This saves hydrazine, and uses the Y-thrusters
rather than the Z-thrusters, which will better balance the hydrazine
throughput between the Y and Z thrusters, and therefore perhaps a
longer life span for the B-branch thrusters. After studying various
options, a final plan has been achieved, and was presented along with
implementation specifics and details on what flexibilities exist for
integration.
Visit the JPL Cassini home page for more information about the
Cassini Project: <http://saturn.jpl.nasa.gov/>
------------------------
Cassini Significant Events
for 10/14/09 - 10/20/09
The most recent spacecraft telemetry was acquired
on Oct. 20 from the Deep Space Network tracking
complex at Canberra, Australia. 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, Oct. 14 (DOY 287):
The main engine cover was opened today completing
the 51st in-flight cycle of the cover. Cycle #52 will begin on Oct. 30.
Cassini scientists participated in a press
briefing at NASA headquarters today on
constructing the first comprehensive sky map of our solar system.
Observations from Cassini complemented data
collected by NASA's Interstellar Boundary
Explorer. Images from the Ion and Neutral Camera
on Cassini's Magnetospheric Imaging Instrument
suggest that the heliosphere, the region of the
sun's influence, may not have the comet-like
shape predicted by existing models. In a paper
published Oct. 15 in Science Express, scientists
presented a new view of the heliosphere, which
suggests that it moves more like a slippery ball
through smoke. The "smoke" in this case is the
interstellar medium, the matter that fills the
local region of our galaxy and is forced to flow
around the heliosphere. Here are the links to the
full story, images, and video:
http://saturn.jpl.nasa.gov/news/cassinifeatures/newsrelease20091015/http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=3700
Thursday, Oct. 15 (DOY 288):
Orbit Trim Maneuver (OTM) #218 was performed
today. This was the cleanup maneuver from the
Titan 62 encounter on Oct. 12. The main engine
burn began at 7:00 PM PDT. Telemetry immediately
after the maneuver showed a burn duration of 4.97
seconds, giving a delta-V of 0.845 m/s. All
subsystems reported nominal performance after the maneuver.
Today marked the 12th anniversary of the launch of the Cassini Spacecraft.
The Instrument Operations Working Group met today
to view presentations relating to changes in
operations processes for the proposed Extended
Extended Mission (XXM). Topics included the XXM
Uplink Sequence Implementation Process that
combines and streamlines the Science Operations
Plan Process and the Science and Sequence Update
Process, XXM RBOT Response, and XXM Integration
rules, contingency plans, and pointing. These
same presentations will be given next week at the
Tuesday plenary session of the Cassini Project Science Group meeting.
Friday, October 16 (DOY 289):
At periapsis on orbit #119, RADAR created a
global map of Saturn's equatorial region. During
the week, Imaging Science (ISS) observed the
transits of Mimas across Rhea and of Tethys
across Titan, and performed lightning searches on
Saturn. The Visual and Infrared Mapping
Spectrometer (VIMS) created regional and global
mosaics of Saturn, and observed the E and G
rings. The Ultraviolet Imaging Spectrograph
(UVIS) executed several slow extreme and far
ultraviolet scans across Saturn's visible
hemisphere, and mapped volatiles in the immediate
neighborhood of Enceladus to test the connection
of volatile changes to plume eruptions. The
Cassini Plasma Spectrometer (CAPS) performed a
Magnetosphere and Plasma Science (MAPS) survey
and led the pointing for the MAPS team Solar
Wind-Aurora Campaign observations. The Composite
Infrared Spectrometer (CIRS) measured oxygen
compounds in the stratosphere of Saturn.
Sunday, Oct. 18 (DOY 291):
An AACS prime reaction wheel friction test took
place on Oct. 18. Wheels 1, 2, and 4 were spun up
to +/-900 rpm and then allowed to coast down to 0 rpm.
Performance was consistent with past friction test results.
Monday, Oct. 19 (DOY 292):
Cassini scientists, operations personnel, and
flight team members gathered this week for the
49th Project Science Group meeting. Instrument
Team meetings, working group meetings, and plenary
sessions were held all week.
Tuesday, Oct. 20 (DOY 293):
Today students from across the United States who
entered the Cassini Scientist for a Day essay
contest called in and asked questions of Cassini
scientists during a live USTREAM TV webcast.
Instrument scientists and observation designers
answered the students' questions. Over 2,000
students in 68 classrooms watched the live event.
The webcast has been archived and is available at
http://www.ustream.tv/recorded/2391081 .
Orbit Trim Maneuver (OTM) #219 was performed
today. This was the apoapsis maneuver setting up
for the Enceladus 7 encounter on Nov. 2. The main
engine burn began at 6:29 PM PDT. Telemetry
immediately after the maneuver showed the
duration was 24.42 seconds, giving a delta-V of
4.16 m/s. All subsystems reported nominal performance after the maneuver.
Visit the JPL Cassini home page for more
information about the Cassini Project:
<<http://saturn.jpl.nasa.gov/>http://saturn.jpl.nasa.gov/>
------------------------
http://www.jpl.nasa.gov/news/features.cfm?feature=2343
Robot Armada Might Scale New Worlds
Jet Propulsion Laboratory
October 27, 2009
An armada of robots may one day fly above the mountain tops of Saturn's
moon Titan, cross its vast dunes and sail in its liquid lakes.
Wolfgang Fink, visiting associate in physics at the California Institute
of Technology in Pasadena says we are on the brink of a great paradigm
shift in planetary exploration, and the next round of robotic explorers
will be nothing like what we see today.
"The way we explore tomorrow will be unlike any cup of tea we've ever
tasted," said Fink, who was recently appointed as the Edward and Maria
Keonjian Distinguished Professor in Microelectronics at the University
of Arizona, Tucson. "We are departing from traditional approaches of a
single robotic spacecraft with no redundancy that is Earth-commanded to
one that allows for having multiple, expendable low-cost robots that can
command themselves or other robots at various locations at the same time."
Fink and his team members at Caltech, the U.S. Geological Survey and the
University of Arizona are developing autonomous software and have built
a robotic test bed that can mimic a field geologist or astronaut,
capable of working independently and as part of a larger team. This
software will allow a robot to think on its own, identify problems and
possible hazards, determine areas of interest and prioritize targets for
a close-up look.
The way things work now, engineers command a rover or spacecraft to
carry out certain tasks and then wait for them to be executed. They have
little or no flexibility in changing their game plan as events unfold;
for example, to image a landslide or cryovolcanic eruption as it
happens, or investigate a methane outgassing event.
"In the future, multiple robots will be in the driver's seat," Fink
said. These robots would share information in almost real time. This
type of exploration may one day be used on a mission to Titan, Mars and
other planetary bodies. Current proposals for Titan would use an
orbiter, an air balloon and rovers or lake landers.
In this mission scenario, an orbiter would circle Titan with a global
view of the moon, with an air balloon or airship floating overhead to
provide a birds-eye view of mountain ranges, lakes and canyons. On the
ground, a rover or lake lander would explore the moon's nooks and
crannies. The orbiter would "speak" directly to the air balloon and
command it to fly over a certain region for a closer look. This aerial
balloon would be in contact with several small rovers on the ground and
command them to move to areas identified from overhead.
"This type of exploration is referred to as tier-scalable
reconnaissance," said Fink. "It's sort of like commanding a small army
of robots operating in space, in the air and on the ground simultaneously."
A rover might report that it's seeing smooth rocks in the local
vicinity, while the airship or orbiter could confirm that indeed the
rover is in a dry riverbed - unlike current missions, which focus only
on a global view from far above but can't provide information on a local
scale to tell the rover that indeed it is sitting in the middle of dry
riverbed.
A current example of this type of exploration can best be seen at Mars
with the communications relay between the rovers and orbiting spacecraft
like the Mars Reconnaissance Orbiter. However, that information is just
relayed and not shared amongst the spacecraft or used to directly
control them.
"We are basically heading toward making robots that command other
robots," said Fink, who is director of Caltech's Visual and Autonomous
Exploration Systems Research Laboratory, where this work has taken place.
"One day an entire fleet of robots will be autonomously commanded at
once. This armada of robots will be our eyes, ears, arms and legs in
space, in the air, and on the ground, capable of responding to their
environment without us, to explore and embrace the unknown," he added.
Papers describing this new exploration are published in the journal
"Computer Methods and Programs in Biomedicine" and in the Proceedings of
the SPIE.
For more information on this work, visit http://autonomy.caltech.edu.
More information on JPL missions is at http://www.jpl.nasa.gov/.
JPL is managed for NASA by the California Institute of Technology.
Media contact: Carolina Martinez/JPL 818-354-9382
Related Links
http://autonomy.caltech.edu
http://saturn.jpl.nasa.gov/mission/flybys/enceladus20091102/
Cassini
Enceladus Flyby - Nov. 2, 2009
E-7: Cassini's Return to the Plumes
On November 2, 2009, Cassini will make its deepest plume passage yet,
flying 102.7 kilometers (63.8 miles) from the surface of Enceladus.
The plume passage will allow in situ measurements by
fields-and-particles instruments such as the Ion and Neutral Mass
Spectrometer and the Cosmic Dust Analyzer, to gain an understanding of
plume and surface composition, and to investigate temporal variability
in the plume by comparing with data from previous flybys.
This is the seventh targeted flyby of Enceladus, sometimes referred to
as "E-7."
Enceladus Flyby
Nov. 2, 2009 (SCET)
*Altitude*
103 kilometers (64 miles)
*Speed*
7.7 km/sec (17,200 mph)
Cassini Significant Events
for 10/21/09 - 10/27/09
The most recent spacecraft telemetry was acquired on Oct. 27 from the
Deep Space Network tracking complex at Madrid, Spain. 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, Oct. 21 (DOY 294):
Wednesday, Thursday, and Friday saw the conclusion of the 49th
Project Science Group meeting held at JPL.
Onboard the spacecraft, the Cassini Plasma Spectrometer performed
three observations as part of the Solar Wind-Aurora campaign. The
Composite Infrared Spectrometer (CIRS) spent about 26 hours this week
mapping the northern hemisphere of Saturn to determine upper
troposphere and tropopause temperatures and executed a stray light
calibration. Sunlight falling on the CIRS telescope can possibly be
scattered into the instrument by mirror imperfections. To quantify
the effects of ring particle impacts on the mirror performance, CIRS
monitored the scattered infrared solar radiation as a function of the
offset angle from the sun. Imaging Science (ISS) spent about 25
hours searching for lightning on Saturn, observed the transits of
Rhea across Dione and Tethys, Enceladus across Tethys, and Titan
across Rhea. ISS also observed the outer moon Bestia for about 6
hours, performed a post equinox, edge-on observation of the E Ring,
and performed Saturn photopolarimetry with the wide-angle camera,
measuring the intensity and polarization of reflected light.
Thursday, Oct. 22 (DOY 295):
Both S55 and S56 are currently in the Science and Sequence Update
Process (SSUP), the final sequence development process before uplink
to the spacecraft. Today teams submitted any final Spacecraft
Activity Sequence Files (SASF) as part of the S55 Final Sequence
Integration and Validation phase. Changes this late in the process
are permitted for health and safety reasons only, rather than for
science enhancement. For S56, the first SASFs were delivered as part
of the Sub-Sequence Generation (SSG) process. Next week the
Preliminary Sequence Integration and Validation (PSIV1) cycle 1
merged background sequence products will be released along with the
stripped subsequences. These stripped subsequences are for review
purposes in the PSIV1 phase and the basis for the detailed
subsequences used to build the PSIV2 cycle 1 sequence products.
Monday, Oct. 26 (DOY 299)
The development process for the S54 E7 DOY 305 Live Update Block
kicked off today. A special orbit determination solution was
delivered at 4:00 PM; the Sequence Phase List of Ancillary Files was
out by 7 PM. The Go/No-go meeting will be Tuesday afternoon at 2:00
PM. The schedule is somewhat compressed as the uplink windows are
Friday night and Saturday night/Sunday morning.
Final products from the S57 Science Operations Plan process were
handed off from Science Planning to Uplink Operations today. The DSN
station allocation file has been posted for team access. Negotiations
are almost complete and are pending only the final two days.
Tomorrow the S57 SSUP kickoff/SSG waiver disposition meeting will be
held.
Tuesday, Oct. 27 (DOY 300)
The USTREAM TV archive of the Cassini scientists answering students'
questions about Saturn has received 630 views since it was posted one
week ago. This translates to up to 19,000 people, depending on how
many viewers were individuals versus classrooms of 30 students. To
view the video go to: http://www.ustream.tv/recorded/2391081.
An encounter strategy meeting was held today to cover the period
between Nov. 2 and Nov. 21, Enceladus flybys E7 and E8, and maneuvers
221-223.
The Cassini-Huygens Analysis and Results of the Mission (CHARM)
teleconference for October was held today. Topic: "The Search for
Activity on Icy Satellites that aren't Enceladus." The presentation
package is online and available at:
http://saturn.jpl.nasa.gov/video/products/MultimediaProductsCharm/
------------------------
Visit the JPL Cassini home page for more information about the
Cassini Project: <http://saturn.jpl.nasa.gov/>
------------------------
Cassini Significant Events
for 11/04/09 - 11/10/09
The most recent spacecraft telemetry was acquired on Nov. 10 from the
Deep Space Network tracking complex at Canberra, Australia. The
Cassini spacecraft is in an excellent state of health and all
subsystems are operating normally.
Wednesday, Nov. 4 (DOY 308)
Today a meeting was held to present and discuss the results of the
Enceladus 7 flyby. The Spacecraft Team used AACS telemetry data
gathered from the 100 km E7 flyby to derive an estimate of the
Enceladus plume density and of the torque experienced by the
spacecraft due to the plume. After reviewing results from AACS and
the Ion and Neutral Mass Spectrometer (INMS), the Project gave the go
ahead to do the E9 flyby on reaction wheels. INMS data was in good
agreement with the AACS analysis. The E9 flyby is nearly identical to
the E7 flyby, but with different instruments having pointing priority.
For the E9 flyby, Science Planning had asked all teams to deliver two
sets of input files, one for reaction wheels, and one for thrusters.
The version on thrusters will be archived and the reaction wheel
version will continue on in the sequence development process.
Thursday, Nov. 5 (DOY 309):
Orbit Trim Maneuver (OTM) #221 was performed today. This was the
cleanup maneuver from the Enceladus 7 encounter on Nov. 2. The main
engine burn began at 2:44 AM PST. Telemetry immediately after the
maneuver showed a burn duration of 1.73 seconds, giving a delta-V of
0.298 m/s. All subsystems reported nominal performance after the
maneuver.
After the S55 final sequence approval meeting was held today, eight
Instrument Expanded Block files were uplinked for five instruments
and Optical Navigation. The background sequence will go up to the
spacecraft on Monday.
A scientist on the Visual and Infrared Mapping Spectrometer team
wrote an update on the JPL Blog about the "First Morsels of Science"
coming back from the Enceladus flyby on Nov. 2. It is available at
http://blogs.jpl.nasa.gov/?p=58. The blog entry notes that mission
managers have cleared the spacecraft to do an April 28, 2010,
Enceladus flyby on reaction wheels, enabling scientists to do very
sensitive radio science measurements.
Friday, Nov. 6 (DOY 310):
At the S59 Science Forum on Nov. 2, it was pointed out that the Dione
2 flyby is only 1.5 days after the Titan 67 flyby, which brought up
an unlikely but not impossible scenario: If something were to happen
during or shortly after the T67 flyby such that the Project needed to
weigh the return of D2 science versus T67 science, which should be
considered of higher science importance?
To start the evaluation it is important to know that in this case the
Project regards the science on both flybys as important. Both Imaging
Science (ISS) and Composite Infrared Spectrometer (CIRS) observations
are tagged as being high priority science for both flybys. Science
Planning pinged members of the instrument teams to get their feedback
on, if they had to choose, which would it be? After reviewing the
responses, the answer was_ both flybys contain observations that are
at the highest priority. It would appear to be a draw. So now the
flight team would have to factor in what is happening operationally
at the time. There is no way in this still hypothetical case to
determine what the exact results would be, but factors in making a
decision include 1) what caused the incident, 2) is the DSN involved,
3) when is the next pass for downlink, 4) what is being kept on the
SSR, what is being overwritten, and when, 5) how much time does the
team have to decide, 6) is there time to command changes to what is
programmed in the background sequence, and, 7) are there other
scheduled onboard events that occur in the near term - such as a
maneuver or engineering activity - that might have an affect on the
plans that are made? It never is a simple decision, but at least the
flight team has given the matter some thought and will be prepared to
respond should it become necessary.
Monday, Nov. 9 (DOY 313)
The Target Working Team (TWT)/ Orbiter Science Team (OST) integrated
products for S60, covering orbits 131 through 133 in May and June,
2010, were delivered today. The integrated products are in their
final form and no re-integration is planned. The next step in
sequence development, Science Operations Plan (SOP) implementation,
will kick off on Nov. 23. The handoff package template from
integration to the SOP process has been updated to better track more
involved prime-rider pointing designs, and two new milestones have
been added to the S60 schedule for prime-rider coordination. Between
now and the kickoff, the instrument teams will be working on pointing
designs for the sequence.
Participating teams delivered Port 1 SASFs today as part of the SOP
process for S59. As was mentioned earlier in this report, the files
include the Enceladus 9 flyby as designed for reaction wheels.
Tuesday, Nov. 10 (DOY 314)
An image of the recently illuminated north side of Saturn's rings was
Astronomy Picture of the Day today. Check it out at:
http://antwrp.gsfc.nasa.gov/apod/ap091110.html
Science in a nutshell: This week ISS obtained wide angle camera data
for Saturn photopolarimetry 1x2 mosaics, collected images for
satellite orbit determination, searched for lightning on Saturn, took
a look at the outer moon Bestla, observed the E-ring at low
resolution, low elevation, and high-phase, and obtained narrow angle
camera images of Titan's shadow on Saturn. Looking at the shadow of
Titan on Saturn is useful for Titan aerosol science. This is a unique
geometry that only occurs a few times during the Extended Mission and
not at all in the prime tour or proposed Extended Extended Mission.
CIRS wrapped up the far-IR hemisphere mapping activity, with scans of
the northern hemisphere and pole of Saturn, and measured oxygen
compounds - H2O, CO2 - in the stratosphere as a function of latitude.
Magnetospheric and Plasma Science (MAPS) instruments continued the
southwest auroral campaign, began a magnetospheric boundaries
campaign, and began a southwest auroral campaign to observe the
auroral magnetosphere and Saturn Kilometric Radiation source regions.
The Cosmic Dust Analyzer conducted an observation that is part of the
ISD survey campaign.
UVIS performed several apoapse system scans of the Saturn
magnetosphere and mapped volatiles in the immediate neighborhood of
Enceladus. These icy atmosphere observations test the connection of
volatile changes to plume eruptions.
Visit the JPL Cassini home page for more information about the
Cassini Project: <http://saturn.jpl.nasa.gov/>
------------------------
http://pluto.jhuapl.edu/news_center/news/111209.php
New Horizons Roused for Long-Distance Checkup
November 12, 2009
Call it a burst of activity between naps: the New Horizons team woke
its Pluto-bound spacecraft from hibernation this week for some onboard
housekeeping.
On pre-programmed commands from controllers at the Johns Hopkins
University Applied Physics Laboratory in Laurel, Md. - transmitted to
the spacecraft in August through NASA's Deep Space Network of antenna
stations - New Horizons came out of hibernation on Nov. 9. The
spacecraft had been "sleeping" since Aug. 27, when it completed its
third annual instrument and system checkout.
"Although we hibernate about 90 percent of the time from August through
May each year, between checkouts we wake the spacecraft up in November
and January to re-point its antenna toward Earth and to conduct some
maintenance activities," says Mission Principal Investigator Alan Stern,
of the Southwest Research Institute. "So far, this wake up is going
smoothly."
Aside from turning the spacecraft's antenna, operators will also upload
some tweaks to New Horizons' fault-protection software. The team puts
the spacecraft back into hibernation on Nov. 20.
Distance milestone: Late tonight, New Horizons will reach 15
astronomical units from the Sun - the equivalent of 15 times the
distance from Earth to the Sun. Cruising between the orbits of Saturn
and Uranus, the spacecraft is speeding toward Pluto at 37,110 miles
(nearly 60,000 kilometers) per hour.
http://saturn.jpl.nasa.gov/mission/flybys/enceladus20091121/
Cassini
Enceladus Flyby - Nov. 21, 2009
E-8: Cassini Returns to the Tiger Stripes
On Nov. 21 Cassini will again fly by Enceladus, this time with a very
different geometry, approaching within 1,606 kilometers (997.9 miles) of
the surface. The closest approach will occur over 82 degrees south
latitude.
The spacecraft will again be under the control of thrusters during the
flyby, to allow for precise tracking of surface features during
closest-approach; the Composit Infrared Spectrograph (CIRS) instrument
will make a map of thermal emission from the tiger stripe Baghdad Sulcus.
This is the eighth targeted flyby of Enceladus; the flyby is sometimes
referred to as "E-8."
Enceladus Flyby
Nov. 21, 2009 (SCET)
Altitude
1,606 kilometers (998 miles)
Speed
7.7 km/sec (17,200 mph)
Details
+ Mission Description (PDF, 1.2 MB)
<http://saturn.jpl.nasa.gov/files/20091102-21_enceladus_mission_description.pdf>
http://www.jpl.nasa.gov/news/features.cfm?feature=2372
Cassini Sends Back Images of Enceladus as Winter Nears
Jet Propulsion Laboratory
November 21, 2009
NASA's Cassini spacecraft has sailed seamlessly through the Nov. 21
flyby of Saturn's moon Enceladus and started transmitting uncalibrated
temperature data and images of the rippling terrain. These data and
images will be processed and analyzed in the coming weeks. They will
help scientists create the most-detailed-yet mosaic image of the
southern part of the moon's Saturn-facing hemisphere and a contiguous
thermal map of one of the intriguing "tiger stripe" features, with the
highest resolution to date.
"These first raw images are spectacular, and paint an even more
fascinating picture of Enceladus," said Bob Pappalardo, Cassini project
scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "The
Cassini teams will be delving into the data to better understand the
workings of this bizarre, active moon."
Scientists are particularly interested in the tiger stripes, which are
fissures in the south polar region, because they spew jets of water
vapor and other particles hundreds of kilometers, or miles, from the
surface. This flyby was scientists' last peek at the tiger stripes
before the south pole fades into the darkness of winter for several
years. The thermal imaging work focused on the tiger stripe known as
Baghdad Sulcus.
The Nov. 21 encounter, which is sometimes called "E8" because it is the
eighth targeted flyby of Enceladus, brought Cassini to within about
1,600 kilometers (1,000 miles) of the moon's surface, at around 82
degrees south latitude. Cassini is now cruising toward Rhea, another one
of Saturn's moons, for more imaging and mapping work.
To see a full gallery of raw images, click here
<http://saturn.jpl.nasa.gov/photos/raw/>. For more information on the
flyby, click here
<http://saturn.jpl.nasa.gov/mission/flybys/enceladus20091121/>.
[Image]
Unprocessed image from Cassini's Enceladus flyby
This unprocessed image was captured by NASA's Cassini spacecraft during
its Nov. 21, 2009 flyby of Saturn's moon Enceladus. It shows the ridges
and fractures on the surface of the icy moon. Image credit:
NASA/JPL/Space Science Institute
Full image and caption
<http://www.nasa.gov/mission_pages/cassini/multimedia/cassini-b-20091121.html>
enlarge image
<http://www.jpl.nasa.gov/images/cassini/20091121/cassini20091121-b-full.jpg>
Cassini Significant Events
for 11/11/09 - 11/17/09
The most recent spacecraft telemetry was acquired
on Nov. 17 from the Deep Space Network tracking
complex at Canberra, Australia. 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/mission/presentposition/ .
Wednesday, Nov. 11 (DOY 315)
Based on analysis of the preliminary data, the
Navigation Team proposed the cancellation of
Orbit Trim Maneuver (OTM) #222, planned to
execute on Nov. 12. This was approved by the
project. NAV also noted that it might be possible
to cancel OTM-223. Cancellation was contingent
upon an update to Enceladus pointing and
agreement by the various instrument teams.
Science Planning performed an OTM cancellation
assessment based on a preliminary spacecraft
ephemeris without the maneuver in it. The results
are very clear: an unplanned Live Inertial Vector
Propagator (IVP) update for Enceladus would need
to be performed should both OTMs be canceled. The
instrument teams completed their evaluation of
the proposed pointing update to Enceladus and
Rhea vectors on DOY 324-325 during the Enceladus
8 flyby period. The unplanned live update is a
go, and OTM-223 has also been cancelled.
In addition to the Live IVP update mentioned
above, Uplink Operations held a kickoff meeting
for the Radio Science (RSS) Enceladus 8 Live
Update Block (LUB) on DOY 324. RSS has evaluated
the most recent data and no updates will be
required to the product developed alongside the
background sequence development in October. These
files will be uplinked to the spacecraft on Nov. 18.
Thursday, Nov. 12 (DOY 316):
A news note on the Cassini Web page highlighted
an image of the massive bright clouds of tiny ice
particles hovering above the darkened rings of
Saturn. The picture was taken on Sept. 22, around
the time of Saturn's equinox, when the icy
particle clouds appeared particularly dramatic
because of the unique lighting geometry of the
equinox period. These levitating icy particle
clouds, which are known as "spokes," have a
radial extent of up to 10,000 kilometers. For the
complete text of the feature link to:
http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20091113/
Judges have selected the U.S. winners for the
Cassini Scientist for a Day essay contest.
Details on the contest, selected essays, and images can be found at:
http://saturn.jpl.nasa.gov/education/scientistforaday8thedition/sfad8thview/
Friday, Nov. 13 (DOY 317):
Science and engineering teams delivered files for
the third and final input port for the S58
Science Operations Plan process. The files have
been merged and released for review. The process
concludes Nov. 30 with the final development
process - the Science and Sequence Update Process -
beginning the following week. S58 execution begins
March 1, 2010.
The S54 sequence concluded and S55 began
execution today at 2009-315T12:44 PST. The
sequence will run for 39 days and conclude on
Dec. 22. During that time there will be two
targeted encounters, one of Enceladus and one of
Titan, and six non-targeted flybys - one each of
Helene, Pandora, Titan, Calypso, Rhea and
Pallene. Six maneuvers are scheduled, numbered 223
through 228.
Science at the start of S55 included observations
for an Optical Remote Sensing Titan cloud
monitoring campaign. Imaging Science then
observed the dark-side of Saturn in search of
lightning, obtained images of the transits of
Titan across Hyperion and Enceladus across Rhea
for orbit determination purposes, conducted
Saturn wide angle camera photopolarimetry
observations, and imaged a couple of stars as
part of a charge transfer calibration.
Magnetospheric and Plasma Science (MAPS)
instruments continued with the solar wind-aurora
campaign, and began a magnetospheric boundaries
campaign. The Ultraviolet Imaging Spectrograph
performed observations as part of a large
campaign to measure Saturn's magnetosphere at
apoapsis, and took a distant look at Enceladus to
map volatiles in the immediate neighborhood.
These observations will test the connection of
volatile changes to plume eruptions.
Tuesday, Nov. 17 (DOY 321)
An encounter strategy meeting was held today to
cover the period between Nov. 21 and Dec. 12,
Enceladus flyby E8 and Titan flyby T63, and
maneuvers 224 - 226. Navigation has determined
that maneuver #224 is a good candidate for early
uplink. After examining the schedule, it appears
that there are two DSN passes early Saturday
morning after the main engine cover is reopened that would work.
Visit the JPL Cassini home page for more
information about the Cassini Project:
http://saturn.jpl.nasa.gov/
------------------------
http://www.jpl.nasa.gov/news/news.cfm?release=2009-176
Cassini Captures Ghostly Dance Of Saturn's Northern Lights
Jet Propulsion Laboratory
November 24, 2009
PASADENA, Calif. - In the first video showing the auroras above the
northern latitudes of Saturn, Cassini has spotted the tallest known
"northern lights" in the solar system, flickering in shape and
brightness high above the ringed planet.
The new video reveals changes in Saturn's aurora every few minutes, in
high resolution, with three dimensions. The images show a previously
unseen vertical profile to the auroras, which ripple in the video like
tall curtains. These curtains reach more than 1,200 kilometers (750
miles) above the edge of the planet's northern hemisphere.
The new video and still images are online at:
http://www.nasa.gov/cassini , http://saturn.jpl.nasa.gov and
http://ciclops.org .
Auroras occur on Earth, Jupiter, Saturn and a few other planets, and the
new images will help scientists better understand how they are generated.
"The auroras have put on a dazzling show, shape-shifting rapidly and
exposing curtains that we suspected were there, but hadn't seen on
Saturn before," said Andrew Ingersoll of the California Institute of
Technology in Pasadena, who is a member of the Cassini imaging team that
processed the new video. "Seeing these things on another planet helps us
understand them a little better when we see them on Earth."
Auroras appear mostly in the high latitudes near a planet's magnetic
poles. When charged particles from the magnetosphere -- the magnetic
bubble surrounding a planet -- plunge into the planet's upper
atmosphere, they cause the atmosphere to glow. The curtain shapes show
the paths that these charged particles take as they flow along the lines
of the magnetic field between the magnetosphere and the uppermost part
of the atmosphere.
The height of the curtains on Saturn exposes a key difference between
Saturn's atmosphere and our own, Ingersoll said. While Earth's
atmosphere has a lot of oxygen and nitrogen, Saturn's atmosphere is
composed primarily of hydrogen. Because hydrogen is very light, the
atmosphere and auroras reach far out from Saturn. Earth's auroras tend
to flare only about 100 to 500 kilometers (60 to 300 miles) above the
surface.
The speed of the auroral changes in the video is comparable to some of
those on Earth, but scientists are still working to understand the
processes that produce these rapid changes. The height will also help
them learn how much energy is required to light up auroras.
"I was wowed when I saw these images and the curtain," said Tamas
Gombosi of the University of Michigan in Ann Arbor, who chairs Cassini's
magnetosphere and plasma science working group. "Put this together with
the other data Cassini has collected on the auroras so far, and you
really get a new science."
Ultraviolet and infrared instruments on Cassini have captured images of
and data from Saturn's auroras before, but in these latest images,
Cassini's narrow-angle camera was able to capture the northern lights in
the visible part of the light spectrum, in higher resolution. The movie
was assembled from nearly 500 still pictures spanning 81 hours between
Oct. 5 and Oct. 8, 2009. Each picture had an exposure time of two or
three minutes. The camera shot pictures from the night side of Saturn.
The images were originally obtained in black and white, and the imaging
team highlighted the auroras in false-color orange. The oxygen and
nitrogen in Earth's upper atmosphere contribute to the colorful flashes
of green, red and even purple in our auroras. But scientists are still
working to determine the true color of the auroras at Saturn, whose
atmosphere lacks those chemicals.
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 mission for the Science Mission Directorate at
NASA Headquarters in Washington. The Cassini orbiter and its two onboard
cameras were designed, developed and assembled at JPL. The imaging team
is based at the Space Science Institute, Boulder, Colo.
Jia-Rui C. Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jia-rui.c.cook@...
Joe Mason 720-974-5859
Space Science Institute, Boulder, Colo.
jmason@...
2009-176
Cassini Significant Events
for 11/18/09 - 11/23/09
The most recent spacecraft telemetry was acquired on Nov. 23 from the
Deep Space Network tracking complex at Canberra, Australia. 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, Nov. 18 (DOY 322)
A news note called "Before Darkness Falls: Cassini to Scan Enceladus
on Winter's Cusp" previewed the upcoming Enceladus flyby, describing
it as "a last peek at the intriguing 'tiger stripes' before winter
darkness blankets the area for several years." Scientists are
particularly interested in the tiger stripes, which are fissures in
the south polar region, because they spew jets of water vapor and
other particles hundreds of kilometers from the surface.
http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20091119/
A web feature story, "Cassini's Big Sky: The View from the Center of
Our Solar System," described how Cassini recently helped rewrite our
understanding of the shape of our solar system. For decades,
scientists pictured our solar system as having a comet-like
appearance. The new results suggest a picture more like a bubble.
http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20091120/
The main engine cover was closed on Nov. 18 at the end of the Orbit
Trim Maneuver (OTM) #223 backup pass.
Port 2 files were due today as part of the S59 Science Operations
Plan process. The files have been merged and a Science Planning
assessment of the product released for review.
Both the Live update and Live Update block for the Enceladus 8 flyby
were sent up to the spacecraft today along with a tweak to the
Magnetometer Subsystem (MAG) Flux Gate Magnetometer (FGM) autorange
boundaries.
Thursday, Nov. 19 (DOY 323):
In addition to the Enceladus 8 flyby, science this week included
Visual and Infrared Mapping Spectrometer (VIMS) leading a joint
Optical Remote Sensing (ORS) E and G ring phase observation and a
joint ORS mosaic of Saturn to look at global dynamics. VIMS spent
some time looking at Saturn's northern hemisphere dynamics, and the
Composite Infrared Spectrometer (CIRS) performed a helium abundance
measurement at the Radio Science (RSS) occultation egress point.
Imaging Science (ISS) acquired data for more Saturn wide-angle camera
photopolarimetry and lightning searches, and observed the transit of
Pandora across Epimetheus for orbit determination purposes.
The Magnetospheric and Plasma Science (MAPS) teams continued the
magnetospheric boundaries campaign and began a campaign to examine
interactions between the rings and the satellites.
The Ultraviolet Imaging Spectrograph (UVIS) observed Dione, measuring
the satellite's albedo in ultraviolet light to determine the phase
function.
This is part of the ongoing campaign to investigate surface
microstructure and frost properties as a function of location. CIRS
and VIMS rode along.
Friday, Nov. 20 (DOY 324):
A non-targeted flyby of Helene occurred today, and tomorrow along
with the Enceladus 8 targeted flyby will be non-targeted flybys of
Pandora, Titan, Calypso and Rhea.
On DOY 324 Cassini Radio Science (RSS) successfully completed the
orbit 121 Saturn occultation experiment. The experiment was an egress
only atmospheric occultation and was covered by Canberra's DSS-43 for
X- and S-band, and DSS-34 for X- and Ka-band. It is the second of a
sequence of three occultations in the Cassini Equinox Mission that
probe Saturn's mid-northern latitude, a region which was sparsely
sampled during the prime mission. The latitude probed on Rev 121 was
about 27.5 deg north as measured near the top of the troposphere.
Measurements of the S-, X-, and Ka-band signals' amplitude,
frequency, and phase provide information about the large- and
small-scale structure of the atmosphere, the temperature and pressure
profile, zonal wind, abundance of microwave absorbing species, the
electron number density profile of the ionosphere, and on variability
of the profiles with latitude and solar zenith angle.
Saturday, Nov. 21 (DOY 325):
The main engine cover was opened today. This was the 53rd in-flight
cycle. The stow position reached a nominal 33.04 degrees.
Just under three weeks after the Enceladus 7 flyby, Cassini once
again flew past Enceladus, this time with a very different geometry,
approaching within 1,600 kilometers of the surface. E8 closest
approach occurred at 2009-325T05:15:03 SCET, at a speed of 7.7 km/sec
at 82 degrees S latitude. The spacecraft was under thruster control
during the flyby to allow for precise tracking of surface features.
VIMS observed Enceladus as the moon emerged from eclipse, followed by
a CIRS fast raster scan of Enceladus' night side. ISS then took over
for high-resolution plume observations obtaining a clear filter
mosaic of terrain on the leading hemisphere, providing the
best-resolution mosaic so far of that hemisphere. This data can be
combined with earlier images of the same region at different
geometries to create high-resolution topographic maps, and will be
used to look for possible temporal variations in the morphology of
the tiger stripes.
CIRS had prime pointing control during closest approach for a high
resolution FP3 scan of Baghdad Sulcus - one of the tiger stripe
features - tracking along the fissure in the south polar region to
examine plume sources and producing the highest-ever-resolution
contiguous thermal map of this region.
ISS and VIMS then mapped the sunlit surface of Enceladus on
departure. UVIS performed a long stare for a tenuous atmosphere
search, which will provide
data to associate plume activity with the quantity of volatiles near
Enceladus. Over the following downlink of data, RSS performed gravity
science to better determine Enceladus' mass.
Shortly after the targeted Enceladus flyby, Cassini flew less than
25,000 kilometers from Rhea, allowing for ISS high-resolution imaging
- around 150-175 m/px - and compositional mapping of regions
including the fractured "wispy terrain," followed by a VIMS
point-and-stare observation. UVIS searched for the Rhea ring,
targeting beta Ori and kappa Ori. This observation was also used to
look for volatiles. Finally, CIRS performed a limb-to-limb fast scan
along Rhea's equator, including night and early morning local times.
To view the flyby page for this encounter link to:
http://saturn.jpl.nasa.gov/mission/flybys/enceladus20091121/
Following the flyby this unprocessed image was posted to the Cassini
webpage. It shows the ridges and fractures on the surface of the icy
moon.
Link to: http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=3749
In a news note called "Cassini Sends Back Images of Enceladus as
Winter Nears," mission managers said the spacecraft sailed seamlessly
through its Enceladus flyby. The spacecraft has sent back temperature
data and spectacular images, including ones of the jets of water
vapor and other particles emanating from the moon's south polar
region. For the full text and links to additional information go to:
http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20091121/
Sunday, Nov. 22 (DOY 326):
On Nov. 21, after the E8 flyby, a solid-state power switch (SSPS)
trip occurred that turned VIMS off and turned the replacement heater
turn on. Real time commands were sent today to turn the instrument
and supplemental heater back on and the replacement heater off. This
was the first SSPS trip since Nov. 26, 2008. VIMS is currently in a
safe state and operating normally.
OTM #224 was performed today. This was the cleanup maneuver from the
E8 encounter on Nov 21. The main engine burn began at 2:44 PM PST.
Telemetry immediately after the maneuver showed a burn duration of
14.94 seconds, giving a delta-V of 2.54 m/s. All subsystems reported
nominal performance after the maneuver.
Monday, Nov. 23 (DOY 327):
The Science Operations Plan process for S60 kicked off today. Two new
milestones have been added to this process for prime-rider instrument
coordination. The first delivery port for this sequence is
scheduled for Dec. 15.
Update:
On Tuesday, Nov. 24, images and a movie were released showing the
tallest known "northern lights" in the solar system, flickering in
shape and brightness high above Saturn. Ultraviolet and infrared
instruments on Cassini have captured images of Saturn's auroras
before, but in the latest images, Cassini's camera was able to
capture the northern lights in the visible part of the light
spectrum, in higher resolution. This is the first visible-light video
of the auroras. The release also features an explanatory video.
Visit: http://saturn.jpl.nasa.gov/video/videodetails/?videoID=198
Visit the JPL Cassini home page for more information about the
Cassini Project: <http://saturn.jpl.nasa.gov/>
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