Author Topic: NASA - Cassini updates  (Read 207676 times)

Online Chris Bergin

NASA - Cassini updates
« on: 03/09/2006 06:37 PM »
RELEASE: 06-088

NASA'S CASSINI DISCOVERS POTENTIAL LIQUID WATER ON ENCELADUS

NASA's Cassini spacecraft may have found evidence of liquid water
reservoirs that erupt in Yellowstone-like geysers on Saturn's moon
Enceladus. The rare occurrence of liquid water so near the surface
raises many new questions about the mysterious moon.

"We realize that this is a radical conclusion - that we may have
evidence for liquid water within a body so small and so cold," said
Carolyn Porco, Cassini imaging team leader at the Space Science
Institute, Boulder, Colo. "However, if we are right, we have
significantly broadened the diversity of solar system environments
where we might possibly have conditions suitable for living
organisms."

High-resolution Cassini images show icy jets and towering plumes
ejecting large quantities of particles at high speed. Scientists
examined several models to explain the process. They ruled out the
idea the particles are produced or blown off the moon's surface by
vapor created when warm water ice converts to a gas. Instead,
scientists have found evidence for a much more exciting possibility.
The jets might be erupting from near-surface pockets of liquid water
above 0 degrees Celsius (32 degrees Fahrenheit), like cold versions
of the Old Faithful geyser in Yellowstone.

"We previously knew of at most three places where active volcanism
exists: Jupiter's moon Io, Earth, and possibly Neptune's moon Triton.
Cassini changed all that, making Enceladus the latest member of this
very exclusive club, and one of the most exciting places in the solar
system," said John Spencer, Cassini scientist, Southwest Research
Institute, Boulder.

"Other moons in the solar system have liquid-water oceans covered by
kilometers of icy crust," said Andrew Ingersoll, imaging team member
and atmospheric scientist at the California Institute of Technology,
Pasadena, Calif. "What's different here is that pockets of liquid
water may be no more than tens of meters below the surface."

"As Cassini approached Saturn, we discovered the Saturnian system is
filled with oxygen atoms. At the time we had no idea where the oxygen
was coming from," said Candy Hansen, Cassini scientist at NASA's Jet
Propulsion Laboratory (JPL) in Pasadena. "Now we know Enceladus is
spewing out water molecules, which break down into oxygen and
hydrogen."

Scientists still have many questions. Why is Enceladus so active? Are
other sites on Enceladus active? Might this activity have been
continuous enough over the moon's history for life to have had a
chance to take hold in the moon's interior?

In the spring of 2008, scientists will get another chance to look at
Enceladus when Cassini flies within 350 kilometers (approximately 220
miles), but much work remains after the spacecraft's four-year prime
mission is over.

"There's no question, along with the moon Titan, Enceladus should be a
very high priority for us. Saturn has given us two exciting worlds to
explore," said Jonathan Lunine, Cassini interdisciplinary scientist,
University of Arizona, Tucson, Ariz.

Mission scientists report these and other Enceladus findings in this
week's issue of Science. The Cassini-Huygens mission is a cooperative
project of NASA, the European Space Agency and the Italian Space
Agency.

JPL, a division of the California Institute of Technology, manages the
Cassini-Huygens mission for NASA's Science Mission Directorate. The
Cassini orbiter was designed, developed and assembled at JPL.

For Cassini images and information about the research on the Web,
visit:

http://www.nasa.gov/cassini

Offline jacqmans

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Re: NASA - Cassini updates
« Reply #1 on: 08/05/2006 09:45 AM »
Cassini Significant Events
for 07/27/06 - 08/02/06

Thursday, July 27 (DOY 208):

It was reported in the Cassini Significant Events last week that the
atmospheric density measured at Titan 16 was higher than expected. The
Titan Atmospheric Modeling Working Group (TAMWG) met this morning to
discuss this result and assess whether the altitudes selected for
upcoming encounters are still acceptable. At the conclusion of the
meeting, the TAMWG recommended no changes to the altitudes of upcoming
encounters. The new T16 data point has not fundamentally changed our
understanding of Titan's atmospheric profile, except to indicate a less
steep falloff in density at high latitudes. Cassini only has one future
Titan flyby at very high latitude, Titan 32. Much like T16, this
encounter is at 84 deg N latitude with a closest approach at 950 km, so
it should be safe as well.

One of the things that presents a challenge to Cassini scientists and
sequence developers is attempting to respond to new scientific
discoveries as they arise. Background sequence S24 completed Science
Operations Plan Implementation in March 2004. At that time the basic
sequence was delivered to the project file repository. Science Planning
was chartered to archive a sequence that if necessary would fly on the
spacecraft "as is." Now roll the clocks forward to July 27, 2006. S24
has been through both the Aftermarket Process and the Science Operations
Plan Update Process. It is currently in final development prior to
uplink. The first of four phases of that development process is
complete. But, due to the discovery of lakes near Titan's north pole
over the weekend, RADAR has requested re-pointing of their T19
observation to cover more of the same region. What to do?

It was decided to stick with the process and have RADAR submit their
pointing changes in the third phase. Although this decreases the number
of iterations available to get the pointing right, it allows the other
instruments and AACS time to properly assess any impacts they might
have. To support the development of this observation, an interim set of
sequence products was produced with the new RADAR pointing, to give the
Attitude and Articulation Control Subsystem (AACS) time to evaluate it
and make a c-kernel available to teams that might wish to examine it. At
this time S24 is on track for final approval in September, and it is
hoped to have lakes in its future.

Friday, July 28 (DOY 209):

Science data archive deliveries for data acquired during the period of
July through September 2005 are now complete. The next archive delivery
port is October 1.

The official port occurred today for S25 as part of the Science
Operations Plan (SOP) Update process. The merged products are currently
being run through end-to-end pointing validation by AACS. The Project
Briefing and Waiver Disposition Meeting is scheduled for August 9. The
SOP Update product is handed off to the sequence leads on August 11 for
the final development process.

Monday, July 31 (DOY 212):

The Cassini RADAR image of Titan's methane lakes is Astronomy Picture of
the Day today.

Tuesday, August 1 (DOY 213):

Orbit Trim Maneuver (OTM) #69, an apoapsis maneuver setting up for the
Titan 17 encounter on September 7, was performed today. This main engine
burn began at 2:30 PM PDT. Telemetry immediately after the maneuver
showed a burn duration of 33.8 seconds, giving a delta-V of 5.4 m/sec.
All subsystems reported nominal performance after the maneuver. A
contingency DSS-15 track that had been retained for the DOY 214 backup
OTM-69 window in case the DSS-14 antenna went red was released at the
successful completion of the burn. Cassini thanks MGS, MER and Odyssey
for their help in making this track available. The next OTM is scheduled
for September 4.

Solar Conjunction occurs when the Sun is between the spacecraft and
Earth. This year it will last from August 2 through August 12, and is a
time of reduced commanding and downlink capability. Cassini enters Solar
Conjunction tomorrow with a separation angle of 4 degrees. During
conjunction, communications with the spacecraft become degraded due to
interference from the sun. For the next ten days the Spacecraft
Operations and Mission Support and Services offices will participate in
a campaign where a command file consisting of 10 no-op commands will be
uplinked to the spacecraft ten times daily. This will allow the teams to
obtain link characterizations and accumulate statistics for uplink
reliability at decreased separation angles. With the exception of these
no-op command files, Spacecraft Operations has asked for and received a
command moratorium. Additional commands will only be sent in the event
of an emergency. On Saturday, the spacecraft will be turned so that the
High Gain Antenna is continuously pointed to Earth, and 1896 bps
telemetry continues while separation is less than 2 deg. Normal playback
downlink rates will resume on August 10.

There is a great write up on conjunction on the Cassini web site. For
more information link to: http://saturn.jpl.nasa.gov/home/index.cfm

Cassini's "For Educators" website has a hands-on activity called
"Monitoring the Sun's Corona." Scroll down the Saturn in your Kitchen
and backyard section to "Saturn System Science" to find it.
http://saturn.jpl.nasa.gov/education/edu-58-kitchen.cfm. In this
activity, students of all ages will learn how, during solar conjunction,
scientists use the relative positions of the Sun, Earth, and a
spacecraft to study the Sun's corona, or outer region.

Wednesday, August 2 (DOY 214):

An artist's rendition of the methane rain on Titan is Astronomy Picture
of the Day today

The data obtained by the six Huygens experiments is now archived in the
European Space Agency (ESA) Planetary Science Archive (PSA). A copy of
the archived data set is also available in the NASA Planetary Data
System (PDS). The data is now accessible by the scientific community and
the general public for downloads. This represents a major milestone in
the Huygens mission. Data from the Aerosol Collector and Pyrolyser
(ACP), Doppler Wind Experiment (DWE), Gas Chromatograph Mass
Spectrometer (GCMS), and Huygens Atmospheric Structure Instrument (HASI)
is accessible along with housekeeping data, calibration information, and
documentation necessary to understand and process the products, and to
carry out scientific analyses. Data from the Descent Imager Spectral
Radiometer (DISR), Surface Science Package (SSP), and the final Huygens
entry and descent trajectory data is to be released in the
September-October timeframe. To access the data, link to:
http://atmos.nmsu.edu/data_and_services/atmospheres_data/Huygens/Huygens.html

A Cassini Saturn Orbit Insertion +2 Years celebration was held in Von
Karman auditorium today for the Cassini Flight team. Talks were given by
the laboratory director Charles Elachi, and by two surprise celebrities,
Robert Picardo and Bill Nye. An additional presentation was given by
Outreach who read to the flight team some of the comments that the
public has sent to the Cassini web site letting us know how much they
appreciate what Cassini is doing, and looking forward to the next two
years of prime mission and extended mission after that. The flight team
says "THANKS" back to the public. We are looking forward to it too!

Your coffee table will never be the same. Outreach has promised the
flight team that they will let us know as books on Cassini/Saturn are
published. The first one is a beauty called Saturn: A New View in
hardcover. The pictures are phenomenal. The book has not yet been
released but may be ordered and will ship as it arrives at distributors.
See your local bookstore - either electronic or traditional.

The July 20 "Cassini Real-time Operations" presentation from the Von
Karman Lecture Series is online at the JPL public website as a
RealPlayer downloadable: http://www.jpl.nasa.gov/events

Wrap up:

The most recent spacecraft telemetry was acquired on Wednesday, August
2, from the Goldstone tracking complex. The Cassini spacecraft is in an
excellent state of health and all subsystems are operating normally.

Check out the Cassini web site at http://saturn.jpl.nasa.gov for the
latest press releases and images.
 

The Cassini-Huygens mission is a cooperative project of NASA, the European
Space Agency and the Italian Spsce Agency. The Jet Propulsion Laboratory, a
division of the California Institute of Technology in Pasadena, manages the
Cassini-Huygens mission for NASA's Science Mission Directorate, Washington,
D.C.  JPL designed, developed and assembled the Cassini orbiter.
« Last Edit: 12/16/2008 02:00 PM by jacqmans »

Offline jacqmans

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Re: NASA - Cassini updates
« Reply #2 on: 08/11/2006 09:04 PM »
Cassini Significant Events
for 08/03/06 - 08/09/06

The most recent spacecraft telemetry was acquired Wednesday, August 9, from
the Goldstone tracking stations. The Cassini spacecraft is in an excellent
state of health and is operating normally. Information on the present
position and speed of the Cassini spacecraft may be found on the "Present
Position" web page located at
http://saturn.jpl.nasa.gov/operations/present-position.cfm .

Thursday, August 3 (DOY 215):

Due to superior conjunction and the reduction in communications quality with
the spacecraft, science this week was limited to Magnetospheric and Plasma
Science (MAPS) instruments, as they performed magnetospheric surveys. More
specifically, the Radio and Plasma Wave Science instrument (RPWS) mapped the
occurrence of plasma waves in the Saturnian magnetosphere to determine their
role in magnetospheric processes, and performed a series of observations to
establish the nature of the solar wind.

NASA Astronauts Stephanie Wilson and Piers Sellars visited the Cassini
real-time operations area this evening.

Monday, August 7 (DOY 219):

Minimum separation angle between Earth, the spacecraft, and the sun occurred
this morning. The Radio Science Solar Corona Characterization Experiment
continued with the spacecraft maintaining a high-gain antenna to Earth
attitude and 1896 bps telemetry.

A project level Operations Readiness Test began today and will run till the
end of the week.  The purpose of the test is to exercise the flight team in
the processes and procedures to be followed in the event that an Orbit Trim
Maneuver fails to execute.  The test conductor, in this case the Spacecraft
Operations Office manager, came up with the fault to use in the test.  It
was decided that at the end of S23 - remember that we are currently flying
S22 on the spacecraft - an OTM would only partially execute, the spacecraft
would be found to have entered safe mode, the next OTM will be due to
execute within three days, and the day after that a live moveable block
would need to be uplinked if we were to salvage a Radio Science Saturn
occultation. Six days after that the next background sequence would be
scheduled to start.  Remember this is only a test!

The Science Operations Plan Update kickoff meeting for S26 was held today.

Wednesday, August 9 (DOY 221):

Cassini's own Project Scientist gave a talk to the flight team today
entitled "Messages from the Icy Saturnian Satellites."

A delivery coordination meeting was held today for a patch delivery of
Mission Sequence Subsystem version D12.0.1. The delivery was driven by the
need to fix problems in SEQGEN core that impact the ability to split
sequences.  It is believed that S25 has a high potential for being larger
than the space available to store it on the spacecraft, and thus splitting
would be necessary. As a patch release, D12.0.1 will overlay D12.0 and will
be invisible to users.

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Re: NASA - Cassini updates
« Reply #3 on: 08/18/2006 10:03 PM »
Cassini Significant Events
 for 08/10/06 - 08/16/06

The most recent spacecraft telemetry was acquired on Tuesday, August 15,
from the Goldstone tracking complex. The Cassini spacecraft is in an
excellent state of health and all subsystems are operating normally.
Information on the present position and speed of the Cassini spacecraft
may be found on the "Present Position" web page at
http://saturn.jpl.nasa.gov/operations/present-position.cfm .

Thursday, August 10 (DOY 222):

The Radio Science S-band equipment was powered on from DOY 219 to 221
during solar conjunction to aid in an experiment being run at Arecibo.

August 9 was the last day of the Cassini command moratorium during
conjunction. Separation angle is now at three degrees and climbing, the
command loss timer has been set to the nominal value of 85 hours, and
normal commanding has resumed. Today the spacecraft played back data
acquired during the 11 days of conjunction. Although this conjunction
was deeper than last year's, spacecraft telemetry was off lock for
shorter periods, indicating quieter solar activity. Superior conjunction
will officially end this Sunday, August 13.

Today was the final day of the 2006 Operations Readiness Test (ORT). The
training obtained by the flight team was invaluable. The test
coordinator described it as "a really hard ORT because it had serious
Navigation recovery, long term Spacecraft and Mission implications AND a
major Science objective coming in less than a week." When the test was
planned, management was looking for both strategic planning and tactical
recovery. In the final analysis, it was felt that the OTM teams really
did well - this should make the real thing - if it ever happens - look easy!

Science activities on board the spacecraft this week included an Imaging
Science Subsystem (ISS) 17-hour ansa movie of the F ring at very high
phase, the completion of several slow scans across Saturn's visible
hemisphere to form spectral images by the Ultraviolet Imaging
Spectrograph (UVIS), and the Visual and Infrared Mapping Spectrometer
(VIMS) observed Saturn to assemble a methane fluorescence mapping, and
tracked many of Saturn's atmospheric features. The Magnetospheric and
Plasma Science (MAPS) instruments simultaneously performed low-rate
outer magnetospheric surveys to observe the variability of
magnetospheric boundaries at a variety of radial distances. The AACS Z
Sigma Ratio error monitor unexpectedly exceeded the threshold on Aug.
10, 2006. The High Water Mark (HWM) value reached 13. The nominal
threshold value is 10. It remained above the threshold for 10 seconds.
This ratio compares the measured star brightness to the expected. The
last occurrence was Christmas Eve, 2005, when it reached 11 for 5
seconds, because Rhea's interference was interpreted as an unexpected
bright body.

Since this monitor triggered two of the four Cassini safing events, the
Spacecraft Team has been following a strategy of masking and unmasking
to prevent it from responding to bright bodies in the Stellar Reference
Unit field of view. This strategy prevents a call to safing, and logs
the event for future analysis. This time there was no bright body
problem so the AACS team is investigating the cause.

Friday, August 11 (DOY 223):

The DSN has examined the Goldstone 70m elevation bearings at DSS-14. The
bearings show normal wear and should have several more years of life
left in them. With this information, DSN personnel will now have a
stable environment for resource planning and track allocation. Now the
only remaining uncertainty affecting the allocation of stations to
support Cassini is related to the launch of STEREO, currently scheduled
for August 31

Monday, August 14 (DOY 226):

Today was a very busy day for sending commands and files to the
spacecraft. A Dione/Mimas/Saturn/Helene/Rhea Live Inertial Vector
Propagator (IVP) update sequence, and a RADAR Dione/Rhea instrument
expanded block (IEB) trigger update movable block sequence were
uplinked. Both files have registered and activated on-board. The IVP
update sequence will begin clocking out on DOY 227 while the RADAR
sequence will begin execution on DOY 228. Additional files uplinked
today included S23 IEBs for ISS, Composite InfraRed Spectrometer (CIRS),
VIMS, Ion and Neutral Mass Spectrometer (INMS), UVIS, Cassini Plasma
Spectrometer (CAPS), and Optical Navigation. The remaining IEBs will be
sent up tomorrow, and the background sequence will follow on Thursday.

Attitude and Articulation Control Subsystem (AACS) gyro calibration
parts A & B were executed today piggybacking on an Inertial Reference
Unit calibration.

Tuesday, August 15 (DOY 227):

Background sequence Reaction Wheel Assembly (RWA) biases were performed
on DOY 224 and today to counter the low RWA RPM rates that otherwise
would have occurred during the execution of this sequence segment. In
addition, Periodic Engineering Maintenance (PEM) was performed today.

The final development process for the S25 background sequence and
associated files kicked off today. Stripped subsequence files have been
provided to the teams to populate, and a set of integrated merged
products was produced and made available to the team. Wednesday, August
16 (DOY 228):

The final sequence approval meeting for S23 was held today. Although all
planned and required activities have been accommodated, there is concern
regarding DSN allocations. Passes are still in heavy contention between
September 2 and September 20 based on the new Stereo launch date of
August 31. Should the situation change, real-time action would be
required and may cause loss of data, and could affect the uplink of
files in mid September to support S24. The allocation schedule is being
worked on a week-by-week basis with upper project and lab management
involvement. S23 will be uplinked to the spacecraft over the Cassini DSN
pass tomorrow.

As of today, real-time commands will need to be sent to deal with DSN
station allocation changes to passes on September 2, 4 and 5. The
commands are needed to preserve the planned data playback. Changes to
the DSN allocation for these days came too late for the sequence leads
to accommodate them in the background sequence. The sequence leads for
S24 reported that an allocation file for the sequence is still not
available. Development work is proceeding on the assumption that all
requested passes will be obtained. Unfortunately, this is unlikely given
the delayed return to service of DSS-63 and the needs of the STEREO and
MRO missions.

As Cassini approached periapsis today, Cosmic Dust Analyzer (CDA) was on
a campaign to obtain Tethys orbit crossing data and E ring measurements.
In addition, the live update files mentioned on DOY 226 of this report
are intended to update this period of periapsis observations - Dione,
Mimas, Helene and Rhea observations are among the planned activities.

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Re: NASA - Cassini updates
« Reply #4 on: 08/25/2006 07:31 PM »
Cassini Significant Events
for 08/17/06 - 08/23/06

The most recent spacecraft telemetry was acquired Wednesday, August 23, from
the Goldstone tracking stations. The Cassini spacecraft is in an excellent
state of health and is operating normally. Information on the present
position and speed of the Cassini spacecraft may be found on the "Present
Position" web page located at
http://saturn.jpl.nasa.gov/operations/present-position.cfm .

Thursday, August 17 (DOY 229):

Today the instrument teams had the closest view of the Saturnian satellite
Helene since the start of the mission. Cassini flew by for a non-targeted
encounter at an altitude of 48759 kilometers, traveling at a speed of around
7.7 kilometers per second. For this event the Imaging Science Subsystem
(ISS), Composite Infrared Spectrometer (CIRS), and Ultraviolet Imaging
Spectrograph (UVIS) observed Helene to obtain color, polarization, shape,
and geology measurements.

Also today the second Enceladus Plume Debris working group meeting was held.
The primary goal of this group is to characterize the Enceladus plumes so
that the orbit 61 flyby can be designed to provide excellent Enceladus
science without presenting a hazard to the spacecraft. The work of this
group is also important for creation and analysis of proposed extended
mission tours. The group needs to develop an engineering model incorporating
dust and gas that can be folded into Mission Planning and Navigation
software for planning flyby scenarios.

Friday, August 18 (DOY 230):

A non-targeted flyby of Titan occurred today.

The preliminary port of the Science Operations Plan update process occurred
today for inputs to the S26 sequence. The inputs have been merged, analyzed,
and status delivered to the teams for review. The official port is scheduled
for Thursday, August 24.

For the final week of S22, the Cassini Plasma Spectrometer (CAPS), Cosmic
Dust Analyzer (CDA), Ion and Neutral Mass Spectrometer (INMS), Magnetometer
Subsystem (MAG), Magnetospheric Imaging Instrument (MIMI), and Radio and
Plasma Wave Science (RPWS) instrument continued to perform simultaneous
magnetospheric surveys to observe the variability of magnetospheric
boundaries at a variety of radial distances. Several of these instruments
also participated in a campaign to study the interactions between icy
satellites, rings, and the magnetosphere. MIMI also imaged the dynamics of
the inner magnetosphere by sampling energetic ions with the Ion and Neutral
Camera sensor.

The Spacecraft Operations Office hosted the S28 Engineering Activities
Review. The objective of the meeting is for the Navigation and Spacecraft
teams to identify any periods where the mission is particularly vulnerable
to a missed Orbit Trim Maneuver during the sequence, and to consider
additional contingency plans, if needed. The principal participants are the
Navigation and Spacecraft teams, but other offices are also represented.

Saturday, August 19 (DOY 231):

The Traveling Wave Tube Amplifier (TWTA) B line B solid-state power switch
(SSPS) changed state from OFF to tripped at 231T09:13:20 SCET, Saturday,
August 19. This event had no effect on TWTA operation as line B is normally
unpowered, and the trip was determined to have no affect on possible System
Fault Protection (SFP) activity going forward. The most recent trip prior to
this event was on June 21 for the SSPS on the Stellar Reference Unit (SRU)
-B replacement heater. This latest trip is the 18th occurrence since launch,
the fourth this year. These trips are expected to occur at a rate of about
two per year and are attributed to Galactic Cosmic Rays. The SSPS was reset
via real time commanding on Wednesday, August 23.

The keys to the spacecraft were handed over to the sequence leads for S23
today. The background sequence began execution at 2006-231T22:06:00.000. S23
will run for 32 days from August 19 through September 20. During the
sequence there will be one targeted flyby of Titan (T17) at 1000 kilometers,
four non-targeted flybys, one each of Methone, Calypso, Atlas, and
Enceladus, orbit trim maneuvers number 70, 71, and 72, one ring plane
crossing, two possible live updates, and a Saturn solar occultation on DOY
258.

At the top of the S23 sequence, three images were taken of Saturn's
satellites that will be used by the Optical Navigation team to accurately
calibrate Cassini's reference trajectory. The Ultraviolet Imaging
Spectrograph (UVIS), Imaging Science Subsystem (ISS), and the Visible and
Infrared Mapping Spectrometer (VIMS) jointly observed Mimas for 7 hours.
UVIS is searching for a possible atmosphere on this icy satellite.

Monday, August 21 (DOY 233):

Recently Cassini Outreach launched an RSS feed. There is now an orange "RSS"
button on the home page on the left. Next to it is a link to a help page
that will help you get started. RSS in this case stands for "Really Simple
Syndication." It is a mechanism that delivers the latest content from a web
site directly to you rather than you having to check the website every day
for what's new. RSS delivers a headline, a short summary and a link to the
full text on the website, making it easy to keep up-to-date on your favorite
websites. On the Cassini website, RSS is used to deliver the latest
information about images, videos, and news coming from the Cassini
spacecraft. Go to http://www.saturn.jpl.nasa.gov and look for the orange
rectangular button on the left labeled RSS.

UVIS performed several slow scans across Saturn's visible hemisphere.
Following this 10.5-hour activity, ISS used the Narrow Angle Camera to
photograph Titan at 140 degrees phase.

Tuesday, August 22 (DOY 234):

A Mission Planning Forum was held today to review and discuss the results of
a study of all Titan Orbiter Science Team requested double playbacks, the
potential effects on other segments, a process for the playbacks, and
recommendations.

The RADAR team obtained 2.5 hours of science and calibration by collecting
radiometer data of distant Titan. This activity was one of a set that
provides coverage of Titan's northern latitudinal variation. RADAR also
performed a nine-hour calibration activity by scanning the Sun, Saturn, and
other microwave sources while collecting radiometry data. In addition, the
spacecraft performed a 6.5-hour roll about its X-axis during a periodic
calibration for MAG.

Wednesday, August 23 (DOY 235):

The Command and Data Subsystem (CDS) turned off the Cosmic Dust Analyzer
(CDA) instrument on Sunday 20, August 20, during an instrument flight
software test. CDA was powered "on" today, and is now running on version
10.0 of CDA flight software.
 
A Delivery Coordination Meeting was held today for the version 3.3.1 patch
for the Cassini Information Management System (CIMS). The patch contains a
fix to the Science Planning Attitude Spread Sheet / Spacecraft Activity
Sequence File comparison process, a performance enhancement for the
"delivery" feature, and some usability updates. There are no updates to the
CIMS Toolkit. The software was installed today and is now being used in
operations.

The Magnetospheric and Plasma Science (MAPS) instruments performed a
6.25-hour low latitude observation of the structure and dynamics of Saturn's
magnetotail, and ISS began a series of periodic, one-hour observations of
Saturn's northern hemisphere in a search for lightning.

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Re: NASA - Cassini updates
« Reply #5 on: 08/26/2006 02:02 PM »
Thanks for the extensive info! I'd been looking for these kind of summaries for quite a long time, it's nice to have them together like this. Keep on with it! :)
-DaviD-

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Re: NASA - Cassini updates
« Reply #6 on: 09/01/2006 09:40 PM »
Cassini Significant Events
for 08/24/06 - 08/30/06

The most recent spacecraft telemetry was acquired Wednesday, August 30, from
the Goldstone tracking stations. The Cassini spacecraft is in an excellent
state of health and is operating normally. Information on the present
position and speed of the Cassini spacecraft may be found on the "Present
Position" web page located at
http://saturn.jpl.nasa.gov/operations/present-position.cfm .

Thursday, August 24 (DOY 236):

A delivery coordination meeting was held today for the Spacecraft Operations
Office (SCO) Downlink Uplink Coherency Tool (DUCT) version 1.1. This is the
tool that automates the insertion of a downlink pause in the sequence at the
point of the transition from one-way to two-way where otherwise a brief
telemetry loss would occur.

The Encounter Strategy Meeting for Titan 17 and Titan 18 was held today.
The time frame addressed was from September 7 through September 23 and
included Orbit Trim Maneuvers (OTM) 71 through 73.  Presentations included a
mission overview covering special mission activities, first time events,
consumables, live updates potentially needed for this period, a sequence
overview and contingency planning for S23, and presentations by SCO,
Navigation, and Uplink Operations.

The deputy Project Scientist gave a presentation on Saturn's rings in Von
Karman Auditorium today.  The presentation included how the rings are made
up of millions of icy particles ranging in size from dust to large boulders,
and how these particles undergo an intricate dance as they orbit Saturn.
Also covered was how gravity from the nearby moons causes the ring particles
to bump into each other and create interesting patterns in the rings such as
waves and wakes. The talk was given as part of the Science Division's
monthly "Science 101" lecture series.

The S26 official port occurred today as part of the Science Operations Plan
Update process.  The input products have been sent to AACS for analysis with
the results to be delivered this week.  The S26 project briefing is
scheduled for September 6.

Friday, August 25 (DOY 237):

The Optical Remote Sensing Instruments were quite busy this week.
Observations included the occultation of the star 8 Nu Cap by Tethys by the
Ultraviolet Imaging Spectrograph (UVIS), along with calibrations performed
by observing the ring occultations of Zeta Opiuchus, Delta Sco, and Lambda
Sco. The Cassini Infrared Spectrometer (CIRS) ran a scattered light test to
quantify the effect of ring particle impacts on the performance of its
mirrors. The Imaging Science Subsystem (ISS) took a standard star image to
monitor instrument sensitivity, three pictures of Saturn's satellites were
taken for the Optical Navigation team to assist with orbit determination,
and a 13.5 hour lightning search of Saturn's northern hemisphere was
performed.  Finally, the Visual and Infrared Mapping Spectrometer (VIMS)
performed a mosaic of the entire ring system near apoapsis, Cassini's
farthest point from Saturn during the 27th orbit. The suite of
Magnetospheric and Plasma Science (MAPS) instruments continued its
magnetotail campaign by observing the structure and dynamics of Saturn's
magnetotail at low latitudes.

Saturday, August 26 (DOY 238):

An AACS Reaction Wheel Assembly (RWA) friction test was performed today on
wheels 1, 2, and 4.  In this test, performed every three months, the RWAs
are spun to +/-900 rpm and allowed to run down to zero.  The longer the
run-down time, the better.  RWA-1 exhibited no change in the counter
clockwise direction since the last test on May 29, 2006, but was poorer in
the clockwise direction.  The rundown time was 20 minutes, equaling the
previous low point in the fall of 2004.  This lower result was caused by the
presence of drag torque spikes throughout the clockwise part of the friction
test.  RWA-2 exhibited no change in either direction, with both directions
having rundown times of greater than 40 minutes.  RWA-4 showed no change in
the counter clockwise direction, but was slightly worse in the clockwise
direction, with a run-down time of 38 minutes.

Monday, August 28 (DOY 240):

The Aftermarket Process for the S28 sequence began today.  This 5-week
process addresses proposed changes that require re-integration of the
segments contained in the S28 sequence.  All proposed science and
engineering changes were submitted via the Cassini Information Management
System by last Friday, August 24, 2006.  A final decision meeting is
scheduled for September 11.

The Cassini-Huygens Analysis and Results of the Mission (CHARM)
teleconference for August was held today. The topic:  Exploring Saturn's
Moon Titan, An Earth-like Alien.  The presentation covered what is known and
what the possibilities are for Titan's atmosphere and geology, what is known
from the Huygens Probe, and specific data acquired from some of the Cassini
instruments,

Wednesday, August 30 (DOY 242):

The Navigation Team announced that OTM-070 could not be cancelled and would
execute as planned on Monday, September 4.  Currently OTM-070 has a
predicted value of 0.227 m/s. Cancellation would increase the mission
delta-V by about 15 m/s.  The preliminary and final cancellation reviews
scheduled for Thursday and Friday have been, well, cancelled.  OTM 70
removes the pointing errors at Titan, but the Enceladus post-Titan pointing
errors remain large.  Final trajectories will be provided Friday for science
evaluation.

The Radio Science Subsystem (RSS) performed a High Gain Antenna boresight
calibration near the middle of today's downlink to the Goldstone 70M
antenna.  An hour of this activity required a cross-hair maneuver that took
Cassini slightly off Earth-point.  As a result, a brief, planned
interruption to the downlink occurred.

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Re: NASA - Cassini updates
« Reply #7 on: 09/09/2006 11:30 AM »
Cassini Significant Events
for 08/31/06 - 09/06/06

The most recent spacecraft telemetry was acquired Wednesday, September 6,
from the Goldstone tracking stations. The Cassini spacecraft is in an
excellent state of health and is operating normally. Information on the
present position and speed of the Cassini spacecraft may be found on the
"Present Position" web page located at
http://saturn.jpl.nasa.gov/operations/present-position.cfm .

Thursday, August 31 (DOY 243):

The Titan 17 flyby, scheduled for September 7, is set for an altitude of
1,000 km. This flyby is at the relatively low latitude of 23 degrees, in the
region where the Titan atmosphere model predicts a greater atmospheric
density. If the results from this flyby indicate that is true, as measured
by the ACS thruster duty cycle and INMS instrument data, trajectory changes
will be considered for Titan 20, which is at 1030 km altitude, but almost
equatorial at 7.5 degrees. A new candidate reference trajectory has been
developed with an increase in the altitude of the Titan 20 flyby from 1030
to 1055 km. The final decision to raise the T20 altitude, or not, will occur
at the Titan Atmosphere Model Working Group meeting on September 11. If the
decision is to raise the altitude, the new trajectory will go into effect on
September 12.

Spacecraft Operations Office personnel held an Exciter RF Loss tabletop
exercise today. This is the first in a periodic sequence of such exercises
for SCO training.

The Radio Science Subsystem (RSS) performed the first of three Operational
Readiness Tests (ORT) today using the Deep Space Network antennas at
Goldstone. Tests two and three will be performed Saturday and Sunday. These
ORTs are used to prepare for the RSS Saturn gravity observation on September
9.

Friday, September 1 (DOY 244):

The S23 sequence leads made the decision to give up the last hour of the
Cassini DSN track over Goldstone today to accommodate station maintenance
work. A glitch with the transmitter was preventing successful uplink of
command files. Maintenance will go toward ensuring the station is available
for the maneuver uplink on Monday. According to Science Planning, only
real-time data was lost. The recorded data will be played back from the SSRs
with no loss.

Monday, September 4 (DOY 247):

Orbit Trim Maneuver (OTM) #70 was performed today. This is the minus 3-day
maneuver setting up for the Titan 17 encounter on September 7. The reaction
control subsystem burn began at 12:45 PM. Telemetry immediately after the
maneuver showed the burn duration was 164.1 seconds, giving a delta-V of
approximately 227.6 mm/s. All subsystems reported nominal performance after
the maneuver.

The Imaging Science Subsystem (ISS) began a 12.5 hour observation of
Saturn's Ring System today. Images of the unlit face of the Cassini Division
at high phase were taken once every 8 minutes. This observation will be used
to search for dust, clumps and variations in the structure of the outer B
Ring.

Tuesday, September 5 (DOY 248):

The kickoff meeting was held today for the S23 Enceladus/Tethys Live
Inertial Vector Propagator (IVP) update for DOY 252-253. The final orbit
determination solution became available last Thursday, and analysis is
scheduled to begin later today. Navigation has recommended that teams look
at the size of the uncertainties as part of the decision process to perform
or not perform the update.

A beautiful image of the white cliffs of Dione was Astronomy Picture of the
Day today.

Wednesday, September 6 (DOY 249):

The Spacecraft Operations Office has requested the S25 sequence lead to
schedule a test of the Titan 20 flyby in the Integrated Test Laboratory.

The Project Briefing, the final meeting held as part of the Science
Operations Plan Update process, was held today for  S26. Input products for
the sequence will be handed off to the sequence leads at the end of this
week, and the final development process will kick-off on September 12.

Today concluded with the spacecraft on approach to Titan for the T17
encounter, an inbound flyby. The Composite Infrared Spectrometer (CIRS)
began a 7+ hour activity to obtain information on the thermal structure of
Titan's stratosphere, with ISS and the Visual and Infrared Mapping
Spectrometer (VIMS) taking advantage of the spacecraft pointing to gather
data on Titan.

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Re: NASA - Cassini updates
« Reply #8 on: 09/16/2006 09:55 AM »
Cassini Significant Events
for 09/07/06 - 09/13/06

The most recent spacecraft telemetry was acquired Wednesday, September 13,
from the Goldstone tracking stations. The Cassini spacecraft is in an
excellent state of health and is operating normally. Information on the
present position and speed of the Cassini spacecraft may be found on the
"Present Position" web page located at
http://saturn.jpl.nasa.gov/operations/present-position.cfm .

Thursday, September 7 (DOY 250):

The Titan 17 flyby (T17), at 1000 km altitude, occurred September 7, 2006.
This flyby was at a latitude of 23 degrees, in a region where the Titan
atmospheric model predicted the atmospheric density to be greater than at
higher latitudes. The project anticipated thruster duty cycling between 40
and 65%, and developed an on-the-shelf reference trajectory to increase the
altitude of the T20 flyby should it be necessary. The duty cycle calculated
by AACS after the flyby was considerably lower than expected, around 20%.

Prior to closest approach, the Imaging Science Subsystem (ISS) searched for
and monitored lightning and aurora, and the Visible and Infrared Mapping
Spectrometer (VIMS) worked on Titan mapping, monitoring, and photometry, and
observed a stellar occultation through Titan's atmosphere.

Titan closest approach was designed with a spacecraft attitude suitable for
both Ion and Neutral Mass Spectrometer (INMS) data acquisition and a short
Synthetic Aperture RADAR (SAR) swath of Titan's surface. INMS data will be
used to help determine atmospheric and ionospheric thermal structure. The
Optical Remote Sensing (ORS) instruments used the time just after closest
approach to continue Titan global mapping and atmospheric analysis.

The Cassini Plasma Spectrometer (CAPS), Cosmic Dust Analyzer (CDA), Ion and
Neutral Mass Spectrometer (INMS), Magnetometer Subsystem (MAG),
Magnetospheric Imaging Instrument (MIMI), and Radio and Plasma Wave Science
(RPWS) instrument performed under the Magnetospheric and Plasma Science
campaign to make inbound approach observations, provide context for the
interaction between Titan and Saturn's magnetosphere, and determine
atmospheric and ionospheric thermal structures.

Friday, September 8 (DOY 251):

The S23 Saturn solar occultation Live Movable Block (LMB) kickoff meeting
was held today. A typical schedule for an LMB process runs from five to
seven days and looks something like this:

LMB kickoff meeting Friday (DOY 251)

Orbit Determination file available Saturday (DOY 252) at 2300 PDT

Epoch update and science analysis Sunday (DOY 253)

Go-No/Go meeting Monday (DOY 254)

Command Approval Meeting Tuesday (DOY 255) at 1600 PDT

Uplink Wednesday (DOY 256)

Execution beginning on Friday (DOY 258)

The S23 leads uplinked files for an Enceladus Live Inertial Vector
Propagator Update to execute tomorrow, September 9, and a RADAR Enceladus
trigger. Both files have been verified onboard and should execute as
planned.

Today concluded the T17 encounter activities. The Imaging Science Subsystem
(ISS) used the Narrow Angle Camera to monitor surface and atmosphere changes
and attempt to see surface color variations on Titan. The spacecraft
performed a 9-hour downlink to the Goldstone 70-meter DSN antenna to play
back the Titan flyby data.

After playback, the spacecraft turned its attention to Saturn's rings and
Iapetus. The ISS instrument made a series of zero-phase Iapetus observations
and captured five Optical Navigation images. CIRS gathered temperature data
on the rings, while UVIS used the opportunity for spectral mapping of the
rings.

Saturday, September 9 (DOY 252):

Non-targeted flybys of Atlas, Methone, Calypso, and Enceladus occurred
today. The Enceladus flyby was at an altitude of 39,932 km.

The first Cassini Radio Science Subsystem (RSS) Saturn gravity observation
in Orbit 28 concluded successfully today. The observation consisted of one
segment slightly over 6 hours in duration, and almost centered on periapsis.
This was the first of two RSS Saturn gravity observations during the Cassini
Tour that were selected as a pair. These two observations are specifically
optimized for measurement of the gravity field of Saturn. The second occurs
during Orbit 68 in May of 2008.

Sunday, September 10 (DOY 253):

Orbit trim maneuver #71 was performed today. This was the T17 post flyby
cleanup maneuver. The main engine burn began at 12:23 PM. Telemetry
immediately after the maneuver showed a burn duration of 41.0 seconds,
giving a delta-V of 6.55 m/s. All subsystems reported nominal performance
after the maneuver. The next maneuver, OTM-072, is scheduled for Thursday,
September 14.

Monday, September 11 (DOY 254):

It turns out that S25 is in conflict with the Messenger Project on October
24, DOY 297, for Deep Space Station 14. Messenger has a critical event, the
Venus-1 flyby, on that day. DSS-14 is required by Messenger to downlink the
flyby data. The current proposal is for Cassini to keep the first 3 hours
over DSS-14 and then hand over to DSS-15 for the remaining 6 hours of the
pass. Messenger will then have the remaining 6 hours over DSS-14 for
downlink.

The Titan Atmosphere Model Working Group (TAMWG) met today to review the T17
Titan flyby results and to recommend whether the T20 closest approach
altitude should be raised. T17 is significant because it is, at closest
approach, the lowest latitude flown to date at 23=B0. The results from AACS,
INMS, and Navigation showed the atmospheric density significantly lower than
predicted. As a result, the previous model, which assumed an increase in
density near the equator, is under serious question.The flybys for T18 on
September 23 and T19 on October 9 will be watched closely since these
altitudes were adopted assuming lower density at higher latitudes. However,
they are considered safe to fly based on the new information from T17. The
T20 altitude is not planned to be changed. The next two TAMWG meetings are
scheduled for September 27 and October 16 after the T18 and T19 flybys.

The Science Operations Plan Update process for S27 kicked off today.

Tuesday, September 12 (DOY 255):

A change board meeting was held today for AACS flight software version
A8.7.5. The four parameter changes approved were: secondary safing vector
pair update, A and B-branch thruster magnitude updates, Inertial Reference
Unit-A scale factor updates, and response script tier count change for a
potential fault protection case following an unexpected reaction wheel to
thruster transition.

The final approval meeting was held today for the S24 background sequence.
The instrument expanded block files will be uplinked beginning today with
the background sequence going up on September 18.

The S23 Saturn solar occultation Live Movable Block was successfully
uplinked today and has been verified as registered onboard. The file should
execute as expected beginning on DOY-258.

The final development process began today for S26. The process will run for
ten weeks with uplink of sequence files occurring during the 11th week. S26
begins execution on Friday, November 24.

A beautiful image of Saturn at night is Astronomy Picture of the Day today.

Wednesday, September 13 (DOY 256):

At the time S24 was going through the final development process, Uplink
Operations was unable to confirm the DSN allocations requested for the
sequence. The uncertainty was part of the STEREO launch and MRO aerobraking
conflict that the flight projects have been working with the DSN. Since the
allocations were uncertain, SSR data margin that is usually released for
instrument use during the development process was withheld, pending possible
station losses and the concomitant data cuts that would be required.

Now that the STEREO launch has been shifted to not earlier than October 25,
allocations are confirmed for most of S24, but not in time for the
instruments to take advantage of the now-available SSR data margin. The S24
leads are handling this by building a mini-sequence to be stored in the
movable block region of memory. It will run for most of the sequence from
DOY 269 through DOY 291. This file will contain the new data policing table
commands, all instrument commands required to take advantage of the sponge
bits, and any new instrument expanded block files required which go straight
to the instrument, and are not stored on the SSR. The mini-sequence will be
uplinked the day after S24 begins execution with a primary window of DOY
264/13:05-18:54, and a backup window of DOY 265/12:50-18:39.

The Magnetospheric and Plasma Science (MAPS) instruments continued the
magnetotail campaign to observe plasma flows and the dynamics of the
magnetotail from large distances downstream. The spacecraft is entering an
important phase of the mission that covers unique geometry optimal for MAPS
coverage of the magnetotail and plasma wake.

First viewed at the Saturn Orbit Insertion anniversary event held at JPL for
the flight team, the SOI +2 years highlights video chronicles some of
Cassini's discoveries in the last two years. Link to:

http://saturn.jpl.nasa.gov/multimedia/videos/video-details.cfm?videoID=128

Outreach has posted some of the images from the Titan 17 flyby on September
7. To view these images go to:

http://saturn.jpl.nasa.gov/news/events/titan20060907/index.cfm

Wrap up:

Check out the Cassini web site at http://saturn.jpl.nasa.gov for the latest
press releases and images.

Online eeergo

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Re: NASA - Cassini updates
« Reply #9 on: 10/13/2006 10:18 AM »

10-11-2006

NASA Finds Saturn's Moons May be Creating New Rings

Cassini scientists are on the trail of the missing moons of Saturn. A recent observation by the spacecraft leads them to believe that they will find the moons near newly discovered rings around the planet. During an unprecedented opportunity, with the sun poised behind Saturn, Cassini scientists discovered two new rings and confirmed the presence of two others. The new rings are associated with one or more small mooCassini scientists are on the trail of the missing moons of Saturn. A recent observation by the spacecraft leads them to believe that they will find the moons near newly discovered rings around the planet.

During an unprecedented opportunity, with the sun poised behind Saturn, Cassini scientists discovered two new rings and confirmed the presence of two others. The new rings are associated with one or more small moons and share their orbits with the moons, while scientists suspect a moon is lurking near a third ring.

http://www.nasa.gov/mission_pages/cassini/media/cassini-20061011c.html

-DaviD-

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Re: NASA - Cassini updates
« Reply #10 on: 07/19/2007 04:10 PM »
Feature   JPL news release                                                                
July 19, 2007                          

Saturn Turns 60

Scientists have recently discovered that the planet Saturn is turning 60 –not years, but moons.

"We detected the 60th moon orbiting Saturn using the Cassini spacecraft's powerful wide-angle camera," said Carl Murray, a Cassini imaging team scientist from Queen Mary, University of London. "I was looking at images of the region near the Saturnian moons Methone and Pallene and something caught my eye."

The newly discovered moon first appeared as a very faint dot in a series of images Cassini took of the Saturnian ring system on May 30 of this year. After the initial detection, Murray and fellow Cassini imaging scientists played interplanetary detective, searching for clues of the new moon in the voluminous library of Cassini images to date.

The Cassini imaging team's legwork paid off. They were able to locate numerous additional detections, spanning from June 2004 to June 2007. "With these new data sets we were able to establish a good orbit for the new moon,” said Murray. "Knowing where the moons are at all times is important to the Cassini mission for several reasons."

One of the most important reasons for Cassini to chronicle these previously unknown space rocks is so the spacecraft itself does not run into them. Another reason is each discovery helps provide a better understanding about how Saturn's ring system and all its billions upon billions of parts work and interact together. Finally, a discovery of a moon is important because with this new knowledge, the Cassini mission planners and science team can plan to perform science experiments during future observations if and when the opportunity presents itself.

What of this new, 60th discovered moon of Saturn? Cassini scientists believe "Frank" (the working name for the moon until another, perhaps, more appropriate one is found)  is about 1.2 miles (2 kilometers) wide and, like so many of its neighbors, is made mostly of ice and rock. The moon's location in the Saturnian sky is between the orbits of Methone and Pallene. It is the fifth moon discovered by the Cassini imaging team.

"When the Cassini mission launched back in 1997, we knew of only 18 moons orbiting Saturn," said Murray. "Now, between Earth-based telescopes and Cassini we have more than tripled that number – and each and every new discovery adds another piece to the puzzle and becomes another new world to explore."

Murray and his colleagues may get the chance to explore Saturn's 60th moon. The Cassini spacecraft's trajectory will put it within 7,300 miles (11,700 kilometers) in December of 2009.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. 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.

 

Related news releases:

+Link to Science and Technology Facilities Council:

http://www.scitech.ac.uk

+Link to Cassini Imaging Team:

http://ciclops.org


Written by: DC Agle
Media Contact: Carolina Martinez 818-354-9382

-end-


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Re: NASA - Cassini updates
« Reply #11 on: 08/02/2007 08:26 PM »
RELEASE: 07-168

CASSINI FINDS POSSIBLE ORIGIN OF ONE OF SATURN'S RINGS

WASHINGTON - Cassini scientists may have identified the source of one
of Saturn's more mysterious rings. Saturn's G ring likely is produced
by relatively large, icy particles that reside within a bright arc on
the ring's inner edge.

The particles are confined within the arc by gravitational effects
from Saturn's moon Mimas. Micrometeoroids collide with the particles,
releasing smaller, dust-sized particles that brighten the arc. The
plasma in the giant planet's magnetic field sweeps through this arc
continually, dragging out the fine particles, which create the G
ring.

The finding is evidence of the complex interaction between Saturn's
moons, rings and magnetosphere. Studying this interaction is one of
Cassini's objectives. The study is in the Aug. 2 issue of the journal
Science and was based on observations made by multiple Cassini
instruments in 2004 and 2005.

"Distant pictures from the cameras tell us where the arc is and how it
moves, while plasma and dust measurements taken near the G ring tell
us how much material is there," said Matthew Hedman, a Cassini
imaging team associate at Cornell University in Ithaca, N.Y., and
lead author on the Science paper.

Saturn's rings are an enormous, complex structure, and their origin is
a mystery. The rings are labeled in the order they were discovered.
From the planet outward, they are D, C, B, A, F, G and E. The main
rings -- A, B and C-from edge-to-edge, would fit neatly in the
distance between Earth and the moon. The most transparent rings are D
-- interior to C -- and F, E and G, outside the main rings.

Unlike Saturn's other dusty rings, such as the E and F rings, the G
ring is not associated closely with moons that either could supply
material directly to it -- as Enceladus does for the E ring -- or
sculpt and perturb its ring particles -- as Prometheus and Pandora do
for the F ring. The location of the G ring continued to defy
explanation, until now.

Cassini images show that the bright arc within the G ring extends
one-sixth of the way around Saturn and is about 155 miles wide, much
narrower than the full 3,700-mile width of the G ring. The arc has
been observed several times since Cassini's 2004 arrival at the
ringed planet and thus appears to be a long-lived feature. A
gravitational disturbance caused by the moon Mimas exists near the
arc.

As part of their study, Hedman and colleagues conducted computer
simulations that showed the gravitational disturbance of Mimas could
indeed produce such a structure in Saturn's G ring. The only other
places in the solar system where such disturbances are known to exist
are in the ring arcs of Neptune.

Cassini's magnetospheric imaging instrument detected depletions in
charged particles near the arc in 2005. According to the scientists,
unseen mass in the arc must be absorbing the particles. "The small
dust grains that the Cassini camera sees are not enough to absorb
energetic electrons," said Elias Roussos of the Max-Planck-Institute
for Solar System Research, Germany, and member of the magnetospheric
imaging team. "This tells us that a lot more mass is distributed
within the arc."

The researchers concluded that there is a population of larger,
as-yet-unseen bodies hiding in the arc, ranging in size from that of
peas to small boulders. The total mass of all these bodies is
equivalent to that of a 328-foot-wide, ice-rich small moon.

Joe Burns, a co-author of the paper from Cornell University and a
member of the imaging team, said, "We'll have a super opportunity to
spot the G ring's source bodies when Cassini flies about 600 miles
from the arc 18 months from now."

The Cassini-Huygens mission is a cooperative project of NASA, the
European Space Agency and the Italian Space Agency. The Jet
Propulsion Laboratory, Pasadena, Calif., manages the Cassini-Huygens
mission for NASA's Science Mission Directorate, Washington. The
Cassini orbiter and its two onboard cameras were designed, developed
and assembled at the laboratory. The imaging team is based at the
Space Science Institute, Boulder, Colo. The magnetospheric imaging
instrument team is based at Johns Hopkins University, Laurel, Md.

G ring movies and images are available on the Internet at:

http://www.nasa.gov/cassini

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Re: NASA - Cassini updates
« Reply #12 on: 08/04/2007 08:16 AM »
With data from the Cassini spacecraft, an international team of scientists may have identified the source of one of Saturn's more mysterious rings. The enigmatic G ring is likely produced by relatively large, icy particles that reside within a bright arc on the ring's inner edge.

Full story at:

http://www.esa.int/SPECIALS/Cassini-Huygens/SEMXOENEW4F_0.html

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Re: NASA - Cassini updates
« Reply #13 on: 08/25/2007 07:33 AM »
Cassini Significant Events
for 08/15/07 - 08/21/07

The most recent spacecraft telemetry was acquired on Tuesday, August 21,
from the Goldstone tracking complex. The Cassini spacecraft is in an
excellent state of health and all subsystems are operating normally.
Information on the present position and speed of the Cassini spacecraft may
be found on the "Present Position" web page located at
http://saturn.jpl.nasa.gov/operations/present-position.cfm.

Wednesday, August 15 (DOY 227):

Cassini entered solar conjunction today when the Sun-Earth-Probe (SEP) angle
reached 5 degrees.  This angle reached a minimum of 1.24 degrees on August
21, and will reach 5 degrees again when conjunction completes on August 27.

Thursday, August 16 (DOY 228.):

The Command Loss Timer (CLT) value was set from the nominal 85 hours to 10
days in the background sequence on August 16, 2007, and was reinforced with
a real-time command August 17 in preparation for conjunction and the period
of time when Cassini is out of communication with Earth.  The CLT decrements
down during conjunction, and will be set to the nominal value of 85 hours on
August 24, when the SEP angle has increased to about 3 degrees.

An Instrument Operations working group (IOWG) meeting was held to discuss
the extended mission processes and schedule.  With just one exception, all
instrument teams concurred that they could support the schedule.

Friday, August 17 (DOY 222):

The S35 science operations plan update (SOPU) completed today.

Saturday, August 18 (DOY 230):

A command moratorium centered around solar conjunction has started today. A
command moratorium is put into place when the SEP angle is 2 degrees or
less.  

A series of commands, which are exempted from the command moratorium because
their receipt on-board is not required, is being sent up daily (August 18 -
August 25, 2007) as part of the Radio Frequency Subsystem (RFS)
characterization of the solar corona.  The RFS team will assess which
commands "got through" the interference from the sun.

Monday, August 20 (DOY 232):

Cassini outreach and visualization activities and products were presented at
the European Planetary Science Congress 2007 in Potsdam, Germany, 20 - 24
August.

The S36 science operations plan update kicked off today.  This process
completes on September 28, 2007.  The preliminary port is scheduled for
September 4, 2007.

AACS presented six papers at the 2007 AIAA Guidance, Navigation, and Control
Conference August 20-23, 2007, in Hilton Head, South Carolina.

CDS V10 flight software preliminary end-to-end Integrated Test Laboratory
(ITL) testing began today and will run through August 24.   The final
end-to-end ITL testing will begin September 4 and run through September 11,
2007.  Uplink is set for the end of September.

Tuesday, August 21 (DOY 233)

In the last week, 1637 Imaging Science Subsystem (ISS) images were acquired,
including nine for Optical Navigation.  Since approach science began in
January, 2004, 128568 ISS images have been acquired.
   
Wrap up:

Check out the Cassini web site at http://saturn.jpl.nasa.gov for the latest
press releases and images.

The Cassini-Huygens mission is a cooperative project of NASA, the European
Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a
division of the California Institute of Technology in Pasadena, manages the
Cassini-Huygens mission for NASA's Science Mission Directorate, Washington,
D.C.  JPL designed, developed and assembled the Cassini orbiter.

Online eeergo

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Re: NASA - Cassini updates
« Reply #14 on: 09/12/2007 03:25 PM »
Cassini Mission Status: Cassini Flies by Walnut-Shaped Moon Iapetus

09.11.07

Cassini completed its closest flyby of the odd moon Iapetus on Sept. 10, 2007. The spacecraft flew about 1,640 kilometers (1,000 miles) from Iapetus' surface and is returning amazing views of the bizarre moon.

All the data were successfully recorded on the spacecraft. Twenty-one minutes into the first post-flyby data downlink, the spacecraft went into a precautionary condition called safe mode. The cause has been determined to be a solid state power switch that was tripped due to a galactic cosmic ray hit.
[...]

Raw images of the flyby: http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-list.cfm?browseLatest=0&cacheQ=0&storedQ=0

-DaviD-

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Re: NASA - Cassini updates
« Reply #15 on: 09/13/2007 08:01 PM »
Cassini scientists are poring through hundreds of images returned from the 10 September fly-by of Saturn's two-toned moon Iapetus.

More at:
http://www.esa.int/esaCP/SEM5E613J6F_index_0.html

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Re: NASA - Cassini updates
« Reply #16 on: 10/09/2007 04:34 AM »
Scientists are on the trail of Iapetus' mysterious dark side, which seems to be home to a bizarre 'runaway' process that is transporting vaporised water ice from the dark areas to the white areas of the Saturnian moon.

More at:
http://www.esa.int/SPECIALS/Cassini-Huygens/SEMQE3V7D7F_0.html

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Re: NASA - Cassini updates
« Reply #17 on: 10/10/2007 07:33 PM »

First direct proof that the jets (formed by water ice in large quantities) indeed come from the moon's surface "tiger stripes"' hot spots.

http://www.nasa.gov/mission_pages/cassini/media/cassini20071010.html

-DaviD-

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Re: NASA - Cassini updates
« Reply #18 on: 10/11/2007 06:00 PM »
IMAGE ADVISORY: 2007-117                                                                     Oct. 11, 2007

 

Cassini Provides New Views of Titan's Land of Lakes and Seas

 

Newly assembled radar images from the Cassini spacecraft provide the best view of the hydrocarbon lakes and seas on the north pole of Saturn's moon Titan, while a new radar image reveals that Titan's south polar region also has lakes.

 

The southern region images were beamed back after an Oct. 2 flyby in which a prime goal was the hunt for lakes at the south pole.

 

A new mosaic image, created by stitching together radar images from seven Titan flybys over the last year and a half,   shows a north pole pitted with giant lakes and seas, at least one of them larger than Lake Superior.

 

Approximately 60 percent of Titan's north polar region above 60 degrees latitude has been mapped by Cassini's radar instrument. About 14 percent of the mapped region is covered by what scientists interpret as liquid hydrocarbon lakes.

 

"This is our version of mapping Alaska, the northern parts of Canada, Greenland, Scandinavia and Northern Russia," said Rosaly Lopes, Cassini radar scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif.  "It's like mapping these regions of Earth for the first time."

 

Lakes and seas are very common at the high northern latitudes of Titan, which is in winter now.  Scientists say it rains methane and ethane there, filling the lakes and seas.  These liquids also carve meandering rivers and channels on the moon's surface.  Now Cassini is moving into unknown territory, the south pole of Titan.  "We wanted to see if there are more lakes present there and, sure enough, there they are, three little lakes smiling back at us.  Titan is indeed the land of lakes and seas," said Lopes.  "It will be interesting to see the differences between the north and south polar regions."

 

It is now summer at Titan's south pole.   A season on Titan lasts nearly 7.5 years, one quarter of a Saturn year, which is 29.5 years long.  Monitoring seasonal change helps scientists understand the processes at work there.

 

Scientists are making progress in understanding how the lakes may have formed. On Earth, lakes fill low spots or are created when the local topography intersects a groundwater table. Lopes and her colleagues think that the depressions containing the lakes on Titan may have formed by volcanism or by a type of erosion (called karstic) of the surface, leaving a depression where liquids can accumulate. Karstic lakes are common on Earth.  For example in parts of Minnesota and central Florida there are hundreds of such lakes.  

 

"The lakes we are observing on Titan appear to be in varying states of fullness, suggesting their involvement in a complex hydrologic system akin to Earth's water cycle. This makes Titan unique among the extra-terrestrial bodies in our solar system," said Alex Hayes, a graduate student who studies Cassini radar data at the California Institute of Technology in Pasadena.

 

"The lakes we have seen so far vary in size from the smallest observable, approximately 1 square kilometer (0.4 square miles), to greater than 100,000 square kilometers (40,000 square miles), which is slightly larger than the Great Lakes in the Midwestern U.S.," Hayes said.  "Of the roughly 400 observed lakes, 70 percent of their area is taken up by large "seas" greater than 26,000 square kilometers (10,000 square miles)."


Future radar flybys will image closer to the southern pole and are expected to show more lakes.


For images and more information visit: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .


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Re: NASA - Cassini updates
« Reply #19 on: 12/12/2007 10:01 PM »
Somewhere deep below Saturn's cloud tops, the planet rotates at a constant speed. Determining this interior period of rotation has proven extremely complicated. Now, with new Cassini results, a team of European scientists have taken an important step forward.

More at:
http://www.esa.int/esaCP/SEMP7SJV3AF_index_0.html

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