Trying to Be Patient

John SpencerJohn Spencer, Cassini Scientist on the Composite Infrared Spectrometer (bio)

Yeah!  We made it!  I wasn’t too worried about the plume passage, as I wrote yesterday, but it was still wonderful to hear last night that Cassini had contacted Earth and was sending home its precious cargo of Enceladus data.  Not only did we survive, which was never much in doubt, but the spacecraft was healthy and the data were looking good.  This morning, the beautiful images of Enceladus posted on the Cassini raw image Web site provided further confirmation that things had gone well.  And there was more welcome news from the folks at Goddard Spaceflight Center in Maryland, where our Composite Infrared Spectrometer (CIRS) instrument was built and is operated.  The CIRS data have been collected from the Deep Space Network, compiled at JPL, transferred to Goddard, and everything looks as expected.  The data are now going through the time-consuming calibration process, converting the raw bits into spectra that will reveal some of the secrets of the active south polar region.  We should be able to transfer the calibrated data to Boulder and start work on it in an hour or two–I can’t wait!

RSS Feeds and More

Carolina MartinezCarolina Martinez, JPL News Team

Thank you to all for the wonderful comments of encouragement on this new blog.  We hope we can live up to your expectations and it’s wonderful to read all the well-wishes.  For those who’d like to get updates via the RSS feed, click here to get updates directly to your computer.  You’ll find the RSS icon in the light gray panel near the top – near where it says Enceladus-flyby-Mar2008. The RSS feed is for all NASA blogs, not just this one.  Thanks for all the inputs as well, we’ll try to incorporate this feedback on future blogs.  When you submit a comment, please keep comments on the subject of this blog and please do not include links to other sites.

A preview of what’s to come . . . later today Todd will join us to tell us what the spacecraft and navigation teams are up to and we hope to post some Optical Navigation images today.  John and/or Amanda are writing up more details on plume hazards.  Meanwhile, Amanda’s at the Lunar and Planetary Society Conference and will be reporting briefly from there.  Speaking of the LPSC, there are lots of Cassini results being presented there; to get summaries on those abstracts check out this feature.

Dipping Our Toes

John SpencerJohn Spencer, Cassini Scientist on the Composite Infrared Spectrometer (bio)

Today’s Enceladus flyby is a bit more adventurous than most satellite flybys by Cassini. 
We are dipping into the jet of water vapor and ice spewing from Enceladus’ south pole, because by doing so we can take full advantage of the amazing opportunity to study
fresh samples from inside this strange world.  The mass spectrometer, dust, and plasma
instruments will be running flat-out, gathering priceless information on the composition
of the gases and the ice particles for the sixty seconds or so that Cassini will be in
the dense part of the plume.

graphic showing Enceladus flybyPlume particles are wonderful things to study, but it’s possible to have too much of a
good thing – at the speed that Cassini is going, particles as small as a millimeter in
size could cause serious damage to the spacecraft if we ran into one.  So the decision to
enter the plume was not taken lightly.  The project convened an “Enceladus plume working group”, led by fellow-blogger Amanda Hendrix, which held a series of meetings to determine whether there was any hazard to the spacecraft from flying as close as we plan to go.  Though we fly 50 kilometers (30 miles) above Enceladus’ surface, this happens near the equator and away from the plumes–the closest approach to the source of the plumes is more like 200 kilometers (120 miles)–see the graphic on the left by David Seal (E3 is the official name of today’s Enceladus flyby).

We know from the Cassini images, and from observations from the dust detector during the July 2005 flyby, that there are many ice particles a few microns (a few 1000ths of a
millimeter) in diameter in the parts of the plume we’ll be traversing, and these provide
juicy samples without posing any hazard.  But was there any way that much bigger
particles could be lofted into Cassini’s path?  We reviewed the observational evidence,
and theories about how the plumes might work (for instance, figuring out how much gas it would take to accelerate an ice grain of a dangerous size to a speed high enough to reach the spacecraft) and we decided that the danger was very small.  Still, it will be good to hear from the spacecraft when it turns its antenna back to Earth and sends home word that the flyby was safely negotiated.  That will be at 7:05 p.m. Pacific time this evening, not that I’m counting…

Future flyby plans could probe even deeper into the plume, coming as close as 100 kilometers (62 miles) from the source on November 2, 2009 (though this depends on official approval of the proposed extended mission).  But we’ll review the results from this flyby before committing to anything that close.  If Cassini reports “come on in, the water’s fine!”, as we expect, we’ll dip our toes in a little further next time.


Post-Flyby Data Less Than Two Hours Away

Todd BarberTodd Barber, Cassini Lead Propulsion Engineer (bio)

Hello again from the realm of Cassini engineering!  Even though many of the engineering events of this flyby are now behind us, I wanted to take a minute to say how much the flight teams (science AND engineering) have enjoyed all your wonderful blog comments.  We are chomping at the bit for the first data playback in less than three hours, just like you.  A lot of hard work and planning went into this daringly close flyby of Enceladus.  We hope all our efforts will be rewarded very soon.
As an engineer, I’m looking forward to seeing telemetry that would show we’ve come through the Enceladus flyby safely and successfully.  However, as a scientist-wannabe myself, I think I’m more anxiously awaiting the first images and science results from this historic encounter. 
Fortunately, my engineering “plate” has been full today, helping the hours and minutes pass more quickly.  Even in the midst of this encounter, we have been preparing to open the main-engine cover and execute a roughly 17-second rocket firing on Thursday afternoon PDT.  This maneuver will change Cassini’s zippy speed by only 2.76 meters per second, or 6.17 miles per hour, but yet it is critical to set up our next encounter, a 1,000-kilometer (621-mile) Titan flyby on March 25, 2008.  Even as we pause briefly to revel in what we hope is the success of our Enceladus rendezvous, the spacecraft always looks forward to the next encounter and a continued flood of science data.  Go, Cassini, go!

Raw (Unprocessed) Images In

Carolina MartinezCarolina Martinez, JPL News Team

To see all of the raw images go to this Web site and click on the “latest images” icon or select Enceladus as the target:

Below is a selection of different views.

Our blog team is still poring over their data but I’m sure they will check in soon. Todd will have a spacecraft checkout report and Amanda and John will fill us in on their reaction to seeing their data come in.  We will also have a post from Linda on all the questions they hope to answer from their treasure trove of goodies.


Enceladus Data Back on Planet Earth!

Todd BarberTodd Barber, Cassini Lead Propulsion Engineer

Howdy, folks.  We’ve just heard from the Cassini mission control area and
can report that the data downlink has started!  The signal was received via
the Goldstone, California, Deep Space Network station at roughly 7:01 pm
PDT.  Our engineers are assessing the first post-flyby data as we speak,
but everything looks great at first blush.

The downlink data playback will run through the evening, and we hope to
have raw images hit the Cassini Web site before dawn, about 5 a.m. Pacific,
Thursday, March 13.  Check here for images:

Just click on the “latest images” icon…or you might select Enceladus from
the drop-down menu.

Yay!  Does this job rock or what?  Now let the flood of science commence!


Enceladus – Then and Now

Linda SpilkerLinda Spilker, Cassini Deputy Project Scientist

As the hours tick down and Cassini gathers data during our closest flyby yet of Enceladus I am thinking about the two Voyager flybys of the Saturn system that took place over 25 years ago.  How in the world did we miss the Enceladus plumes back then???

In a nostalgic mood, I am looking over some of my old Voyager timelines today.  (Yes, I actually kept all of my old timelines from each Voyager flyby)!  I see that we took pictures of Enceladus during the first Voyager flyby in 1980, discovering a tiny, sparsely cratered world at the heart of the E ring. I remember wondering how such a tiny moon could create such a huge, tenuous ring.  That mystery was one of the puzzles left for Cassini to solve.  Remember that Cassini is in orbit around Saturn so we do multiple flybys, but the Voyagers only flew by Saturn, and each only had one encounter with Enceladus in their itinerary.

Enceladus< This view of Enceladus was taken by Voyager 2 in 1981.

My timelines show that we planned to take more pictures of Enceladus during the Voyager flyby in 1981.  Alas, the Voyager 2 scan platform containing the cameras and spectrometers stuck just as we flew close to Saturn, and the observation of our outbound pictures and spectra of Enceladus (and everything else!) were never made.  I remember feeling sad about how much unique data we wouldn’t get on that fateful day and the days that followed.  What discoveries remained for some other lucky scientists to make, I wondered?  Little did I know that I would be one of those lucky scientists! Good thing Cassini is there to keep an eye on Enceladus!

Flyby Complete – Scroll for 'Enceladus Data Back on Earth'

Carolina Martinez Carolina Martinez, JPL News Team

Here is a video clip of the Cassini mission control area with Grant Eller, mission control engineer at the helm, confirming with the Deep Space Station in Goldstone, California that data has begun transmitting from Cassini to Earth. Play clip 

Here is a clip of fellow blogger Todd Barber: Play clip

Follow this link to download high-resolution, broadcast-quality clips:

Be sure to look for Todd Barber’s post: “Enceladus Data Back on Earth!” Also, as some of you have probably noticed, some of the blog entries are out of order.  We apologize for this bug.  We are working on a solution, though, and appreciate the feedback. 
A lot of you have been posting really excellent questions, and the Cassini team has been really great about responding to them individually or responding to them through a blog entry…….but we haven’t had a chance yet to post all the answers to the blog.  I am working on pulling the questions and answers together and we plan to post that in the coming days, as time permits. 
That is it for today.  Check back tomorrow morning with new postings from our scientists and engineers.  Images are expected to hit the raw image site at around 5 a.m. PDT at:

Enceladus Flyby Underway

Amanda HendrixAmanda Hendrix, Cassini Scientist on the Ultraviolet Imaging Spectrograph (bio)

Well our flyby sequence has officially started!! Last night we began our observations of Enceladus! We are very distant, but getting closer all the time, over the northern hemisphere.  The first observation was a long stare at Enceladus, which is still pretty far away and small, but this is a nice opportunity to do compositional measurements. As of 9 a.m. Pacific, radar observation of Enceladus began, which will give us an idea of the roughness of this side of Enceladus, at centimeter scales.  The closest approach is around 1 p.m. Pacific today.

The entire flyby sequence is on-board the spacecraft, and there’s really no opportunity to change it at this point. We’re in it for good. However, the sequence gets thoroughly tested prior to uplink, so we are confident that things will go smoothly. The next time we hear from Cassini will be tonight after the flyby at around 7 p.m. Pacific.  We are being fairly cautious, though: even though Cassini will come about 30 miles of the surface, while flying through the plume we will be 120 miles from the surface. So we’re “dipping our toes” in the plume a little more than we’ve done before!

Cheers from Houston,

Main Engine Cover Successfully Closed

Todd BarberTodd Barber, Cassini Lead Propulsion Engineer

Greetings again from Cassini engineering, as we are literally a day away from our date with destiny and a super-close Enceladus flyby. Another engineering event, critical for the health and safety of the spacecraft, has gone off without a hitch. Earlier this morning, around 4 am Pacific Daylight Time (PDT), we closed (or deployed, in our nomenclature) the main-engine cover. As we planned to head in closer to Saturn and Enceladus, we recognized the potential for a slight dust hazard, not uncommon during our multi-year orbital tour of the ringed planet. Even with minute dust grains, our delicate main-engine columbium coating could be damaged with hypervelocity impacts, so occasionally we have to deploy our “baby-carriage” cover to protect our twin main engines.

Our thermal control and devices team reports to me yet another successful deployment of the main-engine cover, an event that has taken place roughly three dozen times since launch over ten years ago. I can usually tell when this happens as a propulsion engineer because the closing of the cover helps to warm up the area around the engines, causing the temperature readings I monitor to increase. After the dust hazard is behind us, we’ll again open (or stow) the main-engine cover, although this will occur around 7 pm PDT on Wednesday. In other words, this event will occur after the thrilling E3 flyby, an important engineering event to be sure, but likely one that will be buried in the excitement of the prospect of new Enceladus science results mere hours away.