Culling Through It All!

Linda SpilkerLinda Spilker, Cassini Deputy Project Scientist
It’s been a whirlwind here at JPL as the data from the Enceladus flyby comes pouring in, and we scientists have been doing our thing . . . culling through it all! Sometimes there’s so much to choose from that I feel like a kid in a candy story.  There is much excited email chatter among the many Cassini teams, all suggesting awesome findings.  These first-looks are being matured by the team members, and we have begun to share and compare results. 

You may have already seen the press release from JPL explaining that the
Cosmic Dust Analyzer (CDA) had an unfortunate software hiccup at closest approach to Enceladus and their data was not recorded. The CDA instrument measures the composition of small particles that hit the instrument, which is an important thing to do at Enceladus to understand its geyser-like jets.  But like all small bumps on the road to discovery, we will find out what happened, fix it and get on with our business about the Saturn system.  And what an amazing system it is. 
On the very bright side, all of the other fields and particles instruments and remote sensing instruments, worked perfectly at Enceladus.  They are returning fantastic data and providing an incredible look around and inside the plume, and of the surface.  The fields and particles instruments are complementary to CDA and provide information on particle composition and characteristics, among other things.   
As soon as possible in the week or two ahead, we will be able to announce the preliminary results to the world.  Until then, I’m waiting like the rest of you are for these data sets to be analyzed, since the first-looks are looking so great!  Stay tuned for some Earth-shaking — I mean moon-shaking — results!

A Great Day for Engineering

Todd BarberTodd Barber, Cassini Lead Propulsion Engineer (bio)

Hello again from the other side of Enceladus!  I’m happy to report that the engineering teams are very pleased this morning with this historic Enceladus flyby.  I attended a 9 am weekly meeting regarding engineering subsystem status, and all engineers reported a very nice flyby.  The team includes attitude control, command and data subsystem, power, propulsion, thermal, fault protection, and telecommunications engineers.  Our telecom guy brought in some nice pastries from his favorite European bakery to help celebrate another successful Cassini encounter.  Just before the meeting, I did manage to find five minutes to look at the latest Enceladus images from the flyby–they’re breathtaking!  Makes all of the hard work seem more than worthwhile.

We’d love to celebrate this engineering success, but as I mentioned in a prior blog, the show must go on.  We did open the main-engine cover successfully last night, which is vital for today’s main-engine maneuver.  Around 5:30 pm PDT, as seen on the third rock from the sun, Cassini will fire its main engine for about seventeen seconds.  So, as our science teams digest a treasure trove of new data, the engineering teams are looking forward to a thrilling Titan low-altitude flyby in a few weeks.  This friendly give-and-take between science and engineering isn’t always easy, but it’s truly wonderful how the teams support each other and pull off things that seem impossible.  I’m honored to be a part of this world-class team, and I thank you for your continued support of Cassini!


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!

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!


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. 


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

As I write this we are just minutes before closest approach.  The spacecraft is now completing the big turn to get its mass spectrometer and dust instruments facing forward, to best sample the plume as we fly through.  I have the simulator that we use for planning the observations open on my desktop, so I can ride along in my imagination as the flyby happens.  You can ride along too, using the cool CASSIE tool on the Cassini Web site .  After closest approach, we’ll begin the temperature scans of the south pole.  Weeeeeee!

Cassies first screen

Enceladus Approach Maneuver Cancelled — We're Good to Go!

Todd BargerTodd Barber, Cassini Lead Propulsion Engineer (bio)

Monday greetings from the engineering side of the Cassini flight team!  I’m very happy to report via this blog that we just decided to cancel the final Enceladus approach Orbit Trim Maneuver (OTM), OTM-148, and its back-up maneuver labeled JTM-148.  Since these burns were scheduled after midnight local time in California last night and tonight, respectively, I don’t think many of us will mourn their cancellation.  These final targeting maneuvers for Wednesday’s thrilling close flyby of Saturn’s icy companion were deemed unnecessary, largely due to excellent performance at OTM-147 four days ago.  In fact, we were able to save a little bit of propellant for the mission overall by canceling these maneuvers!
We took an engineering image of Enceladus yesterday evening, a so-called “optical navigation” or “op-nav” image.  Rather than being used for science, we actually used this image to measure the position of Enceladus very accurately with respect to known background stars.  This helped us improve our knowledge of Enceladus’ location, and the result of this latest op-nav is that Cassini remains on target for its historic rendezvous with Enceladus and its icy south polar plumes in two short days.  We in engineering wish our science colleagues on the mission a very fruitful and eye-opening close encounter with one of Saturn’s most intriguing moons.