Our short bio: After two decades in space, NASA's Cassini spacecraft is nearing the end of its remarkable journey of exploration. Having expended almost every bit of the rocket propellant it carried to Saturn, we will deliberately plunge Cassini into the planet on Sept. 15. Why? To ensure Saturn's moons will remain pristine for future exploration—in particular, the ice-covered, ocean-bearing Enceladus, but also Titan, with its intriguing pre-biotic chemistry. Only one week remains before the spacecraft's final chapter in the skies of Saturn. What would you like to know about the science and engineering still to come for Cassini? Ask us anything!

Update at 5:11 p.m. ET: We took your questions on Friday, Sept. 8 from 3 to 5 p.m. ET (noon-2 p.m. PT, 1900-2100 GMT). Time to log off and get back to the final week of the Cassini spacecraft. Thanks for joining us here today! We hope you'll be watching on Sept. 15 during the final plunge as we stream live from mission control: http://nasa.gov/live

  • Molly Bittner, Cassini systems engineer
  • Bonnie J. Buratti, Cassini scientist
  • Scott Edgington, Cassini deputy project scientist
  • Jo Pitesky, Cassini science planning & sequencing

  • Bill Dunford, Cassini social media manager

  • Preston Dyches, Cassini media rep

  • Doug Isbell, NASA-JPL science communication specialist

  • Stephanie L. Smith, NASA-JPL social media supervisor

More info on Cassini's #GrandFinale: https://saturn.jpl.nasa.gov/mission/grand-finale/overview/

GrandFinale trailer: https://saturn.jpl.nasa.gov/resources/7628/

Our Proof: https://twitter.com/NASAJPL/status/906236473237577728

Comments: 143 • Responses: 53  • Date: 

rosulek22 karma

I'm sure the science that came out of the Cassini mission has been great, but from a lay-perspective the photography has been absolutely stunning. I always thought that being the "mission photographer" (planning the camera activity) for a planetary probe would be probably the best job in the world.

  • What is the thought process for balancing scientific value vs purely aesthetic/outreach value in how the cameras are used? If there's a chance for a really spectacular shot, is the team willing to alter the orbit? That kind of thing.

  • What kind of stunning photography can we expect from the final approach?

NASAJPL28 karma

We try and choose the most scientifically valuable images, but beauty counts too. Occasionally we just go for the spectacular photo op. To change an orbit, though, we need a compelling scientific reason. The final shot (the day before mission end), we will get spectacular images of the clouds of Saturn. --Bonnie

thessnake0311 karma

How far into the atmosphere will Cassini be photographing? Is there a planned 'final shot'?

NASAJPL17 karma

The final plunge will be all about returning as much atmospheric science as possible. The final images will come the day before, and the last expected shots will be of the cloud tops where Cassini will eventually become part of Saturn. You'll be able to see raw images as they are returned at https://saturn.jpl.nasa.gov/galleries/raw-images --Stephanie

currencyofuncool17 karma

Which picture that Cassini has taken best represents how a human would see it with their naked eye?

NASAJPL22 karma

Great question! It's always been important to Cassini's imaging team to be faithful to the natural appearance of the Saturn system, and they've worked hard to ensure the color is as accurate as possible. One great example is https://photojournal.jpl.nasa.gov/catalog/PIA06193 -- Preston

Anonymoose74125817 karma

What is next for the Cassini team? Do you join existing projects or start on new ones? Or were yall already working on others at the same time? Not really sure how project teams work there.

NASAJPL21 karma

Flight team members are already going off to work on other projects: Mars (rovers and orbiters), Europa, Juno, you name it! Others are working on proposals for missions that are yet to be. And some of us will be working on "closeout", where we make sure that the precious data collected remains accessible and usable for decades to come.

hobbitsden11 karma

If you could do it over again with today's technology; what instrument(s) on the spacecraft would you add and what would you remove?

NASAJPL22 karma

There's a kid's picture book called "More More More Said the Baby"--replace "baby" with "scientists" and you've pretty much got the general feeling.

What I would add is a heck of a lot more capability to the Deep Space Network, which is the only way in which we can get information from our distant spacecraft to us (and send them instructions). Cassini only "speaks" with the DSN about every 2-3 days, and sometimes it has to use lower data rates than we the flight team would like. I would love to be able to not worry about getting enough time on the big 70 meter antennas with their sweet sweet downlink capability - Jo

NASAJPL15 karma

I wouldn't want to remove any of them, as they have all given spectacular results, but I would improve a few with the later-generation technology we have now. The Visible Infrared Mapping Spectrometer would take direct images rather than build up images with mirrors. The Mass Spectrometer would be more sensitive. The fields-and-particle experiments could detect smaller particles and particles at more energies. Bonnie B.

Vectornaut10 karma

I have been following the pictures sent by Cassini for bit over a year now and they are some of the most amazing things I've seen. This seems like a great victory to human engineering, to have such high quality images of planet so far away.

When did you come up with the idea to let Cassini go out in blaze of glory by sending it to dive to Saturn's atmosphere? Or was this the plan all along?

And what are the common feelings about 20 year old mission finally coming to an end? Are you sentimental or is it just another mission done and onwards to the next one?

NASAJPL21 karma

Thanks--we are all really proud of the work we've done.

The plan to go out in a blaze of glory was developed during planning for the final seven year extension--the so-called "solstice" mission. The science return from the Grand Finale--first orbits skimming the outermost edges of the F ring, then the daring dives between the innermost rings and Saturn itself--was so compelling that the science community said "no contest: this is what we want". She is really going out in a blaze of glory AND science.

And yes, many many many team members are very sentimental about this. Cassini--both the spacecraft and the team and people--have been a big part of our lives for many years, sometimes decades. The end is very bittersweet. - Jo

packmanc8 karma

In a tldr format what have you learnt from cassinis epic space journey

NASAJPL20 karma

Hydrocarbon lakes on Titan - the first standing liquid discovered in the Solar System; A spectacular water plume and subsurface ocean on Enceladus; a hexagon, storms and intriguing cloud patterns on Saturn (including a "ring of pearls"); rain on Titan; propellers and "wakes" in Saturn's complex ring system; several new moons; and so much more. --Bonnie

packmanc3 karma

First off what a great project im sure youre all intensely proud of. That's an amazing list of accomplishments. What can you say was the stand out event for yourselves?

NASAJPL10 karma

So many it's really tough to pick. I've done a lot of work planning Titan science, so one standout for me was the the first time that we saw a glint from Titan's lakes, indicating that yes, there really truly were liquid methane bodies on Titan's surface.

The ring images always knock my socks off. The images from equinox, when you could see the shadows cast by large boulders in the rings ONTO the rings still amaze me. Some of the recent high res images like https://saturn.jpl.nasa.gov/galleries/images/ had me gasping out loud and laughing in delight.

Seeing the bloody streaks on Tethys (https://saturn.jpl.nasa.gov/resources/6217/ ) was really exciting at the time and also reminds me of the enormous amount of work that followed immediately afterwards as we worked frantically to retrofit in another Tethys image targeting that same area. The planning that goes into each image usually takes months, even years, so doing a fast (meaning basically a week to plan it!) turnaround was stressful. -Jo

NASAJPL8 karma

I remember being in the JPL newsroom and hearing the plumes of Enceladus being likened to seltzer water. Seltzer water. And Cassini had tasted it with two instruments—INMS and CDA—one is for gas and one is for particles. We've found a lot of life in the salty waters of Earth, and that moment opened up a world of possibilities in my mind about places elsewhere in the solar system. -- Stephanie

mimw8 karma

Hey colleagues, I'm from WSC and work with the TDRS fleet.

With the likes of Cassini and Voyager missions reaching the end of their life, what do you think is the next logical step for deep space exploration? (minus the JWST)

NASAJPL14 karma

NASA is planning a mission to Europa, as well as another Mars Rover. One of the main scientific goals is to search for life, past or present. On the drawing boards, but not yet funded, are proposed missions to Titan and Enceladus. -- Bonnie

Baylordawg167 karma

I know the reason you want to burn up Cassini in Saturn's atmosphere is so you don't contaminate any of Saturn's moons. But Is that really a possibility? Wouldn't Cassini just stay in orbit around Saturn forever?

Additional question: What is Saturn composed of? Is it mainly hydrogen?

NASAJPL10 karma

This is true. The chance of Cassini impacting one of the moons is very small, but the chance is not zero. Additionally, the science that can be gathered when the Spacecraft plummets through Saturn has been determined to be the most valuable way to end the mission. -Molly

ZMareBeaux6 karma

Hi Cassini team!

What are some possible ways that the research from this mission may directly impact our lives on Earth?

P.S. My 3 year old niece says: "Be brave Cassini!", as she has been following the journey closely.

NASAJPL8 karma

Tell your niece that we say thank you! My oldest daughter was just under three when Galileo arrived at Jupiter, so my girls have grown up following along. They like to say that Cassini is my favorite child. :-)

Learning about other planets and moons, how they're different than Earth and how they're the same, tells us a lot about out own planet. For example, the famous image from Titan's surface, taken by the Huygens lander (https://photojournal.jpl.nasa.gov/catalog/PIA08115) looks like it could've been taken here on Earth through an orange filter.

The Saturn system itself is like a miniature solar system; studying it tells us more about how our solar system may have formed and how it continues to evolve. - Jo

And the way in which we explore--the way we build and operate and plan these missions--is something that helps us learn to run projects here on Earth.

NASAJPL4 karma

There are multiple ways where Cassini can directly impact our lives on Earth. One way is improving our knowledge of how giant planets work, how solar systems form, and what physical processes occur under conditions that we are not familiar with in daily life. Hundreds of upcoming students will use the data as the basis of their research as they become scientists. We are also impacted by the generation of new technology used to fly spacecraft. This technology eventually makes it into the public arena where it can be used in the technology that we use in our day-to-day life. -Scott

Patches675 karma

Is there anything you hope to learn from slamming Cassini into Saturn? Will it be able to broadcast any vital information before it burns up?

NASAJPL13 karma

Cassini is doing a quick costume change from orbital mission to planetary probe. That means that the spacecraft will be sampling the upper part of Saturn's atmosphere, and blasting back that precious data almost as soon as it's recorded on board. That's all been carefully planned to maximize science return. - Jo

Oldman_Underhouse5 karma

Your work is constant inspiration to so many people. To me, Cassini and the images it has sent especially. Which is why I was happy about your #CassiniInspires campaign (had to create a poster of the final moments to honor the end of this 20 year old mission)

Will you be releasing some collection of all the artwork somewhere?

Also will you be having some kind of live stream of the final moments? Or just the JPL panel afterwards

NASAJPL10 karma

CiroFlexo5 karma

Since the flow of information from Cassini will end soon, what stage are you at in processing the data that you have already received? Is it all processed and ready for analysis, or is there still a backlog of information that y'all have downloaded but has yet to be deciphered?

NASAJPL10 karma

We process the data within a few days of receiving it, as we're very excited to see the results. Validating and calibrating the data takes a few more days, and then scientists take a few months analyzing, modeling, and understanding it. Within 6-12 months, the data is deposited in NASA's Planetary Data System (PDS) where anyone can access it. Further discoveries can come months or years later, as improved models and ways of analyzing data are developed. Bonnie

Kajiim4 karma

Are there any current plans for a Galileo/Cassini style mission to Uranus or Neptune?

NASAJPL6 karma

Yes. See the link named "study" inside this new Web feature from JPL about a recent study of new mission concepts for the Ice Giants.

https://www.jpl.nasa.gov/news/news.php?feature=6942

-- Doug I.

Brijesh15504 karma

First of all, congratulations to the entire team on such momentous achievements.

  1. I have read the reports of not wanting to contaminate the Titan and other objects, but how high was the risk that team decided to sacrifice the spacecraft? Like, were you very sure they could contaminate these space objects with organisms from earth?

  2. Are there any missions planned in follow-up to Cassini, or any developments in progress?

NASAJPL7 karma

Thanks for the congratulations.

  1. The chance of Cassini eventually colliding with Titan or Enceladus is quite small but it's not zero, which meant that it was too large to risk.

  2. There are several proposed missions that would return us to the Saturn system; these were all submitted under the latest New Frontiers call. Some would look at Saturn, some would look at the moons; we will need to wait until we see what's selected by the process. Of course, we'd all love to go back. :-) - Jo

plegobuilder4 karma

How long after the 15th will it take to process all the data you have collected?

NASAJPL9 karma

We will put all the data into NASA's Planetary Data System (PDS) within a year of the Mission's end, where it will be available to scientists and the public. We will be analyzing the data for years. Pan (a small moon embedded in Saturn's rings) was discovered on Voyager images 10 years after they were taken. We expect to be making discoveries from the data for many years to come. Bonnie

WardAgainstNewbs4 karma

If you could do anything different about the Cassini mission, what would it be (if any)?

NASAJPL10 karma

The original design had a scan platform, in which the instruments could have been pointed independently from the spacecraft. In my opinion, it would have been nice to have had such a platform, so we could take remote sensing and dust/charged particle measurements together. And of course a longer mission would have been nice, at least through a full Saturn year. Bonnie

WardAgainstNewbs3 karma

Who decides whether to create a mission video like the "Grand Finale?" Are there funds allocated to make these / plans to do them for each mission?

IMO, the Grand Finale video is one of the most inspiring space videos on the internet, and more quality pieces like that would go a very long way in inspiring a future generation of scientists, engineers, and even just normal people to care about space.

NASAJPL6 karma

Thank you! We thought Cassini deserved something befitting the mission's legacy. It has many uses, including illustrating how the key events in the mission unfold. Check out this article that compares the animation with the real images that inspired it: (https://saturn.jpl.nasa.gov/news/3016/making-cassinis-grand-finale/) -- Preston & Bill

Tw0Sevenths3 karma

Is there any plan in case Cassini does somehow survive entry far beyond expectations? Or just collect as much data as possible until you lose contact?

NASAJPL8 karma

We will just collect data until we lose contact. We don't have any plans beyond that. Bonnie B.

coryrenton3 karma

for future missions, are there any interesting viable ways of having craft refuel itself indefinitely?

NASAJPL8 karma

Refueling is useful and being studied for Earth orbiting missions, but not outer space missions. Alternatively, electric propulsion provides a method to extend the life of spacecraft propulsion systems. -Molly

maikgroenewegen3 karma

Is there any way for the public to follow the telemetry in realtime during the final moments?

NASAJPL7 karma

Yes! We'll be live streaming from inside mission control at http://nasa.gov/live, http://youtube.com/nasajpl and http://facebook.com/NASAJPL. You can also see a realtime simulation of the spacecraft views at http://eyes.nasa.gov/cassini and signal downlink via the Deep Space Network at https://eyes.nasa.gov/dsn/dsn.html Happy streaming! -- Stephanie

LilyVanBurgh3 karma

At what time eastern will Cassini die? We got a farewell going over here.

NASAJPL8 karma

Loss of signal (LOS) is expected at 4:55 AM Pacific Daylight Time. Saturn's atmospheric conditions could change this slightly - Jo

elba_q3 karma

What plans do you have for #CassiniInspires? What is the best way to contact you? I want to know because my husband wrote a piano piece for Cassini and we want all of your team to be able to hear what you and your work have inspired. (https://youtu.be/-1iwurenb-M)

NASAJPL4 karma

Thank you. We'll check it out! Many #CassiniInspires pieces will be posted at: (https://saturn.jpl.nasa.gov/mission/cassiniinspires/) -- Bill

CiroFlexo3 karma

Even though it's been over a decade since it landed, the Huygens probe was probably one of my favorite aspects of the Cassini mission. Since you often have to balance cost with potential scientific benefit, do you see a future for similar, one-off style probes like Huygens, or is there simply greater benefit in long-term orbiters like Cassini?

NASAJPL5 karma

Each type of mission has its purpose, driven by compelling scientific goals. An orbiter gives the "big picture", providing a reconnaissance of the target as a whole. A lander is the next step, providing ground truth in at least one area. The next step, a rover, tells us about the diversity of the surface (or lake, in the case of Titan). The decision to have an orbiter, lander, or rover, is based on where we are in the process of scientific discovery. Bonnie B.

fohjr3 karma

Congratulations for the incredible and inspiring work you all do! I always wonder if there was any chance of Cassini colliding with little rocks from Saturn's rings? Especially on these last few orbits. From pictures, it looks like Cassini went really close to the rings, but maybe not. How close exactly?

Thanks again, :)

NASAJPL7 karma

The first time that we went through the gap between the rings and the planets (which is around 1200 miles across, give or take), colliding with dust particles was EXACTLY what the flight team was worried about. Hitting something small at 77,000 mph can really ruin your day. :-) We oriented the spacecraft so that the large radio antenna acted like a sort of shield, protecting most of the instruments in the event of a collision.

Some of our orbits did pass slightly into the innermost edge of the rings. Data on those passes is still being analyzed - Jo

Brijesh15502 karma

  1. How does Cassini know how to communicate (the location) of the Earth? Or does it send data in every direction?

  2. How was the orbits around Saturn, its satellites and its rings planned? Was it an intricate planning or some amount of surprises involved?

NASAJPL4 karma

  1. Cassini uses its High Gain Antenna to point directly to Earth when it communicates with the Deep Space Network antennas on Earth's surface. The attitude control team carefully plans the pointing of the Spacecraft so that this direction is held during communications periods.
  2. The orbits around Saturn are carefully/intricately planned by the Navigation team. They run a lot of simulations and models to predict Cassini's "path", and along with the engineering team maneuvers are planned to keep that on us path. These models are very close to the orbits in real life, so no big surprises here! -Molly

RoopChef2 karma

Will it go down near the poles or near the equator?

How deep into the atmosphere can it go before it can no longer transmit radio back?

Where will the cameras be pointed as it sinks?

NASAJPL5 karma

Here are a couple of visualizations showing the expected path: (https://saturn.jpl.nasa.gov/resources/7752/) | (https://saturn.jpl.nasa.gov/resources/7756/) -- Bill

NASAJPL5 karma

The spacecraft is entering near the equator. Due to the speeds that Cassini is traveling at, we will only hear the spacecraft for a few minutes before signal loss. Cassini's fields and particles instruments will be sampling the atmosphere as it enters. The region sampled would be roughly equivalent to the altitudes where satellites, ISS, and the space shuttle flies. Due to the placement of Cassini's cameras relative to the fields and particle instruments, the cameras will be pointed into empty space with the exception of one very quick cut across the rings. -Scott

Down-A-Phalanges2 karma

I was hoping your team would do an AMA! Thank you for everything you did on this mission. Been following since launch! But any my question are - will Hubble or any ground based observatories be able to see Cassini's entry into the atmosphere? Do you expect Cassini to cause scaring in the cloud tops like the shoemaker-levy comet did on Jupiter? Will the plutonium on board be completely destroyed during entry or will it be disbursed into the atmosphere? If it is disbursed would it be able to be detected by a future mission to the Saturn system?

NASAJPL2 karma

The plutonium dioxide inside Cassini's Radioisotope Thermoelectric Generators is expected to completely vaporize and be dispersed around Saturn's atmosphere, where it will soon be indistinguishable from the rest of the contents of the giant planet. -- Doug I.

Pluto_and_Charon2 karma

I never got why more massive rings = older and less massive rings = younger. Can anyone explain it for me? Thanks

Is the reasoning that rings loose mass over time? So a less massive ring must have formed in the recent past because it'll only last a few hundred million years before it disappears/decays? But if that's the case, why can't the less massive rings just be a very old ring that's decayed over 4 billion years and is now much smaller than it originally was? (and surely that's a far more likely scenario, given that collision rates were orders of magnitudes higher back during the late heavy bombardment then they were 100 million years ago?)

NASAJPL4 karma

A more massive ring system implies that there is more material to be worn away over time by the processes that operate within the ring system. You are certainly correct that there is the likelihood that the current ring system can be an "old" one that has decayed over time. This is where other lines of evidence and modeling would be needed to draw a firmer conclusion on the age of the rings. -Scott

J531132 karma

Have you exhausted the learning potential of Cassini? Is there anything else you could possibly learn from the spacecraft besides plummeting it to its death?

NASAJPL5 karma

If we've learned anything over the past 13 years in orbit around Saturn, it's that we are constantly surprised by what the data show us. So it would be pretty much impossible in my opinion to exhaust the learning potential of the spacecraft! We have multiple spacecraft orbiting Earth which are still teaching us a great deal of the planet we know best, so we're a long way from Saturn Fatigue (tm).

Plus, Cassini is still learning new tricks. Last week it did its first-ever active radar observation of Saturn. On Monday, it will do its first-ever Arecibo-like observation to find specular reflection of the Titan lakes. Twenty years in, we are still teaching the old dog new tricks. - Jo

yonaskidd2 karma

Anyone thought about what would happen to Cassini's debris in the days/months afterwards? Would it completely discintegrate or would smaller, more robust parts of the craft remain intact and endlessly bounce around in Saturn's atmospheric currents?

NASAJPL6 karma

The craft will indeed completely disintegrate and vaporize. Nothing will remain that would be identifiably Cassini. Saturn's atmospheric winds and currents will eventually disperse Cassini's atoms. - Jo

MrBark1 karma

With all of the great science that we have gotten out of both Galileo and Cassini, why hasn't there been more of an effort to launch flagship orbiters for Uranus and Neptune? As intriguing as Europa and Enceladus are with liquid oceans, I am disheartened to know that the extent of our knowledge for the ice giants are limited to the Voyager 2 fly-bys from 30 years ago. With Uranus and Neptune, we don't know what we don't know!

NASAJPL2 karma

We would LOVE to have those missions going to ice giants. They're far away, hence that much more difficult to get to. See https://www.jpl.nasa.gov/news/news.php?feature=6942 to learn more about upcoming plans. - Jo

Brijesh15501 karma

What is the team's 'most favorite' pic by Cassini? :)

NASAJPL3 karma

There are so many that it's hard to choose. But take a look at these: (https://saturn.jpl.nasa.gov/galleries/hall-of-fame/) | (https://saturn.jpl.nasa.gov/mission/top-tens/images/) Many team members are partial to the images where Saturn is backlit by the Sun, like this one: (https://saturn.jpl.nasa.gov/resources/3315/) --Bill

YellowSharkMT1 karma

I think you've done a notable job on social media outreach, especially on Twitter (which is where I spend most of my own time).

What sort of insights have you gained over the past year, in terms of connecting with people who maybe weren't aware of the Cassini mission?

Thank you so much for all of your work! It's been amazing to watch, and I appreciate the fact that you've dedicated so much effort to engaging with us regular folks. Can't express enough gratitude.

NASAJPL4 karma

Thanks so much! Like Bill said, so much of how people come to know Cassini is through its imagery. We post an "image of the week" from Cassini every Monday (in addition to scores and scores of raw images and processed science images). Getting to start my week by sharing something like this with its Ansel Adams qualities, and then seeing others share it with their friends is extremely gratifying. https://saturn.jpl.nasa.gov/resources/6302/?category=hall-of-fame -- Stephanie

NASAJPL3 karma

So gratifying to hear. What really helps is that we have a treasure trove of gorgeous images that help tell the story. --Bill

elba_q1 karma

Do you plan to have a conference (like the one you had to announce the Grand Finale mission) to let everyone know what we learned in these final moments of Cassini? I can't wait to see the final images! Congratulations on this final piece of the mission. Cassini has changed our lives and you should be very proud of it. Thank you for taking us closer to science and the universe <3

NASAJPL2 karma

Absolutely! There will be a post end-of-mission news briefing live from JPL (where Cassini's mission control is). Save the date: Sept. 15 at 6:30 a.m. PT (9:30 a.m. ET, 13:30 GMT) http://nasa.gov/live Thank you for your kind words. We love sharing this mission of exploration with you and will do so until the very end (and beyond!) as peer-reviewed science comes out from the data collected during the Grand Finale. -- Stephanie

EquinoctialPie1 karma

What kind of data will Cassini be able to measure as it enters Saturn's atmosphere?

NASAJPL3 karma

Until now, our knowledge of the upper regions of Saturn's atmosphere has been limited to watching stellar/solar photon or radio signals passing through the atmosphere. Cassini's new contribution will be the direct detection of the atmosphere as it scoops up those molecules as it dives into that atmosphere. We expect to learn about the composition (e.g. H2, He, CH4, ...) and structure (i.e. temperature versus pressure) of the neutral atmosphere. We will also learn about the charged particles (e.g. e-, H+, OH-) making up the ionosphere of the Saturn. We are also interested in learn about what molecules from the rings make it into the atmosphere. -Scott

Merari011 karma

Hi!

Is there any new, groundbreaking data that you're expecting to get, what are you guys most exited about learning from Cassini entering the atmosphere of Saturn?

NASAJPL3 karma

Until now, our knowledge of the upper regions of Saturn's atmosphere has been limited to watching stellar/solar photon or radio signals passing through the atmosphere. Cassini's new contribution will be the direct detection of the atmosphere as it scoops up those molecules as it dives into that atmosphere. We expect to learn about the composition (e.g. H2, He, CH4, ...) and structure (i.e. temperature versus pressure) of the neutral atmosphere. We will also learn about the charged particles (e.g. e-, H+, OH-) making up the ionosphere of the Saturn. We are also interested in learn about what molecules from the rings make it into the atmosphere. -Scott

vikinick1 karma

How much delay is there between what we're receiving from Cassini and what is happening?

NASAJPL3 karma

We call this "delay" one way light time (OWLT). This is the time it takes the signal to get to Earth from the Cassini spacecraft. A good average I use for this is 1.5 hours, but this time can vary during the orbit depending on how far away the spacecraft is from the Earth. During the final plunge, this OWLT will be 83 minutes. Additionally, we use the term round-trip light time (RTLT) to refer to the delay when we send commands from Earth to Cassini and have to wait to "hear back" from Cassini afterwards. This is simply one-way light time x2. -Molly

magus-211 karma

What missions will y'all be working on next?

NASAJPL3 karma

I've actually already started to work on the Europa Clipper spacecraft. I will be full-time on Europa once Cassini officially ends. Another exciting mission! -Molly

NASAJPL2 karma

There's never a dull moment in the JPL newsroom. We'll be busy in 2018 with the launch of Grace Follow-On (twin orbiters to track Earth's gravity field) and InSIGHT, our next Mars lander. It will be the first interplanetary launch ever from the West Coast of the US and put the first seismometer ever on the Red Planet. -- Stephanie

NASAJPL2 karma

I'm going to work on the mission's closeout phase for the next year. In addition, I'm a line manager for JPL's Science System Engineering group. - Jo

benjamemes1 karma

What's it like to have all that responsibility? You know, being a scientist and all. And how does it feel to have all that hard work plunge into a planet?

NASAJPL3 karma

Luckily, we are a team. We are each other's safety net. That said, the first time that you do anything which directly "touches" the spacecraft (creating or sending commands, checking to make sure we're not doing something wrong, etc) it does feel intimidating. And then you get used to it.

It's been hard work to figure out the plunge-to figure out what science to prioritize, to figure out how to change long-standing procedures to go into a new region of the Saturnian system. So it actually feels in some ways incredibly fulfilling. - Jo

forava71 karma

When did you have doubts with Cassini, if ever? Can you guys recall that one moment you were like 'uh-oh" regarding this mission?

NASAJPL2 karma

Whenever you do something for the first time on the spacecraft, there's always a bit of nervousness.

Sometimes you get a bit more nervous. A group of us were at a meeting out of town, having dinner. One person was one of the engineers responsible for overseeing the spacecraft during that particular "sequence" (meaning, 6-10 weeks worth of commands). This was during one of the first times that the spacecraft flew between the rings and Saturn. During dinner, her phone rang: it was the ACE, calling from JPL, to say that the Deep Space Network had not heard from Cassini when expected. =8-O

Turned out that there was a problem on the ground, not with the spacecraft--Cassini was just fine. But for a moment, that was very very 'uh-oh'. - Jo

forava71 karma

What is the most interesting thing you guys learned about Saturn? Anything that surprised you?

NASAJPL3 karma

Saturn held many surprises, including the plume of Enceladus and how Earth-like Titan is in some ways. Here are some highlights: (https://saturn.jpl.nasa.gov/mission/top-tens/science-highlights/) -- Bill

NASAJPL3 karma

I was in the ops room for the first dive through the gap between the Saturn and its inner-most ring. We were prepared for a lot of "dust", and planned the orientation of the spacecraft accordingly for this gap dive. After the dive, however, it was found that the dust was very minimal. Scientists are hard at work looking into this finding! -Molly

walkingwanderer1 karma

Since a probe landed on Titan already, why are you sacrificing Cassini to avoid the near-zero chance of it crashing on another moon in the Saturn system?

NASAJPL2 karma

Huygens was specially designed (and cleaned) to enter and land on Titan. Cassini's maneuvering fuel is almost gone, and the Grand Finale is the most productive way to get new science and end the mission in a controlled manner. -- Doug I.

jonasnee1 karma

which moon is the most interesting? and why is it titan?

also any upcoming missions to the Saturn system after Cassini?

NASAJPL5 karma

You misspelled "Enceladus". ;-)

Titan and Enceladus are in my book the top two most interesting, but the enormous variety in moons is also incredibly interesting. We have moons that look like ravioli, like UFOs, like the Death Star, like a walnut, like a yin-yang symbol, like a loofah sponge, like an egg...oh yeah, and some that look a bit like our moon. How am I supposed to choose "most interesting"? :-)

No approved missions to Saturn yet, but maybe one of the proposals currently being reviewed will be the first to return. - Jo