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Space NASA Science

Cassini's Saturn Mission Goes Out In A Blaze Of Glory (npr.org) 74

An anonymous reader shares a report: Controllers at NASA's Jet Propulsion Laboratory sent a final command Friday morning to the Cassini spacecraft orbiting Saturn. Not long after, accounting for the vast distance the message traveled, the order was received, putting the craft into a suicidal swan dive, plummeting into the ringed planet's atmosphere. Flight Director Julie Webster called "loss of signal" at about 7:55 a.m. ET, followed by Project Manager Earl Maize announcing "end of mission" as the spacecraft began to break up in Saturn's atmosphere. "Congratulations to you all," Maize announced to applause. "It's been an incredible mission, incredible spacecraft, and you're all an incredible team." With Cassini running on empty and no gas station for about a billion miles, NASA decided to go out Thelma & Louise-style. But rather than careen into a canyon, the plucky probe took a final plunge into the object of its obsession. Just how obsessed? Its 13-year mission to explore the strange world of Saturn went on nearly a decade longer than planned. It completed 293 orbits of the planet, snapped 400,000 photos, collected 600 gigabytes of data, discovered at least seven new moons, descending into the famed rings and sent its Huygens lander to a successful 2005 touchdown on the surface of yet another moon, Titan. Also read: Cassini's Best Discoveries of Saturn and Its Moons.
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Cassini's Saturn Mission Goes Out In A Blaze Of Glory

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  • RIP (Score:5, Insightful)

    by gerrythegreat ( 5071827 ) on Friday September 15, 2017 @10:47AM (#55202557)
    RIP Cassini you done good stuff for them science folk.
    • Cassini is dead, long live Cassini
  • Some mission scientists were cheering and others crying when the final signal was lost, confirming the end of the craft and mission. It was launched in 1997! https://en.wikipedia.org/wiki/... [wikipedia.org]
    • Re:Cassini (Score:4, Funny)

      by magusxxx ( 751600 ) <magusxxx_2000@y[ ]o.com ['aho' in gap]> on Friday September 15, 2017 @11:38AM (#55202857)

      And yet phones aren't expected to last past their year warranty. ;)

      • It was launched in 1997!

        And yet phones aren't expected to last past their year warranty. ;)

        Well... if the phone cost as mush as the spacecraft, it probably would. I'm guessing that cost was in the $1.4b "pre-launch dev" part. From Cassini–Huygens [wikipedia.org]:

        The total cost of this scientific exploration mission was about US$3.26 billion, including $1.4 billion for pre-launch development, $704 million for mission operations, $54 million for tracking and $422 million for the launch vehicle.

    • Re:Cassini (Score:5, Informative)

      by Arnold Reinhold ( 539934 ) on Friday September 15, 2017 @11:44AM (#55202903) Homepage
      NASA-TV showed displays of the S-band and X-band carriers prior to loss of signal, sharp spikes above a noise background. The S-band signal faded out first, as the spacecraft began to lose pointing accuracy for its high gain antenna when the thrusters could no longer keep up with the atmospheric forces. The X-band signal persisted for a few more seconds (more antenna gain at the shorter wavelength, presumably) before it faded out, but then it reappeared briefly above the noise before going away forever. It was as if the spacecraft gave one last effort to stay in touch with home. A very sad moment.
      • Re: Cassini (Score:5, Informative)

        by Anonymous Coward on Friday September 15, 2017 @12:09PM (#55203063)

        You have it backwards. The upper display was x band. It faded first because the antenna has higer gain at the higher x band frequency, so the pointing is more critical. S band was on the bottom and faded a bit later because the dish has a wider beamwidth at 2 GHz than it does at 11 GHz.

      • by Tablizer ( 95088 )

        Can anyone by chance find a Youtube vid of those band screens during the dive?

  • I saw what you did there.

  • Contamination (Score:4, Interesting)

    by lazarus ( 2879 ) on Friday September 15, 2017 @10:58AM (#55202621) Homepage Journal

    TFA states that plowing the craft into Saturn was necessary to prevent contamination of the moons, but the mission began with dropping a Huygens Lander [wikipedia.org] on Titan.

    Seems like nobody has make the distinction between bacterial contamination and radioactive contamination. I suspect that the latter is actually the concern as the probe used an RTG for power and thus it was safest to de-orbit it into Saturn.

    RIP Cassini. Thanks for all the science.

    • Re: Contamination (Score:5, Informative)

      by Strider- ( 39683 ) on Friday September 15, 2017 @11:06AM (#55202657)

      It was a worry over biological contamination. JPL (and NASA) have very specific protocols for planetary protection. Huygens went through some extreme decontamination prior to launch. Cassini, as an orbiting probe, not so much. Also, at launch we didn't know as much about the Saturn system and it's moons. The RTGs aren't really a concern, as they're not all that radioactive. Pu-238 is primarily an alpha emitter, and is mostly just toxic.

      • Re: Contamination (Score:4, Informative)

        by almitydave ( 2452422 ) on Friday September 15, 2017 @11:41AM (#55202879)

        It was a worry over biological contamination. JPL (and NASA) have very specific protocols for planetary protection. Huygens went through some extreme decontamination prior to launch. Cassini, as an orbiting probe, not so much. Also, at launch we didn't know as much about the Saturn system and it's moons.

        Specifically, we learned that Enceladus has a large subsurface ocean, at the bottom of which may lie hydrothermal vents. Since those on Earth are often teeming with life, we didn't want to risk contamination of Enceladus' oceans.

      • by XXongo ( 3986865 ) on Friday September 15, 2017 @12:07PM (#55203045) Homepage

        TFA states that plowing the craft into Saturn was necessary to prevent contamination of the moons, but the mission began with dropping a Huygens Lander [wikipedia.org] on Titan. Seems like nobody has make the distinction between bacterial contamination and radioactive contamination. I suspect that the latter is actually the concern as the probe used an RTG for power and thus it was safest to de-orbit it into Saturn.

        It was a worry over biological contamination.

        Exactly. Huygens was battery powered: after the battery died, it dropped to a temperature of about 90K, barely above liquid nitrogen. No terrestrial life will contaminate anything at that temperature.

        Cassini, on the other hand, contained several RTGs. In the unlikely case that it did impace into Titan, the RTGs would keep a tiny fraction of the probe debris above the liquidus point of water, and hence in principle terrestrial contamination could survive and even multiply.

        The scenario is absurdly unlikely, of course, but it can't be absolutely ruled out, and since it can't be ruled out, it triggers the planetary protection protocol.

        • by arth1 ( 260657 )

          The scenario is absurdly unlikely, of course, but it can't be absolutely ruled out, and since it can't be ruled out, it triggers the planetary protection protocol.

          Yet it doesn't stop us from dropping dozens of probes and landers onto Mars and Venus...
          Nor did it stop the even more microscopic risk of contaminating life on Saturn itself - slingshoting Cassini at the sun or outer space would have been even "safer".

          I have a suspicion that the real goal was to go out in a spectacular "suicide", in order to create publicity. Nothing wrong with that, but be open about it.

          • by Baloroth ( 2370816 ) on Friday September 15, 2017 @01:23PM (#55203741)

            Yet it doesn't stop us from dropping dozens of probes and landers onto Mars and Venus...

            All of which followed pretty strict decontamination procedures. Well, maybe not the Venus probes, but if Earth bacteria manages to survive on Venus, I say more power to them.

          • by XXongo ( 3986865 ) on Friday September 15, 2017 @01:33PM (#55203841) Homepage

            The scenario is absurdly unlikely, of course, but it can't be absolutely ruled out, and since it can't be ruled out, it triggers the planetary protection protocol.

            Yet it doesn't stop us from dropping dozens of probes and landers onto Mars and Venus...

            Mars probes are sterilized and follow a rigorous planetary protection protocol. This has a large and annoying effect on the Mars program: we're not allowed to land on the spots on Mars that have even a slight likelihood of having life or an environment where any possible form of Earth life could survive.

            Venus probes-- well, the surface of Venus is hostile to any possibly terrestrial forms of life, and while the upper atmosphere could possibly harbor extreme acidophiles, not anything that's likely to contaminate a probe. In any case, though, the missions to Venus went there before planetary protection protocols were put in place.

            Nor did it stop the even more microscopic risk of contaminating life on Saturn itself

            Cassini hit the Saturn atmosphere at a velocity of 34 km/sec-- 76,000 mph. No microscopic life is going to survive.

            Think of it as hitting with the energy of a 1/3 kiloton bomb.[ref [arxiv.org]]

            - slingshoting Cassini at the sun or outer space would have been even "safer".

            "Safer" but utterly impossible. The reason the mission was over was it was pretty much out of fuel.

            I have a suspicion that the real goal was to go out in a spectacular "suicide", in order to create publicity. Nothing wrong with that, but be open about it.

            Uh, no.

          • by Strider- ( 39683 )

            Yet it doesn't stop us from dropping dozens of probes and landers onto Mars and Venus...

            As I mentioned above, there is an entire policy (and in fact a portion of the organization) dedicated to planetary protection. Surface landers, such as what are sent to Mars (and in the future Europa and/or Enceladus) are required to go through very strict decontamination regimens before they are launched. In addition to being assembled in clean rooms (as are all the probes), they are baked/irradiated/cleaned with caustic chemicals/etc... prior to launch to sterilize them as much as possible. They don't wan

          • by Ranbot ( 2648297 )

            I have a suspicion that the real goal was to go out in a spectacular "suicide", in order to create publicity. Nothing wrong with that, but be open about it.

            I don't think the goal was publicity, but I'm sure they don't mind the publicity either. If you read the article at the end it mentions there was science to be done that could only be obtained [hopefully] by a suicidal plunge through the atmosphere. Previously the probe could never get close enough to Saturn to record its exact magnetic tilt or directly analyze the atmosphere, both of which they are hoping to get readings of from Cassini's final descent. With the limited fuel remaining the suicide run was p

          • Slingshot it using what?

        • Re: (Score:3, Interesting)

          by Tablizer ( 95088 )

          dropped to a temperature of about 90K, barely above liquid nitrogen. No terrestrial life will contaminate anything at that temperature.

          Not necessarily. Spores could survive in a frozen state, and then later if a liquid water volcano or similar erupts, the spores could awake and seep toward the core. Unlikely and/or many years away, but not impossible.

    • While it's possible there is life on Titan, it seems improbable; considering the extremely low temperatures. Titan has some of the conditions for life, but a lot of available free energy isn't one of them.

      • The problem with statements like this is that every time we've pointed at somewhere on Earth and said 'That part is missing some essential Requirement for Life,' turns out we've been wrong.
      • by XXongo ( 3986865 )

        While it's possible there is life on Titan, it seems improbable; considering the extremely low temperatures. Titan has some of the conditions for life, but a lot of available free energy isn't one of them.

        Titan almost certainly has a subsurface ocean, which could have hydrothermal energy, which on Earth life can use as an energy source. We don't know of exchange between the subsurface ocean and the surface, but there might be exchange of material. Therefore, even though it's unlikely, we don't want to contaminate the surface.

    • Seems like nobody has make the distinction between bacterial contamination and radioactive contamination. I suspect that the latter is actually the concern as the probe used an RTG for power and thus it was safest to de-orbit it into Saturn.

      I'm pretty sure that because the Huygens lander [wikipedia.org] was designed to land on the surface that NASA already made the distinction decades ago. Landing on the surface might introduce bacterial contamination and that's why most spacecraft are assembled in clean rooms.

  • Farewell Cassini. You were an explorer, a pioneer, a scientist, a teacher, but most importantly, you were an inspiration to us all. You may be gone, but the legacy you left and the knowledge you taught us will outlive us all. Goodbye old friend, you will be missed.

  • Saturn's super advanced civilization is now upset with us for crashing our spaceship into one of their shopping malls. They are preparing their battle fleet for a retaliatory strike.

MESSAGE ACKNOWLEDGED -- The Pershing II missiles have been launched.

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