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Space NASA

Why Didn't Voyager Visit Pluto? 98

Posted by timothy from the personal-spat dept.
Flash Modin writes: NASA built the twin Voyager spacecraft for a rare planetary alignment that put Jupiter, Saturn, Uranus, and Neptune within reach at once. Originally, Voyager 1 was programmed to see Pluto in 1986, but managers targeted Saturn's planet-like moon Titan instead. That choice made Pluto impossible by vaulting Voyager 1 from the orbital plane. Interestingly, Voyager 2, which couldn't reach Pluto, made the case for New Horizons by revealing Neptune's moon Triton as a kidnapped Pluto. "I'm very glad that they chose not to go to Pluto in 1986," says New Horizons head Alan Stern. "We'll do a better job at Pluto with modern instruments than they would have, and they did a much better job at Saturn..."
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Why Didn't Voyager Visit Pluto? More

Why Didn't Voyager Visit Pluto?

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  • I'm not saying it was aliens (Score:5, Funny)

    by known_coward_69 ( 4151743 ) on Saturday June 27, 2015 @03:05PM (#50003231)
    but there is a secret alien base on Pluto

  • Because titan has ice, pluto isn't even a planet (Score:5, Insightful)

    by Anonymous Coward on Saturday June 27, 2015 @03:09PM (#50003251)

    Titan has the possibility of extraterrestrial life, the finding of which would mark one of the biggest discoveries in the history of the human race and end all doubts that we are alone in the universe.
    Pluto is a cold rock on the outskirts of the solar system.
    Which one would you rather investigate?

    • Re: (Score:2)

      by rossdee ( 243626 )

      Back at the time of Voyager, Pluto was a planet

      • Back at the time of Voyager, PlutoÂÂa planet

        Isn't a dwarf planet still a planet? Or did it get demoted to an asteroid recently and I missed it?

    • If you read the commentary at the time, they simple wanted to project one out in the plane of the solar system and one out towards its axis. I believe Voyager 1 still hasn't passed pluto if projected back down onto its orbital plane.

      • Re:Because titan has ice, pluto isn't even a plane (Score:5, Informative)

        by NormalVisual ( 565491 ) on Saturday June 27, 2015 @05:27PM (#50003825)
        I believe Voyager 1 still hasn't passed pluto if projected back down onto its orbital plane.

        Voyager 1 is almost 20 billion miles away from us [nasa.gov] now, and is traveling about 35 degrees out of the ecliptic. Some really rough trigonometry shows that if you project that down onto the ecliptic, it's still about 16 billion miles away from the Sun, which is almost three times the length of the long axis of Pluto's entire orbit.

      • Re:Because titan has ice, pluto isn't even a plane (Score:5, Informative)

        by techno-vampire ( 666512 ) on Saturday June 27, 2015 @07:11PM (#50004153) Homepage
        One of the things accomplished by taking Voyager I behind Titan was a direct measurement of the thickness and density of Titan's atmosphere. They did this, btw, by measuring how much of the probe's signal was absorbed before it was completely occluded and by how long it took the signal to come back to normal strength after it came out on the other side. And to show you how good the navigation was, closest approach was less than two radii out, meaning that if it had been cut in half, Voyager would have collided with Titan instead of just passing closely. I know this, because I spent some time at JPL in the mid 1980s and am slightly acquainted with the man who came up with the idea and did most of the work involved.

    • Titan has the possibility of extraterrestrial life, the finding of which would mark one of the biggest discoveries in the history of the human race and end all doubts that we are alone in the universe.
      Pluto is a cold rock on the outskirts of the solar system.
      Which one would you rather investigate?

      Whichever one has a Steak'n'Shake.

      • Whichever one has a Steak'n'Shake.

        $4.99 double steakburger combo and a kickass chocolate milk shake? I'm in.

    • Titan has the possibility of extraterrestrial life, the finding of which would mark one of the biggest discoveries in the history of the human race and end all doubts that we are alone in the universe.

      Sure, finding extraterrestrial life would be a HUGE discovery; however, the total amount of energy on Titan is negligible and the variety of energy gradients do not lend themselves well to anything but the simplest forms of life. These would be extremely difficult to detect and even more difficult to identify as actual life.

      Europa, with its water and tidal heating from Jupiter is a much more likely candidate for finding extraterrestrial life. The whole ice shell thing is a real issue so I would not pin all

  • Avoiding Yuggoth is smart! (Score:3)

    by trenien ( 974611 ) on Saturday June 27, 2015 @03:23PM (#50003331)
    Come on! Remember your classics. Despite whatever disinformation later propaganda agent/writers may have claimed, Lovecraft himself revealed that Pluto is actually Yuggoth.

    You really don't want to anger those living there now. Those NASA engineers knew what they were doing...

  • Carl Sagan thought Titan was more important (Score:5, Insightful)

    by mbone ( 558574 ) on Saturday June 27, 2015 @03:51PM (#50003417)

    Carl Sagan thought it was more important to get close to Titan, which made a gravity assist for Pluto impossible. I think he hoped that there would be good pictures of the hypothesized Methane seas, but in the event the Titan haze made the surface just a blur.

    What the close Titan approach did provide was a radio occultation of the Titan atmosphere, showing how deep it was and something of its structure.

    In space flight, as in life, you have to chose, and they chose Titan.

  • Pluto was on away at the time (Score:5, Funny)

    by backslashdot ( 95548 ) on Saturday June 27, 2015 @04:02PM (#50003459)

    Pluto was on away on a planetary midgets conference.

  • https://en.wikipedia.org/wiki/Planetary_Grand_Tour (Score:5, Informative)

    by Richard Kirk ( 535523 ) on Saturday June 27, 2015 @04:13PM (#50003493)
    The original "Planetary Grand Tour" project would have visited Pluto, but it relied on a planetary alignment that would have to have started in 1976 or 1977. It was originally announced as a single craft, which became four before it was cancelled (I don't remember that, but for a brief history, see https://en.wikipedia.org/wiki/... [wikipedia.org]). This was replaced by the two Voyager satellites launched in 1977. The later launch date made Pluto harder to visit, but it was still possible.

    • Re:https://en.wikipedia.org/wiki/Planetary_Grand_T (Score:4, Interesting)

      by Solandri ( 704621 ) on Sunday June 28, 2015 @01:41AM (#50005221)
      While the planetary alignment was convenient, it isn't exactly necessary on RTG-powered spacecraft. Pioneer 11 [honeysucklecreek.net] visited Jupiter, then flew to almost the opposite side of the solar system to visit Saturn. Longer travel time (and greater chance of equipment failure during that time) is the only drawback.

      Another factor working against a Pluto encounter was the lack of sunlight that far out. During Voyager 2's encounter with Neptune (which was slightly further away from the sun than Pluto at the time), sunlight was so dim that NASA had to reprogram the cameras to take longer exposures than they were originally designed. Then someone calculated that Voyager 2 would be moving so fast that the photos of Neptune would be blurred just by the changing parallax between the spacecraft and Neptune. So they programmed the spacecraft and cameras to rotate slightly during the exposures, effectively panning the camera to cancel out the changing parallax.

      All this happened so quickly they got just one shot at it, and they had to do it blind. By the time the first near photos reached Earth, if they had turned out to be blurred, any correcting instructions sent to Voyager 2 would have arrived after the spacecraft had passed Neptune. So NASA wasn't even sure if the closest Neptune and Triton photos would even be aimed correctly. Heck, they weren't even sure they were going to make it to Triton (Voyager 2 flew less than 5000 km over Neptune's North pole to get to Triton). But as it was the last major destination and they'd recently discovered an atmosphere on Triton, they figured what the heck and rolled the dice. As it turned out, they got everything right, and Voyager returned some spectacular Neptune and Triton photos.

      A Pluto encounter would've run into the same problem. Except Pluto is a much smaller target than Neptune, whose mass (and therefore gravity) is much less accurately known so properly aiming the camera is even trickier. Even New Horizons (with newer, more sensitive cameras) is going to have to use the same panning trick Voyager 2 used at Neptune. New Horizons is moving fast enough it could cover the distance from the Earth to the Moon in less than 8 hours, so all the close-up photos and measurements of Pluto are going to be over in a matter of hours. And it's basically guiding itself - providing the most accurate measurements we have of Pluto's mass so we can fine-tune its trajectory as it approaches Pluto.
      • I wonder what's the furthest planet we have put something in orbit around? Trying to orbit Pluto would be interesting

  • Hello my baby! (Score:4, Funny)

    by MobileTatsu-NJG ( 946591 ) on Saturday June 27, 2015 @04:19PM (#50003509)

    Why Didn't Voyager Visit Pluto?

    Because of the bark, you dummies!

  • No coins to pay the Ferryman to navigate from the sea to the netherworld.

  • It was to avoid her destroying our spacecrafts as proportionate response to demoting her from the planetary status.

  • What don't I like about this headline? (Score:5, Informative)

    by wonkey_monkey ( 2592601 ) on Saturday June 27, 2015 @04:29PM (#50003557) Homepage

    Why Didn't Voyager Visit Pluto?

    Why is this asked as a question, when the summary does in fact have the answer? Why not just headline it thus:

    Why Voyager didn't visit Pluto

    Then I'd be less likely to mistake it for another speculative piece of guff from a professional blog writer, which we already have plenty of.

    • Re: (Score:2)

      by vux984 ( 928602 )

      I agree with you. Especially about the speculative 'guff' from click-hungry bloggers.

      I do have a question though; especially given the content of your post: why did you phrase your subject as a question instead of a declarative statement?

      Was it deliberately ironic or just inadvertently so?

    • Still, it's refreshing to see an astronomy story that isn't from StartsWithABang.

      If he'd written it, the title would be "Why NASA should have made Voyager visit Jupiter" and the article would be a rambling string of ad hominems, baseless assumptions, and Monday morning quarterbacking.

  • The real reason (Score:5, Interesting)

    by gvanbelle ( 1400327 ) on Saturday June 27, 2015 @04:41PM (#50003607)
    I had the opportunity to ask Ed Stone, the JPL Director & Voyager scientist, this question. His rather glib answer was, "well, Titan was 3 hours away, and Pluto was 3 years away - and I had to make payroll." I think the broader answer is that JPL assumed they'd get another mission funded if they simply skipped it (and they almost did).
  • Except Pluto. Attempt no landing there.

  • If he didn't get a planet named after him, the dog certainly didn't deserve one.

  • Imo, while Pluto is an interesting planet to check out. It has less promising details than other planets. For all we know it could be very well just a bigger dwarf planet. There's definitely more action around Jupiter and Saturn because these giants have so many moons that are like a mini solar system.

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