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  • Every 176 years, the four planets in our outer solar system present us with a rare opportunity.

  • Theyll align in such a unique way, that it’s possible to use their gravitational

  • forces to slingshot from one planet to the next.

  • A PhD student figured this out back in 1965 during his summer job at the Jet Propulsion

  • Laboratory, using just a slide rule and simple computer programs.

  • This insight became part of an ambitious mission to send two probes and golden records out

  • into space for a grand tour.

  • The Voyagers took some of the first detailed snapshots of planets and moons.

  • And after cruising for over 43 years with 18 billion kilometers traveled, theyre

  • taking humanity into the next great beyond: interstellar space.

  • The Voyager probes are two obscure looking robots, weighing about 800 kilograms with

  • giant arms and big ears designed to sense what’s out there.

  • And it took 1,500 engineers and scientists to bring these robotic explorers to life.

  • I started working on Voyager right out of college.

  • It was my very first job as an engineer.

  • Good morning, and welcome to the 5 o'clock edition of voyager update, I'm your host, Suzanne

  • Dodd.

  • So, Voyagers were really developed in the early 70's.

  • They were launched in 1977, and the original goal was just a 4 year mission to explore

  • the Jupiter and Saturn systems.

  • With the possible opportunity to go further out to Uranus & Neptune, the NASA engineers

  • developed a mission within a mission, outfitting the probes with 11 different instruments redundant

  • systems and autonomous controls.

  • They each also carried a golden record for a potential extraterrestrial to decipher.

  • That's a time capsule of us here on Earth.

  • And if any other being were to find it, they would know what we on Earth were like in 1977.

  • We have liftoff of the Titan Centaur carrying the first of two Voyager spacecraft to extend man’s

  • senses farther into the solar system than ever before.

  • As they hit each planet, the Voyagers beamed back observations of Jupiter’s turbulent

  • atmosphere, Saturn’s moons, and Titan’s hazy layers.

  • I really think that the Neptune encounter was probably the most significant thing in

  • my career.

  • I was involved with all the design on the closest approach sequence,

  • I really felt like I owned what the spacecraft was going to execute.

  • And it went flawlessly.

  • We got a big send-off afterwards.

  • The Planetary Society had Chuck Berry come and play because his Johnny B. Goode song

  • is on the record.

  • I'll always remember that as one of the highlights of my career.

  • If not, the highlight.

  • As the Voyagers cruised beyond our neighborhood, Carl Sagan convinced NASA to tell Voyager1

  • to flip its camera around, and take the first planetary family portrait.

  • That’s us, 6 billion kilometers away, the pale blue dot.

  • And that should have been the end of the mission.

  • But to everyone’s surprise, the Voyagers kept going, entering a place no one had ever

  • seen before, the final frontier.

  • Since flying past all the planets, we turned off the instruments basically that were designed

  • to take pictures and repurposed the memory for this long Voyager Interstellar Mission.

  • The space beyond the planets is very empty, very dark, very cold.

  • And as you travel further and further, you see less strength of the Sun.

  • The heliosphere is the bubble of charged particles around our star, our Sun.

  • They expand out, and then eventually they stop.

  • And they stop due to the pressure from the interstellar medium and the wind from the

  • interstellar medium.

  • The interstellar medium wind is actually created by exploding stars, supernova, all the other

  • stars and material that are out there are pushing on our bubble and that is what keeps

  • the shape of it.

  • In 2012, Voyager 1 started detecting changes in its immediate environment.

  • We started to see dropouts in particles from the Sun, and increases in particles from the

  • interstellar medium.

  • They dropped down, and then they'd go back up again.

  • And then on August 25 of 2012, they just dropped down and stayed down.

  • And similarly, the particles from interstellar space do the opposite.

  • They bumped up, and they stayed up.

  • The plasma instrument on Voyager 1 wasn’t working properly, so it was hard to confirm

  • if it really crossed the boundary.

  • There was a lot of debate and by a nice coincidence there was a solar flare that happened 13 months

  • previously.

  • Finally reached Voyager 1, and that solar flare excited the plasma around the spacecraft.

  • That was when the particle instruments said, "Hey, we're in interstellar space.

  • We see the change in the particles.”

  • Voyager 2 has an active working plasma science instrument.

  • So we saw the density of the plasma change almost instantaneously.

  • As they travel through the interstellar medium, the sheer scale of the universe really comes

  • into perspective.

  • It's studying the interaction of our star, our Sun, with what's beyond it.

  • And when you study our Sun, you're studying the energy that's giving us life here on Earth.

  • Voyager 1 detected unexpected pressure at the edge of our solar system for the first

  • time, giving scientists clues about the dynamics we might find in other star & planetary systems.

  • To keep data like this coming in, the Voyager Flight team has to make careful energy management

  • decisions We use a nuclear power source that decays

  • at 4 watts per year, and so one of our biggest concerns now, and what will really limit the

  • lifetime of the mission, is just how much power the spacecraft has to continue operations.

  • We also have to pay attention to the temperature of the spacecraft.

  • We don't want to freeze the propellant lines that we use to keep the antenna pointed at

  • the Deep Space Network.

  • It's 20 hours to get the signal from Earth to the spacecraft, and 20 hours for the spacecraft

  • to turn around and acknowledge that they got that signal.

  • Which really means that the Voyager spacecraft have to be autonomous.

  • They have to be able to sense for themselves what's going wrong, put itself in a safe state

  • if it feels like it's under stress.

  • Our day to day engineering activities relate toward keeping the spacecraft warm enough,

  • making determinations of whether we have to turn off another instrument heater or not,

  • and then which instrument would you turn off?

  • All of these instruments have been on since 1977.

  • Now these principal investigators who are in their 80's now, they don't want to see

  • their instrument turn off.

  • The Voyager engineers are still manning this mission today until the signals eventually

  • stop.

  • One day we'll come in to the office, and it won't be there.

  • And that will be the loss of the spacecraft.

  • And that will be a very sad day but also one where you can reflect on how great the mission

  • was. I think Voyager has touched humanity in many ways.

  • And I think that connects us, as humans, to space exploration.

Every 176 years, the four planets in our outer solar system present us with a rare opportunity.

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太陽系邊緣之外有什麼? (What Lies Beyond the Edge of Our Solar System?)

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    林宜悉 發佈於 2021 年 01 月 14 日
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