Many people remember exactly where they were when humans first set foot on the Moon.
But for those of us born after 1969, we’ve got to hang on to other epic moments in spaceflight
history.
I vividly remember watching the first launch of the space shuttle in 1981 when I was 9
years old, and I remember when NASA’s Voyager spacecraft swept past each of the outer giant
planets in the Solar System: Jupiter, Saturn, Uranus and Neptune.
It’s been nearly 40 years since the Voyagers blasted away from Earth, on their voyage into
interstellar space, and here’s the most amazing part.
They’re still operational.
Still working hard to deliver us science, from the outer Solar System.
As I record this video, Voyager 1 is the most distant object ever created by human beings,
more than 20 billion kilometers away from Earth, more than 4 times the distance to Pluto.
Here’s the really mind bending part.
Voyager 1 is the farthest object we know of in the entire Solar System.
But I’m getting ahead of myself, it’s time to look back, nearly 40 years and remember
the Voyager missions and their amazing accomplishments over the decades.
The Voyager missions were developed in the early 1970s to take advantage of a rare alignment
of the giant planets in the Solar System.
With the right launch speed, trajectories and planetary slingshots it could be possible
to send a spacecraft past each of the large planets in the Solar System: Jupiter, Saturn,
Uranus and Neptune.
Over the course of their primary mission, the spacecraft were to visit Jupiter and Saturn,
but the mission controllers couldn’t help but add Uranus and Neptune to the list, reprogramming
the spacecraft as they explored the Solar System to continue onward.
Between them, the twin spacecraft observed 4 planets, 48 moons, as well as their rings,
and magnetospheres.
Their original mission should have been only 5 years, but they were extended to 12, and
now, almost 40 years later, they’re still going and going.
Voyager 2 lifted off first, on August 20, 1977 with a trajectory that gave it the option
to add Uranus and Neptune later on in its trip.
Voyager 1 went second on September 5, 1977 but followed a faster, shorter trajectory.
Their first destination was Jupiter, the largest planet in the Solar System.
Voyager 1 arrived at the giant planet on March 5th, 1979, passing within a few hundred thousand
kilometers of Jupiter’s cloud tops.
It observed the incredible storm systems in Jupiter’s upper atmosphere, and helped to
discover that Jupiter, like Saturn, has a ring system.
Perhaps the biggest discovery at Jupiter was with its moons.
The Voyagers discovered that Jupiter’s innermost large moon Io has active volcanoes, spewing
lava high into space - the first time volcanism had been seen anywhere else in the Solar System.
They observed cracks on the surface of Europa and Ganymede, indicating that both worlds
have some kind of subsurface ocean beneath an icy crust.
Between them, the two spacecraft took more than 33,000 pictures of Jupiter and its moons.
Next up was Saturn, and in my opinion, the highlight of the whole Voyager program.
Although the Ringed Planet had already been visited by Pioneer 11 in 1979, the Voyagers
took things to the next level.
Voyager 1 arrived in November, 1980 and sent back high resolution images of Saturn, as
well as its moons and rings.
Voyager 1 was selected to make a closer flyby of Titan, Saturn’s largest moon and the
second largest moon in the Solar System.
It discovered that Titan’s atmosphere is mostly made of nitrogen, like Earth.
Unfortunately it was too dense to see down to the surface.
We’d need to wait for Cassini to show us what’s down there.
Voyager 1 discovered that Saturn’s upper atmosphere seems to contain less helium than
scientists were expecting, which indicates that the helium is slowly sinking down into
the center of the planet.
Voyager 2 arrived 9 months later in August, 1981.
It passed within 41,000 kilometers of Saturn and made even more observations of the planet
and its environment.
Together, the Voyagers provided the first tantalizing hint of geysers emanating from
Enceladus - which Cassini confirmed decades later.
And together they discovered the huge hexagonal vortex at the planet’s north pole.
At this point, the Voyagers parted company.
Voyager 1 continued on from Saturn with no more destinations, while Voyager 2 performed
a slingshot maneuver that put it on course to visit the outer ice giants.
Voyager 2 still had two more destinations to go.
Its next destination was Uranus in January, 1986, when it passed within 81,500 kilometers
of the planet.
This was the first time (and so far last) time that any spacecraft ever reached Uranus.
These are the only close up pictures we have of Uranus and its moons, thanks to Voyager
2.
The spacecraft made several new discoveries about Uranus.
The planet was flipped over onto its side by some collision in the ancient past.
Voyager discovered that not only does Uranus have a magnetosphere, but the it’s twisted
into a corkscrew shape that trails behind the planet as it orbits the Sun.
Voyager 2 observed the planet’s rings, and collection of moons.
But perhaps the strangest discovery was its moon Miranda.
Voyager 2 observed huge cracks and canyons on the surface of Miranda as deep as 20 km.
Is it possible that the moon was smashed up in the ancient past, and then reformed from
the shattered pieces?
The final stop on the Grand Tour was Neptune, visited by Voyager 2 in the summer of 1989.
I remember this image vividly, on television and in the newspapers, it was the summer I
graduated from high school.
Voyager 2 passed just 4,950 kilometers above Neptune’s north pole, closer than any other
object during its voyage.
Since this was Voyager 2’s last stop, NASA was willing to throw caution to the wind.
The spacecraft discovered that the winds on Neptune blow faster than anywhere else in
the Solar System, triple the speed of Jupiter.
It discovered that the planet has storms swirling across its surface like the other giant planets.
It fine tuned estimates of Neptune’s mass, discovered six new moons and observed its
ring system up close for the first time.
Perhaps the most tantalizing was the close up images of Neptune’s moon Triton.
A bizarre moon that dominates the Neptunian system, and orbits backwards from all the
other large moons in the Solar System.
Scientists think it was a captured Kuiper Belt Object, stolen in the ancient past.
With Triton in its rearview mirror, Voyager 2 carried on, out into deep space.
Once the Grand Tour was over, but the Voyagers still had more science to do.
We’ll talk about that in a moment, but first I’d like to thank:
Anton Velmozhniy John Clark
Alex Boisselle
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In August, 2012, the spacecraft officially made the leap to interstellar space, escaping
the Sun’s heliosphere.
In case you weren’t familiar, the heliosphere is a region of ionized plasma that surrounds
the Sun, blown out into space by its solar wind, like an inflated balloon.
This bubble is what separates the Sun’s solar wind from the collective solar winds
of all the other stars in the Milky Way.
The Voyagers crossed the region dominated by the Sun into interstellar space.
Even though they’re now more than 20 billion kilometers away, they still emit signals of
about 23 watts; as much power as a refrigerator light bulb.
Although, by the time these reach Earth, they’re a billion-billionth of a watt.
And yet, they continue onwards.
Now, let’s look into the future.
What happens next for these spacecraft?
At their current pace, they’ll reach the Oort Cloud in about 300 years.
That’s the huge cloud of icy objects thought to surround the Solar System, and the source
of the long period comets we see from time to time.
Unfortunately, they’ll be dead much sooner than that.
Sometime in the next couple of years, the the radioisotope thermoelectric generator
that powers the spacecraft isn’t going to be able to give it enough electricity to keep
its equipment going.
The gyroscopes that allow NASA to re-orient the spacecraft will cease operations.
The data recorder will shut down.
And in 2020 or so, NASA will start to shut down their scientific instruments one by one
as the power levels continue to decline.
Finally, by 2025 to 2030, the Voyagers won’t have enough electricity to do anything else.
We got 40 years from them, but we’ll be lucky to get to 50.
And then, they’ll continue to drift off into the darkness.
Their journey through the Oort Cloud will last 30,000 years, and in 40,000 years or
so, they’ll get within a couple of light-years of the star Gliese 445.
But the Voyagers were built to last.
Each was equipped with a Golden Record, containing sounds and images selected by Carl Sagan.
Aliens who encounter the Voyagers will enjoy the sounds of Earth, like whales, surf and
the wind, as well as musical selections.
Oh, and a handy map to Earth using a map of pulsars.
The records were made of gold and etched with a sample of Uranium-238, which has a half
life in the billions of years.
Future alien civilizations could use this to determine when the Voyagers were constructed.
Ann Druyan, the co-creator of Cosmos, says that the records themselves will be playable
for a billion years.
The Voyager spacecraft were some of the most ambitious robotic spacecraft humans ever built.
They carried our senses out to Jupiter and Saturn, and then Voyager 2 helped us see Uranus
and Neptune for the first time ever.
We still depend on and reference the images and observations from these hardworking spacecraft
for so much of our understanding of the outer Solar System.
I’ll miss them when they’re gone.
What about you?
Do you have nostalgic memories about the Voyager spacecraft?
Let me know your thoughts in the comments.
In our next episode, we look at the Van Allen Belts.
The radiation that surrounds the Earth; another dangerous hazard that astronauts face - as
if they need any more ways that the Universe is trying to kill them.
That’s next time.
Of course, I’ve got a playlist of videos about the Voyager missions.
First up, a video from NASA a few years ago when Voyager 1 reached interstellar space,
Tom Scott visits the Voyager control room at NASA, Vsauce has message for the future,
including Voyager’s golden record, and then a pair of longer lectures from NASA scientists
working with Voyager.