Back in 1973, a spacecraft named Pioneer 11 launched into space, on a mission to explore
the Asteroid belt and the solar system's largest planets, the mighty gas giants.
Travelling at 32,000 miles per hour, which is 51,500 kilometres per hour, Pioneer 11 sped
away from Earth on a journey that would ultimately help pave the way for the future, Voyager probes.
Although this mission was an incredible success story, in the end, it wasn't
without its problems. Plagued with a number of malfunctions, Pioneer 11 has sometimes
been referred to as the "luckiest spacecraft" ever launched. Mainly, because it narrowly
avoided a devastating collision with an object, that at the time, was unknown.
So how close did the lucky spacecraft come to being obliterated?
This is the true story of the time, NASA nearly crashed into an unknown object in the outer solar system.
Pioneer 11 was the sister spacecraft to Pioneer 10 that launched the year before it. Both were
designed and managed as "pathfinders" for the future Voyager probes, to ensure that
they could travel through the Asteroid belt and survive Jupiter's immense radiation environment.
When it came to space missions such as this one, building two identical spacecraft was normally
a good idea, as the possibility that one might fail seemed high. After all, no spacecraft had
ever ventured through the Asteroid belt, which is a doughnut shaped region just beyond Mars
that contains Asteroids ranging in size from dust particles to rock chunks as big as Alaska.
Although there was no significant chance of hitting anything large,
hitting a few hundred grains of an asteroid would be just as bad.
As originally conceived, Pioneer 11 was intended as a backup to Pioneer 10. However, by the time
the second spacecraft launched, the first had already safely passed through the Asteroid belt,
becoming the first to do so, and was well on its way to its encounter with Jupiter.
Pioneer 10 was the first spacecraft to visit Jupiter, successfully completing
its observations while plunging deep into the mighty gas giant's powerful radiation belts,
and as it turned out they were every bit as strong as expected.
After a 92 minute round trip, electronic systems functioned erratically, resulting in some major
data losses, but Pioneer 10 did manage to emerge intact, although battered and singed.
During its flyby of Jupiter, Pioneer 10 obtained the first close up images of the planet,
charted its intense radiation belts, located the planet's magnetic field
and discovered that Jupiter is predominately a liquid planet.
As the primary mission had been a success, mission planners placed its sister craft, Pioneer 11 on
a different trajectory, one that would take advantage of Jupiter's massive gravitational
field, slingshotting it back across the solar system, so that it could also encounter Saturn.
In December 1974, while using the gas giant for a gravity assist, Pioneer 11 captured the
most detailed images of the Great Red Spot ever seen. As these dramatic images reveal.
At its closest point to Jupiter, Pioneer 11 was travelling faster than any human made object
at the time, more than 106,000 miles per hour, which is more than 171,000 kilometres per hour.
Although on a different path, In the end, Pioneer 11’s experience at Jupiter was
much like Pioneer 10’s, with erratic electronic behaviour but no permanent
damage. And so while still in communication with Earth, the hardy spacecraft was on its
way to the ringed world, Saturn. But it certainly wasn’t out of the woods yet.
Since it launched, Pioneer 11 endured a number of malfunctions, including the momentary failure of
one of its power supplies, called the RTG boom, a problem with an attitude control thruster which
controls the orientation of the spacecraft, and a partial failure of the asteroid dust detector,
which analysed dust particles. But regardless of these malfunctions, it had successfully
traversed the Asteroid belt and survived the bombardment of Jupiter's immense radiation.
Then in late July 1979, nearly 5 years later, Pioneer 11 began its first observations of
Saturn. But by that time, the famous Voyager 1 and Voyager 2 had already been launched,
had completed their fly-bys of Jupiter, and were on their way to Saturn as well. Taking
advantage of a rare planetary alignment of the outer planets that happens once every 175 years,
reducing their journey time between planets.
Based on this, NASA decided to place Pioneer 11 on a path that would provide maximum support for
Voyager 2, which would eventually use Saturn for a gravity assist, so that it could later
visit Uranus and Neptune. Completing the Voyager grand tour of the solar system.
However, although this planned trajectory seemed like the safest and most worthwhile
in aiding Voyager 2, it almost caused an unexpected end to Pioneer 11's already
perilous journey, as the spacecraft nearly collided with an unknown object.
Without warning, on September 1st 1979, Pioneer 11 suddenly began
detecting something very large and unknown in front of it for around eight seconds,
and its magnetometer recorded a major disturbance in Saturn's magnetic field.
It then became clear, that the spacecraft had pierced through the magnetic "wake"
of a previously undiscovered moon roughly 125 miles wide,
which is 200 kilometres wide. It passed the mysterious undiscovered moon, at a distance of
no more than a few thousand miles. The closest it had come to anything since leaving Earth.
Soon after the near collision, the moon was tentatively identified as Epimetheus,
an object discovered to have been captured by Pioneer's imaging the previous day.
However, after both the Voyager spacecraft passed Saturn, it was found that there are actually two
similar sized moons in the same orbit. The suspect, Epimetheus but also, the moon Janus,
causing some uncertainty about which one was the object that Pioneer 11 nearly collided with.
To add a little bit more confusion, both the moons exchange a little momentum as they get
closer to each other, causing them to trade orbits once every four years,
meaning the inner moon becomes the outer and the outer moon becomes the inner. Creating a bizarre
orbital dance unlike any other in the solar system as can be seen in this incredible clip.
After the near miss, Pioneer 11 passed within just 13,000 miles of Saturn’s cloud tops, which is only
21000 kilometres. During the encounter, it sent back groundbreaking data on the planet, its rings,
and many of its satellites, including 440 incredible images. Data that would have never been
collected if it had been on a slightly different trajectory or arrived at Saturn slightly earlier.
Although the achievements of both the Pioneer spacecraft were somewhat eclipsed later on by
the far greater Voyager probes, they were true to their name, they were "Pioneers"
when it came to the exploration of the Asteroid belt and the gas giant planets.
After leaving Saturn, Pioneer 11 continued outwards, in the general
direction of Sagittarius, towards the centre of the Galaxy. Eventually,
it passed the orbit of Neptune in February 1990, beginning its long
journey into interstellar space, and becoming one of only a handful of spacecraft to do so.
The so called "lucky" spacecraft, which narrowly missed an undiscovered moon
and that was only planned to operate for 21 months, ended up functioning,
in some way or another, for more than 22 years. An incredible feat of human engineering.
After one of the most exciting journeys made by any spacecraft,
Pioneer 11's final signal was received in September 1995, when it was more than 4
billion miles from Earth. Which is 6.4 billion kilometres from Earth.
Now, it is a dormant relic, floating through the darkness of space, serving only as a remember
of a once great mission that revealed so much about our fascinating solar system.
I hope you enjoyed this video, I thought it was a really interesting story that reveals
the dangers and the mysteries of space. And how far we have come in exploring our solar system.
If you did enjoy it, tap the like button and subscribe,
there are plenty more videos to come. Thank you for watching and I'll see you next time.