Wrote about the Voyager probes two days ago in my blog - The two Voyager spacecraft are the greatest love letters humanity has ever sent into the void.

Voyager 2 actually launched first, on August 20, 1977, followed by Voyager 1 on September 5, 1977. Because Voyager 1 was on a faster, shorter trajectory (it used a rare alignment to slingshot past both Jupiter and Saturn quicker), it overtook its twin and became the farther, faster probe. As of 2025, Voyager 1 is the most distant human-made object ever, more than 24 billion kilometers away, still whispering data home at 160 bits per second.

Voyager 2 was the real beneficiary of the rare outer planet alignment, as it went on the famous Grand Tour, visiting all four of the giants. It did gravity assists at Jupiter, Saturn, and Uranus. [1] shows the rough velocity of V2 over time.

Voyager 1 was directed to perform a flyby of Titan, at the cost of being thrown out of the ecliptic and being unable to visit the ice giants like its sister. But this was deemed acceptable due to Titan's high science value.

[1] https://commons.wikimedia.org/wiki/File:Voyager_2_-_velocity...

To save someone two seconds of searching,

NASA animation of Voyager 2's trajectory (time in the bottom-left corner): https://youtu.be/l8TA7BU2Bvo

I know that space is incredibly empty, but the vast expanse of space just boggles my mind so much. Even a slight miscalculation could have meant that the spacecraft hit that massive grid rotating around the orbit of Neptune.

This is great. I did not realize Voyager 2 also left the ecliptic at the end of its tour.

That happened because Voyager 2 went over Neptune's north pole rather than an equatorial trajectory. Both to get a look at a giant planet's polar regions, and because that would get it closest to the moon Triton. So Voyager 2's trajectory got bent southward out of the ecliptic plane as a result of that.

While I'm here: why didn't Voyager 2 continue to slingshot to Pluto? The answer is that its trajectory would have had to bend by about 90° at Neptune, which would have required an apex closer to Neptune's center of mass than the planet's own radius - it would have crashed into the planet instead.

How much do/can they use their own thrusters to change/correct their directions? I'm guessing it's just fractions of a degree? And needs to be extremely precise, done weeks? before reaching the next planet to slingshot around?

There isn’t much value in gravity assists from Uranus or Neptune since they move much more slowly than Jupiter and Saturn.

Yes, but the trajectory change was also needed at Uranus. It’s not only about magnitude, it’s also about direction :)

And that love letter came with a very nice mixtape. https://en.wikipedia.org/wiki/Voyager_Golden_Record

Yea, I mentioned that too.

Is this HN discussion about your blog post? If not, can you share it? I would like to read it.

Extended piece from my blog.

The two Voyager spacecraft are the greatest love letters humanity has ever sent into the void.

Voyager 2 actually launched first, on August 20, 1977, followed by Voyager 1 on September 5, 1977. Because Voyager 1 was on a faster, shorter trajectory (it used a rare alignment to slingshot past both Jupiter and Saturn quicker), it overtook its twin and became the farther, faster probe. As of 2025, Voyager 1 is the most distant human-made object ever, more than 24 billion kilometers away, still whispering data home at 160 bits per second.

Each spacecraft carries an identical 12-inch gold-plated copper phonograph record.

The contents:

- Greetings in 55 human languages.

- A message from UN Secretary-General at the time and one from U.S. President Jimmy Carter.

- 115 analog images encoded in the record’s grooves: how to build the stylus and play the record, the solar system’s location using 14 pulsars as galactic GPS, diagrams of human DNA, photos of a supermarket, a sunset, a fetus, people eating, licking ice cream, and dancing

The record is encased in an aluminum jacket with instructions etched on the cover: a map of the pulsars, the hydrogen atom diagram so aliens can decode the time units, and a tiny sample of uranium-238 so they can carbon-date how old the record is when they find it.

Sagan wanted the record to be a message in a bottle for a billion years. The spacecraft themselves are expected to outlive Earth. In a billion years, when the Sun swells into a red giant and maybe swallows Earth, the Voyagers will still be cruising the Milky Way, silent gold disks carrying blind, naked humans waving hello to a universe that may never wave back.

And it was Sagan who, in 1989, when Voyager 1 was already beyond Neptune and its cameras were scheduled to be turned off forever to save power, begged NASA for one last maneuver. On Valentine’s Day 1990, the spacecraft turned around, took 60 final images, and captured Earth as a single pale blue pixel floating in a scattered beam of sunlight — the photograph that gives the book its name and its soul.

It was the photograph that inspired this famous quote -

"Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there-on a mote of dust suspended in a sunbeam.

The Earth is a very small stage in a vast cosmic arena. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot.

Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.

The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.

It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known. "

That picture almost didn’t happen. NASA said it was pointless, the cameras were old, the images would be useless. Sagan argued it would be the first time any human ever saw our world from outside the solar system. He won. The cameras were powered up one last time, the portrait was taken, and then they were shut down forever.

That legacy of the Pale Blue Dot has been something that has been repeated to remind us again. I personally like the Cassini one - https://science.nasa.gov/science-research/earth-science/23ju...

There's also the MESSENGER family portrait https://science.nasa.gov/resource/a-solar-system-family-port...

> - 115 analog images encoded in the record’s grooves: how to build the stylus and play the record

To learn to play the record you've gotta play the record?

That thing is such a D/K pop-sci manifestation.

The writers of the Star Trek movie understood that Sagan's extra-solar artifact is merely a time capsule; humanity talking to its future self.

Some great grandchild of a millennial vinyl nerd, who lives and loves on the engineering deck of some Hyatt Regency in space, will have kept a perfectly maintained Technics, handed down across the generations, leading to a future crowd in ""Ten Forward"" being regaled by Sagan's Cosmos on a similarly well-maintained Magnavox 32-inch tube TV and VHS. "Billions of fucks were given for V'Ger to come back to us..." The meetup will be hosted by a curiously bald supermodel, a hunky but demure mensch, and an AI Carl Sagan.

The instructions aren't encoded in the grooves, that makes no sense. Rather the schematics are etched on the back sides of the records, and with those you can build the stylus and decode the images.