A great thread by @justinhendrix over on Twitter:

The solar eclipse Monday is set to overshadow another significant event for space nerds like me. Tomorrow, August 20th, is a special day.

August 20th is the 40th anniversary of the 1977 launch of @NSFVoyager2, the first of two Voyager probes to explore the outer planets.

Its sister probe, Voyager 1, was launched 16 days later. These two probes represent one of humanity’s most extraordinary achievements.

Voyager 1 is nearly 13 billion miles from Earth; it takes a ray of light more than 19 hours to travel from here to its position.

Voyager 2 is nearly 11 billion miles and 16 light hours away. 5 years ago Voyager 1 entered interstellar space, on 25 August 2012.

Incredibly, both spacecraft are still sending scientific information about their surroundings through the Deep Space Network.

In the late 1960s that NASA determined a once-every–176 year alignment would allow a spacecraft to to visit all four outer planets.

Voyager delivered the first single frame photo of the Earth and the Moon together from space. twitter.com/justinhen…

The probes carried radioisotope thermoelectric generators powered by plutonium, and carry an array of scientific instruments. twitter.com/justinhen…

The computers aboard the Voyager probes each have 69.63 kilobytes of memory in total. That’s about enough to store one average .jpg.

The probes used assembly languages such as FORTRAN. Recently the Voyager program hired a new FORTRAN programmer. www.popularmechanics.com/space/a17…–1-voyager–2-retiring-engineer/

The probes visited all the giant outer planets, including Jupiter, Saturn, Uranus and Neptune. They made numerous important discoveries.

For instance, erupting volcanoes on Jupiter’s moon Io, the first evidence of volcanic activity elsewhere in the solar system. Alt text

The volcanos on Io were discovered by a JPL Voyager imaging scientist named Linda Moribito Kelly. www.planetary.org/blogs/gue…

Voyager discovered an ocean beneath the icy crust of Jupiter’s moon Europa, waves and fine structure in Saturn’s icy rings, Neptune’s…

Great Dark Spot and 1,600 kilometer-per-hour winds, geysers erupting from the polar cap Neptune’s moon Triton, and eventually…

The termination shock where supersonic solar wind slows down, forming the final frontier of the solar system. ibex.swri.edu/students/…

You can see many of the images that the Voyagers took during their trek through the outer planets here: www.jpl.nasa.gov/voyager/g…

Jupiter. twitter.com/justinhen…

Saturn. twitter.com/justinhen…

Uranus. twitter.com/justinhen…

Neptune. twitter.com/justinhen…

And the famous Pale Blue Dot photo, which inspired Carl Sagan’s speech, which we should all listen to & consider www.youtube.com/watch

The Voyagers also famously carry a Golden Record, which carries the sounds of earth into space- Sagan’s idea. www.npr.org/2017/08/1…

Blind Willie Johnson’s ‘Dark Was the Night, Cold Was the Ground’ is one of the songs now in interstellar space www.youtube.com/watch

The Voyagers represent the best of humanity. The best scientific thinking, engineering, ambition, curiosity, passion, arts and culture.

We’d do well at this moment, 40 years hence, to look at the legacy of these probes, and consider what we can learn from their journey.

It’s more than the sum of their scientific discoveries. They explore the universe, but they also tell us something about ourselves.

Our best selves. Voyager is the best of humanity. We need to remember the aspiration to be our best selves, to advance the species.

So enjoy the eclipse, but spare a moment tomorrow at 10:29 AM Eastern to remember the launch of @NSFVoyager2, a great human achievement.

Here is an excellent hour on the history of Voyager from the BBC. h/t @acinonnap www.bbc.co.uk/programme…