Voyager: the farthest leap humanity has ever made

Introduction

There are many space probes made by humans, all with the ulterior motive of enhancing the knowledge of humanity. There's the Hubble Space Telescope, designed for looking at the stars. You have the Curiosity rover, designed to search Mars for signs of human life. However, there are two probes that aren't like the others, two probes that took a special trajectory that only happens once every 175 years, two probes that have long outlived their lifespan, two probes that are still functioning today.

These are the Voyagers.

Beginnings

NASA had previously run the Mariner missions to send probes to orbit or fly by Mars, Venus and Mercury to study them, such as Mariner 9 on Mars and Mariner 10 on Mercury. It had also sent the Pioneer 10 and 11 probes to Jupiter and Saturn, with the ulterior motive of sending them to interstellar space, before ending contact in the 90s and early 2000s. However, in 1965, Gary Flandro discovered that in the next decade, the outer planets had aligned in such a way that using Jupiter, you could send probes to the outer planets with minimal energy required. Thus began the planning of the Grand Tour.

The Grand Tour

  • ​The Grand Tour was a program planned out by NASA and JPL to send two groups of identical probes called the TOPS probes to study the outer planets. 
  • One group would go past Jupiter, Saturn and Pluto (because Pluto was a planet then), and would launch in 1977, the year the two Voyagers launched.
  • The others would fly by Jupiter, Uranus, and Neptune, and launch in 1979.
  • This project would have cost nearly $1 billion USD in total, which is why this version never went through. Instead, it was recommended that the Mariner program be extended instead.
From Mariner to Voyager

Planning

Mariner 11 and 12

On July 1, 1972, the budget for the Mariner Jupiter-Saturn missions had been approved. Soon after, the project heads, designers, and scientists at the Jet Propulsion Lab in Pasadena all got together to start planning for the mission. Since this was a Mariner mission, the only objective the managers had in mind, based on the budget, was to only have the probes observe Jupiter and Saturn like the Pioneer mission, and Uranus and Neptune if they were lucky. The ship designers, being the smart-alecks they were, quietly nodded their heads and thought, "Forget that, let''s make sure these things reach interstellar space." For the next 5 years, they continued developing the probes, with the development remaining relatively uneventful.

The probes were built for redundancy, with each of them having the exact same systems, so that way, if one of the probes had major failures, the other could pick up the slack. That's something that space agencies don't do anymore, but at the time, probe failures were significantly more likely. They also had 2 communications systems each (because communications is important for space probes), and in fact, Voyager 2's primary comms failed in 1978, so it has been using the backup system since then.

Components

  • ​Imaging Science System (it takes photos!) - disabled on both probes
  • Radio Science System (it uses radiowaves to get info about celestial surfaces!) - disabled on both probes
  • Infrared Interferometer Spectrometer (it uses spectroscopy to study atmospheres and get temperatures!) - disabled on both probes
  • Ultraviolet Spectrometer (it uses spectroscopy to measure radiation!) - disabled on both probes
  • Triaxial Fluxgate Magnetometer (it measures magnetic fields!) - operational
  • Plasma Spectrometer (it uses spectroscopy to analyze plasma!) - broken on Voyager 1
  • Low Energy Charged Particle Instrument (measures ion and electron energy!) operational
  • Cosmic Ray System (it gathers data on cosmic rays!) - operational
  • Planetary Radio Astronomy Investigation (it gathers data from radio signals from planets!) - disabled on both probes
  • Photopolarimeter System (it bends light to gather info on planetary surfaces!) - broken on Voyager 1, disabled on Voyager 2
  • Plasma Wave Subsystem (it measures electron density!) - functional on Voyager 1, partly functional on Voyager 2
  • Computing: The Voyagers have a combined 64 kilobytes of memory and very slow chips. A modern chipset would be faster and more efficient, and would allow the Voyagers to run for much longer.

Golden Records

The Voyager Golden Records are two records that contain sounds from the Earth, music, pictures, and a video address from Jimmy Carter. The cover of the record has some information on how to play the record, as well as a bit of information about where we are.

Launch

Pre-launch checklist

  • Competition to come up with a new name because these new probes are more than Mariners? Check. (NASA admin James C. Fletcher announced the change of name to Voyager.)​
  • Two golden records with both audio and video recordings on them, as well as some introductory information about us? Check. (They also came with needles so that aliens can play them.)
  • Plutonium RTGs to power the two probes? Check. (At launch they provided ~160 watts.)

Milestones before Jupiter

  1. Voyager 2 launched on August 20, 1977, on a Titan IIIE rocket from Cape Canaveral's Launch Complex 41.
  2. A month later, Voyager 1 also launched from the same launch complex on another Titan IIIE.
  3. 2 weeks after launch, Voyager 1 took the photo that's in the background, the first shot of Earth and Moon in a single frame.
  4. Voyager 1 went past Voyager 2 on their way through the asteroid belt. (There's a reason it's called Voyager 1.)
  5. Voyager 2's primary comms went down in April 1978, and the backup system could only receive transmissions at a specific frequency, so each time a command is sent to Voyager 2, the engineers have to calculate the specific frequency on the fly using an algorithm.
  6. A year after entering, both probes exited the asteroid belt. (The asteroid belt is big.)
  7. On January 6, 1979, Voyager 1 begins the Jupiter flyby. On April 25, Voyager 2 does the same. (Now we're getting at the good stuff.)

Jupiter

The Jupiter tenure

Voyager 1 reached Jupiter in January 1979, and saw some pretty cool things. NASA commanded the probe to take a picture of Jupiter's surface every 96 seconds for the next 4 days, and stitched it together into a neat timelapse that shows Jupiter's rotation. And yes, it also features the Great Red Spot. After that prolonged photo op, Voyager focused on 4 nearby moons. 

- Europa, which has a lot of saltwater and an icy surface. It has twice the amount of saltwater that Earth has, in fact. Scientists believe this to be a potential location of life.
- Ganymede has lots of ice. By ice, I mean actual water ice, not dry ice or any other kind of ice. It also has rock. You could probably find life here as well. 
- Callisto's surface is the oldest known surface in the solar system. Also, did anyone say craters? Callisto has probably set a solar system record for the number of craters it has.
- Io, also known as hell, since it has a lot of volcanoes which erupt often with sulfur and oxygen, which often goes straight into Jupiter. Voyager 2 managed to capture one of these eruptions, and boy, does it look violent. This planet is not a potential candidiate for life, since anylife on its surface will die.

Jupiter timelapse

Io - Voyager 1

Europa above Jupiter, with the shadow of Io - Voyager 1

Jupiter - Voyager 2

Yes, Jupiter has rings - Voyager 2

Callisto - Voyager 2

Io erupts - Voyager 2

Ganymede - Voyager 2

Saturn

What goes down around Saturn

In April of 1979, Voyager 1 was given a course correction to prepare for its Saturn flyby. Turns out, this course correction had also set it on a crash course for Titan, which was probably not a good thing (citation needed). The course was corrected in October that year, and needless to say, Voyager 1 did not crash into Titan.

The Voyagers discovered a lot of new things around Saturn, which boils down to these things:

- A lot of stuff about its rings (Saturn's rings are made of tiny dust, and Voyager 2 got hit by a lot of dust while heading through the rings.)
- 5 new moons
- 6 existing moons, and the fact that they have a lot of ice, also Titan might have water
    - Titan actually has all the things needed to support life, except for one teeny tiny thing - the surface temperature is 93 kelvin, so you would freeze to death on the surface.

Once the Saturn mission was complete, Voyager 1 was sent towards interstellar space, while Voyager 2 was sent towards Uranus and Neptune.

Titan - Voyager 1

Saturnine montage - Voyager 1

Uranus

Voyager 2 gets to do more

What's coming up

Voyager 1 did a focus on Titan during its Saturn flyby, which cost it a chance to see Pluto. As a result, they sent it out of the solar system instead. Meanwhile, Voyager 2 was sent on its way to fly by Uranus and Neptune, finally getting to take the Grand Tour that was envisioned back in the 60s. Voyager 2 didn't stay long near Uranus, however; it only got 5 and a half hours of close observation to gather as much data on Uranus as it could. 

Discoveries around Uranus

  • ​The Uranus axis tilt (lopsided 55 degree axis)
  • 2 more rings (bringing the total of known rings to 11)
  • Boiling water below the cloud surface
  • Very high wind speeds
  • 10 new moons (with names from Shakespeare plays)
  • Photos of Ariel, Miranda, Oberon, Titania, and Umbriel (with a particularly close approach to Miranda)

Miranda - Voyager 2

That is one weird surface

Triton

Neptune

Reaching the end

Neptune discoveries

The Voyager 2 flyby of Neptune was the first time a space probe has ever gone past Neptune. Here's what it discovered:

- 6 new moons (with Shakespeare names to match)
- 4 new rings
- The Great Dark Spot (a giant storm like Jupiter's Great Red Spot)
- Triton is very cold (so cold it has a frozen nitrogen volcano) 

Triton

Voyager Interstellar Mission

Voyager probe long-term support

Exiting the solar system

Once the Voyager 2 Neptune flyby was over in November 1998, nonessential functions of Voyager 2 were turned off and it was set on a course towards the way the Sun is believed to orbit around the Milky Way. Voyager 1 was sent in a similar direction. In the past decade, both probes entered interstellar space (Oort cloud notwithstanding). They still send data from the 5 functional instruments, and could continue to do so until 2026.
The background image is the famous 'Pale Blue Dot' image.

Solar System Family Portrait - Voyager 1

The main purpose of the Voyager mission was to take a grand tour of the outer planets and their moons, to gain as much information as possible, so that if we were to ever go to the outer solar system, we would know where to look for resources. Another goal was to see where the edge of the solar system is, and how long it takes to get there. The final goal was to put the message out there to some distant civilization that we're here, that we exist, and to give them a little taste of human culture.

To be able to do all that and still function today, nearly 43 years after the initial launch, is a feat in itself.
I would say that not only did the Voyager program fulfill its purpose, it has outdone itself in what it was expected to do and what it ended up doing.

Mission accomplished.

References

Mack, Pamela Etter, et al. From Engineering Science to Big Science: The NACA and NASA Collier Trophy Research Project Winners. University Press of the Pacific, 2006.

Mann, Adam. “Interstellar 8-Track: How Voyager’s Vintage Tech Keeps Running.” Wired, Sept. 2013. www.wired.com, https://www.wired.com/2013/09/vintage-voyager-probes/.

Mars, Kelli. “40 Years Ago: Voyager 2 Explores Jupiter.” NASA, 3 July 2019, http://www.nasa.gov/feature/40-years-ago-voyager-2-explores-jupiter.

Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. Second edition, National Aeronautics and Space Administration, Office of Communications, NASA History Division, 2018.

“THE FANTASTIC VOYAGE OF ‘VOYAGER.’” The Attic, https://www.theattic.space/home-page-blogs/2020/1/9/the-astonishing-voyage-of-voyager. Accessed 17 June 2020.

Voyager - Mission Timeline. https://voyager.jpl.nasa.gov/mission/timeline/. Accessed 17 June 2020.

Voyager - Planetary Voyage. https://voyager.jpl.nasa.gov/mission/science/planetary-voyage/. Accessed 17 June 2020.

Voyager FAQ - The Interstellar Mission. 21 July 2011, https://web.archive.org/web/20110721050617/http://voyager.jpl.nasa.gov/faq.html.