A Bon Voyage – The Story of the Voyagers in Space
By Punyae Bhatia
Cosmofluencer (Season 03)
In what can only be described as the loneliest journeys in our cosmic history, Voyager 1 and Voyager 2 left Earth in 1977 on a one-way trip to the edges of our solar system, never to return to Earth again.
An Idea Germinates
Conceived by Gary Flandaro, an aerospace engineer, in the late 1960s, the Planetary Grand Tour was a space exploration program designed to leverage a rare planetary alignment occurring once every 175 years. This alignment saw the 4 gas giants of our solar system lined up together. It allowed a craft to reach all the outer planets using gravitational assists; i.e. the planets’ gravity to accelerate and slingshot itself towards the other planets. It would also help save a lot of fuel.
In 1972, when funding for this mission was pulled, a similar mission using 2 probes to explore the 4 outer planets was proposed; and on March 4, 1977, the mission was officially renamed to Voyager.
The Twin Probes
Two mission trajectories were established. JST aimed at Jupiter, Saturn, and a flyby of Titan, while JSX served as an extension of the JST path, allowing a probe to continue further towards Uranus and Neptune.
Voyager mission paths (lasp.colorado.edu)
If JST succeeded, JSX could proceed with the Grand Tour, but if JST failed, JSX would be redirected to a separate flyby of Titan, forfeiting the Grand Tour.
Voyager 2 followed the JSX trajectory, allowing it to continue towards Uranus and Neptune. Upon the completion of Voyager 1’s Saturn flyby, Voyager 2 was ordered to proceed forward to continue towards Uranus and Neptune.
The Mission Begins
Voyager 2 was the first to launch on August 20, 1977, followed by its twin, Voyager 1. on September 5 from the NASA Kennedy Space Center at Cape Canaveral, Florida.
On September 6, Voyager 1 returned the first space image of our Earth and her moon.
Meet the Family
1979 saw the twin probes approach their first target: Jupiter. Voyager 1 was the first one to reach the gas giant on March 5, while Voyager 2 arrived on July 9.
Voyager 1 captures Jupiter on approach (nasa.gov)
Highlights of the encounter with Voyager 1 include the discoveries of the first active volcanoes spotted beyond Earth at Jupiter’s moon Io. the Jovian ring system, two new moons (Thebes and Metis), and the assertion of the Great Red Spot being a huge cyclone-like storm.
Voyager 2 imaged the ring system of Jupiter, discovered by Voyager 1. Adrastea also became the third moon of Jupiter, which was discovered during the course of the entire mission.
Voyager 1 images Saturn in 1980 (nasa.gov)
Just 20 months after having encountered Jupiter; on November 9, 1980, Voyager 1 crossed paths with its ringed neighbour Saturn, shortly followed by Voyager 2 on August 25, 1981.
Voyager 1 was responsible for the discovery of 3 new moons; Atlas, Prometheus, and Pandora. The latter 2 were found around the F-ring of the planet.
Titan was found to have a thick, Earth-like atmosphere – the first nitrogen-rich atmosphere found beyond our home planet, suggesting the possibility of seas of liquid methane on the surface.
This encounter with Saturn finally sent Voyager out of the plane of the solar system on the loneliest journey in space, never to return again.
Voyager encounters Uranus on January 24, 1986 (nasa.gov)
Voyager 2’s closest approach to Uranus marked the first time the planet had been seen up close. Voyager’s images revealed 11 new moons. Scientists also learned that the magnetic field of the planet is tilted, with the poles being at the equator of the planet.
Temperatures as low as minus 353 degrees Celsius were detected, making Uranus the coldest planet in our solar system.
(nasa.gov)
Exactly 8 years after Voyager’s approach to Saturn, it reached its final destination; Neptune. Voyager 2 became the first spacecraft to observe Neptune up close and to visit the 4 planets beyond Earth.
It discovered a huge, counter-clockwise rotating storm in Neptune’s southern hemisphere, dubbed “The Great Dark Spot”.
Having completed its mission, Voyager 2 retired into space, leaving the planets and the solar system plane forever.
Interstellar Journey
Voyager trajectories out of the solar system (www.bigthink.com)
Just two months after crossing Neptune, engineers at mission control turned off the cameras aboard Voyager 2 to conserve power required for other instruments that collect key data on the solar wind and interstellar space.
Now 6 billion km away from the Sun, Voyager 1 took the last photos of the mission; the “Solar System Family Portrait”. They featured images of Venus, Earth, Jupiter, Saturn, Uranus, and Neptune, arranged in light of the Sun.
(science.nasa.gov)
The image of Earth as a tiny speck silhouetted in the light of the Sun inspired Carl Sagan to think about the uniqueness and wonders of our home planet; “the pale blue dot”.
Engineers now turn off the Voyager 1 cameras to conserve the power required for other instruments.
Key Events
February 17, 1998;
Voyager 1 becomes the farthest human-made object in space, surpassing the distance covered by Pioneer 10.
December 16, 2004;
Voyager 1 crosses the termination shock, the inner boundary of the heliosheath, where the solar winds abruptly slow down and heat up.
August 30, 2007;
Voyager 2 now crosses the termination shock.
August 13, 2012;
Voyager 2 became NASA’s longest operating mission and is still operational to this day (17,129 days as of writing this article).
August 25, 2012
Voyager 1 enters interstellar space, passing the heliopause, the boundary of the solar system where the Sun’s solar wind is stopped by the interstellar medium, marking the first time a human-made object crossed the threshold of interstellar space.
November 5, 2018
Voyager 2 now becomes the second spacecraft to enter interstellar space.
Current Status
Both the Voyager spacecrafts are still operational, as of July 2024. They are currently travelling interstellar space, 24 billion km away from home and continuing.
(voyager.jpl.nasa.gov)
A few instruments aboard the crafts are still operational, gathering and sending data to the engineers at JPL.
These spacecraft are amonstg the greatest innovations in space exploration in our history. The next time Voyager 1 will ever see another star up close will be in about 40,000 years when it reaches Proxima Centauri.
NASA still provides public information on the current status of both Voyagers. You can access this information here- https://voyager.jpl.nasa.gov/mission/status/