In August and September 1977, two Voyager spacecraft were launched on a Grand Tour of the solar system. In 1973, the mission had been named Mariner Jupiter-Saturn 1977 (MJS ‘77) and was intended to go only as far as Jupiter and Saturn.
In March 1977 the mission name was changed to Voyager. In October 1978, a Voyager Fact Sheet mentioned the possibility of sending Voyager 2 to Uranus and Neptune. It would happen only if the primary science objectives were met at Saturn first. Even though the extended mission was not certain before launch, Voyager engineers (unofficially) designed and built the spacecraft to be capable of navigating to Uranus and Neptune, and surviving the longer trip. On-board computers were reprogrammed during the voyage, giving the spacecraft the ability to successfully return many more images and much more information than were expected. It’s unlikely the Voyager team imagined that both spacecraft would still be operating 40 years after launch.
For more information about the history of JPL, contact the JPL Archives for assistance. [Archival and other sources: Various Voyager and JPL History web pages; Voyager Fact Sheet, 10/6/1978; Section 260 photo album and index.
Most people know about the scenes, greetings, music and sounds from Earth found on the Voyager Golden Record. They may not know that there is also a handwritten message etched into the surface of the record. Timothy Ferris, who worked with Carl Sagan and the rest of the team that produced the record, wanted something done directly by a human hand to appear on the record. “To the makers of music – all worlds, all times” appears on the finished record, in between the photoengraved label and the record grooves.
The inscription can also be seen on some of the 14-inch recording masters that are found in the JPL Archives. There are several sets of the records, with a metal core and lacquer surface. From these masters, the copper records (“mothers”) were cut, then they were gold plated, etched, enclosed in aluminum containers and mounted on the sides of the Voyager 1 and 2 spacecraft.
In the early 1960s, a new large-aperture, low-noise Advanced Antenna System was in its planning and early development stages for the Deep Space Instrumentation Facility (later known as the Deep Space Network). Compared with the 85-ft (26-meter) antennas then in use, the new antenna was to give a 10-decibel performance increase, with an order of magnitude increase in the data rate from future spacecraft. Feasibility studies and testing were conducted by NASA's Jet Propulsion Laboratory in Pasadena, California, and subcontractors for various technologies and antenna components.
This January 1962 photo shows a 960-mc one-tenth scale Cassegrain antenna feed system study for the Advanced Antenna System. The objective was to establish the electrical performance capabilities and operational feasibility of this type of feed system for large antennas. The mount of the test system was covered with epoxy fiberglass and polystyrene foam to limit reflection of energy during testing.
A 210-foot (64-meter) antenna, using the new technology and designs, was built at the Goldstone site in California and became operational in 1966. The antenna, DSS 14, became known as the Mars antenna when it was used to track the Mariner 4 spacecraft. It was later upgraded to 70 meters in order to track Voyager 2 as it reached Neptune.
Winds of charged particles race outwards from the sun at 300,000 miles per hour. They are so faint that, here on the outer edge of the solar system, they would be undetectable if it were not for the very sensitive instruments carried by spacecraft.
From this distant, dark void, the sun is 100 times farther away than it is from Earth. Even so, our star is a million times brighter than Sirius, the brightest star seen from Earth. All around is a near-perfect vacuum, with only the most capable of instruments able to detect an ambient magnetic field that is 200,000 times weaker than the field back on Earth. To top off the loneliness factor, nothing from Earth has ever journeyed this far from home.
This remote zone is the domain now for Voyager 1 and 2. After 31 years of exploration, the twin spacecraft are the elder statesmen of space exploration, robotic envoys in the most distant reaches of our solar system. Voyager 1 is now 107 times farther from the sun than Earth is; Voyager 2 is 87 times farther. It takes about 15 hours for a signal leaving Earth to reach Voyager 1. (By contrast, it takes a little more than 20 minutes for a signal to go to Mars, even when the red planet is farthest from Earth.)
The twin spacecraft do not rest on the laurels of their discoveries at Jupiter, Saturn, Uranus and Neptune - the planets they flew by between 1977 and 1989. In fact, their findings at our solar system’s edge are changing scientists’ theories about what happens “way out there” and how interstellar space affects our solar system.
The Voyagers have shown that the heliosphere - the sun’s protective bubble surrounding our solar system — is not smooth and symmetric, as was originally thought. The robotic team discovered that this bubble is being pushed in and deformed by the pressure from the interstellar magnetic field outside our solar system. Another surprise came when the spacecraft passed an important milestone near the edge of the solar system, called the termination shock. The energy released from the sudden slowing of the sun’s supersonic wind had an unexpected outcome - it was absorbed not by the wind itself, but by ionized atoms that had come from outside our solar system. And inevitably, as theories are shattered in the wind, more questions arise. There are cosmic rays we know come from this distant region, for example, but their origin is yet to be found and explained.
After all this time, Voyager’s discoveries continue to do what they have always done - take us to new places we have never been, and shed light on the how our solar system interacts and interconnects with the surrounding regions of the Milky Way.
Both Voyagers have enough power to run until 2025. Voyager 1 will probably cross into interstellar space by about 2015. At that moment, Voyager 1 will become Earth’s first interstellar spacecraft, leaving the sun behind as it enters the interstellar wind produced by the supernova explosions of other stars.
Until their final transmissions — hopefully many years in the future — the Voyagers still have a long way to go and lots to tell us.