10 Interesting Facts about the Voyager 1 Probe

Voyager 1
Artist's concept of Voyager 1 spacecraft by NASA/JPL-Caltech

According to some reports, many of the mission scientists working on the Voyager space exploration program are “amazed” that both Voyagers are still functioning after forty years in service. This sentiment becomes clear when one considers that the Voyagers run on technology that was developed in the 1970’s, which incidentally, has not suffered any major breakdowns and malfunctions in four decades.

The fact that Voyager 1 had made it to outer space is a testament to the skill, knowledge, and dedication of the engineers who designed, built, and still operate the craft. Furthermore, Voyager 1 has made major contributions to our knowledge of the outer planets over the years, and is expected to continue collecting and returning data to Earth until about 2025. Below are ten interesting facts about this amazing craft.

Voyager 1 is the furthest space craft from Earth

The image below shows Voyager 1 being propelled into space by a Titan IIIE lift vehicle. Launched on September 5, 1977, sixteen days after Voyager 2 which lifted off on August 20, Voyager 1 is now the furthest manufactured object from Earth, even further than the dwarf planets Eris and V774104, which are 96 AU and about 103 AU away, respectively. From a distance of 140 AU away (as on September 22, 2017), Voyager 1 is still in regular contact with the Deep Space Network, and receiving control inputs and return data. In practice, this means that Voyager 1 is the most distant object in the solar system whose exact location is known at all times.

Voyager 1 Launch

Voyager 1 was originally part of the Mariner 11 program

When NASA first conceived of a “Grand Tour” of the solar system in the 1960’s, the proposed craft that would conduct the tour was designed to be a part of the Mariner 11 program. However, based on the lessons on solar radiation learned from the Mariner 10 program, (as well as severe budget cuts), the craft was designed to be able to cope more effectively with the strong radiation fields around Jupiter, which it was meant to visit. Eventually, the design and specifications of the proposed craft started to deviate from the Mariner designs so radically that the proposed craft was renamed as Voyager 1.

Voyager 1 has three nuclear reactors that generate power

Voyager 1 nuclear reactorsThe probe uses three radioisotope thermoelectric generators (RTGs) (shown above) in order to generate electricity to power its instruments. Each generator has 24 compressed plutonium-238 oxide pellets that generate heat through nuclear decay. When the craft was launched in 1977, the three generators’ combined output was about 470 Watts, with some losses through waste heat. The fuel pellets have a half-life of 87.7 years, which together with degradation of the thermocouples that conduct the heat, means that by the year 2025, the generators will not be able to provide power for all the on-board instruments. A planned scaling-down is now in progress to conserve power, with the crafts’ imaging equipment already deactivated.

Voyager 1 is the third craft to reach solar system-escape velocity

After completing its planetary mission in November of 1980, Voyager 1 became one of only a handful of spacecraft to obtain enough velocity (about 17 km/sec) to escape from the solar system, the other craft being Pioneer 10, Pioneer 11, and Voyager 2. Apart from the New Horizons craft, Voyager 1 also had the fastest launch speed; it overtook Voyager 2 a few months after launch, flew past Pioneer 11 in the late 1980’s, and passed Pioneer 10 on February 17, 1998. Incidentally, New Horizons will, despite its high velocity, never overtake either of the two Voyagers.

Voyager 1 discovered the source of Saturn’s excess heat

Voyager 1 detected during the Saturn fly-by that the planet’s upper atmosphere contains only about 7% helium, which was surprising considering its helium abundance was expected to be about 11%, or the value for both the Sun and Jupiter. Investigators are surmising that the heavier helium is sinking downward through the less-dense hydrogen in the planets’ atmosphere creating heat, which might explain why Saturn radiates more heat than it receives from the Sun. Voyager 1 also discovered winds that blow at more than 500 m/sec (1,100 mph) through Saturn’s atmosphere in an easterly direction.

Voyager 1 also discovered volcanoes in the Jovian system

Voyager 1 discovers volcanoes on Io

Since it was long thought that Earth is the only body in the solar system on which active volcanoes are present, this image taken by Voyager 1 of an erupting volcano on Jupiter’s moon Io came as a major surprise. Voyager also discovered that material ejected from volcanoes on Io permeates the entire Jovian system, since sulphur, oxygen, and sodium was detected by Voyager 1 right at the outer limits of Jupiter’s magnetosphere, which is the region of space around the system that is affected and influenced by Jupiter’s magnetic field.

Voyager 1 took the first solar system “family portrait”

Family portrait by Voyager 1

The assembled mosaic above represents the first ever image of the solar system taken from outside of the solar system. This image was taken by Voyager 1 on February 14, 1990, shortly before the crafts’ imaging equipment was purposely disabled by deleting the software that control the cameras. This was done to conserve both power and computer resources, but also because Earth-based technology to receive and “read” images from the craft are no longer available.

The modified image below shows one small part of the above mosaic. This image is known as the Pale Blue Dot, and it shows Earth as the bright spot at the centre of the blue circle, with Voyager 1 having taken the photo on February 14, 1990 from a distance of 4 billion miles (6.4 billion km). The brown line in which Earth appears is one band of sunlight that is reflecting off a part of the spacecraft.

Pale Blue Dot

Voyager 1 is now officially in outer space

While the question of when Voyager 1 had left the solar system, or even if it had left at all, was the subject of heated debate among scientists for several years, most investigators now accept August 25, 2012 as the date on which the craft officially exited the solar system. This was decided based upon the increase of the average density of electrons in the craft’s vicinity, which in turn is based on a solar outburst that had occurred March of 2012, and the frequency of plasma oscillations caused by the outburst. The final conclusion was that since the electron density outside of the Sun’s heliosheath is expected be twice that of the electron density inside it, Voyager must be in the interstellar medium.

Despite the above, Voyager 1 is still in the solar system proper

While many people consider leaving the heliosheath as being synonymous with leaving the solar system,, the fact is that the two are vastly different. The Sun’s heliosheath merely refers to the region of space that is influenced by the Sun’s gravity and radiation, while the term “solar system” refers to the region of space that is inhabited by all the bodies that orbit the Sun.

Based on the above, Voyager 1 is still in the solar system, since it will take another three hundred years or so for it to reach the inner edge of the Oort cloud and another 30,000 years or so for it to exit the Oort cloud. Note that while Voyager 1 is not headed toward any particular star, it will pass within 1.6 light years of the star Gliese 445 (which is approaching us at about 119 km/s (430,000 km/h; 270,000 mph), in about 400,000 years’ time.

Voyager 1 carries a message of love

Interstellar probes
Much has been written about the golden record aboard both Voyagers, and we need not rehash it here. However, as Voyager 1 leaves the solar system (shown here relative to other craft leaving the solar system), its golden record carries an hour-long recording of the brain waves of Carl Sagan’s wife, Ann Druyan. The recording of her brain activity was made while she was thinking of such diverse topics as Earth’s history, everyday challenges faced by various previous civilizations, and the emotions people experience when they fall in love. If the record is ever recovered by an alien civilization, it is hoped that their scientists might be able to figure out how to operate the playback system. However, it remains an open question what any given alien civilization will think of the confused jumble of brain waves of a person who is in love.

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