Voyager program
Gary Flandro, an aerospace engineer at the Jet Propulsion Laboratory, conceptualized a Planetary Grand Tour in 1964. This ambitious plan relied on a rare planetary alignment that occurs only once every 175 years. The alignment allowed a single craft to visit Jupiter, Saturn, Uranus, Neptune, and Pluto using gravitational assists. NASA endorsed the program in 1966 after gaining momentum from early studies. Funding for the full-scale mission vanished in December 1971 when resources shifted toward the Space Shuttle program. A scaled-down version emerged in 1972 as Mariner 11 and Mariner 12. These spacecraft were derived from the existing Mariner series design. Engineers utilized gravity-assist techniques previously demonstrated by Mariner 10 to achieve significant velocity changes. The mission name changed to Voyager in March 1977 following a public competition. William Pickering had originally suggested the name Navigator decades earlier.
Voyager 2 lifted off first on the 20th of August 1977, followed by Voyager 1 on the 5th of September 1977. The second probe took a shorter trajectory designed specifically for an optimal flyby of Titan. This encounter with Saturn's moon sent Voyager 1 out of the ecliptic plane. Had Voyager 1 failed its Titan maneuver, engineers could have redirected Voyager 2 to explore that moon instead. That contingency would have required sacrificing visits to Uranus and Neptune. Voyager 2 followed a JSX trajectory allowing it to continue past Saturn to the ice giants. The probes communicated data using magnetometers, spectrometers, and other instruments during their planetary encounters. They flew by Jupiter and Saturn before diverging into separate paths through the solar system. Voyager 1 overtook Pioneer 10 and Pioneer 11 during the 1990s to become the most distant human-made object from Earth.
Voyager 1 crossed the termination shock where solar wind slows to subsonic speed in December 2004. It entered the heliosheath region where solar wind becomes compressed and turbulent due to interactions with interstellar medium. Scientists reported in June 2012 that Voyager 1 was very close to entering interstellar space based on sharp rises in high-energy particles. NASA announced in September 2013 that the spacecraft had officially crossed the heliopause on the 25th of August 2012. This made it the first spacecraft to enter interstellar space. Voyager 2 reached the termination shock about 14 billion kilometers closer to the Sun than Voyager 1's crossing point. Data indicated the Solar System is asymmetrical because of this difference. Voyager 2 crossed its own heliopause boundary on the 5th of November 2018 according to reports released in December 2018. Both probes now monitor conditions in the outer expanses beyond the influence of the solar wind.
Each Voyager spacecraft weighed approximately 825 kilograms at launch but has since lost mass through fuel usage. The flight data subsystem contains two 16-bit word machines with modular memories holding 8198 words each. The computer command system features two 18-bit word interrupt-type processors with 4096 words of non-volatile plated-wire memory. These custom-built computers run continuously since the 20th of August 1977 without interruption. Engineers used CMOS and TTL medium-scale integrated circuits mostly from the 7400 series of Texas Instruments. A high-gain antenna with a three-meter diameter dish points toward Earth for communication. Three radioisotope thermoelectric generators sit end-to-end on a lower boom extending from the main body. The scan platform holds instruments including infrared interferometer spectrometers and ultraviolet spectrometers. Two imaging science subsystem cameras provide wide-angle and narrow-angle views of planetary targets.
Three MHW-RTG radioisotope thermoelectric generators supplied approximately 470 watts at 30 volts DC when launched. Plutonium-238 decays with a half-life of 87.74 years causing power output to drop by about 0.79 percent annually. By the 7th of October 2011, Voyager 1 generated 267.9 watts while Voyager 2 produced 269.2 watts. This represented roughly 57 percent of their initial launch power levels. Spacecraft loads must be turned off as electrical power decreases to eliminate some capabilities. Communications may become impossible by 2032 due to insufficient power generation. A revised power management plan implemented in July 2019 prioritized essential systems over scientific instruments. Engineers deactivated entire instrument suites like the Voyager 2 scan platform in 1998 to conserve energy. Gyro operations ended for Voyager 2 in 2016 and for Voyager 1 in 2017 to extend operational life further.
Both spacecraft carry a golden phonograph record containing pictures and sounds of Earth. The record includes symbolic directions on its cover for playing it back along with data detailing Earth's location. Carl Sagan chaired a committee that selected contents for this combination time capsule and interstellar message. Timothy Ferris also served on the selection committee alongside other experts. The record was intended for any civilization or far-future human that might recover either probe. Images captured from space show Earth as a Pale Blue Dot taken on the 14th of February 1990. That photograph came from a distance of approximately 6 billion kilometers away during the Family Portrait series. Print and electronic media outlets regularly documented discoveries made during the primary mission phase including new close-up color photos of major planets.
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Common questions
Who conceptualized the Voyager program in 1964?
Gary Flandro, an aerospace engineer at the Jet Propulsion Laboratory, conceptualized a Planetary Grand Tour in 1964. This plan relied on a rare planetary alignment that occurs only once every 175 years to allow a single craft to visit Jupiter, Saturn, Uranus, Neptune, and Pluto using gravitational assists.
When did Voyager 2 cross its heliopause boundary?
Voyager 2 crossed its own heliopause boundary on the 5th of November 2018 according to reports released in December 2018. Both probes now monitor conditions in the outer expanses beyond the influence of the solar wind after crossing their respective termination shocks.
What happened to Voyager 1 during the 1990s regarding distance from Earth?
Voyager 1 overtook Pioneer 10 and Pioneer 11 during the 1990s to become the most distant human-made object from Earth. The second probe took a shorter trajectory designed specifically for an optimal flyby of Titan which sent Voyager 1 out of the ecliptic plane.
How much power do the Voyager spacecraft generate as of October 2011?
By the 7th of October 2011, Voyager 1 generated 267.9 watts while Voyager 2 produced 269.2 watts. This represented roughly 57 percent of their initial launch power levels due to Plutonium-238 decaying with a half-life of 87.74 years causing power output to drop by about 0.79 percent annually.
Who selected the contents for the golden phonograph record on each Voyager spacecraft?
Carl Sagan chaired a committee that selected contents for this combination time capsule and interstellar message alongside other experts including Timothy Ferris. The record includes symbolic directions on its cover for playing it back along with data detailing Earth's location for any civilization or far-future human that might recover either probe.