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Why is Voyager 1 great? The photo she took made humans rethink the universe and themselves

Voyager 1 uses higher quality data to help further study the Jupiter and Saturn systems. The significance of the photographs of the Earth taken during its long voyages – the "faint blue dots" – transcends astronomy and becomes one of the important starting points for human philosophical thinking about the universe, the earth and humanity itself. Voyager 1 was also the first artificial object to leave the Solar System and the farthest from Earth to date. Its success also directly laid a solid foundation for the subsequent Voyager 2 to complete the "planetary grande".

Written by | Wang Shanqin

As pathfinders for the "Planetary Gala" project, the success of Pioneer 10 and Pioneer 11 opened two skylights for the detection of exoplanets (Jupiter, Saturn, Uranus and Neptune). However, on December 16, 1971, before the two probes were launched, NASA announced the cancellation of the "Planet Gala" project. It had only been two years since the project was officially launched (1969).

The reason for the cancellation of the "Planet Gala" project was due to funding. At the time, the budget for the project was as high as $1 billion, equivalent to about $5 billion today. On the other hand, since 1965, NASA's funding has decreased year by year; After the success of the Apollo lunar landing program in 1969, President Nixon, who took office that same year, further cut NASA's annual funding. In 1971, NASA had to choose between the Space Shuttle program and the Planetary Gala program. NASA chose the Space Shuttle project.

Voyager: The rebirth of the "Planet Gala"

The cancellation of the "Planetary Gala" project is undoubtedly a great tragedy.

Fortunately, NASA's Outer Planets Working Group, which recommended the Planetary Gala in 1969, also recommended an alternative: a program that only explored Jupiter and Saturn, with a much lower budget. In 1971, at the final discussion and vote on the "Planetary Gala" project, the Expert Group adopted the project while emphasizing this option. NASA also gave high praise to the alternative when it finally decided to cancel the "planetary grande" project.

This alternative gives the Planet Gala project a chance to be reborn. In January 1972, the Jet Propulsion Laboratory (JPL) began to move on to the preparation of this alternative project; In May of the same year, NASA officially approved this alternative project, which was the Mariner Jupiter-Saturn (MJS) project.

The MJS project will launch 2 identical detectors, with the second detector serving as a spare part for the first detector. When the MJS project was proposed, JPL was already operating Mariner 1 through 9 to explore Mercury, Venus and Mars, and Mariner 10 was about to be launched. The two detectors of the MJS project were therefore named Mariner 11 and Mariner 12. The budget for the project is $360 million.

Because Mariner 11 and Mariner 12 of the MJS project were exploring outer planets and were quite different from other probes in the Mariner series, they were renamed Voyager 1 and Voyager 2 respectively on March 7, 1977, so that they were no longer part of the Mariner series, but were still operated by JPL's team.

Voyager 1's detection targets are Jupiter, Saturn and Titan, and its orbital code is "JST", and these three letters are the English initials of the above three objects.

Schematic diagram of the orbits of Voyager 1 and Voyager 2. Voyager 1 moves in the direction of "JST" and Voyager 2 in the direction of "JSX". X has two possibilities, X = TB means including the Titan flyby mission (for the failure of Voyager 1); X=U indicates the inclusion of the Uranus flyby mission (for the success of Voyager 1). The timescale on the orbit is measured in 0.5 years. 丨Image source: NASA; Translated by Wang Shanqin

Structure and instrumentation

Voyager 1 has a mass of 825.5 kg, of which the spacecraft itself has a mass of 721.9 kg. It has 16 MR-103 hydrazine thrusters for attitude control, 8 spare thrusters, a three-axis stabilized gyroscope, celestial coordinate reference equipment, a radio communication system, an energy system, 11 scientific instruments, a solid engine for midway orbit changes, and 8 propulsion rocket engines.

Model drawings of Voyager 1 and 2丨Image source: NASA/JPL

Voyager 1's radiocommunication system consists of a parabolic high-gain antenna with a diameter of 3.7 meters, which receives signal instructions from three Deep Space Network (DSN) stations on Earth and sends the resulting data to the DSN.

An engineer and Voyager have yet to complete high-gain antenna on July 9, 1976丨Image source: NASA/JPL

Voyager 1 also has a data memory on it, the Digital Tape Recorder (DTR), which can hold 64 kilobytes of data, which allows it to delay sending images. For comparison, Pioneer 10 and 11 did not have DTR on them, and the data from the shots had to be sent immediately.

Voyager 1's electrical energy is provided by three radioisotope thermal motors (RTGs). Each RTG contains 24 balls of compressed plutonium-238 oxide, hence the name plutonium nuclear battery. At the first launch, the heat generated by the RTG can produce about 470 watts of electrical power. Due to the decay of radioactive materials, the power of RTGs is constantly decreasing.

A unit of the radioisotope thermomotor in Voyager 1 and 2丨Image source: NASA/JPL

Voyager 1's scientific instruments include: Imaging Science System, Radio Science System, Infrared Interferometer Spectrometer, Ultraviolet Spectrometer, and Triaxial Fluxgate Magnetometer), Plasma Spectrometer, Low Energy Charged Particle Instrument, Cosmic Ray System, Planetary Radio Astronomy Investigation System Photopolarimeter system, plasma wave subsystem.

Structural diagram of Voyager 1 and 2丨Image source: NASA/JPL

In Voyager 1's instrument, the imaging science system weighs 38.2 kilograms and includes a telephoto narrow-field camera and a short-throw wide-field camera, which uses telescopes with apertures of 17.7 cm and 5.7 cm, respectively. The filters on both cameras cover multiple bands of UV to visible light. With these filters, the camera captures monochrome images that are synthesized by astronomers into stunning color images with resolutions of up to thousands of meters per pixel.

According to previous calculations, the launch window of the original "Planetary Gala" spacecraft and the later replacement Voyager 1 and 2 was between 1976 and 1980. On September 5, 1977, Voyager 1 was launched aboard a Hercules 3 E-Centaur rocket. Sixteen days before (August 20, 1977), Voyager 2 had been launched with the same rocket. Voyager 1 was delayed several times before launch, leading to this reversed sequence. However, under the design of orbital dynamics experts, Voyager 1 will pass through the asteroid belt and visit Jupiter and Saturn before Voyager 2.

Voyager 1 took off with a rocket丨Image source: NASA

On December 10, 1977, Voyager 1 entered the asteroid belt. On December 19, 1977, Voyager 1 flew in front of Voyager 2. On September 8, 1978, Voyager 1 left the asteroid belt.

Flyby of the Jupiter system

On January 6, 1979, Voyager 1 began observing Jupiter.

On February 25, 1979, Voyager 1 photographed Jupiter containing parts of the Great Red Spot. At this time, Voyager 1 was 9.2 million kilometers from Jupiter. The resolution of the image reaches 160 km. Image source: NASA/JPL

Over a 28-day period from January 6 to February 3, 1979, Voyager 1 continued to take multiple photographs of Jupiter. During this time, Voyager 1 flew from 58 million kilometers from Jupiter to 31 million kilometers from Jupiter. Later, the photos were stitched together into a film.

Why is Voyager 1 great? The photo she took made humans rethink the universe and themselves

Voyager 1 photographs composed of photographs between January 6 and February 3, 1979, were chosen to stitch together images taken every 10 hours (Jupiter's rotation period) to reflect changes in the same feature. During this time, Jupiter's Great Red Spot position remains almost unchanged, but it rotates at high speed, and clouds at different latitudes show different moving characteristics. The black dots that appear in the video are projections of Jupiter's moons, and the white dots of light are Jupiter's moons themselves. Video source: NASA/JPL

On February 10, 1979, Voyager 1 entered the Jupiter system. In early March, it discovered a thin ring around Jupiter that was less than 30 kilometers thick. This is the first time that Jupiter has been confirmed to have rings. On March 4 and 5, 1979, Voyager 1 discovered Ganymede XIV and Ganymede XVI respectively.

Image of Jupiter's rings taken by Voyager 1丨Image source: NASA/JPL

At 12:05:26 on March 5, 1979, Voyager 1 reached Jupiter's periapsis about 280,000 kilometers from Jupiter's cloud tops. Before and after its flyby, it took a large number of high-quality images, detecting Jupiter's magnetic field, gravitational field, atmosphere, and more.

Pseudochromatic map of the Great Red Spot synthesized from data obtained by Voyager 1 on Jupiter丨Image source: NASA/JPL

After the flyby of Jupiter, Voyager 1 flew by Europa (20,570 kilometers) and Europa (733,760 kilometers) on the same day.

Jupiter, Europa (left) and Europa (right) taken by Voyager 1 in March 1979. Image source: NASA

Compared to the distance between Pioneer 10 and Pioneer 11 flyby by Europa (357,000 km and 314,000 km, respectively), Voyager 1 is much smaller from Io, allowing a lot of detail to be observed.

A heart-shaped region formed by merging images of Ioda taken by Voyager 1 at 450,000 kilometers on March 5, 1979 (left) and material falling back from the Pele eruption (right). Near the Pell crater is the Loki volcano. The black fissure in the center of the heart-shaped area is a crater, and the material ejected after the eruption descends to form a heart-shaped area. Image source: NASA/JPL

Voyager 1 directly photographed the eruption of volcanoes above Europa. This is the first time that a volcanic eruption has been detected on a celestial body other than Earth. Interestingly, shortly before this discovery, astronomers had predicted volcanic activity on Europa from theoretical calculations. Studies have shown that Ioda is the most volcanically active object in the solar system. The sulfur-rich material from the volcanic eruption above it falls on its surface, forming a red, orange, and yellow surface.

Parts of Callisto taken by Voyager 1 on March 4, 1979 (left) and parts of Callisto taken by Voyager 1 on March 5, 1979 (right). At that time, Voyager 1 was 490,000 kilometers and 128,500 kilometers away from Europa, respectively. The image on the left shows the eruption of the Rocky volcano, where the material from the eruption is thrown to an altitude of more than 160 kilometers. Image source: NASA/JPL

Although Voyager 1 flew by Europa more than Pioneer 10 to Pioneer 11 (32.1/586,700 km), it still achieved higher definition images thanks to its high-quality imaging system. The images it took showed cracks crisscrossing Europa's surface. Astronomers at the time theorized that the cracks came from surface fractures or tectonic processes.

Europa photographed by Voyager 1 at a distance of 286,252 million kilometers on March 2, 1979. The dark lines on the surface are cracks on Europa's surface. Image source: NASA/JPL

On March 6, 1979, Voyager 1 flew by Europa (distance 114,710 km) and Europa (distance 126,400 km). Because the flyby distance was much smaller than Pioneer 10 and Pioneer 11, it obtained higher quality images of Ganymede and Europa.

Parts of Europa taken by Voyager 1 on March 5, 1979 (left) and parts of Europa taken by Voyager 1 on March 6, 1979 (right). At the time of the photo, Voyager 1 was 246,000 kilometers and 200,000 kilometers away from Ganymede and Ganymede, respectively. Image source: NASA/JPL

Although Voyager 1 observed Jupiter for about 3 months, it was able to detect Jupiter's magnetic field and radiation only 48 hours before and after reaching its periapsis. The duration of detailed observations of Jupiter's rings and moons is only a few days. During this time, Voyager 1 discovered 8 moons of Jupiter.

Over the course of several months of imaging observations and several days of close-up observations, Voyager 1 obtained a large amount of data from the Jupiter system, which provides important basis for planetary scientists to further study the Jupiter system.

Flyby of the Saturn system

On April 9, 1979, Voyager 1 completed orbital correction and flew towards Saturn. To avoid hitting Titan , it made another orbital correction on October 10 , 1979. On August 22, 1980, Voyager 1 began observing Saturn.

On November 12 , 1980 , Voyager 1 entered Saturn and flew by Titan on the same day , with its closest approach to the surface of Titan at the time of its flyby being only 3915 km , which was 1/90 of the distance ( 362,962 km ) when Pioneer 11 flew by Titan .

Titan photographed by Voyager 1 at a distance of 435,000 kilometers on November 12, 1980. The tip of Titan is a thick fog. Image source: NASA/JPL

Data obtained by the Voyager 1 spectrometer indicate that Titan's atmosphere contains methane, ethane, a variety of other organic compounds and large amounts of nitrogen. However , the thick smog of organic matter in Titan 's atmosphere made the images obtained by Voyager 1 appear featureless.

Based on Voyager 1 radio occultation data, astronomers deduced that Titan has a diameter of 5152 km, a surface temperature of about 94 K, and an atmospheric pressure of 1.47 bar (1 bar = 100,000 Pascals, and the Earth's standard atmospheric pressure is 1.01325 bar). Its data also suggest that Titan has a dense atmosphere, and its surface may host liquid material.

On November 12, 1980, Voyager 1 flew by Enceladus (at a distance of 415,670 km). At 23:46:30 on the same day, Voyager 1 reached Saturn's periapsis (the closest point to the center of gravity on the central object), 126,000 kilometers from Saturn's cloud tops.

Saturn's rings photographed by Voyager 1 on November 13, 1980, when it was 1.5 million kilometers away from Saturn. Image source: NASA/JPL

On November 13, 1980, Voyager 1 flew by Enceladus (88,440 km), Enceladus (202,040 km), Enceladus (73,980 km) and Enceladus (880,440 km) on the same day.

Titan (left, 425,000 km) and Enceladus (right, 1.2 million km) photographed by Voyager 2 on November 12, 1980. In these images, Crater Herschel on the upper right of Enceladus and Ithaca Chasma above Enceladus are clearly visible. Image source: NASA/JPL

Titan (left, 240,000 km) and Enceladus (right, 73,000 km) photographed by Voyager 2 on November 12, 1980. Numerous craters on their surface are clearly visible. Image source: NASA/JPL

On November 14, 1980, Voyager 1's observation mission to the Saturn system ended. During its flyby, Voyager 1 observed the chemical composition of Saturn's upper atmosphere, the complex structure of Saturn's rings, Saturn's auroras, Titan and several other previously confirmed moons, and discovered Saturn's five new moons and Saturn's G-rings.

Saturn's rings photographed by Voyager 1 on November 16, 1980, when it was 5.3 million kilometers away from Saturn. The shadow formed by sunlight shining on Saturn casts on Saturn's rings. Image source: NASA/JPL

When Voyager 1 flew close by Titan, Titan's gravity caused it to pass by Saturn's south pole and fly away from the ecliptic plane (the orbital plane of the Earth's orbit is the ecliptic plane, and the orbital plane of other planets in the solar system orbiting the sun is basically coplanar with the ecliptic plane), and then away from the solar system.

Family portrait of the solar system and the "faint blue dot"

On February 14, 1990, Voyager 1, which had been drifting in the empty solar system for more than 12 years, was about 6 billion kilometers from Earth. At this time it is 32 degrees above the ecliptic plane, which is suitable for photographing several planets in the solar system. The Voyager team gave instructions to point it in the direction of the sun, took 60 pictures, and put together a family portrait of the solar system. To avoid overexposure to sunlight, the exposure time for each photo is only 0.005 seconds.

This family photo shows Jupiter, Earth, Venus, Saturn, Uranus and Neptune in the solar system. Mercury is too close to the Sun to be identified. Mars' position at the time made it just a crescent from Voyager 1's view, and therefore unrecognizable.

A family portrait of the solar system taken by Voyager 1 on February 14, 1990. FROM LEFT TO RIGHT: JUPITER, EARTH, VENUS, SATURN, URANUS AND NEPTUNE. Image source: NASA/JPL

The most famous of this set of family portraits is the image of the earth. In the photograph of Earth, the Earth is just a tiny 0.12-pixel bright spot, which is almost drowned out by the colored light bands formed by the camera's reflection of sunlight.

In an image of Earth taken by Voyager 1 on February 14, 1990, the pale dot in the bright light red band on the far right is our Earth. Image source: NASA/JPL

The photo prompted thought by Carl Sagan (1934-1996), a renowned astronomer, astrobiologist, popular science writer and science fiction writer. He called the Earth in the picture "Pale Blue Dot" and published the book Pale Blue Dot: A Vision of the Human Future in Space in 1994.

In the book, Sagan says emotionally, "Think about that point again. That's here, that's home, that's us. At this point, everyone you love, everyone you know, everyone you've ever heard of, everyone, whoever they are, is here for the rest of their lives. "Some people say that astronomy humbles and shapes character. Probably nothing shows more foolishly than this distant picture of our tiny world. For me, this photo underscores our responsibility to be kinder to each other and to protect and cherish this pale blue dot – the only home we know today. [Note 1]

The marriage of this image taken by Voyager 1 to Sagan's book gave Earth the nickname "faint blue dot." The name quickly spread and broke the circle, becoming one of the most important entry points for human beings to think about the earth and the universe.

Fly out of the frontiers of the solar system

After concluding the exploration mission for exoplanet systems, astronomers launched the Voyager Interstellar Mission (VIM) for Voyager in 1989. At that time, Voyager 1 was 40 AU (1 AU 149.6 million km) from Earth.

VIM mainly detects phenomena related to the solar wind. VIM is divided into three phases: Termination Shock, Heliosheath, and Interstellar Space.

The heliosphere is a huge bubble of solar wind emitted by the sun that forms around the sun (light gray area in the figure below), and its boundary with interstellar space is the heliopause, where solar wind particles stop. When the solar wind blows near the heliopause, it comes into contact with the interstellar medium and is hindered by the interstellar medium to form terminal shock waves, which are called "terminal shock regions".

At the end of the direction of the Sun's motion, the area between the terminal shock zone and the heliopause is shaped like a scabbard or scabbard, hence the name "heliospheric scabbard".

Schematic diagram of heliosphere, terminal shock, heliospherical sheath, heliopause top, bow shock. Image credit: NASA/Goddard/Walt Feimer; Translated by Wang Shanqin

Therefore, in the direction away from the Sun, from the inside to the outside, the terminal shock zone, the heliospheric sheath and the heliopause are the heliopause. The heliopause hits the interstellar medium, forming a bow shock. According to some astronomers, beyond the heliopause is interstellar space.

On February 17, 1998, Voyager 1 overtook Pioneer 10, at which point it was about 69.419 AU (10.41 billion kilometers) from Earth. Since then, it has been the farthest spacecraft from the Sun.

On 17 December 2004 , Voyager 1 entered the heliospheric sheath via the terminal shock zone. In June 2012, astronomers noticed a sharp increase in the number of energetic particles received by Voyager 1 from interstellar space, and judged it to be about to pass through the heliopause.

On August 25 , 2012 , Voyager 1 passed through the heliopause at a distance of 121 AU ( about 18.15 billion km ) from Earth. By some astronomers' definitions, Voyager 1 became the first spacecraft ever to enter interstellar space on this day. [Note 2]

To celebrate Voyager 1's arrival in interstellar space, astronomers took radio images of Voyager 1 with a Very Long Baseline Array (VLBA) on February 21, 2013.

A radio image of Voyager 1 taken by the Very Long Baseline Array (VLBA) on February 21, 2013. Image source: NRAO/AUI/NSF

As of February 18, 2023, Voyager 1 is 159.1 AU (about 23.801 billion kilometers) from the Sun [Note 3]. It now has a velocity of 17 kilometers per second (3.57 AU per year) relative to the Sun, far more than its third cosmic velocity (the speed at which it is free from the Sun's gravity and thus out of the Solar System), so it will stay away from the Sun and will continue to advance towards the galactic center thereafter. It can also fly out of the galaxy and roam the universe beyond the galaxy.

Gold records for aliens

In order to give possible aliens a chance to learn about Earth, astronomers placed a gold-plated copper disk on both Voyager 1 and 2, with a diameter of 12 inches (30 cm), which recorded information about Earth's location and humans. These two gold-plated copper discs are the famous "gold records".

The gold record on Voyager 1丨Image source: NASA/JPL

The golden record includes greetings in 55 languages (including Chinese Mandarin, Cantonese, Hokkien, Wu), 35 sounds of life on earth, 90 minutes of "Voice of the Earth" (including the sound of whales, the cry of babies, the sound of waves crashing on the coast, and 27 world famous songs from the earth, including the Chinese guqin song "Flowing Water", Mozart's "The Magic Flute", etc.); 115 photographs (including human mathematics, physics, the solar system and its inner planets, animals on Earth, plants, DNA, human anatomy and reproduction, topography and scenery of parts of the earth, food, architecture, human daily life, etc.) and audio recordings of greetings from some politicians of the time.

The meaning of the information on the gold record丨Image source: NASA/JPL

The lower left corner of the record cover indicates the solar system and 15 lines and the dumbbell-shaped figure in the lower right corner is the same as the nameplate of Pioneer 10 and 11, and its significance has been introduced in the article introducing Pioneer 10 ("Pioneers Exploring the Frontiers of the Solar System: Pioneer 10丨Planetary Gala"), which will not be repeated here.

In the upper left corner of the record cover are drawings and styluses for gramophone records. The binary symbol around it indicates the time it takes for the record to spin one revolution, from which it can be calculated that the time for a record to rotate one revolution is 3.6 seconds. Below the large circle is a side view of the record and the stylus, which explains that it takes about 1 hour to finish the record.

The upper right corner of the record cover shows the waveform of the image signal, the binary symbol of the scan time (8 milliseconds), and the drawing method of the straight lines that make up the image. The bottom indicates that if decoded correctly, the figure is a circle.

Brilliant achievements and great sacrifices

Although Voyager 1 was not the first probe to explore Jupiter and Saturn up close, it did get better images of the members of both systems than Pioneer 10 and 11. In addition, it discovered the volcanic eruption of Europa, discovered the rings of Jupiter, discovered 8 new moons of Jupiter, flew by Titan up close, discovered Saturn's G ring, discovered 5 new moons of Saturn, and so on. Its observations of the Jupiter and Saturn systems have further deepened the understanding of the physical, chemical and even biological properties of the two gas giants, their moons and rings.

A "family portrait" of Jupiter (top right), Europa (top left), Europa (center), Europa (bottom left) and Europa (bottom right) taken by Voyager 1. These images are not taken in the same photo, but are a combination of multiple photos. They are not scaled in the figure. Image source: NASA

The significance of the photograph of the Earth ("faint blue dot") taken by Voyager 1 during its long voyage goes beyond the scope of astronomy: after Sagan's infectious statement was widely disseminated, this image of the "faint blue dot" became one of the important starting points for human philosophical thinking about the universe, the earth and human beings themselves, giving people a direct understanding of the smallness, loneliness, fragility and preciousness of the earth, and also giving human beings an intuitive understanding of the vastness of the universe.

In addition, Voyager 1 was the first man-made object to leave the solar system. It is also by far the farthest man-made object from Earth. Due to its enormous speed, none of the other man-made objects that have been lifted off can break its record in terms of distance.

Despite its many outstanding achievements, Voyager 1 has also come at a cost. Due to its close detection of Titan, its orbit changes significantly under Titan's gravity, making it impossible to fly to Uranus and Neptune after a flyby of Saturn. This is a plan that was made from the beginning.

At that time, the Voyager team even made a plan: if Voyager 1 failed to detect Titan, Voyager 2 would repeat Voyager 1's mission. We are glad that Voyager 1 successfully completed the exploration plan of Titan, so that Voyager 2 can later achieve the mission of exploring Uranus and Neptune, thus basically realizing the previous ambitious "planetary grand" plan. In other words, Voyager 2's ability to complete the feat of "planetary grandeur" is due to the sacrifice and fulfillment of Voyager 1.

exegesis

[注1]原文:“Consider again that dot. That's here, that's home, that's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. ”“It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known.” 对其他段落感兴趣的读者可以进入以下链接:

https://www.goodreads.com/quotes/337712-from-this-distant-vantage-point-the-earth-might-not-seem。

[2] Astronomers dispute the boundaries of interstellar space. Some astronomers believe that the heliopause is not the dividing line between the Solar System and interstellar space. That's because astronomers believe that farther away there are a large number of small bodies orbiting the sun, an area known as the Oort cloud. If the outer edge of the Oort cloud is used as the frontier of the solar system, Voyager 1 will need to fly for nearly 30,000 years to leave the boundary of the solar system and enter interstellar space.

[Note 3] Real-time updates on the distance of Voyager 1 (and Voyager 2) and other information can be found at:

https://voyager.jpl.nasa.gov/mission/status/

Produced by: Popular Science China

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