Shulou(Shulou.com)11/24 Report--

This article comes from the official account of Wechat: ID:fanpu2019, by Wang Shanqin

Pioneer 11 was the first probe to detect Saturn up close and the first to successfully observe the north and south poles of Jupiter. It carries Pioneer 10 and Voyager 2. Its success has made mankind's exploration of "exoplanets" (Jupiter, Saturn, Uranus and Neptune) a big step forward, and has accumulated valuable experience for some exoplanet probes to carry out missions later. In particular, it checked the safety of the scheduled route for Voyager 2, paving the way for the latter to successfully explore Uranus and Neptune, thus playing an irreplaceable role in realizing the feat of "planetary tour" for mankind.

The success of Pioneer 10 not only realized the human dream of exploring Jupiter at close range, greatly enhanced human confidence in exoplanet exploration, but also enabled its sister probe, Pioneer 11, to switch from spare mode to independent probe mode.

The Pioneer team at NASA's Ames Research Center (ARC) has officially launched Pioneer 11 to explore Saturn. The specific steps of this plan are as follows: the Pioneer 11 will first visit Jupiter, then accelerate and change orbit with the help of Jupiter's gravitational slingshot effect, and then go straight to Saturn to realize the ice-breaking journey of Saturn exploration.

More or less the same: the structure of Pioneer 11 is exactly the same as that of Pioneer 10. They all have nuclear batteries to provide electricity, antenna systems to maintain communications and data transmission, important instruments for detection and systems for positioning and navigation.

Pioneer 11 carries basically the same equipment as Pioneer 10 (pictured below) [1] but Pioneer 11 has one more instrument than Pioneer 10: the fluxgate magnetometer (Fluxgate Magnetometer). The addition of this instrument makes it 0.5kg heavier than Pioneer 10, so its total mass is 258.5 kg.

The structure diagram of Pioneer 11 (also Pioneer 10). What is not marked in the middle of the main antenna (high gain antenna) is the medium gain antenna. Photo Source: NASA,Vectors by Mysid; Photo text Translation: Wang Shanqin in addition, due to the launch more than a year late, the instruments on Pioneer 11, especially those related to detecting magnetic fields and radiation, have been improved to a certain extent. The propulsion system, communication system and nuclear battery system of Pioneer 11 are also exactly the same as those of Pioneer 10.

02:11:00 on April 6, 1973 (international standard time, the same below), Pioneer 11 was launched on board an Atlas-Centaur rocket. The rocket that sent it to the sky was matched with a solid motor to give the probe a higher speed. At this time, Pioneer 10, which launched about 13 months ago, has left the asteroid belt and is on its way to Jupiter, but has not yet begun to explore Jupiter.

Pioneer 11 was launched on a rocket. Image: NASA Marshall Space Flight Center (NASA-MSFC) Pioneer 11 passed safely through the asteroid belt in mid-March 1974. On April 11, 1973, Pioneer 11 made an orbital correction.

A key orbit change on January 1, 1974, Pioneer 10 successfully ended the Jupiter mission. Pioneer 11 will no longer serve as a spare for Pioneer 10 and will instead carry out a program to explore Saturn. But it still has to fly past Jupiter in order to change its orbit and accelerate with the help of Jupiter's gravitational slingshot effect.

After confirming the great success of Pioneer 10, the Voyager team hopes Pioneer 11 will get closer to Jupiter and find the way for Voyager to fly past Jupiter in the future.

A closer route meant greater risk, so some members of the Pioneer team opposed the proposal. But after weighing the pros and cons, the Pioneer team finally agreed to the proposal. after all, getting closer means not only risks, but also huge benefits: access to high-definition images of Jupiter.

On April 26, 1974, the Pioneer team issued instructions to modify the orbit of Pioneer 11 in order to achieve three goals.

First, Pioneer 11 will be closer to Jupiter than Pioneer 10 and will be able to make higher-definition observations.

Second, the orbital plane of Pioneer 11 will have an angle of 52 degrees from the equatorial plane of Jupiter. This brings two benefits: (1) it can observe the north and south polar regions of Jupiter as it enters the Jupiter system. (2) it can minimize the radiation dose to Jupiter received by Pioneer 11-the previous exploration by Pioneer 10 showed that Jupiter's magnetic field is a circumferential magnetic field around Jupiter's equatorial plane. The duration of Jupiter's magnetic field and radiation influence instruments can be shortened as much as possible.

Third, the revised orbit will fly past Jupiter in a retrograde way, that is, its path is opposite to the direction in which Jupiter rotates. This allows it to see more of Jupiter's surface and better measure Jupiter's magnetic field in a short time.

Exploring the Jupiter system on November 7, 1974, Pioneer 11 made a change of orbit and began to enter the Jupiter system. 03:39 on November 25, Pioneer 11 passed through Jupiter's bow shock. Next, Pioneer 11 began to fly past Jupiter and its moons.

Pioneer 11 and Pioneer 10 fly over the road map of the Jupiter system (Jupiter and its moons) (orbital plane view of the Jupiter system). It can be seen that Pioneer 11 and Pioneer 10 are going in the opposite direction around Jupiter. Photo source: https://www.nasa.gov/ feature / 45-years-ago-pioneer-11-explores-jupiter, photo translation: Wang Shanqin, Pioneer 11 flew over Callisto (distance 78.65 thousand km) and Ganymede (6923 thousand km) on December 2, 1974, and Pioneer 11 flew over Io (distance 314,000km) and Europa (distance 586700 km) on December 3. [2] compared with Pioneer 10, Pioneer 11 flew near and far over Jupiter's four moons.

On December 2, 1974, Pioneer 11 photographed half-moon-shaped Io at a distance of 756,000 kilometers. Source: NASA / Ames

In 1973 and 1974, Pioneer 10 and Pioneer 11 captured images of Jupiter's four Galileo moons, from left to right, Io, Europa, Ganymede and Callisto, respectively. The image of Io was obtained by Pioneer 11. Image: 5:02 on December 3, https://history.nasa.gov/ SP-349 / p180.htm1974, Pioneer 11 passed behind Jupiter (in view of Earth). 19 minutes later, Pioneer 11 reached closer to Jupiter, 4.2828 kilometers from Jupiter's cloud top. For comparison, the distance between the near point of Jupiter and the top of Jupiter's cloud on Pioneer 10 is 132,000 kilometers. As a result, Pioneer 11 is much closer to Jupiter than Pioneer 10, only 1 stroke 3 of the latter's distance, allowing it to get a much clearer image of Jupiter than the latter.

Pioneer 11 captured a clear image of Jupiter's Great Red spot, when Pioneer 11 was at 31 degrees south latitude and 545,000 kilometers from Jupiter. Image: before NASA reached the near point of Jupiter, Pioneer 11 reached a speed of 47.5km / s, making it the fastest man-made object so far.

Like Pioneer 10, Pioneer 11 does not have a data storage device, so it can only send data as soon as it gets the data, so any data it takes cannot be transmitted to Earth as it enters the back of Jupiter.

5:44 on December 3, 1974, Pioneer 11 emerged from behind Jupiter and began to resend the acquired data. Then it flew at high speed over Jupiter's north pole. Pioneer 11 captured Jupiter's northern region at 09:27 on December 3, when it was 435,000 kilometers from Jupiter. This is the first time humans have seen the polar region of Jupiter.

In the Pioneer 11 images of Jupiter's north pole, the resolution reached 152 kilometers per pixel. [3] previously, astronomers speculated that the atmosphere in Jupiter's polar region is more transparent than that in the equatorial region, and that observing the north and south polar regions can take a deeper look into the interior of the atmosphere.

Images taken by Pioneer 11, including Jupiter's north pole region. Image source: due to its higher speed than Pioneer 10 and a large angle between the orbital plane and Jupiter's equatorial plane, NASA suffered less damage from Jupiter's annular radiation belt during its flyby than Pioneer 10.

On December 3, 1974, Pioneer 11 flew over Rhea (distance 1275 km) to determine its mass. Pioneer 10 did not fly it before.

On January 1, 1975, Pioneer 11 stopped exploring Jupiter. During the exploration of the Jupiter system, Pioneer 11 sent back hundreds of photos of Jupiter and its moons, made infrared measurements of Jupiter and obtained data on magnetic fields and charged particles.

Flying to Saturn: argument, compromise and sacrifice the orbit of Pioneer 11 deflected at a large angle due to Jupiter's great gravity. Since then, the Pioneer team issued instructions to change its orbit twice on May 26, 1976 and July 13, 1978, further correcting its orbit to Saturn on the other side of its orbit.

The trajectory filmed by Pioneer 11. It was launched from Earth in April 1973 and flew over the Jupiter system in December 1974. Under the influence of Jupiter's gravity, the orbit changed significantly. Since then, the probe itself ejected propellant, changed its orbit and flew to Saturn. It passed through the Saturn system in September 1979 and then left the solar system. Photo Source: NASA; Photo text Translation: Wang Shanqin at that time, the Voyager project had been approved before, and the relevant team had been set up and confirmed the future plan: Voyager 1 would continue to explore the Jupiter and Saturn systems to get clearer images. Voyager 2 will perform the Voyager 1 mission (if Voyager 1 fails), or explore Jupiter, Saturn, Uranus and Neptune (if Voyager 1 succeeds).

A key step for Voyager 2 to fly to Uranus is to change orbit and accelerate through Saturn's A ring with the help of Saturn's gravitational slingshot effect. To ensure safety, the Voyager team advised Pioneer 11 to pass through Saturn's A ring to determine whether the particles in the A ring would damage the probe. After discussion, the Pioneer team agreed to the plan.

However, the two teams disagreed on the route of the probe after passing through Saturn's A ring: the Pioneer team wanted Pioneer 11 to move toward Saturn's inner ring and directly detect Saturn's inner ring. and determine whether the previously controversial D-ring exists. The Voyager team asked Pioneer 11 to move in the direction of Saturn's outer ring, pass through Saturn's E ring, and then leave Saturn's system to determine whether Voyager 2's probe will be harmed by Saturn's outer ring particles as it passes through this route.

The Pioneer team believes that if Pioneer 11 takes the route given by the Voyager team, it will be farther and farther away from Saturn, unable to get higher-definition observations of interest to astronomers, let alone directly detect Saturn's inner rings. The Voyager team also adheres to its own advice: if Pioneer 11 does not take this route, Voyager 2 does not risk taking this route, and the observations of Uranus and Neptune are out of the question.

The two sides argued repeatedly, but neither side could convince the other. The matter came to the NASA headquarters, the common superior department of the two teams. NASA headquarters agreed with the Voyager team's recommendation because the route sacrificed observations of Saturn's inner rings and closer observations of Saturn itself, but it was worth the sacrifice to allow Voyager 2 to explore Uranus and Neptune.

When the head of NASA's planetary science department announced the decision, members of the Pioneer team at the scene booed and protested. Nevertheless, the Pioneer team must implement the decision of NASA headquarters.

Flyby Saturn system on July 31, 1979, Pioneer 11 began observing Saturn. At this time, Voyager 1 and Voyager 2 have also finished their exploration of Jupiter and are heading towards Saturn.

On August 26, 1979, Pioneer 11 photographed Saturn, Saturn's rings and Rhea (the white spot on Saturn's lower right). Image: on August 29, NASA1979, Pioneer 11 entered the Saturn system and flew over Iapetus (103.2535 km) and Enceladus (1371.3574 km). [2]

On August 31, 1979, Pioneer 11 flew over Enceladus (distance 66.6153 km). [2] on the same day, it detected Saturn's bow shock wave 1.5 million kilometers from Saturn, thus proving Saturn's magnetic field for the first time. [1]

On September 1, 1979, Pioneer 11 flew over Epimetheus (6676 km), Enceladus (4.596 km), Enceladus (29.1556 km) and Enceladus (10.4263 km), and passed through the plane outside Saturn's outer ring to approach the A ring. At 16:29:34, Pioneer 11 reached the nearer of Saturn, which was 2.0591 kilometers from Saturn's cloud top and reached a speed of 31.7 kilometers per second.

In the process of approaching and leaving Saturn, Pioneer 11 took 440 photos of the Saturn system, about 20 of which have a resolution of 90 kilometers per pixel. [1] during this period, it also discovered Saturn's F ring and two new moons.

After flying by Saturn, Pioneer 11 flew over Enceladus (22.8988 km), Enceladus (32.9197 km), Enceladus (22.2027 km), Enceladus 14 (10.9916 km) and Rhea (34.5303 km) on the same day. [2]

On September 1, 1979, Pioneer 11 photographed Saturn and part of its rings. Photo: pioneer 11 flies over Titan (36.2962 kilometers) on September 2, NASA1979. It takes pictures of Titan with a resolution of up to 179 kilometers per pixel. These images show that Titan is an orange satellite with no surface atmospheric features. Based on images of different bands, astronomers have determined that Titan is 5690 or 5760 kilometers in diameter. The data also show that the temperature at the top of Titan's clouds is about 75K (minus 198 degrees Celsius). [4]

On September 2, 1979, Pioneer 11 filmed Titan at a distance of 360,000 kilometers. Image source: NASA during the flyby of Saturn, the Pioneer 11 infrared radiometer measured the infrared radiation of Saturn's upper atmosphere, combined with the radio occultation method to determine the temperature, structure and other properties of Saturn's upper atmosphere. Its data show that Saturn's average temperature is about minus 180 degrees Celsius, and Saturn's main component is liquid hydrogen, so it is not suitable for life. [1]

Then Pioneer 11 sped toward Saturn's E ring and left Saturn.

On October 5, 1979, Pioneer 11 ended its observation of the Saturn system.

Flying away from the sun, the orbit of Pioneer 11 deflected under the influence of Saturn's gravity. Then it flew out of the solar system toward the center of the Milky way and began an interstellar mission. It should be noted that it flew away from the sun in almost the opposite direction of Pioneer 10.

In 1995, Pioneer 11 could no longer power its instruments, and NASA decided to shut it down. On November 24, 1995, humans completely lost contact with Pioneer 11.

Today, Pioneer 11 is about 111 astronomical units (about 166 billion kilometers) from the sun. It now travels at a speed of 11.182 kilometers per second relative to the sun, moving in the direction of the current shield at a speed of 2.36 astronomical units per year. [2] its speed has also exceeded the third cosmic speed, so it can leave the solar system in the future.

Pioneer 11 also carried a metal plate with exactly the same symbol and pattern as the one on Pioneer 10. (for more information, see "Pioneer exploring the Frontiers of the Solar system: pioneer 10") since Pioneer 10 flew only Jupiter, and Pioneer 11 also flew over Saturn, the two orbits are different. Therefore, the road map on Pioneer 11 is not accurate. But it's a small problem.

In 2019, it was inferred from the star position, velocity and direction obtained by Gaia satellite that Pioneer 11 would fly past the dwarf star TYC 992-192-1 in about 9283 million years, with a distance of 0.8 light-years from it. This is the closest star it will encounter in the next 25.7 million years.

Episode: pioneer from spare parts to copy H1971, Pioneer 10 and 11 have not yet been launched, and their numbers are Pioneer F and Pioneer G. This year, the Pioneer team plans to launch Pioneer H as a spare for Pioneer G (Pioneer 11) in the future.

According to the plan, Pioneer H will be launched in 1974 and fly by Jupiter in July 1975. Its orbital plane is perpendicular to Jupiter's equatorial plane, so it can fully observe Jupiter's south and north poles. If it successfully launches, it will be renamed Pioneer 12.

Unfortunately, NASA headquarters rejected the plan before Pioneer H was launched. Later, H, the pioneer who removed the nuclear battery, was placed in the museum as replicas of pioneers 10 and 11.

Pioneer H, who was hung in the museum, was used as a copy of Pioneer 10 and Pioneer 11. Image source: the name CamWow Pioneer 12 is used by the pioneer Venus Orbiter (Pioneer Venus Orbiter), also known as Pioneer Venus 1 (Pioneer Venus 1), which launched on May 20, 1978.

When Pioneer 11 flew by Jupiter, it was at an angle of 52 degrees from Jupiter's equatorial plane, observing parts of Jupiter's north and south poles, so it partly achieved the goal of Pioneer H. What really realized the orbital model of Pioneer H was the solar probe Ulysses and Jupiter Juno, which were later launched. The angle between Ulysses and the equatorial plane of the sun reaches 80.2 degrees, almost perpendicular. Juno is completely perpendicular to the equatorial plane of Jupiter (with an angle of 90 degrees) and is a typical polar orbit detector.

The historical contribution of Pioneer 11 Pioneer 11 is the first probe to detect the Saturn system at close range, realizing the human dream of detecting the Saturn system at close range.

After entering the Saturn system, various instruments on Pioneer 11 obtained data on Saturn, Saturn rings and Saturn moons. The near infrared data obtained by it enables astronomers to determine the temperature and structure of Saturn's upper atmosphere and the temperature of Titan; the image quality obtained by it in the visible band exceeds that obtained by all telescopes on Earth at that time, becoming the first precious images for astronomers to study the details of Saturn's system. The data of Saturn's magnetic field obtained by it enables astronomers to draw Saturn's magnetosphere and magnetic field distribution, intensity, direction and structure, and to determine the details of the interaction between solar wind particles and Saturn's system magnetic field; its close observation provides a lot of details of Saturn's rings and helps astronomers discover the F rings of Saturn's rings; it accurately determines the mass of Saturn and some of Saturn's moons by flyby.

In addition, Pioneer 11 is not the first probe to detect the Jupiter system at close range, but it has obtained a clearer image of Jupiter at a closer distance and an image of Jupiter's poles for the first time. Its exploration of Jupiter has further deepened mankind's understanding of the nature of Jupiter.

To commemorate the great contribution of unmanned spacecraft in exploring the planets and moons in the solar system, the United States Postal Service issued a set of 10 stamps on October 1, 1991. It describes the "nine planets" of the solar system and how the moon was explored (when Pluto was still considered a planet). In this set of stamps, Jupiter's one goes with Pioneer 11, not Pioneer 10, which was the first to detect Jupiter, while Saturn, Uranus and Neptune all match Voyager 2.

The author's personal point of view is that although Pioneer 11 and Voyager 2 made clearer observations of Jupiter and Saturn respectively, Pioneers 10 and 11 successfully approached and sent back data for the first time. Therefore, a more reasonable match might be Jupiter-Pioneer 10, Saturn-Pioneer 11, Uranus and Neptune-Voyager 2.

Stamp No. 11 of Jupiter and Pioneer issued on October 1, 1991. Image source: the success of United States Postal Service Pioneer 11 also accumulated the first valuable experience for Voyager 1, Voyager 2 and Cassini-Huygens probes to explore Saturn and cleared the way for Voyager 2 to explore Uranus and Neptune. In particular, it validates the granular environment inside Saturn's ring and ensures that Voyager 2 can safely cross its intended route in the future.

At that time, members of the Pioneer team were aggrieved that Pioneer 11 sacrificed their final exploration target for Voyager 2, but they were relieved when Voyager 2 successfully explored Uranus and Neptune. Because they know that Pioneer 11 pioneered Voyager 2, thus making its own important contribution to the exploration of these two ice giant planets.

reference

[1] In Depth: Pioneer 11, https://solarsystem.nasa.gov/missions/pioneer-11/in-depth/

[2] Wikipedia: Pioneer 11, https://en.wikipedia.org/wiki/Pioneer_11#cite_note-Pioneer_11-1

[3] Andrew LePage, Our First Good Look at Jupiter's North Pole-1974, https://www.drewexmachina.com/2016/06/28/our-first-good-look-at-jupiters-north-pole-1974/

[4] Andrew LePage, Voyager 1: The First Close Encounter with Titan, https://www.drewexmachina.com/2015/11/12/voyager-1-the-first-close-encounter-with-titan/

Bailer-Jones, Coryn A. L. & Farnocchia, Davide, Future Stellar Flybys of the Voyager and Pioneer Spacecraft, Research Notes of the American Astronomical Society, 2019, 3, 59. For an extended version of this paper, see arXiv:1912.03503 (https://arxiv.org/ abs / 1912.03503).

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