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Pioneer 11 to Jupiter and Saturn

The spacecraft was launched into a flight path with open options. This is a waiting path in the asteroid belt where the spacecraft waits for a signal from Earth directing it to the final path.

The Pioneer 11 spacecraft against the background of the planet Jupiter. Image: NASA
The Pioneer 11 spacecraft against the background of the planet Jupiter. Illustration: NASA

In the previous chapter we dealt in the Pioneer 10 spacecraft, the first spacecraft launched towards the planet Jupiter. This time we will deal with its twin spacecraft, which was also the first to visit Saturn.

The Pioneer 11 spacecraft was launched on April 5, 1973. Before its launch, several changes were made to its work plan. The distance it will have to pass near Jupiter depends on the success of Pioneer 10. If Pioneer 10 is not damaged by Jupiter's strong radiation belts, its transit distance from the star will be less. The distance will be 35,000 km. If Pioneer 10 is destroyed by the radiation, Pioneer 11's transit distance will be greater.

The spacecraft was launched into a flight path with open options. This is a waiting path in the asteroid belt where the spacecraft waits for a signal from Earth directing it to the final path. The options are:

1. Transit flight over Jupiter's equator - small or large transit distance.

2. A flyby over the south pole of Jupiter to enable ground photographs of Jupiter. It was assumed that the atmosphere at the poles is transparent.

3. A transit flight that allows a passage near Saturn and an exit from the solar system. Instead of leaving the solar system like Pioneer 10, the spacecraft heads for Saturn after completing its measurement of Jupiter. The flight time is seven years. After passing by Jupiter, the spacecraft's speed increased to 173,000 km/h and it reached Saturn in 1980.

The possibility of bringing Pioneer 11 closer to one of Jupiter's two large moons has been raised. A final decision will be made only four months after the passage of Pioneer 10. Pioneer 11 is another research instrument. A magnetometer for measuring the magnetic fields in the vicinity of Jupiter and instead of one nuclear engine it has two. The spacecraft is also stamped with a drawing similar to the one on Pioneer 10. Only the information written on it is different.
After a careful examination of Pioneer 10's findings, it was decided that Pioneer 11 would make the short, short-distance flyby of Jupiter, and from there continue on to Saturn. The danger lurking for the spacecraft on the transit flight near Saturn is a collision with its outer ring. The expected transit by Saturn is in September 1979. In the path chosen for Pioneer 11 the transit begins near Jupiter's south pole and is rapidly pulled upward by its own gravity. The spacecraft crosses the equatorial region at an angle of 53 degrees towards the North Pole. The speed that will be reached is 173,000 km/h. Its angle of approach moves it quickly through the radiation zone so that its effect on the spacecraft is reduced. Pioneer 11 appears on the left side of Jupiter and is discovered on its right side.
The measurement range of Pioneer 11 after the encounter with Jupiter is 160 million km above the Melaka plain. The spacecraft should serve as a touchstone for determining the masses of Jupiter and its moons.
The course of the flight of Pioneer 11
The spacecraft's flight can be divided into five stages.
1. The flight from Earth to the asteroid belt.
2. The flight in the asteroid belt.
3. The flight from the asteroid belt to Jupiter.
4. The flight from Jupiter to Saturn.
5. Crossing near Saturn.

First phase, from April 5 to August 18, 1973
6 In April - a fault was discovered in the nuclear power unit of the spaceship and it was later fixed when the first correction was made to the flight path.


Second phase, from August 18, 1973 to March 18, 1974
From the passage of the two spaceships, it became clear that the serious concerns about being hit by high-speed particles were largely misplaced. In the center of the strip are tiny particles orbiting the sun at a speed of 64,200 km/h, a speed sufficient to give a particle with a mass of one thousand grams the ability to penetrate one centimeter of an aluminum plate. Such particles may penetrate spacecraft and cause serious damage to them. It turned out that most of the particles observed by the spacecraft's instruments were smaller and their total number was less than expected. By mid-February 1974, Pioneer 11 had been struck by eight micrometeoroids.

Third phase, from March 18 to December 3, 1974
April 1 - a correction was made to the flight path.
9 in September - at the request of Dr. Van Allen, the speed of rotation of the spacecraft around itself was increased in order to obtain more and better information during the transit near Jupiter.
November 2 - Pioneer 11 began transmitting photographs.
November 30 - First photograph of Ganymede and Callisto in the ultraviolet photometer to discover traces of hydrogen and helium.
From December 1 to 14 - photographs of Jupiter and two photographs of Ganymede and Callisto to discover traces of hydrogen and helium in them. It was hoped that Callisto would be used in the future as a landing site for the investigation of Tzedek.
From December 2 to 8, photographs of Jupiter's south pole. Continuing the search for traces of hydrogen and helium in Ganymede and Callisto, measuring the heat prevailing on the surface of these moons and later measuring the heat of Io and Amalthea. As of today, the photopolarimeters are also involved in measuring the gases above Jupiter's cloud cover. Similar measurements are also made regarding moons, except that they are performed at angles that were not possible with Pioneer 10.
December 3 - transit flight. Pioneer 11 performs a sort of corkscrew flight over the star. This flight reduces the duration of the spacecraft's exposure to the high radiation that exists at the equator to half an hour, and takes the spacecraft to make another lap around Jupiter and from there a direct flight towards Saturn. This path was designed so that the photographs would be a continuation of those of Pioneer 10 and not coincide with them, as well as photographs that cannot be taken from Earth and a deeper look at the layers of the atmosphere at the South Pole if the atmosphere here is transparent.
11 photographs of the South Pole and one of an island were taken. Four hours and 21 minutes before the transit, Jupiter was imaged in infrared for 23 hours. One hour and 39 minutes after the transit, Jupiter was photographed for two and a half hours, also in infrared. Pioneer 11 passed at a distance of 42,700 km from the face of the star at a speed of 171,200 km/h.
December 4 - At the end of the day, 22 photographs of Jupiter were taken as it recedes.

Pioneer 11 findings from Jupiter measurements
In the 48 hours that Pioneer passed near Jupiter, it photographed it 22 times from every possible angle. It turned out that its magnetic field is twice as large as that of the Earth and that its surface temperature is 40 times greater than that of the Sun. The red spot is a hurricane vortex caught between atmospheric bands moving in opposite directions in the right-left direction above it and in the left-right direction below it. It moves counterclockwise. On its way to Saturn, the spacecraft photographed the south pole of Jupiter. It turned out that in the high latitudes the atmospheric bands break into spots that have needle formations that move with hurricane-like storms. These storms occur at the border of counter-storms where the wind speed reaches 480 km/h. It turned out that the moon Callisto is covered in ice at the poles. The moon Amalthea was also photographed.


Fourth stage, from December 5, 1974 to September 5, 1979
On its way to Saturn, Pioneer 11 measured the interstellar magnetic field, the structure and flux of the solar wind, the impact concentrations of cosmic radiation and its directions, and the properties of interstellar dust. She studied the complex relationships between the solar wind, the interstellar magnetic field and cosmic radiation and found the limit of the thin solar atmosphere and the impact of meteorites.


Fifth stage, the flight to Saturn
Since Pioneer 11 successfully passed Jupiter, it was headed for Saturn. It was to reach it in September 1979. Pioneer 11 will pass at a distance of 2,960 km from the top of its clouds. It will fly between Saturn's inner ring and its clouds and through its gravity will fly towards its large moon Titan. To prevent a collision between the spacecraft and the moon and to prevent its contamination with terrestrial bacteria (if these are adjacent to it even after being disinfected before launch). The transit distance from the moon is 19,200 km. At the end of the program, the spacecraft will fly towards leaving the solar system. It will continue to transmit data at least until it reaches the orbit of Uranus in 1985.

At the beginning of 1978 it was decided to change the flight route. This is out of a trend to use the spaceship as a tracker for the Voyager spaceships. The spacecraft will begin the encounter with Saturn from a distance of 28,800 km from the outer edge of the outer ring and will pass through the rings until it comes within 24,000 km of Saturn.

On November 20, 1975, the first observations of Saturn were made. According to instructions, the photopolarimeter was turned on for a few hours and it surveyed Saturn. This is an opening observation for the observations you will conduct in July 1976, this time is a particularly good opportunity for observation because of the condition of the planet. Like the relationship between the light side and the dark side, which cannot be checked by observations from Earth, Pioneer 11 is now 1280 km from Saturn.
The speed of the spacecraft was increased by 108 km, thus enabling two options for making the transition flight. On the first path the spacecraft will pass between Saturn and its rings and on the second path the spacecraft will pass outside the Saturn system - its rings.

The spacecraft will pass under the rings upwards, so that you can survey them from the bottom edge to the top edge. This maneuver is conducted using the open-ended method. It was performed here for the first time. A fixed antenna spacecraft that has a continuous connection with the Earth. To perform the maneuver, the spacecraft had to be deflected so that the distance of the antenna from the link line with the Earth would be 25 degrees. For several hours there was no contact with Earth. The disadvantage of the method is the loss of potential telemetric information. The control center named after Ames cannot have any way to fix the fault. Any solution is nothing more than a guess.
August 28, 1979 - The spacecraft began photographing Saturn from a distance of six million km and it served as a preliminary reconnaissance for the Voyager spacecraft.
September 1 - The spacecraft crossed the rings of Saturn twice and reached a distance of 21,000 km above the clouds of Saturn. Contrary to predictions that it would crash during its passage through the rings, it encountered only two particles that are only half the thickness of a human hair. These particles caused slight shocks in the spacecraft and they were recorded in its instruments.
September 2 - On this journey, Pioneer 11 reached the other side of Saturn and from there continued on its way towards photographing Titan from a distance of 356,000 km.

Saturn is a cold and desolate world that has a small rocky core covered by an atmosphere whose surface is marble-like and transparent. The atmosphere contains mainly hydrogen and helium and traces of methane and ammonia that give the high cloud layers their yellow hue. The atmosphere also has a blue-green tint. The bands visible in the photographs cover Saturn and are alternately bright and dark. The northern hemisphere is divided into at least 10 thin bands of color. South of them, in the area of ​​the equator, it is the brightest. Saturn has many more bands of currents than expected.

magnetic field
Saturn has a magnetic field 700 times greater than Earth's, but five times weaker than expected. Since Saturn captures particles from the Sun like Earth and Jupiter, it is surrounded by radiation belts like these two planets. In contrast to them, the magnetic field lines are perfectly arranged in the north-south direction. The radiation stopped when the spacecraft was below the rings.

the rings
Pioneer 11 discovered that Saturn has six rings, not four. The rings are transparent and more fragments are visible between them than can be seen through telescopes from Earth. The F ring is probably 3,520 km from the D ring. Its distance from Saturn is 96,000 km. The temperature on the rings is 202 degrees below zero. The rings cast a heavy shadow near the center of Saturn. This shadow is so dark that it creates an almost eternal night in this area. When Pioneer 11 was close to the rings it detected a bombardment of charged particles. The bombing stopped for 12 seconds and then resumed. The rings are able to serve as protection for instruments and astronauts against various radiations. Their defense range is 137,600 km.

Its diameter is 5,790 km. Probably has a landscape similar to that of the moon. The temperature on its surface is low and its atmosphere is cloudy. Its reddish brown color is probably created by a layer of fog that absorbs the sun's heat and keeps it. In the atmosphere an abundance of carbon and ammonia. The temperature at the top of the clouds is 200 degrees below zero.
The moon has a bright side that is probably covered with an ice crust.
This moon is also covered in ice.
Another moon
Pioneer 11 discovered another moon. This is the 11th moon and it was named Pioneer Rock. The sign of this moon is 197 S -1 because it is the first moon of Saturn discovered that year. Its diameter is 600 km and it is 90,000 km away from it.

2 תגובות

  1. awake
    This article, like my other historical articles, was written in the 70's according to what the N.A.S.A. said. In order to keep the spirit of things and since these were the findings of that time (nowadays, of course, there is more information), I left these data as they were reported. If I were to introduce changes, it would be from the point of view of thinking today and based on the information that is known today and that is what I wanted to avoid.

  2. Interesting article, thanks.
    You need to check some numbers like "surface temperature".
    of Jupiter is 40 times higher than that of the Sun", or the spacecraft passed
    1,280 km from Saturn…… and its speed was increased by 108 km/h…..
    Or Jupiter's magnetic field is 2 times greater than Earth's
    And that of Saturn is 700 times bigger ……?

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