Pioneer to Jupiter Second Exploration

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Pioneer Encounters Jupiter

Pioneer to JupiterSecond Exploration

NOVEMBER 1974


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Launching Pioneer 10


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Pioneer to Jupiter 5

PIONEER PROJECT OBJECTIVES

The Pioneer Project, managed by NASAs Ames Research Center in Mountain View, California, has been one of the most beneficial space

exploration programs in United States history. The program has never veered from its objective to increase the basic knowledge of our solar

system so that future generations will be better able to deal with the problems here on Earth.

While there is reason to believe that most of the large components of the solar system were created at about the same time, some five to ten

billion years ago, it is not yet clear how the planets came to be so different. By gaining an insight into the factors responsible for those

differences, scientists hope to achieve a better understanding of Earth and the universality of physical laws that can be applied to new proc-

esses on Earth.

Helping in this quest for basic scientific knowledge, the Pioneer spacecraft act as an extension of our senses in seeking knowledge to be

used to the greater benefit of mankind.

Currently, the Pioneer Project has six spacecraft operating in deep space. Four of these,Pioneers 6, 7, 8 and 9, are orbiting the Sun acting

as a solar network of monitoring stations. Pioneer 10, however, which made its historic flyby of Jupiter last December, is racing through

unexplored space and will eventually be the first man-made object ever to leave the solar system. Pioneer 11 continues toward its

rendezvous with Jupiter, and with a gravitational assist from the planet, will continue on to Saturn.

PIONEER HISTORY

The Pioneer Program began in 1958 whenPioneer 1 was launched to a record altitude of 70,700 miles and returned 43 hours of data. Within

five months, four more Pioneers were launched, each achieving its own mark of success. Pioneer 5 was the first of the series to attain solar orbit.

Pioneer is one of the most efficient programs in terms of science data returned per dollar invested. Pioneers 6, 7, 8 and 9 are still operating

as a network of solar monitors and interplanetary investigators as they orbit the Sun.

Each designed to operate six months in space, the Pioneer 6through 9 spacecraft have long exceeded that life expectancy and have given

the United States an unexpected national asset.

Pioneer 6, the first in the series, was launched in December 1965 and orbits the Sun elliptically between 0.814 AU and 0.985 AU. (AU

stands for Astronomical Unit and is the distance from Sun to Earth 93 million miles.) Pioneer 6takes 311.3 days to orbit the Sun.

Pioneer 7, launched in August 1966, has an orbit just outside the Earth (1.010 AU to 1.125 AU) and gets around the Sun every 402.9 days.

Pioneer 8 orbits between 1.0 AU and 1.1 AU very close to Earths orbit and takes 387 days to circuit the Sun. It was launched in

December 1967.

The last of the solar orbiters in the series,Pioneer 9, was launched in November 1968 and moves around the Sun each 297.5 days, having

an orbit about three-fourths that of Earth (0.75 AU to 1.0 AU).

The mission of the Pioneer 6through 9 series is to acquire data on the solar wind, energy particles, and the magnetic and electric fields

radiating outward from the Sun toward Earth. By doing so, they act as a warning system of solar disturbances.

These warnings are supplied to the National Oceanic and Atmospheric Administrations Space Disturbance Forecast Center in Boulder,

Colorado, which issues them to about 100 primary users. These include the Federal Aviation Agency, commercial airlines, power

companies, communications organizations, and organizations doing electronic prospecting, surveying, and navigation.

Geomagnetic storms from the Sun have always caused problems for equipment dependent on a stable magnetic field. There is evidence that

solar storms have disrupted electric power utility systems, especially in the northern latitudes. As these utility operations become more

geographically dispersed and require larger interconnected power networks, the disruptions could cause even greater problems.

The Pioneer solar weather stations provide up to two weeks warning on the effects of solar activity on Earth, thereby giving power

companies a chance to prepare for them and minimize their effects.

It is assumed the data gathered by the Pioneers will help us improve our ability to predict and even control certain aspects of our terrestrial

environment. U.S. weather scientists have statistical correlations between solar disturbances, and the frequency and intensity of Earth

storms. Even earthquakes are believed to be directly related to solar activity.

Already a wealth of information has been produced from the study of data returned by the Pioneers. Scientists now have a better idea of

the functions of the magnetosphere which shields the Earth from high energy solar particles. A measurement of cosmic dust populations

has revealed that the spatial density of micrometeorites is considered low enough to pose no hazard to missions in this region of space. Data

on the changes in the electrical and magnetic characteristics of the Suns corona are being studied, as are other solar phenomena being

explored by the Pioneers.


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Pioneer to Jupiter6

Pioneer Begins A Long Journey


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PIONEER 10 RESULTS

The most famous Pioneer to date has of course beenPioneer 10, which flew past Jupiter in early December 1973. A wealth of information

was received from that dramatic flight, much of which is still being studied and scrutinized. (See Data Processing section of this document.)

The information that has been analyzed gives us a new picture of Jupiter which supports some theories and contradicts others we have had

about the giant planet. The following description of Jupiter is based on data fromPioneer 10.

Jupiters Interior

Jupiter, the largest planet in our solar system, is made up almost entirely of liquid hydrogen, and may have a small rocky core thousands of

miles below its heavily clouded atmosphere. Even with its enormous internal pressures of millions of atmospheres, Jupiter is just too hot

to solidify.

Unlike Earth, Jupiter shows no rigid crust or other concentration of solid mass areas. The planet is in a hydrostatic equilibrium. However,

the gravity analysis, which is not yet complete, may show Jupiter to have a small rocky core, perhaps containing some iron.

There is a dramatic rise in temperature and pressure as one goes deeper into the planet. At the transition zone to liquid, some 600 miles

below the top of the atmosphere, the temperature is calculated to be 3,600 degrees F. At approximately 1,800 miles down, where the

pressure is 90,000 Earth atmospheres, the temperature increases to 10,000 degrees F. At this point, the weight of the Jovian atmosphere has

compressed the hydrogen into a liquid about one quarter the density of water.

At 15,000 miles below the top of the atmosphere, the 20,000 degrees F temperature and the pressure of three million atmospheres

compresses the liquid hydrogen into a liquid metallic hydrogen.

Interior of Liquid JupiterPlanet is mainly hydrogen

The temperature at the center of the planet is calculated to be about 54,000 degrees F, which is about six times the temperature on the surface

of the Sun.

Looking at these temperatures from the center outward, we see that Jupiter loses heat at a tremendously rapid rate, with temperatures

decreasing steadily from 54,000 degrees F to perhaps 10 degrees F at a point somewhat below the cloud tops. This means Jupiter radiates

two to three times more heat than it receives from the Sun.


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Pioneer to Jupiter8

The tremendous internal heat of Jupiter is believed to be primordial heat left over from the planets formation. This high heat of formation

is confirmed by Pioneer measurements of Io and Europa, the closest of the large moons, which are rocky and unlike the planet-sized ice

moons lying farther out. It is thought that a hot primordial Jupiter radiated enough heat to prevent water vapor from condensing into ice

during formation of Io and Europa.

An alternative explanation for the high internal heat is that it is energy released by the fractionation of hydrogen and helium, a process

believed to be currently under way somewhere near the center of the planet.

Pioneer data indicating that Jupiters magnetic field is tilted and displaced from the center of the planet supports the theory that the planet

is a huge, flattened, fast-spinning ball of liquid hydrogen.

Jupiters field, like Earths, is believed to result from a dynamo effect caused by eddies within the liquid interior that generate electric

currents and, hence, magnetic fields. Only a planet with a tremendously active interior could produce a magnetic field as far offset from its

center as Jupiters.

Jupiters hot, churning interior sends heat up to the surface through convective currents that circle and eddy their way from the center of the

planet to the top of the atmosphere, moving as fast as 1,500 miles per year. These currents take up to 50 years to cover the 44,000 miles

from the planet center to the atmosphere.

This rapid convection of heat is reflected in the constant rise and fall of the atmosphere. This is seen as the prominent, semi-permanent

features in the planets clouds. The striking white ovals are rising atmosphere surrounded by darker borders of descending atmosphere.

Jupiter Atmosphere Model*

Atmosphere depth to liquid zone is 1,000 km (600 mi)

Jupiters Atmosphere

Accounting for about one per cent of the planets total mass, Jupiters atmosphere is 600 miles deep and consists primarily of hydrogen and

helium gas and some very small amounts of other elements.

Pioneer calculations put the ratio of hydrogen to helium in the upper atmosphere at about 80 per cent to 20 per cent, with less than one per

cent for all the other elements. This is similar to the ratio of elements found in the Sun.


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Jupiters Clouds and Heat Balance

Jupiters clouds are believed to be made up of four distinct layers. Ammonia ice crystals, measured from Earth, are believed to form the top

of Jupiters clouds. Below this are red-brown clouds, probably of ammonia hydrosulfide crystals, and below that, water ice crystals. Still

lower, liquid water droplets containing ammonia in solution may be present. However, water, it must be noted, has never been observed.

ThePioneer 10 infrared experiment indicates the topmost cloud layer of ammonia ice crystals to be at a level where pressure would be 700

millibars and temperature at -184 degrees F. This is the temperature / pressure combination at which ammonia would condense out. The

transparent outer atmosphere about the clouds is believed to contain some ammonia, plus some well-mixed methane.

Eight miles above the cloud tops, at the 300 millibar pressure level, the temperature falls to -229 degrees F. Farther out a haze of ammonia

crystals may exist, extending up to a layer where solar heat is absorbed by the atmospheric methane. This would produce an inversion layer

in which the atmosphere is warmer. The inversion layer appears to be 21 miles above the visible clouds at a pressure level of 100 millibars

(1/10th of an Earth atmosphere) and a temperature of -247 degrees F.

Still higher, there appears to be a haze layer of aerosols and hydrocarbons (such as ethane and acetylene, recently identified from Earth)

which also may absorb sunlight and heat the atmosphere.

By some interpretations,Pioneer 10s infrared and radio occultation experiments do not agree on temperature levels at the top of the atmosphere.

If the occultation findings are correct, the cloud regions and zones of Earth-like temperature may be far higher than believed near the very top of

the atmosphere, or else estimates of the amount of ammonia in Jupiters atmosphere may have to be revised downward drastically.

However, several other calculations place the clouds at about 150 miles below the atmosphere top. The difference may be resolved through

further analysis or eventually by sending a probe into Jupiters atmosphere.

Jupiters atmosphere is somewhat warmer near the equator than at the poles, though there are warm belts near the poles. The temperatures

are the same in the northern and southern hemispheres and on the day and night sides of the planet.

The cloud particles in the cloud tops in both the light and dark zones tend to be smaller than those in the Earths cumulo-stratos clouds. In

both belts and zones, the cloud particles tended to be very reflective indicating either ice particles or shiny droplets.

Jovian Weather

Jupiters 17 relatively permanent belts and zones appear to be comparable to the continent-spanning cyclones and anti-cyclones which

produce most of the weather in the Earths temperature zones. On both planets these phenomena are huge regions of rising or falling

atmospheric gas, powered by the Sun. (And in Jupiters case, also by its internal heat source.)

On Earth, huge masses of warm light gas rise to high altitudes, cool off, get heavier, and then roll down the sides of new rising columns of

gas. General direction of this atmospheric heat flow on Earth is from the tropics toward the poles.

Coriolis forces, produced by planetary rotation, cause the descending gas, which would normally move north or south, to flow around the

planet west to east. On Earth the unstable flow converts this west-east motion into the enormous spirals known as cyclones and

anti-cyclones.

These coriolis forces are very strong on Jupiter because of the 22,000 mph equatorial rotation of the planet. Because of the same instabilities

that Earth has, Jupiters flow would be expected to be in even more violent spirals.

However, Jupiters internal heat source and circulation, and lack of a solid surface have a calming effect so that the motion is mostly linear

and the planets large permanent weather features are stretched completely around the planet, forming the belts and zones.

Because of this calming effect, heat radiated from Jupiters center reaches all parts of the planets surface in equal amounts. By contrast,

Earths heat from the Sun is received mostly in the tropics and circulates toward the poles.

The tops of Jupiters bright zones are 15 degrees F cooler and an estimated 12 miles higher than the tops of the dark belts. This confirms

theories about the overall circulation pattern. The gray-white zones are warm, upward-rising stretched weather cells whose tops are

probably high clouds of ammonia crystals, while the lower red-brown areas are cooler descending weather cells, believed to be clouds of

ammonia hydrosulfide crystals.

The tops of the bands of warm, lightweight, upward-rising white clouds flow from the center to the edges. Cloud material in the cooler,

heavier dark belts flows downward from the edges to the center of the belts. The forces just described produce atmospheric streams alongthe bands, going in opposite directions on either side of each zone, with the greatest velocities at zone edges.

These same mechanisms mean that Jupiters bands are streams of atmosphere whose speeds of flow can differ by as much as 360 mph. This

amounts to 360 mph winds. In general, these atmospheric streams flow most rapidly near the equator. The greatest contrasts in flow speeds

occur at mid-latitudes.

The Great Red Spot

The most startling and well-known feature of Jupiter is the Great Red Spot. Lying in the South Temperature Belt, it is a brick-red oval which

Pioneer data indicates to be 25,000 miles wide.

While not completely explaining the Great Red Spot, Pioneer has shown it to be a centuries-old vortex of a violent storm. It is calculated

to rise some five miles above the surrounding cloud deck. Most previous theories on the nature of the mysterious Spot seem to have been


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Pioneer to Jupiter10

eliminated by the fact that the Spot was not recorded by Pioneers gravity sensing experiment (which should have seen even small variations

in density) and by the observation of Jupiters liquid make-up.

Pioneer pictures show the Spots internal structure to be a pinwheel-like vortex. Its rapid circulation pattern makes it rigid enough to

displace the clouds of the South Tropical Zone toward the north.

A second red spot, about one-third the size of the Great Red Spot, can be seen in the Pioneer pictures. Located in the northern counterpart of

the southern hemisphere zone, the Little Red Spot is cooler than the surrounding clouds, and is believed to rise as high as the Great Red Spot.

Discovery of the second spot lends support to the idea that red spots are occasional meteorological phenomena on Jupiter found in the middleof the planets bright zones where the atmosphere is rising.

Jupiters Ionosphere

Jupiters ionosphere, which rises 1,800 miles above the 1/10 millibar level, is ten times thicker and five times hotter than had been predicted.

Average temperature of the ionosphere is about 1,800 degrees F. It has at least three sharply defined layers of differing density, and its

unexpected depth is due to the diffusion of its ionized gas by high temperatures. The high temperatures, in turn, are due to the impacts of

high energy particles and to hydromagnetic waves from Jupiters magnetosphere.

Jupiters Moons

Jupiters four planet-sized moons show a progression of densities the farther they are from the planet. The closest moon, Io, is 3.5 times

the density of water; Eurpoa is 3.14 times; Ganymede, 1.94 times; and Callisto, 1.62 times.

Thus, the two inner moons, having a density a little more and a little less, respectively, than that of the Earths moon, must be primarily

rocky. The outer two probably consist largely of water-ice, as indicated both by their density and by Jupiters heat characteristics.

Pioneer measurements have shown that the masses of the moons are as follows: Io, 1.22 Earth-Moon masses; Europa, 0.67 lunar masses;

Ganymede, 2.02 lunar masses; and Callisto, 1.44 lunar masses.

Ganymede is larger than the planet Mercury, while Callisto is about the same size, and Io and Europa are somewhat smaller. The average

surface temperature of the four large moons on the sunlit side is -230 degrees F.

A Pioneer picture of Ganymede appears to show a south polar mare (dark area) and another central mare about 480 miles in diameter, plus

various large meteorite craters and a bright north polar region.

Io, the closest large moon, is 23 percent heavier than previously thought, and has a tenuous atmosphere, making it the smallest known

celestial body with an atmosphere.

Ios extended ionosphere is almost as dense as that of Venus, reaching to about 420 miles on the day side. This dense ionosphere may mean

an unusual gas mixture and may indicate the presence of sodium, hydrogen and nitrogen on Io. Earth measurements show the presence of

sodium on Io while Pioneer measurements indicate hydrogen.

For about 10 minutes after it emerges from behind Jupiters shadow, Io is the most reflective object in the solar system. Then it begins to

turn from white to a pronounced orange color again. Apparently, during its 21 hours in the freezing Jovian night, methane snow flakes form

in its atmosphere, which then evaporate in the sunlight.

The radio occultation experiment found a density of 60,000 electrons per cubic centimeter in the ionosphere on the day side of Io, compared

with only 9,000 electrons per cubic centimeter on the night side.

An entirely new and unexpected phenomenon discovered by Pioneer is the hydrogen cloud embedding Io and extending a third of the way

around its orbit. And, for the record, Pioneer pin-pointed Ios position more precisely by 30 miles.

Magnetic Field

The magnetic field strength of Jupiter at its cloud tops is more than ten times the strength of Earths at the Earths surface, and the total

energy of the Jovian field is 400 million times that of Earths.

Jupiters inner magnetic field extends into space about 800,000 miles from the planets cloud tops. However, the outer field extends from

the cloud tops a minimum distance of 2.1 million miles and a maximum distance of 6.5 million miles.

A Jovian compass would point south since the poles of Jupiters field are reversed from those of Earth. The inner field is tilted about 10

degrees to the planets axis of rotation, and the center of the field does not coincide with the center of the planet. The fields center lies

about 1,320 miles north of the center of the planet and 4,840 miles outward from the rotational axis in a direction parallel with the equator.

Because of this non-coincidence, the strength of the field as it emerges from the cloud tops is calculated to vary over the clouds surface

from 3 to 10 Gauss. At its closest approach, 81,000 miles above the cloud tops,Pioneer 10 measured a field strength of 0.2 Gauss. (Earths

field at the surface is 0.35 Gauss.)

Because Jupiters magnetic field is tilted 10 degrees to the planets axis of rotation, the inner field, as seen from space, wobbles up and down

through an arc of 20 degrees once every 10-hour rotation of the planet.


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Radiation Belts

As on Earth, the high-energy particles which form Jupiters inner radiation belt are trapped within the planets inner magnetic field. In the

weak outer magnetic field, particles bounce around but eventually make their way to the fields outer edge and are spun off into space by

the high-speed rotation of the planet and by the radiation belts themselves. The total energy of the particles in the belts is many millions of

times the total energy of those in the Earths belts.

The greatest threat to spacecraft flying close to Jupiter or orbiting the planet are the belts intense particle radiation. Of the four large moons,

only Callisto lies outside the region of intense radiation, and would therefore be the most feasible site for a manned landing.

Surprisingly, there were 100 times more high energy electrons in the inner radiation belt than the more damaging high-energy protons

(hydrogen nuclei).

By far the highest radiation intensities were found in the inner belt which forms a doughnut-shaped ring around the planet. Like the inner

magnetic field that contains it, the inner belt extends out about 800,000 miles from the top of Jupiters ionosphere.

The outer radiation belt extends out beyond the inner belt in a relatively flat ring, a minimum distance of another 1.3 million miles or a

maximum of almost 6 million miles.

Average thickness of the outer radiation belt is 445,000 miles. However, the zone of high radiation intensity in the outer belt forms a thin

sheet which bisects the outer belt horizontally, and lies parallel with the planets equator. High energy particles in the outer belt are mostly

electrons with a maximum intensity several hundred times less than the maximum intensity levels of the inner belt.

The inner belt is contained in and shaped by Jupiters internal magnetic field and therefore wobbles up and down 20 degrees every ten hours

with each Jupiter rotation as does the field. The greatest radiation intensities of the inner radiation belt coincide with the equatorial plane

of Jupiters magnetic field. Radiation levels decline rapidly going either north or south from the magnetic equator. Spacecraft trajectories

could be planned to pass rapidly through this region of intense radiation.

Peak radiation intensity measurements revealed an enormous one billion electrons per square centimeter per second striking the skin of the

spacecraft. Of the total electrons, 90 per cent were in the energy range from 3 million to 30 million electron volts (MeV).

For all the protons with energies above 35 MeV, intensity was 70 million protons per square centimeter per second. Numbers of low energy

protons (0.3 to 35 MeV) were not as great as would have been expected from totals of higher energy protons.

In the outer radiation belt intensities of all electrons over 60,000 electron volts reached three million per square centimeter per second at

times. For all the protons with energies higher than 0.5 MeV intensity at times reached several hundred thousand protons per square

centimeter per second.

Bow Shock Wave

A bow shock wave is produced when the million-mile-an-hour solar wind rushes out from the Sun and strikes a planets magnetosphere and

flows around it. Jupiters bow shock wave is similar to Earths except that it is on a much greater scale.

Pioneer 10 crossed Jupiters bow shock wave outbound at 8.24 million miles. This means a line from one side of the shock to the other

passing through the planets day-night boundary would be 16.5 million miles long, about 80 per cent of the distance between the orbits of

the Earth and Venus.

WhenPioneer 10 crossed the bow shock, the solar wind changed direction 40 degrees as it flowed around the planet. The winds density

increased three times and its temperature 100 times as it crossed the shock front.

Magnetosphere

Jupiters magnetosphere, the region of space occupied by the planets magnetic field, has an average diameter of nine million miles. If it

could be seen from Earth, a half billion miles away, it would occupy two degrees of the sky, whereas the Sun occupies only a half degree

as we see it from 93 million miles away. Compared to the Earths magnetosphere, Jupiters is 100 times bigger in diameter and a million

times larger in volume.

It rotates like a large wheel at several hundred thousand miles per hour along with Jupiter which acts as the hub. Like the radiation belts

which it contains, the magnetosphere consists of two regions. The inner magnetosphere is created by the planets internal magnetic field

and is shaped like a doughnut with the planet in the hole.

The highly unstable outer magnetosphere is like an extension of the inner magnetosphere which is shaped as like the flattened outer part of

the doughnut.

The outer magnetosphere, which is created by the internal field plus its current sheet magnetic field, is spongy and pulsates in the solar

wind like a huge jellyfish, often shrinking to one third of its largest size.

The inner magnetosphere has a diameter of 1.8 million miles. The outer magnetosphere measures 4.4 million miles across when squashed

in and 13.2 million miles when extended. The magnetospheres constantly changing size explains whyPioneer 10 crossed the bow shock

17 times as it left Jupiter.


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Jupiters Magnetosphere

Scientists think the study of Jupiters magnetosphere may produce some new physics. Its rapid rotation constantly forces ionized particles

outward, moving the outer magnetospheres boundary farther and farther from the planet. Strong gusts of solar wind then squash the

magnetosphere inward. As the solar wind pressure declines, the outward-moving ionized particles push it out again and the cycle repeats again.

The charged particles spun out from the equator have the greatest outward velocities and hence flow out as a flat equatorial ring or sheet.

Since moving ionized particles produce an electric current, the particle sheet is actually a sheet of intense electric current which in turn

produces a magnetic field that appears flat and stretched. This flat ring-field in combination with Jupiters internal field produces the

planets outer magnetosphere. It is a relatively feeble, constantly varying field averaging 5 gamma (1

/20,000th

Gauss) in strength and is easilypushed around by the solar wind.

The thin disk of intense radiation in the outer magnetosphere coincides with the current-sheet because the particles follow the current-sheet

magnetic field. Both above and below the sheet is the outer radiation belt, 890,000 miles thick. Above and below the belt is the rest of the

outer magnetosphere. This region appears to be devoid of energetic particles. In total, the outer magnetosphere is believed to be about 4.5

million miles thick.

The current-sheet would be parallel with Jupiters equator (where the rotation is the greatest) except for Jupiters magnetic field. In the inner

magnetosphere, the strong inner field forces the electrified particles outward along Jupiters tilted magnetic equator.

However, in the outer magnetosphere, Jupiters field becomes so weak that the particles take control. They continue to move out in a flat

sheet, but the sheet lies parallel to the planets geographical equator. Because the inner magnetosphere is tilted and the outer is parallel to

the equator, the current-sheet can be visualized as a fedora hat with the front brim lower than the back one.


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Jupiter as a Radiation Source

The masses of high-energy particles being spun off from Jupiters magnetosphere are a new discovery which makes the giant planet a second

source of radiation in the solar system, the other being the Sun.

Pioneer 10 saw these particles 140 million miles away from Jupiter and it is thought these particles have probably been seen for several

years from Earths orbit but scientists did not know their source. Of great interest to scientists now is the behavior of these Jupiter particles,

some of which travel into the Suns magnetic field instead of away from it.

A recent correlation ofPioneer 10

s scientific data by Dr. Edward J. Smith of the Jet Propulsion Laboratory and Professor John A. Simpsonof the University of Chicago, indicates that bursts of energetic electrons, or runaway electrons as they are called, are escaping from Jupiters

magnetosphere and streaming back towards the Sun, along the interplanetary magnetic field. Measurements for the study were obtained

from the spacecrafts Helium Vector Magnetometer and Charged Particle Instrument.

Dr. Smith and Professor Simpson have found that the electron bursts occur when the interplanetary magnetic field points either towards or

away from Jupiter. They also observed these electrons to be accompanied by large amplitude hydromagnetic waves with a characteristic

period of ten minutes.

Apparently, the waves are generated by the runaway electrons as they travel up stream through interplanetary space. The origin of the waves

appears to involve plasma instability, as observed in the laboratory during thermonuclear plasma research about ten years ago. This may

be one of the true scientific relationships linking thermonuclear research and space research.

Electron Bursts from Jupiter


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Pioneer 10-11 Flight Trajectory

PIONEER 11 MISSION TRAJECTORY

Pioneer 11s final aiming point near Jupiter was not selected until 11 months after the spacecraft was launched from Earth. Until that time,

success ofPioneer 10 had not been demonstrated and scientists could not conclude what trajectory would most enhance our knowledge

about the giant planet.

Two candidate aim points were obvious favorites long before launch: the same one that had been chosen for the first exploration with Pioneer

10, to the right of Jupiter; and a new path very close to the left of Jupiter, which would subsequently project across the solar system to Saturn.

A third, less desirable, possibility was to skirt Jupiter more widely ifPioneer 10 was seriously damaged by the intense radiation belt.

An interim target point was chosen for the initial mid-course maneuvers during the first month after launch ofPioneer 11. This interim

point was placed such that a later final selection could be made by accelerating along the spacecrafts spin axis while pointing toward Earth.

On April 19, 1974Pioneer 11 was accelerated by 133 mph away from Earth. The Jupiter flyby was thereby moved westerly, to the left of

Jupiter, and more southerly, for a 50 south latitude approach. Date of arrival was advanced by nearly two days, and was carefully adjusted

to coincide with overlapping coverage between large tracking antennas located at Goldstone, California and Canberra, Australia. This

overlapping view of Jupiter and its vicinity occurs for about four hours during which the Earths rotation is within the correct angular range.

The approach trajectory causes the spacecraft to lead Jupiter upon arrival at the planet. The spacecraft will be accelerated sharply northward

and forward in a spiral motion as it swings around in Jupiters intense gravitational field. The result of such an encounter will be to send

Pioneer 11 on a new eliptical path around the Sun, this time inclined about 15 to the ecliptic plane.

The post-Jupiter trajectory will descend through the ecliptic plane again about September 5, 1979, where it is designed to intercept Saturn.

Extension ofPioneer 11s flight to Saturn is almost an ideal fit to the criteria laid down by scientists for enhancement of the knowledge

gained fromPioneer 10: close-in measurement of Jupiters radiation belt will be made to learn whether its intensity diminishes, as predicted


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by some theorists, or intensifies at close range to the planet. The high latitude approach and departure will allow such close flyby at a total

radiation dose level similar to that already survived by Pioneer 10, and will indicate whether the strong latitude correlation of radiation

intensity persists into the inner volume. Travel clockwise, rather than counter-clockwise, around Jupiter will provide a good sweep in

magnetic longitude for measurements in the magnetosphere. Pioneer 10s co-rotation with the planet was relatively restricted in longitude

(as well as latitude) at close range from Jupiter.

Imaging and polarimetry of the planet near both its south and north poles are facilitated, in contrast withPioneer 10s near equatorial flyby.

Determination of the planets gravity field characteristics, and probing of its atmosphere by radio occultation, also will gain added precision

and perspectives from the new encounter trajectory.

Pioneer 10-11 Encounter Trajectory

SATURN

Certainly one of the most beautiful sights to be seen through a telescope is the planet Saturn with its yellowish hue and magnificent

encircling rings. Saturn was the outermost planet known by the ancients who named it after the father of Jupiter.

The first telescopic observations of Saturn were made by Galileo in 1609-1610. Because his telescope was not powerful enough to reveal

a clear definition of the planet, Galileo was puzzled by what he saw. He thought he was viewing three planets. What he observed, of course,

were the rings of Saturn, which at that time were tilted at a narrow angle to the Earth.

Saturns rings lie precisely in the plane of the planets equator which is inclined some 28 degrees to the plane of the Earths orbit. During

its 29 year sidereal period, we see the south pole, which is tilted toward the Sun, for 13 years and 9 months. During the remaining 15

years, 9 months, the north pole is tilted toward the Sun and the rings can easily be seen. In between these alternative periods, we view the

planet with the rings edge-on. The next such viewing will be in 1980.

When first seen by Galileo, the rings were approaching an edge-on appearance. When he did view them edge-on later, Galileo thought

Saturn had suddenly lost its two companions. Unfortunately, Galileo was never able to correctly interpret what he saw.


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It took a much improved telescope in the hands of Christian Huygens in 1655 to see the rings. Huygens proposed the ring theory in 1659

and was met with strong opposition. However, the later observations of men such as Robert Hooke and G.D. Cassini proved Huygens right

and the ring theory found acceptance in 1665.

Saturn is the second largest planet in the solar system and is not unlike the much larger Jupiter. Saturn has an equatorial diameter of 75,100 miles

and a polar diameter of 67,200 miles. Its bulging equatorial belt rotates faster than the rest of the planet by as much as twenty minutes or more.

Its volume is over 700 times that of Earth but its low density (less than water) gives it a mass of only 95 times as great low by planetary standards.

Saturns average distance from the Sun is 886 million miles. It has an orbital velocity of 6 miles per second. As mentioned previously, itssidereal period is 29 years, compared with Earths one year, and has an average rotation of 10 hours, 14 minutes. This rapid spin would

give Saturn some 25,000 days each year.

While having similarities to Jupiter, Saturn is a more quiescent planet. Periodical outbursts of activity on Saturn are usually milder than

Jovian outbreaks. Apart from its cloud belts, Saturn has no prominent semi-permanent features such as Jupiters Great Red Spot.

However, this does not mean Saturn experiences no large scale disturbances. In 1933, for example, a great white spot was observed near

the equator. A year later it was replaced by a white equatorial band.

Actually the similarities in the atmospheric phenomena of Saturn and Jupiter are more striking than the differences, the latter being more in

degree than in kind. Even the colors of the planets are similar, except for an occasional greenish tint in Saturns polar areas.

While not a strong source of radio noise like Jupiter, Saturn does seem to radiate more energy than it receives from the Sun. Despite its low

average density of 0.7, Saturns distribution of matter is highly concentrated in the center, much like Jupiters.

The planets internal structure and atmosphere is assumed to be similar to Jupiters though different in proportions. Spectrographic analysis

reveals Saturns atmosphere to contain more methane and less ammonia than Jupiters. Since Saturn is much colder (-290 degrees F) than Jupiter,it is assumed that more of the ammonia has frozen out of its atmosphere and that the reflected sunlight penetrates a thicker layer of methane.

The lower temperature may also explain the more sluggish changes in the cloud formations and the less complex structural detail of Saturn.

Ten moons are known to orbit Saturn. Of these, Titan, a planet-sized satellite of yellowish hue is the most important in that it has the

distinction of being the first satellite known to have an atmosphere. (Pioneer 10 has revealed an atmosphere on Io, one of the Jovian moons.)

Since Titans escape velocity is only about 1.7 miles per second, the fact that it has an atmosphere is attributed to its low temperature. It

has been pointed out by G.P. Kuiper, who discovered the atmospheres presence, that if Titans temperature were raised to -100 degrees F,

the methane atmosphere would escape.

Titan may well be the largest satellite in our solar system. Its diameter is uncertain but estimates range from 2,700 miles to 3,500 miles.

The Earths Moon measures only 2,160 miles in diameter. The only moons possibly larger than Titan would be the Jovian moons Ganymede

(3,200 miles in diameter) and Callisto (thought to be about 3,000 miles in diameter), or Triton, one of Neptunes two moons which is

estimated to be 3,000 miles in diameter.

Titan has a mean distance from the center of Saturn of 760,000 miles, making it seventh in order of distance from the planet.The closest, Janus, was only discovered in December 1966 and little is known about it except that its diameter may be about 150 miles.

The other three inner moons, Mimas, Enceladus, and Tethys, have been described as snowballs and are about as dense as water. They

measure about 300, 400, and 700 miles in diameter, respectively.

The fifth satellite, Dione, is about the size of Tethys but is much denser and more massive. After that comes Rhea, a distinctly brighter

moon with a density between that of Dione and the inner moons.

Beyond Titan lie Hyperion, a small moon measuring about 200 miles across, and Iapetus. The latter is interesting in that it is brighter when

west of Saturn than when it is east. It could be that it has a surface of unequal reflecting power or is irregular in shape.

The outermost moon is Phoebe. It is small, has a highly inclined retrograde orbit and is probably a captured asteroid.

For more than 300 years the exact nature and structure of Saturns rings has been an enigma to scientists. We know that they are neither

solid nor liquid sheets because they lie within the Roche limit for Saturn and therefore could not exist as a continuous ring. (The Roche

limit is the distance from the center of a planet, or other body, within which a second body would be broken up by gravitationally induced

tidal distortion.)

Recent studies indicate the rings to be composed of small particles about 1/3,000 inch in dimension and covered with a rough surface. It has

been suggested that the particles are amonia ice crystals.

One theory has it that the particles are the debris of a former satellite which was broken up when it approached the Roche limit, while another

suggests the particles to be a cloud mass which was never formed into one body.

The system is made up of three principal rings known as A, B, and C. The outermost ring, A, is bright, though not as reflective as B, and

measures 169,000 miles across and 10,000 miles in width. Between Rings A and B is a distinct 2,500-mile-wide gap known as Cassinis

Division after G.D. Cassini. It is an area constantly swept clean of ring particles by the gravitational effects of Saturns inner satellites.

The 16,000-mile-wide Ring B is the brightest of the rings and has an albedo greater than Saturn itself. The third ring with a width of 10,000

miles is Ring C, generally known as the Crepe or Dusky Ring. Discovered in 1848, it is much fainter and more transparent than A or B,

and extends to within 9,000 miles of Saturns surface.


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Since 1907 there have been occasional reports of a dusky fourth ring (Ring D) outside Ring A. However, there is no proof of its existence

to date.

The study of Saturn spectrograms is quite fascinating. Sometimes the rings cross the line of sight to a star which becomes completely

obscured behind Ring B and flashes to near normal brightness when seen through Cassinis division. Behind Ring A the star will show

irregular fluctuations.

When observed almost at precise opposition to the Sun, the rings brighten considerably. It has been suggested that the many small ring

particles shadow each other so that only at opposition can we see the surface of the particles directly without appreciable effects of shadowing.

Saturns ring system, while measuring 169,000 miles in diameter, is thought to be less than 10 miles thick (some observers say the thickness

can be measured in yards), and is visible from Earth only as a very slender line of light when viewed edge-on.

PLANETARY DATA


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SATELLITE DATA

Thousands of miles.

* Indicates retrograde motion.

DISCOVERY OF JUPITERS 13TH MOON

A new Jovian moon, perhaps the smallest yet identified in our solar system, has tentatively been logged as Jupiters thirteenth (J-XIII).

Charles Kowal, astronomer with the Hale Observatory, discovered J-XIII while reviewing a series of photographic plates he made from

September 10th through 12th on the 48 Schmidt telescope at the Mt. Palomar Observatory.

Kowal suggests from his observations that this new moon would be less than five miles in diameter, traveling in a retrograde, or clockwise,

orbit about 14 million miles from the giant planet, Jupiter. Four of Jupiters twelve other moons are also known to have retrograde orbitsat approximately the same distance.

Some astronomers speculate these small moons could be asteroids, captured by the tremendous gravitational pull of Jupiter. Others hint that

many more objects of varying sizes may also be captured and as yet undetected.

By computing an orbit for the new object based on Kowals photographs, Brian Marsden of the Smithsonian Astrophysical Observatory

indicates there is a possibility it is a comet within the orbits of Jupiter and Saturn, but more likely a captured asteroid

Questioning whetherPioneer 11 would be able to observe this new find, a project spokesman said, Since the new moon was very small

and far away from the planet,Pioneer 11 would have to come very close to detect it and that possibility is rather doubtful.

Additional observations will be necessary to confirm Kowals discovery. Until then, we may ponder whether Jupiters thirteenth moon will

be a lucky omen for the upcomingPioneer 11s encounter.


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THE ASTEROID BELT

If one looks at a plan of the solar system he sees a gap between Mars and Jupiter in the orderly positioning of the planets orbits. It seems

there should be another planet orbiting the Sun.

There is a mathematical relationship to support this idea. Take the numbers 0, 3, 6, 12, 24, 48, 96, 192, and 384, each of which is double

its predecessor (except 3). Now add four to each: 4, 7, 10, 16, 28, 52, 100, 196, 388. Taking 10 as the Earths distance from the Sun, these

numbers give the remaining distances of the other planets to scale with remarkable accuracy. This is known as Bodes Law, after Johann

Bode who, though he didnt come up with the formula, popularized it around 1772.

The law indicates there should be a planet at 28, a fact which sent astronomers in 1800 looking for it. What they found, but didnt realize

at the time, was the Asteroid Belt.

On January 1, 1801, Piazzi, who was compiling a star catalogue, noticed a starlike object that moved. He made note of it, but was unable

to monitor it the following night because of illness. However, the great mathematician Gauss took Piazzis calculations and redetected the

object a year later and realized it was a planet, not a star or comet. Piazzi named the new planet Ceres after the patron Goddess of Sicily.

It was found to have a distance on the Bode scale of 27.7 and many astronomers thought the solar system to be complete.

Then another planet was discovered in 1802, another in 1804, and yet another in 1807. The four were called the Minor Planets or Asteroids.

More were discovered and by 1807 a total of 109 had been sighted and named.

Then in 1891 a method of detecting asteroids was introduced by Max Wolf that led to an amazing increase in the number of minor planets.

Wolf adjusted a camera so that it was fixed to follow the ordinary stars as they moved across the heavens. Because an asteroid moves against

the stars, the latter appear on a time exposed photographic plate as streaks. Today the number of asteroids varies in estimates from 40,000

to 100,000. The latter estimate is from the Russians who are the only ones to keep close records on asteroids.

As their numbers grew, it became increasingly difficult to find names for new asteroids. The mythological names began giving out. Thefirst departure was No. 25, Phocaea, named after a seaport in Ionia. No. 45, Eugenia, was named after Napoleon IIIs wife. Soon discoverers

began finding any source a suitable namesake. Ekard is the word Drake spelled backwards, and was named by two Drake University

members. Halawe is named after its discoverers favorite dessert, halawe, an Arab sweet. Today some of the names read like a high school

student trying to fake a Latin lesson: Photographia, Limburgia, Hooveria, Rockefellia, and so on.

The Big Four asteroids, Ceres, Pallas, Juno, and Vesta are the largest. Ceres is about 480 miles in diameter. Most of the asteroids are lumps

of material, not even spherical and not massive enough to have even a trace of atmosphere. All the asteroids combined would be less than

one-tenth the mass of the Moon.

Where did the minor planets come from? Some scientists theorize they are material that didnt form into a planet because of the disruptive

influence of Jupiter or perhaps are the remains of other planets. Another theory suggests they are the fragments of a planet that exploded.

However, what could cause a catastrophic internal explosion that would blow up a planet is not clear.

The first asteroid to be detected in close proximity to the Earth was Eros, which was discovered in 1898. Eros appears to be a slab of rock

17 miles by 4 miles, tumbling end over end. It has an eccentric orbit. Its aphelion takes it beyond Mars and its perihelion can come within

14 million miles of Earth. In 1931 it was observed a minimum of 17 million miles from Earth and is due for another close approach in 1975.

Soon after Eross fly-by of Earth, Amor, a smaller asteroid, came within 10 million miles of Earth in March 1932. Then, as if Earth-grazing

became fashionable, Apollo zipped by at 6.5 million miles, and in 1936 Adonis whooshed past at a mere 1.3 million miles away. Then in

1937 Hermes became the champion Earth-grazer when it missed us by 485,000 miles less than twice the distance to the Moon.

Hermes is a mile in diameter and astronomers have calculated it could come as close at 220,000 miles to Earth.

Other asteroids have eccentric orbits, too. Icarus, at perihelion, passes the Sun at 18 million miles, closer in than Mercury, and then recedes

to 183 million miles at aphelion, beyond the orbit of Mars. Another interesting asteroid is Hidalgo which goes beyond Saturn at aphelion,

and cuts inside Mars orbit at perihelion.

As you may have gathered by now, all the asteroids dont stay within the confines of the Asteroid Belt. Many have orbits that take them to

the outer reaches of the solar system, yet the majority are concentrated within the proximity of the belt.

Its possible there would be more asteroids in the belt, were it not for Jupiter, whose strong gravitational pull acts like a giant vacuum cleaner of the

asteroid belt. Once a slow moving asteroid comes within the clutches of the Jovian gravitational pull, it is wrenched from its orbit and disappears

beneath the clouds of Jupiter. Others not sucked into the cloud belt have been wrested from their orbits and catapulted down new paths.

This penchant of Jupiters for disturbing the orbits, not only of asteroids but of some of the other major planets, is called perturbation. While

each planet pulls upon one another to some extent, Jupiters size makes it the bad boy of the solar system. These perturbations make life

very difficult for mathematical astronomers trying to plot the orbits of the heavenly bodies.

Two groups of asteroids living in peace with Jupiter are the Trojan clusters, so named because the first one discovered was dubbed Achilles

and subsequent ones (16 in all) were named after the combatants in the war between Greece and Troy.

Moving in the same orbit as Jupiter, one cluster of Trojans travels about 60 degrees ahead of Jupiter while the other travels about 60 degrees

behind forming an equilateral triangle with the Sun and therefore balancing themselves with Jupiter.

This mathematical relationship between the Trojans, Jupiter, and the Sun is termed a Lagrangian point, after the French mathematician

Lagrange who first called attention to the problem of a massive body, and a tiny asteroid moving around the Sun in the same plane, same

orbit, and with equal periods.


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About 1772 Lagrange found that if the bodies are 60 degrees apart, they will always remain 60 degrees apart. In 1906 when the first Trojan,

Achilles, was discovered, it was found to behave in this manner. Subsequently, the other Trojans were discovered and also found to behave

similarly.

Of the 16 Trojans detected, two have been lost because they were not observed long enough to have their orbits plotted.

The Trojans do not stay strictly 60 degrees ahead of and behind Jupiter. They are in elliptical orbits, and perturbations caused by Saturn

influence them. The largest Trojan, Hector, is about 150 miles in diameter, while Menelaus is only about 10 miles wide.

It has been suggested that Jupiters seven outer satellites are captured Trojans, or, on the other hand, that the Trojans are ex-satellites thatsomehow got away.

ORIGIN OF THE SOLAR SYSTEM AND UNIVERSE

Theories on the creation of the universe have abounded since Biblical times and as yet we still have no generally accepted satisfactory

answer. The problem with all theories is that none stand up against the severe tests of mathematical analysis. However, it is this analysis,

along with the abundance of new discoveries every year that are leading us closer to an answer.

Today, instead of having to depend entirely upon an all-embracing hypothesis, as scientists did in the past, we are able to approach the problem

more meticulously with the applications of modern physics and the principles of dynamics which each theory must be consistent with.

By the time of Issac Newton (1642-1727) we had made considerable progress in that we could intelligently speculate on the creation of the

universe and the creation of the solar system as separate problems.

So far as the former is concerned, scientists are still in a quandry, although discoveries during the past century have increased our knowledge

of the universe tremendously.

The Solar System

As for the solar systems origin, there is general agreement on several matters. To begin with, it is fairly safe to assume that the planets

were formed either from the Sun or a companion star, or from a diffused cloud of matter which once surrounded the Sun.

One of the first scientific theories on the origin of the solar system was presented by the French mathematician Pierre Simon de Laplace in

1796. His Nebular Hypothesis supposed the Sun to be formed from a gas cloud which, as it contracted, grew hotter and began rotating. The

more it shrank, the more the rate of spin increased until the centrifugal force at its edge became equal to its gravitational pull. A ring of

material from its bulging equator was then spun off. This discarded ring then condensed gradually into a planet which in turn spun off a

ring of matter. This process was repeated several times until all the planets were formed.

Several attacks were launched on the Nebular Hypothesis and by early 1900 it had been discarded completely in favor of a new wave of

theories involving the near collision of the Sun and a passing star. These latter theories were modified to a more acceptable form in the

early Twentieth Century by Sir James Jeans who suggested the gravitational attraction of a star passing by the Sun drew a cigar-shaped

filament of matter from the Sun. As the passing star receded, it set this matter into motion around the Sun and the matter ultimately

condensed into planets. Neither of the theories have been able to completely withstand the close scrutiny of the mathematical analysis; but

since about 1950 the Nebular Hypothesis, in a vastly improved form, seems once again to be the favorite.

Age of the Solar System

Curiously enough, we dont know the origin of the solar system, but we claim to know its age. This has been determined by finding the age

of the Earth, which is assumed to have been created at the same time as the rest of the solar system. Therefore, by establishing the Earths

age, we in turn establish the age of the solar system.

The former is accomplished by dating the remains of radioactive substances in the Earths crust. Uranium, which is found naturally on

Earth, is not a stable element. It decays spontaneously and ends up as lead. For one type of uranium, known by scientists as U238, it takes

over 4 billion years for only half of it to become lead. This is known as its half-life. The lead produced from uranium can be distinguished

from ordinary lead so the quantity of uranium-lead found with remaining uranium tells us how long ago the decay started. It is through this

method of radioactive clock dating that we have been able to determine the age of the Earth as 4.7 billion years old.

Studies of meteorites are offered as further evidence. Examination of the visitors from space reveal they have not been solid for measurablylonger than the calculated age of the Earth. Since meteorites represent fragments of the solar system, it is concluded from their

corresponding ages that the system is coeval with the Earth. Whatever it was, some (probably catastrophic) event occurred some 4.7 billion

years ago that produced our solar system as it is known today.

The Milky Way

Within the universe, our Solar System is a tiny part of a somewhat larger than average galaxy, of which there are about one billion within

photographic range of a 200-inch reflector. Our galaxy rotates so that the Sun takes 225 million years to complete one journey around the

center. Radio astronomers have confirmed that it is a loose spiral containing 100 billion stars. It has a diameter of 100 billion light years,

with our Sun located near the main plane about 30,000 light years from the galactic center. Commonly known as the Milky Way, our

galaxy is a member of what has come to be called the Local Group, which is made up of 27 known galaxies. Of these the most important,

in order of size and mass, are the Andromeda Spiral, the Milky Way, the Triangulum Spiral, and the Large and Small Clouds of Magellan.


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The Universe

As for knowing how and when the universe was created, scientists have to admit quite a bit of ignorance, although 10 billion years is often

accepted as the age of the universe. One of the most important discoveries in astronomy during the past century has been the realization

that the universe is expanding. Three prevalent theories have emerged about the creation of the universe the big-bang theory, the

oscillating theory, and the steady state theory.

Because the universe is expanding, the clusters of galaxies we observe in the sky are getting farther and farther apart. From this we could

assume that many years ago the galaxies were much closer together, and that in the very distant past all the matter in the universe must have

been packed into an extremely small volume. The big-bang theory, of which there are variations, contends that there was a primordialexplosion of this super-condensate of primeval hydrogen about 17 billion years ago, and the expansion we detect today is the remaining

impetus of this explosion.

The universe may continue to expand forever, or, as some scientists believe, the expansion will slow and stop and then the universe will

begin contracting. This oscillation theory proposes that at intervals, which may be as great as 60 billion years or as small as 25 billion years,

all matter in the universe comes together. This contraction is then followed by expansion and the cycle goes on indefinitely.

In 1948 two scientists, Bondi and Gold, proposed that the universe has always existed and will exist forever with new material

spontaneously being created out of nothing at a rate too slow to be observationally detectable. In other words, the universe is in a steady

state. The steady state theory sees the universe expanding but perhaps as the distances between clusters of galaxies increase, new galaxies

are created to fill the void. In essence, the number of galaxies in a cubic billion light years, for example, would be essentially the same as

it is today.

Conversely, in the distant past we would also have approximately the same density of galaxies and matter in the universe as we do today.

Galaxies are not required to be crowded on top of each other as in the early stages of the big-bang theory because many of the galaxies we

see today did not exist then.

Choosing a Theory

Which theory is correct? All the theories have received some flak over the years, but recent radio astronomy investigations have dealt the

steady state theory the hardest blows. Since very distant galaxies are billions of light years away, then we are seeing them as they were

billions of years ago. If the big-bang theory is correct, then the galaxies were closer together in the past than they are now, and therefore

distant galaxies ought to appear to be closer together than nearer ones. According to the steady state theory, there should be no difference.

However, evidence gathered by radio astronomers seems to suggest that there is a difference and that the galaxies were closer together in the

past than they are now. Based on this evidence, therefore, the big-bang theory gains some credence, and the steady state theory loses some.

Pioneer Ground Data System


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PIONEER GROUND DATA SYSTEM

The Pioneer Ground Data System is the vital link between Earth and the Pioneer spacecraft. It is a worldwide network of tracking antennas,

high speed data lines, and computers used to transmit, receive, and process communication signals to and from the spacecraft.

Providing both real time and off-line information, the Ground Data System enables project personnel to make timely and accurate decisions

affecting spacecraft operations using real time information. Off-line information allows experimenters to meticulously analyze and verify

observations made by the spacecrafts instruments.

The Ground Data System consists of the NASA Deep Space Network (DSN); the Mission Control and Computing Center (MCCC) at theJet Propulsion Laboratory in Pasadena, California; the Pioneer Mission Operations Center (PMOC) at Ames Research Center, Mountain

View, California; and the Pioneer Mission Computing Center (PMCC), also at Ames.

The Deep Space Network is made up of Deep Space Stations located around the globe. These stations are approximately 120 degrees apart

in longitude so the spacecraft is always in view of at least one of the large (85- or 210-foot diameter) tracking antennas.

Signals from the Pioneer spacecraft are received by the tracking station, recorded on magnetic tape and simultaneously transmitted over

high speed data lines to Ames Research Center where further computer processing gives mission controllers the information necessary to

control the spacecraft.

Command instructions originated at Ames are sent over the high speed data lines to the MCCC and sent to Deep Space Stations where a

computer controls the uplink signal to the spacecraft to relay these instructions. Results of the command functions are detected within the

downlink telemetry data, completing a semi-automatic control loop. Control of the spacecraft during the cruise and encounter phases of the

mission is handled by personnel at Ames, where telemetry analysis and video reconstruction is performed using the PMCC computers.

Deep Space Network

LAUNCH VEHICLE

The vehicle that launched bothPioneer 10 and 11 on their journeys to Jupiter was an Atlas-Centaur. ThePioneer 10 launch marked the

first time an Atlas-Centaur was used with a third stage the 15,000 pound thrust, solid fuel TE-M-364-4 engine.

Centaur was developed under the direction of NASAs Lewis Research Center and is in the process of being integrated with the Titan III to

launch the Viking spacecraft to Mars in 1975.

The AC-30 vehicle constructed to launch Pioneer 11 consists of an Atlas SLV-3C booster combined with a Centaur second stage, and the

TE-M-364-4 third stage. The first two stages are 10 feet in diameter and are connected by an interstage adapter. Both Atlas and Centaur

stages rely on internal pressurization for structural integrity.


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The Atlas booster develops 411,353 pounds of thrust at liftoff, using two 174,841 pound thrust booster engines, and one 60,713 pound

thruster sustainer engine and two vernier engines developing 676 pounds of thrust each.

Insulation panels carried by Centaur were jettisoned just before the vehicle left the Earths atmosphere. The insulation panels, weighing

about 1,154 pounds, surrounded the second stage propellant tanks to prevent heat or air friction from causing excessive boil-off of liquid

hydrogen during flight through the atmosphere.

The solid-fueled TE-M-364-4 third stage develops almost 15,000 pounds of thrust. It is an uprated version of the retromotor used for the

Surveyor Moon-landing vehicle.

Both third stage and spacecraft were enclosed in a 29-foot long, 10-foot diameter fiberglass shroud which jettisoned after leaving the atmosphere.

The Centaur has also been successfully used on other programs to launch unmanned space probes such as Surveyor, Mariner, Orbiting

Astronomical Observatory, Applications Technology Satellite, and Intelsat Satellite.

210 DSN Tracking Antenna


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Pioneer 11 Being Prepared For Launch


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Pioneer Spacecraft and Launch Vehicle Assembly


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PIONEER 11 ENCOUNTER TIME LINE

NOTE: All times in Pacific Standard Time (PST).

11/02/74 8:00 am Begin imaging (picture taking) and polarimetry 4 to 8 hours per day through 11/24/74. Imagery primarily to support

photopolarimetry measurements. Ames operations personnel will run the University of Arizona Imaging

Photopolarimeter until 11/18/74 when Arizona imaging photopolarimeter team will join them.

9:00 am Conscan measurements are made every other day throughout the Jupiter encounter to verify pointing accuracy of

spacecraft antenna at the Earth. Last change in antenna pointing direction before periapsis was October 17; nextchange December 6, four days after periapsis.

11/07/74 4:30 am Cross orbit of Jupiters outermost moon, Hades, 23, 632,000 km (14,683,000 miles) from Jupiter 165 Jupiter

diameters (one Jupiter diameter = 142,744 km) from planet.

4:49 pm Cross orbit of Poseidon, the second of the four outer moons, at 23,204,000 km (14,417,000 miles) 162 Jupiter

diameters from the planet.

11/08/74 7:50 pm Cross orbit of Pan, third of the four outer moons, at 22,276,000 km (13,841,000 miles) 156 Jupiter diameters from planet.

11/10/74 7:29 pm Cross orbit of Andrastea, closest of the four outer moons, at 20,634,000 km (12,820,000 miles) 1.45 Jupiter

diameters front planet.

11/18/74 8:00 am University of Arizona team arrives to begin intensive imaging and photopolarimetry activity. Imaging and

polarimetry operations will continue up to eight hours per day through 11/24/74.

11/21/74 10:03 am Cross orbit of Hera, outermost of Jupiters middle group of moons, at 11,667,000 km (7,248,000 miles) 82 Jupiter

diameters from planet.

10:50 am Cross orbit of Demeter, second of Jupiters three middle moons, at 11,639,000 km (7,231,000 miles) 81.5 Jupiter

diameters from planet.5:21 pm Cross orbit of Hestia, closest of Jupiters three middle moons, 11,403,000 km (7,084,000 miles) 80 Jupiter

diameters from planet.

11/25/74 All Day Eleven images of Jupiter, polarimetry of Jupiter, Callisto, Europa and Ganymede.

4:00 pm Begin 23 hours a day imaging and polarimetry for 14 days through December 9. Both imaging and polarimetry of

Jupiter will occur every day through this period; imaging a little more than half the time.

11/25/74 8:00 am Earliest time for bow shock wave crossing, inbound.

11/26/74 All Day Twenty five images of Jupiter. Polarimetry of Jupiter and Io.

8:00 am Earliest time for magnetopause crossing, inbound.

12:00 pm Resolution of pictures sent back byPioneerequals that of typical Earth telescope pictures.

9:00 pm Most likely time for magnetopause crossing, inbound. (Time period when crossing likely is 19 hours; from 11/26/74,

9:00 pm to 11/27/74, 4:00 pm.)

11/27/74 All Day Seventeen images of Jupiter. Polarimetry of Jupiter, Io, and Europa.

9:21 pm Pioneerfive days from periapsis, 5,905,000 km (3,669,000 miles), 41.5 Jupiter diameters away.

9:21 pm Planet occupies 1/10th (1.4) ofPioneers 14 field of view. Would have a 2 inch diameter on a 21 inch TV screen.11/28/74 All Day Twenty two images of Jupiter. Polarimetry of Jupiter and lo.

9:21 pm Pioneerfour days from periapsis, 4,919,000 km (3,050,000 miles), 34.5 Jupiter diameters from the cloud tops.

9:21 pm Planet occupies 1.6 ofPioneers 14 view field; 2 inch diameter on a 21 inch TV screen.

11/29/74 All Day Fifteen images of Jupiter. Polarimetry of Io, Europa, Jupiter.

9:21 pm Pioneerthree days from closest approach, 3,895,000 km (2,420,000 miles) 27 Jupiter diameters from cloud tops.

9:21 pm Planet occupies 1/7th (2.1) ofPioneers 14 view field; 3 inch diameter on a 21 inch TV screen.

11/30/74 All Day Twenty four images of Jupiter. Polarimetry of Ganymede, Callisto and Jupiter.

9:21 pm All pictures from now until 48 hours after periapsis better than typical Earth telescope pictures. Average resolution

in this 96 hour period 2 to 3 times better than telescope pictures. During these 96 hours,Pioneerwill return 40

pictures of the full planet, many pictures of portions of Jupiters surface, three of Callisto, one each of Ganymede

and Io.

11/30/74 9:21 pm Two days from periapsis. Pioneer2,813,000 km (1,748,000 miles) 20 Jupiter diameters from the cloud tops.

9:21 pm Planet occupies 2.8 ofPioneers 14 view field; 4 inch diameter on a 21 inch TV screen.

11:28 pm Ultraviolet photometer measurement of Callisto.12/01/74 All Day Fourteen images of Jupiter, two images of Callisto. Polarimetry of Callisto, lo, and Jupiter.

11:26 am Ultraviolet photometer measurement of Ganymede.

5:27 pm Cross orbit of Callisto, outermost Galilean moon, at 1,812,800 km (1,125,295 miles).

9:21 pm Pioneerone day from periapsis, 1,617,000 km (1,005,000 miles) 11.5 Jupiter diameters from the cloud tops.

9:21 pm Planet occupies one-third (4.8) ofPioneers 14 view field; 7 inch diameter on a 21 inch TV screen.

9:21 pm Begin best pictures of Jupiter. During the 24 hours before and after periapsis whenPioneeris within one million

miles of the planet, pictures are much better than any from Earth, the best ever made of Jupiter except those taken

byPioneer 10.

10:18 pm Infrared measurements of Callisto, inbound.

12/02/74 All Day Eight images of Jupiter, one image of Callisto, one image of Ganymede. Polarimetry of Jupiter.

12:21 am Closest approach to Callisto, 786,500 km (488,730 miles) at 21 hours from periapsis.

1:50 am Ultraviolet measurements of Ganymede, 19 hours 31 minutes from periapsis.


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8:01am Cross orbit of Ganymede, second outermost Galilean moon, at 1,001,140 km (624,953 miles), 7 Jupiter diameters

from cloud tops, 13 hours 33 minutes from periapsis.

8:21 am Last full disc picture of Jupiter. Subsequent pictures will more than fill spacecrafts 14 view field.

1:56 pm Infrared measurement Ganymede, inbound; 7 hours 25 minutes before periapsis.

2:06 pm Cross orbit of Europa, second closest Galilean moon, at 601,780 km (372,803 miles), 4.2 Jupiter diameters from the

cloud tops, 7.25 hours from periapsis.

2:09 pm Closest approach to Ganymede, 692,300 km (430,195 miles), 7.2 hours from periapsis.

2:45 pm Ultraviolet measurement of Europa, 6 hours 36 minutes before periapsis.

3:21 pm Inter-radiation belt at 3.5 Jupiter diameters from clouds, 6 hours from closest approach.4:00 pm Begin two-hour scan for last picture on incoming trajectory, thus showing Red Spot portion of Jupiters surface.

During picture, taken from 4:00 pm to 6:00 pm,Pioneerwell inside radiation belt. Range 265,000 miles; resolution

five times Earth telescope resolution.

5:00 pm

to 7:45 pm Infrared measurements of Jupiter, 2 hours 45 minutes of measurements starting at 4 hours 21 minutes from periapsis.

5:13 pm Infrared measurement of Amalthea, 4 hours 8 minutes from periapsis.

5:23 pm Cross orbit of Io, the innermost Galilean moon, at 352,560 km (217,945 miles), 2.45 Jupiter diameters from cloud

tops, 4 hours from periapsis.

7:02 pm Infrared measurements of Io at 2 hours 19 minutes before periapsis.

7:09 pm Closest approach to lo, 314,000 km (195,120 miles), 2.2 hours before periapsis.

7:58 pm Crossing ofPioneer 10s previous closest approach distance of 81,000 miles.

8:10 pm Cross orbit of Amalthea, closest Jovian moon, at 137,260 km (68,630 miles), 0.77 Jupiter diameters from cloud tops,

1.18 hours before periapsis.

8:15 pm Closest approach to Europa, 586,700 km (364,575 miles); 1.1 hours before periapsis.9:00:21 pm Enter 33 minutes 31 seconds solar occultation; starts at 20 minutes 58 seconds before periapsis.

9:00:42 pm Enter Jupiter radio occultation (blackout) duration 42 minutes 2 seconds. Starts 20 minutes 18 seconds before periapsis.

9:22 pm Periapsis Pioneeris 42,828 km (26,613 miles), 0.31 Jupiter diameters from cloud tops.

9:33:52 pm Exit solar occultation, 12 minutes 33 seconds after periapsis.

9:43:30 pm Exit Jupiter radio occultation, 21 minutes 44 seconds after periapsis.

10:30 pm Closest approach to Amalthea, 127,500 km (79,229 miles), 1.15 hours after periapsis.

10:52 pm Infrared measurement of Amalthea, outbound, 1 hour 31 minutes after periapsis.

11:00 pm Start 4 hour Jupiter viewing period, outbound, for infrared instrument. Begins 1 hour 39 minutes after periapsis.

12/03/74 All Day Eleven images of Jupiter, one image of Io. Polarimetry of Jupiter, Ganymede, and Callisto.

1:30 am End 4 hour Jupiter viewing period for infrared instrument, outbound. Ends 4 hours 9 minutes after periapsis.

3:21 am Exit Radiation Belt at 3.5 Jupiter diameters from cloud tops, 6 hours after periapsis.

7:58 am Infrared measurement of Io, outbound, 10 hours 37 minutes after periapsis.

9:21 pm One day after periapsis. Pioneeris 1,617,000 km (1,005,000 miles) 11.3 planet diameters from Jupiter.

11:43 pm Infrared measurement of Ganymede, outbound, 26 hours 22 minutes after periapsis.12/04/74 All Day Fifteen images of Jupiter. Polarimetry of Jupiter, Io, Ganymede and Europa.

9:21 pm Two days after periapsis. Pioneeris 2,813,000 km (1,748,000 miles) from Jupiter.

9:45 pm Infrared measurement of Callisto, outbound, 48 hours 24 minutes after periapsis.

12:00 am Jupiter occupies 1/5th of 14 view field.

12/05/74 All Day Eighteen images of Jupiter. Polarimetry of Europa, Ganymede, Callisto, and Jupiter.

9:21 pm Three days after periapsis. Pioneeris 3,895,000 km (2,420,000 miles) from Jupiter.

12/06/74 All Day Ten images of Jupiter. Polarimetry of Jupiter and Ganymede.

5:30 am

to 1:30 pm First precession maneuver after periapsis to change pointing angle at the Earth ofPioneerradio antenna. Maneuver

lasts 6 to 8 hours and will change pointing direction about 2.

9:21 pm Four days after periapsis. Pioneeris 4,919,000 km (3,050,000 miles) from Jupiter.

12/07/74 All Day Twenty two images of Jupiter. Polarimetry of Jupiter, Ganymede, Io, and Callisto.

12:00 pm Jupiter occupies 1/10th ofPioneerview field.

9:21 pm Five days after periapsisPioneeris 5,906,000 km (3,669,000 miles) from Jupiter.12/08/74 All Day Twenty eight images of Jupiter. Polarimetry of Jupiter, Ganymede and Callisto.

12:00 pm Earliest time for magnetopause crossing, outbound; 20 hour period when crossing expected is 12:00 noon, 12/8/74

to 4:00 am, 12/9/74.

12/09/74 All Day Nineteen images of Jupiter. Polarimetry of Jupiter.

3:00 pm End of 23 hour per day imaging and photopolarimetry. Return to 4 to 8 hours per day operation through 1/3/75.

Arizona imaging photopolarimetry team goes home, but will return for full day of operations on 12/17/74. After

today (12/9/74) imaging photopolarimeter will be run by Ames personnel and will be used primarily for

photopolarimetry, not imaging.

8:00 pm Latest possible time for magnetopause crossing, outbound.

12/10/74 12:00 am Latest time for bow shock crossing, outbound.

12/17/74 All Day Fifteen images of Jupiter by Arizona Ames team. Arizona then returns instrument to Ames operation. Imaging and

polarimetry 4 to 8 hours per day through 1/3/75.


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12/20/74 4:45 am

to 12:45 pm Second precession maneuver after periapsis to change pointing angle at the Earth ofPioneer radio antenna.

Maneuver lasts 6 to 8 hours, changes pointing direction about 2.

12/30/74 6:00 am

to 2:00 pm Third precession maneuver after periapsis to change pointing angle at the Earth ofPioneerradio antenna. Maneuver

lasts 6 to 8 hours changes pointing direction about 2.

01/03/74 8:00 am End of 4 to 8 hour per day imaging and photopolarimetry.

4:00 pm End encounter period.

Pioneer 11 Distance vs. Encounter Time at Jupiter


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Pioneer 11 Distance vs. Velocity Relative to Earth

PIONEER PLAQUE

SincePioneer 10 will eventually leave our solar system, there is a chance it will encounter intelligent beings somewhere in space. If so, a

message in the form of a 6- by 9-inch gold anodized plaque bolted to the spacecrafts main frame will tell them of the spacecrafts origin.

On the plaque a man and a woman stand before an outline of the spacecraft. The mans hand is raised in a gesture of good will. The physical

make up of the man and woman were determined from the results of a computerized analysis of the average person in our civilization.

The key to translating the plaque lies in understanding the breakdown of the most common element in the universe hydrogen. This

element is illustrated in the left hand corner of the plaque in schematic form showing the hyperfine transition of neutral atomic hydrogen.

Anyone from a scientifically educated civilization having enough knowledge of hydrogen would be able to translate the message. The

plaque was designed by Dr. Carl Sagan of Cornell University and drawn by Linda Sagan.


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Pioneer Plaque

The internal atomic structure of the hydrogen atom has a hyperfine transition between the nuclear and electronic spins which relate to aspecific time interval. The period of this spin, or the time interval it takes to complete one transition, is 0.7040 x 10-9 seconds. By

converting this period to length, we get 21 centimeters or approximately 8.25 inches. The vertical line just under the horizontal line of the

Hyperfine Transition Schematic relates to a binary value of 1 for each transition. To the right of the woman are two tote marks. Four

marks (binary values) are shown between each tote mark and have weights of 1, 2, 4, and 8. Reading from top to bottom, the lower mark

turned in a horizontal position indicates a true binary weight of 8. The actual size of the woman can now be determined by taking this

value (8) and multiplying it by the transition period (8.25 inches or 21 centimeters) to get the following:

8.25 inches (transition value) x 8 (binary weight) = 66 inches

21 centimeters (transition value) x 8 (binary weight) = 168 centimeters

To the left center are 14 major signal transmitting pulsars in the galaxy. The transmitting period of the pulsars at launch can be determined

by multiplying the binary value shown on each line by the transition period (0.7040 x 10 -9). The radial pattern indicates the relative position

of each pulsar in the galaxy viewed from the center of our solar system. The long line extending to the right behind the human figures

represents the distance from the launching planet to the galactic center.

The symbols shown on the lower part of the drawing indicate the relative position of the planets to the Sun described by the binary values

near each planet. Also indicated is a schematic trajectory of the Pioneer spacecraft passing by Jupiter and leaving the solar system with its

antenna pointing back to Earth.

PIONEER EXPERIMENTS

One additional instrument, the Fluxgate Magnetometer, was included on-board the Pioneer 11 spacecraft to measure the strength and

direction of Jupiters magnetic field at close distances. Pioneer 10 approached within 81,000 miles of Jupiter, whilePioneer 11 has been

targeted for an approximate 26,613 mile flyby. Details of the instruments and scientific experiments to be conducted by the principal

investigators are described in the following sections.


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Magnetic Fields Experiment

Instrument: Magnetometer

Principal Investigator: Edward J. Smith, Jet Propulsion Laboratory, Pasadena, California

Co-Investigators: Palmer Dyal, NASA Ames Research Center, Mountain View, California

David S. Colburn, NASA Ames Research Center, Mountain View, California

Douglas E. Jones, Brigham Young University, Provo, Utah

Paul J. Coleman, Jr., University of California at Los Angeles

Leverette Davis, Jr., California Institute of Technology, PasadenaCharles P. Sonett, University of Arizona

The helium vector magnetometer is a sensitive instrument which measures the interplanetary magnetic field in three axes from the orbit of

the Earth out to the limits of spacecraft communication. By studying the solar wind interaction with Jupiter, and mapping Jupiters strong

magnetic fields, the instrument may give us a key to the fluid composition and other characteristics of Jupiters interior.

The magnetometers sensor is mounted on the lightweight mast extending 21.5 feet from the center of the spacecraft to minimize

interference from spacecraft fields. The instrument operates in any of eight different ranges. The lowest covers fields from 0.016 gamma

to 4 gamma; the highest up to 140,000 gamma (1.4 Gauss). The Earths surface field is 50,000 gamma. The instrument weighs six pounds

and uses five watts of power.


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Plasma Analyzer Experiment

Instrument: Plasma Analyzer

Principal Investigator: John H. Wolfe, NASA Ames Research Center

Co-Investigators: Louis A. Frank, University of Iowa, Iowa City

Reimar Lust, Max-Planck-Institute fur Physik and Astrophysik Institute

fur Extraterrestrische Physik, Munchen, Germany

Devrie Intriligator, University of Southern California, Los Angeles

William C. Feldman, Los Alamos Scientific Laboratory, New MexicoThe plasma analyzer will map the density and energy of the solar wind; determine solar wind interactions with Jupiter (including the planets

bow shock wave); and will look for the boundary of the heliosphere (Suns atmosphere).

A high resolution and a medium resolution analyzer look toward the Sun through the spacecrafts dish antenna, and solar wind enters the instrument

like the electron beam in a TV tube. The instrument measures the direction of the travel, energy (speed) and number of ions and electrons.

Voltage applied across the instruments plates in one of 64 steps allows only particles in a given energy range to enter.

Detectors in the high-resolution analyzer are 26 continuous-channel multipliers which measure ion flux in energy ranges from 100 to 8,000

electron-volts. The medium-resolution analyzer measures ions from 100 to 18,000 electron-volts and electrons from 1 to 500 electron-volts.

The instrument weighs 12 pounds and uses four watts of power.

Charged Particle Composition Experiment

Instrument: Charged Particle Instrument

Principal Investigator: John A. Simpson, University of ChicagoCo-Investigators: Joseph J. OGallagher, University of Maryland, College Park

Anthony J. Tuzzolino, University of Chicago

The charged particle detector contains two particle telescopes used during interplanetary flight, and two measuring systems which measure

trapped electrons and protons inside the Jovian radiation belt.

The telescopes will identify nuclei of the first eight chemical elements of the Atomic Table (hydrogen through oxygen) and separate the

isotopes deuterium, tritium, helium-3 and helium-4. In addition, the telescopes will be used for studying particles in the bow shock and

outer magnetosphere.

To handle the high intensities of Jupiters trapped radiation, two new sensors had to be developed. One is a silicon detector used as a

solid-state ion chamber that operates below -40 degrees. It measures high energy electrons that may generate the radio waves that reach

Earth. Th

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Pioneer to Jupiter Second Exploration