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M I S S IO N T O J U P I T E R

•w ol 3

already set many records. Pioneer traveled

Atlas Centat r

beyorde M o o n in 11 hours. But even this speed

0 is the f irst spacecraft to f ly be

e S olar Systemtars of the

e Galaxy.

. the spacecraft f l ies with unbelievablears o f f light

ough space i t is schedu led to arr ive atl i ter within less t in one minute of the

anion are the f i rst

and to operate there for as

on miles, possibly more. Fo r such aspacecraft needs extreme reliability;

ng mu st fall. And the spacecraft must

r vast distances, and since it can-

Pioneers are stabil ized by rotation,oth are controlled largely

ne-shaped antennag out from the dish of the com -

ure (Figure 1). T he spacecraft's spin

beneath the antenna.

ed to one side o fe science equipment is mount-

Figure 1. Pioneer Ju p iter Spacecraft

f rom the atomic bm akdow n of P lutonium'238 into e lectric ity. They are exp ected toprove & pow er for at least f ive years afterlaunch.

A third, single -od extension carr ies morescienti fic egwp m ,nt. All the booms wereextended in flight a f ter launching.

S mall rocket lets change the velocity of thespacecraf(, change its attitude, :)r change itl,speed of rotation. They are controlled by

commands from E arth or automatically bycommands stored in the spacecraft 's elec.t ronic memory. A n automat ic system alsouses these thrusters to kee p the spin axis,and therefore the communications antenna,po e nted direct ly towards E arth.

The P ioneers follow a cured path to Jup iter -some 620 mill ion miles long covering about160 degrees around the S un between theorbits of Earth and Ju piter (Figure 2). About120 days after launch each Pioneer entersthe Asteroid B elt, a zone of small planetarybodies between the orbits of Mars andJupiter. The largest of these bo dies is C eres,480 miles in diameter. M ost are very muchsmal ler. A planet was probably preventedfrom forming here be cause o f the influenceof Jupiter, and astronomers thought that theregion might be strewn with high velocitydebr is down to the s ize of specks o f dust .

Z _ _ ^ I

I he number of small particles was unknoand could have presented a major hazarspacecraft traveling to the outer p lanets.

Almos t 300 days after launch, P ioneerpassed on the far side of the Sun from EaRadio communication wis interrupted ffew days

Witir Pioneer 10 well on its way through A steroid B elt without incident, the secspacecraft, P ioneer 11, was launched overy similar I ath to Jupiter. Leaving A5, 1973 , i t is scheduled to arrive at Jupa year after Pioneer 10, namely in comber, 1974. Its path is ordered so thdepending upo n the findings of P ioneerthe second I-ioneer can fly closer to or furf rom Ju piter, f ly to S aturn in 1980, or foPioneer 10 g ut of the Solar System.

W H A T T H E S P A C E C R A F T D O

Both spacecraft are designed to investigJu piter in three ways:

1 ) meas ureme nts of par t ic les, f ie lds, radiation

2) television imaging to provide picturethe planet and several of its satellites

3 ) accurate ob servation of the path ofspacecraft to meas ure the forces (sucthe gravity of Jupiter ► acting upo

The spacecraft also provides informationinterplanetary space from the Earth's oto the orb it of Saturn and be yond.

A numb er of experiments have been desigv,ith the ob jectives listed.

I N VE S T I G A T I O N O F IN T E R P L A N E T AS P A C E O N T H E W A Y T O A N D B E YOJ U P I T E R

• M ap the m agnetic f ield in interplanespace between Earth's orbit and Jupiorbit, and beyond.

A TA S T E R O I D B E L TJ U P I T E R

L A T E RO R B I T

EARTH R A D I O 5 / 0 N A 14 % M I N U T E S E A R T H J U P I T E RL I F T O F F A N 0 E N T E R 4 5 M I N U T E S JUPITER E A R T .

FART. SHADOW_'-- -'

• - J U P I T 6 At N C < A / 1 / T

INITIAL

S oI AR PI AN FT`O R I F N T A T I O N

(N.lUl1ATI IJ f IP F N I M f A R T SNF1"I AM"

f E P F . I M F N T S

F I," M I D C d 1 R S E S E C O N D M I D C O U R S EC O R R F C T I O N < D A Y S C O R R F r T IO N 7 C , D A Y S 1RDETF O R M

_ -TRAJ[^TORT S-/O F , , - O R S D--'----- -__._. ' IY ECC

J U P I T E R A TIAUNCM

Figure 2. Mission Events

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rection of cosmic rays—fas ! moving parts

of atoms—rushing out from the Sun andalso into the Solar System from theGalaxy.

P I O N E E R G P I C T U R E

"CAMER A'S" WX1A° IMAGE SIZE FOR

10 5 m i n O F O B S E R V A T I O N

Figure 3. Picture Coverage at E ncounter

charged particles from the Sun—varies

with distance from the Sun.

solar wind, the interplanetary magneticfield, and cosmic rays.

sphere (the heliosphera).

Interplanetary dust.

SYSTEM

charged particles in the radiation belts of

Jupiter, and the extent of these belts.

does (glows in the upper atmosphere overthe polar regions).

metric and decametric radio waves from

Jupiter.

tween the magnetic field of Jupiter andthe ;.Ind of charged particles from the

Sun, like the bow wave of a ship.

outeratmosphera of Jupiter above the cloud

tops.

ons of hydrogen and

helium in Jupiter's atmosphere.

• Measure the structure of the planet'svisible atmosphere and also of the higherregions where molecules of gases becomeelectrically charged and produce an iono-sphere.

• Measure the brightness, color, and polari-zation (the direction of vibration) of re-

flected light from Jupiter.

• Photograph Jupiter from a distance, and

later close to, with better resolution thanthat obtainable from Earth; obtain pic-tures of the terminator (the region ofsunrise and sunset) and of a crescentJupiter with the Sun shining from behind

the planet,

• Photograph the satellites from a distance,and some of them close-up; measure their

sizes and determine w hich, if any, possessan atmosphere.

• Calculate with greater accuracy the orbitsand masses of the satellites and the g ,avi-tational field of Jupiter itself.

To achieve these objectives each spacecraftuses a battery of scientific instruments. Theseinclude a magnetomoter to measure magneticfields, a plasma analyzer to m easure the ionsand electrons f l owing through space fromthe Sun (solar wind), a composite device to

detect and measure electrons and protons inthe radiation belts and nuclei of chemical

elements from hydrogen to oxygen, and acosmic ray telescope to detect and measurecosrsic rays.

Ageigertube telescope and a radiation detec-tor also detect and measure particles in the

radiation belts.

An asteroid-meteoroid detector measurespaths of space particles in the vicinity of the

spacecraft to find the distribution of dustand other particles in the space between theplanets of the Solar System , and in the vicin-ity of Jupiter. A meteoroid detector alsokeeps tags on these particles as they punc-

ture its pressurizes cells.

An ultraviolet photometer (light measurer)and an infrared radiometer (heat measurer)

look at interplanetary space and the J'ovian

system in ultraviolet and infrared—the radia-tion on either side of the visible spectrum of

light that extends from violet to red

colors of the rainbow). The ultraviolet'inment determines how much helium ein the atmosphere of Jupiter, and how m

hydrogen and helium is flowing intoSolar System from the Galaxy. The infr

instrument measures heat radiated Jupiter and from features such as the G

Red Spot. It also checks the proportiohydrogen and helium in the atmospher

An imaging photopo larimeter moves a nbeam in sweep s across the surface of Jand builds up a picture like a televisio

builds its picture by a series of lines athe tube face. The instrument measureintensity and the polarization (howlight waves are vibrating) of light Jupiter and its satellites. It is also usscan space on the way to Ju piter. This iment, through a computer back on Eprovides television-type images—picturJupiter that are expected to be better

those obtained by telescopes from Eartat viewing angles impossible from ETextures and shapes of clouds should be

Pictures also will be constructed of Jup

large Galilean satellites. Since radio si

are continuously coming from the spacto Earth, these can be used to probethe atmosphere of Jupiter and the satlo, by measuring fading of these signals the spacecraft passes behind Jup iter ansatellite. This experiment provides info

tion about the composition and densthe atmosphere, and the numbers of elecmoving freely in it.

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significant results.

low alongEarth's orbit. There is no

Thees declined in numbe rs as the

Sun. Somewhat

belt. However

nstruments

s of much less numerous larger pa r-

THE ENCOUNTER AND AFTER

In late November 1973 Pioneer 10 glides intowards the brightly colored and enormousJupiter--passing the four small outer satellitesat 25 days be fore closest approach, the threemiddle satellites at 1 t days, and, in the grip

of the immense gravity, the four planet-sized

Galilean satellites and the any inner moonIn a rush on the day of closest approach,December 3.

At the closest approach to 81,000 miles,Jupiter fills the black sky, an enormousyellow-orange and blue-gray-belted sphere.

And six hours earlier, Pioneer begins to test

the Intense radiation belts while controllerson Earth anxiously await confirmation thatthe belts are not damaging thu equipment ofthe spacecraft.

Low resolution pictures are taken of the five

Inner satellites and of Jupiter itself, whilethe battery of instruments probe into sur•

rounding space , the satellites and the planet.

Spacecraft operation during the encounter

are complicated by 92 minutes of round trip

time for radio signals to pass back and forthand a need to send 10,000 commands to thespacecraft in the two weeks centered onclosest approach.

After Jupiter, Pioneer 10 heads out of theSolar System, crossing Saturn's orbit in 1976,Uranus' orbit in 1979, Neptune's orbit in1983, and in 1987, 15 years after launch,

the orbit of Pluto, the known limit of theSolar System. Pioneer's destination among

the stars of the Galaxy is then somew here inthe Zodiacal constellation of Taurus (TheBull). The spacecraft heads out from theSolar System at 25,000 miles per (tourcarrying a plaque that tells any intelligentspecies who may find it millions or billions

of years from now, who sent it and fromwhere it came.

A project of NASA's O ffice of Space Scthe Pioneer project is managed by NA

Ames Research Center, near San FranCalifornia. The two spacecraft are buTRW Systems, Redondo Beach, CalifThe scientific instruments are suppliNASA Centers, universities, and privadustry. Tracking is by NASA's Deep S

Network, operated by the Jet PropuLaboratory, Pasadena, California.

STUDY PROJECTS

ONE

On the map of the Solar System, madeproject for leaflet #1 of this series, drapath of Pioneer 10. Work backwardsthe encounter on Decem ber 3 using Figas a guide to find the position of the at launch. Put the path of Pioneer 11 omap, too, using the correct positioJupiter and Earth for the launch an

counter dates. Remember Earth goes t

times around the Sun when J upiteraround once.

TWO

If Pioneer 10 leaves the Solar Syste25,000 miles per hour 15 years hence

heads towards the stars at this conspeed, calculate hove long it takes to

the distance of the near star, Proximatauri, which r is 4 y, light years away. (Ayear is the distance light, speeding at 18miles a secon d, travels in one year). Calchow fast a spacecraft has to travel to rthis near star in 10 years.

READING LIST

NASA SP-268, The Pio neer M ission toter (GPO $0 30 i Fl.

Science News, 11 March 1972, Pioneegin—Dourney to Jupiter.

Science News, 24 February 1973, The

teroia t.

*CFO 702