NASA Facts The Pioneer Spacecraft

8/7/2019 NASA Facts The Pioneer Spacecraft

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N A S A ~ f f i ~ ~ A N EDUCAT IONAL PUBLICATION OF THE

NAT IONAL AERONAUTICS AND SPACE ADM INISTRATIONNF -31 / VOL. IV, NO. 3

The Pioneer SpacecrallMONITORS OF INTERPLANETARY SPACENASA's sun-orbiting Pioneer spacecraft are surveying interp lanetary space and cont ributing toknowledge by which the great solar f lares thatcould peril travelers to the moon and beyond maybe forecast. Solar flares are particularly sharp outbursts of the sun, some of wh ich hurl dangerousradiation into space.Pioneers also increase understand ing aboutevents on earth because sola r and interstellarphenomena have to pass th rough interp lanetaryspace to reach and influence our terrestrialenvironment.Today's Pioneers have the same name as severalearlie r spacecraft. The last of the ea rlie r groupwas Pioneer V, la unched March 11 , 1960. Radiocommunication was maintained with Pioneer Vuntil June 26, 1960, when the craft was 22.5million miles from earth , establish ing a recordfor long-distance communication that stood forseveral years . Among its other achievements,Pioneer V confirmed the existence of previouslytheorized interplanetary magnetic fields.

First of the new Pioneers wa s Pioneer VI ,launched December 16, 1965, into an orbitbetween earth and Ven us. On August 17, 1966,Pioneer VII was laun ched into an orb it betweenearth and Mars. In addition to such orbits, planscall for launching Pioneer into rou ghly the sameorbit as earth but leading or lagging ou r planet byseveral million miles. The Pioneer program ismanaged by NASA 's Ames Research Center , Mountain View, Cali fornia.

1 Model of Pioneer superimposed upon a simulated spacebackground .

The ob jective of the Pioneer program is to studyin terp lanetary space continuously from widelyseparated points during an entire solar cycle. Thesolar cycle is an eleven -year period duri ng wh ichthe frequency and intensity of sola r eruptions gofrom a maximum to a minimum and then again toa maximum.


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Scientists are correlating data from Pioneersand also comparing such data with informationfrom other interplantary spacecraft such as Marine r and from earth-orbiting satellites such as theOrbiting Geophysical Observatories and Explorers.Scientists believe that greater knowledge ofinterplanetary events and their effects on theearth's environment gained through such studiescan contribute to weather forecasting and controland to communications on earth .A NEW LOOK AT INTERPLANETARY SPACEAs Pioneers soar along their distant paths throughspace, they report on the solar wind, also calledthe solar plasma . The wind speeds outward fromthe sun's turbulent surface to well beyond the orbitof Mars. Scientists now consider the wind anextension of the sun's corona, or atmosphere .

The wind is unlike that which we know on earth .Fo r one thing, it is extremely thin and can bedetected only by sensitive instruments. PioneerVI data indicate the wind is made up of 50 to 150ions (atomic particles) of hydrogen, helium , andother elements per cubic inch of space. Earth 'satmosphere is made up of about 3XI020 (300quintill ion or 3 followed by 20 zeros) atoms ofair per cubic inch. The best artificial vacuums onearth have several million atoms of air per cubicinch .


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2 Pioneer V.3 Space coverage provided byPioneers VI and VII.4 Diagram shows magnetic lines offorce emanating from the suninto interplanetary space. (See te xt .)s Diagram shows how Pioneer VIImay have pased through ear:th 'smagnetic field at a distance of morethan 3 million miles from earth .

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The maximum velocity of the solar wind hasbeen clocked by Pioneer VI at nearly 1,700,000miles per hour. The wind's velocity varies withsolar activity during a solar cycle. Abrupt increasesin velocity follow solar flares .The indicated temperature of particles in thesolar wind is about a million degrees Fahrenheit.The high temperature and extreme veloc ity makethe solar wind more comparable to the blast of arocket than to any other thing we know here onearth.

Other data from Pioneer VI indicate that thesolar wind arrived at the spacecraft as much as10 degrees off of a straight line between thePioneer VI and the sun. The solar wind had beenthought to move straight outward from the sun'ssurface.

The solar wind draws out the sun's magneticfield to form interplanetary magnetic fields. Pioneer and other studies indicate that the lines offorce of the magnetic field transported in to spaceby the solar wind are twisted like streams of waterfrom a whirling lawn sprinkler. This effect iscaused by the sun's rotation in combination withthe radial (outward) motion of the solar wind. Thesun makes a complete rotation on its ax is aboutevery 27 days.

Pioneer VI indicated that the sun 's magneticfield appears to be snarled near the sun andbecomes more so as it is drawn out by the solarwind . The magnetic lines of force also appear tobe twisted about each other.The solar wind also affects ea rth's magneticfield (the geomagnetic field) . On t he side towardthe sun, the solar wind compresses the geomagnetic field to a distance of 25 ,000 to 40,000miles. On the other side, it blows the geomagneticfield an indeterminate number of miles out inspace. Pioneer VII detected the effects of the geomagnetic field more than 3 mill ion miles out inspace. It also indicated that the wind may causethe lengthy wake, or ta i l, of the geomagnetic fieldto wave back and forth like a flag in a stiff breeze.Another form of matter generated by the sunis cosmic rays. Cosmic rays in ou r solar systemalso originate el sewhere in interstellar or intergalactic space.Cosmic rays , like the solar wind , are atomicpa rticles. They are made up of protons (nucleiof hydrogen atom s) , alpha partic les (nuclei ofhelium atom s) , nuclei of atoms heavier thanhydrogen or helium , and elect rons . Cosmic raysare the most penetrating form of harmful radiation known. Solar flares and other erupt ions gen-

---=::::::::::::-----___ SOLAR WIND -===========--_---=-===


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erally produce cosmic rays.The energies of cosmic rays range in themillions , billions, and trillions of electron volts asompared to the hundreds and thousands of elec

the solar wind particles. The electronis a unit employed by scientists to measure

. It is a tiny base for measure-because the matter measured is in itselfnfinitesimal. A particle would need 550 sexti ll ion

5 followed by 22 zeros) electron volts to equalenergy used by a 25-watt bulb in an hour.Although cosmic rays are many times more, the aggregateof the solar wind is far greater than thatall cosmic rays in the region of the solar systemr which spacecraft have provided measurements.

in this region solar wind particlesto outnumber cosmic rays by about a billionone.Pioneers have provided data indicating thatl around the linesforce of the solar magnetic field which the solarhas pulled out into space. As a result , solarosmic rays speed through interplanetary spacewell-defined streams. Other data have showna stream of solar cosmic rays may last for

, indicating the possibility that the sun stores

cosmic ray particles near its sljrface and releasesthem gradua lly .SPACECRAFT DESCRIPTIONToday's Pioneers are drum -shaped, 35 inches highand 37 inches in diameter. They weigh about 140pounds on earth .

The design and construction of the craft emphasize simplicity which is one way of gain ing maximum reliability. For example, all orientationmaneuvers are conducted by means of a singlegas jet which operates in brief spurts. The manythrusts at one point produce wobbling, but this istaken care of by a wobble damper, con sisting oftwo small balls floating inside of a f luid-filledcylinder. Friction of the balls moving through theflu id converts the ki netic energy (motion) of thewobble into heat which is dissipated into space.

The craft's cylindrical exterior is covered withsolar cells divided by a narrow band conta iningapertures for experiments and sun sensors fororientation. Solar cells convert sunlight to electricpower for running spacecraft equipment. The10,368 solar cells can generate 80 watts of powerat earth's distance from the sun. They generatemore when nearer the sun; less, when fartheraway. Pioneer is also equipped with a rechargeable


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storage battery for use during peak power demandsor when the solar cells are not in ma ximum sun light.Equally spaced around the curved outs ide of thespacecraft are three booms , each of which is fivefeet four inches in length. One holds the gas jetfor spacecraft orientation. Another holds the sensorfor detecting magnetic fields . A thi rd is tipped bythe wobble damper.Projecting from the middle of one end is thespacecraft's radio antenna. Extending from therim of the other end is a special radio antennaused in the radio propagation experiment. Electrons affect radio waves. The radio propagationexperiment indicates the number of electronsbetween the spacecraft and earth. For example,

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PIONEER MOUNTED ON DELTA THIRD STAGE

PION EER

PARTOF TADSECONDSTAGE.

PIONEERI

TADTHIRDSTAGE

FAIRING(SHROUD)ENCLOSESAND PROTECTSCRAFT DURINGFLIGHTTHROUGH THEATMOSPH ERE.IT FALLS AWAYIN SPACE.

Pi oneer VI found an average of 90 electrons pecubic inch in the regi on between 78 and 92 milliomiles f rom th e sun .Pi onee r is made up of 56,000 parts. It is con

st ructed principa lly of light-we ight but durablaluminum .Pioneer is ke pt point ing in one direction i

spa ce by spin stabil izat io n. Th e spacecraft spinat a rate of 60 revolut io ns per minute. In effectPio nee r is like a gy roscope in th at it spins in ordeto point stead i ly in on e direction .The spin precludes th e nee d for more complestabil izat ion dev ic es. It also ena bles Pioneer tsee and report mu ch mo re tha n ot herwise, becausea ch expe ri ment can scan a full circle, rather t hanbe limited to a single di rection .

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SHOR T THRU STSAGA INST SPINAXIS BRINGFORCE TO BEARIN A PLA NE ~ PERPENDI CULARTO DIR ECT ION "OF THRUSTS SPAC ECRAFT (GYROSCOPE MOV ES THIS WAEFFECT) . ...,

. . . . AN D TURSP IN AXIS (ANSPACECRA FT)ABOUT ASELECTED AXI

7 Diagram shows Pioneer, the fa irin g (shroud) that protects 8 Diagram provid es examp le of how spacecraft 's or ientatthe spacecraft during flight through the atmosphere , the is changed .TAD third stage, and part of the TAD se cond sta ge.6

- - - . - - -----_ ._ -- ----- - - - - - - - - - - - - -


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10 Workers are dwarfed by the massive dish of th e 210-ftdiameter antenna at the Goldstone , California , Deep SpaceStation.Pioneer is set to spinning by the whirling thirdstage of its Thrust-Augmented Delta (TAD) launch

veh icle. The third stage is rotated by a turntablelocated on the second stage. This turntable istimed to start just before separation of t he secondand th i rd stage.

TAD is an improved Delta vehicle wh ose fi rststage thru st has been increased by three attachedsol id-propellant rockets. Without its Pi oneer pa y-load , Delta stands 90 feet high on t he launch pad.It has a first-stage th rust of 332 ,000 pounds.CONTACT MAINTAINED BYDEEP SPACE NETWORKContact with Pioneer spacecraft across mill ions ofmiles of space is maintained by means of theNASA globe-girdling Deep Space Network. Th enetwork is equipped to track , monitor , and gathersc ient ific data f rom spacecraft sent to the moonand beyond.

11 Ano ther view of th e 210-foot diamet er t racking andcommunicatio ns antenna.

Stat ions are located at Goldstone, California ;Madrid , Spain ; Woomera and Canberra , Australia ;Johannesburg, Republ ic of Sou t h Af rica; andMadrid , Spain . The stations are so spaced aroundthe globe that communication with spacecraft isunb roken despite the earth 's ro tati on . Th eir 85-foot diameter antennas can communicate with aspacecraft like Pioneer over a distance of about50 million miles.Con tact with Pioneer VI is possible throughoutits journey around the sun when it will re ach amaximum distance of about 180 million miles fromearth. This contact is made by NASA's newesttracking and telemetry antenna dedicated at Goldstone, California , on April 29, 1966. As tall as a23-story buildin g and with a dish re flector 210 feetacross (almost an acre in area) , the antenna cancollect radio signals as faint as one billionth of abillionth of a watt and amplify them to usefulstrength.

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