nasa facts mariner spacecraft - planetary trailblazers

8/8/2019 NASA Facts Mariner Spacecraft - Planetary Trailblazers

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- -AN EDUCATIONAL PUBLICATION OF TH E

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

NF-39/2-68 9ri

PLANETARY TRAILBLAZERSThe atmosphere of Venus is many times denser than Mariner V survey of Venus, and presents highlightsthat of earth while the atmosphere of Mars is abou t of other Mariner planetary and interplanetaryone per cent as dense as earths. The surface of experiments.Venus may be hot enough to me lt lead. The surface VENUS REVISITEDof Mars appears pockmarked by craters and looksmore like the surface of the moon than that of earth. Although the closest planet to earth, Venus is stillThe above and much other new information about one of the most perplexing of heavenly objects.our planetary neighbors has been acquired throu gh Because Venus appears to be constantly shroudedthe relatively close range observations made pos- by clouds, i t s surface cannot be seen. And thesible by NASAs Mariner spacecraft. This NASA composition of the clouds themselves is subject toFacts features the latest of these missions, th e disagreement.A composite of photographs of the stars, of Venus, and ofMariner V has provided this conc eption of the spacecrafts approach to Venus.


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The world's first relatively close-up observationof Venus was made possible by Mariner I I in 1962.Mariner II instruments indicated an apparentVenusian surface temperature t hat may be as h ot as800" F, much too hot for life as we know it.Mariner II came within 21,645 miles of Venus toprovide man with one of his most significantadvances in knowledge about the planet. Mariner Vwas launched to Venus on June 14, 1967, to refinethe results from Mariner II and from other studiesand to acquire new information. Sweeping with inabout 2,500 miles of the planet on October 19,1967, Mariner V provided data that enabled sci-entists to draw several conclusions. Among them:The atmosphere of Venus has critic al refractivity.This means that the atmosphere is so deep anddense tha t it could capture ligh t and rad io waves sotha t they circle the planet rather than go to thesurface or shoot out into space. This capture couldproduce bizarre optical effects fo r an earthly visitorto Venus.

The major constituent of Venus' atmosphereappears to be carbon dioxide.0 The Venus corona (its exosphere, or outermostregion of its atmosphere) is made up largely ofhydrogen, as is earth's corona. The temperature of700" F in the Venusian corona is significantly lowerthan the 1,300" F average temperature of earth'scorona. (The hydrogen gas atoms i n this region areso far apart that no passing object would absorbappreciable heat from them.)0 No ree oxygen was detected in the exosphere. Itis believed that if the lower Venusian atmospherecontained water vapor, the water molecules wouldbe broken in to separate hydrogen and oxygen atomsas they rose toward the outer atmosphere.An ionosphere exists on both the day and nightsides of the planet. A planet's ionosphere is gen-erated by the break-up, due to solar radiation, ofneutral atmospheric molecules and atoms i nto elec-tron s with negative electrical charges and ions withpositive charges. It was found that the electrondensity o f V enus' dayside ionosphere ranged from100 t o 1,000 times that of the night side.0 Mariner V detected no magnetic field attributableto Venus nor any concentrated radiation like theVan Allen Radiation Region around earth. This con-firms information previously sent by Mariner II.And Mariner V did much more. On its mult i-mil l ion mile journey to and even after it passedVenus, it regularly reported on conditions in inter-planetary space during a period of rising solar ac-tivity. On January 4, 1968, it came within about 5 4

millio n miles of the sun, closer than any other ma n-made object has come to the solar system's fierycenter.Tracking data gathered on how Venus' gravityaffected Mariner's flight path have helped to refinethe estimate on Venus' mass which is now calcu-lated at about 0.815 of that of earth. Mass is thetota l amount of ma tter in an object.Mariner V, of course, could not provide completeanswers on Venus' surface, atmosphere, and thepossibility of life. Flights carrying more elaborateinstruments are required before additional conclu-sions can be drawn about the planet.

THE VIEW FROM VENUSSome scientists say that the clouds of Venus arecomposed mostly of volcanic dust. If this is so, avisitor to Venus may find a turbulent land whoseblist erin g surface is studded w ith perpetually erupt-in g volcanos.According to radar studies made from earth,

Venus rotates completely about its axis every 243earth days. Observations through telescopes onearth indicate that the cloudy atmosphere of Venuscircles the planet about every five earth days. Thisis roughly fifty times as fast as the planet rotatesand could m ean tha t i ts surface is constantly lashedby scorching winds.Other scientists claim that their instruments onearth have detected life-sustaining water dropletsor ice crystals in the Venusian clouds. And theypoint out that the radio emissions picked up byMariner II, on which the assumed high Venusiantemperatures are based, may be generated by at-mosphe ric processes unrelate d to heat-for ex-ample, lightn ing-like electrical discharges or chemi-cal reactions.Just a day before the Mariner V fly-by of Venus,the Soviet Union's Venus 4 entry probe was para-chuted down toward the planet. It reported tem-peratures as high as 518" F and atmospheric pres-sures as high as 2 2 times tha t of earth.Some scientists speculate tha t i f the surface ofearth were as hot as the su rface of Venus appears tobe all of the carbon dioxide in earth's oceans andearth's carbonate rocks, such as limestone, wouldrise into the atmosphere. Thus, the atmospherewould be much denser, only a small proportionwould be nitrogen, and oxygen would be barelytraceable.Based on data from Mariner V and atmospherictheories, scientists calculate that the Venusianatmosphere is composed of 69 to 8 7 percent carbon

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The view from Venus compared to that from earth.

dioxide, i f the other ma jor constitutent is nitrogen.Earth's atmospheric composition (excluding water)is 78 percent nitrogen, 2 1 percent oxygen, and 1percent other gases, among which are argon, car-bon dioxide, hydrogen, helium, krypton, and neon.Scientists suggest tha t i f later exploration provesthat the Venusian atmosphere has more neon thannitrogen, it could mean that Venus is geologicallyyounger tha n earth. Earth's primeval atmosphereis believed to have contain ed large amo unts of neon,an extremely light gas, most of which drifted awayinto space lon g ago.If Venus' atmosphere is as dense as currentmeasurernents indicate, it could act like a giantlens, refracting, or bending, light and radio wavesin such a path that they circle the planet and mayeven return to where they started.As a result, if an explorer could reach and sur-vive on Venus, he may be subjected to wierd opticaleffects. Sunlight filtering through the Venusianclouds would strike an object and when reflectedfrom it would bend around the planet. The explorercould theoretically see reflections from objects be-yond the actual horizon of Venus.If ligh t rays actually circle the planet, the explorerwill be subjected to another unbelievable sight.Theoretically, he would see the b ack of h is own headin the distance.The horizon itself w ould also appear to be abovethe explorer due to the be nding of its reflected ligh t

by the Venusian atmosphere. The surface of Venuswould seem t o rise on all sides of the explorer, giv-ing him the impression that he is on the bottom ofa giant bowlshap ed depression.Sunsets on earth have been the subject of manybeau tiful paintings, b ut sunset on Venus is tru ly ou tof this world. As the sun drops below the actual

Venusian horizon, its reflections are picked up sothat it becomes a band across the sky. The bandmay be colored like a rainbow if the atmosphereproduces the believed effect of a prism.On Venus there may truly be no night as such.Because the atmosphere routes sunlight around theplanet, it is possible that the night sky is aglow.Perhaps, this explains the so-called ashen light ofVenus-the faint illumination of the darkened partof the planet that has puzzled astronomers viewingit hrough telescopes on earth.Mariner V data also showed that Venus is sur-rounded by a shock wave similar but not identicalto the one surrounding earth. The shock wavearound earth is created by the impact of the speed-in g solar wind* against earth's magn etic field. Solarwind speeds have been clocked at nearly 1,700,000miles per hour by NASA's Pioneer VI spacecraft.The size of the shock wave around Venus i s muchsmaller than that around earth. Scientists are no tcertain whether the solar wind was impinging di-rectly on the Venusian ionosphere, a Venusian mag-netic field too weak to be detected by Mariner'sinstrume nts, or both. Data fro m Mat'iner V indicatethat a Venusian magnetic field, if one exists, is nogreater than 1/500th of earth's.EXPLORING SPACE WITH MARINER CRAFT

The Venus fly-by of Mariner V marked the thirdtime that American spacecraft have made close-range observations of other planets. The world'sfirst such observation was made by Mariner I1whenit flew in the vicinity of Venus on December 14,1962.Mariners I an d Il l failed, but on July 14, 1965,Mariner IV swept by Mars. Its h istoric close-range

*For definition, see "Exploring Space with Marine r Craft." below.

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photographs showed a Martian surface pockmarkedby craters and looking more l ike the moon than theearth. Among the other information it deliveredwas the fact that the atmosphere of Mars is onlyabout one per cent as dense as earths, much lesstha n needed for most types of ea rthly life. MarinerIV detected no Martian magnetic field nor a radia-tion region such as exists around earth.In November 1967, scientists completed a two-year study of Mariner IV Mars photographs, usingnew computer interpretation techniques. Theyfound that Mars may be at least three times asdensely cratered as preliminary photographsrevealed.Based on the num ber of craters tha t could be dis-tinguished i n the original photographs, scientistshad projected tha t Mars may be p itted by more than10,000 craters of the sizes observed (diameters 3to 7 5 miles) and Ta ny smaller craters. The newcrater count approaches tha t of earths moon.

However, the craters of Mars are more erodedthan those on the moon and are, therefore, shal-lower and less precipitous . The principa l erosionagent on M ars may be wind-blown dust.In addition, analyses of Mariner IV photographsthrough color f i l ters show that the soil of Mars isreddish i n color. This c onfirms observations throughtelescopes on earth.An unexpected scientific bonus of Mariner IVlongevity was furnished during the period Auwstto October 1967. At one time, M ariner IV, earth,and Mariner V were located along an imaginary lineextending radially from th e sun. The spacecraftwere abou t 70 mill ion m iles apart with the earth inbetween. This provided an oppo rtunity to make asimultaneous three-point measurement of the mo-t ion of the solar wind and the suns magnetic fieldlines tha t are embedded in the wind. The data in -creased knowledge about the properties of th e solarwind.Artists sketch of line-up of Mariner IV, earth, and Mariner V fo r three-point study of solarradiation during 1967.

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Mariner V is tested at C ape Kennedy, Florida, prior to launch.The solar wind, or solar plasma, is made up ofatomic particles of hydrogen, helium, and otherelements constantly speeding outward from thesuns surface. It is extremely thin and can be de-tected only by sensitive instruments. It is con-sidered an extension of the suns corona, or outeratmosphere.The velocity and density of the wind vary not on lywith distance from the sun but also with solar ac-tivi ty durin g a solar cycle. The solar cycle is aperiod of about 11years during which so lar activitygoes from a maximum t o a m inimu m and then r ises

again to a maximum. Mariners IV and V acquireddata during a period of increasing solar activity;Mariner II, during a period when solar activity wassignificantly lower.(NASAs Pioneer spacecraft have also contrib utedto investigations of the solar wind and other inter-planetary phenomena.)

At another time, the three observing stations(Mariner V, earth, and Mariner IV) were in positionsalong an imaginary spiral l ine originating from thesun. Data acquired from the three stations aug-mented knowledge about the propagation of solarcosmic rays that spiral through space along mag-netic field lines stretching from the sun.The magnetic field lines are drawn out by thesolar wind to form interplanetary magnetic fields.The combination of the solar winds radial (outward)movement and the suns rotation causes the mag-netic f ie ld l ines to tw ist l ike streams of water froma whirlin g lawn sprinkler. The sun completes arotation every 27 days.Cosmic rays are atomic p articles as are those ofthe solar wind. They are made up of protons (nucleiof hydrogen atoms), alpha particles (nuclei ofhelium atoms), nuclei of atoms heavier than hydro-gen and helium, and electrons and are generally

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produced by solar flares and other sudden solareruptions. Cosmic rays in our solar system alsooriginate in interstellar or intergalactic space. Cos-mic rays are the most penetrating form of particleradiation that is known.Plans call for two television-equipped Marinersto give mankind a longerand closer, and better,look at Mars in 1969. The spacecraft are expectedto be half again as heavy as Mariner IV with theadded weight reflected in improved instrumentation.The planned approach to Mars is within 2,500miles as compared to the 6,118 miles at whichMariner IV sped by Mars. The fly-by is chosen toenable experimenters to get a broad overview ofthe planet and prevent possible contamination ofthe Martian surface by microorganisms from earth.

In October 1967 , experimenters on earth againturned on the picture transmission equipmentand fired the rocket engine of Ma riner IV . Thiswas the firs t tim e either had been operated inroughly 21/2 years. Mariner IV was about 56milli on miles from earth when these operationswere performed. The successful picture trans -mission and rocket fir ing after such a longperiod helped give engineers confidence forfuture missions to Jupiter and beyond.For additional information on Mariner IV, seeNASA Facts, A Report from Mariner IV, Vol.I l l , No. 3.

SPACECRAFT DESCRIPTIONMariner V is a windmill-shaped craft consistinof an octagonal structure to which are attached solarpanels and radio antennas. The octagonal frame-work is 4 feet 2 inches across. With solar panelsextended, the vehicle spans 18 feet. It weighed 540pounds at launch.The octagonal framework has eight compart-ments, or bays. Seven are occupied by instrumen ts:and one, by a rocket system designed to achievesma ll changes in the spacecraft's trajec tory, orflight path, by increasing or decreasing its speed.The velocity change may be as fine as % th mphor as much as 1 88 mph. The engine provides 5 1

pounds of thrust.Mariner V began life as a back-up for the br il-liantly successful Ma riner IV spacecraft. Majo rchanges were made to prepare Ma riner V for a f l ighttoward rather than away from the sun and to meetother Venus mission requireme nts. Relative to this,a secondary objective of the Mariner V project was

Upper view of Mariner V.to acquire engineering experience in converting aspacecraft designed for flight to Mars into one thatcould explore Venus.Among the changes made in Mariner V was a re-duction in the size of the solar panels. The fourpanels, looking like the blades of a windmill, arecovered with photovoltaic cells tha t convert sunlightto electricity for spacecraft power. The amount ofelectricity they generate depends for the most parton the intensity of the light strik ing them. Sincesunlight near Venus is brighter than near Mars,fewer photovoltaic cells could provide the same watthours of electricity.

The Canopus sensor on Mariner V is a photo-mu ltiplie r tube. In a photom ultiplier tube, lightstr ik ing a grid knocks of f electrons that in turnknock off electrons in succeeding grids. Theresulting stream of electrons becomes ameasurable electric current. Ground person-nel know how much current the light from thestar Canopus can eventually generate andthus can ascertain when Mariner is locked ontothis reference point.Because Mariner V was t o head closer to t he sunthan any other spacecraft, its sensitive instrume ntshad to be carefully insulated. The sun's heat was

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Lower view of Mariner V.reflected by a deployable sunshade which works likean awning, and by paint patterns and polished me talsurfaces. In addition, therma l blankets made up ofseveral layers of aluminized Teflon and Mylar sur-rounded instruments. These also served to retardloss of heat through th e cold dark side of the craft.In airless space, the pa rt of a spacecraft facing thesun may be intensely hot while the other side i s in

subzero cold. A certain amount of interna l warmth,derived largely from working instruments, is neededto keep a craf t operating.Other modifications included relocation, removal,or add ition of instrume nts as needed. However,equipment for steering, stabilizing, and communi-cating with the cra ft was basically similar to th at ofMariner IV.

Sensor Detects Planet, Star tRecording Ultraviolet DataI

Mariner V fly-by of Venus.Start Recording

Begin Occultation(The Pass Behind Venus ----

End Recording Play-Back

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ACQUISITION OF SCIENTIFIC INFORMATIONThe instruments employed by Mariner V for ac-quisition of scientific information included an ultra-violet photometer, radio receivers and transm itters,a magnetometer, a plasma (solar wind) detector,and a trapped radiation detector. The photometermeasured the brightness, or intensity, of ultraviolet

light in selected wave length ranges that signifiedthe presence of hydrogen an d oxygen.Early in Mariners flight, as the craft sped fromearth, its photometer measured the hydrogen andoxygen in earths corona t o a greater distance ou t-ward tha n ever before accomplished. During itsfour-month flight between the planets, the photo-meter measured ultraviolet emanations far and nearin our galaxy. Since hydrogen is the most abundantelement of stars and of the clouds of dust and gasin interstellar space, these measurements addedsignificantly to scientific knowledge about the M ilkyWay. The inform ation abou t backg round galacticradiation also contributed to the accuracy of meas-urements taken of the Venusian corona.Mariner found that the ultraviolet band for hydro-gen in Venus corona was abou t as brig ht as that forearth, indicating comparable hydrogen content.There was no indication of oxygen around Venus.The two radio experiments conducted near Venusare called the occultation experiments. Occultationhas been defined as the disappearance of one bodybehind another of larger apparent size. A solareclipse, for example, is the occultation of the sunby the moon.

The atmosphere of Venus and Venus itself camebetween earth and Mariner V in the occultation ex-periments. Radio waves were trans mitte d in to theVenusian atmosphere. From analyses of how thesewaves were refracted, attenuated, or blocked werederived conclusions on atmospheric density, tem-perature, and composition.In one occultation experiment, the 210-footdiameter tracking antenna of NASAs Deep SpaceNetwork station at Goldstone, California, picked upMariners tra ckin g signals before and after Marinerwas occulted by the plane t. Even before Marin er wasocculted by the solid body of the planet, the space-crafts signals to earth were cut off.Scientists theorize tha t the signals were bent a ndcontained within the Venusian atmosphere. For anatmosphere to do this, they say, it would have to beat least seven to eight times as dense as that atearths surface.

Signal cut-off occurred at a radial distance (dis-tance from Venus center) of about 3,785 miles.Because of Venus thic k cloud cove r, scientists arenot certain about the actual size of its solid body.But recent radar measurements indicate a Venusradius of roughly 3,765 miles.On these bases, it appears tha t Venusian atmos-pheric pressure at a 20-m ile altitude is at leastseven to eight times tha t at earths surface. Evengreater pressures are expected at lower altitudesand at the Venusian surface. Using the data fro mthe tracking signals, scientists were also able, bya complex process, to derive temperature rangesand major constitutents of the Venusian atmos-phere.In the other occultation experiment, called dual-frequency, the 150-foot-diam eter antenna of theStanford Center for Radar Astronomy at Palo Alto,California, transmitted radio signals to Mariner a ttwo different frequencies. Comparison of the dif-ferences on how the two signals were affected intransit t o M ariners receiver gave inform ation aboutthe Venusian ionosphere and about charged atomicparticles in interplanetary space.

A planets ionosphere results when solar radia-tion causes neutral atmospheric molecules andatoms to give up electrons. The remaining parts ofthe atoms or molecules are called ions, and theStanford University radio antenna at Palo Alto, California.

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process by which neutral atoms an d m olecules arestripped of one or more electrons is called ioniza-tion. The part of a planet's atmosphere where ioni-zation takes place is usually referred to as theionosphere.One property of the ionosphere is that it refractsand reflects radio waves. This ability dep ends onthe de nsity of its electrons and the frequency of th eradio signals. As frequencies rise, increasing elec-tron density is required.The magnetometer, plasma detector, and trappedradiation detector of Mariner V were designed toreport on the environments of Venus and of inter-planeta ry space. The absence of a region of higherradiation around Venus appears consistent with th eapparent lack of a Venusian magnetic field. Scien-tists believe that a radiation belt like the Van AllenRadiation Region around earth is a creation of aplanet's magnetic field which captures chargedatomic particles as they speed near the planet.

A t the tim e when Ma riner V was taking a closelook at Venus, Venus was approximately 49,-563,200 miles from earth.

Mariner V was also equipped with a newly de-signed data automation system t o facilitate prepara-t ion of scientific information it acquires for trans-mittal to earth. To get this information to earth, i tshigh-gain antenna focussed its radio energy into anarrow beam to direct maximum radio signalstrength to receivers on earth. Mariner V also hasa low gain omni-antenna . The omni-antenna radiatesa broader beam tha n the high-gain antenna. Al-though the signal received from the omni-antennais w eaker, it enables trackers on earth to maintaincontact with the spacecraft durin g periods when thehigh-gain antenna is not poi ntin g toward earth; fo rexample, during a mid-course maneuver.

The 210-foot diameter antenna atthe Goldstone, California, stationof NASA's Deep Space Network.

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TRACKING AND DATA ACQUISITIONFrom launch un til spacecraft separation from thelaunch vehicle (see Journey to Venus, below),Mariner V was tracked by the facilit ies of the AirForce Eastern Test Range and stations of NASAsManned Space Flight Network and Deep Space Net-work (DSN). Afterwards, contact with the spacecraft

was maintained by NASAs DSN stations in Cali-fornia, Spain, Australia, and the Republic of SouthAfrica .The DSN is a network fac ility of the NASA Officeof Tracking and Data Acquisition under the systemsmanagement and technical direction of the Jet Pro-puls ion Laboratory. The DSN supp orts NASA un -manned lunar, interplanetary, and planetary mis-sions. Among such missions, in addition t o M ariner,have been Pioneers, which are exploring interplan-etary space, and the Ranger, Lun ar Orb iter, an dAtlas-Agena stands ready to launch Mariner V.

10 Vehicle dimensions on launch pad.


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Surveyor spacecraft, w hich have revolutionized m an-kind's knowledge of the moon.

Mariner V began its lonely and magnif icent jo ur-ney to Venus aboa rd a two-stage Atlas-Agena launchvehicle rocketed from Cape Kennedy, Florida, onJune 14, 1967. After the Atlas had ceased fir ing,the shroud, which protected M ariner from the buffet-in g of the atmosphere at lower altitudes, separated,followed seconds later by falling away of the first-stage Atlas. The Agena then p ropelled itself andMariner into an orbit about 115 miles above earthand shut off its engine.This inter im trajectory of Mar iner V is known asa parking orbit. The combined cra ft was continuedin this orbit unt i l reaching the best point for alaunch towa rd Venus. Then, the Agena ig nited againand accelerated the combined vehicle from earth-orbital speed of about 17,500 mph to more than25,000 mph. The craft was so aimed that it wouldtravel along a solar orbit that would enable it andVenus to be near each other o n October 19.Mariner V and the Agena were then separated,and Agena maneuvered so that it would neither hit

Venus nor interfere with Mariner. Mariner unfoldedits solar panels and oriented itself toward the sun.About 17 hours later, it also locked on Canopus,brightest star over earth's southern hemisphere.This or ientat ion permitted the po int ing of the highgain antenna toward earth.Mariner V was originally launched on a fligh t pathwell away from Venus to insure that impact wouldnot occur. Review of trac king data indicated tha tif Mariner continued on this trajectory, it wouldmiss Venus by about 42 ,00 0 m iles. On June 19, th eSpace Flight Operations Center ordered a mid-course maneuver which included precise position-ing and f ir ing of the craft 's rocket motor to br ing thecraft within approximately 2,500 miles of Venus.(This was but one of 62 commands that Mariner Vobeyed dur ing i ts 217 -mil l ion m ile curving journeyto Venus. In thi s period of about four months, italso returned to earth data on interplanetary weatherdur ing a period of r ising solar activity.)Mariner V was now a planetoid in solar orbit. Be.cause it was launched backward with respect toearth, its speed relative to the sun was about 6 0,00 0mph as compared to the earth's speed of 66,000mph and Venus' 78,000 mph.

The path of Mariner V f rom earth to Venus, 1967.


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. '. Marinei's'speed s. oo slow to stay in the sameorbit as earth, and it began to fal l toward the sun.The combination of the sun's inward pull andMariner's kinetic energy that would keep it movingstraight ahead produced an orbit that intersectedthe orb it of Venus. As M ariner curved toward thesun, it accelerated, overtook and passed earth, andgradually caught u p with Venus.By October 11, Mariner V was 1.4 mill ion milesfrom Venus and approaching the planet at a speedof 6,900 mph. Pulled by the gravity of Venus,Mariner V continued to accelerate. On October 19,1967, M ariner swept by Venus at a speed of 19,157mph relative to the planet.Marine r's radio signals were occulted-or blackedout-for a period of 20 minutes 5 1 seconds asMariner V went behind the planet relative to earth.The pull of Venus caused the spacecraft's orbitto curve even more toward the sun, bringing it, onJanuary 4, 1968 , as near as about 5 4 m illion miles.Long before its closest approach to the sun,

Mariner had been ordered to return its informationon Venus. It had spent two hours in Venus' vicin ityand recorded a million bit s of information. These itreturned to earth at a rate of 8% bits per secondover a period of 34 hours. The Space Flight Opera-tions Facility completed the first playback of dataon October 21, 1967. Although q uality of data wasexcellent, with only four errors in the million bitstransmittsd, the recording was played a second timeon October 23, 196 7 as insurance. In November1967, a combination of distance and antenoa-

pointing direction caused termination of communica-tion w ith M ariner V.MANAGEMENT

The Mariner program is managed by the NASAHeadquarters Office of Space Science and Applica-tions. Project managem ent as well as responsibilityfor the spacecraft, mission operations, and trackingand data acquisition is handled by the Jet Propul-sion Laboratory, Pasadena, California. The labora-tory is managed for NASA under contra3 by theCalifornia Institute of Technology.

On December 20, 1967, m ore than three yearsafter launch, the Mariner IV experiment pro-gram was officially closed. The 575-poun dspacecraft, launched November 28, 1964,which took the w orld's first close-range photo-graphs of Mars on July 15, 1965, is the long-est working interplanetary spacecraft. Duringits operating lifetime, the craft covered over11/2 billio n miles of space.Mariner IV l iterally ran out of gas-the nitro -gen gas used to keep its solar panels pointedto the sun for power and its antenna pointedto earth for communication. When its gastanks were empty, it was sp in stabilized in thehope of extending its usefulness. However, itwas not sufficiently stable to keep adequatesun orientation and its radio signal becametoo weak for reception on earth.

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