nasa facts mariner

8/7/2019 NASA Facts Mariner

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Page 1NASA FACTS (0-62)An Educational Services Publication of the

National Aeronautics and Space Administration 1/MARINER N 6 ~ / ) Y 0 5 : S l ( O r ; ' {

Mariner in space (artist' s conception) .Ever since man first viewed Venus through a

he has conjectured about the secretsits perpetual cloud layers. With th eof a Mariner spacecraft on August 27,man took a great step forward toward

the earth ' s sister planet and peranswering a fundamental scientific ques

i on: Does l ife ex i st elsewhere than on earth?Earth contact with Mariner as it passes in the vicinity

of Venus will set a new record in long-dis tance communication, 36 million miles. The current record is 22.5million miles established on June 26, 1960, with NASA'sPioneer V space probe. Pioneer V is still in solar orbit.

A successful Mariner f l ight will pass Venus atdistance of about 10,000 miles, giving man-

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kind the first nearby observation of the mysterious planet. During the fly-by, Mari ner ' s instruments will scrutinize Venus fo r signs of water'vapor, oxygen, and other atmospheric constitue nts and attempt to ascertain the planet ' s surface temperature . It wil l also gather informati on on magnetic f ields, radiation, and cosmicdust in th e Venus space environment, and ininterplanetary space between the earth andVenus. Moreover, Mariner wil l test basic elements of space technology required fo r advancedinterplanetary missions of the future.

The information expected from Mariner cancontr ibute signif icantly not onl y to scientificknowledge but also to planning fo r the day whenman himself journeys to other planets.

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Venus-Ocean or Dust Bowl?

VENUS-OCEAN OR DUST BOWL?

Although Venus is the earth's closest planetaryneighbor, relatively little is known about it .Scientists agree that the planet's diameter isabout 7,800 miles . This makes it , in size, almostthe twi n of the earth, whi ch has a 7,926- milediameter. Also known is that Venus revolvesaround the sun every 225 days; its averagedistance from the sun is 67.2 million miles; an dthe planet's mass - t h e a mount of matter composing i t - and gravitat ional f ield are similarto those of the earth.

Beyond these facts, information is fragmentary. This has led to divergent views on thecharacter of the Venusian landscape. Imaginedcondit ions range from a planet inundated bywater to one that is dry and hot a nd whoselower atmosphere is laden with wind-drivendust because there is no rain to wc;:Jsh it down.

Our knowledge of Venus has been dependent on such techniques as analysis of radarechoes and sunlight reflection over a distance ofmore than 26 mill ion miles. Scientists seriouslydebate the results of these ex peri ments.

Microwave scanning of the planet indicates anear-surface temperature of about 615 degreesFahrenheit. If this is true, then l ife such as thaton earth could not survive on Venus. However,

since these temperatures were taken from sucha great distance, there is disagreement as towhether they are located on the surface or athigher altitudes. Infrared measurements indicate temperatures of 38 degrees below zeroFahrenheit somewhere in th e atmosphere.Spectographic observations , through whichmatter is identif ied by its absorption and emis-sion of light, suggest that Venus' atmosphere iscomposed principal ly of carbon dioxide andnitrogen and contains negligible quantit ies offree oxygen and water vapor. This may indicate an absence of vegetation, at least of thetypes prevail ing on earth. However, there isdissent as to how much water vapor and freeoxygen the atmosphere contains.Among puzzling visual features of Venus arethe l ight and dark markings of its cloud mantle.There is speculat ion that these may be holesin the seemingly solid cloud blanket.

NASA launched Mariner during the Venus " launchwindow," a time interval when the positions of the earthan d Venus are favorable to flight between th e tw oplonets. This period occurs once every 19 months. Thenext is du e in 1964.

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FACTS (0-62) Page 3OMNI ANTENNA

MAGNETOMETER SENSOR

RADIOMETER REFERENCE HORNS

RADIOMETER

TEMPERATURE CONTROL SHiElDSOLAR PLASMA DETECTOR

TEMPERATURE CONTROL LOUVERS

COMMAND ANTENNA

HIGH GAIN ANTENNA

SECONDARY SUN SENSORCOSMIC DUST DETECTOR

LONG RANGE EARTH SENSOR

MARINER 1 SPACECRAFTMariner spacecraft with pr incipal instrumentation indicated .

SCIENTIFIC EXPERIMENTSMariner's scientific experi ments, designed to

information on Venus and on interplanespace between the earth and Venus, are

the direction of NASA ' s Je t PropulsionPasadena, Calif. In the followingorganizations collaborating with

in a particular Mariner experiment arein parentheses after the experiment

1. MICROWAVE RADIOMETER-to provideon the surface temperature of Venus

report the existence of water vapor inabove a minimal concentration.

e experiment will also attempt to determinethe high temperature readings received

Venus are due to a dense ionosphere,

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thereby testing a theory that a Venusian ionosphere, thousands of ti mes denser than earth 's,gives the impression that the planet is hot.(Harvard University, Cambridge, Mass.; Massachusetts Institute of Technology, Cambridge; andArmy Ordnance Missile Command, Huntsville,Ala.)

2. INFRARED RADIOMETER-to be alignedwith the microwave radiometer thereby providin g composite measurements relative to thetemperatures and atmosphere of Venus. Datafrom the infrared radiometer will also help determine whether the l ight and dark markings inVenus' clouds are breaks in the cover and, if so,how much of the planet's heat escapes from them .(University of California, Berkeley, Calif.)


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Man has called Venus his morning and evening "star."Atfer the su n and moon, Venus is the most brilliant object in hi s sky. This is because of it s proximity to sunand earth and it s reflective cloud layer .

3. MAGNETOMETER-to measure strengthand direction of interplanetary and Venusianmagnetic fields. Existence of a Venus magneticfield would suggest a surrounding radiationregion simi lar to earth's and such events asauroras and magnetic storms on Venus. Awidely accepted theory is that a planet's magnetic field originates from fluid motion in its in terior . If this is true, then the existence of aVenusian magnetic field would indicate that theplanet has a molten core. Mariner will correlate its measurements of interplanetary magnetic fields with measurements near earth andwith solar events to increase u'nderstanding oftheir relationships. In addition to its scientificvalue, knowledge of magnetic fields can contribute to design of communication systems fo rl inking spacecraft and earth over interplanetarydistance .

4. IONIZATION CHAMBER AND GEIGERMUELLER TUBES- to measure the number andintens ities of energetic particles in interplanetaryspace and near Venus. Representing much ofthe high-energy radiation in space, the particlesare primari ly cosmic rays which are made up ofprotons, alpha particles, nuclei of atoms heavierthan hydrogen and helium, and electrons, another constituent of the atom. This experimentis vital to planning the safety of personnel oninterplanetary fl ights. Moreover, a significantadvance will have been made when th e compi icated interrelationship of these particles witheach other and with magnetic fields is ful lyunderstood. For example, a decrease in thequantity and intensities of cosmic rays detectedby Mariner as it moves closer to the sun wouldindicate that the sun's magnetic field is deflectin g from the solar system cosmic rays originating in the interstellar space. (CaliforniaInstitute of Technology, Los Angeles, Calif.;State University of Iowa, Iowa City, Iowa.)

NASA FACTS (0-62)5. SOLAR PLASMA DETECTOR - to measure

the concentration, flow, and intensities ofcharged particles (chiefly protons of the hydrogen atom) that continually stream from the sun.Relatively l itt le is known about this steady outrushing of hot gas which is termed both thesolar plasma and the solar wind, but its existence is widely accepted. This ex peri mentwill be correlated with magnetometer data toincrease knowledge about the interaction of thesolar wind with magnetic fields th roughout thesolar system.

Mankind's first Venus probe, launched by the SovietUnion on February 12, 1961, provided no scientific in -formation because it s radios went dead. Soviet trackerssaid the probe passed within 62,000 miles of Venus .Three other Soviet Venus probes were reported to havefailed to leave their parking orbits .

6. COSMIC DUST DETECTOR-to measurethe rate of f low, velocit ies, and direct ion ofmicroscopic dust particles in interplanetaryspace and near Venus. Satellites and soundingrockets are studyi ng cos mic dust near earth;Mariner wil l be the first to study them beyondearth's space environment. Scientific interestin cosmic dust is concerned with their o r i g i n -whether they are leftovers of a great cloud ofdust and gas from which the solar system mayhave been formed or whether they originatedoutside the solar system. These clues couldhelp solve the riddle of the solar system ' s birthand evolution. Data from this experimentwould also contribute to determining the potenti al danger to manned spacecraft of these microscopic dust particles and to des ign of spacecraftstructures that can cope with the danger.

On May 10 , 1961, NASA's giant rad io telescope facilit y a t Goldstone, Calif. completed a two-month experiment during which radar signals were bounced of f Venus.Data ind ica ted tha t Venus ro ta ted abou t once every22S days , which is the length of the Venusian year .This means t ha t Venus a lways keeps the s a m e sidefacing the sun.


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Technicians check Mariner spacecraft.

SPACECRAFT DESCRIPTIONAt launch, Mariner is 5 feet in diameter at itsand 9 feet 1 1 inches high; cruise position

6.5 feet across and 11 feet 11 inches high.e spacecraft weights 446 pounds. The scien-

experiments weigh 40 pounds; and structure,supply, propulsion, communication, elec

and other support equipment make upe remainder.In space, Mariner must keep its solar cells foc-

the sun to create electric power for its instruits high gain antenna pointedearth fo r communication. This is accom

through a complex system of sun andsensors, gyroscopes, and nitrogen gas jets,keep Mariner in proper attitude.

The solar pane ls - 27 square feet of surface9,800 solar cel ls-conver t sunlight to

They can furnish a minimum of 148d a maximum of 222 watts. Power no t used

y the instruments is stored by a rechargeablezinc storage battery with a 1,000-wattcapacity. The battery goes into action dur-

Page 5i ng peak power demands upon the spacecraftand during correction of Mariner's path in spacewhen the solar panels temporar i ly are turnedfrom the sun. It also supplies electricity fromlaunch of the probe to deployment of solar panels.

Other major equipment on Mariner is an omnia ntenna which is employed fo r communicationwhen the high gain antenna is no t f ixed on earth,other radio equipment, temperature controls, a50-pound-thrust mid-course correct ion rocketsystem, and associated electronics .

Atlas-Agena B starts Mariner on journey to Venus .

FROM EARTH TO VENUSImagine attempting to hit a fast-flying claypigeon from a spinning merry-go-round, using a

rifle fastened to the merry-go-round. An evenmore difficult situation confronted the mathematicians who had to figure out how to reach Venusfrom the earth.

In aiming Mariner, they had to consider, amongother things: the speeds of earth and Venusaround the sun; the spin of the earth; the movement of the sun; the pressure of sunlight; and thegravitational forces of the earth, sun, Venus, andJupiter.

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Mariner trajectory correction upon radio command from earth. High-gain antenna is moved up to avoid blast frommid-course correction rockets; rockets are fired; high-gain antenna realigned with earth and solar panels again lockedon sun.

planetoids: lunik I, Pioneers IV and V,Soviet Venus probe whose radio died before i t

useful information, and Ranger III.

MID-COURSE MANEUVEROn September 4, Mariner executed perfectly

commands fo r a complex midmaneuver, a scheduled event in the Mar

ner mIssIon . The maneuver altered Mariner'sfrom the initial path which would have

the craft no closer than approximatelymiles from Venus to one which passes

10,000 miles of the planet. The correc-carried out when Mariner was about 1.5

miles from earth, represents the greatest

The maneuver comprised a sequence of threeactions: (1 ) lengthwise roll of about 9.3 degrees;(2) pitch of about 139.9 degrees, turning Mariner almost completely around; (3 ) and rocketfir ing of about 29 seconds. Because the craftha d swung around, its rocket decelerated itslightly relative to the earth.

: ~ : n u ~ ; e ~ t wh;ch man has mad;fied a space-

Before the mid-course maneuver could be ac-complished, the craft had to be stabilized orpositioned on tw o axes. The first, achieved bylocking the solar panels on the sun, occurredshortly after launch. The second, accomplishedby aiming the high-gain antenna at the earth,was scheduled fo r about seven days after launchwhen Mariner was more than a million milesaway . This time lapse was necessary becausethe earth sensor employed to align the antennais so sensitive it would not have operated properlyi f used earlier.


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Advanced Mariner, designed to fly by either Venus or Mars and rocket an instrumentedpackage to the planet's surface .

ADVANCED MARINERNASA is developing a series of Advanced

Mariners fo r launches to the vicinities of Marsand Venus beginning in 1964. These craft willbe three times heavier, carry more equipment,and be able to make more refined observationsthan the Mariner now on its way to Venus.

While flying by Mars or Venus, Advanced Mar-

NASA FACTS format is designed fo r bulletin-board displayuncut, or fo r 8 x 10)1, looseleaf notebook insertion whencut along dotted lines and folded along solid lines. Fo rnotebook ring insertion, punch at solid dots in the margins.

mer scans the planet with television cameras andradiometers, among other apparatu s. It rocketsan instrument package to the planetary surfaceto search fo r signs of l ife.

Advanced Mariner will be launched by Atlas -Centaur, now under development.

NASA FACTS will be mailed only to addressees who requestit from : Office of Educational Programs and Services, NASA,400 Maryland Avenue, S. W., Washington 2S , D.C.

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