NASA Facts Mariner II Reports

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I N63 1656 3 /5-- ' ) PageNASA FACTS~ , . ~ ' " An Educational Services Publication of the &du /

(NF B-4-63) National Aeronautics and Space AdministrationMARINER II REPORTS

Mariner II scans Venus (artist's cancept-not in scale).On December 14, 1962, NASA's Mariner II

spacecraft flew past Venus at a distance of 21 ,648miles, giving man his first relatively close-up observation of earth's mysterious planetary neighbor. This Venus fly-by climaxed an epic spaceflight experiment that has significantly advancedthe world's knowledge about Venus and aboutinterplanetary space and contributed to planningfo r man's eventual journeys to the moon and toother planets.

After passing Venus, the 449-pound Marinercontinued for some additional time to transmitdata about interplanetary space, adding to theabundance of information it had sent while en-

route to the planet. On January 3, 1963, wheradio contact was lost, Mariner was nearly smillion miles beyond Venus and almost 54 milion miles from earth. Since launch on Augus27, 1962, Mariner sent about 90 million bits (frombinary digit, meaning a unit of information) tearth.

This issue of NASA FACTS presents highlighof the new scientific knowledge gained througanalyses of the voluminous quantities of data received from Mariner and from earth-based experments carried ou t in conjunction with the spacecraft's activities.


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The Mariner observations, together with radaran d optical studies made from earth, have relegated to discard any romantic conception thatmay have persisted of Venus as a place withearth-like qualities. Mariner found that the temperature of Venus ma y be as ho t as 800 Fahrenheit. This temperature is hot enough to melt leadand precludes the possibility of life like that onearth.

Mariner detected no openings in the densecloud mass that starts about 45 miles above theVenusian surface and reaches an altitude as highas 60 miles. The spacecraft reported that cloudtemperatures were 200 F. at the base; - 30(3 0 beiow zero) F. at the middle level; and- 60 F. at the upper level. There is speculation that the clouds are composed of condensedhydrocarbons like those found in the smog ofsome of our world's cities. Mariner detected nocarbon dioxide gas above the Venus clouds, in-

NASA FACTS (NF B-4-63)dicating a negligible quantity, i f any, at thisaltitude.

Mariner 's information on temperature, carbondioxide, and the unbroken nature of the cloudsis based on data from the spacecraft's infraredand microwave radiometers. The radiometersmade three scans of the planet: one across thenight side; one across the terminator, or line, separating the dark from the sunlit side; and oneacross the sunlit side. The scans were carriedout as Mariner flew closest to Venus on December 14 , 1962, and lasted from 1:59 p.m. EST to2:34 p.m. EST.

Radiometers operate by measuring energy inthe form of infrared rays (heat) and of radiomicrowaves. The sensitive radiometers can pickup these emissions, even from great distances;and scientists can convert them to indicate temperature as well as certain other features.

Earth-based microwave scans of Venus, madebefore the Mariner experiment, suggested a sur-

Venus surface an cloud temperatures as ind icated by Mar iner da ta (a rti st' s concept ).


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NASA FACTS (NF B-4-63)face temperature of 600 0 F. Because of the dis-tance at which these measurements were made,scientists debated whether they showed temperature at the surface or were reflections from ion-ized particles in an ionosphere many times asdense as earth's. (Earth's ionosphere is formedby break-up of neutral atmospheric moleculesinto negatively charged electrons and positivelycharged ions.) While flying close to Venus,Mariner made detailed observations that ruledou t the postulated super-ionosphere.

Analysis of spectroscopic data obtained bymeans of earth-based telescopic observations in-dicates that carbon dioxide is a constituent of theVenusian atmosphere. These results coupled withother assumptions lead to the conclusion that theVenusian atmosphere is 10 to 30 times denserthan earth's. Presumably, these atmospheric con-ditions contribute to the planet's high temperatureby creating a greenhouse effect in which the sun's

Radiometer scanning of Vt:nus consisted of 18 dota readings covering the night and da y sides of the planet andthe terminator which separates them (artist's concept).

Pagheat reaches the planet's surface but is hinderin rising.

Radar studies, carried out by NASA's Gostone, California, radar station, provide evidenthat Venus rotates once each 225 earth dawhile orbiting the sun in the same time perioThus, each day or night on Venus lasts abo112112 earth days, or half the planet's rotationperiod . Presumably, the Venusian clouds screou t most of the sunlight that would otherwiilluminate the day side, keeping that hemisphein twilight.

The long Venusian day and night wouldexpected to result in the side facing the sun bcoming quite hot and the other becoming colMariner, however, did not find any appreciabdifference in temperature. This indicates that tdense atmosphere must be circulating vast quatities of heat from the da y to the night side. Sua massive heat transfer could generate searinwinds that lash the planet's scorching surface.

Radar reflections from the Venusian surface athose characteristically made by sand or dirt-limaterial. If sand covers the ground, the higwinds could create sand storms of tremendoproportions.

. Radar studies also suggest that Venus rotatbackwards with respect to earth and to all othplanets of the solar system except Uranus, anperhaps Pluto. (Pluto's direction of rotationunknown.) Thus, on Venus, the sun rises in thwest and sets in the east.

Mariner's instruments also detected a mysteous spot in the clouds that was about 20 0 F. coolthan the surrounding clouds. Scientists attributhis phenomenon either to higher or more opaquclouds or to a hidden surface feature. In thconnection, earth-based radar studies of Venuhave indicated existence of a prominent surfacfeature. However, its relationship to the cospot in the clouds is uncertain .


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Mariner II pass of Venus as would be seen from a point between Venus an d the sun (artist's concept) .

NO VENUS MAGNETIC FIELD ORRADIATION BELT DETECTED

If Venus has a magnetic field, it does no t ex-tend to the altitudes and locations at which Mariner passed the planet. While flying near Venus,Mariner detected no increase in magnetic forcesover those observed-in interplanetary space. Thespacecraft's instruments were set to pick up magnetic fluctuations as low as five gamma. (Agamma is about YJo ,ooo of the earth's magneticforce at the equator.)

The absence of a magnetic field accords withthe fact that Mariner reported no increase in ra-diation as it soared near Venus. A comparablespacecraft approaching earth would have re-corded the high-intensity radiation of earth's VanAllen Radiation Region. This region is createdby the earth's magnetic field that captures manyenergetic particles (particles of atoms such aselectrons and protons).

There is a possibility that the solar wind (seebelow) is pushing Venus' magnetic field close tothe surface on the sunlit side where Marinerpassed. Scientific satellites have provided evi-dence that the solar wind compresses earth's magnetic field to a 40,000-mile altitude on the sunnyside and that i t stretches to at least 80,000 mileson the night side.

SOLAR WIND IN INTERPLANETARY SPACEAnalysis of Mariner II data on interplanetary

space produced evidence that solar wind, alsocalled the solar plasma, is a predominant featureof interplanetary space. The wind, consistingprincipally of electrically charged protons andelectrons (atomic particles, mostly from hydrogenatoms), was shown as rushing outward constantlyfrom the turbulent surface of the sun.


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NASA FACTS (NF 8-4-63)Indicated speeds were from 250 to 450 miles

per second, and temperature was about a milliondegrees Fahrenheit. Although called a wind, thisstream of hot electrified gas is more comparableto a rocket's blast than to an y other thing knownhere on earth. The matter constituting the windis scant, however, consisting of 10 to 20 particlesper cubic inch.

It is theorized that the solar wind pulls awayparts of the sun's magnetic field and distributesthem throughout the solar system. These mag-netic fields deflect from the solar system manylower-energy cosmic rays (see below) streakingfrom interstellar space.

Sudden solar eruptions such as flares appear

Pageto increase temporarily the density, velocity, antemperature of the solar wind. This is said tenable it to carry more magnetic fields ou t intspace, with the result that more cosmic rays ardeflected.

It has been observed that a decrease in cosmradiation around earth an d disturbances in thearth's magnetic field often follow solar eruptionsIt is believed that the augmented solar wincaused by the eruptions produces these effects bsending strengthened magnetic fields into spacand by interacting with the earth's magnetic fieldDisturbances in the earth's magnetic field are associated with radio interference, or black-out, anwith aurorae such as the Northern and SoutherLights in the polar regions.

Principal instrumentation of Ma r i ner II. The radiometers were employed du ring the Venus pass. The other experimentswere used du ri ng most of the f l ight to acquire information on both Venus and the interplanetary env ironment .

MAGNETOM ETER

RADIOMETER REFERENCE HORNS

RADIOMETER

TEMPERATURE CONTROL SH IHDSOLAR PLASMA DETECTOR

TEMPERATURE CONTROL LOUVERS

COMMAND ANTENNA

HIGH GAIN ANTENNA

OMNI ANTENNA

SECONDARY SUN SENSORCOSMIC DUST DETECTOR

PRIMARY SUN SENSOR

LONG RANGE EARTH SENSOR


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Page 6MAGNETIC FIELDS FOUND

EVERYWHERE IN SPACEData from Mar iners magnetometer, an instru-

ment that detects and gauges the force and direc-tion o f magnetic fields, were remarkab le in theirgreat number and continuity. Mariner reportedthat magnetic fields were nearly always present asit raced through interplanetary space.

Scientists believe that the interp laneta ry mag-netic fields are parts o f the suns magnetic fieldthat the solar wind has distributed throughoutspace. Typically, the inte rplane tary magneticfields were found to be weak compared to earths.Generally, they ranged from five io ten ~ammrj ,with precipitous increases to 25 or more gammafollowing sudden solar disturbances.

NASA FACTS (NFB-4-63)craft. This i s because, in this region at least,solar wind particles outnumber cosmic r ay parti-cles by about a billion to one.

Mariner reported a scarcity of cosmic ray pro-tons below the level of 800 million electron volts.This scarcity i s attributed to interplanetary mag-netic fields that permeate the solar system anddeflect lower-energy cosmic rays.

If a space traveler had journeyed to Venus atthe time of the Mariner flight, he would have ab-sorbed a total of 3 roentgens of radiation. Thisdosage i s well within the tolerable limits for manduring a four-month period.

0

COSMIC RADIATION ININTERPLANETARY SPACEDuring its entire flight, Mariner reported about

the same amount and intensity of cosmic radia-tion. This constancy i s considered a significantadd ition to scientific knowledge; but its implica-tions will have to be clarified by additionalexperiments.

Cosmic rays are made up of protons (nuclei ofhydrog en atoms), alph a particles (nuclei of he-lium atoms), nuclei of atoms heavier thanhydrogen and helium, and electrons. They havevelocities almost a s great as the speed of light(about 186,000 miles per second) and energiesin the millions, billions, an d trillions o f electronvolts. (The electron vo lt i s a scientific measure-ment unit for energies of atomic particles.)

Cosmic rays are the most penetrating kind ofradiation, theoretically being able to pass throughlead walls as thick as a thousand feet. Mostcosmic rays come from outside of the solar sys-tem, usually from within our vast Milky Waygalaxy but sometimes from other galaxies. Ourown sun produces some cosmic rays, particularlyduring solar flares and other disturbances.

Both cosmic rays and the matter in the solarwind are atomic particles. However, solar windparticles have comparatively low energies, in thehundreds and thousands of electron volts. De-spite the great disparity in individual energies,the aggregate energy of the solar wind is fargreater than that of all cosmic rays in the regionof the solar system studied b y scientific space-

MlCROMETEOROiD iMPACTS FEWIn 17 00 hours of recorded data, Mariner

registered only two impacts with micrometeor-oids-tiny bits o f matter in space. Comparisonof these data with information from earth satel-lites would indicate that micrometeoroids are10,000 times more abundant near earth thanalong Mariners trajectory i n interplanetary space.Moreover, no concentration of micrometeoroidswas detected around Venus such as occurs around

0earth.Information about micrometeoroids i s of prac-tical importance in design of spacecraft a nd i sbelieved essential to study of the o rigin and evo-lution of the solar system.TRACKING DATA ADDING TO KNOWLEDGE

The precise tracking da ta acquired through theMariner II experiment have provided basic info r-mation that i s contributing to refinement of im-por tant measurements. Among them: the massof the moon; the mass of Venus; the Astronomi-cal Unit (AU) which i s the mean distance fromearth to sun and the yardstick for measuringdistance in the solar system; and the exact loca-tions o f spacecraft tracking stations on earth.These figures not only will increase scientificknowledge but also are vital to planning ofmanned lunar and interplanetary voyages.

MARINER ESTABLISHED NEWCOMMUNICAT10NS REC0RD

0Contact was maintained with Mariner II untilit was 53.9 million miles from earth. This shat-tered the previous long-distance communications

Page 6MAGNETIC FIELDS FOUND

EVERYWHERE IN SPACEData from Mariner's magnetometer, an instru

ment that detects and gauges the force and direction of magnetic fields, were remarkable in theirgreat number and continuity. Mariner reportedthat magnetic fields were nearly always present asit raced through interplanetary space.

Scientists believe that the interplanetary magnetic fields are parts of the sun's magnetic fieldthat the solar wind has distributed throughoutspace. Typically, the interplanetary magneticfields were found to be weak compared to earth's.Generally , they ranged from five to ten gamma,with precipitous increases to 25 or more gammafollowing sudden solar disturbances.

COSMIC RADIATION ININTERPLANETARY SPACEDuring its entire flight, Mariner reported about

the same amount and intensity of cosmic radiation. This constancy is considered a significantaddition to scientific knowledge; but its implications will have to be clarified by additionalexperiments.

Cosmic rays are made up of protons (nuclei ofhydrogen atoms), alpha particles (nuclei of helium atoms), nuclei of atoms heavier thanhydrogen and helium, an d electrons. They havevelocities almost as great as the speed of l ight(about 186,000 miles per second) and energiesin the millions, billions, and trillions of electronvolts. (The electron volt is a scientific measurement unit for energies of atomic particles.)

Cosmic rays are the most penetrating kind ofradiation, theoretically being able to pass throughlead walls as thick as a thousand feet. Mostcosmic rays come from outside of the solar sys-tem, usually from within our vast Milky Waygalaxy bu t sometimes from other galaxies. Ourown sun produces some cosmic rays, particularlyduring solar flares and other disturbances.

Both cosmic rays and the matter in the solarwind are atomic particles. However, solar windparticles have comparatively low energies, in thehundreds and thousands of electron volts. De-spite the great disparity in individual energies,the aggregate energy of the solar wind is fa rgreater than that of al l cosmic rays in the regionof the solar system studied by scientific space-

---------------------------------------NASA FACTS (NF 8-4-63)

craft. This is because, in this region at least,solar wind particles outnumber cosmic ray parti-cles by about a billion to one.

Mariner reported a scarcity of cosmic ray protons below the level of 800 million electron volts.This scarcity is attributed to interplanetary magnetic tields that permeate the solar system anddeflect lower-energy cosmic rays.

If a space traveler had journeyed to Venus atthe time of the Mariner flight, he would have absorbed a total of 3 roentgens of radiation. Thisdosage is well within the tolerable limits fo r manduring a four-month period.

MICROMETEOROID iMPACTS FEWIn 1700 hours of recorded data, Mariner

registered only two impacts with micro meteoroids-tiny bits of matter in space. Comparisonof these data with information from earth satellites would indicate that micro meteoroids are10,000 times more abundant near earth thanalong Mariner's trajectory in interplanetary space.Moreover, no concentration of micrometeoroidswas detected around Venus such as occurs aroundearth.

Information about micrometeoroids is of practical importance in design of spacecraft and isbelieved essential to study of the origin and evo-lution of the solar system.TRACKING DATA ADDING TO KNOWLEDGE

The precise tracking data acquired through theMariner II experiment have provided basic information that is contributing to refinement of important measurements. Among them: the massof the moon; the mass of Venus; the Astronomical Unit (AU) which is the mean distance fromearth to sun and the yardstick for measuringdistance in the solar system; and the exact locations of spacecraft tracking stations on earth.These figures not only will increase scientificknowledge but also are vital to planning ofmanned lunar and interplanetary voyages.

MARINER ESTABLISHED NEWCOMMUNICATIONS RECORDContact was maintained with Mariner II unti

it was 53.9 million miles from earth. This shat-tered the previous long-distance communications


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The 85-foot diameter antenna at Woomera, Australia, one of three that tracked and communicated with Mariner II . Othersare located near Johannesburg, Republic of South Africa, and at Goldstone, California .

record of 22.5 million miles set with NASA'sPioneer V spacecraft on June 26, 1960.

The Mariner II experiment has demonstratedthat reliable communications can be kept up overinterplanetary distances. Mariner's transmitter,incidentally, had an output of about three watts,a power level lower than the standard "nite lite"(7V2 watts).

WHITHER MARINER II?The loss of radio contact with Mariner on Jan

uary 3, 1963, raises the question of Mariner'sfate. Mariner II is no w a planetoid sailing in anever-ending orbit around the sun (see i l lustra-

tion). It joins such other man-made planetoidsas Lunik I; Pioneers IV and V; a Soviet Venusprobe whose radio died before it supplied useful

ENCOUNT12/ 14/ 6

The solar orbits of Venus, Mariner, and earth (artist'sconcept).


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information; a Soviet Mars spacecraft; and Rang-ers III and V, lunar spacecraft that went into orbitaround the sun . Calculations indicate that thousands of years wil l pass before Mariner againcomes as close to Venus as it did on December14, 1962.

MARINER MARS MISSION NEXTNASA plans to launch a fly-by of Mars in 1964.

The experiment will be aimed at obtaining tele-vision pictures of the planet's surface and gaining information on possible magnetic fields,trapped particle regions, and micrometeoroids.

Plans for a mission to Venus duplicating theMariner II experiment were cancelled becauseof th e success of Mariner II. The next Venusobservation will await development of advancedspacecraft and launch vehicles.

NASA FACTS 0-62 described th e Mariner II spacecraft,it s experiments , and it s planned mission to Venus.

NASA FACTS (NF 8-4-63)

NASA FACTS will be mailed to addressees who request itfrom: Office of Educational Programs and Services, NASA,4 00 Maryland Avenue, S.W., Washington 25, D.C.

MARINER MID-COURSE MANEUVEROn September 4, 1962, ground controllers

commanded Mariner to execute a complex midcourse maneuver that changed its trajectory fromone that would have reached no closer than230,000 miles to Venus to one that passed asclose as 21,648 miles from the planet. At thetime, Mariner was more than a million milesfrom earth and moving at 60,117 miles per hourrelative to the sun. The correction added 51miles per hour to this speed. Such a relativelyminute adjustment to an enormous velocity is considered a tremendous engineering achievement.

The planned increase was 49 miles per hour,and this would have brought Mariner within10,000 miles of Venus. Although initial computations indicated this plan had been fulfi l led,continued tracking showed that the actual velocityincrement was 51 miles per hour. The tw o milesper hour difference, magnified by the great dis-tances in space, more than doubled the planneddistance at which Mariner passed Venus.

One of the designs under consideration for Mariner spacecraft to be used on Mars mission .

U. S. GO VERNMENT PRINTIN G OF f iC E : 1963 OF- 685 530For sale by the Superintendent of Documents , U.S. Go ve rnme nt Printing Office

Washington 25 , D.C.-Price 15 cents per copy

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