space exploration - why and how

8/8/2019 Space Exploration - Why and How

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EP-25SPACE EXPLORATION-WHY AND HOW

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By EDGAR M. CORTRIGHTDeputy Associate Administratorfor Space Science and Applications

N A T I O N A L A E R O N A U T IC S A N D SP AC E A D M I N I S T R A T I O N

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FIGURE 1. WHAT ARE WE EXPLORING?

SPACE EXPLORATION-WHY AND HOW

Edgar M . Cortright was appointed Deputy As-sociale Administrator fo r Space Science and Ap-plications on November I , 1963. In this position,he shares responsibility with Dr. Homer Newell,Associate Administrator for Space Science andApplications, in planning and directing NASAsprograms fo r the unmanned scienti f ic explorationand utilization of space. The se programs includethe lunar and planetary probes, the geophysicaland astronomical satellites and probes, bio-sciences, applications satellites, and the develop-ment and use of light and m ed ium launch vehiclesthrou gh t he A tlas-Centaur class.

By EDGAR M. CORTRIGHTDeputy Associate Administratorfor Space Science and Applications

The material in this booklet is sitbsrantidlly thetex t of an address delivered before the N orwegianGeographical Society on September 27, 1964.


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.Ea ch gen eration faces the perennial crisis of run-ning out of new frontiers to explore. Space explora-tion is the m ost recent of these last fron tiers.The re is nothing esoteric abou t it. It is exploration

in the truest and most roma ntic sense. It requiresall of the classical ingred ients: men , machines, curi-osity, and determination.For those who would worry about last frontiers,the vastness of space is not likely to yield up all itssecrets in the foresee able future-if ever. Th is isobvious when one considers. he awesome setting forspace exploration. (Figure 1 )Within the 11 billion trillion mile range of ourlargest telescopes, there are some trillion galaxiescontain ing several billion stars each. W hat liesbeyond one can only surmise. Th e great spiralgalaxy of And rome da shown h ere is similar to ou rown galaxy, the Milky Way. Ou r sun is but oneof the billions of stars within the Milky W ay. T henearest star to our sun is over 25 trillion miles away.

A major goal of exploration, including earth ex-ploration, has been to understand how our solarsystem was form ed. Since the solar system contain sthe sun, 9 planets, 31 moons, 30,000 asteroids orminor planets, and thousa nds of com ets, we cann othope to reach many of these celestial objects in thenear future. We are thus concentrating on theearth, its moon , Ma rs, Ven us, and the sun. Onlyour orbiting telescopes will peer beyond into thestarry, timeless, endless universe with its awesomelessons in humility.SUMMARY

The question is often asked, Why explore spacewhen much of our earth remains unex plored? Inthis booklet, I hope t o provide som e of the answers.Most of these answers stem from the fact that spaceexploration is intimately related to earth exploration.In reaching out into space and to other worlds, weare providing a unique look at our own.

The main sections of this paper are:S PA CE A R O U N D T H E E AR THATMOSPHERIC CIRCULATION ANDTH E WEA TH ERTH E EA R THT H E M O O N AN D T H E P L A N E T S


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SPACEAROUND

THE EARTH

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Earth exploration has always been limited by timeand distance. Space flight constitutes a gigantic stepforward in overcoming these limitations. Man cannow make direct observations of th e earth and itsenvirons on a global scale in a m atter of hou rs, ifnot minutes.

Som e of the im po rtan t chara cteristics of o ur earthwhich are now being studied with instrumented satel-lites are illustrated in Figure 2. They include theearths shape, its magnetic field, the great radiationbelts, auroras, the ionosphere, and the atmosphere.

Most of these earthly phenomena are stronglyinfluenced by the radiations from the sun. Hen ce,any comprehensive study of the earth and its en-vironment must include a study of the sun.

Let us first examine the earths magnetic field ormagnetosphere, and the trapped radiation beltswithin it . In this figure, a cross section of the beltsis shown as they were envisioned several years ago.Th ese belts consist of electrons and protons spiralingab ou t the earths magnetic lines of force. Some arehighly energetic and can damage both men andequipmen t. The escape and replenishment of thesetrapped particles from the belts is not fullyunderstood.

Figure 3 illustrates our current understanding Ofthe shape of the magnetosphere, in which lie theradiation belts. Th e flight of Marine r I1 to Venusin 1962 proved the hypothesis of a solar wind, thatis, a steady outward streaming of electrons and pro-tons from the sun. These particles are thought toflow around the moon and the earth much likewater around boulders. In the case of the mo on,which has little or n o magnetic field according to

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FIGURE 2

FIGURE 3

Soviet measurements, the surface deflects the flow.With the e arth, how ever, the flow is deflected by t heearths magne tic field. Mo st of the particles dontget much closer than about 37,000 miles on thesunlit side. T he flow distorts the earths magneticfield, causing a wake-like shape on the side of theearth away from the sun. Whe re the fast movingsolar wind (180 to 360 miles/sec) first encountersthe earths field, there appears to be a shock wavemuch like those caused by supersonic aircraft.

One of the satellites with which we are studyingthese phenomena is Explorer XVIII, also called In-terplanetary Monitoring Platform or IMP. Itsapogee is about 1 1 5,800 miles and is high enoughfor the IMP to encounter and detect the moonswake, which we think it has. As the orbit precesses,it sweeps out different portions of the earths mag-netosphere and is giving us a much better pictureof its true shape and nature. Spacecraft designedto orbit the moon will provide similar coverage ofthis body.

What is probably the worlds most advanced satel-lite for investigating the space around the earth isthe Orbiting Geophysical Observatory or OGO,shown in Figure 4. This 1000 pound spacecraft isdesigned to carry over 20 experiments in orbitsranging out to 78,000 miles. It is designed to befully stabilized, using a combination of reactionwheels and gas jets. OGO can thus simultaneouslypoint selected equipment toward and away from theearth, toward and away from the sun, and in thedirection of flight. O n the first flight, the OGOfailed to extend several of its many folding boom s.As an indirect result, too much of its stabilizing gaswas used in the first day, so we were forced to allow

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bthe spacecraft to remain spinning. M ost of th eexpe rime nts are yielding good dat a, howeve?. Sev-eral more OGOs are being built.Another important phenomenon of the spacearoun d the earth is the ionosphere. Figure 5. T heionosphere consists of a layer of ions and free elec-trons in the outer fringes of the earths atmosphere.It is believed, to be generated primarily by the ioniz-

ing effects of solar ultraviolet radiation. We depe ndon the ionosphere to reflect radio signals from onespot on the earths surface to another as shown inthe figure. Because of its changeable nature, theionosphere is not an entirely dependable link in longrange communication, particularly at high latitudes.For this reason, and for purely scientific ones, theionosphere has been the subject of intensive research.Before earth satellites, we were able to measurethe variation of the concentration of electrons withaltitude by means of reflected radio signals from the

groun d. This only works for the lower half of theionosp here in the vicinity of the tran sm itting station.Sounding rockets provided some measurements inthe upper ionosphere but it was impossible to gain

FIGURE 4. ORBIT ING GEOPHYSICAL OBSERVATORY. Gross Weigh t-1,000Ibs Instrum ent Weight-150 Ibs Investigations--20/SpacecraftPower-560 wat ts Stabiliz ation-A ctive 3 Axis Design Life-oneyear Launch Vehic les-Atla s-Age na, TAT-Agena Orbits-highly ellip-tic al inclined orbit, near circular polar orbit plan-first flight-1964.

FIGURE 5

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a full understanding of the ionosphere by these tech-niques. Now earth satellites ar e used in three ways.The Alouette, a Canadian-built and U . S.-launchedsatellite, and the recent Explorer XX, measure theirown reflected radio signals to determine the upperprofile of the ionosphere over the entire world. Th eBritish-built and U . S.-launched Ariel makes directmeasurements like the sounding rocket, but withworld-wide coverage. A new Explorer satellite,soon to be launched, will be monitored by about 150scientists a t 80 stations in 32 countries to determinethe total electron count in their areas and thus estab-lish world-wide variations.Another element of the space around the earthis the uppe r atmosphe re. E ar th satellites are prov-ing to be an invaluable tool in the study of the

earths upper atmosphere above 120 miles wheresounding rockets can only infrequently and locallysample. Fo r example, Figure 6 illustrates the effectof solar radiation on the density of those rarefiedgases. Simply stated, the figure shows how the dragof seven tracked satellites increased immediately fol-lowing the occurrence of several large solar flares.This results from an expansion upward of the radia-tion warmed atmosphere below the satellites.

Tracking of Echo I led M arcel Nicolet of Belgiumto suggest the existence of a layer of helium betweenthe oxygen/nitrogen inner atmosphere and the hy-drogen outer atmosphere. We later confirmed thiswith a special satellite, Explorer XVII which madedirect spectrometric analyses and telemetered theresults to earth.

FEURE 6. S Q U R EFFECTS M1 EARTWS ATMOSPHERE.

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ATMOSPHERICCIRCULATION

A N D WEATHER

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We are all interested in the weather. (Figure 7)It affects our comfort, health, safety, and economicwelfare. But what we think of in very personalterms as a local phenomenon is in reality but onemanifestation of a gigantic pattern of circulating airover the entire globe. Th is global circulation canbe likened to the movement of a huge heat enginepowered by the sun and the rotation of the earth.Th e earth satellite is now providing the meteorol-ogist what he has always wanted, a chance to lookat the weather on a global scale. The sparsely

covered regions of the earth such as the poles, theoceans, and much of the southern hemisphere cannow be completely observed several times each day.Because satellites cannot yet measure pressure, tem-perature, and wind velocities at various altitudesbelow them, they are as yet only additional toolsto help the meteorologist. But instruments arebeing developed to incre ase the utility of the m ete-orological satellite. In add ition, they are beingdeveloped to collect and report measurements fromunattended meteorological stations on the land andsea, and in the air.In the meantime, cloud pictures are providing aglorious representation of the earths atmospherein action. Lets look at a few examples of meteoro-logical photography. This classic montage of cloudphotographs was made from TIROS television pic-tures in May 1960. The coverage stretches fromthe coast of Japan to the Great Lakes of the UnitedStates. In the lower half of the figure is shown thecorresponding conventional weather map of isobarswith highs, lows, and fronts. A n artist has rectifiedthe upper montage and superimposed it upon the

map. Th e correspondence is impressive. Note thecyclonic cloud patterns at the three lows, and thecloud lines along the temperature fronts. To da ywe can prepare such cloud pictures for the entireworld on a daily basis using our new TIROS andNimbus satellites.Nine T IR OS and one N imbus satellites have beenlaunched to date. All were highly successful.They have provided hundreds of thousands of cloudphotographs, detected dozens of hurricanes and ty-phoons, provided thousands of weather alerts and

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FIGURE 9. LIMITATION OF SATELLITE RADARMEASURIWC PR ECIPITATION.F16iE 7. STORMS AND F R O N U FAMILY OF WEATHER SYSTEMS. MOSAIC OF TIROS PHOTOGRAPHS.WEATHER MAP, MAY 20, 1960, WITH TlROS CLOUD DATA.~~~

Instantaneous View.3 hour Integrated (Smperinposed om Tins pictu

FIGURE 8. LIFE CYCLE OF A CYCLONE.

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warnings to all regions of the world, and have beenused operationally by airlines on transoceanic flights.These meteorological satellites have also provideda w ealth of valuable research information which willimprove their effectiveness in years to come. Figure

8 illustrates how TIROS photographs of severalhurricanes in various stages of development can berelated to the theories of Bjerknes and Solberg, twoNorwegian meteorologists. From left to right andtop to bottom, the birth, life, and death phases of ahurrican e are clearly shown. Only by relating cloudphotographs to other measured atmospheric phe-nomena can cloud photography reach its fullpotential.

Because of the direct importance of rainfall onthe comfort and welfare of the people of the world,and its indirect effect on atmospheric circulation,we have been interested in the possibility of measur-ing global rainfall distribution with satellite radar.Figure 9 shows the result of an early expe rimen t.Rainfall over several midwestern states in the UnitedStates, as determined by ground-based radar, hasbeen superimposed on a cloud photograph obtainedwith a TIR OS flying overhead. Th e outlines ofthe states are shown, with Iowa located in the center.The dark spots buried within the cloud patterns inthe left hand picture are areas where i t was rainingat the time of the picture. This then indicates theinstantaneous view of rainfall that satellite radarmight have given. Th e right hand picture shows

FIGURE 10 . METEOROLOGICAL SATELLITES.

the total rainfall pattern over a 3-hour period, whichis much la rger. Clearly , the fast moving satellitecould not have given a true picture of the total rain-fall. Because of conside rations such as this, we arelooking with increased interest at weather satellitesin the synchronous orbit at 36,000 kilometers abovethe equ ator. Such satellites remain overhead andcould watch a storm develop from beginning to end.The evolution of meteorological satellites is illus-trated in Figure 10. The first 8 TIROS satelliteswere spin-stabilized like a gyroscope, and the cam-eras, which pointed along the spin axis, could onlysee the earth during a portion of each orbit. TOovercome this limitation, we learned to turn thespin axis in flight so that the wheel-shaped TIROSappe ars to roll along its orbit. By pointing thecameras out the side and placing the satellite in apolar orbit, world-wide coverage can be obtained.The first such satellite TIROS IX, was launched

January 22, 1965 . Th e United States Weather BU-reau has elected to use this type satellite in its firstoperational system.The Nimbus, the most advanced weather satelliteever constructed, was launched into a polar orbitin August, 1964. This satellite, is fully stabilized

so as to maintain its sensors pointing at the earthand its solar panels at the sun. By selecting theorbit with the proper inclination (80 retrograde)the Nimbus always passes overhead at noon andmidnight.8


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FIGURE 11. NIMBU S. 6ms W e ig h t4 35 Ibs. Sensor Weight-150Ibs. PEAK P O WE R4 7 0 w a t ts S t a b i t i z a t id c t iv e 3 Axis Des ignlife-six months to one year Launch Vehicle-Thor-Agena B Orbit-Apogee47 4 mi., Peri gee-2 53 mi., Period-98.2 Min., Inclination-98 "Firs t Fligbt-August 28, 1964.

FEURE 12. PORTIONS OF NORWAY, SWEDEN AN0 DENMARK-TIROS VFEBRUARY 18, 1963s

The Nimbus is further illustrated in Figure 11.Because of its high pow er, a variety of advancedinstruments can be carried. T he primary photo-graphic system is an array of three high resolutiontelevision cam eras for w orld-wide day light cloud cov-erage at a resolution of about 3% miles. TheNimbus also carries an infrared camera system forglobal night-time cloud coverage at a resolution ofabout 5 miles. It further carries an Automa ticPicture Transmission system which continuouslybroadcasts about 1080 by 1080 mile pictures of th eclouds beneath it to the countries beneath it. Thesepictures are also of high quality, having a resolutionof .7 mile or twice the resolution of TIR OS pictures.Receivers can be homemade, or purchased at nomi-nal cost. Ab ou t fifty such receiving stations arealready in operation all over the world. Ten ofthese are 6wned and operated by participating na-tions. Th e A P T station in Copenhagen , for ex-ample, can receive each day from the Nimbus anumber of pictures much like that shown in Figure12 , but with many times the area coverage. (Th isparticular picture was taken in 1963 by TIROS andis not an actual APT transmission.)

Three striking examples of Nimbus photographyare shown in Figures 13, 14 and 15.Figure 13 shows a 1020 x 4080 mile strip extend-ing from Hudson Bay, Canada, to Venezuela,, South

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FIGURE 13. NIMBUS DAYLIGHT CLOUD PHOTOGRAPHY-APT's.

Am erica. From top to bottom, the following canbe seen: Canada and the Hudson Bay were coveredwith clouds. The Great Lakes of the United Stateswere free of clouds and show clearly. Th e Eastcoast of the United States from Maine to Floridawas blanketed with clouds, most of which were asso-ciated with hurricane Cleo. Cleo is shown locateddirectly over northeast Florida. Southern Floridawas relatively clear. Following the figure on dow n,one sees the islands of Cuba, Jamaica, Haiti, andthe Dominican Republic, and Puerto Rico. At thebottom of the picture, the Gulf of Venezuela is seenbetween the northernmost projections of Colombiaand Venezuela.This particular strip was assembled from APTphotographs, taken on August 31. All of the pic-

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-FIGURE 14. NIMBUS-AVCS PICTURES.

tures were obtained on the same orbit by a singlereceiving station near W ashington, D.C . This illus-trates that A PT coverage actually extends for severalthousand miles in all directions from the groundstation.

Figure 14 shows a partial mosaic of Europe ob-tained with the three camera system on a singleorbital pass. T h e British Isles are visible at thetop with clouds over northern Ireland and haze overScotland and southern England. France is rela-tively cloud free, but cumulus fields obscure the lowcountries and western Germ any. The snow coveredPyrenees are visible with cloud fields to the south.Most of Spain is cloudless, however. Gi bral tarstands out clearly, as do the Balearic Islands, Cor-

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FIGURE 15. NIMBUS NIGHT CLOUD PHOTOfiRAPHY-HRIR

sica, and Sardinia. Th e cloudless Sahara desert isbright enough under the noonday sun to appearcloud covered.Figure 15 shows ano ther exciting strip photographtaken at night with the infra-red came ra. Thiscamera does not take individual frames, but con-tinuously records the scene passing beneath thesatellite. Th e way the system works is to scan theearth with a reflecting telescope that sees only asmall spot at any instant. Th e infrared radiationintensity from this spot is recorded on magnetic tape.In reconstructing the picture on the ground, coldsources are printed white and warm sources black,with various shades of gray in between. Th us, highaltitude clouds a re show n very white and low altitude

clouds less white. Th e snow-covered poles arewhite even without clouds. Land m asses can bedistinguished from surrounding water because oftheir tempe rature differences. This came ra alsoworks in daylight but with less contrast. From bot-tom to top, one can see the south polar cap withinteresting cloud fields extending n orthward to south-ern Australia. Th e west coa st of Australia isclearly seen from 30" to 20" south latitude. SharkBay and Exmouth Gulf are the key landmarks.North of Australia, Java lies under cloud s. Borneoand Sarawak, however, can be seen straddling theequator, partially covered with high clouds. Thepicture extends north to Manchuria, but the coast-lines are indistinguishable.

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THE EARTH

Seeing these pictures leads naturally to the ques-tion of whether one can improve on our knowledgeof both the shape of the earth and the location of itsland masses by use of satellites. T he answer is yes.To illustrate the techniques, I will use a figuredepicting various communications satellites launchedby the United States.

The Echo passive communication satellites, whichyou have a11 seen, are giant balloons which, whenilluminated by the sun, are visible to the naked eye.They are normally used to reflect radio signals forlong range communications. By simultaneouslyviewing these balloons from various locations, simpletriangulation can be used to locate th e viewing pointswith great precision.

In addition to determining the precise location ofland masses, satellites improve ou r knowledge of th eshape of the earths geoid, which is the effectiveshape of the earth. This knowledge comes fromprecise tracking of satellites, such as those shownhere, and analysis of the changes in their orbits dueto the irregularities in the earths mass. On e ofthe first results was the determination that the earthwas very slightly pear-shaped. Later measurementshave established irregularities in the shape of theequ atorial geoid-which is no t circular bu t is ou tof round by about 197 feet. One of the most pre-cise determinations of this has come from the SYN-COM communications satellite, which is designed toremain overhead in a synchronous orbit. Actually,it drifts slowly due to the equatorial irregularitiesand must occasionally be repositioned.

Figure 17 shows the results of one geodetic analy-sis of satellite orbits. A depression or deficiencyof mass is shown in the Indian Ocean, and an eleva-tion or excess is shown in the western Pacific. In-terestingly, these anomalies can be related to anom-alies in the flow of heat from the earths interior.In turn, these may relate to the local rising of extrahot and hence relatively lighter molten material inthe earths core. An d in this mann er, our continu-ing web of data gathered from space sharpens ourknowledge of the earth.

What place has man in this array of scientificexploration? So far, most of the exploration has

Figure 16.


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FIGURE 18. PHOTOGRAPH OF THE HIMALAY AS. Take nby Astronaut 1. Gordon Cooper, Jr., during orbitall i g h t .

_ -IIGURE 19. PHOTOGRAPH OF CALCUTTA AREA. Take nby Astronaut I. Gordon Cooper, Jr. during orbitalflight.FIGURE 20. BLUE EARTH AND GREEN AIRGLOWLAVER. Taken by Astronaut 1. Gordon Cooper, Jr.during orbital flight.

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been don e by unmann ed spacecraft. But, howevereffective these spacecraft may be, they can do nomore than man designs into them. Mans pricelessability to cope with the unforeseen must ultimatelycarry him into space as an explorer. Just now, manis occupied with learning to live and function inspace. His main observations are of himself andI will not dwell on these in this pap er. In passing,however, I want to show you a few of the sightsseen firsthand by only ten living individuals.

Figure 18 shows a segment of the Himalayas asphotographed by Gordon Cooper from his space-craft, Faith 7. An ordinary 70 mm Hasselbladcamera was used, so this is an unmagnified repre-sentation. T he detail of snowy peak s, green valleys,partially frozen lakes, and rivers is striking. Und ersuch viewing conditions, Cooper was able to detectsmall villages and even individual buildings. In asimilar photograph, geologists located a domewhich may be an excellent place to drill for oil.

Figure 19 shows the Calcutta area, as photo-graphed by Astrona ut Cooper. Wan dering throughthe upper center of the picture is the Hoogly Riveron which lies the city, here obscu red by a haze. Inthe lower right quadrant can be seen the Bay ofBengal and the mo uths of the Gan ges. Movingclockwise, one notices color variation attributableto the currents near the coastal canal which is clearlyseen in the left bottom quadrant. In the far upperleft corner is the Damo dar River. T he full scientificpotential of color photography of the earth fromsatellites has yet to be realized.

Figure 20 is a photograp h of night air glow, oneof the scientific experiments of the Cooper flight.The two-man spacecraft Gemini flights will permita large number of scientific and technological ex-periments during flights of up to two weeks. Inlater Gemini flights, the astronauts will be able toemerge from the spacecraft and float free in space.All of these steps lead toward the day when manachieves what appears to be his ultimate destiny inspace. the exploration of the moon and planets.


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I.

THE M00mA N D PLANETS

The exploration of other planets in the solar sys-tem has just begun. O n Decemb er 14 , 1962, thesecond U.S. attempt t o send an instrumented space-craft to another planet culminated with the successfulfly-by of Venus by Mariner 11.The fly-by is illustrated in Figure 21 . During the109-day flight to Venus, Mariner I1 travelled about

35 million miles away from the earth. During theflight, the trajectory was refined so that the space-craft passed the p lanet a t a distance of about 21,000miles. At Venus, the Ma riner scanned the planetwith radiometers and telemetered the data back toearth.

Mariner I1 provided such information as: thereis a solar wind; Venus has no appreciable magneticfield or radiation belt at 20,400 miles; facts whichare consistent with the slow rotation of Venus andthe theory which holds that planetary magneticfields are genera ted by their rotation. Th ere wereno large scale breaks in the Venu s clouds. Th eapparent high temperatures of Venus do not comefrom a hot ionosphere. An d the surface is indeedvery hot (above 752OF).On November 28, 1964'Mariner IV was launchedtowards Mars on a trajectory which will take it pastthe planet, at a distance of 5000 miles, on July 14,and make measurements of this planet. Th e space-craft is shown in Figure 22 against the backgroundof a photograph of the planet. This is a much mo redifficult mission than the Mariner I1 flight to Venus.

At Mars, the spacecraft will have travelled about144 million miles from the earth and will have beenin transit about 8 months.

As difficult as these missions are, Mars has asingular attraction which cann ot be denied. Eac hMartian summer, there is a wave of visible darke n-ing, much as could be expected from the growthof surface vegetation. In addition, astronome rshave detected radiations from Mars indicating thepresence of hydrocarbon bonds which might indicateorganic substances. If there is extra-terrestrial life,

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FIGURE 21. MARINER II PASS OF VENUS-AS SEEN FROM EARTH.

FIGURE 22. MARS ENCOUNTER.

FIGURE 24. SIGNIFICANCE OF HIGH RESO-LUTION LUNAR PHOTOGRAPHY.

FIGURE 23. RANGER BLOCK 111. (Based OnRanger VI1 Data.) Gross Wei ght- 807 .Ibs :Inst rum ent Weight-382 Ibs. lme st lg at io ns-6 TV cameras Power From Sola r Panels-180 wat ts * Power Required-117 wa tt s *S t a b i l i z a t i o n 3 Axis At t i tude Cont ro l (co ldgas! D es ign L i f e 4 9 h r . t r ans i t Launc hVehicle-Atlas D/Agena B Traje ctory -luna rImp act Plan-two f l igh ts in 1s t qua r t e1965.

RANGER V IPHOTO

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-we must find it, identify it, and relate it to our own.T he im plications are staggering even if such lifeassumes only the most elemental forms.Many astronomers have long held that the"vacuum packed" moon may hold on or near itssurface the secret to the 4% billion-year history ofthe earth-m oon system. Being airless, the moo n has

no wind or rain to weather or erode it. However,it is eroded by the radiations from the sun and outerspace, by the continuous bombardment of meteroidsand dust, and by the thermal stresses of the extremeday-to-night temperature range. To what depth,we do not know.Being closer than the planets, and easier to reach,the moon was selected as the target for man's firstextraterresrriai expioraiion. BefGie iiiaii g ~ e sz themoon, however, enough unmanned scientific explora-tion must be conducted to both insure his safety andto maximize his effectiveness once there. From anoperational point of view, there are three prime ques-tions. Ho w rough is the surface? How hard isthe surface? Where are the best landing sites?

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The United States has a three-pronged program toget these answers. On July 31, 1964, the successfulphotographic mission of Ranger VI1 provided 43 16excellent photographs to help astronomers and geol-ogists check their concepts of th e lunar surface.lWithin the next two years, an unmanned Surveyorspacecraft will hopefully land and determine bearingstrength. In add ition, we are building a lunarorbiter to conduct detailed photographic reconnais-sance with millions of times the coverage possiblewith the Rang er series. By the time man goes, theway should be well charted.The Ranger spacecraft which made the historiclunar flight is shown in Figure 23. Ranger VI 1 wasactually our fifth Ranger flight to the moon, our thirdimpact, and our first total success of the series.Ranger V I flew to within 20 miles of its target, bu tthe cameras failed to operate. Ranger VI1 flew towithin 8 miles of its target and functioned perfectly.Before the flight of Ranger VII, we could onlysurmise the nature of the lunar topography. Th eextent of our ignorance is illustrated in Figure 24.In the upper right is an excellent photograph of themoon taken fro m earth. Th e optical resolution isabout 2508 feet. Below it is an aerial photogr aphof the U.S. city of Boston, Massachusetts, at a reso-lution of 394 feet. Were Boston to be located onthe moon, we might notice a small blur but would

have no knowledge of what it was. On the lowerleft is Boston at a resolution of 5 feet. Thank s toRanger VII, we were able to fill in the upper leftwith a photograph of the lunar surface showingwhat may be a partially buried rock about the sizeof a large building. Mare Nubium is not likeBoston!

Let's take a further look at what the moon is like.Figure 25 shows a 222 mile square taken from analtitude of 461 miles. Thi s picture closely dupli-cates the resolution of earth photography, about onehalf mile. Th e shar p deep crater is Darney. It isabout 10 miles across and one mile deep. Theimpact area is just south of the small moun tainridge in the upper right. The outline of the nextphotograph is shown.

Figure 26 shows this next picture taken from analtitude of 228 miles. T he picture is 110 miles ona side and craters of about 984 feet are discernible.'On February 20 , 1965 R anger VIII acquired an additional7,162 photographs of th e moon's surface , this t ime o f anarea in the Sea of Tranquil i ty . Ranger I X , on March 24 ,1965, sent 5,814 pictures of an area at the edge of the Seaof Clouds .

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Darney is in the lower left and the small mountainridge is in the uppe r right. Fo r the next picture,cho ose as your reference the pair of craters belowthe mountain ridge. The impa ct point is slightlyabove and to the left of these craters.Figure 27 shows the next photograph taken from

82 miles. It is 39 miles on a side and 482 feetcraters are clearly visible. In addition to the sharpprimary craters made by meteoroid impact, largeclusters of secondary craters of som ewh at softer out-line are becoming visible. Th ese are believed tohave been created by some of the m aterial splash edout when the crater Tycho was formed. TheRanger impact point was slightly above the regularcluster of six craters to the northwest of the twolargest primary craters.

Figure 28 shows this area more clearly.. Thispicture was taken from 33 miles and is 15 miles ona side. Craters as small as 164 feet are visible.The impact point missed the center of this batteredarea and is above the regular cluster of six.For Figure 29, Ranger VI1 was down to 11 miles.Th e picture is about 5% miles on a side and cratersof about 46 feet are visible. Th ese craters looksoftly rounded because they are softly rounded.Occasional clearly-discernible small conical cratersattest to the sharpness of th e photog raphy and d em-onstrate that the soft or blurred appearance of thesecondary and tertiary craters is their true appear-ance. In the uppe r left of the outline of the nextframe is an oblong object.

Figure 30 indicates that the oblong object shown

FIGURE 25-LU NA R PHOTOGRAPH TAKEN BYRANGER VI1 ON JULY 31, 1964-Vertical Altitude- 4 6 1 m iles .

FIGURE 28. LUNAR PHOTOGRAPH TAKEN BYRANGER V1 ON JULY 31, 1964-Ver tical Alti tude-33 miles.

FIGURE 26. LUNAR PHOTOGRAPH TAKEN BYRANGER VI1 ON JULY 31, 1964 -Verti cal Altit ude-228 miles.FIGURE 27. LUNAR PHOTOGRAPH TAKEN BY

-82 miles.RANGER VI1 ON JULY 31, 1964-Vertical Altitu de

FIGURE 29. LUNAR PHOTOGRAPH TAKEN BYRANGER VI1 ON JULY 31, 1964-Ve rtical Altitude-11 miles.FIGU RE 30. LUNAR PHOTOGRAPH TAKEN BYRANGER VI1 ON JULY 31, 1964-Vertical Altitude-3% miles.

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APOLLO LAUNCHVEHICLES

L 2 0 S I O R Y

350'

300'

250'

. SATURN V 2001 5 0

I

100'

50'

FIGURE 35. THE APOLLO TM-1 MOCK-UP.

FIGURE 33.

FIGURE 34. APOLLO MISSION PROFILE-LUNAR ORBITAL RENDEZVOUSMODE.ure 34. A three-day flight will take them to themoon where they will go into orbit. A speciallanding craft carrying two of the three men willdetach itself from the main spacecraft and descendto the lunar surface. After a relatively short periodof surface exploration, these men will take off andrendezvou s with the basic Apollo spacecraft. The ywill then transfer into the reentry vehicle for the3-day return flight. An other chapte r in history willbe written.

The last figure shows a full scale mock-up of th elunar landing spacecraft (Figure 3 5 ). Th e work-man gives an idea of the size. How ever fantasticthe con cept of this craft sitting on the luna r surfacemight have seemed a few short years ago, most ofus should live to see it happen.