NASA Facts Project Ranger

8/6/2019 NASA Facts Project Ranger

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Page 2crashed in the northwest corner of Mare Nubiumthe Sea of Clouds-about eight miles from itstargeted impact area. This area now has beendesignated th e Mare Cognitum by the International Astronomical Union. The t e rm" Mare,"which is "sea" in lat in, was given to certainareas of the moon by early astronomers.IOPENS NEW ERA IN LUNAR ASTRONOMY

Although relatively near earth as compared toother celestial bodies, the moon is fundamentallystill a scientific mystery. Astronomers havemapped the moon's visible face and have namedits perceptible craters, mountains, valleys, andplains. But, unable to discern the fine detailsof the lunar surface, they debate its structure andstrength.

As a result, engineers designing the landinggear for the Surveyor soft-landing spacecraftand the Apollo section that American explorerswill land on the moon ' s surface (the section iscalled the Lunar Excursion Module, or LEM) areconcerned whether a landing site that appearsfrom earth to be smooth and firm is actually so.They ask whether it could be a vast dust bowlcapable of engulfing a spacecraft. They wonderwhether it is strewn with boulders or pitted withcraters to o small to be seen from earth.

Ranger VII opened a new era in lunar astronomy by sending pictures of the moon showingfeatures 2000 times smaller than previously detectable through earth based telescopes. Dr.Gerard P. Kuiper, who heads a team of scientificinvestigators studying the Ranger VII photographs,presented an interim report on August 28, 1964.Highlights of the report included:

. . The seemingly smooth Sea of Clouds isdotted by thousands of small craters that do notshow up on photographs taken through tele-scopes on earth.

.. An outlying ray of the Crater Tycho ispeppered with craters. Lunar rays appearthrough earth telescopes as l ight streaks radiatingfrom some craters.

. . With the exception of several chunks ofmatter in one crater, no boulders were visible.

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NASA FACTS Vol. II, No. 6

5Photograph af moon (above) outlines aiming point area in Se aof Clouds where Ranger VII landed a t 6:25:49 a.m. EDT , July 31 .Map (be law photagraph) shaws t a rge ted and actual impactpoints.

Also notable was the absence of fissures in thelunar surface.

. . . Based on a study of pictures taken about1600 feet above the moon, 90 percent of theslopes of the lunar surface are calculated to bebetween one and fifteen degrees. This appearsto be more level than previously anticipated.

. . . While some areas are clearly unsafe fo rlanding, others are believed to be sufficientlylevel an d smooth fo r touchdown by the ApolloLunar Excursion Module as presently designed;however, no knowledge of the surface strengthcould be obtained from the Ranger photographs.


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RANGER VII is the first of the Ranger seriesof spacecraft to provide close-up photographs of the moon. Plans call forRangers VIII and IX t o a ugm e n t this in formation. Of earlier spacecraft in thisseries, Rangers I and II were test vehiclesnot in tended for lunar picture taking;Rangers III and V missed the moon andsoared into orbit around the sun; andRangers IV and VI s t ruck th e moon butfailed to send data.

Photo taken by Ranger VII a t 3000-foot altitude shows arearoo feet in each side. Note rounded shoulders of secondarycraters (see text).

. . . Most of the craters revealed fo r thefirst time by Ranger photographs are believedcaused by debris that was thrown up by colli-sions of meteoroids (random chunks of matterspeeding through space) with the moon. Themain crater created by the meteoroid impact hasbeen termed a primary crater. The debris fromthese primary craters may fl y many miles beforefalling back to the lunar surface. The cratersresulting from matter thrown up by the impactof this debris are called secondary craters.There may also be craters created by matterthrown up from the secondary craters.

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Page 3 .. Primary craters ma y be identified by

their sharply defined edges as contrasted withthe relatively rounded shoulders of the second-ary craters. The rounded instead of sharpedges are believed to be partly due to thelower impact velocities of the debris thrownfrom the larger primary craters.

.. What appear to be lava flow lines arevisible. One lunar theory holds that somecraters are the remains of extinct volcanoes.For a long time, scientists believed that the moonhad no further volcanic activity. In recent years,however, astronomers on earth have observedthrough their telescopes what appear to be gas-eous emissions from the moon's interior.

. . Erosion seems to be a significant forceon the moon despite the absence of wind andwater. It is theorized that incessant bombard-ment by meteoroids and by protons (particles ofatoms) emanating from the sun may have pul-verized the boulders, filled the fissures, andsmoothed the edges of the less sharp secondarycraters.

Experimenters cautioned that the Rangerphotographs which cover a relatively small areaof the moon are not necessarily typical of themoon as a whole and they strongly emphasizedthat their findings are preliminary. They stressedthat the Ranger pictures are designed to ad-vance knowledge about the moon's topographyonly an d that the Surveyor program is intendedto provide information about the strength, orhardness, of the moon'!. surface.

Ranger VII sent an aggregate of 4316 picturesof the moon as it plummeted to the lunar surface.The photographs have been made available toscientists throughout the world. It is anticipatedthat these photographs will receive close atten-tion and study by lunar scientists fo r many yearsto come.

The only other spacecraft to provide man withphotographs of the moon is the Soviet Lunik 3.In 1959, Lunik 3 took about 30 pictures of themoon's hidden side (see "The Moon," below)from distances of 4300 to 43,000 miles. Thepictures gave no fine detail, but did indicate thatpossibly the moon's hidden portion may not beas rugged as the area visible from earth .


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picture by Ranger VII, taken ab o u t 1600 fee t above th ereveals features as small as 1 5 inches across. Receiverpat te rn a t r ight results from spacecraf t crash on thewhile t ransmitt ing.

THE MOONAlthough many lunar features are beyond the

of his ground-based instruments, man doessignificant facts: The moon's diameter ismiles, about one-fourth that of earth. Its

is one-sixth that of earth, meaning that aman on earth would weigh only 26

on th e moon. The moon's mean altiin its elliptical orbit around earth is 238,857

The moon takes about 27 Y3 days to revolveearth and the same t ime for one com

rotation on its axis. For this reason, thealways presents the same face to earth.

However, about 59 percent rather than the50 percent of the lunar surface is visible

earth. This is due to the moon's librations,are to and fro, or nodding, motions that

NASA FACTS Vol. II, No. 6result from slight changes in velocity and the.gravitational pulls of the sun and planets as themoon circles earth.

The moon is believed to have no appreciableatmosphere to diffuse light and heat nor to shieldit from bombardment by meteoroids and radiation. Day an d night, the stars, sun, and earthand other planets shine steadily in the moon'sje t black sky. During the day (which is about1 3% earth days and nights), the moon's surfacemay be as hot as 260 degrees Fahrenheit whileduring the equal ly long night the temperaturefalls as low as 243 degrees below zeroFahrenheit.

Some scientists believe that the primeval moonwas captured by earth's gravity as it flew nearby during an early stage in the solar system'sformation. Others theorize that the moon wastorn from the primordial earth.

Eroded by neither wind nor rain, the moon'smatter immediately below the level affected bymeteorites and radiation may have changedlittle during th e satellite's lifetime. As a result,the moon may offer an opportunity to study thematter of the solar system as it wa s billions ofyears ago. Just as th e Rosetta Stone gave thefirst clue toward deciphering Egyptian hieroglyphics, study of lunar material may help answerkey questions regarding the origin and evolutionof th e solar system and perhaps how life mayhave begun.

Some telecasts by Ranger VII asit plunged toward moon's sur-face. In each picture, the areacovered by the next photographis outlined in white. Blacklines, dr a w n on camera lens,are used for scale referencesand as an indication of whetherpicture is distorted. North isa t top.

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NASA FACTS Vol. II, No . 6

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Picture taken at analtitude of 480 miles,has about the sameresolution as photographs by earth-basedte lescopes. A numbe rof phys ica l f ea t u re svisible from ea r tha re ident i f ied.

Altitude: 235 miles.Area: 113 miles on a side.Smallest Visible Crater:

About 1000 feet indiameter.

Feature: Note increase indetail of Bonpland Hand it s twin crater (toleft of Bonpland H).


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Altitude: 85 miles.Area: 41 miles on a side.Smallest Visible Crater:


Features: C:luster of sec-ondary craters in partof a ray of the CraterTycho becomes distinct(center of picture.Lunar rays appear fromearth to be light linesradiating from somecra te rs) . Detail ofBonpland H and twincra ter is increased.

Altitude: 34 miles.Area: 16 miles on a side.Smallest Visible Crate r :

About 150 feet indiameter .

Features: Greater resolu-tion of craters in out-lying ray of Tycho.

Picture series continuedon poge 7.


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Altitude: 1 1 miles.Area: 5.5 miles on a side.5mallest Visible Crater:


Features: Crater nearupper left of area out-lined in white.

Altitude: 3.6 miles.Area: 1.8 miles on a side.Smallest Visible Crater: 30

feet in diameter; 10feet deep.

Features: Angular rockmass in crater (notedin picture above) a tupper left. Preliminarystudy indicates th e massto be several separatechunks.


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Page 8THE RANGER TELEVISION SYSTEM

The remarkably clear pictures of the moontelecast by Ranger VII were accomplished by acomplex high quality system of television camerasand transmitters on Ranger and a ground receiv-ing network at the Goldstone, Calif., station ofNASA's global Deep Space Network. Thisnetwork tracks, controls, and gathers information from NASA spacecraft sent to the moon andbeyond.

Ranger is equipped with six television camerasand associated transmitters and power supplies.The system is mounted on the spacecraft's hex-agonal base within a compartment shaped. likea truncated cone.

The system includes tw o full-scan (F) and fourpartial-scan (P) cameras. Their difference is thatthe F cameras shoot a larger area than that ofthe P cameras bu t the P cameras can pick upmore detail.

The television system is designed to telecastabout 300 pictures a minute during the 15 to 20minutes before Ranger crashes on the moon.The first pictures show about as many details asthe best telescopes on earth. The last few tele-casts reveal lunar features smaller in size than abushel basket.

Behind the shutter of each camera is a vidicontube about the size of a water glass. The tube'sfaceplate is coated with a photo-conductive material on which light and dark areas seen throughthe camera shutter form an image. This imageis rapidly scanned by a beam of electrons. Thebeam can differentiate l ight and dark areas bytheir comparative resistance (light areas havehigh resistance; dark areas, low). As theelectron beam sweeps across the image, it isconverted into an electrical signal that is amplified and radioed to earth. The vidicon faceplate image is erased so that it can take ne wpictures by saturation with high intensity speciallights and high frequency electron beams. Thewhole process takes a fraction of a second.

The radio signals from Ranger are picked upby the 85-foot diameter antennas at the Gold-

NASA FACTS Vol. II. No. 6

Head-an view of Ranger's si x television cameras. The picturesreceived from Ranger are more than twice as good as thosereceived on ordinary home television sets .

stone station, amplified, and fed to two kinescopes which are similar to small television sets.Before these sets are 35-mm. cameras. Thesignals are also recorded on magnetic tapesimilar to that used by television studios to recordlive shows fo r later telecasts.

The radio signals appear on the television setsas a do t of light moving across the screen. Thecamera lenses are set to stay open long enoughto photograph the light through a completesweep over the screen. By this means, thecameras make meaningful still photographs.


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TV SU I SYSTEMAND SHROUD

ATTITUDE CONTROLELECTRONICS

HIGH-GAIN ANTINNA

CAMERA APERTURE

SOLAR PANEL LATCH

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Principal equipment afRanger. . (On-boar.drocke t is not vis ible inth is v iew. ,

AnlTUDE CONTROLGAS-STORAGE IOTTLE

THE RANGER "BUS"The Ranger "bus" is the basic vehicle to which

the experiments (in this case, the televisionsystem) are attached. It contains Ranger's principal power supply; telemetry instruments to report on the spacecraft's condition and operation;a command system to enable personnel on earthto control the craft; timing, orientation, and temperature control devices; and a small rocketsystem fo r in-flight correction, i f required, ofRanger's course.

Ranger sends information to earth principallythrough a dish-shaped, high-gain antenna. Thiskind of antenna focusses radio signals in a narrow beam, thus sending a signal with maximumstrength in a given direction.

Ranger is also equipped with an omni-directional antenna which disseminates radio signalsin al l directions. Although the signals from theomni-directional are fa r weaker than those fromthe high-gain antenna, they serve as a communi-

cations link when the high-gain antenna is no tpointed to earth (as during launch and midcourse correction. See "From the Earth to theMoon," below.) The omni-directional antennaalso functions at al l times to receive commandsfrom earth to the spacecraft.

During Ranger's flight, two solar panels extend from it l ike butterfly wings. The panelshold a total of 9792 solar cells. These photoelectric devices convert sunlight into 200 watts ofelectricity for powering spacecraft equipment.Auxiliary power is furnished by two silver zincstorage batteries which are used when the solarpanels are not functioning, particularly duringlaunch when they are still folded and during midcourse correction.

During its flight, Ranger must be positioned sothat its solar panels face the sun fo r power an dits high-gain antenna points to earth. A complex system of sun and earth sensors, gyroscopes, and nitrogen gas jets keep the craftoriented.


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rocket engine can operate in burstsshort as 50 milliseconds (50 / 1OOOths of a

It can generate as much as 50 poundshrust for 98 1/2 seconds.

Telephone statement by PRESIDENT LYNDON B. JOHNSONto Dr . Homer E. Newell, NASA Associate Adm inistrotor forSpace Science and Applications, an d Dr . Will iam H. Pickering, Director, Jet Propulsion Laboratory, Pasadeno , Col if .July 31, 1964 . . .

"O n behalf of the whol e count ry, I wan t tocongratulate yo u and those associated with you inNASA and the Jet Propulsion loboratory and inth e industrial l a b o r a t o r i ~ s . All of you have con-t ributed th e skills to ma ke this Ranger VII flightthe grea t success that it is. We are proud of th etremendous technical achievement which this suc-cessful fl ight represents .

"This is a basic step forward in ou r orderly pro-gram to assemble the scientific knowledge neces-sary fo r man 's trip to the moon.

"The pictures obtained of the lunar sur faceshould prove ex t r em" ly useful . They will be aguide in constructing \ he lunar excursion moduleand in planning the trip. We shall now be ableto bet ter map out our descent route. We'll beable to build our lunar landing e qui pme nt withgreater certainty and knowledge of th e conditionswhich our astronauts will encounter on th e moon.

"I recognize that this grea t success has comeonly after a number of failures an d partial failuresin our efforts to send probes to the moon. Thissuccess should spur us on to added effort in thefuture .

"The fact that Our Soviet competitors have ha dmany unpublicized failures to th e moon and th eplanets also confirms th e complexity of today 'ssuccess.

"On behal f of a grateful nation le t me agoincongra tula te yo u on this magnificent achieve-ment. All of you today : ,ave helped further thepeaceful exploration of space."

SPACECRAFT DIMENSIONSAt launch, Ranger is 5 feet in diameter at its

base and 8V" feet long. Whenin space with solar panels and high

antenna extended, Ranger spans 15 feetpanels and is 10 1/ " feet long. Ranger

806V2 pounds, of which 381 1/2 pounds isTV system.

NASA FACTS Vol. II, No.6LAUNCH CONSIDERATIONS

Among major considerations governing Rangerlaunches are the requirements that it must obtainuseful photographs of the moon and that theorienation system must be able to do its work.

The launch must be timed so that Rangerreaches the moon's sunlit portion when longshadows will be cast by any but smooth physicalfeatures. Caught by the cameras, the shadowsindicate how rugged or flat the land is. Suchinformation is important to science and vital formanned landings.

Moreover, attitude control requirements makeunacceptable the periods of the new and fullmoon. The spacecraft must lock upon the earthand sun for orientation, and in these periods, thesun and earth sensors cannot adequately orientRanger. Technical l imitations on target areasand on satisfactory lighting angles precludelaunchings during the moon's first quarter.

These two factors limit Ranger's launch to aperiod during the moon's third quarter (seesketch).

Other constraints are the location of the CapeKennedy, Fla., launch site and the two thousandmile per hour speed at which the moon circlesearth. As a result of these and other considerations, the launch window (time interval) fo rRanger's flight to the moon is restricted to periodsof from 90 to 150 minutes daily during a 6-dayperiod that occurs about every 28 days.

When rocketed to the moon at about 24.,500miles per hour, Ranger must be centered withina ten-mile-wide imaginary corridor leading towhere the moon will be when Ranger reaches thealtitude of the moon's orbit. In aiming theircraft along its narrow curving Aight path, launchpersonnel must consider not only the effects ofthe gravitational pulls exerted by the earth andmoon but also by the sun, Jupiter, Mars, andVenus. All inAuence the motion of a spacecraftcoasting between the earth and moon.

FROM THE EARTH TO THE MOONIn brief, Ranger's Aight plan is as follows:A two-stage Atlas-Agena launch vehicle

rockets Ranger from Cape Kennedy. The Atlasexhausts its fuel and falls away. The Agena


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NASA FACTS Vol. II, No.6Diagram illustrates why moon'sthird quarter is only acceptablet ime fo r launching Ranger. SUN

NEWMOON

SHADED REGIONS UNSATISFACTORYBECAUSE SPACECRAFT'S EARTHAND SUN SENSORS CANNOT

THIS REGION UNSATISFACTORY ~ ' 1 1 f T I 8 i . : ! P ? ~ BECAUSE NEARVERTICAl ONLY REGION WHERERANGER IMPACTSNEARVERTICAllY ONSUNLIT SIDE OF

FIRST

MOON AND WHERE

/SPACECRAFT ORIENTATION IS ADEQUATE

\

QUARTER _ L -__ THIRDQUARTERMOONOON

Q--FUl lMOON

MID-COURSE MANEUVER: The mid-course maneuver of RangerVII was conducted on July 29 , 1964, when the spacecraft wa sabout 100,000 miles from ear th. Th e maneuver , initiated at6 a.m. EDT and completed a t 7:2S a.m. EDT, changed Ranger'sspeed by 67 mph. Even if th e maneuver had not been made,Ranger would have struck th e moon. However, it would havecurved around the moon' s leading edge and landed on th emoon's hidden side.

Typical Ranger Launch to Moon.

lSi AGENAFIRING

IN CIRCULARPARKING ORBITAT 17 .500 MPH .ALTITUDE 115 MI.

NORTH POLEMIDCOURSE MANEUVERCORRECTS INITIAL GUIDANCEERRORS OF POSITION

FINALAGENA FIRING

\I IN SPACE FOR ANYONE LAUNCH DAYIF RANGER ENTERS IOMILEDIAMETERCIRCLE WITHIN 16 MPH OF DESIREDIN JECTION VELOCITY. THEN MIDCOURSEMOTOR CAN ADJUST TRAJECTORY FORLUNAR IMPACT. DESIRED INJECTIONVELOC ITY VARIES FROM 24.463 TO 24.48 7MPH DEPENDING ON DATE OF LAUNCH

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Atlas-Agena rocket vehicle launches RangerVII to Moon.

OTHER UNMANNED LUNAR PROGRAMS: Ranger is on e of three NASAprojects designed to provide information about th e moon with unmannedspacecraft. Another, Surveyor , willbe equipped with braking rockets toenable it to make a gent le landingon th e moon. Surveyor will telecastth e moonscope, analyze lunar surfacea nd subsurface material , measuremoonquakes and meteori te impacts,and check th e moon's surface forstrength and stability. A third project, called Lunar Orbiter , is ai med atdeveloping an unmanned spacecraf tto be guided into a low-altitude lunarorbit, photograph the moon's surface,and provide more information on th emoon's s ize, shape, and gravity.


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NASA Facts Project Ranger