NASA Facts Lunar Orbiter

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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

- J I-NF-3UVOL. IV , NO. 4 . -.--

Lunar QrbiIes

BLAZING A TRAIL FOR MAN TO FOLLOW

By the end of th is decade, American ast ronaut-

explorers are scheduled to land on the m oon.

Lunar Orbi ter is one of three unm anne d space-

craf t programs undertaken to help select s i tes for

these manned landings and, at the same t ime, togather and report bas ic sc ient if ic data which cannot

be obtained by observations f rom earth. The other

two: Projects Ranger and Surveyor. The Lunar

Orbiter project was managed by NASA’s Langley

Research Center, Hampton, Virginia, for the Off ice

of Space Science and Applicat ions, NASA Head-

quarters.

Lunar Orbiter spacecraft were placed into rela-

t i ve ly low orb i t s around the moon to take sharp

close-up pho togra phs of extensive areas. The ph oto-

graphs are pr imari ly for use in select ing s i tes for

manned landings and in increas ing our sc ient i f ic

knowledge of the m oon’s surface. In addi t ion, the

spacecraf t are prov iding informat ion about the

moon’s size, shape, and gravitat ional f ield and

about radiat ion and micrometeoroids ( t iny par-t ic les of matter in space) in the moon’s v ic in i ty .

In a closely coordinated effort , NASA Surveyor

spacecraf t were sof t - landed on the moon. As an

example, Surveyor I which landed gent ly i n the

Ocean of Storms on June 2, 1966 , t rans mi t t ed

p ic tures and other in format ion about the lunar sur -

face in i ts general v ic inity. These were coordinated

wi th the more extens ive overhead views f rom Lunar

Orbi ter I launched August 10, 1966. Ear l ier ,

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...

1Close-up of part of th e vast Crater Copernicus taken by th e camera of Lunar Orbiter 1 1 . Mountains rise as high as 1000

feet fro m the crater floor. Horizontal distance: about 17 miles. Distance from base of photograph to horizon: about150 miles.



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2

1

Ranger spacecraft had provided our f i rst c loseups

of selected lunar areas before crashing as intended

on the moon. The Ranger program was completed

in 1965.

VOYAGE TO THE MOON

A typical Lun ar Orbi ter voyage to the m oon starts

at Cape Kennedy, Fla. The spacecraft i s mountedins ide of a shroud (nose cone) on top o f the 90-

foot -high two-stage At las-Agena laun ch vehic le. The

shroud protects the spacecraf t against damage

f rom w ind buf fe t ing and other hazards dur ing

launch.

The At las igni tes and boosts the spacecraf t

through the th icker pa r ts o f ear th ’s a tmosphere.

Af ter a l i t t le more than f ive m inutes, the At las s tops

f i r ing and short ly af terw ard detaches i tsel f an d fal ls

back to earth. Seconds later, the pro tect ive shroud

is thrown of f .

About 50 seconds after At las separat ion, thesecond stage Agena engine ignites brief ly to place

i tsel f and the spacecraf t into a pa rk ing ( temporary)

orb i t about 100 miles above the earth.

The combined vehic les coast in orb i t un t i l reach-

ing the bes t po in t for launch to the moon. A t th is

point , the Agena’s engine f i res a second t ime,

accelerat ing the vehic les f rom 17,500 (orb i ta l

veloc i ty) to abo ut 24,500 miles per hour (escape

veloc ity , i .e . , the speed needed to pu l l away f ro m

the ear th) . I t s job done, Agena stops f i r ing, sepa-

rates f rom Lunar Orbi ter, and uses smal l gas jets

to move out of the spacecraf t ’s v ic in i ty . This event

occurs about 40 minutes af ter l i f t -of f .

A few minutes later, Orbi ter extends i ts broad

solar panels that convert sunl ight to elect r ical

power , and i t s rad io antennas for communicat ion

wi th earth . The panels lock on the sun. About

11/2 hours later, the f inal del icate or ientat ion ma-

neuver is conducted. Orbi ter locks on Canopus, th e

br ig htes t s tar in the Southern Hemisphere. By

or ient ing i tsel f on these reference points , Orbi ter

remains in a pos i t ion known to cont ro l le rs on ear th .

The cont ro l le rs mus t know the spacecraf t ’ s or ien-ta t ion to send proper commands for maneuvers .

Groun d personnel care ful ly analyze t rack in g data

f rom the spacecraf t to determine whether the

spacecraf t w i l l reach the p lanned a im po in t near

the moon. I f a s l ight path ad jus tment i s ind icated,

they rad io appropr ia te commands to the space-

craf t . Such commands cal l for the spacecraft to

pos i t ion i tsel f appropr iately and then f i re i ts rocketfor a spec i f ied per iod a t a cer ta in t ime, usua l l y



2 Lunar Orbiter I photograph of area whereSurveyor I landed. The area was shown bypictures from both spacecraft t o be relativelysmooth. Center coordinates are 43" W.Longitude; 2" 20 ' s . Latitude. Note mountainswhich appear as white areas at north (top).

together. In the background are crests of the

mountains photographed by Lunar Orbiter I inanother illustration on page 2.

4 A large crater is superimposed on part of anolder smaller crater in this Lunar Orbiter Iphotograph of the side of the moon never seenfro m earth. The larger crater is about 31 milesacross.

3 Two pictures f rom Surveyor I are pieced

5 Possible manned landing sites which LunarOrbiters I and II photographed at close range.

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6 Lunar Orbiter I photographed earth when all buta crescent was i n darkness. To an observer

on the moon, the earth goes through phases asdoes the moon, viewed from earth. The

phases in both cases are due to the positionsof the earth and moon relative t o the sun as the

moon revolves around the earth.

7 Typical Lunar Orbiter flight path from earth topicture-taking orbit around the moon.

8 Atlas-Agena launches Lunar Orbiter I fromCape Kennedy, Florida, on August 10, 1966.

7 APO L U N EI150 ST M I

ALT ITUDEIN J EC T IO N IN T O f

PH O T O G R APH ICORBIT

OF IN T ER EST

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b t C O N D M I DC O UR S EC O R R F C T I O N

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JETTISONA T L A S

'& r l R S T M I D C O U R S EC O R R E C T I O N

SEPAR AT EAT L AS AN DN O SF SH R O U D

( IN J EC T IN T OPAR KIN G O R R IT I

SO L AR PAN EL7 N D AG EN A

IGNIT ION /% A N D A N T E N N AD E P L O Y M E N T

I IN J EC T IN T OT R AN SL U N AR

C O A5 T INPAI lK IN C , O l l l l l T

A G E N A S E P A R A T I O N

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about ten hours after launch, t o impar t the requ i red

velocity change. (One or m ore mid -cours e ma

neuvers of this type may be required to speed up

or decelerate the spacecraft so t ha t it reaches the

target po int near the moon.)

I SATELLITE OF THE MOON

About three days after launch, the spacecraftarrives at the moon. Calculat ions are made as to

the requirements for slowing the spacecraft so that

it wi l l orbi t the moon rather than sweep by it and

head more deeply into interplanetary space.

Commands are sent f rom earth across almost a

quarter mi l l ion m i les of space to Lunar Orbi ter. The

spacecraft reorients i tself and f ires i ts rocket. Lunar

Orbiter’s speed i s reduced f rom about 4500 mi les

per hour to about 2200 mi les per hour. A t that

speed, it i s captured by lunar grav i ty and becomes

a satel l ite of the moon. I ts orb i t ranges f rom an

apolune (highest alt i tude) of about 1150 mi les t o aper i lune ( lowest al t itude) of about 12 0 mi les.

Engineers moni tor the spacecraf t ’s performance

and tracking data for several days while the space-

craft is in i ts in i t ia l orbi t around the moon. They

make plans for a maneuver to lower the spacecraft

to i ts pic tur e-tak ing orbi t .

After several days, the spacecraft is oriented

prec isely and i ts rocket is f i red at the r ight t ime

for a few seconds. The peri lun e is lowered to less

than 30 miles above the moon. (Lunar Orbiter I

had a pic tur e-tak ing per i lune of about 24.7 miles.)

After it takes and sends i ts photographs to earth,

Lunar Orbi ter m ay be thrust into new orbi ts to con-

t inue i ts studies of micrometeoroids, radiat ion and

the moon’s gravitat ional f ield.

SELF-CONTAINED CAMERA SYSTEM

Unlike Ranger and Surveyor which telecast pic-

tures di rect ly to earth, Lunar Orbi ter is an orbi t ing

photograp hic laboratory. I ts camera system,

housed in a pressur ized and temperature-control led

container, snaps pictures, develops f i lm, and con-

verts the images on the negatives into electrical

s ignals for t ransmiss ion to earth.

The Lunar Orbiter camera system is designed

to prov ide, f rom a 25 -m i le al t i tude, high-resolut ion

photographs showing objects as small a s three feet

across and medium-resolut ion photographs showing

features as small as 27 feet across. The smallest

objects on the m oon that can be seen throu gh tele-

scopes on earth are about a half mile across.

Moreover, the medium -resolut ion photographs of

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the same general area may overlap oart ial ly, per -mi t t ing s tereoscopic v iewing that indicates s lope of

the surface. Such informa t ion is impo rtant because

to o steep a slope-even if the area i s smooth-

could ov erturn a la nding spacecraft .The camera takes i ts hig h- and m edium-resolu-

t ion pictures simultaneously by means of a dual

lens. The high-re solut ion image is centered wi thin

the area covered by the medium -resolut ion pic ture.

(See sketch.) The camera is loaded wi th a 20 0-fo ot-

long ro l l of 70-mm f i lm . A device cal led a velocity-

height sensor prov ides informat ion needed to co m-

pensate for the spacecraft 's motion and prevent

b lur r ing. I t does this by sending appro pr iate elec-

6

t r ical s ignals that regulate the movement of the

f i lm s l ight ly d ur ing exposure.

Af ter exposure, the f i lm i s brought in contac t

wi th a web-l ike mater ia l that has been soaked in

deve loping solut ion. The processed f i lm i s laterdr ied by pass ing i t before a t iny e lec t r ica l heater .

GETTING ORBITER'S PHOTOGRAPHS TO EARTH

Trans fer r ing the deta i led photographs to ear th

involves an exact ing piecemeal process in which

some 4 5 minutes are req u i red for one h igh - and

med ium-reso lu t ion exposure. Key to the process i s

an elect ronic dev ice that p rojects an intense l igh t

beam about f i ve mic rons (A mic ron i s .000039-



HIGH RESOLUTION PHOTOaMEDIUM RESOLUTION PHOTO

9 Orbiter I photograph of rugged area just westof Crater Landsberg. Area is 25 x 29 miles.Center coordinates: 30 " 45 ' W. Longitude and1 " 45' N. Latitude.

i o Lunar Orbiter I view of the m oon's eastern limb(edge), which is the right side relative to an

observer on earth. This region is rarely seenfrom earth. Area covered: about 106 x 89 miles.Approximate location: 90" E. Longitude; 0"

Latitude.

11 Dual-frame photographs taken by Lunar Orbiterappear as indicated in sketch above.

inch.) in d iameter . The t iny l ig ht spot t ravels back

and fo r th across the one- ten th inch o f f i lm, mak ing

some 17,000 passes (scan l ines) to read out the

width o f the f i lm. The f i lm is advanced after each

scan, and the process repeated.The l ight beam passes through the negative

on to a pho tomul t ip l i e r tube. Th is converts the l i gh t

str ik in g i t in to a vary ing electric curren t that c orre-

sponds to the l i gh t and dark a reas on the negat ive .

For example, the darker areas of the negative re-

duce the amount o f l i gh t tha t can pass th rough.

The e lectr ica l current is then fed t o an ampl i f ier

and to the spacecra f t ' s rad io wh ich t ransmi ts the

i n fo rma t i on to ea r th .

PICTURE SIGNALS PICKED UP AND

PROCESSED ON EARTH

The 85- foo t -d iame ter an tennas of NASA's Deep

Space Network keep in constant touch wi th O rbi ter :

commanding i ts maneuvers, moni tor ing i ts condi -

t i on , t rack ing it , and acqu i r ing i ts p i c tu re and o ther

scient if ic data. The great antennas p ick up the

fa int s ignals (down to about a b i l l ionth watt of

power) received from Lunar Orbi ter and ampl i fy

them to useful strength. They relay the signals t o

magnetic tape recorders and to kinescopes, which

are somewhat l ike the p icture tubes in home te le-

vision sets.

7



12 An 85-foot diameter antenna at theGoldstone, California, Deep Space Network

station.

13 Equipment at Goldstone, California, for receivingthe pictures from Lunar Orbiter. Note camera,

upper right, pointed at kinescopepicture tube.

14 Naturally occurring protuberances cast longshadows across the moon's Sea of Tranquility in

this Lunar Orbiter I I photograph taken shortlyafter local sunrise, when the sun was about

11" above the horizon. Reference marks (whitecrosses) are used for measurements andrepresent 25 feet on the moon's surface.

Cameras in front of the kinescopes photographthe images appearing on them . Each image ini t ial ly

recorded on Lunar Orbiter f i lm one-tenth inch by

2.4 inches is enlarged to three-quarter inch by16% inches. The resu lt ing photograph is cal led a

framelet.

A number of framelets, properly pieced together

length-wise, makes up a photograph. M edium -

resolut ion photographs are made up of about 26f ramelets. High resolut ion p ictures are made up

of about 86 framelets. It takes approximately 295

weeks to receive a l l of Lunar Orbiter 's photographs

a t stations on earth.

SPACECRAFT DESlGN

At launch, the 8 50-p oun d Lunar Orbi ter is 5 feet

in d iameter and 51/2 feet long. In space, wit h i ts

solar panels and radio antennas unfo lded, the c raf t

measures 12 feet 2 inches across the panels and

l81/2 feet to the outer ends of i t s antennas.

The spacecraft i s structural ly composed of two

sections. One i s the main equipment mount ing

deck. This holds the camera system, radiation

detectors, and electr ical and electronic equipment

such as communication and orientation devices.The other i s cal led the upper module. It holds

the propulsion equipment that enables control lers

on earth to change the spacecraft 's f l ight path.

This equipment includes a 100 -pound th rus t l i qu i d -

prope l lant rocket engine, ni troge n gas jets for orien-

tation changes, and storage tanks for propel lants.

The spacecraft has two kinds of radio antennas.

One, looking l ike a dish, i s cal led a high-gain or

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1 5 Lunar Orbiter is lowered into a space simulati onchamber during tests preparing it for space

flight.

16 Principal parts of Lunar Orbiter.

17A large crater whose floor is nearly coveredwith a layer of dark material is prominent i n thi s

Lunar Orbiter I l l photograph of the moon’s fa rside. Scientists believe that thi s dark material is

pushed up from below the surface like lavafrom a volcano.

18The Cordillera Mountain range forms aconcave curve leading off the southwest part of

the moon’s visible face. Sweeping around thisarea, Lunar Orbiter I V took a photograph

showing that t he mount ains formed a vast ringaround the 600-mile-diameter Orientale Basin.

Within th is ring are several smaller rings, givingthe effect of a giant bulls-eye. The beautifully

preserved texture of the surface and thesharpness of the mountain ranges suggest that

thi s i s a relatively young l unar feature.

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16

ICRO METEOROID

SOLARPANEL

IOMNl D IRECTIONAL

ANTENNA

directional antenna. It focusses radio signals for

max imum intensi ty in a s ingle d i rection. I t is used

pr im ar i ly for sending p icture s ignals.

The other, shaped l ike a wand, is a low-gain or

omnid i rect ional antenna. It sends radio signals in

every direction; al though it t ransmi ts a weaker

signal, it can be received at any tracking stat ion

regard less of the or ientat ion of Orbi ter in space.

The low-gain antenna is used for t racking, receiv ing

commands, and equipment checks.~~ ~~~

NASA Lunar Orbiter I , launched August 10,1966, provided the f i rs t occasion in which photo-

graphic t ransmissions from a Uni ted States space-

craf t were re leased to the publ ic at Deep Space

Network stat ions located at Robledo de Chavela

(near Madrid), Spain; and Woomera, Austral ia.

A th i rd s ta t ion is at Goldstone, Cal i fornia.

Lunar Orbi ter I i s the f i rs t p i c tu re - tak ing space-

cra f t p laced in orb i t around a body other than earth.

I t i s the f i rs t spacecraft to photograph the earth

f rom the moon and to take h igh ly de ta i led pho to -

graphs of the s ide of the moon perpetual ly h iddenfrom earth. These gave ma nkin d perspect ives not

avai lab le f rom earth.

1 1



19 Lunar Orbiter V snapped this photograph ofth e Crater Tycho, located at 1 1 " West

Longitude and 43" South Latitude on the moon.Tycho is about 50 miles from rim to rim. Note

the central peak, a characteristic of manylarge lunar craters.

20 While circling the moon, on August 8, 1967

Lunar Orbiter V snapped this first picture ofa nearly full earth. Clearly visible are Africa, theEastern Mediterranean area, and the Arabian

Peninsula. A part of the Indian Peninsula maybe seen through the clouds which obscure much

of Asia and the Indian Ocean.

21 The meandering Prinz Valleys I and II,running downhill, are among the major

features of this Lunar Orbiter V photograph of

the moon's Harbinger Mountain area. Somescientists attribute these valleys t o volcaniceruptions and the flow of fluidal material. At

left is Prinz Valley II, 8,000 feet wide at itshead (below) and narrowing to about 1,500 feet

near it s end. To i ts right i s Prinz Valley I.

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