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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 ,
c!
...
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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t
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
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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.
3
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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
AL T lT l lO t
b t C O N D M I DC O UR S EC O R R F C T I O N
/
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-
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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.
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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
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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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