To Mars- The Odyssey of Mariner IV

8/8/2019 To Mars- The Odyssey of Mariner IV

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JPL TECHNICAL M EMORANDUM NO. 33- 229-L

(-8% CR O R TMX OR AD NUMBER) (CATSOORY)


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ContentsLandfall at MarsAnother WorldTh e SpacecraftMarine r Leaves PortIn -Flight EventsLong-Distance CommunicationTh e Scientific Experiments

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Mars-and After

T h e p h o t o g ra p h s of Mars on pages2 , 4 , an d 5 are reprin ted throught h e co u r t esy of M t . Wilson an dP a l o ma r Ob serva t o r i es .

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NATIONAL AERONAUTICS AND SPACE ADMINISTRA TION

JPL TECHNICAL MEMORANDUM

TO MARS:

NO. 33-229

The Odyssey of Mariner IV

JET PROPULSION LABORATORY/CALIFORNlA INSTITUTE OF TECHNOLOGY


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Copyright 0 1965Jet Propulsion LaboratoryCalifornia Institute of TechnologyPrepared Under Contract N o . NAS 7-100National Aeronautics & Space Administration


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PREFACET h e M a r i n e r M a r s P r o j e ct o f 1964-65 i s one of a f a m i l y of

f l ight projects conducted by the Je t Propu l s ion L abora tory f o rthe Nat ional Aeronaut ics and Space Adminis t ra t ions Of ice o fSpace Science and Appl ica t ions . Th e Project has been made pos-sible by the valued assis tance and supp ort of m a n y gover nm entagencies and indus t r ia l concerns . Included are NASAs LewisResearch C en t er ( L au nc h Veh ic le Sys t e m Manag er ) and t he i rpr ime contractors : Lockheed Missi les and Space Company andGenera l Dynam ics /As t ronau t i c s ; he Goddard Space F l igh t C en t er(L au nc h Operat ions) a nd o ther agencies at C a p e K e n n e d y ; t h eagencies of the Au s t r a l i an and South Afr ic an governme nts whichoperate overseas trac king s tations; and ma n y hun dre ds of in dus-tr ial contractors and vendors.

N A S A authori zed t he Pro ject in late 1 9 6 2 , with the objectiveof conduct ing scienti fic observat ions on th e planet M ar s and ret urn -i n g t h e d a t a t o Earth for st ud y and analysis . Secon dary object iveswe re to develop and s tu dy the equipment and techniques involvedin carrying out t he Mar s mission, and t o ma ke cer ta in sc ien ti fi cmeasu remen t s of t he i nt erp lane tary env i ronmen t on t he w a y t oM a r s .

M a r i n e r IV wa s launched on N o v e m b e r 28, 1964.


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LANDFALL AT MARS

This summer, mankinds horizon recedes about 150 million miles, toa spacecraft coasting past the planet Mars.

In 1957-58, during the International Geophysical Year, our horizonstretched around the Ea rt h and into space above for little more tha n 100miles ; each year thereafter, science has extended ou r knowledge of thisnear region of space, while at the same time probing further into theunknown. S ta rti ng in 1958 with th e Pioneer spacecraft we pushed closer tothe Moon, a quarter of a million miles away. Late in 1962, Mariner 11,mans first emissary to other worlds, scouted the planet Venus, 36 millionmiles distant fro m th e Ear th. By the summer of 1964 and early sprin g1965, th e Moons surface w as being examined at close range by Rangerspacecraft , and, neare r home, manned vehicles were making orbital flights.

Meanwhile, far beyond the Moon, past the Earth-orbiting spacecraft,Mariner I V was headed fo r Mars. It was to rendezvous with the planet at0105 Greenwich Mean Time, July 15, 1965, or about dinner time, July 14,in California.

Mariner IV was launched from Cape Kennedy on November 28, 1964,by an Atlas/Agena D rocket without incident. Two days later, it was nearlyhalf a million miles out, moving at more than 7,000 miles per hour. Itappeared to be following Mars at a range of 127 million miles and a speedof over 60,000 miles per hour relative to the planets motion. The sp acecraftwas oriented facing the Sun, and was drawing electrical power from thesolar panels; it had just stabilized its attitude by locking on the starCanopus.

On December 5, Mariner was commanded t o change its course slightly,using the 50-pound-thrust rocket motor built into the spacecraft. Themaneuver changed the rendezvous point at Mars from 150,000 miles aheadof the planet and north of the equator on July 16, 1965,t o 5600 miles behindth e planet a nd above the south pole on July 15.

A s th e rang e lengthened, Mariners radio output was stepped up onschedule to maintain contact with Earth. On December 13, a longer-lifeand slightly more powerful transmitting amplifier was turned on. Then,

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Mar8 in r ed light, 1 9 5 6

early in March, as the range became excessive for the omnidirectionalbroadcast antenna and Ea rt h entered the beam of the fixed parabolic-reflector antenna, antenna s were switched by on-board command.On the hundredth day, March 8,1965, Mariner IV was near ly 30 millionmiles fr om Eart h, and less than 45 million f rom Mars. A few weeks later, byApril 14, it had bested the U.S. long-distance communication record, justunder 54 million miles, set by Mariner IIs Venus flight.

So far in its journey, Mariner has measured the fields and particlesaround Ear th f ar above the night side and in interplanetary space; it hasobserved the Class I1 solar flares of Februa ry 5 and April 11 and 17; andit has sampled the sparse but increasing cosmic dust between Earth andMars.

Now it approaches Mars.

ANOTHER WORLD

Though Mars has often been populated, irrigated, and civilized inspeculation and in fiction, its characteristics are relatively unearthly. Itappears to be a small orange-red desert world ;ours is a robust green-and-blue world of jungle, grassland, and rive r, three-quar ters ocean.

Mars has about half Ear th s diameter, a ninth of E arths mass, resultingin a surface gravity 38 per cent of Earths, and an escape velocity of some3.1 miles per second, as compared with 6.9 for Earth. Therefore, Mars isill-equipped to retain much of an atmosphere ; he Martian surface pressureis probably less than Earths pressure at five- to fifteen-mile al titudes.What air there is appears to lack oxygen and contains only enough watervapor to make its detection barely possible from Ear th . The lack of oxygenand scarcity of water vapor, in turn, rule out liquid water (which mus treach equilibrium with a vapor pressure above it) except very temporarilyor underground. There are polar caps of ice or frost-possibly of carbondioxide ra the r than water-though probably extremely thin by Ear thstandards.

However, Mars marked surface and th in atmosphere permitted astron -omers to measure its 241h-hour day and the annual change of seasons asearly as 1659. Mars axis is tilted about t he same as Earths, so its seasonsare comparable, though scaled to the 687-Earth-day Martian year. Earth


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M a r s 1666 (Cass in i )

vacationers might tend to regard t he four Mars seasons as little more th anvariations in a bad winter: a hot midsummer afternoon might bring theground tempe rature up to 85-100F, but dur ing the night it would dropto a hund red below, and six feet off the ground th e air wouldnt get abovefreezing all day.

A Dim View of CanalsLike the Moon, Mars abounds with what we now know to be waterless

seas, bays, an d th e like. However, by this century, when i t was realizedthat they werent water, the names had already been established, and thesmal ler bluish regions remained mare, sinus, and lacus.

Even with the most powerful telescopes and under the most favorableatmospheric conditions, astronomers cannot get high-resolution p ictu res ofMars . To apprecia te the difficulties under which the observers of Marslabor, imagine yourself watching moonrise at the end of a hot day. TheMoon rises above an asphalt road still warm from the afternoons baking.The faint, glowing disk wavers and dances in the warm rising air. Yourimpression of the Moon might be compared to the way astronomers seeMars. Mars is never closer to Earth than about 35 million miles, and thatonly abou t every 15 years. At opposition (th e Sun and Mar s a re opposite,Ea rt h and Mars a dja cen t), which occurs every 25 months, it may be asf a r a s 62 million miles, as it was on March 5, 1965. And our atmosphereis always in th e way.

Two and a half centuries after Galileo had been barely able to distin-guish the disk of Mars in the fi rst astronomical telescope, Guido Schiaparelli,working a t Milan Observatory in 1877, noted surface features which havebeen argued about ever since. He called them ca~zali-canals or chan-nels-because they were da rk and seemed to reach across the lands fro msea to sea. Thus began a great i nternational dispute which was to makeMar s famous to the public and somewhat infamous among astronomers.

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M a r s 1777 ( H e m c h e l )


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M a r s , A u g u s t 1,956 ( M t . Wilsoti,o iawg c l i g h t )

Sc h iapawl l i s wiap (1877-88)

Not everyone saw the canals to which Schiaparelli, and then anAmerican , Percival Lowell, referr ed. Lowell was convinced of the implica-tions of the word canal ; he founded an observatory, whose contributionsto science would include the discovery of Pluto, but whose early activitycentered on Mart ian inland waterways. Lowells maps showed wha tdeVaucouleurs describes as a veri table cobweb of cana ls ( 400 in 1900,almost 700 by 1909-including parallel (spare channels) . His books, M a r sa?idI t s Canal s and M a m as t h c A b o d e of Life (published in 1906 and 1908,respectively), with speculations about irrigation from the polar caps, ledto a considerable reaction. A popular idea was to attempt to communi-cate with the Martians by digging a canal in the shape of a huge righttriangle in th e Sa hara, wirelesfi communication being, of course, impossibleover such a distance. Most astronomers saw th e other side of the question.(Nobody has ever seen a true Martian canal, wrote one eminent observerafter prolonged study through a powerful instrument. Others comparedthe drawings of different observers made on the same night, referredcharitably to optical illusion, or suggested that the smaller the telescope,the more canals were claimed.

Photographic advances have resolved some differences by apparentlyresolving some canal-like features, but even photographs are subject tointerpretation : there are still partisans, pro and con.


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Interestingly, there do not seem to be any mountains of Rocky orHimalayan proportions on Mars : gradual slopes, modest east-west chains,o r small prominences could not be spotted from Ea rt h, and no shadows-thetell-tale index of the luna r mountains-have been resolved.

The Thin AirStudie s of Mars atmosphere indicate th at it probably consists of nitro-

gen, argon, some carbon dioxide, a trace of wa ter vapor, and a spec tro-scopically undetectable amount of oxygen ( if any) .This sta temen t is basedon well-founded speculation for the nitrogen and argon, and extremelyskillful spectroscopy fo r the rest.

The spectroscope is an instru ment used to analyze a beam of light forthe chemical constituents of t he luminous gas in which i t originates (suchas a flame or the Sun) or the partly opaque gas through which it shines(such as the atmosphere of Venus or Mar s). Its output is a wide photo-gr ap h of the color spec trum laced with a pat tern of parallel bright (lumi-nous) or da rk (absorption) lines.

Carbon dioxide was detected first on the planet Venus. Nitrogen lacksa str ong spectrographic sign ature of absorption lines in visible light and,in addition , Ear ths nitrogen-rich ai r would mask the weaker indicationsfro m anothe r planet. The same problem dogged the hunters fo r oxygen andwat er vapor on M ars af ter Gera rd Kuipers subsequent discovery of carbondioxide on Mars. They calculated that if they shot the spectrogram whenMars and Earth were moving apart or together at the maximum speed,the doppler effect would shif t the indications of Martian oxygen and w atervapor out fro m under those of t he terr est rial atmosphere. The latt er refine-ment led at last to the conclusion tha t wa ter vapor was barely in evidenceand oxygen w as too spar se to detect. Spectral evidence th at the polar capswere water ice had been obtained in 1948.

The atmosphe ric pressure, which corresponds to the weight of theatmosphere per unit area a t the surface, is a function (given Mars gravi-tational field) of the total amount and kind of gases making it up. It canbe measured only by very indir ect means from E arth , related to the effectsof the atmos phere on light. Some of t he methods have involved studyin gthe diffusion of various colors, the polarization, the variation of color acrossthe disk, and the brightness of surfa ce spots as they rotate from one limbof the disk to an other a nd ar e seen through different slant thicknesses ofthe Martian air.

A very recent approach to the question of Martian atmospheric pres-sure, which may provide the most accurate estimate, is based on thetool used to examine the composition of the atmosphere. The spectralabsorption lines from the carbon dioxide on Mars are broadened or smeared,according t o the theory, as a func tion of the gas pressure . Comparisonwith carbon dioxide spectra obtained a t various pressures in the laboratorygives, af te r much analysis, t he press ure value. Kaplan, Munch, and Spinrad,

M a r t i a n a t m o sp h e r i c h a z e, S e p -t e m b e r 1 9 5 6 ( M t . W i l s o n , o ra n g el i g h t )

5SPECTROSCOPEPHOTOGRAPH ICPLATE

DIFFRACTION ,:-\G R A T I N G / \!--YSLIT-c -a

FROM TELESCOPE


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who applied thi s method to Mars , produced a value of 25 millibars, with anunce rta inty of 15 millibars. Subsequent refinement raised this value slightly.Eart h's standard sea-level pressu re is jus t over 1013 millibars. Values esti-mated by othe r methods, with much gr eate r uncertainties, yield a possiblerange from 20 0 millibars down to about 14 (corresponding to the pre ssure4% to 18 miles above Eart h's surf ace) .

With Mars' smaller gravitational field, the atmosphere is not huggedcIvuL L.v Lire pLllcL b u l l a ~ t :s is Earth's. Yeiiow ciouds, presumed t o befine dust swept up off the deserts, ar e frequently observed at altitudes fro m3 to 6 miles, and occasionally much higher. The clouds have been observedto move as fast as 85 miles per hour, though more often in th e 20- to 30-mile-per-hour range. Wind velocities necessary to pick up the dust mayrange as high as 125 miles p er hour at 300 feet altitude.

n.l,,crn tn +h --,L)- -....I-

30% hours

1967 oppositionMars and it s m o o n s Mars receives from 36%to 52% as much solar

radiation as Earth does.Its equatorial plane is 24-2 5"from its orbital plane(23%' for Earth).

55.8 mil l ion miles

1973 opposition40.4 million miles

Oppositions 1960-1 97 5


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The Mars PatrolMars, as we have seen, is a tough nut to crack. The speculations asso-ciated with t he question of canals doubtless helped to t ur n astronomers

away from Mars, and planetary investigation in general remained a back-yard branch of astronomy fo r some years. The age of space explorationhelped in the gro wth of the new science of planetology, which lures geolo-gists, biologists, meteorologists, chemists, and engineers into the field ofastronomy, and, during t he last five years has wrought a great renaissancein planeta ry studies, particularly of the Moon, Venus, and Mars.

In 1963 th e Inte rnatio nal Astronomical Union's planetary commissionestablished planetary data centers at Meudon in France and at Flagstaff,Arizona. Observatories in the U.S.A., J apan, USSR, South Africa, France,an d many othe r nations contribute to this program of collecting directphotographs of Mars and other planets. The 1965 Mars opposition will addconsiderably to t he collection. JPL's Table Mountain Observatory and othe rnearby facilities are being used in a special effort in conjunction withMariner. In addition, here and abroad, spectrographic searches fo r newand supplementary information about the surface and atmospheric com-position and properties a re being carried out. Thus, Mariner is not alonein investigating Mars.

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THE SPACECRAFT

When the Mariner Mars 1964 Project was authorized by the NationalAeronautics and Space Administration in late 1962, it was recognized astasks a re characteristic of most aspects of space exploration in its presentdawn age. The distances, forces, and hazards of interplanetary space a rehuge; though our knowledge and technical skill are growing rapidly, theunknown aspects remain extensive.

Mariner's Venus 1962 mission, then ju st successfully concluding, gaveencouragement and contributed vital knowledge and experience to th e M arsmission, bu t th e scale of t he problem was larg er in all aspects. It was tothe successful Mariner Venus team t ha t the new problem w as presented.

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I

Mariners PedigreeThe Mariner Mars system would be the first of its kind, but not th e first

of its family. The dynasty was founded in lat e 1958 and 1959 , when NASAand JPL worked out a linked series of unmanned lunar an d pIanetarymissions which would advance the technology of space explorat ion whileaccumulating basic and practical knowledge about the Moon, the planets,and th e solar system.

A three-stage launch-vehicle system would have been needed, but thedevelopment of restar table second-stage rockets (which in effect made twostages out of one) made this unnecessary. Atlas/Agena was to be the launchvehicle for Ranger, the first. lunar member of the s eries ; early Marine rplanetary and t he Surveyor luna r spacecraft developments were first asso-ciated with AtlaUCentaur, a higher-performance system then being de-signed. Subsequent schedule changes, together with advancements in Agenaand spacecraf t technology, necessitated and made possible th e quick devel-opment of an Atlas/Agena-boosted, lightweight planeta ry spacecraf t andits successful use in t he Mari ner I1 mission to Venus.

Now the same switch was suggested for t he Mars mission: ma rry thebest elements of the Ranger-Mariner II-Atlas/Agena system with theheavy Mars-spacecraft development and launch a Mars mission in 1964 .There were less than two years to do the job, and a rigid deadline wasimposed by the Mars launch opportunity. The Venus mission had beendeveloped in less than a year. It could be done-just barely .

R a n g e r I ( 1 9 6 1 )

On a larger ScaleThe energy required to ship a pound of payload to Mars in 1964/65 is

actually a little less than t ha t which was needed to send it to Venus in 1962 .The slightly lower energy requirement, however, turned out to be ju st aboutthe only aspect of Mariner Mars t hat wasnt twice or three times as diffi-cult as the earlier mission.

Consider service life, fo r example. New cars ar e guaranteed f or yearsor tens of thousands of miles, if serviced regularly. TV sets are guaran-teed for a year (except the tubes ). A fine watch is guaranteed practicallyforever-just send it back to the factory. However, you cannot send aspacecraft back to the factory, or adjust the valves, or check the tubes,when its a hundred million miles out in space, and still going.

Mariner I1 had had to operate for about 2500 hours on its flight toVenus ; Mariner IV had t o be designed fo r 6000 to 7000 hours of flight life,on the way to Mars, at th e planet, and beyond.

Then there was electrical power. Mariner Mars would need only a little-less than 200 wat ts- but it must come fro m sunlight, whose powerdecreases as you go away from the Sun. Mariner I1 had one solar panelpartly disabled enroute to Venus but dr ew near ly as much power from the


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undamaged one at Venus as it had received from both panels near Earth.Going out from E ar th to Mars, the solar power decreases instead of in-creasing. Mariner Mars must have more than twice the solar-panel areaof its predecessor-70 square feet as aga ins t 27.

Considering the environment through which the spacecraft mu st travel,we again see a sh arp difference fro m any mission attempted before. Mar inerI1 flew toward th e Sun, braving increas ing solar radiation, which helpedwi th the power problem but aggrava ted the temperature-control problem.Mariner I1 had become hotter and hotter on the way to Venus; MarinerMars would become colder on its journey.

Beyond Mars, where one might expect to find another planet, is theasteroid belt, consisting of thousands of planetoids in independent solarorbits . Accordingly, astronomers believed t ha t the meteoritic intens itymigh t be expected to increase in the direction of this belt. In addition, theMars path lay across several cometary meteor streams. Mariner mightbe expected, then, to run into more space dust than had previously beenexperienced. Mariner 11s detector had recorded only two impacts in itsflight, while Mar iner IV has indicated well over 100 in the first five monthsof its journey. Since the total area of the spacecraft i s about 200 timesth at of the small dust detectors, the detectors record only a fract ion of theparticles actually hitting the vehicle.

In addition to the increased flight time and the change of direction,another inevitable dimension put a strain on the Mariner Mars mission:sheer distance. At Mariner 11s maximum 54 million miles, radio wavestook nearly 5 minutes to come back to E ar th ;communication with t he Marsspacecraft would be delayed about thr ee times as long. More important, thecommunications system would have to be be tt er . . .nine times better, sinceradio strength decreases as the square of increasing distance. Both theground and flight units would have to be improved.

Mariner IV

9

The Weight WatchersMariners planners early decided they would need more spacecraft

weight than the 450 pounds that the Atlas/Agena B vehicle had launchedto Venus in 1962. A new version of the second stage of the launch vehicle,Agena D, basically a collection of improvements from hetter prope!!sr,tutiiization t o lightweight mate rials, added up to a n 80-pound weight bonusfor t he spacecraft. The energy difference between Venus 1962 and Mars1964 contributed 40-odd pounds. Thus, the spacecraft could weigh about575 pounds ; something could be done with that.

Question: How do you increase the scientific experiments, more thandouble the solar power, get nine times as much radio power, and guaranteea flight time two-and-a-half times as long, all within a mere 575 pounds?Answer: Get tough with the design.


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A b o v e : S p a c e c r a f t u p p e r d e c k iscovered with b l ack - suv f aced t hey -m a l s h i e l d . I o n i z a t io n c h a m b e r i sm o u n t e d on l o w - g ai n a n t e n n a t u b e( t o p of pic t icre) ; be low ell ipt ical h i g h - g a i n a n t e n n a , a t l e f t , a r et r a p p e d - r a d i a t i o n , cosni c- d u s ,a n d p l a s m a - p r o b e s e ns o rs . Pri-m a r y s u n s e n so r i s n e a r b o t to m ofp i c ti c r e ; f o u r d i s k s a t l o w er r i g h ta r e a b s o r p t i v i t y s t a n d a r d s f o r .t h e r m a l e n g i n e e r i n g t e s t . B e l o w :S p a c e c r a f t l o w e r d e c k h a s a l u m i -n i z e d t h e r m a l s h i e l d , w i t h C a n o p u ssensor at l e f t , TV s c a n p l a t f o r wp r o t r u d i n g in c e n t e r .

Fo r example, the bones of b irds an d the I-beams of gi rde rs indicate tha tnatu re and man have found ways to get more streng th fo r less str ucturalweight. Mariners struct ural designers went furt her ; hey nearly eliminatedthe skeletal structure. Mariners forebe ars were built around a hexagonalskeleton belted with electronic-equipment packages and crowned with atower. Fo r Mariner Mars the packages became the stru ctur al foundations,the tower a slim waveguide.

Eight shallow trays, deriving pa rt of their stre ngth from thei r close-packed contents, were joined in a ring ; electrical cables were contained intwo smaller concentric rings. A thermal shield was spread across the topand bottom of the larger r ing. The fixed elliptical-dish ante nna , solar-paneldampers, and th e waveguide, which ended in a small omnidirectional low-gain antenna, were mounted topside; the Canopus sensor and planetaryscanners were on th e shady-side deck. Between decks, t he attitude-controlgas bottles and the fuel tank fo r the deep-space rocket motor (mounted ina shear plate replacing one unit of the octagonal ring) were stowed. Thespacecraft battery, too big for a shallow tray, also protruded i nto the spacebetween th e decks.

Mariners fou r solar panels were conventional in appearance, bu t radicalin construction. Corrugation-stiffened sheet-metal floor st ructu res weresupported by stamped-aluminum-sheet-metal spars about the gauge ofkitchen aluminum foil. The panel s truc tur es weighed only one-half poundper square foot.

Controlled TemperaturesAn object in space will be warmed by the rays of the Sun, and cooled

by its own radiation to the black sky around it , at a rat e dependent on itstemperature. It will thus eventually stabilize at a temperature primarilydependent on its distance from the Sun: near Earth it would be about125F warmer than a t Mars distance. Its sun lit side, if it is not rotating,might be several hundred degrees hotter than the shady side.

Mariner couldnt tolerate such conditions. It s electronic components havecertain temperature limits within which they will operate properly, evenas we humans do . Their temperatures must be controlled.The isolation and vacuum of outer space rule out contact conduction andconvection ; the only controllable heat-transfer factor affecting the space-craft is surfac e radiation. The surface s, then, must be controlled. If paintedblack, they will radiate or absorb ; f polished like mirrors, they will reflectand neither absorb nor radiate.

Explorer, the very first United Stat es spacecraft, had been painted withblack and white stripes, the area of black s tripes (ra diat ing surface) cal-culated to maintain the necessary temperature in Earth orbit. A moreadvanced development, a h eat blanket of layers of very thin aluminized-Mylar plastic, gave Mariner Mars good, yet lightweight, insulation coverage.


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M a g n e t o m e t e r ( 1 % l b )

L o w - g a i n a n t e n n a

I o n i z a t i o n c h a m b e r (2% l b )

H i g h - g a i n a n t e n n a

T h e r m a l c o n tr o l l o u v er s ( s i x s e t s ,1 1 p a i r s o f l o u v e r s p e r s e t , a b o u t

TV s c a n p l a t f o r m a n d c a m e r a

e r e c o r d e r a n d r a d i o e q u i p m e n tl a ) . R a d i o r e c e i v e r , t r a n s p o n -a t a e n c o d e r a n d c o m m a n d s u b -s y s t e m (4 1 l b ) : 9800 e le c t r o n icc o m p o n e n t s , i n c l u d i n g t r a n s i s t o r s ,d io d e s , c a p a c i to r s , e t c .

t r o n i c s (39 l b ) : a t t i t u d e c o n t r o l

s p a c e c r a f t . cc&S c o n t a i n s 703S c i e n t i f i c e q u i p m e n t ( p l ap r o b e , c o s m i c - r a y t e l e s c o p e ,

P r o p u l s i o n s u b s y s t e m ( 51 l b ) :5 0 . 7 - lb -th r u s t ? n o n o p r o p e l la n t h y -d r a z i n e e n g i n e c a p a bl e of t w o s ep -a r a t e t h r u s t p e ri o d s. L S o l a r p a n e l ( a b o u t 21 lb e a c h ) :

7056 s o l a r c e l l s p e r p a n e l .

1


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-M a r i n e r M a r s t e m p e r a t w e m o de lp r e p a r i n g f o r tes t in J P L s 2.5-foots p a c e simiclator.

SCIENCE DATA , TELEMETRY RADIOINSTRUMENTS - UTOMATIONSCIENTIFIC

A sophisticated thermal-control device, a set of polished aluminum shut-ters which could open to expose a radiating surface beneath, was testedon one compartment of Mariner I1 in its flight to Venus. The shuttersar e activated by bimetallic strips , like inexpensive dial the rmometers o rthe thermostat in an electric blanket. As the temperature rises, the str ipuncoils, the sh utte rs open, and hea t rad iates away to space. Then, a s the com-par tme nt cools, the s tr ip coils up again , closing the shu tter s to conserve heat.

Thermal-control louvers of this ty pe were designed for six of Mar ine r selectronics tr ay s ; hey would keep the temperature inside between 55 and85F. An aluminized-Mylar shield would protect the sunny upper deckand the shady lower deck; the upper blanket was surfaced with blackDacron. The backs of the solar panels, which absorb a great deal of solarheat in t he process of tap ping th e Su n for photoelectric power, were black-ened to re-radiate heat and keep the solar cells within th eir opera ting rangeof 10 to 130F.Most other exposed metallic surf ace s were polished ;exposedcables were wrapped with fiberglass or aluminized-Mylar tape. Th e fixedhigh-gain antenna dish was painted green: it would cool from its upperoperating limit near Ea rth to about room temperature a t Mars.

Put Them All TogetherSome philosopher has r emarked t hat you cant get from 1 + 1 to 2

jus t by understanding the 1. Systems engineering might be likened toth e + sign. It sta rted with a job to be done. Each of the Sy stems of theMariner Mars 1964 Project (Launc h Vehicle, Spacecraft , Deep Space Net,and Space Flight Operations) was divided into subsystems or units.

In the case of the Mariner Mars spacecraft, the functional units ar e:structure, radio, command, telemetry, central computer and sequencer,power, at tit ude control, pyrotechnic-actuator control, therma l control,cabling, and postinjection propulsion ; these make up what is often calledthe spacecraft bus. The scientific-experiment passenger units are

I +CC&S COMMANDTTlTUDECONTROLROPULSION

r - - - - - vAS JETSSTRUCTURE, CABLES,1 ANDPACKAGING POWER C0NTR0L


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. .

science data au tomat ion, planetary scan system, television a nd i ts recorder,and six interplanetary-environment instruments : magnetometer, plasmaprobe, ionization chamber, trapped-radiation and cosmic-dust detectors, andcosmic-ray telescope.

All in all, near ly 140,000 pa rts were carefully screened and pu t together,inspected, subsystem-tested and system-tested, and re-tested. All membersof the M ariner t eam labored long and hard in the development and fab ri-cation of the components and th e assemblies they constitute ;Mariner IV isthe sum of these parts.

Outer Space on EarthThough space exploration serves experimental science, it is not itself

purely experimenta l ; his is evidenced by the ais tas te with which spacecraftdevelopers brush off such labels as cut an d try, file to fit, shoot andhope. With the exception of extremely long missions such as Mariner IV,most space projects live nine lives on the test bench before they areallowed one life in flight : the emphasis is on performance as predicted fromtest experience.

Mariner Mars development schedule allowed less than 1000 hours fortesting each flight article for a 6000-hour mission-a tigh t schedule fo r alarge and exacting job.

A Mariner Mars temperatu re-control model-a full-scale spacecraftduplicating the heat-generating and heat-transferring properties designedinto the flight articles-was built and tested as long as possible in JPLs%-foot space simulator, which was equipped to approximate the black, cold

A b o v e : Ma r in e r s o n - b o a r d r o c k e tmotorwasfired in aspace-simltlatort e s t of s y s t e m i n t e r a c t i o n ( p r o o f -t e s t m o d e l ) . L e f t : M a r i n e r s s o l arp a n e ls p o w e r t h e s p a c e c r a f t a t t h eb o t t o m o f E a r t h s a t m o s p h e r e in au n i q u e t e s t .

13


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S y s t e m t e s t i n g i n JPLs Spacecraf t Assembly Fac i l i t y .

vacuum of space and the blazing radiance of t he Sun. Correction factorslearned from the flight of Mar ine r Venus had been engineered in to th is tes tdevice to achieve the best possible Earth-surface reproduction of spaceconditions.

Before the flight space craft were built, a pro totype or proof-test modelwas put together. Serving as a final test bed in subsystem development,as well as the initial system-test vehicle, this spacecraft was at one endof the development loop : modifications found necessary in proof tes tingwere themselves retested on th e same cra ft. A t the end of the design evolu-tion and aft er 1100 hours of system test, the proof-test model had evolvedinto a functional duplicate of the flight space cra ft; they, in tur n, werespared the rigors of prolonged design evaluation by the existence ofthe tes t spacecraft which could never fly a mission. The proof-test space-cra ft was also used fo r inter-system testing, verify ing compatibility of thespacecraft with ground equipment. It then. supported both flight missionsby simulating observed flight situations so that they could be studied atclose range.


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r .

MARINER LEAVES PORT

Three Mariner Mars spacecraft began the journey to the planet Marsfrom a canyon north of Pasadena, California, a t the Jet Propulsion Labora-tory, where they had been designed, assembled, and tested f or months. Twoof t he three would fly; the thir d was a spare. They were par tly disassem-bled, carefully packed, and loaded on moving vans. On September 11, 1964,af ter a four-day journey, the last van reached the Air Force Eas tern TestRange, Cape Kennedy, Florida.

Here each spacecraft was carefully inspected and retested. There werespare par ts for th e individual plug-in units of the Mariner spacecraft. Thecalendar and the high quality standa rds would allow no tinkering or repairin the conventional sense : replacement of modules, if necessary, shouldsolve faulty-parts problems.

At the Cape, two 100-foot-high AtlasIAgena D ockets were waiting,each standing in its own launch complex. The engineers could select eitherone for th e first launch, and could launch the two missions as close as tw odays apart if desired.

Spacecraft and launch vehicles were given separate system tests, assur-ing tha t each would function in every phase of its role in the mission.The mechanical, electrical, and radio compatibility of spacecraft, vehicle,ground equipment, and tracking system were tested. Finally, at the begin-ning of November, the Mariner I11 spacecraft and launch vehicle stood onthe pad, going through a dress rehearsal. The actual Mars launch periodopened on November 4 and lasted for only about a month.

In e r planet ary Naviga tionUnlike a conventional aircraft, a spacecraft spends most of its time

falling. The first few minutes of the flight, and then, a day or a week later,a few more seconds, are all the powered flight it ever has. Accordingly, itscaptain must plot his course before the ship leaves port; the charting ismore gunnery than navigation.Eve ry planet of the Sun travels a n ellipse, a closed curve which resem-h!es 8 circle stretched nfi t ir, o ~ eimef is inn. The S u n i s a t on e fociis of theellipse, not a t the geometric cen ter. As the plane t comes closer to th e Sun,it speeds up ; as it goes outward, it slows.An interplanetary spacecraft is as subject to these laws as are theplanets. It mu st be given th e correct velocity-speed and direction-sotha t i t will arri ve at the intersection of its orbit with that of the planetjust as the planet gets there. Most of the necessary velocity can be pickedup from Earth-which orbit s the Sun at an average of 66,600 miles perhour-but th e rest mus t be provided by the booster vehicles.

Nose f a i r i n g 13 5 M t d i a m e t e rWeight about 350 I spacecraft inside

Atlas D main s

bout 130 on s15


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The velocity required to reach Mar s is lowest, and within reach ofpresent-day rocket power, when the Earth launch and the Mars arrivaloccur almost on opposite sides of the Sun. Such conditions prevail only f ora few weeks every 25 months, limiting the practical launch periods tothose times. The absolute minimum velocity would be needed when theinjection point, the Sun, and the arrival point form a straight line but,because of t he ti lt of Mars orbi t plane relative to Earth s, thi s coincidencehardly ever happens.Xear Earth, the entry point of the Earth-to-Mars ellipse is relativelyfixed in space. Since the Ear th tur ns under th is point, it is within the s afefiring angle (24 degrees south from due East) for Cape Kennedy for onlya few hours per day; as the injection point sweeps from East to West,the rocket must be guided to meet it. Using the Atlas/Agena D, the tech-nique is to launch in to Ear th orbit, coast until t he injection zone is almostreached, and then resta rt the Agena to trans fer fr om E ar th or bit to solarorbit.

Several thousand Marine r M ars traj ectorie s were calculated, accom-modating the changing relationship of the planets day by day, and th echanging angles near Ea rt h from minu te to minute. They took into accountnot only Eart h, Su n, and Mars, but the pe rturbing effects of the Moon andthe planet Jup iter , and the pressu re of light fr om the Sun. The latt er would,over the course of t he mission, push Mariner about 10,000 miles away fr omthe Sun.

Mariner 111: Nine HoursMariner I11 was launched tow ard Mars about midday on November 5 .

Minor launch vehicle difficulties encountered on the first days countdownhad been solved to the engineers satisfaction ; the prelaunch countdownwas normal ; the weather was good. The tall, snub-nosed space vehicle rosefrom Launch Complex 13 with an a ir of confidence.

Nevertheless, within minutes the mission was doomed, though it tooknearly nine hours for it to die. The cylindrical fiberglass-honeycomb nosefair ing , or shield, designed t o protect the spacecraft during the smashingthrust up through the atmosphere and then to be jettisoned, failed duringthe climb through the air. When the time came, it could not be ejected.

Ear ly indications of trouble came at the end of powered flight. Becauseof the drag of the nose fairing, the velocity was too low. The spacecraftwould not reach its target.

About 5% minutes later, after spacecraft and Agena had separated, thespacecraft unsuccessfully attempted to deploy its solar panels. Withoutsolar panels, there was no solar power. Studying the telemetry fromMariner, building UP piece-by-piece a pi ctur e of th e trouble, and conduct-ing failure-mode tests on the proof-test spacecraft, the operations teams


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commanded Mariner I11 to conserve power by switching off the scientificequipment, repeatedly commanded panel deployment, and were in theprocess of igniti ng the spacecraft rocket motor in an attempt t o removethe nose shield by force when, 8 hours 43 minutes after launch, the space-cr af t battery ra n out of power.

Mariners team wasted no time. The problem was identified, studied,an d solved. A quick, thorough te st prog ram detailed and verified the condi-tions which had caused the failure. Experiments were conducted wi thfiberglass nose shields, and a new all-metal shield was designed, developed,and built in record time by the Launch Vehicle team. A little over threeweeks after the launch of Mariner 111, another Mariner/Atlas/Agenastood ready on the pad, with the new metal nose shield installed.

Mariner IV: A Good SendoffOn November 27, th e first countdown of the new Mariner was inter-

rupted by radio difficulties. On Saturday, November 28, at 1:37 in themorning, EST, the launch countdown began for the Atlas and Agena ; thespacecraft was activated at 4 :32 a.m. Launch operations crews wentthro ugh t he long list, establish ing and checking communications, forecas t-ing the flight weather, monitor ing spacecraf t and launch vehicle condition,filling the Agena oxidizer tank, and switching equipment into a state ofreadiness. At 9 :22 a.m. EST, the clock had counted to zero without a hit ch;the repor t was clear to launch. Liftoff occurred 1.309 seconds lat er.

As i t rose, the space vehicle rolled to an azimuth of 91.4 degrees, jus tSouth of due East, and began to pitch over from its vertical ascent. Shed-ding its two massive booster engines, Atlas carried on with the single sus-tainer. A ground computer fed guidance commands to the vehicle untilthe sustainer engine was shut down and the velocity properly adj usted w ithtwo small rocket engines. Then the huge, empty Atlas was detached andAgena took over. Before the Agena engine was started, the aerodynamicnose cover had to be jettisoned. As designed, i t came off easily.

Agenas 16,000-pound-thrust engine couldnt lift the weight of th eAgena vehicle and the encapsulated Mariner spacecraft if they were onthe ground. Bu t st art ing a t an altitude of 100 nautical miles and a velocitynf 13,nOn miles per hour, it could and did thrus t Mariner to orbi tal velocity,about 17,500 miles per hour. The Agena engine then shut off, and thevehicle coasted for almost 41 minutes. Swinging around Ea rt h to bear onits target, Agena flamed into action again. When Agena shut down forgood, th e spacecra ft was traveling a t 25,598 miles pe r hour along a pathth at led within 150,000 miles of Mars. The application of one-fifth of t hespacecraft on-board propulsion power would bring that path within thedesired tar ge t zone, between 4000 and 8000 miles above th e planets sur face.

Launch operations were described as nominal; i t was a good shot.

17


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2

3

1

6 7


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4 5

h

12

A t t h e C a p e , t w o f l i g h t s p a c e c r a f t a n d as p a r e w e r e a s s em b l e d a n d t e s t ed ( 1 ) . P r e s i -d e n t L y n d o n B. J o h n s o n ( 2 ) i n s p e c t e d t h es p a c e c r a f t d ur i n g a s s e m b l y ; t h e n (3) M a r i -n e r IV w a s i n s t a ll e d in i t s n o s e f a i r i n g , r e a d yf o r t h e l a u n c h ve h ic l e. M e a n w h i l e, t h e A g e n aD v e h ic l e w a s m a t e d t o t h e A t l a s D b o o s te r( 4 ) . T h e n t h e e n c a ps u la t ed s p a c e c ra f t w a sm o u n t e d ( 5 ) o n t h e l az cn c h v e h i c l e ; t h ea s s e mb le d s p a c e v e h ic le ( 6 ) w a s t es t ed t h o r -o i i g h ly , w h i l e J P L e n g i n e e r s in t h e s p a c e c r a f tb u i l d in g m o n i t o r ed t h e p e r f o r m a n c e (7). T h eM a r i n e r IV l a u n c h (8-12) w a s c o n t r o ll e df ,-om t h e s p a c e c r a f t m i s s io n d i r e c to r s a r e a( 13 ) a n d th e la u n c h c o mp le x b lo c k h o u s e (14) .

1 3

1 1

14


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IN-FLIGHT EVENTS

A minute and a half aft er entering the path to Mars, Mariner and Agenapassed into Earths shadow for a period of almost 12 minutes. There, i nthe dark, spacecraft and Agena separated. A three-minute timer wasstarted, and: simiiltqnen~?s!y, b c spacecraft radio power was switched upand the interplanetary scientific instruments were turned on. When thethree-minute timer ran out, electric current was applied across the solar-panel pin-puller squibs.

Mar i ner s four s o l a r p a n e l s a r e folded fo r launch.

A squib is a small, electrically fired explosive charge attached to a cylinder-piston arrangement, enabling a one-stroke internal-dombustionengine to open or close a bolt or valve. These mechanisms would be usedlater to tur n the propulsion system on and off and to release the scanningplatform carrying the TV camera. Eight pair s of squibs (they a re usuallymounted in pairs for increased reliability) were mounted on the spider-like legs which held up and steadied the four solar panels during launch.Now they fired, pulling the pins and releasing the panels.

Power From the SunUnder spr ing tension, the panels hinged away to the deployed position.

At the end of each opening panel, a silver fan unfolded and spread. Thesefa ns ar e solar pressure vanes, a new attitude-control tri m device in a firstflight tes t ; hey were designed to balance th e spa cecraft against t he endlesspressure of sunlight, saving attitude-control-jet gas and permit ting a longerstable flight.

Now the spacecraft came back into the sunlight, and, the attitude-control system having already been switched into a Sun-seeking operationby the central computer and sequencer, Mariner turned toward the Sun.

Usually called CC&S, a c entral computer a nd sequencer serves as com-bination brain a nd alarm clock fo r the Ranger-Mariner family. It providesthe master synchronization f or spacecra ft operations, the rhythm for telem-etry transmission and command interpretation, and a number of set com-


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mands (such as Sun search, st ar search, and midcourse maneuver), andconducts complex maneuvers in accordance with instructions sent fromEarth.Searching for the Sun consists of placing the pitch and yaw controlsystems under the command of the Sun sensors. The spacecraft is trea tedas though it were a ship o r ai rc ra ft traveling in the direction in which thesolar panels face : yawing moves the prow o r nose to the lef t or right, pitch-ing moves it up o r down, and rolling spins the ship around. Mariner leftthis mode of travel behind with the launch vehicle, and normally movesalmost at righ t angles to the nose direction, but the names stuck. InMariners cruise mode, pitching or yawing means rotating around one orthe other pair of solar panels, and rolling means turning like a propeller.

There a re S un sensors on Mariners upper and lower decks ; their outputsignals drive control-amplifier chains, which use puffs of nitrogen gas frompaired jets on the tips of the solar panels to tu rn the spacecraft until thepanels face the Sun, and to stop it in that position. This process took12 minutes.

Now Mariners 28,224 solar cells were converting sunlight into 700wa tt s of ra w electrical power, which, in tu rn , was converted to variousforms to ru n the spacecraft and recharge the battery. At Mars distancefro m the Sun, the spacecraft would still generate 300 watts, leaving a goodmargin i n case of solar cell damage in the space environment.

Like a big jewelled windmill, the spacecraft rolled slowly through spacefor the next fifteen hours; the known roll rate was used to calibrate themagnetometer, one of the interplanet ary sensors, so tha t the spacecraftsown magnetic field could be subtracted from the magnetometer readings.

Lock on CanopusImagine a weight suspended from a single long cord : it spins and spins.

A second cord, approximately at right angles, will steady it in a moment. Aline of sigh t on the s ta r Canopus, second brightes t in the sky, and locatednear the ecliptic south pole, was to be Mariners second stabilizing cord.

Mariner Mar s was the first space mission using o r needing a st ar as areference object ; earlier missions, remaining near Earth or travelingto Venus, had sighted on the home planet. But during this flight, Earthwould tr an si t across the face of the Sun, and through much of the flight:+ ..7,..,,l,av u u i u a p p c u in n n n r an 2 ,1 c i ~ L i v c l ~d i i ~rescent . A bright r e f e ~ e n c c GUYCC,at a wide angle away from the Sun, was necessary. Canopus filled therequirements fo r such a reference source.

Mariners Canopus sensor is mounted on the shady side of t he space-craft ring, pointing outward at an angle, so tha t its field of view coversan a rea in the shape of a shallow cone. As the spacecraft moves around theSun, the angle between the Sun line and the Canopus line changes slowly ;one of the tasks of the CC&S is to alter the sensors angle four times dur ingthe flight to keep the star in view.

,TOWARD MARS

2

c-TO

TO CANOPUS[r;< ,\ I


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CANOPUS 1GAMMA-VELA

REGULUS- i wAy2,0jALUtHAMJN

MARKAE41 ROLLSEARCH

- 00 -BRIGHTNESS4

F l i g h t t e l e m e t r y is m o n i t o r e dc l o s e l y be f or e m i dc our s e m ane u v e r .

An electronic logic in the attitude-control system was set to respondto any object more than one-eighth as brig ht as Canopus. IncludingCanopus, there were seven such objects visible to the sensor as Marinerswung around in the search mode; it was no surprise when the systemacquired one of the other six. The engineers had prep ared brightness chart s,corresponding to s ta r maps of t he ribbon of sky the star tracker wouldinspect, and the stars were recognized as they came around. It took moret ,hm a day of star-hopping to find Canopus.

Trajectory AdjustmentA lunar or planetary mission has too great a range and too small a

tar get to be accurately guided from the brief initial powered flight. Th rus tmust be applied later, in what has come to be called the midcourse cor-rection maneuver-a double misnomer, in th at it occurs earlie r tha n themidpoint of the flight, and, rat her than correcting a mistake, increases thepossible accuracy. All members of the Ranger-Marine r fami ly used essen-tially the same type of small rocket engine to apply this thrust. MarinerIVs propulsion system was modified so that it could be used twice if neces-sary, and its thrust was calibrated so accurately that the resulting changeof velocity could be metered by the bu rning time alone.

After about a week of tracking to determine the flight path and Marsarrival time, the thrust maneuver was scheduled for December 4. Allthe necessary ground commands had been received by the spacecraft, whenit suddenly lost lock with Canopus, though Sun lock was not disturbed.


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Since the spacec raf t had no baseline fro m which to orient its rocket motor,the maneuver was postponed with anot her ground command until Canopuslock could be re-established.It was theorized that a dust particle of pin-point size, floating a fewfeet from the Canopus sensor and shining fiercely in the sunlight, mighthave so increased th e brightness registered in the attitude-control systemth at the spacecraft released its lock on Canopus and began t o track thedus t particle. As the par ticle dr ifted out of the field of view of the sensor,the spacecraft was left in a star-searching mode. After several days ofobservation - he phenomenon repeated itself a number of times- heexcessive-brightness reac tion was removed by ground command. The reac-tion had been intended to prevent Earth-lock, and Earth was moving wellout of the way.

On December 5 , the thrust maneuver was successfully carried out.Three quantitative commands from Earth had the CC&S store in its elec-tronic memory the dimensions of the required maneuver, which were anegative pitch tu rn of 39.16 degrees, a positive roll turn of 156.08 degrees,an d a thr us tin g time of 20.07 seconds. Then thr ee direct commands toldthe spacecra ft to cock the system, tak e off the electrical safety catch, andignite the engine. Since the motor was initially pointed almost along the

Ldirection of flight, the tur ns aimed it back in the general direction of Ea r thbut high above th e plane of the orbit. The pitch and roll were performedwith better than 1 per cent accuracy, the velocity change with about 2%per cent accuracy. As planned, the angle of flight was changed less than% degree, and the velocity was increased a little more than 37 miles perhour. Mariner was headed straight for its target.

M idcourse m o t o r

23

21- me z i v e r successfully c o m p l e t e d !


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.

LONG-DISTANCE COMMUNICATION

A fundamental characteristic of the Mariner class of mission is th ephysical separation of t he spacecraft pe rforming the flight fro m the oper-ato rs who conduct it. Uniuue to Mariner IV is the extent of t he sepa ratio n-up to 150 million miles. T his gr eat distance imposes, a t encounter, a com-munications delay of about 1219$ minutes each way. In spite of t he delay,the spacecraft must be able to maneuver, to switch from one operationalsequence or equipment chain to another, and to interrupt o r cancel anoperation on command from its crew on Earth. Furthermore, details ofits operating per formance and condition, its precise position and motion,and the outputs from its scientific equipment mus t be readily and frequentlyavailable to the operating team. This vital function is carried out by thetelecommunications subsystems of the spacec raft and, on the ground, by aworldwide network of track ing station s and a complex of computers, datadisplays, and other equipment.

Keeping in TouchSt ar tin g before liftoff a t the Cape and throug hout it s flight mission,

Mariner I V has been an d will be sending a steady st ream of informationback to Ea rth . Its radio, put ting out about 10 wat ts of power a t about 2300megacycles in the S-band, has two transm itti ng amplifiers ( a Mariner-II-type cavity amplifier and a longer-life traveling-wave tube), and twoantennas : a low-gain, omnidirectional broadcast antenna and a high-gain,narrow-beam elliptical reflector dish. Either antenna can be used for com-mand reception as well as transmission ; he dish, whose direction is fixedon the spacecraft, was switched into the transmission link on March 5 ,when the range became extreme f or the omni and the Ea rt h entered thenar row beam of t he reflector.

The 10 watts transmitted by Mariner IV has shrunk to as little as.0000000000000000001 watt (10 1:) watt) as measured at the input tothe receiver. Signal s of such low power call fo r extremely sensit ivereceiving equipment on th e ground. Th e Deep Space Stations, spotted a tabout 120-degree intervals around the globe, are equipped with steerablereflector antennas 85 feet in diameter. The heart of the traveling-wave-mase r receiving amplifier fed by each of these an tenn as is a synthetic rub ycrystal immersed in liquid helium; this radical design keeps the internalor system noise low enough th at the fa int spacecraf t signal can be heard.

The direction or angu lar position of Marin er in its flight is calculatedfro m the pointing angles of th e narrow-beam ground antennas. T he velocity


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of the spacecraft is determined by tracking the radio carrier frequencyvery precisely a nd then measurin g the amount of stretching of the f re-quency due to the doppler effect. The operating frequency is controlledeither by a n oscillator on the spacecraft or, fo r more precise determination,a stable oscillator on the ground, which generates a signal that is trans-mitted to the spacecraf t, multiplied by a known facto r (240/221), amplified,and sent back t o Earth .

Listening Post: EarthIn 1958 and 1959 the first Deep Space Station was constructed in theSouthern California desert near Goldstone Dry Lake. Its huge 85-foot-

diameter reflector antenn a is mounted like a telescope so that it can tracka spacecraft a t planeta ry distance. This Pioneer Station, modified with t headvances of technology, is in service today, track ing Mariner IV almost 12hours per day. Th ere a re two more stat ions at Goldstone now, capable ofhandling multiple missions (in Feb ruary and March, Ranger and M arinermissions were tracked simultaneously) and carrying out research an ddevelopment in telecommunications.

In Australia there are two stations. The one at Woomera trackedMariner until it was converted to another fr equency t o support two Rangerflights in February and March. A brand-new station a t Tidbinbilla, nea rthe capital city of Canberra, stepped into the breach, and has coveredMariner IV since that time.

The first Deep Space Station to track Mariner IV was the one nearJohannesburg, South Africa. Johannesburg tracked Mariner 10 hours aday until the Range r missions were flown. After the Ranger flights, Johan-nesburg reconverted to the S-band, and Mariner was again in touch withEar th 24 hours a day. A new stat ion being built i n Spain will alleviate suchconflicts in the future,


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LS F O F c o m pu t er s

Space F l i gh t O pera t i ons D i yec t or

S F O F M i s si o n C o nt r o l

The international trac king network is woven together by means of landlines, undersea cables, an d radio links ; at the hub of th e net, in Pasadena,is the Space Flight Operations Facility, whose computers an d data-handlingand control equipment support Mariners crew. Here operations teamsspecializing in the flight path, spacecraft performance, and space sciencemonitor the information received from Mariner IV and translated by thecomputers. Fro m these da ta th e command decisions ar e made. The scientific.Cf+:nW Ll l ab l W , l isinterpretation by the scientists.

concerted into tabdar ani: graphic f o r m fo r analysis am?

Dropping the Lens CoverOne of the major events that took place during Mariners flight was

the removal of the television camera lens cover, originally scheduled forthe latt er pa rt of the mission. Because of the problem with the Canopussensor, the engineers believed that removing the cover might release dustparticles, which, in tur n, might dr ift past the sensor and cause an abnormalreaction. To prevent such an occurrence ju st before encounter, they decidedto play it safe. By conducting the clear-for-action ear lier, closer to Earth,they would ga in more time to absorb and recti fy any possible after-effects.The operation was rescheduled for February 11, during the Goldstonetracking shift. F ir st , a verification series of five commands was taped ,proofread, and sent from Goldstone ; he spacecrafts reaction to each wascarefully monitored before the next was sent. The telemetry mode wasshifted, and power distribution in critical areas was checked. With allsystems g o , the operational series of five commands went off, leaving t helens uncovered, the shutte r closed, and the scan pl atform aimed in t he bestdirection fo r encounter-ready fo r action.

I


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The commands were sent to the spacecraft in the form of binary words,each word consisting of an arrangement of 26 zeroes and ones (b its ). Thecommand signal was superimposed on the radio-f requency c ar rie r ; whenit reached the spacecraft, it was demodulated from the carrier and sentto the particular subsystem for which it was intended. By means of elec-tronic logic circuits, the commands could activate various mechanismsaboard the spacecra ft, and the results could be determined by monitoringthe telemetry signals received back on the Ear th.

Engineering TelemetryMariners signals back to Earth outnumber Earths infrequent wordsof command. Exclusive of scientific data (packaged separate ly by the da ta

automation system for trans mission), M ariner reports almost 90 spacecraftmeasurements : tempe rature s, voltages, currents, pressures, angles, and th elike, described in a seven-bit word each. There are four event counters,which note receipt of commands an d th e passage of time. Up to Januar y 3,the spacecraft chattered away at 33% bits per second; on that date, thera te was slowed down by a f acto r of four, due to the lengthening range toEa rt h (about six million miles) .

The spacecraf t data encoder ga ther s these measurements into decksof ten measurements, sampling each in turn. Most of th e decks aremultiplexed-time-shared, so that they are sampled every tenth, or everyhundredth, or every two-hundredth time rather than each time around.Some measurements, most of them temperatures, which change veryslowly, may be sampled only every 2y hours ;others, more critical or fas ter -changing, come as often as once a minute. These rates are based on theencounter data rate of 81$ bits per second.

Goldstone Contro l

SFOF Space Science A r e a

S p a c e c r a f t A n a l y si s A r e a2


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THE SCIENTIFIC EXPERIMENTS

A b o v e aw d b e l o w : E x p e r i m e x t e r s

Mariner IV carrie s eight scientific experiments, monitored by about twodozen scientists from te n universities and laboratories. The experimentsar e divided into two categories : the in terplanetary experiments, which areperformed throughout the entire journey to Mars ; and t he planetary experi-ments, which are expected to increase our knowledge of the planet. Thescientific package consists both of scientific instruments and of auxiliaryequipment required to process the data.

Interplanetary ExperimentsSix scientific instr ument s were turn ed on a few minutes aft er th e launch

of Mariner last November ; the helium magnetometer, the solar-plasmaprobe, the ionization chamber, the trapped-radiation detector, the cosmic-ray telescope, and the cosmic-dust detector. Fo r the pas t 7 months, theseinstruments have been gathering scientific data about the interplanetarymagnetic field, the cosmic dust found in space, the solar wind, solar flares,and other deep-space phenomena. By the time Mariner reaches Mars, itwill have taken approximately 18 million scientific measurements-enoughto keep scientists busy fo r the next several years.

The interplanetary experiments will be of special interest as Marinerapproaches the vicinity of the planet ; hey may tell us, for instance, whetherMars is surrounded by a magnetic field like the E ar th is, and whether thereare intense radiation belts around the planet like the Van Allen beltsaround Earth .

The plasma probe suffered a component failure in December, 1964,making its readings unintelligible until the telemetry rate change early inJanuary, 1965, made a par tia l recovery possible. Decreasing temp erat ureslowly made the crippled instrument unreadable again by early May.The Geiger tube, one of t wo senso rs in th e ionization-chamber experiment,failed after an apparent overdose of ionizing radiation, and the ex-periment stopped return ing dat a in March.

Planetary ExperimentsAs Mariner IV passes Mars, it will attempt to take 18 to 21 pictures

of the surface. The electrical signal, representing 64 different shades of


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-

black a nd gr ey with a resolution about as good as Earth-based telescopesphotographing the Moon, will be recorded on a 300-foot loop of magnetictape. Each picture will cover an area approximately 120 miles square.The occultation exper iment is the only experiment on Marine r th at doesnot use a special scientific instrument. It relies on the telecommunicationssystem and on the extraordinary accuracy of the flight path. If you imaginebowling a str ike in a bowling alley that reaches from Los Angeles to SanFrancisco, you will have a good idea of the pin-point accuracy of Marinerstrajectory.

About an hour after coming within 5600 miles of the Martian surface,Marine r will seem to disappear behind the planet (as viewed from Ea rt h) ,entering occultation near Mars south pole and emerging near the northpole. As Mariner begins to disappear behind the Martian disk, its radiosignals will pass obliquely through the planets atmosphere and will beattenuated and bent, just as a stick appears to be bent when stuck into apool of water. By measuring th e changes in the characteristics of the radiosignals, scientists hope to learn more about the composition and densityof Mars atmosphere.

Auxiliary Science EquipmentThe science data automation system serves as a control center and d ata

handler fo r th e seven scientific in struments carried by Marine r IV . In thecruise mode, th e science dat a automation system assembles dat a from thesix interplane tary experiments, translate s the information into constant-ra te form, and transm its i t to the d ata encoder, where i t is passed on tothe tran smitter , and eventually to Earth. During the encounter, somescience data will be sent directly to E ar th while the picture data ar e beingrecorded. 29

\

1 2 1 4INCHES


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MARS AND AFTER

In mid-July, Mariner IV reaches its destination, and, bar rin g accidents,it will carry out the complicated and long-awaited planetary sequence. Atclosest approach, it will make the historic flyby traveling at a speed of66,678 miles per hour relative to E ar th or 11,518 miles per hour relative toMars. Some time prior to closest approach, the wide-angle sensor locatedon the scan platform will begin searching fo r the light of Mars. When t heMartian disk comes into view, the scan platform will stop searching andthe wide-angle sensor will begin to track the planet. Then th e large red diskwill come into the field of view of t he narrow-angle sensor, which willtrigger the tape recorder to sta rt recording the television pictures of thesurface. The pictures, taken alternately through red and green filters, willtake about 25 minutes to record.

Several hours after it leaves Mars vicinity, Mariner will slowly playback its tape recording through the dat a encoder, transmitti ng the picturesin digital-bit form to the Ea rt h at the rat e of more than 8 hours per picture.Intervals of engineering telemetry will be sandwiched between pictures.The whole picture-and-telemet ry ser ies will take almost 10 days to send. Theplan is to repeat the series a second time to ensure receiving every bit onEarth ; then Mariner will be ordered back to interplanetary investigation.

Coming so close to Mars will influence Mariners orbit. The currentprediction for the post-Mars orbit is that i t will be longer (i n period andsp an ), less elongated, and more sharply tilted relative to Earth s orbitalplane. Traveling in th is far-flung ellipse between Earth s orb it and t ha t ofMars, Mariner will be a satellite of the Sun forever.

Next autumn, Ear th will pass from the beam of the high-gain antenna.Mariners telemetry will go on transmitting-no one really knows howlong-but we shall not receive its signal. Per ha ps in 1967, when th e space-craft again approaches Earth, we shall hear from Mariner once more.


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Experiment Data

Experimentersescription

TV subsystem: u p t o 21 pictures of Martian surface R. 6. Leighton,* B. C. Murray. and R. P. Sharp, all of CIT,an d R. K. Sloan and R. D. Allen of JPL

E. J. Smith* of JPL,p, J, coleman ~ , f ucLA,L. Davis Jr. of CIT. andHelium magnetometer: planetary and interplanetarymagnet ic f ields D. E . Jones of Brigham Young University and JPL

Solar-plasma probe: quantity rate and energy ofposit ive ion wind H. L. Bridge* and A. Lazarus of MIT, andC. W. Snyder of JPL

Ionization-chamberiparticle-flux detector:corpuscular-radiation dose rate H. V. Neher* of CIT,H. R. Anderson of JPL

Trapped-radiation detector: low-energy solar charged J. A. Van Allen,* L. A. Frank, and S . M. Krimijis, all ofState University of Iowaarticles and planetary radiation belts

31Cosmic-ray telescope: high-energy charged particles J. A. Simpson and J. OGallagher of Un ive rsit y of Chicago

W. M. Alexander,* 0. E. Berg, C. W. McCracken, andL. Secretan, a ll of NASA/GSFC, and 1. L. Bohn, and0.P. Fuchs of Temple University, Philadelphia

Occultation (no instrument): Martian atmosphere asdeduced f rom its ef fect on spacecrafts signaldur ing occultat ion by the planetA. J. Klior e, 0. L. Cain, and G . S . Levy, all of JPL,V. R. Eshelman of Stanford Electronics Laboratory, andF. Drake of Cornell University

*pr incipal invest igator


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. '

Orbit DataEarth Mars Ma rine r 111 Mar iner IVaf te r l aunc h Mar iner IVafter maneuver Mar iner IVaf te r enc ounter

Length of ell ipse, milesPer ihel ion dis tance, mi lesAphelion distance, milesTi l t of ecl ipt ic . degreesPeriod, daysInc l inat ion of roll planePer? e !O!?!O"

(equator) l o orbit plane

195,794,WO91,342 00094,452,000

0036 5

231%'__7 hr 56 man

283,090,MH) 214,000,000128,330,000 92,0130,M)O1Y,760,000 122,000,000

10 51'687 449

24-25" ??? h ? E!" ?

231,100,MM92,180,000346,920,0130

00 852 8900!

239,640,WO92,230,000147,410,000

00 7% '52 9900!

2 5 1 , 5 3 3 . N104,557,000146,976,000

20 58570900n

SUN

EARTH AT ENCOUNTERJULY 14. 1965

MARS AT LAUNCH NOV 28MARS ORBIT

MARINER ORB11

MIDCOURSE MANEUVER DEC 5EARTH AND MARINER AT LAUNCH

EARTH ORBIT

NOV 28

Mariner IV positions at 10-day intervals starting Dec. 1, 1964Straight l ine dis tance. mi Veloc ity . mi lh rDistance traveled Relative to Earth Relative to M iate along t laiectorv. mi From Earth From Mars From Sun- . .

Dec I, 1964 525 782 517.870Dec 11 22 649,177Dec 21Dec 31Jan 10 1965Jan 20Jan 30Feb 9Feb 19March 1March 11March 21M a r c h 3 1Apr i l 10Apr i l 20Apr i l 30Ma y IOMay 20May 30June 9June 19June 29July 9EncounterJuly 14

40,241,57557,574,47174,583,45191,219,961

107,451,878123,261.850138,644,479153,605,290168.155.150182,311,410196,094,740209,528220222,636.480235,445,090247,980,100260,267,760272334,370284,206,150295,909,130307,469,390313,123,300325,741.140

2,203,9953,873,4885,575,0797,450,2699,670,634

12.394.12715,769,34119,858,10224,680,27830,232,66036,456,45943,301,21550.705.88958,579,83066,823,34275,427,22084,264,04693,270,057

102,362,02011 ,453,380120,485.400123,375,820134.398.880

~~ ~-~ ~~ --26 953 200 91 82 4 713 7 288 61.438116,862.720106,848,83097,078.05487,615,43678,740.11670,342,94362,528.06855,316,41148,709,72642,634,44737,244,94532.326.12227,835,44323,904.58620,315,23517,042,16414,044,67211,266,9758,655,9166,162,7743,744,8291,366,265

5,675

92,624,15894,011,32095.924.27098,281,742

100,994,350103,372,235107,131.110110,394,380113,695,700116,378,530120.195.680123.308.240126,284,444129,038,570131,719,930134,151,990136,371.970138,368.640140,133,630141,660,360142,943,780143,980,310144,468,580

6,9736.9777,4068,58610,36212,74815,56118,56121,81525,16728,50131,92935.32038,62141.94445,19048,34251,52154.59857,61060,66763,63266,678

57,05052,86948,67244.54840,57336,80133,26929.99626,98724,24321,75919.52817,54415,80414,30813,04312,01011.20210.60810.2069.9719,872

11,518


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November 28,19641422 :01.39 GMT1504:281510:lO1531 :04

November 290659 :03November 301102:47December 4

1305-2402

December 5December 6December 7December 9December 13

1305-1658

December 17

January 3,1965

January 10-13February 5February 7-22February 11March 5March 10-25March 17April 16Ma y 3May 26June 5June 15

The Log of Mariner IVLiftoff.Space separation.Solar panels deployed.Su n lock completed.Canopus search started.Canopus lock completed.Midcourse maneuver attempted by ground command ;Canopuslock lost. Maneuver cancelled from E a r th ; Canopus reacquiredafter 7 ground-commanded star-hops.Successful midcourse maneuve r (6 ground commands).Component failu re i n plasma probe ; cientific da ta unintelligible.Canopus lock lost, Gamma-Vela acquired.St ar lock lost, Gamma-Vela reacquired twice.Transmitting amplifiers switched (to traveling-wave tube) byground command ; star lock lost, reacquired.Star lock lost, reacquired. Star-hop commanded from Earth ;Canopus reacquired. Star sensor desensitized to excess bright-ness by groun d command.Telemetry bit rate switched by on-board command fr om 33% to8% bits per second (most frequent readouts ever y 50 seconds).Plasma-probe d ata partly recoverable at new rate.Johannesburg ground station assigned to R an ge r t e s t 6 W hourdaily telem etry blackout.Sola r flare detected by science instr ument s.Johannesburg station assigned to Ranger VI11 test flightmission.TV lens cover dropped, planetary science equipment checkedand prepared by 12 ground commands.Spacecraft transmission switched from omni to high-gainantenna by on-board command.Johannesburg station assigned to Ranger IX test and flightmission.Ionization-chamber/Geiger-tubeystem fails.Solar-flare phenomena detected.Plasma-probe data below threshold due t o decreasing temperatur e.Sola r flare detected.Solar f lare detected.Sola r flare detected.


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NATIONAL AERONAUTICS AND SPACE ADMINISTRATIONJET PROPU LSION LABORATORY/CALIFORNIA INST ITUT E OFNATIONAL AERONAUTICS AND SPACE ADMINISTRATIONJET PROPU LSION LABORATORY/CALIFORNIA INST ITUT E OF TECHNOLOGY

To Mars- The Odyssey of Mariner IV

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