report from mars mariner 4 1964 - 1965

8/8/2019 Report From Mars Mariner 4 1964 - 1965

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1.\cc.Z3242S?~ AUG 1977 ~..... c>Jco RECEIVED ~

NASA STl FACILITY ---' ,\ INPUT BRANCH ~ ; : ;/ ! ~/O/S ~ J Ss

REPORT FROM MARS: Mariner IV 1964 -1965


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Contents

Expedition From EarthMa rs Before Mariner 4Two Years to Make Ready 9Mar ine r Leaves Port 18To Mars 22Th e Interplanetary Pulse 29One Day With Another Planet 33New View of an Old World 38

TH E COVER: Th e fir'st close-up IJictur'e ofMar's (in black and w hite on the cover') wastaken by Mar'iner IV at a range of 10,500 milesfr'om the r'egion in the center' of the pictur'e,T he 410-mile-wide r'egion shown is betweenTr'ivium Char'ontis and Pr'opontus II , The lightar'ea called Phlegr'a is on the hor'izon, T he pictur'e was assembled fr'om 240,000 digital bit str'ansmitted by the spaceC1'aft after' the Mar'sencounter' and pr'ocessed by the IBM 7094 computer to remove bi t er'r'or's and fiducial (identification) marks ,

Th e color photogr'aph of Mars wa s obtainedby R, B, L eigh ton of t he Calif ontia Institute ofT echnology eigh teen days bef01'e the oppositionof September 1956, using the . Mt . Wilson 60 -inch r'efiector' telescope , The photogr'aph sug-gests that dar'ker' ar'eas ar'e not necessarily"gr'een" as sometimes descr'ibed, bu t ma y be adar'ker' shade of the pr'evailing yellow-orange.T he br'illiant white south polar cap is pr'obablya thin layer' of fr'ozen water', per'haps hoarfr'ost,(In accord wi th astr'onomical convention, southis at the top.) Cra ters photogr'aphed by Mar'inCl?' near' the evening terminator appear' /r'osted,(Page 42 .) Th e na tur'e of the /r'ost is unknown,bu t conditions would be consistent with it s beingwatCl?'.

The photographs of Mars on pages4 and 6 are from theMt. Wilson and Palomar Observatories.

Jet Propuls ion LaboratoryCa li forn ia In st itute of TechnologyPrepare d under Contract No. NAS 7-100National Ae ronautics an d Sp ac e Adminis trationFo r sa le by th e Super intendent of Documents, U.S.Governmen t Pr i nt ing Oflice, Was hington, D.C ., 20402 .Pr ice 50 cen ts.


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PREFACE

The successful mission of Mariner IV is a most gratifying conclusionto the first generation of lunar and planeta1"y exp l01"ation, which has be enbased on lightweight automatic unmanned spacecraft in constant com-munication with Ea1th, designed for luna1' impact 01' planeta1'y encounter.The flight of this first MaTS probe is notew01"thy not only f01' the outstand-ing quantity and quality of scientific data but also as the verification oflarge and useful advances in a number of technological areas.

The Ma1 'iner MaTS Project of IfNJ4- 1965 was conducted for the NationalAeronautics and Space Administration by th e Jet Propulsion Laborat01'y;it 1vas made possible by the valued assistance and SUPP01't of many gov-e1nment agencies, scientific institutions, and industrial concerns, Amongthese are NASA's Lewis Resea'rch Center (Launch Vehicle Systems Mana-ge1) and their prime contract01's, Lockheed Missiles and Space C01'-lJOration and General Dynamics/Convair; Goddard Space Flight Cente1'(Launch Op erations) and other agencies at Cape Kennedy; the agenciesof th e Australian, South African, and Spanish governments which operateoveTSeas tracking stations; many hundreds of American indust'rial con-tractors and vendors; and a number of scientists in va1"ious fields ofendeavor.

Th e Project was established in lat e 1962 with the objective of conduct-ing scientific obseTvations nea1' the planet MaTs and 1'etu1'ning the datato Ea1'th for' study and analysis; secondary objectives we1'e to deve lop andstudy the equipment and techniques involved and to make certain scien-tific measurements of the interlJlanetary environment on the way to Man ,Successful accomplishment of these objectives under the seve1'e constraintswhich W81'e a pa1't of the mission is a t?"ibute to eVe1"y single individualwho sha1'ed in the p1'eparation and execution of the Mariner Mars P1'oject.

- - ~ ~OMER [ NEWELLASSOCIATE ADMIN ISTRATOR fORSPACE SCIENCE AND APPLICATIONSNATIONAL AERONAUTICS AND

SPACE ADMINISTRATION


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EXPEDITION FROM EARTH

Mariner has gone to Mars.Though it sounds like a simple task, in retrospect the challenge was

awesome. A journey of 8 months in space, 325 million miles long, had tobe devised in less than two years and with less than 600 pounds of flightspacecraft weight.

Pha e by phase the design, development, fabrication, assembly, andtest were completed. Second by econd the launch operations were carriedout. Mile by mile the trip to Mars :was accompli hed. Bit by bit the engi-neering and scientific data were recorded, reduced, and studied.A Giant Ins t rumen t

Mariner is far more than a pacecraft. I t is a complex organism, amajor new device of this age, called a system, which combines men andmachines, techniques and plans, radar arrays, and computers. I t is a huge,complex scientific instrument, engaged with remarkable versatility in amultiple scientific experiment to extend man's knowledge of Mars andthe solar system by a quantum jump.

Only a tiny part of this instrument-the Mariner IV pacecraftjourneyed to Mars . Becau e of it s monumental phy ical leap, and becausethe spacecraft is a fascinating object in it s own right, there is a tendencyto regard it as the whole instrument . Mariner consists of a large numberof elements, all essential to it s functioning: the spacecraft; the two-waycommunications stations of the Deep Space .[ etwork sp read around theworld; the Atlas/Agena launch vehicle, which placed the spacecraft on atrue flight path; the Space Flight Operations Facility at JPL in Pasadena,where, from the ovember 28, 1964, launch to the commanded missiontermination on October 1, 1965, the operations crews were on station everyhour of every day; and an intangible something in the heart and heads ofMariner's human element.


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Spacecraft assembly and testing

Launch operations mission con-trol

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This instrument has scaled off th e solar system and weighed Mars,observed almost a dozen solar flares in the season of the quiet Sun, photographed the craters of the Martian surface, measured the thin atmosphereof Mars, and sensed the radiation, magnetic, and cosmic-dust environmentof interplanetary space from Earth's orbit ou t beyond Mars.Trip Report

The Mariner IV mISSIOn commenced mid-morning on November 28,1964, with a flawless launch from Cape Kennedy . Within 2 days, itwas nearly half a million miles out, going more than 7,200 miles per hour;it was drawing power from the Sun, and had stabilized its attitude bylocking on the sta r Canopus.

On December 5, Mariner was commanded to change it s course slightly,using th e 50-pound-thrust rocket motor built into th e spacecraft. Themaneuver shifted th e rendezvous point at Mars from Ju ly 16, 1965, passing150,000 miles ahead of th e planet and north of the equator, to July 15,6,100 miles behind the planet and above the south pole.

In mid-February and late March, Mariner shared the DSN trackingnetwork and operational facilities with the Ranger VIn and IX lunarmissions, giving up a 6% -hour communications period daily fo r 2 weekseach month. The Rangers were in flight fo r 2% days in their historicmissions to the Moon, attaining a maximum distance of less than a quarterof a million miles from Earth.

On March 27, Mariner IV equalled th e deep-space endurance record se tby Mariner II's 129-day mission past Venus; it bested th e Mariner IIlong-distance communications record of just under 54 million miles onApril 14.


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I t took a little less than 1 day from the time Mariner's planetaryencounter mode was turned on by ground command, early in the morningof July 14, 1965, until the first elements of the first close-up picture ofMars were received. During that day, the space environment near theplanet was measured and examined, 21 pictures and a fragment ofanother picture were obtained and recorded on th e spacecr-aft tape recorder, the spacecraft passed within 6,118 miles of Mars' surface, Marinersent its radio signal-still transmitting information on magnetic fieldstrength, radiation, and cosmic dust-through the Martian atmosphere inthe occultation operation, and then, eme::-ging, continued making spaceenvironment measurements until it was time to play back the taped picturedata .

After the 9-day picture-playback sequence, with periods of engineeringtelemetry transmission sandwiched between the pictures, the tape was runthrough a second time to minimize errors in transmission. Finally, onAugust 2, Mariner was returned to the cruise mode in which it had sailedto Mars.Two months later, as Earth left the beam of the high-gain antenna,transmission was returned by ground command to the low-gain omnidirectional antenna: the long stream of telemetry is no longer audible,though the primary carrier signal may be detected. A few minutes past3 p.m., Pacific Time, October 1, Mariner's last message was received.

The Deep Space Network will track Mariner IV from time to time as aradio beacon, using the new extreme-range 210-foot antenna. I f Marinerremains on the air long enough, Earth will again pick up it s telemetry inSummer 1967.

Au revoir.Encounter op erations at Gold-stone

Spacecraft perf o1mance analysis


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~ .' : " . " .. -, ,} . ," ."~ ~ , j... .Top: Sketch by Cas -sini (1666)Cente7': Sketch byH e?'schel (1777)Bottom: Mt , Wilsonphotogmph (1956)

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MARS BEFORE MARINER

Though Mars has often been populated, irrigated, and civilized inspeculation and in fiction, it s characteristics are relatively unearthly. Itappears to be a small orange-red desert world; ours is a robust green-andblue world of jungle, grassland, and river, three-quarters ocean.

Mars has about half Earth's diameter, a ninth of Earth's mass, resultingin a surface gravity 38 per cent of Earth's, and an escape velocity of some3.1 miles pe r second, as compared with 6.9 for Earth. Therefore, Mars isill-equipped to retain mu .:h of an atmosphere; the Martian surface pressureis probably less than Earth 's pressure at 5- to 15-mile altitudes. What ai rthere is appears to lack oxygen and contains only enough water vapor tomake its detection barely possible from Earth. The lack of oxygen andscarcity of water vapor, in turn, rule out liquid water (which must reachequilibrium with a vapor pressure above it ) except very temporarily orund erg round. There are polar caps of ice or frost-possibly of frozencarbon dioxide rather than water-though probably extremely thin byEarth standards.

However, Mars' marked su rface and thin atmosphere permitted astronomers to measure its 24% -hour day and the annual change of seasons asearly as 1659. Mars' axis is tilted about the same as Earth's, so it s seasonsare comparable, though scaled to the 687-Earth-day Martian yea r. Earthvacationers might tend to regard t he four Mars seasons as little more thanvariations in a bad win ter: a hot midsummer afternoon on the equatormight bring the ground temperature up to 85-100F, bu t during the nightit would drop to 100 0 below, and 6 feet off the ground the air wouldn'tge t above freezing all day.A Dim View of Canals

Like the Moon, Mars abounds with so-called seas, bays, and the like.By this century, when the essentially waterless condition of the surfacewas recognized, the names had already been established, and the smallerbluish regions remained "mare," "sinus," and "lacus."

Even with the most powerful telescopes and under the most favorableatmospheric conditions, Earth's astronomers cannot ge t high-resolutionpictures of Mars . To appreciate the difficulties under which the observersof Mars labor, imagine yourself watching moonrise at the end of a hotda:y. The Moon rises above an asphalt road still warm from the afternoon'sbaking. The faint, glowing disk wavers and dances in th e warm rising air.Your impression of the Moon might be compared to the way astronomerssee Mars. Mars is never closer to Earth than about 35 million miles, andthat only about every 15 years. At opposition (the Sun and Mars areopposite, Earth and Mars adjacent), which occurs every 25 months, itmay be as far as 62 million miles, as it was on March 5, 1965. And ouratmosphere is always in th e way.


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Canal map by Schiaparell i (1877-88)

Two and a half centuries after Galileo had been barely able to distinguish the disk of Mars in the first astronomical telescope, Guido Schiaparelli,working at Milan Observatory in 1877, noted surface features which havebeen argued about ever since. He called them ct1nt1li- "canals" or "channels"-because they were dark and seemed to reach across the "lands" from"sea" to "sea." Thus began a great international dispute which was to makeMars famous to the public and somewhat infamous among astronomers.Not everyone saw the "canals" to which Schiaparelli, and then anAmerican, Percival Lowell, referred . Lowell was convinced of the implications of the word "canal" ; he founded an observatory, whose contributionsto science would include the discovery of Pluto, but whose early activitycentered on Martian inland waterways. Lowell's maps showed whatde Vaucouleurs describes as "a veritable cobweb" of canals (400 in 1900,almost 700 by 1909-including parallel "spare" channels) . His books, Mt1?st1nd Its Ct1nt1ls and Mt1TS t1S th e Abode of L if e (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 communicate with the Martians by digg ing a canal in the shape of a huge righttriangle in the Sahara, wireless communication being, of course, impossibleover such a distance. Most as t ronomers saw the other side of the question."Nobody has ever seen a true artian 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 ar e still partisans, pro and con.


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Ef fect of atm ospherichaze, 1956; M t. W i l-son p hotog?'a ph s inorange li gh t, J u ly(t o p) an d A u gu st

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Interestingly, no Martian mountains of Rocky or Himalayan proportions have been identified: gradual slopes, modest east-west chains, orsmall prominences could not be .spotted from Earth , an d no shadows-thetell-tale index of the Moon' s mountains- have been resolved.The Thin A ir

Studies of Mars ' atmosphere indicate that it probably consists of ni t rogen, argon, some carbon dioxide, a trace of water vapor, and a spectroscopically undetectable amount of oxygen (i f any). This statement is basedon well-founded speculation fo r th e nitrogen and argon, and extremelyskillful spectroscopy fo r the rest.

The spectroscope is an instrument used to analyze a beam of light fo rth e chemical constituents of th e luminous gas in which it originates (suchas a flame or the Sun) or th e partly opaque gas through which it shines(such as the atmosphere of Venus or Mars). Its output is a wide photograph of th e color spectrum laced with a pattern of parallel bright (luminous) or dark (absorption) lines.

Carbon dioxide was detected first on the planet Venus. Nitrogen lacksa strong spectrographic signature of absorption lines in visible light and,in addition, Earth's nitrogen-rich air would mask the weaker indicationsfrom another planet . The same masking problem dogged the hunters fo roxygen and water vapor on Mars after G. P. Kuiper's subsequent discoveryof carbon d '0 ide on Mars. They calculated that if they shot the spectrogram when Mars and Earth were moving apart or together at th e maximum speed, the doppler effect would shift the indications of Martianoxygen and water vapor out from under those of th e terrestrial atmosphere. The latter refinement led at last to th e conclusion that water vaporwas barely in evidence and oxygen was too sparse to detect. Spectral evidence that the polar caps were water ice had been obtained in 1948.

The atmospheric pressure, which corresponds to the weight of th eatmosphere per unit area at the surface, is a function (given Mars' gravitational field) of the total amount and kind of gases making it up. I t canbe measured only by very indirect means from Earth, relat ed to th e effectsof th e atmosphere on light. Some of the methods have involved stUdyingthe diffusion of various colors, th e polarization, the variation of color acrossth e disk, and the brightness of surface spots as they rotate from one limbof the disk to another and are seen through different slant thicknesses ofthe Martian air.

A very recent approach to th e question of Martian atmospheric pressure, which may provide th e most accurate Earth-based estimate, is basedon th e tool used to examine the composition of the atmosphere. The spectralabsorption lines from the carbon dioxide on Mars are broadened or smeared,according to th e theory, as a function of the gas pressure. Comparisonwith carbon dioxide spectra obtained at various pressures in the laboratorygives, after much analysis, the pressure value. Kaplan, Munch, an d Spinrad,who applied this method to Mars, produced a value of 25 millibars, with an


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uncertainty of 15 millibars. Subsequent refinement raised this value slightly.Earth's standard sea-level pressure is just over 1013 millibars. Values estimated by other methods, with much greater uncertainties, yield a possiblerange from 200 millibars down to about 14 (corresponding to the pressure4% to 18 miles above Earth's surface) .

With Mars' smaller gravitational field, the atmosphere is not huggedclose to the planet's surface as is Earth's. Yellow clouds, presumed to befine dust swept up off the deserts, ar e frequently observed at altitudes from3 to 6 miles, and occasionally much higher. The clouds have been observedto move as fast as 85 miles per hour, though more often in the 20- to 30-mile-per-hour range. Wind velocities necessary to pick up the dust mayrange as high as 125 miles per hour at 300 feet altitude.

1973 opposition40.4 million miles

Mars orbit: 687 days, 142. m i l ~ i miles, ~e = 0.093, Inclination 1 51 . .1969 opposition4.5 million milesEarth orbit : 3651f. day s,93 million miles, e = 0.016.

Mars receives from 36 0/0to 52 0/0 as much solarradiation as Earth does.Its equatorial plane is 2425 'from its orb ital plane(231f2' f or Earth).

(after 51 ipher)

301/3 hours

PhobosDeim os

1967 opposition55.8 million miles

_ _ _ _ 14 .600 miles5800 miles2100 miles


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L eft: Space simulator test preparation

TWO YEARS TO MAKE READY

When the Mariner Mars 1964 Project was authorized by the NationalAeronautics and Space Administration in late 1962, it was recognized asan assignment somewhere between difficult and imposs ible. However, suchta sks a re characteristic of most aspects of space exploration in its presentdawn age. The dista nce s, forces, and hazards of interplanetary sp ace arehuge; though our knowledge and technical skill are growing rapidly, theunknown aspects remain extensive .

Mariner's Venus 1962 mission, then just success fully concluding, gaveencouragemen t and contributed vital kn owledge and exper ience to th e Mar smiss ion, but the scale of the problem was larger in a ll aspects. I t was tothe successfu l Mariner Venu team that the new problem was presented.

Mariner' s PedigreeThe Mariner Mars system would be the first of it s kind, bu t no t the first

of its family. The dynasty was founded in late 1958 an d 1959, when NASAand JPL worked out a linked se ries of unmanned lunar and planetarymissions which would advance the technology of space exploration wh ileaccumulating basic and practical knowledge about the Moon, t he planets,an d the solar system .A three-stage launch-vehicle system would have been needed, but th edevelopment of restartable second-stage rockets (which in effect made twostages out of one) made this unnecessary. At las/Agena was to be the launchvehicle fo r Ranger, the first lunar member of the series ; early Marinerplanetary and the Surveyor lunar spacecraft developments were first associated with Atlas/Centaur, a higher-performance system then being designed. Subsequent schedule changes, together with advancements in Agenaand spacecraft technology, necessitated and made possible the quick devel-opment of an Atlas/ Agena-boosted, lightweight planetary spacecraft andit s successful use in the Mariner II mission to Venus.

Now the same sw itch was suggested for the Mars mission : marry 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 2 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. I t could be done- j u s t barely.

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

actually a little less than that which was needed to send it to Venus in 1962.The slightly lower energy requirement, however, turned out to be just aboutthe only aspect of Mariner Mars that wasn't twice or three times as difficult as the earlier mission.

Ma? 'iner II

Ma?'iner IV


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Consider service li fe, fo r example. New cars are guaranteed fo r yearsor tens of thousands of miles, if serviced regularly. TV sets are guaranteed fo r a year (exce pt 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 adj ust the va lves, or check the tubes,when it's 100 million miles out in space, and sti ll going.

Mariner II had had to operate fo r about 2500 hours on it s flight toVenus; Mariner IV had to be designed fo r 6000 to 7000 hours of flight life,on the way to Mars, at the planet, and beyond.

Then there was electrical power . Mariner Mars would need only a little- less than 200 watts - but it must come from su nlight, whose powerdecreases as you go away from the Sun. Mariner II had one solar panelpartly disabled en route to Venus but drew nearly as much power from theundamaged one at Venus as it had received from both panels near Earth.Going out from Earth to Mars, the solar power decreases instead of increasing. Mariner Mars must have more than tw ice the solar-panel areaof it s predecessor-70 square feet as against 27.

Co nsidering the environment through wh ich the spacecraft must travel,we again see a sharp difference from any mission attempted before . MarinerII flew toward the Sun, braving increas ing solar radiation, wh ich helpedwith t he power problem but aggravated the temperature-control problem.Mariner II had become hotter and hotter on the way to Venus; MarinerMars would grow colder on it s journey.

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 II's maximum 54 million miles, radio waves

In outdOOT test (w i th in p1'otective plastic tent), solar pane ls dTaw poweT fTorn Sun t oope1'ate PToo f- tes t-mode l sp acecTa ft


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Prepa1'ations on an tenna range f or m ap pin g actual charac te1'is tics of Ma rin er's two?'adio an tennas

took nearly 5 minutes to come back to Earth; communication with the Marsspacecraft would be delayed about three times as long, More important, thecommunications system would have to be better, , , nine times better, sinceradio strength decreases as the square of increasing distance, Both theground and flight units would have to be improved,


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Beyond Mars, where one might expect to find another planet, is theasteroid belt, consisting of thousands of planetoids in independent solarorbits. Accordingly, astronomers believed that the meteoritic intensitymight 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 II's detector had recorded only two impac::ts in it s3-month flight. Since the total area of the spacecraft is about 200 timesthat of the small dust detectors, the detectors record only a fraction of theparticles actually hitting the vehicle.The Weight Watchers

Mariner's planners early decided they would need more spacecraftweight 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 better propellantutilization to lightweight materials, gave an 80-pound weight bonus forthe spacecraft. The energy difference between Venus 1962 and Mars 1964contributed 40-odd pounds. Thus, the spacecraft could weigh about 575pounds ; something could be done with that.

Initial checkout of octagonal s t r u c t u ~


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Highgain antenna

Solar panel (about 21 Ib each ), 7056 solar cellsper panel. )

Magnetometer (11/3 Ib)

Lowgain antenna

Ionization chamber (2"h Ib)

Thermal control louvers (six sets, 11 pairs oflouvers per set, about 2 Ib per set)Propulsion sUbsystem (51 Ib), 5 0 . 7 - l b . t h r ~ J ~mon opropellant hydrazine engine capable of f) , ).11

two separate thrust periods II lII- - : : : : : : : : : = = ~ : : : ; ; : ; ; : = = ~ ~

Data encoder and command subsystem (41Ib ), 9800 electronic components,transistors, diodes, capacitors, etc.

Scientific equipment (plasma probe, cosmic ray telescope , TV and sca n platform electronics) and science data automation, 48 Ib

JI ,( .P

~ ~ ~ ~ ; : ~ ; ; = " . ; ~ ~ ~ ; J Tape recorder and radio equipment (62 Ib ).Radio receiver, transponder. and two transmitter amplifiers contain 1247 electronic parts


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Preparation f or test firing of midcou1"S e motor in 25-fo ot space simu lator

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.

For example, the bones of birds and the I-beams of girders indicate thatnature and man have found ways to get more strength for less structuralweight. Mariner's structural designers went further; they nearly eliminatedthe skeletal structure. Mariner's forebears were built around a hexagonalskeleton belted with electronic-equipment packages and crowned with atower. For Mariner Mars the packages became the structural foundation,the tower a slim waveguide.

Eight shallow trays, deriving part of their strength from their closepacked contents, were joined in a ring; electrical cables were contained intwo smaller concentric rings . A thermal shield was spread across the "top"and "bottom" of the larger ring. The fixed elliptical-dish antenna, solar-paneldampers, and the waveguide, which ended in a small omnidirectional lowgain antenna, were mounted topside; the Canopus sensor and planetaryscanners were on the shady-side deck. Between decks, the att itude-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 into the spacebetween the decks.

Mariner's four solar panels were conventional in appearance, but radicalin cons t ruction. Corrugation-stiffened sheet-metal floor structures were


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supported by stamped-aluminum-sheet-metal spars about the gauge ofkitchen aluminum foil. The panel structures weighed less than 1 2 poundper square foot.Keeping Co o l and Keep ing Warm

An object in space will be warmed by the rays of the Sun, alld cooledby its own r adiation to the black sky around it , at a rate dependent on itstemperature. It will thus eventually stab ili ze at a temperature primarilydependent on its distance from the Sun: near Earth it would be about125F warmer than at Mars' distance. Its sunlit side, if it is not rotating,might be several hundred degrees hotter than the shady side.

Mariner couldn't tolerate such conditions. Its electronic components havecertain temperature limits within which they will operate properly, evenas we humans do. Their temperatures mu st be controlled.The isolation and vacuum of outer space rule ou t contact conduction andconvection; the only controllable heat-t ransfer factor affecting the spacecraft is surface radiation. The surfaces, th en, mu st be controlled. I f paintedblack, they will radiate or absorb; if polished like mirrors, they will reflectand neither absorb nor radiate.

Explorer, the very first United States spacecr aft, had been painted withblack and white stripes, the area of white stripes (reflecting surface) calculated to maintain the necessar y temperature in Earth orbit. A moreadvanced development, a heat blanket of layers of very thin aluminizedMylar plastic, gave .Mariner Mars good, yet lightweight, insulation coverage.

A sophisticated thermal-control device, a se t of polished aluminum shutters which could open to expose a radiat ing surface beneath, was te stedon one compartment of Mariner IT in its fligh t to Venus . The shuttersare activated by bimetallic strips, like inexpensive dial thermometers orthe thermostat in an electric blanket. As the temperature rises , the stripuncoils, the shutters open, and heat radiates away to space. Then, as the c o m ~partment cools, the strip coils up again, closing the shutters to conserve heat.

Thermal-control louvers of th is type were designed fo r six of Mariner'selectronics trays; they would keep the temperature inside between 55 and

....... .... !,/ ", . '",. : ':It. :-

, / ". ''' -, /"" , ,.,

, /, /,/


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85 F. An aluminized-Myla r 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 th e process of tapping the Sun fo r photoelectric power, were blackened to re-radiate heat and keep the solar cells within their operating rangeof 10 to 130 F. Most other exposed metallic surfaces were polished; exposedcables were wrapped with fiberglass or aluminized-Mylar tape. The fixedhigh-gain antenna dish was painted green: it would cool from its upperoperating limit near Earth to about room temperature at Mars.Put Them All Together

Some philosopher has remarked that you can't get from "1 + I" to "2"just by understanding the "1." Systems engineering might be likened tothe "+" sign. I t started with a job to be done. Each of the Systems of theMariner Mars 1964 Project (Launch 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 are:structure, radio, command, telemetry, central computer and sequencer,power, attitude control, pyrotechnic-actuator control, thermal control,cabling, and postinjection propulsion; these make up wha t is often calledthe spacecraft "bus." The scientific-experiment "passenger" units ar escience data automation, planetary scan system, television and it s recorder,and six interplanetary-environment instruments : magnetometer, plasmaprobe, ionization chamber, trapped-radiation and cosmic-dust detectors, andcosmic-ray telescope.

PROPULSION

GAS JETS

SCIENCE DATAAUTOMATION

STRUCTURE, CABLES,ANDPACKAGINGTEMPERATURE

CONTROL

All in all, nearly 140,000 parts were carefully screened and put together,inspected, subsystem-tested and system-tested, and re -tested . All membersof the Mariner team labored long and hard in the development an d fabr ication of the components and the assemblies they constitute; Mariner IV isthe sum of these parts.


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System test

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

purely experimental; this is evidenced by the distaste with which spacecraftdevelopers brush off such labels as "cut and 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 fo r a 6000-hour mission-a tight schedule for alarge and exacting job.A Mariner Mars temperature-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 JPL's25-foot space simulator, which was equipped to approximate the black, coldvacuum of space and the blazing radiance of the Sun. Correction factorslearned from the flight of Mariner Venus had been engineered into this testdevice to achieve the best possible Earth-surface reproduction of spaceconditions.

Before the flight spacecraft were built, a prototype or proof-test modelwas put together. Serving as a final test bed in subsystem development,as well as the initial sys tem-test vehicle, this spacecraft was at one endof the development loop: modifications found necessary in proof testingwere themselves retested on the same craft. At the end of the design evolution and after 1100 hours of system test, the proof-test model had evolvedinto a functional duplicate of the flight spacecraft; they, in turn, werespared the rigors of prolonged design evaluation by t he existence ofthe test spacecraft which could never fly a mission. The proof-test spacecraft was also used fo r inter-system testing, verifying compatibility of thespacecraft with ground equipment. I t then supported both flight missionsby simulating observed flight situations so that they co uld be studied atclose range.


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MARINER LEAVES PORT

Three Mariner Mars spacecraft began the journey to the planet Marsfrom a canyon north of Pasadena, California, at the Jet Propulsion Laboratory, where they had been designed, assembled, and tested fo r months. Twoof the three would fly; the third was a spare. They were partly disassembled, carefully packed, and loaded on moving vans. On September 11, 1964,after a four-day journey, the last van reached the Air Force Eastern TestRange, Cape Kennedy, Florida.

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

At the Cape, two 100-foot-high Atlas /Agena D rockets were waiting,each standing in its own launch complex. The engineers could select eitherone fo r the first launch, and could launch the two missions as close as 2days apart if desired.


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Spacecraft and launch vehicles were given separate system te'sts, assur-ing that each would function in every phase of it s 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 III spacecraft and launch vehicle stood onthe pad, going through a dress rehearsal. The actual Mars launch periodopened on ovember 4 and lasted for only about a month .

Interplanetary NavigationUnlike a conventional aircraft, a spacecraft spends most of it s time

fa ll ing. 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; this process ismore gunnery than navigation.

Every planet of the Sun travels an ellipse, a closed curve which resem-bles a circle stretched out in one dimension. The Sun is at one focus of theellipse, not at the geometric center. As the planet comes closer to the Sun,it speeds up; as it goes outward, it slows.


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\ INose fair ing: 13 ft high, 5'12 ft diameter.Weight about 350 lb. 574lb spacecraft inside .

Agena 0 stage (Lockheed single 16,000.lb.thrust, h y d r a ~ i n e / n i t r i c ac i Bell engine. Stageis 23 ft high, 5 ft in dia eter, weighs about15 ,300 Ib when fuelled.

I-II(- il-0 main st ge (Ge era I 0 namics): single lbthrust Rocke yne s stainer engine ,

500lb ver ier en nes, I burning Rpj) and iquid xygen. Stage is 67 ft10 ft in di meter weigh ~ b o u t 130 tonsfuelled.

20

An interplanetary spacecraft is as subject to these laws as are theplanets. I t must be given the correct veloc ity-speed and direction-sothat it will arrive 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 orbits the Sun at an average of 66,600 miles perhour-but the rest must be provided by the booster vehicles.

The velocity required to reach Mars 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 fora few weeks every 25 months, limiting the practicable 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 the tilt of Mars' orbit plane relative to Earth's, this coincidencehardly ever happens.

Near Earth, the entry point of the Earth-to-Mars ellipse is relativelyfixed in space. Since the Earth turns under this point, it is within the safefiring angle from Cape Kennedy (24 degrees south from due East) foronly a 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 technique is to launch into Earth orbit, coast until the injection zone is almostreached, and then restart the Agena to transfer from Earth orbit to solarorbit.

Several thousand Mariner Mars trajectories were calculated, accommodating the changing relationship of the planets day by day, and thechanging angles near Earth from minute to minute. They took into accountnot only Earth, Sun, and Mars, bu t the perturbing effects of the Moon andthe planet Jupiter, and the pressure of light from the Sun. The latter would,over the course of the flight to Mars, push Mariner about 10,000 milesaway from the Sun.

Left: President Johnson inspects Mariner prelaunch operations. Right: Inside the block-house at launch


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2 1

Nine HoursMariner III was launched toward Mars about midday on November 5.

Minor launch vehicle difficulties encountered on the first day's countdownhad been solved to the engineers' satisfaction; the prelaunch countdownwas normal ; the weather was good. The ta ll , snub-nosed space vehicle rosefrom Launch Complex 13 with an air of confidence.

Nevertheless, within minutes the mission was doomed, though it tooknearly 9 hours fo r it to die. Th e cylindrical fiberglass-honeycomb nosefairing, or shield, designed to 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 no t be ejected.

Early indications of trouble came at the end of powered flight. Becauseof the dead weight of the nose fairing, the velocity was too low. Thespacecraft would no t reach it s target.About 51h minutes later, after spacecraft and Agena had separated, thespacecraft unsuccessfully attempted to deploy it s solar panels. Withoutsolar panels, there wa s no solar power. Studying the telemetry fromMariner, building up piece by piece a picture of the trouble, and conducting failure-mode tests on the proof-test spacecraft, th e operations teamscommanded Mariner III to conserve power by switching off the scientificequipment, repeatedly commanded panel deployment, and were in theprocess of igniting the spacecraft rocket motor in an attempt to removethe nose shield by force when, 8 hours 43 minutes after launch, the spacecraft battery ran out of power.

Mariner's team wasted no time . The problem was identified, studied,and solved. A quick, thorough test program detailed and verified the conditions which had caused the failure. Experiments were conducted with

f i b e r g l a ~ s nose shields, and a newall-metal shield was designed, developed,and built in record time by the Launch Vehicle team . A little over 3weeks after the launch of Mariner III, another Mariner/Atlas/Agenastood ready on the pad, with the new metal nose shield installed.Mariner IV: A Good Sendoff

On November 27, the first countdown of the new Mariner wa s interrupted 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 wentthrough the long list, establishing and checking communications, forecasting the flight weather, monitoring spacecraft 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 hitch;the report was "clear to launch." Liftoff occurred 1. 309 seconds later.

As it rose, the space vehicle rolled to an azimuth of 91.4 degrees, justSouth of due East, and began to pitch over from it s vertical ascent. Shedding it s two mass ive booster engines, Atlas carried on with the single sustainer .A ground computer fed guidance commands to the vehicle until


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22

the sustainer engine was shu t down and th e velocity properly ad ju sted withtwo small rocket eng ines. Then the huge, emp ty Atlas was detached andAgena took over. Before the Agena engine was started, the aerodynamicnose cover had to be jettisoned. This time, it came off easily.

Agena's 16,000-pound-thrust engine couldn't lift the weight of theAgena vehicle and t he encapsulated Mariner spacecraft if they were onthe ground. But starting at an alt itude of 100 nautical miles and a velocityof 13,000 miles per hour, it could and did thru st Mariner to orbital velocity,about 17,500 miles per hour. The Agena engine then shut off, and thevehicle coasted for almos t 41 minutes . Swinging around Earth to bear onit s target, Agena flamed into action again . When t he big engine shut downfo r good, the spacecraft was trave ling at 25,598 miles per hour along apath t hat led within 150,000 miles of Mars. Th e application of one-fifthof the spacecraft on-board propulsion power would bring that path with inthe desired target zone, between 4000 and 8000 miles above the planet'ssurface.

Launch operations were described as nominal: it was a good shot.

TO MARS

A minute and a ha lf after entering the path to Mars, Mariner and Agenapassed into Earth 's shadow for a period of almost 12 minutes. There, inthe dark, spacecraft and Agena separated. A 3-minute timer was started,and, simultaneously, t he spacecraft radio power was switched up and theinterplanetary scientific instruments were turned on. When the 3-minutetimer ran out, electric current was applied across the solar-panel pin-pullersquibs.

A squib is a sm all, electrically fired explosive charge a ttached toa cylinderopiston arrangement, enabling a one-stroke internal-combustionengine to open or close a bolt or valve. Th ese mechanisms would be usedlater to tu rn the propulsion system on and off and to release the scanningplatform carrying the TV camera . Ei ght pairs of squibs (they are usuallymounted in pairs for increased reliabili ty) were mounted on the sp iderlike legs which held up and steadied the four solar panels du ring launch.Now they fired, pulling the pins and releasing the panels.Open ing fo r Business

Under sp ring tension, the panels hinged away to the deployed position.At the end of each opening panel, a silver fa n unfolded and spread. Th esefans are so la r pressure vanes, a new attitude-control trim device in a first


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23

/ '

flight test; they were designed to balance the spacecraft against the endlesspressure of sunlight, saving attitude-control-jet gas and permitting a longerstable flight.

Now the spacecraft came back into the sunlight, and, the attitudecontrol 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 central computer and sequencer serves as combination brain and alarm clock for the Ranger-Mariner family. I t providesthe master synchronization for spacecraft operations, the rhythm fo r telemetry transmission and command interpretation, and a number of se t commands (such as Sun search, star search, and midcourse maneuver), andconducts complex maneuvers in accordance with instructions sent fromEarth.

Searching fo r the Sun consists of placing th e pitch and ya w controlsystems under the command of the Sun sensors. The spacecraft is treatedas though it were a ship or aircraft traveling in the direction in which th esolar panels face: yawing moves the prow or nose to the left or right, pitching moves it up or down, and rolling spins the ship around. Mariner leftthis mode of travel behind with the launch vehicle, and normally movesalmost at right angles to the "nose" direction, but the names stuck. InMariner's cruise mode, pitching or yawing means rotating around one orthe other pair of solar panels, and rolling means turning like a propeller.

ROll

PITCH

T


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TO SUN

24

There ar e Sun sensors on Mariner's 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 turn the spacecraft until thepanels face the Sun, and to stop it in that position. This process took12 minutes.

Now Mariner's 28,224 sola r cells were converting sunlight into 700watts of raw electrical power, which, in turn, was converted to variousforms to run the spacecraft and recharge the battery. At Mars' distancefrom the Sun, the spacecraft would still generate 300 watts, leaving a goodmargin in case of solar cell damage in the space environment.

Like a big jewelled windmill, the spacecraft rolled slowly through spacefor the next 15 hours; the known roll rate was used to calibrate themagnetometer, one of th e interplanetary sensors, so that the spacecraft'sown magnetic field could be subtracted from the magnetometer readings.S tar Lock

Imagine a weight suspended from a single long cord: it spins an d spins.A second cord, approximately at right angles, will steady it in a moment. Aline of sight on the star Canopus, second brightest in the sky, and locatednear the ecliptic south pole, was to be Mariner's second stabilizing cord.

Mariner Mars was the first space mission using or needing a star as areference object; earlier missions, remaining near Earth or travelingto Venus, had sighted on the home planet. But during this flight, Earthwould transit across the face of the Sun, and through much of th e flightit would appear as a relatively dim crescent. A bright reference source,at a wide angle away from the Sun, was necessary. Canopus filled therequirements for such a reference source. Mariner's Canopus sensor ismounted on the shady side of the spacecraft ring, pointing outward at anangle, so that it s field of view covers an area in the shape of a shallowcone.

An electronic "logic" in the attitude-control system was se t to respondto any object more than one-eighth as bright as Canopus . IncludingCanopus, there were eight such objects visible to the sensor as Marinerswung around in the search mode; it was no surprise when the systemacquired one of the other seven. The engineers had prepared brightnesscharts, corresponding to star maps of the ribbon of sky the star trackerwould inspect, and the stars were recognized as they came around . I t tookmore than a day of star-hopping to find Canopus.Change of Course

A lunar or planetary mission has too great a range and too small atarget to be accurately guided from the brief initial powered fl ight. Thrustmust be applied later, in what has come to be called the "midcourse correction" maneuver- a double misnomer, in that it occurs earlier than themidpoint of the flight, and , rather than correcting a mistake , increases the


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25

MARKAB

EARTH

CANOPUS

Star b?'ightness graph in ci?'culaT f orm, with spacecTaft locked on Ganopus; predictedb?'ightness indicated by distance in fTom ci?'l;-umference

possible accuracy. All members of the Ranger-Mariner family used essen-tially the same type of small rocket engine to apply this thrust. MarinerIV's 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 burning 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,the spacecraft had no roll reference from which to orient it s rocket motor,and the maneuver had to be postponed by ground command until Canopuslock could be regained.

Next day, the thrust maneuver was successfully carried out. Threequantitat ive commands from Earth had the CC&S store in its electronicmemory the dimensions of the required maneuver, which were a negativepitch turn of 39.16 degrees, a positive roll turn of 156.08 degrees, and athrusting time of 20.07 seconds. Then three direct commands told the MidcouTse motor


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SUN

26

Flight-path analysts calculate t?ajec to1y and midcourse maneuve1.

spacecraft to cock the system, take off the electrical safety catch, andignite the engine. Since the motor was initially pointed almost along thedirection of flight, the turns aimed it back in the general direction of Earthbut high above the plane of the orbit. The pi tch and roll were performedwith better than 1 pe r cent accuracy, the velocity change with about 2112per cent accuracy. As planned, the angle of flight was changed less than14, degree, and the velocity was increased a little more than 37 miles perhour . Mariner was headed straight fo r its target, which was 7 monthsand 300,000,000 miles ahead.

PITCH MANEUVERROll MANEUVER

MOTOR BURNREACQUISITION


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The Routine o f SpaceDuring the long cruise to Mars, it was hou sework and homework for

Mariner. The housework consisted of many routine tasks, programmed inthe CC&S and supplemented with a few ground-commanded operations,designed to maintain the spacecraft in condition to carry out its missionat th e planet. The homework consisted of a constant examination of spacecraft condition and performance and the space environment throughwhich it was passing, and the reporting of these measurements to Earth,where they were correlated and studied.

The CC&S, which was counting the time until a number of Marsencounter operations should be ordered, sent counting pulses back to Earthabout every 2%. days, permitting the operators to check the clock operation. As the spacecraft moved around the Sun, Canopus tended to driftsideways out of the field of the star tracker, and on four occasions theCC&S adjusted the angle of the tracker .

The attitude-control system kept Mariner's roll axis pointed within 1,4degree of the Sun, using puffs of nitrogen gas from jets on the solar-paneltips each time the attitude reached the prescribed limit. The fan -shapedsolar vanes on the ends of the panels were automatically adjusted to helpmaintain Mariner's balance against solar pressure. Similarly, the spacecraft was stabilized in the roll direction on the star Canopus, after someinitial l i g h t ~ s e n s i n g difficulties. The disturbance of December 4 was repeated, probably because tiny dust particles, brightly li t by th e Sun, moving with the spacecraft drifted in front of the tracker the total imageappeared too bright to be Canopus, and the control system turned on thegyros to roll Mariner in search of the correct brightness. After several

Fo?' the fi?'st 2% months of fi,ight ,TV optics (lower center, point-in g ?'ight) and planet sensorswe1 'e protected by a metal cover(shown hin ged to lef t and down) ;on Feb?"Ua?'Y 11 , the cover wastm locked an d pi voted open bycommand from Earth.


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fi x ed high-gain ancove1's a long, nan'ow re-

of space, pointed abou t 38egr ee s forw ard from th e Stmection ; Earth was within thisegion fo r th e last 7 months ofe m1ssion.

days, the spacecraft was commanded to ignore excessive brightness, andthe trouble ceased.

The radio subsystem provides Mariner's tenuous link with Earth.Broadcasting continuously at 2300 megacycles with about 10 watts ofpower, the radio carries scientific measurements, data on the conditionof the instruments, and some 90 meter reading on the spacecraft performance and status. The measurements are coded digitally, after themanner of teletype or Morse, rather than in analog form as used by commercial radio and TV and the Ranger spacecraft, and are imposed on theradio signal by a technique called phase-shift-keyed modulation.

On December 13, the radio was switched from a cavity power amplifierto the longer-life, slightly more powerful traveling-wave tube. The rateat which telemetry was transmitted was lowed from 33% bits per second,or one readout every 12 lj:l seconds for the most frequently sampled measurements, to 8% bits, or one readout every 50 seconds, on January 3.Most of the measurements were sampled much less often: every 500, every5,000, or even every 10,000 seconds. Scientific measurements occupy twothirds of the transmission time, except during certain maneuvers, whenthey are turned off, or on special occasions, like Mars encounter, whenthey take over the whole transmission. On March 5, the radio was transferred by on-board command from the omnidirectional broadcast antennato the fixed narrow-beam parabolic dish. The range had lengthened to 6million miles, and Earth had entered the beam of the antenna, where itwould remain until well after th e spacecraft had passed Mars.

ENCOUNTERJULY 15 , 1965

MARINER IV

ANTENNA SWITCHOVER MAR. 5, 1965

TELEMETRY RATE CHANGE

LAUNCHNOV . 28, 1964

OCT. 1, 1965


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THE INTERPLANETARY PULSE

Mariner's voyage to Mars involved an extended presence in the environment-meaning the magnetic fields, solar and cosmic radiation, andwhatever matter or particles were there- of the solar system. Study ofthis environment during the earlier mission of Mariner II to Venus hadprovided understandings to the benefit of th e Mariner Mars project, aswell as adding to scientific knowledge of the and its surroundings.Six instruments to observe and measure these fields and particles wereaccordingly flown on Mariner IV.Si JC Sensors

The solar-plasma probe was designed to measure the charged particlesmaking up the solar wind, a hot ionized gas streaming out at hypersonicvelocity from the corona of the Sun. Electrons, protons, and alpha particles(helium nuclei) are detected in 32 energy bands ranging from 30 to 10,000electron volts. The energy of the stream varies continuously, solar surfacedisturbances giving rise to plasma storms. Unfortunately the failure of aresistor in the instrument's circuitry 8 days after launch rendered its dataexceedingly difficult to interpret. Reduction of the data transmission ratereturned a number of readings to intelligibility, but a progressive declinewas observed. Partial calibrations during the flight gave hope that muchmore information might be salvaged from the data.


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3 0

Next in energy range among the charged-particle or radiation detectorsis the trapped-radiation detector, designed to measure the Van Allen belt sof Earth, similar formations around Mars, and related phenomena inspace. Four detectors with acceptance angles of 60 degrees, three pointed70 degrees and one 135 degrees away from the Sun, detect electrons above40,000 and 150,000 electron volts and protons above % million, above 3.1million, from % to 11 million, and from 0.8 to 4.0 million electron volts.

The ionization chamber and Geiger-Mueller tube measured the i o n i z a ~tion caused by charged particles, and the number of particles, in the rangeabove 112 million electron volts fo r electrons and 10 million electron voltsfor protons. The Geiger tube was saturated, possibly by the solar flare ofFebruary 5, and fa i led on March 3; the companion ionization chamberfailed, probably as a consequence, shortly afterwards.

The cosmic-ray telescope is mounted on the shadowed side of th e spacecraft and has a 40-degree field of v i ~ w I t detects protons in three rangesfrom 0.8 to 190 million electron volts, and alpha particles in three rangesfrom 2 to far more than 320 million electron volts .

Mariner's helium magnetometer ha s a sensitivity of 0.5 gammas anda dynamic range of 360 gammas along each of three axes. (A t Earth'ssurface, the magnetic fie ld is about 50,000 gammas.) I t is mounted highon the spacecraft's low-gain antenna boom to minimize the effect of spacecraft fields, which were calibrated ea rly in the mission.

The cosmic-dust detector consists of an aluminum plate perpendicularto the spacecraft velocity vector. Two surface penetration detectors (oneither face) and a microphone attached to the plate indicate the momentum of each hit (greater than 0.00006 dyne-sec), th e direction, and thenumber of hits.Near Earth

During the first 2 days of the mission, Mariner IV passed through theregion of space influenced by the Earth: the Van Allen belts, the attenuating magnetic fie ld which holds them together, and the interface betweensolar plasma and geomagnetic field which is their source. The layers of thecandle-flame-shaped interaction between Earth and Sun were pierced andmeasured in turn, leaving their traces in th e data of the magnetomete r ,plasma probe, trapped-radiation detector, and ionization chamber, andcosmic-ray te lescope.

Two months later Mariner again passed through what was expected tobe a zo ne influenced by Earth, when at a range of about 12% million milesit came close to opposition-directly behind the Earth as seen from theSun. Any magnetic-plasma disturbance here, corresponding to Earth's"wake" in the interplanetary sea, was too faint to detect.Between Planets

From Earth to Mars, Mariner IV indicated the impact of about 200micrometeorites, compared with two impacts noted between Earth and


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./ - - - - - -/ -- /-/ / ' ---- --- --~ ~ - - - - - ~ ~I / . / ------I / / - - - - ......... ,/ / / /' -.........................I I SOLAR P A R T \ ' .........I / . -- - - - - --- .JI MARINER IV .........I

I / / ' / ' """"1t .........\ 1./ .-- -- - '- ,\ \ f / / . / / ' . __ - - - _........ .................., '\ \ I / / / ' --:- _ _ _ , ,-, , ' - ~ " , " "\

SUN \ Th e solar flare of F ebruary 5, 1965

Venus in 1962. The pattern was generally one of irregular increase goingtoward Mars, with a falling off as the orbit of Mars was approached, suggesting that each planet sweeps a relatively dust-free path fo r itself as ittravels around the Sun, and that-over the region from Venus to Marsat least-the particles become fewer as one nears the Sun. No well-defineddust streams were identified, though encounter with a few c o m e t a r y ~ o r b i tstreams associated with shooting-star events had been predicted.

Mariner made its journey during the period of the "quiet sun": theminimum-activity portion of the ll-year solar cycle. Nevertheless, en routeto Mars, it detected the effects of solar flares in February, April, May,and June. These were evidenced as magnetic disturbances (caused by thepassage of charged particles), as increases in the flow of the particlesthemselves at various energy ranges, and even as indications from thecosmic-ray telescope, which points away from the Sun but apparentlydetected solar particles scattered or reflected by disturbances in the interplanetary magnetic field. A number of these flares were observed opticallyin the Sun's atmosphere from Earth.

Experiment DataDes cri pt ion

TV subsystem : up to 21 pictures of Martian surface

Helium magnetometer: planetary and interplanetarymagnetic fields

Solarplasma probe: quantity rate and energy ofpJsi tive ion Hwind "

lonizationchamber /particleflux detector:corpuscularradiation "dose rate"

Trappedradiation detector: lowenergy solar chargedparticles and planetary " radiation belts"

Cosmicray telescope : highenergy charged particlesCosm icdust detector: miGrometeor ite COUflt andmomentum

OCCUltation (no instrument): Martian atmosphere asdeduced from its effect on spacecraft ' s signalduring OCCUltation by the planet

* principal investigator

Experi mentersR. B. Leighton* , B. C. Murray, and R. P. Sharp, all of CIT,and R. K. Sloan and R. D. Allen of JPLE. J. Smith* of JPL ,P. J. Coleman Jr. of UCLA ,L. Davis Jr. of CIT,and D. E. Jones of Brigham Young University and JPLH. L. Bridge' and A. Lazarus of MIT,and C. W. Snyder of JPLH. V. Neher* of CIT,and H. R. Anderson of JPLJ. A. Van Allen *, L. A. Frank, and S. M. Krimijis, all ofState University of IowaJ. A. Simpson * and J. O Gallagher of University of ChicagoW. M. Alexander*, O. E. Berg, C. W. McCracken , andL. Secret an , all of NASA / GSFC ,and J. L. Bohn and O. P. Fuchs of Temple Univers ityA. J. Kl iore*, D. L. Cain, and G. S. Levy , all of JPL ,V. R. Eshe lman and G. Fjeldbo of Stanford University,and F. Drake of Cornell University Proj ect scien tists and experi-mente?'s


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ONE DAY WITH ANOTHER PLANET

Mariner IV approached its rendezvous with Mars in good condition tocarry out its mission. All critical elements were working well; most s p a c e ~craft measurements were close to ideal. The plasma probe was still functioning, though in a limited sense, and the ionization chamber was out ofservice. Chances for recovery seemed remote. But the spacecraft attitudewas stable, the temperatures were within expected margins, and the radiosignal was coming in steadily.to the Earth at about 0.0000000000000000001watt: a bit faint fo r conventional receivers*, but well above the thresholdfo r the fantastically sensit ive Deep Space Instrumentation F acility stationsat Johannesburg, Madrid, Canb erra, Woomera, and Goldstone. Periodicallyduring the flight, the ground transmitters were turned on for commandtransmission or two-way tracking; now, as encounter approached, theywere in two-way operation.

The spacecraft's planetary science platform, containing the TV cameraand planet sensors and capable of scanning through a wide angle to pointthe camera at Mars, had been partly exercised by ground command ea rlierin the flight, an d the len s cover had been re moved. But the tape recorderand other elements had not been operated since before launch.Landfall

Mariner-Mars encounter began properly with an event on Earth, not onein space. The Johannesburg DSIF station transmitted a command to turnon the TV scan platform, anticipating by about an hour a similar on-boardcommand from the CC&S. This was the first of eleven ground commandstransmitted to the spacecraft during encounter operations.

Unlike the Ranger Project, which kept constant two-way contact withthe spacecraft, Mariner communications we re mostly spacecraft-to -Earth,with the ground transmitters brought into use only periodically: fo rtesting, fo r precise doppler tracking-when a stable oscillator's frequencyis sent to the spacecraft, multiplied by a known factor (240/221), and sentback fo r comparison with the original signal so accurately that a changein velocity of 1 millimeter per second can be observed-and for commandtransmission. The commands are coded digitally, like the telemetry: eachcommand is a string of 26 1-second-Iong bits, each bit recognizable aseither a one or a zero, and each command corresponding to a particularswitch closure leading to an action on board. At Mars' distance, it took12 minutes fo r the command to travel to the spacecraft, and 12 minutesmore for the resulting action or acknowledgement to be observed back onEarth.

Acting on the first encounter command, the camera platform begancycling back and forth through a I80-degree arc, making a complete..An average home TV se t signal is about 0.0000001 watt .


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N ew S-band t?'acking station n ea?' Mad?'id, Spain , ?noni to?'ed th e encounter with Ma?s.

circuit every 12 minutes. The TV camera began exposing pictures every48 seconds, alternating between red and green filters, but no pictureinformation was recorded at this stage: Mars was not yet in view.

Two hours and 42 minutes after turning on the platform, the operatorscommanded it to stop, po itioning it only %. degree from the optimumangle for photographing Mars . Backing up this command, a wide-anglesensor would have stopped the cycling on sighting the planet. Now anarrow -angle sensor would activate the tape recorder and begin recordingpictures of Mars as soon as it was actually in front of the lens.

A third command was sent 5 hours after the platform had been positioned, switching off spacecraft-bus te lemetry so that the entire transmission was given over to the scientific experiments, their status, and theirfindings . Of particular interest at this critical time was the condition andbehavior of the TV subsystem.Shutterbug

Mariner's searching eye is built around the vidicon, a TV image tubewhose compact dimensions and modest power requirements recommend itfor spacecraft use. (The Ranger spacecraft also employed vidicons.) Thescience control subsystem shutters the camera optics every 48 seconds, placing red and green filters alternately before the lens. A telescope of I2 -inchfocal length and I -degree field of view brings the image to the TV tube, onwhose faceplate it is about 0.22 inch square. Scanning the image in 200lines (of 200 dots or picture elements each), the TV camera produces adigital signal of 240,000 bits per picture, which is recorded on a two-track


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1,4-inch magnetic tape loop 300 feet long, capable of recording a little morethan 21 pictures. The tape runs over the recording head at about 13 inchesper second and stops between pictures to save tape. Only two out of everythree pictures taken are r ecorded on th e tape, resulting in a chain of pairsof overlapping alternate-color pictures extending all the way across thedisk of Mar s.

The picture recording seq uence was st arted automatically at 0018 15Ju ly Greenwich Mean Time (the standard 24-hour system used in spaceoperations) ; 12 minutes later, at 5 :30 p.m., July 14, Califo rni a time, theGoldstone DSIF station received notice of this event from the spacecraft.While the 26-minute sequen ce was still underway, two signals were re ceived indicating that the end of the recording tape had been reached,prematurely and perhaps disastrously. Other telemetry r eceived arguedthe contrary. Mariner's captain and crew, back on Earth, could only wa itit out.

Two backup commands had been sent to sh ut off the picture-recordingoperations and ret urn the spacecraft to the cruise mode of mixed engineering and science data; the second command was repeated six times, toensur e the turn-on of the cruise science, which was dependent upon groundcommand. The television subsystem, having r ecorded part of picture No. 22and filled its magnetic tape, shut itself off and ordered the telemetry systeminto cruise mode, and the cruise science came on as soon as commanded.

The spacecraft ha d been approaching th e Martian surface throughoutthe picture-taking sequence : the range had been 10,500 miles (a long thecamera ax is) for the first picture, and had shrunk to 7,400 miles whenpicture No. 17 was exposed. A quarter of an hour later, Mariner IV camewithin 6,118 miles of Mars, which was going around the Sun more than11,000 miles per hour faster than Mariner.

134 MILLION MILES TO EARTH (12 MINUTES BY RADIO)................

Space Flight Ope1'ations Di?'ector


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~ - - - ____MA_RS ORBIT

.A '

Behind Mars

LEAVING OC CU LTATI ON t0325 :07 GMT "*-

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~ ENTER ING0 ' .Xl. OCCULTATION"C t . ' r : / ; ~ - r . t 0231:12 GMTS\\.tl' . ' )\ I ' \ ~

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....... . S \ C , ~ I ' \ . S~ I ' O \ O

Occul tation geometry (Ma?'s fixed)The mission had been designed to occult t he spacecraft behind the

planet, so that the Martian atmosphere could be observed from its effecton Mar iner's radio signal. The occultation of stars behind planets hadpreviously played a part in various planetary investigations, and observa-tions of the occultation of the satellites of J upiter by the planet fromopposite sides of Earth' orbit led to the first accurate estimate of th e speedof light (the apparent delay across 186 million miles being about 1,000seconds, a value of 186,000 miles per second was calculated) .

Going one stage further, Mariner provided a "coherent source" of pre-cisely calibrated frequency, backed up by detailed predictions and extremelyaccurate equipment. The po ition and motion of the tracking stations, theac tual spacecraft flight path, the transmission of the signal across 150million miles, and the effects of Earth's atmosphere all had to be and wereprecisely known. I t would be the apparent changes in spacecraft motion,ca used by the refraction of th e signal, which would reveal the propertiesof Mars' atmosphere.

About n ~ hours after closest approach, the radio signal grazed Mars'ionosphere. Then, like a fishing line cutting the water, it sliced through.


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37

For 2 minutes, the 2300-megacycle s ignal was bent and slowed by theatmosphere, and then it vanished. For the first time in 7112 months noMariner signal was beaming to Earth . Almost an hour later Mariner'ssignal reappeared on the other side of Mar s, and tracking began again.

Mariner's flight path was bent slight ly by Mars' gravity during thespacecraft's close brush with the planet. The tilt of its orbit relative tothe Earth's was changed f rom 8 minutes to 21/2 degrees, the period of theorbit was extended from 529 to 587 days, and the orbit was widenedconsiderably.Home Run

Mariner continued sampling t he space environment just ou tside theorbit of Mars for 81;2 hours; then the spacecraft's CC&S turned off thecruise science and began the playback mode, in which engineeri ng telemetrywould alternate with playback of the TV picture data at 1/100 inch persecond by the tape recorder-if picture data had been recorded. Doubt stillclouded the air in the control rooms on Earth as the first segment of engineering telemetry began to appear: had the end-of-tape signal receivedduring the picture-taking phase been an erroneous signal or a true indication of erroneous spacecraft behavior?

A long hour and 8 minutes later what should h ave been the first elementsof picture No.1 began to appear in the te lemetry . At 21/2 minutes per lineof the picture, it was several minutes before enough lines had been received0 that the edge of the Martian di k could be recognized.

The Mariner crew of technicians, engineers, scientists, and managershad waited and worked more than 21/2 years since the start of the project,7% months since the start of the mission and, on th is sleepless day ofencounter, 23 hours for this picture of Mars . But they were not too tiredto cheer.


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The tape recorder continued to read out the brigh tness of each elementof the first picture until it was complete. In the interval between pictures,corresponding to stopping the tape and starting it again, almost 2 hoursof engineering measurements were transmitted. Th is process, the slow andpainstaking buildup of each picture followed by 2 hours of spacecraftdiagnostic te lemetry, co nti nued t hrough the fragmentary twenty-secondpicture and through a econd run of the whole tape, while t he spacecraftdrew on past Mar s and away f rom Earth, and beneath it the Earth turned,bringing one after an other each of the great receiving antennas to bearon the spacecraft, until a ll of the data had come home to Earth.

NEW VIEW OF AN OLD WORLD

Twenty-one pictures don't go very far in covering a whole planet; nordo two passes through the atmosphere with a sing le radio beam, or a fewhours of mag ne t ic and charged-particle data. But by comparison with th etenuous and indirect sources of information previously available fo r thestudy of Mars, in the context of the various theoretical models of Martianconditions, and given the elegant modern techniques of da ta-handling, correlation, an d calculation, Mariner's view of Mars is a broad and profoundone indeed.


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Th? 'ee ea?'Zy pictures of the Martian su?face, Picture No, 1 (top) shows th e light region Phlegra on th e limb of th e planet,The spacecmft was appToxi mat ely 10,500 miles from th e area in the cen ter; a r ed filter was used, "Raw" picture is at Zeft,computer-processed version at right, B elow, pictu7'es 3 (l eft ) and 4 (right) show th e light r egion southeast of Phleflra andTr ivium Charontis , The Su n is 14 deg from th e zenith; slant range is 9500-9300 miles. Green filter was us ed on No , 3, whosecontrast enhancement facto?' is 5; No.4 is through a red filt er , and it s contrast is tripled. No . 3'8 lower right corner overlapsNo, 4's up per left ; north is approximately at top,


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40

CratersThe most arresting single phenomenon of the entire mission is the dis

covery of dense-packed lunar-style impact craters on the Martian surface.Though the television experiment's principal investigator had casuallymentioned the possibility of Mars craters in a press briefing before theencounter, and the scientific literature reveals at least one prediction of aMoon-like surface on Mars, the actual presence of craters as they appearedin the developing pictures amazed the watching group of scientists.

More than 70 craters appear in th e Mariner IV pictures, which coverless than 1 per cent of the surface : if these areas are representative ofMars, there might be 10,000 craters within the 75- to 3-mile size rangeshown in the photographs. Slopes measured so far range only up to 10degrees; no features sharp enough to cast shadows were observed. Craterrims rise perhaps hundreds of feet above the surrounding terrain, andtheir interiors are depressed in the thousands of feet. One large elevationchange, possibly that of a giant crater only partially seen, was estimatedat 13,000 feet.


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TM ee photographs of Ma1 ,tiancrate1'S, P icture No, 5 (top,p, 40), taken through a r ed filte r at a range of 8400 miles, de finitely pu t Martian craters onthe map, Ghostly craters alongthe n01,thern border of Phaethon tis, pictured on this page, mayhave been rimmed with f1'ost ,Pictu1'e 13 (top) was ta k entMoug h a re d filter, No, 14throngh gr een ; slan t range is7600 miles, a1'ea of each pictur eabout 175 by 140 miles (west by1w1,th) , Lower 1-ight cot-ner of13 overlaps uppe1' left corner of14 ; Su n was 30-3 5 degrees abovenorthern hm'izon, North is at topin all three pictures, and contrast is appt'oximately dou bled,


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A number of craters near the evening terminator-and hence in the coolof the afternoon- appear frosted. The nature of this frost is unknown, butthe conditions would be consistent with its being water.No clear evidence of the famous Martian canals was apparent in theMariner pictures . We must remember that the glistening lunar crater rayswere resolved on magnification by Ranger cameras into chains and clustersof small secondary-debris craters. Possibly some equally unsuspectedexplanation may link the Earth-based and spacecraft views of the Martiansurface.

The unearthly appearance of Mars as seen from the spacecraft had amajor impact on' our idea of Mars . This Martian topography is very oldand, apparently, very little changed. Impact craters of Martian and lunarproportions very likely existed on Earth at one time, bu t the processes ofgrowth and weathering, of mountain-building and canyon-carving, havelong since ground all but a very few away to nothing. Mars is more likethe Moon in its apparent lack of such smoothing.The Thinnest Air

Mars' ionosphere and atmosphere, as measured by the impinging radiobeam from the departing Mariner spacecraft, are somewhat less dense thanhad been expected. The maximum electron density encountered by the beamwas 90 ,000 electrons per cubic centimeter, at an altitude of about 80 miles.From this the density at the subsolar 'point was calculated to be 150,000.Indications of a second ionized layer below the den ser one were observed.The atmospheric pressure at the surface was estimated at 4 to 7 millibars (0.4 to 0.7 % of Earth 's surface pressure), depending on the argon/nitrogen/carbon dioxide proportions assumed for the composition .

According to the principal investigator fo r this experiment, comparisonof various atmospheric properties suggests that carbon dioxide is themajority constituent, and that the proportion of nitrogen is very small.This would provide the best agreement with the telescopic Mars atmosphere studies which were based on carbon dioxide spectral lines. Moreover,a thin blanket of air correlates very well with the cratered appearance ofthe surface, for a dense atmosphere might have shielded the planet frommost of the meteoritic impacts, believed to be responsible for the craters.

Mars occulted the spacecraft with its sunl it side, between Electris andMare Chronium. The signal emerged above Mare Acidalum, on the nightside; the ionosphere was so tenuous as to be indetectab le.Martian Fields

Mariner's interplanetary instruments searched in vain for evidence ofEarth-like radiation belts or magnetic fields. The radiation levels to whichthe scientists had become accustomed in the interplanetary phase of themission continued virtually unchanged through the encounter with Mars .

From the perturbation of Mariner's orbit at encounter, the trajectoryanalysts deri ved the mass of the planet Mars as being 0.03227 % of the


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Sun's mass (that is, Mars contains about 1,428,000,000,000,000,000,000,000pounds of mass) .

The magnetometer experimenters estimated that Mars' magnetic moment is no greater than 0.03 of Earth's. Th i would account fo r theab ence of radiation belts and magnetic shock layers around Mars, thoughthey have been observed above Earth . The more interesting problem lies inaccounting fo r the absence of Mar ' magnetic field or conversely, the presence and strength of Earth's.

The initial exploration of space in the past several years, of the Moonin 1959-65, of Venus in 1962, and now of Mars, has increasingly turned ourattention inwards toward our own planet. Reporting the results of theMariner Mars Project to Pre ident Johnson, the experimenters spoke of"the uniqueness of Earth" in our olar system . Yet the buried secrets ofEarth's origin and early evolution may lie exposed upon these di tantworlds, waiting to be picked up.

Mariner IV has opened Mars as we might open a book at random, toglance at one page. We have th e whole book- and the rest of the l ibraryyet to read .

P1esenting Ma1 iner IV result s to Pr esident L yndon B. J ohnson


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The Log of Marine r I V

November 28, 19641422:01.39 GMT1507:101515:001530:57

November 290659:03

November 301102:47

December 41305:00to 2402:44

December 51305:00to 1658:19

December 6

December 7-9D e c e r r . ~ e r 13

December 17

January 3, 1965

January 10-13

February 5February 7-22

February 11

March 3

March 5

LiftoffSpacecraft/Agena separationSolar panels deployedSun lock completed

Canopus search started

Canopus lock completed

Midcourse maneuver attempted by ground command;Canopus lock lost. Maneuver cancelled from Earth,Canopus reacquired after seven commanded "starhops"

Successful midcourse maneuver (6 ground commands)

Component failure in plasma probe: scientific datapartly unintelligibleCanopus lock lost, Gamma-Vela acquired repeatedlyTransmitting amplifiers switched (to Traveling WaveTube)Star lock lost, reacquired; star-hop commanded fromEarth, Canopui reacquired. Star sensor desensitizedto excess brightness by ground commandTelemetry rate switched by on-board command from33113 to 813 bits per second; plasma-probe data improved at new rateJohannesburg station assigned to Ranger VIII test:61/2-hour daily telemetry blackoutSolar flare detected by science instrumentsJohannesburg station assigned to Ranger VIII test andoperations; 61h-hour daily telemetry blackoutTV lens cover removed , planetary equipment checkedand prepared (12 ground commands)Plasma-probe failure mechanism analyzed, permitting70% data recoverySpacecraft transmission switched from omni to highgain antenna by on-board command

March 10-25

March 17

Apri l 16May 26June 5 and 15July 14

1427:55

1440:321710:181722:55

July 150017:210043:450100 :570219:11

0231:120313:04

0325:061141:501301 :582138:072332:27

July 24August 2

August 26

August 30 -September 2October 1

45

Johannesburg station assigned to Ranger IX test aoperations; 61/2-hour daily telemetry blackoutlonizationchamber instrument failure (Geiger-Muelltube failed March 3)Solar-flare indicationsSolar-flare indicationsSolar-flare indications

Mars encounter science command transmitted froEarthCommand received: encounter science onCamerapointing command transmitted from EarthCommand received: camera pointed

TV picture recording sequence started at spacecraftTV picture recording sequence completeClosest approach to Mars (6118 miles above surfaSpacecraft passes behind Mars at 55S, 177E, 15,8milesSpacecraft signal loss on EarthSpacecraft emerges from occultation at 60 0 N, 34 24 ,260 milesSpa cecraft signal reacquired at EarthPicture playback mode initiatedFirst data from Picture 1 observed on EarthPicture 1 data complete on EarthStart of Picture 2 reception on EarthPicture playback complete; second run startedSecond picture playback complete; spacecraftturned to cruise mode by ground commandConditioning commands transmitted to spacecraftprevent accidental midcourse sequence) for pencounter cruise

TV test: five pictures of black sky obtained and tramitted to EarthSpacecraft transmission switched from high-gainomni antenna by ground command; telemetry no londetectable on Earth


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N O V ~ O - - - - - M A R S ORBITFEB. 5sr"

\14

/ SOLAR FLAREFEB . 5!:: ~ LAUN CHIf I SUN NOV. 28, 1964'i 0- 0JOCT.

U ~ V~ ~ 1OCT. 1 _..

Mariner's Course

Distance traveledDate along trajectory,

mi

Dec. 1, 1964 525,782Dec. 11 22,649,177Dec. 21Dec. 31Jan. 10, 1965Jan . 20Jan. 30Feb. 9Feb. 19March 1March 11March 21March 31April 10April 20April 30May 10May 20May 30June 9Jun e 19June 29July 9

En counterJuly 14July 29Aug. 8Aug. 18Aug . 28Sept. 7Sept. 17Sept. 27Oct. 1

Farthest from Earth

40,24 1,57557,574,47174,583,45191,219,961

107,451 ,878123,261,850138,644,479153,605,290168,155,150182,311 ,410196,094,740209,528,220222,636,480235,445,090247,980,100260,267,760272,334,370284,206,150295,909,190307,469,390319,123,300

325,982,177344,383 ,125356,021 ,476367,628,758379,223,366390,823,717402,448 ,24 3414,11 5,356418,798,296

Dec. 30 , 1965 527,941 ,670Closest to SunJun e 7, 1966 768,384 ,900

Closest to EarthSept. 8, 1967 1,374, 126,700

Mariner position and velocity log

From Earth

517 ,8702,203,9953,873 ,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

102,362,020111,453 ,380120,485 ,400129,375,820

134,400 ,890146,806 ,930154,772,430162,416,900169,701,290176,561 ,700182 ,962,130188,870,060191,082,640

215,830 ,190

196,945 ,440

29,167,205

Straight line distance, mi

From Mars

126,953,200116,862,720106,848,830

97,078,05487,675,43678,740,11670,342,94362,528,06855,316