Mariner I Press Kit

8/8/2019 Mariner I Press Kit

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N EWS R ELEASENATIONAL AERONAUTICS AND SPACE ADMINISTRATION400 MARYLAND AVENUE, SW, WASHINGTON 25, D C.TELEPHONES WORTH 2-4155-WORTH 3-1110FOR RELEASE: THURSDAY A"M'sJuly 19, ].9b62

Belease No. 62-157MARINER SPACECRAFT

Mariner I, the first of a series of spacecraftdesigned for interplanetary exploration, will belaunched within a few days (no earlier than July 21)from the Atlantic Missile Range, Cape Canaveral, Fla.,by the National Aeronautics and ,,,ace Adminlstration.The mission of the initial Mariner is to flyby the planet Venus and make infrared and microwavemeasurements of the planet; communicate this infor-matron to earth over an interplanetary distance of36 million miles, and obtain data on interplanetaryphenomena during the trip to Venus.The closest approach of Mariner to Venus willbe about 10,000 miles.Five scientific experiments will be aboard theMariner to provide data on deep space during the ex-tended flight. Plight times wall vary from 100 to

1)10 days depending on the launch date.Project Management for the Venus Mission wasassigned to the California Institute of TechnologyJet Propulsion Laboratory by the National Aeronauticsand mpace Administration. This includes responsi-bility for the spacecraft system and space flightoperations. The Marshall Space Flight Center has theresponsibility for providing the launch vehicle, withthe support of the U.S.A.F. Space Systems Division.


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The Atlas D first stage is provided by GeneralDynamics Astronautics, and the Agena B second stageis provided by Lockheed Missiles and Space Company.FKey personnel in the Mariner Project are:Fred D. Kochendorfer, Mariner Program Chief, NASAHeadquarters; D. L. Forsythe, Agena Program Chief;Robert J. Parks, Planetary Program Director for JPL;J. N. James, JPL, Mariner Project Manager; W. A.Collier, JPL, Assistant Project Manager, Dan

Schneiderman, JPL, Spacecraft System Manager;Friedrich Duerr, MSFC, Launch Vehicle SystemsManager; Major J. G. Albert, Mariner Launch VehicleDirector for AFSSD; and H. T. Luskin, Director forNASA Programs, Lockheed Missiles and Space Company.NASA has assigned two launches for Mariner totake advantage of the period during which Venus willbe close to earth this year. The next launchopportunity for Venus occurs in 1964. Mariner 2 isat Cape Canaveral and will be launched as soon aspossible after Mariner 1. The major factor in thedecision to launch two Mariners is the difficultnature of the mission.This mission is. a difficult one because ofseveral factors: the long life of the flight, extend-ing up to 140 days; the spacecraft will be subjectedto a prolonged variation in temperature caused by thevariation in distance from the sun and increasingintensity of the sun; radiation effects in interplane-tary space are not fully known, and the difficulty oftransmitting a considerable amount of information overan extreme range.Mariner tracking and communication will be pro-vided by JPL's Deep Space Instrumentation Facility withpermanent stations at Goldstone, California, Woomera,Australia, and Johannesburg, South Africa and mobilestations at Cape Canaveral and near the permanentstation at Johannesburg. Data flowing into thesestations from the spacecraft will be routed to JPL'sSpacecraft Flight Operations Center for correlationby an IBM 7090 computer system.

3PACECRAFT DESCRIPTIONThe Mariner weighs 446 pounds and, in the launchposition, Is xive feet-in-diameter at the base and 9feet, 11 inches in height. In the cruise position, withsolar panels and high-gain antenna extended, it is 16.5feet across in span and 11 feet, 11 inches in height.

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The design is a variation of the hexagonalconcept used for the Ranger series. The hexagonframework base houses a liquid fuel rocket motor,for trajectory correction, and six modules contain-ing the attitude control system, electronic circuitryfor the scientific experiments, power supply, batteryand charger, data encoder and command subsystem,digital computer and sequencer, and radio transmitterand receiver. "uri sensors and attitude control jetsare mounted on the exterior of the base hexagon.

A tubular superstructure extends upward fromthe base hexagon. Scientific experiments are attachedto this framework. An omnidirectional antenna ismounted at the peak of the superstructure. A parabolic,high-gain antenna is hinge-mounted below the basehexagon. Two solar panels are also hinged to thebase hexagon. They fold up alongside the spacecraftduring launch, parking orbit and injection and arefolded down, like butterfly wings, when the craft isin space. A command antenna for receiving transmissionsfrom earth is mounted on one of the panels.

The solar panels contain 9800 solar cells in27 square feet of area. They will collect energy fromthe sun and convert it into electrical power at aminimum of 148 watts and a maximum of 222 watts. Theamount of power available from the panels is expectedto increase slightly during the mission due to theincreased intensity of the sun. Each solar cell hasa protective glass filter that reduces the amount ofheat absorbed from the sun, but does not interferewith the energy conversion process. The glass coversfilter out the sun's ultraviolet and infrared radiationthat would produce heat but not electrical energy.

Prior to deployment of the solar panels,power will be supplied by a 33.3-pound silver-zincrechargeable battery with a capacity of 1000 wattnours. The recharge capability is used to meet thelong-term power requirements of the Venus Mission.The battery will supply power directly for switchingand sharing peak-loads with the solar panels and alsosupply power during trajectory correction when thepanels will not be directed at the sun.

The power subsystem will convert electricityfrom the solar panels and battery to 50 volt, 2400 cps;26 volt, 400 cps, and 25.8 to 33.3 volt DC.

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s led communication aboard the Marines issupplied by the receiver/transmitter, two transmittingantennas: the omnidirectional and high-gain antenna;and the command antenna for receiving instructionsfrom earth. Transmitting power will be 3 watts.The high-gain antenna is hinged and equippedwith a drive mechan>-m allowing it to be pointed at

the earth on command. An earth sensor is mounted onthe antenna yoke near the rim of the high-gain dish-shaped antenna to search for and keep the antennapointed at the earth.Stabilization of the spacecraft for yaw, pitchand roll, is provided by ten cold gas jets, mounted infour locations (3,3,2,2,), fed by two titanium bottlescontaining 4.3 pounds of nitrogen gas pressurized to3500 PSI. The jets are linked by logic circuitry tothree gyros in the attitude control subsystem, to theearth sensor on the parabolic antenna and to six eunsensors mounted on the spacecraft frame and on theback of the two solar panels.The four primary sun sensors are mounted onfour of the six legs of the hexagon, and the twosecondary sensors on the backs of the solar panels,These are light-sensitive diodes which inform theattitude control system -- gas jets and gyros -- whenthey see the sun. The attitude control system respondsto these signals by turning the spacecraft and pointingthe longitudinal or roll. axis, toward the sun. Torquingof the spacecraft for these maneuvers is provided bythe cold gas Jets fed by the nitrogen gas regulated to15 pounds per square inch pressure. There is calculatedto be enough nitrogen to operate the gas jets to main-tain attitude control for a minimum of 200 days,Computation for the subsystems and the issuanceof commands is a function of the digital CentralComputer and Sequencer. All events oL' the spacecraftare contained in three CC&S sequences. The launchsequence controls events from launch through the cruisemode. The midcourse propulsion sequence controls themidcourse trajectory correction maneuver. The encountersequence provides required commands for data collectionin the vicinity of Venus.The CC&S provides the basic timing for thespacecraft subsystems. This time base will be supplied

by a crystal control oscillator in the CC&S operatingat 307.2 kc. This is divided down to 38.4 kc fortiming in the power subsystem and divided down againto 2400 and 400 cps for use by various subsystems.-4-


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The control oscillator provides the basic "counting"rate for the CC&S to determine issuance of commandsat the right time in the three CC&S sequences.The subsystems clustered around the base ofthe spacecraft are insulated from the sun's heat bya shield covered with layers of aluminum coatedplastic film. At the bottom of the spacecraft, justbelow the subsystem modules, is a second TemperatureControl Shield. It prevents too rapid loss of heatinto space which would make the establishment of re-quired temperatures difficult to maintain. The twoshields form a sandwich that helps to minimize theheat control problem.Temperature control of the attitude controlsubsystem is provided by louvers actuated by coiledbimetallic strips. The strips act as coil springsthat expand and contract as they heat and cool.This mechanical action opens and closes the louvers.The louvers are vertical on the face of the attitudecontrol box and regulate the amount of heat flowing

into space. This is a critical area as some of theequipment may not function properly above 1300F.Pairtpatterns, aluminum sheet, thin goldplate and polished aluminum surfaces are used on theMariner for passive temperature control of internaltemperatures. These surfaces control both the amountof internal heat dissipated into space and thetamountof solar heat reflected away, allowing the establish-ment of temperature limits. The patterns were de-termined from testing of a Temperature Control Model,The TCM was subjected to the variations of temperature

anticipated in the Venus Mission in a space simulationchamber at JPL.Communication with.the spacecraft will be indigital form. The command subsystem aboard theMariner will decode incoming digital commands and senothem to the designated subsystems. Data from engineei-ing and scientific sources will be encoded to digitalform for transmission to earth.Synchronizing pulses will be spaced at regularintervals between the data signals from Mariner.

Ground based receiving equipment will generateidentical pulses and match them with the pulses fromthe spacecraft. This will provide a reference todetermine the location of the data signals allowingreceiving equipment to separate data signals fromnoise.-5-


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Seven scientific experiments will be carriedaboard the Mariner. Five of these are designed tocollect information in space and in the vicinity ofVenus. The other two will provide information solelyon Venus and only operate as Mariner passes the planet.The experiments are:1. Microwave radiometer experiment to measuretemperature distribution on the planet's surface.2. Infrared radiometer experiment to provide

information on the distribution of thermal energy inthe planet's atmosphere.3. Magnetometer experiment to determine thethree mutually perpendicular components of the magneticfield in the interplanetary space between earth andVenus, and in the vicinity of Venus at planetaryencounter.4. Charged particle experiment to detect thedistribution, variations and energies of electricallycharged particles in space and in the vicinity of Venus.5. Ionization chamber to detect the rate atwhich charged particles lose energy.6. Plasma experiment to obtain information onthe extent, variations in, and mechanism of the solarcorona.7. Micrometeorite experiment to measure thedensity of cosmic dust particles which exist in inter-planetary space and in the vicinity of Venus.The microwave radiometer is mechanized so it,can scan Venus during the fly-by. Initially, it willhave a fast scan search. W4hen it detects the planet,the radiometer will adopt a slow scan mode. Theinfrared experiment is attached to the rim of thedish-shaped microwave device and will scan with thelarger instrument.

MISSION DESCRIPTIONThe launch vehicle for the Mariner will be anAtlas D-Agena B. The Atlas and the Agena will boost

Mariner to an altitude of 115 statute miles and anorbital speed of 17,450 miles an hour.Mariner will use the parking orbit techniquewhich is a means by which the geometry imposed on aVenus launch by the location of the Atlantic MissileRange at Cape Canaveral, Florida, is corrected byusing the second-stage rocket as a mobile launchingplatform in space 6


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During the launch phase, the Mariner space-craft is protected against aerodynamic heating by ashroud. After Atlas cutoff, approximately 5 minutesafter liftoff, the shroud is jettisoned by eightspring-loaded bolts which shove it ahead of thevehicle. At almost the same time, the Agena Bseparates from the Atlas. The Agena B then pitchesdown from an attitude almost 15 degrees above thelocal horizon to almost level with the localhorizon.In this horizontal attitude the Agena B fires

for the first time and burns for almost two and a halfminutes to reach orbital speed of 17,450 miles an hour.After this burning time, Agena B shuts down and coastsin a parking orbit for more than 13 minutes until itreaches the optimum point in its orbit to fire forthe second time.The second Agena B burn injects the Agena Band Mariner, still as one unit, on an escape trajectoryat a velocity of about 25,820 miles an hour. Injectionoccurs approximately over Ascension Island in the SouthAtlantic Ocean and approximately 23 to 34 minutes after

launch, depending on time of launch.A little more than two minutes after secondburn cutoff or injection, Mariner is separated fromAgena, again by spring-loaded bolts. Agena then yaws140-degrees in the local horizontal plane and performsa retro maneuver which reduces the agena velocity andmoves the Agena into a differert trajectory. Pro-;ulsion for the retro maneuver is provided by ejectingthe unused fuel on the Agena t'Arough small jets. Theretro maneuver serves two purposes: To prevent the Agenafrom impacting Venus: and foll)Wng Mariner too closelyso that the spacecraft optical sensors might mistakereflected sunlight from Agena B for the sun or earthand confuse its acquisition system.Separation from the Agena will cause theMariner to begin a tumbling motion. These residualseparation rates are cancelled out by the yaw, pitchand roll gyros acting on the gas jet stabilizationsystem.Mariner now is on a trajectory that sill takeit fairly close to Venus. The omnidirectional antennais working and radiating the radio transmitter's fullthree watts of power. Before and during launch, thetransmitter had been kept at about 1.1 watts. Thisis required during the period the launch vehicle passesthrough a critical area between 150,000 and 250,000feet, where a tendency exists for devices using highvoltage to arc over and damage themselves; hence,the transmitter is kept at reduced power until thisarea is passed. -7-


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Following is the sequence of events thatMariner will conduct on its flight to Venus.The first command Is issued by the CC&S 44minutes after launch. Explosive pin pullers holdingthe solar panels and the radiometer in their launchposition are detonated to allow the spring-loadedsolar panels to open and assume their cruise positionand free the radiometer to scan Venus as it passesby the spacecraft. Although the radiometer will notfunction until Venus encounter, It is convenient tounlock it at this point.At launch plus 60 minutes, the CC&S turns onthe attitude control system and the sun acquisitionmode will begin. The sun sensors, linked to thevalves controlling the gas jets, jockey the space-craft about until its long axis is pointed at thesun thus aligning the solar panels with the sun.Both the gyros and the sun sensors can activate thegas jet valves. A backup radio command capabilityis provided to initiate the CC&S function and sunacquisition.In order to conserve gas, the attitude controlsystem permits a pointing error toward the sun of onedegree, or .5 degree on each side of dead on. Themixing network in the attitude control system iscalibrated to keep Mariner slowly swinging throughthis one degree of arc pointed at the sun. Theswing takes approximately 60 minutes. As Marinernears the .5 degree limit on one side, the sensorssignal the gas jets and they fire again. This processis repeated hourly through the effective life ofMariner. It is calculated that the gas Jets willfire one-fiftieth of a second each 60 minutes to

keep the spacecraft's solar panels pointed at thesun. When the sun has been acquired, the gyros areturned off to conserve their life and to lower thepower demanded or the solar panels.The sun acquisition process is expected totake less than 30 minutes. When it is completed,the secondary sun sensors on the backs of the solarpanels are turned off to avoid having light fromthe earth confuse them.As soon as the solar panels are locked on

the sun, the power system will begin drawing electricpower from the panels. The battery will now onlysupply power in the event of a peak demand that thepanels cannot handle. Excess power from the solarpanels will be utilized to recharge the battery.- 8-


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The next event initiated by the CC&S is theacquisition of earth by the high gain directionalantenna. This does not occur, however, until 167hours (seven days) after launch. The earth sensorused to align the antenna is so sensitive that itwould not operate properly if used earlier, Onceagain, a radio command capability is provided toback up the initiation of this event.

During earth acquisition, the spacecraftmaintains its lock on the sun, but with its high-gain directional antenna pointed at a preset angle,it rolls on its 'long axis and starts to look forthe earth. It does this by means of the three-section, photo-multiplier-tube operated earthsensor mounted on and aligned with the high-gainantenna. During the roll, .the earth sensor willsee the earth and inform the gas jets. The jetswill fire to keep the earth 4n view of the sensorand thus lock onto the earth. The sensor has alens system to magnify the earth image.The spacecraft now;is stabilized on two-axes--the solar panel-sun axis and the earth-directionalantenna axis. There is some danger that the earthsensor, during its search for the earth, may see themoon and lock onto that, but telemetry later will informearth stations if this has occurred, and Goldstone hasthe ability to send an override command to the attitudecontrol system to tell it to look again for the earth.If this is not sufficient, the stations can send ahinge override command to change the hinge angle andthen order another roll search. When the earth is

acquired, the transmitter stops transmitting on theomni-antenna and starts transmitting on the high-gain,antenna.A rise in signal strength will be an indicationthat earth acquisition has been achieved by theparabolic antenna. Positive proof will be afforded byanalysis of telemetry to determine the angle of theantenna hinge.With sun and earth acquisition achieved,Mariner is now in its cruise mode.The cruise mode will continue until time forthe midcourse trajectory correction maneuver. Afterlaunch, most of the activity on the Venus Mission willbe centered at the DSIF stations and at the SpaceFlight Operations Center at JPL.-9-


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Tracking data collected by the DSTF stationswill be sent to JPL and fed into the 7090 computersystem. The computer will compare the actual tra-jectory of the Mariner with the course required toyield a 10,000 mile fly-by. If guidance errorsbefore injection have put Mariner of' the optimumtrajectory, the computer will providt, t;he necessaryfigures to command the spacecraft Lvo alter itstrajectory. This involves commands for roll, pitchand motor burn. Roll and pitch point Mariner forthe trajectors correction. Motor burn will providethe additional velocity required to change direction.The first command from Goldstone will give thedirection and amount of roll required, the second willgive the direction and amount of pitch needed and thethird will give the amount of velocity incrementneeded. This data is stored in the CC&S untilGoldstone transmits a "go" command.Prior to the "go" command, Goldstone willhave ordered Mariner's transmitter to switch fromthe dish-shaped directional antenna, at the base ofthe craft, to the omni-directional antenna mountedat the peak of thesuperstructure.Commands preprogrammed in the CC&S for themidcourse sequence initiate the following: the earthsensor, mounted on the dish-shaped antenna, is turnedoff; the hinged-mounted directional antenna itself ismoved out of the path of the midcourse motor's exhaust,and the gyros will have been turned on an hour earlierto warm up. During the maneuver the gyros will informthe attitude control subsystem of the rate of pitch

and roll as they occur for reference against the ordersfrom earth. A pulse balanced accelerometer will beturned on to provide acceleration rates during motorburn to the CC&S. Each pulse from the accelerometerrepresents a velocity increment of 0.03 meters persecond,The roll maneuver requires a maximum of 12minutes of time, including two minutes of settling time,and the pitch maneuver requires a maximum of 22 minutes..When these are completed, the midcourse motor is turnedon and burns for the commanded time. As the attitude

control gas jets are not powerful enough tc, maintainthe stability of the spacecraft during the propulsionphase of the midcourse maneuver, moveable jet vanesextending into the exhaust of the midcourse motorcontrol the attitude of the spacecraft in this period.- 10 -


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The jet vanes are controlled by an auto pilotsubsystem in the attitude control system that functionsonly during the midcourse maneuver, The auto pilotaccepts information from the gyros to direct the thrustof the motor through the spacecraft's center of gravityto stabilize the craft.The liquid monopropellant motor weighs, withfuel and the helium pressure gas system 31.3 pounds.Hydrazine fuel is held in a rubber bladder inside a

door knob-shaped container called the pressure dome.On the command to fire, nitrogen under 3000 pounds ofpressure per square inch, is admitted inside thepressure dome and squeezes the rubber bladder, forcingthe fuel into a combustion chamber.Because hydrazine is a monopropellant, it needsa starting fluid to initiate combustion and a catalystto maintain combustion. The starting fluid, in thiscase nitrogen tetroxide, is admitted into the com-bustionchamber by means of 4 pressurized cartridgeand causes ignition. The catalyst, aluminum oxide

pellets is stored in the combustion chamber. Burningstops when the valves tourn off helium pressure andfuel flow.The midcourse motor is so precise that it canburn in bursts of as little as 50 milliseconds and canincrease velocity by as little as seven-tenths of afoot per second or as much as 148 feet per second. Ithas a thrust of 50 pounds for a maximum of 43 seconds.After the midcourse maneuver nas put Marineron the desired trajectory, the spacecraft again goesthrough the sun and earth acquisition modes.During midcourse Mariner has been transmittingthrough the omni-antenna. When earth is acquired, thetransmitter is switched to the high-gain directionalantenna. This antenna will be used for the durationof the flight.Mariner will continue in the cruise mode untilplanet encounter. During this period, tracking datafrom the three permanent DSIF stations will be sent toJPL where the 7090 computer system will refine theearlier calculations for planet encounter made atlaunch.The CC&S was programmed to begin the encountersequence ten hours in advance of encounter. Thisallows time for calibration of the planetary scientificinstruments before encounter in the event that the

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MARINER SCIENTIFIC EX e!*RIMUlNT3SEXXPlRIME.NTS DESCRIPTION iXP~'UII4ENER3Microwave Determine the temperature of 1Dr. . H. arrett,Radiometer the planet surface and de- Massachusetts Insti-tails concerning its atmos- tute of Tiechnology;

phere. D. . Jones, JPr[, Or.J. Co.eland, ArmyOrdnance MissileCommand; 1r. ;.i:.TLilley, HarvaraCollege Observatory.

Infrared Determine any fine structure Dr. L.D. Kaplan,Radiometer of the cloud layer. JPL and tJniversityof Nevada; Dr. C.Neugebauer, JPL:Dr. C. Sagan, Uni-versity of Calif.at Derkeley.

Magnetometer Measure changes in the P.J. Coleman., NASA,( planetary and interplane- Dr. L. Davis, Caltech;tary magnetic fields. Dr. E.J. Smith, JPL;Dr. C.P. Sonett, NASA.Ion Chamber and Measure charged-particle Dr. H.R. Anderson,Particle flux intensity and distribution JPL; Dr. H.V. Ncher,Detector in interplanetary space and Caltech; Dr. J. Vanin the vicinity of the Allen, State Uni-

planet. versity of Iowa.Cosmic Dust Measure the density and W.M. Alexander,Detector direction of cosmic dust. NASA Goddard SpaceFlight Center.Solar Plasma Measure the intensity of M. Neugebauer, andSpectrometer low energy protons from Dr. C.W. Snyder, JL.the sun.

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MARINER SCIENTIFIC EXPER1IMENTS

The Mariner spacecraft contains six scientific experimentsrepresenting the efforts of scientists at nine institutions;The Army Ordnance Missile Command, the California Instituteof Technology, the Goddard Space Flight Center, Harvard CollegeObservatory, The Jet Propulsion Laboratory, the MassachusettsIntitute of Technology, the State University of Iowa; theState University of Nevada, and the University of Californiaat Berkeley.

The two planetary experiments are a microwave radio-meter and an infrared radiometer. They will operate duringa period of approximately 30 / minutes from a distance ofabout 16,000 miles as Mariner approaches Venus. The closestapproach of Mariner to Venus will be about 10,000 miles. Theseradiometers will obtain information about the planet's temper-ature and atmosphere.

The other experiments will make scientific measurementsduring the cruise through interplanetary space and in thenear vicinity of Venus. They are a magnetometer; energeticparticle detectors, including an ionization chamber andseveral Geiger-Mueller counters; a cosmic dust detector, anda solar plasma detector.One of the important considerations in choosing these

experiments was the compromise between what scientists wouldlike to measure during the mission, and what was technologi-cally possible. For example, of the 446 pounds that couldbe placed in a trajectory to intercept Venus, only about40 pounds could be allocated to scientific experiments.

Another restricting factor is time. Venus is in afavorable position for investigation by a Mariner-type space-craft during a period of only a few weeks every 19 months.

In addition, scientists will ask Mariner to convertelectrical power from the sunlight, report its findings fromas far as 36 million miles, and, though sensitive and un-attended, remain in precise working order during three tofive months in the void of space.Although Venus is our closest planetary neighbor thereare many things about it that remain a mystery. Its surfaceis continually hidden under a mask of dense clouds whichare impenetrable in the small region of the electromagneticspectrum visible to the eye. Spectrographic observations

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( oI ;1O Itiono mIIorf l l a! acco r'(Ing to thee manner In whichh).;0 1) 'LfI emIit I.1 h t,) 3U1rreS I; that, the atmosphere ofill .;(0oLnjins carbhoni (diOXide, but. has probably i.1ttle freeoxy;;n .oprwater vapor.

fir npr I -atlimrc mea siurement (of Vonus have been made frome;'ihL in the microwave and Infrar'ed reglons of the electro-manl-ntin :spectrum. The former IndIcates near surface temper-;,.1er(es of about; (15 defrces Fahrenhelt, while the latter showsr(a(Utnfs of minus 38 dcgrees Fahrenheit in the upper atmos-phere. Because of' the tremendous distances over which thesemneasurements were made sclentilstn cannot be sure of the exactIi t. i.tu in t;he atmosphere where these temperature readings()!)] Y.

As a result of' the f'ram[tenta)ry infonnation about Venus,;, vi.ral theories have been proposed that attempt to explain' Ih( nature of the atmosphere and the reason for the widetNinrge or temperatures.,;rome sci.entits bo:lleve that because of the carbondioxl.de in the atmosphere a "greenhouse" effect is created

1;that; hoUL.1 most of Lhc heat absorbed from the sun beneaththlr thick blanket of' clouds. This theory relies on thefS:;unlpt1tn that, wal;er vapor is present in the atmosphere of',T0 nu s.

olther scientists say that Venus has an ionosphere withan electron density thousands of times that of the earth.[' this 'is the case this layer of electrons could easilymislead sclentist,, measuring temperatures of Venus fromearth.

Another theory states that Venus is heated by frictionproduced by high winds and dust clouds.

There are still other theories that describe Venus asa swamp, a desert covered with oil and smog, and containingcarbonat;ed water.One of the missions of the Mariner spacecraft will beto make several scientific measurements of the planet whichmay substantiate one of these theories, or call for the

formulation of a new one. These measurements will be madewith the microwave and infrared radiometers.

During the cruise through interplanetary space andencounter of Venus, the Mariner will be telemetering in-formation to earth. As the sensors of the six experimentsreceive information they feed it to a data conditioningsystem (DCS) which is located in one of the modules in thehexagonal base of the spacecraft. The DCS prepares-15-


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Information from the experiments for transmission to earthin the Colin of a digital code.Since all of thL data collected by Marlner cannot betransmnitted at the same time, an electronic clock has beenhuilt; into the DCS. This clock controls the equipment sothat the receiver "listens" to one experiment at. a time forabout "one second. After 20.16 seconds the i'(X switches offthe scientific telemetry and starts to send spacecraftengineering data for 16.8 seconds. This cycle is continuedduring the cry-.se in interplanetary space.At ten hours before it passes Venus, however, thespacecraft devotes its telemetry system to the full-timetransmission of scientific information from its six experi-ments.The integration of the scientific experiments and thegeneration of a number of the experiments was carried out atJPJ.. under the direction of Dr. M. Eimer. JPL projectscientist was R. C. Wycoff. J. S. Martin was responsiblefor the engineering of scientific experiments.

THEr EXPERTMEIMTS:MICROWAVE' RADIOMETER

This experiment should help to resolve two vitalquestions about Venus: What is the atmosphere like, andwhat is the temperature of the surface.As the Mariner spacecraft flys past Venus, the micro-wave radiometer will scan its surface to detect electromag-netic radiation at two wave lengths, 13.5 and 19 millimeters.In the electromagnetic spectrum 13.5mm is the location of a

microwave water absorbtion band. If there is any watervapor above certain minimal concentration in the atmosphereit will be possible to detect it.The 19mm wave length, however, is not affected bywater vapor, and should be capable of "seeing" through theatmosphere to the surface.Scientists studying the results of this experiment willbe able to determine whether water vapor exists in theVenusi.an atmosphere by noting the difference in temperaturesobtained from measurements at the two wave lengths.The 19mm wave length, in addition to measuring the sur-face temperature, may be able to test two of the theoriesabout the atmosphere of Venus by detecting one of twoconditions called "limb brightening" or "limb darkening."-16-


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The former effect may be detected if the apparent hightemperatures are due to a dense ionosphere. As the microwaveradiometer scans the planet it would detect larger concen-trations of electrons around the limb or edge of the plane-tary disk. This is somewhat analogous to looking at theearth from thousands of miles out in space on a day whenit was completely covered with a fine mist. The mist wouldbe more evident at the limbs than in the center, since theobserver would be looking through a thicker layer of mistat the limbs. In much of the same way, the microwave radio-meter would detect higher temperatures around the limb ofVenus.

On the other hand, a limb darkening wouLd indicatethat the high temperatures originate from the surface. Inthis case a limb-to-limb scan would show a gradual increaseand decrease of temperature readings.The microwave radiometer is mounted on the hexagonalbase of the Mariner. Both wave lengths are detected by aparabolic antenna that is 20 inches in diameter and three

inches deep.At ten hours prior to Venus encounter the radiometeris turned on. Driven by an electric motor it starts a scanningor nodding motion of 120 degrees at the rate of one degreeper second. When its signals determine that it has acquiredthe planet the DCS sends a command to slow the scan rate to1/10 of a degree per second.In order to confine its attention to the planet'sdisk, a special command system has been built into the DCS.Whenever the radiometer indicates that it has reached the limb

and is about to look out into space, the DCS reverses thedirection of the scan.In this mode it scans Venus for about 30 minutes.Since the spacecraft will be going roughly in the directionof the sun, the radiometer will first scan part of the darkside of Venus and then part of the sunlit side.The microwave antenna is only capable of moving in anodding motion. Lateral movement is provided by the motionof the spacecraft across the face Of the planet.

As the radiated microwave energy is collected by theparabolic antenna it is focused onto a receiving hornlocated opposite the face of the antenna on a quadripod.The energy from both wave lengths travels down two hollowlegs of the quadripod called wave guides.-17-


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Located on top of the antenna are two reference hornsthat are matched to receive the same two microwave bandsan the parabolic antenna. These horns point at an angle of60 degrees away from the axis of the dish antenna, and conse-quently are always looking at empty space.

The signals from the dish antenna and the referencehorns are alternated or chopped electronically. Then theyare sent I;o a crystal video-type receiver located behind thr: ,dish antenna. Thus, this receiver measures the differencebetween the signals from Venus and the reference signals fromspace.

This information is then telemetered to earth.The microwave radiometer weighs 22 pounds and require.,;3.5 watts of power when operating, and 8.9 watts duringCalibration. The calibration sequences are automatically Jinitiated by the DCS a number of times during the mission.Experimenters on the microwave radiometer are Dr. A.H.

Barrett, Massachusetts Institute of Technology, Dr. J.Copeland, Army Ordnance Missile Command, D. E. Jones, JetPropulsion Laboratory, and Dr. A. E. Lilley, Harvard CollegeObservatory.

This is a companion experiment to the microwave radio-meter. As the Mariner spacecraft flys past Venus simultane-ous measurements from the two experiments will enablescientists to get a better idea of the temperature and atmos-pheric conditions of the planet.

The infrared radiometer is rigidly attached to themicrowave antenna. In this way both scan the same surfaceareas of Venua.

The infrared experiment operates in the 8 to 9 and the10 to 10.8 micron wave length regions of the electromagneticspectrum.Measurements from earth in these two wave lengths indi-

cate temperatures below zero. It is not clear it o scientistswhether all of this radiation comes from the eloud tops,or whether some of it eminates from the atmosphere or plane-tary surface.

T&e close approach of Mariner to Venus may enablescientists to measure some of the finer details of the-18 -


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atmosphere. Thili, will primarily Involve finding out if thereare any "breaks" in the cloud cover of Venus, and if so,the amount of heat that escapes through them into space. Formany years some astronomers have 1ken able to see occasionallysome kind of markings on Venus' cLoud cover that change withno apparent regularity. The lack of regularity in thesemarkings has left their nature in doubt.If these markings are indeed cloud breaks, they willstand out with greater contrast in the infrared than if ob-

served in the visible part of the spectrum. If the radiantenergy detected by this experiment comes from the cloud top,and there are no breaks, then the temperatures obtained atboth infrared wave lengths will follow a similar pattern.If there are appreciable breaks in the clouds a substantialdifference will be detected between measurements at the twowave lengths.The reason for this is that in the 8 to 9 micron regionthe atmosphere is transparent, (except for clouds). In the10 to 10.8 micron region, the lower atmosphere is hiddenby the presence of carbon dioxide. Through a cloud break the

former would penetrate to a much lower point in the atmosphere.By a comparison of temperatures from both regions, combinedwith microwave data, scientists will have a more detailedpicture of conditions on Venus.The infrared radiometer is six inches long and twoinches wide. It weigns 2.7 pounds and consumes two watts ofpower.It contains two opti'al sensors, one of which scansthe surface of Venus while the other obtains referencereadings from space. The latter is aimed at an angle of

115 degrees away from the planetary scanner.Radiation from Venus is collected by two f/2.4 opticalsystems with three inch focal lengths. As the infraredenergy enters the optical system it first passes through arotating disk with two apertures. TheEe are positioned sothat the two sensing devices can alternately see Venus andempty space. The infrared beam is chopped in this way atthe rate of 20 cycles per second.After the beam passes the disk, it is split by adichroic filter into the two wave length regions. A second

pair of filters further refines these wave lengths beforethey reach the radiometers sensing devices. The sensingdevices are two thermistor bolometers, which are sensitiveto infrared energy. The electrical output from these de-tectors is amplified and sent to the Mariner's DCS for-19-


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processing and transmission to earth.Experimenters on the infvrared rii-.mci.oter are Dr. L.D.Kaplan, and Dr. G. Neugebauer, of the Jet Propulion Labora-tory, and Dr. C. Sagan, of the University of California atBerkeley.

MAGNETOMETER

The magnetometer aboard Mariner is designed to measurethe strength and direction of interplanetary and Venusianmagnetic fields.Many scientists believe that the magnetia field of aplanet is due to a fluid motion in its interior. If such aVenusian field exists then it could be detected as Marinerapproached the planet. This would depend, of course, on thestrength of the field and the distance of Mariner at en-counter. Also the trajectory of Mariner will permit themeasurement of interplanetary magnetic fields and any vari-

ation with respect to time and distance from the sun.Present-day theories of magnetohydrodynamics--the studyof the relation between the motion of charged particles andthe magnetic field which surrounds them--say that the plasmawhich flows away from the sun should drag with it the localsolar magnetic field, since the motion of charged particlesnot only responds to but also creates magnetic fields. Themathematical description of this interaction between triostream of charged particles leaving the sun and the magneticfield which surrounds the sun is extremely complicated. Thetheories which have been used to describe these phenomenal

are incomplete and often contradictory.The measurement of interplanetary magnetic fields byMariner will be combined with simultaneous measurements fromearth to help scientists understand something about the inter-relationships of these fields.Moreover, by investigating the magnitude of any Venusianfield it may be possible to draw some conclusion about theinterior of the planet, as well as about planetary radiationbelts, magnetic storms, and aurorae.The magnetometer is a three axis fluxgate type. Thesensors of the experiment are housed in a metal cylindersix inches long and three inches in diameter. It is locatedjust below the Mariner's omnidirectional antenna. In this

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way the sensors are as far away as possible from any space-craft components that may have magnetic fields associatedwith them.Inside the cylinder are three mu-metal tubes, eachalligned..along a-different axis. Each tube has two windingsof copper wire around it, much the same as some transformers.The primary winding leads from a frequency oscillator which

produces a current. The secondary winding leads to anamplifier.

In the absence of a magnetic field the current inducedin the secondary winding has a special symmetrical wave shape.The presence of a magnetic field changes the symmetry of thiswave and produces a component with amptitucVin proportionto the field strength. A third winding around the rods pre-vents magnetic interference from the spacecraft. This rendersthe three axis of the instrument sensitive to E gamma, ora field strength roughly 100,000 times weaker than that ofthe earth.'The magnetometer weighs 4.7 pounds and consumes sixwatts of power.Experimenters are P.J. Coleman and Dr. C.P. Sonnet ofthe National Aeronautics and Space Administration, and Dr.L. Davis and Dr. E.J. Smith of JPL.

HIGH ENERGY RADIATION EXPERIMENT

This experiment consists of an ionization chamber anda group of three Geiger-Mueller tubes. Together they willmeasure the number and intensity of energetic particles ininterplanetary space and neat. Venus.

These particles are primarily cosmic rays, which aremade up of protons (the nuclei of hydrogen atoms), alphaparticles (the nuclei of helium atoms), the nuclei ofheavier atoms, and electrons.

The measurement of these particles may contributesignificantly to the knowledge of hazards to manned spaceflight.

Scientists have theorized that the sun has a pro-nounced effect on cosmic rays. During solar activity (sunspots or flares), for example, huge quantities of plasmarace outward from the sun. These plasma clouds, or solar

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wind, carry along magnetic fields. In a rather complicatedmanner, not fully understood by scientists the plasma'smagnetic fields interact with those of the sun and planets.Scientists have noticed that following this solar activity,there is a considerable change ir the character of' theradiation that reaches the earth.Unfortunately, because of our atmosphere and magneticfield, we cannot measure all of these complicated inter-relationships from earth. We must take measurements from

spacecraft traveling far from the earth. In this way we maylearn something about the sun's influence on radiation.A decrease in the number and intensity of cosmic radi-ation detected as we go closer to the sun would indicatethat the sun's magnetic field is deflecting cosmic raysaway from the solar system.Thus by comparing the intensity of magnetic fields,with the amount of cosmic radiation at earth, Venus, and ininterplanetary space, some insight may be gained to thesecomplicated inter-relationships.The ionization chamber is of the Neher type. It con-sists of a five-inch-in-diameter stainless steel shellwith a wall thickness of 1/100 of an inch. The sphere isfilled with argon gas and is located on the superstructureof Mariner. Inside the sphere a quartz fibre is placednext to a quartz rod. Initially, both fibre and rod havethe same electric potential.As charged particles penetrate the wall of the spherethey leave behind a wake of ions in the argon gas. Negativeions accumulate on the rod, giving it a static electric ,

charge. This causes the fibre to be attracted to the rodin proportion to the amount of the charge. Eventually, asthe charge increases the two touch. This produces anelectric pulse which is amplified and sent to earth. Therod is recharged, and the fibre returns to its startingposition.In order to penetrate the wall of the ionizationchamber, particles must have an energy greater than 10million electron volts (Mev) for protrons, i Mev for elec-trons, and 40 Mev for alpha particles. Thus, the instru-ment measures the rate of ionization of cosmic rays.Two of the GM tubes are considered companion instrumentsto the ionization chamber. They can be directly penetratedby particles above the same energy levels as the chamber,and can count these particles.

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Both tubes consist of an enclosed volume of gas withtwo electrodes, at a different electrical potential. Thewall of the tubes serve as the negative electrode and a thincentral wire is the positive electrode. The tubes generatea current pulse each time a charged particle encers.One of the GM tubes is shielded by a sleeve of glassand an 8/1000 of an inch thickness of stainless steel.The second tube has a beryllium shield 24/1000 of aninch thick. Both tubes are 2.3 inches long and .6 of aninch in diameter. Because of the difference in shields,it will be possible for scientists to infer the ratio ofelectrons to other particles. These two GM counters alongwith the ionization chamber make it possible for scientiststo measure the flux (velocity times the density) and theaverage amount of ionization of particles.A third GM sensor is of the end window type. Itmeasures the flux of particles not capable of penetratingthe other detectors. The window is made of mica and admits

protons with ernrgies greater than one Mev, electrons over40,000 electronvolts.A magnesium shield around the rest of the GM tubepermits passage of protons over 20 Mev and electrons over1 Mev. This gives the counter the ability to determinethe approximate direction of particles which penetrate thewindow.The GM detectors are mounted on the superstructure ofthe spacecraft where they will be as far as possible fromlarge masses that tend to produce secondary particles when

struck by cosmic rays.The three GM tubes protrude from a box that housestheir electronic circuitry. The box is six inches wide,six inches long and two inches thick. The end window GMttl


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SOLAR PLASMA DETECTOR

The purpose of this experiment is to determine theflow and density' of solar plasma and the energy of itsparticles.Solar plasma is frequently called "solar wind" andconsists of charged particles that are continually strearm-ing outwa d frcon the sun. Since direct measurements suchas the one on Mariner have been infrequent, scientistsknow very little about the solar plasma. Some feel that ;is merely an extension of the sun's atmosphere, or corona.Although there are many theories, some conflicting, we doknow that during solar activity (sun spot, or flares) theflux of plasma increases.One of the most complicated and interesting ar3as oCspace science is the study of how solar plasma intc.ractswith the magnetic fields in space. Since the plasma carr esan electrical charge, it not only is affected by magneticfields, but also creates one of its own,If a field is strong enough it may control and divertthe solar winds, and, conversely,if the electrical energyin the plasma is great enough, the planetary magneticfields may be trapped in the cloud and move with it throughspace.Therefore, to study the complex interactions betweensolar wind and magnetic fields, space probes that carryplasma experiments generally carry magnetometers.Most particle detectors are designed to operate insidea sealed tube and the tube walls keep out very low energypartif;lps. The solar plasma detector on Mariner, however,is opern to space and can collect and measure positively-charged particles of very low energy.The sensor for this experiment is mounted on the out-side of one of the electronic boxes in the base of theMariner. Tne aperture of the analyzer is pointed alongthe roll axis of the spacecraft, and during most of themission will be facing the sun.As a charged pariicle enters the analyzer it findsitself in a curving tunnel. The two sides of this tunnelare metal plates carrying static electric charges--onenegative, and the other positive. The charged particle isattracted by one plate and repelled by the other, and so

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-'4

follows a cirved path dowen the curved tunnel. If it ismov.ng too slowly or too rapidly, it Yuns into one wallor the other, but if it is moving at just the rough'.: speed,it passes to the end and is detected by a charge collectingcup. The electric current produced by the flow of char~edparticles is measured by a very sensitive electrometercircuit,

Thus, all "he particles moving in the right directionto enter the tvnnel and moving with the right speed to Fetall the way through will be detected.Periodically the voltage on the plates is changed anda different energy is required by the particles to gotthrough to the collector cup. The voltage is automaticallychanged ten times. In this way Jt is possible to measurea spectrum of particle energies of 240 to 8400 electronvolts.The plasma detector has a total weight of 4.8 pounds

and a power requirement of 1 watt. Experimenters areDr. C. W. Snyder and M. Neugebauer of JPL.COSMIC DUST DETECTOR

This experiment is designed to measure the flux andmomentum, of cosmic dust in interplanetary space andaround Venus. It may contribute to an understanding of thehazards of manned flight through space.

This information will help scientists in understandingthe history and evolution of the solar system.There are many theories about these dust particles.One is that when the solar system was formed billions cfyear ago by the condensation of a huge cloud of gas anddust, these cosmic particles were debris left over. Alsothey could be remnants of comets that rush through thesolar system leaving a trail of dust behind. Some scientistsbelieve cosmic dust has its origin in gallactic space andis somehow trapped by the interaction of magnetic fieldbfrom the sun and planets.Scientists have been trying to study cosmic dustrecently with earth satellites and sounding rockets, butMariner may provide the first opportunity data on' theirdistribution in interplanetary space.

( The experiment is located on the top of Mariner's-25-


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hexagonal bus. It consists of a rectangular magnesium"sounding board" five inches wide and 10 inches long. Acrystal microphone is located in the center of this plate.This acoustical device measures the impact of particles ofcosmic dustsAs a particle hits the acoustical plate it is recordedby the microphone whose output excites a voltage-sensitiveamplifier. The number of dust particles striking the plateis recorded on two counters, one for particles with highmomentum and one for particles with low momentum.During the cruise part of the trajectory the dataconditioning system will read-out the counters every 37seconds and telemeter this to the ground. During planetaryencounter the counting rate will be reduced to 20-secondintervals.The cosmic dust detector weighs 1.85 pounds andconsumes .08 milliwatts of power. It was designed by agroup at NASA's Goddard Space Flight Center, Greenbelt,Maryland, under the direction of W. M Alexander.

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VENUS TRAJECTORY

The boost portion of the Mariner mission consistsof three phases: Ascent into a circular parking orbit ofapproximately 115 statute miles, coast in the parking orbitto a pre-determined point in space, and burning out of theparking orbit to greater than escape speed.

The Atlas D/Agena B space booster will rise verticallyand pitch over in the required direction determined by theexact time of launch. The vehicle will gain speed andaltitude until a signal from the ground guidance systemcommands shutdown of the Atlas engines and separation ofthe Agena/Mariner from the Atlas. The Agena engine ignitesafter a short coast period and accelerates itself and thespacecraft into the parking orbit at a speed of 17,450 mph.The Agena/Mariner will be traveling in a southeasterly

direction over the Atlantic Ocean towards the coast ofSouth Africa. Just before reaching Africa, at a point inspace determined by the launch date, time of launch, anddesired flight time to Venus, the Agena engine will re-ignite and accelerate the spacecraft to a speed of about25,820 mph.

Shortly after the Agena engine shuts down, the Marinerspacecraft is separated from the Agena. This is "injection."'The speed of the spacecraft exceeds the escape velocityat this altitude by 1215 mph and the spacecraft moves offin the hyperbolic orbit relative to earth. Because ofthe rapid change of altitude, the rate at which it movesaround the earth decreases until it is traveling essentiallyin a straight line outward from earth. During the timefrom injection to escape, the radius vector from the earth'scenter to the spacecraft moves through an angle of about1450.

At the same time it is moving out, the spacecraftis slowing down relative to earth because of earth'sgravity. When it reaches a distance of about 600,000miles, after about three days, and has essentially"escaped earth", the velocity will have decreased fromthe original 25,820 mph to 6550 mph. The time of thesecond Agena burn will have been chosen so that thisvelocity relative to earth is in a direction opposite tothat of the earth in its orbit about the sun. Thus, thespacecraft will be moving about the sun 6550 mph. lowerthan the earth's approximate 'j'000 mph; that is, about59,100 mph.

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Because of the lower orbital velocity about the sun,the spacecraft will be moving too slowly to maintain acircular orbit against the sun's gravity. It will, there-fore, start falling inward toward the orbital Venus. Thecombination of the inward motion and the circular motionaround the sun produces an ecliptic orbit that will inter-sect the orbit of Venus some 100 days later.About eight days after launch the accumulated trackingdata will be used to compare the trajectories of the space-craft with the trajectory necessary to provide the plannedVenus encounter. The midcourse maneuver will depend onthe difference between these two trajectories.Now Mariner will begin to curve in towards the sunand gradually increase its speed. Eventually, due to theinward curving path, Mariner's speed will exceed that ofthe earth and it will catch up and pass earth. Later, itwill catch up with rapidly moving Venus, approaching theplanet on its dark side at a speed of over 83,000 mphrelative to the sun.Entering the sphere of gravitational influence ofthe planet, Mariner's path will begin to be deflected dueto its pull. Its speed will be increased even greater,reaching over 90,000 mph relative to the sun, as itpasses Venus on its sunny side at a distance of about10,000 miles from the surface. In addition, Mariner'spath will be bent about 36 degrees in traveling past theplanet.At about 65 minutes before closest approach, or ata distance of 18,600 miles from the planet's surface, theplanetary experiments will begin to scan Venus. Theywill operate for 30 minutes, after which the mission isofficially over.The path of the spacecraft in the vicinity of Venushas been designed so that Venus will not black the space-craft'sview of either the sun or earth. This is necessaryto insure continuous communication with earth and properfunctioning of the sun and earth sensors. The latterprovide reference directions for attitude control of thespacecraft. The communication distance at the time ofarrival is more than 33 million miles.After leaving the sphere of influence of Venus, the

spacecraft will have even greater speed than when itentered. In essence, it will experience an increase in-28-


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energy and speed due to the bending of its course byVenus. This phenomena is similar to that sometimesexperienced by comets which travel too close to theplanet Jupiter. The energy increase is sometimes suffi-cient to cause the comet to escape the solar system.Such will not be the case for Mariner however.

Designing an interplanetary trajectory is acomplex task that taxes the capabilities of high-speedcomputers. The trajectory engineer faces a task compli-cated by the interactions of the motion of the earthabout the sun, the motion of Venus, the spin of theearth, and the effect of gravitational fields of earth,sun, moon, Venus, Jupiter and even the pressure of thesun's radiation, on the path of the spacecraft.

The trajectory designer, therefore, must calculatea trajectory from minute to minute for that portion ofeach day during the launch opportunity that launch couldoccur. He must keep his trajectory with range safetylimits (the early portions of the launch must be overwater, not land masses) and he must keep the trajectorywithin range of the tracking stations.

Meshing all these factors into a successful tra-jectory, spanning millions of miles and nearly fourmonths in time, is a formidable task.

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THE PLANET VENUS

During the centuries man has been studying Venus,he has accumulated relatively little in the way of indis-putable scientific information.Astronomers are hampered in their attempts to in-vestigate the planet because it is continually covered bya dense blanket of clouds.Venus, our closest planetary neighbor, is in a orbitbetween the earth and the sun. Travelling at the speed of78,300 miles an hour it has a sidereal period, (or year)of 225 days. Its average distance from the sun is 67,200,000miles.During its nearly circular orbit, Venus comes within26,300,000 miles of the earth at closest approach orinferior conjunction. At superior conjunction, or pointat which the earth and Venus are at opposite sides of the

sun, it is 162 million miles away. Inferior conjunctionoccurs every 584 days. As Venus approaches inferior con-junction Mariner will be launched to intercept the planetthree to four months after launch.One of the puzzling features of Venus is the change-able dark and light markings that appear on its cloud layer.Scientists have speculated that these markings could bebreaks in the cloud cover, but as yet there seems to belittle evidence of any regularity.One of the outstanding features of Venus is its

brightness. Because it is close to the sun, and has areflective cloud layer, Venus is the third brightest objectin our sky, after the sun and moon. Its reflectivity ismeasured at about 60 percent, as compared to 7 percent forour moon.B-ecause it was not observed throughout the night, butappeared in the morning and evening skies, ancient astron-

orner. thought Venus to be two bright stars.Venus has been referred to as the earth's twin. Ithas an estimated diameter of 7800 miles, as compared to

7926 miles 'forthe earth. Also, it is believed to have amass and gravitational field similar to that of the earth.Spectrographic studies (identification of materials bytheir absorptive or reflective qualities) seem to indicatethat Venus contains carbon dioxide and nitrogen but probablylittle free oxygen or water vapor. Measurements taken in

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the infrared region of the electromagnetic spectrum indi-cate that temperatures; oi minus 38 degrees fahrenheitexist somewhere in the atmosphere. The microwave regions,however, show temperatures of 615 degrees fahrenheit at orsomewhere near the surface.Scientists are not in agreement as to the altitude fromwhich these temperatures emanate. Indeed, there is one theory

that a Venusian ionosphere, with thousands of times theelectron density of the earth, gives the impression that theplanet is extremely hot. Another explains that the hightemperatures are due to a "greenhouse" effect in which thesun's energy is trapped beneath the dense clouds. A thirdtheory holds that the surface of Venus is heated by frictionproduced by high winds and dust clouds.Recent radar measurements suggest that Venus rotatesat a slow rate, perhaps once every 225 days, which is thelength of the Venusian year. This would mean that Venusalways keeps the same side facing the sun, much the same way

our moon keeps the same side facing the earth.

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DEEP SPACE INSTRUMENTATION FACILITYTwo-way communications with Mariner will be provided by theDeep Space Instrumentation Facility (DSIF), a world circlingnetwork of three permanent tracking stations, a mobile trackingunit and at the Atlantic Missile Range, Cape Canaveral, Florida,a launch checkout station.The DSIF is under the technical direction of the CaliforniaInstitute of Technology Jet Propulsion Laboratory for the

National Aeronautics and Space Administration. Dr. EberhardtRechtin is JPL's DSIF Program Director.The DSIF will track Mariner throughtout the 100 to 140-daymission, receive and record telemetry from the spacecraft andtransmit commands to the spacecraft.The three permanent stations are at Goldstone in theCalifornia Mohave Desert, near Woomera Village in Australia, andnear Johannesburg, South Africa.The mobile station will be located approximately one mile

east of the DSIF installation at Johannesburg. The mobile stationwill acquire Mariner shortly after injection when the spacecraftis too low to be readily picked up by the larger installation.The mobile station is equipped with a 10 foot-in-diameter dishantenna with a wide beam width (9 degree) and a fast trackingcapability of 10 degrees a second.The larger 85 foot-in-diameter antenna of the permanentinstallation hasi a 1 degree beam width and a 1 degree per secondtracking capability.As soon as the mobile station has acquired Mariner, trackinginformation and the position of the spacecraft will be sent tothe permanent installation telling it where to look. It isexpected that the large antenna will lock onto Mariner shortlythereafter.The installations at Johannesburg and Goldstone have thecapability of sending commands to Mariner, as well as to receivetelemetry. The Woome-ra installation, the mobile unit andlaunch checkout station cannot command, but can transmit a signalto the spacecraft for doppler calculations. The mobile andlaunch checkout stations do not have the range of the largerantennas and function only in the initial stages of the mission.The three permanent installations are located approximately120 degrees apart around the earth. Their ranges overlap toprovide continuous contact with the spacecraft.The following are visibility times based on one possiblelaunch date and time. The figures would change slightly relativeto actual date and hour that launch occurred. Since the mobile.

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and South African stations are close together they have the samevi.sibility periods. The times when the spacecraft will bevisible to the different stations are as follows. "IVetands forinjection, which is the end of Agena second burn.VTSIBILITY PERIODS

TJo:annesburg and mobile 1 plus 3 mins. plus 30 mins.c,)omera 3 plus 15 mins. I plus 5 hrs.50 mins.

Johannesburg and mobile 1 plus 1 hr. 20 mins. I plus 13 hrs.25 mins.Goldstone 5 plus 12 hrB. 10 mins. ] plus 22 hrs.10 mine.Wioomera I plus 18 hrs, 45 mins. I plus 30 hrs.20 mins.Johannesburg I plus 26 hrs. I plus 37 hrs,35 mins.

Throughout the mission the stations will continue to lockonto the Mariner, track it until the rotation of the earth carriesthe station to the limits of its horizon, and then pass the space-craft on to the next station.

During the first ten days of the Venus Mission the DSIFctatioiis will maintain contact with Mariner 24 hours a day. Thisw ill be lowered to ten hours a day during the cruise portions ofthe mission. During midcourse maneuver and planet encounterthe stations will revert to 24-hour contact,Each station is manned by a 25-man staff. It takes threehours to prepare a station to acquire the spacecraft and one hourto shut down following a tracking period.Each station is linked with the Spacecraft Flight Operationsrenter at JPL by leased teletype circuits over which is sent all

t'racking and telemetry information to JP13 for processing by an3B M 7090 computer system.The launch checkout station at Cape Canaveral has two trailers;one for the transmitter and receiver and the other for test equip-ment, recording equipment and equipment fbr processing portions ofthe received signal for real-time display on strip charts; atix foot-in-diameter dish antenna for receiving and transmitting,and a collimation tower for calibrating and checking of stationequipment. The tower simulates the spacecraft for checkout pro-

cedures, transmitting on the same frequency to be used by Mariner.The station has a 15-man crew.Function of this station is to receive telemetry from the

1.;ariner during pre-launch tests and record spacecraft telemetryfrom launch until the station loses contact as the spacecraftpasses over the horizon. -33-


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The Goldstone station is operated for JPL by the BendixRadio Corporation. PL's engineer in charge is Walter Larkin.Goldstone has three 85 foot-in-diameter antennas separated byseven miles and a ridge of hills to minimize interference.The Australian station is 15 miles from Woomera Village andhas one 85 foot-in-diameter receiving antenna. The station isoperated by the Australian Department of Supply, Weapons ResearchEstablishment. Dr. Frank Wood represents the WRE. RichardFahnestock is the resident engineer for JPL.The South African station is equipped with an 85 foot-in-diameter receiving antenna and it is located in a bowl-shapedvalley approximately 40 miles northwest of Johannesburg. Thestation is operated by the South African government through theNational Institute for Te2.ccommunications Research, Dr. FrankHewitt, Director. NITR is a division of the Council forScientific and Industrial Research. Resident engineer for JPLis Paul Jones.

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LAUNCH VJEHICLE

NASA's launch vehicle for the Mariner R Venus Fly-By is the Atlas Agena-B -- the reliable combinationthat sent America's first payload to the moon.An Atlas Agena-B vehicle launched Ranger IV April23 on such a trajectory that the Ranger payload landed

on the moon, even without a midcourse maneuver.The Atlas "D' serves as the boosier and the Agena-B as the vehicle's second stage.The vehicle is provided to NASA by the Air Forcesystems Command's Space Systems Division whtch functionsas a "prime contractor" to th e NASA vehicle group --the Marshall Space Flight Center, Huntsville, Ala.This relationship is spelled out in the NASA-USAFagreement which provides for NASA procurement through

the Air Force of a number of vehicles consisting ofmodified Atlas booster with modified Agena-B's servingas second stages. The Agena was developed for theDiscoverer satellite program in which it has achieveda significant reliability record.It has also been used in four Ranger flights.Major contractors involved in the vehicle operationare Lockheed Missile and Space Company and GeneralDynamics/Astronautics. The vehicle is launched bythese companies under the direction of NASA's Launch

Operations Center, Cape Canaveral.(The Venus mission flight plan is described inanother section of the press kit entitled "VenusTrajectory.")

AGENA-B SECOND STAGEThe Agena-B stage of the rocket is an improvedand enlarged version of the Agena-A, which was used inthe Discoverer satellite program.The Agena-B vehicle has integral, load-carryingpropellant tanks with twice the capacity of Agena-Atanks and is powered by a Bell Aerospace turbopump-fedengine. It burns unsymmetrical dimethylhydrazine (UDMH)as fuel and inhibited red fuming nitric acid (IRFNA) esthe oxidizer.

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The new engine gives substantially higher perform-ance than prior Agena engines and has a shutdown andrestart capability.An inertial reference system is capable of estab-lishing attitude control during the coast and engineoperation phase. An on-board timer initiates programmedsignals for the starting, stopping and maintaining ofvarious equipment during flight.Here is a description of the Agena B:Propulsion: Single rocket engine using liquidpropellants -- inhibited red fuming nitric acid andunsymmetrical dimethlhydrazine.Thrust. 15,000 pounds at altitude.Size: Approximately ?2 feet long including adapterto accept Mariner-R spacecraft.Control Systems: Pneumatic using high-pressure gasmetered through external Jets for use during coast phases6Hydraulic through gimballing rocket engine for pitch andyaw control during powered portions of flight. Correctionsprovided by airborne guidance system.Guidance: The guidance system -- which is made upof timing devices, an inertial reference system, avelocity meter and an infrared horizon sensing device --is entirely self-contained.Contractors: Lockheed Missile and Space Company,prime-contract( ; Bell Aerosystems Co., engine.

ATLAS "D" BOOSTERThe Atlas booster used for the Atlas Agena-B programis a modification of the Air Force ICBM and has beenoperational for some time. An Atlas booster is alsobeing used in the NASA Project Mercury manned-flightprogram. Many of America's satellites were sent aloftby Atlas boosters.Here is a description of the Atlas "D" space booster:Propulsion: Cluster of three rocket engines; twoboosters, one sustainer; using liquid oxygen and kerosene

propellants.

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Speed: Approximately 12,000 stiatute miles per hourfor the Mariner missions.Thrust: Total nominal thrust at sea level morethat 360,000 pounds.Size: Approximately 78 feet high including adapterfor Agena; 16 feet wide across flared engine nacelles.Ten feet wide across tank section.Weight: Approximately 260,000 pounds at moment oflaunch, fully loaded with propellants.Guidance: Radio command guidance. Ground radarssense velocity vectors, transmitting this data to groundcomputer. Computir determines corrections necessary andinformation is transmitted to airborne unit which signalsc;ontrol system. Control is accomplished through gimballingand engine burning time.Contractors: Airframe and assembly -- General

Dynamics/ Astronautics; propulsion -- Rocketdyne Divisionof North American Aviation; radio command guidance --Defense Division of General Electric Company; groundguidance computer -- Burroughs Corporation.

KEY MANAGEMENT PERSONNELOverall direction for the Agena program is providedat NASA Headquarters by the Office of Space Sciences,headed by Homer E. Newell, director. Dixon Forsytheis thie program manager. MSFC is assigned responsibilityfor the Agena vehicle system management for the variousAgena programs. In particriar this assignment includos

administration and technical responsibility from vehicleprocurement through launch. Within MSFC the Light andMedium Vehicles Office, directed by Hans Hueter, directsthe Agena program. Friedrich Duerr is the Agena systemsmanager.Major John G. Albert is the director of the NASAAgena B program for the AF Space Systems Division,assisted by Major Charles A. Wurster.Harold T. Luskin is the Lockheed Missiles and SpaceCompany manager for NASA programs.Dr. Kurt H. Debus heads the NASA Launch OperationsCenter which directs launchings.

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SUBCONTRACTORS

Mariner I is part of the National Aeronautics and -paceAdministrationts lunar and planetary space exploration program.The California Institute of Technology Jet Propulsion Laborator,-,under contract to NASA, has responsibility for project manage-ment. Thirty-four subcontractors to JPL provided instrumentsand hardware for Mariners I and 2. These contracts amounted to$6.5 million.Aeroflex Corporation Jet Vane ActuatorsLong Island City, New YorkAmerican Electronics, Inc. Transformer-Rectifiers LorFullerton, California Flight TelecommunicationsAmpex Corporation Tape Recorders for GroundInstrumentation Division Telemetry and Data HandlingRedwood City, California EquipmentApplied Development Corporation Decommutators and TeletypeMonterey Park, California Encoders for Ground TelemetryEquipment-o3brodaua, Incorporated Time Code Translators, Timek.naheim, California Code Generators, and Space-craft Signal Simulators

for Ground Telemetry Equip--ment.Barnes Engineering Company Infrared RadiometersStamford, Connecticut Planet SimulatorBell Aerospace Corporation Accelerometerzs and Associ-.Bell Aerosystems Division ated Electronic modulesCleveland, OhioComputer Control Company, Inc. Data Conditioning SystemsFramingham, MassachusettsConax Corporation Midcourse PropulsionBuffaio, New York Explosive Valves SquibsConsolidated Electrodynamics Oscillographs for Data

Corp. ReductionPasadena, California

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Subcontractors

Consolidated Systems Corporation Scientific InstrumentsMonrovia, California Operational Support EquipmentDynamics Instrumentation Company Isolation Amplifiers fo rMonterey Park, California Telemetry OperationalSupport EquipmentElectric Storage Battery Company Spacecraft BatteriesMissile Battery DivisionRaleigh, North CarolinaElectro-Opvical Systems, Inc. Spacecraft Power ConversionPasadena, California EquipmentFargo Rubber Corporation Midcourse Propulsion Fuel TankLos Angeles, California BladdersG'entronics, Inc. Power Supplies for DataGlendora, California Conditioning SystemGroen Associates Actuators for Solar PanelsSun Valley, CaliforniaHouston Fearless Corporation Pin PullersTorrance, CaliforniaKearfott Division GyroscopesGeneral Precision, Inc.Los Angeles, CaliforniaMarshall Laboratories Magnetometers and Associ-Torrance, California ated Operational SupportEquipmentMatrix Research and Development Power Supplies for

Corporation Particle Flux DetectorsNashua, New HamapshireMenasco Manufacturing Company Midcourse Propulsion Fuel TanksBurbank, Californaa and Nitrogen TanksMidwestern Instruments Osc~llographs for DataTulsa, Oklahoma ReduactionMincom Division Tape Recorders for GroundMinnesota Mining & Manufacturing Telemetry and Data HandlingLos Angeles, California Equipment

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Subcontractors

Motorola, Incorporated Spacecraft Command Sub-Military Electronics Division systems, Transponders,Scottsdale, Arizona and Associated OperationalSupport EquipmentNortronics Attitude Control GyroA Division of Northrup Corp. Electronic, Autopilot Elec-Palos Verdes Estates, California tronic, and Antenna ServoElectronic Modules, LongRange Earth Sensors andSun SensorsRansom Research Verification and GroundDivision of Wyle Laboratories Command Modulation Equip-San Pedro, California mentRantec Corporation Transponder CirculatorsCalabasas, California and MonitorsByan Aeronautical Company Solar Panel StructuresAerospace DivisionSan Diego, CaliforniaSpectrolab Solar cells and theirA division of Textron Electron- installation and electricalics, Incorporated connection on Solar PanelsNorth Hollywood, CaliforniaState University of Iowa Calibrated Geiger CountersIowa City, IowaSterer Engineering & Manu- Valves and Regulators forfacturing Company Midcourse Propulsion andNorth Hollywood, California Attitude Control SystemsTexas Instruments Incorporated Spacecraft Data EncordersApparatus Division and Associated OperationalDallas, Texas Support Equipment, GroundTelemetry DemodulatorsTrans-Sonics, Incorporated TransducersBurlington, Massachusetts

In addition to these subcontractors, there were over1000 industrial firms who contributed to Mariner. These

Mariner I Press Kit

Documents

Transcript of Mariner I Press Kit