unmanned spacecraft of the united states

8/2/2019 Unmanned Spacecraft of the United States

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o NITED STATESBY EDGAR M. CORTRIGHT, Deputy Associate Administrator fo r Space Science and Applications

A E R O N A U T I C S A N D S P A C E A D M I N I S T R A T I O N


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EDGAR M. CORTRIGHT

Edgar M. Cortright was appointed DeputyAssociate Administrator for Space Scienceand Applications on November 1, 1963. Inthis position, he shares responsibility withDr. Homer Newell, Associate Administratorfor Space Science and Applications, in planning and directing NASA's programs for theunmanned scientific exploration and utilization of space. These programs include thelunar an d planetary probes, the geophysicaland astronomical satellites and probes, biosciences, applications satellites, and thedevelopment an d use of light and mediumlaunch vehicles through the Atlas-Centaurclass.D epu fJI Associate A dm inislralorfo r Sp aee eiena an d App l ications Mr. Cortright joined the National AdvisoryCommittee for Aeronautics, the predecessorof NASA, as an aeronautical research scientist at Lewis Flight Propulsion Laboratory (now Lewis Research Center) in1948. From 1949 to 1954, he was head of the Small Supersonic Tunnels Section; from 1954 to 1958, he was Chief of the 8 x 6-foot Supersonic Wind Tunnel Branch. In January 1958, he was appointed Chief of the PlasmaPhysics Branch.When NASA was organized, Mr. Cortright became Chief of AdvancedTechnology Programs and directed initial formulation of NASA 's meteorological satellite program, including TIROS and Nimbus. Later, he becameAssistant Director for Lunar and Planetary Programs in the former Officeof Space Flight Programs. On November 1, 1961, Mr. Cortright wasappointed Deputy Director of NASA's Office of Space Sciences.A native of Hastings, Pennsylvania, Mr. Cortright served as an officer inthe U.S. Navy from 1943 to 1946. He earned a Bachelor of AeronauticalEngineering degree in 1947 and a Master of Science in AeronauticalEngineering degree in 1948, both from Rensselaer Polytechnic Institute.During his research career, before the establishment of NASA , Mr. Cortright specialized in high-speed aerodynamics, particularly problems related

to air induction system design, je t nozzle design, and interactions of a je twith external air flow. He is the author of numerous technical reports andarticles. He is an Associate Fellow of the Institute of the AeronauticalSciences. He is a recipient of the Arthur S. Flemming Award for 1963.Mr. Cortright is married to the former Beverly Hotaling. Mr. and Mrs.Cortright and their two children, Susan J. an d David E., live at 6909 GranbyStreet, Bethesda, Maryland.


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UNMANNED SPACECRAFTOF THE UNITED STATESBY EDGAR M. CORTRIGHT, Deputy Associate Administrator fo r Space Science and Applications

In 1957 th e first earth satellite ushered in th e age of space flight. Sincethat historic event, space exploration has become a major national objectiveof both the United States and the Soviet Union. These two nations haveattempted a total of well over 200 space flight missions. Other nations arealso participating in various degrees in what will continue to grow as acooperative world effort.

In the years since 1957, man has successfully flown in earth orbit. He hasinitiated programs to land on the moon and return. He has made dramaticapplications of earth satellites in meteorology, communications, navigation,an d geodesy.

A host of scientific satellites continue to advance understanding of theearth's environment, the sun, and th e stars. Automated spacecraft arebeing flown to the moon, deep into interplanetary space, and to the nearplanets, Mars an d Venus.

One of the most exciting technological aspects of space exploration hasbeen th e development of automated spacecraft. Most of the scientific explo-ration of space and the useful applications of space flight thus fa r have beenmade possible by automated spacecraft. Development of these spacecraftand their many complex subsystems is setting the pace today for manybranches of science an d technology. Guidance, computer, attitude control,power, telecommunication, instrumentation, and structural subsystems arebeing subjected to new standards of light weight, high efficiency, extremeaccuracy, an d unsurpassed reliability and quality.

This publication reviews the automated spacecraft which have been de-veloped and flown, or which are under active development in the UnitedStates by th e National Aeronautics an d Space Administration. From thefacts and statistics contained herein, certain observations can be made andcertain conclusions drawn.

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SCIENTIFIC SATELLITE HISTORY

Flight experience with scientific satellites through 1963 is summarized inthe chart on this page. This experience illustrates the gradual maturing ofthe United States program to its record of 100% successful missions in 1962and 1963. (This includes the Canadian-built satellite, Alouette, and theBritish-instrumented satellite, Ariel.) Prior to 1962, th e more modest success rate was almost entirely attributable to th e use of unproven launchvehicles which have since been discarded. With one exception, Vanguard II,all satellites performed quite well when successfully orbited, at least duringtheir initial days of operation. Among the prime lessons learned from theseearly experiences were the following: (1) To accomplish effectively spaceexploration, one should develop a limited family of reliable launch vehiclesand use them; (2) Long-lived satellites are required to observe and monitorspace phenomena; (3) Reliability and long life are the two most importantingredients of economical space exploration; (4) Reliability is best achievedon the ground; by sound design, skilled workmanship, strict quality control,and a very thorough environmental test program. I will have more to sayabout these points later.

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TYPICAL SCIENTIFIC SATELLITESEXPLORER XII

GROSS WEIGHT-83 L8S INSTRUMENT WEIGHT-18 L8S EXPUIMENTS - 6 POWER-16 WATTS' STABILIZATION-SPIN' DESIGN LlfE-l YEAR' LAUN(H VEHICLE-DElTA' ORBIT-APOGEE41,717 NM PERIGEE 158 NM INClI NATION JJ o STATUSLAUN(HED 1SAUGUST 1961.

EXPLORER XVII

GROSS WEIGHT-41D Las' INSTRUMENT WEIGHT-47 LBS EXPERIMENTS-B' POWER-110 WAnS STABILIZATION-SPIN'DESIGN LlFE-J TO 4 MONTHS' LAUN(H VEHICU-DELTA ORBIT-A POGEE 495 NM PERIGEE 138 NM INClINATION 57.6 STATUS-LAUN(HED 2 APRIL 1963 ,

Explorers XII, XVII, and the Orbit-ing Solar Observatory, are representa-tive of scientific satellites launched todate. Explorer XII is typical of aseJjes of geophysical satellites designedto survey th e earth's magnetosphere,th e magnitude and direction of theearth's magnetic field, the chargedparticles trapped therein, and the fluxof solar and galactic cosmic rays. Ac-cordingly, the satellite is designed tooperate in highly elliptical orbits. I tfeatures the simple spin stabilizationand solar power system used on manyof our satellites. Another area of geo-physics being studied with satellites isthe structure of the atmosphere. Ex-plorer XVII was launched in 1963and is unique in that it measures at -mospheric ,temperature, pressure, andcomposition directly. In order toeliminate all possible sources of con-tamination from the spacecraft itself,including vaporizing solids, all equip-ment was hermetically sealed within astainless steel shell.

Another satellite already flown isthe Orbiting Solar Observatory (OSO).The OSO is unique in many respects.I t was the first true observatory inorbit, and was designed to point se-lected experiments at the center ofthe sun with the direction measurableto within one minute of arc. Theseexperiments are mounted on the solarpanel which is despun by gas jets inthe course pointing mode and finelypointed 'by electric servomotors to anaccuracy of between 2 and 3 arc-minutes. This spacecraft must re-acquire and stabilize on the sun onceeach orbit, which it has done thou-sands of times with great precisionsince its launching well over two yearsago . Below this pointing section is aspinning electronics compartment3


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ORBITING SOLAR OBSERVATORY

GROSS WEIGHT -454 LBS INSTRUMENT WEIGHT -173 LBS EXPERIMENTS-13 POWER - 16 WATTS' STABILIZATION-SPIN'DESIGN l I fE-6 MONTHS' LAUNCH VEHICLE-DELTA' ORBIT APOGEE 322 NM PERIGEE 299 NM INCLINATION 33 STATUSLAUNCHED 7 MARCH 1962 .

whose plane of rotation includes thesun. This section, spinning at 30rpm, carried experiments which thussaw the sun for 2 seconds per revolu-tion. Another feature worth notingis the very high ratio of instrumentweight to gross weight.

With regard to that important areacalled ionospheric physics, the Cana-dian Satellite Alouette, is particularlynoteworthy. Alouette, which utilizesthe topside sounding technique, hashad an outstanding flight record.There were a minimum of malfunc-tions during developmental testing,and Alouette is functioning perfectlyafter almost two years in orbit andhas recorded thousands of ionograms.I t has not even been necessary toactivate any of the redundant systemsbuilt into this satellite.

APPLICATION SATELLITE HISTORYExperience with applications satel-lites has been even more encouragingas shown in the chart on this page.There have been only two mission

failures since th e program began in1960. The initial attempt to launchthe Echo communications satellitewas the first and only failure of theDelta launch vehicle. Because ofprior experience with stages of theDelta, however, it was possible to cor-rect th e deficiencies so that all nine-teen subsequent Delta launches havebeen entirely successful. Because allof the applications satellite missionsexcept TIROS I were based on theDelta, th e spacecraft have had un-paralleled opportunities to perform.All of th e NASA satellites and the twoTelstar satellites sponsored by privateindustry were successful except forthe first Syncom, which malfunctionedafter achieving a near 22,300 milecircular orbit.4


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TYPICAL APPLICATIONS SATELLITES

TIROS VI, Relay, and Syncom aretypical of the many applications satellites launched to date. TIROS VIis spin-stabilized, as were most firstgeneration satellites, but has an addedfeature of a magnetic coil which caninteract with the earth's magneticfield and precess the spin axis oncommand. Picture taking is limitedto 32 stored pictures per orbit takenalong the spin axis. It is plannedthat a later version of this spacecraftwill be magnetically torqued so thatthe spin axis is parallel to the earth'ssurface. On this satellite, the twocameras will be pointed perpendicularto the spin axis so as to see the earthtwice during each revolution throughout the entire orbit. In another experiment, TIROS may be flown to a22,300-mile apogee to explore theeffectiveness of weather photographyfrom that altitude. Thus, this spacecraft has shown an excellent and somewhat unexpected growth capability.

The Relay satellite, like Telstar, isan experiment in wide bandwidthcommunications via signal relay beyond the horizon by an active transponder aboard a satellite. Relay differs from Telstar in it s communication frequencies as well as it s designdetails . Both spacecraft achievedmost of their design objectives including high quality real-time television transmission between Europeand the North American continent.An operational system would includeat least 20 to 30 such satellites.

The Syncom communication satellite is designed fo r operation at 22,-300 miles altitude. At this altitude,it takes only three operating satellitesto provide worldwide coverage at allbut very high latitudes. Quasi-fixed5

TIROS VI

RECEIVING ANTENNA

- - SOLAR/ ' . CEllS. -./ ' ~ w a J \ '-. " ; : : - - - - - ; ' / (;.

. l ,>" S P i N - u p U A N S : ~ : ! ROCKETANTENNA ;" DESPIN

MECHANISMTELEVISIONCAMERA

GROll WEIGHT - 281 L81 INITRUMENT WEIGHT- 72 II I EXPERIMENTI-2 TV CAMERAS' POWER-20 WAnS STABllIZA TlON - SPIN OEIIGN l I F E - ~ MONTHS' LAUNCH VEHIClEDElTA ' ORBIT -APOGEE 390 NM PERIGEE 368 NM INCLINATION58 0 \TATUS-TIROS VI LAUNCHED 18 SEPTEM8ER 1962 .

RELAY SPACECRAFT

GROIS WEIGHT-I72 LBS " INSTRUMENT WEIGHT - 47 LBS EXP E R I M E N T S - ~ POWER-4l WAnS STAB ILIZATION-SPIN'DESIGN LIFE - I YEAR LAUNCH VEHIClE-DElTA' ORBIT-APOGEE ~ D 1 2 NM PERIGEE 7 1 ~ NM INClINATION STATUSRELAY I LAUN CHED 13 DEC 1962.


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SYNCOM SPACECRAFT

GROSS WEIGHT-110 LBS INSTRUMENT WEIGHT-40 LBS'POWER-2S WATTS' STABILIZATION-SPIN' OESIGN LIFE-ONEYEAR LAUNCH VEHIClE-OEllA ORBIT-APOGEE 19,9B1 NMPERIGEE 18.103 NM INClINATION 33 0 STATUS-LAUNCHED 13FEB 1963.

but large ground antennae are re-quired. The first Syncom achievedits orbit but failed to function thereafter. Syncom II , however, has beensuccessfully orbited and maneuveredprecisely onto a predetermined station. It is working well and on Au-gust 23, 1963 was used for the firsttelephone conversation between headsof state via satellite transmission.(The United States and Nigeria.)

DEEP SPACE PROBE HISTORY

In contrast with scientific and ap-plications satellite missions, experi-ence with deep space probes as de-picted on the chart, has recorded fewcomplete successes to date. PioneerIV was the first United States spaceprobe to reach escape velocity andorbit the sun, and was NASA's firstsuccessful deep space mission. Com-munication was maintained with thePioneer spacecraft to 22.5 millionmiles. Since Pioneer V, the outstanding Mariner II flight to Venus hasbeen NASA's only completely success-ful deep space mission. Whereasprior to 1962 al l failures resulted fromlaunch vehicle malfunctions, 1962 sawthree Ranger spacecraft experiencemalfunctions on their flights to themoon.. There are some additional lessonshere. The deep space missions areth e most difficult of all automatedspacecraft missions. They demandthe utmost in performance from bothlaunch vehicles and spacecraft.NASA's newest and least-developedlaunch vehicles must be used for thesemissions; and th e spacecraft will con-tinue to be complicated. I t will bevery difficult to equal the reliabilityof earth satellite missions with mis-sions to the Moon, Mars, and Venus.

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TYPICAL DEEP SPACE PROBES

Pioneer V, Ranger, and Mariner illustra t e past spacecraft experiencewi th interplanetary, lunar, and planet ary flight, respectively.Pioneer V was a spin-stabilized,solar-powered spacecraft bred fromearth satellite technology. I t was

designed to make particle and fieldmeasurements in interplanetary space.The success of this relatively simplespacecraft in returning valuable datafrom up to 22.5 million miles convinced NASA that interplanetarymonitors of this type should becomea basic part of it s program. NASAwill begin a new Pioneer series in1965 in support of the InternationalQuiet Sun Year (IQSY) .

The Ranger is really a second orthird generation spacecraft. I t wasdesigned to fly to th e moon and landan inst rumented capsule at a velocityof less than 250 feet per second within a fifty-mile circle. Because of theunique requirements of this mission,Ranger incorporated a number oftechnica l innovations. Three-axis stabilization was achieved with an earthsensor, which pointed the directionalan tenna and locked the spacecraft inroll, and with a sun sensor whichpointed t he roll axis and solar panelsat t he sun and locked the spacecraftin pitch and yaw. The spacecraftcould be programmed to any att itudefor a mid course velocity correction capable of reducing the dispersion atthe moon from several thousand milesto about fifty miles. After th e midcourse maneuver was complete,Ranger could reacquire its earth-sunlock until arrival at the moon. Uponarrival, t he Ranger could be programmed to the proper attitude toalign it s capsule retrorocket axis with

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PIONEER V SPACECRAFT

GROll WEIGHT - 91 18I INITRUMENT WEIGHT- 9.5 lBS EX PERIMENTI-4 PQWER ITEAOY - I S WAITS PEAK- IOO WAITS STABILIZATION-IP IN LAUNC HED - I I MARCH 1960 LAUNCHVEHIClE - THOR-ABlE TRAJECTORY - INTERP LANETARY , COMMUNICATEO TO 22 .5 MILLION MLEI.

RANGER SPACECRAFT (3-5)

GROll WE IGHT -716 LBS PAYlOAD WEiGHT - 147 L81 EXPERIMENTI-4 POWER- IJO WAnS PROPULIION-MIOCOURSE-MOTOl (liQUIDI CAPSULE IElRO-(SOLIDI STUllILATlDN - ACTIVE 3 AXil lIFE- 66 HR . TRANSIT 30 DAY CAPSUU LAUNCH VEHIUE-ATlAS-AGENA 8 TRAJECTORY-LUNAR IMPACT VIA PUKING ORBIT ITATUS- 3 IPACECRAFT LAUNCHED IN1962.


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the vertical descent velocity vector.The retrorocket would be triggeredby a radar altimeter and would slowdown the instrument capsule to aprobable resultant impact velocity ofless than 250 feet per second. Theextremely sensitive seismometer capsule could withstand this impact byvirtue of a ruggedized design and aprotective layer of balsa wood. Onthe most successful .of the three flightsmade with this spacecraft, it performed all automatic functions properly prior to arrival at the moon andexecuted the first midcourse correction made by a spacecraft. Two ofthe Rangers hit the moon but nonereturned lunar data. Plans call foradditional Rangers of this type.

Mariner II was by far NASA's mostsuccessful deep space probe. It s attitude control and midcourse maneuver subsystems were functionally similar to those of the Ranger just described. On it s 109-day, 180-millionmile flight to Venus, Mariner II performed beautifully despite minor problems including excessive temperatures,a solar-panel short, and a weak earthsensor signal. Less than 4 pounds ofnitrogen were consumed for attitudecontrol. Mariner's midcourse maneuver corrected the Venus miss distance from about 233,000 miles to21,000 miles. Mariner was intendedto miss Venus by 10,000 miles butwas designed to scan Venus effectivelyat a distance of as much as 40,000miles. All experiments worked verywell and returned invaluable radiometric observations of the planet's atmosphere and surface. The telemetrysignal strength at earth was less than10-18 watts but was well within thedesign signal-to-noise ratio. Thetechnology developed by Ranger andMariner will continue to be used inNASA lunar and planetary spacecraft.

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MARINER II

GROSS WEIGHT -449 lBS INSTRUMENT WEIGHT -4 0 liS EX PERIMENTS-6 POWER-ISO WATTS' STABlliZATION-AGIVE3 AXIS' DESIGN lIFE-4 MONTHS' lAUNCH VEHIClE-ATlASAGENA TRAJECTORY-INTERPLANETARY, VENUS FlYBY AT21 ,600 MilES' STATUS-MISSION SUCCESSFUllY COMPLETEDON 14 DECEMBER 1962 .


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.._ _ _ ._

TEST EXPERIENCES AND FLIGHT OPERATIONS

VIBRATION 4.0 22 2 .8 61 6 .8 30

As noted earlier, there is nogood substitute for extensiveground testing in the development of spacecraft. The tablepresents the test history of anaverage Explorer spacecraft.In th e five test phases, checkout, vibration , temperature,vacuum, and thermal vacuum,this average spacecraft experienced 18.2 electrical failuresand 4.6 mechanical failuresMost electrical failures occurred during thermal vacuum and most mechanical failures during vibration.

.6 3

10 .2 56TOTAL 18 .2 100

.6

10 .8

22 .847100

The long-term effectivenessof such thorough testing standards is illustrated in th e graphentitled Space Flight Operations. The average time tothe first malfunction of anysort in flight of all of NASA's unmanned spacecraft had climbed to about 2months in 1963. The average useful life has reached eight months and isstill rising because some spacecraft launched in prior years are still functioningat a useful level.During the same time period, our space launch vehicles had risen to ademonstrated reliability of 100%, paced by the Delta, which has now had 22

out of 23 successful launches.

SPACEFLIGHTOPERATIONS

MON THS OFOP ERATIONS

8

6

4

0

PERCENTSUCCESS100

LAU NCH75 VEHICLE50

25

060 61 6 2 6 3 S8 59 60 61 62 63CALENDAR YEARS

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SPACECRAFT COMPLEXITY

A real challenge is involved in maintaining these upward reliability andlife trends in the face of increasing complexity. The chart below illustratesthis fact by listing the approximate number of piece parts by subsystem forthree advanced spacecraft: Mariner II, which has been described, and the Sur-veyor and Orbiting Geophysical Observatory which are ye t to be described .These spacecraft contain about 54,000, 82,000, and 100,000 parts respectively.A sizeable percentage are critical for effective mission performance. Onlytime will tell whether we have moved too fast to this degree of sophistication.

SPACECRAFT COMPLEXITYMARINER II

TELESIJ8. COMMUNI GUIDANCE

SYSTEM SCINCE CATIONS , CONTROL POWER PROPULSIONPIECE 8,600 12,500 11,200 10,708 11,000 50

TOTAL PARTS 54,000 PARTSSURVEYOR

TEUSUB COMMUNI GUIDANCE

SYSTEM SCIENCE CATIJNS & CONTROL POWER PROPlll.SIINPIECE 19,300 23 ,600 18 ,800 5,900 2,700

TOTAL PARTS 82,000 PARTS

COMMUNICATION

SUB AND DATA STABILIZATION THERMALSYSTEM SCOCE HANDLING & CONTROL CONTROL POWER STRUCTUREPlCE 24,000 34,200 2,600 2,000 33,500 4,000

PARTS 100,000 PARTS

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SPACECRAFT UNDER DEVELOPMENTORBITING GEOPHYSICAL OBSERVATORY

GROSS WEIGHT-I ,DOO LBS INSTRUMENT WEIGHT-ISO LBS'EXPERIMENTS-2D POWER-SOD WATTS' STAIILlZATlOHACTIVE 3 AXIS' DESIGN LIfE-ONE YEAR LAUNCH VEHICLESATLAS AGENA THOR AGENA ORBITS-HIGHLY ELLIPTICAL INCLINED ORBIT-NEAR mCULAR POLAR ORBIT' STATUS-fiRSTfLIGHT 1964 .

ORBITI NG ASTRONOMI CAL OBSERVATORY

GROSS WEIGHT-3 ,600 LBS INSTRUMENT WEIGHT-I,ODD LBS EXPERIMENTS-II' STABILIZATION-ACTIVE 3 AXIS' DESIGNLlfE-1 YEAR' LAUNCH VEHICLE-ATUS-AGENA ORBIT-CIRCULAR-434 NM INCLINATION 32 STATUS-fiRST fliGHT1965 .

Among th e most scientifically important spacecraft under developmentare the observatory class of satellites.The Orbiting Geophysical Observatory (OGO), a 1000-pound satellite, isdesigned to carry from 20 to 50 experiments in either circular polar orbits ataltitudes less than 1000 miles whenlaunched with a Thor-Agena, or inhighly eccentric inclined orbits withapogees of around 70,000 miles whenlaunched with th e Atlas-Agena. Thespacecraft is designed to hold its attitude with the bottom looking directlytoward the earth, its solar panels toward the sun, and selected experiments toward earth , space, sun, or inth e direction of motion. A prime feature of the OGO is its data-handlingsystem which can store up to 43.2 million bits of data at an input rate of1000 to 4000 bits per second and areadout rate of 64,000 to 128,000 bitspe r second .One of NASA's most ambitious andsignificant scientific satellites is the3600-pound Orbiting AstronomicalObservatory (OAO) to be placed in a500-mile circular inclined orbit in1965. Basically, the spacecraft is designed to sense an d point the opticalaxis to any point in the celestialsphere, with the exception of a 90-degree cone about the sun line, to anaccuracy of 1 minute of arc. Using theexperimenter's prime optics an d a suitable error sensor, the spacecraft control system is designed to achieve afine pointing accuracy of 0.1 second ofarc for extended periods of time. Thisha s turned out to be a formidable taskwith which we are still having someproblems. A combination of gas jetsand inertia wheels are the primemovers.The scientific experiments aboardth e OAO are among it s most excitingfeatures. Initial flights will stress theultra-violet portion of the spectrum.The first flight will carry the sk y survey experiment of the SmithsonianAstrophysical Observatory and thebroad-band photometry experiment

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ADVANCED ORBITING SOLAR OBSERVATORY

GaUSS WEIGIIT-'OO LIS IIISTlUIIEJlT WEiGHT-2SO lIS EX ~ I I I I E l f T S - S E V E I A l 'OWEI-400 w m ~ STAlILIlATIONACTIVE 3 AXIS DESIGN lIFE-otiE n u LAUNCH YEHIUEAGENA ORBIT -CI RCULAR 300 NM STATUS-FIIST FLIGHT1967.

NIMBUS

GlOSS WEIGHT-67S LIS INSTRUMENT WEIGHT-116 LISmElIMENTS - 3 POWEI-400 WATTS STABILIZATION-ACTIYE3 AXIS OESIGN LIFE-ONE YEA! LAUNCH VEHIClE-THOIAGENA 011 IT - CIRCULAI SOO Nil INCLINATION 10 IETROGUOE STATUS-FIRST fliGHT 1964.

of th e University of Wisconsin whichtogether total nine separate opticalsubsystems plus spectrometers. Thesecond OAO will contain a NASA Goddard Space Flight Center system forth e study of absolute spectrophotometry of several thousand stars and nebulae. This system features a 36" primary mirror . The third unit willcarry Princeton University equipmenthaving a 32" fuzed quartz primarymirror and intended for the study ofinterstellar matter.A new observatory called the Advanced Orbiting Solar Observatory(AOSO) has recently been initiated.This observatory is designed for extensive and detailed observations of thesun not possible with th e first generation OSO . The field of view will extend to about ten degrees centered onthe solar disk; ye t a 5 arc second pointing precision will permit some 400 observations in one pass across the sun'sdiameter. This will permit spectralanalysis of individual sun spots andother detail structure. A particularlychallenging technical problem is to locate and record in the brief time available major solar flares which occurrelatively infrequently and emanatefrom a small portion of the solar disk.The most advanced meteorologicalsatellite is the Nimbus, designed to flyearly in 1964. The 750-pound Nimbuswill initially fly in a circular 80 retrograde orbit so that th e orbital precession will maintain th e earth illumination relatively constant (i.e., 12 o'clocknoon orbit). The Nimbus is fully stabilized to look at the earth while itssolar panels seek th e sun. Multiplevide con TV cameras provide completedaylight observation of the earth onceeach 24 hours. Cloud pictures arestored fo r readout at two wide-bandreadout stations in Alaska and Canada, once each orbit. As a furtherservice, the Nimbus will continuouslytransmit cloud pictures of a lOOO-milesquare immediately under the satelliteto any user throughout the world willing to invest in some modest receivingand data-processing equipment.The follow-on Pioneer deep spaceprobes are designed to monitor particles and fields at distances up to 50 to

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90 million miles from earth. Twoprobes launched ahead of and trailingthe earth , plus earth satellites, willmake possible th e monitoring of alarge segment of the solar sector.This small probe will deliver a datarate of 16 bits per second up to 80 mil-lion nautical miles, with much higherrates early in the flight.

NASA's next planetary pro be is aMariner, designed to duplicate theMariner II feat of a close planetary fly-by. In this case, however, the targetis Mars. Although Mariner-Marsdoes not look much like Mariner II , ituses much of th e same technology.Some interesting variations includethe following: the use of a fixed high-gain antenna, made possible by th eparticular earth-sun-planet geometricrelationships for this flight; a changefrom earth reference to Canopus ref-erence for one axis; and the additionof solar pressure vanes at the tips ofth e solar panels to supplement andback up the gas stabilization system.The Mars mission is more difficultthan the Venus mission because of in-creased lifetime, increased communication distance and power require-ments, an d a decreased solar constant.The Mariner-Mars payload will in-clude a TV telescope for surfacephotography.

For the 1966 Mars mission, a versionof this spacecraft will be fitted with acapsule to land and survive on th eMartian surface. The Atlas-Centaurlaunch vehicle will be required. Thecapsule landing will not be attemptedunless we can be assured that it is bio-logically sterile. Th e basic spacecraft,as on the 1964 flight , will not be sterilebut will use a trajectory providing lessthan one chance in 10,000 of impact .From a technological point of view,we have found the use of hea t , gas,liquids, and radiation to achieve com-plete spacecraft sterilization withoutdegradation of reliability to be beyondthe state of art at this time. Thus,lunar spacecraft, such as th e Rangerand Surveyor to be described, will set-tle for surgically clean procedureswhich are now deemed sufficient forthe moon .

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PIONEER

GROSS WEIGHT - 11S Les INIIIUMENT WEIGHT-20 LIS EXPERIMENTS - 4 POWER-SO WATTS meILilAIION-SPIN DESIGN L1fE-6 MONTHS LAUNCH VEHICLE-OELTA TW(TORY-INTERPLANETARY STATUS- FIRST FLIGHT 1965.

MARINER MARS

GROSS WEIGHT -S IO LBS INSTRUMENT WE IGHT - 40 LBS EX PERIMENTS-6 POWER-120 wms STABIlIZATION- ACTIVE 3AXIS OE SGN L1FE - B MONTHS LAUNCH VEHICLE - ATLASAGENA TRAJECTORY - INTERPLANETARY , MARS FLY BY STATUS-FIRSTFLIGHT IN 1964 .


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RANGER (6-9)

GROSS WEIGHT -807 l IS ' EXPERIMENT-TElEVISION (6 CAliERAS) TELEVISION SUBSYSTEM WEIGHT-l71 lBS POWER-170 WAns PROPUlSION-MIDCOURSE MOTOR (LIQUID) STAIllIZATION-mlYl: 3 AXIS' lIfE-66 HR . TRANSIT' LAUNCHVEHICLE-ATLAS AGENAB TRAJECTORY-LUNAR IIiPm VIAPARIING ORIIT STATUS-NEXT fLIGHT 1964.

SURVEYOR SPACECRAFT

GROSS WEIGHT-2 . IOO LBS' INSTRUMENT WEIGHT-l00 LIS'EXPERIMENTS-B POWER-B8 WAnS STABILIZATION-AmYl:l AXIS' PROPULSION RETROROCKET -SOLID' VERNIER ROCK ETS-liQUID DESIGN lIfE-lO90 DAYS' LAUNCH VEHICLEATlAS .CENTAUR TRAJECTORY -DIRECT ASCENT OR PARKING OR8IT STATUS- fiRST fliGHT 1964 .

The next block of Ranger fligh ts isscheduled as a series of four spacecraft, Rangers 6 through 9. Thesespacecraft are similar to those illustrated earlier, but with a high-resolution television subsystem substitutedfor the landing capsule and its retrorocket. This TV subsystem will takepictures of th e lunar surface duringdescent. The last full frame beforeimpact should resolve objects of about1 meter in diameter within a square 60meters on a side. These :flights willprovide spot sampling of the manyconflicting theoretical models of thelunar surface. Our detailed surfacereconnaissance must await the Surveyor and a lunar photographic orbiter on which work has recently beeninitiated.Surveyor, a 560-pound spacecraft,weighs 2150 pounds when coupledwith its retrorocket. It will fly to themoon in a stabilized mode similar tothe Ranger but with a Canopus ratherthan an earth sensor. Two midcoursemaneuvers can be made with threesmall liquid rockets which are alsoused for landing. During descent, themain retrorocket is fired by a markingradar altimeter an d attitude is maintained during this firing with the threesmall liquid rockets. After firing themain retrorocket is jettisoned and theSurveyor will land under its own control using a dual Doppler radar system. Once on the moon, the surfacewill be observed with television cameras, seismic activity will be monitoredand local physical and chemical surface properties will be analyzed. LaterSurveyors may carry a small rovingvehicle. When these local sites are observed from orbit and interrelatedwith broad area photographic coverage, we should be in a good positionnot only to describe the moon scientifically with some accuracy, but to select a landing site for man.The primary goal of th e Lunar Orbiter is the photography of considerable areas of the lunar surface for theexploration and selection of landingsites for the Surveyor and Apollo missions. Additional investigations consist of measurements of the lunar

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gravity field and th e environment of anear surface lunar orbit. On a typicalmission, the spacecraft is launchedfrom the AMR an d injected into translunar trajectory by an Atlas / Agenabooster. Mter separation from th eAgena, the attitude control subsystemorients th e spacecraft with the solarpanels facing the sun and then rollsth e spacecraft until the star sensorlocks on Canopus. This attitude ismaintained at all times except for midcourse correction, lunar orbit injectionor transfer, or orientation forphotography.At approximately 72 hours afterlaunch, th e retro into lunar orbit ismade at a nominal lunar altitude of574 miles. After several orbits the elements of the spacecraft orbit areknown from tracking by th e DeepSpace Instrumentation Facility withsufficient precision to command a retromaneuver into an elliptical orbit,which has a perilune altitude of 29miles over th e area of interest. Photographs are taken from this final orbitas the spacecraft passes over th e specific target on one or more orbits, whiletelemetry records the conditions underwhich photos are taken. At this altitude , the photographic system is designed to provide coverage of 24,800sq. miles at 26 lA feet resolution and4,960 sq. miles at 3 Y.J feet resolution.The Biosatellite program is designed to determine th e biological effects on plants and animals of weight-

15

LUNAR ORBITER

PROPULSIONHI-GAIN .0 oT 0ANy - = - ~

. - .... . -.- "'0 .J q : < A ~ , /'~ " ' - "N'/

CAMERAPACKAGE OMNI ANTENNA

GROSS WEIGHT -819 L8S IN STRUMENT WEIGHT-1l6 LIS INVESTIGATIONS - TElEMETERED FILM PHDTOGRAPHY SELENODESY ENVIRONMENTAL MEASUREMENTS POWER-24S wms(MAX) STABllIZATlON-3 AXIS' DESIGN lIFE-6 MONTHS TOI YR . I MONTH PHOTOG . LAUlKH YEHI(l-ATlASAGEIIA TRAJECTORY -ECCENTRIC LUNAR ORBIT STATUS-DESIGNPHASf.


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BIOSATElLITE

GROSS WEIGHT IN ORBIT- i l lS lBS RECOVERED CAPSULE-2S0 LBS INVESTIGATIONS - WEIGHTlESSNESS . RADIATION . ANDBID-RHYTHMS POWER -F UEl (ElLS TIME IN ORBIT-3 TO30 DAYS RECOVERY - AIR SHAHH OR WATER LAUNCH VE Hm-DElTA ORBIT - CIRCULAR 230 MI. INllINATIDli 2B .S PLAN-SIX FLIGHTS. FIRST LAUNCH LATE 1961.

lessness, radiation, and the absence ofa diurnal cycle. A series of six biosatellites are planned with the first flightscheduled for late 1965. The satelliteswill be launched from the AMR into a230 mile circular orbit inclined at 28.5 0to the equator. Biosatellites will remain in orbit for periods of 3 to 30days depending upon the investigations being conducted.

The Biosatellite spacecraft consistsof the re-entry vehicle, which containsthe experiments along with the heatshield and recovery system, and anadapter, which houses all of the lifesupport supplies and equipment required during orbital flight. The recovery capsule itself is sealed andtemperature and humidity controlled.Upon completion of time in orbit aground command will orient the spacecraft for separation of the re-entryvehicle and firing of the retrorocket.Upon re-entry, the capsule will be recovered in th e ai r or from the sea.

SUMMARY

The automated spacecraft constitute a unique addition to the rapidly evolving engineering and scientific scene. From a technological point of view, theyoffer unique opportunities for imagination , creativIty, design excellence, craftmanship, and skilled flight operations. From a scientific point of view, theyoffer a unique opportunity to extend our electronic sensors to distant worlds.In a broader sense , they offer a unique opportunity to weld scientists andengineers into a cooperative effort which can lead us-who knows where?

u.s. GOVERNMENT PRI NTI NG OFFICE . 1964 OF-731-129

For sa le by Ihe Superintendent of Documents, U.S. G ove rnmen t Printing OfficeW as hing ton , D.C ., 20402 - P rice 15 ce nts16


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DEFINITIONS

EARTH SENSOR - a photoelectric device that detects the earth and provides a riferencefor spacecraft atlitudecontrol.NODES - The points at which an earth satellite's orbit crosses the plane of the earth's equa tor.ORBITAL PLANE -a n orbit plane is the plane d ~ f i n e d ~ ) I the curved path of a satellite and passes through thecenter of the earth or other celestial object about which the satellite orbits.PRECESSION - change in direction of the axis of rotation of a spinning bodJi or of the plane of the orbit of anorbiting body whm acted upon fry an outside force .REDUNDANT SYSTEMS - duplicate systems intended to prevent failure of the entire vehicle or spacecra}l if asingle system fails.RETROGRADE ORBIT- An orbit, resulting from a launching to the west of a meridian, which precesses in thedirection of the earth's rotation.SPECTROPHOTOMETRY - measuring the intensities of radiation as a function of the frequency or wavelength ofthe radiation .SPIN STABIliZE - maintaining a satellite's orielltation by means of gyroscopic forces that result from itsspinning.

TOPSIDE SOUNDING -a tech Izique for measun'ng electron density in the ionosphere fry transmitting radio signals downward from a point abo !'e the earth. Contrasted with bottomside sounding carried out b), means ofradio transmitters on the ground.TORQUE -a turning or twist ing force; that which tends 10 produce rotation of a body.TRANSPONDER- a radio communications device consisting of receiving, amplifjing, transmitting, and associ-ated equipment that automatically responds and transmits when triggered by another signal, not necessarily onthe same frequency as received.


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NASA EP 16

TAB LE OF CONTENTSScientific atellite History . . . . . . . . . . .Typical Scientific atellite

Page23

App lication Satellite History ............... 4Typical Applications Satell ites . . 5Deep Space Probe History ....... . . . . . . . . . . . 6Typical Deep Space Probes . . 7Test Experiences an d Flight Operations . . 9

pace craft Complexity. . . . . . . . . . . . . . . . . . 10pacecraft Under Development ..... . . . 11Definitions . . ...... . . .......... . . . . . 17