U. S. Explorer Satellites

8/7/2019 U. S. Explorer Satellites

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External Publicat ion No. 491

u. QS. ~ E X P L O R E R SATELLITES

(CATEGORY)

j E T ~ R R 6 ' U L S I O N ' ~ A 8 0 R A T O R Y .,CALlPQlNfA.INSTITUTE OF TECHNOLOGY ' p ~ D i N A 3, CALIFORNIA

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Copy No.pp. 1-21 46

ORDCIT ProjectContract No. DA 04-495-0rd-18Department of the Army ~ ORDNANCE CORPS. ~ ~ ~ _ C i - t - 4 9 . 5 - ( ! > R . V -I'D -Ct, ('-; ~ c : \

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External Publicat ion No. 491( u. QS. ~ E X P L O R E R SATELLITES

W. K: Victor

JET PROPULSION LABORATORYCalifornia Institute of TechnologyPasadena 3, CaliforniaMay 1, 1958


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Jet Propulsion Laboratory External Publication No. 491U. S. EXPLORER SATELLITES1

I . I N T R O D l ~ T I O N

This is the history of the birth of the f i r s t U. S. earthsa te l l i te , Explorer I:

May, 1955: A feasibi l i ty study was begun which led tothe complete definit ion of the Jupiter Cvehicle.

April, 1956: This study was presented to the Army by theMissile Laboratories at Redstone Arsenal andthe Jet Propulsion Laboratory (JPL). I tindicated that the sa te l l i te project wasdefini tely feasible.

September, 1956: The Jupiter C vehicle was successfullylaunched at Cape Canaveral, achieving arecord al t i tude of 650 miles and a recorddistance of 3,000 miles southeast from thecoast of Florida.

1956, 1957: Two subsequent launchings of the Jupi ter Cvehicle successfully completed the prooftesting of the re-entry nose cone designedfor Jupiter .

4 October, 1957: The f i r s t ar t i f ic ia l earth sate l l i te waslaunched by Russia, a major scient if icachievement bringing world-wide recognition.

- - - - - ~ l - T - h - i - s - - p - a - p - e - r - - p - r - - e - s - e - n - t - s - - t - h - e - - r - e - s - u l t s of one phase of researchcarried out at the Jet Propulsion Laboratory, California Inst i tuteof Technology, under Contract No. DA-04-495-0rd 18, sponsored by theDepartment of the Army Ordnan e Corps.Page 1

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Jet Propulsion Laboratory External Publication No. 4913 November, 1957: The second ar t i f ic ia l earth sa te l l i te was

launched by Russia, a spectacular demonstratioof rocket power and experimentation in the l i fesciences.

6 November, 1957: A formal presentation was made to the technicapc1el on the Earth Satel l i te Program proposingthe launching of two earth sate l l i tes usingthe Jupiter C vehicle. The proposal wasapproved at the panel meeting on that date.

8 November, 1957: The announcement was made by the Secretary ofDefense that the Army would part icipate inthe IGY sa te l l i te program.

31 January, 1958: The bir th of the f i r s t u. S. earth sa te l l i te ,Explorer I , occurred at 5 sec af ter 10:55 PM,Eastern Standard Time.

5 March, 1958: The Explorer I I launching was unsuccessfuldue to ignit ion fai lure of the fourth-stagerocket motor.

17 March, 1958: The f i r s t Vanguard sa te l l i te was placed inorbi t .

26 March, 1958: Explorer III"was placed in orbi t at 12:38 PM,Eastern Standard Time.

The Je t Propulsion Laboratory of the California Inst i tute ofTechnology in submitting i t s proposal to the National ScienceFoundation to launch two ful ly instrumented earth sate l l i tes duringthe Internat ional Geophysical Year l i s ted the following asobjectives of the sa te l l i te experiments:

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Jet Propulsion Laboratory External Publication No. 491Explorer I . The f i r s t experiment should be performed at the

ear l ies t possible date. I ts objectives would be (1) to gatherenvironmental data for engineering purposes, (2) to f l ight - tes tmajor items of hardware, and (3) to make measurements of scientif icvalue. The f i r s t experiment emphasized the importance of obtainingengineering data which could improve the probabili ty for success ofthe second experiment; however, the f i r s t experiment containedcosmic-ray and micrometeorite equipment which provided informationto scient is ts enabling them for the f i r s t time to evaluatequantitatively the regions of space beyond the earth 's atmosphere.

Explorer I I I . The primary objective of the Explorer I I Iexperiment was scient i f ic in nature. The experiment was designedto achieve a comprehensive survey of cosmic-ray intensity withrespect to geographic and geomagnetic lat i tudes and longitudes,al t i tudes above the earth, and time. Secondary objectives were toobtain addit ional information of a s ta t i s t i ca l nature regardingthe densi ty and size of micrometeorites and to gather additionaldata regarding the external and in ternal temperatures of orbitingvehicles.

The micrometeorite experiment was performed in cooperation withthe Air Force Cambridge Research Center (AFCRC). The cosmic-rayexperiment was performed in cooperation with the State Universityof Iowa (SUI). The launchings of Explorers I and I I I were performedin cooperation with the Army Bal l is t ic Missile Agency, (ABMA).

The design of the sate l l i te and, where necessary, thecoordination of the redesign, for both the scientif ic experimentand the sa te l l i t e structure, were accomplished by JPL. The in tegri t

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Jet Propulsion Laboratory External Publication No. 491of the design and the fabrication of the completed payloads werechecked, uti l izing the environmental tes t faci l i t ies at JPL priorto delivery for launch. The Explorer s a t e l l i t e ~ weighed approximate18 1 /2 Ib each. With the empty fourth-stage rocket motor attached,the tota l weight of each of the orbiting vehicles was approximately31 lb .

I I . THE JUPITER C VEHICLEThe Jupi ter C vehicle is a four-stage rocket. The f i r s t stage

is a modified Redstone missile developed by the Army Ball is t icMissile Agency in Huntsville, Alabama. The Redstone missi le ,or booster, was used to carry the high-speed rocket stages and thepayload to the injection al t i tude. The modified Redstone boosterwas conventionally guided by an autopilot and used je t vanes andat t i tude je ts for control . The atti tude control system was carriedin the instrument compartment in the forward portion of the missile.One of the modifications necessary was the inclusion of electr icmotors in the instrument compartment to spin the high-speed clusterof rocket motors. A second modification was the use of a fuel ofhigher performance than is normally used in the Redstone missile .A th ird modification was the lengthening of the fuel tanks to permitan i .Icrease in fuel-carrying capacity.

The second, th ird , and fourth stages of the Jupiter C missilewere designed and developed by JPL. All stages used ident icalsolid-propellant rocket motors. These motors are about 3 feet longand 6 in . in diameter. The second stage used eleven of thesemotors clustered in a concent ic ring. The third stage used three

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Jet Propulsion Laboratory External Publication No. 491motors grouped together and nested inside the concentric secondstage. The fourth stage util ized a single rocket motor to whichthe payload was attached. The ent ire assembly of high-speed stageswas placed atop the Redstone booster, attached by means of a largeshaft , and rotated at a speed of 750 rpm to minimize dispersionduring the burning of tll ,) high- speed stages.

The payload is a bullet-shaped instrument compartment attachedwith machine screws to the f o u r ~ h - s t a g e motor. I t has approximatelythe same dimensions as the rocket motor; i t s size and shape wereselected for compatibility with the rocket motor and with theelectronic instrumentation contained within. The primary materialsused in i t s construction were sta inless steel , f iberglass, andmicarta. The bullet-shaped nose cone was made of stainless steelto res is t aerodynamic heating encountered during the launch. Theouter cylinder was also made of sta inless s teel to carry the thrustloads and to preserve the alignment of the payload through theassembly, checkout, and spin-up on axis. Fiberglass was used toform the insulating rings between the nose cone and cylinder andbetween the cylinder and the rocket motor. The electronic componenwere mounted on micarta chassis boards to insulate them from theouter shel l . The proper balance between heat absorption and 11eatref lect ion was maintained by means of aluminum oxide str ipes onthe nose cone and cylinder.

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Jet Propulsion Laboratory External Publication No. 49I I I . THE EXPLORER I SATELLITE

The Explorer I sa te l l i te contained two complete radio telemetrsystems, providing a to ta l of eight channels of continuous telemetrSeven sensors supplied data to these eight channels. One of thesensors, the cosmic-ray tube, was common to both telemetry systems.Four of the seven sensors detected changes in temperature (seeTable 1).

All four of the temperature sensors changed their resistancewith temperature. The sensor formed part of an oscil lat ing circui tso that when the resistance increased, the frequency of theosci l la tor increased also. The information transmitted by thesa te l l i te and picked up by the ground receiving stations was thefrequency of these resistance-controlled osci l la tors .

Two of the sensors measured the effects of micrometeoriteimpact (see Table 2). A small ultrasonic microphone was placed inspring contact with the steel cylinder of the payload. The impactof a micrometeorite on the steel shell was amplified by a high-gaint rans is tor amplifier to the point where a part icle with a verysmall momentum would provide a pulse of suff ic ient amplitude tot r igger a f l ip-f lop. When the output of the f l ip-f lop was in the"zero" st2te, the current-controlled telemetering subcarrierosci l lator connected to i t had a frequency of about 900 cps. Whenthe sa te l l i te collided with the next micrometeorite, the f l ip-f lopwould go to the "one" state and cause the telemetering osci l latorto change i t s frequency to approximately 1000 cps. With the nextcol l is ion, the frequency would alternate back to 900 cps. With

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Jet Propulsion Laboratory External Publication No. 491such a telemetering system i t was re la t ive ly simple for anyoneto ascertain the ra te a t which Explorer I coll ided withmicrometeorites.

The wire-grid micrometeorite detector operated in the followingmanner: As each wire grid was severed, the subcarr ier osci l la torexperienced a small step increase in frequency. The wire-griddetectors were wound with very fine wire, approximately 17 ~ indiameter. Since the nominal impact veloci ty of the sa te l l i t e anda micrometeorite i s 20,000 to 30,000 mph, a micrometeorite ofapproximately 5 - ~ diameter or greater has been estimated to becapable of severing one of the wires when i t encounters the gauge.Each wire gauge detector is 1 sq cm in area. The set of twelvewire gauge detectors was placed in a ring around the fourth-stagemotor.

The cosmic-ray sensor detects the penetrat ion of high-energyatomic part ic les through the s ta inless-s tee l wall of the GeigerMueller tube. This tube was manufactured by the Anton ElectronicLaboratory and is the i r Model 314. I t is a halogen-quenched tubeabout 1 in . in diameter and 6 in . long.

The elect ronic payload for Explorer I comprises three majorsubassemblies: the cosmic-ray-micrometeorite package, the high-power t ransmit ter , and the low-power t ransmit ter . The cosmic-raymicrometeorite subassembly has four parts : the cosmic-ray tube,a scale of 32, a high-voltage power supply, and the microphoneamplifier and scaler . Assuming that the las t stage of the scaleris in a "zero" posi t ion, the frequency of the subcarr ier osci l la tormonitoring the cosmic ray will be about 1200 cps. As soon as 16

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Jet Propulsion laboratory External Publication No. 491high-energy part ic les have penetrated the tube 's s teel shel l , theoutput f l ip-f lop of the cosmic-ray scaler will change to the "one "state and the frequency of the subcarrier osci l lator wil l shi f t toabout 1350 cps. Thus, by noting each time the subcarrier changesfrequency and multiplying by 16 i t is possible to determine therelat ive cosmic-ray intensity in space without further information.Because the information is transmitted as the event occurs, thesurvey of primary cosmic-ray intensi ty by Explorer I is limited tothose areas where receiving stations are located. The averagecounting rate expected was approximately 32 penetrations per sec,which, when scaled down by 32, applies a l-cps square wave to thesubcarrier osci l lator . With a maximum square wave response of 20cps for this channel, the telemetering system was capable ofhandling information up to 20 times the normal rate expeGted i fsuch an increase in cosmic-ray intensi ty occurred due to intensesolar or magnetic storms.

The high-power transmitter is completely t ransis tor ized andoperated on a frequency of 108.03 mc with a power output of 60milliwatts. The t ransmit ter is composed of an osci l lator operatingon 54.015 mc and a frequency-doubling RF amplifier operating withan input of 54.015 me and an output of 108.03 mc. I t is amplitudemodulated with a modulation index of approximately 50%. The f inalstage of the t ransmit ter is collector-modulated in a ratherconventional manner. The high-power t ransmit ter obtained i t sprimary power from a set of 24 RM-12 mercury batteries manufacturedby the P. R. Mallory Company. This t ransmit ter delivered i t sradio-frequency energy to a turnst i le antenna system extending from

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Jet Propulsion Laboratory External Publication No. 491the sa te l l i te between the instrument compartment and the rocketmotor. The high-power transmitter has a set of four subcarrierosci l la tors operating on standard FM/FM channels 2, 3, 4, and 5.The channel-2 osci l lator frequency is centered around 560 cps, andthis channel measures the skin temperature of the cylinder. Thechannel-3 osci l lator freluency is centered about 730 cps and isused to measure the internal temperature of the sa te l l i te . Thechannel-4 osci l lator frequency :is 960 cps; this channel operatesin conjunction with the m i c ~ o p h o n e system described previously.The channel-5 osci l la tor frequency is centered about 1300 cps andm e a s u r ~ s the cosmic-ray count. The l i fe of the high-powert ransmit ter was approximately 2 weeks, as predicted.

The low-power transmitter is located in the nose of thesa te l l i te . I t operated on a frequency of 108.00 mc and deliveredapproximately 10 milliwatts of power to the dipole antenna formedby the nose cone and the cylinder. I t was powered by a set of sixRM-42 mercury batteries and consisted of a 54 mc osci l lator followedby a frequency doubler. The low-power t ransmit ter is phasemodulated by a set of four subcarrier audio osci l la tors operatingwithin the standard FM/FM channels 2, 3, 4, and 5. Channel 2measured the temperature of the nose cone. Channel 3 was used tomeasure the nose-cone temperature during launch. Channel 4 measuredthe number of micrometeorites (of suff icient size and momentum tosever the wire) coll iding with the wire gauge detectors. Channel 5measured primary cosmic-ray intensi ty. The l i fe of the low-powert ransmit ter was 2 to 3 months as predicted.


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Jet Propulsion Laboratory External Publication No. 491IV. THE EXPLORER II I SATELLITE

The Explorer II I sate l l i te differs from Explorer I in severalrespects, as shown in Table 3. The sensors used in Explorer I I Iare shown in Table 4

The two major electronic subassemblies comprising the payloadwere the low-power transmitter and the SUI Cosmic Ray Package,modified. The low-power transmitter was essential ly the same asthat used in Explorer I . Channel-3 telemetry measured internaltemperature .in Explore..r I II instead of nose-cone temperature, as inExplorer I .

The SUI Cosmic Ray Package is comprised of several pancakefoam-potted decks. The decks are stacked one upon the other andbolted together to form a cylinder about 5 1/2 in. in diameter and12 in . long. The stack of pancakes is sl id into a t ight- f i t t ingaluminum can for structural r igidi ty. The functions performed bythe various decks are:

Deck ADeck BDeck C

Deck DDeck EDeck FDeck G

Deck H

G-M tube, cover plate, turn-on plugVHF receiverHigh-power transmitter, modulator,high-voltage power supplyTuning fork osci l la tor and scale of 4Scale of 128Scale of 128Record-drive amplifier, playback circuitrelay control circui tsMercury batter ies (receiver, transmitter

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Jet Propulsion Laboratory External Publication No. 491Deck I Mercury batteries (tape recorder and

interrogation cycle)Deck J Magnetic-tape recorderThe original Vanguard experiment, with the SUI package, is

compared with Explorer I II to indicate some of the reasons for andthe effects of the modification. I t is seen (Table 5) that byseparating the functions of tracking and stored-data transmissionthe expected operating l ifet ime of the equipment was increased fromone to two months without increasing battery weight. In addition,i t was possible to include one more channel of continuous telemetry.

One major mechanical problem and one major electr ical problemwere encountered in modifying the SUI Cosmic Ray Package for theJupi ter C vehicle: '

Mechanical ProblemThe system would not interrogatewhile spinning at a rate in excessof 450 rpm. (Jupiter C spin rateis 750 rpm).

Electr ical ProblemModulation sidebands on the low-power transmitter interfered withthe operation of the receiver,causing self- interrogation.

Solutiona. Move the latching relays

nearer the spin axis.b. Modify the tape-recorder

release mechanism.Solution

a. Use a separate localosci l la tor for the receive

b. Add a 10B-mc t rap in thereceiver-input transmissionl ine.

The receiver used in Explorer I I I was designed, fabricated,and supplied by the Naval Research Laboratory (NRL). I t is a

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Jet Propulsion Laboratory External Publication No. 491sensit ive, completely t ransistorized, printed circui t , doublesuperheterodyne receiver operating in the VHF band with thefollowing characterist ics:

Threshold sensi t ivi tyBandwidthNoise figureSupply voltagePower consumption,non-interrogatedPower consumption,interrogated

-100 dbm10 kc/s

>30 db10.4 v21 mw

210 mw

The design of the receiver was excellent for the application; theactual hardware supplied by NRL passed a l l of the environmentaltests without a single fai lure.

v. CALIBRATION PROCEDURESTemperature. In general, the calibration of the telemetry

channels was accomplished in two steps. First , the subcarrierosci l la tors were placed in an oven, and their frequency variationas a function of temperature was recorded. Simulated detectors,placed outside the oven, were connected to the osci l la tors andvar:ed over the expected range of resistance. Then the osci l la torswere removed from the oven, and the actual detectors were placedin the oven for calibration. Calibration curves were plottedshowing the frequency change of the osci l la tor as a function ofthe temperature of the sensor and the temperature of the osci l la tor .

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Jet Propulsion Laboratory E x t e r n a ~ Publication No. 491Micrometeorite Microphone Detector. Small glass beads were

dropped onto the steel cylinder of the assembled payload. Themomentum was calculated knowing the mass of the beams and i t sterminal velocity at impact. A conversion factor relating largemass, low-velocity particle momentum to small-mass, high-velocityparticle momentum is being determined experimentally by AFCRC.

Micrometeorite Wire Gauge Detector. This will be an afterthe-fact calibration performed under the direction of AFCRC. I twill be accomplished by shooting high-velocity particles of knownmass at the wire gauge detectors to determine the minimum particlesize and momentum required to sever the wire.

Cosmic-Ray Detector. Four calibrations were performed on theGeiger-Mueller tubes prior to f light:

a. Relative counting rate as a function of temperature.b. Relative counting rate as a function of supply voltage.c. Standard source-standard distance measurement to serve

as a reference for la ter absolute calibrations.d. Absolute efficiency based on a ratio of a 3-fold to 2-fold

count in an omnidirectional f ield.An after-the-fact calibration will be performed by the State

University of Iowa to determine the effective length of the G-Mtube in the payload configuration and to assist in determiningabsolute magnitude of the omnidirectional f ield for a given recordedcount rate.

Calibration data for Explorer I is contained in JPL PublicationNo. 130, entitled "Calibration Record for the IGY Earth Satel l i te

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Jet Propulsion Laboratory External Publication No. 4911958 Alpha." Calibration data for Explorer I I I is contained inJPL Publication No. 127, enti t led IICalibration Record for the IGYEarth Satel l i te 1958 Gamma."

VI. INFORMATION TRANSMITTED BY THE EXPLORERS

Questions relat ing 0 the density and size of meteorites astelemetered by Explorers I and I II should be directed to Dr. E.Manring or Dr. M. Dubin at the Air Force Cambridge Research Centerin Cambridge, Mass. Questions relat ing to the absolute intensi tyof primary cosmic rays should be addressed to Dr. J . Van Allen atthe State University of Iowa, in Iowa City, Iowa. Questionsrelat ing to the external and internal temperatures encountered bythe Explorer satel l i tes in space should be directed to Dr. A. Hibbsof the Jet Propulsion Laboratory, Pasadena, California.

When this report was written Explorer I had been in orbit twoand one-half months. During this time the coldest temperaturereached by the nose-cone skin sensor was -30C; the hot testtemperature, +75C. However, for anyone orbi t i t appears thatthe outer skin experienced a to ta l temperature variation of about80 to 90 oC. The internal temperature of the payload varies muchless than the outside temperature due to the insulation provided.The temperature inside Explorer I varies from 0 to 35C inside thecylinder and from 5 to 40 0 C inside the nose cone. Data fromExplorer I II indicate that the temperatures i t will experience willbe similar to those measured in Explorer I . Internal temperaturesmeasured during a 2-week observation period were 0 to 30 0C insidethe nose cone and 5 to 35C inside the cylinder.

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- - - --------------Jet Propulsion Laboratory External Publication No. 491

VII. EXPLORER SATELLITES IN ORBITAs the sa te l l i tes continue to encircle the earth, their paths

can be described quantitatively in the manner shown in Table 6.The accuracy to which the orbital parameters are known can bestbe determined by using them to predict the position of the sa te l l i teat some time in the future. If the parameters of Explorer I areused to predict i t s position 3 days in advance, an error in timeof about one min (or 300 miles along the path) might be expected.The Explorer III orbit will be more dif f icul t to predict accurately,because the unknown effects of atmospheric drag at the lower perigeaalt i tudes are more pronounced. On the other hand, Explorer I IIwill provide scient ists with a great deal more information aboutthe atmospheric density at this alt i tude.

Although the density of the atmosphere at perigee is extremelysmall compared with that at the surface of the earth, the sa te l l i tes t i l l collides with enough a ir molecules to slow i t down a smallfraction of i t s to ta l speed. As the speed at perigee decreases,the alt i tude at apogee and the time to complete one orbit alsodecreases. Therefore, by noting the rate at which the perioddecreases, i t is possible to predict the expected l ifetime of thesa te l l i te . Just before the sa te l l i te is about to enter theatmosphere and burn up, the satel l i te orbit becomes circular . Therate of decay for the Explorer I period is 0.01 min/day, and theestimated l ifetime is 5 to 10 years. The rate of decay for theExplorer I I I period is 0.3 min/day, and i ts estimated lifetimeis 4 to 6 months.

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Jet Propulsion Laboratory External Publication No. 491VIII. FUTURE COMMUNICATION TECHNIQUES

One of the signif icant things demonstrated by the Explorersa te l l i tes is that a communication system can operate effect ivelywith milliwatts of radiated power at ranges up to 2500 miles. Thetechnique is successful because the information rates are low andbandwidths of the receivers are narrow. Further exploi tat ion ofthis technique will make i t possible to communicate at distancesmeasured in millions of miles with only a few watts of t ransmit terpower.

Table 1. Temperature Sensors Used in :p orer IMeasurement

Nose cone, launchNose cone, skinCylinder, skin

Internal , RF chassis

DetectorTypeTemperatureResistancewireResistance

wireThermistorThermistor

Manufacturerand ModelDetectors

ArnouxNo. 52714H-13Arnoux

No. 2202L-8GE CarboloyRF 11

VECONo . 32A12

MeasurementRange, C

-50 to 450-100 to 150-50 to 150-10 to 80

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Jet Propulsion Laboratory External Publication No. 491Table 2. Micrometeorite Sensors Used in Explorer I

Measurement

Number of gaugesopened by meteoritecoll isons

Micrometeoritecoll isons withcylinder as theyoccur

DetectorType Manufacturerand ModelMeteorite Detectors

17-J.-L wireon 1 sq cmpatch

Ultrasonicmicrophone

AFCRC

TempleUniversityand AFCRC

MeasurementRange

Will regis terup to 12 opgauges bycoll ison wimeteoritesgreater tha5 J-L in diamDetects a llmeteorites

withmomentums o6 to 18milligramcm/sec andabove

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Jet Propulsion Laboratory External Publication No. 491Table 3. Characteristic Differences BetweenExplorers I and I I I

CharacteristicSensors

Temperature detectorsMeteorite detectors

Cosmic-ray measurement

Data storageData transmission

Radio receiverAntennas

Transistors, totalHigh-power t ransmit ter

Explorer I742

Single G-M tube;2 continuousreadoutsNone

Continuous only

None1 dipole1 turnst i le

42Continuous for2 weeks

Explorer I I I421

Single G-M tube;1 continuous read1 stored t ransmissionMagnetic-tape recorContinuous plusplayback uponcommandTransistorized VHFreceiver2 dipoles, oneduplexed withreceiver

107Intermittent for2 months


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Jet Propulsion Laboratory External Publication No. 491

Measurement

Nose-cone skinInternal , at baseof G-M tube

Number of gaugesopened bymeteoritecoll isons

Primary cosmic-rayintensity

Table 4. Explorer I I I SensorsDetectorType Manufacturer andModel

Temperature DetectorsThermistorThermistor

GE CarboloyRF 11VECaNo. 32A12

Meteorite Detector17-/J. wire onon 1 sq cmpatch

AFCRC

Cosmic-Ray DetectorGeigerMuellertube

Anton ElectronicLabs. No. 314

MeasurementRange, c

-50 to 150

-10 to 80

Register up to12 open gaugby coll isonwithmeteoritesgreater than5 /J. in diam.

o to 640part ic les /sec

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Table 5. Comparison of Explorer I I I with Original Vanguard Package IIExplorer I I I

TelemetryAssignment I Information TransmittedHP I Stored cosmic-ray data108.03 mc on command

LP5

LP4

LP3

LP2

Continuous cosmic ray

Meteorite abrasion, 12wire gauge detectors

Internal temperature,direct (thermistor)

Shell t e m ~ e r a t u r e , direct (thermistor)Two-months battery l i fe ,weight, 18.5 lb

Vanguard SUI Package I ITelemetry Assignment

HP108.00 mc3500-cps subcarrierpulse FM3500-cps subcarrierzero signalfrequency3500-cps calib withstandard res is tor

Information TransmittedStored cosmic-ray dataon commandContinuous cosmic ray

Meteorite abrasion, 12wire gauge detectors

Internal temperature,Indirect (freq vstemp)None

One-month battery l i fe ,weight, 20.5 lb

"

'

tXcCI:O.

'C0.

,oOc,o:Zo~ \I


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Jet Propulsion Laboratory External Publication No. 491Table 6. Orbital Parameters of Explorers I and I I IOrbitalCharacterist ic Explorer I(af ter 2 1/2 monthsin orbit)

Explorer I I I(af ter 2 weeks iin orbit.)- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ~ - - - - - - - - - - - - - - - - - - - - - - r _ - - - - - - - - - - - - - - - - Perigee, miles

Apogee, milesEccentricity

Semimajor axis/earth radiusNodal period, min

Rate of decrease of period,min/dayInclination to equatorialplane, degMotion of apogee in directionof sa te l l i te motion,deg/dayWestward precession,deg/dayWestward motion of ascending

node (includes precession),deg/periodWestward motion of earth;deg/period

Orbit numberDateTime of crossingLongitude crossingascending nodeLongitude of perigeeAltitude

2201563

0.13831.2248114.58

0.0133.14

6.45

4.3129.06

28.687864/4/5816 H 8M 42S, GMT20 49' 20 11 east

1530 east1500 miles

1171740

0.1661 ~ 2344115.65

0.333.46

6.29

4.25

714/1/589H 38M 17S, GMT114 0 4 ' 4111 west

11 0 -east1320 miles

U. S. Explorer Satellites

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