p-14 magnetometer-plasma probe press kit

8/8/2019 P-14 Magnetometer-Plasma Probe Press Kit

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NEWS R E L E A S ENATIONAL AERONAUTICS A! J SPACE ADMINISTRATION1 5 2 0 H S T R E E T , N O R T H W E S - W A S H I N G T O N 2 5 . D . c .T E L E P H O N E S' D U DL E Y 2 - 6 3 2 5 . E X E CU T I VE 3 - 3 2 6 0FOR RELEASE: Thursday, PM's

RELEASE NO. 61-55 March 23, 1961P-14 Magnetometer-Plasma Probe

Within a f e w days, t h e National Aeronautics and Space Adminis-t rat ion 's Goddard Space F l i g h t Center w i l l launch a space probein t ended t o gather th e mo s t de f i n i t i ve i n form ation ye t ob t ained onear th and in ter p la ne ta ry magnet ic f i e l d s and t h e way these f i e l d sa f f e c t and are a f f e c t e d by s o l a r plasma.The 78-pound payload i s t o be launched from Cape Canaveral,F lor ida , on a Thor-Delta rocket . The fou r -day f l i gh t w i l l be

programmed t o c a r r y t h e payload outward i n a h i g h l y e c c e n t r i cea r th o r b i t t o a dis tan ce of over 100,000 s t a t u t e miles and backt o t h e edge of t h e e a r t h ' s atmosphere,

Payload ins t rumentat ion w i l l i nc lude a rubidium vapor magne-tometer , two fl ux ga te magnetometers, a plasma probe and an op t ica la spec t s enso r .While t h i s f l i g h t i s a c o nt i nu a ti o n of s c i e n t i f i c i n v e s t i g a t i o n smade w i t h e a r l i e r s a t e l l i t e s and space probes, i t a l s o i s a newe f f o r t i n many r e s p e c t s . I t w i l l be t h e f i r s t f l i g h t i n to deepspace w i t h a h i g h l y accurate rubidium vapor magnetometer. T h i sabso lu te ins t rument w i l l m a k e p o s s i b l e t h e f i r s t measurements ofhydromagnetic and wave shocks, (One ty pe of hydromagnet ic wavemight b e v i s u a l i z e d as vib ra t in g l i ne s of magnetic fo rce . )The plasma experiment w i l l g ive t h e f i r s t measurements andd i r e c t i o n of th e f low of very low energy prot on s coming t o theear th from t h e sun . I n add i t ion , t h e probe i s expected %o deter-mine t h e geometry and s t r en g th o f i n t e r p l an e t a r y o r so l a rmagnetic f i e l d s , and t h e d i s t r i b u t i o n and s tr e n g t h of e l e c t r i cc u r r e nt s i n t h e o u t e r r a d i a t i o n (Van Allen) b e l t of t h e e a r t h .The experiment i s expected t o determine more precisely t h ena tu re o f the i n t e r a c t i o n of' magnetic f i e l d s and so l a r co rpuscu l a rr a d i a t i o n . T h i s e f f o r t -- t o ob ta in t o t a l f i e l d measurem ents anddetermine the ef fe c t of magnetic f i e ld s on charged pa r t i c le s --i s e xp ec te d t o l e a d t o a b e t t e r understanding of t h e phenomenawhich a f f e c t t h e e a r t h and i t s surroundings. These f i e l d andpart icle phenomena w i l l c o n s t i t u t e man's environment as heven tu res i n to deep space, New knowledge on t h i s environment

w i l l make i t p o s s i b l e t o c h a r t f l i g h t paths through t h e . l e a s th o s t i l e r eg i on s of i n t e r p l a n e t a r y space.


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PAY OADRubidium Vapor Magnetometer

The heart o f this payload is the 1.5 poundrubidium vapor magnetometer. It is a relatively newinstrument -- development began only two years ago = -which is extremely sensitive and accurate. The P-14model measures field intensities rqnging from .01 to7000 gammas. It is an absolute instrument, that is,its measurements depend only on fixed constants whichdo not require calibration.

The underlying principle on which the rubidiumvapor magnetometer measures 'field strength is expressedin the equation:f(cyl1es per second) = 699,632 (H) where (H) isthe field strength in gauss.In other words, the rate at which the rubidium87 isotope spins around its nucleus is known preciselyand produces a frequency of nearly 7 cycles per secondin a weak magnetic field o f 0.00001 gauss. Thefrequency is directly proportional to the field --the stronger the field, the higher the frequency.

works This 2s the way the rubidium vapor magnetometerLight from a small rubidium lamp passes througha filter, lens and polarizer. This sequence producesa circumstance in which polarized light at a wavelength characteristic o f rubidium vapor passes into acell containing rubidium vapor.The light is abaorbed by the rubidium 87 atomshaving a particular orientation in the cell. Whenthis condition exists, the cell is opaque to thepassage of light, which is detected with a siliconphotocell, whose output is fed to an amplifier.As the opaqueness exists f o r only one-halfcycle of the spin of the rubidium atoms, the cell isalternately opaque and transparent at the spinfrequency, which is determined by the strength of themagnetic field.

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This produces a fluctuating light at the photo-cell which is then amplified and fed back as a smallalternating magnetic field. The purpose of thisalternating magnetic field is t o produce an orderedalignment of the rubidium atoms such that the processwill be self-continuing.Fl um at e Magnetometersabout one pound each, are considerably more sensitivethan those flown before. They are intended to measurefields from O,5 to 25 gammas. These magnetometers areintended primarily t o determine the direction of weakmagnetic fields.

The two fluxgate magnetometers, which weigh

However, the fluxgates are oriented on thispayload at a unique angle, such that the spin of thepayload makes it possible to also make total fieldmeasurements. Thus, the fluxgates redundant withrespect to each other and with respect to therubidium vapor magnetometer in very weak fields.Plasma Probeis designed t o measure the density,direction and bulkveloc3.ty of interplanetary plasma. Positive andnegatlve particles enter the probe through a 6-inchcircular aperture and pass through a series of gridsbehind which there is a collector.

This instrument, which weighs about 2.5 pounds,

The arrangement is such that the probe issensitive only to protons -- positive particles --with a velocity ranging from 6 miles/sec, to 1000/sec.The purpose of the experiment is to determinethe direction as well as the density and velocity ofclouds or streams of protons.This information may help answer basic questionsabout magnetohydrodynamics -- the behavior of ionizedgases and the interaction of these gases with magneticfields,

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Payload ParticipantsWork on this experiment began about two yearsat the Goddard Space Flight Center, where the payloadwas designed, built and tested. The Fields andParticles Branch of the Space Sciences Division ofthe Goddard Space Flight Center has the responsibility

for project management.James P, Heppner and the payload coordin@tor isThomas L. Skillman,The project manager is Dr.

There are six experimenters associated with theproject. They are:Rubidium vapor and fluxgate magnetometers --Dr. Heppner, Skillman and C. So cearce, all of theGoddard Space Flight Center.Plasma probe -- Dr. Bruno Rossi, Dr. HerbertBridge and Dr. Frank Scherb of the Laboratory ForNuclear Science, Massachusetts Institute ofTechnology, and E. F, Lyon of the Lincoln Laboratory,MIT.Opitical Aspect Sensor -- J. S. Albus and D. H.Schaeffer of the Goddard Space Flight Center.The experimenters drew up the proposals for thestudies with which they are associated and were re-sponsible for the construction of the experimentalinstruments and establishing technical requirements,They also are responsible for supervising the analysisof the data and publishing results of the experiments.The rubidium vapor magnetometer was developedby Varian Associates, Palo Alto, California, under thedirection of the Goddard Space Flight Center, Thefluxgate magnetometers were built by the SchonstedtEngineering Company, Silver Spring, Md. The MIT groupconstructed the plasma probe experiment and the opticalaspect sensor was built by the GSFC.The payload structure and all supporting electronicsystems in the payload such as transmitters, telemetryencoders, and programming units were designed and built

by the Payloads System Division at the Goddard SpaceFlight Center. - 4 -


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Tra.4 ectoryThe "window" o r period during which r,he probe may be launchedOnlys r e s t r i c t e d t o three hours per day on about ten days per month,within these restricted periods i s i t possible t o program a t r a jec to rythat provides the p rope r re la t ive posi t ions fo r the ea r th, sun, mQonand payload. This llwindoullmust be such that :- Solar noise w i l l not d i s to r t OT block ou t transmissionsfrom the probe.- The opt ical aspect system w i l l have proper look anglesf o r t he sun, earth and moon t o determine the payload'sor ienta t ion i n space f o r correlation with eransmitted data.- The payload i s i n the proper or ienta t ion t o detect andmeasure par t ic les emitted from the sun.The tr aje cto ry calculated to sa ti sf y these conditions andobtain representative data on magnetiu f i e las and charged pa rt ic le s i n

intsrplanetary space i s a highly ecuentric earth orbit with an inclina-t i o n of 33 degrees, apcgee of over 100,000 s t a t u t e mil es and perigee ofabout 105 s ta tu t e miles , (With such a low perige e, th e probe probablyw i l l be dragged into the atmosphere and burn up.)

The trajectory was planned by the Douglas Aircraft Company,Flight Sequence

The f i r s t stage of the Thor-Delta vehicle i s scheduled t o burnab0u.t 2*minutes and ca rr y th e probe out about 46 s t a t u t e miles.first-stage burnout, the f i r s t and second stages are separated by firingexplo sive bo lt s. About 40 seconds a f te r eecond-stage ignition, t h espring-loaded nw e fa ir in g i s jettisoned by means of explosive bo lt swhich separa te s tr ap s holding togethe r the fa i r ing .

After

The second sta ge burns about 2 minutes. A t second stageburnout, th e probe should be about 98 s t a tu t e miles above the surfaceof the earth.seconds,explosive bolts.Af te r second s ta ge burnout, the probe coasts about 40Second and third stage separation i s accomplished with

After coast, i n rapid sequence, the t h i r d stage i s spun up t o95 rpm by small spin rockets to stabil ize the third stage and payload,The stage then ignites and i s separated from the second stage with explosivebo l t s .a l t i t u d e o f about 115 s t a t u t e miles and i n j e ct i o n i n to o r b i t a t a veloci ty ofab0u.t 24,300 miles per hour.the t h i r d stage and payload are separated by means of explosive b o l t s and asp ring mechanism.from th e launch site.

The th i rd s tage f i r e s f o r about 40 seconds.carrying the probe t o anAbout two minutes af t e r th ird stage burnout,

A t separation the payload i s about 890 miles downrangeThere i s no propulsion i n the payload.

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Launch VehicleThis probe i s t o be launched with a three-st age Delta veh icl ehaving the following characteristics:Height - 92 f e e tM a x . diameter - 8 f e e tLift-off weight - a l i t t l e less than 112,000 pounds

F i r s t sta ge (modified USAF Thor, Douglas Ai rc ra ft Company) :Fuel - l iqu id (LOX and kerosene)Weight - about 107,000 pounds fueledThrust - about 150,000 poundsBurning time - 159 secondsGuidance - radio guidance system (mounted on second stage) and

r o l l and pi tc h programmersSecond s t w e (Aerojet General) :

Fuel - l iqu idWeight - more than 4,000 poundsThrust - about 7,500 poundsBurning time - 114 secondsGuidance - radio guidance system (Douglas Aircraft flightcontroller plus Bell Telephone Laboratory)

Thif-d stage (Alleganp Bal li st ic s Laboratory) :Fuel - sol idWeight - more than 500 poundsThrust - about 3,000 poundsBurning time - 4.2 secondsGuidance - spin-stabilizedA l l stages were assembled and checked by Douglas, the prime

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Tracking and TelemetryA new ground system f o r telemetry r ecep t ionand dop l e r t rack ing in format ion was des igned for

GSFC, This system was i n s t a l l e d a t the s t a t i o n si n England and H a w a i i , as w e l l as a t a number ofM i n i t r a c k s t a t i o n s ,Data from t h e experiments i s t r a n s m i t t e d t oth e ea r th by a 108 megacycle transmitter employingphase modulation,

the P-1 2 probe by the Radio Systems Branch of the

The spec ia l ly designed t ran sm i t t e r opera tesa t 35 percent e ff ic ie nc y and produces 5 t o 6 wattso f outpu t power,

The probe w i l l be t racked by r ece iv ings t a t i o n s a t J o d r e l l Bank, England (250-fOot d is h; Goldstone, Cal i fornia (85-foot d i s hantennantenna l ; Woomera, Aust ra l ia (85-foot d i s h antenna) jH a w a i i (60,-foot d i s h antenna ); and Essl en Park(Johannesburg), outh Africa ( a 22 db yagi arrayantenna) ,

Secondary t racking and data a c q u i s i t i o ns t a t i o n s f o r t h i s launch are Quito, Ecuador;Sant iago, Chi le ; Blossom Point, Maryland; and t h eM i n i t r a c k s t a t i o n a t Woomera, Australia, Thef a c i l i t y on Ascens ion I s l a nd w i l l provide onlyt rack ing in format ion ,

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p-14 magnetometer-plasma probe press kit

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