ionosphere direct measurement satellite explorer viii) s-30 press kit

8/7/2019 Ionosphere Direct Measurement Satellite Explorer VIII) S-30 Press Kit

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NEWS R E L E A S ENATIONAL AERONAUTICS AND SPACE ADMINISTRATION1520 H S T R E E T . N O R T H W E S T . 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 D L E Y 2-6325 . E X E C U T I V E 3 - 3 2 6 0FOR RELEASE: HOLD FOR RELEASEUNTIL LAUNCH

Release No, 60-287IONOSPHERE DIRECT MEASUREMENT SATELLITE (S-30)

BACKGROUND

This satellite is designed to provide basic information onthe ionosphere by direct measurement.

E i g h t experiments are included in the satellite. Most ofthe instrumentation will measure: the positive ion and electroncomposition of the ionosphere.

The satellite is a project of the National Aeronautics andSpace Administration, under the management of the Goddard SpaceFlight Center. The NASA George C, Marshall Space Flight Centerprepared the payload, and designed, developed and launched theJuno 11 carrier rocket, The scientific experfments were originatedand built by the Goddard Center.provided the vehicle's three-stage high-speed upper assembly.

The NASA Jet Propulsion Laboratory

Launch is at a 50 degree inclination to the equator. It isdesired to obtain an orbit of at least 200 miles perigee and about1000 miles apogee. The orbital period would be about 113 minutes.Expected lifetime of the experiments is about two t o three months .The payload is expected to orbit f o r several years.

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In addition to the investigation of the ionosphere,satellite has a,secondary mission of gathering data on thefrequency, momentum and energy of micrometeorite impacts.

the

Themomentum range which will be scanned is considerably larger thanthat of previous U. S. satellites.

This will be the first attempt to take direct, continuousThe purpose is toeadings on the ionosphere at such altitudes.

lead to a better understanding of the structure and properties oft h e ionosphere, and how the region changes in composition due tosuch variable conditions as sunlight and shadow.

The ionospnere begins at about 50 miles above the earth andextends several nundred miles into space. It is essentially tne"fringe" of the atriios:d,iere -- a region where atoms of tne atmosphereare acted upon IY - itni.:olet radiation from the sun and becomeionized, tnat I s , L k l z ? w e i r electrons. Tne result of this contact1.s a gaseous substance whlcn scientists call a plasma -- a gas, theconstituents of which have become fully ionized,

The measurements taken by this payload will be in the upperThe particles to be investigated are ofayers of the ionosphere.

low energies, a group which exerts the greatest influence oncommunications.

Long-range radio communications are dependent upon the bounc-ing o f signals off the ionospheric layers.ionosphere, for reasons which are not fully explored, varies withconditions of the region, the angle of the beam and with the radiofrequency used.pletely reflected, while in others the signals are lost due to

The reflectivity of the

In some cases the signals are readily and com-


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absorptien in the ionosphere. The effectiveness of this reflectionalso varies from season to season, and from day t o night.

These are some of the questions which scientists hope will beat least partially answered by this and subsequent experiments.

The most immediate application of the data derived from thissatellite will be in the area of communications, but this isprimarily an experiment in basic ionospheric physics.

There are basically two means of investigating the structureand properties o f the ionosphere with earth satellites. One is theradio propagation technique. In this method, ground stations re-ceive signals from satellites, the position and transmissionstrength of which are known fairly accurately. Several satelliteshave provided this type of data, and a special payload equipped witha immber of radio transmitters operating on different frequenciesand Levels of power will be launched by NASA in the f'uture t o f'urtherexplore the region by this technique.

The other method o f investigation is the one employed by thissatellite -- that o f direct measurement. The payload incorporatesa number of sensors which "sample" the positive i o n and electronconcentration, and their temperatures, as the vehicle passes throughspace.

The method used here has two major advantages over the propa-gation method: it measures considerably more ionospheric characteris-tics, and it is much less sensitive to the rapid time variations ofionospheric conditions, On the other hand, the success of the ex-periments depends on competent evaluation o f the disturbance createdin the region by the presence of the satellite, a factor which does

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- 4 -not affect propagation methods appreciably.

Ionospheric characteristics which will be studied includethe concentration of electrons and positive ions, the electrontemperature, and the mass distribution of positive ions, Simultaneousmeasurement of electron and ion concentration will resolve the questionof the charge balance in the region. Electron temperature data, whencompared with temperatures of the rarefied gas in space will resolvethe question of thermodynamic equilibrium.

If equilibrium is established, the measurement of electrontemperature could be the most convenient means of studying temperaturesin the outer regions of space.

Studies of the ion mass distribution will establish the altitudeof the base of the exosphere, the layer above the ionosphere.

Another objective is the meaurement of' the charge accumulation -th? static electricity -- on the satellite's aluminum surfaces.These d a t a can be related to electrical drz:, and are expected to besignificant t o studies of the density of the region, which presentlya r e being computed from satellite orbital decay observations with-t3ut regard to electrical drag.

The other secondary objective, the micrometeorite study, willuse an improved version of an experiment carried on Explorer VII.Comparison of the energy and nomenturn data will determine the massesand the velocities of micrometeorite pdrticles. Because of the lowperigee, observations will be made of the effects of "sputtering"on the surface of the micrometeorite EA!zrgy detector. "Sputtering"is erosion of the vehicle surfaces by collison with all types ofparticles, including the micrometeorites themselves.


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- 5 -PAY OAD

The configuration of the satellite is very similar to that ofExplorer VII.bases attached to a cylindrical band, or equator,30 inches in height and diameter, and weighs 90 pounds,shell is constructed of aluminum, instead of the fiber-glass usedon Explorer VII.mit the accumulation and measurement of the static charge as thesatellite orbits.separate f rom the payload,which will slow the rate of spin from 450 to about 30 rpm.channels of data will be telemetered to ground stations carrying 77separate pieces of information. Only one transmitter will be used,operating on 108 -megacycles,

It is in the form of two truncated cones, with theirThe satellite is

The outer

Aluminum was used primarily because it would per-

The fourth stage mo t o r case, after burnout, willThe payload has two de-spin mechanisms

Six

Following is a list of the scientific experiments and theirobjectives:

1. The radio frequency impedance probe will measure ionospherice1e::'cron concenkration. It compares the measured capacitance of thesensor - or how much of an electrical charge it will hold - to i t sfree-space value,concentration surrounding the satellite,antenna, each arm of which is 10 feet long, which radiates a verysmall amount of power.made 25 times every second,

These data can then be related to the electronThe sensor is a dipole

The measurement of capacitance will be

2 , One single-grid ion trap will be used to determine ion con-centration and mass distribution,similar to vacuum tube techniques, One sensor in the form of acylinder three inches in diameter is located on the upper "cone"

The techniques involved are very

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r- 6 -near the spin axis , The sensor consists of a g r i d , flush with andinsulated from the satellite skin, behind which is located acollector. An electrical "sweep voltage" varying between -5 andf 25 volts is introduced to the grid. At a given time during the3o-voit sweep, any ion particle, which, due to its kineticis able to pass through the grid, will be registered by the collector.The data is derived c mpari g the collector current with theapplied sweep voltage.

3. Four multiple-grid ion traps measure positive ion con-centmtion and mass distribution. This experiment has essentiallythe same mission as that of the single-grid traps. Three sensorsare located on the equator of the satellite and the fourth on the

I 1upper cone" near the spin axis. Each sensor consists of fourconcentric grids and a collector. The comparison of the single-gridda.ta with the multiple-grid data will evaluate the effects of theion sheath surrounding the vehicle upon the ion data.

4. The Langmuir Probe Experiment measures electron tempera-'cure, One sensor is located on the sabellite equator. The sensorconsists of a collector in the form of a circular plate flush withand insulated from the satellite skin. In the case of the Langmuirprobe, t o t a l diffusion current to the satellite is measured.

5. The electric field meter is designed t o measure the dis-tribution of charge which accumulates on the surface of the vehicle.The sensor, located directly on the spin axis, is termed a rotating-shutter type electric field meter.(static) electric field due to the ion sheath which forms around

Its purpose is to measure the


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- 7 -the satellite. The four-bladed shutter or r o t o r is motor-driven,and is grounded to the satellite by the use of brushes. A four-b l a d e d stator o r sensor is located behind the r o t o r , The fieldmeter system will measure electric fields ranging from 50 to 10,000volts per meter.

6, The micrometeorite photomultiplier experiment is de-signed to (1) measure the light energy given off as a micro-rieteorite hits upon a surface and to relate this measured energy'GO the !cinetic energy of the particle, and (2) to determine theeroslve effects of micrometeorite impacts. The sensor is a con-ventional 6199 photomultiplier vith a thin layer of aluminum ont h e P r o n t surface. Particles penetrate the aluminum coating andreE;fster isible-light energy on the photocathode. The resultingpulses, varying in length and amplitude, will be amplified andtL.ansI.ated into a meaningful telemetry signal,

7. The micrometeorite microphone experiment will measuretiic rrequency and momentum of microneteorite impacts. The micro-.if?'ieoritetargets" are two sounding boards located on the lowercone of the satellite, acoustically insulated from the satelliteskin, To each sounding board is attached a small microphone whichwil l . sense the impulse of an impact. By preflight calibration thedetected impulse can be related to the momentum of the incomingparticle.

8, There are a total of four thermistors to provide tempera-ture readings in various locations within the instrument compartmenta,nd on the satellite's surface.

The elements of the payload include --Timer and separation mechanism. A battery-operated timer is

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- 8 -attached to the base of the instrument column in the center of thepayload. It activates a release mechanism separating the payloadfroxlz the empty fourth-stage rocket about two minutes after burnoutand i t initiates first-stage despin shortly thereafter.

First-Stage Despin Mechanism. Its function is to reduce thepayload's spin rate from 450 to about 100 rpm.weighted wfres wrapped around the equator.is 206 inches each. The weight on the ends of the wires is 30 gramseach., (The second-stage despin device is the radio frequencyimpedance probe.from the payload, this release triggers the extension of theimpedance probe, which further slows the payload to about 30 rpm.)

It consists of twoLength of these wires

When the first-stage despin wires are released

Sensors. In addition to the 15 sensors for the experiments,there is an aspect, or spatial orientation sensor.

Instrument Column, The instrument column is 193 inches highand consists of 20 modules, and a separation timer on the bottom.The inodules are: commutator, sweep generator, two electrometeramplifiers, electric field meter amplifier, two RF impedance units,two aspect RF memory units, command program, meteorite amplifier,meteorite counter, computer pulser, aspect-digitalizer, twooscillators, two encoders, command receiver, and transmitter.

Power and Telemetry Systems. The satellite is powered byeight packs of mercury batteries, weighing 29.67 pounds.ponents are operated continuow@except the electric field meterwhich is active f o r two minute periods only on command from aground station.

All com-

This experiment will be operated about six minutes

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- 9 -for every 100 minutes of orbit,

The single transmitter will double as telemetry and trackingtramsmitter. It will operate on 108 megacycles.

The telemetry system will operate continuously so that alldata transmission will be on a real time basis. The system is adescendent of that used in the Vanguard program; the transmittercontains bursts o f amplitude modulation separated by periods ofno oscillation referred to as blanks. The long-term averageradiated power output during modulation is 100 milliwatts. Thesatellite has a linearly-polarized quadriloop (cloverleaf) antennasituated at the base o f the payload, similar to that used onExplorer VII. The same antenna is used f o r receiving thecommand from ground stations which activates the electric field meterexperiment

The weight breakdown of the payload is as fo l lows:WEIGHT DISTRIBUTION FOR SATELLITE s-30

ITEM WEIGHT (lbs)-Structure 20 52I4a.i.n Batteries (including housings) 32 0Instrument ColumnSensors (Instrumentation)First-Stage DespinRF Impedance Probe

11.907-47OD756.54

108-~~ntenna Assembly 3.20Battery f o r Separation Timer 1.20Balancing Weights 0.70Miscellaneous (Wiring, connectors,

Totals 90.00thermal coatings, special finishes) 5.32

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- 10 -TRACKING

"Quick look" - the f i r s t evaluaGion of data t o determineveh ic le per fo rmance and i n i t i a l o r b i t a l el ements i s under d i rec t ionof the Marshall Space Flight Cen ter , The long-range trac Mn g anddata reduction program will be under the d i rect ion of the GoddardSpace Flight Center e

Quick look r e l i e s pr imar i ly on data received from Atlant icMissile Range radar, and eight microlock s ta t ions . Th i s data r ev ea l sboos te r and c lu s te r performance of th e Juno I1 l aunch veh ic le . I naddi t i on , some o r b i t a l data i s received from the network of mini t racks t a t io ns opera ted under superv i s ion of the Goddard Space Flight Center,Greenbelt , Md.

Resu l t s of the quick look evaluat ion will be re layed to a l lp a r t i c i p a t i n g t r ac M ng s t a t i o n s t o ass i s t them i n con tinued t rack ingof" the o r b i t e r . Q ui ck l o ok i s expected t o terminate a f t e r the s a t e l l i t e ' sf i r s t tw o o r b i t a l r e v o l u t i o n s .

Zong t e r m t racking and receiving w i l l b e ca r r i ed o u t l a rg e l yby the Goddard Center ' s mini t r ack s ta t i o ns .

The Millstone H i l l radar, Westford, Mass., operated by theLincoln Labarator ies of the Massachusetts I n s t i t u t e of Technologywill t r ac k b ot h c l u s t e r o p e ra t io n and the s a t e l l i t e , and the Goldstones t a t i o n opeieszed by the NASA J e t Propulsion Laboratory a t Camp Irwin,Cal i f . , w i l l t r a c k t h e s a t e l l i t e .

Microlock s t a t i o n s p a r t i c i p a t i n g i n c l u d e : Madkin Mountain,Huntsv i l l e , A l a . , operated by t h e Marshall Center's Guidance andContr ol Divisi on; Redstone Arsenal, Ala., opcrated by the Army Rocket

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and Gi-'-Jed M is si le Agency; Cape Canav eral, F la ., ope ra ted by theMarshall Center 's Launch Operations Dir ect ora te; th re e mobile s t a t i o n soperated by the Goddard Center and ioc,rlted a t Atlan t i c , N. C. , St,Johns, Newfoundland, and Pa i n t e r s H i l l , Bermuda; Ft. Monmouth, N. J . ;and Aberdeen Proving GrounC, Md., operated by t h e Ba l l i s t i c Res ea rchLaborator ies .

Mi n it r ack s t a t i o n s p a r t i c i p a t i n g i n c l ud e : Sant iago , Chile;Woomera, A us tr al ia ; Johannesburg, South Af ric a; Anto fag asta , Ch ile ;Lima, Peru; Quito, Ecuador; Antigua, B.W.I.; F t . Myers, Fla . ; SanDiego, Ca l i f .; and Blossom Poin t , Md.

The m i n it r ac k s t a t i o n s are being operated for Goddard by theBendix Corpo ration. Bendix a l s o ope ra tes the Goddard Center's threemobile microlock stat ions.

Microlock s t a t i on s t r ac k by measuring th e speed of a veh ic lei n space through the Doppler effect -- the change i n tone of thetracking s i g n a l as the vehicle speeds away.

Mi n i t r ack s t a t i o n s t r ack by determllning the di rec t ion f romwhich a s i g n a l i s received.

LAUNCH VEHICLE:The launch vehicle for the experiment i s NASA's Juno 11, based

on th e J u p i t e r r o c k e t .se rv ing as t h e f i r s t stage and a three-stage c l u s t e r of s o l i d p ro p e ll an trocke t s p laced i n a spinning "tub" mounted on the nose of the f i r s ts tage .

The v eh i c l e co n s i s t s of a modif ied Jupi ter

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- 12 -The high-speed upper assembly of the Juno 11 i s i d e n t i c a l

f ; ~h a t of the Jupi ter-C, as i s the v e h i c l e ' s staging technique,Standing 76 f e e t i n height , th e rocket weighs about 60 tons

a t l i f t o f f .I n p revious f i r i ng s , Juno 11% launched Pioneer I V and the

Explorer V I 1 r ad ia t i on s a t e l l i t e ,Main Stage Propulsion. The J u p i t e r b o o st e r, for th is space

role, i s modified t o increa se fu el capaci t y. The boos ter sec t io n andf u e l t a n ks are extended three f ee t . Fuel f o r the boos te r propuls ionsystem i s a high grade of kerosene; oxidiz.er i s l iquid oxygen.

A bell-shaped th r us t chamber i s used t o combine high a l t i t u d eeff ic iency wi th m a x i m u m performance a t low a l t i t u d e . The chamber i sgimballed t o allow use of th e eng ine th r us t vec to r i n con t ro l l i ngd i r e c t i o n . To provide cool ing fo r chamber during operat ion, f u e lf o r the engine circulates through the chamber walls before being fedthrough the in jec tor in to the combust ion area.

Moving the fuel and ox.idizer through the engine a t tremendousflow and pressure rates i s the engine ' s turb ine assembly with twinpumps roughly equa l i n s i ze t o household pressure cookers. Thet u rb ine i t s e l f i s dr iv en by ho t ga se s provided by combustion of t h emain prope l lant s i n a gas gener ator . Ekhaust from the l a t t e r i s addedt o t he th r us t c rea ted by the eng ine .

Upper Stages, The upper stages of this launching vehic le wereor ig in a l ly deve loped f o r the JQpi ter -C (Composite Reentry T e s t Vehic le ) .The upper assembly i s f i t t e d i n t o a r o t a t i n g I1 tub" or launcher, whichg iv e s s t a b i l i t y i n p o st -s ep ar at io n f l i g h t , much as a r i f l e b u l l e t i s

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s t ;abf l ized by spinning.the f r o n t end of the b o o s t e r .

The assembly i s r o t a t e d by motors mounted i n

The second stage of th e rocke t cons i s t s o f a c l u s t e r of 11 s o l i dpropel l an t motms ,rocke t s . Atop th e t h i r d stage i s th e single rocket which makes up thefo u r t h and f i n a l s ta ge .

I n se r te d i n t o t h i s r i n g i s the t h i r d s tage of three

The three t ~ ptages provide the f i n a l impulse needed t o propelthe space payload beyond the earth's atmosphere. At burnout of the mains tage , th e rocke t i s t r a v e l l i n g a t about 11,000 miles per hour. Theupper stages i g n i t e i n r a p id s uc ce ss io n -- requ i r ing l i t t l e more than25 seconds -- and push the v e l o c i t y of t h e p ay load t o t h e d es i r ed l ev e l .

Shroud, A specially-designed shroud encases the launching vehicleshigh-speed upper assembly and pay loa d, The shroud has t h r e e mainfu.n,ctions:flow P i C $ b I l ; t o e l imina te the dynamic forces t3 which t h e upperstages would otherwise be subjected; and t o provide support for th eangPe-sf-attack meter which i s r eq u ir ed i n t h i s conf igura t ion to g ive

t o protect the assembly from the heat generated by a i r

adequate cc-dre.t;rsld ur in g i n i t i a l s ta ge s o f f l i g h t .- u i d a c e , The small s t ab i l i z ed p la tform, l o ca ted i n th e upper

s e c t i o ~ , f the booster , i s a l igned very p rec i se ly t o th e I t ta rge t" i nspace.en t i r e propel l ed f l i g h t , the pla t fo rm is constrained t o the sameangulap d i rec t ion , The miss i le t i l t s and arcs through the sky, butthe p lat form remains constant , or space-f ixed.

Fmm the moment the rocke t S i f t s o f f the earth and through the

11 I 1


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Any deviations in vehicle attitude relative to the stabilizedplatform resulting from wind o r thrust misalignment are sensed and theinformation is fed into the vehicle's computer. Necessary correctionsare issued automatically by the system's control computer to keep thevehicle continuously directed on path.

I 1After the corrections have been issued by the brains" of thevehicle, the rocket's attitude is altered accordingly by swivellingthe nozzle on the booster engfne for control in the pitch and yawplanes, and swivelling the turbine exhaust nozzle for r o l l control.

Flight Procedure. During the burning time of the first stage,approximately three minutes, the rocket is tilted into the trajectoryinclined at a pre-determined angle. A few seconds after cutoff, thebooster (combined tank and engine section of first stage) is separatedfrom the instrument compartment by activating explosive bolts. Wrappedaround the bolts are coil springs. When the explosions destroy theb o l t s , the springs exert a gentle push on the instrument compartmentand separate it cleanly from the booster. This is followed by thefiring of four small lateral k i c k rockets contained in the boosterwhich cause the booster to slow down slightly in speed and move to theside. This eliminates the possibility of the booster interfering withthe flight of the separated upper stages.

The booster falls to the earth, while the upper assemblycontinues on its path.depending on the mission, and then a second separation occurs in a

The upper element coasts f o r a varying period,

similar manner. The nose cone of the shroud is removed by explosive

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bol t s and spr ings , and a k i c k rocket moves i t t o t h e s i d e . After acoas t per iod (in t h i s case about 4; minutes), t h e second stage o f th erotat ing upper assembly within the shroud i s ig n i te d . The assembly,r o t a t i n g a t about 450 revalu t ions pe r minute, rap idly pu l l s out of theshroud, and t h e t h i r d ard fo u r t h s t ag es are f i r e d i n qu ick succession .After th e four% s tage "boosts the p ay l oad ' s v e l o c i t y t o t h e d es ir edl e v e l , t h e burned- ut. noksr case separates, a f t e r a lapse of about t w ominutes, leaving t k e i t-sstrumnted payload h continue i t s journey.

Tota l t i m e from t h e l i f t o f f t o t h e i n j e c t i o n of th i s payloadi n o r b i t will be about eight minutes.

RFSPONSIBILITIES

The experiment i s being conducted by the National Aeronauticsand Space Administration.a r e t h e NASA e lements respons ib le f o r the p r o j ec t , Rober t E . Bordeauof Goddard and B i l l Gyeever of Marshall are the project managers ,

The Goddard and Marshall Space Flight Centers

Vehicle , The durn 11 first stage was designed and f ab r i ca t edby th e Marshall Cer,ter, m d was laurrched by the Center's LaunchOperat ions Dir ectora te , Cape Cmaveral .

Major boo ste r s ubc ontr act ors includ e the Rocketdyne Divisio nof Nor%h America? Av iati on, which fu rn is he d th e engine, and t h e FordInstrument C h . , which mamfac%ured components of the guidance system.

The high-speed upper stage c l u s t e r was designed by the NASAJet Propulsion Labcratory .The clus ter was b G i 3 - t by th e Cmper Development Corp. of Monrovia, C a l i f .

Casper F. M~hl s th e JPL pro jec t eng ineer .

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- 16 -Pay l c i d , The sciel?_t ffbcexperiments were or ig ina t ed and

pycvbded Sy . t~ .eT..Td.dard Cen+erThe payload was asserrbled and tested by the Marshall Center.

The leading r s l e i9. the prepara t ian of' th e payload was by the Guidanceand Control Divis ion.

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ionosphere direct measurement satellite explorer viii) s-30 press kit

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