the interplanetary pioneers. volume 1 summary

8/7/2019 The Interplanetary Pioneers. Volume 1 Summary

1/135

NASA SP-278

THE INTERPLANETARYPIONEERSVOLUME I: SUMMARY

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION


2/135

NASA SP-278

THE INTERPLANETARY PIONEERSVOLUME I. SUMMARY

byWilliam R. Corliss

Scientific an d Technical In fo rmat ion Office 1972NATIONAL AERONAUTICS AND SPACE ADMINISTRATIONWashington, D.C.


3/135

For sale by the Superin tend en t of Docum entsU.S. Government Prin t ing Office, Washington, D.C. 20402Price $1.25 (paper cover) S tock Num ber 3300-0447Library of Congress Catalog Card N u m b e r 74-176234


4/135

PRECEDING PAGE BLANK NOT FILMED

ForewordS O M E E X P L O R A T O R Y E N T E R P R I S E S start with fanfare and end with aquie t buria l ; some s tar t w i th hardly a not ice , yet end up signif icantlyadvancing mankind 's knowledge . The Interplanetary Pioneers moreclosely fit the lat ter description. When the National Aeronaut ics andSpace Ad m inis t ra t ion star ted the program a decade ago i t rece ived l i t t lepubl ic a t tent ion. Yet the four spacecraft , designated Pioneers 6, 7, 8,and 9, have fai thfully lived up to the i r name as def ined by Webster,"to discover or explore in advance of others." These pioneering space-craf t were the first to systematically orbit the Sun at widely separatedpoints in space, collecting information on conditions far f rom theEarth 's dis turbing inf luence. From them we have learned much aboutspace, the solar wind, and the fluctuating bursts of cosmic radiation ofboth solar and galactic origin.These Pioneers have proven to be superbly reliable scientific ex-plorers , sending back informat ion far in excess o f the i r design l i fe t im esover a period that covers much of the solar cycle.This publ ica t ion a t tempts to assemble a full account ing of thisremarkable program. Wri t ten by William R. Corliss, under contractwith NASA, it is organized as V ol ume I: Summa ry (NASA SP-278);Volume II: System Design and Developm ent (NASA SP-279); andVolume III : Ope rat ion s and Scientif ic Results (NASA SP-280). In asense it is ne cessarily incom plete , fo r u n t i l the last o f these remote andfai thful sent inels falls silent, the f inal word is not at hand.

HANS M A R KDirectorAmes Research CenterNational Aeronaut ics andSpace Adminis t ra t ion


5/135

BNO PAGE BLANK NOT FttMED

ContentsChapter 1. ORIGIN AND HISTORY OF THE INTERPLANETARY

PIONEER PROGRAM 1The Scientific Challenge of Interplanetary Space 1The Am es Solar P robe Studies 2Selecting a Contractor 4The Pioneer Organization 5The Pioneer Schedule 11The P ioneer Cost P icture 14Pioneer Chronology 22

Chapter 2. PIONEER SYSTEM DESIGN AND DEVELOPMENT _ _ _ . 25Defining the Pioneer System 25Pioneer Launch Trajectory and Solar Orbit Design 29Spacecraft Design Approach and Evolution 34The Spacecraft Subsystems 37Scientific Instruments 62The Delta Launch Vehicle 76Tracking and Communicating with the Pioneer Spacecraft 78Pioneer Data Processing Equipment 84

Chapter 3. PIONEER FLIGHT OPERATIONS 89Prelaunch Activities 89Launch to DSS Acquisition 93From DSS Acquisition to the Beginning of the Cruise Phase 98Spacecraft Performance during the Cruise Phase 99

Chapter 4. PIONEER SCIENTIFIC RESULTS 103The Goddard Magnetic Field Experiment 103The MIT Plasma Probe 105The Am es Plasma Probe 107The Chicago Cosmic-Ray Experiment _ 109The GRCSW Cosmic-Ray Experiment 111The Minnesota Cosmic-Ray Experiment 115The Stanford Radio Propagation Experiment 116TRW Systems Electric Field Experiment 120


6/135

VIPage

The Goddard Cosmic Dust Measurements 121The Pioneer Celestial Mechanics Experiment 123Solar Weather Monitoring 125

BIBLIOGRAPHY 127Appendix. MEMORANDUM: ORGANIZATION OF AMES SOLAR

PROBE TEAM 129


7/135

C H A P T E R 1

Origin and History of the InterplanetaryPioneer ProgramTHE SCIENTIFIC CHALLENGE OF INTERPLANETARY SPACET A 7 H E N WE L O O K UP AT TH E S T A R S , we think we see the real universe,* but the stars constitute only about 1 percent of the matter in theuniverse . The other 99 percent exists as dust and gas and occupies thespace between the stars. The real drama of cosmic evolution may beunfo ld i ng in the cold space between the stars rather than in hot stellarinteriors. But until recently, science has confined its study mainly toth e astronomical bodies that shine by their own emissions or by re-flected light. The bulk of the universe has been by necessity virtuallyignored.

The only direct, in situ measurements we can make of thisdominant fraction of the universe are f rom space probes and satel-l i tes that reach well beyond the distorting inf luences of the Earth'satmosphere and magnetic field. Even then, the probes measure inter-planetary space rather than interstellar space. The region betweenthe planets is swept by the solar wind and bursts of solar cosmicrays which usually overwhelm galactic phenomena. Still, this can beadvantageous to science, because spacecraft in interplanetary spacecan monitor the i n t e r face between a typical starthe Sunandin ters te l lar space, recording the outward flow of solar electromagneticenergy, solar cosmic rays, and solar plasma. Similarly the inflowof galactic cosmic rays can be measured. Like all interface regions,i n t e rp l ane t a ry space is ful l o f turmoil and is a rich region fo rscientif ic research.

The scientif ic mission of Pioneers 6 through 9l has been thesynopt ic measurement of the interplanetary milieu as it is affectedby the Sun. The Pioneers have measured and transmitted back toEar th data on solar plasma, solar and galactic cosmic radiation,magne t i c and electric fields, and the specks o f cosmic dust thatpervade interplanetary space. All of these phenomena, even theflux of galactic cosmic rays, are strongly affected by events occurring

' Also called Pioneers A through D prior to launch. Pioneer E, which would havebeen pioneer 10, was a launch fa i lure . Pioneers 1 through 5 were early lunar probes.


8/135

2 THE INT E R PLANE T AR Y PIO NE E R S

on the Sun. Spotted strategically around the Sun in the plane of theecl ipt ic , they have moni tored the ever-changing fluxes and fieldstha t wax and wan e w ith solar act ivi ty. In purpose, the Pione ershave been akin to weather satell i tes , except that they are ar t i f ic ialplanets of the Sun and not satellites of the Ea r th . In fact, dataf rom the Pioneers have been used exten sively in pre paring "spaceweather" forecasts.The main pulse of solar act ivi ty is the 11-year cycle of sunspots ,a periodic phenomenon felt the length and breadth of the solarsystem. In 1961, when the Nat iona l Aeronaut i cs and Space Ad-m inist rat ion (NASA) form ulated the Pioneer Program, scientistsaround the world were organiz ing a concent ra ted s tudy of solarevents expected dur ing the 1964-1965 so la r min imum. It seemedhighly desirable to have some unmanned i n s t rumen t ed spacecraf tout in deep space to suppor t the growing number of In t e rna t iona lQuie t Sun Year (IQSY) projects. Data radioed back f rom theseproposed spacecraft would supplement those received f rom NASA'sOGOs, OSOs, and Explorer satell i tes in orbit a round the Ear thand a worldwide array of scientif ic sensors on the ground. A uniquef ea tu re o f such spacecraf t in heliocentr ic orbi ts lay in the fact t ha tthey wo uld range far ahead an d be hind the Earth as i t swun ga round the Sun, giving scientists a more comprehensive pictureof in terplanetary space at var ious az imuths along the plane of theecliptic. As the following chapters will show, the unexpectedly longlives of the Pioneers extended deep-space scient i f ic coverage throughthe 1969-1970 solar maximum. Furthermore, lunar and solar occulta-t i ons a n d un us ua l spacecraf t alignments have occurred which increasedthe scientif ic payoff of the Pioneer Program far beyond or iginal ex-pecta t ions . As Chapter 4 demonst ra tes , the Pioneers added immeasur-ably to our knowledge of the region between 0.8 and 1.2 Ast ronomica lUni t s (AU)2 as well as to our knowledge of the Sun i tself .

THE AMES SOLAR PROBE STUDIESThe Pion eer P rogram began as an in fo rm al study of solar probesat the Ames Research Center in May 1960. At this t ime, NASA hadbeen in exis tence only a year and a half , and the prev ious Nat iona lAdvisory C o m m i t t e e fo r Ae ro n autics (NACA ) laborator ies, such asAmes , were s t i l l working at def in ing the i r ro les in space. The solar-probe study was an a t t e m p t to demons t ra t e Ames ' po ten t i a l as aspacecraf t projec t manager and to also interest top m a n a ge m e n t at

2 The As t r onomi ca l Un i t is equal to the mean d i s tance f rom the Ear th to theSu n ; i .e . abo ut 92.95 m il l io n m iles o r 149.6 mil l ion k i lometers .


9/135

ORIGIN AND HISTORY 3

Ames in this role which departed from Ames' traditional function as anaeronautical research center.The informal study team was headed by Charles F. Hall, who

enlisted a dozen other Ames engineers in the effort .3 The results o fthe study were published as an internal Ames report on July 22,1960, bearing the title: "A Preliminary Study o f a Solar Probe."The spacecraft conceived during the study was conical in shape

and was designed to point continuously at the Sun as it approachedto about 0.3 AU. The Ames solar probe was quite di f f e ren t f romthe Pioneer spacecraft that i t was to engender. However, the scientif icrationale quoted in the report differed little f rom that adopted fo rthe Pioneers: "The desirability o f a solar probe was indicated bythe thought that an increase in knowledge o f solar phenomenathrough measurements made near the Sun would aid in an under-s t and ing o f terrestrial phenomena in such areas as communication,weather prediction and control, and atomic and nuclear physics."The spacecraf t was envisoned as small, simple, an d long-lived, justas its progeny were to be in fact.Although considerable opposition developed at Ames to gettinginto spacecraf t project work, Smith J. DeFrance, the Center Director,among others, supported the solar-probe project. On September 14,1960, DeFrance organized a formal Ames Solar Probe Team. (Thet ex t of the memorandum setting up the team is reproduced inthe Appendix.) Headed by Hal], the team retained many of themembers of the informal group and was charged with recommend-ing a "practical system."

The Solar Probe Team now ;bent its efforts to fleshing out theskeleton concept described in the July 22, 1960, report. The objectivewas to show the practical feasibility of the Ames concept and dem-onstrate to NASA Headquarters Ames' capability for heading upa hardware project. The basic spacecraft concept changed somewhatduring these studies. The major problem involved keeping thespacecraf t and i ts instruments cool as it neared the Sun. Fullerdescr ipt ions of the spacecraft, its trajectory, and the proposed in -s t r umen t s can be found in references 1 and 2.D u r i n g late 1961 and early 1962, Hall and others tried to stimulatein te res t in the concept at NASA Headquarters. At one presentation,Jesse Mitchell, f rom NASA's Office of Space Science, became in -t r igued with the Ames spacecraf t . Mitchell subsequently arrangeda meeting between Hall and Edgar M . Cortright, who was the

3 Specifically: Bader, M., Beam, B. H., Dimef f , J., Dugan, D. W, Eggers, A. J., Jr.,H a n s e n , C. F., Hornby, H., Jones, R. T., Matthews, H. F., Mersman, W A., Robin-son , G. G., and Tingling B. E.


10/135

4 THE INTERPLANETARY PIONEERS

Deputy Director of the Office of Space Science at that time.4Cortright pointed out that A mes had no spacecraft experience, buthe also remarked that he would like to see Ames get into the"hardware business." He posed the question: Would Ames be in-terested in building an Interplanetary Pioneer as a step on the wayto the solar probe? Hall returned to Ames and received a go-aheadf rom Ames management. A mes management also recommended thatan industrial contractor be brought in to do a feasibil ity study.

SELECTING A CONTRACTORThe industrial contractor chosen was Space Technology Labora-

tories (STL)5 at Redondo Beach, California. STL, acquainted withthe Ames work, submitted an unsolicited proposal that was sub-sequent ly funded . In April 1962 STL completed the 21^-month,$250000, feasibil ity s tudy (ref. 3 ) under NASA Contract NAS2-884.

The STL Pioneer feasibil ity study was particularly significantbecause, during the 2y2 months in early 1962, almost all of thei m p o r t a n t system-design decisions were made by STL engineers work-ing in conjunction with NASA-Ames personnel. The key concept o fa spin-stabilized spacecraft, with i ts spin axis perpendicular to theplane of the ecliptic, and a flat, fanlike, high-gain antenna pat-tern was originated by Herbert Lassen, of STL. As discussed in Vol.II, Chapter 1, this concept helped meet all the severe design con-s t ra in ts placed upon Pioneer by weight, cost, and schedule.

The next big step was obtaining formal project approval f romHeadquarters. The Ames group, backed by DeFrance, made theke y presentation to NASA Associate Administrator Robert C. Sea-mans , Jr., on June 6, 1962. Afte r Congress approved the NASAbudget, Seamans signed the Project Approval Document (PAD)on November 9, 1962.

Pressing their advantage, STL followed up the feasibili ty studywith an unsolicited proposal to design and fabricate four spacecraft ,q u o t i n g a price of $10 million on a cost-plus-fixed-fee basis (ref. 4).Ames wished to go ahead with a sole-source procurement, but thiswas disapproved and competitive selection was stipulated.Using the STL feasibili ty study as a foundation, Ames wrotethe specif icat ions for the Pioneer spacecraf t and on January 29,1963, issued a Request for Proposal (RFP-6669) to industry. Eightcompan i e s responded on March 4, 1963. Because of the price dis-

4 In te rv iew wi th Charles F. H a l l , J a n u a r y 26 , 1971.* STL's n a m e was later changed to TRW Systems. TRW refers to Thompson-Ramo-Wooldr idge , the p a r e n t company .


11/135

ORIGIN AND HISTORY O

pari ty between the two technically superior proposals ( from Hughesand STL), NASA requested that these two companies resubmitbids on a fixed-price-incentive (FPI) basis.6 The second submissionswere received on May 24, 1963. STL was selected over Hughes inthe final competition (ref. 5). The terms of a letter contract wereagreed upon in July, and the letter contract was awarded on August5, 1963. The contract authorized expenditures up to $1.5 million.Work began immediately at STL. The def ini t ive contract (NAS2-1700)was negotiated later and was approved by NASA Headquarters onJuly 30, 1964. It is interesting to note here that the incentive provisionsof the contract (as opposed to the cost-plus-fixed-fee contract thencommon in aerospace work) forced NASA to define everything i twanted with high precision. Contract negotiations were lengthy,an d approximately 80 changes were made to the basic statement o fwork originally stated in RFP A-6669. With a contractor hard atwork, Pioneer moved ahead rapidly toward the first launch,planned for 1965.

THE PIONEER ORGANIZATIONThe Pioneer hardware, described in the next chapter, consistedof fou r major systems:(1 ) The spacecraft itself(2) The scientific instruments(3 ) The launch vehicle(4) The ground-based tracking and data acquisition stations

NASA assigned teams of engineers and scientists to each of thesefour technical elements. Many contractor personnel, especially atTRW Systems and the Deep Space Network (DSN) stations, wereclosely involved in the program.The purpose o f this section is the general recounting of howPioneer was organized and who some of the key personnel were.

The overall NASA Pioneer organization is shown in figure 1-1,beginning with the NASA Administrator an d showing the principalchains o f command. This diagram shows overall management re -sponsibil i ty but does n o t highlight the groups where the bulk o fthe work wasdone. The actual work entailed:(1) Spacecraft design, testing, an d launching(2) The design an d testing of the scientific instruments and thepresen ta t ion of final scientif ic results

' While the con t r a c t was being firmed up, STL was given a small side study toinvestigate the effects o f uprating the Delta launch vehicle and going to a largerspacecraft .


12/135

THE INTERPLANETARY PIONEERS

e 2"" a. B 3.!S w~

Mr 1If QJC/5 ^

0IS ag S 311ll

TS" 1


13/135

ORIGIN AND HISTORY

(3 ) The routine, but highly important, day-by-day control of thespacecraft and its tracking and data acquisition(4) The huge volume o f management chores that accompanies aprogram of this sizeThe shaded boxes on the diagram indicate the focal points o factivi ty , but only those within NASA. Important contractorsTRWSystems and the experimenters, in particularare not shown. Whatfigure 1-1 does show well is the dual nature of the NASA organiza-tion. The Ames Research Center, for example, reported administra-t ively through the Headquarters Office o f Advanced Research andTechnology, but project direction came from the Headquarters Officeof Space Sciences and Applications. The Pioneer Program was oneof the few NASA spacecraf t programs assigned to a NASA research-oriented center. Obviously, the unusual arrangement worked verywell in the case of Pioneer.Basically Ames built, tested, an d controlled the spacecraft and thescientific instruments provided by the experimenters; Goddard pro-cured a Delta rocket an d launched the spacecraf t ; the Je t PropulsionLabora to ry (JPL), which operated the DSN, tracked the spacecraf tand passed the acquired data on to Ames. Headquarters providedoverall direction. This situation is spelled out more thoroughly intable 1-1 and figure 1-2. Figure 1-2 shows how the Ames PioneerProjec t Manager, C. F. Hall, organized his group to tie together thed i f f e r en t elements o f NASA into a smoothly f u n c t i o n i n g team. The

TABLE I-}.Responsibilities in the Pioneer ProgramTask Organizat ion Individuals

Overal l program direction

Project managementSpacecraft systemDesign, fabrication, an dtes t ing of spacecraftand mission-dependentground operationale q u i p m e n tScientif ic instrument systemAssuring that overallscient i f ic objectives aremet\f anagemen t of scientifici n s t r u m e n t systemsProvid ing scientific i n s t r u -men t s , data reductionan d analysis, and scient i -fic reporting:

L u n a r a n d PlanetaryProgram Office, Officeof Space Science andApplicat ions, NASAHeadquartersA m e s Research CenterAmes Research CenterTRWSystems

Ames Research CenterAmes Research Center

Kochendor fe r , F.D.(1962-1963)Reiff , G.A. (1963-1970)Kochendor f e r , F.D.(1970 to date)Hall, C.F.H ol tzc law, R.WMickelwai t , A.G.(1962-1967)O'Brien, B.J.(1967 to date)Wolfe , J.H.Cross, H.V.Lepetich, J.E.(1962 to date)


14/135

TH E INTERPLANETARY PIONEERSTABLE 1-1. Respon sibilit ies in the Pioneer ProgramConcluded

TaskMagne tomete r (P io-neers 6, 7, 8)Magnetometer (Pio-neers 9, E)Plasma probes (Pio-neers 6, 7, 8, 9, E)Plasma probes (Pio-neers 6, 7)Cosmic-ray telescope(Pioneers 6, 7)Cosmic-ray exper iment(Pioneers 6, 7, 8, 9,

E)Cosmic-ray expe r imen t(Pioneers 8, 9, E)Radio propagat ion ex-per iment (Pioneers.6, 7, 8, 9, E)Electric-field detec-tor (Pionee rs 8, 9,E)Cosmic dust detector(Pioneers 8, 9, E)Celestial mechanics(Pioneers 6, 7, 8, 9,

Organ iza t ionGoddard Space FlightCenterAmes Research CenterAm es Research CenterMassachusetts I ns t i t u t eof TechnologyUnivers i ty of ChicagoGraduate Research Cen-ter of the SouthwestUnivers i ty o f Minneso taStanford Unive r s i tyTRW SystemsGoddard Space Fl ightCenterJet PropulsionLaboratory

IndividualsNess, N.F.Sonett, C.P.Wolfe , J .H .Bridge, H.Simpson, J.A.McCracken, K.G.Webber , W.R.Eshleman , V.R.Scarf , F.L.Berg, 0.Anderson, J .D.

Eng ine e r i ng i n s t r u m e n tsystemProvision of a convolu t ion-al coder and analysis ofresults (Pioneers 9, E)Launch vehicle systemPr ocu r emen t of Deltalaunch vehicleDesign and f abr ica t ion ofthe Del ta laun ch veh ic leLaunch activitiesDirect ion of launch opera-t ionsTrack ing and data acquisi-t i o n dur ing poweredflightSpacecraf t - launch vehiclei n t e r f ace an d coord ina-t ion o f launch vehicleopera t ionsFlight operat ionsMission p lann ing and con -t r o lTracking , data acqu is i t ion ,and command t r ans -mission

Ames Research^Cente r

Goddard Space FlightCenterMcDonnell-DouglasAircraf t C o m p a n yGoddard Space FlightCente rUSAF Eastern TestRangeAmes Research Center

Ames Research Center

Jet Propuls ionLaboratoryData processing and an alysis Am es Research Cen ter

Lumb, D.R.

Schindler, W.R.

Gray, R . H .

H of s te t t e r, R .U .

Jagiello, L.T.(1962-1966)Nunamaker , R.R.(1966 to date)Thatcher, J.W.(1962-1966)Siegmeth, A.J.(1966 to date)Evickson, M.D.(1966-1969)Natwick , A.S.(1969 to date)


15/135

ORIGIN AND HISTORY

L

>-1*.a* .si "B.= Ms I'iIo gl

-ae


16/135

10 THE I N T E R P L A N E T A R Y PIONEERSPioneer Project group at Ames was originally split into five groups,with almost a one-to-one correspondence wi th the four Pioneersystemsspacecraft , experiments , launch vehicle , tracking and dataacquisit ion. Later, the correspondence was made exact when thefive projec t groups were con solidated in to fo ur groups re sponsiblefor the spacecraft , the exper iments , the flight operat ions (mainlyt racking an d data acquis i t ion) , and the launch vehicle an d launchoperations with groups from Goddard and JPL support ing the proj-ect. Figures 1-3 through 1-8 show some of the individuals who con-tributed to the Pioneer Program. In practice, Ames personnel fromthe Pioneer Project worked directly with those people in the supportgroups assigned to Pioneer, even though they reported throughJPL, Goddard, or con t rac to r managements . This synthesis of project-o r ien ted and funct ionally oriented personnel has been qui te com-mon and very effect ive in the aerospace ind ustry .Dur ing any project extending over a decade, one would expectconsiderable turnover of key people wi th in gove rnmen t and thecontrac tor organizat ions . Pioneer is an exception to this rule in

F I G U R E 1-3.NASA Headquarters inspec t ion of the m ockup o the Pioneer i n s t ru -men t p la t fo rm. Le f t t o r igh t : R . F . Garba r in i , J . E . Naugle , C. F. H all (Ames) ,A. B. Mickelwai t (TRW Systems) , O. W Nicks, H. E. Newell , and H. A. Las-se n (TRW Systems) .


17/135


F I G U R E 1-4.Part of the Ames Pioneer Project team. Left to right: to p row, G. J.Nothwang , C. F. Hall; middle row, A. J. Wilhelm, R. U. Hofstetter, R.I,. Edens; bottom row, D. W Lozier , J. E. Lepetich, R. W H oltzclaw.

that personnel changes have been minor. People and organizationst ruc tures have stayed remarkably stable. The important changesthat have occurred are summarized in table 1-1. One of the mostimpo r t a n t factors in the success of the Pioneer Program has un-doubtedly been the permanence, high capabil i ty, and dedicat ion ofthe Ames Pioneer Project personnel .TH E PIONEER SCHEDULE

The Pioneer Program consis ted of five flight spacecraft , the fiveDelta rockets for launching them, the experiments , and al l the

4 6 5 - 7 6 8 O - 72 - 2


18/135


F I G U R E 1-5.Inspection of the Pioneer prototype at TRW Systems in 1965. Far le f t ,A. B. Mickelwait; second from le f t , G. A. Reiff (NASA Headquarters) ; f ou r t hfrom le f t , C. F. Hall (Ames) . (Courtesy of TRW Systems.)

F I G U R E 1-6.Part o f Pioneer management team at Cape Kennedy in 1967. Left toright: B. J. O'Brien (TRW Systems) , J. Mitchell (NASA Headquarters), M.Aucremanne (NASA Headquarters) , C. F. Hall (Ames) .


19/135


F I G U R E 1-7.R. Gr ay , second f rom left , headed Goddard Operations at the Capeduring the Pioneer Program. W. R. Schindler, third f rom lef t , managed Goddard'sDel ta program. At far l e f t , J. Schwartz (WTR) ; at far right, H . V a n Goey.

F I G U R E 1-8.JPL DSN personnel assigned to Pioneer. Left to right, A. J. Siegmeth,J. W. Thatcher, and N. A. Renze t t i . (Courtesyof JPL.)


20/135

14 T H E INTERPLANETARY PIONEERSnecessary ground equipmen t to r t rack ing and the acquisit ion andprocessing of the data. Table 1-1 reveals many, but not all , of thegove rnmen t and con tractor organizat ions that had to work togetherto produce scientific measu remen ts from deep-space instrument plat-forms. In such a complex program, one can expect schedule slip-pages here and there. In the case of Pioneer, the schedule changesdue to spacecraft engineer ing and fabr ica t ion were all relativelym in o r . The first two spacecraft were launched close to the originalschedule, during the period of low solar activity as the scientistshad in tended .Two kinds of schedules are presented here. First, figure 1-9 re-produces the Pioneer master schedule f rom the original ProjectDevelopment Plan which was issued in March 1965. This particularschedule is of historical interest and, in addition, shows the m a n ydiverse program elements that had to be completed for a t imelyl aunch.The second set of schedules is prese nte d in figures 1-10 thro ugh1-14one for each of the five flight spacecraft . Each scheduleslippage is explained in the r ight-hand margin; these explanationsare ind ica t ive of the m a n y dif ferent factors affect ing the PioneerProgram.Pioneers 6 and 7 were launched fairly close to the original targetdates. The slippages in the launch schedules of the remain ing th reespacecraft were much greater . Many of the delays were attr ibutableto t roubles with the exper imen ts . In the case of Pioneer 9, launchwas delayed to provide a larger t ime interval between Pioneers 7and 8 and to permit cer ta in t rajector ies la ter . The launch date o fthe ill-fated Pioneer E was slipped for the same reasons.

TH E PIONEER COST PICTUREOne o f the original co nstrain ts placed upon the Pione er Programwhen i t was being fo rmula ted in 1962 was that the total cost bearound $30 mil l ion .7 During the years, the Pioneer Program wasexpanded for a number of reasons, as enumerated below and infigure 1-15. The net result has been that the entire Program hascost abou t $70 mil l ion . H e r e are the major reasons for the cost

increases:(1) Addit ion of data processing(2) Addi t ion of a fifth spacecraft(3) Unexpected long lives of the spacecraf t , r equ i r ing addi t ionalfunds fo r t racking and data acquis i t ion7 Other constraints were the use of the Delta launch vehicle, and the use of theDeep Space Network.


21/135


T3

O


22/135

16 THE IN TERPL A N ETA RY PIONEERS

1(


23/135


R

oshuech

o

a

f

S i

O

G

sciie*IO

SpduoaedvyoGCmomeareuoada1

dmonrum

1

.

8is82iSco!*iia.Z4

^ o>

irVC|1(1ii.l

1 S ina "5i!

UO

3

o

O

ojpej

uo Aej

uo AE

UO E

1 uoiu 1.0 erg)(2) Low-energy, hyperveloci ty part icles (< 1.0 erg)(3 ) Relatively large, high-velocity particles (> 10-10 g)

As a high-energy, hypervelocity particle pierces the f r on t filmsensor (fig. 2-24), some of its kinet ic energy generates ionizedplasma at the f ron t , or "A" film. The electrons in the plasma arecollected on the positively biased grid ( + 24 V) creat ing posi t ivepulses as shown. The posi t ive ions in the plasma are collected onthe negatively biased f i lm ( 3.5 V), producing a positive pulse thatis pulse-height-analyzed to measure the particle's kinetic energy. Thesame thing occurs at the rear sensor or "B" film, generating asecond set of plasma pulses. Impact on the plate produces an acousti-cal pulse. A peak-pulse-height analysis is pe r f o rmed on the acousticalsensor ou tput as a measure o f the par t i c l e ' s r emain ing momentum.A low-en ergy, hype rvelo city particle will yield all of i ts kin et icenergy at the "A" film. A pulse-height analysis measures the parti-cle's kine t i c ene rgy. A high-en ergy , hyperveloci ty part icle may beerroneously registered as a low-energy hyperveloci ty part icle if, be-cause of i ts angle o f en t ry , it fails to hit the "B" film. If a relativelylarge, high-velocity particle enters, i t may pass through the f r o n tand rear film arrays without generat ing detectable plasma becauseof i ts compara t ive ly low veloci ty; but i t may s t i l l impar t a measur -

Cosmic dustparticle 7V -3.5V+24VFront film-grid array

5c mRear film-grid arrayand impactplate

MicrophoneFIGURE 2-24.Schematic of the Goddard micrometeoroid sensor.

465-768 O - 72 - 6


81/135


able impulse to the acoustical sensor. An electronic "clock" registersthe t imes of flight of particles. The time lapses between positivepulses f rom the "A" and "B" films are used to derive particle speeds.The t ime-of-fl ight sensor is one of 256 similar sensors that com-prise the portion;,of the Pioneer instrument measuring particle speedand direction. Four vertical film strips are crossed by four horizontalgrid strips that create 16 front and 16 rear film sensor arrays (each2.5 by 2.5 cm) or 256 total combinations. Each grid strip and filmstrip connects to a separate output amplifier. The output signalsf rom these amplifiers are used to determine the segment in whichan impact occurred. Thus, by knowing the f r on t film-grid segmentspenetrated and the rear f i lm-grid segment affected by the impact,one can determine the direction of the incoming particle withrespect to the sensor axis and the spacecraft attitude. The solar-aspect sensor determines the Sunline at the time of an impact.The JPL Celestial Mechanics Experiment (Pioneers 6, 7, 8, 9, and E)The celestial mechanics experiment required no special equipment

on the spacecraft or at the tracking stations. The tracking data pro-vided by the Deep Space Stations (DSS) were sufficiently accurateto support the following primary objectives:(1 ) To obtain better measurements of the masses of the Earthand Moon and of the Astronomical Unit (AU)(2) To improve the ephemeris of the Earth(3) To investigate the possibility of testing the General Theoryof Relativity using Pioneer tracking dataThe methods employed in obtaining the tracking data are discussedin Chapter 4, where the results f rom all experiments are presented.

THE DELTA LAUNCH VEHICLEThe Delta launch vehicle, sometimes called the Thor-Delta, has

been one of NASA's most successful launch vehicles. The use of theDelta was basic in planning the Pioneer Program, primarily becauseit was low cost and also because it had already proven to be areliable spacecraf t launcher when the Pioneer Program w as beingf o rmul a t ed in 1962.

The Delta is basically a three-stage rocket. The liquid-fueled firstand second stages are topped by a small solid-propellant third stage(fig. 2-25). The first-stage core is the Thor military rocket, burninga hydrocarbon fue l similar to kerosene (RP1, RJ 1, etc.) withliquid oxygen. This stage is manufactured by the McDonnell DouglasAst ronaut i cs Company. The liquid first-stage engines are made by


82/135

SYSTEM DESIGN AND DEVELOPMENT 77

Fairing

Spin tableTransponder ]VHF TLM antenna-Range safety antenna -

C Band antennaWECO antenna.Helium sphere (3),Attitude and roll control system Adapter section.Control battery

InverterRange safety antenna .

Fuel tank

Telemetry _Range safety receiver .

100% Level LOX floatswitch-

Solid motor noise fairing .

Solid motor

^Spacecraft attach fitting,X-258 or FW-4DmotorGyroscope assy

- Fuel tank.Oxidizer tank. Nitrogen spheres(8),TTS on Pioneers C,D, and E'Thrust chamber assemblyxRate gyro distributionboxJ921 Interface connector' Flight controller

- AC Distribution box

- Pitch and yaw rate gyro

- Oxidizer tank

- Vernier engine- First stage engine

F I G U R E 2-25.The thrust-augmented improved Del ta (TAID) .


83/135


the Rocketdyne Division of North American Rockwell. The solid,th rus t -augmen ta t ion rockets strapped on the first stages o f latermodels are Castor rockets, usually produced by the Thiokol ChemicalCorporation. The much smaller second stage uses unsymmetricaldimethyl hydrazine (UDMH) as fuel , oxidized by inhibited redf u m i n g nitric acid (IRFNA). The second stage is also a productof McDonnell Douglas Corporation. It employs an Aerojet-Gen-eral engine. The third-stage solid rockets have been manufacturedby various concerns during the evolution of the Delta: AlleghenyBallistics Laboratory, United Technology Center, and Thiokol Chemi-cal Corporation. The Delta is one of NASA's smaller launch vehicles(first-stage thrust, about 175 000 Ib; plus about 160 000 Ib f rom solidstrap-ons on later models).No launch vehicle that has seen as much use as the Delta re-mains unchanged. Almost every launch vehicle is dif fe ren t at leastin some minor detail, because the interface with each payload isdif fe ren t . More signif icant changes arise when rocket motors areuprated, propellant tank sizes are changed, and solid-fuel rocketsare strapped on for first-stage augmentation. The Delta has gonethrough over a dozen of these upratings and improvements. Thecharacterist ics of the Pioneer Deltas are summarized in table 2-7.

TRACKING AND COMMUNICATING WITH THEPIONEER SPACECRAFTWhen the Pioneer Program began in 1962 there was no questionab o u t network choice. The DSN was the only one of NASA's threenetworks that could track and communicate with a deep-space

probe. Like the Delta launch vehicle, the DSN became a pillar ofthe Pioneer Program. It helped shape spacecraft design as well asthe launch trajectories and heliocentric orbits.

Three basic concepts are necessary to the successful tracking o fand acquisition o f data f rom Pioneer space probes that are tenso r hundreds of millions of miles out in space:(1) The concept of a high-gain, highly directional, paraboloidalantenna with a large diameter shown in figure 2-26. (High gainpe rm i t s reception o f very weak spacecraft signals; high directionalityprovides the accurate angular bearings needed fo r tracking.)(2) A measure of two-way Doppler shift (in the coherent mode)of radio signals between Earth an d spacecraft an d back again(Spacecraft radial velocity comes f rom these measurements.)(3 ) The JPL phase-lock-loop, conceived by JPL's Eberhardt Rech-

tin during the 1950's, and adopted by the DSN and later by the


84/135

SYSTEM DESIGN A ND DEVELOPMENT 79I WIs

U

, o1 C

s -_ X

u -C O

U

O

1s

uo. anja -TJB S O * a j r t Q JS S3 S

00 00

a -13

"& S .S J5" 5 3 2 'K "3S B Q & *

ac

" w

" *

'

?

fm1D

9

9

S ~ 2boI

.nH _ o ,1-

a%aSaI'!A3ui S


85/135


F I G U R E 2-26.The first 85-ft paraboloidal antenna installed at Goldstone (Pioneersite) .

Manned Space Flight Network (MSFN) for its unified S-Band track-ing dur ing the Apo llo Program (The phase-lock-loop con cept isfundamen t a l to the detection of signals by the DSN.)In general terms, the DSN carries out the t racking, data acquisi-t ion, and c omma nd func t ions l is ted above using three dist inct fa-cilit ies:(1) The Deep Space Instrumentation Facil i ty (DSIF), whichconsists of the DSN t racking and data acquisit ion stations shown intable 2-8.(2) The Space Flight Operations Facility (SFOF), located at


86/135


TABLE 2-8. The DSN StationsSta t ionn u m b e r

11121 314414251616271

Loca t i on

Golds tone, Cal i f . (Pioneer) Goldstone, Calif . (Echo)Golds tone, Cal i f . (Venus) bGoldstone, Calif . (Mars) cWoomera, Aus t ra l i aCanberra, Aus t ra l i a "dJohannesburg , South Afr icaMadrid, Spain (Robledo) *Mad rid, Spain (Cebreros)Cape K e n n e d y , Florida

Dishsize

85 ft85 ft85 ft

210 ft85 ft85 ft85 ft85 ft85 ft4 f t

Pr ima ry du r i ngPioneer nights6 7 8

XX X XX X XXX XX X X

XXX X X

9 EXXXXXXXX X

" MSFN Apollo Wing located here; used during some Pioneer flights.b Used primarily for research and development.c Used on extended Pioneer missions.d Also called Tidbinbilla.JPL, in Pasadena, Ca l i for nia , whic h m on i tors a ll spacecraft data ,issues com m ands, and perform s all necessary m iss ion calcula t ion s(3 ) The Ground Communicat ion Faci l i ty (GCF), which t ies allDSIF s ta t ion s to the SFOF w ith high-speed, real- tim e co m m unic a-t ions (The bulk of DSN c ommun i c a t i on traffic is carried via NAS-COM, which con tr ibutes c i rcui ts to the GCF.)Despite the size and capabilities of the DSN, NASA had to poolthe fo l lowing facil i t ies to fully cover the Pioneer flights:(1) The DSN, which included the DSIF, GCF, and SFOF(2) The MSFN, which provided 85-ft dish support on occasion(3 ) NASCOM, which c on t r i bu t e d ma ny c i rcui t s to the DSN's GCF(4) The Air Force Eastern Test Range (AFETR), which suppl iedm u c h of the g round e nv i r onme n t from the l aunch pad downrange5000 m iles to Ascen sion Island; i .e ., the Ne ar-Ear th Phase Ne two rkThe Pioneer flights were divided logically into two main phases:ne ar-Earth an d deep-space. The successful injection of the space-craft in to a hel iocentr ic orbi t was the event that separated thetwo phases (fig. 2-27). At this point , somewhere over the IndianOcean, the spacecraf t wo uld be handed over co m plete ly to the DSNand cooperating MSFN stations. Each phase of tracking requireda dif fe ren t configurat ion o f t racking, data acquis i t ion , command, andg round c o m m un i c a t ion e qu ipme n t .

The equ ipmen t commi t t ed to the Pioneer Program dur ing thenear-Earth phase varied sl ightly f rom flight to flight, as detailed intable 2-9. The s ta t ions along the AFETR had the primary responsi-bili ty fo r t racking (o r me t r ic da ta ) dur ing the l aunch and Ear th-


87/135

82 THE INTERPLANETARY PIONEERS IoBbeB

aaiS ;


88/135

SYSTEM DESIGN AND DEVELOPMENT

so 5s^j<

7.toegS

X X X X

X X X X

X X X X

X X X X

C

Knd

Ano

Jonbg

SOPn

C^l r^ xf>

zGOC

X

X

X

X

*

"*8.cdOo "bocisi


89/135


orbit portions of the flights. The Cape itself is well-equipped withradars , radio in ter ferometers , and a great variety of optical trackingequ ipmen t . AFETR and MSFN downrange s tat ions and RangeInstrumentat ion Ships (RIS) also possess full complemen ts of track-ing radars and te lemetry receiving equipment. Data are fed backto the Cape via submarine cables and radio links.The DSN stat ion at the Cape (DSS 71) provided prelaunchsuppor t to assure spacecraft compatibi l i ty with DSN conf igurat ionssupporting Pioneer flights. JPL also main tains a field station atCape Kennedy that provides an operational tracking in ter face be-tween the SFOF, in Pasadena, and the Kennedy Space Center andGoddard Space Flight Center groups. Considering the manifold oper-a t ions at the Cape, their complex interactions, and the immensedetail required fo r effective coordination, such in ter face groups areessential. The JPL Field Station also contained an Operat ions Cen-ter with displays to help JPL personnel monitor the status o f rangeinstrumentation during Pioneer launches. Crit ical tracking and telem-etry data were also routed to the SFOF through the field station.All launches at Cape Kennedy are under the direct control ofthe Air Force un t i l the spacecraft leaves Eastern Test Range (ETR)jur isdic t ion somewhere beyond Ascension. Because it is responsiblefor range safety, the Air Force monitors launch vehicle status dataand t r ack ing in fo rmat ion . Commands to t e rmina te the missionthrough the destruct ion of the launch vehicle are also an Air Forceprerogative-one that was exercised during the launch of Pioneer Eon August 27, 1969.After leaving Earth orbit , the Pioneer spacecraft quickly ascendedbeyond the 500 to 1000 mile ranges of the AFETR and MSFNt racking radars. From here on they were t racked, communicatedwith , and commanded by the pr imary DSN stations listed in table2-8. MSFN and other DSN stations worked the Pioneer spacecrafton an as-needed basis (fig. 2-28).Each of the p r ima r y DSN stations was out f i t t ed with mission-dependent equipment that accommodated general-purpose DSIF m a-chinery to specific Pioneer requirements . The DSN gear was calledGround Operat ional Equipmen t (GOE). No special equipment wasinstalled at the SFOF, although a general-purpose mission-supportarea was reconf igured for the Pioneer m issions. Add it io na l m ission-dependen t equ ipmen t was installed at Ames.

PIONEER DATA PROCESSING EQUIPMENTPioneer spacecraft radioed back to Earth two kinds of data:scientif ic data for the exper imen te rs and engineer ing data fo r mis-


90/135


.Cape KennedyPalo Alto

Telemetry(TTY) science, engineering

LJOB, ->Johannesburg

41(.AOMJ,Woomera^* DSS 42 backup for DSS 41** OSS 41 prime acquisition station*** These TTY circuits (using CP) are to have hardwire backup.

FIGURE 2-28.GCF channels established for Pioneer 8.

Tidbinbilla

sion controllers to use in assessing the "health" of the spacecraft.The telemetry data follow two separate paths between the DSNstat ions (which receive it direct ly f rom the spacecraft) to the experi-men te rs and Pioneer project personnel. As they arrive from deepspace, Pioneer telemetry data are recorded directly on magnet ictape at the DSN stations and airmailed to JPL for verif ication andthen to Ames Research Center . This is the first route , and all datafollow it. At Ames, they are processed on the Pioneer Off-LineData-Processing System (POLDPS) fo r subsequent transmission tothe exper imenters on digital magnetic tapes in formats compatiblewith the i r computer facili t ies. Some of the telemetry data also followa second route. These are dispatched immediately from the DSNto Ames Research Center via teletype through JPL's SFOF. These


91/135

86 TH E INTERPLANETARY PIONEERS

F I G U R E 2-29.Pioneer Off -L ine Data Processing System (POLDPS) at Ames ResearchCenter.

are called "quick look" data; they are used fo r checking the scien-tific ins t rumen ts and for retransmission (after some processing) tothe Enviro nm en tal Science Services Adm inistrati on (ESSA) to helpforecast solar act ivity. Da ta fro m the Stanford radio propagation ex-pe r imen t are handled differently. Proper operation of this experi-ment requires the near-real-time feedback to Stanford o f i n f o rma-t ion on the Stanford receiver status. This in formation is relayedby teletype from Ames Research Center to Stanfo rd a few milesaway. In addition, engineering data f low via teletype f rom the DSNto the SFOF and from there to both Ames and TRW Systems fo ranalysis. At Ames, these engineering data are used to assess thehealth of the spacecraft and guide operational decisions.Originally JPL had been assigned the task o f processing Pioneerscientific data, but in 1964 JPL co m puters we re heavily loaded,and it w as decided to co nst ruc t the processing line at Am es ResearchCenter . Magnetic tape represented the only practical way to t ransmitthe bulk o f data from Pioneer spacecraftteletype facilities couldnot handle the volume. At each DSN station, two Ampex FR-1400tape recorders operating in parallel prepare analog tapes of thet ransmissions received from the Pioneers. Tape loading times foreach mach in e are staggered to avoid the loss of data. One set of


92/135


tapes containing all recorded data is selected and shipped firstto JPL where it is examined (verified) to ensure the quality ofreproduction. The tapes are then sent to POLDPS at Ames ResearchCenter.During 1969, Pioneer tape shipments averaged four hundred 9200-f t tapes per month, each containing 4 hr of data with half-houroverlaps. POLDPS processed and sorted out these data, preparingan average o f four hundred 2400-ft tapes per month for the experi-mente rs . The preparation of over 15 experimenter tapes per workingday indicated that POLDPS was extremely active during 1969, whenfour Pioneers were transmitting data back to Earth (fig.2-29).

POLDPS processes these tapes in a two-level system. The firstlevel, called the Tape Processing Station (TPS), produces a mul t i f i l edigital tape that serves as the input to the second level of processing,which consists of the Pioneer Off-Line Direct Coupled System(POLDCS). POLDCS generates separate experimenter tapes that areIBM-compatible and in the formats and densities desired by theindividual Pioneer experimenters.


93/135

Page Intentionally Left Blank


94/135


CHAPTER 3

Pioneer Flight OperationsPRELAUNCH ACTIVITIES

H E S U C C E S S F U L C O M P L E T I O N of the spacecraft 's Preship Review atthe TRW Systems plant in Redondo Beach, California, signals thebeginn ing of pre launch ac t iv i t ies . The spacecraft is carefully packedand shipped to Cape Kennedy by air. Its arr ival at the Cape ini t iates

a 6 to 10 week series of additional tests and checkout procedures de-signed to assure both the readiness of the spacecraft and its compati-bil i ty wi th the Delta launch vehic le , the DSN, and the ETR. If allgoes well and the pieces fit together, the spacecraft is launched.More people and facil ities par t ic ipate dur ing the Pioneer prelaunchand launch act ivi t ies than at any other t ime. Although the CapeKennedy and ETR downrange s ta t ions are the focal points duringthis phase of operat ions, the Deep Space Network, JPL's SpaceFlight Operations Facility, and Am es Research C en ter's Pione erMission Operat ions Center are all involved. As the m o m e n t o flaunch approaches, more and more of the NASA and Air Forcegeneral-purpose facil ities "come on the line" for the launch. Duringthe m i n u t e s after l i f t o f f , radars , opt ical inst rumentat ion , an d te lem-e t ry antennas at the Cape and downrange are all wai t ing for theDelta and i ts Pioneer payload. Likewise, cr i t ical antennas at someof the DSN's Deep Space Stat ions break off f rom t racking Marinersand Pioneers already out in space and swing toward the po in tswhere the new Pioneer is expected to come over the horizon.The fun c t io ns of the m ajor fac i l i ties concerned w i th a Pioneer launcha r e :

(1) Cape Ke nn edy provides facil i t ies fo r spacecraft tests, checkout ,and in tegrat ion and fac i li t ies for m at ing o f spacecraf t wi th launchvehicle and for launch vehicle assembly and launch. The Pioneer Elec-tr ical Ground Support Equipment (EGSE) provides an i n t e r facebe tween the spacecraft and the launch pad environment .(2) Eastern Test R'ange (ETR) provides track ing and data acquisi-tion services from laun ch through D SN acquisi t ion at Johann esburg.(3 ) The Deep Space Ne two rk (DSN) provides tracking, data acqui-si t ion, and t ransmission of command signals to the spacecraft. The

89


95/135


Pion eer Ground Ope ratio nal Equipm en t (GOE) at selected DSN sta-tions provides an interface between the spacecraft and the generalizedDSN equipmen t .The prelaunch phase of activit ies consists of so many hundredsof separate i tems and events that the checkout and countdown l istsare of ten pr in t ed by computers . Three groups of processes andevents stand out as par t icular ly impor tant:(1) Training in operational procedures(2) Integrated systems tests (ISTs)(3 ) Operational readiness testsTraining in operational procedures was most impor tan t during

the preparat ions for the launch of Pioneer A in 1965, when thePioneer Program was new to ETR and DSN personnel. The Deltawas already fam iliar , and the ETR and o f course DSN had handledmore complex spacecraft. The different aspects of the Pioneer launcheswere:(1) The unusual or ien tat ion maneuvers fo l lowing launch(2) The narrow launch window associated with injecting the space-craf t into an orbit roughly parallel to the plane of the ecliptic(3 ) The eject ion of the TTS satellites from the Block-II Pioneers(4) The occultations and flights through the Earth's magnetic tail .

The orientation maneuvers, especially, required careful t ra in ing atthe Goldstone DSS site and, in the case of Pioneers 6 and 9, atJohannesburg an d Goldstone, respec tively, where pa rtial Type-IIor ie n tat ion m aneuvers were car ried out .

Pioneer-A Prelaunch Narrative*Both the proto type and flight models were sent to the Cape. Theprototype arr ived October 1, 1965, for use in practicing prelaunchoperations.The Pioneer-A flight model arr ived on December 5. During pre-l iminary al ignmen t checkout a Total Indicator Runout (TIR) o f0.25 in. was noted, ind icatin g a physical m ism atch. The attach f i t t ingwas modif ied to br ing the al ignment within to lerance. Tests and

checkouts proceeded normally through F 1 day, with only minor ,easily corrected problems.December 15, F 0 Day, was relatively calm with visibility ofonly 0.125 to 2 miles. Countdown commenced 30 min early at 1630.Everything went smoo th ly un t i l T -90 min when the second-stageumbil ical plug was inadvertently pulled, causing loss of power tothe Delta second stage and the spacecraft i tself . No one could be sure


96/135

FLIGH T OPERATIONS 91exactly what would happen if the plug were reinserted. Conceivably,some unforeseen signal could cause serious damage by firing someof the ordnance . The spacecraft and the Del ta were thereforerevalidated. The built-in 60-min hold and ultimately the launchwindow had to be extended while fur ther checks were made. Thet e rmina l count resumed at 0145, December 16, at T 35 m i n .At T 2 min an abnormal i ty in the radio guidance equipmentcaused another hold. The situation seemed to correct itself, and thecount was recycled to T 8 m in . Liftoff occurred at 0231:20 EST,December 16, 1965 (fig. 3-1).

F I G U R F . 3-1.The launch of Pioneer A on Delta 35.

4 6 5 - 7 6 8 O - 72 - 7


97/135

92 THE INTERPLANETARY PIONEERSPioneer-B Prelaunch Narrative

The prelaunch operat ions fo r Pioneer B were comparat ively un-eventful. The flight spacecraft arr ived at Building AM on July 17,1966. On August 9, it was discovered that a connect ion openedwhen the Chicago cosmic-ray experim en t warm ed up, signalling anonex is ten t lo w radiat ion level at all t imes. The exper imen t flewin this condition.F 0 day, August 17, had superb weather , with 5-knot winds anda visibility of 10 miles. The countdown proceeded normally to T 3min , when a hold was called due to the loss of commun ica t ionsdownrange on the ETR. Com m unic at ion s were restored after 2 minand l i f t o f f occurred at 1020:17 EST.

Pioneer-C Prelaunch NarrativePioneer C was the first of the Block-II spacecraft. In addit ion ,this flight was the first to carry a Test and Training Satellitemo u n t ed in the Delta second stage. The Pioneer-C flight model wasreceived at Building AM on No v. 11, 1967. The 1ST of No vem ber

15 iden t i f ied a faul ty decoder, which was replaced. On November22, the Am es plasma probe was rem oved to correct a wiring error .F 2 day, December 11, was plagued by bad weather , twiceforcing personnel to clear the pad. At 1520, electrical power waslost for 25 min, causing some concern because the spacecraf t aircondi t ion ing was also lost. On F 1 day, the fa ir ing had to beremoved to repair the wir ing to the third-stage velocity meter .Terminal count began at 0543, December 13, and Pioneer C waslaunched successfully at 0908:00 on December 13, 1967.Pioneer-D Prelaunch Narrative

This spacecraft was the f irst to incorporate the convolutionalcoder exper iment and the Ames magnetometer . Pioneer D arr ived atBuildin g AM on October 6, 1968. The begin nin g of the co untdo wnwas delayed for two days while tests and adjus tmen ts were made tothe second-stage programmer. The countdown then proceededsmoothly to 0900 EST, when anomalies appeared in the exper imen ta ldata and exper iment per formance. Holds were cal led to investigatethese problems, which were found to be due to radio and electr icalin terference from the launch vehicle. No troubles were encountereddu r i ng F 1 day countdown act iv i t ies . At 1850 EST, November 7,1968, F 0 day checks began. Spacecraft power was tu rned on at1920. Spacecraft systems checks ran ahead of schedule and a 20-


98/135


99/135

94 THE INT E R PLANE T AR Y PIONEERS

Launch MECO DSNacquisitionDeltalaunchvehicleNear-Earthphasenetwork

Spacecraft

Instruments

Housekeeping telemetry only

Instruments onFIGURE 3-2.Status of the four Pioneer systems from launch through DSS acquisition.

Performance of the Delta Launch VehicleThe Delta launch vehicle performed superbly during the first fourPioneer launches. The fifth mission, Pioneer E, had to be aborted bythe Range Safety Officer when the vehicle began to stray off course.

Tracking and Data AcquisitionAs a spacecraft and its launch vehicle rise from the launch padat Cape Ken nedy, they are viewed downrange by a var ie ty of radio andoptical tracking devices. Until the spacecraft is handed over to theJohannesburg Deep Space Station, the pooled radars, optical track-ers, guidance eq uipm en t, and telem etry receivers of the Air ForceEastern Test Range and some statio ns of NASA's Deep Space Net-

work and Manned Space Flight Network are crucial to missionsuccess.The facili t ies assigned to each of the Pioneer missions f romlaunch through DSS acquisit ion are listed in table 3-2. The AFETRwas the primary agency responsible fo r providing metr ic ( t racking)data during this phase. The MSFN stations in table 3-2 providedr edundan t radar suppor t . Metr ic requirements were me t by t rack ing


100/135

FLIGHT OPERATIONS 95

i0".!!o a a

I I I ! 5c Ts ~ *o o 2


101/135


o

8ICg

K< 3g

-So

u

Ss00

s MP0O0

. Ot- W01Mg< ""

ss

W

1i -ii l- > !

3 - SISe ou e

. S Sb b.


102/135

FLIGHT OPERATIONS 97

the C-band beacon aboard the Del ta and the S-band telemetry signalfrom the spacecraft. From liftoff to 5000 ft al t i tude, AFETR opticale q u i p m e n t provided addi t ional metr ic data .Spacecraft Performance

The spacecraft were near ly dormant dur ing powered-flight stages.Abou t 5 min before launch, each spacecraft was put on in ternalpower. The spacecraft low-gain antenna 2 was connected to thet ransmi t ter -dr iver ra ther than to one of the TWTs, to conserveba t t e ry power. Consequently, only about 40 mW of signal powerwere broadcast until the TWT was switched on. H ousekeeping te lem -etry during launch was se t a t 64 bps-a relatively low r a t etoincrease the likelihood o f obtaining good diagnostic data at thelo w power level should the TWT fa i l to tu rn on.As soon as the spacecraft separated from the Delta third stage,the booms and Stanford antenna automat ical ly deployed and lockedTABLE 3-2.Tracking and Data Acquis i t ion Support Sta t ion s throughDSS Acquisit ion

Range/ne tworkAFETR

MSFN

DSN

Sta t ion1 Cape Kennedy and Patr ick AFB3 Grand Bahama I7 Grand Turk I91 Ant igua I

12 Ascension I13 Pretoria,S.A.Twin Falls (ship)Coastal Crusader (ship)Sword Knot (ship)Mer r i t t I.BermudaGra nd Ba ha maAnt i guaAscension ITananarive, Malagasy Rep.Vanguard (ship)DSS-71, Cape KennedyDSS-72, Ascension I.DSS-51, Johannesburg, S.A.DSS-41, Woomera, Australia'

Used6XXXXXXXX

X

XXXXX -

during Pioneer flights7XXXXXXXXXX

XXXXX

8XXXXXXXX

X

XXXXXX

9XXXXXXXX

X

XXXX

EXXXXXX

XXXXXXX

X"

Commanded par t i a l Type-II orientation This maneuver was commanded f romGolds tone on Pioneer 9.b Scheduled, but not actually used due to abort." The primary DSN acquisi t ion stat ion for Pioneer 8.


103/135

98 THE INTERPLANETARY PIONEERSin to pos i t ion. Power was applied to the TW T and the or ienta t ionsubsystem, again automat ical ly. The Type-I or ien ta t ion maneuverthen began and proceeded in the manner described in Chapter 2.When the low-gain antenna was switched from the t r ansmi t t e rdriver to the TWT, the telemetry signal from the spacecraft fadedfor about a minute whi le the TWT warmed up. By the t ime Johan-nesburg rose, the spacecraft was transmitting at about 7 W. It wasfully operat ional and had completed one Type-I or ien ta t ion maneu-ver. Upon acquisition the first com m ands generally sent were:(1) Switch to 512 bps(2) Repeat the Type-I or ienta t ion maneuver .

FROM DSS ACQUISITION TO THE BEGINNING OF THECRUISE PHASEThe period o f several hours stretching between the initial acquisi-t ion of the spacecraft by one of the DSN stat ions and the beginning ofthe cruise phase encompasses several events crucial to the successof the mission:(1) Two types of or ienta t ion maneuvers(2) Experiment turn-ons(3 ) The first thorough assessment of spacecraft health in flight(4) The first passes over all part ic ipat ing DSN stationsPrio r to DSS acquisition , the spacecraft automat ical ly went throughthe Type-I or ien ta t ion maneuver . This even t was started by switchestriggered when the deploying appendages locked into position. Bythe t ime the spacecraft was acquired by DSN, spacecraft power wason and the t ransmi t t e r was sending telemetry. In addit ion, the spinaxis was almost perpendicular to the sunline by virtue of the

automat ic Type-I or ien ta t ion maneuver .The firs t command dispatched after a two-way lock had beenestablished was usually that which changed the te lemetry bit rate fromFormat C, 64 bps, to Format C, 512 bps. Next , a command in i t i a t ingthe Type-I or ie nta t ion m anuever w as sent to ref ine the alignmentmade automat ical ly pr ior to acquisition and, more impor tan t , topreclude the possibil i ty that the automatic orientat ion sequence mayhave terminated prematurely. The third in the series o f preparatoryc om m a nds was "Undervoltage Protect ion On," but this was sent onlyif analysis by the Spacecraft Analysis and Command (SPAC) Group(located at the SFOF during launch) was conf ident that the space-craft power level was no rma l and tha t the spacecraft was operat ingproperly. Following the spacecraft 's execut ion of Undervoltage Pro-tec t ion On, the Pioneer was ready for experim ent turn-on and theall i m po r t a n t Type-II or ien ta t ion m aneuvers .


104/135

FLIGHT OPERATIONS 99The purpose of the Type-II maneuver was the rotation of thespacecraft spin axis about the Sunline until the spin axis was per-pendicular to the plane of the ecliptic. As explained more fully in

Chapter 2, this maneuver was normally controlled f rom Goldstonewhere Operations Orientation Director (OOD) maximized the telem-etry signal received f rom the Pioneer's high-gain telemetry antenna.Generally, hundreds of Type-II orientation commands were relayedto the spacecraf t , each giving rise to a pulse of gas f rom the orienta-tion subsystem. There was some jockeying back and forth acrossthe peak in the signal-strength reception curve. On occasion, thenormal Type-II orientation process was interrupted for anotherType-I maneuver to remove any spin-axis misalignment inadvertentlyintroduced by cross coupling during Type-II maneuvers.Preliminary trajectory analysis in the cases o f Pioneers 6 and 9indicated that partial Type-II orientation would be desirable early inthe flight to preclude an unfavorable spacecraft orientation later inthe flight. This special maneuver was necessary because the low-gainomnidirectional antenna used fo r communication early in the f l ighthad a very lo w gain within about 10 aft of the spin axis. Duringthe partial Type-II orientation maneuver the gas pulses torqued thespin axis sufficiently so that Goldstone antennas would not be lookingup this cone at the spacecraft during the final Type-II orientationmaneuve r . The final Type-II orientation maneuvers were always di-rected f rom Goldstone. Special equipment fo r this task, as well as theOOD and h'isteam, were located there.

SPACECRAFT PERFORMANCE DURING THE CRUISE PHASEThe Pioneer spacecraf t were designed for a minimum life o f 6months each. Each greatly exceeded this goal. In fact , each space-craft functioned well fo r several years, their longevity confirming

the design decisions made by Ames and TRW Systems in the early1960's. This section is concerned with spacecraft performance inorbit around the Sun.Pioneer6 Performance

The nominal Pioneer-6 mission extended f rom December 16,1965,to June 13 , 1966a. total of 180 days. However, because spacecraftperformance at the end of 180 days continued to be good and the210-ft dish at DSS-14 became available fo r long-distance tracking,the mission was extended.Although each Pioneer surpassed the goals set for i t , each space-craf t had its share o f minor problems. On Pioneer 6, for example, a


105/135


106/135

FLIGHT OPERATIONS 101the Sun sensors, a special test was conducted on February 5, 1969,the 89th day of flight. Telemet ry ind icated that Type-I and Type-IIcommands were executed proper ly. The ultraviolet filters had ap-parently solved the Sun-sensor de gradat ion problem.The space craft reache d perihelion at 0.754 AU on Apr i l 8, 1969.The spacecraf t was designed to penet ra te to only 0.8 AU, but itreached 0.754 AU w itho ut ove rheat ing, al though the cosm ic-ray ex-p e r i m e n t r eached i t s upper t empera ture l imi t .All spacecraf t system s opera ted no rm ally thr oug hou t the 180-daymiss ion . Dur ing the ex tended miss ion , i n May 1969, t he commun i ca -t ion range reached 130 m i l lion km (78 m i ll ion m i les) us ing on lythe 85-ft DSN a n t e n n a s . This extens ion of the commun i ca t i on r angecan be a t t r i bu t ed to three factors:(1) Use of l inear polar izers at some DSN s ta t ions(2) I m p r o v e m e n t o f no i se t em pe ra tu r e s at the DSN s ta t ions(3 ) Use of the Convolut ional Coder Uni t on Pioneer 9 (See be-low.)

The CCU, descr ibed in Chap t e r 2, was added to Pioneers D andE as an enginee r ing exper iment . -It can be swi tched in or out ofthe t e l emet ry s t r eam. CCU per fo rmance has been good , con t r ibut inga b o u t 3 dB to the communica t ion power budge t . In effect , theCCU increased the m a x i m um c o m m un i c a t i o n r a n ge fo r Pioneer 9at each bi t rate by 40 perce nt .Between the l aunch da te on Novembe r 6, 1968, and December 10,1968, the spacecraf t operated in the uncoded mode at 512 bps,except for CCU fu n c t io n al checks. Since Decem ber 10, the CCU hasbeen in a lmost C9nstant use except when the spacecraf t was beingworked by a DSN w i t ho u t P io n e e r G r o un d O pe r at io n a l E qu i pm e n t(GOE).A bo u t J a n ua r y 7, 1969, P ionee r 9 was far enough away f rom theCCU to provide a "coding gain" for DSN sta t ions conf igured forreceiving circularly polarized waves.13 Up to March 6, 1969, GOE-equipped DSN s ta t ions t r acked P ioneer 9 fo r about 1000hr with theCCU in opera t ion ; 680 hr were in the coding gain region. As aresul t of the CCU's coding gain, 4.43 X 10 s addit ional bi ts werereceived dur ing this per iod . The 3 dB gain at 512 bps was verif iedby d i rec t compar i son wi th uncoded da ta at 256 bps. The CCU ex-per iment has been so successful on P ioneer 9 tha t convolu t iona lcoding is being applied to othe r spacecraf t.

11The Pioneers t r ansmi t l i nea r ly polarized signals. A 3 dB loss is incurred whena DSN receiv ing ci rcular ly polar ized s ignals is used.


107/135


C H A P T E R 4

Pioneer Scientific ResultsrT"' H E S C I E N T I F I C L E G A C Y of the Pioneer Program will not be complete

* for m a n y years. Scientific papers based upon th e data telemeteredback f rom deep space are still being published in abundance. Mean-while, all f ou r successfully launched spacecraft at this writing continueto operate successfully. The Pioneer scientific record, though incom-plete, is impressivesome 150 contributions to the literature as ofearly 1971. Some of these papers and their implications are summa-rized in the following pages.

THE GODDARD MAGNETIC FIELD EXPERIMENTBy December 1965, when Pioneer 6 was launched, satellites hadconf i rmed the theoretical prediction of a basically spiral solar mag-ne t i c field imbedded or "frozen" in the streaming solar plasma. The

Sun's rotation about its axis imposed the "water sprinkler" patternon the outwardly rushing plasma (fig. 4-1).Pioneer-6 data confirmed that the interplanetary magnetic fieldo f t en changes direction abruptly without changing magnitude. This

phenomenon was interpreted at that time in terms o f intertwinedf i lamentary or tube-like structures in interplanetary space which, o na large scale, display the classical spiral structure but which, o n asmall scale, create a twisted microstructure.General ly early Pioneer magnetometer data tended to conf i rm theEarth shock structure, the magnetopause, and the spiral sector struc-tu re of the interplanetary f ield in f e r r ed f rom previous spacecraf tflights.Outward-bound Pioneers carried Goddard magnetometers throughthe region where the geomagnetic tail was expected to exist. Thisregion was crossed by Pioneer 7 between September 23 and October3, 1966, at distances ranging from 900 to 1050 Earth radii. A co-he ren t , well-ordered geomagnetic tail with an imbedded neutral sheetwas no t observed by Pioneer 7. However, the rapid field reversalsrecorded are characteristic of the neutral sheet region observedcloser to Earth. The conclusion at Goddard was that the geometryof the tail changes to a complex set of intermingled filamentary

103


108/135


tester ,IAUx \ Sun c^V'/^,iVWvX V1^ "A\ Vfi\.Y \. .\.v\ \

F I G U R E 4-1.Sector structure of the interplanetary magnetic field f rom Pioneer 6data telemetered between Dec. 18, 1965, and Jan. 14, 1966. Each arrow representsan equivalent flux of 5-y for 6 hr. Shaded regions are those where the field isdirected away from the Sun; field was antisolar elsewhere. From: Schatten, Ness,and Wilcox: Solar Physics, vol. 5, p. 250, fig. 8, 1968.

flux tubes at several hundred Earth radii. Later analysis led to a"discontinuous" model.

The new model recognizes the fact that field discontinuities onthe mesoscale and microscalein both magnitude and direction-are more prevalent than previously suspected, and that their characterdoes no t always imply the existenceof f i lam ents.

Pioneer magnetometer results have also helped provide insightinto what happens in interplanetary space when a major solar event,such as a large flare, occurs. The following observations based on


109/135

SCIENTIFIC RESULTS 105

Pioneer-8 telemetry represent about what one would expect f romthe general model of a solar disturbance propagating through space.(1) A rather steady field of 4 to 6y was observed during theearly hours of February 25.(2) The field increased rapidly to near 10y between 2000 and2022, then it rose slowly to about 14y.(3 ) Long-period variations were observed between 0200 and 0500,February 26.(4) A very quiet field of about 6y occurred between 2000 and0500, February 27.(5) The next group o f telemetered data at 2149, February 27,again revealed a high field (over 10y). Large variations were noticed.

(6 ) In the last time interval telemetered, between 0200, February28, and 0500, February 29, the field had dropped to normal values.THE MIT PLASMA PROBE

The preliminary MIT data indicated first, that sharp changes inthe plasma density preceded the dramatic changes in the magneticfield recorded by the Goddard magnetometer, and second, that thepeaks in number density were followed by periods of increasedbulk velocity.

The MIT group later published additional correlations betweentheir plasma-probe and magnetometer data. The simultaneouschanges in plasma and magnetic parameters were consistent withwha t one would expect f rom tangential discontinuities. High-velocityshears were observed across these discontinuities; the largest wasa b o u t 80 km/sec. The discontinuities observed by the MIT plasmaprobe were undoubtedly due to the same filament boundaries ord iscon t inu i t i es discussed in the papers published by the Goddardgroup.

The MIT plasma-probe and Goddard magnetometer data alsoshowed that these discontinuities have preferred directions in space,with a tendency for the solar wind to be fast from the west an dslow f rom the east. This east-west asymmetry in solar-wind velocityis a natural result of the rotation of the Sunthe water sprinklereffect again.Pioneer 6 carried the MIT plasma probe through the magneto-shea th in the dusk meridian on December 16, 1965. While the dataconf i rmed some portions of the various theories developed to de-scribe the magnetosheath, the proton distribution measured was bi-Maxwel l ian rather than the classical single-peaked curve. Roughly10 percent of the total number density was estimated to reside inthe high-energy tail (fig. 4-2). Apparently the high-energy tail was


110/135


100

H 801/1 i3? 60W _i| 40

200

5040

> 30aloi 20100

13 14 15 16 17 18

13 14 15 16Universal time 17 1812 13 14 15 16 17 18 19 20

Earth radii21

F I G U R E 42.Pioneer 6 magnetosheath proton observations showing velocity, thermalspeed, and number density. From: Howe: J. Geophys. Res., vol. 75, p. 2434, fig. 4,May 1, 1970.


111/135

SCIENTIFIC RESULTS 107composed of solar plasma par t icles penetrat ing through the magneto-sheath and eventually swerving to t ravel in the direct ion of thebulk flowwithin the magnetoshea th.The e lec t ron f lux was m ore com plex, w i th three dis t in c t regionsbe ing observed. The first region , f rom 9 to 11.5 Earth radi i , wascharacter ized by angularly isotropic fluxes in all fou r elect ron chan-nels. The elec t ron energy spec t rum indica ted tha t the elect ronsf o rmed a plasm a sheet in this region. The second region, 1.5 Ea rthradii thick, was bounded at the outer edge by the magnetopause .The elec t ron dis t r ibut ion in this region could be explained by twomodels. Using a t he rmodynamic mode l , the di s t r ibu t i on ma tchedthat of a Maxwell ian having a pressure of about 300 ev/cu cm,wi th the t empera ture para l le l to the local magnet ic field a b o u ttwice that perpendicular to the field. In the thi rd region, themagnetosheath, i tself , the fol lowing parameters were typical: thermalelectron energy40 eV; electron speed2700 km/sec; electron t em-perature-100 000 K.

THE AMES PLASMA PROBEThe Block-I and Block-II plasma probes built by Ames Research

Center record the energy spectra of electrons and posit ive ions inthe solar plasma as func t i ons o f az imu th and elevation angles. Fora more comple te unders tanding of the in te rplane tary medium, i tis essent ial to relate plasma probe results to the magne tome te r da taand, of course, the somewhat di f f e ren t perspectives apparent to theMIT Faraday-cup plasma probe and the TRW Systems electricfield detec tor .Figure 4-3 shows one type of data acquired by the Ames plasmaprobe: energy spectra and angular spectra. The energy spec t rumind icates a proton peak at 1350 V, corresponding to a proton veloc-ity of approximately 510 km/sec . The second peak in the curvewas due to alpha par ticles. H owever , analysis of subsequen t datarevealed the possible presence of singly ionized helium in the solarw in d th e f i rs t t im e this had been detected.

The early data also revealed an average solar wind elect ron tem-perature of abo ut 100 000 K during quiet t imes when the solarwind w as blowing at about 290 km/sec , wi th a m a x i m u m io n t em-perature of 50 000 K.As Pioneer 6 passed through the Earth 's magnetopause, the Amesplasma probe measured the temperature of solar elect rons in thebow shock at 500 000 K. H ere , ion tem perature s w ere about thesame as elect ron tem peratures , but , in co ntrast , the ions did no t coolo f f downs t r eam f rom the Earth.

4 6 5 - 7 6 8 O - 72 - 8


112/135

108 THE I N TERP L A N ETA RY PIONEERS10

10'

lio6

10

10"

10

Dec 26,1965, 2231 UT

1 3 51 I I I I

7 8 9 10 11 12 13400 1200 2000 2800 3600

E/Q, volts per unit charge44001

F I G U R E 4-3.Pioneer 6 Ames plasma probe /Q spec t rum, Dec. 26, 1965, 2231 UT,showing the hydrogen peak at approximately 1350 V, with the helium peak es-t ima t ed at 2700 V. From Wol fe , et al.: J. Geophys. Res., vol. 71, p. 3330,fig. 2, Ju ly 1, 1966.

Pioneers 7 and 8 were outward missions and swept through theEarth's ta i l early in the i r f l ights . Inst ruments on both spacecraftdetected evidence of the Earth's tail or "wake" with their magnetom-eters and plasma probes. The Ames plasma probes detected thewakes at about 1000 and 500 Earth radii for Pioneers 7 and 8,respectively.The Ames invest igators felt , on the basis o f their data, that thefol lowing i n t e rp re ta t io ns were poss ib le :(1) The observations could represent a turbulent downstreamwake if the Earth's magnetosphere closed between 80 and 500 E ar t hradi i .(2) If the solar wind diffuses i n t o the magnet ic ta i l , the plasmaprobe measurements could be due to the tail "flapping" past thespacecraft .(3) The ta i l might have a f i lamentary st ruc ture at these dis-tances (500 and 1000 Earth radi i ) and the dis turbed data couldarise at f i lam ent bo undar ies .


113/135

SCIENTIFIC RESULTS 109(4) Possibly, the t a i l might have disintegrated into "bundles" at

these distances.(5) If magnetic merging occurred, subsequent acceleration ofpinched-off gas may have caused the disturbed conditions that weremeasured.

Prior to Pioneer 6, few spacecraf t were capable of making detailedmeasurements of the solar wind. Consequently, the collisionlessinterplanetary plasma was treated as a single magnetofluid. How-ever, the Ames plasma probes have revealed that the solar protondistribution is def in i te ly anisotropic, with the temperature parallelto the local magnetic field being larger than that perpendicular tothe local magnetic field.

THE CHICAGO COSMIC-RAY EXPERIMENTThe Chicago cosmic-ray telescope on the Block-I Pioneers pro-

vided the opportunity for scientists to investigate the direction ofarrival of cosmic-ray particles near the plane of the ecliptic. Theexperiment also had a short enough time resolution so that rapidf luc tua t i ons in cosmic-ray intensity could be recorded. The first testcase came shortly af te r the launch of Pioneer 6, when solar-flareprotons were detected on December 30, 1965.

The solar flare that erupted about 2 weeks a f t e r the launch ofPioneer 6 was given an importance rating of 2. The effects werenoted for almost a week, as indicated in figure 4-4. Interplanetaryconditions during most of this period were remarkable free of solar-flare blast effects capable of modulating the galactic cosmic-rayflux. Solar protons in the energy range 13 to 70 MeV first arrived atthe spacecra f t at about 0300 UT, December 30, 1965, w i t h lowerenergy particles arriving later. The anisotropy of these protons wasstriking. The average direction of particle flow about halfway be-tween the Sunline and the angle would be expected if the particlestraveled along the water-sprinkler spiral lines. However, the detaileddata reveal a more complex situation:(1) The direction of the peak amplitude was highly variable,changing direction by as much as 90 within 10 min.(2) Relative to the intensities in other directions, the peak in-tensive varies rapidly.(3 ) Occasionally, the angular distribution was strongly peakedwithin a 45 sector.(4) Rarely, two intensity peaks 180 apart were noted.

The strong collimation of solar protons with energies greaterthan 13 MeV suggests that there are few irregularities in the propaga-tion path f rom the Sun that could scatter the protons. However, the


114/135


8 0 OM ^^(puooes jad siunoo)

O 00M ?

I t ! II*!3P O,_Lto a"S -2

r - su , k O C3 g 'Sj.2J 2 a- u "'S 2

- s E 3 o S

- iti "~0) ti (O "^ us 5 > ^o1"=- B?$- f^-o .2 'C rt^J bo ori to 4J'S i- . C O, -U t -^B =3 i >11^2


115/135

SCIENTIFIC RESULTS 111rapid changes in direction of the peak flux vector supports theconclusion f rom Goddard magne tome te r and GRCSW cosmic-rayant i so t ropy data tha t there are m an y short- ter m , rathe r localizedchanges in the E arth 's ma gne tic f ield.Corotat ion effects were noted early in flight by the Chicago in -s t rumen t , suppor t ing the joint observations o f several other Pioneer-6i n s t rumen t s and similar inst ruments on spacecraft elsewhere in thesolar system .Proton flux increases over the period f rom December 1965 throughSeptember 1966 have been unambiguously associated with specificsolar flares. Enhanced solar proton fluxes in the energy range o f0.6 to 13 MeV have been recorded f rom specific active regions f romranges as great as 180 in longitude. The enhanced fluxes werecharacter ized by def in i te onsets when their associated active centersreached points from 60 to 70 east of the central solar meridian.Cutoffs occurred at f rom 100 to 130 west. Coupled with the de-tect ion of assoc iated modulat ions of the galactic cosmic-ray flux,these observations again point to the existence o f coro tat ing magnet icregions associated with the active centers on the Sun. Observationsseem to show that solar-flare protons propagate along the spiralinterplanetary f ield from the Sun's western hemisphere. Presentevidence supports the view that the solar protons arise from proc-esses continually occurring in the solar active centers.

Further in fe rences f rom the Chicago data are:(1) Most of the particles observed during the so lar . m in im um areof galactic origins.(2) Relativist ic electrons were detected only in the neutral shee tof the geomagnet ic ta i l , poin t ing to the possible acceleration of thesee lec t rons by the spl i t m agnet ic field.THE GRCSW COSMIC-RAY EXPERIMENT

The pr imary mission of the GRCSW exper iment was the measure-ment of anisotropy in the distr ibution of cosmic rays within thesolar system, but still far enough away f rom the Earth to avoid itsper tu rb ing magne t i c field. The cons t ruc t ion o f a theoret ical modeldescribin g how co sm ic rays are propagated throu gh the solar systemdepends upon the accura te measuremen t o f cosmic rays with energiesless than 1000 MeV. Because the weaker cosmic rays, especiallythose originating on the Sun, are affected by the solar magnet icfield and the plasm a in whic h i t is im bedded, the GRCSW dat amus t be examined in con junc t ion wi th the results of the Pioneerplasma and magnetometer exper iments .The ex ten t of the anisotropy o f low-energy solar protons during


116/135


117/135

SCIENTIFIC RESULTS 113

Equilibriumanisotropy

Direction ofcosmic rayflow

, Solar flare

Nonequilibriumanisotropy

EquilibriumanisotropyAnisotropyscale

i_ Mar 27,0100To Sun

F I G U R E 45.The difference between the equilibrium and nonequilibrium classeso f cosmic-ray anisotropy. The amplitudes and azimuths of the mean anisotropyfo r each hour are plotted as a vector addition diagram. Note definition of < f > c .From: McCracken, Rao, and Ness: J. Geophys. Res., vol. 73, p. 4160, July 1, 1968.

the direction of maximum flux aligned parallel to the magnetic fieldvector during the first part of the solar event.(2) During the late portion of the flare, the cosmic rays are indiffusive equilibrium.(3) Under some circumstances, the propagation of cosmic raysf rom the Sun to Earth is completely dominated by a "bulk motion"propagation mode. Here, the cosmic rays do not reach the space-cra f t until the magnetic regime into which they were injected en -gulfs the Earth.(4) In two cases, the anisotropy and cosmic-ray times of flight in-fer diffusion of the cosmic rays to a point on the western portionof the solar disk before injection into the magnetic f ield.(5) Simultaneous observation by both Pioneers when separated by54 of azimuth indicate density gradients of about tw o orders ofmagni tude per 60 sector during the initial stages o f a solar flare.(6 ) A study of cosmic-ray scattering within the solar system indi-cates a mean free path o f about 1.0 AU for large-angle scattering.A second paper dealt with the energetic-storm-particle event,


118/135

114 THE INTERPLANETARY PIONEERSwhich was defined as the very marked enhancement of cosmic raysin the 1 to 10 MeV range near the onset of a strong terrestrialmagnetic storm. Data relating to seven such events were extractedf rom Pioneer-6 and Pioneer-7 telemetry. The data indicated a near1-to-l correspondence between the energetic-storm-particle eventsand the beginning of a Forbush decrease. It was shown furtherthat the bulk of the energetic-storm particles are apparently nottrapped in the magnetic regime associated wth the Forbush decrease.The Pioneer cosmic-ray data tend to support the Parker "blastwave" model, in which the charged particles are accelerated bythe magnetic f ield wi th in the shock f r on t .

The GRCSW group also compared the characteristics of corotatingthe flare-induced Forbush decreases as derived f rom cosmic-ray dataobtained f rom Pioneers 6 and 7. The results of this investigationare summarized in table 4 1 .Several solar-flare events have been examined in detail in the lightof GRCSW cosmic-ray data and readings taken at several groundstat ions. By way of illustration, the results of the studies of theJanuary 28, 1967, and March 30, 1969, events are summarized below.The salient f ea tures of the first event were:

(1) The probable location of the responsible solar flare was about60 beyond the west limb of the Sun.(2) Low-energy particles (500 MeV) detected at Earth arrivedafter diffusion across the interplanetary magnetic field. Both groupsof particles displayed remarkable isotropy.(3) The flux that would be observed by a detector ideally locatedin azimuth would be greater than 2000 particles cm-2-sec-1-si~1 above7.5 MeV.TABLE 4-1.Comparison of the Properties of Corotating and Flare-

Initiated Forbush DecreasesCorotating Forbush Flare-initiated Forbushdecrease decrease

Not accompanied by solar-generated Accompaned by solar cosmic rays andcosmic rays an energetic-storm-particle event

Onset time difference due to corota- Probably simultaneous onset up to 100( ion off the axis of the Forbush decrease

No amplitude dependence over 60 Amplitude varies by a factor of 4.0of solar azimuth over 60 of solar azimuth

The energy dependence of both classes of events is essentially the same


119/135

SCIENTIFIC RESULTS 115(4) Pioneer observat ions ind icated low-ene

the interplanetary pioneers. volume 1 summary

Documents