The S intillating Fibre Dete tor(SFD)Te hni al Note A(version 1.0)J. LemaireC. LippensV. Pierrard M. CyamukunguGh. Gr�egoire

Louvain-la-Neuve, January 1997

ContentsPrefa e iiUseful adresses ivUseful e-mail adresses and phone numbers vHistori al notes viIntrodu tion 11 Me hani al details / Mission analysis / Orbit / A omodation of theSFD on satellite 31.1 General properties of s intillation dete tors . . . . . . . . . . . . . . . . . . 31.2 The S intillating Fibre Dete tor (SFD) . . . . . . . . . . . . . . . . . . . . 41.2.1 The Probe Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . 51.2.2 The Ele troni s Unit . . . . . . . . . . . . . . . . . . . . . . . . . . 61.2.3 The inter onne ting opti al �bres . . . . . . . . . . . . . . . . . . . 101.3 A omodation of the dete tor on the satellite . . . . . . . . . . . . . . . . 101.4 Mission analysis and orbit . . . . . . . . . . . . . . . . . . . . . . . . . . . 151.4.1 EQUATOR-S payload . . . . . . . . . . . . . . . . . . . . . . . . . 151.4.2 EQUATOR-S orbit . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 Exposure to spa e radiation 212.1 Coverage of EQUATOR-S in geographi and magneti oordinates . . . . . 212.2 Mean energy spe trum on EQUATOR-S orbit . . . . . . . . . . . . . . . . 212.3 Time dependen e of parti le uxes on orbit . . . . . . . . . . . . . . . . . . 292.4 Con lusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373 Response of SFD to ele tron and proton uxes of spa e environment 383.1 SFD thresholds and limits . . . . . . . . . . . . . . . . . . . . . . . . . . . 383.1.1 SFD thresholds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383.1.2 SFD limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383.2 SFD response to ele tron and proton alibration beams . . . . . . . . . . . 403.3 SFD output ba kground . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413.3.1 Ba kground originating from gamma and some heavy ions . . . . . 423.3.2 Ba kground originating from protons and ele trons . . . . . . . . . 433.4 Comparison of NSF and SSF hannel output urrents . . . . . . . . . . . . 453.5 In- ight NSF and SSF hannel output urrents . . . . . . . . . . . . . . . . 453.6 Con lusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48i

List of Figures 50List of Tables 51A The SFD: Te hni al proposal 52

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Prefa eThe present Te hni al Note-A des ribes the work a hieved during the Phase-1 of theproje t entitled : Performan e of the analysis of results of the S intillating FiberDete tor on EQUATOR-S. The work is detailed in, in order of pre eden e, ESA'sWork Order Statement and Te hni al Requirements, ref. TDP/RA/S in-EQS/SOW.It orresponds to the Work Pa kages WP1.1, WP1.2 & WP1.3 of the Contra tor's pro-posal under over 11516/51.22/CONT.RECH, dated 27.03.1996. This work is part ofthe Work Order 2 to ESTEC/Contra t No 11711/95/NL/JG(SC) signed between theDire tor of ESTEC and the Dire tor of BISA, 11 July 1996.The ESTEC te hni al manager is Dr. Len Adams (QCA). The Belgian Institute forSpa e Aeronomy (BISA), Brussels, is the main Contra tor, and the Nu lear Physi s In-stitute (FYNU) of the Universit�e atholique de Louvain (UCL), Louvain-La-Neuve, isSub-Contra tor for this proje t.The proje t manager is J. Lemaire (BISA). The other members of the team of Co-Isare M. Cyamukungu (UCL), Gh. Gr�egoire (UCL), C. Lippens (BISA), and V. Pierrard(BISA). Their e-mail adresses and phone numbers are listed below, as well as the adressesof BISA and UCL.The S intillating Fibre Dete tor (SFD) was ommissioned by the European Spa e Agen y(ESA) whi h supports the osts of the design, alibration and exploitation of the results olle ted with the SFD. The dete tor and the ele troni equipment asso iated with theSFD was built by SENSYS. Mr. Cees Boeder is the dire tor of SENSYS. This Companyis lo ated in Noordwijk, The Netherlands.Len Adams, head of the division QCA at ESTEC, Noordwijk, is the Prin ipal Investigatorfor the SFD experiment. Bob Ni kson (QCA), Eamonn Daly (WMA), and A. Robelet,(FTD) are the ESTEC Co-Investigators, responsible for the te hni al, the s ienti� andthe �nan ial aspe ts respe tively.In January 1996, Joseph Lemaire, hef de se tion at the Belgian Institute for Aeronomy,Brussels, has been approa hed by E. Daly, ESTEC-WMA, to submit to ESA a soli itedproposal related to the SFD. The statement of work issued by ESTEC and given in Ap-pendix A, requested the elaboration and delivery of a omprehensive te hni al do umen-tation des ribing (i) the me hani al details of the SFD, (ii) the mission analysisdetails, (iii) the a ommodation of the SFD on the satellite, (iv) the radiationenvironment along the orbit in the magnetosphere and (v) the response of theSFD to this environment. This set of tasks forms the mandatory program and work-pa kages (WP) of the phase 1. The outputs of these WPs are ontained in the presentTe hni al Note A (TN-A). iii

The phase 2 of this proje t orresponds to the analysis of the SFD data if they are avail-able before the end of this proje t i.e. by 31.08.97. Otherwise an equivalent e�ort willbe requested to the Belgian team in repla ement of the initially envisaged phase 2. Theresults of the phase 2 will be presented in the TN-B.A proposal was prepared by J. Lemaire and Ghislain Gr�egoire, Professor at the Nu learPhysi s Institute of the Universit�e atholique de Louvain (FYNU-UCL). In addition tothe tasks listed in the statement of work, this proposal o�ered (vi) to perform the soft-ware alibration of the SFD using the GEANT Monte Carlo ode from CERN, and (vii)to ompare it to the hardware alibration performed by the ESTEC team. The GEANT ode is available at UCL and is urrently used by Gh. Gr�egoire's group. This tool hasenabled us also (viii) to predi t the response of the dete tor to the radiation environmentwhen it will be in the transitional and �nal orbits.The proposal whi h is reprodu ed in Appendix A, was submitted to ESTEC on 9 May1996. It was dis ussed and approved by the ESTEC te hni al manager and ontra t oÆ- er. A formal agreement and ontra t between ESTEC and BISA was signed 11.07.96.A formal agreement was signed between BISA and UCL whi h a epted the responsibil-ity of all work-pa kages on erning the simulation of the SFD response in the alibrationbeams, and in an Earth's radiation environment, as des ribed with the AP-8 and AE-8empiri al models provided in ESABASE.The �rst Progress Meeting was held at ESTEC, 23 O tober 1996. Three team membersvisited, on 3 De ember 1996, the Max Plan k Institute in Gar hing where the EQUATOR-S1 satellite is assembled and tested. Three brainstorm meetings have been held at BISAand UCL in De ember 1996 and January 1997 to prepare this Te hni al Note A.The EQUATOR-S Data Center (EDC) is lo ated at Max-Plan k-Institute f�ur Extrater-restrial Physi s (MPE) Gar hing, where W. Baumjohann is the EDC Proje t S ientist,and K. Prokopiu, the EDC Data Center Manager.The Prin ipal Investigator (PI) of EQUATOR-S is G. Haerendel (MPE); R. Torbert(UNH) is the Deputy Prin ipal Investigator; G. Pas hmann is the Proje t S ientist forEQUATOR-S.

1Sometimes alled EQ-S, throughout this do ument.iv

Useful adressesBelgian Institute for Spa e Aeronomy3 avenue Cir ulaire, B-1180 Brussels, BelgiumFAX: 32 2 374 8423 TEL: 32 2 374 8121Institut de Physique Nu l�eaireUniversit�e Catholique de Louvain2, hemin du Cy lotron,B-1348 Louvain-La-Neuve, BelgiumFAX: 32 10 45 2183 TEL: 32 2 47 3273ESTEC - QCAPostbus 299Keplerlaan 1, 2201 AG Noordwijk, The NetherlandsFAX: 31 71 565 6637 TEL: 31 71 565 4283Max-Plan k-Institut f�ur Extraterrestris he PhysikEDC Data Center & EQUATOR-S Data CenterD-85740 Gar hing, GermanyFAX: 49 89 3299 3569 TEL: 49 89 3299 3520SENSYS SystemsP.O.Box 4112201 AG Noordwijk, The NetherlandsFAX: 31 71 361 5525 TEL: 31 71 361 5525

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Useful e-mail adresses and phonenumbersLen Adams TEL: 31 71 565 3872 ladams�este .esa.nlBob Ni kson TEL: 31 71 565 3455 BNi kson�este .esa.nlA. Robelet TEL: 31 71 565 4047 arobelet�este .esa.nlEamonn Daly TEL: 31 71 565 3787 edaly�este .esa.nlCees Boeder TEL: 31 71 361 5525 -Joseph Lemaire TEL: 32 2 373 0407 joseph.lemaire�bira-iasb.oma.beCarlos Lippens TEL: 32 2 373 0383 arlos.lippens�bira-iasb.oma.beViviane Pierrard TEL: 32 2 373 0416 viviane.pierrard�bira-iasb.oma.beGhislain Gr�egoire TEL: 32 10 47 3216 gregoire�fynu.u l.a .beMathias Cyamukungu TEL: 32 10 47 3213 yam�fynu.u l.a .beHerwig Hoefner TEL: 49 893299 3513 hhh�mpe-gar hing.mpg.deKonstatin Prokopiu TEL: 49 893299 3520 okp�mpe-gar hing.mpg.deGerhard Haerendel TEL: 49 893299 3516 hae�mpe-gar hing.mpg.deGoetz Pas hmann TEL: 49 893299 3868 gep�mpe-gar hing.mpg.deWolfgang Baumjohann TEL: 49 893299 3539 bj�mpe-gar hing.mpg.de

vi

Histori al notesThe S intillating Fibre Dete tor development proje t was started in 1990 as a ollabo-rative ba kground resear h proje t between ESTEC Radiation E�e ts Unit (QCA) andthe Dut h ompany SENSYS. The aim of this proje t was to hara terize the dete torresponse to di�erent types of radiation and to determine its appli ability to monitoringof the spa e radiation environment. This work resulted in a publi ation at RADECS '93,'S intillating Fibre Dete tor System for Spa e raft Component Dosimetry' by C.P.W.Boeder (SENSYS), L. Adams and R. Ni kson (ESTEC).In 1994 an experiment was proposed under the ESA Te hnology Demonstration Pro-gramme to investigate spa e radiation e�e ts in Power-MOS transistors. The arrier forthis experiment was to be EQUATOR-S. At that time it was also proposed to in orporatea 3- hannel S intillating Fibre Dete tor with two �bres o-lo ated with the transistors tomonitor the internal environment and the third �bre mounted outside the unit to monitorthe external environment.The Power-MOSFET experiment was later withdrawn and it was proposed to y theS intillating Fibre Dete tor (SFD) as a stand-alone experiment to monitor the spa e en-vironment. For this purpose one �bre was heavily shielded to ex lude ele trons and thetwo remaining �bres lightly shielded to respond to both ele trons and protons. For thelatter the ele troni s was modi�ed so ea h �bre overed a di�erent range of ount rateswhile maintaining high sensitivity.One of the lightly shielded �bres was subsequently repla ed by a developmental Spinels intillator whi h should provide higher sensitivity. This is the �nal on�guration of theEQUATOR-S experiment. L. AdamsESTEC-QCA

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Introdu tionThe EQUATOR-S mission is part of the International Solar-Terrestrial Physi s(ISTP) program. It is also a spa e raft ommissioned by the German Spa e agen y tobe laun hed in 1997. This mission is planned to be operative for a period of four years.The laun h of this satellite has been delayed re ently, as a onsequen e of the failed laun hof ARIANE-5 and the destru tion of the CLUSTER spa e raft. Indeed, one of the ex-periments of the EQUATOR-S payload, the "Ele tron drift instrument", will be removedand transferred to the PHOENIX spa e raft whi h is foreseen as a repla ement for thefour CLUSTER satellites. Building a new opy of this instrument and installing it on theEQUATOR-S platform will delay the laun h till the end of 1997.The EQUATOR-S payload ontains nine other s ienti� instruments whi h are listed inSe tion 1.4 of Chapter 1 in this Te hni al Note A.The �nal orbit of EQUATOR-S is planned to be highly ellipti at low latitudes, lo atednear the equatorial plane, with an apogee hanging from 350 to 800 km and a perigeeof 10-11 Earth's radii. The spa e raft will traverse the radiation belts every 21 12 hours.This makes it a suitable platform to monitor the energeti harged parti les trapped inthe inner and outer Van Allen belts. This is why the payload of EQUATOR-S in ludesthe S intillating Fibre Dete tor (SFD). The aim of this dete tor is to survey the uxes ofthe energeti parti les with energies above 10 MeV, forming the Van Allen belts. Theseparti les onstitute a potential hazard for the instrumentation on board of EQUATOR-S.The observations of the SFD will primarily serve the engineering ommunity to evaluatethe radiation hazards of future satellites on similar orbits.Note that the payload ontains two other experiments whi h measure the energy spe traof ele trons and ions at lower energies. These elaborated measurements may be an im-portant omplement to those whi h will be olle ted with the SFD.The �nal spin period of EQUATOR-S is one se ond. The axis of rotation will be perpen-di ular to the E lipti plane. This orientation will enable the dete tor to sample parti lesfrom all azimuthal dire tions.The Belgian team of Co-Is for this study of the Performan e of analysis of results ofthe SFD on EQUATOR-S, is working at BISA and at UCL/FYNU.At BISA it is omposed of:Joseph Lemaire, proje t manager. He is responsible for the administrative matter re-lated to this proje t, for o-ordinating the work between UCL and BISA; for the deliveriesof Te hni al Notes, of the databases, the progress reports, the �nal report; he is in hargeof organizing progress meetings and the �nal presentation; he wrote the Prefa e and In-trodu tion of this TN-A.Carlos Lippens, afdelingshoofd at BISA. He des ribed in Chapter 1 the details of the1

SFD; he is in harge of transferring the SFD data to BISA, and to build a database whi hwill be used later for s ienti� investigations.Viviane Pierrard, Ph. D. student at BISA. She des ribed the EQUATOR-S mission(orbit, attitude of the spa e raft, B-L o-ordinates along the traje tory, view angle ofthe dete tor,...); she des ribed in Chapter 2 the spa e radiation environment; she de-termined the energy spe trum of trapped ele trons and protons averaged along typi alEQUATOR-S orbits, using empiri al ux models AP-8 and AE-8.At UCL-FYNU:Ghislain Gr�egoire, is responsible for the management of the software simulations. Hemade many of the s hemati s in this do ument available in POSTSCRIPT format.Mathias Cyamukungu, Ph. D., resear h asso iate, analyzed the detailed response ofthe SFD using various simulation pa kages and in parti ular the GEANT software libraryfrom CERN. He evaluated the respe tive sensitivities of the SFD s intillating elementsto ele trons, protons and heavy ions in the spa e environment. He assembled the presentte hni al note in LATEX format, based on the inputs from all other Co-Is.Mathias Cyamukungu and Ghislain Gr�egoire wrote Chapter 3: Response of SFDto ele tron and proton ux of spa e environment"This Te hni al Note A is a merger of the Te hni al Notes 1, 2 and 3 mentioned in theproposal.

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Chapter 1Me hani al details / Mission analysis/ Orbit / A omodation of the SFDon satelliteEven though the terms S intillating Fibre Dete tor (SFD) are used herein to name thedete tor a omodated on EQUATOR-S, this dete tor shares its properties with manyothers in whi h only the type of s intillating materials and their layout di�ers. In orderto emphasize the SFD parti ular features, the general properties of s intillation dete torsare presented in the �rst se tion of this hapter. The SFD is then des ribed and itsa omodation on EQUATOR-S is shown. A typi al EQ-S mission is analysed to end the hapter.1.1 General properties of s intillation dete torsThe emission of visible light by some materials hit by ionizing radiation is known sin ethe very �rst days of parti le physi s when Crookes dete ted the so- alled athode rays.Sin e then this property was extensively studied and used for the dete tion of all kindsof parti les [1, 2℄.In inorgani rystals the s intillation is related to (impurity indu ed) de�nite energy levelsin the gap between the ondu tion band and the valen e band. These energy levels serveas traps for ele trons liberated when an ionizing parti le travels a ross the material. Thetrapped ele trons are then later released with an a ompanying emission of light.In organi mole ules the s intillation is due to mole ular transitions from relatively long-lived triplet states to fundamental singlet states. A doping impurity a ts as a wavelengthshifter and allows some �ne tuning of the emitted light.The s intillation hara teristi s of a material when a parti le deposits a fra tion of itsenergy may be brie y summarized by three quantities: the lifetime of the light emission,the light yield and the physi al properties.The light emitted by a s intillating material after the passage of an ionizing radiationde reases more or less exponentially with time. This de rease an be hara terized byde ay time onstant(s), - the lifetime -. Its value varies from a fra tion of a nanose ond(for organi plasti materials) to a mi rose ond (for inorgani rystals) and even to severalse onds (or even minutes) for materials as zin sul�de. One generally speaks of uores-3

en e for the shorter ones (up to 100 nanose onds) and of phosphores en e for longerlifetimes.The light yield, - the number of photons emitted per unit energy deposition -, stronglydepends on the number of traps, and the absorption properties of the material. To obtaina useful s intillator, one obviously needs a material whi h is transparent to its own radi-ation. The light yield also depends on the amount of energy deposited by the in identparti le.The dete tion of a given type of radiation depends strongly on the physi al propertiesof the s intillator (average atomi number, average atomi mass, density, ionization po-tential,...). For harged parti les whi h dire tly release atomi ele trons, the ionizationpotential should be as low as possible; for gamma rays whi h intera t via pair produ tion,Compton intera tions and/or photoele tri e�e t, the best hoi e would be a materialwith the highest possible atomi number. For neutral parti les as neutrons, the dete -tion o urs only via nu lear intera tions with protons and the s intillator should have thehighest possible hydrogen ontents.S intillating opti al �bres represent a ompromise between the dete tion of harged par-ti les and the simultaneous requirement of spatial information at the rossing point ofthese parti les [3℄. These �bres are onstru ted by embedding a s intillating ore with agiven index of refra tion into a ladding with a lower index. In prin iple this on�gurationgives a lossless transmission of light along the �bre.The photodete tor assembly represents an essential part of any devi e using s intillating�bres. Its hoi e is based on arguments su h as spe tral mat hing to a given s intillator,speed of response, linearity, parti le ux and - obviously- ost. Low ost photodete torsare operated in urrent mode: they are well adapted to the measurement of parti le uxes.On the other hand, the operation in pulse mode is unable to ope with high uxes butgives information on individual parti les (energy deposition, time of traversal, parti letype ...).1.2 The S intillating Fibre Dete tor (SFD)The S intillating Fibre Dete tor (SFD) was designed to measure the omnidire tional en-ergy ux of protons and ele trons on EQUATOR-S orbit. Ideally, a dis riminating s in-tillating �bre - based dete tor should be implemented using one of the following methods:1. Operate in PULSE MODE and perform pulse shape dis rimination;2. Use many shields of di�erent thi kness for ea h s intillating probe. Ea h probewould dete t a given part of the proton/ele tron spe trum and the parametersof the a tual spe trum model would be dedu ed from a �t of the experimentallymeasured SFD output urrents to the predi ted output urrents. The more thenumber of di�erently shielded probes, the more a urate the resulting proton orele tron spe tra;3. Use s intillating material of di�erent s intillation eÆ ien y or di�erent stoppingpower for ea h probe, and the same thi kness and type of shield around all of them.Dedu e the dis riminated ele tron and proton spe tra by �tting model parameters4

to experimental results, like in 2. This method is to re ommend when no informationabout the spe trum shape (espe ially the uto� energies) is available.The SFD operates a tually in a kind of ombination of mode 2) and 3). It is made ofthree subsystems [4℄:� The Probe Assembly (mass: 141 g)� The Ele troni s Unit (mass: 256 g)� The opti al �bres inter onne ting probe and ele troni s1.2.1 The Probe Assembly

Figure 1.1: SFD probe subsystemThe SFD probe assembly (see Figure 1.1) is made of 1 mm diameter doped polystyrene(C8H8)1 s intillator (referred to as the almost Naked S intillating Fibre (NSF)) weaklyshielded with an aluminum tube of 2 mm outer and 1.6 mm inner diameter, and 1 mmdiameter doped polystyrene s intillator (referred to as the heavly Shielded S intillatingFibre (SSF)) shielded with a 0.25 mm thi k tube of 58.5 % by weight gold, 20 % opper,1index 1.60, density 1.05 oated with approximately 0.05 mm PMMA of index 1.495

20 % silver, less than 1.5 % zin and admium, inside a 4 mm thi k aluminum tube. Boths intillators are 100 mm long. The third s intillator is a 5 mm diameter, 39 mm longspinel2 s intillator (referred to as Spinel) shielded with a 0.5 mm thi k aluminum tube.The �bres are apped by a small mirror. The Probe Assembly has 3 SMA onne torsfrom whi h ea h s intillating probe is onne ted to the photodete tor (en losed in theele troni s box) by a 110 m long polystyrene �bre-opti able.In order to avoid solar light penetration into the satellite, a 0.1 mm thi k aluminum foil onstitute the SFD front panel.The SFD probe box is shielded against undesirable ba kground from the rear by a 3 mmthi k aluminum plate.

Figure 1.2: SFD ele troni s box.1.2.2 The Ele troni s UnitThe ele troni s are housed in an aluminium box with mounting plate (Figure 1.2). Foot-print : 85 x 65 mm. Height : 60 mm. Mass : 256 g. The mounting plate has 4 mounting22(MgO) + 5(Al2O3) doped with Mn, density 3.63, index 1.728.6

holes, diameter : 4 mm.The Ele troni s Unit has 3 SMA onne tors and a male 15 pin D-type onne tor with thefollowing pin allo ation:Pin Allo ation1 ase ground2 remote analog ground3 NC (no pin)4 +12V power input5 +12V power input6 NC (no pin)7 analog output signal8 analog ground9 ase groundPin Allo ation10 remote analog ground11 power return (ground)12 external lo k pulse(repetition rate : 1/4 Hz ,duration : 1 s at 0 V, 3 s at +5 V)13 power return (ground)14 analog ground15 output signalNote: ase ground is internally onne ted to analog ground and power return.The Ele troni s Unit houses 3 dete tor hannels and their asso iated logarithmi ampli-�ers, temperature measuring ir uitry, a 1 pA alibration sour e and an 8 hannel analogmultiplexer driven by the external 1/4 Hz lo k. The multiplexer swit hes the analogoutput hannel every 8 se onds between (see Figure 1.3):

Figure 1.3: SFD signal multiplexer system.7

1 0V referen e ( a. 2 mV)2 4V referen e ( a. 3.9 V)3 signal maximum ( a. 4.7 V)4 spinel hannel temperature referen e ( a. 2.3 V)5 SF hannel temperature referen e ( a. 2.7 V)6 spinel hannel7 highly shielded SF hannel (SSF)8 weakly shielded SF hannel (NSF)Every 128 external lo k pulses (every 512 s) the 1 pi o-Ampere alibration urrent sour eis toggled between on and o�. This alibration urrent is summed with the dete tor ur-rent. So a omplete SFD y le takes 1024 s.The output voltage is onverted to dete tor urrent a ording to the following equations:Standard s intillating �bre dete tor urrent:Idet = Ir eC Vout5 � 1eC Vtmp5 + Vout5R (1.1)with the following de�nitions of variables:t : operating temperature in ÆC (1.2)Tr = 273:15 + t (1.3)R = 8:6 1011 (1.4)C = 11608:71:001T (1.5)T = Tr Vtmp5 � VgVr � Vg (1.6)Ir = Vg � Vr104 (1.7)Vg = 1:1557 (1.8)Vt = 2:680 (1.9)Vr = Vt5 (1.10)(1.11)High sensitivity spinel s intillator dete tor urrent:Idet = Ir eC Vout2 � 1eC Vtmp2 + Vout2R (1.12)with the following de�nitions of variables:t : operating temperature in ÆC (1.13)Tr = 273:15 + t (1.14)R = 8:6 1011 (1.15)C = 11608:71:95T (1.16)8

T = Tr Vtmp2 � VgVr � Vg (1.17)Ir = Vg � Vr105 (1.18)Vg = 1:822 (1.19)Vt = 2:278 (1.20)Vr = Vt2 (1.21)(1.22)These formulas are plotted in Figure 1.4.Power requirements: +12 � 1 V DC at 9 mA with a power return at ground level.

Figure 1.4: SFD urrent vs. Output voltage hara teristi sPower supply noise shall be below 2 mV p-p measured in a bandwith of 20 Hz to 10 MHz.Operating power onsumption is 105 mW at 12 V.Temperature range : operational :�10 ÆC to +30 ÆC ; non-operational �45 ÆC to+80 ÆC. 9

1.2.3 The inter onne ting opti al �bresThe 3 inter onne ting PMMA opti al �bre ables are 1.1 m long. The attenuation of thes intillating light is negligible (less than 5 %). As stated above, they onne t:� bottom SMA onne tor (nr. 1) on the Ele troni s Unit to the short ylinder(SPINEL) on the Probe Assembly.� middle SMA onne tor (nr. 2) on the Ele troni s Unit to the heavly shielded SSFon the Probe Assembly.� top SMA onne tor (nr. 3) on the Ele troni s Unit to the weakly shielded NSF onthe Probe Assembly.1.3 A omodation of the dete tor on the satelliteThe EQUATOR-S satellite has roughly a ylindri al form, 1066.5 mm high with a radiusof 663 mm (See Figures 1.5, 1.6, 1.9). It has two platforms [5℄: The upper platformis alled the System Platform, the lower the Experiment Platform. To des ribelo ations on the satellite, a oordinate system Xs,Ys,Zs is de�ned. Xs lies along the spinaxis of EQ-S pointing upwards, and the YsZs plane is the separation plane (xs = 0)between the satellite and the laun h vehi le. The +Ys axis points in the dire tion of the3D Plasma Analyser Experiment (EX 4 1).The SF Probe Assembly is lo ated in the middle of side pannel 15 (See EX 5 1 on Figures

Figure 1.5: EQ-S System Platform.1.6 and 1.8). Its enter of gravity has the following ylindri al oordinates: � = 631:0,� = 315:0, xs = 318:5 (See Figures 1.7 and 1.8).The SFD Ele troni s Unit is lo ated on the System Platform (EX 5 2 on Figure 1.5).10

Figure 1.6: EQ-S Experiment Platform.

Figure 1.7: SFD probe box position on EQ-S11

Figure 1.8: SFD probe subsystem12

Its enter of gravity has the following ylindri al oordinates: � = 324:5, � = 236:5,xs = 507:0.The three opti al �bres inter onne ting the Probe Assembly with the Ele troni s Unit rundownwards from the Probe Assembly along side pannel 15 to the Experiment Platform,from there to the strut lo ated behind panel 15, they run upwards along this strut tothe System Platform, traverse this platform through one of the utouts and arrive at theEle troni s Unit.Sin e the 3 mm thi k Al baseplate of the Probe Assembly does not prevent all energeti protons oming from the ba k from rea hing the SF, an attempt was made to assess theshielding apabilities of the other spa e raft elements (See Figure 1.10). The Experimentand System Platforms hardly present any obsta le at all for protons. They are made ofa arbon �bre - foam sandwi h. The top plane, solar pannel planes and the side planesare made of an Al-PMI sandwi h, where the Al foil on both sides of the foam is 0.5 mmthi k.Based on the available do umentation (MPE drawings 499 000x 3, x=1,2,3,4,5,6,7 anddimensions [5℄) the Figure 1.11 drawing was made representing the azimuth and elevationangles at whi h the most important metalli spa e raft elements are seen from the entreof the SF Probe Assembly. It an be seen from this drawing that in ertain dire tions thespa e raft is almost transparent for protons.

Figure 1.9: EQ-S Stru ture (side view).13

Figure 1.10: A omodation of the most important elements on EQ-S (side view).

Figure 1.11: Azimuth and elevation angles of the most important metalli spa e raftelements 14

1.4 Mission analysis and orbit1.4.1 EQUATOR-S payloadThe satellite EQUATOR-S will perform near equatorial measurements of the Earth'souter magnetosphere inside 10 Earth radii for the investigation of aspe ts of global solar-terrestrial relations. The satellite transports di�erent s ienti� instruments for the studyof the magnetospheri plasma from altitudes lower than 200 km to altitudes higher than10 Earth's radii [6℄. The main s ienti� instruments are:� a magnetometer (H. Luehr, luehr�geophys.nat.tu-bs.de)� an ele tron drift instrument giving the ele tri �eld and the gradient of the magneti �eld in 3 dimensions (G. Pas hmann, gep�mpe-gar hing.mpg.de)� a 3D plasma analyzer giving the 3D ele tron and ion distributions for energy rangingfrom 10 eV to 30 keV/ harge (G. Parks, parks�geophys.washington.edu)� an ion omposition instrument or 3D mass spe trometer for energy ranging from 15eV to 40 keV/ harge (L. Kistler, kistler�rotor.sr.unh.edu)� an energeti parti le instrument giving ele tron spe tra from 20 keV to 1 MeV andprotons spe tra from 20 keV to 11 MeV (T. Sanderson, tsanders�est s1.este .esa.nl)� a potential ontrol devi e whi h keeps the spa e raft potential lose to 0 V (K.Torkar, torkar��wf01.dnet.tu-graz.a .at)� a GPS re eiver to study the GPS apabilities as a fun tion of the spa e raft altitude(B. Eissfeller, eis�ifen1.bauv.unibw-muen hen.de)� a solar ell diagnosti giving the temperature and degradation by radiation (K.Bogus, kbogus�vmprofs.este .esa.nl)� a mass memory for temporary storage (R. Torbert, torbert�unhedi1.unh.edu)� and the s intillating �bre dete tor des ribed in details in the �rst part of this Te h-ni al Note (L. Adams, ladams�vmprofs.este .esa.nl).The data of the 3D plasma analyzer, of the 3D mass spe trometer and of the energeti parti le instrument are parti ularly interesting to omplete the observations of the s in-tillating �bre dete tor in other spe tral domains.The spa e raft will be laun hed as an auxiliary passenger on Ariane 4 at the end 1997.The main passenger on Ariane 4 will be INTELSAT VII or VIII satellite. The laun hwindow is di tated by the main passenger. Two laun h windows are possible: either UT00:00 - UT 01:00 ( ase A) or UT 06:50 - UT 08:50 ( ase B).1.4.2 EQUATOR-S orbitTransfer orbitEQUATOR-S will be �rst delivered into a geostationary transfer orbit GTO [6℄. Theperigee will vary from about 180 km to about 300 km and the apogee will be around36000 km. The orbital period is 10h30. 15

Laun h window Su Sv Sw True anomaly of ki k v[deg℄A 00:00-01:00 -0.80 +0.60 0.00 87B 06:50-08:50 +0.80 +0.60 0.00 273Table 1.1: Spin dire tion Su;v;w of the satellite at separation for the two laun h windows.The rotation rate raises from 7 to 50 rpm by magnetotorquing in about 6 days. A singleburn ki k motor then brings the spa e raft into its �nal orbit.Spa e raft attitude in transfer orbit is given by two possible orientations at �ring of theki k motor. The spin dire tion S at separation an be given in the GTO orbital planereferen e oordinate system de�ned by the unit ve tors (u;v;w) with u in dire tion fromthe enter of Earth to the perigee, w perpendi ular to the orbital plane pointing into thenorthern hemisphere and v in the orbital plane ompleting the right-handed oordinatesystem. The attitude of the satellite following the laun h window is given in Table 1.1and is illustrated on Figure 1.12.

Figure 1.12: Attitude of the satellite following the laun h window.Final orbitInsertion into the �nal orbit needs raising of both perigee (to around 570 km) and apogee(to around 65693 km) with a one-impulse maneuver. That is possible applying a tangentialki k with velo ity in rements �V ' 380 m/s. The total burn time of the ki k motor is16.63 s. In the �nal orbit, the perigee varies a tually between about 350 km and about800 km and the apogee from about 65000 km to about 65800 km. Perigee, apogee heightand orbital period are very stable within 4 years as shown in Figures 1.13, 1.14 and 1.15.The orbit evolution depends on the orientation of the initial orbit, thus of the laun hwindow. The stability of the perigee is very important to avoid the satellite penetrationinto the lower layers of the atmosphere. The orbital period is around 21h30.The spin axis will be ere ted out of the orbital plane to be ome perpendi ular to thee lipti plane (into the dire tion of the e lipti al north pole). This operation takes around180 days. The �nal spa e raft spinup is 60 rpm.16

Figure 1.13: Evolution of the �nal orbit perigee heights in km for Cases A and B.The Table 1.2 summarizes the mean values of the EQUATOR-S transfer and �nal orbitsmain parameters. Some of these parameters vary during the mission ( f Figures 1.13, 1.14and 1.15). Moreover, the exa t values of these parameters depend on the laun h window,the spa e raft separation time and the pre ision of the ki k maneuver. The maximumdeviations of the perigee and apogee heights due to ki k maneuver exe ution amount 50km and 0.3 Re.Following the laun h window, the spa e raft is not always visible for the groundsta-tions. The visibilities for the ground stations Madrid (MAD), Weilheim (WHM), Can-berra (CNB) and Goldstone (GDS) are given in the Figure 1.16 with a resolution of 12min for the �rst 6 days of the �nal orbit, onsidering a midnight laun h ( ase A) at 1-3-1997. For a morning laun h (Case B), di�erent visibility onditions would be obtained.But for a possible di�erent laun h epo h, the time s ale is simply orrespondingly shifted.Visibilities for thresholds of 5Æ (-) and 10Æ (*) are indi ated. Apogees and perigees aremarked with 'A' and 'P' in the �rst line (A/P). Apogees are numbered inside the plots(nA). The o uren e of the Earth shadow is indi ated by 'S' in the se ond line of ea hdiagram (SHAD).

17

Figure 1.14: Evolution of the �nal orbit apogee heights in km for Cases A and B.Geostationary Finaltransfer orbit (GTO) orbitPerigee [km℄ 200 570Apogee [km℄ 36000 65693 (10.3 Re)Argument perigee [Deg℄ 175 175In lination [Deg℄ 7 7Mean anomaly [Deg℄ 4.827 6.165 (Case A) or 353.989 (Case B)Semimajor axis [km℄ 24466 39350E entri ity 0.73112756 0.82355Orbital period [hours℄ 10.5 21.5Right as ension 331.132 (Case A) 328.725 (Case A)of as ending node [Deg℄ or 77.439 (Case B) or 74.957 (Case B)Duration 7 days 4 yearsAttitude Spin axis in the orbital plane Spin axis ere ted perpendi ularlyto the e lipti plane in 180 daysSpinup [rpm℄ 7 to 50 60Table 1.2: Main mean parameters of the EQUATOR-S transfer and �nal orbits.18

Figure 1.15: Evolution of the �nal orbital period in hours for Cases A and B.

19

Figure 1.16: Ground station visibilities on the �nal orbit for a midnight laun h.20

Chapter 2Exposure to spa e radiationA radiation analysis for the EQUATOR-S mission has been performed using the UNIRADsoftware pa kage updated and distributed by the Belgian Institute for Spa e Aeronomy(BISA). This software is used with the AP8 and AE8 radiation belt models. Separate al ulations were made for the GTO and the FO orbits. The orbit parameters used arethose given in Table 1.2 (Case A).In this hapter, the overage of EQUATOR-S in geographi and magneti oordinates,the proton/ele tron mean energy spe tra on EQUATOR-S orbit and the time depen-den e of proton/ele tron uxes on orbit are su essively presented. The main results aresummarized in a on lusion.2.1 Coverage of EQUATOR-S in geographi and mag-neti oordinatesOn the basis of the mission analysis data, we an evaluate the overage of EQUATOR-Sin geographi oordinates as well as in magneti oordinates B and L. Two di�erentmagneti models are onsidered, but the resulting oordinates are indistinguishable. The overage and the radiation exposure depend on the laun h epo h. We will illustrate atypi al example onsidering that the orbit start datum is 1-1-1998 at 0h00. This datumde�nes the epo h of the �rst perigee. The Figure 2.1 represents the orbital parameters asa fun tion of the orbital time for the �rst transfer orbit.The Figure 2.2 represents the orbital parameters as a fun tion of the orbital time for one�nal orbit. The variations in latitude are very weak sin e the in lination is only 7 degrees.A proje tion map of 10 �nal orbits of EQUATOR-S is shown on Figure 2.3. More thanone orbit has to be onsidered to over the di�erent longitudes rossed by the satellite.2.2 Mean energy spe trum on EQUATOR-S orbitUNIRAD permits to evaluate the mission-averaged spe tra of trapped protons and ele -trons. The radiation evaluation is based on NASA models AP8 [7℄ and AE8 [8℄ built withdata obtained in the sixties and seventies. We onsider solar maximum onditions ande�e ts of solar protons with the Feynman and Gabriel's (1990) are model. Note thatother empiri al ele tron and proton ux models ould have been used for the radiationevaluation: CRRES-ELE, CRRES-PRO and the RADMOLS dose models implemented21

Figure 2.1: Geographi and magneti oordinates for the �rst transfer orbit onsideringthe typi al example of an orbit datum starting on 1-1-1998 at 0h00.

22

Figure 2.2: Geographi and magneti oordinates for one �nal orbit onsidering the typi alexample of an orbit datum starting on 1-1-1998 at 0h00.

23

Figure 2.3: Proje tion map of EQUATOR-S positions during 10 (�nal) orbital periods.Sin e the orbital period of the satellite is 21h30, the geographi al longitude of the satelliteperigee will drift.24

Figure 2.4: Integral and di�erential trapped ele tron spe trum averaged over the 7 daysof the transfer orbit mission.by A. L. Vampola. These models are available at BISA.Figure 2.4 illustrates the GTO mission-averaged spe trum of trapped ele trons for thetypi al example of a transfer orbit starting on 1-1-1998 at 0h00. Integral and di�erential uxes are represented as a fun tion of the energy of the parti les. We assume that thesolar a tivity is maximum and the models used are AE8 for the ele trons and AP8 for theprotons. In the analysis of the GT orbit, a perigee of 200 km has been used as a worst ase. The duration of the GT orbit of the satellite is 7 days.Figure 2.5 illustrates the trapped proton spe trum averaged for the GTO mission.Figure 2.6 illustrates the �nal orbit averaged mission spe trum of trapped ele trons. Theassumed duration of the mission on the �nal orbit is 4 years. To obtain the averagedspe trum, we onsider 13 orbits to assure that the satellite overs the di�erent longitudes.No signi� ant modi� ations would be obtained for the averaged spe trum if we use 26orbits instead of 13 orbits.Figure 2.7 illustrates the �nal orbit mission-averaged spe trum of trapped protons.Figure 2.8 illustrates the di�erential spe tra of trapped ele trons during the �rst minutes25

Figure 2.5: Integral and di�erential trapped proton spe trum averaged over the 7 days ofthe transfer orbit mission.

26

Figure 2.6: Integral and di�erential trapped ele tron spe trum average over 13 (�nal)orbital periods to over the di�erent longitudes.

27

Figure 2.7: Integral and di�erential trapped proton spe trum average over 13 (�nal)orbital periods to over the di�erent longitudes.

28

Figure 2.8: Di�erential trapped ele tron spe tra during the minutes 4 to 22 of a typi al�nal orbit starting on 1-1-1998.(4 to 22) of a typi al �nal orbit starting on 1-1-1998. Figure 2.9 illustrates the di�erentialspe tra of trapped protons during the �rst minutes (4 to 22) of a typi al �nal orbit startingon 1-1-1998.Figure 2.10 illustrates the �nal orbit averaged mission spe trum of the solar protons. Solar are parti le events, be ause of their unpredi tability and large variability in magnitude,duration and spe tral hara teristi s, are treated statisti ally in the UNIRAD software.Solar are proton spe trum is generated with the Feynman and Gabriel model (1990).This predi tive model is based on observations made from 1956 through 1985. UNIRAD omputes the mission time during solar a tive years.These spe tra are useful to predi t the response of the instruments.2.3 Time dependen e of parti le uxes on orbitUsing UNIRAD, the time dependent uxes of trapped protons and ele trons an be de-termined. 29

Figure 2.9: Di�erential trapped proton spe tra during the minutes 4 to 22 of a typi al�nal orbit starting on 1-1-1998.

30

Figure 2.10: Integral and di�erential solar proton spe trum for the �nal orbit mission.

31

Figure 2.11: Integral trapped ele tron uxes for one typi al transfer orbit starting on1-1-1998 at 0h00. The orbital period of the transfer orbit is 10h30.Figure 2.11 illustrates integral trapped ele tron uxes J(E > 0:2 MeV ) and J(E >2 MeV ) for the GTO orbit illustrated on Figure 2.1.Figure 2.12 illustrates integral trapped proton uxes J(E > 5MeV ) and J(E > 30MeV )for the GTO orbit illustrated on Figure 2.1.Figure 2.13 illustrates integral trapped ele tron uxes J(E > 0:2MeV ) and J(E >2MeV ) for the �nal orbit illustrated on Figure 2.2.Figure 2.14 illustrates integral trapped ele tron uxes J(E > 5MeV ) and J(E > 30MeV )for the �nal orbit illustrated on Figure 2.2.These integral uxes will vary during the mission. Sin e the period of one �nal orbit isnot equal to 24h00 but 21h30, the geographi al longitude of the satellite perigee will drift.The variations on 6 days are shown Figure 2.15 for the proton uxes on the �nal orbit.From these results, it is seen that the EQUATOR-S radiation environment is severe. The uxes are very important when the satellite rosses the Earth's radiation belts. Moreover,the ux in reases very qui kly during the passage of the satellite in the radiation zones.As only one measurement of the ux is obtained every 64 se onds, large variations will32

Figure 2.12: Integral trapped proton uxes for one typi al transfer orbit starting on 1-1-1998 at 0h00.

33

Figure 2.13: Integral trapped ele tron uxes for one typi al �nal orbit starting on 1-1-1998at 0h00.

34

Figure 2.14: Integral trapped proton uxes for one typi al �nal orbit starting on 1-1-1998at 0h00.

35

Figure 2.15: Integral trapped proton uxes for 6 �nal orbits.

36

Figure 2.16: Integral trapped proton uxes during the entran e of the satellite in theradiation belts. The in reasing of the ux is very important in a few minutes.be observed sin e the gradient of the ux is important. The ux measurements alongthe orbit will not be very detailed. This is illustrated on Figure 2.16 where the di�erentpoints are given every 2 minutes.These evaluations permit to predi t the response of the dete tor to the environment.2.4 Con lusionsFrom these results, it is seen that the EQUATOR-S radiation environment is severe. The uxes in rease very qui kly when the satellite rosses the Earth's radiation belts, so thatthe ux values will onsiderably vary due to the long time between ea h measurement.The uxes depend on the laun h epo h and hour, whi h are not pre isely known up tonow. The ases illustrated here are only typi al examples based on the AP-8 and AE-8empiri models. 37

Chapter 3Response of SFD to ele tron andproton uxes of spa e environmentThe previous hapters gave us a des ription of the SFD and the radiation environmentit will monitor. In this hapter, these data and in-beam alibration results are used topredi t the SFD response to ele tron and proton uxes of the spa e environment.After a se tion where the SFD thresholds and limits are presented, its response to ele tronand proton alibration beams is given, followed by a detailed a ount of the ba kgroundproblem, a omparison of the NSF and the SSF hannels, estimations of in- ight NSFand SSF hannel output urrents and a on lusion.3.1 SFD thresholds and limits3.1.1 SFD thresholdsAs des ribed in Chapter 1, ea h s intillating material in the SFD is en losed in a shieldingtube and all the SFD hannels are prote ted against sunlight by an aluminum thin foil.An important role is played by those shields in the dis rimination of parti le type andenergy. This dis rimination pro edure will be des ribed in detail in the Data Analysis hapter of Te hni al Note B, we hereafter set our fo us to the energy thresholds stem-ming from the shields.Unlike ele trons, protons don't undergo signi� ant straggling while penetrating the shields.It is therefore possible to al ulate their average range for any shield material and thi k-ness. We found it however more informative to take into a ount the range stragglingfor both protons and ele trons. The tabulated (Table 3.1) values of energy thresholdsare energies for whi h less than 50%, 1% and 0.1% of parti les rea h the s intillatingmaterials, through a 0.1 mm thi k aluminum foil and the shielding tubes.3.1.2 SFD limitsIf the SFD system orre tly resists to radiation damages, its output urrent is proportionalto the parti le ux/energy but its thermal ele troni ba kground (dark urrent) shouldnot ex eed the signal originating from the parti les to dete t. Table 3.2 [4℄ summarizessome of the SFD limits in terms of parti le ux and energy.38

Channel Parti le Threshold energy Dete tion probability(MeV) (%)Ele tron 0.49 50NSF 0.28 10.26 0.1Proton 6.4 506.3 16.3 0.1Ele tron 6.5 50SSF 4.0 11.9 0.1Proton 35.6 5035.1 134.9 0.1Ele tron 0.79 50Spinel 0.49 10.44 0.1Proton 9.7 509.5 19.5 0.1Table 3.1: NSF, SSF and Spinel hannel shresholds.Photo urrent range : linear from 0.01 fA to > 100 nA:Baseline stability : typi ally 0.2 fA/10 min,: 1 fA long-term:Dete tion limits : 0.04 fA (250 ele trons/se ) rms(approximate) : 110 beta parti les/se � 3 MeV: 6 protons per se ond � 50 MeV:Irradiation limits : beta 100 nA= m2 short-term � 3 MeV: protons > 1 pA= m2 (50-300 MeV):Fibre dose limit : estimated to be in ex ess of 1 MRad:Table 3.2: SFD limits.39

3.2 SFD response to ele tron and proton alibrationbeamsFrom the user's point of view, the SFD an be hara terized, - as an energy depositionsensor,- by its response (A=(W= m2)) to a given ux of known parti les having a de�niteenergy. These hara teristi s were dedu ed (for the NSF hannel1) from the measurementsby Boeder et al. [4℄: using the output urrent as a fun tion of the ux at 3 MeV (SeeFigure 3.1) for ele trons and at 100 MeV and 300 MeV for protons (See Figure 3.2),one gets the NSF hannel response to ele tron/proton uxes at energies given herein.The NSF hannel outputs 1:1 10�8 pA=(e�=s= m2) when irradiated by a 3 MeV ele tronbeam. The output urrents are 2:1 10�6 pA=(p=s= m2) and 0:9 10�6 pA=(p=s= m2) foran irradiation by 100 MeV and 300 MeV protons respe tively. Using the values of energylosses of protons and ele trons in the NSF, - whi h are 0.16 MeV, 0.61 MeV and 0.30MeV for 3 MeV ele trons, 100 MeV and 300 MeV protons, respe tively-, one gets theNSF response displayed in Table 3.3.

Figure 3.1: NSF hannel output urrent in fun tion of ele tron ux at onstant energy (3MeV)From the alibration urves, the output urrent at null ux ("dark urrent") was esti-mated to be 0:35 10�8 A, 0:26 10�12 A and 0:18 10�12 A, in the onditions of experimentswith 3 MeV ele tron beam, 100 MeV proton beam and 300 MeV proton beam, respe -tively. These dark urrent values should not be onsidered as reliable, however, sin e anextrapolation to low uxes of data from su h a (high ux) alibration seems hazardous.Therefore, one an onsider the SF hannel hara teristi s given in Table 3.3 useful only1An assumption is made, from now, that the SSF response is the same as the NSF one.40

Figure 3.2: NSF hannel output urrent in fun tion of proton ux at onstant energies(100 MeV and 300 MeV)when the output urrent is suÆ iently high to keep this dark urrent negligible (or to orre t for it). In su h onditions, one an predi t the NSF hannel output urrent withhigh a ura y as shown in Figure 3.3.For an integral proton ux J(E = Ep) >> 105 p= m2=s at 0:3 MeV � Ep � 300 MeVor an ele tron ux J(E = Ee�) >> 1010 e�= m2=s at 0:16 MeV � Ee� � 3 MeV , theSF hannel output urrent is expressed here as Idet;i;SF = Ri;SF�Ei;SF , where i = protonor ele tron, �Ei;SF is the total energy loss of parti les i per unit time and unit surfa e,in probe material SF and Ri;SF is the response of the SF hannel to parti le i. Figure3.3 (smooth line) shows the NSF hannel output urrent as a fun tion of proton energy( onstant ux is 7 106 p= m2=s) as dedu ed from the values of Ri;SF given in Table 3.3.To al ulate �Ep;SF , the average energy loss of a proton in the SF ( al ulated usingVRANGE ode [11℄) is multiplied by the number of protons (i.e the ux). This resultis ompared to those given by the use of GEANT ode [13℄ and the in-beam alibrationresults [4℄. The observed 10% deviations between GEANT and VRANGE re e ts thea ura y of the stopping power/range algorithms with respe t to experimental data.3.3 SFD output ba kgroundBesides the thermal ele troni ba kground from whi h some of the SFD dete tion limitshave been al ulated, attention must be paid to the ontribution of the other parti lesthan proton and ele trons whi h EQ-S may en ounter on-orbit and those parti les (protonsand ele trons) travelling through the satellite and rea hing the SFD probe box throughits ba k-plate. 41

In−beam calibration results GEANT simulation results Calculated from 1 p energy loss

Incident proton energy (MeV)

10 100

NS

F c

hann

el c

urre

nt (

A)

0

2e−11

4e−11

6e−11

8e−11

1e−10

1.2e−10

1.4e−10

1.6e−10

1.8e−10

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*#*#� ���2+����� ���+������+ ���� +���� ��� ���� &���� ����

6 �������� ���� ��4� ��+3 � �"+3 � �-������� �� ����� ��� ���- �� /.0 ��+������ � ��������; .� �������� � �� � ���� .��� � ���4��.�� ����� ���������� � ��-��� � �� ����� ���� ��� ���� ��� ������� 8���� �� �� �������� � ��� 6���������; ���.�� � &�� �� ����4 ��.���.� ����

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��

Parti le : Threshold energy : 10 keV[4℄d : 8.6 MeVt : 10.2 MeV3He : 23 MeV� : 26 MeV12C : 144 MeV14N : 182 MeV16O : 216 MeV40Ar : 800 MeVTable 3.4: Threshold energies of possible other sour es of ba kground signal.3.3.2 Ba kground originating from protons and ele tronsAssuming that the rear panel and SFD ba k-plate stop all the protons with an energybelow Ebth, the signal to ba kground ratio varies as a fun tion of the proton energyspe trum. Using the mean energy spe trum en ountered by EQUATOR-S on its �nalorbit, a uniform spe trum overing 5 to 300 MeV range and the spe tra given in Figure2.9, we undertook pre ise al ulations of both ontributions to the SFD output urrent:� 105 proton energy values were generated using the fun tion FUNLUX from theCERN program library, the probability density fun tions were either supplied or al ulated using UNIRAD. (See Figure 3.4 (a) for typi al spe trum at minute 6 onorbit);� These energy values and relevant properties of aluminum were supplied as inputsto VRANGE, whi h gives among other things, the residual energy spe trum of the105 protons emerging from a [0.1 + 0.2℄ mm thi k aluminum foil (Figure 3.4 (b)),or a [0.5 + 0.5 + 3 + 0.2℄ mm thi k aluminum plate (Figure 3.4 ( )) or a [0.5 +0.5+ 10 + 3 + 0.2℄ mm thi k aluminum plate (Figure 3.4 (d)).� The residual proton energies al ulated above and the SF properties2 known to uswere supplied as inputs to VRANGE, whi h gives among other things, the energyloss orresponding to ea h input energy.� The energy losses al ulated above were �nally summed up and multiplied bythe SF hannel response to protons, Rp;SF . The resulting output urrents namedIfront(0:3 mm), Iba k(4:2 mm) or Iba k(14:2 mm) (fun tion of the rossed aluminumplate thi kness and indexed to indi ate their origin), are displayed in Table 3.5 asfun tion of orbital time.All the estimations show that the ratio of the ba kground output urrent (due to protonsof energy E > Ebth rea hing SFD through the ba k-plate) to the urrent produ ed bythe protons from the SFD side fa ing the spa e, is of the same order of magnitude as theintegral ux ratio J(E > Ebth)=J(E > 5MeV ). The energy values Ebth = 30 MeV and 60MeV have been used as good approximations of values (29 MeV, 58 MeV) orrespondingto 4.2 mm proton range and 14.2 mm proton range in aluminum respe tively. The ratio2The mean thi kness 0.785 mm of the SF probe was used as input to VRANGE, sin e it is not suitedfor parti le tra king. 43

Figure 3.4: Changes in proton energy spe trum due to several shielding platesIba k(4:2 mm)=Ifront(0:3 mm) is greater than 10% from T = 4 to 16 minutes. It is greaterthan 10% during approximately the same amount of time even when an additional 10 mmthi k aluminum plate is added to the a tual 3 mm thi k one. The titanium ki k motornozzle (whi h o upy mu h of the spa e behind the SFD probe box) would be more orless as eÆ ient as the 10 mm thi k aluminum plate, but it does not over the whole SFDangle of view (See Figure 1.11). In the a tual on�guration, it will just slightly redu ethe SFD ba kground ontribution.To solve this ba kground problem, one would need to stop (with 8 m thi k aluminumplate, for example!) the 150 MeV protons entering EQ-S through the rear panel. Forsu h protons, J(E > 150 MeV )=J(E > 5 MeV ) an rea h 35% in the radiation belt.Time Ifront(0:3 mm) Iba k(4:2 mm)Ifront(0:3 mm) J(E>30 MeV )J(E>5 MeV ) Iba k(14:2 mm)Ifront(0:3 mm) J(E>60 MeV )J(E>5 MeV )(min) (A) (%) (%)4 4.7 10�13 0.71 75 0.49 466 2.8 10�13 0.84 98 0.71 858 4.3 10�13 0.57 80 0.38 6510 6.2 10�13 0.37 63 0.22 4714 9.2 10�13 0.15 31 0.07 2118 1.1 10�12 0.04 7 0.01 422 9.7 10�13 0.01 2 0.003 0.7Table 3.5: Time dependen e of radiation ba kground urrent.44

The ele tron energy spe trum is su h that all the ba kground problems would be solvedwith an additionnal 10 mm thi k plate, but this is useless as long as the proton problemremains.All in all, it is seen that with the present shielding the SFD will not dis riminate theproton spe trum from the ele tron one in the radiation belt. Even modi�ed with anadditional 10 mm thi k aluminum plate, it will not give reliable results ex ept during 2/3of the time spent in the radiation belt.An adequate shielding of the SFD should be possible only in a dedi ated mission, if one onsiders the ne essary additionnal weight.The SFD will be hara terized in its a tual state (with a 4.2 mm aluminum shielding forparti les oming from the rear panel), keeping in mind its ineÆ ien y during one third ofthe time spent in the radiation belt.3.4 Comparison of NSF and SSF hannel output ur-rentsThe GEANT ode has been used to simulate the a tual SFD response to omnidire tionalele tron and proton uxes of 105 parti les=s= m2. The hoi e of GEANT was due toits ability to simulate both ele trons and protons, whereas VRANGE is suited for heavyparti les only. The pro edure was similar to the one des ribed in se tion 3.3, with theonly di�eren e that GEANT dire tly gives the energy losses of parti les o uring in anyelement of a me hani al system. The results are summarized in Table 3.6 for ele tronsand Table 3.7 for protons. Two main on lusions may be dedu ed from these results:� The SSF3 hannel is not hit by ele trons, due to the low value of J(E > 2 MeV )for ele trons in the radiation belt. The urrent of about 10�20 Ampere outputby the SSF hannel is due to 1 to 10 ompton and photo - ele trons produ ed inthe s intillating �bre following bremsstrahlung gamma rays originating from thealuminum shields. The numbers given in the SSF olumns are only to indi atean order of magnitude, sin e those values are subje ted to signi� ant variations hara terizing the rarity of events (� 1=105) whi h ontribute to this output urrent.� From T = 4 to 14 minutes, in the radiation belt positions, the SSF and NSF output urrents to whi h protons from all the dire tions ontribute almost equally. The urrent produ ed by protons entering the SFD probe box through the ba kplatedominates the NSF output urrent produ ed by ele trons.3.5 In- ight NSF and SSF hannel output urrentsUsing typi al in- ight energy spe tra, it is possible to determine the SFD response to anintegral ux J(E > 5 MeV ) = 105 protons=s= m2 of protons and J(E > 0:2 MeV ) =105 e�=s= m2 of ele trons. Those parti les are supposed to impa t perpendi ularly the3The gold tube is taken into a ount as one of the shields in all the estimations of the SSF hanneloutput urrent, though only the aluminium thi kness is the argument of output urrent expressions.45

NSF SSFTime Ifront(0:3 mm) Iba k(4:2 mm) Ifront(4:1 mm) Iba k(8:0 mm)(minute) (A) (A) (A) (A)4 6.3 10�16 2.3 10�20 1.3 10�19 8.4 10�206 2.5 10�16 3.9 10�19 2.3 10�20 2.2 10�208 1.8 10�16 2.7 10�19 1.0 10�19 1.2 10�2010 2.1 10�16 5.1 10�19 3.5 10�19 1.0 10�2014 2.2 10�16 8.8 10�19 3.8 10�19 4.2 10�2018 2.1 10�16 6.9 10�19 3.9 10�19 8.8 10�2122 2.0 10�16 6.2 10�19 1.9 10�19 4.6 10�20Table 3.6: NSF and SSF response to 105 e�=s= m2 ele tron ux.

NSF SSFTime Ifront(0:3 mm) Iba k(4:2 mm) Ifront(4:1 mm) Iba k(8:0 mm)(minute) (A) (A) (A) (A)4 4.9 10�13 3.4 10�13 3.4 10�13 2.8 10�136 2.8 10�13 2.4 10�13 2.4 10�13 2.2 10�138 4.4 10�13 2.5 10�13 2.4 10�13 2.0 10�1310 6.3 10�13 2.3 10�13 2.2 10�13 1.7 10�1314 9.3 10�13 1.4 10�13 1.3 10�13 8.9 10�1418 1.1 10�12 4.1 10�14 3.6 10�14 2.0 10�1422 9.8 10�13 1.3 10�14 1.2 10�14 5.8 10�15Table 3.7: NSF and SSF response to 105 p=s= m2 proton ux.46

shields and the s intillators, sin e the angular and energy probability density fun tion4fE�(E; �) is not available yet for all the orbital position. Thus, the resulting output ur-rents may be onsidered as minimum values, sin e every parti le whi h impa t obli allythe SF deposits more energy and ontributes more to the SFD output than the perpen-di ularly dire ted parti les.One an noti e, obviously that the integral uxes J(E > 5 MeV ) and J(E > 0:2 MeV )are not onstant neither in time, nor in spa e. The a tual output urrent is obtainedby renormalizing the urrents omputed for 105 parti les=s= m2 ux, to �t the a tualparti le integral uxes. Table 3.8 ontains the NSF and SSF hannel urrents, for orbitaltimes running from 4 minutes to 420 minutes for ele trons. The assumption is made thatthe spe tra for minute 60 to 420 are similar to the spe tra at minute 22. Analog resultsfor protons are shown in Table 3.9.Time J(E > 0:2 MeV ) NSF SSFIfront(0:3 mm) Ifront(0:3 mm)(minute) (e�=s= m2) (A) (A)4 16 10�19 2 10�236 1206 3 10�18 3 10�228 270000 5 10�16 3 10�1910 9038700 2 10�14 3 10�1722 94262000 2 10�13 2 10�1660 15683000 3 10�14 3 10�17180 8906100 2 10�14 2 10�17300 276310 6 10�16 5 10�19420 3604 7 10�18 7 10�21Table 3.8: A tual on-orbit ele tron ux and SFD output urrents.Time J(E > 5 MeV ) NSF SSFIfront(0:3 mm) Ifront(0:3 mm)(minute) (p=s= m2) (A) (A)4 4 2 10�17 10�176 216 6 10�16 5 10�168 1944 9 10�15 5 10�1510 11017 7 10�14 2 10�1422 556960 5 10�12 7 10�1426 650900 6 10�12 8 10�1460 1458 10�14 2 10�1676 1 10�17 10�19Table 3.9: A tual on-orbit proton ux and SFD output urrents.4E is the parti le energy and � is the angle between the SF probe and the parti le velo ity.47

3.6 Con lusionOn the basis of the SFD hara teristi s presented throughout this hapter, it is ob-vious that this dete tor a hieves a reasonable ompromise between sensitivity to pro-tons/ele trons and omplexity.Even though it does not operate in PULSE MODE, the SFD is based on a prin iple whi hmakes it suitable for indire t in-beam or in- ight proton and ele tron spe tra dis rimina-tion.The SFD output urrent will be of the order of 10�14 Ampere (10�11 Ampere) for in- ightele tron (proton) uxes of about 106 parti les=s= m2. An improvement of the SFD gainby a fa tor 102 to 103, without signi� ant raise in ba kground level, may result in morea urate dete tion of spa e radiation by the SFD.The most worrying weakness of the SFD is its ba kground signal due to parti les om-ing from the rear side of the probe box. Fortunately, on EQ-S orbit, this ba kground ontribution to the SFD signal is limited in time.

48

Bibliography[1℄ Glenn F. Knoll, Radiation dete tion and measurement; John Wiley & Sons, In .(1979).[2℄ L. Mi hel, Etude des propri�et�es des s intillateurs organiques liquides; Th�ese dedo torat, Louvain-la-Neuve, (1995).[3℄ V. Lemaitre, Les �bres plastiques s intillantes permettent d'�elaborer des dispositifssimples et robustes pour la mesure pr�e ise de pro�ls de fais eaux �ele triquement harg�es ou neutres; Th�ese annexe, Louvain-la-Neuve, (1995).[4℄ C. Boeder, L. Adams and R. Ni kson, S intillating �bre dete tor system for spa e- raft dosimetry; Pro eedings of RADECS '93 IEEE 1994[5℄ ST�OCKER, EQUATOR-S map, (1995).[6℄ Kiehling, R., EQUATOR-S mission analysis do ument, Part 1: Orbit, GermanSpa e Operations Center, (1996).[7℄ Sawyer, D. M., and J. I. Vette, AP-8 trapped proton environment for solar maxi-mum and solar minimum, NSSDC/WDC-A-R&S 76-06, (1976).[8℄ Vette, J. I., The AE-8 trapped ele tron environment, NSSDC/WDC-A-R&S 91-29,(1991).[9℄ Heynderi kx, D., M. Kruglanski and J. Lemaire, UNIRAD v3.0: Trapped radiationsoftware, ESTEC, (1996).[10℄ Kruglanski, M., and J. Lemaire, Trapped proton anisotropy at low altitudes, TrendTe hni al Note 6, ESTEC, (1996).[11℄ Gh. Gr�egoire, VRANGE and VSTOP are range/stopping power programs based onZiegler's tables, Williamson's tables and Hubert's tables (See referen es hereafter);private ommuni ation.[13℄ CERN, GEANT Version 3.21/05 Released on 15.03.96.[14℄ C. Williamson et al., Sa lay report CEA-R3042 (1966).[15℄ Hubert et al., Annales de Physique, vol. S-5 (1980).49

List of Figures1.1 SFD probe subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.2 SFD ele troni s box. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61.3 SFD signal multiplexer system. . . . . . . . . . . . . . . . . . . . . . . . . 71.4 SFD urrent vs. Output voltage hara teristi s . . . . . . . . . . . . . . . . 91.5 EQ-S System Platform. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101.6 EQ-S Experiment Platform. . . . . . . . . . . . . . . . . . . . . . . . . . . 111.7 SFD probe box position on EQ-S . . . . . . . . . . . . . . . . . . . . . . . 111.8 SFD probe subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121.9 EQ-S Stru ture (side view). . . . . . . . . . . . . . . . . . . . . . . . . . . 131.10 A omodation of the most important elements on EQ-S (side view). . . . . 141.11 Azimuth and elevation angles of the most important metalli spa e raftelements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141.12 Attitude of the satellite following the laun h window. . . . . . . . . . . . . 161.13 Evolution of the �nal orbit perigee heights in km for Cases A and B. . . . 171.14 Evolution of the �nal orbit apogee heights in km for Cases A and B. . . . . 181.15 Evolution of the �nal orbital period in hours for Cases A and B. . . . . . . 191.16 Ground station visibilities on the �nal orbit for a midnight laun h. . . . . . 202.1 Geographi and magneti oordinates for the �rst transfer orbit onsideringthe typi al example of an orbit datum starting on 1-1-1998 at 0h00. . . . . 222.2 Geographi and magneti oordinates for one �nal orbit onsidering thetypi al example of an orbit datum starting on 1-1-1998 at 0h00. . . . . . . 232.3 Proje tion map of EQUATOR-S positions during 10 (�nal) orbital periods.Sin e the orbital period of the satellite is 21h30, the geographi al longitudeof the satellite perigee will drift. . . . . . . . . . . . . . . . . . . . . . . . . 242.4 Integral and di�erential trapped ele tron spe trum averaged over the 7 daysof the transfer orbit mission. . . . . . . . . . . . . . . . . . . . . . . . . . . 252.5 Integral and di�erential trapped proton spe trum averaged over the 7 daysof the transfer orbit mission. . . . . . . . . . . . . . . . . . . . . . . . . . . 262.6 Integral and di�erential trapped ele tron spe trum average over 13 (�nal)orbital periods to over the di�erent longitudes. . . . . . . . . . . . . . . . 272.7 Integral and di�erential trapped proton spe trum average over 13 (�nal)orbital periods to over the di�erent longitudes. . . . . . . . . . . . . . . . 282.8 Di�erential trapped ele tron spe tra during the minutes 4 to 22 of a typi al�nal orbit starting on 1-1-1998. . . . . . . . . . . . . . . . . . . . . . . . . 292.9 Di�erential trapped proton spe tra during the minutes 4 to 22 of a typi al�nal orbit starting on 1-1-1998. . . . . . . . . . . . . . . . . . . . . . . . . 302.10 Integral and di�erential solar proton spe trum for the �nal orbit mission. . 312.11 Integral trapped ele tron uxes for one typi al transfer orbit starting on1-1-1998 at 0h00. The orbital period of the transfer orbit is 10h30. . . . . . 3250

2.12 Integral trapped proton uxes for one typi al transfer orbit starting on1-1-1998 at 0h00. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332.13 Integral trapped ele tron uxes for one typi al �nal orbit starting on 1-1-1998 at 0h00. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342.14 Integral trapped proton uxes for one typi al �nal orbit starting on 1-1-1998 at 0h00. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352.15 Integral trapped proton uxes for 6 �nal orbits. . . . . . . . . . . . . . . . 362.16 Integral trapped proton uxes during the entran e of the satellite in theradiation belts. The in reasing of the ux is very important in a few minutes. 373.1 NSF hannel output urrent in fun tion of ele tron ux at onstant energy(3 MeV) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403.2 NSF hannel output urrent in fun tion of proton ux at onstant energies(100 MeV and 300 MeV) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413.3 NSF output urrent in fun tion of in ident proton energy at onstant ux(7 106 p= m2=s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423.4 Changes in proton energy spe trum due to several shielding plates . . . . . 44

51

List of Tables1.1 Spin dire tion Su;v;w of the satellite at separation for the two laun h windows. 161.2 Main mean parameters of the EQUATOR-S transfer and �nal orbits. . . . 183.1 NSF, SSF and Spinel hannel shresholds. . . . . . . . . . . . . . . . . . . . 393.2 SFD limits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393.3 Response of SFD hannels to ele tron and proton beams. . . . . . . . . . . 423.4 Threshold energies of possible other sour es of ba kground signal. . . . . . 433.5 Time dependen e of radiation ba kground urrent. . . . . . . . . . . . . . . 443.6 NSF and SSF response to 105 e�=s= m2 ele tron ux. . . . . . . . . . . . . 463.7 NSF and SSF response to 105 p=s= m2 proton ux. . . . . . . . . . . . . . 463.8 A tual on-orbit ele tron ux and SFD output urrents. . . . . . . . . . . . 473.9 A tual on-orbit proton ux and SFD output urrents. . . . . . . . . . . . . 47

52

Appendix AThe SFD: Te hni al proposalSummary and Obje tivesThe obje tives of this proposal are to evaluate the a ommoda-tion and exposure of the ESA provided S intillating Fiber Dete -tor mounted on the EQUATOR-S satellite and to analyze the �rstdata sets obtained during the ight. The laun h of EQUATOR-Sis expe ted in February 1997. It is �rst on a GTO, then on a 7in lination orbit; the perigee is at 500 km, the apogee at 60000 km.The orbital period should be 21. h The spin rate is 60 rpm. A 1year routine operation is expe ted.Te hni al proposalIntrodu tionSENSYS has developed under ESA ontra t 10988/94//NL/NB a S intillating Fiber De-te tor to be own in February 1997 on board of the satellite EQUATOR-S into theRadiation Belts of the Earth's magnetosphere.This sensor is a short, 1 mm diameter opti al �bre that has been spe ially doped with as intillating material.The light output is olle ted, integrated and pro essed by a small ele troni unit. Evalua-tion of the dete tor system showed that it has onsiderable potential for spa e appli ationand the development of a ight unit has been initiated in 1995.A ight opportunity on the EQUATOR-S satellite was agreed under the ESA Te hnologyDevelopment Program and the ight unit was tailored to the interfa e and a ommoda-tion requirements of EQUATOR-S. This resulted in a 3-�bre dete tor head exposed to thespa e environment and an ele troni s unit interfa ing to an 8-bit housekeeping telemetry hannel. Two �bres are lightly shielded and expe ted to respond to all omponents of thespa e radiation environment. and one �bre is shielded with aluninum and gold in orderto largely suppress ele trons. The detailed des riptions of the dete tors, ele troni s unitand satellite me hani al stru ture and mission operations will be made available to the ontra tor. 53

It is the a ommodation of this new dete tor on the satellite and its expe ted response tothe radiation belt environment that is proposed in the Phase I of this proposal. Duringthe Phase 2 the analysis of the �rst sets of data will be undertaken.Appli able referen e do uments� Contra t ESA ontra t 10988/94//NL/NB "Development of a S intillating FiberDete tor" SENSYS-NL� "S intillating Fibre Dete tor for spa e raft dosimetry" Pro eedings of RADEX 93IEEE 1994� EQUATOR-S Proje t meeting O t. 95 MPI Gar hing.Phase 1: Evaluation of experiment a ommodationand operationWP 1.1: Me hani al details / Mission analysis / Orbit / A om-modation of dete tor on satellite (V. Pierrard, C. Lippens, Gh.Gr�egoire)V. Pierrard who is a post graduate student at IASB in ollaboration with C. Lippens,.engineer, who parti ipated in the Atlas and Miras missions, will study the do umentsprovided by the Agen y at the ki k o� meeting on erning the me hani al details ofthe dete tors, the EQUATOR-S mission, and the a ommodation of the dete tor on thesatellite. A detailed and omprehensive des ription of this material will be presented andsummarized in the Te hni al Note 1.This part of WP would start 1 September 1996 and be ended 31 De ember 1996.Using a omputer model of the me hani al stru ture of the satellite and the dete torsprovided by the Agen y, IASB, in lose ollaboration with Gh. Gr�egoire at the Institutefor Nu lear Physi s of the Universit atholique de Louvain an also determine, if requiredby ESTEC, the average mass density of shielding material and path lengths along allviewing dire tions of the dete tors. This would be a negotiable addendum to WP 1.1 andto Te hni al Note 1. This part of the study would be ompleted by 1 Mar h 1997.WP 1.2: Exposure to spa e radiation /Time & spatial resolutionof experiment (J. Lemaire, V. Pierrard)Under the ondu t of J. Lemaire, V. Pierrard will determine the uen e, and exposureof the dete tor using UNIRAD, ANISO, and ESABASE. Di�erent radiation environmentmodels available in UNIRAD will be used to determine the doses, onsidering the shield-ing, parti le energy and dire tionality. On the basis of the mission analysis data IASB willevaluate the overage in B,L as well as other geomagneti and geographi al oordinates.The time and spatial resolution of the experiment along di�erent parts of the orbit will beevaluated. For this workpa kage the advise of D. Heynderi kx and M. Kruglanski whi hare experts of UNIRAD and ANISO software at IASB will be soli ited.54

The results of this study will be reported in Te hni al Note 2. This WP will start 1O tober 1996 and be �nalized 31 January 1997.WP 1.3: Response of dete tor to spa e radiation environment(Gh. Gr�egoire, V. Pierrard)On the basis of the a tual dete ting devi e, we plan to determine the a tual responsefun tion of the �bre+photodete tor from the parti le level up to and in luding the analog-to-digital onversion.The ele tron and proton uxes as fun tions of the orbital position and satellite orientationare modi�ed by the materials traversed in the satellite vessel before the parti les rea hthe s intillating �ber module. It is easy to orre t for the energy loss in the surroundingshields. The intrinsi light yield in a �ber at the traversal point is obtained from the energydeposited inside the �ber ore material: this requires prior knowledge of the material omposition and emission spe trum of the s intillating dye.The photon trapping eÆ ien y, propagation and/or absorption towards the photodete torand �nal onversion into a voltage signal is obtained using the appropriate indi es ofrefra tion, spe tral dependen e of the absorption, olle tion and quantum eÆ ien ies ofthe photodete tor.The resulting voltage signal is shaped by the atta hed preampli�er before being eventually onverted by the analog-to-digital onverter.In the end we plan to obtain the theoreti al dete tion eÆ ien ies in a spa e environmenton the basis of dire tion and energy spe tra given by WP 1.2. Parti le identi� ation ouldbe envisaged if pulse shape information would be available.Of ourse to a hieve these tasks ESA should provide detailed te hni al des riptions� of the s intillating �ber (the emission and absorption spe tra versus wavelength,photon yield, refra tion indi es ...),� of the photodete tor (spe tral response, quantum eÆ ien y...)� of the asso iated ele troni s will be provided by the Agen y.A one meter long sample of the �ber would be needed to ompare the theoreti al anda tual responses of the SF. A prototype of the SFD is desirable, as well as a spare opyof photodete tor and of the asso iated ele troni s.This analvsis will be started 1 O tober 1996 and terminated 31 De ember 1996.The results will be reported in Te hni al Note 3.55

Phase 2: Analysis of dataWP 2.1: Experimental data / Satellite housekeeping data & for-mat (J. Lemaire, V. Pierrard, C. Lippens,Gh. Gr�egoire)We will ompare our theoreti al predi tions with the a tual data re orded in spa e. We ould probably rea h on lusions about a possible parti le dis rimination.The satellite SFD data will be transfered to IASB and reviewed. The satellite housekeep-ing data and format details provided by MPI Gar hing will be reviewed. The data will bedisplayed and browsed to eliminate spurious data sets. Qui k look plots will be produ edfor a limited amount of data. The software will be delivered with the PSS-05 do uments.The data will be displayed in time sequen e and in spatial oordinates (geomagneti andothers).This work of WP 2.1 will start as soon as the satellite data will be available to IASB, butnot later than 3 months before the termination of the ontra t: i.e. 31 August 1997. In ase no useful data are available by I June 1997, the ontra tors are willing to envisageanother task. This new task will have to be agreed by ESA's te hni al manager and the ontra tors.The results will be reported in the Te hni al Note 4.WP 2.2: S ien e data base for SF measurements / satellite posi-tions & orientation (J. Lemaire, V. Pierrard)J. Lemaire and V. Pierrard will prepare a s ien e database ontaining separately the mea-surements or all di�erent hannels appropriate to the operation of the instrument. Thisdatabase will in lude the satellite positions & orientations along the orbit of EQUATOR-Sfor all data re eived before 1 June 1997. It will also ontain relevant geomagneti andsolar a tivity indi es.The results will be reported in the Te hni al Note 5.The database and the software will be delivered at ESTEC with the PSS-05 do uments.Possible extension (phase 3)WP 3.1: Data pro essing / Separation of parti le spe ies / uxes/ doses (V. Pierrard, Gh. Gr�egoire)In addition to data pro essing and as possible extension of this work we propose to studythe separation of ele trons from the protons and obtain inforrnation about the uxes ofboth types of harged parti les. We may also then determine the doses.These results would be reported in an additional part of the Te hni al Note 5.56