-T-8-047 AD-A21 5 953

DEVELOPMENT AND USE OF DATA ANALYSIS PROCEDURES FOR THE CRRESPAYLOADS AFGL-701-2/DOSIMETER AND AFGL-701-4/FLUXMETER ANDAPPLICATION OF THE DATA ANALYSIS RESULTS TO IMPROVE THE STATIC ANDDYNAMIC MODELS OF THE EARTH'S RADIATION BELTS

Bronislaw K. DichterFrederick A. Hanser

PANAMETRICS, INC.221 Crescent Street " tWaltham, MA 02254 D 1

DEC 1 41989

SCIENTIFIC REPORT NO. 1

2 October 1989

Approved for Public Release; Distribution Unlimited

GEOPHYSICS LABORATORYAIR FORCE SYSTEMS COMMANDUNITED STATES AIR FORCEHANSCOM AFB, MASSACHUSETTS 01731-5000

89 12 111

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ELEMEN.T NO NC NO NC

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,See Back) I

12 PERSONAL AUT.OR(S

Bronisla. K. Dich.er, Frederick A. Hanser13& T -0E OF REPORT 13b TIME COVERED 4 CATE OF REORT ,' , o 5oa., 15 PAGE COLNT

Scientific =1 FROM _ TO 1989 October2 1416 SLJPPLEME14TARY NOTATIOll

17 COSATI CODES 18. SUSECT TERMS Contine on re erse f ' nc's~ar- and4 identif> by block numb cr,

FIELD GROUP SUB GR Dosimeter Protons.-

Fluxmeter Bismuth Germanate (BGO) ScintillatorCr i oElectrons Nuclear Star Ev~nt.

19 ABSTRACT ICortnueon reversef neceiot aidentify by block rnbe-

Earth's magnetospheric radiation enviroment is a major hazard for spaceborne electronicsystems. This report documents work aimed at providing the U. S. Air Force with accurate,

time dependent radiation belt and cosmic ray environmental specifications. The data for

this effort is obtained from two instruments to be flown aboard the Combined Realeaseand Radiation Satellite (CRRES). These instruments are the Energetic Particle Dosimeter

and the High Energy Fluxmeter.

20 OIS-R BUTICN A AILABILITY OF ABSTRACT 21 ABSTRACT SECURITY CLASSIFICATION

UNCLASSIFIEC J-L, .i TE 0 SAME AS RPT OTIC USERS E Unclassified

22a NAME OF RESPO',S,.LE NOIIVIU AL 22b TELEPHONE NUMBER 22c OFFICE SYMBOL

(Include lva Cod,

MIarilvn Ahorhardt (617) 377- 3 991 GL/PHE

DO FORM 1473 3 APR F rOT'nN IF I AN 73 S )RSOi ETFi

UnclassifiedSECURITY CLASSIFICATION OF THIS PAGE

Ii. TITLE

Development & Use of Data Analysis Procedures for the CRRES Fayluads AFGL-701-2/Dosi-

meter & AFGL-701-4/Fluxmeter & Application of the Data Analysis Results to Improve the

Static & Dynamic Models of the Earth's Radiation Belts

ii SECURITY CLASSIFICATION OF TMIS FAGS

CONTENTS

Page

LIST OF ILLUSTRATIONS iv

LIST OF TABLES iV

1. INTRODUCTION 1

2. PHASE I EFFORT 2

2.1 AFGL-701-2/Dosimeter 22.2 AFGL-701-2/Fuxmmneter 7

3. SUMMARY 7

REFERENCES 10

cc esioi r

Disti.:>

LIST OF ILLUSTRATIONS

Figure Title Pa

2.1 Isometric View of the CRRES Dosimeter 3

2.2 Cross Section of the CRRESS Fluxmeter 8

LIST OF TABLES

Table Title Page

2.1 Characteristics of CRRES Dosimeter 4

2.2 CRRES Dosimeter Compression Couiter Charts 5

2.3 Typical Number of CRRES Orbits Required 6for an Overflow

2.4 CRRES Fluxmeter Channel Geometric Factors 9and Particle Detection Ranges

iv

1. INTRODUCTION

The Earth's magnetospheric radiation environment is animportant hazard for spacecraft electronic systems in the altituderange from several hundred km to several Earth radii. The SpacePhysics Division of the Geophysics Laboratory (GL) is engaged in aprogram to provide the USAF with accurate and time dependentradiation belt and cosmic ray environmental specifications. Muchof the data for this effort will come from the Combined Releaseand Radiation Effects Satellite (CRRES), which is presentlyestimated to be launched in mid 1990. Two of the particledetection systems on CRRES have been designed, fabricated andcalibrated by Panametrics, Tnc.: the AFGL-701-2/EnergeticParticle Dosimeter and the AFGL-701/High Energy Electron Fluxmeter(Refs. 1-3).

The general objective of this contract is for PArametrics toprovide support to GL in analyzing the data from the Dosimeter andFluxmeter and aid in GL's efforts to update and improve theradiation belt models. The specific objectives of the contractare:

(a) Prior to the launch of CRRES - provide support indeveloping the data analysis procedures for the AFGL-701-2/Dosimeter and the AFGL-701-4/Fluxmeterinstruments.

(b) Following the launch of CRRES - apply these proceduresto the CRRES data to provide the Dosimeter and Fluxmeterdata in a reduced form in a timely manner.

(c) Use the obtained CRRES data to update and improve thestatic radiation belt and cosmic ray models and toprovide inputs for dynamic radiation belt and magneticstorm models.

The program is split into two parts, Phase I, covering the periodbefore the CRRES launch and Phase II, covering the post launchpe-iod. During Phase I a modest level of effort will be expendedto develop the Dosimeter and Fluxmeter data analysis and datadisplay procedures. A higher level of effort will be expendedduring Phase TI to finalize the data handling procedures and usethe data to update and improve the radiation belt and cosmic raymodels.

n~mgn amn m~li m~m1

2. PHASE I EFFORT

The work carried on during this period, as stipulated in theTechnical Proposal, has been at a low level of activity. Theprimary reasons for this are the distant and uncertain CRRESlaunch date and the possibility of change of the parameters of theCRRES orbit. The count rates in the Dosimeter and Fluxmeterdetectors are quite sensitive to the actual spacecraft orbit, sothat at this time it is not feasible to construct the finalalgorithms for the analysis of CRRES data.

2.1 AFGL-701-2/Dosimeter

The CRRES Dosimeter measures electrons above 1 MeV andprotons above 20 MeV in 4 channels (Domes), with both flux anddose being measured. Nuclear star events are also measured foreach detector. The Dosimeter, shown in Fig. 2.1, is described inRef. 1, and is similar to the DMSP/F7 Dosimeter described in Ref.2. The primary detection characteristics of the CRRES Dosimeterare listed in Table 2.1. The flux and dose channel compressioncount characteristics are given in Table 2.2.

The dosimeter detectors have a 2x sr field-of-view andseparate detected pulses into electron (LOLET = 50 to 1000 keYenergy loss) and proton (HILET = 1 to 10 MeV energy loss). Thestar thresholds (40 or 75 MeV) are only sensitivc to high energyproton nuclear interactions ("stars") or to heavy cosmic rays.Ref. 2 provides a detailed description of the basic operation ofthe Dosimeter, including energy loss curves for the four Aldome/detector sets.

The CRRES dosimeter dose channels have been adjusted tooverflow in approximately 2 to 40 orbits so that more detaileddose increment data can be obtained. (The DMSP dosimeter requiredmonths to overflow.) The overflow intervals for each of the fourelectron and proton dose channels are listed in Table 2.3. Theelectron flux used in the calculations was AE4 (Ref. 4) and theproton flux was AP8 MIN. A comparison of flux and dose incrementallows the average particle energy loss to be calculated, and canbe used to separate protons and electrons in the LOLET channels.Note that LOLET (Low Linear Energy Transfer) and HILET (HighLinear Energy Transfer) are actually better descriptions for theelectron and proton channels.

2

.N Domes

J12Control and Signal.QTest Connector

(with cap)PI Power andMonitor Connector

Interface Connector

Fig%. 2. 1 Isometric View of the Ci'11\V. Dosimeter.

'3

,,i I e I a a

Tdbl e Z

I)aracteristics of the CRRiS Dosimeter

Dome At shield Det. art-a G r th re-No. ( ;/cm2 ) (c.)(n-zrI __ .________,

I 0.5 0.0 015 , 0. >, 40

2 1.55 0.05 0 1 .,--

3 3.05 0.051 0.1b 41

4 5.91 i .000 3.>.

Dose chanr,A caliLraraotrDome Prcton flux Pads CSi)t (cu'u ose cNo. prescale Electron (LOLET rotcn

1 1 1.16 x 0 - . x

2 1 1.85 x 10- 3 5 x

3 1 1.85 x 10 - 3 i. 3 X

4 8 1.94 x 10- 4 8.7 x I -

Dom e Elect ron channel range MeV) Protc- Kornel rang. i<t "No. Elect rons Protons Prctors

I > 1 > 130 L -13C

2 > 2.5 > 135 5-135

3 > 5 > 140 51-]40

4 > I > 155 7-1_ 5

" i i I III

Table 2.2

CRRES Dosimeter Compression Counter Characteristics

Flux Count--s: Output counts

Minimum count = M x 2E

Electron Channel: F x M = 4 x 4 bits/overflow at 524288

Proton Channel: E x M = 3 x 5 bits/overflow at 4096

Notes: Proto,, Channel No. 4 has a prescale Kpf ,

so input count = Kpf x M x 2'

Dose Counters: Output counts used with Dose calibration factors

Counters: = R + E x M

= 4 + 4 x 4 bits

Modified counter version: output counts are

C = 16n + R + 16M x 2 L, E . 7 (or E < 8)

where 0 < n < 2 E- , "I 2E x 16 (for ..M = ])

D = 16n ± R + 16 (M + 8 (E - 7)) 128, E> 7 (or E 8)

where 0 < n < 127, A = 128 x 16 (for .^M = 1)

D at overflow = 16 x 10,240

5

Table 2.3

Typical Number of CRRES Orbits Required for an Overf~c",

DoseChannel ___ ____

Electrons Protons

1 1.4 23.4

2 2.58 41.5

3 245.0 39.(

4 35.60~

2.2 AFGL-701-2/Fluxmeter

The CRRES Fluxmeter measures primarily electrons in the 1 to10 MeV range in ten intervals. Secondary data provide someinformation on high energy proton fluxes. The Fluxmeter,illustrated in Fig. 2.2, is designed to measure electrons in thepresence of high energy protons. Two solid state detectors and aBGO (Bismuth Germanate) scintillator form the primary triple-coincidence electron detection scheme. A cylindrical anti-coincidence plastic scintillator around the BGO scintillator isused to reject electrons which scatter out of the side of the BGOcrystal, to reject edge-cutting proton for some coincidenceconfigurations, and to reduce interference from side-entry highenergy protons. The Fluxmeter can have any coincidence or anti-coincidence requirement set by ground command, so there are eight(8) possible operating configurations. The nominal electronchannel geometric factors and particle detection energy ranges aregiven in Table 2.4. A more detailed discussion of the Fluxmeterdesign and operation is given in Ref. 3.

The CRRES Fluxmeter is designed to measure 1-10 MeV electronsin ten channels, in the presence of large fluxes of high energy (>100 MeV) protons. This is particularly necessary for measuringthese electrons in the inner radiation belt. It is expected thatthe normal mode of operation will have the two solid statedetector coincidences and the plastic scintillator anti-coincidence all enables. However, in-orbit data will be used toverify that this mode provides the most reliable results. TheFluxmeter has a 7.50 half-angle detection cone, so pitch angledistributions will be measured. The nominal geometric factor is0.012 cm 2 -sr, so that low flux pitch angle distributions may haveto he averaged over several spins. Much of the 1-10 MeV electronflux measurements will be the first reliable measurements of thiscomponent of the earth's trapped radiation environment.

3. SUMMARY

We are developing algorithms that utilize the known Dosimeterand Fluxmeter responses and various trapped radiation models toestimate the expected on orbit count rates. The preliminarycalculation of Dosimeter count rate is complete. Data analysis todetermine the Fluxmeter response to electrons is currently underway.

As soon as a firm launch date for CRRES is determined, theDosimeter and Fluxmeter instruments will be refurbished inpreparation for satellite integration. At that time, the effortdevoted to this program will increase to insure that all requireddata analysis algorithms are completed by launch time.

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REFERENCES

1. P. R. Morel, F. A. Hanser and B. Sellers, "Fabricate.Calibrate and Test a Dosimeter for Integration into the CRRESSatellite," report AFGL-TR-86-0001, (December 1985).Scientific Report No. 3 for Contract Nc. F19628-82-C-0090(ADA168566)

2. B. Sellers, R. Kelliher, F. A. Hanser, and P. R. Mcrel,"Design, Fabrication, Calibration, Testing and SateliiteIntegration of Space-Radiation Dosimeter," report AFGL-TR-P.1-0354 (December 1981). Final Report for Contract No. F196?2-78-C-0247 (ADA113085).

3. R & D Design Evaluation Report for Design, Fabricate,Calibrate, Test and Deliver Two Satellite Electron FluxDetectors (Panametrics, Inc., November 1982). For ContractNo. F19628-79-C-0175. (See also) Final Report, AFGL-TR-0205(ADA190799).

4. The Trapped Radiation Handbook, J. B. Cladis, G. T. Davidson,and L. L. Newkirk, Compilers and Editors-in-Chief, DNA 2524H(up to - Change 5, 21 January, 1977).

10