INSTRUMENTATION FOR · Experiment Hookup 118 GSE Interfacer Circuits 118 References . 123 Appendix:...

APL/JHU

CP 030

NOVEMBER 1973

Space Systems

INSTRUMENTATION FORTHE ATMOSPHERE EXPLORERPHOTOELECTRON SPECTROMETER

by D. P. PELETIER

(NASA-CL~-138986) INS2 hULtENTA ALICr FOz THE N74-2102

ATI~SPHE'IC EXPICL. PHOiOELECTO,:ZPECiCHEiT (Applied Physics Lab.)A4-- p HC $10.25 CSCL 14B Unclas

T.JIs G3/14 3U24N3

THE JOHNS HOPKINS UNIVERSITY a APPLIED PHYSICS LABORATORY

INSTRUMENTATION FOR

THE ATMOSPHERE EXPLORER

PHOTOELECTRON SPECTROMETER

- i

THE JOHNS HOPKINS UNIVERSITY

APPLIED PHYSICS LABORATORYSILVER SPRING, MARYLAND O

- I

PHOTOELECTRON SPECTROMETER

- 11 --"- 1 I

APL/JHU

CP 030

NOVEMBER 1973

Space Systems

INSTRUMENTATION FORTHE ATMOSPHERE EXPLORERPHOTOELECTRON SPECTROMETER

by D. P. PELETIER

This work was supported by the National Aeronauticsand Space Administration Office of Space Science andApplications under Task I of Contract N00017-72-C-4401

THE JOHNS HOPKINS UNIVERSITY * APPLIED PHYSICS LABORATORY8621 Georgia Avenue o Silver Spring, Maryland o 20910


APPLIED PHYSICS LABORATORYSILVER SPRING. MARYLAND

ABSTRACT

The Photoelectron Spectrometer (PES) is part ofthe complements of scientific instruments aboard threeNASA Atmosphere Explorer (AE) satellites. The launchof the first spacecraft, AE-C, is planned for December1973.

The PES measures the energy spectrum, angulardistribution, and intensity of electrons in the earth'sthermosphere. Measurements of energies between 2 and500 eV are made at altitudes as low as 130 km. The de-sign, characteristics, and performance of the instrumentare described in this document.

Section 1 outlines the basic operation and summar-izes overall performance. Section 2 is devoted to detailedcircuit design and performance. Section 3 describes themechanical design, and Section 4 describes the ground sup-port system built to simulate the spacecraft/instrumentinterface and to test the instrument's electronics.

-v-



ACKNOWLEDGMENT

The author wishes to thank the personnel in the AEProject Office, at the support facilities at NASA GoddardSpace Flight Center, and at RCA-AED for their assistanceduring the development of the Photoelectron Spectrometer.

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APPLIED PHYSICS LABORATORYSILVER SPRING,. MARYLAND

CONTENTS

List of Illustrations ix

List of Tables xii

1. General Instrument Description . . .

Scientific Objectives 1

Instrument Configuration and Operation . 2Data Format 19

Specifications and Performance 24

2. Circuit Description 35

Electron Multiplier 35

Analog Electronics 38Electron Multiplier Bias Supply 43

Input-Output Board . . . . 48

Minor Mode Command System . . 52

Deflection Sweep Supply 57

Mode Control Logic . . . . 64

Sweep Calibrator 65Digital Data System 80Main Converter . . 87

3. Instrument Mechanical Design 93

Electrostatic Analyzer 93Electron Multiplier Bias Supply . . 98

Sensor Assembly 99

Main Electronics Assembly 103

4. Ground Support Equipment 109

General 109

Data Encoding 109

"Free Run" Operation (Digital Data Only) . 110

"Stop on Step" Operation 113

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GSE Operation Instructions 114Experiment Hookup 118GSE Interfacer Circuits 118

References . 123

Appendix: Mechanical Drawing List 125

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APPLIED PHYSICS LABORATORY3iLVER SPRING MARYLANO

ILLUSTRATIONS

Photoelectron Spectrometer. Frontispiece

1 Location of the Photoelectron Spectrometer onthe Atmosphere Explorer-C Upper Baseplate . 3

2 Block Diagram of Photoelectron SpectrometerSensor . 4

3 Block Diagram of Photoelectron SpectrometerMain Electronics . . . . 9

4 Deflection Sweep Operating Modes 12

5 A Typical Analyzer Sweep for Satellite SpinRates below 4 RPM 13

6 A Typical Analyzer Sweep for Satellite SpinRates above 4 RPM 14

7 Particle Data Timing 17

8 PES Particle Data Location in the AE-C MainFrame 20

9 Outline Drawing of Photoelectron SpectrometerSensor Assembly 26

10 Outline Drawing of Photoelectron SpectrometerSensor No. 2 and Main Electronics 27

11 Sensor Temperature Change Caused by Aero-dynamic Heating 31

12 Sensor Temperature Change Caused by SolarHeating 33

13 Schematic Cross Sections of the MM-1-5NGElectron Multiplier . . . . 36

14 Schematic Diagram of Electron MultiplierInterface Board 37

15 Schematic Diagram of Analog Electronics . . 39

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16 Photoelectron Spectrometer Hybrid Amplifier 42

17 Schematic Diagram of Electron MultiplierBias Supply 45

18 Tuned Oscillator Voltage/Current Charac-teristics 49

19 Schematic Diagram of Input-Output Board . 51

20 PES Minor Mode Command Bits and ClockTiming 54

21 Schematic Diagram of Minor Mode CommandSystem 55

22 Clock Timing for the Subcom Digital DataParallel Load 58

23 Timing for the PES Subcom Digital DataEnable Signals 59

24 Schematic Diagram of Deflection Sweep Supply 61

25 Schematic Diagram of Timing and ModeControl Logic . 67

26 Mode Control Logic: Calibrate Forces theInstrument to Mode I, Low Sweep Rate 69

27 Mode Control Logic: Mode I - High/Low SweepRate . 70

28 Mode Control Logic: Mode II - High/LowSweep Rate 71

29 Mode Control Logic: Modes III, IV, and V -High/Low Sweep Rate 72

30 Schematic Diagram of Sweep Calibrator 73, 75

31 Dual-Slope Integrating A/D ConverterBlock Diagram 78

32 Timing for the PES Particle Data Word Enables 81

33 Schematic Diagram of PES Digital Data System 83

34 Timing for Main Frame PES Bit Readout 85

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APPLIED PHYSICS LABORATORYSILVER SPRING MARYLAND

35 Block Diagram of the PES Digital Data System 86

36 Truth Table for Digital Data Section 88

37 Schematic Diagram of Main Power Supply 89

38 Assembly Drawing of Dual Hemisphere Analyzer 95

39 Molybdenum Aperture Ring for Dual HemisphereAnalyzer 97

40 Bias Supply Construction and Cockcroft-WaltonComponent Isolation to Reduce CoronaEffects 100

41 Assembly Drawing of Photoelectron SpectrometerSensor 101

42 Main Electronics Assembly 105

43 PES GSE Special Purpose Interfacer 115

44 PES GSE Signal Flow 119

45 Photoelectron Spectrometer GSE - ExperimentTiming 120

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TABLES

1 Nominal Sensor Temperature MonitorCharacteristics 18

2 Experiment Protoflight Level Vibration andAcceleration Limits 32

3 Electron Multiplier Bias as a Function of CommandState 47

4 Variation of 350-Js One-Shot Pulse Width as aFunction of Power Supply Voltage andTemperature 50

5 Minor Mode Command Functions 53

6 Relationship of Range Bit "States" to Full-ScaleElectron Energy Level 65

7 PES GSE Digital Data Code Assignments 111

8 PES GSE Analog Data Code Assignments 112

9 "Step" Meaning for Digital Data in the "FreeRun" and "Stop on Step" Modes 114

10 GSE Minor Mode/Subcom Status Assignments 116

11 PES GSE "Code" Truth Table 121

- xii -



1. GENERAL INSTRUMENT DESCRIPTION

The principal investigator for the PhotoelectronSpectrometer experiment (Ref. 1) is Dr. J. P. Doeringof The Johns Hopkins University Department of Chemistry;Dr. C. O. Bostrom and J. C. Armstrong of the AppliedPhysics Laboratory are coinvestigators. The experimentis similar to those used by Doering et al. (Refs. 1 and 2)on sounding rocket experiments, but modifications are in-corporated that make the instrument suitable for satelliteuse.

SCIENTIFIC OBJECTIVES

The objective of the experiment is to provide infor-mation about the intensity, angular distribution, and energyspectrum of low-energy electrons in the thermosphere.The instrument measures electrons with energies from 2to 500 eV. Two high-resolution modes allow detailed ob-servation of electrons with energies between 2 and 100 eVand between 2 and 25 eV. This capability is particularlyvaluable, since there are no data about the electron dis-tribution below 10 eV.

Electron fluxes between approximately 105 and 109electrons cm- 2 s-1 sr-leV- 1 are measured at altitudes aslow as 130 km. The experiment sweeps through a 64-stepenergy ramp in 1 second; consequently at a 1 RPM (revolu-tion per minute) satellite spin rate, a single energy sweepis completed within 60 of satellite rotation. At faster spinrates, the experiment sweeps through a 16-step energyramp in 0. 25 second, so that adequate angular resolutionis maintained.

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INSTRUMENT CONFIGURATION AND OPERATION

The Photoelectron Spectrometer contains two identi-cal electron detectors (sensor assemblies) and one controland data-handling package (main electronics assembly).Sensor No. 1 is mounted on the satellite upper baseplateapproximately 200 off the +X axis, as shown in Fig. 1.Sensor No. 2 is mounted on the main electronics assemblyand secured to the upper baseplate approximately 200 offthe -X axis. The sensors protrude through the spacecraft'sthermal blanket and solar panel and are rotated so that thesensor field of view is not obstructed by the spacecraft sur-face. In this configuration the sensors are capable of moni-toring simultaneous electron activity in both directionsalong the geomagnetic field lines.

In order to avoid shadowing of electrons by thespacecraft, the sensors should be as close to the space-craft's upper (or lower) surface as possible (Ref. 3). Asa mechanical configuration compromise, the sensors areelevated from the upper baseplate by 5. 5 inches, resultingin a vantage point 6 inches below the spacecraft's uppersurface.

Sensor Assembly

Each sensor contains a concentric hemisphere elec-trostatic analyzer, an electron multiplier and its associatedhigh-voltage bias supply, and analog electronics, includinga preamplifier, amplifier, discriminator, and rate limiter.Figure 2 is a block diagram of the sensor.

Electrostatic Analyzer. Electrons enter the elec-trostatic analyzer via a 90 by 200 collimator. If the voltagedifference between the hemispheres is AV, electrons withenergy of approximately 2AV will be bent in a semicirclebetween the hemispheres and will strike the electron multi-plier. Electrons with energy of less than 2AV are collectedon the inner hemisphere, and electrons with energy of morethan 2AV are collected on the outer hemisphere.

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THE JOHNS HOPKINS UNIVERSITY5P'LIED PHYSICS LABORATORY

SILVER SPRING MARYLAND

PES SENSOR NO. 2UPPER /_ - MOMENTUM 6 INCHESSOLAR PES SENSOR I

W H E E L

HAT NO. 1 SUPPORTUPPER PES MAIN

BASEPLATE ELECTRONICS

S-BANDANTENNA

CENTER

COLUMN 45.0 INCHES

II I LOWER BASEPLATELOWERSOLAR I

HAT EPARATIONADAPTER

,- 53.5 INCHES

+YREF NOTE: THE SENSOR COLLIMATORS

RESTRICT THE INSTRUMENTLOOK ANGLES TO 90 X 200

90

90

UVNO

PES-1

+X ---- X

NACE PES PES-2

ELECT

NACEELECT CEP

PSA ELECT

P-3-PSA ELECT go

ELECT

9

-YREF

DATUM LINE

Fig. 1 LOCATION OF THE PHOTOELECTRON SPECTROMETER ON THE

ATMOSPHERE EXPLORER-C UPPER BASEPLATE

-3-

-tz

> cw

CU K

S~~i ELI) To X7

4. U sircE GRID f..

7 U TNER tOOTPLETU 4

5CEE PO 6 E -PE .RELECTRO~~ ELECLOG~ ELCTcS

24 CN - G S G f

Fi.ALOKDIGAMO PHOTELECTRO PECTROMETEROSENSORFLDGR



A ground plane is provided near the collimator en-trance to reduce the effect of the spacecraft electric fieldson the electrons' trajectories prior to their entering theanalyzer. After entering the analyzer, the electrons re-main subject to path distortion because of magnetic fields,including those generated by the spacecraft and the earth;therefore the hemispheres are enclosed with magneticshielding material. The highly permeable shields arecomposed of 80% Ni, 15% Fe, and 5% Mo and are a mini-mum of 0. 030 inch thick. Joints are overlapped and inintimate contact, and holes in the shield are minimized.A Helmholtz coil used to test the effectiveness of the shieldindicated that a field strength of 7 gauss could be appliedalong the most susceptible axis before particle data wereseriously compromised. The shield of the electron gun(used as the particle source) may have become ineffectiveat the higher field intensities, and therefore 7 gauss is theminimum upper useful limit of the flight magnetic shield.

Distortion of the magnetic field in the vicinity ofthe instrument muddles a clear interpretation of the ap-parent measured electron energy and angular distribution.A field of several hundred gamma may in fact distort thedistribution of low-energy electrons entering into the in-strument field of view. Consequently a great deal of atten-tion has been given to the problem of assuring a magneti-cally clean spacecraft. This will be discussed in detail inlater reports concerning the reduction of scientific data.

If ultraviolet light is allowed to pass through theanalyzer into the electron multiplier, the light will causecounts that are indistinguishable from electron counts. Toreduce this possibility, holes are cut in the outer hemi-sphere to baffle the light. Secondary electron emission iscollected on an electron trap composed of a copper platebiased at +50 volts.

The baffle hole in the exit portion of the electro-static analyzer is a convenient opening for f particlesfrom a Ni-63 radioactive source. These 0 particles pro-vide a known background count to calibrate the electron

-5-



multiplier gain. The nominal calibration count rate is 2to 3 per second, which exceeds the estimated cosmic raybackground count of less than 1 per second.

Electron Multiplier. After the electron emergesfrom the electrostatic analyzer, it strikes the first dynodeof a 20-stage Johnston Laboratories focused mesh electronmultiplier (MM-1-5NG). The screen of the multiplier isbiased at 9% of the total multiplier voltage and is used toaccelerate the electron to an energy sufficient to producesecondary emission upon contact with the first dynode ofthe multiplier. Each subsequent dynode liberates addi-tional electrons, resulting in a nominal gain of 106 for amultiplier bias voltage of 3000 volts (screen voltage of270 volts). Increasing the bias to 4500 volts raises thegain to about 109. One should note, however, that theseare average gain values, and the multiplier actually dis-plays a rather broad pulse height distribution that must beconsidered during calibration of the instrument.

The electron multiplier is housed in a compartmentseparated from the other electronic circuits and kept freeof materials that may degrade the exposed multiplier.Only the necessary bias and filter components are mountedwith the multiplier.

Electron Multiplier Bias Supply. As the electronmultiplier operates, degradation occurs in the final dynodestages because these stages emit the greatest number ofelectrons per pulse. The resulting loss in multiplier gainis offset by the use of a commandable bias supply. Initiallythe multiplier is biased near the minimum bias supply out-put of 3000 volts. The bias is increased upon command asrequired in seven equal increments to a maximum outputof 4500 volts.

Analog Electronics. The charge output of the elec-tron multiplier is collected at the input of a charge-sensi-tive preamplifier. Two pulse shaping and amplifyingstages, a discriminator, and a rate limiter follow the pre-amplifier.

-6-

THE JOHNS HOPKINS UNIVIRSITY

APPLIED PHYSICS LABORATORYSILVIE SPRING. MARYLAND

Experimental results show that a discriminator set-ting of 105 electrons is adequate to produce a counting effi-ciency of approximately 80% at a bias supply setting of3200 volts when the multiplier is new.

Bipolar pulse shaping is used with a zero crossingtime of about 0. 5 As in the unsaturated mode, resulting inamplifier rate limiting of about 2 million pps (particles persecond). The buffer circuit is rate-limited so that the maxi-mum electron count rate from the sensor is nominally250 000 pps.

Main Electronics Assembly

The main electronics assembly houses the circuitsthat produce the required sensor signals including power,hemisphere sweep voltages, and high-voltage commands.

The main electronics circuits also adjust the ex-periment operating mode, calibrate the hemisphere deflec-tion sweep supply, accumulate the sensor output pulses,monitor housekeeping items, and handle data going to andfrom the spacecraft subsystems. All PES/spacecraft elec-trical interfaces are made through a 50-pin connectormounted in the main electronics assembly. Figure 3 is ablock diagram of the main electronics assembly.

Deflection Sweep Supply. The PES electrostaticanalyzer selects electrons with energy of 2AV if AV voltsare applied across the hemispheres. However the electron

Senters the analyzer on a zero-potential electric field linewith respect to the spacecraft chassis. Therefore the ratioof hemisphere potentials must be carefully selected to main-tain the electron path at zero potential so that the electronwill travel in a smooth semicircle between the hemispheres.It has been determined (Ref. 4) that for the PES analyzerdimensions, a 500 eV electron requires +140. 35 volts ap-plied to the inner hemisphere and -109. 65 volts applied tothe outer hemisphere.

The deflection sweep supply is a digital/analog(D/A) converter that produces synchronized positive andnegative linear ramps with maximum voltages of +140. 4and -109. 6 volts. The ramps contain 64 steps and have

-7-

THE JOHNS HOPKINS UNIVERSITYAPPLIED PHYSICS LABORATORY

SILVER SPRING. MARYLAND D1

u 2 2 J I

C-)j 0'a > p 0 -0. o

c C6 +' . . COMM103, -fD i

17 - A-A. G E~oF TINPUT-OUTPUT TBOA.R7 AC.--7 GA D EF

A ) 1# 1 MAZ-A.Vi-tO L T 25 C.. GE.v OONITO

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TN Iv SIT 1 L A5-B 5EMSR I TEMP

ATMVL+I IbETURvW R, - ? JSt ^_. AG AB6 S US 0 " TMPe- TRAP SIAS 4 P

A V "" I mo-TO I I -i 4 11 2f. C QCNA .S GRD 14 'TOLUC

ZO C_ PMUL l F-2 IGV I ON/OFF

JMUL-- F A-S GVAO I ONFES lL GRD IS Z -- 41 MAIN FRAM ~C

43-8 V - I VA0MVDR. IJ-It 14L 128 WORD UBCDM SYC

Sc COM AND WORD

DEFLECTON SWEEP SUPPLY 23 2Z 2420 .10 JD 2AP IM MMM LOWO

NCEGATIVE SWEE 124 .-- oE O14 IE BOD COMANDWO 9 COMMAND CLOCNEC.ATIE SWEEP RETURN 25 NoA-' 34 5 EALE SUBGOM %DaTAl DATA

POSITIVE SWEEP 21 -er a - - DIGTA. DATA APOSITIVE WEEP RETURN 22 - - - - - - - 49 SUBCOM 1I2A A TA O

BUFFER 7 RFETURN I O J3 A-B V 2I- O OV IE ___UI7. TIMN

TO LUG~ 14 C4ASI6 cR1GENEoR I

4A V TIMODE WTAlT US 54 IF-L I0

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+ GV I W

TERMSTOR e E--t wo0TH4ERMITOR .RETORN 17 - oEcaI5

e8 TRAP 4 I / t 18 1 ENBLE MAN woRD 3484940A4-A. WVw2 MO-ITOR 7- -. 36-1 . woa .0 11 ENABE M~ssa WOtDS 1o3,Soglo4Ckali$6St GPO 14 -ToLLY. 2 - 1.

MUL7012 GAIN BIT 1 8 ) M IN FRc LMULT E GA\lN BIT 2 9 WOR Z 2MULTZ GASN IT a 10 o U 2SIG GRO 15 J21-9 C c ocx GTAL 4 S.

S \ELD GRD , - D-T1-NT A 20

BUFFER Ca2ETTO I 2 30

ARO 2 C-1 cAL MODE EILEC

Z'6 al V7-4 Ca ENIA3,/

NEGATIVE SWEEP 244EGATVE SWEEP RET.'TURN 25 se%.SR -Z

POS17IVE SWEEP 21 415V \/ 2DoePTI-PE SWEEP RETORN 2+ -,2

BV 7,2+4 60

BUFFER 0 RETURV IP +WOV &) S L-4.5VIPUT+10.0 REF -3 19

\O.OV rtf RETURN It

J4 %%G G;Da 9, aCay s -s <-)24.5y RETURM

O *- 724 MAIN

Fig. 3 BLOCK DIAGRAM OF PHOTOELECTRON SPECTROMETER MAIN ELECTRONICS

-9-



commandable gain networks that provide for a selection ofone of three sweeps with maximum sweep energies of 500,100, or 25 eV. Consequently the theoretical analyzer reso-lution is 25 eV/63- 0.4 eV. Local electric and mag-netic fields, however, limit the practical resolution toabout 2 eV.

Experiment Operating Modes. The three deflectionsweeps are used in combinations that produce five energyrange operating modes (see Fig. 4):

1. In Mode I, all three ramps are used, with the25 eV ramp being used 50% of the time and theremaining time being equally shared by the100 and 500 eV ramps.

2. In Mode II, the 25 and 500 eV ramps are alter-nated.

3. Modes III, IV, and V use single ramps withpeaks of 25, 100, and 500 eV, respectively.

In addition to the five energy range modes, thereare fast and slow modes. When the satellite spin rate isless than approximately 4 RPM, the deflection sweepoperates in the slow mode in which there are 64 voltagesteps and 64 data words per ramp, as shown in Fig. 5.At higher spin rates, the deflection sweep operates in thefast mode in which there are still 64 steps per ramp butonly 16 data words per ramp; i. e., each data word con-tains data from four steps on the ramp (see Fig. 6).

The PES is allotted four main frame telemetrywords for sensor (particle) data. These words may beused to transmit any of the following information:

1. Sensor No. 1, particle data only;

2. Sensor No. 2, particle data only;

3. "Sensor Alternate, " in which particle data aretaken alternately from each sensor at 4-secondintervals; and

-11- N TppCDING PAGE BLANL9

,ECi~r,,DVG



500 eV - - -

MODE I0c( (T EFRAME PERIOD)

's 100 eV

25 eV

64T TIME(16T AT FAST RATE)

500 eV MODEMODE II

cc

z

25 eV

S 32T "-- TIME(8T AT FAST RATE)

Vp = 25 eV FOR MODE III

Vp = 100 eV FOR MODE IV

Vp = 500 eV FOR MODE V

LU Vz

16T P TIME(4T AT FAST RATE)

Fig. 4 DEFLECTION SWEEP OPERATING MODES

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APmLIED PHYSICS LABORATORYSILVER SPRING. MARYLAND

64 STEPS

T -SATELLITE TM

FRAME PERIOD

16T - TIME

T = FRAME PERIOD = - SECOND16

T/4 = 15.6 MSWORD

4

WORD

WORD

WORD

-- T/4

T (FRAME PERIOD)

Fig. 5 A TYPICAL ANALYZER SWEEP FOR SATELLITE SPIN RATES BELOW 4 RPM

- 13 -

THE JOHNS HOPINS UNIVERSITY

-%mLIED PHYSICS LABORATORYSiLVER SPRiNG MARYLAND

64 STEPS

T -SATELLITE TM

FRAME PERIOD

>-

zI

16T TIME

T/4

-T/16 --

- WORD-- WORD

1 2

Fig. 6 A TYPICAL ANALYZER SWEEP FOR SATELLITE SPIN RATES ABOVE 4 RPM

- 14 -



4. Deflection sweep calibration data, an 8-second

sequence, initiated by command, which mea-

sures and transmits the deflection sweep volt-

age at each step of the deflection sweep ramp.

Command System. The PES uses three relay pulsecommands, a logic pulse command, and a 12-bit logic com-

mand word.

One relay is in series with the 16 volt power line

to each of the two electron multiplier bias supplies. Con-

sequently either or both high-voltage supplies may be

turned off without affecting the operation of the rest of the

instrument. Since the 16 volt power comes from the PES

main converter, neither high-voltage supply can be turned

on unless the PES power is on.

The deflection sweep calibrator precludes particle

counting during the calibration sequence. As a safety pre-

caution, a relay is used to "enable" power to the calibra-

tor. If the calibrator fails in the active condition, the re-

lay is used to disable the calibrator power and thereby re-

turn the instrument to the particle counting mode.

In normal operation, the calibrator is enabled, but

the 8-second calibration sequence does not occur until the

cal initiate logic pulse command is sent.

The 12-bit PES logic command word is (in space-craft terms) part of the PES minor mode command word.

The word is used to make adjustments in the operatingmode of the instrument and covers the following items:

1. Three bits select the operating voltage of the

sensor No. 1 bias supply.

2. Three bits select the operating voltage of the

sensor No. 2 bias supply.

3. Three bits select one of the five energy rangemodes.

- 15 -



4. One bit selects fast or slow operation.

5. Two bits select data from the desired sensoror select the "Sensor Alternate" mode.

PES Data System. The PES digital data system con-sists of four 12-bit accumulators and four 12-bit temporarystorage registers. Each accumulator counts for one-fourthof a spacecraft main frame. At the beginning of each newframe, the data are parallel-transferred into temporarystorage and the accumulators are reset. Data are read outone frame after they are accumulated. This sequence issynchronized with the spacecraft telemetry system and isindependent of the operational mode of the experiment.Figure 7 illustrates the data system timing.

Data are transferred to temporary storage withinthe PES data system at the beginning of each frame. Par-ticle counting at this time is inhibited for 350 Cjs, which notonly allows adequate time for data transfer but also allowsadequate time for the sweep supply to return to zero at theend of its sweep.

Housekeeping. The PES is allotted six analog wordsthat are read every 8 seconds.

The PES signal ground and the 5 volt output fromthe secondary of the PES converter are monitored to verifyoverall instrument integrity and to indicate any offsetbetween the PES signal ground and the spacecraft ground.The 5 volt monitor is attenuated to 4 volts in order for thevoltage to fall within the range of the spacecraft A/D con-verter.

Two analog words are transmitted to indicate thevoltage applied to each electron multiplier. The signal isattenuated 1000:1, so that a 3 volt reading indicates anapplied bias of 3 kV.

Each PES sensor contains a thermistor that issecured with epoxy in an aluminum housing and mounted to

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,APPLIED PHYSICS LABORATORYSILVER SPRING. MARYLAND

ACCUMULATE 1ACCUMULATORS

PES WORD1 64 SECOND-350/.S 350lps INHIBITED

ACCUMULATEPES WORD 2

SSECOND

ACCUMULATEPES WORD 3 -C 1

64

ACCUMULATE - C 1PES WORD 4 64

MAIN FRAME 60/lSSYNC

TRANSFE 350PS

SPACECRAFT ENABLE WORDS 38, 39, 40 24(READ PES WORDS 1 AND 2 16384 SECOND

SPACECRAFT ENABLE WORDS 102, 103, 104 24(READ PES WORDS 3 AND 4) 16384 SECOND

Fig. 7 PARTICLE DATA TIMING

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T)4E JOHNS HOPKINS UNIVERSITY


the aluminum wall between the electron multiplier and thebias supply. The thermistor therefore gives a temperatureindicative of the average case temperature of the sensorelectronics.

Table 1 compares nominal voltage out of the bufferwith temperature within the sensor. Assuming a 5 ± 1 MOload, the voltage error caused by loading uncertainty is± 0. 04%, which is small compared with the design goal of1%. If either of the redundant outputs is shorted to ground,the voltage at the remaining output must be multiplied by1. 196 in order to use the table.

Table 1

Nominal Sensor Temperature MonitorCharacteristics

Input LoadedTemperature Nominal Output by 5 M2

(0C) (volts) (volts)

-40 4.822 4. 812-30 4.460 4.449-20 3. 970 3. 960-10 3. 385 3. 377

0 2. 756 2. 750+10 2. 156 2. 151+20 1. 634 1. 630+30 1. 214 1.211+40 0. 893 0. 890+50 0. 654 0. 653+60 0.481 0.480+70 0. 356 0. 355+80 0. 265 0. 265

DC/DC Converter. The PES main converter re-ceives power from the -24. 5 volt regulated spacecraft busand converts this to power at voltages between -130 and+160 volts. The converter features input current limiting,foldover current limiting, and an overvoltage protectioncircuit.

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There is no DC line regulation since the spacecraft'sregulation of 2%0 is adequate for most of the PES require-ments. Only the 10. 000 volt calibrator reference voltagerequires additional regulation.

DATA FORMAT

Main Frame Digital Data

The spacecraft main digital data telemetry framecontains 128 eight-bit words and repeats at a rate of 16frames per second. The PES is allotted words 38, 39,and 40 and words 102, 103, and 104, which are used tostore the four PES 12-bit particle data words (see Fig. 8).PES word 1 contains particle data accumulated during thefirst quarter of the previous frame, PES word 2 contains

particle data accumulated during the second quarter of theprevious frame, etc.

Subcom Analog Data

The six PES analog housekeeping words are located

in the 8-second subcom frame. This subcom uses word 68

of the main frame to transmit 128 different informationwords, of which subcom words 91 through 96 contain the

PES analog housekeeping data shown below:

PES Analog Item 8-Second Subcom Word

PES signal ground reference 91PES low-voltage monitor 92PES high-voltage monitor 1 93

PES high-voltage monitor 2 94PES sensor No. 1 temperature 95

PES sensor No. 2 temperature 96

Subcom Digital Data

The three PES relay status bits are also transmitted

on the experiment 8-second subcom. The word and bit

assignments are listed below:

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1 2 3 4 5 6 7 8

9 16

17 24

25 32

33 38 39 40

-PES WORD 2-- -.*-PES WORD 1

41 48

49 56

57 64

65 66 67 EXP 68 EXP 724-SECOND 8-SECONDSUBCOM SUBCOM

73 80

81 88

89 96

97 102 103 104--PES WORD 4 -*-PES WORD 3"

105 112

113 120

121 122 123 124 125 126 127 128

Fig. 8 PES PARTICLE DATA LOCATION IN THE AE-C MAIN FRAME (Frame Period = Second)-20 -Second)

-20-



8-Second SubcomPES Relay Status Bit Word Bit

PES high-voltage monitor 1 on/off 12 1PES high-voltage monitor 2 on/off 12 2PES calibration mode enable/disable 12 3

The PES also transmits a 16-bit status word con-taining bits that show the present instrument mode of opera-tion. This 16-bit word is transmitted once every 4 secondson main frame words 68 (8-second subcom) and 67 (4-sec-ond subcom). The 8- and 4-second subcom word enablesare joined to produce the required 16-bit enable. The bitassignments are shown below:

4-Second SubcomPES Digital Status Bit Word Bit

Spare 55 1Spare 55 2Spare 55 3

PES calibration mode on/off 55 4PES multiplier 2 gain bit 1 55 5PES multiplier 1 gain bit 3 55 6PES multiplier 1 gain bit 2 55 7PES multiplier 1 gain bit 1 55 8

8-Second SubcomWords Bit

PES mode select bit 1 55 and 119 1PES sweep rate fast/slow 55 and 119 2PES multiplier 2 gain bit 3 55 and 119 3PES multiplier 2 gain bit 2 55 and 119 4PES sensor alternate/alternate 55 and 119 5PES sensor No. 1 data/sensor

No. 2 data 55 and 119 6PES mode select bit 3 55 and 119 7PES mode select bit 2 55 and 119 8

-21 -



When the PES calibration mode on/off is "1, " thedeflection sweep calibrator is in operation, and calibra-tion data are read out as shown below:

8-SECOND SUBCOM SYNC 8SECONDS

CALIBRATOR IN OPERATION

CALIBRATION DATA READOUT ONE FRAME DELAY

4-SECOND SUBCOM WORD 55, BIT -FOUR FRAME DELAY

4 SAMPLED 1 1 0(PES CALIBRATION MODE ON/OFF)

The remaining subcom status bits verify that thePES 12-bit minor mode command word is correctly re-ceived at the instrument.

Minor Mode Commands

The spacecraft provides a 32-bit minor mode com-mand word to adjust the operating mode of the PES. Only12 of the available 32 bits are required, and the relation-ship of the PES minor mode command bits to the PES minormode command word is shown below:

THIS BIT IS RECEIVED FIRST

PES MINOR MODE 1 2 120 21 22 23 24 25 26 27 28 29 30 31 32COMMAND WORD I I I 1

12 11 10 9 8 7 6 5 4 3 2 1

PES MINOR MODE BIT NUMBERS

- 22 -

•HE JOHNS HOPKINS UNIVERSITY


The first three PES command bits select the operat-ing voltage of the sensor No. 1 bias supply as follows:

PES bit 1 0 1 0 1 0 1 0 1

PES bit 2 0 0 1 1 0 0 1 1

PES bit 3 0 0 0 0 1 1 1 1

Commandedhigh voltagemonitor 1 (kV) 3. 00 3. 21 3. 43 3. 65 3. 86 4. 07 4. 29 4. 50

The next three PES command bits similarly adjustthe high-voltage monitor 2 voltage. PES command bit 7 isused to set the PES deflection sweep rate:

Fast sweep rate = "1"Slow sweep rate = "0"

Bits 8, 9, and 10 select one of the five energy sweeps asfollows:

PES bit 8 0 1 0 1 0 1 0 1

PES bit 9 0 1 1 0 0 0 1 1PES bit 10 1 0 0 0 0 1 1 1

Sweep Mode I II III IV V *

where

Sweep Mode Sweep Sequence

I ABACABAC..II ACAC.......III AAAA.......

IV BBBB.......V CCCC.......

and A = 0 to 25 eV, B = 0 to 100 eV, and C = 0 to 500 eV.

These conditions are considered "illegal. " If they aresent,. the experiment will be placed in Sweep Mode V.

- 23 -

THl JC'lMNS HOPKINS UNIVERSITY

APPLIED PHYSICS LABORATORY"'LV~" 5""1"0, lII ...."L.....O

PES bits 11 and 12 are used to seLect data from thedesired sensor or to select the sensor aLternate mode. Inthe sensor alternate mode, these bits are used in conjunction with an 8-second squarewave (128 T s ) that is synchronized with the 8-second subcom. The mode is selected asfollows:

Command Bits Sensor SeLectedBit 11 Bit 12

128 TSensor No. 1 Sensor No. 2s

0 0 0 X1 0 0 X1 1 0 X1 1 1 X

¢ = Do not careX = Sensor active

SPECIFICATIONS AND PERFORMANCE

Serial Numbers

The PES assemblies are numbered sequentiaLLy,SN01 through SN06 for the sensors, and SN01 through SN03for the main electronics. The experiment serial numbersare three-digit numbers derived from the assembly serialnumbers. The seriaL number for sensor No. 1 (the remote sensor) appears first, followed by the seriaL numberfor sensor No.2 (Located on top of the main electronics)and finally the main electronics number. For example, ifsensor No. 1 is SN06, sensor No. 2 is SN02, and the mainelectronics is SN03, then the experiment serial number is:

SERIAL NO. 623

~I~SENSOR NO.1

SERIAL NO.

SENSOR NO.2

SERIAL NO.

- 24 -

MAIN ELECTRONICS

SERIAL NO.


APPLIED PHYSICS LABORATORY

Dimensions, Look Angle, and Alignment

The experiment dimensions are shown in Figs. 9and 10. The location of the center of gravity of eachassembly is also indicated.

The sensor surface, which is flush with the thermallight shield, is the reference for collimator and hemispheres. It is therefore used during the optical alignmentof the experiment. The perpendicular to this surface isset at go ± 1° with respect to the spacecraft +X axis forsensor No. 1 and 18go ± 1° for sensor No.2. This allows4-1/2° of clearance between the sensor field of view andthe outer spacecraft surface.

The sensor field of view is go by 20°, as shown inFig. 9.

'J<Weight

PresentSerial Nos.

SN121SN342SN563

ExperimentDesignahon

Protoflight instrumentFirst flight instrumentSecond flight instrument

Sensor No. 1

1338 g*'"1274 g1266 g

Sensor No. 2 plusMain Electronics

2827 g**2771 g2761 g

*Weights include the thermal shields and the test connectorcover but not the external cables.

'J<*Sensors SN01 and SN02 use Kel-F (2. 1 glee) and the orig-inal thermal shields. Sensors SN03 through SN06 useVespel-1 0.4 glee) and the modified thermal shields(which are lighter than the original design).

- 25 -

l-I-m

T 74

t. -r-- 2.,8°__0. -3000- T4 7

.F I RAAC - I /

cooo

3. 090 D 2

.25 zIK-.5

Fig. 9 OUTLINE DRAWING OF PHOTOELECTRON SPECTROMETERSENSOR ASSEMBLYSENSOR ASSEMBLY


SILVER SPRING. MARYLAND

o .DBM-25P (JZ)LOOK .

_ DBM-2ss (3s4 .25 TkERAL. o (390FROM OM-ZSS (J 4)

TI .50 CALE r/ e 4

II

4.o4. Z 4

3.105

I l :J il1 I- O

=.. 970

O "A3.150 ./444TEEROMAL LIGHT S2IE AND AEECoR O

.250 -

D.5M-5 P(AC)

/ 4ootIf/a/ 5./E.< 1111/-Es:,ei.'lel/ / e.,1,e T ./Y - - ,- (,/4/#

oll4r ® 0 I qce - &

. 1

.)55 SPAcE..

4.500

3.940

1.000

.70 L

3.200TY

4. GO TyP

SG.00) .

Fig. 10 OUTLINE DRAWING OF PHOTOELECTRON SPECTROMETERSENSOR NO. 2 AND MAIN ELECTRONICS

- 27-



Power Consumption

Experiment Configuration Current DrainHigh-Voltage High-Voltage Calibrator from -24. 5 Volt Bus (mA)

Monitor 1 Monitor 2 SN121 SN342 SN563

Off Off Off 80 80 81Off Off On 105 105 106

NormalOperating 3. 86 kV 3. 86 kV Off 103 103 105Condition

4.5 kV 4. 5 kV Off 108 108 110

Energy Scale Calibration

Calibration data taken at The Johns Hopkins Univer-sity indicate that the six PES sensors exhibit full-scaleenergies that are within the following limits:

Theoretical full-scale energy (eV) 25 100 500

Measured full-scale energy (eV) 24. 6 ±4% 96 ±2% 445 ±3%

Radioactive Source Calibration

Data taken during thermal vacuum tests at GSFC indi-cate the following radioactive source counting rates:

Sensor Radioactive Count RateSerial No. Source Serial No. (counts/s)

01 VIII 2. 002 II 2.003 VII 2.004 VI 1.505 III 2. O006 IV 1.5

Counting Rate

The preamplifiers are designed to rate limit at250 000 pps. The actual output count rate versus inputparticle rate for each sensor is somewhat lower becauseof interaction between the discriminator and buffer circuits.A rate calibration is presently being done at JHU, andcurves will be available for each sensor.

-29-jgyjoTz~



Dead Time

Particle counting is inhibited for 350 gs at the startof each main frame.

Angular Resolution/Data Rate

The PES data rate is 64 12-bit words per second.This corresponds to one energy sweep per second in thePES slow sweep rate mode and four sweeps per second inthe PES fast sweep rate mode, resulting in the followingangular resolution:

Satellite Angular ResolutionSpin per SweepRate Slow Sweep Fast Sweep

1 RPM 60 1. 504 RPM 240 60

Thermal Analysis

The PES main electronics assembly is entirelywithin the spacecraft and will exhibit a temperature that isvery similar to the upper baseplate temperature (nominally+16 0C).

A 22-node mathematical thermal model** was usedto estimate the temperature variations in the PES sensor.During the aerodynamic heating caused by the spacecraftspinning at 1 RPM in a 120-km perigee, 3800-km apogeeorbit, the PES sensor outer metal parts (far removed fromany electronic parts) will reach a temperature as high as+54*C. The temperature of the main sensor structuralmember, which holds the electronic subassemblies, risessmoothly from +160 to +30 0 C, as shown in Fig. 11.

*Recent spacecraft measurements indicate that all tem-peratures in this section should be increased by about100C (including Figs. 11 and 12).

**Prepared for GSFC by Fairchild Industries under con-tract NAS5-11823PC402-65428.

- 30-


AP'LIED PHYSICS LABORATORYSILVER SPRING. MARYLAND

OF OC

130o I I I I I 54

PERIGEE = 120 KM

SPACECRAFT SPINNINGAT 1 RPM

50

SENSORMAGNETICSHIELD(EXTERNAL TOSPACECRAFT)

110 -

w - 40

I-

< 100 -

IL

90 -

30

SENSORALUMINUMBASE PLATE

80 - (INDICATIVE OFELECTRONICSTEMPERATURES)

70 -- 20

60

I

0 1 2 3 4 5 6 7 8 9 10 11 12

TIME FROM START OF AERODYNAMIC HEATING (minutes)

Fig. 11 SENSOR TEMPERATURE CHANGE CAUSED BY AERODYNAMIC HEATING

- 31-



When the spacecraft is spinning at 1 RPO (revolu-tion per orbit) in a 150-km perigee, 3800-km apogee orbit,solar heating causes the sensor temperature to change fromapproximately 150 to 25 0C, as shown in Fig. 12.

Stress Analysis

A stress analysis (Ref. 5) was undertaken to estab-lish the capability of the PES instrument to withstand theAE-C protoflight vibration levels listed in Table 2. Subse-quent environmental tests verified the integrity of themechanical design.

Table 2

Experiment Protoflight Level Vibrationand Acceleration Limits

Protoflight Vibration Test

Random" Sinusoidal "

Parameter (Three Orthogonal Axes) (Three Orthogonal Axes)

Bandwidth 20-2000 Hz 5-2000 HzDuration 2 minutes/axis 4 octaves/minVibration level 0. 2 g2 /Hz (20 g rms) 10 g, 0 to peak

A 12-dB/octave minimum rolloff shall be applied at both ends of thefrequency bandwidth. Prior to testing, the prototype component andvibration facility shall be equalized for a flat response within ±3 dBwith a low-level vibration input (1. 5 g rms maximum) for eachorthogonal axis. An equalization plot shall be obtained for eachaxis and held on record.

When the specified accelerations cannot be attained because ofarmature displacement limitations, the input may be a constantdisplacement not less than 0. 5 inch, double amplitude.

Protoflight Steady-State Acceleration Test

Description Level (g) Duration No. of(minutes) Tests

Positive, in each of three axes 24 ± 2 1 ± 0. 1 1Negative, in each of three axes 24 ± 2 1 ± 0. 1 1

-32 -


AP DLIED PHYSICS LABORATORYSILVER SPRING. MARYLAND

OF OC90 I 32.2

SOLAR-,INPUT

EARTH

PERIGEE = 150 KM

SPACECRAFT SPINNING AT 1 RPO

VELOCITY VECTOR80 - SENSOR 26.7, MAGNETICo90o SHIELD

I-I

EXPERIMENT

: SENSOR- ALUMINUM

- 70 - BASE PLATE - 21.1

60 - 15.5

50o I I I I 100 20 40 60 80 100 120

ww TIME (minutes)

Fig. 12 SENSOR TEMPERATURE CHANGE CAUSED BY SOLAR HEATING

- 33 -



2. CIRCUIT DESCRIPTION

ELECTRON MULTIPLIER

The PES electron multiplier is a MM-1-5NG focusedmesh type manufactured by Johnston Laboratories. It is a20-stage secondary emission electron multiplier and usesactivated copper-beryllium dynodes, each of which has manycusp-shaped surfaces separated by holes. A cross-sectionalview is shown in Fig. 13. Attached to all dynodes except thefirst is a guard plate with many holes exactly aligned withthe points of the cusps. Adjacent dynodes are separated byceramic insulators and connected electrically by 5 MQ inter-dynode resistors. The first dynode differs from all theothers in that it has a very fine, high-transmission meshplaced in front of it. This mesh is biased positively withrespect to ground via a 10 MQ resistor and negatively withrespect to the first dynode via a 1. 5 MQ resistor. Thusparticles are accelerated from the analyzer toward the firstdynode with a net voltage of:

11.5 MDxV 0. 1 V

R BMQ bias ~ biasB

where RB is the total bias resistance of 112. 8 MQ, includingfilter and protection resistors. For example, if 4000 voltsbias is applied, the electron energy is increased by 400 eVbefore it strikes the first dynode. Since the grid is nega-tively biased with respect to the first dynode, the secondaryelectrons are driven toward the second dynode, and so on.

The bias and filter resistors are located on a Vespel-1board mounted at the anode end of the multiplier (see Fig.14). R4 and C3 make up the final stage of a three-sectionRC filter that reduces the ripple on the bias line to lessthan 0. 5 mV. The first two filter stages are in the biassupply. R3 is part of a voltage-limiting circuit that pro-tects the preamplifier input stage from damage caused by

35- ,,i , ' ij o-



INPUT PARTICLES OR PHOTONS

MESH

I I I I I I I IPLATES1 GUARD

I I I., I Ik," IPLATE

TYPICAL PATHS OF SECONDARY ELECTRONS

(a) LONGITUDINAL CROSS SECTION THROUGH FOCUSED MESH MULTIPLIER

r ,- DYNODES -- \ 5M 2 _1 2 3 19 2C4 GUARD

1* RING

* •I I I4 " I BACK

i* IPLATE

1.5M92 5M41 5M 5M2 5M 5MISUPPRESSOR GUARD PLATE ANODE BACK

GRID (TYPICAL) PLATE

(b) ELECTRICAL CONNECTIONS TO MM-1-5NG MULTIPLIER

Fig. 13 SCHEMATIC CROSS SECTIONS OF THE MM-1-5NG ELECTRON MULTIPLIER

- 36 -


.PPLIED PHYSICS LABORATORYSILVER SPRING MARYLAND

NOTES: UNLESS OTHERWISE SPECIFIED.1. ALL RESISTORS ARE 1/8W, 1%

R2

A R FEEDBACK

ELECTRON 10M,%W,1% FROM MULTIPLIER

MULTIPLIER SCREEN SCREEN

Cl39 pF SIGNAL GRD

C2 R3

ANODE O860 pF 150 PREAMPLIFIER

I INPUTR1100 K

R4

BACK PLATE - O HIGH VOLTAGE

383K

860 pF C3

Fig. 14 SCHEMATIC DIAGRAM OF ELECTRON MULTIPLIERINTERFACE BOARD

- 37 -



arcing. The remaining limiting components are on the pre-amplifier board mounted in a separate compartment con-taining no high voltages.

ANALOG ELECTRONICS

The PES analog electronics* consists of a charge-sensitive preamplifier, a pair of amplifiers, a voltage dis-criminator, and an output buffer, as shown in Fig. 15.

Preamplifier

The preamplifier collects the charge appearing atthe electron multiplier anode and produces a voltage out-put proportional to the magnitude of charge collected.Coupling between the multiplier and the preamplifier isthrough a 6 kV, 860 pF capacitor.

A network containing CR1, CR2, RI, and a resistormounted with the electron multiplier is used to protect thepreamplifier input transistor from damage caused bycorona discharge in the multiplier compartment.

The basic components of the preamplifier circuitare a field-effect transistor, Q1, driving a common basestage, Q2, with the collector load bootstrapped by an emit-ter follower, Q3. The value of the feedback capacitor, C3,establishes the preamplifier sensitivity at approximately30 nV per electron. The overall current drain is 2. 2 mAfrom the +6 volt supply and 0.8 mA from the -6 volt supply,or 18 mW total.

Pulse Amplifiers

The output signal from the preamplifier is processedby a cascaded pair of pulse amplifiers before being applied

The analog electronics circuit design was done by S. A.Gary (Ref. 6).

- 38 -



eZ4224

RIC. R/ / R /oZ -/7

2 t 4 C C17

A..30.~.4 + z/7 8 ,

.01.T 4To+W CR4 15___ _wr _e_

SIT D + or t 019CR1 I 40- l. 3 oo~,+ zo ,,

. ,. 09- +C1 R0.I -NPU 4 I4F- 47 0c3

1 C R9 r-- N 4 ZUFFE

S L 5 o 5/OUTPuT AOTES: --5s Pct/s'o orWA6'5e

C.2. IR I _ T c 1 06 lez 9

3- 39-

- 2.o4_v 2o Q3 -3+W

RNPo -62N4208

,O -W 22222A

1P2 _ _ __ - 2N2 Z 2907A

Z/Z2 - CMEo/or

Fig. 15 SCHEMATIC DIAGRAM OF ANALOG ELECTRONICS

- 39 -

LapF ZOF/4e zSIG Gqo Z~Z/L

Fig15 CHMATC DAGAM FANLO



to the pulse height discriminator. The amplifiers arehybrid integrated circuits with decoupling and feedbackelements connected externally. Figure 16 is a schematicdrawing of the internal circuitry for these amplifiers.

Both amplifiers are connected in a noninvertingconfiguration (see Fig. 15) with a DC feedback ratio of 23(determined by R13, R14, R18, and R19). Inputs to eachstage are through RC differentiation networks (C7, R9 andC13, R15) having equal time constants of 220 ns. The firstamplifier stage contains a capacitor, C12, in parallel withthe feedback resistor to yield a single integrating timeconstant at 220 ns. Dynamic stability considerations re-quire the compensation capacitor, C9, in the integratingstage.

The recovery time for return of the amplifier towithin the system noise level is 3. 0 As for a signal of 107electrons and 3. 5 As for 2. 0 x 107 electrons.

Power consumption for the amplifier pair is 3. 8mA from each of the supply voltages, or 45 mW total. Thepreamplifier and amplifiers account for most of the systemtemperature drift, which is on the order of 5% gain varia-tion between -200 and +50 0 C and 10% between -300 and +50 0 C.This is adequate for the experiment objectives.

Pulse Height Discriminator

The output of the second amplifier is coupled to thediscriminator through the capacitor, C15. The transistorpair, Q4, serves as a differential comparator between theanalog signal amplitude and a DC reference voltage set byR27 and R28. Feedback through R29 turns on Q6, reduc-ing the reference voltage and causing regeneration. In theon state, Q6 is in saturation and the reference is within afew millivolts of zero. When the input voltage goes throughits zero crossover, regeneration in the opposite directiontakes place and the circuit returns to the quiescent state.

- 41 - PRECEDING PAGE BLANK NOT FIL-4-NOTn4



V+ 4

2.2k OCOMPENSATION

NONINVERTING 1INPUT

7 OUTPUTINVERTING 3 0

INPUT

1k 20k 10k

V- 8

1 -14 t

- INCH8

7 8

INCHFig. 16 PHOTOELECTRON SPECTROMETER HYBRID AMPLIFIER

- 42 -


APPLIED PHYSICS LABORATORYSILVER SPRING, MARYLAND

The dead time associated with the discriminator istherefore governed primarily by the shape of the amplifiersignal and is equal to the width of the positive lobe, or500 ns under nonoverload conditions. This leads to a maxi-mum repetition rate for the discrimination of 2 MHz.

The nominal design value for the Q4 reference levelis 200 mV, corresponding to 1. 0 x 105 electrons at thepreamplifier input.

Output Buffer

The output buffer serves a dual function. It con-verts counts from the discriminator into pulses of fixedamplitude, width, and transition time from a low imped-ance source, suitable for coupling into the data systemthrough a long transmission line. In addition, it limitsthe experiment counting rate by establishing a fixed deadtime between successive counts. The relation between thedata system count rate and the electron intensity incidenton the multiplier is thus determined by the characteristicsof the output buffer.

ELECTRON MULTIPLIER BIAS SUPPLY

The electron multiplier bias supply (Ref. 7) (seeFig. 17) consists of a tuned-transformer sinewave oscil-lator (Q11 and Q12), which provides a 500 to 600 voltspeak-to-peak sinewave at the secondary of T1. The sec-ondary drives a Cockcroft-Walton multiplier, which de-velops a 4. 5 kV maximum output to bias the electron multi-plier. A resistive divider taken from the multiplier screenproduces a known fraction of the high voltage output, whichis buffered by AR2 and fed back to AR1 via R21 and R22where it is compared to a reference voltage (set by CR1).An error signal thereby produced controls the multiplierbias.

The feedback ratio is changed by switching any orall of R27, R32, or R36 across R22. The result is seven

- 43 -

THE JOHNS HOPKINS UNIVERSITYAPPLIED PHYSICS LABORATORYSILVER SPRING. MARYLAND

(-)V ,2 oo jr c I

LOUP

S-42 R43 FEEDBACK FROM15 -I MULTIPLIER SCREE.E

+tGV O C__- 09 R2G R29R 2 R - 50V P " - U , . I75 AWV MONITOR A - - -5V MON .TOR A0 RC14 CIG C15 C ? Co P2 C4 C2G C 1 C5o Csz

WV MONITOR B 4 R lo.1l)F C_ .

I.V 2N 5 V R3 CR5 CR7 CR CR CRhI CRIS CR7 CRS CR

1 ZOK -3 7\G VOLTAGE( R o 20o.oK TP) B5 G35,Q-4 " o-r : esG oP

IY 2N70G - v -G-L

..5v,, 4.02 .. .+1+ C5*F 0' 12ov 0.Iu :IouF 4 NODE A oV FLI

"it 20-_ N A. O L -47

4.3K 18 74 LZR25 R27 RBI RS3 "R35 R3NG 0 2499+ C IM 18.7K IM 9.3 IM 4.534 Qi 1V

O.lup TooPF 2 Pi9 2N511G s 2N51 G 2N511rO o 9SIGSAL GROUND

I 5K QG 4 v3- D j 40 5* GooT

7 ISOT 30T 020.OK RZj P24 R2 R-30 R63 R3451K looK K IOOK 511K 1ook 2Nc499 r

MULT GAIN BIT I 7 7

MULT GAIN BIT 2 \/4]

MUL GAIN BIT 3

10 NV OSCILLATOR TEST

NOTES-UNLES6 OTHERWISE SPECIFIED:

I. ALL RESISTORS ARE -oW %.2.ALL RESISTORS MARKED * ARE -W,5%I. EST REIFSI3.ALL DIODES ARE MW402s2KV, P V. R43 Ca

.4.ALL CAPACITORS ARE IOOOP \,KV. c I - I5.ALL TRANSISTORS ARE 2N222ZA. ARz FL3G.OPERATOINAL AMPLIFIER S (ARI ARZ) ARE LMIOBH.7. CORES FOR LI +TI ARE FERROXCUE 2213-3B7.S. FILTERS( LI,FLZFLS) ARE FERRITE SEADS SG-590-GS-3B.9.TAILOR. Rc9 BY SETTING RI9 AT APPROX 2.5K AND

TAILORING R9 TO MAKE NODE A POTENTIAL ABOUT I.OOV.IO.SET POTENTIAL AT NODE A TO I.OOOV BY AD OUSTNG RI9.\I.TALOR PRZG AFTER SELECTING R9 AND ADJUSTING R19.

CHOOSE R2G SUCH T AT HV MONITOR = 4.SV WHEI "V OUTPUT= 4.5KV UNDER 10 MEGO LOAD.

Fig. 17 SCHEMATIC DIAGRAM OF ELECTRON MULTIPLIER BIASSUPPLY

- 45 -PRECEDIG AG BLANK NOT FMED



equal bias increments from 3 to 4. 5 kV. The FET switchesare controlled by three minor mode commands, multipliergain bits 1, 2, and 3. The electron multiplier bias as afunction of command state is shown in Table 3.

Table 3

Electron Multiplier Bias as a Function ofCommand State

Multiplier gain bit 1 0 1 0 1 0 1 0 1Multiplier gain bit 2 0 0 1 1 0 0 1 1Multiplier gain bit 3 0 0 0 0 1 1 1 1Electron multiplier

bias (kV) 3. 0 3. 21 3.43 3. 65 3. 86 4.07 4. 29 4. 5

A current-limiting signal developed across R16,R17, and R18 forward-biases the emitter-base junction ofQ4 when the load current exceeds about 40 mA at room tem-perature. R12 and R14 provide an additional feedback volt-age that is proportional to the output voltage. As the out-put voltage drops, R12 and R14 further limit the current,thus reducing the power dissipation in the series passtransistor, Q2. The equation describing the limiting cir-cuit is:

R14V = R I + (16 - V R14be po o R20 + R14 + R

p

where

Vbe = the Q14 base-to-emitter voltage,

Vo, I° = oscillator drive voltage and current, and

R = R16//R17//R18.p

Substituting the actual resistor values yields:

V be 11 x 103 I - 0. 015 V + 0. 240.

- 47 -

ReUDING PAGE BiAui. i'ul i.±



Q4 turns on when Vbe is about 500 mV, and the nominalvoltage/current charcteristics are shown in Fig. 18. Thetemperature dependence is due to Vbe shift.

A high-voltage monitor is telemetered as one ofthe PES 8-second analog subcom words. The redundantoutputs (R2 and R3) are voltage-limited to 8 volts by CR22to protect the spacecraft A/D converter if a PES malfunc-tion shorts R7 to +16 volts. A drive voltage of 4. 5 kVyields a 4. 5 volt monitor voltage.

CR23 is used to protect AR3 in case arcing in theelectron multiplier chamber causes excessive voltagetransients at the R43 terminal.

The Cockcroft-Walton multiplier is electrostati-cally shielded from the tuned oscillator to prevent pickup.A double RC filter reduces the ripple on the high-voltageoutput to about 40 mV peak to peak. A third RC filterlocated at the electron multiplier reduces the ripple toless than 0. 5 mV peak to peak. The high-voltage powersupply leads are returned directly to the +16 volt return,eliminating ground loops through the electron multiplier.

The oscillator draws about 22 mA at 12 volts anddelivers 40 AA at 4. 5 kV. The oscillator efficiency istherefore about 75%. The control circuitry requires about3 to 4 volts to operate the series pass transistor, and con-sequently the bias supply power consumption is about 360mV when operating at 4. 5 kV. The power drain is reducedto about 250 mW when operating at 3. 0 kV.

INPUT-OUTPUT BOARD

Certain interface and miscellaneous circuits inthe PES cannot be conveniently packaged in any of the ex-periment subassemblies. Instead these circuits aremounted in a separate subassembly called the input-outputboard. These circuits consist of the main frame sync buf-fer and one-shot, the thermistor No. 1 and thermistor

- 48 -


pcPLIED PHYSICS LABORATORYSILVER SPRING. MARYLAND

14

SHORT CIRCUIT FEEDBACK CURRENT = 0

4o-

12

0 10 20 30 40 50 60 70

> 8

OSCILLATOR CURRENT DRAIN,

-J

0 2 /

Fig. 18 TUNED OSCILLATOR VOLTAGE/CURRENT CHARACTERISTICS

- 49 -



No. 2 buffers, and the relays for the +16 volt switchedNo. 1 and +16 volt switched No. 2 voltages. Figure 19 isa schematic of the input-output board.

PES Main Frame Synchronization

The main frame sync buffer is the standard inter-face circuit required in GSFC Specification SK-2260216.The sync signal from U1 pin 3 passes through an overridegate. In normal operation, pins 1 and 2 of U1 are pulledhigh by R8, and the override gate acts as an inverter. Themain frame sync signal (from the satellite) triggers a3 5 0 -1s one-shot, which is constructed from the remaininggates of U1 and U2. In the override condition, U2 pin 3 isforced high by grounding pins 1 and 2 of U2, and the 350-As one-shot is triggered only by the main frame sync over-ride signal, which is generated in the PES ground supportequipment (GSE).

The buffered and stretched main frame sync signalis renamed "T" and is used to parallel-dump data in thePES command and digital data systems. T goes high whenthe main frame sync goes active. It remains high for atime determined primarily by C14, R28, and R29. Thepulse width variation caused by temperature and power sup-ply changes is shown in Table 4.

Table 4

Variation of 3 5 0 -ps One-Shot Pulse Widthas a Function of Power Supply Voltage and

Temperature

Pulse Width Variation (us)Power Supply Voltage

Temperature +4. 5 +5. 0 +5. 5

+600C 360 337 315+400C 365 340 320+25 0C 370 350 325+100C 380 355 330-200C 387 360 340-500C 390 365 340

- 50 -

-u

L)~~~~~( .0. I Z!0<'

z~~~ I .7

MAIN FRAME 15,(NC 15u i 8 6 (

MAINI FRAMEE SYNCi

OVERA~iDE ENAZLE.cr _ 'p pit c

vr -tr RO SENSOR I TEMP Z;

T&ER 6 7,~ 2tLJ 75 OK rC 3. L +E I T0 . M AR4.I.(E 10 0 K 14R E - B

24.1-K 8.7 C I bS N O .Z T M .~~ E 0 N 40 11 N 4I

PN.0 0.01750K C-RE9.21 <a10 P; 1. AL RE I S PINE -LF.I W I IGAR

v 1 2Z SENSOR. 2 TEMP G.OPE.A TIONAL O.MPLI~iE;S ARI*A.R2,TIAEqmiSToR~l2 23 R7 . IRZ 4 MA-- I._5 (NCe) A.P-E LMtOSP,.

21.)V9P10 9 G C1.0 RZ3Ti4FRMISTORl R< -AF ..CSN 78.0 cs- sVF 28 +5vRETURNZ TZ4 0 1. C5-

IAV "'I ON/OFF 4( 7( LO 50TAG MONTOR

WV~l ON (r-.) 5( 4A(E -1 7.7~L-. 10.0~o

+IG 9 ... I LOW VOLTA.GE MONITOP.

-R .01< (2Az- B)Lfl

KZ2 422-18 LLL3I +16(/ >7 SPARE

IAV-2 ON/OFF: IZ - 7 z(F- -) E )s +IG l

I-It2 ON (c.-() it 5- E.CGZ 0 -s.kiI( IN~~HV""2ZOFF (C1-) 113 - lo 9rV -- 17 SIGNA~L GIZO RR147 (AI-A.) .

C5 CR% f-w -- .1 SIGNAL G;.0 REF oo 7 E~AD 017,ENTAION

COMMA~ND GRO Z b1-.V (esoT v I E-

R(44 IO.OOV REF z1§)(I.-V

C-) C.V

SIGN6,L 10

Q RD 2G

27

Fig. 19 SCHEMATIC DIAGRAM OF INPUT-OUTPUT BOARD



Temperature Sensors

Each PES sensor contains a thermistor that is se-cured with epoxy in an aluminum housing and mounted tothe aluminum wall between the electron multiplier and thebias supply. The thermistor therefore gives a temperatureindicative of the average case temperature of the sensorelectronics.

Table 1 compares nominal voltage out of the bufferwith temperature within the sensor. Assuming a 5 ± 1 MQload, the voltage error caused by Loading uncertainty is

±0. 04%, which is small compared with the design goal of1%. If either of the redundant outputs is shorted to ground,the voltage at the remaining output must be multiplied by1. 196 in order to use the table.

Command Relays

The command relays, K1 and K2, supply or remove+16 volt power to the sensor No. 1 and No. 2 electron multi-plier bias supplies, respectively. They are Teledyne Inc.No. 422-18 latching relays, which have a nominal DC coilresistance of 1130 ohms and a maximum required pulsewidth of 1. 5 ms at the nominal coil voltage of 18 volts. Therelay will activate at any voltage between 13. 5 and 24 volts.Redundant clamping diodes and flag contacts are providedin accordance with GSFC Specification SK-2260216.

A resistive divider (R21 and R22) monitors the +5volt line from the main power supply. The information istelemetered as one of the PES 8-second subcom analog words.The signal ground reference is also telemetered (R26 andR27) to monitor the offset between the spacecraft A/D con-verter ground and the PES signal ground as well as the off-set voltage of the A/D converter.

MINOR MODE COMMAND SYSTEM

Commands that make small adjustments to experi-ment operational modes aboard the AE-C satellite are

- 52 -



classified as minor mode commands. This section describesthe electronics that receive the PES minor mode commandword and produce a 16-bit word indicating the mode status ofthe experiment.

The command word is 32 bits long, as shown inFig. 20.

The command word is clocked into a 12-bit shiftregister (U6, U9, U12) in the PES minor mode commandsystem (see Fig. 21).

When the 34 command clock pulses stop, the de-sired PES command word resides in the shift register.The enable command word signal that brackets the clockpulses parallel-enters the command word into U5, U8, andU11, which distribute the commands to the experiment sub-assemblies.

The last 12 bits of the PES command word performthe functions listed in Table 5, which are discussed in thewriteup of each applicable subassembly.

Table 5

Minor Mode Command Functions

PES Bit No. PES Command Function

1 Multiplier 1 gain bit 12 Multiplier 1 gain bit 23 Multiplier 1 gain bit 34 Multiplier 2 gain bit 15 Multiplier 2 gain bit 26 Multiplier 2 gain bit 37 Sweep rate, fast/slow8 Mode select bit 19 Mode select bit 2

10 Mode select bit 311 Sensor No. 1 (only)/Sensor No. 2 (only)12 Sensor alternate/alternate

- 53 -



ENABLE

COMMAND WORD 15S MAXIMUM

MINOR MODECOMMAND WORD . .N. cjCN I -N (ON N (CN NN (N CNmo

PES BIT NOS.oUNUSED BITS

PES COMMANDS PES BIT NOS.

500 S -- 250 /S

COMMAND CLOCK1000 BPS

Fig. 20 PES MINOR MODE COMMAND BITS AND CLOCK TIMING

- 54 -

THE JOHNS HOPKINS UNIVERSITY -FOLDOl -UTAPPLIED PHYSICS LABORATORY

SILVER SPRING. MARYLAND F'ILDOUT FRAAM! ,

MULT *I GAIN BIT I 13

MULT 'I GAIN SIT 8

MULT 'I GAIN BIT 24(

MULT *2 GAIN BIT I 23

MULT ZGAIN %TT z 32(

MULT * GAIN BIT 3 15

SWEEP RATE IU4G4JLOW31

MODE SELECT BIT I 14

MODE SEL.ECT BIT 2 34 +sy,

MODE SELECT BIT 5 17

SENSORI OuNL.Y/SENsoR O#oLY ywe% +sYFSENSoR -~ EZWA' 6 44

ALTERN4ATE 422K CZ Z1. 2 1 6 9 0 .2 'A 6"a s. lt

+ sv 28+MOE5 o U o COMMAND WORD OT- U ES-UNLESS OTERWISL SPECIFIED:

o oU.Ts, ,4 ' o. L EG/ / TE D C//(.TS ARE:o S14541LO - UIU17,U15

R C +5F _ _ SNSLOO- U43,U TUtS. S L95N -S4 T4. U U044.2-2K .C' R14 5N 4L73- U14

S2 COMMAN 2. ALL TRASISTOR AE 2N222ZAo < 1 / o u l - 4 4 +1,.. 2 WO N" ALL DIODES ARE IN4I15.

/Ut WOD us tSulz 3 L5 4.1.C.POWER 15 PIN 4 +SV,;,PI:N I SIG G,,D.

C6&L 5o Ur1kooFI 5.ALL RESISTORS ARE rvWI %cL MODE ON/OrFF 18 -- o W 20 Pr

SPARE BIT 19 ' I U5

PARE BIT 21 1 1 3 4 12 - . COMMAND

Ull Is Rr. CR4 5004.22Y SUBsCOM

- DIGITAL DATA ASIGNAL IR RIGROUND 2 Q V 4 Zoo

za 3 3 -2 3 4 9

l 7 1 7) a R)-I DIGI TAL OATA Is

CLc< , ,Iuus ' U -U-- DIGITAL. DA A20( C3 ,o R 0

4.2 . 4U.22

CLOCK-GV 25<

+ ov REF 29 <+ CV 30<

SPARE II <

Fig.21 SCHEMATIC DIAGRAM OF MINOR MODE COMMAND

SYSTEM- 55 -



The commands received in the experiment areparallel-dumped into U4, U7, and U10 at the beginning ofeach frame by the buffered main frame sync signal, T (seeFig. 22). These bits are read as part of the PES subcomdigital data and are used to verify proper receipt of the PEScommand word.

A cal enable/disable signal indicates when +16 voltpower is made available to the calibrator. Should a cali-brator malfunction occur, a cal disable relay command willbe sent, and +16 volt power is removed from the calibrator.In addition, a cal mode on/off signal indicates when the cali-brator is in use, i. e., when it is drawing current from the+16 volt line. Both the cal enable/disable and the cal modeon/off indicators are telemetered as part of the PES 16-bitsubcom digital data word.

A 16-bit-long enable subcom digital data signal isrequired from the spacecraft to read the PES subcom digitaldata. Readout occurs at a 4-second rate on word 55 of the64-word subcom and words 55 and 119 of the 128-word sub-com (see Fig. 23).

The minor mode command system power consump-tion is 230 mW at +5 volts.

DEFLECTION SWEEP SUPPLY

The sweep voltages for the analyzer hemispheresare obtained from the digital staircase generator"' shownschematically in Fig. 24.

D/A Converter

The transistor switches, Q1 through Q14, the pre-cision resistors, R27 through R33, and the AR1 summingamplifier constitute the D/A converter that is the basis for

The PES deflection sweep supply and associated controllogic were designed by R. W. Young (Ref. 8).

-57-



3511 SECOND16

350 1 S

. 1 I .T non -aaaBL[L1I~l~l --- __ - IIIIRLRI1

CLOCK 2

LOADU4, U7, U1O, U13 1J JUJ13

Fig. 22 CLOCK TIMING FOR THE SUBCOM DIGITAL DATA PARALLEL LOAD

-58 -



ENABLE WORD 55 - 4SECONDSOF 64 WORD 8

SUBCOM 84 SECOND

ENABLE WORD 55OF 128WORD SECOND

SUBCOM 16384

ENABLE WORD 119 8 SECONDS eOF 128 WORD

SUBCOM

ENABLE PES SUBCOM SECONDDIGITAL DATA 1

Fig. 23 TIMING FOR THE PES SUBCOM DIGITAL DATA ENABLE SIGNALS

- 59 -

THE JOHNS HOPKINS UNIVERSITY 90JY ,.OJT FRAMW EAPPLIED PHYSICS LABORATORY


49 R57 RGI (46 I%R7 3

_ I 0 7 )/6 POSITIVE SWEEP MONITOR.

+5V, +LIV RF% zzSV R14SR20 )3 POSI"'%VE SWEEP

, S.y Z5N294- 2358 o. _r-)7 POSITIVE SWEEP RETURNI

2N2222AW~o% .015 UF RGG6V , + 1 0 1o (Ph. K > 3,)'

qz.'75 RG7 > 32

SEot. 7 V 0 6PA.RESca4 R28 15>Y5 6 .- 'ZK, 40.0I. > o

>00 *t.14v+_4 _ _.Noo++K =N_

+s - , +Iov .,s o I .- I*I/ ,.' I__A I, I

++• a sR8 --- o l--

Yp R %.K 0.11 R4s Q5127K Is wZoor. 1.4 V. 5 4OO I. OP EI.

Y4_ 5 IK Bt.GG )G3.R%

22Z R57- _CCCyZ__ I ( I2 U2 6

2 142222A -EF LU R.E.1*/. 1C.

"'F *.o" R23 ' C. ; +RV)

IS_ -'g 320.0- Alo.GC TCr,-

R 8 S A C --l'a C tR.-

_- 2 .-. -. oas .s>e to GI: DUND

?M222A. 0o.1 i2 2 '2

+$.O+REF 29o-A./v-- --?. A IO.OVREFF V R 4-

+OOK RIG 2. 3t + CZ41

-II -iz 40.OV N*25 . N. V .E2 WEG ,TIvE SW EE o l-rI ED4 - VF -

O. R40 0.1% C CI

LC0.1% CR5 15K RNVER 1. 8 8 CRFi

-t - s

(-+C.V S -- -.a(-oRv

CR1L -I-Ec. -

F IU M 2. ALL ESISTO MA, I

- -- - ISO

.Jt .o s +

SiV 34 3.ALL ODES ARE N4o

Fig. 24 SCHEMATIC DIAGRAM OF DEFLECTION SWEEP SUPPLYREFERENCE

RECDNG PAGE BLANK NOT FIL D - 61 -

GR lETR" I~f - - S R G vGOR .2R7

nECEDINWG PAE BLAN11r NT Fl I LIMED



the deflection sweep supply. The Y1 through Y6 signalsare derived from a binary counter, and R27 through R32provide the corresponding binary weighted currents thatare summed in ARI. The resulting AR1 output is a 64-steplinear ramp with a maximum value of (-) 2. 500 volts and aprecision of 0. 1%.

At the 0. 00 volt step, a reverse voltage is appliedto the hemispheres via the background bit (Q7). This pre-vents low-energy electrons from traversing the analyzerso that the 0. 00 volt step provides a true indication of thebackground count rate caused by the radioactive calibrationsource plus cosmic rays.

High-Voltage Amplifiers

The basic high-voltage amplifier is shown below:

Rf

In the case of the positive sweep, R5 is a combination ofR77, R79, and R81; Rf is R68, R66, and R67; and the OAconsists of AR3 (which provides gain) and Q17 and Q18(which provide high-voltage capability).

Loop stability is provided by C29, C27, and R63.

Q21 and Q23 switch various combinations of sourceresistors to obtain the three desired maximum sweep volt-ages:

PRECEDING PAGE LANK NOT "7? ~T

- 63 -



Maximum Positive CorrespondingSweep Voltages Electron Energy

140. 4 volts for 500 eV28. 1 for 100

7. 02 for 25

The operation of the negative high-voltage amplifieris analogous and produces maximum sweep voltages of:

(-)109. 6 volts for 500 eV(-) 21.9 for 100(-) 5.48 for 25

Performance

The primary sources of DC error are the AR1 andAR2 voltage offsets and resistor temperature drift. In theworst case, this error could be 0. 3% full scale (on allranges), which is about one-fifth of the value of the leastsignificant bit and which more than satisfies the experimentrequirements.

The majority of the sweep supply power is consumedin the high-voltage amplifiers. Since Q17 and Q20 are con-stant current sources, power dissipation is essentially con-stant at 320 mW.

MODE CONTROL LOGIC

The mode control logic accepts signals from thecommand system and the timing signal generator, and com-bines them to determine the dwell time of the positive andnegative high-voltage supplies in their various gain ranges.The control logic outputs drive the gain switching network,which adjusts the sweep supplies to three full-scale outputlevels (corresponding to 25, 100, and 500 eV). The com-mand signals are combined to obtain the three ranges, whilethe timing signals determine the range dwell. The dwell isalso variable and corresponds to either fast or slow spin rate.

- 64 -



Refer to Fig. 25 for the mode control logic imple-mentation. There are five deflection swept range modes(Figs. 26 through 29). Y7 and Y8 are timing signals fromthe timing signal generator. The period of Y7 is either32T (slow spin rate) or 8T (fast spin rate). The period ofY8 is always twice the period of Y7. The signals from thecommand system are cal and mode select bits 1, 2, and 3.The mode signals, Modes I, II, III, IV, and V, are gen-erated from the commands by the mode control logic. Rangebits A and B are the mode control logic outputs to the gainswitching circuit. These range bits adjust the sweep sup-ply gains for the three full-scale swept outputs.

The logic equations were written by observing thewaveform relationships of Figs. 26 through 29. The modecontrol output "states" that define the three gain ranges aregiven in Table 6.

Table 6

Relationship of Range Bit "States" to Full-ScaleElectron Energy Level

Range Bits Full-Scale Electron Energy Level

A B 25 eV 100 eV 500 eV

1 1 X

1 0 X

0 0 X

SWEEP CALIBRATOR

The sweep calibrator makes an 11-bit A/D conver-sion of each step of the positive and negative deflectionsweeps. Figure 30 is a schematic diagram of the calibra-tor. All steps are monitored by forcing the experiment into

The sweep calibrator circuit was designed by R. W. Young(Ref. 9).

- 65 -

THE JOHNS HOPKINS UNIVERSITYAPPLIED PHYSICS LABORATORYCU FRAM. , ,


.A4 8

MODE5 SELECtr BIT I -4

monL B I RANGE BT

MODE IEOECT ST'r 3 kT-e- ( IT, B

CLMODE EL OhI/F

I Gul ou l_

+'W W.NOTEC-U4NLCSS OTRWI E SPECIFIED:

S 7 2. I.C.POW R PN 4 IPIN I S

25G PPS SYNC t4: I ':4.u.L DIOS TB I 4S.

SN4L - UIZU3,U4US

___________tK _ 4NS4LOO- UtiIzUIazUI7,IUI9,U.OUZ.

-S, PS SYNC o4.5oY4 SN54LIO - UIo,UIUI5SL)IMODE SELECT( ~ NS4L04- U -UI>, I4IUIG

OVEIDE EC ) G Y5 SH4LS.O- UG,USZS5 PPS SYNC 2E t ,J 2t

uK "1 9 9 -- +A B

OVDE .SELECT BITLE 17

2.S WORD WUBCOM SYNC. ." a IT,.500 20, 0Uo'V. " 0 z I -

s

OVDE SELECT BIET 1 1k DE I GSy

SWEEP RATE IGI4/LOW ,.1

+ SIGNAL o ( WI. .. s

CROUND 26 < s627 318 BkrrVr;ZOUD BIT

CARL MODE 33 <(FF U

Fig. 25 SCHEMATIC DIAGRAM OF TIMING AND MODE CONTROL LOGIC

- 67 -

PRECEDING PAGE BLANK NOT FLMED


APOLIED PHYSICS LABORATORYSILVER SPRING MARYLAND

Y7

1

Y8

0CAL 0CALIBRATECONTROLSREGARDLESSOF MODE COMMANDS; CAL ON FORCES MODE I

64T

500 eV DEFLECTION SUPPLYSWEPT RANGES

100 eV

25 eV

RANGE A

RANGE B

0

Fig. 26 MODE CONTROL LOGIC: CALIBRATE FORCES THE INSTRUMENT TO MODE I,LOW SWEEP RATE

- 69 -



Y7

1

I 64T -----

CAL (16T AT FAST RATE)

0

1

MODE I 0 I

500 eV

DEFLECTION SUPPLYSWEPT RANGES

100 eV

25 eV

RANGE A

0

1

RANGE B0

Fig. 27 MODE CONTROL LOGIC: MODE I-HIGH/LOW SWEEP RATE

- 70 -


APPLIED PHYSICS LABORATORY


Y7

1

Y 8 64 T I

1 (16T AT FAST RATE)CAL

0

1MODE II

DEFLECTION SUPPLY500 eV

SWEPT RANGES

25 eV

RANGE A

RANGE B

Fig. 28 MODE CONTROL LOGIC: MODE II-HIGH/LOW SWEEP RATE

- 71 -

THE JOHN5 HOPKINS UNIVERSITY

APC'LIED PHYSICS LABORATORYSILVER SPRING MARYLAND

Y7

Y8 I I I I

64T a1 (16T AT FAST RATE)

CAL

MODES III, 1IV, V 0

0

DEFLECTION SUPPLY SWEPT RANGES

25, 100, 500 eV

RANGE AMODE III 0

25 eV RANGE B 1

0

RANGE AMODE IV 0100 eV I 1

RANGE B0

1SRANGE A

MODE V 0 --

500 eV 15 RANGE B 10

Fig. 29 MODE CONTROL LOGIC: MODES III, IV, V-HIGH/LOW SWEEP RATE

- 72 -

THE JOHNS HOPKINS UNIVERSITY - ... ' . '''

APPLIED PHYSICS LABORATORYSILVIR SPRING. MARYLAND

/SUFF. / SIG NAL Swt'rCMING - TP1 / REF SUPPLY

Rill RIGF/0aR46 I TP2

90.9K TAILOR(3.09K NO) m 19.6K

S 16 y oPF 2N 16 TAILOR I 19.6KM+) swea 71 5 2 ss Cjk15 015 (1.87K NOM)

ITO 511K 162K A . 6 2N5116

/I -.o -ov sw I 8K

SI r K 3K --- /O- SPF Ca 2 -8R

FJT1000 rS6 1 5.1M 20.OK I 0 6 +7.000V REF)

27KCAL ON/OFF 27K +16V REFSW -s W 3 4 7

-- 4 .,% 2N2907A IZ -1'O

22907 ) N2907A Rs s 2N2222A (7.15K NOM)

2K 4L I 2 cat

LRG 2N2907AFp

(7.50K NO"M) R4R loon '; (+v v : I--- -O1CAL V S 15SK 13K

90.K +16V SW GO

p 22 2 4 4.7K 1

MODE0DISABLE I 10 - / a 1. ALL RESISTORS ARE W 5%

S= Ic= v K3. ALL DIODES ARE 1N4153

511K 165 6 K O INi I

Fig. 30 SCHEMATIC DIAGRAM OF SWEEP CALIBRATOR

90.9- 73 -

+4 qn R39 is. SW 2N5116

-M ZCOPF 2 K L O 2 11. I

3K UZZ Gal

+ SW 15PF

F ++ 22 %K +5V SW 16V R 2222A

18K R11) S1 270 -+VS S

G0P 33 30 10K 3K

U13L 20K 27K3K

SI I 2N2907A 3K QZZ.

CAS 5. elK 105

ND 10V 2SW 52 9s PM ++

Fig.30 4E T 6DIAGRAMRls OSW(F-4 7 -0

4.WC.' NZ- 4L0 - U j'7%tO U l ICOMAD3 4O4-U6,bl tj;ELO-U ;53Qj--Q4 4 V -2U3V

GN o S ... PW W S I S4r:tkUZ U SU4 +V74FPCAL t-wt i PN i i.CP0

C0VMEABE kOErP4

THE JOHNS HOPKINS UNIVERSITYAPPLIED PHYSICS LABORATORY FO D U FRAM

SILVER SPRING. MARYLAOLDOUT RANDE ; rC

C LOCA C, -> )26 L-)1V

C54 RIO" RII t

-22op 06.1 K TAILOR

+ 1 ( 5 1 1 i N O M )

1K 2N2907A >17

S2 + 8 1 K5. 2 > P A R E

+5V RK 4 >2SW 15K cI ( I

C 6.8K O 3Ct9 .4F

0LS 399PF rto2N2222A

39.2K

275.V< - 20.0 K 20. OK

- +5V SW

INTEGRATOR ,C21CMOMPA.TORINPUT P8 8

178K A R o 41 LM108A 6 3 7 4 U 2 12 14 S 49 12 14 U 12

.OK 7 SN54L93 SN5493 SN4L93+ 7

LMIO O 111

R94 4 2 +178K 2 1 Rt 22 2 (ovcaFLow

4c• s 1K lI. ,T4 )- TL C . yCio

Fig3 3.ICFM14I 9D09I M (ouNERM OTSE(T)y95 -AF IAF opF

i P E P104 100

A0

S-lov +16v +5V c d)UNTE /SW SW SW

-10V SW +I6V SW

S7 ..U9, R.oo 4Uot o( R z + S3 1w1

U! 9 ,K to

7- 75 -

PRECEDING PAGE NK NOT 10PPF



Mode I (ABAC sweep sequence) during calibration. Theexperiment is also forced into the slow sweep rate modeand synchronized with the 128 word subcom sync signal.The positive sweep steps are measured during the first 4seconds after the subcom sync signal, and the negativesweep steps are measured during the remaining 4 seconds.

During the calibration sequence, particle data areinhibited and the PES digital data system is used to storeand transmit calibration data.

Calibration Enable and Initiate

The basic A/D converter is synchronized with thetelemetry main frame sync signal and makes conversionsat 4 times the main frame data rate. However the cali-brator power is normally off. When a cal initiate com-mand is received, the power switching network (U12, U14,and Q4) looks for the next 128 word subcom sync signal andthen turns the calibrator on. When the next sync signalarrives (8 seconds later), the switching network shuts thecalibrator off.

A relay, K1, is used as an override to removepower from the calibrator in case of calibrator malfunction.

The A/D Converter

The A/D converter is a dual-slope integrating type.It consists of a voltage reference, an integrator, a com-parator, an oscillator, and an 11-bit counter with an over-flow bit, as shown in Fig. 31. At the beginning of the con-version, the integration capacitor is charged to the com-parator reference voltage, Vc . The unknown voltage, VA,is inverted and applied to the integrator input, the compara-tor output changes, and clock counts are gated into thecounter. When the counter overflows, the reference volt-age replaces the unknown voltage and discharges the inte-gration capacitor to V c , at which time the comparator out-put changes and the conversion is complete.

- 77 - pEGCEDING PAGE BLANK NOT FILI



E VA

Z? .t

I VR

o E< VI E0 > V I COMPARATOR OUTPUT

AT t 0 T

I I

1 A I ER

0 EO < Vc E° > Vc COMPARATOR OUTPUT

o II1111 ..JlllJ ll[i....ill GATED CLOCK TO COUNTER

COUNTER

OVERFLOW AT t = T

AT T = CLOCK

VR ATt = TAc COMPARATOR

AT t = TA + T ROVERFLOW SWITCHES

INTEGRATOR INPUT 11 BIT

FROM VA TO VR

Fig. 31 DUAL-SLOPE INTEGRATING A/D CONVERTER BLOCK DIAGRAM

- 78 -



The charge added to the capacitor by the unknownvoltage must equal the charge removed by the referencevoltage. In equation form:

V VA R

R A R R'

where

Q = charge transfer,

VA = average input voltage during TA,T A = time to counter overflow = integrating

capacitor charge time,

VR = reference voltage, and

T R = integrating capacitor discharge time.

In terms of the oscillator period, Tosc

11A osc R osc

where n is the number of counts received by the counterafter overflow. Solving for VA:

V RV =n

A 11

Figure 30, sheet 1, shows the buffer amplifiers forthe positive sweep (AR1, inverting) and negative sweep(AR2, noninverting). Selection of the positive or negativesweep monitor mode is controlled by the 128T squarewave;which is switched to the low state by the 128 word subcomsync signal. During the first phase of the 128T squarewave,the FET switch, Q1, is on and the positive sweep steps aremeasured. During the next squarewave phase, Q6 is onand the negative sweep steps are measured.

The reference voltages, VR and VC, are set byCR22 and AR3, and VR is switched via Q24. The unknown

- 79 -


APPLIED PHYSICS LABORATORYSILVER SPRINo. MARYLAND

voltage, VA, is switched via Q15, and a 1 volt signal usedto drive the initial integrating capacitor voltage to Vc isswitched via Q21.

Figure 30, sheet 2, contains the integrator, com-parator, clock, and counter discussed earlier and also theassociated control logic.

The clock runs at 300 kHz ±3% over a -500 to +60 0 Ctemperature range. The maximum conversion time istherefore 14. 1 ms plus an additional 1 ms for turn-on andinitializing times.

The integration time constant is 4. 8 ms, whichallows a maximum integrator output voltage of 10. 5 volts.Initial capacitance tolerance and temperature sensitivitymay extend this maximum to 12 volts.

The accuracy of the converter is 0. 2% ± 1 bit overthe temperature range. The timing of the converter issuch that it puts out one count more than the expected num-ber. The PES digital data system, however, is set up toput out one count less than it receives as an aid in datasystem checkout (see following Section). Consequentlythe PES reads the expected calibration number.

The calibrator power consumption is 575 mW whenoperating and is essentially zero when in standby.

DIGITAL DATA SYSTEM

The PES digital data system consists of four 12-bitaccumulators and four 12-bit temporary storage registers.Each accumulator counts for one-fourth of a frame. At thebeginning of each new frame, the data are parallel-trans-ferred into temporary storage and the accumulators are re-set. This sequence is in sync with the spacecraft teleme-try system and is independent of the operational mode ofthe experiment. Figure 32 illustrates the data systemtiming.

- 80 -


APLIED PHYSICS LABORATORYSILVER SPRING. MARYLAND

ACCUMULATE 1 SECOND-350/S 350S ACCUMULATORSPES WORD 1 64 INHIBITED

ACCUMULATEPES WORD 2 SECOND

ACCUMULATEPES WORD 3 SECOND

ACCUMULATE SECONDPES WORD 4 64

MAIN FRAME 6SYNC0 P S

TRANSFER --- 350SPULSE (T)

SPACECRAFT ENABLE WORDS 38, 39, 40 24 SECOND(READ PES WORDS 1 AND 2) 16384

SPACECRAFT ENABLE WORDS 102, 103, 104 24 SECOND(READ PES WORDS 3 AND 4) 16384 SECOND

Fig. 32 TIMING FOR THE PES PARTICLE DATA WORD ENABLES

-81-



Figure 32 shows that the data are read out oneframe after they are accumulated. At the beginning ofeach frame, the 3 5 0 -us transfer and reset signal, T, isgenerated, and during this time accumulation is inhibited.The accumulation time for every fourth word is thereforereduced by 350 ;As, or about 2%. Since the 350 As is ±10%stable with temperature, the error variation is 0. 2% from-50" to +60 0 C. A temperature calibration could be used toreduce the error further, but this is considered unneces-sary.

The T signal resets the accumulators to all "l's. "Consequently the first particle count causes the accumula-tors to read all "0's, " and the data must be adjusted byadding one count to the transmitted numbers.

The word enables from the spacecraft occur eightbits prior to the word positions in the main frame. Theenable for PES words 1 and 2 occurs during main framewords 37, 38, and 39, and the data appear in 38, 39, and40. Similarly, words 3 and 4 are clocked out during mainframe words 101, 102, and 103 and appear in positions102, 103, and 104.

Figure 33 is a schematic of the PES digital datasystem. P-channel enhancement mode MOS/LSI chips(U8 through U15) perform the storage functions. Eachchip contains an eight-bit accumulator and an eight-bitshift register. PES word 1, for example, consists of eightbits from U8 and four bits from U12.

The words 1 and 2 shift registers are connected inseries via the Q1 buffer. Data from these two registersare clocked out of the experiment via a one-bit delay (U17).The enable, clock, and bit relations are shown in Fig. 34.

PES words 3 and 4 are clocked out in a similar man-ner when the enable for main words 102, 103, and 104occurs. All four PES words are "or-ed" to a single outputand presented to the spacecraft via redundant buffers, asshown in Fig. 35.

- 82 -


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- ?- 83 -


APPLIED PHYSICS LABORATORYSILYER SPRING. MARYLAND

r PES WORD 2 e PES WORD 1 i

I-

SPACECRAFT ENABLE -1WORDS 38, 39, 40 4 5 PS - 15 S

(WE )

(W E ) (p1 2 )

RACE GENERATEDPULSE

Fig. 34 TIMING FOR MAIN FRAME PES BIT READOUT

- 85 - PRECEDING PAGE BLANK NOT F~LEM



SPES MAIN FRAME,. ,DATA A

SENSOR NO. 1 <CAL - - MPX I "

SENSOR NO. 2 - OW

CL PES MAIN FRAMEWORD 3 WORD4 DATA B

Fig. 35 BLOCK DIAGRAM OF THE PES DIGITAL DATA SYSTEM

- 86-



Low-power TTL gates are used to select and multi-plex the data into the accumulators. U1, for example, isused to select either sensor data if the cal mode on/off sig-nal is low or calibration data if the cal mode on/off signalis high. In addition, minor mode commands are used toselect which sensor data are accepted by the digital datasystem. The defining truth table is shown in Fig. 36.

The digital data system consumes about 130 mWdistributed in the following manner: 4. 8 mA at -6 volts,- 0 mA at -10 volts, 8. 0 mA at +5 volts, and 8. 0 mA at7. 75 volts.

MAIN CONVERTER

Circuit Design

The design of the PES main converter* is a two-transformer squarewave oscillator of the type described byJensen. The first transformer, T1 (see Fig. 37) is drivento saturation flux levels and determines the operating fre-quency. T2 is a nonsaturating design from which the out -put voltages are taken from secondary windings. The 16volt output is used in the high-voltage regulator for theelectron multiplier. The load on this line varies from no

load to as high as 690 mW, depending on the anode voltagesrequired on the two electron multipliers. A separate sec-ondary winding on T2 prevents changes in the 16 volt loadcurrent from causing copper loss voltage drops in the otheroutput windings.

All output voltages except the +10 volts do not re-

quire a highly regulated source. The input voltage varies±2%, and thermal changes in the rectifier diodes give amaximum change of ±5% for the 5 volt output and lesser

amounts for the others since the diode drop is a smallerpercentage of the output voltage. This is adequate exceptfor the reference voltage for the D/A converter in the

sweep supply and for the A/D converter in the in-flight

The main converter circuit was designed by R. E. Cashion(Ref. 10).

- 87-



INPUTS OUTPUTS

- a U-00 < 0 0

OZ< ZZ < z

z 0 0 X-cnz O <z z<J 0,.

0 0 x

0 1 0 X

1 0 1 0 X

1 1 1 0 X

Sx

= DO NOT CARE

X = OUTPUT DATA

Fig. 36 TRUTH TABLE FOR DIGITAL DATA SECTION

- 88 -


APPLIED PHYSICS LABORATORYOUT FSILVER SPRINO. MANRYAND

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calibrator. Here a voltage stable to 0. 1% or better is

needed. The regulator made up of CR18, Z1, and Q5 gives

an output of +10. 00 ±0. 01 volts over a 100*C temperature

variation and the required load changes.

Circuit Protection

The input is current limited by the foldback limit

circuit made up of Q1 and Q2. The foldback point is set at

200 mA, or twice the nominal load, and folds back to 60 mA

at a dead short. The most attractive feature of the current

limit circuit is protection during testing phases.

The current is limited at turn-on to 2 amperes bythe dynamic damper made up of L1, L2, R2, C2, and C3.

The voltage swing at turn-off is similarly limited by the dy-

namic damper of R1 and C1.

Electrical specifications in the AE-Experiment In-

terface Specification SK-2260216 give a transient overvolt-

age of ringing to -47 and -36 volts for 100 ms. The outputvoltages are prevented from following the input by the zener

diode, CR2. Current into the zener diode is limited to about

100 mA by the current limiter, Q2.

All output lines are filtered to remove converter

noise. The inductor-capacitor pairs are located in a sepa-

rate shielding enclosure.

-91-

C



3. INSTRUMENT MECHANICAL DESIGN*

ELECTOSTATIC ANALYZER

The PES dual-hemisphere electrostatic analyzer ismodeled after the rocket instruments flown by Doeringet al. (Ref. 2). The analyzer consists of two metal hemi-

spheres mounted concentrically and insulated electricallyfrom each other as well as ground (see Fig. 38). The insu-lator (item 7 of Fig. 38) also acts as the base for construc-tion and alignment of the hemispheres. The inner hemi-sphere is located with respect to the insulating base via astainless steel pin (item 9) and mounted via a single cen-trally located screw (item 17). The location of the outerhemisphere with respect to the inner hemisphere is thendetermined by the precision of machining of the insulatingbase.

A molybdenum annulus restricts particle access tothe analyzer except through a 1. 3-mm hole at the analyzerentrance and a 1. 3-mm by 61 ' opening at the exit (seeFig. 39). Molybdenum was chosen for this application be-cause of its dimensional and surface stability. Surfacestability is essential for preventing charge accumulation(and therefore field distortion) at the analyzer apertures.

An aluminum alignment plate (item 3 of Fig. 38)locates the hemispheres and insulating base with respect tothe molybdenum ring and is used to mount them. Thestructure is then surrounded by a magnetic shielding mate-rial (item 5) and secured with a retaining ring (item 4).

Lugged wires are screwed to each hemisphere as amethod of applying the voltages from the deflection sweepsupply.

The PES mechanical design was done by R. S. Glaeser,and layouts were done by J. T. Mueller. See the Appen-dix for a mechanical drawing list.

93 -PAGE A Tn


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- 95 -

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Fig. 39 MOLYBDENUM APERTURE RING FOR DUAL HEMISPHEREANALYZER.

-4



Ultraviolet light entering the analyzer and reflect-ing from the hemisphere surfaces could strike the elec-tron multiplier and cause counts that are indistinguishablefrom counts caused by electrons. Consequently both theentrance and exit apertures are baffled to reduce the amountof data contamination from ultraviolet light. The bafflesconsist of holes in the outer hemisphere large enough to in-clude the solid angle determined by the entrance and exitcollimators, yet small enough to leave the electric fieldbetween the hemispheres virtually undisturbed. Ultravioletlight passing through the entrance baffle causes secondaryelectron emission when it strikes the rear cover. A cop-per plate biased at ±50 volts is installed behind the en-trance baffle to collect these secondary electrons.

A Ni-63 radioactive source (item 10 of Fig. 38) isinstalled in the magnetic shield directly above the exitaperture baffle hole. Because of this position, the p emis-sion from the source passes through the baffle and strikesthe electron multiplier, producing a background count forcalibration of the sensor electronics. The integrity of themagnetic shield is maintained by machining the sourcemount from magnetic shielding material and welding it tothe shield prior to heat treatment. The Ni-63 source isdeposited on the end of a special screw made from mag-netic shielding material. The source is then sealed andthe holder is gold plated, screwed into its mount, andlocked with a small set screw.

ELECTRON MULTIPLIER BIAS SUPPLY

The electron multiplier bias supply (Ref. 7) pro-duces voltages up to 4500 volts, and special packaging tech-niques are required to avoid damage from corona discharge.

All materials outgas to some degree in a high vac-uum. It is likely that a high-voltage supply will experienceoccasional arcing because of increased local pressurecaused by outgassing either in a vacuum chamber or in

-98-



orbit. Encapsulation helps protect the supply from theatmosphere, but under the relentless vacuum of space thepotting material itself may outgas and produce high internalpressure regions and associated arcing. Since most pottingmaterials are organic, low impedance carbon paths may beformed during a corona discharge and may cause permanentdamage to the supply. Although there are several excellentpotting materials, their successful use depends upon thecare and control exercised during the potting procedure.

Increasing the spacing between components in criti-cal areas reduces but does not eliminate the likelihood ofarcing. A compromise fabrication technique used for thePES uses an inorganic material to house and isolate eachindividual component in the Cockcroft-Walton multiplier.The components are laid out with minimum spacing, andcavities are machined into an inorganic material (in thiscase Vespel-1), as shown in Fig. 40a. Corona paths existonly in the seams between cavities. If arcing occurs, nopermanent low impedance paths are formed.

The low-voltage components of the bias supply aremounted on a printed circuit board but separated from thehigh-voltage section by an electrostatic shield. The entiresupply is then placed in a metal enclosure, as shown in Fig.40b.

SENSOR ASSEMBLY

A housing (item 1 of Fig. 41) machined from a sin-gle piece of aluminum is used to mount the analyzer andbias supply as well as the analog electronics and the elec-tron multiplier. The electron multiplier (item 7) is in aseparate compartment, which contains only the necessarybias and filter components (item 6). Electrical connectionsin this compartment (as well as in the analyzer) are eitherwelded or crimped to avoid placing the electron multipliernear solder, which would contaminate the dynodes. How-ever, braid on the preamplifier coaxial cable is soldered

- 99 -



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5 SPECTROMETER SENSOR

- 101 -

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SPECTROMETER SENSOR

- 101 -


APPLIED PHYSICS LABORATORYSILVER SllING. MARYLAND

since this is considered the only reliable method of con-necting the braid. Nevertheless, this solder connection Iscoated with conformal coating and protected with a Kel-Fcover.

The sides of the analyzer collimator are machinedas part of the aluminum housing, and a rectangular molyb-denum plate is screwed to the front of the collimator. Theplate contains a 5. 8 by 2. 6 mm hole and is located 16. 5 mmin front of the hole in the analyzer entrance aperture. Thecollimator holes thereby restrict the sensor look angle to acone of approximately 90 by 200.

Three coaxial test connectors (item 17 of Fig. 41)are mounted on a Vespel-1 bracket (item 15) to isolate theshields (which are at signal ground) from chassis ground.A single 25-pin Cannon connector (item 16), which connectsto a cable going to the main electronics assembly, is alsomounted on the Vespel-1 bracket, but its shell is in contactwith chassis ground.

MAIN ELECTRONICS ASSEMBLY

The main electronics assembly drawing is shownin Fig. 42. All subassemblies (items 2 through 8) pluginto a "mother board" (item 9). Wiring goes directly fromthe mother board to the spacecraft interface connector (J5),the sensor assembly interface connectors (J3 and J4), andthe PES ground support equipment connector (J6).

The main power supply (item 2) is mounted in anelectrostatically shielded enclosure to minimize radiatedRFI (radio frequency interference).

The PES digital data system (item 3) contains PMOSdata registers, which are more susceptible to radiationdamage than are TTL registers. Consequently the PESdigital data system is placed in a location that takes maxi-mum advantage of incidental shielding. In addition, two

- 103 - .. -A

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- 105 -

pRECEDING PAGE BLANK NOT FILME



0. 063-inch aluminum plates are riveted to the side of themain electronics cover to increase shielding against radia-tion that impinges perpendicularly to the solar panels.

Sensor assembly No. 2 is mounted on top of themain electronics assembly. Items 12 and 13 provide theproper spacing and mechanical support for the sensor.

pcEDING PAGE BLANK NOT FILMED

- 107 -



4. GROUND SUPPORT EQUIPMENT

GENERAL

The PES ground support equipment (GSE) stimulatesand monitors the PES experiment in all of its operationalmodes. It is used during the PES assembly and experimen-tal level checkout, during calibration tests, and during en-vironmental qualification tests.

The GSE consists of a printer and a special-purposeinterfacer, which contains a digital voltmeter with BCD(binary coded decimal) outputs. This allows the experimentanalog and digital data to be monitored visually and/or re-corded as permanent test records.

The experiment is set into the desired operatingmode by a command system simulator that is activated byswitches on the front panel of the GSE. Panel lights indi-cate the command states.

In addition to command simulation, the GSE readsand logs analog housekeeping data and generates the clock,timing, and enable signals required to read the experimentdigital data. (Digital data include command status andscience data. )

DATA ENCODING

Both the analog and digital data received by the GSEare identified and recorded according to the following eightcolumn format:

Code Step Data

XX XX XXXX

The code identifies what type of data is being readand indicates the operational mode of the experiment. The

- 109 -

M =iG PAGE BLANK NOT FILMED



code is octal and takes values from 00 to 77. Code num-bers from 00 to 47 indicate that digital data are being re-ceived from the experiment (see Table 7). Code 77 indi-cates that analog data are being read and codes 50 through76 are unassigned.

The step has had two different meanings, dependingon whether analog or digital data are being displayed. Ifanalog data appear (code 77), the step indicates the positionof the analog multiplexer which feeds data to the digitalvoltmeter. Table 8 shows the assignment of analog datafor each analog step.

If digital data appear (codes 00 through 47), the stepindicates the position on the energy sweep corresponding tothe data being displayed. For example, the format:

Code Step Data

12 31 3729

indicates that the experiment is in fast sweep rate, Mode Ion the 0 to 500 eV sweep. Furthermore, since there are64 steps per sweep starting from 0, step 31 is 31/63 of themaximum sweep energy. Consequently the data indicatethat 3729 electrons of 246 eV energy have been observedby sensor No. 1

"FREE RUN" OPERATION (DIGITAL DATA ONLY)

If the GSE clock is allowed to "free run, " digitaldata will be obtained from the experiment at the rate offour words per second, which is the maximum reliableprinter speed. Four lines per second, however, is 16times slower than the spacecraft readout rate. In order tocheck the complete experiment, the GSE operates at a slowenable speed and reads every digital data word. In addition,to check the experiment time response at the satellite clockrate, the GSE also operates at a fast enable speed and readsevery sixteenth digital data word. For example, the code 00through 02 (positive calibration) would be as follows:

- 110 -


APPLIED PHYSICS LABORATORYSILVER SPRINo. MARYLAND

Table 7

PES GSE Digital Data Code Assignments

Code00 Positive cal, 0 to 25 eV01 0 to 100 eV02 0 to 500 eV03 Unassigned04 Negative cal, 0 to 25 eV05 0 to 100 eV06 0 to 500 eV07 Unassigned10 Sensor 1 data, slow rate, Mode I, 0 - 25 eV11 Mode I, 0 - 100 eV12 Mode I, 0 - 500 eV13 Mode II, 0 - 25 eV14 Mode III, 0 - 25 eV15 Mode IV, 0 - 100 eV16 Mode V, 0 - 500 eV17 Mode II, 0 - 500 eV20 Sensor 1 data, fast rate, Mode I, 0 - 25 eV21 Mode I, 0 - 100 eV22 Mode I, 0 - 500 eV23 Mode II, 0 - 25 eV24 Mode III, 0 - 25 eV25 Mode IV, 0 - 100 eV26 Mode V, 0 - 500 eV27 Mode II, 0 - 500 eV30 Sensor 2 data, slow rate, Mode I, 0 - 25 eV31 Mode I, 0 - 100 eV32 Mode I, 0 - 500 eV33 Mode II, 0 - 25 eV34 Mode III, 0 - 25 eV35 Mode IV, 0 - 100 eV36 Mode V, 0 - 500 eV37 Mode II, 0 - 500 eV40 Sensor 2 data, fast rate, Mode I, 0 - 25 eV41 Mode I, 0 - 100 eV42 Mode I, 0 - 500 eV43 Mode II, 0 - 25 eV44 Mode III, 0 - 25 eV45 Mode IV, 0 - 100 eV46 Mode V, 0 - 500 eV47 Mode II, 0 - 500 eV

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Table 8

PES GSE Analog Data Code Assignments

Step, Step,Code GSE Trigger DVM Self-Trigger Analog Data

77 1 0 ' -24. 5 Volts77 2 1 -24. 5 Volt current drain77 3 2 Al-A, Ground reference77 4 3 A2-A, Low-voltage monitor77 5 4 A3-A, High-voltage monitor 177 6 5 A4-A, High-voltage monitor 277 7 6 A5-A, Sensor No. 1 temperature77 8 7 A6-A, Sensor No. 2 temperature77 9 8 Electron trap bias77 10 9 +16 Volt switched No. 277 11 10 +7. 75 Volt77 12 11 +5 Volt77 13 12 -10 Volt77 14 13 +160 Volt77 15 14 +16 Volt switched No. 177 16 15 10. 0 Volt REF77 17 16 +6 Volt77 18 17 -6 Volt77 19 18 -130 Volt77 20 19 Blank77 21 20 Blank77 . Blank77 . Blank

77 31 31 Blank

GSE = ground support equipmentDVM = digital voltmeter

- 112 -



Code Slow Enable Data Sequence Fast Enable Data Sequence

00 0, 1, 2, ... ,. 63 15, 31, 47, 6301 0, 1, 2 ... ,. 63 15, 31, 47, 6300 0, 1, 2,.... 63 15, 31, 47, 6302 0, 1, 2,..., 63 15, 31, 47, 63

Total print time = 64 seconds Total print time = 4 seconds

"STOP ON STEP" OPERATION

Two thumbwheel switches on the GSE front panel canbe set to monitor data continuously at any step. In this mode,the GSE clock runs until the desired step is reached and thenstops. Once the GSE clock stops, no further timing or dataenable signals are generated, and further data must be ob-tained via external trigger signals.

To obtain continuous digital data, set the enable tog-gle switch to "ext" and send a transfer pulse and then anenable pulse, either by the pushbuttons or the BNC's locatedon the GSE front panel. If the BNC's are used, a 10-Ws clo-sure to ground is required for each signal.

Note: The experiment data system stores data forfour steps prior to transferring the digital data to the GSE.Consequently the GSE clock has been advanced by four stepswith respect to the experiment sync signals. Table 9 showsthe implication of this statement.

Accurate analog data can be obtained in the "stop onstep" mode only. A complete analog readout can be obtainedby stopping on step 00 and incrementing the thumbwheels byhand at about 1-second intervals. In this condition, oneDVM conversion and one print command occur per step.

A toggle switch on the rear of the GSE allows the DVMto self-trigger for continuous monitoring of a particular ana-log voltage. A one-step delay is incurred in this mode, asillustrated in Table 8.

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Table 9

"Step" Meaning for Digital Data in the"Free Run" and "Stop on Step" Modes

Step Energy,"Stop-on-Step" "Free-Run" Using 500 eV

Mode Mode Full Scale as an Example(eV)

60 0 061 1 7.9462 2 15.963 3 23. 8

0 4 31.81 5 39.72 6 47.6

58 62 592. 159 63 50060 0 0

GSE OPERATION INSTRUCTIONS

Figure 43, which shows the GSE special-purposeinterfacer, will be useful in the following discussion.

Minor Mode Commands and Subcom Status ("Free Run"Mode)

To transmit the PES minor mode command word, 12toggle switches (marked C10 through C21) are set in the de-sired position (high = "1, " low = "O0"). Hold the enable sub-com button in the depressed position; depress and releasethe load command button once; depress and release the en-able command button once; then release the subcom statusbutton.

- 114 -

"0-

< Io

m-<

1E LA AUS

igS 4 P.E G SB E S ECL T ATE P O I T F C

CM' lEz

R AATA I

SEND COMMAND FAST 0 N STEP

NES SWCEP MONITOR SLOW FREE RUN

PHOTELECTRON SPECTROMETER GSE OWER (

Fig. 43 PES GSE SPECIAL PURPOSE INTERFACER

U X NF$Vti~r ::--- :::::ii-~ii-::-ii ;-::~- ri~ iff: :i rEA~


APPLIED PHYSICS LABORATORYSILVER SPRIING. MARYLAND

If the command is received properly by the experi-ment, the last 12 subcom status lights (W1-5 through W2-8)will reflect the position of the command toggle switches(see Table 10).

Status light W1-1 indicates that the experiment isin the sweep calibration mode. W1-2, W1-3, and W1-4are spares and should not be lit.

Note: The enable signals required to send the com-mand word and receive the status word are generated bythe GSE and are inhibited during the "stop-on-step" mode.Consequently the experiment must be in the "free-run"mode to send minor mode commands and update the sub-com status word.

Table 10

GSE Minor Mode/Subcom Status Assignments

Subcom Minor ModeStatus Command FunctionLight Toggle Switch

W1-1 Sweep calibrationW1-2 SpareW1-3 SpareW1-4 SpareW1-5 C10 Multiplier 1 gain bit 1W1-6 C11 Multiplier 1 gain bit 2W1-7 C12 Multiplier 1 gain bit 3W1-8 C13 Multiplier 2 gain bit 1W2-1 C14 Multiplier 2 gain bit 2W2-2 C15 Multiplier 2 gain bit 3W2-3 C16 Sweep rate, fast/slowW2-4 C17 Mode select bit 1W2-5 C18 Mode select bit 2W2-6 C19 Mode select bit 3W2-7 C20 Sensor No. 1 only/Sensor No. 2 onlyW2-8 C21 Sensor alternate /alternate

- 116 -



Multiplier Gain Bits Result Mode Select Bits Result

1 2 3 High-Voltage (kV) 1 2 3 Mode

0 0 0 3. 00 0 0 0 V0 0 1 3. 21 0 0 1 I0 1 0 3.42 0 1 0 III0 1 1 3. 65 0 1 1 Not

used1 0 0 3. 86 1 0 0 IV1 0 1 4. 07 1 0 1 Not

used1 1 0 4. 29 1 1 0 II1 1 1 4.50 1 1 1 Not

used

C20 C21 128T s Result

0 0 0 Sensor No. 2

1 0 0 Sensor No. 11 1 0 Sensor No. 1

1 1 1 Sensor No. 2

Relay Commands

The desired relay command is selected via a six-position switch, and the command is executed by depressingthe send command button.

Three panel lights indicate the relay status. Thelight is on when the relay is active.

Digital and Analog Data

The printer cable (J13) must be connected and theprinter must be turned on before the code, step, and datadigits will be meaningful.

For more information see the General Section underSection 4.

- 117 -



EXPERIMENT HOOKUP

There are three cables connected to the rear of theGSE interfacer. J10 (50 pins) mates with the experimentflight connector, J11 (25 pins) with the experiment test con-nector, and J13 (25 pins) with the HP5055A printer.

Note: Do not interchange the 25-pin cables.

GSE INTERFACER CIRCUITS

There are eight plug-in circuit boards as well as apower supply and incidental circuits within the GSE inter-facer. Figure 44 shows the primary signal flow pathswithin the interfacer; Fig. 45 shows the significant GSEtiming signals; Table 11 is the GSE "code" truth table. TheGSE schematic drawings SRA-5112 through SRA-5123 are in-cluded in Ref. 11.

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"

12 COMMAND 16 COMMAND n xSWITCHES ON LIGHTS ON O

PANEL PANEL m zSUBCOM DATA A (J10)

SUBCOM DATA B (J10) PANEL COMMAND LIGHT OPANEL LOAD BUTTON COMMAND AND PANEL SUBCOM LIGHT L

ENABLE COMMAND WORD SUBCOM COMMAND ENABLE (J10) ;ENABLE SUBCOM DATA (J1) SUBCOM DATA ENABLE (J10)

COMMAND WORD (J10)

TIMING SIGNAL - 6 24-BIT ANALOGGENERATOR CLOCK MULTIPLEXER 19 ANALOG INPUTS FROM J10(J6) 128 TS _j 1 (J7)

_o a v ANALOG OUTPUT(. z. 02 CLOCKO, , CODE lL , GENERATOR SIX CODE LINES

N (J4)

' f STOP ON STEP/zaS24-BIT ENABLE PANEL ,w 16 LINES w

(J5) DVM BCD

0 u. " r m 121

S o ANALOG/DIGITAL

C/ <D PANEL SWITCH

MAIN FRAME DATA 12-BIT BINARY TO OENABLE AND PRINT 12 MAIN DATA LINES BCD CONVERTER 16 LINES £(J3) (J2) BCD

MAIN DATA A (J10) 0

MAIN DATA B (J10) SIX STEP LINES

F 4G N

xw

Fig. 44 PES GSE SIGNAL FLOW

-u

rIl< I

EXP SYNC - 128 TD 64 TD *32 TD 16 T *8 TD 4 TD. 2 TD (Tr D'K=t1-60 /S 128 WORD SUBCOM SYNC 2

TD 3.91 MS IIIIIfJnIfJ l 0UL

16 (62.5 MS) I I<TD 7 813MS

8 (125 MS)TD 15.63 MS...... U711

4 (250 MS)II4 (3125 MS I 1 2 3 4 5 6 7 8 10 112 1 4

2 (500 MS)

TRANSFER (T) ill II I ITD 62.5 MS ENABLE1, 2 ENABLE 3,4 ENABLE ,2JENABL E3 4

(1 sec)I IT T D r-, 1.95 MS

16 \8 1 4 ) (31.3 MS)

E TRIGGER I

SLOW PRINTTRIGGER I I

2 TD 125 MS(2 sec)

4 TD 250 MS(4 sec)

E . TD . 2 TD • 4 TD (NORMAL ENABLE TRIGGER)

P D *TD 2 D*4TD IF2

Fig. 45 PHOTOELECTRON SPECTROMETER GSE-EXPERIMENT TIMING



Table 11

PES GSE "Code" Truth Table

Function Mode Mode Mode Y7 Y8 Sensor 128 T,, Sensors Cal Rate

Bit 1 Bit 2 Bit 3 Alternate No. I/No. 2 On/Off Fast/Slow Code

J4 Pin 19 17 18 20 21 5 13 7 22 8

0 0 0 0 1 0 0 0 1 0 0 0

1 0 0 0 Ii

1 1 0 0 12

0 3

0 0 0 1 0 1 0 1 0 4

1 0 1 0 5

1 1 1 0 6

0 7

0 0 1 0 1 0 0 1 0 0(1) 1(2) 0

0 0 1 1 0 0(1) 1(2) 1

0 0 1 1 1 0(1) 1(2) 2

1 1 0 0 0 0(1) 1(2) 3

0 1 0 0 0 0(1) 1(2) 4

1 0 0 0 0 0(1) 1(2) 5

0 0 0 0 0 0(1) 1(2) 6

1 1 0 1 0 0(1) 1(2) 7

0 0 1 0 1 0 0(1) 3(4) 0

0 0 1 1 0 0(1) 3(4) 1

0 0 1 1 1 0(1) 3(4) 2

1 1 0 0 0 0(1) 3(4) 3

0 1 0 0 0 0(1) 3(4) 4

1 0 0 0 0 0(1) 3(4) 5

S 0 0 0 0 0(1) 3(4) 6

1 1 0 1 0 0(1) 3(4) 7

Note: Analog = Code 77

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REFERENCES

1. J. P. Doering, W. G. Fastie, and P. D. Feldman,"Photoelectron Excitation of N 2 in the Day Airglow, "J. Geophys. Res., Vol. 75, No. 25, September1970, pp. 4787-4802.

2. P. D. Feldman, J. P. Doering, and J. H. Moore,"Rocket Measurements of the Secondary ElectronSpectrum in an Aurora, " J. Geophys. Res. , Vol.76, No. 7, March 1971, pp. 1738-1745.

3. J. C. Armstrong, Spacecraft Interference with LowEnergy Electron Measurements, APL/JHU CP 014,April 1972.

4. C. O. Bostrom, "AE-PES Deflection Plate Poten-tials, " APL/JHU S1P-841-71, 1971.

5. S. Cooper, "Stress Analysis of Photoelectron Spec-trometer Atmosphere Explorer-C, " APL/JHU S4M-2-260, June 1972.

6. S. A. Gary, "Analog Electronics for AE Photoelec-tron Spectrometer, " APL/JHU S1P-910-72, April1972.

7. D. P. Peletier, "A High Performance 4500 VoltElectron Multiplier Bias Supply for Satellite Use,"IEEE Trans. Nuclear Sci., Vol. NS-20, No. 1,February 1973, pp. 107-112.

8. R. W. Young, "AE-C/PES Deflection Sweep Sup-plies and Mode Control Logic Design, " APL/JHUS4F-72-240, May 1972.

9. R. W. Young, "AE-C/PES In-Flight Calibrator De-sign," APL/JHU S4F-72-241, June 1971.

- 123 - - PAG BLANK NOT FIL,



10. R. E. Cashion, "Main Power Supply for AE Photo-electron Spectrometer, Final Design, " APL/JHUS1P-899-72, April 1972.

11. D. P. Peletier, "The Photoelectron SpectrometerGround Support Equipment, " APL/JHU S1P-914-72(A), April 1973.

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APPENDIX

Mechanical Drawing List

Drawing SRASize IJawing No. Revisions Irawing Description

0 C 6726 D Outline DIrawing Sensor Assembly1 D 6738 B Plate Alignment lemispheric Analyzer2 C 6739 A Ring Aperture lHemispheric Analyzer3 C 6740 B Base, Ilemisphere, Inner Hemispheric Analyzer4 C 6741 C Hemisphere Inner lemispheric Analyzer5 D 6742 D lIemisphere Outer Hlemispheric Analyzer6 C 6743 B Light Shield Hemispheric Analyzer7 D 6744 B Magnetic Shield8 C 6745 B Magnetic Shield Entrance Aperture Detector Head9 B 6746 C Ring Tie Down llemisphcric Analyzer

10 D 6747 D Housing Sensor11 C 6768 C D Insulator 'Multiplier Sensor12 C 6775 B Collector Photoelectron Ilemispheric Analyzer13 C 6776 B Cover Electronic Sensor14 C 6777 C Cover Multiplier Sensor15 D 6778 A Sensor Assembly Photoelectron Spectrometer16 D 6779 A Hemispheric Analyzer Assembly Sensor17 D 6780 A Electronics Assembly Photoelectron Spectrometer18 B 6781 A Cap Aperture Ilemispheric Analyzer19 D 6782 B Schematic Electron Multiplier Bias Supply20 D 6783 B Artwork E Multiplier Bias Supply21 D 6784 C Assembly E Multiplier Bias Supply Detector Head22 A 6785 A Parts List F Multiplier Bias Supply23 B 6786 A Inductor E Multiplier Bias Supply24 C 6787 B Transformer E Multiplier Bias Supply25 C 6794 B Cover Multiplier Bias Supply Sensor26 C 6795 C End Plate Bias Supply27 C 6796 A Shield Bias Supply Sensor28 , D 6797 A Wiring Diagram Sensor29 C 6798 A B Thermistor Assembly Sensor30 D 6799 C Insulator Top Bias Supply Sensor31 C 6800 C Insulator Bottom Bias Supply32 C 6801 A Solder Board Top Bias Supply33 C 6802 A Solder Board Bottom Bias Supply Sensor34 D 6803 B Insulator Components Bias Supply35 C 6804 B Bracket Connector Sensor36 D 6805 B Electron Multiplier Bias Supply Assembly Sensor37 B 6806 B Entrance Aperture Sensor38 D 6810 B Schematic Analog Electronics39 D 6811 C Artwork Analog Electronics40 D 6812 D Assembly Analog Electronics41 A 6813 B Parts List Analog Electronics42 D 6814 B Schematic Digital Data Systems43 D 6815 D Artwork Digital Data Systems44 D 6816 C Assembly Digital Data Systems45 A 6817 B Parts List Digital Data Systems46 D 6818 D Schematic Minor Mode Command47 D 6819 C Artwork Minor Mode Command48 D 6820 C Assembly Minor Mode Command49 A 6821 C Parts List Minor Mode Command50 D 6822 D Schematic Deflection Sweep Supply51 D 6823 C Artwork Reflection Sweep Supply52 D 6824 E Assembly Deflection Sweep Supply53 A 6825 C D Electronics Parts List Deflection Sweep Supply54 C 6826 Block Diagram Magnetometer Experiment

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Drawing SRASize Drawing No. Revisions Drawing Description

55 B 6827 C Spacer General Usage

56 B 6828 A Spacer General Usage

57 B 6829 A Shield Analog Electronics

58 B 6834 B Source-Holder

59 C 6835 A Schematic Diameter Input Output Board

60 D 6836 B Artwork Input Output

61 D 6837 B Assembly Input Output Board

62 A 6838 A Electronics Parts List Input Output Board

63 D 6839 C D E Schematic Diameter Main Power Supply

64 D 6840 C Artwork Main Power Supply

65 D 6841 C D E Assembly PC Main Power Supply

66 A 6842 B C D Electronics Parts List Main Power Supply

67 B 6843 A Schematic Diagram Electron Multiplier Interface Board

68 C 6844 B Artwork EM Interface Board Sensor

69 C 6845 B Assembly EM Interface Board Sensor

70 A . 6846 A Electronics Parts List EM Interface Board

71 B 6847 B Post Welding Component EM Interface Board Sensor

72 C 6848 B C Resistor Assembly EM Interface Board Sensor

73 C 6851 A Transformer Main Power Supply

74 B 6852 A Transformer Main Power Supply

75 B 6853 A Transformer Main Power Supply

76 D 6854 B Schematic Timing and Mode Control Logic

77 D 6855 B Artwork Timing and Mode Control Logic

78 D 6856 B Assembly Timing and Mode Control Logic

79 A 6857 A Electronics Parts List Timing and Mode Control Logic

80 B 6858 A Block Tie Down PC Board Main Electronic Assembly

81 C 6859 A Spacer Prt. Circuit Board Main Electronic Assembly

82 B 6860 A Insulator TTL Main Electronic Assembly

83 D 6861 B Frame Mother Board Assembly Main Electronics

84 C 6862 A Brace Tie-Down Cover Main Electronic Assembly

85 B 6864 A Insulator MSI Main Electronic Assembly

86 C 6865 A Block Mounting Connector Input-Output Board M E

87 C 6866 C Block Diagram Sensor

88 B 6867 B Heat Sink Transformer Main Power Supply

89 D 6868 A B Main Power Supply Assembly Main Electronic Assembl

90 C 6869 B Artwork Transformer T2 Assembly

91 D 6870 B C Transformer T2 Assembly Main Power Supply

92- D 6871 A Housing Main Power Supply

93 D 6872 B C D Outline Drawing Sensor and Main Electronics

94 D 6873 B Block Diagram Main Electronics

95 B 6875 A Spacer Electron Multiplier Sensor

96 C 6876 B Support Cover MB Frame Assembly Main Electronics

97 D 6877 B Plate Base Main Electronic Assembly

98 C 6878 A Housing Filter Main Power Supply Main Electronics

99 D 6879 C D Cover Assembly Main Electronics

100 C 6880 A Channel Main Electronics Cover Assembly

101 C 6881 A Angle Shield Main Electronics Cover

102 B 6882 B Plate Shield Main Electronics Cover

103 C 6883 B C Insulator EM Interface Board Sensor

104 D 6884 A Artwork RF Section Main PS Main Electronics

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Drawing SRASize Drawing No. Revisions Drawing Description

105 D 6885 A B Assembly Printed Circuit RF Section Main RS Main Electronics106 B 6886 B Cup Insulator Screw Sensor107 D 6887 A Schematic Sweep Calibrator108 D 6888 C Artwork Sweep Calibrator109 D 6889 A Assembly Sweep Calibrator110 A 6890 A Electronics Parts List Sweep Calibrator111 C 6891 A Spacer "A" Bracket112 C 6892 A Spacer "B" Bracket113 D 6893 A Artwork Master Mother Board114 D 6894 A Mother Board Frame Assembly Main Electronics115 D 6895 A Artwork Silk Screen Mother Board116 B 6896 A Top Board Transformer Main PS Main Electronics117 B 6897 A Cup Transformer Main PS Main Electronics118 B 6898 A Cover Filter Main PS Main Electronics Assembly119 D 6899 A Mother Board Assembly MB Frame Assembly Main Electronics120 B 6900 A Cushion Ring Viton Sensor121 B 6901 A Seal Light Sensor122 B 6902 B Cover, Test Connector Main Electronics123 C 6903 A B Insulator Interface Board Sensor124 B 6904 A Cap Coaxial Connector Sensor125 D 6905 A Wiring Diagram MB0 Frame Assembly Main Electronics126 C 6906 A Nameplate Sensor127 C 6907 A Nameplate Main Electronics128 C 6908 B C Shield Light Thermal Sensor129 B 6910 A B Gasket, Shield, Light, Thermal130 C 6991 A Isolation Assembly Kit - Outline )rawing

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