JPL PUBLICATION 85-82 

Characterization of EM1 Generated 

by the Discharge of a “VOLT” 

Solar Array 

Final Report 

Philip Leung 

November 1,1985 

NASA 

National Aeronautics and 

Space Administration 

Jet Propulsion Laboratory 

California Institute of Technology 

Pasadena, California 
The research described in this publication was carried out by the Jet Propulsion 

Laboratory, California Institute of Technology, under a contract with the National 

Aeronautics and Space Administration. 

Reference herein to any specific commercial product, process, or service by trade 

name, trademark, manufacturer, or otherwise, does not constitute or imply its 

endorsement by the United States Government or the Jet Propulsion Laboratory, 

California Institute of Technology. 
ABSTRACT 

The interaction of a high-voltage solar array with the space plasma environment is investigated in a laboratory simulation experiment. Discharges are 

observed to occur when the solar array is at a sufficiently high negative bias 

with respect to the plasma. The frequency of occurrence of discharge is found 

to depend critically on the plasma density and on the geometry of the array. 

The electromagnetic interference (EMI) associated with a discharge is also 

measured. The amplitude of EM1 increases with the magnitude of the high voltage. 

on the performance of systems in space must be evaluated. 

Since the discharge-generated EM1 is of significant amplitude, its effect 

iii 

CONTENTS 

I. INTRODUCTION 1 

11. EXPERIMENTAL SETUP 1 

A. Plasma Source 3 

B. The Solar Array Sample 5 

C. Diagnostic Instruments for Measuring Discharge Characteristics 8 

111. EXPERIMENTAL RESULTS 11 

A. Discharge Rate Measurements 

B. RF Radiation Measurements 

C. Conducted Emissions 

IV. SUMMARY 

REFERENCES 

Figures 

1. Schematic of the experimental setup 

2. Schematics of the synthesis plasma source: (a) The electron 

emitter is an indirectly heated cathode. 

emitter is made of tungsten wires. 

(b) The electron 

3. A typical Langmuir probe I-V trace 

4. The "PIX" array: (a) photograph, (b) test configuration 

5. The "VOLT" array: (a) photograph, (b) test configuration 

6. Schematic of the pulse counting circuit 

7. Discharge rate as a function of biased voltage 

8. Discharge rate as a function of plasma density 

9. The spectra of RF radiation generated by a discharge. 

biased voltage is 1000 V. 

The 

10. The spectra of RF radiation as a function of the biased 

voltage 

11. The spectra of RF radiation generated by the "VOLT" array 

with and without an external capacitor 

11 

14 

14 

17 

18 

2 

4 

6 

7 

9 

10 

12 

12 

15 

15 

16 

12. A typical capacitive probe signal. 

array is 626 V. 16 

The bias on the "VOLT" 

P 

V 
CONTENTS (Continued) 

Tables 

1. 

2. Operating conditions for the electron and ion sources 

3. Summary of "PIX" array discharge rate measurements 

4. Summary of "VOLT" array discharge rate measurements 

Plasma parameters produced by the synthesis plasma source 5 

5 

13 

13 

vi 
I. INTRODUCTION 

Future space missions will require very large, high-power spacecraft for use 

in near-earth-orbit missions. To meet this need, 100-kW space power systems 

are being developed using high-voltage solar arrays. However, previous 

e~perimentsl-~ have shown that discharges are generated in the interaction 

of a high-voltage array with an ambient plasma. Discharges are undesirable 

because the electromagnetic interference (EMI) generated during a discharge 

may cause temporary or even permanent disruption in the operation of spacecraft systems. Consequently, the occurrence of discharges may be the limiting 

factor in the operating voltage of a high-voltage array. The Plasma 

Interaction Experiment (PIX) I1 flight experiment, which was designed and 

managed by NASA Lewis Research center, has verified the occurrence of the 

discharge phenomenon in low-earth orbits. 

Lewis Research Center is currently developing the Voltage Operating Limit 

Tests (VOLT) experiment to further investigate the interaction of high-voltage 

solar arrays with the space plasma environment. 

performed on the Shuttle. It is expected that discharges will occur during 

the VOLT experiments. 

charges on the shuttle and its payload, it is essential that the magnitude of 

the discharge-generated EM1 be determined through ground tests. For this reason, a ground-based laboratory program to investigate the interaction of a 

high-voltage array with an ambient plasma has been carried out. 

tives of this investigation are as follows: 

The VOLT experiment will be 

In order to predict the adverse effects of these disThe objec- 

(1) To determine the discharge rate as a function of the high-voltage bias on 

the solar array and as a function of the plasma density. 

(2) To characterize the radiofrequency radiation (RF) generated during a discharge event. 

The results of this investigation are presented below. 

11. EXPERIMENTAL SETUP 

Figure 1 shows the experimental setup, which has three essential 

components: 

(1) The plasma source 

(2) The solar array sample 

(3) The diagnostic for measuring the transient current and the RF radiation 

The plasma source and the solar array sample are installed inside a vacuum 

chamber. For this investigation, a large vacuum chamber with acrylic walls is 

used. Since acrylic is transparent to RF, the observed RF characteristics 

will not be dominated by cavity effects. The details of this acrylic facility 

are discussed in a previous publication.6 

1 
1 

/ 

I 

/ 

/ 

/ 

/ 

\ COVER S L I DE 

I \ I \ 

I \ 

I \ 

I \ 

I 

I 

f \ 

\ 

\ 

ELECTRONS AND 

LITHIUM IONS 

METALL IC INTERCONNECTS 

LANGMU I R PROBE 

I 

k 

ilk. - 

/ UNITY GAIN AMPLIFIER 

OUTPUT TO TRANSIENT DIGITIZER 

- - 

Figure 1. Schematic of the experimental setup 

2 
A. Plasma Source 

Since the emphasis of this investigation is the discharge phenomenon and the 

characterization of discharge-generated EMI, severe restrictions are imposed 

on the experimental setup, particularly on the plasma source. In order to 

achieve the objectives, the plasma source must satisfy the following 

requirements: 

(1) It must not be a source of EMI. 

(2) 

(3) 

It must be capable of operating at low neutral pressure (< 10-5 torr). 

It must be capable of generating a plasma with a density of 105/cm3 

or higher. 

The most common plasma sources, such as an ion thruster plasma source, use 

gaseous discharge to generate a plasma. This type of plasma source is not 

suitable for this investigation because of the following reasons: 

(1) 

(2) 

A high neutral pressure is required for its operation. 

The EM1 level associated with a discharge source is usually much higher 

than the ambient EM1 level. 

Therefore, the investigators developed a novel plasma source that is basically 

a synthesis plasma source, consisting of separate electron and ion emitters. 

The ion emitter is a l3-eucryptite source that emits lithium (Li7) ions; the 

electron emitter is an oxide-coated cathode or tungsten filaments. Figures 2a 

and 2b show two different configurations of this synthesis plasma source. 

These two configurations differ by their electron emitters. 

The ion sources in both plasma configurations are identical. The potential 

difference between the grid and the case controls the ion current. The ion 

energy is determined by the potential of the case with respect to ground. 

In a typical operation, the electron source is electrically grounded. That 

is, the case of the cathode (figure 2a) or the filaments (figure 2b) is connected to ground. The presence of the ions creates a positive space potential 

in the vicinity of the electron source. The resulting electric field enhances 

the emission of the electron source, creating a high-density plasma. The 

observed enhancement factor of electron emission is in the range of 5 to 10. 

Table 1 shows the plasma parameters obtained with this synthesis plasma 

source. The higher electron temperature is obtained with the configuration 

shown in figure 2b. The electron temperature of this configuration is in the 

range of 3 eV and is attributed to the potential drop across the filaments. 

3 
ION SOURCE 

A. MECHANICAL CONSTRUCTION B. ELECTRICAL CONNECTION 

90% TRANSPARENCY 

STAINLESS STEEL TUBING 

1" O.D., 7/8" I.D. 

WIRE 

CASE MESH 

A BTYPICAL OPERATION 

A = 12V B = 6V 

1 

ELECTRON SOURCE 

MECHANICAL CONSTRUCTION 

CASE 

CONNECTION 7 

1.5" IF 

L BORON 

NITRIDE 

STANDOFF 

STAINLESS STEEL TUBING 

1 1/2" O.D., 1 l/P I.D. - *'I1 

4 ION EMITTERS 

COPPER 

BAR 

10 MILS TUNGSTEN WIRE (6) 

(ELECTRON EM1 TTER) 

(b) 

Figure 2. Schematics of the synthesis plasma source: 

emitter is an indirectly heated cathode. 

emitter is made of tungsten wires. 

(a) The electron 

(b) The electron 

4 
Table 1. Plasma parameters produced by the synthesis plasma source 

Plasma Electron 

Density Temperature Ion Energy 

Condition (particles /em3 (eV 1 (ev) 

Optimum 

Typical 

5 x 106 

6 x lo5 

0.8 6 

0.8 to 3 6 to 12 

Table 2 shows the power requirement for the plasma sources. Since the operation of this synthesis plasma source does not require neutral gas, the vacuum 

pressure during its operation is usually at the background level. For the 

vacuum facility used in this experiment, this pressure level is in the range 

of 10-6 torr. 

Table 2. Operating conditions for the electron and ion sources 

Source 

Heater Voltage Heater Current 

(V 1 (A) 

Ion Source 

Cathode Electron Emitter 

Tungsten Wire (6 x 10 mils) 

12 

12 

4 

8.5 

15 

7/wire 

A Langmuir probe is used to characterize the electron temperature and the 

plasma density. Figure 3 shows a typical Langmuir probe I-V curve obtained in 

this experimental setup. 

electron current (knee) can be identified. 

shows that the electron distribution of this synthesis plasma source is nearly 

thermal. The design of this source precludes the existence of ener etic elecexcited in this plasma. Consequently, the EM1 level of the plasma generated 

by this source is at the ambient level. 

In most cases, a distinct saturation region for the 

The Langmuir trace of figure 3 

trons (electron beam); for this reason, electrostatic instabilities 9 are not 

B. The Solar Array Sample 

Two solar arrays with different geometries are used in this experiment. 

_. 

(1) One array has twenty-four 2-cm by 2-crn solar cells. 

lar to the arrays used in the PIX program5y8 and is herein referred to 

as the "PIX" array. A picture of this array is shown in figure 4a; the 

electrical connections are shown in figure 4b. 

This array is simi5 
-5 

Figure 3. A typical Langmuir probe I-V trace 

6 
I N SERl ES 

I yn I 1 

27 st 

(b) 

Figure 4. The "PIX" array: (a) photograph, (b) test configuration 

7 
(2) The second array has four 5.9-cm by 5.9-cm solar cells (figure 5a). This 

array is similar to the array used in the VOLT pr~gram,~ and is herein 

referred to as the "VOLT" array. The electrical connection of this array 

is shown in figure 5b. 

In each array, a fused silica cover slide is placed on top of each solar cell 

and the cells are electrically connected in series with the solar cells. The 

area of each array is approximately 100 cm2. Each array is mounted on a 

fiberglass board. 

is applied to the interconnects. 

that discharges only occur when the solar array is at a negative potential, 

all the experiments in this investigation are performed with a negatively 

biased array. 

To simulate a high-voltage solar array, a high-voltage bias 

Since previous e~perimentsl-~ have shown 

C. Diagnostic Instruments for Measuring Discharge Characteristics 

A capacitive probe is constructed by attaching a copper electrode to the back 

of the fiberglass board on which the solar array is mounted. 

occurs, the potential at the interconnect drops, and a fast transient signal 

is coupled to the probe. The signal detected by the capacitive probe is processed by a fast time response voltage follower circuit.3 The capacitance 

of the capacitive probe ranges from 5 pF to 25 pF. The input impedance of the 

follower circuit is 50 0; therefore, the follower circuit has a maximum RC 

time constant of 1.25 ns. The signal from the follower circuit is digitized 

and stored on a disk for later analysis. The time integral of this signal 

To avoid the effect of the stray capacitance due to the cables, the follower 

circuit is placed inside the vacuum chamber and is installed directly underneath the solar array. 

When a discharge 

provides information on the voltage drop (charge loss) during a discharge. 3 

In order to determine the rate of discharges, a pulse counting circuit is 

developed. Figure 6 shows a schematic of this circuit. In this circuit, the 

sensitivity of the 7A26 amplifier and the trigger level of the scope acts as a 

discriminator for the discharge pulse. Previous experiments3 have shown that 

discharges of various amplitudes are generated during the discharge of a solar 

array. For each biased voltage, the level of the discriminator is set such 

that only discharges of significant size will be registered, i.e., discharges 

that produce a voltage drop of >30% of the applied high voltage. The results 

of discharge rate measurements presented in this paper are derived from data 

on large amplitude discharges. 

The RF radiation generated during a discharge is measured by antennas with 

different frequency responses. 

the radiated signal is measured, for redundancy, y two monopole antennas: the 

Singer 95010 and the Empire VA-105. 

ferent bandwidths. The Singer antenna system has a flat frequency response 

from 0.04 MHz to 40 MHz. The signal from this antenna is digitized and stored 

on a disk. During the data reduction process, the frequency spectrum of RF 

radiation is obtained with a Fourier transform of the time domain signal. The 

Empire VA-105 antenna system has a narrower bandwidth. The receiver is of 

resonant-type LC circuit and has six selectable frequency bands, spaced logarithmically. The bandwidth of each frequency band is approximately equal to 

In the frequency range of 0.1 MHz to 40 MHz, 

These antennas have receivers with dif- f) 

8 
Figure 5. The "VOLT" array: (a) photograph, (b) test configuration 

9 
SOLAR ARRAY 

- 

HP 5245L 

TEK 7633 SCOPE 

GATE OUT 

7A 26 

PLUG IN 

&2 - 

- 

TIME BASE 

TRI GGER 

LEVEL 

COUNTER 

Figure 6. Schematic of the pulse counting circuit 

10 
the center frequency. The RF spectra derived from these two instruments agree 

well (2 3 db). 

sured by a biconical antenna (EMCO 3104), and the RF radiation in the frequency 

range of 200 to 1000 MHz is measured by a log-conical antenna (EMCO 3101). The 

signals from these antennas are processed by detectors with bandwidths ranging 

from 100 to 300 MHz. 

The RF radiation in the frequency range 30 to 200 MHz is mea111. EXPERIMENTAL RESULTS 

A. Discharge Rate Measurements 

Discharges are observed on a negatively biased solar array under various plasma 

conditions. Figure 7 shows the discharge rate as a function of the bias voltage for a plasma density of 5 x IO5/cm3. 

encountered in low-earth orbits. Under the same condition, the discharge rate 

for the "PIX"-type array is about an order of magnitude higher than that for 

the "VOLT"-type array. 

This is the typical density 

There is a significant difference between the geometries of the interconnects 

of the "VOLT" and "PIX" arrays. The interconnects of the "PIX" array are made 

of braided conductors and are directly exposed to the plasma environment. The 

interconnects of the "VOLT" array are of "wraparound type" and are not exposed 

to the outside environment. Although the areas of both arrays are approximately equal, the area of exposed interconnects is much higher for the "PIX" 

array. Visual inspection also indicates that the braided conductor of the 

"PIX" array has much sharper geometries than the "VOLT"-type array. The drastic difference in the geometries of these two arrays probably accounts for the 

difference in the observed discharge rates. 

The effect of the plasma density on the "PIX" array is illustrated in figure 8. 

The bias on the array is 626 V. The data indicate that there is a threshold 

plasma density at which a discharge occurs; for the 'qPIX" array, this density 

is approximately 104/cm3. 

increases rapidly. 

Above the threshold density, the discharge rate 

A summary of the discharge rate measurements is presented in Tables 3 and 4. 

The variables in these tables are the plasma density and the biased voltage. 

The numerical values in the tables are the discharge rates; a discharge rate 

of zero means no discharge was observed during the experiment. The minimum 

time interval of the experiment is 20 minutes. In boxes where there are no 

entries, no experiment was performed under those conditions. With a few 

exceptions, the expected discharge rate corresponding to the no-entry boxes is 

zero. By comparing the data in tables 3 and 4, it is obvious that the *'PIX" 

array is more prone to discharge. 

The data displayed in figures 7 and 8 and tables 3 and 4 were obtained within 

two hours after the commencement of each experiment; the discharge rate decreases after an extended experimentation time. For example, the discharge 

rate measured two hours after the start of the experiment can be 3 times lower 

than the discharge rate measured at the beginning of the experiment. The magnitude of the capacitive probe signal and the RF radiation are not affected by 

time . 

11 
PLASMA DENS ITY (crn3) 

B I AS VOLTAGE (V) 

Figure 8. Discharge rate as a function of plasma density 

12 
Table 3. Summary of "PIX" array discharge rate measurements 

(discharge rate in discharges/sec) 

Plasma Density (particles /cm3 

Bias 

Voltage 

(V) 6 x lo5 105 6 x lo4 3 104 104 

626 6.2 1.2 0.23 0.02 0.0009 

532 1.3 0.15 0.02 --- 

438 0.15 --- 0.005 --- 

344 0.12 --- 

250 0.08 --- 

218 0.017 --- 

0 

0 

0 

0 

0 

0 --- 

0 

0 

--- 

--- 

Table 4. Summary of "VOLT" array discharge rate measurement 

(discharge rate in discharges/sec) 

plasma Density (part ie les / cm3 

Bias 

Voltage 

(V 1 6 x LO5 105 6 x lo4 3 104 104 

13 
B. RF Radiation Measurements 

High-frequency electromagnetic radiation is generated by a discharge of a 

solar array. A measurement of the amplitude of the RF radiation as a function 

of distance shows that the radiation emitted by a discharge roughly resembles 

the radiation emitted by a dipole. 

distance (r) as 

The amplitude (E) decreases with the 

where n is in the range of 2 to 3. The average value for n is 2.5. 

Figure 9 displays the spectra of RF radiation generated during discharges for 

the "PIX" and the "VOLT" arrays. The data were obtained with a biased voltage 

of 1000 V and were obtained during discharges of significant magnitudes. 

Due to the size of the vacuum system, the antennas were placed at a distance 

of 2 to 4 rn from the solar arrays. The data displayed in figure 9 are the RF 

electric field at a distance of 1 m from the solar array. Their numerical 

values are extrapolated from measured data using equation 1, with n = 2.5. 

The error bars show the uncertainty introduced by the extrapolation process. 

The amplitudes of RF radiation generated by the discharge of both arrays are 

approximately the same. In order to illustrate the effect of dischargegenerated RF on spaceflights, the levels of RF radiationlo allowed for the 

space shuttle are also displayed on figure 9. 

Figure 10 shows the dependence of the RF radiation on the biased voltage. The 

amplitude is a nonlinear function of the biased voltage. In a typical discharge, the transient current involved in a discharge is proportional to the 

amount of charge lost in a discharge; consequently, the amplitude of RF radiation increases with the voltage bias. Experimental observation indicates that 

when the biased voltage is at 626 and 1000 V, approximately 80 to 100% of the 

stored charge is released during a discharge. However, at a biased voltage of 

250 V, only 30 to 40% of the stored charge is released. Therefore, the 

observed amplitude of the discharge generated RF is a nonlinear function of 

the biased voltage. 

The test samples in this experiment are small solar arrays. In a large solar 

array, the capacitance between the interconnects and the ground structure is 

substantially larger, and the resulting discharge may have a higher amplitude. In an attempt to simulate the effect of discharge of a large solar 

array, a 2000-pF capacitor was connected between the interconnect of a "VOLT" 

array and the ground structure. Figure 11 shows the resulting data; in the 

presence of the 2000 pF capacitor, the measured electric field is 20 dB higher. 

C. Conducted Emissions 

Due to the large limiting resistor (100 Nsz) in the high-voltage supply 

circuit in the test configuration, the main source of conducted noise is 

derived from capacitive coupling between the array and a possible victim circuit. That is, the transient current that can be coupled into circuits is 

proportional to dV/dt. The value of dV/dt can be derived from the signals of 

the capacitive probe. Figure 12 shows a typical signal detected by the 

capacitive probe during a discharge event. If the surface voltage of the 

14 
200 

150 

N 

- I 

E 

> 

a 

\ 

a 

-0 

Y 

- 100 

50 

I I I I I I 

+ "PIX"-TYPE ARRAY 

-*- "VOLT"-TYPE ARRAY 

COMPOS ITE PAYLOAD 

LOCATED ON AFT FLIGHT DECK 

I I I I I II 

0.01 0. 1 1 10 100 1,000 lo, 000 

FREQUENCY (MHz) 

Figure 9. The spectra of RF radiation generated by a discharge. The 

200 

h 150 N 

-c 2 

E 

> 

=L 

m 

3 

- 

100 

50 

' '. 

Ql 0. 01 LO 10 100 1, oal lo, OOO 

FREQUENCY (MHz) 

Figure 10. The spectra of RF radiation as a function of the biased voltage 

15 
I I I I I I 

+ 2000 pF CAPACITOR 

-0- WITHOUT CAPAC ITOR 

COMPOS ITE PAYLOAD 

IN PAYLOAD BAY 

LOCATED ON AFT FLIGHT DECK 

0.01 0.1 1 10 100 5OOo lo, OOO 

FREQUENCY (MHz) 

Figure - 11. The spectra of RF radiation generated by the "VOLT" array 

with and without an external capacitor 

I I I I I 

0.4 0.8 1.2 1.6 

TIME (US) 

Figure 12. A typical capacitive probe' signal. 

array is 626 V. 

The bias on the "VOLT" 

16 
cover-slides remains unchanged during a discharge event, the value of dV/dt 

can be derived from the following equation: 

dV/dt = V,/RC (2) 

where Vs is the capacitive signal, R is the input impedance of the follower 

circuit, and C is the capacitance of the capacitive probe. 

array, R is 50 Q and C is 7.5 

For the "VOLT" 

. The data in figure 10 show that the 

peak value of dV/dt is 2.7 x10 tF VIS. 

The transient current (I) that can be coupled into a nearby circuit is given 

by: 

I = C dV/dt (3) 

where C is the capacitance between the array and the victim circuit. 

above equation is only valid if C is smaller than the capacitance between the 

array and ground (this condition is usually satisfied.) The "VOLT" array has 

a capacitance of 30 pF with respect to ground; the data in figure 10 indicate 

that the maximum current that can be coupled to a unshielded victim circuit is 

0.08 A. 

waveform of figure 12. 

The 

The waveform of the transient current pulse will be similar to the 

IV. SUMMARY 

Discharges were observed to occur at a negatively biased array. 

discharge is proportional to the plasma density and to the biased voltage. 

The rate of discharge and the threshold voltage for the occurrence of discharge is also geometry dependent. The "PIX" array has a large area of 

exposed interconnects, and the interconnects have much sharper geometries than 

the "VOLT" array interconnects; consequently, the discharge rate of the 

"PIX"-type of array is higher than the rate of a "VOLT" array. The results 

suggest that the threshold discharge voltage of a high-voltage array can be 

lowered by the proper design of interconnect geometry. 

The rate of 

The data displayed in figures 9 through 11 indicate that the RF generated by a 

discharge exceeds the emission level allowed by the shuttle. 

VOLT experiment should take precautions to control the possible adverse 

effects of discharge-generated RF. One possible solution is to install the 

solar array far away from sensitive electronic subsystems. 

tance depends on the susceptibility of the subsystems involved. 

Therefore, the 

The required dis17 
REFERENCES 

1. Stevens N., "Interaction Between Large Space Power Systems and LowEarth-Orbit Plasmas," Spacecraft Environmental Interactions Technology, 

1983, NASA CP-2359, pp. 263, 1985. 

2. Snyder D., "Discharges on a Negatively Biased Solar Cell Array in a 

Charge Particle Environment," ibid., pp. 379. 

Leung P., "Discharge Characteristics of a Simulated Solar Cell Array," 

IEEE Transactions on Nuclear Science, Vol. NS-30, pp. 4311, 1983. 

3. 

4. Konradi A., McIntyre B., and Potter A., "Experimental Studies of Scaling 

Laws for Plasma Collection at High Voltages," Journal of Spacecraft and 

Rockets, Vol. 21, No. 3, pp. 287, 1984. 

5. Grier N., "Plasma Interaction Experiment I1 (PIX-11): Laboratory and 

Flight Results," Spacecraft Environmental Interaction Technology 1983, 

pp. 333, 1985. 

6. Leung P. and Plamp G., "Characteristics of RF Resulting from Dielectric 

Discharges," IEEE Transactions on Nuclear Science, NS 29, pp. 1610-1614, 

1982. 

7. Bekefi G., "Radiation Process in Plasmas," Wiley, New York, 1980. 

8. Grier N. and Stevens N., "Plasma Interaction Experiment (PIX) Flight 

Results," Spacecraft Charging Technology - 1978, NASA CP-2071, 1979, p. 

295. 

9. Carruth M. and Purvis C., "Space Test Program of High-Voltage Solar 

Array/Space Plasma Interactions," Spacecraft Environmental Interaction 

Technology 1983, pp. 619, 1985. 

10. Interface Control Document (ICD 2-19001), Johnson Space Center. 

18 
TECHNICAL REPORT STANDARD TITLE PA( 

Characterization if EM1 Generated by the Discharge of 

a "VOLT" Solar Array 

7. Author(s) 8. Performing Organization Report Nc 

Philip Leung 

1 

9. Performing Organization Name and Address I IO. Work Unit No. 

JET PROPULSION TABORATORY 

California Institute of Technology 

4800 Oak Grove Drive 

Pasadena-, California 91109 13. Type of Report and Period Coverec 

2. Sponsoring Agency Name and Address JPL Publication 

14. Sponsoring Agency Code NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 

Washington, D.C. 20546 RE65 DY-481-59-02-04-95 ~ ~-__ 

15. Supplementary Notes 

16. Abstract 

The interaction of a high-voltage solar array with the space plasma environment is 

investigated in a laboratory simulation experiment. Discharges are observed to occur 

when the solar array is at a sufficiently high negative bias'with respect to the 

plasma. 

the plasma density and on the geometry OS the array. 

(EMI) associated with a discharge is also measured. The amplitude of EM1 increases 

with the magnitude of the high voltage. Since the discharge-generated EM1 is of 

significant amplitude, its effect on the performance of systems in space must be 

evaluated. 

The frequency of occurrence of discharge is found to depend critically on 

The electromagnetic interference 

Ground Support Systems and Facilities Unclassified; unlimited 

Spacecraft Propulsion and Power 

(Space) 

JPL 0184 ROl83