The 1983 solar cell calibration balloon flight was successfully completed and met all objectives of the program. Thirty-four modules were carried to an altitude of 36.0 kilometers. The calibrated cells can now be used as reference standards in simulator testing of cells and arrays. Cell calibration data are tabulated as well as the repeatability of standard solar cell BFS-17A (35 flights over a 21-year period)

Downing, R. G.

Weiss, R. S.

English

NASA Technical Reports Server

216 oV --v
JPL PUBLICATION ,83-100 .
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https://ntrs.nasa.gov/search.jsp?R=19840013541 2020-03-20T23:47:19+00:00Z
JPL PUBLICATION 83-100
Results of the 1983 NASA/JPL
Balloon Flight Solar Cell
Calibration Program
R.G. Downing
R.S. Weiss
February 1, 1984
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 contract with the National
Aeronautics and Space Administration.
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ABSTRACT
The 1983 solar cell calibration balloon flight was successfully completed
on July 12, meeting all objectives of the program. Thirty-four modules
were carried to an altitude of 36.0 kilometers. The calibrated cells can
now be used as reference standards in simulator testing of cells and arrays.
ACKNOWLEDGMENT
The authors wish to extend appreciation for the cooperation and support
provided by the entire staff of the National Scientific Balloon Facility
located in Palestine, Texas. Gratitude is also extended to assisting JPL
personnel, especially B.E. Anspaugh, for providing cell spectral response
information and data reduction assistance. The cooperation and patience
extended by all participating organizations are greatly appreciated.
IV
CONTENTS
Page
I. INTRODUCTION 1
II. PROCEDURE 2
III. SYSTEM DESCRIPTION 5
IV. DATA REDUCTION 5
V. MONITOR CELLS 7
VI. CONCLUSIONS 11
REFERENCES 11
Tables
1. Cell Calibration Data 8
2. Repeatability of Standard Solar Cell BFS-17A 9
Figures
1. 1983 Solar Module Payload 3
2. Balloon Mount 4
3. Flight 1983 Altitude Versus Time 6
4. 1983 Module Location Chart 10
I. INTRODUCTION
The primary source of electrical power for unmanned space vehicles is the
direct conversion of solar energy through the use of solar cells. As advancing
cell technology continues to modify the spectral response of solar cells to
utilize more of the sun's spectrum, designers of solar arrays must have
information detailing the impact of these modifications on cell conversion
efficiency to be able to confidently minimize the active cell area required
and, hence, the mass of the array structure.
Since laboratory simulation of extra-atmospheric solar radiation has not been
accomplished on a practical scale with sufficient fidelity, high altitude
exposure must be taken as the best representation of space itself. While a
theoretical prediction (Reference 1) and experimental evidence have suggested
that an altitude greater than 30 kilometers is sufficient to give space-
equivalent calibration, the final decision as to an adequate altitude must
await the results of the space shuttle solar cell calibration experiment
scheduled for May 1984.
To reach and maintain the chosen altitude of 36 kilometers, the calibration
program makes use of balloons provided and launched by the National Scientific
Balloon Facility of Palestine, Texas.
II. PROCEDURE
To insure electrical and mechanical compatibility with other components of
the flight system, the cells are mounted by the participants on JPL-supplied
standard modules according to directions in Reference 2, which details mat-
erials, techniques, and workmanship standards for assembly. The JPL standard
module is a machined copper block 3.7 cm x 4.8 cm x 0.3 cm thick, rimmed by
0.3 cm thick fiberglass, painted a high reflectance white, with insulated
solder posts and is permanently provided with a precision (0.1 percent, 20
ppm/°C) load resistor appropriate for scaling the cell output to the telemetry
constraints. This load resistor, 0.5 ohm for a 2 cm x 2 cm cell, for example,
also loads the cell in its short circuit current condition.
The mounted cells are then subjected to preflight measurements in the JPL X25L
solar simulator. These measurements, when compared to postflight measure-
ments under the same conditions, may be used to detect cell damage or insta-
bilities. Prior to shipment to the launch facility, the modules are mounted
on the sun tracker bed plate (Figure 1). Upon arrival at the Palestine
facility, the tracker and module payload are checked for proper operation, and
the data acquisition and Pulse Code Modulation telemetry systems are calibrated.
Mounting of the assembly onto the balloon is then accomplished (Figure 2).
At operating altitude the sun tracker bed plate is. held pointed at the sun to
within ± 1 deg. The response of each module, temperatures of representative
modules, sun lock information, and system calibration voltages are sampled twice
each second and telemetered to the ground station, where they are presented in
teletype form for real-time assessment and are also recorded on magnetic tape
Figure 1. 1983 Solar Module Payload
Figure 2. Balloon Mount
for later processing. Float altitude information is obtained from data
supplied by the balloon facility. A plot of altitude in kilometers versus
Central Daylight Time for the 1983 flight is shown in Figure 3.
III. SYSTEM DESCRIPTION
A solar tracker mounted in a frame on top of the balloon carries the module
payload, while the transmitter of the data link is located in the lower
gondola along with batteries for power and ballast for balloon control. At
completion of the experiment, the upper payload and lower gondola are returned
by parachutes and recovered. A more complete description of the system,
including the sun tracker, can be found in Reference 3.
IV. DATA REDUCTION
The raw data as taken from the magnetic tape is corrected for temperature and
sun-earth distance according to the formula (Reference 4):
V28,l = VT,R<R2) -«(T-28)
where
Vj R = measured module output voltage at temperature T and distance R
R = sun-earth distance in astronomical units
a = module output temperature coefficient (supplied by participants)
T = module temperature in °C
38
36
34
32
30
28
J 26
LU
a
I U
22
20
18
16
14
12
1000 1100 1200 1300 1400 1500
CENTRAL DAYLIGHT TIME
Figure 3. Flight 1983 Altitude Versus Time
The calibration value is taken to be the average of 200 consecutive data
points taken around the time of solar noon after indicated temperature stabil-
ity.
The flight data were thus reduced, and modules with their data and calibration
values were returned to the participants. This information is collected in
Table 1. The placement of modules on the field of the tracker bed for the
1983 flight is shown in Figure 4.
A detailed discussion of data reduction and an analysis of system error may
be found in Reference 3. The error in the calibration values due to radiation
absorption and scattering by the residual atmosphere at float altitude is
estimated to be less than 0.2 percent (Reference 1).
V. MONITOR CELLS
Several standard modules have been flown repeatedly over the 20-year period
of calibration flights. The record of the one with the longest history, BFS-
17A, appears in Table 2. This data shows a standard deviation of 0.23 percent
and a maximum deviation of 0.58 percent from the mean.
In addition, the uniformity of the solar irradiance (i.e., no spurious
reflections, shadowing) over the field of the modules has been demonstrated
since the location of this module was changed in that field from flight to
flight.
Table 1. Cell Calibration Data
BALLOON FLIGHT 83-1 DATE 7-12-83 ALTITUDE 36.0 KM RV=1.0166
CHANNEL
NUMBER
MODULE
NUMBER
ORGANIZATION
CODE
TEMP. INTENSITY
ADJ. AVERAGE
STANDARD
DEVIATION
AMO, SOLAR SIM.
1 AU, 28 DEC. C
PRE-FLT POS-FLT
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
39
40
41
42
83-181
83-120
83-110
83-151
BFS-17A
83-124
83-105
83-155
83-115
83-139
83-170
83-126
83-101
83-154
83-160
73-182
83-180
73-183
83-111
83-121
83-106
83-130
83-116
83-140
79-132
83-157
83-129
83-153
83-133
83-103
83-152
74-204
83-159
78-110
100-MV
80-MV
50-MV
0-MV
SPL
HUGHES
COMSAT
ASEC
JPL
HUGHES
SHARP
ASEC
COMSAT
HUGHES
SLRX
HUGHES
MELCO
ASEC
ASEC
JPL
SPL
JPL
COMSAT
HUGHES
SHARP
HUGHES
COMSAT
HUGHES
TRW
ASEC
HUGHES
ASEC
HUGHES
MELCO
ASEC
COMSAT
ASEC
HUGHES
83.26
91.94
69.97
78.53
60.10
79.71
80.08
79.55
96.62
69.02
74.57
77.34
61.85
87.74
78.25
68.03
86.83
67.10
95.32
89.62
80.01
83.44
61.20
84.27
72.69
76.28
82.18
86.78
76.56
61.62
79.74
88.85
76.73
95.42
99.80*
79.97*
50.21*
.00*
.06290
.05680
.04913
.06323
.04222
.04553
.05038
.04982
.07774
.05670
.05827
.05392
.05392
.04121
.02967
.05079
.07637
.07936
.06805
.07508
.07107
.07063
.06682
.08991
.07675
.06245
.06752
.07338
.06633
.07685
.05917
.11647
.05150
.07420
.02741
.04688
.03636
.00000
82.60
90.30
69.60
78.70
60.90
78.20
79.60
78.60
94.60
69.10
74.40
77.10
61.10
86.50
77.60
68.70
85.40
68.20
93.90
88.20
79.40
83.50
60.90
82.60
72.80
75.90
82.50
85.90
77.00
60.60
80.00
87.60
75.90
93.10
.00
.00
.00
.00
81.80
90.30
69.30
78.10
60.90
78.20
79.50
78.80
94.60
68.80
74.40
77.20
61.30
86.70
77.50
69.00
85.10
68.30
93.90
88.10
79.60
83.70
60.70
82.90
72.90
75.90
82.60
86.00
77.20
61.30
79.70
86.80
75.90
93.40
.00
.00
.00
.00
COMPARISON
SIMULATOR
PRE-FLT
VS.
POS-FLT
(PERCENT)
-.97
.00
-.43
-.76
.00
.00
-.13
.25
.00
-.43
.00
.13
.33
.23
-.13
.44
-.35
.15
.00
-.11
.25
.24
-.33
.36
.14
.00
.12
.12
.26
1.16
-.38
-.91
.00
.32
.00
.00
.00
.00
, SOLAR
& FLT
FLIGHT
VS.
PRE-FLT
COMMENTS
(PERCENT)
.80
1.81
.54
-.22
-1.31
1.93
.61
1.20
2.13
-.12
.23
.31
1.22
1.43
.84
-.97
1.67
-1.61
1.51
1.60
.77
-.07
.49
2.02
-.15
.50
-.39
1.03
-.58
1.68
-.32
1.43
1.10
2.49
.00
.00
.00
.00
K4
K716
AEG
STANDARD
AUSSAT
2 MIL
BENT BLOCK
K7 2 BY 6
AEG 2 BY 6
K5
GA-AS
TEMP MONITOR
K5
TEMP MONITOR
K7
K716
2 MIL
K6.75
AEG 2 BY 6
K7 THIN
REPLY
K6. 75
K4.75
GA-AS
REFLY
REFLY K7
* INDICATES CHANNEL FOR WHICH NO TEMPERATURE COEFFICIENT WAS PROVIDED.
AVERAGE TEMPERATURE (DEG.C) AT FLOAT ALTITUDE = 52.75
Table 2. Repeatability of Standard Solar Cell BFS-17A
(35 flights over a 21-year period)
Flight Date Output, mW Flight Date Output, mW
9/5/63
8/3/64
8/8/64
7/28/65
8/9/65
8/13/65
7/29/65
8/4/66
8/12/66
8/26/66
7/14/67
7/25/67
8/4/67
8/10/67
7/19/68
7/29/68
8/26/69
9/8/69
7/28/70
8/5/70
60.07
60.43
60.17
59.90
59.90
59.93
60.67
60.25
60.15
60.02
60.06
60.02
59.83
60.02
60.31
60.20
60.37
60.17
60.42
60.32
4/5/74
4/23/74
5/8/74
10/12/74
10/24/74
6/6/75
6/27/75
6/10/77
8/11/77
7/20/78
8/8/79
7/24/80
7/25/81
7/21/82
7/12/83
Mean
Std. Deviation
Maximum Deviation
60.37
60.37
60.36
60.80
60.56
60.20
60.21
60.35
60.46
60.49
60.14
60.05
60.07
59.86
60.10
60.22
0.23
0.58
Each data point is an average of 20 to 30 points per flight for period
9/5/63 to 8/5/70.
For flights on 4/5/74 through 7/1/75 each data point is an average of
100 or more flight data points.
For flights starting in September 1975, each data point is an average of
200 data points.
©83-115
COMSAT
®
79-132
TRW
83-181
SPL
(jo)
83-139
HUGHES
©
83-157
ASEC
83-120
HUGHES
©
©
83-170
SOLAREX
83-180
SPL
©
@
83-129
HUGHES
83-110
COMSAT
©
83-126
HUGHES
73-183
JPL
T4 (46)
®
(28)
83-153
ASEC
83-151
ASEC
©
©
83-101
MELCO
83-111
COMSAT
©
®
83-133
HUGHES
BFS-17A
JPL
©
©
83-154
ASEC
83-121
HUGHES
®
(30)
83-103
MELCO
83-124
HUGHES
©
©
83-160
ASEC
83-106
SHARP
©
©
83-152
ASEC
83-105
SHARP
©
©
Tl @
73-182
JPL
83-130
HUGHES
©
©
74-204
COMSAT
83-155
ASEC
©
83-116
COMSAT
®
©
83-159
ASEC
83-140
HUGHES
@
®
78-110
HUGHES
(J INDICATES CHANNEL.NUMBER
H - Tl STD CELL @
L - T2 TRACKER ELEC. @
T4 STD CELL @
T5 VOLTAGE REF. BOX (a)
H
Figure 4. 1983 Module Location Chart
10
VI. CONCLUSIONS
As emphasized by the history of repeatability of cell BFS-17A, viz, ± 1%
(see Table 2), silicon cells, when properly cared for, are stable for long
periods of time and may be used as standards with confidence.
REFERENCES
1. Seaman, C. H., and Weiss, R. S., Results of the 1979 NASA/JPL Balloon
Flight Solar Cell Calibration Program. JPL Publication 80-31, Jet Pro-
pulsion Laboratory, Pasadena, CA, May 1, 1980.
2. Greenwood, R. F., "Solar Cell Modules Balloon Flight Standard, Fabrication
of," Procedure No. EP504443, Revision C, Jet Propulsion Laboratory,
Pasadena, CA, June 11, 1974 (JPL Internal Document).
3. Yasui, R. K., and Greenwood, R. F., Results of the 1973 NASA/JPL Balloon
Flight Solar Cell Calibration Program, Technical Report 32-1600, Jet Pro-
pulsion Laboratory, Pasadena, CA, November 1, 1975.
4. Solar Cell Array Design Handbook, JPL SP 43-38, Vol. 1, p 3.6-2,
Jet Propulsion Laboratory, Pasadena, CA, 1976.
NASA—JPL—Cwnl, L.A., CaW 1 1


Results of the 1983 NASA/JPL balloon flight solar cell calibration program

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