McNatt, Jeremiah S.

Myers, Matthew G.

Wolford, David S.

NASA Technical Reports Server

National Aeronautics and Space Administration 
www.nasa.gov  
U.S. High Altitude PV Measurement 
 for Primary Calibration Standard 
Certification 
16th AM0 Workshop 
December 3-6, 2012 
Takayama, Gifu, Japan 
https://ntrs.nasa.gov/search.jsp?R=20150009576 2019-08-31T07:53:46+00:00Z
National Aeronautics and Space Administration 16th AM0 Workshop-Japan2012-McNattNASAGRC 2 
• Background 
 
• Current Capability 
 
• Future Options 
 
• Comparison of Learjet 25 and ER-2 Platforms 
 
 
Overview 
National Aeronautics and Space Administration 16th AM0 Workshop-Japan2012-McNattNASAGRC 3 
[1] 
• AM0 primary calibration standards are required to 
calibrate laboratory solar simulators for 
measurement of space PV cells 
• Ideally calibrations standards would be measured 
using a helium balloon platform above all but 
negligible absorbing and scattering components 
of the atmosphere (120,000 ft./36.6 km) 
- Maintaining funding for balloon measurement 
platforms have been problematic 
• Currently U.S. standards are measured on board 
aircraft flying at the ceiling of their flight 
envelopes. 
- This method requires correction for ozone for 3J 
cells 
 
Background 
National Aeronautics and Space Administration 16th AM0 Workshop-Japan2012-McNattNASAGRC 4 
Atmospheric Correction 
• Isc data is corrected for current earth-sun distance and 
ozone levels. 
- Ozone correction based on satellite measurements of total 
ozone column density and a pressure dependent distribution 
model. 
• Air Mass number calculated from pressure and sun 
declination angle.  
- Sun angle change is negligible during a 20 minute flight at 
local noon. 
- Pressure can be used directly. 
National Aeronautics and Space Administration 16th AM0 Workshop-Japan2012-McNattNASAGRC 5 
Langley Plot Generated - Semi log plot of Isc vs. 
Air Mass is fit linearly and AM0 Isc extrapolated 
National Aeronautics and Space Administration 16th AM0 Workshop-Japan2012-McNattNASAGRC 6 
Current Capability – Learjet 25 
• Based at NASA – Glenn Research Center (GRC) Cleveland OH 
• High Altitude testing has been conducted since 1963 
• Operational Ceiling – 45,000 ft. (13.7 km) – 50,000 ft. (15.2 km) ASL 
• Good correlation with balloon (1J, 3J) and shuttle tests (1J) 
• Standard deviation in Isc (AM0) ~ 0.75% for top cell, ~ 0.5% for middle 
and bottom cell 
• Isc measurement for all cells, I-V curve for limited number of cells 
 
National Aeronautics and Space Administration 16th AM0 Workshop-Japan2012-McNattNASAGRC 7 
• Fly along 45th Parallel 
• Ascend to 48,000 – 50,000 ft. (14.5-15 km) ~AM 0.2 
• Data collection starts at local solar noon ± 10 min 
• Descend at 1000-1500 ft./min (300-450 m/min) to 30,000-35,000 
ft. (9 -11km) while collecting data 
Method – Flight Plan 
National Aeronautics and Space Administration 16th AM0 Workshop-Japan2012-McNattNASAGRC 8 
Sun Sight 
• Enables aircraft pilot to align 
collimating tube with sun 
• Sight is calibrated to tube prior to 
flight 
Collimating Tube and Cell 
Fixture 
• Temperature controlled within 
±1°C 
• Angle can be set between 20-50° 
from horizontal 
National Aeronautics and Space Administration 16th AM0 Workshop-Japan2012-McNattNASAGRC 9 
Future U.S. Capability Options 
  
• NSCAP Balloon 
- NASA and DOD joint effort 
- Not currently funded 
 
• NASA ER-2 High Altitude Aircraft – Dryden 
Flight Center 
- Under consideration 
 
National Aeronautics and Space Administration 16th AM0 Workshop-Japan2012-McNattNASAGRC 10 
• The ER-2 AMO project would use NASA’s ER-2 high altitude aircraft as a 
platform for solar cell measurements. 
• The ER-2 can fly significantly higher (65,000 ft. vs. 48,000 ft. (19.8 km vs. 
14.5 km))  than the Learjet-25. 
• ER-2 flight parameters would compliment the Learjet 25 flight season and 
extend the overall testing season. 
• Uses similar hardware and methods as the Learjet to accomplish the 
same goal – Obtain AM0 performance data on solar cells. 
• ER-2 would reduce the degree of ozone correction required and thus 
improve upon uncertainty for data  
collected at lower altitudes. 
ER-2 Overview 
• Larger measurement stage area 
allows for increased size or 
number of samples. 
• Use of 2 wing pods is a 
possibility. 
National Aeronautics and Space Administration 16th AM0 Workshop-Japan2012-McNattNASAGRC 11 
National Aeronautics and Space Administration 16th AM0 Workshop-Japan2012-McNattNASAGRC 12 
38.2˚ maximum angle from vertical 
3:1 length to diameter collimation ratio 
Concept of Collimation Tube Design 
Cross section 
of wing pod 
National Aeronautics and Space Administration 16th AM0 Workshop-Japan2012-McNattNASAGRC 13 
Comparison of ER-2 and Learjet Platforms 
Cell capacity comparison 
• Preliminary cost analysis indicates that costs per standard will be 
similar for either platform under certain conditions 
 
• Factors that affect standard measurement costs per piece 
- Number of cells being measured 
- Number of flights required 
- Time of year 
National Aeronautics and Space Administration 16th AM0 Workshop-Japan2012-McNattNASAGRC 14 
~33% Reduction in Atmospheric Ozone vs. Learjet 
Ozone column above test cell (DU) 
National Aeronautics and Space Administration 16th AM0 Workshop-Japan2012-McNattNASAGRC 15 
Atmospheric Correction 
 
Present Lear Analysis suggests Langley Plot 
extrapolation will be valid for ER2 
 
• Less extrapolation (<½ air mass) 
• Still need to correct for ozone 
• Water vapor may be more of an issue for increased junctions 
- Need 4J tests/analysis 
- Need 6J tests/analysis (UV (ozone) and IR (water) 
- Smaller bandwidth increases sensitivity to absorption bands 
(O2, H20, O3)  
- Correction methods may be developed 
National Aeronautics and Space Administration 16th AM0 Workshop-Japan2012-McNattNASAGRC 16 
Other NASA GRC PV Measurement Capabilities 
• Triple source (xenon arc/tungsten filament/filtered 
tungsten filament) solar simulator 
• Spectral response measurement 
• Thermal cycling measurement 
• Large area I-V curve measurement 
• High concentration I-V curve measurement 
• Low temperature I-V curve measurement 
• Low intensity illumination measurement 
National Aeronautics and Space Administration 16th AM0 Workshop-Japan2012-McNattNASAGRC 17 
 


U.S. High Altitude PV Measurement for Primary Calibration Standard Certification

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