Anz-Meador, Phillip

Buckalew, Brent

Cowardin, Heather

Frith, James

Lederer, Susan

Reyes, Jacqueline

NASA Technical Reports Server

National Aeronautics and Space Administration
Infrared Studies of the Reflective Properties of Solar 
Cells of the HS376 Spacecraft
James Frith1
September 2016
1Univ. Texas El Paso
2JETS/Jacobs
3NASA Johnson Space Center
Jacqueline Reyes1, Phillip Anz-Meador2, Heather Cowardin1, Brent Buckalew2, Susan Lederer3
https://ntrs.nasa.gov/search.jsp?R=20160011590 2019-08-29T16:30:01+00:00Z
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United Kingdom Infrared Telescope
• Long history of providing high quality infrared 
observations to the astronomical community
• Capable of both photometry and spectroscopy
• NIR Camera
• 1-5 micron low resolution spectroscopy
• 5-25 micron high resolution spectroscopy
• Extremely efficient software pipeline via the 
Cambridge Astronomical Survey Unit 
• Both telescope and software pipeline have been 
recently modified for man-made object tracking and 
analysis.
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MCAT UKIRT - WFCAM
Wide Field Camera (WFCAM)
4 separated Rockwell Hawaii-II (HgCdTe 2048x2048) 
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Hughes/Being HS-376 Spacecraft
• Simple geometry
• More than 50 launched from 1980 to 
2003 into Geo orbits.
• Roughly 2 meter diameter spin-
stabilized cylinder covered primarily in 
solar cells
• Near-identical physical characteristics 
and similar materials help constrain 
albedo/size ambiguity
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• K4 3/4: Shallow junction n/p Si cell with back surface reflector
• K7: Shallow junction n/p Si cell with back surface field, back 
surface reflector and textured front surface
• GaAs/Ge: p/n single junction GaAs device grown on Ge
substrate
• GaInP2/GaAs/Ge: Dual junction n/p device grown on inactive 
Ge substrate 
Solar Cells Used
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Light Curves
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Color vs Phase
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Mean Color vs Launch Date
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GaAs/Ge 
Solar Cells
Dual 
Junction: 
GaInP2/GaAs 
on Ge
Silicon K4 
3/4
Silicon K7
Spectra collected in the Optical Measurement Center at NASA JSC
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OMC Spectroscopy: Solar Cells
 ~200 spectral measurement readings of various solar cells
 Ge QE correlates with peak at ~850nm
 CT Dual Junction: GaInP2/GaAs on Ge
 GaInP2 QE correlates with peak at ~700nm
(nm)
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OMC Spectroscopy compared to UKIRT photometry
Z
Y
J
H
K OMC Spectra of K7 Solar Cell
Filter bandpass convolved with Spectra
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Future Work
• Continue studies with UKIRT spectra
• Observe HS376s with non-silicon based solar cells and compare
• Spectral unmixing spectra for material analysis (in progress)
• Investigate known space weathering effects
• Better refine ground based spectra to on-orbit comparison
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Backup
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Spectroscopy
 Spectrum Measuring light energy at various wavelengths 
 Spectrometer Reflectance Curve (spectrum)
 Reflectance curve material composition in FOV of instrument  
 Examine maxima and minima of reflectance curves
 Minima Molecular Absorption = Absorption Bands
 Maxima Reflecting areas
Reflectance Spectrometer
 Broad Range from 300-2500 nm
 3 spectrometers in system
1. VNIR: 300nm – 1,000nm
2. SWIR 1: 1,000nm – 1,850nm
3. SWIR 2: 1,850nm – 2,500nm
Procedure
 Pistol and lamp @ 90°
 Pistol perpendicular to target surface
 Calibrate using Spectralon (white reference material)
 Computer program records data
Requirements
 Dark Lab
 Powder Free Latex Gloves
 Patience & a steady hand
Analyzing Slopes on 
Reflectance Curves
Material Characterization
 Aluminum = 850 nm
 Copper/Gold = 450 nm
 Solar Panels = close to 0 (flat)
 Organics
 White Paint
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Color vs Phase
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Mean Color vs Launch Date
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Magnitude Comparison
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Detection Filtering
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Nov 2014 Observations
• Objects chosen based on year of their launch and availability over 
Hawaii during campaign.
• Each object tracked for an entire night except for losses due to 
weather
• 5 second exposures with 5 second co add
• Cycled through ZYJHK filters with about 10 min per filter
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Light Curves


Infrared Studies of the Reflective Properties of Solar Cells of the HS376 Spacecraft

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