NSA/SKYRAD/C1 - NSA B&W nighttime offset in Barrow too large

This problem only became apparent as NSA C1 nights became long enough for full darkness. 
The shaded global diffuse instrument (Eppley 8-48) showed a negative nighttime offset 
larger than the expected 0 to -4 W/m2. Typically -5 to -8 W/m2. This size of offset is not 
uncommon with Eppley PSPs but not observed with Eppley 8-48s.  The problem was corrected 
with replacement of mounting screws which were creating a ground loop.

Data to be used at users discretion.

• (Raw data stream - documentation not supported)

• Downwelling Shortwave Diffuse Hemispheric Irradiance, Pyrgeometer, Minima(down_short_diffuse_hemisp_min)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Pyranometer, Standard
  Deviation(down_short_diffuse_hemisp_std)
• PSP shaded mean(psps_mean)
• Downwelling shortwave diffuse hemispheric irradiance, pyranometer, maxima(down_short_diffuse_hemisp_max)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer(down_short_diffuse_hemisp)
• PSP shaded minimum(psps_min)
• PSP shaded standard deviation(psps_sd)
• PSP shaded maximum(psps_max)

• Downwelling Shortwave Diffuse Hemispheric Irradiance, Pyranometer, Standard
  Deviation(down_short_diffuse_hemisp_std)
• Downwelling shortwave diffuse hemispheric irradiance, pyranometer, maxima(down_short_diffuse_hemisp_max)
• PSP shaded mean(psps_mean)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer(down_short_diffuse_hemisp)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Pyrgeometer, Minima(down_short_diffuse_hemisp_min)
• PSP shaded minimum(psps_min)
• PSP shaded standard deviation(psps_sd)
• PSP shaded maximum(psps_max)