SGP/SIRS/E4 - Sun tracker failure

Direct too low by visual inspection and Diffuse too high. Downwelling and upwelling IR, 
global and upwelling shortwave all indicate clear or mostly clear sky conditions during  
daylight hours, yet direct is near zero. Probable cause: sun tracker failure.

Do not use data

• 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)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer(down_short_diffuse_hemisp)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)
• Shortwave Direct Normal Irradiance, Pyrgeometer, Standard Deviation(short_direct_normal_std)
• Downwelling shortwave diffuse hemispheric irradiance, pyranometer, maxima(down_short_diffuse_hemisp_max)
• Shortwave direct normal irradiance, pyrheliometer, minima(short_direct_normal_min)
• Shortwave direct normal irradiance, pyrheliometer(short_direct_normal)

• Direct-beam normal solar irradiance(nip)
• Shaded pyranometer voltage(short_diffuse)