SGP/SIRS/E19 - Ventilator failure

Dowenlling shortwave hemispheric instrument signal (Eppley PSP) is very erratic due to 
failed ventilator fan which was replaced during PM on 04/13/2006.

Compute global from direct and diffuse components during the affected time period.

• Instantaneous Downwelling Hemispheric Shortwave, Pyranometer Thermopile Voltage(inst_global)

• Downwelling shortwave hemispheric irradiance, pyranometer, maxima(down_short_hemisp_max)
• Down-welling unshaded pyranometer voltage(down_short_hemisp)
• Downwelling Shortwave Hemispheric Irradiance, Pyranometer, Minima(down_short_hemisp_min)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Standard
  Deviation(down_short_hemisp_std)

• (Raw data stream - documentation not supported)