SGP/SIRS/E21 - Ventilator Fan Failure

Start time is uncertain due to length of time this problem existed.  During the time frame 
specified the PSP (down_short_hemisp) and 8-48 (down_short_diffuse_hemisp) ventilator 
fans failed. PM replaced the fans 7/1/2008 1500. 
Ventilator failure does adversely affect thermopile radiometer measurements but the extent 
has not been quantified. The 8-48 is significantly less affected than the PSP. Mentor 
suggests using component sum method detailed in SIRS
instrument handbook where down_short_hemisp = down_short_diffuse +
short_direct_normal * cos (zenith angle) for each time record.

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• Instantaneous uncorrected downwelling shortwave diffuse, shaded pyranometer
  thermopile voltage(inst_diffuse)
• Instantaneous Downwelling Hemispheric Shortwave, Pyranometer Thermopile Voltage(inst_global)

• (Raw data stream - documentation not supported)

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