SGP/BRS/C1 - Loose cable connections

During the specified period the short_direct_normal (NIP instrument) measurement signal 
occasionally dropped out.  Site ops found a bad connection on the instrument and corrected 
it. 

Any missing short_direct_normal (NIP instrument) data are not recoverable but can be 
derived from existing down_short_hemsip and down_short_diffuse measurements.  However, this 
results in generally lower quality (i.e. higher uncertainty) data.  Users are advised to 
use measurements from the co-located SGP/SIRS/C1 datastream.

Use sgpsirsC1.b1 data

• Shortwave Direct Normal Irradiance, Pyrgeometer, Standard Deviation(short_direct_normal_std)
• Shortwave direct normal irradiance, pyrheliometer, minima(short_direct_normal_min)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)
• Shortwave direct normal irradiance, pyrheliometer(short_direct_normal)