SGP/SIRS/E15 - Missing NIP data

The radiometer tracker over-wound and pulled the pyrheliometer (NIP) cable from its 
connector resulting in missing short_direct_normal data during the specified time ranges. 

Cable repaired on 5/28 but only lasted two days.  Cable was replaced 6/6 resolving the 
problem.

The short_direct_normal data are not recoverable. The data can be approximated from the 
two other shortwave datastreams available using the following relationship:
short_direct_normal = (down_short_hemisp - down_short_diffuse)/cos(zenith angle)

• Instantaneous direct normal shortwave irradiance, pyrheliometer thermopile
  voltage(inst_direct_normal)

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