SGP/SIRS/E5 - NIP obstruction around sunrise

Due to instrument supports blocking the NIP, the short_direct_normal measurement readings 
dip for about 15 minutes at approximately 1200 UTC (at or near sunrise) on clear days 
during the bracketed time ranges for the entire duration of this deployment.  Affected time 
periods are 4/15-5/15 and 7/28-8/27 annually.

The instrument was removed from service 20091102.

Disregard NIP data 30 minutes before and after 1200GMT

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

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