TWP/SKYRAD/C2 - Tracker failure

Tracker failed on 6/16/2011. Ops replaced with a spare tracker. The affected instruments 
are the 8-48 (down_short_diffuse) and NIP (direct_normal) shortwave instruments.

The down_long_hemisp1 and 2 (PIR1 and PIR2) performance may have been affected by exposure 
to direct sun.

• inst_down_long_hemisp2_case_temp
• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer2(down_long_hemisp2)
• Radiation, shortwave, downwelling diffuse hemispheric irradiance, 1-min avg(down_short_diffuse_hemisp)
• down_long_hemisp1_min
• Radiation, shortwave, direct normal irradiance, 1-min avg(short_direct_normal)
• inst_down_long_hemisp2_tp
• down_long_hemisp1_max
• inst_down_long_hemisp1_tp
• down_long_hemisp2_std
• down_short_diffuse_hemisp_std
• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Minima(down_short_diffuse_hemisp_min)
• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer1(down_long_hemisp1)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Minima(short_direct_normal_min)
• down_long_hemisp1_std
• inst_down_long_hemisp1_dome_temp
• short_direct_normal_std
• down_long_hemisp2_max
• down_long_hemisp2_min
• inst_down_long_hemisp2_dome_temp
• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Maxima(down_short_diffuse_hemisp_max)
• inst_down_long_hemisp1_case_temp

• inst_diffuse
• inst_down_long_hemisp2_tp
• inst_direct_normal
• inst_down_long_hemisp1_tp
• inst_down_long_hemisp1_case_resist
• inst_down_long_hemisp2_case_resist
• inst_down_long_hemisp2_dome_resist
• inst_down_long_hemisp1_dome_resist