TWP/SKYRAD/C3 - IRT power supply

The 12-to-24V DC converter the provides power to the IRT had shut down and was restarted 
by power-cycling.

• Sky Infra Red Temperature Minima(sky_ir_temp_min)
• Sky Infra-Red Temperature(sky_ir_temp)
• Sky Infra Red Temperature Maxima(sky_ir_temp_max)
• Standard Deviation of Sky Infra Red Temperature(sky_ir_temp_std)

TWP/SKYRAD/C3 - Contamination

The IRT exhibited a positive bias compared to AERI. The problem was corrected when the 
lens and mirror were cleaned.

• Sky Infra Red Temperature Minima(sky_ir_temp_min)
• Sky Infra-Red Temperature(sky_ir_temp)
• Sky Infra Red Temperature Maxima(sky_ir_temp_max)
• Standard Deviation of Sky Infra Red Temperature(sky_ir_temp_std)

TWP/SKYRAD/C3 - Direct normal instrument failure

The NIP instrument (short_direct_normal data stream) failed giving bad data during this 
time period.  The failure start time coincides with a reported DC power failure but no 
connection between the reported power failure and the failure of this instrument could be 
determined. 

Ops also reported the tracker clock running 2.9 minutes slow during maintenance on 12/22 
0300GMT (see CS-2008-0714).  Again, the slow clock is not suspect and did not appear to 
affect alignment.

Ops replaced the NIP instrument on 12/30 and short_direct_normal data resumed normal 
operation.

Disregard the short_direct_normal (NIP) data during this time period or calculate using 
the global and diffuse instruments and the following relationship:
short_direct_normal = ((down_short_hemisp - down_short_diffuse_hemisp))/cos(zenith angle)

• Shortwave Direct Normal Irradiance, Pyrgeometer, Minima(short_direct_normal_min)
• Shortwave Direct Normal Irradiance, Pyrgeometer(short_direct_normal)
• Shortwave Direct Normal Irradiance, Pyrgeometer, Maxima(short_direct_normal_max)
• Shortwave Direct Normal Irradiance, Pyrgeometer, Standard Deviation(short_direct_normal_std)

• Instantaneous Direct Normal Shortwave Irradiance, Pyheliometer Thermopile
  Voltage(inst_direct_normal)