NSA/SKYRAD/C1 - itermittant IRT bias

A problem with the SKYRAD IRT that itermittantly produced a gradual increase in the sky 
temperature measurement then a sudden correction, as compared to AERI, appears to have been 
caused by a combination of a failing IR detector, a poor signal cable, a contaminated 
(with condensation or frost) mirror or lens, and low ambient temperatures. The positive 
bias was apparently not consistant in either frequency or duration but on days when the 
unusual behavior is observed, it usually occurred from about 00:00 to 06:00 local time. 

The instrument was repaired and recalibrated and the signal cable replaced.

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

NSA/SKYRAD/C1 - IRT failure

The IRT failed and was replaced with a spare.

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

NSA/SKYRAD/C1 - Power outage affecting some SKYRAD instruments

During the power outage the downwelling global measurement from the PSP instrument and 
downwelling diffuse 8-48 instrument shows a slight increase from -5 to +0 W/m2.  This is due 
to removal of thermal offsets induced by the AC heater during the power outage.  This 
heater is installed within the PSP ventilator - it is necessary for the NSA/C1 climate.
The downwelling longwave PIR instrument is unaffected due to case and dome temperature 
corrections.
The IRT is AC powered and was not operational during this time period.

• null(Raw data stream - documentation not supported)

• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer,
  Minima(down_short_diffuse_hemisp_min)
• Down-welling unshaded pyranometer voltage(down_short_hemisp)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyranometer, Maxima(down_short_hemisp_max)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyranometer, Standard
  Deviation(down_short_hemisp_std)
• Sky Infra-Red Temperature(sky_ir_temp)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer,
  Maxima(down_short_diffuse_hemisp_max)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyranometer, Minima(down_short_hemisp_min)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer(down_short_diffuse_hemisp)
• Downwelling Shortwave Hemispheric Irradiance, Pyranometer, Standard Deviation(down_short_diffuse_hemisp_std)

• Instantaneous Downwelling Hemispheric Shortwave, Unshaded Pyranometer Thermopile
  Voltage(inst_global)
• Instantaneous Sky/Cloud Infrared(inst_sky_ir_signal)
• Instantaneous Uncorrected Downwelling Shortwave Diffuse, Shaded Pyranometer
  Thermopile Voltage(inst_diffuse)