NSA/GNDRAD/C1 - Frosting/Condensation

The GNDRAD PIR and IRT comparison was showing the IRT 2-4 W/m^2 greater than the PIR.  
Suspected snow or frost on the instrument(s).  Corrective maintenance performed 10/15/04 at 
21:30 UT.  Optics of both instruments were cleaned.  Upwelling longwave measurement 
agreement restored (+/- 5 W/^2).

Although the relative performance (agreement) of the two instruments improved after 
corrective maintenance (+/- 2 W/m^2), no correction is suggested because the agreement remains 
with the estimated measurement uncertainty of +/- 4 W/m^2 (IRT) and +/-10 W/m^2 (Inverted 
PIR)

• Upwelling Longwave Hemispheric Irradiance, Pyrgeometer, Minima(up_long_hemisp_min)
• Net Radiation, Standard Deviation(net_std)
• 10 meter Upwelling Longwave Hemispheric Irradiance, Pyrgeometer(up_long_hemisp)
• Surface infra-red temperature(sfc_ir_temp)
• Surface Infra-Red Temperature, Minima(sfc_ir_temp_min)
• Upwelling (10 meter) Longwave Hemispheric Irradiance, Ventilated Pyrgeometer,
  Standard Deviation(up_long_hemisp_std)
• Upwelling longwave hemispheric irradiance, pyrgeometer, maxima(up_long_hemisp_max)
• Surface Infra-Red Temperature, Standard Deviation(sfc_ir_temp_std)
• Surface Infra-Red Temperature, Maxima(sfc_ir_temp_max)

• (Raw data stream - documentation not supported)

• Instantaneous PIR1 uncorrected irradiance(pir1_voltage)
• Instantaneous PIR1 dome thermistor(pir1_dome_therm)
• Instantaneous Upwelling Pyrgeometer Case Thermistor Resistance, Pyrgeometer(inst_up_long_case_resist)
• Instantaneous Upwelling Pyrgeometer Thermopile Pyrgeometer(inst_up_long_hemisp_tp)
• Instantaneous PIR1 case thermistor(pir1_case_therm)
• Instantaneous Upwelling Pyrgeometer Dome Thermistor Resistance Pyrgeometer(inst_up_long_dome_resist)