Table 2.
Overview of the sources contributing to the FPH uncertainty budget. Combining the frost stability, manufacturing variability, and thermistor calibration uncertainties in quadrature can be calculated for a fixed interval in the FPH profile.
| Uncertainty parameter | Value | R/S1 |
|---|---|---|
| Frost control stability, u_Frost_Control | 0.1–1.5 K | R |
| Temperature uniformity of the mirror, u_Mirror_ Uniform | < 0.1 K | S |
| FPH electronics board thermistor measurement, u_FPH_ ADC | < 0.02 K (stratosphere), < 0.17 K (troposphere) | S2 |
| Manufacturing uncertainty total, u_Manuf | = (u_Mirror_Uniform2+ u_FPH_ADC2)1/2 | S2 |
| Thermistor calibration fit, u_Cal_Fit | 0.06 K (three-point fit), 0.01 K(six-point fit) | S |
| Thermistor calibration repeatability, u_Cal_Repeat | 0.043 K (three-point fit), 0.028 K (six-point fit) | S |
| Reference thermometer, u_Ref_Therm | 0.01 K after 1998, 0.075 K before 1998 | S |
| Thermistor calibration total, u_Therm_Cal | = (u_ Cal_Fit2+ u_Cal_Repeat2+ u_Ref_ Therm2)1/2, 0.1 K < 1990, 0.07 K > 1990 (three-point fit), 0.03 K (six-point fit) | S3 |
| NOAA FPH uncertainty total, u_FPH | = (u_ Frost_ Control2+ u_Manuf2+ u_Therm_Cal2)1/2 |
1
Random or systematic;
2
dependent on frost point temperature;
3
constant in profile.