Calibration and Validation
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Laboratory Calibration

Calibration of the radiometers and bulk temperature sensors deployed at the

Lake Tahoe CA/NV (http://laketahoe.jpl.nasa.gov)

and

Salton Sea CA (http://saltonsea.jpl.nasa.gov)

sites is undertaken at JPL and the facilities are summarized below, the other equipment is calibrated by the manufacturer.

The radiometers and bulk temperature sensors are calibrated using a laboratory blackbody and a temperature controlled water bath respectively. Both systems are NIST traceable. In addition, JPL has developed a portable cone blackbody for field calibration (Rice et al. 2002).  The specifications for the NIST traceable laboratory cone blackbody and readout system are:
•    NIST designed cone in a 44 liter temperature controlled bath. Stability at 25 C: +/- 0.0007 C (7008-IR)
•    Thermistor standard probe with an accuracy specification of 0.0015 ° C over 0-60 ° C and stability/yr of 0.005 ° C. (Model 5643-R) and Secondary PRT.
•    Readout system with an accuracy of 0.0025 ° C at 25 ° C and resolution of 0.0001 ° (Chub E4)
The specifications for the NIST traceable temperature controlled water bath are:
•    Deep, mid-range (-10° C to 110 ° C), water bath with a stability specification: ± 0.0008 ° C from 0-25 ° C. (Model 7012)
•    Thermistor standard probe with an accuracy specification of 0.0015 ° C over 0-60 ° C and stability/yr of 0.005 ° C. (Model 5643-R) and Secondary PRT.
•    Readout system with an accuracy of 0.0025 ° C at 25 ° C and resolution of 0.0001 ° (Chub E4)
Calibration of the radiometers and bulk temperatures is performed in a ramp and soak mode where the blackbody or water-bath temperature is increased by a set interval and allowed to soak for several minutes and then the temperature is measured. The measured temperatures are then compared to the standard probe temperatures to derive calibration coefficients for the radiometer or bulk temperature sensors. After calibration the bulk temperature sensors and radiometers have accuracies of ± 0.1 ° C and ± 0.08 ° C respectively.

 

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