Abstract
Highly precise (~±0.05% k=2), traceable, infrared radiance calibrations are typically achieved through the use of large aperture, deep cavity, temperature controlled blackbodies. The combined need for high emissivity, which requires deep blackbody cavities, and high temperature accuracy, which requires high thermal conductivity throughout the cavity, typically results in a design that is thermally massive. Such blackbodies can take many hours (4 to 6 hours) to change temperature and stabilize to ~30 mK or less. For calibrations where multiple blackbody temperatures are measured, these delays in testing significantly increase test duration and cost. In addition, for systems that have embedded temperature sensors, maintaining the traceability to the International Temperature Scale can be cumbersome, costly and potentially cause interruptions in test scheduling. In an effort to overcome these drawbacks Jung Research and Development Corp. (JRAD) and Orbital ATK have developed a large aperture blackbody that is temperature controlled through the use of a rapidly circulating fluid to achieve rapid temperature changes and yet have the required temperature accuracy. In its current configuration where it has been fully tested, this blackbody has an operational temperature range of 230 K to 430 K over which it has a positive temperature ramp rate that ranges from 4 K/min to 8 K/min, a negative ramp rate of -2 K/min to -1 K/min, and a settling time of approximately 15 to 30 minutes. It also has a radiance uncertainty of 0.06% (k=2) or less over the 1.5 um to 5.5 um spectral range and the temperature scale can be very easily recalibrated with less than a 15 minute delay in testing. This presentation will discuss the design, operation, and testing of this blackbody, as well as the emissivity and thermal modeling that was used to justify its radiance accuracy. It will also be argued how this type of performance can be easily increased to a temperature range of 180 K to 560 K, or greater with more significant changes.
Northrop Grumman Corporation High Speed and High Accuracy Blackbody Radiance Primary Standard
Highly precise (~±0.05% k=2), traceable, infrared radiance calibrations are typically achieved through the use of large aperture, deep cavity, temperature controlled blackbodies. The combined need for high emissivity, which requires deep blackbody cavities, and high temperature accuracy, which requires high thermal conductivity throughout the cavity, typically results in a design that is thermally massive. Such blackbodies can take many hours (4 to 6 hours) to change temperature and stabilize to ~30 mK or less. For calibrations where multiple blackbody temperatures are measured, these delays in testing significantly increase test duration and cost. In addition, for systems that have embedded temperature sensors, maintaining the traceability to the International Temperature Scale can be cumbersome, costly and potentially cause interruptions in test scheduling. In an effort to overcome these drawbacks Jung Research and Development Corp. (JRAD) and Orbital ATK have developed a large aperture blackbody that is temperature controlled through the use of a rapidly circulating fluid to achieve rapid temperature changes and yet have the required temperature accuracy. In its current configuration where it has been fully tested, this blackbody has an operational temperature range of 230 K to 430 K over which it has a positive temperature ramp rate that ranges from 4 K/min to 8 K/min, a negative ramp rate of -2 K/min to -1 K/min, and a settling time of approximately 15 to 30 minutes. It also has a radiance uncertainty of 0.06% (k=2) or less over the 1.5 um to 5.5 um spectral range and the temperature scale can be very easily recalibrated with less than a 15 minute delay in testing. This presentation will discuss the design, operation, and testing of this blackbody, as well as the emissivity and thermal modeling that was used to justify its radiance accuracy. It will also be argued how this type of performance can be easily increased to a temperature range of 180 K to 560 K, or greater with more significant changes.