I write this towards the end of the CALCON Conference at the Utah State University Campus in Logan, Utah. The conference is here because the Space Dynamics Laboratory is part of Utah State. CALCON is the "Conference on Characterization and Radiometric Calibration for Remote Sensing".
What is the difference between the radiometric calibration they speak of and the radiometric calibration I speak of when referring to radiation thermometry? In some aspects, I can answer this by saying “Nothing.” However, I could also answer this by saying “Everything.”
For some background information, most of the papers from this conference speak to satellite systems measuring the atmosphere or earth’s surface. These systems have to be put together on earth and assured that they work very reliably long before they go into space. Many of their measurements are done in the visible region. Others are done in the NIR band. Some are done in the SWIR, MWIR, LWIR, and even the FIR and microwave bands.
By contrast, in the application of radiation thermometry, the measuring distance is generally around one meter. Other bands are used, but the bulk of the work is done in the LWIR band. Typically when these measurements are done, the user is in close proximity to the radiation thermometer.
There are many similarities. Both types of systems collect thermal radiance for their measurement system. Many of the papers from CALCON mentioned measurement uncertainty. This is important for any measurement system and the VIM tells us that traceability doesn’t exist without an uncertainty analysis. Emissivity is also a great concern in both fields of calibration.
Both types of calibrations need a thermal radiation source. In radiation thermometry, this source can be a blackbody cavity or a flat-plate source. Some satellite applications use an onboard cavity blackbody. Many others use natural objects such as the Sun, the Moon, or terrestrial objects such as deserts, oceans, Antarctica/Greenland, or deep convected clouds.
It was interesting that at this conference and the International Temperature Symposium in 2012, both keynote speakers spoke of climate change and the importance of making accurate measurements to quantify climate change. Without traceable measurements, nothing can be quantified.
If you are interested in the topic of infrared thermometry, you might be interested in this video: Emissivity Makes a Temperature Difference