Abstract
Satellite instruments operating in the thermal infrared wavelength range >3 µm provide information for applications such as land surface temperature (LST), sea surface temperatures (SST), land surface emissivity, land classification, soil composition, volcanology, fire radiative power, cloud masking, aerosols, and trace gases. All these instruments are dependent on blackbody (BB) calibration sources to provide the traceability of the radiometric calibration to SI (Système International d’Unités). A key issue for flight BB sources is to maintain the traceability of the radiometric calibration from ground to orbit. For example, the temperature of the BB is measured by a number of precision thermometers that are calibrated against a reference Standard Platinum Resistance Thermometer (SPRT) to provide the traceability to the International Temperature Scale of 1990 (ITS-90). However, once calibrated the thermometer system is subject to drifts caused by on-ground testing, the launch and space environments. At best the uncertainties due to thermometer ageing can only be estimated as there is no direct method for recalibrating. Comparisons with other satellite sensors are useful for placing an upper limit on calibration drifts but do not themselves provide a traceable link to the SI. In this paper, we describe we describe some of the technology developments, including phase change cells for use as reference standards, thermometer readout electronics and implementation of novel coatings, that are in progress to enhance the traceability of flight calibration systems in the thermal infrared.
Highlights
The Planck radiation law predicts that for temperatures that cover the typical range of earth scenes from 180 to 350 K, the peak of the radiation distribution occurs within the range 3–20 μm
Thermal InfraRed (TIR) measurements from satellite instruments have a range of applications ranging from global climate change monitoring, improved weather forecasting through assimilation of data into Numerical Weather Prediction (NWP) [1] and monitoring urban pollution, Table 1, presents a summary of applications from hyperspectral TIR imagers [2]
It is not possible to demonstrate the radiometric calibration of TIR instruments within the required uncertainty levels
Summary
The Planck radiation law predicts that for temperatures that cover the typical range of earth scenes from 180 to 350 K, the peak of the radiation distribution occurs within the range 3–20 μm. The radiances cover a wide dynamic range, at wavelengths
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
