Abstract
Wildfire detection and characterization from space critically depend on accurate thermal infrared measurements across a wide dynamic range. OroraTech’s SAFIRE payloads feature MWIR and LWIR bands optimized for this purpose, yet the volume and power constraints of many CubeSat platforms preclude the use of onboard calibration sources. This reflects a broader limitation of current Earth observation systems: the absence of robust calibration and validation methodologies at high brightness temperatures relevant to active fires.
We evaluate the potential of using thermophysical models (TPM) of the lunar surface as a vicarious calibration reference for calibration transfer between instruments. The Moon reaches surface temperatures of up to 400 K, offering a stable target in the thermal domain that is visible from many different orbits. Previous research has established the use of TPMs for observations in the long-wave infrared; however, uncertainties in surface properties remain, particularly in the midwave infrared. We investigate these effects using SAFIRE observations of the lunar surface acquired over a wide range of lunar phase angles (±120°).
We constrain the TPMs using observations from the Sentinel-3 Sea and Land Surface Temperature Radiometer (SLSTR) fire channels and demonstrate their ability to uncover systematic differences between the calibration of SLSTR-A and SLSTR-B at high brightness temperatures. Applying the same methodology to observations of our SAFIRE payloads yields radiometric accuracies of approximately 3% in both MWIR and LWIR bands.
These results establish lunar vicarious calibration as a viable approach in the thermal domain for high-temperature applications, providing a pathway toward improved fire radiative power retrievals and enhanced global wildfire monitoring.
Applicability of Lunar Thermophysical Models for Vicarious Calibration of High-Temperature Thermal Infrared Sensors
Wildfire detection and characterization from space critically depend on accurate thermal infrared measurements across a wide dynamic range. OroraTech’s SAFIRE payloads feature MWIR and LWIR bands optimized for this purpose, yet the volume and power constraints of many CubeSat platforms preclude the use of onboard calibration sources. This reflects a broader limitation of current Earth observation systems: the absence of robust calibration and validation methodologies at high brightness temperatures relevant to active fires.
We evaluate the potential of using thermophysical models (TPM) of the lunar surface as a vicarious calibration reference for calibration transfer between instruments. The Moon reaches surface temperatures of up to 400 K, offering a stable target in the thermal domain that is visible from many different orbits. Previous research has established the use of TPMs for observations in the long-wave infrared; however, uncertainties in surface properties remain, particularly in the midwave infrared. We investigate these effects using SAFIRE observations of the lunar surface acquired over a wide range of lunar phase angles (±120°).
We constrain the TPMs using observations from the Sentinel-3 Sea and Land Surface Temperature Radiometer (SLSTR) fire channels and demonstrate their ability to uncover systematic differences between the calibration of SLSTR-A and SLSTR-B at high brightness temperatures. Applying the same methodology to observations of our SAFIRE payloads yields radiometric accuracies of approximately 3% in both MWIR and LWIR bands.
These results establish lunar vicarious calibration as a viable approach in the thermal domain for high-temperature applications, providing a pathway toward improved fire radiative power retrievals and enhanced global wildfire monitoring.