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Question:

Where can I find the solar exoatmospheric spectral irradiances (ESUN) for the Landsat sensors?

Answer:

 

The recommended ESUN values Landsat 1-7 are listed in the table below. These values used with Landsat products currently generated at EROS ensure consistent radiometric calibration of data from all these sensors. (Note: although the data are consistently calibrated, calculated TOA reflectance over the same target may differ among the sensors due to the spectral bandpass difference.)

Recommened Solar Exoatmospheric Spectral Irradiances (ESUN) Values
(in W/m2/μm) 
Band # Landsat 7 ETM+ Landsat 5 TM Landsat 4 TM Landsat 1-5 MSS*
1 1970 W/m2/μm 1958 1958 1848
2 1842 1827 1826 1588
3 1547 1551 1554 1235
4 1044 1036 1033 856.6
5 225.7 214.9 214.7
7 82.06 80.65 80.70
8 1369

*The values listed can be applied to all MSS sensors, due to cross-calibration of all the MSS sensors to match the Landsat 5 instrument.

ESUN values are not provided for Landsat 8 data because they are not required for converting data to reflectance. Landsat 8’s Operational Land Imager (OLI) adopted two independent National Institute for Standards and Technology (NIST) traceable radiance and reflectance calibration methods. The Landsat 8 metadata file provides coefficients necessary to convert to radiance and reflectance from the quantized and calibrated Digital Numbers (DNs) of the product. Thus, ESUN values are not required for reflectance conversion.

Relative Spectral Response (RSR) of the OLI spectral bands can be used along with the user’s preferred solar spectrum to calculate ESUN values corresponding to Landsat 8 OLI bands. (NOTE: ESUN values calculated from RSRs were not used for OLI calibration).

ESUN values are derived from the ChKur spectrum. The ChKur spectrum is the combined Chance-Kurucz Solar Spectrum within MODTRAN 5 (2011, Berk, A., Anderson, G.P., Acharya, P.K., Shettler, E.P., MODTRAN 5.2.0.0 User's Manual).