Calibration of Band 6

In the fall of 2000, two Landsat 7 science team investigator groups discovered a band 6 calibration bias in Level 1 ETM+ data products emanating from the EDG (i.e. LPGS) at the EROS Data Center. This bias apparently results from limitations in the pre-launch calibration of the ETM+. The magnitude of the correction is estimated to be 0.31 W/(m^2 sr um) or about 3-4% radiance error at typical surface temperatures. This apparent systematic error in Band 6 radiance calibration translates into estimated temperatures derived from Landsat 7 ETM+ being about 3°C too high for typical Earth surface temperatures.

To remedy the situation, several changes were made to the product generation software and CPF. The band 6 biases and instrument component view coefficients were changed in the October 1, 2000 release of the CPF. The calibration equation used by LPGS software was operationally updated on December 20, 2000. Users need to be aware of the impact these changes have on level 1 products.

LPGS Level 1 products - pre 12/20/00
Users should subtract the bias value (0.31 W/(m^2 sr um)) from the radiances obtained from Level 1R and Level 1G data products generated since launch by LPGS for both high and low gain band 6 data. The changes made to the October 1, 2000 CPF effectively remove the temperature bias but only if the product generation software uses the changed CPF values. The LPGS software in place prior to December 20th does not.

LPGS Level 1 products - post 12/20/00
Users can safely use temperatures derived from band 6 radiance values. No bias correction is necessary.

Other Systems - pre 10/01/00
If the CPF gains and biases are used then the band 6 radiance values should be adjusted for the bias described in paragraph three above.

Other Systems - post 10/01/00
If the CPF gains and biases are used then no adjustments are necessary after this date.

Other systems that employ a band 6 calibration equation are outside NASA/USGS configuration and control. For accurate processing, please consult with your product provider.

Back to Chapter 11

Last Update: April 5, 2001