 The Landsat 8 satellite carries a thermal imaging instrument called the thermal infrared sensor, TIRS, which captures images in two bands centered at approximately 10.9 and 12 micrometers. The TIRS has a spatial resolution of 100 m and coincides with the operational land imager, OLI, on Landsat 8. The TIRS instrument has an internal calibration system consisting of a variable temperature black body and a special viewport and can be calibrated twice per orbit using two-point calibration. A rigorous vicarious calibration program was started immediately after launch to validate the absolute calibration of the system. However, initial results showed a large error in both bands with TIRS data being too hot. The error was found to be caused by out-of-field stray light and additional work is ongoing to characterize the stray light contribution and improve the vicarious calibration. While band 10 data can be useful for a wide range of applications, band 11 data should not be used where absolute calibration is required due to the larger effect of stray light in that band. This article was offered by Julia A. Barsi, John R. Schott, Simon J. Hook and others. We're article.tv, links in the description below.