The Thermal Infrared Sensor (TIRS) contains two thermal bands, which measure land surface temperature at 100-meter resolution. (The product provided is resampled and delivered as 30-meter). In the thermal bands, dark pixels represent cool temperatures and light pixels represent hot temperatures. Thermal band data provide important information about water irrigation use in arid land, as well as heat units in urban areas.
While the two thermal bands were designed to allow the use of split-window surface temperature retrieval algorithms, the following information describes two issues being investigated: Stray Light and the Scene Select Mechanism (SSM) Anomaly.
Since the launch of Landsat 8 in 2013, thermal energy from outside the normal field of view (stray light) has affected the data collected in Bands 10 and 11 of the Thermal Infrared Sensor (TIRS). This stray light increases the reported temperature by up to four degrees Kelvin (K) in Band 10 and up to eight K in Band 11. The errors vary throughout the scene and depend upon radiance outside the instrument field of view, which users cannot correct in the Landsat Level-1 data product.
The amount of stray light in the scenes is estimated using scenes acquired before and after the target scene, as well as the edge pixels of the target scene. The stray light estimate is then subtracted from the target scene. Users are cautioned that the results after this correction may still not be considered precise enough for a split-window algorithm application and it is recommended that users refrain from using band 11 data in science studies.
For more information see: (Montanaro, M.; Gerace, A.; Lunsford, A.; Reuter, D. Stray Light Artifacts in Imagery from the Landsat 8 Thermal Infrared Sensor. Remote Sens. 2014, 6, 10435-10456)
More details about the stray light are documented in Appendix A of the Landsat 8 Data User Handbook.
Scene Select Mechanism (SSM) Anomaly
On December 19, 2014, the TIRS instrument on Landsat 8 was reconfigured due to detection of anomalous current levels associated with the scene select mirror encoder electronics. After extensive investigations and testing the TIRS Mechanism Control Electronics were switched from the primary (A-side) to redundant (B-side) on Monday, March 2, 2015. TIRS resumed normal imaging operations on March 4, 2015, and nominal blackbody and deep space calibration data collection resumed on March 7, 2015. TIRS data for a number of scenes were not processed due to non-nominal instrument configuration, and the scenes were processed as OLI-only products. See the May 8, 2015 notice on the Landsat 8 Calibration Notices web page for more details.
In October 2015, an increasing trend in the B-side electronics current was discovered, and in early November, testing will be conducted to characterize the Scene Select Mirror in alternative modes of operation. More information will be posted to this website when it becomes available.