Since the current anomaly associated with the scene select mirror encoder electronics forced a suspension of TIRS Level-1 data processing on December 19, 2014, an exhaustive study has been conducted to determine the root cause of the anomaly and to develop plans for reconfiguring the instrument for a return to nominal operations. During this time TIRS data continued to be collected and archived, although Level-1 processing was suspended.
On March 2, 2015, the TIRS mechanism control electronics (MCE) were swapped to the redundant side (“side-B”) and TIRS data collection resumed on March 4, 2015. It will still take several weeks of commissioning the instrument with the side-B MCE and obtaining sufficient calibration data to resume Level-1 processing. Likewise, TIRS data collected December 19, 2014 through March 1, 2015 will require updated calibration parameters before these data can be processed to generate Level-1 products.
The table below summaries the dates ranges during which TIRS data have been acquired, when provisional products will become available, when reprocessing will take place, and when reprocessed data will become available.
| Acquisition Date Range | Sensor Imagery Acquired | Provisional TIRS Product Availability | Reprocessing Period | Nominal TIRS Data Product Availability | Notes |
|---|---|---|---|---|---|
| December 19, 2014 – March 1, 2015 (23:57:34 UTC) | OLI & TIRS | N/A | April 30, 2015 – May 18, 2015 | May 18,2015 | Several lost TIRS scenes in the period; TIRS imaging stopped in preparation for TIRS side-swap |
| March 2, 2015 (13:53:23 UTC) – March 3, 2015 (00:40:35 UTC) | None | N/A | N/A | N/A | No TIRS or OLI imagery acquired due to TIRS side-swap activities |
| March 3, 2015 (00:40:35 UTC) – March 4, 2015 (00:02:18 UTC) | OLI | N/A | N/A | N/A | OLI imaging resumes |
| March 4, 2015 (00:02:18 UTC) – March 4, 2015 (16:20 UTC) | OLI & TIRS | N/A | N/A | N/A | TIRS engineering imagery acquired |
| March 4 (16:20:00 UTC) – March 7 (00:00:00 UTC) | OLI & TIRS | N/A | April 13, 2015 – April 20, 2015 | April 20,2015 | Mode-4 without TIRS cals |
| March 7 (00:00:00 UTC) – April 13, 2015 (23:59:59 UTC) | OLI & TIRS | March 16, 2015 | April 13, 2015 – April 20, 2015 | April 20,2015 | Nominal TIRS that includes regular BB & DS cals |
A more comprehensive summary of the issues and impacts to TIRS data collection will be posted on the USGS Landsat 8 Calibration Notices web site: https://www.usgs.gov/landsat-missions/calibration_notices.php
