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Landsat 9 OLI and TIRS Calibration Notices

Calibration notices for Landsat 9 OLI and TIRS instruments.

March 1, 2023 - Landsat 9 Reprocessing Event

The USGS Landsat Project will begin reprocessing of the Landsat 9 Collection 2 Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS) data from the first year of operations beginning March 1, 2023, to take advantage of calibration updates identified by the USGS/NASA Calibration and Validation team. The original image data will be replaced in the archive with the reprocessed imagery. Reprocessing is expected to take approximately 6-8 weeks.

Listed below are the updates being applied to the data and potential impacts these changes may have on use of the data. Users are encouraged to assess these improvements and impacts against their science work and applications to determine if their Landsat 9 data should be replaced with the updated data.  Please note, the Product ID contains the most recent processing date and that will facilitate identification of scenes included in this reprocessing effort. All reprocessed imagery will have a processing date that is March 1, 2023 or later.

Calibration Updates Affecting OLI

OLI Sensor Chip Assembly (SCA) Relative Gains (Banding)

This update reduces the visible banding between the 14 focal plane modules in the SWIR-2 spectral band (Band 7) of Landsat 9's OLI over bright targets (Figure 1). This banding was corrected in imagery processed after March 8, 2022, and this current reprocessing effort will correct the remaining imagery processed prior to March 8, 2022.

Landsat 9 OLI Sensor Chip Assembly Relative Gains Calibration Update
Figure 1. This Landsat 9 Operational Land Imager (OLI) band 7 image shows banding (left), with the right image showing how less banding is visible after calibration updates were made and implemented into Level-1 processing in early 2023. Images created with Landsat 9, Path 165 Row 47, acquired February 28, 2022. 

OLI Cross-Calibration (Reflectance and Radiance)

Cross-calibration between the OLI sensors on Landsat 9 and Landsat 8 was performed using data collected during the November 2021 underfly activity.  After the initial cross-calibration during Landsat 9 commissioning, the analysis was refined during the first year of operations, and updated calibration parameters improve the consistency of Landsat 8 and Landsat 9. This update provides a modest correction to all Landsat 9 OLI bands, with largest improvements of ~0.5 percent in Green spectral band (Band 3) reflectance and ~5 percent in Cirrus spectral band (Band 9) radiance (Table 1).

Table 1. Landsat 9 OLI cross-calibration/absolute calibration updates
Band  Reflectance Mean Radiance Mean
Band 1 1.001 0.999
Band 2 1.002 1.000
Band 3 0.996 0.9978
Band 4 1.000 0.996
Band 5 1.001 0.996
Band 6 1.003 0.9923
Band 7 1.002 0.990
Band 8 0.999 0.9962
Band 9 1.0077 0.945

Calibration Updates Affecting TIRS

TIRS Absolute Bias (Radiance)

Updates were made to TIRS absolute radiance, which affects top of atmosphere, brightness temperature, and surface temperature. Throughout the first year of Landsat 9 operations, comparisons between Landsat 9 products and NASA JPL and NOAA buoy-data showed the need to update absolute thermal calibration (Figure 2). This update ties Landsat 9 calibration to the same reference as Landsat 8. Prior to this update Landsat 9 absolute thermal calibration was tied to pre-launch laboratory measurements. The amount of effect is variable across different measured temperatures: Figure 3 shows the impact in Kelvin at various temperatures.


Landsat 9 Thermal Band Absolute Radiance Bias Updates
Figure 2. This graph displays the absolute radiance bias updates made to the Landsat 9 thermal bands after calibration updates were made and implemented into Level-1 processing.
Landsat 9 BT Delta Temperature Impact Profile
Figure 3. This graph displays the brightness temperature delta temperature impact of radiance updates made to the Landsat 9 thermal band 11 after calibration updates were implemented into Level-1 processing.


TIRS Detector Swaps/Relative Gains (Striping)

Sixteen detectors in Band 10 and three detectors in Band 11 were replaced with their redundant detectors to reduce striping due to changes in responsivity. The resulting stripes could appear at any time and could not be adequately corrected for with quarterly calibration updates. The detector swap will result in more stable detectors being used to generate the Level-1 and Level-2 image products and should result in a lower level of striping across Bands 10 and 11. 

Landsat 9 Thermal Sensor Detector Swap Improvements
Figure 4. These Band 10 images over the Salton Sea in California show a stripe due to a failing detector (left) and the same scene with the failed detector replaced with its backup detector after calibration updates (right). This Landsat 9 image was acquired on November 24, 2022, from Path 39 Row 27. 

Improvements to Systematic Terrain (L1GT) scenes

An along track alignment adjustment of the OLI instrument improves L1GT accuracy by up to 20 meters. Although all L1GT products benefit, the greatest improvement is observed in areas where L1GT are the only products ever created (i.e., in areas where little or no ground control exits). (Figure 5, Table 2). All scenes over Antarctica will be improved, along with several islands, Greenland, and coastal images made up largely of water. Figure 6 shows an example of the improvement.

Landsat 9 Sensor Alignment for L1GT Improvements Map
Figure 5. Location of scenes that benefit the most from the track alignment improvements. As Table 2 shows, most of the improved scenes are from the Antarctic region. 
Table 2. Number of scenes in areas that will benefit most from this update. The largest number of scenes are over Antarctica, where no ground control exists. Other areas of improvement are Greenland, islands and coastal slivers of lands, and open ocean and nighttime images.
Path/Row Type Description Number of 

L1GT Scenes
Antarctica WRS Rows 101 to 133 32,930
Greenland 100% Land, Rows 2-15 2,081
Island/Coastal Sliver Between 0.001% to 0.94% Land 583
Open Ocean 0% Land, Rows 1-100, 247-248 8,204
Night/Ascending No Percent Land Available


The magnitude of the change associated with the Sensor Alignment calibration can be seen in the Geodetic Accuracy pre-fit means results where the term pre-fit refers the measured offset between the reference imagery and the Landsat product prior to ground control being applied to the imagery.  These results are shown in Figure 7 where each geometric calibration site is shown along with a moving average (MA) of that data to better demonstrate the changes over time that is occurring with respect to the sensor alignment parameters.


Animation of Landsat 8-Landsat 9 Antarctica image
Figure 6. Animation of an Antarctica Landsat 8 image compared to both a Landsat 9 image prior to the calibration update and one after the calibration parameters are applied. The Landsat 8 image was acquired from Path 125 Row 108 on December 29, 2022 and the Landsat 9 image is from December 30, 2022, Path 124 Row 108. Both images use the panchromatic spectral band (Band 8)
Sensor Alignment Calibration Ranges for Improved Landsat 9 L1GT Scenes
Figure 7. This graphic displays along track (AT) and across track (XT) residuals from geometric calibration sites. The solid curves are moving window averages (MA) of the single AT and XT scene residuals. There was a 20m offset in the AT direction between 03-01-2022 and 12-31-2022.  ​​   


TIRS to OLI Alignment

Adjustment will improve TIRS to OLI co-instrument alignment for all scenes in the archive (Figure 8).

Landsat 9 Roll, Pitch, Yaw Alignments with Updated Calibration Parameters
Figure 8. These plots display the roll, pitch, and yaw residuals between TIRS and OLI, red dots. The blue lines, Collection 2 Calibration Parameters File (CPF), are previous calibration values, while the black lines, Quarter Average, are the undated alignment calibration parameters. There was a 15 µradian, 10m, offset in the pitch direction between TIRS and OLI.

Science and Application User Impacts

A select number of Landsat 9 scenes were selected to quantify the impact of calibration updates on Landsat 9 Level-2 products. This included 25 globally distributed scenes to capture extreme atmospheric conditions and different land cover types and a stack of 22 scenes over Path39/Row37 (Southwestern United States) for time series analysis. Figure 9 shows the geographic distribution of the Landsat 9 scenes used for impact assessment.

Geographic Distribution of Test Scenes Used for Landsat 9 Level-2 Impact Analysis
Figure 9. Geographic Distribution of Landsat 9 Test Scenes Used for Level-2 Reprocessing Impact Analysis. 

The overall impact of calibration updates on the atmospherically compensated Level-2 Surface Reflectance and Surface Temperature products is minor. The magnitude of the change in Level-2 products is within the uncertainty range of atmospheric correction algorithms. The enhancements in Visible to Short Wave Infrared (VSWIR) banding and Thermal Infrared (TIR) striping artifacts described for the Level-1 also apply for the Level-2 science products. The following sections provide a more detailed description of the change in Level-2 Surface Reflectance and Surface Temperature products.

Summary of VSWIR Bands Changes

The change in Level-2 Surface Reflectance for the VSWIR spectral bands was minimal and well-correlated with the Level-1 Top of Atmosphere (TOA) reflectance changes. Figure 10 summarizes the Mean Absolute Difference (MAD) for the Level-1 TOA (grey bars) Reflectance and Level-2 Surface Reflectance (yellow bars). As expected, the operational Land Surface Reflectance Code (LaSRC) algorithm used for atmospheric correction introduces larger differences in the Level-2 Surface Reflectance product compared to Level-1. On average, the Green spectral band (Band 3) shows largest Surface Reflectance difference (0.0013) followed by the SWIR1 (0.0010) and SWIR2 (0.0009). The Level-1 TOA Reflectance change was minimum for the Cirrus spectral band (8.2e-5 units of reflectance; Band 9).

Figure 11 shows the relative change in TOA and Surface Reflectance using the Mean Absolute Percent Difference (MAPD) statistic. Due to its low dynamic range, the small reflectance changes in the Cirrus band (8.2e-5)(Band 9) can translate to relatively large (~1.1 percent) MAPD in Level-1 TOA Reflectance.

Relative change in Level-2 Surface Reflectance is mainly controlled by the approximation of aerosol path radiance. The Aerosol Optical Thickness (AOT) in the operational LaSRC algorithm is estimated using the ratio between the Red (Band 4), Blue (Band 2), and Coastal Aerosol (Band 1) spectral bands. The path radiance decreases with wavelength. Therefore, shorter wavelengths are expected to be relatively more sensitive to any Level-1 radiometric variation. The Coastal Aerosol spectral band has highest relative sensitivity (MAPD of 4.6 percent) in Level-2 Surface Reflectance among the VSWIR spectral bands.

As indicated in cross-calibration table (Table 1), most VSWIR spectral bands are expected to show slightly brighter reflectance values on average after applying the calibration updates. The Mean Difference in Figure 12 below illustrates a slight increase in reflectance of most VSWIR spectral bands. The Green spectral band (Band 3) will be slightly darker (decreased reflectance), while the Red spectral band (Band 4) is almost unchanged on average.

Mean Absolute Difference in Landsat 9 TOA and SR Summary
Figure 10. Summary of the mean absolute difference (MAD) between Landsat 9 Level-1 Top of Atmosphere and Level-2 Surface Reflectance bands. 
Mean Absolute Percent Difference in Landsat 9 TOA and Surface Reflectance
Figure 11. Summary of Mean Absolute Percent Difference (MAPD) in Level-1 Top of Atmosphere and Level-2 Surface Reflectance
Mean Difference in Reflectance Values of Landsat 9 TOA and Surface Reflectance
Figure 12. Summary of the mean absolute difference (MAD) between Landsat 9 Level-1 Top of Atmosphere and Level-2 Surface Reflectance bands. 


The left panel in Figure 13 shows the Surface Reflectance difference for SWIR2 (Band 7) as a result of calibration updates. The SCA bandings in the difference image are due to enhancements in the relative gain. The scatterplot on the right panel shows the strong overall agreement between the Surface Reflectance before and after the reprocessing.

Example of Landsat 9 Surface Reflectance Change for SWIR2 Channel
Figure 13. Example of Surface Reflectance change for SWIR2 channel. The left pane shows the Surface Reflectance difference for SWIR2 (Band 7) as a result of the calibration update that was implemented into Landsat 9 Level-1 processing in early 2023. The middle panel displays a histogram of the update; and the right panel displays a scatterplot of the update. Landsat 9, Path 39 Row 37, acquired February 9, 2022.  

Figure 14 shows an example of on-demand Level-2 Aquatic Reflectance Band 1 (Coastal Aerosol) generated for a pair of scenes acquired during the Landsat 8/Landsat 9 underfly in November 2021. The reprocessed Landsat 9 image (right image) reveals less SCA Banding compared to the original image (middle).

Example of Less Banding in Landsat 9 Aquatic Reflectance
Figure 14. These images show the lessening banding in Landsat 9 Level-2 Aquatic Reflectance Band 1 (Coastal Aerosol) for a pair of scenes acquired during the Landsat 8 / Landsat 9 underfly in November 2021. The left image is Landsat 8 Aquatic Reflectance; the middle image is Landsat 9 prior to calibration updates, and the right image is the Landsat 9 after the calibration update.

Summary of Thermal Band Changes

Landsat 9 Thermal Bands Mean Absolute Difference and Mean Absolute Percent Difference
Figure 15. Mean Absolute Difference in Kelvin (left) and Mean Absolute Percent Difference (Right) for Landsat 9 TIRS Band 10 and 11. 

The overall impact of the calibration updates on the TOA Brightness Temperature at Band 10 and the Level-2 Single Channel Surface Temperature product calculated using this band is negligible. Figure 15 shows that the Mean Absolute Difference for ST Band 10 is 0.06 Kelvin for the test scenes. This is well within the range of Level-2 Surface Temperature uncertainty.

TIRS Band 11 is expected to change more significantly compared to Band 10. The Mean Absolute Difference for the Top of Atmosphere Brightness Temperature at Band 11 is ~0.37 Kelvin for the studied scenes. The boxplot of difference in Figure 16 illustrates that all studies scenes will have a greater Brightness Temperature after applying the calibration updates.

Landsat 9 Top of Atmosphere Brightness Temperature Difference Boxplot
Figure 16. Boxplot ofLandsat 9 thermal Band 11 Brightness Temperature difference. 

Figure 17 shows an example of a Level-2 Surface Temperature product generated by applying the single channel algorithm on Band 10. The striping artifacts over the water body are clearly improved after applying the calibration updates.

Landsat 9 Surface Temperature Striping Artifact Mitigation
Figure 17.  Example of Surface Striping Artifact Mitigation in Temperature Product. Landsat 9 image acquired over Path 39 Row 37 on April 30, 2022. Top image is the natural color composite, middle image is Surface Temperature before applying calibration updates, and bottom image is the Surface Temperature after applying the calibration updates.

Changes in Quality Assessment Layer

The impact on Pixel Quality Assessment (QA_PIXEL) generated using the C Function of Mask (CFMask) algorithm is very minor. The total difference in QA_PIXEL is less than 3.0 percent for the studied scenes. This difference is less than 0.3 percent and 0.5 percent for the Cirrus and Snow bits, respectively.



March 8, 2022

The USGS and NASA Calibration/Validation team updated the Landsat 9 calibration parameters on March 8, 2022. These updates reduced banding between the 14 focal plane modules visible in the SWIR-2 band (Band 7) of Landsat 9's Operational Land Imager. The update was not applied to Landsat 9 images acquired before March 8, 2022.

NOTE: These updates do not affect the absolute calibration or cross-calibration between Landsat 9 and Landsat 8. 

Landsat 9 Sensor Chip Assembly Banding Example
Left image shows Sensor Chip Assembly (SCA) banding in the Landsat 9 shortwave infrared 2 (SWIR-2) band. On the right is the same image with updated calibration parameters to reduce banding between the focal plan modules. Landsat 9 image acquired on January 23, 2022, from Path 201 Row 46. Learn more about Landsat Calibration and Validation.