Collection 6.1 

After the successful implementation of MODIS Collection 6, work began to find improvements for the next iteration of calibrated data products. Collection 6.1 marks an incremental improvement over Collection 6.

For Terra MODIS data products, in response to science user feedback and in coordination with the MODIS science team, MCST developed and implemented a correction to cross-talk effects observed in the PVLWIR bands (27-30). The correction is based on lunar observations and reduces the impact of cross-talk on L1B data as well as higher level data products. Collection 6.1 results for these bands where reprocessed using the crosstalk correction. Implementing this correction also improved detector performance in the effected bands. Several detectors classified as noisy or inoperable ('dead') in Collection 6 have been upgraded to 'operable' status in Collection 6.1 (see tables 1 and 2, below). The remaining TEB are unchanged as compared to Terra Collection 6. Bands 1 and 2 data was also reprocessed from the start of 2012 to reduce the impact of forward predictions to the calculated gain. Forward processed results start on 2017/057 for these bands. Beyond bands 1 and 2 reprocessing, the RSB mimics the Terra Collection 6 results.

Aqua Collection 6.1 is primarily a continuation of the algorithm used in Collection 6, with only the addition of Earth-view data incorporated in the gain calculation of bands 1-4. The same approach was introduced in Terra Collection 6 and is similarly applied in Collection 6.1 for Aqua data. Data for these bands was reprocessed, using this updated algorithm to mission-start to produce a complete data set. Aqua data for other RSB and TEB are unchanged from Aqua Collection 6.

Collection 6.1 does not include a full-mission reprocess of all MODIS data products, only the bands addressed with changes differ from currently produced Collection 6 results. Higher-order data products that use tests based on a combination of bands (such as the cloud mask) may see an impact.

     Figure 1: Band 27 image comparison of Hurricane Fabio of the coast of Baja, California on July 3, 2018 for Collection 6 (left) and Collection 6.1 (right).  In Collection 6, crosstalk contamination introduces striping, false land/water boundary features near the top of the image, and a temperature inversion of the clouds relative to the water.  In Collection 6.1, the striping is greatly reduced, the land/water boundary features are removed, and the temperature inversion is corrected.¹

Table 1: Terra QA change summary from Collection 6 to Collection 6.1

Table 2: Terra QA changes from Collection 6 to Collection 6.1 (detectors listed in SBRS order)

     Figure 2: Aqua MODIS reflectance long-term drift (%) as a function of frame number from the on-board-based RVS approach.²

     Figure 3: Aqua MODIS reflectance long-term drift (%) as a function of frame number from the EV-based RVS approach.²

References:
[1] Wilson, T., A. Wu, A. Shrestha, X. Geng, Z. Wang, C. Moeller, R. Frey, and X. Xiong, "Development and Implementation of an Electronic Crosstalk Correction for Bands 27–30 in Terra MODIS Collection 6", Remote Sensing, vol. 9(6), issue 569, 2017.

[2] Angal, A., X. Xiong, A. Wu, X. Geng, and H. Chen, "Improvements in the On-Orbit Response Versus Scan Angle Characterization of the Aqua MODIS Reflective Solar Bands", IEEE Transactions on Geoscience and Remote Sensing, vol. 56, issue 3, pp. 1728-1738, 2018.