Collection 6 has been under development for a number of years. MCST, in consultation with representatives of the science disciplines, developed improvements to the calibration algorithms and methodologies to handle known issues with the aging MODIS sensors. Terra and Aqua forward processing and reprocessing using L1B Collection 6 (C6) started in 2012. The following references document the major changes implemented in MODIS Collection 6 LUTs as compared with the Collection 5 (C5) LUTs.
Brian N. Wenny ; Aisheng Wu ; Sriharsha Madhavan ; Zhipeng Wang ; Yonghong Li ; Na Chen ; Kwo-Fu Chiang ; Xiaoxiong Xiong; MODIS TEB calibration approach in collection 6. Proc. SPIE 8533, Sensors, Systems, and Next-Generation Satellites XVI, 85331M (November 19, 2012); doi:10.1117/12.974231.
Junqiang Sun ; Amit Angal ; Xiaoxiong J. Xiong ; Hongda Chen ; Xu Geng ; Aisheng Wu ; Taeyoung J. Choi ; Mike Chu; MODIS RSB calibration improvements in Collection 6. Proc. SPIE 8528, Earth Observing Missions and Sensors: Development, Implementation, and Characterization II, 85280N (November 28, 2012); doi:10.1117/12.979733.
Toller, G., X. Xiong, J. Sun, B. N. Wenny, X. Geng, J. Kuyper, A. Angal, H. Chen, S. Madhavan, and A. Wu, "Terra and Aqua Moderate-resolution Imaging Spectroradiometer Collection 6 Level 1B Algorithm", Journal of Applied Remote Sensing, vol. 7, issue 1, 2013.
Changes that are either new to C6 or not previously applied to all C5 processing are summarized below.
|Nature of the Change||Description of Upgrades for Both Terra and Aqua|
|Code||New treatment of data from inoperable detector|
|Code||Fixed the sector rotation issue|
|Code||Addressed PCLW electronics issue|
|LUT||RSB correction for SDSM D9 degradation|
|LUT||New m1 tables (includes SDSM D9 degradation correction)|
|LUT||Using EV data at several AOI and lunar data to derive m1 and RVS for Terra bands 1-4, 8-9 and Aqua bands 8-9|
|LUT||Time-dependent RVS for bands 13-16|
|LUT||Detector-dependent RVS for in bands 8 through 12 (plus Terra band 3)|
|Code, LUT||RVS fit using a 4th-order polynomial|
|LUT||Modified derivation of TEB offset and nonlinear calibration coefficients|
|Code||New computation of the uncertainty index (UI)|
|New LUTs||Added 6 RSB and 11 TEB LUTs for improved uncertainty determination|
|Removed LUTs||8 RSB and 5 TEB LUTs no longer needed by new uncertainty algorithm|
|Code, New LUT||Quality assurance flags expanded from a detector basis to a subframe basis|
|Output||Added a product file attribute that indicates noisy subframes|
|Output||Added a noisy subframe list|
|Output||Added a dead subframe list|
|Output||Added a product file attribute that indicates pixels affected by dead subframes|
|Nature of the Change||Description of Other Terra Upgrades|
|LUT||Time-dependent RVS for bands 17-19|
|Nature of the Change||Description of Other Aqua Upgrades|
|LUT||Treatment of RSB MS 2 RVS|
|Code, New LUT||New calibration treatment during WUCD band 33,35,36 saturation. Added 3 new LUTs for determining default band 33,35,36 b1 values|
|LUT||Modified derivation of a0, a2 coefficients to account for cold FPA fluctuations|
The major impacts to the reflective solar band data L1B products are striping reduction, improved reflectance values and Earth-view data quality, and mitigation of long-term trend drifts. The major thermal emissive band improvements include temperature retrievals, uncertainty index assessment, and Terra:Aqua agreement at cold scene temperatures.
Terra band 10 EV-based RVS: The EV-based m1 and RVS algorithm currently used for bands 8 & 9 was extended to band 10. A special LUT was delivered to OBPG for testing. The results demonstrated that the LUT produced very similar results to the correction applied by OBPG. It was recommended that the new band 10 approach be implemented in the official Collection 6 LUT. A new LUT was delivered containing this update (22.214.171.124_OC) prior to the start of an OBPG reprocessing. MCST will begin a similar implementation in the forward C6 to eventually synchronize the OBPG and forward C6 LUTs. To avoid any sudden jumps or discontinuities for band 10 products, a gradual implementation of the updated LUT will occur over the next 4-6 months. The link below has results from the OBPG testing as well as information on the MCST LUT.
Terra band 5 correction: MCST observed a systematic upward drift in trending of the Terra band 5 TOA reflectance for all desert targets used for the calibration monitoring of MODIS, increasing reflectance about 1.2% over the mission period. MCST delivered a new LUT to fix this for the entire mission period with the needed correction applied in the forward processing. This fix to correct for the observed trending in band 5 will also result in change to reflectance in band 26 since a SWIR band crosstalk related correction in Level 1B uses band 5 to correct band 26. More details can be found in the attached document