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Updated:
27 July 2004
January - March 2004
22 January 2004 ACRES Landsat 5 'Bumper Mode' ProductsThe Landsat 5 Thematic Mapper instrument has operated in 'bumper mode' since April 2002. The generation of Landsat 5 TM products using the ‘bumper mode’ method was introduced after the preferred Scan Angle Monitor method of aligning the forward and reverse swaths of imagery failed. As the mechanical bumpers can be expected to continue to wear, bumper timing parameters are all slowly varying with time and must be maintained through periodic calibration updates. USGS (United States Geological Survey), normally issues two versions of the Calibration Parameter File (CPF) for each month, the .01 version containing predicted parameters (generated at the end of the prior month), and the .02 version containing refined parameters (generated within a few days after the end of the current month). When cloud-free calibration scenes are sparse or the bumper behaviour deviates from its previous trend then a 3rd or 4th version of the CPF may also be introduced covering the same month.Bumper mode calibration processing is currently performed on a monthly schedule, in the last week of each month. Initial results presented at the Landsat Calibration Working Group Meeting (South Lake Tahoe, California, December 2003) indicate that:
When ordering non time-critical Landsat 5 'Bumper Mode' products from ACRES, it is recommended waiting for the refined parameters whenever possible, using the predicted parameters only for time-critical applications. The use of predicted parameters in the first version of the CPF file may result in scan-misalignment (up to 1 pixel) to be visible in Landsat 5 TM products. 22 January 2004 Terra MODIS Direct Broadcast data back onlineNASA engineers isolated a problem in the data key header field that resulted in an interruption to the availability of TERRA DB (Direct Broadcast) data for MODIS. During recovery operations the Terra Science Formatting Equipment (SFE) was successfully recycled and MODIS Direct Broadcast data returned to normal around 1340 UTC on the 15th January 2004. ACRES has received data successfully for Australian overpasses — first pass 15 January 2004, 15:15:04 UTC. Passes since 19 January 2004 are available on the ACRES MODIS download page. All outstanding TERRA passes are currently being processed and will be available within the next few days.
22 January 2004 Landsat 7 SLC-Off productsACRES continues to acquire Landsat 7 data in SLC-Off mode.ACRES is currently in the process of acquiring a software upgrade to enable processing and production of Landsat 7 imagery in SLC-Off mode. This software upgrade is expected to be delivered by 6 February 2004 and ACRES plans to release Landsat 7 SLC-Off products in March 2004. In the meantime, since Landsat 7 developed a problem with the onboard Scan Line Corrector (SLC) in June 2003, ACRES has continued to acquire and catalogue SLC-Off data though the imagery is not yet available for viewing in the Digital Catalogue. Please monitor ACRES What's New for further news on the availability of SLC-Off products.
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