20 June 2003
ACRES will resume acquisition of Landsat 5 data from Alice Springs ground station commencing 1 July 2003.
The Landsat 5 satellite, launched on 1 March 1984, is still operational and providing high quality data, though operating in bumper mode since April 2002. This required ACRES to upgrade its processing software to correct for bumper mode effects. As part of the software upgrade, ACRES is implementing a significant improvement to the calibration of Landsat 5 data, following the revised calibration parameters recently published by USGS (United States Geological Survey). As a result of this upgrade, ACRES Landsat 5 products will be consistent over time and also consistent with Landsat 7 products.
Over the last few weeks ACRES have acquired several Landsat 5 passes to test modifications to the cataloguing and product generation software. These browse images are available on ACRES digital catalogue.
ACRES have requested USGS to routinely schedule all Landsat 5 passes over Australia from 1 July 2003 for downlinking at Alice Springs, however, there is no guarantee at this stage that all requests for data will be granted.
ACRES will accept orders for Landsat 5 data from 1 July 2003. There are no changes to ACRES Landsat 5 products, delivery and distribution arrangements that are currently in place, however, product prices are currently being reviewed and will be announced soon.
29 May 2003
The Transcription Project commenced in November 1999, and set out to transfer the ACRES archive of remote sensing satellite data recorded on redundant Optical Tape (OT) to newer media, Digital Linear Tape (DLT).
Though DLT's have a storage capacity of only 35 gigabytes compared to Optical Tapes' incredible 1 terabyte (1,000 gigabytes), DLT's are designed for operation in robotic tape libraries that can hold hundreds or thousands of tapes. This capability along with advanced database and tape management software add up to significant advantages for ACRES.
Image data from a total of 26,487 satellite passes was transcribed. Passes included MultiSpectral Scanner (MSS) data from Landsat 2, 3, 4 and 5, Thematic Mapper ( TM ) data from Landsat 4 and 5, Multispectral and Panchromatic data from SPOT 1, 2, 3 and 4 and Synthetic Aperture Radar (SAR) data from the European Radar Satellites (ERS) 1 and 2.
In total, some 88 million megabytes or 88 terabytes of data were transcribed to around 4,500 DLT's. Back up copies of the archive, for off-site storage of this irreplaceable data, were also created during the project.
The project also provided an opportunity for ACRES to systematically reassess the quality of its data archive and to update catalogue records and metadata.
9 May 2003
ACRES proposes to change the default radiometric calibration for all Landsat 7 products from the currently used method (CCRS algorithm) to NASA algorithm. This change will come into effect from 12 May 2003.
The CCRS algorithm uses a reference detector (within the 16 detectors) for each band. The brightness values for the other detectors are adjusted to match the brightness values of the reference detectors.
The new NASA algorithm treats forward and reverse detectors as the same detector. For each band a reference detector is derived from the average of 32 detectors, and the brightness values for these 32 detectors are adjusted to match the brightness values of the reference detector.
The reason for this change is to improve the destriping in Landsat 7 products especially over areas with low brightness values. ACRES applications group has compared Landsat 7 products generated from CCRS and NASA algorithms and found that the variation is within - 1 brightness value.
From 12 May 2003, the default radiometric correction method for all ACRES Landsat 7 products will be set as NASA algorithm. However, CCRS algorithm will still be supported and customers need to specify on the order form if they want CCRS algorithm as the radiometric correction method.