19 September 2003
Following the unsuccessful attempt by USGS/NASA to correct the problem with the Scan Line Corrector (SLC) on Landsat 7, ACRES is now planning the changes that will occur to Landsat 7 products, so-called SLC-off products.
Firstly, USGS has assured ACRES that the Landsat 7 mission will continue. USGS have already performed studies which show that the utility of the data for many applications is sufficient to warrant the continuation of the mission. Therefore, the challenge is to optimise the utility of the data obtained without the Scan Line Corrector. Theoretical options include modifications to the processing software to remove redundant data and to interpolate some or all of the missing data, and modifications to the spacecraft attitude and orbit.
ACRES have already been in contact with the supplier of our processing software, and expect to quickly install a modification to process SLC-off data. The first objective is to provide some sample SLC-off data for evaluation via the ACRES ftp site (a separate announcement will be made about this). With user feedback from this evaluation, ACRES will then be able to develop a future operational scenario for the continued Landsat 7 mission.
This scenario will be presented at an International Landsat Meeting for International Co-operators to be held 13-17 October, where the views and proposals of all the ground stations receiving Landsat 7 data will be shared and discussed. A final plan for Australia will then be presented to the management of Geoscience Australia for their approval.
USGS expect to be providing SLC-off Landsat 7 data in November 2003, and ACRES is working towards a similar timetable.
Meanwhile, new Landsat 5 data is being routinely acquired by ACRES, and acquisitions can be previewed in the ACRES Digital Catalogue. Archived Landsat 7 data acquired before 31 May 2003 is also available.
Please monitor ACRES What's New for the release of Landsat 7 evaluation data, and for further information about future plans.
18 September 2003
The ETM+ sensor on Landsat 7 was turned off by USGS (United States Geological Survey) on 6 June 2003 due to an anomaly with the onboard Scan Line Corrector.
Since then NASA, USGS and the instrument manufacturer have been analysing information from the satellite and reviewing options to correct the anomaly. The following message comes from USGS:
18 September 2003
ACRES has recently implemented a number of improvements to its MODIS products and services.
In response to recommendations by the Australian MODIS coordination group, ACRES has recently replaced the Goddard processor with IMAPP V1.4 software to process MODIS data acquired at the Alice Springs and Hobart stations.
As a result of this change, ACRES can now process and offer full-pass level 1B products as well as segmented level 1B products. Level 1B products are considered as standard input to generate higher level products and are useful to those users who are interested in making use of additional science data. ACRES will continue to offer the current map oriented band sequential product as a number of users expressed interest in this data. This product is available only as segmented scenes.
ACRES is now offering an increased number of MODIS passes, introducing data from the AQUA satellite and night passes from both TERRA and AQUA. Also, ACRES has updated its MODIS server in order to cope with the increased data volume.
MODIS archive products are similar to online products. These are processed using post-pass ephemeris/attitude information to improve geolocation accuracy. There is a nominal charge of $400 per pass to meet data handling costs.
1 July 2003
Newly acquired ACRES Landsat 5 TM satellite image data is now available to order. Following valuable feedback from our customers and users, ACRES has added some new options for ACRES Landsat imagery products. A new half-scene image, 130km x 130km, is available as map oriented and orthocorrected data, and a small-scene (25km x 25km) image is available as an orthocorrected image.
There have also been some minor price adjustments and a reduced price differential between Path/Map and Orthocorrected products. Prices for both Landsat 5 and Landsat 7 have been revised. Landsat MSS prices remain unchanged.
A major contribution to the price reductions has been the processing efficiencies that have resulted from the use of Supplemental Control Points (SCPs) for generating orthocorrected products. SCPs or geocoded image chips have improved positional accuracy and resulted in consistency of product quality.
Orthocorrected products using SCPs are currently available for two-thirds of the area of Australia covering the eastern and western regions. It is planned to have complete SCP coverage of Australia by the end of 2003.
1 July 2003
ORBIMAGE has announced the successful launch of the OrbView-3 high-resolution earth imaging satellite on 26 June from California, USA.
Initial data indicates that the satellite's main systems are operating nominally. It will take several more days to manoeuvre the satellite into its final 470km circular orbit inclined at 97.29 degrees to the equator and to confirm that all of OrbView-3's sub-systems are operational.
OrbView-3's high-resolution camera will acquire one-metre resolution panchromatic (black and white) and four-metre resolution multispectral (colour) imagery. This means that OrbView-3 is the third commercial satellite system to offer data with a resolution of 1 metre or less, following the successful earlier release of IKONOS and QuickBird data. Orbview will have a revisit time of three days or less, enabling ORBIMAGE to continually update its imagery archive.
"The Landsat anomaly team attempted recovery of the Scan Line Corrector (SLC) on Sunday, September 7, 2003. The recovery included switching the instrument to the redundant (B-side) electronics. The attempted recovery was unsuccessful in regaining the use of the SLC. The team concludes the probable failure is thus mechanical versus electrical. The SLC has redundant electronics but not redundant mechanical components. Since no mechanical redundancy exists, the SLC malfunction appears to be permanent."
"The Landsat team will return the instrument to the primary (A-side) electronics and continue to collect data with the SLC off. Efforts are underway to alter processing systems for SLC-off data. The schedule for availability of the SLC-off products is November 2003."