Validation of the Landsat 7 Long Term Acquisition Plan                   

Samuel N. Goward, Darrel Williams (GSFC), Terry Arvidson (LM), John Gasch (GSFC)

 

This study was developed to validate the Landsat 7 Long Term Acquisition Plan (LTAP).  It is being carried out under a cooperative agreement with staff from the Landsat Project Science Office at Goddard.  The objective of the LTAP is to provide comprehensive global coverage with Landsat 7 in support of the science objectives of NASA’s Earth Science Enterprise. An example showing coverage for North America is noted in the accompanying figure.  Each rectangle is a single L7 image acquisition.

Continued inspection of LTAP results has been undertaken since July 1999, when Landsat 7 became operational.  However, no systematic evaluation of the LTAP relative to NASA science goals has been carried out until now.  With better than four  years of Landsat 7 operations now completed, sufficient experience with LTAP is available to judge its effectiveness in meeting Landsat 7 scientific goals. A systematic analysis of the LTAP results as archived at the USGS (US Geological Survey) EROS (Earth Resources Observation Systems) repository is being pursued, looking at all aspects of the LTAP protocol including seasonality, cloud avoidance, gain setting, and niche community coverage.

Failure of the scan line corrector mirror in the ETM+ instrument in May 2003, has disrupted the progress of this study and redirected some of the goals of the analysis toward an assessment of how scene pairs, as close in time as possible, may be acquired to produce merged scenes that address the observations lost in a single scene as a result of the SLC failure.  We are now merging the understanding developed in our early LTAP validation results with the new demand to revise the LTAP to acquire scene pairs as a unified problem.

Our cooperative efforts to develop, validate, revise and update the L7 LTAP have produced the most exceptional coverage from any of the multiple Landsat systems operated over the last 30 years.  We anticipate that the lessons learned here will have a large impact on the design and development of future Landsat-type observatories.

Example publication: Arvidson, T., Gasch, J., and Goward, S.N. (2001) “Landsat 7's Long Term Acquisition Plan - An Innovative Approach to Building a Global Archive,” Special Issue on Landsat 7. Remote Sensing of Environment, 78(1-2), 13-26.