Building a global, consistent, and meaningful Landsat 7 data archiev

摘要

The mission of Landsat 7 is to acquire and periodically refresh a global archieve of sun-lit, substantially cluod-free land scenes. For the U.S. archive, Landsat 7 is acquiring every l and scene at least once every year, at an average rate of 250 scenes each day or 90,000 scenes each year. This is the first time in the 25 year history o f Landsat data acquisitions that there is a deliberate goal to build this archive such that any data of interest to the majority of users will already be in the archive when they go looking for it-at the right gain setting, at the right time, sugbstantially clud-free, and at the right frequency of acquisition. Anticipating most suers' data needs is the key to achieving this lofty goal. The Long Term Acquisition Plan (LTAP) dictates the optimum acquisition refresch cycle for each scene, based on change detection and special interest inputs. The plan also specifies monthyly optimum gain setting to maximize scene data return. Scheduling software automatically schedules acuisitions in accordance with this LTAP, making decisions as to acceptable cloud cover levels, urgency of acquisition, and availability of resources to fulfill the plan.