A new Landsat 5 Thematic Mapper (TM) acquisition scheduler was released on May 6, 2010. Similar to that employed by Landsat 7 operations, the new scheduler incorporates daily global cloud forecasts along with seasonal cloud climatology to increase the relative likelihood of acquiring usable imagery. This system has the goal of extending the Landsat 5 Mission while targeting scene opportunities most likely to yield high quality imagery for the global archive.

Source:
USGS Landsat Website