The Landsat satellites are not considered tasking instruments and collections are made on a continual basis. Data acquisition requests are not available to the public. The Landsat 8 and Landsat 7 satellites each acquire data in accordance with their respective Long Term Acquisitions Plan (LTAP):
Each LTAP directs the acquisition of Landsat scenes, using parameters such as seasonality, land definition, historical cloud cover, gain settings, and sun angle.
The Landsat Acquisition page provides acquisition calendars and information about daily schedules.