The Landsat series of satellites has had a series of sensors ranging from relatively low resolutions Multispectral Scanner (MSS) in the 1970s, to Thematic Mapper starting with Landsat4 in 1982, to Enhanced Thematic Mapper Plus with Landsat7 in 1999, and the Operational Land Imager (OLI) and Thermal Infrared (TIR) sensors onboard Landsat8. You can download Landsat sensor data from http://earthexplorer.usgs.gov/ or http://glovis.usgs.gov/