On this day in 1984, Landsat 5 was launched into orbit. To this day Landsat 5 is still collecting data; the 27 year life span of Landsat 5 is unprecedented.
+ More about Landsat 5

Ten Years of TIRS: Data for a Thirsty World
Landsat 8 very nearly flew without a thermal infrared sensor. This is the backstory of how TIRS made it onto Landsat 8.