Artificial satellites have discovered many uses in the modern era, including but not limited to: telecommunications, espionage, research, and navigation. These also range in shape and size from microsats, which are by definition less than one meter in diameter (including Sputnik, the first satellite ever launched), to large communications satellites which can be some twenty meters or more in diameter. Typically, however, satellites are classified by weight instead of size, due to the particular constraints of launching objects into various Earth orbits.