Several private companies are planning to launch large, low-Earth-orbit (LEO) satellite constellations. NASA, who generally doesn't comment on these types of developments, recently published a stark warning for AST & Science, which intends to launch a massive constellation of hundreds of large 5G satellites. 

NASA engineer Samantha Fonder expressed concern about AST's 5G mega constellation of satellites in a recently penned letter to FCC's Marleen Dortch, about how the space agency worries its assets in orbit could experience a "catastrophic collision," reported Ars Technica. 

"NASA submits this letter during the public comment period for the purpose of providing a better understanding of NASA's concerns with respect to its assets on-orbit, to further mitigate the risks of collisions for the mutual benefit of all involved," Fonder wrote.