This happens sometimes. For example, GPS and DMSP (Defense Meteorological Satellite Program) had many blocks of identical satellites. One of the DMSP spacecraft

This happens sometimes. For example, GPS and DMSP (Defense Meteorological Satellite Program) had many blocks of identical satellites. One of the DMSP spacecraft will never launch and has been ordered to be scrapped, since it is now so out-of-date after being in storage for so long. https://en.wikipedia.org/wiki/Defense_Meteorological_Satellite_Program https://en.wikipedia.org/wiki/Defense_Meteorological_Satelli... http://space.skyrocket.de/doc_sdat/dmsp-5d3.htm http://space.skyrocket.de/doc_sdat/dmsp-5d3.htm The out-of-date aspect probably explains why this doesn't happen more. I worked on JPSS-1, a polar orbiting weather satellite. It was a follow on to NPP, but it was not an exact copy. After having experience using NPP in production (in space), naturally improvements and better technology could be integrated. These two satellite launches were separated by 6 years and a new satellite takes 4-5 years to design, build, and integrate. Think how much technology changes in 6 years.