The Envisat Flight Operations Segment (FOS) provides the services needed to
operate the Envisat platform and its instruments during the Launch and Ear
ly Orbit Phase (LEOP), the Commissioning Phase and the Routine Phase of the
mission. In developing the FOS, extensive use has been made of existing co
mponents already developed and tested for the ERS missions. The resulting F
OS is a distributed system, with a widely variable configuration depending
on the different mission phases for which it will be used.