ISRO announcced it is going to launch IDRSS system.
one of the requirement of the ground station to communicate with station is to communicate with satellite is that a clear view or line of sight is required.
when we do not have a clear view or lone of sight the then communication between ground station and satellite became difficult.
so avoid such a situation, space agency needs to build communication center across the world. It can became an expensive job.
so to address this problem relay satellite came into picture.
these satellite mostly kept in geo synchronous or geostationary orbit and they will always have line of sight in india.
the relay satellite they relay or handover the command received from ground station to other satellite that are not in line with line of sight with ground station.
sometime a single relay satellite may not have a clear view with all the satellites for it to communicate, in such scenario multiple satellite are deployed.
This multiple satellite system is called as relay satellite system.
Relay satellite also work in a similar manner as it passes information from the ground station to the satellite in space and it also can receive information from the satellites in space and can relay it to the ground station.
India has to lunch it, it is expected in 2021.
It is most important because, we need to send this to space before we try to send gaganyaan mission.
Because once we launch gaganyaan mission space station has to stay in touch with ground station all the time for that we need relay system. so it is clear now.
relay satellite launched in geo syncronous orbit give better coverage than relay satellite launched in mini orbit.