Wanted to know if anyone here can list and describe the different ways of communicating in space? whether the messages are say from moon to ISS or earth and ofcourse vice versa. Also is there any protocols if communications are down? Can video signals be achieved if voice communications are down?
Well the only way is through electromagnetic radiation, AKA radio, main problem with space is that is BIG, from the earth to moon, about 2 seconds delay round trip for the signal, from the ISS so close that is realtime for audio an video I think, things goes complicated when you are really far, when Mars is close to earth its take 3 minutes, when the orbit is far away 22 minutes... hats off to the guys that designed the radio equiment for the Voyagers...
I don.t know about the protocols if transmiters are down on the ISS, voice and video communication probably uses the same trasmitter with a only voice (that uses a more simple and need less power) transmitter as backup, the ISS has a Russian Soyuz "lifeboat" permanently attached to the station for emergencies that has its own transmitter, if radios fails completely they just need to wait someone down here to notice the "silence" (almos instantly due to the amount of constant telemetry I'm sure they receive) and then probably check the integrity of the station through optical/radar and prepare a flight as soon as posible to reach it.
