• Question: How long does the process of communicating with Tim Peake take?

    Asked by Sally to Elie on 10 Mar 2016.
    • Photo: Elie Allouis

      Elie Allouis answered on 10 Mar 2016:

      It depends, but usually there is a few seconds delay for the return trip of the signal.

      The ISS uses the Tracking and Data Relay Satellite System (TDRSS) placed in geostationnary orbit, so the signal goes from Earth to 36000 km and then back down to the ISS at 100km…so about a 72000km round trip, just to say “Hi!”…and then another 72000km for the return signal, like the video.
      While this is usually quick, there are plenty of systems involved that each add a bit of delay..leading up to these few seconds of delay…