• Question: How do you get a signal in space?

    Asked by 932tch24 to Andrea, Charlie 🚀, Col Op, Kirsty on 14 Jun 2016. This question was also asked by callommmm.
    • Photo: Andrea Boyd

      Andrea Boyd answered on 14 Jun 2016:

      We use the Tracking and Data Relay Satellite System (TDRSS)

      The International Space Station is only about 400km above the surface of the Earth and we use the TDRSS network of relay satellites much higher up (35,000km) to bounce the signals to/from ISS and Earth. http://tdrs.gsfc.nasa.gov/tdrs/Missions-Enabled.html

      The single receiving station is in the USA. But you have to have line of sight to send/receive a signal and the ISS orbits all around the Earth so it sends signals up to the TDRS satellites as it passes underneath different ones, like when you pass the baton in a relay race to the next person, and the TDRS satellites all communicate with each other. One of them can always see the USA receiving dish and send the signal. This way we can have a signal in space with the ISS 24 hours a day without having to build hundreds of extra ground stations on Earth.

      Then the signal goes to Houston and from Houston it goes to Huntsville and Tsukuba and Munich. It goes from Munich to all the ISS Control Centres in Europe and to Moscow.

      It’s all very very fast though, so when you’re talking it seems instant.

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