Astronauts seen as well as heard

Seeing ESA astronaut Andre Kuipers on the International Space Station is a regular incidence these days. You turn on your TV or check Twitter and there he is. Since present are no cable sprawling from the Station to Earth, just how does this come about?

The reply, of course, is via satellite. While the reply may be simple, the method is more complex. Behind Andre's smiling face is a compound system of jargon-filled amplifiers, multiplexers, antennas, nodes and signal modulation.

Thanks to satcoms, the team can directly take delivery of emails on the Space Station, they can create private calls via IP phones, and we can see them during televise video conference.

The Station is airborne in a low orbit - around 400 km up - which income that shortest communications can happen only when it passes over a ground station. In its place, signals from the Station are primary sent to 'geostationary' satellites balanced 36 000 km above the equator.

Geostationary satellites take precisely a day to circle Earth, creation them appear stationary in our skies. This allows continuous contact with ground stations; enable them to communicate the Station's signals to a middle ground station on Earth additional often.The procedure is upturned when sites such as the Columbus control centre in Munich, Germany, send signal up to the Station.