Answers Your Questions
From: Alfonse, of Orlando,
Great question! There are three
sets of communications equipment, two S-band and one Ku-band, that are
powered from different sources on the shuttle. It is very unlikely that
we would lose all three systems. If we do, the crew could use a fourth
system, which is primarily only used during ascent and post landing.
This is a UHF system that can only communicate with the ground when
over a very limited set of ground stations. We can coordinate the shuttle
landing with this link. Thanks for the great question.