In 2011, after more than 30 years of service, America's space shuttle took to the skies for the last time. Its story has been characterised by incredible triumphs, but blighted by devastating tragedies - and the BBC and Horizon have chronicled every step of its career. This unique and poignant Horizon Guide brings together coverage from three decades of programmes to present a biography of the shuttle and to ask what its legacy will be. Will it be remembered as an impressive chapter in human space exploration, or as a fatally flawed white elephant?