NASA will this week launch the shuttle Atlantis and seven astronauts into orbit on a high-risk last service mission to the space telescope Hubble.
The US space agency has warned there is no room for error, in the fifth and final maintenance operation on the Hubble before the shuttle fleet is retired.
Nasa says if all goes well, the telescope's long-overdue service will extend the telescope's life by at least five years.
A journey to Hubble carries more risk of being hit by space debris or micrometeorites than a flight to the International Space Station, as the telescope orbits at almost twice the height of the ISS.
