Space shuttle Atlantis launched today, to service the Hubble Space Telescope for the forth and final time. Astronauts will replace several new cameras and
spectrographs (which will be used to measure the composition of stars, planets, galaxies, etc), and repair others. Astronauts will also replace one of two redundant devices that handle data, will replace Hubble's batteries, and will replace all of the HST's six gyroscopes (which orient the telescope), of which only half now work. One of three Fine Guidance Sensors--which also help point the telescope and are used to hunt for extra-solar planets--will also be replaced. A ring will also be attached to the telescope's backend, so that a rocket can at a later date be attached and used to deorbit Hubble at the end of its life. Hubble has been operating for 18 years, and has been one of the most productive telescopes ever. This servicing mission should extend its life for another 5+ years.