The main camera on the Hubble Space Telescope has shut down unexpectedly for the second time this year, the operators of the orbiting observatory announced Friday.

The Space Telescope Science Institute, which coordinates use of the telescope, said the camera shut down Saturday. Program managers at NASA's Goddard Space Flight Center in Greenbelt and at the institute were investigating the cause and what action to take.

In the meantime, observations on the Hubble were being rescheduled to use other instruments, the Baltimore-based institute said.

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The orbiting Hubble telescope, launched in 1990 by the space shuttle, has revolutionized the study of astronomy with some of the most striking images ever seen in space.

However, a servicing mission by the space shuttle is needed to install two new instruments as well as fresh batteries and gyroscopes to keep the telescope working until 2011 or 2012. N

ASA, which has not decided whether to send astronauts to repair the Hubble, is planning to replace it with a new, improved version, the James Webb Space Telescope. It's scheduled for launch in 2011.