The problem is a payload computer that stopped working last
Sunday, the US space agency said.
It insisted the telescope itself and scientific instruments
that accompany it are "in good health."
"The payload computer's purpose is to control and
coordinate the science instruments and monitor them for health and safety
purposes," NASA said.
An attempt to restart it on Monday failed.
NASA said initial evidence pointed to a degrading computer
memory module as the source of the computer problem.
An attempt to switch to a back-up memory module also failed.
The technology for the payload computer dates back to the
1980s, and it was replaced during maintenance work in 2009.
Launched in 1990, the Hubble Space Telescope revolutionised
the world of astronomy and changed our vision of the universe as it sent back
images of the solar system, the Milky Way and distant galaxies.
A new and more powerful one, called the James Webb Space
Telescope, is scheduled to be deployed late this year. It is designed to peer
deeper into the cosmos than ever before.