The Subaru telescope, one of the world's biggest, has been out of service for the past two months due to damage to its mirror supports, officials of the National Astronomical Observatory of Japan said Friday.

Repair work has recently restored the telescope's functions. However, more extensive work is required, which is expected to delay a plan by astronomers from around the world to use the telescope for joint research, the officials said.

Subaru, which has a mirror measuring 8.2 meters across, is located directly beneath the summit of Maunea Kea on the island of Hawaii.

The problem apparently began in September last year, when one of the three mirror supports went out of alignment. The problem was fixed, but in March the same problem occurred to another of the supports.

The second time, however, the support became separated and took a layer of between 2 mm and 3 mm of glass with it.

The incident came after someone forgot to set the telescope's safety equipment -- which is designed to absorb unexpected forces -- so the supports were subjected to forces 12 times what they were designed to withstand, the observatory said.

In addition, the supports and the mirror's glass were not properly connected.

The telescope, which made its first observations in early 1999, is known for its complex control system, which in addition to the supports, relies on 261 actuators on the mirror's rear surface.

The mirror has a relatively thin surface, given its large size.

The joint research program will be the first of its kind. Its original starting date in October is expected to be delayed until late this year at the earliest.