Serious Hardware Incident with the Subaru Telescope Interrupts Its Operation

Report 1 (July 4, 2011 Hawaii Time)

While shutting down the observation system at the end of the night shift during the early morning of Saturday, July 2. 2011, the telescope operator detected an error signal from the top unit of the telescope. The top unit, which includes the Subaru Prime Focus Camera (Suprime-Cam) and auxiliary optics, is located at the center of the top ring of the Subaru Telescope.

The operator contacted the Telescope Engineering Division (TED) and continued to check the status of various parts of the top unit. The TED summoned three staff members who immediately left Hilo for the summit to assess the situation. Meanwhile, the operator, support astronomer, and nighttime observers left the control building and descended safely down to the mid-level dormitory at Hale Pohaku. The incident did not harm any observatory staff or observers.

When the TED staff members arrived at the telescope, they saw extensive leakage of coolant (ethylene glycol) from the top unit. Although they promptly shut off the supply of coolant, a significant amount of leakage had already occurred all over the telescope--from the top unit itself and Suprime-Cam down to the tertiary mirror, the primary mirror and some of its actuators, the Faint Object Camera and Spectrograph (FOCAS, a Cassegrain instrument) and its auxiliary optics, and the telescope floor.

TED staff members attempted to clean up and remove as much coolant as possible. However, such areas as optics, control circuits, and the inside of Suprime-Cam and FOCAS were inaccessible during the initial clean-up. Inspections have shown that the spillage is confined to the enclosure itself and did not spread into the environment of the site.

The damage assessment is ongoing. During the clean-up and recovery of equipment, nighttime observations as well as daytime summit tours of the Subaru Telescope are temporarily suspended. Scheduled observers as well as tour visitors are being contacted.

As updates become available, they will be posted on this website.

Photo: Coolant on the Primary Mirror.

An orange-colored liquid covers the mirror surface. This is the coolant for the electronics and other equipment at the top unit. The coolant consists of a mixture of water and ethylene glycol, a liquid commonly used in a vehicle's radiator for cooling. The coolant is not corrosive and does not damage the primary mirror, which has a foundation of glass. The nozzles shown in the upper part of the photo are part of the CO2 cleaning device used to remove dust from the mirror.

Subaru Primary MIrror

National Astronomical Observatory of Japan

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