GMAGAO-X R-07 Instrument Safety During Large Earthquake

[dmkelly42]

Risk creation date: 8/23/2023

Last Modified: 8/23/2023

Risk type: Cost, Schedule

Risk Approach: Mitigate

Risk Owner: Adam Fletcher

Risk Statement:

If a strong earthquake hits while GMagAO-X is observing, then the optical instrument might be damaged excessively if it cannot be clamped down before the main shaking takes place.

Risk Effects:

Earthquake motions will cause rolling and shaking that is likely to cause some misalignment. Having large motions while floating could cause strong accelerations and shocks that threaten structural damage to items on the optical table.

Risk Assessment:

Risk Ratings	Likelihood	Consequence
Initial	3	4
Current
Target	1	4

Initial Risk Notes:
GMagAO-X is being designed to survive an operational level earthquake (OLE) (average recurrence period (ARP) of 100 years), but with the expectation that some damage and misalignment might occur. GMT sets the goal of instruments being ready to resume operations within 30 days after an OLE. The rigidity level earthquake (RLE) has an ARP of 2 years, and GMagAO-X is expected to survive without need of repair after an RLE. We can expect an earthquake between RLE and OLE levels every 2 years over the life of the instrument, with a 1% likelihood of an OLE event in any given year.

When GMagAO-X is not observing, clamps will hold the optical assembly so that it cannot rotate. But while it is observing, GMagAO-X will be floating, and a large earthquake could result in impacts that cause vibrations or shocks that exceed design margins.

This risk is addressing the possibility of damage that requires more than 30d of recovery time or that comes with large financial costs due to an earthquake within about a factor of two of the OLE level.

Risk Notes/Updates:

Cost Impacts:

Estimated cost if risk is realized: $2M

Explanation for cost risk: The replacement cost for DMs or detectors

Risk mitigation list:

• Design optical instrument clamps so that they can be applied quickly and without perfect instrument alignment

• Tap into the GMT early earthquake alert system so that we can respond as quickly as possible to a large earthquake

• Perform analyses to determine what items are expected to break in a large earthquake

• Develop a spares strategy based on the analysis that allows recovery from instrument damage

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