LIGO Document G2401028-v4

Picket Fence Poster - SSA Alaska 2024

Document #:
LIGO-G2401028-v4
Document type:
G - Presentations (eg Graphics)
Other Versions:
LIGO-G2401028-v3
01 May 2024, 16:40
Abstract:
The Advanced LIGO detectors are leading the field of gravitational wave astronomy. The detectors measure the change in length of 4-km long resonant interferometers to attometer precision to achieve their goal. Not surprisingly, the resonance condition for operation is delicate and can be lost if elaborate isolation of external disturbances is not complete. The Rayleigh waves produced by earthquakes challenge this isolation. In the past five years, LIGO has implemented a control configuration called earthquake (EQ) mode to allow LIGO instruments to maintain resonant operation or “lock” during earthquake events whose strength would have previously impaired their functioning, which helped restore some of their duty cycle. EQ mode works best when it can be used preemptively, before the arrival of surface waves to the LIGO observatories.

The 'Picket Fence' is a newly implemented early alert system aimed to increase the warning time for surface waves approaching the LIGO observatories, enabling the possibility to engage EQ mode before their arrival. It works by monitoring seismic signals from an array of seismic stations hundreds of kilometers away from each LIGO site. The stations are streamed in real-time using a SeedLink connection. The work presented shows the effectiveness of the Picket Fence in providing between 30 and 100 seconds of accurate forewarning for most teleseismic events of interest for the functioning of the LIGO detectors. This development has the potential to increase the duty cycle of the detectors, boosting their scientific output. We also show a preliminary study of the potential benefits of including such an early warning system into the automated control workflow of the observatories.

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