(23 May 2024 update; next update 15 June 2024 or sooner)

O4b: LIGO, Virgo, and KAGRA are considering an extension of O4b by a few months to better accommodate the post-O4 upgrade schedule. We will update this text and timeline as soon as a definitive decision is made. The plan would be to delay the start of O5 by the same amount of time, leaving the downtime between runs at the same interval.

The two LIGO detectors are now running with a sensitivity of 140-180 Mpc, and with duty cycles of 70-80%. There will be further minor adjustments to optimize the performance during the O4b observing period.

During the first month of O4b, the Virgo detector has been running with a sensitivity of 50-55 Mpc. Initially, the duty cycle has been limited to 60% due to hardware problems, but these issues have been resolved and we are now operating at 80% duty cycle or higher. All planned weekly downtimes have been synchronized between LIGO and Virgo to maximize the 3-detector uptime. Further adjustments will be made during the run to improve the performance of the Virgo detector. Currently, the Virgo Collaboration is reassessing its plans for O5 and both the entry date into O5 and the target sensitivity are unclear. This work is progressing and we expect to be able to define our plans for O5 in the second half of 2024.

On 1 January 2024, a 7.6 magnitude earthquake struck near the KAGRA site, marking the most significant seismic tremor in the area of the KAGRA site in the past century. Among the nine mirror suspensions, eight suspensions were recovered. However, we newly found that the output mode cleaner stack had malfunctions, and its repair is ongoing. We hope to finish other recovery works as soon as possible and restart commissioning, then join O4b before the end of O4 with a sensitivity of around 10 Mpc.

For more information, see:

OpenMMA wiki - IGWN public alert user guide -


The gravitational-wave observing schedule is divided into Observing Runs, down time for construction and commissioning, and transitional Engineering Runs between commissioning and observing runs. The current best understanding of the long-term observing schedule is shown below (or Since BNS (Binary Neutron Star) mergers are a well-studied class of gravitational-wave signals, this figure gives the BNS range for for a single-detector SNR threshold of 8 in each observing run.

Long-term observing schedule

The O5 start dates, duration, and sensitivities are current best guesses, and will likely be adjusted as we approach that run for all the detectors (see text).

Live Status

A public web page that report live status of the LIGO/Virgo detectors and alert infrastructure is at