(19 January 2023 update; next update 15 April 2023 or sooner)

With this update on the timing of the O4 LIGO-Virgo-KAGRA observing run, we wish to indicate two changes to the planning from previous announcements.

On the timing of the start of O4, the detectors continue to present challenges to reach the level of stability and sensitivity that we hold as pre-requisites for the start of the run. All of the detectors need further work to advance to the O4 starting sensitivity goals. We now plan to start the observing run on 24 May; this will be preceded by a one-month engineering period.

In addition, we now plan on 18 calendar months of observing for O4 (as a change from the previous 12-month duration). This change is motivated by upgrade plans for the O5 observing run. The sensitivity improvement for O5 comes primarily from lower noise mirror coatings that are still in the development phase, and are not expected to be available by the original O4 end date. The additional observing time will increase the scientific output of O4, while the coating development is being finalized and the test masses required for O5 are being coated. The 18 month observing period may be interleaved with one or two month-scale gaps for maintenance.

The goal sensitivity of the detectors remains unchanged: LIGO aims for a sensitivity of 160-190 Mpc for binary neutron stars. Virgo aims for a target sensitivity of 80-115 Mpc. KAGRA should be running with greater than 1 Mpc sensitivity at the beginning of O4, and will work to improve the sensitivity to about 10 Mpc toward the spring of 2024.

Please check the OpenLVKEM pages for the timing and coordinates for telemeetings. We will continue to hold calls on the third Thursday of each month through March 2023 and with increasing frequency as we approach the start of O4. The schedule of calls is posted at the OpenLVKEM wiki (see below), along with Agenda and pointers to materials.

Reference Material:


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. Since BNS (Binary Neutron Star) mergers are a well-studied class of gravitational-wave signals, this figure gives the BNS range for 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.

Live Status

There are a handful of public web pages that report live status of the LIGO/Virgo detectors and alert infrastructure.