LIGO, VIRGO AND KAGRA OBSERVING RUN PLANS

(15 March 2025 update; next update 15 May 2025 or sooner)

The O4 LIGO, Virgo, and KAGRA Observing run continues, with the following roadmap:

  • Observation continuing until 1 April 2025 15:00 UTC

  • Maintenance/commissioning break from 1 April 2025 at 15:00 UTC to 4 June 2025 at 15:00 UTC

  • Observation currently planned to restart on 4 June 2025 at 15:00 UTC; there may be an engineering period of around a week at the beginning of the run

  • O4 ending on 7 October 2025 at 15:00 UTC

  • After the close of O4, final characterization of the O4 detectors will be followed by installation of equipment to prepare for the O5 configuration

  • O5 is currently planned to start in late 2027

The April/May break in observing is prompted by the importance of repairing a faulty beam tube gate valve at LIGO Livingston site before this year’s hurricane season and other work on the other detectors of the network that will reduce risk related to the O4-O5 transition. The extension of O4 to early October yields approximately the same amount of calendar observing time as was planned to obtain with the previous June 2025 end date, after accounting for the time lost from this April/May 2025 break, plus that lost from unplanned interruptions in 2024.

The LIGO Livingston detector has been observing with a BNS range around 170 Mpc, and a duty cycle of 67%. LIGO Hanford has been observing at around 160 Mpc, and a duty cycle of around 60%.

Virgo continues observing in O4c, with a duty cycle around 75-80% and a 50-55 Mpc BNS range. Currently, the Virgo Collaboration is reassessing its plans for O5 and both the entry date into O5 and the target sensitivity are being finalized. We expect to be able to define our plans for O5 in the first half of 2025.

KAGRA continues noise hunting and cooling the main mirrors. The laser input to the main interferometer is planned to be increased to 10 W to reduce shot noise, in order to improve sensitivity in the high-frequency range. We expect to rejoin the observing run before the end of O4 with a sensitivity of around 10 Mpc.

The planned end date for O4 is 7 October 2025 at 15:00 UTC. LIGO, Virgo and KAGRA (LVK) are continually assessing planned commissioning and upgrade activities. Should there be any changes to the current planning, we would communicate them here as soon as they are adopted by the LVK.

For more information, see:

OpenMMA wiki - https://github.com/scimma/openMMA/wiki IGWN public alert user guide - https://emfollow.docs.ligo.org/userguide/

Timeline

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 https://dcc.ligo.org/LIGO-G2002127/public). 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

– Page Design adapted from the LIGO/Virgo/KAGRA Public Alerts User Guide –