LSC logo - click to go to LSC homepage

Observing Plans and Public Alerts

LIGO, Virgo and KAGRA Observing Run Plans

[15 September 2021 update; next update by 15 November 2021]
The LIGO-Virgo-KAGRA Collaboration is continuing to evaluate and respond to the ongoing impacts of COVID-19 and adverse weather on preparations for the O4 observing run. As a result, we reiterate that O4 will not start before August 2022 and note that it may be further delayed. We will provide a more concrete plan in our next update, by 15 November 2021.

The readiness of both the LIGO-Hanford and the LIGO-Livingston detectors remains uncertain as delays due to COVID-19 and Hurricane Ida hitting Louisiana have affected the construction schedule for the Frequency Dependent Squeezing system. Hurricane Ida has also impacted the LIGO Livingston Observatory staff and their families. The full impacts are still being evaluated and mitigations are being identified.

Virgo has completed the integration of the upgrades for O4 and is now in a commissioning phase. The uncertainty in readiness of the Virgo detector is mainly driven by the progress of the instrument commissioning.

KAGRA is working to join O4 with Virgo and LIGO. A later start than August 2022 is preferable due to COVID-19 and staff limitations.


If you have any questions, please contact the Spokespersons:
  • Patrick Brady (Spokesperson, LIGO Scientific Collaboration); lsc-spokesperson@ligo.org
  • Giovanni Losurdo (Spokesperson, Virgo Collaboration); virgo-spokesperson@ego-gw.it
  • Jun’ichi Yokoyama (Board Chair, KAGRA Scientific Congress); yokoyama@resceu.s.u-tokyo.ac.jp

O3 observing run timeline

  • Start date: 1 April 2019
  • Commissioning break: 1-31 October 2019
  • Observing ended: 27 March 2020

Public Alerts in O3

  • Public Alerts for O3 ended on 27 March 2020.
  • Alerts are issued through the GCN/TAN system.
  • For more information and usage examples, see the LIGO/Virgo Public Alerts User Guide.
  • The official candidate event database is GraceDB.
  • For the general public, a more accessible view is maintained on the Chirp website; mobile apps are also available there.

triangulation of GW170817

GW170817 Localization and Triangulation Annuli. We can pinpoint sources like GW170817 much more accurately now that we can triangulate the signal between Hanford, Livingston, and Virgo. The rapid Hanford-Livingston localization is shown in blue, and the final Hanford-Livingston-Virgo localization is in green. The gray rings are one-sigma triangulation constraints from the three detector pairs. [Credit: LIGO/Virgo/NASA/Leo Singer (Milky Way image: Axel Mellinger)]

Find us on Facebook   Follow us on Twitter    Follow us on YouTube    Follow us on Instagram