Observing Run

The term Observing Run is currently used for surveys carried out by gravitational-wave detectors to detect gravitational waves (GW detections). They typically run on the order of a year, the time between them used for maintenance and upgrades. Currently, the different GW detection efforts coordinate (LVK, the LIGO-Virgo-KAGRA Collaboration), attempting to operate over the same such time-periods: a number of detections of each detected event offers considerable value: simultaneous detections provide clearer confirmation that the event truly occurred (i.e., the detection wasn't merely noise), and offers data regarding to the direction of the source, increasing the chances of establishing a counterpart transient such as an optical transient or gamma-ray burst. The Observing Runs so far have been numbered 1 through 4, with letter suffixes to indicate subdivisions of the run (e.g., 4a, 4b), typically separated by periods of a few weeks for maintenance and minor upgrades. Between the full runs are longer outages, typically for substantial upgrades, which require on the order of a year or more. Observing Runs:

Note that in some of these, Virgo and KAGRA did not operate for the run's entire time interval. IR1 stands for interim run 1, which will incorporate some small improvements to the detectors, whereas O5 will incorporate major upgrades.

Initial development and testing of these detectors lasted for years, including successive upgrades and some pilot operation. LIGO's pilot runs included six labeled Science Runs (1 through 6), during which there were no detections.