LIGO science operations begin!

Gary Sanders, Caltech

At 8:00 am Pacific time on August 23, LIGO began its first science run, dubbed S1. As the S1 run draws to a close on September 9 it appears to have succeeded in delivering a large data set from which the first analysis effort for scientific results now departs.

In the previous report in MOG, Stan Whitcomb described the dress rehearsal for S1, the engineering run E7. Since E7, the LIGO Scientific Collaboration (LSC) upper limits analysis groups have labored over the data, exercising the analysis codes, developing algorithms and characterizing instrumental properties. The interferometer commissioning teams, consisting of personnel from the LIGO Laboratory and the LSC, have learned much from E7 and incorporated the insights into further development of the interferometers in the march to design sensitivity and to sustained predictable detector operation.


To benchmark the progress in interferometer sensitivity, Figure 1 displays the progress in approaching LIGO design sensitivity for the Livingston 4 km interferometer. The December 2001 curves mark the sensitivity before E7. As LIGO began S1, the three LIGO interferometers were much improved and roughly equally matched in sensitivity and this is displayed in Figure 2.


All three interferometers have operated in the power-recycled mode with individual interferometers operating in good "science" configuration roughly between 50% and 70% of the time. Intersite coincidences in lock have been logged typically about 1/3 of the time. Triple coincidences are logged in the data about 20 - 25% of the time.

As in E7, LIGO and GEO have coordinated their running and the GEO 600 interferometer has been operating with high reliability much of the time. LIGO and GEO have also been joined in coincidence with the veteran TAMA 300 interferometer which skirted construction disturbances at the TAMA site by running in coincidence with LIGO and GEO over the August 30 to September 2 weekend. Arrangements have been put into place between LIGO and GEO, and LIGO and TAMA for coordinated analyses of the data sets.

The LIGO Scientific Collaboration is planning to complete a scientific analysis of the S1 data by the end of the year, prior to S2, the next in the series of progressively more sensitive science runs. S2 and S3 should be carried out at much improved sensitivity, and these runs will extend for progressively longer periods.,

LIGO is funded by the US National Science Foundation under Cooperative Agreement PHY-0107417. This work is a collaborative effort of the Laser Interferometer Gravitational-wave Observatory and the institutions of the LIGO Scientific Collaboration.

More information about LIGO can be found at:

Jorge Pullin 2002-09-23