The US Program in Ground-Based Gravitational Wave Science: Contribution\n from the LIGO Laboratory

Recent gravitational-wave observations from the LIGO and Virgo observatories\nhave brought a sense of great excitement to scientists and citizens the world\nover. Since September 2015,10 binary black hole coalescences and one binary\nneutron star coalescence have been observed. They have provided remarkable,\nrevolutionary insight into the "gravitational Universe" and have greatly\nextended the field of multi-messenger astronomy. At present, Advanced LIGO can\nsee binary black hole coalescences out to redshift 0.6 and binary neutron star\ncoalescences to redshift 0.05. This probes only a very small fraction of the\nvolume of the observable Universe. However, current technologies can be\nextended to construct "$3^\\mathrm{rd}$ Generation" (3G) gravitational-wave\nobservatories that would extend our reach to the very edge of the observable\nUniverse. The event rates over such a large volume would be in the hundreds of\nthousands per year (i.e.tens per hour). Such 3G detectors would have a 10-fold\nimprovement in strain sensitivity over the current generation of instruments,\nyielding signal-to-noise ratios of 1000 for events like those already seen.\nSeveral concepts are being studied for which engineering studies and reliable\ncost estimates will be developed in the next 5 years.\n