Beyond O4: What lies ahead for Terrestrial Gravitational-Wave Detectors

In the O4 observation run the Advanced LIGO gravitational-wave detectors reached their original design sensitivity and are now observing multiple transients from binary black hole and neutron star collisions every week. For the first time we can now optimize future upgrades and detectors with good guidance on observable signals. Intriguingly, it is feasible to observe binary black hole mergers throughout cosmic times, all the way back to mergers of remnants of the first stars.

In this talk I will review the Advanced LIGO detector performance limits in O4, highlighting the importance of a network of gravitational-wave detectors. I will then describe the planning for the A# upgrade to Advanced LIGO after its O5 run. Further on the horizon, I will discuss the design work for Cosmic Explorer, which is now underway with NSF funding support. Along the way I will discuss project timeline, challenges, and milestones.