Status of Space-based Gravitational-wave Observatories (SGOs)

The direct observation of gravitational waves in the 0.1 mHz to 1 Hz band is possible only from space. This band is expected to be rich with astrophysical sources that will yield a wealth of information measured with an accuracy and precision that can be obtained no other way. The Laser Interferometric Space Antenna (LISA) mission concept remains the reference design for this type of mission, but budget and programmatic constraints have forced reformulation of the original concept. This paper will briefly summarize recent activity in the US and Europe toward realizing a gravitational wave mission in space.