The New Worlds, New Horizons in Astronomy and Astrophysics (2010) report by the Board on Physics and Astronomy (BPA) and the Space Studies Board also describes the Laser Interferometer Space Antenna (LISA)
LISA is a gravity wave observatory that would open an entirely new window in the universe. Using ripples in the fabric of space-time caused by the motion of the densest objects in the universe, LISA will detect the mergers of black holes with masses ranging from 10,000 to 10 million solar masses at cosmological distances, and will make a census of compact binary systems throughout the Milky Way. LISA’s measurements of black hole mass and spin will be important for understanding the significance of mergers in the building of galaxies. LISA also is expected to detect signals from stellarmass compact stellar remnants as they orbit and fall into massive black holes. Detection of such objects would provide exquisitely precise tests of Einstein’s theory of gravity. There may also be waves from unanticipated or exotic sources, such as backgrounds produced during the earliest moments of the universe or cusps associated with cosmic strings.
Using three “drag-free” spacecraft launched into an equilateral triangular configuration in an Earth-trailing orbit, LISA would explore the low-frequency (0.1- to 100-mHz) portion of the gravitational wave spectrum, observable only in space, to achieve its scientific objectives. The sides of the triangle are 5 million km, and the “laser-connected” spacecraft would measure their separations to an accuracy enabling detection of tens of picometers relative motions induced by passing gravitational waves. The mission lifetime is planned as 5 years. LISA has been studied for more than 20 years and was recommended by the 2001 astronomy and astrophysics decadal survey and also by two NRC reports
In the committee’s independent cost and readiness analysis, the NASA 50 percent portion of the project cost is estimated to be $1.5 billion (at 70 percent confidence), with time to completion of about 9.5 years. The remaining technical risk was rated as medium if the currently identified main technical risks—involving micro-Newton thrusters, drag-free control, and a gravitational reference system—are all retired by a successful LISA Pathfinder (LPF) mission, now scheduled for launch in 2012. The largest remaining technical challenge for the mission is identified as the successful deployment and operation of all three antennas. Assuming a successful Pathfinder, a 2016 new start should enable launch in the middle of the next decade.