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P.L. Bender (JILA, University of Colorado), S.M. Merkowitz (Goddard Space Flight Center), H. Peabody (Swales Aerospace), B.L. Schumaker (Jet Propulsion Laboratory)
The dominant source of measurement uncertainty for the Laser Interferometer Space Antenna (LISA) gravitational wave mission at frequencies below about 3 millihertz is expected to be spurious accelerations of the carefully shielded test masses between which laser interferometric measurements are made. The test masses are the reference objects in Gravitational Reference Sensors (GRSs) on each of 3 spacecraft that form a triangle 5 million km on a side. The spacecraft are servo-controlled with micronewton thrusters to stay accurately centered on the test masses. A LISA Pathfinder mission is planned by the European Space Agency as a validation flight in 2007 for both European and US GRS units.
Based on continued studies of spurious acceleration sources for GRS units by a number of groups in Europe and the US, an update on our understanding of the main error sources at frequencies down to 3 microhertz will be given. These include the following: fluctuations in the test mass charge interacting with dc electrical fields; gravitational effects of thermal distortion of the spacecraft; fluctuating thermal radiation pressure; fluctuations in the interplanetary magnetic field; and cross-talk from non-axial displacements of the spacecraft and from test mass rotations. A spurious acceleration level of 0.03 picometers/s2/root Hz at 3 microhertz for each test mass appears to be a feasible goal. High gravitational wave sensitivity at low frequencies is expected to be valuable in studies of massive black hole coalescences.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.