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P. L. Bender (JILA-University of Colorado)
The LISA mission has been studied since 1993 both in Europe and the US. The present baseline mission design is based on sending carefully stabilized 0.5 W cw laser beams from NdYAG lasers between 3 spacecraft at the corners of an equilateral triangle 5 million km on a side. The triangular antenna is located 20 deg behind the Earth in a 1 yr circular orbit around the Sun. Each spacecraft sends and receives laser beams along the adjacent sides of the triangle through 30 cm diam telescopes. Changes in the optical path lengths between freely floating test masses in the different spacecraft are measured for frequencies of 0.00001 to 1 Hz. A procedure is used which permits both the laser phase noise and changes in the antenna arm length differences to be measured.
Below 0.003 Hz, there will be so many galactic binaries that their signals can't be resolved even with a year of data. >From about 0.0001 to 0.003 Hz, the resulting confusion noise will dominate the instrumental noise. Above 0.003 Hz, signals from several thousand compact binaries throughout the galaxy can be resolved. There also will be some observable signals from known binaries. However, the main objective of the mission is to observe and study signals from several promising types of binaries involving massive black holes (MBHs) out to cosmological distances. For example, the last year before coalescence of two 500 solar mass black holes could be observed out to z=5. Questions of particular interest involve the abundance and surroundings of 100,000 solar mass and larger MBHs, the pathway for formation of MBHs, possible MBH coalescences after galaxy mergers, and tests of general relativity under extreme conditions.
This talk is based on studies by ESA, NASA, ESA's LISA Study Team, and NASA's LISA Mission Definition Team.
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