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How
does LISA work?
 LISA is a constellation of three identical satellites forming an
equilateral triangle with an armlength of 5 million kilometers.
The center of this triangle is following the earth, 20° behind on
its orbit around the sun. The plane of the triangle is tilted
60° against the ecliptic so that the constellation is stable.
Each satellite carries two telescopes with a diameter of
40 cm. They catch the light coming from the far spacecraft. At the core of each satellite are two free floating test masses.
They are extremely well shielded from all external forces.
They act as end
mirrors of a laser interferometer that is formed by the LISA
arms. Gravitational waves alter the distance between the two spacecraft.
Measurement of the
distance between the test masses is done with a
heterodyne interferometer that is sensitive down to
10 pm/sqrt(Hz). Additionally, the angle of the test mass is
monitored. This information is used to align the satellite with
respect to the test masses. Ion thrusters - "Field Emission
Electric Propulsion" (FEEPs) - are
installed for this purpose. They mainly compensate the solar
pressure with a force of a few μN.
 LISA - Technical Challenge in Space (back to LISA main page)
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