ausblenden:
Schlagwörter:
Astrophysics, Instrumentation and Methods for Astrophysics, astro-ph.IM
Zusammenfassung:
The Laser Interferometer Space Antenna (LISA) is a European Space Agency
mission that aims to measure gravitational waves in the millihertz range. The
three-spacecraft constellation form a nearly-equilateral triangle, which
experiences flexing along its orbit around the Sun. These time-varying and
unequal armlengths require to process measurements with Time-Delay
Interferometry (TDI) to synthesize a virtual equal-arm interferometer, and
reduce the otherwise-overwhelming laser frequency noise. Algorithms compatible
with such TDI combinations have recently been proposed in order to suppress the
phase fluctuations of the onboard ultra-stable oscillators (USO) used as
reference clocks.
In this paper, we present a method to compute improved algorithms, which
provide exact cancellation of the USO noise for a large class of TDI
combinations, even for time-varying armlengths, if we neglect Doppler effects.
We account for errors present in the sideband signals used in the algorithm,
and include a new step to reduce it. We propose analytic models for the power
spectral densities of residual noises, including residual clock noise due to
the filters used on board to downsample data before telemetry. We present the
results of simulations, which include realistic USO noise. We show that our
model agrees very well with the simulated data, and that our algorithms are
able to reduce clock jitter well below other noises, and the mission
requirements.
