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Modulation-assisted time-delay interferometric ranging for LISA
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DOI：doi:10.1088/1361-6382/adecd3.png)
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Abstract
En 中文
Laser Interferometer Space Antenna (LISA) represents the next frontier in gravitational-wave (GW) astronomy, targeting the detection of millihertz gravitational signals. Central to LISA’s operation is the nanosecond-precision estimation of the light travel times (LTTs) between its constituent spacecraft. Precise LTT estimates are critical for suppressing dominant laser noise with time-delay interferometry (TDI) and ensuring the required sensitivity to GW signals. The baseline method is to modulate a pseudorandom noise (PRN) code on the laser beams exchanged between the spacecraft. Time-delay interferometric ranging (TDIR) was proposed as a simpler alternative LTT estimation method. TDIR LTT estimates are chosen to minimize the TDI residual noise over the full LISA frequency band. TDIR can be used in case of PRN failure, or to calibrate the biases of the PRN method. In this study, we introduce modulation-assisted TDIR (MATDIR), an enhanced variant of TDIR that significantly improves LTT estimation precision and resilience. MATDIR achieves this by modulating the laser phase at specific frequencies, close to 1 Hz, thereby artificially elevating the laser phase content relative to secondary, unsuppressed noises. This modulation strategy not only enhances the signal-to-noise ratio for TDIR but also mitigates the impact of GW signals and instrumental artifacts, enabling more reliable LTT estimates with reduced integration times. We develop the theoretical framework of MATDIR, incorporating the full constellation of three spacecraft, laser locking, and multiple Michelson TDI combinations. Analytical predictions, confirmed by numerical simulations, indicate that MATDIR can achieve LTT estimates comparable to the 1 m-rms at of the PRN-based baseline method. We therefore suggest that the possibility to modulate lasers is added to the laser system requirements of LISA.
Keywords:
LISA
gravitational waves
time-delay interferometry
laser phase modulation
nanosecond-precision estimation
Journal
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3.7
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1.3W
Citations:
3.0W