Основные понятия
This article presents the noise models and spectral density functions used to characterize the various disturbances and noises affecting the Laser Interferometer Space Antenna (LISA) mission, which aims to detect gravitational waves.
Аннотация
The LISA (Laser Interferometer Space Antenna) mission is a future space-based gravitational wave observatory being developed by the European Space Agency (ESA). The main goal of the mission is to detect gravitational waves, which are undulatory perturbations of the space-time fabric, in order to provide experimental evidence for the General Relativity Theory.
The article discusses the different noise sources that affect the LISA system, which can be categorized into actuation noises, sensing noises, and environmental disturbances.
For the actuation noises, the authors model the noise contributions from the Micro Propulsion System (MPS), the Gravitational Reference Sensor (GRS), and the Optical Assembly (OA) motor. The sensing noises include those from the interferometer, the Differential Wavefront Sensor (DWS), and the GRS.
The environmental disturbances considered are the solar radiation pressure, the test-mass stiffness and self-gravity, and the environmental noises acting directly on the test-mass.
The article provides the mathematical models and spectral density functions used to characterize these different noise sources. Specifically, it presents the zero-pole filters that approximate the noise spectral densities, along with the corresponding parameter values. Plots are included to visualize the simulated noise profiles and their approximations using the proposed shape filters.
The noise modeling approach described in this article is crucial for the design and analysis of the Drag-Free and Attitude Control System (DFACS) in the LISA mission, as it allows for the accurate representation of the various disturbances that can affect the performance of the gravitational wave detection system.
Статистика
The article provides the following key figures and metrics:
GRS Force Noise (y-z component):
$H_{HRay_z} = 5 \cdot 10^{-15} \frac{(s + 1.257 \cdot 10^{-4})^2}{(s + 2.81 \cdot 10^{-6})^2} \frac{N}{\sqrt{Hz}}$
GRS Torque Noise:
$H_{HRat} = 5 \cdot 10^{-17} \frac{(s + 1.257 \cdot 10^{-4})^2}{(s + 2.81 \cdot 10^{-6})^2} \frac{Nm}{\sqrt{Hz}}$
Thruster Noise Spectral Density:
$H_T = 10^{-7} \frac{(s + 6.283 \cdot 10^{-2})^2}{(s + 8.886 \cdot 10^{-3})^2}$
Interferometer Sensing Noise:
$H_{IFO} = 1.5 \cdot 10^{-12} \frac{(s + 1.3 \cdot 10^{-2})^2}{(s + 1 \cdot 10^{-4})^2} \frac{m}{\sqrt{Hz}}$
GRS Sensing Noise (longitudinal and lateral position):
$H_{HRsxy} = 1.8 \cdot 10^{-9} \frac{(s + 3 \cdot 10^{-2})(s + 5.4 \cdot 10^{-3})(s + 9.6 \cdot 10^{-4})(s + 1.7 \cdot 10^{-4})}{(s + 2.58 \cdot 10^{-2})(s + 2.933 \cdot 10^{-3})(s + 4.333 \cdot 10^{-4})(s + 6 \cdot 10^{-5})} \frac{m}{\sqrt{Hz}}$
GRS Sensing Noise (vertical position):
$H_{HRsz} = 3 \cdot 10^{-9} \frac{(s + 3 \cdot 10^{-2})(s + 5.4 \cdot 10^{-3})(s + 9.6 \cdot 10^{-4})(s + 1.7 \cdot 10^{-4})}{(s + 2.58 \cdot 10^{-2})(s + 2.933 \cdot 10^{-3})(s + 4.333 \cdot 10^{-4})(s + 6 \cdot 10^{-5})} \frac{m}{\sqrt{Hz}}$
GRS Sensing Noise (test-mass roll):
$H_{HRstx} = 2 \cdot 10^{-7} \frac{(s + 3 \cdot 10^{-2})(s + 5.4 \cdot 10^{-3})(s + 9.6 \cdot 10^{-4})(s + 1.7 \cdot 10^{-4})}{(s + 2.58 \cdot 10^{-2})(s + 2.933 \cdot 10^{-3})(s + 4.333 \cdot 10^{-4})(s + 6 \cdot 10^{-5})} \frac{rad}{\sqrt{Hz}}$
DWS Sensing Noise (test-mass pitch/yaw):
$H_{DWS} = 5 \cdot 10^{-9} \frac{(s + 6 \cdot 10^{-3})^2}{(s + 1 \cdot 10^{-5})^2} \frac{rad}{\sqrt{Hz}}$
DWS-SC Sensing Noise (azimuth-elevation):
$H_{DWS_SC} = 1.167 \cdot 10^{-10} \frac{(s + 6 \cdot 10^{-3})^2}{(s + 6 \cdot 10^{-5})^2} \frac{rad}{\sqrt{Hz}}$
Solar Flux Noise:
$H_{SP} = 7.87 \cdot 10^{-11} \frac{(s + 7.09 \cdot 10^{-2})(s^2 + 5.78 \cdot 10^{-3}s + 2.954 \cdot 10^{-4})}{(s + 4.712 \cdot 10^{-3})(s^2 + 4 \cdot 10^{-3}s + 4 \cdot 10^{-4})} \frac{N}{\sqrt{Hz}}$
Environmental Force Noise on Test-Mass:
$H_{TMd} = 1.07 \cdot 10^{-15} \frac{(s + 9 \cdot 10^{-3})(s + 1.62 \cdot 10^{-3})(s + 2.88 \cdot 10^{-4})(s + 5.1 \cdot 10^{-5})}{(s + 7.74 \cdot 10^{-3})(s + 8.88 \cdot 10^{-4})(s + 1.3 \cdot 10^{-4})(s + 1.8 \cdot 10^{-5})} \frac{N}{\sqrt{Hz}}$
Environmental Torque Noise on Test-Mass:
$H_{TMD} = 4.92 \cdot 10^{-17} \frac{(s + 9 \cdot 10^{-3})(s + 1.62 \cdot 10^{-3})(s + 2.88 \cdot 10^{-4})(s + 5.1 \cdot 10^{-5})}{(s + 7.74 \cdot 10^{-3})(s + 8.88 \cdot 10^{-4})(s + 1.3 \cdot 10^{-4})(s + 1.8 \cdot 10^{-5})} \frac{Nm}{\sqrt{Hz}}$