The University of Florida LISA interferometer simulator
Abstract
Interferometric gravitational wave detectors such as LISA are built around two major subsys-tems. Gravitational reference sensors (GRS) consist of several freely-falling proof masses which follow variations in space time caused by passing gravitational waves. Spurious accelerations of the proof masses caused by technical or environmental forces have to be below the fN/rtHz level in the frequency band of interest. Interferometer measurement systems (IMS) measure the changes in the distances between the proof masses with sufficient sensitivity. The GRS-system for LISA has been developed over the last ten years and will be tested in a dedicated test mission, the LISA Test Package (LTP), scheduled for launch in 2012. The IMS of LISA is one of the most dynamic and longest interferometers ever envisioned. It consists of many subsystems which depend on the long light-travel times, the changes in the light-travel times and the induced Doppler shifts. The signals of the IMS are beat tones taken between vari-ous lasers at various locations on the three spacecraft. The phase evolution of each signal is measured against on-board clocks, after which linear combinations between appropriately time-shifted signals are formed to cancel about 10 orders of magnitude of laser frequency noise and thereby reach LISA sensitivity. Achieving 10 orders of magnitude of common mode rejection is already a daunting task for a small static interferometer in an optical laboratory. LISA is a very large and highly dynamic interferometer with constantly changing arms which for exam-ple requires to adapt permanently the noise cancelling linear combinations to the current arm lengths and spacecraft velocities while continuously monitoring the relative noise between the three independent on-board clocks. The University of Florida LISA Interferometer Simulator (UFLIS) is a hardware-in-the-loop simulator which includes multiple lasers, LISA-like signal travel-times and LISA-like Doppler shifts. UFLIS generates signals that currently are the most LISA-like signals in the world; these can be used to develop, test, and verify various techniques and algorithms proposed to achieve the required LISA performance. In this presentation I will discuss the core elements of UFLIS and how these elements are used to generate LISA-like signals. I will present results from tests we have performed and discuss our future test plans. This work is supported by NASA grants NNX08AG75G and NNX09AF99G
- Publication:
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38th COSPAR Scientific Assembly
- Pub Date:
- 2010
- Bibcode:
- 2010cosp...38.3763M