The 10 m prototype facility at the Albert-Einstein-institute (AEI) in Hanover, Germany, employs three large seismic attenuation systems to reduce mechanical motion. The AEI seismic-attenuation-system ...(AEI-SAS) uses mechanical anti-springs in order to achieve resonance frequencies below 0.5 Hz. This system provides passive isolation from ground motion by a factor of about 400 in the horizontal direction at 4 Hz and in the vertical direction at 9 Hz. The presented isolation performance is measured under vacuum conditions using a combination of commercial and custom-made inertial sensors. Detailed analysis of this performance led to the design and implementation of tuned dampers to mitigate the effect of the unavoidable higher order modes of the system. These dampers reduce RMS motion substantially in the frequency range between 10 and 100 Hz in 6 degrees of freedom. The results presented here demonstrate that the AEI-SAS provides substantial passive isolation at all the fundamental mirror-suspension resonances.
LISA mission overview Danzmann, K.
Advances in space research,
2000, 2000-1-00, 20000101, Letnik:
25, Številka:
6
Journal Article
Recenzirano
Odprti dostop
More than 80 years ago, Einstein has predicted that accelerated masses will emit gravitational waves, propagating distortions of the spacetime fabric. The gravitational wave spectrum of known and ...expected sources covers many decades in frequency. While sources in the audio-frequency regime above 1 Hz are accessible to ground-based detectors, sources in the low-frequency regime can only be observed from space because of the unshieldable background of Newtonian gravitational noise. LISA is a laser-interferometric gravitational wave detector in space designed to observe gravitational wave signals from galactic as well as cosmological sources in the frequency range from 0.1 mHz to 1 Hz. LISA comprises a cluster of three spacecraft at the corners of an equilateral triangle of 5 Mio km size. The cluster is in an earth-like heliocentric orbit trailing the earth by 20 degrees. Each spacecraft carries lasers and free-flying proof masses and is kept on a purely inertial orbit by drag-free technology using field emission electric propulsion.
In this article we discuss possible design options for the optical phase reference system, the so called backlink, between two moving optical benches in a LISA satellite. The candidates are based on ...two approaches: Fiber backlinks, with additional features like mode cleaning cavities and Faraday isolators, and free beam backlinks with angle compensation techniques. We will indicate dedicated ghost beam mitigation strategies for the design options and we will point out critical aspects in case of an implementation in LISA.
Optical testbed for the LISA phasemeter Schwarze, T S; Fernández Barranco, G; Penkert, D ...
Journal of physics. Conference series,
05/2016, Letnik:
716, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The planned spaceborne gravitational wave detector LISA will allow the detection of gravitational waves at frequencies between 0.1 mHz and 1 Hz. A breadboard model for the metrology system aka the ...phasemeter was developed in the scope of an ESA technology development project by a collaboration between the Albert Einstein Institute, the Technical University of Denmark and the Danish industry partner Axcon Aps. It in particular provides the electronic readout of the main interferometer phases besides auxiliary functions. These include clock noise transfer, ADC pilot tone correction, inter-satellite ranging and data transfer. Besides in LISA, the phasemeter can also be applied in future satellite geodesy missions. Here we show the planning and advances in the implementation of an optical testbed for the full metrology chain. It is based on an ultra-stable hexagonal optical bench. This bench allows the generation of three unequal heterodyne beatnotes with a zero phase combination, thus providing the possibility to probe the phase readout for non-linearities in an optical three signal test. Additionally, the utilization of three independent phasemeters will allow the testing of the auxiliary functions. Once working, components can individually be replaced with flight-qualified hardware in this setup.
The Laser Interferometer Space Antenna (LISA) is a joint ESA/NASA mission proposed to observe gravitational waves. One important noise source in the LISA phase measurement will be on-board reference ...oscillators. An inter-spacecraft clock tone transfer chain will be necessary to remove this non-negligible phase noise in post processing. One of the primary components of this chain are electro-optic modulators (EOMs). At modulation frequencies of 2 GHz, we characterise the excess phase noise of a fibre-coupled integrated EOM in the LISA measurement band (0.1 mHz to 1 Hz). The upper phase noise limit was found to be almost an order of magnitude better than required by the LISA mission. In addition, the EOM’s phase dependence on temperature and optical power was determined. The measured coefficients are within a few milliradians per kelvin and per watt respectively and thereby negligible with the expected on-board temperature and laser power stability.
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