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Logo: Sonderforschungsbereich geo-Q
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A07 - Multichannel interferometry optics for gradiometry

Multi-dimensional laser interferometer
Multi-dimensional laser interferometer

Measurement of gravity gradients from spacecraft has been shown to be extremely valuable for recovery of the earth’s gravity field by the GOCE mission. Gradiometers provide a high-sensitivity measurement of gravity gradients and their fluctuations, thus sensing variations in the gravitational field of the Earth or other celestial bodies. GOCE has used 6 test masses to measure second derivatives of the Earth’s gravitational potential. Going one step further, by adding one more test mass at the center of the array, third derivatives could be determined in addition. Moreover, by replacing the electrostatic readout of the test mass position by multichannel laser-interferometric techniques, the resolution and noise-level could be drastically improved. That requires simultaneous readout of several degrees of freedom of multiple test masses in a single, compact and reliable instrument. Such laser interferometers require

  • stable, miniaturized, optical systems, for example fiber-optic interferometers,
  • light sources that produce adequately modulated light for the chosen readout technique,
  • a phasemeter that processes the interferometer photocurrents,
  • auxiliary stabilization loops to mitigate noise sources originating e.g. from beam pointing fluctuations and laser noise.

Laser interferometry for test mass readout aboard satellites has been developed at the AEI for LISA Pathfinder, where a total of six degrees of freedom of two test masses (one translational and two rotational per test mass) are measured. Simple upscaling of that technology is, however, not feasible due to the size and mass of the known system and due to exponentially increasing crosstalk problems between the channels. In a multichannel system to measure third derivatives of the potential, for example, at least seven test masses need to be sensed, ideally with six (three translational and three rotational) degrees of freedom each, which results in 42 channels and 21 distinct laser beams. This project will concentrate on the experimental and instrumental aspects of such a system with the objective of building free-beam and fiber-optical laser interferometer prototypes and their corresponding phasemeter systems that allow a thorough understanding and model-verification of the sensitivity, noise sources and limitations. After an initial stage of table-top breadboarding, the performance of an optimized system will be evaluated in the torsion balance of project A06. The long-term goal beyond the first funding period is to develop a multi-testmass sensor system with a sensitivity at the 10−13 . . . 10^−14 ms^−2/√Hz level, i.e. one to two orders of magnitude better than GOCE, as central sensor for a future gravity gradiometer mission. A well understood path to flight compatibility will be established in close cooperation with the gradiometer system study of B07.

Scientists working on this project

Dr. Oliver Gerberding
email: oliver.gerberdingaei.mpg.de

phone: +49 511 762-17064
details

Katharina-Sophie Isleif
email: katharina-sophie.isleifaei.uni-hannover.de

phone: +49 511 762-17041
details

Thomas Schwarze
email: thomas.schwarzeaei.mpg.de

phone: +49 511 762-17033
details

Selected Publications


Peer-Reviewed Literature

Isleif K.-S., Gerberding O., Mehmet M., Schwarze T.S., Heinzel G. and Danzmann K. (2016): Comparing interferometry techniques for multi-degree of freedom test mass readout, Journal of Physics: Conference Series 716, 012008 (2016)
DOI: 10.1088/1742-6596/716/1/012008

Isleif K.-S., Gerberding O., Schwarze T.S., Mehmet M., Heinzel G. and Guzmán Cervantes F. (2016): Experimental demonstration of deep frequency modulation interferometry, Opt. Express 24, 1676-1684 (2016) more
DOI: 10.1364/OE.24.001676

Gerberding O., Diekmann C., Kullmann J., Tröbs M., Bykov I., Barke S., Brause N.C., Delgado J.J.E., Schwarze T.S., Reiche J., Danzmann K., Rasmussen T., Hansen T.V., Enggaard A., Pedersen S.M., Jennrich O., Suess M., Sodnik Z. and Heinzel G. (2015): Readout for intersatellite laser interferometry: Measuring low frequency phase fluctuations of high-frequency signals with microradian precision, Review of Scientific Instruments, Volume 86, Issue 7, 074501
DOI: 10.1063/1.4927071

Schütze D., Stede G., Müller V., Gerberding O., Bandikova T., Sheard B. S., Heinzel G. and Danzmann K. (2014): Laser beam steering for GRACE Follow-On intersatellite interferometry, Optics Express, Volume 22, Issue 20, page 24117-24132
DOI: 10.1364/OE.22.024117

Ward R. L., Fleddermann R., Francis S., Mow-Lowry C., Wuchenich D., Elliot M., Gilles F., Herding M., Nicklaus K., Brown J., Burke J., Dligatch S., Farrant D., Green K., Seckold J., Blundell M., Brister R., Smith C., Danzmann K., Heinzel G., Schuetze D., Sheard B. S., Klipstein W., McClelland D. E. and Shaddock D. A. (2014): The design and construction of a prototype lateral-transfer retro-reflector for inter-satellite laser ranging, Classical and Quantum Gravity, Vol. 31, Issue 9, 095015
DOI: 10.1088/0264-9381/31/9/095015



Presentations, Talks and Posters

Isleif K.-S. (2016): The journey to noise reduced & ultra stable interferometers, DPG Frühjahrestagung, Hannover, Germany, 01 March, 2016

Isleif K.-S. (2016): The LISA Backlink & Deep Frequency Modulation Interferometry, Midterm PhD Report, Albert Einstein Institute, Hannover, Germany, 31 March, 2016