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Logo: Sonderforschungsbereich geo-Q
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B06 - Nanometer ranging systems for low Earth orbiter links

Optical ground support equipment set-up for testing GRACE Follow-On LRI acquisition strategies and overall
Optical ground support equipment set-up for testing GRACE Follow-On LRI acquisition strategies and overall

This project covers the constellation aspects of a future laser-interferometric inter-satellite ranging mission, as opposed to the ‘local’ aspects in A05. It consists of two closely related parts, the study of mission designs including the noise budget breakdown and, on the other hand, experimental investigations of the link acquisition.

The overall ranging noise of a GRACE-type mission consists of many contributions that depend partially on the properties of individual subsystems (like the laser stability), and very often also on properties of the satellite and constellation as a whole. For the GRACE Follow-On Laser Ranging Instrument (LRI) with its 80 nm/√Hz noise level, it is known that the most important contributions to the noise budget are due to laser frequency noise and satellite pointing jitter. In order to achieve 10 nm/√Hz for future missions, improvements in many areas are necessary: The pointing stability, for example, can be improved if interferometric signals are used in the Attitude and Orbit Control System (AOCS) of the satellite. Pointing jitter couples into the length measurement by several mechanisms such as misalignments between the optical axes and rotational pivot points, traversing variable paths through the optical system, moving diffraction artefacts etc. The overall noise budget must be balanced between these and many other contributors, such as thermal stability, phase readout, wavefront quality, alignment of optics, shot noise, clock noise etc. This task is intimately linked with the design of the interferometer, e.g. its laser beam divergence, beam routing, pointing mechanism (if any), imaging optics, phase detection scheme etc. In this project the capabilities and constraints of the individual subsystems of the interferometer will be evaluated and joined to a coherent design that optimizes the science return. One output is the expected ranging performance and its frequency dependence which will be used to predict the science return. Another output will be the noise budget breakdown that translates into requirements to the subsystems as to what performance they have to deliver under which circumstances. Furthermore the breakdown will be used to steer the subsystem development, e.g. in A05, towards the most rewarding improvements.

The second, experimental, part of this project concerns the initial link acquisition, a recurring problem in long distance laser interferometry. In short, five degrees of freedom (two angles at each spacecraft and one laser frequency) all have to be within a narrow range simultaneously to enable operation of the laser link. This can be achieved by synchronized spirals and frequency scans, the design of which depends on the interferometer design and alignment accuracy, but also on the orbits and satellite attitude control. Although link acquisition needs to occur only once (or infrequently) before science operation commences, it is in many respects the most challenging aspect of interspacecraft interferometry. A well-understood and proven acquisition procedure is not only an absolute necessity for operation, but also implies that the interferometer as a whole is well understood and under control. While many aspects can be studied by computer simulations, the most reliable and informative test is an experiment, which constitutes a major part of this project. The output of this part will be robust acquisition procedures tested by simulation and experiment, and a flexible testbed that allows testing of alternative procedures as well as testing of flight-like hardware.  

Scientists working on this project

Alexander Görth
email: alexander.goerthaei.mpg.de

phone: +49 511 762-17021
details

Dr. Norman Gürlebeck
email: norman.guerlebeckzarm.uni-bremen.de

phone: +49 421 218-57857
details

Vitali Müller
email: vitali.muelleraei.mpg.de

phone: +49 511 762-14003
details

Dr. Josep Sanjuan
email: sanjuanzarm.uni-bremen.de

phone: +49 421 244-201277
details

Gunnar Stede
email: gunnar.stedeaei.mpg.de

phone: +49 511 762-19135
details

Selected Publications


Peer-Reviewed Literature

Luo Z., Wang Q., Mahrdt C., Görth A. and Heinzel G (2017): Possible alternative acquisition scheme for the gravity recovery and climate experiment follow-on-type mission, Applied Optics, Vol. 56, Issue 5, pp. 1495-1500
DOI: 10.1364/AO.56.001495

Görth A., Sanjuan J., Gohlke M., Rasch S., Abich K., Braxmaier C. and Heinzel G. (2016): Test environments for the GRACE follow-on laser ranging interferometer, Journal of Physics: Conference Series 716
DOI: 10.1088/1742-6596/716/1/012011

Sanjuan J., Gürlebeck N. and Braxmaier C. (2016): Mathematical model of thermal shields for longterm stability optical resonators, Optics Express, Vol. 23, Issue 14, pages 17892-17908
DOI: 10.1364/OE.23.017892

Schütze D., Müller V., Stede G., Sheard B. S., Heinzel G., Danzmann K., Sutton A. J. and Shaddock D. A. (2016): Retroreflector for GRACE follow-on: Vertex vs. point of minimal coupling, Optics Express, Volume 22, Issue 8, page 9324-9333
DOI: 10.1364/OE.22.009324

Shabanloui A. and Müller J. (2016): Mass variations in the Siberian permafrost region based on new GRACE results and auxiliary modeling, International Association of Geodesy Symposia, pp. 1–8.
DOI: 10.1007/1345_2015_186

Ales F., Mandel O., Gath P.F., Johann U. and Braxmaier C. (2015): A Phasemeter Concept for Space Application that Integrates an Autonomous Signal Acquisition Stage Based on the Discrete Wavelet Transform, Review of Scientific Instruments, Vol.86, 084502
DOI: 10.1063/1.4928489

Sanjuan J., Gohlke M., Rasch S., Abich K., Görth A., Heinzel G. and Braxmaier C. (2015): Interspacecraft link simulator for the laser ranging interferometer onboard GRACE Follow-On, Applied Optics
DOI: 10.1364/AO.54.006682

Ales F., Gath P.F., Johann U. and Braxmaier C. (2014): Modeling and Simulation of a Laser Ranging Interferometer Acquisition and Guidance Algorithm, Journal of Spacecraft and Rockets, Vol.51 No.1, pp.226-238
DOI: 10.2514/1.A32567

Schütze D., Farrant D., Shaddock D. A., Sheard B. S., Heinzel G. and Danzmann K. (2014): Measuring coalignment of retroreflectors with large lateral incoming-outgoing beam offset, Review of Scientific Instruments, Volume 85, Issue 3, 035103
DOI: 10.1063/1.4866682

Schütze D., Müller V., Heinzel G. (2014): Precision absolute measurement and alignment of laser beam direction and position, Applied Optics, Vol. 53, Issue 28, page 6503-6507
DOI: 10.1364/AO.53.006503

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

Wuchenich D. M. R., Mahrdt C., Sheard B. S., Francis S. P., Spero R. E., Miller J., Mow-Lowry C. M., Ward R. L., Klipstein W. M., Heinzel G., Danzmann K., McClelland D. E. and Shaddock D. A. (2014): Laser link acquisition demonstration for the GRACE Follow-On mission, Optics Express, Volume 22, Issue 9, page 11351-11366
DOI: 10.1364/OE.22.011351


Non Peer-Reviewed Literature

Abich K., Bogan C., Braxmaier C., Danzmann K., Dehne M., Gohlke M., Görth A., Heinzel G., Herding M., Mahrdt C., Müller V., Nicklaus K., Sanjuan J., Schütze D., Sheard B., Stede G. and Voss K. (2015): GRACE-Follow On Laser Ranging Interferometer: German contribution, Journal of Physics: Conference Series
DOI: 10.1088/1742-6596/610/1/012010

Ales F., Gath P.F., Johann U. and Braxmaier C. (2015): Line of Sight Alignment Algorithms for Future Gravity Missions, Proceedings of the AIAA Guidance Navigation and Control Conference, Kissimmee (FL), USA
DOI: 10.2514/6.2015-0094

Ales F., Mandel O., Gath P.F., Johann U. and Braxmaier C. (2015): Design and Development of a Laser Fine Pointing Sensor, Proceedings of the AIAA Guidance Navigation and Control Conference, Kissimmee (FL), USA
DOI: 10.2514/6.2015-0332


Presentations, Talks and Posters

Görth A. (2016): The GRACE Follow-On Laser Ranging Interferometer – On track for launch in 2017, EGU General Assembly, Vienna, Austria

Görth A. (2015): Test environments for the GRACE Follow-On Laser Ranging Interferometer, 11th Amaldi Conference on Gravitational Waves, Gwangju, South Korea, 21 - 26 June, 2015

Görth A. (2014): The GRACE Follow-On Laser Ranging Interferometer, DPG Spring Meeting, Berlin, 17 – 21 March, 2015