Sarah Paczkowski

PhD student in the Space Interferometry group

What is your current position at our institute?

I am a PhD student in the Space Interferometry group.

Can you please describe your research?

Since the Nobel Prize in 2017 was awarded for observation of gravitational waves with the LIGO detectors, gravitational waves became quite well known among scientists and the general public. Indeed, they can be used as an additional way to observe the universe. However, some interesting cosmic objects are sources of gravitational waves which cannot be measured with detectors on Earth. That is why the ESA Mission LISA is being prepared to detect gravitational waves in space. However, it is a technology challenge to detect gravitational waves both on ground and in space. To show the feasibility of LISA, the LISA Pathfinder mission has been operated between March 2016 and July 2017. The aim of the LISA Pathfinder mission was to show that we are able to have a free-falling test mass in space which is undisturbed by its surroundings such that the level of the remaining undesired acceleration is below some dozen femto-g, that is 10-15 of the standard gravitational acceleration on Earth at frequencies between 1 and 30 mHz.

To measure these tiny accelerations, there is a pair of test masses on board the satellite. The extremely small changes of the relative distance in between these two test masses are measured by a heterodyne laser interferometer. My research is about this high-precision optical readout system. It contributed to the big success of LISA Pathfinder: the measured residual accelerations have been much smaller! See for example this publication. The LISA Pathfinder data is a unique opportunity to investigate the behaviour of such a system in space. In the course of the mission we have performed many experiments to understand the excellent performance in great detail. The whole LISA Pathfinder team aims to learn as much as possible from LISA Pathfinder for future technology development. My research focuses on the necessary stabilisation of laser frequency fluctuations for the precision readout of the distance in between the two test masses and on the investigation of couplings from the remaining laser frequency fluctuations. I am also very much interested in the drift mode or free-flight experiment on LISA Pathfinder and I recommend you to have a look at its great results here!

Do you have a favorite figure from a publication you co-authored?

aus „Laser Frequency Noise Stabilisation and Interferometer Path Length Differences on LISA Pathfinder“ (Journal of Physics: Conference Series, Volume 840, conference 1)

Here is a viewgraph published in Laser Frequency Noise Stabilisation and Interferometer Path Length Differences on LISA Pathfinder. It illustrates the design of one of the experiments performed to investigate the coupling of laser frequency fluctuations to the differential readout. It also allowed us to measure the unstablised laser frequency noise.

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