SAMOP 2023 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 62: Precision Measurements: Gravity II

Q 62.6: Talk

Friday, March 10, 2023, 12:15–12:30, E214

Experimental Results on Cavity-Laser-Locking for Future Gravimetric Satellites — •Martin Weberpals, Vitali Müller, Malte Misfeldt, and Gerhard Heinzel — Max Planck Institute for Gravitational Physics, Hannover, Germany

The precise measurement of satellite distance variations in a low earth orbit can reveal the structure of Earth's gravity field, which is directly related to the mass distribution underneath the satellites.

The satellite pairs GRACE (2002-2017) and GRACE Follow-On (2018-) provided monthly maps of Earth's gravity field, which are extremely valuable for climate research and the understanding of mass redistribution processes on Earth. Future missions, in which laser interferometry will be the primary means of determining the inter-satellite range, are currently being prepared.

In this presentation, we give a short overview on the heterodyne laser instrument concept and address our experimental activities conducted so far in supporting European instrument development. We show our setup for achieving a classical Pound-Drever-Hall (PDH) lock, based on commercial RedPitaya devices as an initial stage. We also present the status of our work on an extension to the PDH lock, allowing us to read out the free spectral range of a cavity. This measurement can be used to calculate the absolute laser frequency, which is required to convert ranging phase data into biased inter-satellite distance. In the end, we show how these activities contribute to the development of European Instrument Control Electronics potentially to be used in future missions.