EGU2020-10566
https://doi.org/10.5194/egusphere-egu2020-10566
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Laser Ranging Interferometer on GRACE Follow-On: Current Status

Vitali Müller1,2 and the GRACE Follow-On LRI Team*
Vitali Müller and the GRACE Follow-On LRI Team
  • 1MPI Gravitational Physics, Space Laser Interferometry, Hannover, Germany (vitali.mueller@aei.mpg.de)
  • 2Institut für Gravitationsphysik, Leibniz Universität Hannover, Germany
  • *A full list of authors appears at the end of the abstract

The GRACE Follow-On satellites were launched on 22nd May 2018 to continue the measurement of Earth’s gravity field from the GRACE satellites (2002-2017). A few weeks later, an inter-satellite laser link was established with the novel Laser Ranging Interferometer (LRI), which offers an additional measurement of the inter-satellite range next to the one provided by the conventional microwave ranging instrument. The LRI is the first optical interferometer in space between orbiters, which has demonstrated to measure distance variations with a noise below 1 nm/rtHz at Fourier frequencies around 1 Hz, well below the requirement of 80 nm/rtHz.

In this talk, we provide an overview on the LRI and present the current status and results regarding the characterization of the instrument. We will address the scale factor, which is needed to convert the phase measurements to a displacement, and the removal of phase jumps that are correlated to attitude thruster activations. Moreover, the results comprise the coupling of attitude variations into the measured range, which is determined by means of the center-of-mass calibration maneuvers. This coupling is expected to be one of the major error sources at low frequencies, however, it is not directly apparent due to the large gravity signal.

We conclude with some learned lessons and potential modifications of the interferometry for future geodetic missions.

GRACE Follow-On LRI Team:

Gerhard Heinzel, Henry Wegener, Malte Misfeldt, Alexander Koch, Germán Fernández Barranco, Christopher Woodruff, Robert Spero, Josep Sanjuan, Samuel Francis, Brent Ware, Jehhal Liu, ...

How to cite: Müller, V. and the GRACE Follow-On LRI Team: Laser Ranging Interferometer on GRACE Follow-On: Current Status, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10566, https://doi.org/10.5194/egusphere-egu2020-10566, 2020

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Display material version 2 – uploaded on 05 May 2020
finalized the slides.
  • CC1: Comment on EGU2020-10566, Jakob Flury, 07 May 2020

    Vitali, thank you for the presentation.

    What is the content of the CNR plots on slide 3? And how does "Sample No" on slide 7 convert to a time scale?

    Jakob

    • AC1: Reply to CC1, Vitali Müller, 07 May 2020

      Thanks Jakob.

      For the CNR plot: the oscillations are related to change in distance (1/rev and 2/rev). These are more proncounced on GF1, since GF1 is currently in master mode, while GF2 is transponder. The change i.n envelope is related to the fact that the satellites were entering full-sun phase on these days. Might be related to change in temperature, as we see such changes more often. CNR changes in the LRI are less important than for the KBR, because the KBR ranging noise depends on the CNR. In case of LRI, it is not the case.

      Conversion from sample-no to time-scale: This is phase data. The phase data (level1A) has a sampling rate of 9.664 Hz on GF1, and 9.664198 Hz on GF2.  These numbers can be used to convert to time.

Display material version 1 – uploaded on 04 May 2020, no comments