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From the Planetary Society Blogpost InSight Update, sols 25-42: Seismometer sensors working! Tricky setup and cable management on Mars

This is an animated GIF: It's fairly subtle, you may not notice at first!

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IPGP / David Ducros

VBB RECENTERING

Animation showing the "recentering" operation of the InSight seismometer's Very Broad Band (VBB) seismic pendulums. Recentering is a calibration activity that fine-tunes the instrument's sensitivity to slow seismic waves. There are three VBB sensors in the SEIS instrument.

In some more technical detail, what is the effect of the recentering operation on the VBB seismic pendulums? Is it as simple as just making sure their equilibrium position is centered (which doesn't sound like a proper calibration) or is there more going on?

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According to this paper the recentering operation seems to be adjusting the instrument's center of gravity (via the motor unit seen on the right of the animation). From the paper...

To ensure the fine equilibrium of the highly sensitive pendulum, a balancing mechanism (fig.1g) adjust the center of gravity position

This is a translation from the original French, so the syntax is slightly odd.

Here's a more comprehensive discussion of the instrument, including an interactive PDF.

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  • $\begingroup$ Okay I'm starting to understand. It sounds like it adjusting the equilibrium position, but not really "calibrating" from what I can read in these links so far. However, perhaps it does have a calibrating function as well. $\endgroup$
    – uhoh
    Commented Mar 1, 2019 at 22:20
  • $\begingroup$ Have a look at the inclined orientation in Fig. 2 in your first link, I think that it could serve as a basis for an answer to a question How was InSight's vertical seismometer (accelerometer) tested in Earth's stronger gravity? $\endgroup$
    – uhoh
    Commented Mar 1, 2019 at 22:22

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