Randall Peters,

You have advocated a "soft" feedback scheme for seismometers owing to 
improved sensitivity at long periods.  Conventional PID force feedback 
schemes, such as that used in the STS-1, are well described in numerous 
publications.  I assume you are suggesting an "I only" scheme (no P or 
D).  Is the feedback current deliberately weak so as to allow some 
movement of the reference mass, yet strong enough to keep it from 
hitting the pins?  Is the idea to integrate over one frequency range and 
observe events in another frequency range?  Or do you suggest allowing 
the integrator to see the entire frequency range of interest?

Thanks for any details you can provide.

Charles Burch
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