Before closing the doors on the HAM-ISI in the staging building (assembly 1), we measured ASDs of the instruments. The horizontal GS13 in corner 3 (POD SN68 – GS13 SN805) had a bad response at low frequency (see spectra) which is a typical characteristic of a stuck proof mass.

After opening the vacuum pod, we verified that:

-         The kinetic feet could not move and the cross bar was not loose.

-         We could feel the mass moving when the geophone was tilted

-         The mass is centered when the geophone is horizontal (Level on the second circle)

We measured a spectrum while making sure the geophone was horizontal and the proof mass was centered. The spectrum still looks bad.

After taking apart the geophone, we could feel that the mass is not moving freely (sticky). We will replace this geophone with a new one.