5 horizontal GS13s and 4 vertical GS13s were received from LLO in shipment load # 3523. Huddle tests were performed.

Horizontal GS13s were initially set with the same orientation: as installed in the ISI. Two of them were then failing. Pods can be installed with 3 orientaions. Each orientation set up is distant of 120˚. We tried rotating the pods by increments of 120˚ to see if the test would be more successful then. GS13s were gently tilted back and forth after each rotation to make sure that the mass was not stuck. For some orientation the mass still felt stuck. The instrument's power spectrum would then reveal a failure of the instrument's response below 20Hz. 

The rotation test was performed two times: 04/10 and 04/10. The working set up found for both times correlated:

• Horizontal Pod# 37 - +240˚ CCW
• Horizontal Pod# 20 - Regular (as in ISI)
• Horizontal Pod #84 - Regular (as in ISI)
• Horizontal Pod #27 - +120˚ CCW 
• (No working orientation was found for Horizontal Pod #18)

However, when tried later this afternoon, this configuration would feature a failure of Pod #20, as reported by Corey.

The combination [leveling of the instruments in their pod + approximate level of the table used for test] could be an explanation for the need to rotate the instruments. Another explanation could be that loose flexures, as some were observed, would impact the symetry of their pull, causing the mass to get stuck in some positions and not in others.

As usual, Vertical GS13s appeared to be robust. Their spectra are all fine.

Test pictures and results are attached.