The test item, referred to as the HESSI Bare Structure,
consisted of a base ring, primary support struts, secondary support struts,
central cylinder, deck, imager support ring, solar array support struts and
a solar array support ring.
The modal survey was conducted using a SIMO testing method.
The data acquisition system included an HP35670A Dynamic Signal Analyzer, an
HP3566A Dynamic Signal Analyzer, an APS Dynamics Model 113 long stroke
electro-dynamic exciter and PCB instrumentation.
Sample mode shapes are shown below.