The focal plane assembly ofthe Sounding ofthe Atmosphere using Broadband Emission Radiometry (SABER) instrument is supported using Fiber Support Technology (FiST) which utilizes high performance fibers in tension to mechanically support and thermally isolate a cooled component from a warm environment. Details ofthis approach were presented in detail at 5Pm meeting in Denver in 1996. The SABER team deemed it necessary to perform optical stability testing on this never-beforeflown technology for supporting focal plane assemblies to determine ifprecise positioning could be maintained through vibration and thermal cycling. After subjecting the support system to vibration and thermal cycling, the angular orientation between the warm outer support structure and the inner cold block was measured. Since the outer support structure serves as the reference location for positioning the focal plane assembly and the cold block is where the detectors reside, it was possible to determine ifFiST meets the optical stability requirements for the SABER instrument. The results from this testing are presented, discussed, and compared to the optical requirements ofthe SABER instrument. A briefsummary ofcurrent thermal and mechanical enhancements to the system will also be discusse