The interferometry program experiment (IPEX) I and II are a series of flight experiments designed to characterize microdynamics of structures in space. These technology demonstration flight experiments are precursors to the Space Interferometry Mission (SIM), Next Generation Space Telescope (NGST) and Terrestrial Planet Finder (TPF), and will address the missions' nanometer-level structural stability requirements. Of particular interest is potential thermal snapping when space structures undergo rapid thermal variations, such as a sun-to-shade transition. This information is needed to characterize uncontrollable high frequency disturbances, and to validate structural designs and modeling approaches for joint-dominated extruding structures. Another objective of the experiments is to characterize typical mechanical disturbances of spacecraft while on-orbit for the purpose of modeling and disturbance response prediction for future optical space missions. Both experiments are performed on the German DARA/DASA free- flying platform Astro-Spas, which is sorted out of the shuttle and retrieved after an independent 10-day mission. IPEX-I, performed during the STS-80 mission in December 1996, characterized the on-board dynamics of the spacecraft during normal operations and quiescent periods. IPEX-II, performed during the STS-85 mission in August 1997, monitored the microdynamic behavior of a representative 9- bay AEC-ABLE mast. The flight data demonstrates the existence of transient microdynamic events that are correlated with temperature transitions. However, the overall spacecraft flight disturbances and broadband boom stability meet the requirements of precision space optical systems.