Why are there multiple designs for the IXO spacecraft?
Conceptual development for an international scientific space mission begins with engineers and scientists from each agency grasping very early ideas and giving them form. Because IXO is an international cooperative project, the mission design has been independently studied by ESA as well as by NASA. Both designs are based on a common set of features including a single large X-ray mirror assembly and an extendible optical bench with a focal length of ~20 m, and a suite of focal plane instruments. IXO science requires a low mass telescope with large effective area and high angular resolution. Currently such performance can be achieved via two innovative X-ray optics technologies pursued independently by each agency. The baseline technology for IXO is represented by the Silicon Pore Optics (SPO) developed by ESA, with the back-up technology as the Segmented Glass Optics (SGO) developed by NASA. Both technologies are compatible with the Flight Mirror Assembly Module and can be accommodated
