Summary: The Advanced X-ray Astrophysics Facility (AXAF) is to be the third in the National Aeronautics and Space Administration's (NASA) series of four "great observatories," which are expected to provide new data and insights into the age, evolution, and composition of the universe. By redesigning and dividing the AXAF into two satellites, NASA has been able to make the program more affordable. The restructuring cut program costs by 54 percent without compromising the AXAF's scientific mission. Affordability for the AXAF-I--the satellite devoted to high-resolution x-ray imaging--may still be a concern, however, because funding reserves for it may fall short. Also, NASA may not have fully accounted for the increased technical risks inherent in the new design. As now designed, AXAF-I cannot be repaired in orbit, which means that hardware failures could scuttle a mission. Further minimizing the risk of hardware failures demands the highest quality parts and rigorous testing, which would boost costs significantly. NASA expects the restructure program to achieve most of the original science objectives set for AXAF. The objectives should be achieved because, owing to a higher orbit for AXAF-1 and greater individual use of instruments, the satellites would operate more efficiently than the originally planned single satellite.
