  The Chandra X-ray Observatory, one of NASA's Great Observatories, has an
outstanding record of scientific and technical success. This success results
from the efforts of a team comprising NASA, its contractors, the Smithsonian
Astrophysical Observatory, the instrument groups, and other elements of the
scientific community -- including the thousands of scientists who utilize this
powerful facility for astrophysical research. We discuss the role of NASA
Project Science in the formulation, development, calibration, and operation of
the Chandra X-ray Observatory. In addition to serving as an interface between
the scientific community and the Project, Project Science performed what we
term "science systems engineering". This activity encompasses translation of
science requirements into technical requirements and assessment of the
scientific impact of programmatic and technical trades. We briefly describe
several examples of science systems engineering conducted by Chandra Project
Science.
