Orbital measurement and verification of the Chandra X-Ray Observatory's PSF

The recently launched Chandra X-Ray Observatory (CXO) was designed to have the sharpest angular resolution yet of any X-ray telescope. Detailed modeling and metrology of the optics followed by extensive testing at the X-Ray Calibration Facility at the Marshall Space Flight Center in Huntsville, Alabama indicated that the optics were performing exceedingly well. While our analysis accounted for distortion of the mirrors due to gravity and the effects of finite distance and size of the X-ray generator, it was only on-orbit that we expected to directly observe the specified half are-second performance. We present here results of the on-orbit calibration of the point spread function (PSF), comparing it with our predictions. We discuss how the PSF varies with source location in the telescope field of view, as well as with the spectral energy distribution of the source.