Characterizing X-ray Optics for OGRE and its Pathfinder Mission

The Off-Plane Grating Rocket Experiment (OGRE) will flight-test high-precision X-ray technology in a three-component spectrometer comprised of a Wolter-I telescope, X-ray reflection gratings and electron-multiplying charge-coupled devices (EM-CCDs). OGRE will demonstrate cutting-edge X-ray mirrors known as mono-crystalline silicon optics which are planned for use on several proposed X-ray Probe missions, and fly X-ray reflection gratings that after our recent characterization campaign, indicate high-precision spectral resolution. This X-ray technology serves as a great candidate for space-based X-ray astronomy as we move towards a Lynx-like flagship mission, and OGRE will be the first mission to test such gratings and optics in space. However, mono-crystalline silicon optics are still in development, while the gratings and electronics section of OGRE will be ready for a flight-test in the immediate future. In the interim, it is proposed that OGRE achieves a pathfinder flight which incorporates the Joint European Telescope for X-ray astronomy (JET-X) as a substitute optic, establishing an initial flight for the gratings and electronics on board. A pathfinder flight will reduce risk and gain insight for a full OGRE launch which will fly mono-crystalline silicon optics for the first time. Through an extensive characterization campaign for JET-X, the mono-crystalline silicon optics, EM-CCDs and a reflection grating, we have measured the performance of the OGRE spectrometer for its pathfinder flight. We confirm the continued ability of the JET-X optic, and that both the OGRE and Pathfinder OGRE spectrometers are capable of meeting the science requirement of R > 1500¹² Additionally, we motivate that with more detailed analysis, even higher spectral resolutions could be possible, alongside a result for the resolution of the grating itself.