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 monocrystalline 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 Lynxlike 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 > 1500. 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.
The Off-plane Grating Rocket Experiment is a soft X-ray grating spectrometer payload to be launched on a suborbital rocket. The spectrometer will use three technologies – monocrystalline silicon X-ray optics (NASA Goddard Space Flight Center), X-ray reflection gratings (The Pennsylvania State University), and electron-multiplying CCDs (XCAM Ltd., The Open University) – to achieve the highest performance on-sky soft X-ray spectrum to date when launched. To realize this performance, not only must each of the three individual spectrometer components perform at their required level, but these components also must be aligned to one another to the required tolerances and integrated into the payload. In this manuscript, we report on the alignment and integration plan for each component within the spectrometer.
The Off-plane Grating Rocket Experiment (OGRE) is a soft x-ray grating spectrometer to be flown on a suborbital rocket. The payload is designed to obtain the highest-resolution soft x-ray spectrum of Capella to date with a resolution goal of R ( λ / Δλ ) > 2000 at select wavelengths in its 10 to 55 Å bandpass of interest. The optical design of the spectrometer realizes a theoretical maximum resolution of R ≈ 5000, but this performance does not consider the finite performance of the individual spectrometer components, misalignments between components, and in-flight pointing errors. These errors all degrade the performance of the spectrometer from its theoretical maximum. A comprehensive line-spread function (LSF) error budget has been constructed for the OGRE spectrometer to identify contributions to the LSF, to determine how each of these affects the LSF, and to inform performance requirements and alignment tolerances for the spectrometer. In this document, the comprehensive LSF error budget for the OGRE spectrometer is presented, the resulting errors are validated via raytrace simulations, the implications of these results are discussed, and future work is identified.
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