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3 February 2004 Characterizing nonlinearities in the Chandra LETGS + HRC-S dispersion relation
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The dispersion relation for the Chandra Low Energy Transmission Grating Spectrometer (LETGS) is known to better than 1 part in 1000 over the wavelength range 5-150 Å. A recent resolution of a data processing software bug that lead to a systematic error in the computation of photon wavelengths has allowed us to trace further discrepancies in the dispersion relation to the boundaries between different microchannel plate segments of the HRC-S imaging detector. However, data acquired during in-flight calibration with the HRC-S detector have always shown the presence of additional non-linear deviations in the positions of some spectral lines by as much as 0.05 Å, which is of the order of a full width half maximum (FWHM) of a line profile. These latter effects are thought to be caused by spatial non-linearities in the imaging characteristics of the HRC-S detector. Here, we present an improved dispersion relation for the LETG+HRC-S and new methods to help characterize the spatial non-linearities. We also describe an empirical approach that might be used to help improve the position determination of photon events.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Sun Mi Chung, Jeremy J. Drake, Vinay L. Kashyap, Peter W. Ratzlaff, and Bradford J. Wargelin "Characterizing nonlinearities in the Chandra LETGS + HRC-S dispersion relation", Proc. SPIE 5165, X-Ray and Gamma-Ray Instrumentation for Astronomy XIII, (3 February 2004);

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