MOSES Inversions using Multiresolution SMART
Abstract
We present improvements to the SMART inversion algorithm for the MOSES imaging spectrograph. MOSES, the Multi-Order Solar EUV Spectrograph, is a slitless extreme ultraviolet spectrograph designed to measure cotemporal narrowband spectra over a wide field of view via tomographic inversion of images taken at three orders of a concave diffraction grating. SMART, the Smooth Multiplicative Algebraic Reconstruction Technique, relies on a global chi squared goodness of fit criterion, which enables overfit and underfit regions to "balance out" when judging fit quality. "Good" reconstructions show poor fits at some positions and length scales. Here we take a multiresolution approach to SMART, applying corrections to the reconstruction at positions and scales where correction is warranted based on the noise. The result is improved fit residuals that more closely resemble the expected noise in the images. Within the multiresolution framework it is also easy to include a regularized deconvolution of the instrument point spread functions, which we do. Different point spread functions among MOSES spectral orders results in spurious doppler shifts in the reconstructions, most notable near bright compact emission. We estimate the point spread funtions from the data. Deconvolution is done using the Richardson-Lucy method, which is algorithmically similar to SMART. Regularization results from only correcting the reconstruction at positions and scales where correction is warranted based on the noise. We expect the point spread function deconvolution to increase signal to noise and reduce systematic error in MOSES reconstructions.
- Publication:
-
American Astronomical Society Meeting Abstracts #224
- Pub Date:
- June 2014
- Bibcode:
- 2014AAS...22441406R