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| The direct demodulation method |
Since it is very difficult to fold the hard X-ray photons,
none of the current telescopes can obtain a hard X-ray map
directly, i.e., the data are far different from a direct
map. An image reconstruction method is therefore needed to
derive a hard X-ray map from the observational data. The
main image reconstruction method for the HXMT mission is the
Direct Demodulation method (DD method) developed by T.P. Li
and M. WU in early 1990s. This method solves the observation
equations under non-linear control, allowing sensitive image
reconstruction with high spatial resolution from the
observational data of a simple collimated telescope.
Since early 1990s, using the DD method, we have analyzed
various space X-ray data, published more than 30 papers and
got a lot of important results. This proves the power of the
DD method. In the following we give a few examples and main references.
Fig.1: Comparison of the X-ray intensity maps for a
region of the Galaxy obtained from EXOSAT-ME scan
observations with the usually used cross-correlation method
(left) and the direct demodulation method (right).
Fig.2: Hard X-ray map (right) of the Galactic center
region from the HEAO1-A4 all-sky survey data (left) with the
direct demodulation method.
Reference:
1. Improving the spatial resolution of XMM-Newton EPIC
images by direct demodulation technique, Feng, H., Chen, Y.,
Zhang, S.N., Lu, F.J., & Li, T.P. 2003, A&A, 402, 1151
2. Observations of the supernova remnant G54.1+0.3: X-ray
spectrum and evidence for an X-ray jet, Lu, F.J.,
Aschenbach, B., & Song, L.M. 2001, A&A, 370, 570
3. Direct Demodulation imaging analysis of the combined two
sets of SCC data of RXTE ASM, Chen, Y., Song, L.M., Li,
T.P., & Cui, W. 2000, ACASn, 41, 214
4. Direct demodulation technique for rotation modulation
collimator imaging, Chen, Y., Li, T.P., & Wu, M. 1998, A&AS,
128, 363
5. COMPTEL observation of the flaring quasar PKS0528+134,
Zhang, S., Li, T.P., & Wu, M. 1998, A&A, 340, 62
6. X-ray map from the EXOSAT galactic plane survey and a
direct demodulation technique, Lu, F.J., Li, T.P., Sun,
X.J., Wu, M., & Page, C.G. 1996, A&AS, 115, 395
7. Image reconstruction in high energy astrophysics by
direct demodulation method, Lu, F.J., Li, T.P., Sun, X.J., &
Wu, M. 1995, in Proceedings of the international conference
on computing in high energy physics' 95, Nguyen, T.D., &
Shellard, R. eds, P.848
8. Reconstruction of objects by direct demodulation, Li,
T.P., & Wu, M. 1994, Ap&SS, 215, 213
9. A direct restoration method for spectral and image
analysis, Li. T.P., & Wu, M. 1993, Ap&SS, 206, 91
10. Modulation imaging based on a direct de-convolution
technique, Li, T.P., Wu, M., Lu, Z.G., Wang, J.Z., Zhang,
C.S. 1993, Ap&SS, 205, 381
11. A direct method for spectral and image restoration, Li,
T.P., & WU, M. 1992, Astronomical data analysis software and
systems, ASP conference series, Vol. 25, 1992, Diana
M. Worrall et al. eds, P.229
12. Galactic gamma-ray sources in the 40-50 MeV range, Li,
T.P., & Wu, M. 1990, ACASn, 31, 390
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