1. WG1: Techniques and Applications Wed AM: imaging comparison Wed PM1: source positions Wed PM2: source sizes Thu AM1: new algorithms Thu AM2: source fluxes (imaging spectroscopy) Special session: microflares (Thu before lunch) This is a workshop!

2. WG1 (Wed AM): Comparing imaging algorithms CLEAN (Schwartz, Krucker) UV smooth (Massone) MEM (Prato) Pixon (Schwartz) Forward fit (Schwartz) VIS forward fit (Hurford) VIS CLEAN (Hurford)

3. Selected events

4. Similar statistics for both energy ranges

5. Selected events Similar statistics for both energy ranges Excellent statistics at 10-15 keV; Poor at 30-50 keV

6. Feb 20: 10-15 keV CLEAN nat g3-9 CLEAN uni g3-9 CLEAN nat g1,3-9 UV smooth MEM PIXON fwd fit VIS fwd fit

7. Feb 20: 30-50 keV CLEAN nat g3-9 CLEAN uni g3-9 CLEAN nat g1,3-9 UV smooth MEM PIXON fwd fit VIS fwd fit

8. Feb 20: 30-50 keV (contours 10-15 keV) CLEAN nat g3-9 CLEAN uni g3-9 CLEAN nat g1,3-9 UV smooth MEM PIXON fwd fit VIS fwd fit

9. Feb 20: 10-15 keV (contours 30-50 keV) CLEAN nat g3-9 CLEAN uni g3-9 CLEAN nat g1,3-9 UV smooth MEM PIXON fwd fit VIS fwd fit

10. April 15: 10-15 keV CLEAN nat g3-9 CLEAN uni g3-9 CLEAN nat g1,3-9 UV smooth MEM PIXON fwd fit VIS fwd fit

11. April 15: 30-50 keV CLEAN nat g3-9 CLEAN uni g3-9 CLEAN nat g1,3-9 UV smooth MEM PIXON fwd fit VIS fwd fit

12. April 15: 30-50 keV (contours 10-15 keV) CLEAN nat g3-9 CLEAN uni g3-9 CLEAN nat g1,3-9 UV smooth MEM PIXON fwd fit VIS fwd fit

13. April 15: 10-15 keV (contours 30-50 keV) CLEAN nat g3-9 CLEAN uni g3-9 CLEAN nat g1,3-9 UV smooth MEM PIXON fwd fit VIS fwd fit

14. Comparing: Flux, position, size Northern footpoint is compact, ideal for comparison.

15. Feb 20, 30-50 keV: FLUX

16. Feb 20, 30-50 keV: POSITION

18. Feb 20, 30-50 keV: SIZE

19. beam size deconvolved size

20. Feb 20, 30-50 keV: SIZE beam size deconvolved size

21. CLEAN

22. Some comments on weighting Natural: all sc are weighted equal Uniform: Weighting in UV plane (more weight to finer sc) Example: Feb 20, 10-15 keV No clear source seen in sc1 grid 1 grid 3 grid 4 grid 5 grid 6 grid 7 grid 8 grid 9 UNIFORM NATURAL

23. CLEAN Uniform: Including g1: Most weigh to sc1  Noise image Natural: Including g1 does not change backprojction much Smaller clean beam gives better resolution.

24. CLEAN Uniform: g3-9 with reduced beam size (to get same resolution as natural g1,3-9)

25. CLEAN Uniform: g3-9 with 1 arcsec beam (beam size is equal to pixel size) CLEAN components

26. Imaging with different sc

27. vis_fwdfit

28. Feb 20, 2002 11:06:02-11:06:32 10-15keV Comparison of vis_fwdfit models ellipse Χ 2 =1.50 circular sources Χ2=1.24

29. Apr 15, 2002 00:05:00-00:06:00 10-15keV Comparison of vis_fwdfit models ellipse Χ 2 =3.77 loop Χ2=2.48

30. VIS CLEAN

31. Visibility-Gaussian Clean - vgclean (to be renamed) Starts with visibility bpmap At each iteration, estimates size of source at peak location Display shows sum of gaussian components Not fully debugged yet Thorough recoding is in progress Displays are not finished

32. Feb 20, 2002 11:06:02-11:06:32 vgclean 10-15 Χ 2 =2.5 30-50 Χ 2 =2.5

33. Apr 15, 2002 00:05:00-00:06:00 vgclean 10-15 Χ 2 =9.7 30-350 Χ2=1.5

34. The influence of radiation damage

35. Imaging test of C1 flare on 2009 July 6 17:05UT How does radiation damage influence the RHESSI imaging capability?

36. Spectrogram plots for each sub-collimator log scaling scaling is the same for each plot like all flares from 2009, only very little non-thermal emission is observed, if at all. imaging at 5-10 keV.

37. backprojection map for each sub-collimator subcoll 1 subcoll 2 subcoll 3 subcoll 4 subcoll 5 subcoll 6 subcoll 7 subcoll 8 subcoll 9 images look ok, but relative calibration is off. Combined image sc 3,4,5,6,8,9

38. ‘Default’ clean subcoll 3,4,5,6,8,9 uniform weighting contours are 30, 50, 70, 90 % Because radiation damage is different for different detectors, the relative weighting of the sub- collimators is off.  side lobes are still visible in cleaned image.

39. without sc 3+5 subcoll 4,6,8,9 uniform weighting contours are 30, 50, 70, 90 % works ok. clean is hiding remaining uncertainties.

40. EIT 195A & RHESSI subcoll 4,6,8,9 uniform weighting contours are 30, 50, 70, 90 % RHESSI source seen later in EUV after it cooled.

41. MEM_NJIT sc 3-9 subcoll 3,4,5,6,8,9 contours are 30, 50, 70, 90 % software gives WARNING message: flux was not consistent does not work because calibration is off

42. MEM_NJIT without sc 3+5 subcoll 4,6,8,9 contours are 30, 50, 70, 90 % superresolution?

43. EIT 195 & RHESSI MEM_NJIT subcoll 4,6,8,9 contours are 30, 50, 70, 90 % superresolution?

44. conclusions Radiation damage does not prevent us to make images that are useful for science updated calibration would improve performance there are no flares to check performance at higher energies (>20 keV)