Hinode/XRT stray light correction 2015

XRT Stray Light Study 2015 -- Phase 1 (before 14-Jun-2015).

Link to the 2014 summary page.
Link to the 2015 phase 2 summary.
Link to the 2016 summary.

(10 May, 2015 by Aki Takeda)
(2 June, 2015 revised.)
(28 September, 2015 added synthsizing Ti-poly sl-image.)

1. Purposes of the project 2015.

collect 2015 light curves of the XRT eclipses.
take stray-light images with each X-ray filter.
evaluate the change of the stray-light intensity/pattern from 2014.
evaluate the effect of dust accumulating on the CCD.

2. Summary of Results.

Ti-poly and C-poly filters show stray light patterns similar to 2014.
No stray light component detected in other filters (same as 2014).
For Ti-poly images:
- The wood-ring paterns are quite stable.
- 2015 stray-light intensity was increased by ~3% compared with that of 2014.
- Accumulating dust on CCD yields ~5% increase of stray light intensity.
- Attempt to Synthesize stray light images.
For C-poly images:
- The bright-arc paterns are NOT stable even with the same pointing.
- 2015 stray-light intensity was increased by ~2% compared with that of 2014.
- Accumulating dust on CCD yields ~3% increase of stray light intensity.

3. Measurements 2015 at a glance.

ID No.	date & time (UT)	XOB	purposes (link: obtained plots & images)	memo
Test	6-May-2015, 18:25:30	1A7A	light curve of non-hard-eclipse, cadence check, with Alpl, Cpl, tnBe.	delay from simulation < 10s.
1	7-May-2015, 17:23:00	1A7C	light curve, Al-poly (1s), Thick-Al (32s) at Disk Center
2	7-May-2015, 22:18:30	1A7E	light curve, Ti-poly (2s), C-poly (2s) at DC
3	8-May-2015, 17:59:00	1A7D	light curve, Thin-Be (5.6s), Med-Be (32s) at DC	mdBe to be 22.6s next time.
4	9-May-2015, 18:35:00	1A7F	light curve, Al-mesh (1s), Med-Al (22.6s) at DC	mdAl to be 32s next time.
5	10-May-2015, 17:32:00	1A80	light curve, Ti-poly (2s), C-poly (2s) at DC
6	11-May-2015, 18:08:00	1A81	light curve, Thick-Be (64s) at DC
7	12-May-2015, 12:10:30	1A83	light curve, Ti-poly (4s), C-poly (4s) on S-pole (HOP 81)
8	13-May-2015, 17:41:30	1A82	light curve, Ti-poly (2s), C-poly (2s) on W-limb at (945,0)	images are noisy.
9	13-May-2015, 22:36:30	1A82	light curve, Ti-poly (2s), C-poly (2s) on E-limb at (-945,0)	noisy Tipl, telem-drop in Cpl.
10	14-May-2015, 16:39:00	1A84	light curve, Ti-poly (4s), C-poly (4s) on N-pole (HOP 81)	telemetry drop in Ti-poly.
11	18-May-2015, 17:23:30	1A85	light curve, Ti-poly (2s), C-poly (2s) at DC (right after CCD bakeout).

4. Stray light images 2015, at a glance.

Ti-poly, 20150507 DC	Ti-poly, 20150510 DC	Ti-poly, 20150518 DC

Ti-poly, 20150512 SP	Ti-poly, 20150513 WL	Ti-poly, 20150513 EL	Ti-poly, 20150514 NP

C-poly, 20150507 DC	C-poly, 20150510 DC	C-poly, 20150518 DC

C-poly, 20150512 SP	C-poly, 20150513 WL	C-poly, 20150513 EL	C-poly, 20150514 NP

Al-poly, 20150507 DC	Thick-Al, 20150507 DC	Thin-Be, 20150508 DC	Med-Be, 20150508 DC
Al-mesh, 20150509 DC	Med-Al, 20150509 DC	Thick-Be, 20150511 DC

5. Comparison of the Stray-light images.

5.1 Ti-poly (at DC pointing)

Movie of PREPed & normalized stray light images.

Image 1 :  7-May-2015 22:24:54 (15 days after the previous CCD bakeout)
Image 2 : 10-May-2015 17:38:24 (18 days after the previous CCD bakeout)
Image 3 : 18-May-2015 17:28:45 (0  day after the previous CCD bakeout)
Image 4 : 15-May-2014 18:25:03 (0  day after the previous CCD bakeout)

comparing 2014 and 2015 images ([18-May-2015] - [15-May-2014]).

comparing before and after CCD bakeout ([10-May-2015] - [18-May-2015]).

5.2 C-poly (at DC pointing)

Movie of PREPed & normalized stray light images.

Image 1 :  7-May-2015 22:26:12 (15 days after the previous CCD bakeout)
Image 2 : 10-May-2015 17:38:55 (18 days after the previous CCD bakeout)
Image 3 : 18-May-2015 17:28:56 (0  day after the previous CCD bakeout)
Image 4 : 27-May-2014 20:46:01 (12 days after the previous CCD bakeout)

comparing 2014 and 2015 images ([7-May-2015] - [27-May-2014]).

comparing before and after CCD bakeout ([10-May-2015] - [18-May-2015]).

6. Light curves 2015, collection.

Test	1 (Alpl & tkAl)	2 (Tipl & Cpl)	3 (tnBe & mdBe)

4 (Alms & mdAl)	5 (Tipl & Cpl)	6 (tkBe)	7 (S-pole)

8 (W-limb)	9 (E-limb)	10 (N-pole)	11 (after Bakeout)

12 (Alms & Tpol)	13 (Apol & tnBe)	14 (Tpol & Cpol)	15 (after Bakeout)
			data lost (2015/06/30)
16 (Alms & Tpol, WL)	17 (Alms & Tpol, SP)	18 (Tpol & Cpol, NP)	19 (Tpol & Cpol, EL)

20 (Alms & Tpol)	21 (Alms & Tpol)	22 (C-poly)	23 (C-poly)

[ memo ]

stray light images should be preferably taken soon after the CCD bakeout. (less dust spots appeared on the image).
2014 stray-light image is clearer than 2015's (even right after the bakeout) with respect to the number of dust spots and noise due to high energy particles. Since the Ti-poly stray light image turned out quite stable, we can keep using 2014 stray-light image for correcting 2015 images (with consideration of ~3% increase from 2014.5 to 2015.5).
Use level0 data for intensity comparison. Do not mix QL analysis with that of level0, as treatment of dark is different between QL and level0.
In my next CO week, I will ...
- take more stray-light images with better quality at DC.
- re-take of T-poly N-pole pointing (compensate dropped telemetry).
- try other pointings (popular position?)