Hinode/XRT stray light correction 2022

XRT Stray Light Study 2023 -- phase 6 (after 5-May-2023).

Link to the 2014 summary page.
Link to the 2015 phase 1 summary. (after 9-May-2012 ← 1st pre-filter failure event)
Link to the 2015 phase 2 summary. (after 14-Jun-2015 ← 2nd failure event)
Link to the 2016 page and 2017 phase 2 page.
Link to the 2017 phase 3 page (after 27-May-2017 ← 3rd event).
Link to the 2018 phase 4 page (after 29-May-2018 ← 4th event).
Link to the 2019 phase 4 page.
Link to the 2020 phase 4 page.
Link to the 2021 phase 4 page.
Link to the 2022 phase 4 page.
Link to the 2022 phase 5 page (after 8-Jun-2022 ← 5th event).
Link to the 2023 phase 6 and 7 page (after 11-May-2024 ← 7th event).

(15 May 2023 initial version by Aki Takeda)
(02 Jun 2023 light curves and image plots prepared by R. Fleming)
(20 Jun 2023 pointings and after PREP plots added by AT)
(21 Dec 2023 stray light images for hicorona study added by AT)

1. Purposes of the stray light measurement in 2023.

New increase of stray light level was reported to occur on 5/5 (cf. XRT DV report by L. Guliano for 5/8 [xrt_co:47011]). This means that we have entered the 6th stray light phase. This page reports the results of the measurements performed in May 2023 (phase 6).

We had initial plan to measure stray light intensity at several pointings requested by S. Saar that fill out the sparse area not measured by 2021 and 2022 observations.

2. Summary of Results.

[timing of new pre-filter failure : 5/5 4:30UT]
The timing of new pre-filter failure is estimated as 5/5 between 01:48:20 - 04:39:13UT from the 2 G-band images show intensity jump (no other G-band image in between). The analysis of Al_poly FLD images is unable to determine the exact timing. We were running Al_poly only AR program (HOP401 with XOB#1CE5) until 03:58 then have data gap until the start of HOP349 at 04:37. Since Al_poly images during HOP401 do not show noticable change due to stray light component increase, we will assume the pre-filter failure occured during the SAA+NGT passage between HOP401 and HOP349, at around 4:30UT. This assumption makes data calibration simple, while we still don't know exactly when the failure occurred.
[Al_mesh & Al_poly]
The stray light level was increased by the factor of 1.25, relative to the phase 5 data. Change in pattern not observed.
[thin_Be & Al_poly/Ti_poly]
The stray light is in the negligible level for these filters.
[special pointings requested by S. Saar]
The observations No. 5,7,8,9 & 10 (marked with *) are the pointings requested by S. Saar. The pointings with Priority 1 and 2 were measured, while no time for those with Priority 3.

3. Measurements 2023 (phase 6) at a glance.

ID No.	date & time (UT)	XOB	purposes (link: obtained plots & images)	memo
1	6-May-2023, 19:30:00	1CF8	light crv., Al-mesh (1.4s) and Al-poly (2.0s) at DC.	previous bakeout + 10 day.
2	7-May-2023, 18:26:30	1CF9	light crv., thin-Be (11.3s) at DC.	prev. b.o. + 11 day.
3	8-May-2023, 19:01:00	1CFA	light crv., Al-poly/Ti-poly (4.0s) and Al-poly (2.0s) on W-limb	prev. b.o. + 12 day.
4	9-May-2023, 16:19:30	1CF8	light crv., Al-mesh (1.4s) and Al-poly (2.0s) on N-pole.	prev. b.o. + 13 days.
5*	9-May-2023, 17:57:30	1CF8	light crv., Al-mesh (1.4s) and Al-poly (2.0s) on (500,0)	prev. b.o. + 13 days.
6	9-May-2023, 22:52:30	1CF8	light crv., Al-mesh (1.4s) and Al-poly (2.0s) on E-limb	prev. b.o. + 13 days.
7*	10-May-2023, 18:32:30	1CF8	light crv., Al-mesh (1.4s) and Al-poly (2.0s) on (300,700)	prev. b.o. + 14 days.
8*	11-May-2023, 17:29:00	1CF8	light crv., Al-mesh (1.4s) and Al-poly (2.0s) at (250,0)	prev. b.o. + 15 days.
9*	12-May-2023, 18:03:30	1CF8	light crv., Al-mesh (1.4s) and Al-poly (2.0s) at (-250,0)	prev. b.o. + 16 days.
10*	13-May-2023, 18:38:00	1CF8	light crv., Al-mesh (1.4s) and Al-poly (2.0s) at(-500,0)	prev. b.o. + 17 days.
11	17-May-2023, 17:40:30	1CF8	light crv., Al-mesh (1.4s) and Al-poly (2.0s) at DC	prev. b.o. + 0 days.
12	18-May-2023, 00:13:30	1CF8	light crv., Al-mesh (1.4s) and Al-poly (2.0s) at N-pole.	prev. b.o. + 1 days.
13	18-May-2023, 18:15:00	1CF8	light crv., Al-mesh (1.4s) and Al-poly (2.0s) at S-pole	prev. b.o. + 1 days.
14	19-May-2023, 18:50:00	1CF8	light crv., Al-mesh (1.4s) and Al-poly (2.0s) at W-limb	prev. b.o. + 2 days.
15	19-May-2023, 23:45:00	1CF8	light crv., Al-mesh (1.4s) and Al-poly (2.0s) at E-limb	prev. b.o. + 2 days.
16	20-Jul-2023, 18:44:00	1CF8	light crv., Al-mesh (1.4s) and Al-poly (2.0s) at SE-quad.	prev. b.o. + 22 days.

(* : special pointings requested by S. Saar)

4. Stray light images 2023 (phase 6), at a glance.

Al_mesh filter

The stray light component included in the Al_mesh filter was increased by the factor of 1.25 compared with the corresponding 2021 July data (phase 5). E-limb images started to show new stray light pattern.

- DC pointings
[NOTE] pnt. indicates the satellite pointing at the time of data acquisition, i.e., (index.xcen, index.ycen) corrected by the the coalignment DB.

Al-mesh, 20230506(1.4s) [pbo+10d] pnt.(-15.9, 17.3)	Al-mesh, 20230517(1.4s) [pbo+0d] pnt.(-18.2, 22.4)	Al-mesh, 20220709(1.4s) phase 5 [pbo+3d] pnt.(-20.5,28.2)	Al-mesh, 20180712(1.4s) phase 4 [pbo+2d] pnt.(-22.1,19.8)

After PREP comparison with phase 4 & 5	After PREP comparison before/after bakeout

- limb pointings

Al-mesh, 20230509(1.4s) [pbo+13d] pnt.(-14.4, 869.1)	Al-mesh, 20230509(1.4s) [pbo+13d] pnt.(-986.3 46.7)

Al-mesh, 20230518(1.4s) [pbo+1d] pnt.(-35.7, 952.6)	Al-mesh, 20230519(1.4s) [pbo+2d] pnt.(-978.4, 3.4)	Al-mesh, 20230519(1.4s) [pbo+2d] pnt.(945.0, 46.5)	Al-mesh, 20230518(1.4s) [pbo+1d] pnt.( 2.4,-926.2)

- Other pointings

Al-mesh, 20230509(1.4s) [pbo+13d] pnt.( 483.7, 7.0)	Al-mesh, 20230510(1.4s) [pbo+14d] pnt.( 301.1, 712.8)	Al-mesh, 20230511(1.4s) [pbo+15d] pnt.( 231.9, 24.4)	Al-mesh, 20230512(1.4s) [pbo+16d] pnt.(-266.8, 17.0)	Al-mesh, 20230513(1.4s) [pbo+17d] pnt.(-516.6, 12.7)

Al-mesh, 20230720(1.4s)
[pbo+22d]
pnt.(-540.4,-513.9)

Al_poly filter

The stray light component included in the Al_poly filter was increased. The the same factor as Al_mesh, 1.1 (compared with 2018) is aplicable to the Al_poly filter. The West pointing anomaly (significant amount of stray light intensity near West-limb pointing) is now the level of ~44 DN/sec/half-res pix).

- DC pointings

Al-poly, 20230506(2.0s) [pbo+10d] pnt.(-15.9, 17.3)	Al-poly, 20230517(2.0s) [pbo+0d] pnt.(-18.2, 22.4)	Al-poly, 20220709(2.0s) [pbo+3d] pnt.(-20.5, 28.2)	Al-poly, 20180712(2.0s) [pbo+2d], pnt.(-22.2,19.8)

After PREP comparison with phase 4 & 5	After PREP comparison before/after bakeout

- limb pointings

Al-poly, 20230509(2.0s) [pbo+13d] pnt.( -14.4, 869.1)	Al-poly, 20230509(2.0s) [pbo+13d] pnt.(-986.3, 46.8)	Al-poly, 20230508(2.0s) [pbo+12d] pnt.( 935.4, -3.4)

Al-poly, 20230518(2.0s) [pbo+1d] pnt.( -35.6, 952.6)	Al-poly, 20230519(2.0s) [pbo+2d] pnt.(-978.4, 3.5)	Al-poly, 20230519(2.0s) [pbo+2d] pnt.( 944.5, 46.5)	Al-poly, 20230518(2.0s) [pbo+1d] pnt.( 2.3, -926.2)

- Other pointings

Al-poly, 20230509(2.0s) [pbo+13d] pnt.( 483.7, 7.0)	Al-poly, 20230510(2.0s) [pbo+14d] pnt.( 301.1, 712.8)	Al-poly, 20230511(2.0s) [pbo+15d] pnt.( 232.0, 24.4)	Al-poly, 20230512(2.0s) [pbo+16d] pnt.(-266.8, 17.0)	Al-poly, 20230513(2.0s) [pbo+17d] pnt.(-516.6, 12.7)

Al-poly, 20230720(2.0s)
[pbo+22d]
pnt.(-540.4,-513.8)

Other filters

Stray light level in the thin_Be and Al_poly/Ti_poly images are in negligible level.

thin_Be,20230507 (11.3s), pnt.(-15.9,17.5)	Apol/Tpol,20250507 (4.0s), pnt.(935.6,-3.4)