Hinode/XRT stray light correction 2024

XRT Stray Light Study 2024 -- phase 6 and 7 (after 11-May-2024).

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 page (after 5-May-2023 ← 6th event).

(12 Jun 2024 initial version by Aki Takeda)

1. Purposes of the stray light measurement in 2024.

Initial purpose was to confirm the stray light level of the phase 6 (since 5-May-2023) after one year. However, the new pre-filter failure event was reported on 11-May-2024 ([xrt_co:53006] by Lucas Guliano), which means that we have entered the phase 7 of stray light level. In response, the disk cetner measurements were added on 23- and 24-May. The measurement on 22-June was to obtain the stray light image for the high corona study planned on the same day.

2. Summary of Results.

[timing of new pre-filter failure : 5/11 06:15 UT]
The timing of new pre-filter failure is estimated as 5/11 between 06:05 and 08:52 UT 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.
(cf: G-band image intensity variation
Al_poly FLD image intensity variation
GOES/XRS flux variation ) and
AIA 131 intensity variation )
We will assume the pre-filter failure occured during the SAA+NGT passage between 5/11 06:11 and 06:58 UT.
We will switch the parameters for calibration used in software on 2024/05/11 6:15 UT.
[Al_mesh & Al_poly]
The stray light level was increased by the factor of 1.22, relative to the phase 6 data. Change in pattern not observed.
[thin_Be & med_Be]
The stray light data obtained with these filters are only for the phase 6. The stray light component is in the negligible level for these filters.

3. Measurements 2024 (phase 6 and 7) at a glance.

ID No.	date & time (UT)	XOB	purposes (link: obtained plots & images)	memo
1	4-May-2024, 18:53:30	1D14	light crv., Al-mesh (1.4s) and Al-poly (2.0s) at DC.	previous bakeout + 10 day.
2	5-May-2024, 17:49:00	1D15	light crv., thin-Be (11.3s) at DC.	prev. b.o. + 11 day.
3	6-May-2024, 18:25:30	1D16	light crv., med-Be (22.6s) at DC.	prev. b.o. + 12 day.
4	7-May-2024, 18:57:00	1D14	light crv., Al-mesh (1.4s) and Al-poly (2.0s) on W-limb	prev. b.o. + 13 day.
5	8-May-2024, 17:52:30	1D14	light crv., Al-mesh (1.4s) and Al-poly (2.0s) on E-limb.	prev. b.o. + 14 days.
6	9-May-2024, 18:26:30	1D14	light crv., Al-mesh (1.4s) and Al-poly (2.0s) on N-pole	prev. b.o. + 15 days.
7	10-May-2024, 17:22:00	1D14	light crv., Al-mesh (1.4s) and Al-poly (2.0s) on S-pole	prev. b.o. + 16 days.
-	11-May-2024, 06:15:00	-	The 7th stray light increase event likely to have happened.	* entering phase 7 *
8	11-May-2024, 17:55:30	1D14	light crv., Al-mesh (1.4s) and Al-poly (2.0s) at (-528.4,-528.4)	prev. b.o. + 17 days.
9	15-May-2024, 18:35:00	1D14	light crv., Al-mesh (1.4s) and Al-poly (2.0s) at (528.4,-528.4)	prev. b.o. + 0 days.
10	16-May-2024, 19:09:00	1D14	light crv., Al-mesh (1.4s) and Al-poly (2.0s) at (528.4,528.4)	prev. b.o. + 1 days.
11	17-May-2024, 18:04:30	1D14	light crv., Al-mesh (1.4s) and Al-poly (2.0s) at (-528.4,528.4)	prev. b.o. + 2 days.
12	23-May-2024, 18:10:30	1D14	light crv., Al-mesh (1.4s) and Al-poly (2.0s) at DC	prev. b.o. + 8 days.
13	24-May-2024, 18:44:30	1D15	light crv., thin-Be (11.3s) at DC.	data lost after 18:46UT
14	22-Jun-2024, 18:42:30	1D14	light crv., Al-mesh (1.4s) and Al-poly (2.0s) at (-530, -530)	prev. b.o. + 3 days.

4. Stray light images 2023 (phase 6 and 7), at a glance.

Al_mesh filter

The stray light component included in the Al_mesh filter was increased by the factor of 1.22 compared with the corresponding data on 4-May-2023 (phase 6). The new stray light pattern started to appear since 2023 on the E-limb images was reproduced.

- 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, 20240504(1.4s) phase 6 [pbo+10d] pnt.(-13.0, 12.0)	Al-mesh, 20240523(1.4s) phase 7 [pbo+8d] pnt.(-17.6, 28.5)	Al-mesh, 20230506(1.4s) phase 6 [pbo+10d] pnt.(-15.9, 17.3)	Al-mesh, 20220709(1.4s) phase 5 [pbo+3d] pnt.(-20.5,28.2)	After PREP comparison with phase 6 & 7 pnt.(-20.5,28.2)

- limb pointings

Al-mesh, 20240507(1.4s) [pbo+13d] pnt.(896.8, 31.1)	Al-mesh, 20240508(1.4s) [pbo+14d] pnt.(-967.3, 3.9)	Al-mesh, 20240509(1.4s) [pbo+15d] ver.2 pnt.(-32.6, 904.9)	Al-mesh, 20240510(1.4s) [pbo+16d] pnt.(-2.6, -948.9)

- Other pointings

Al-mesh, 20240511(1.4s) [pbo+13d] pnt.(-537.8, -516.8)	Al-mesh, 20240515(1.4s) [pbo+14d] pnt.(517.2, -498.5)	Al-mesh, 20240516(1.4s) [pbo+15d] pnt.(505.6, 558.5)	Al-mesh, 20240517(1.4s) [pbo+16d] pnt.(-550.8, 547.6)	Al-mesh, 20240622(1.4s) [pbo+17d] pnt.(-541.9, -505.0)

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, 20240504(2.0s) phase 6 [pbo+10d] pnt.(-13.0, 12.0)	Al-poly, 20240523(2.0s) phase 7 [pbo+8d] pnt.(-17.6, 28.5)	Al-poly, 20230506(2.0s) phase 6 [pbo+10d] pnt.(-15.9, 17.3)	Al-poly, 20220709(2.0s) phase 5 [pbo+3d] pnt.(-20.5, 28.2)	After PREP comparison with phase 6 & 7

- limb pointings

Al-poly, 20240507(2.0s) [pbo+13d] pnt.(897.3, 31.1)	Al-poly, 20240508(2.0s) [pbo+14d] pnt.(-967.2, 3.9)	Al-poly, 20240509(2.0s) [pbo+15d] pnt.(-32.6, 904.9)	Al-poly, 20240510(2.0s) [pbo+16d] pnt.(-2.6, -948.9)

- Other pointings

Al-poly, 20240511(2.0s) [pbo+17d] pnt.(-537.8, -516.8)	Al-poly, 20240515(2.0s) [pbo+0d] pnt.(517.2, -498.5)	Al-poly, 20240516(2.0s) [pbo+1d] pnt.(505.6, 558.5)	Al-poly, 20240517(2.0s) [pbo+2d] pnt.(-550.8, 547.6)	Al-poly, 20240622(2.0s) [pbo+3d] pnt.(-542.0, -505.0)

Other filters

Stray light level in the thin_Be and med_Be images (at phase 6) are in negligible level.

thin_Be,20240505 (11.3s), pnt.(-16.5, 14.4)	med_Be,20240506 (22.6s), pnt.(-15.3, 15.5)