XRT Stray Light Study 2026 -- phase 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).
Link to the 2024 phase 6 & 7 page (after 11-May-2024 ← 7th event).
Link to the 2025 phase 7 page

(08 May 2026, initial version by Aki Takeda)

1. Purposes of the stray light measurement in 2026.

Initial purpose was to confirm the stray light level of the phase 7 (since 11-May-2024) after two years. This year, we have multiple HOPs to support in early May and thus the data volume was not enough to perform as many stray light measurements as we did in the past years. The 2026 CCD bakeout schedule was not favorable for the stray light measurements.

2. Summary of Results.

3. Measurements 2026 (phase 7) at a glance.

ID No. date & time (UT) XOB purposes (link: obtained plots ) memo
1 3-May-2026, 17:47:00 1D4B light crv., Al-mesh (1.4s) and Al-poly (2.0s) at DC. previous bakeout + 11 days.
2 4-May-2026, 18:18:30 1D4C light crv., thin-Be (11.3s) at DC. prev. b.o. + 12 days.
3 5-May-2025, 18:50:00 1D4B light crv., Al-mesh (1.4s) and Al-poly (2.0s) at W-limb. prev. b.o. + 13 days.
4 8-May-2026, 18:46:30 1D4B light crv., Al-mesh (1.4s) and Al-poly (2.0s) at E-limb prev. b.o. + 16 days.
5 9-May-2026, 17:39:30 1D4B light crv., Al-mesh (1.4s) and Al-poly (2.0s) at S-limb prev. b.o. + 17 days.
6 11-May-2026, 00:43:30 1D4C light crv., thin-Be (11.3s) on AR. prev. b.o. + 19 days.
7 11-May-2026, 18:43:00 1D4B light crv., Al-mesh (1.4s) and Al-poly (2.0s) at (-800,-520) prev. b.o. + 19 days.
8 12-May-2026, 17:36:00 1D4B light crv., Al-mesh (1.4s) and Al-poly (2.0s) at N-pole prev. b.o. + 20 days.
9 13-May-2026, 18:07:30 1D4B light crv., Al-mesh (1.4s) and Al-poly (2.0s) at (810, 430) prev. b.o. + 21 days.
10 14-May-2026, 00:40:00 1D4B light crv., Al-mesh (1.4s) and Al-poly (2.0s) at on AR prev. b.o. + 22 days.
11 14-May-2026, 18:38:30 1D4B light crv., Al-mesh (1.4s) and Al-poly (2.0s) at on AR prev. b.o. + 23 days.
12 15-May-2026, 19:21:00 1D4B light crv., Al-mesh (1.4s) and Al-poly (2.0s) at on AR prev. b.o. + 24 days.
13 10-May-2025, 17:48:30 1D32 light crv., thin-Be (11.3s) at E-limb prev. b.o. + 10 days.
14 11-May-2025, 18:21:00 1D32 light crv., thin-Be (11.3s) at N-limb prev. b.o. + 11 days.
15 12-May-2025, 17:15:00 1D32 light crv., thin-Be (11.3s) at S-limb prev. b.o. + 12 days.
16 23-Jul-2025, 18:24:00 1D31 light crv., Al-poly/Ti-poly (4.0s) and Al-poly (2.0s) at (-530,530) prev. b.o. + 0 days.

4. Stray light images 2025 (phase 7), at a glance.

The stray light component included in the Al_mesh filter was at the same level as that of 2024. 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, 20250503(1.4s)
phase 7 [pbo+3d]
pnt.(-15.0, 9.8)
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)
After PREP comparison
with phase 7 & 6

- limb pointings

Al-mesh, 20250506(1.4s)
[pbo+6d]
pnt.(-33.1,955.5)
Al-mesh, 20250506(1.4s)
[pbo+6d]
pnt.(3.7,-926.0)
Al-mesh, 20250506(1.4s)
[pbo+6d]
pnt.(-983.9,-3.5)
Al-mesh, 20250507(1.4s)
[pbo+7d]
pnt.(933.2,34.1)

- Other pointings

Al-mesh, 20250508(1.4s)
[pbo+8d]
pnt.(-23.1, -477.1)
Al-mesh, 20250508(1.4s)
[pbo+8d]
pnt.(-40.7, 413.8)
Al-mesh, 20250723(1.4s)
[pbo+0d]
pnt.(-547.5, 557.1)
The stray light component included in the Al_poly filter was the same level as that taken in 2024 (phase 7). The West pointing anomaly (significant amount of stray light intensity near West-limb pointing) was also reproduced.

- DC pointings

Al-poly, 20250503(2.0s)
phase 7 [pbo+3d]
pnt.(-15.2, 9.8)
Al-poly, 20250508(2.0s)
phase 7 [pbo+8d]
pnt.(-32.8, 12.9)
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)
After PREP comparison
with phase 7 & 6

- limb pointings

Al-poly, 20250506(2.0s)
[pbo+6d]
pnt.(-33.1,955.5)
Al-poly, 20250506(2.0s)
[pbo+6d]
pnt.(3.6,-926.0)
Al-poly, 20250506(2.0s)
[pbo+6d]
pnt.(-983.9,-3.5)
Al-poly, 20250507(2.0s)
[pbo+7d]
pnt.(933.2, 34.1)

- Other pointings

Al-poly, 20250508(2.0s)
[pbo+8d]
pnt.(-32.8, 12.9)
Al-poly, 20250508(2.0s)
[pbo+8d]
pnt.(-40.7, 413.8)
Al-poly, 20250723(2.0s)
[pbo+0d]
pnt.(-547.5, 557.1)
The stray light component included in the thin_Be filter was the same level as that of phase 6 (2024) and is still negligible.

- DC pointings

thin_Be,20250504(11.3s)
phase 7,
pnt.(-15.5,12.8)
thin_Be,20240505(11.3s)
phase 6,
pnt.(-16.5, 14.4)
After PREP comparison
with phase 7 & 6

- limb pointings

thin_Be, 20250509(2.0s)
[pbo+9d]
pnt.(933.1,38.2)
thin_Be, 20250510(2.0s)
[pbo+10d]
pnt.(-959.6,-0.4)
thin_Be, 20250511(2.0s)
[pbo+11d]
pnt.(-37.0,964.3)
thin_Be, 20250512(2.0s)
[pbo+12d]
pnt.(2.7,-923.7)
The stray light component included in the med_Be filter was the same level as that of phase 6 (2024) and is still negligible.

med_Be,20250505
(22.6s), pnt.(-16.4,14.0)
med_Be,20240506
(22.6s), pnt.(-15.3, 15.5)
After PREP comparison
with phase 7 & 6
The stray light component included in the med_Al filter was measured for the first time after 2021. The stray light level turned out ~4 times larger than that in 2021 (phase 4), it is still at a negligible level.

med_Al,20250506
(32.7s), pnt.(-14.4, 14.8)
med_Al,20210512
(32.7s), pnt.(-17.0, 14.4)
After PREP comparison
with phase 7 & 6
The stray light component included in the Al_poly/Ti_poly filter was measured for the first time after 2022. The stray light level turned out to be the same level as that in 2022 and still negligible.

Apol+Tpol,20250508
(4.0s), pnt.(-32.8,12.9)
Apol+Tpol,20220712
(4.0s), pnt.(-20.0, 29.0)