Hinode/XRT stray light correction 2018 -- Phase 4.

XRT Stray Light Study 2018 -- phase 4 (after 29-May-2018).

Link to the 2014 summary page.
Link to the 2015 phase 1 summary.
Link to the 2015 phase 2 summary.
Link to the 2016 page and 2017 phase 2 page.
Link to the 2017 phase 3 page (after 27-May-2017).
Link to the 2018 phase 3 page (before 29-May-2018).
Link to the 2019 phase 4 page will come here.

(7 August, 2018 by Aki Takeda)

1. Purposes of the stray light measurement in 2018, phase 4 .

It was reported by T. Jibben that another stray light increase observed in the late May, 2018. The G-band intensity monitor shows a jump appeared after the CCD bakdout of 26-29 May. Since we don't take data during the bakeout, we can't specify the timing any further but we will assume it on 29-May-2018 for the convenience of reference.

According to the analysis by K. Yoshimura, the G-band stray light intensity was increased by 1.33 times. The purpose of this page is to measure the stray light level on the thin X-ray filters in this new phase (phase 4) since 29-May-2018.

2. Summary of Results.

[Al_mesh] The stray light intensity near disk center at the DC pointing increased about 30%. (14 DN/sec from 11 DN/sec)
[Al_poly] The stray light component was increased to ~4 DN/sec, from ~2.5 DN/sec. Stray light enhancement near West-limb was reproduced. Report by K. Yoshimura
[thin_Be] Stray light component is still in a negligible level.

3. Measurements 2018 (phase 4) at a glance.

ID No.	date & time (UT)	XOB	purposes (link: obtained plots & images)	memo
22	10-Jul-2018, 17:42:00	1C02	light crv., Al-mesh (1.41s) and Al-poly (2.00s) at DC.	prev. bakeout + 0 day.
23	11-Jul-2018, 18:17:30	1C03	light crv., Al-poly (2.83s) and thin-Be (11.3s) at DC.	prev. b.o. + 1 day.
24	12-Jul-2018, 17:14:30	1C02	light crv., Al-mesh (1.41s) and Al-poly (2.00s) at DC.	prev. b.o. + 2 day.
25	13-Jul-2018, 17:50:00	1C03	light crv., Al-poly (2.83s) and thin-Be (11.3s) at DC.	prev. b.o. + 3 days.
26	31-Jul-2018, 18:37:30	1C04	light crv., Al-mesh (1.41s) and Al-poly (2.00s) on N-pole.	prev. b.o. + 0 days.
27	1-Aug-2018, 19:13:00	1C04	light crv., Al-mesh (1.41s) and Al-poly (2.00s) on S-pole.	prev. b.o. + 1 days.
28	2-Aug-2018, 18:10:30	1C04	light crv., Al-mesh (1.41s) and Al-poly (2.00s) on E-limb.	prev. b.o. + 2 days.
29	3-Aug-2018, 18:46:00	1C04	light crv., Al-mesh (1.41s) and Al-poly (2.00s) on W-limb.	prev. b.o. + 3 days.

[NOTE]

4. Stray light images 2018, at a glance.

Al_mesh filter

The stray light intensity near disk center at the DC pointing increased to around 14 DN/sec, while it was around 11 DN/sec before 29-May-2018. This means roughly 30% increase.

- DC pointings

Al-mesh, 20180710(1.4s) [bd+0d]	Al-mesh, 20180712(1.4s) [bd+2d]	After PREP comparison

- Limb pointings

Al-mesh, 20180731(1.4s) [bd+0d]	Al-mesh, 20180801(1.4s) [bd+1d]	Al-mesh, 20180802(1.4s) [bd+2d]	Al-mesh, 20180803(1.4s) [bd+3d]

Al_poly filter

The stray light component was increased to ~4 DN/sec, from ~2.5 DN/sec. The anomaly (significant increase of visible light component) noticed last year near West-limb pointing was reproduced.

- DC pointings

Al-poly, 20180710(2.0s) [bd+0d]	Al-poly, 20180711(2.8s) [bd+1d]	Al-poly, 20180712(2.0s) [bd+2d]	Al-poly, 20170713(2.8s) [bd+3d]	After PREP comparison

- Limb pointings

Al-poly, 20180731(2.0s) [bd+1d]	Al-poly, 20180801(2.0s) [bd+2d]	Al-poly, 20180802(2.0s) [bd+2d]	Al-poly, 20180803(2.0s) [bd+3d]

thin_Be filter

Stray light included in thin_Be images is still in negligible level.

thin-Be,20180711(11s) DC [bd+1d]	thin-Be,20180713(11s) DC [bd+3d]	after PREP comparison