Hinode/XRT stray light correction 2016

XRT Stray Light Study 2016.

Link to the 2014 summary page.
Link to the 2015 phase 1 summary.
Link to the 2015 phase 2 summary.
Link to the 2017 page.

(22 May, 2016 by Aki Takeda)
(15-jun-2016: added after PREP comparison.)
(1-jul-2016: added 2016/06/23 measurements.

1. Purposes of the stray light measurement in 2016.

Judging from the intensity level of G-band images and FLD images (Ti-poly 8x8), we expect no further increase in stray light level since the end of last eclipse season (Aug-2015). The 2016 measurement is to confirm this with real data taken during eclipses.

2. Summary of Results.

The Ti-poly stray light intensities are not significantly changed since the end of last eclipse season(after the 2nd pre-filter failure).
No change in the slight stray light patern detected in Al-mesh filter since last June. The intensity is still not significant (5 to 7 DN/sec).
The stray light components in Al-poly, thin-Be, med-Be, & med-Al are negligible.

3. Measurements 2016 at a glance.

ID No.	date & time (UT)	XOB	purposes (link: obtained plots & images)	memo
1	10-May-2016, 17:24:30	1B31	light curve, Ti-poly (1s) and Al-mesh (2.83s) at DC.	prev. bakeout + 8 days.
2	11-May-2016, 18:00:30	1B32	light curve, Al-poly (4s), Thin-Be (11.3s) at DC	prev. bakeout + 9 days.
3	12-May-2016, 16:57:30	1B33	light curve, med-Al (32s) at DC	prev. bakeout + 10 days.
4	13-May-2016, 17:33:00	1B34	light curve, med-Be (22s) at DC	prev. bakeout + 11 days.
5	23-Jun-2016, 18:52:30	1B3E	light curve, Ti-poly (1s) and Al-mesh (2.83s) at DC.	prev. bakeout + 8 days.

[NOTE] X-ray light curve of No. 3 is low contrast due to the coronal hole (and no AR) located at the sample region.

4. Stray light images 2016, at a glance.

Note: exposure times are different from 2015 measurements. The Ti-poly "After PREP comparison" plot shows that the stray light intensity in 2016/05/10 is ~6 % larger than that of 2015/07/18. Considering the difference of the time past since their previous bakeout (+8 days for 2016 while +1 day for 2015), this increase may be due to the increased amount of contamination.

Ti-poly,20150718(1.4s)	Ti-poly,20160510(1.0s)	After PREP comparison	Ti-poly,20160623(1.0s)

In plots below exposure difference is not corrected yet.

Al-mesh,20150718(1.0s)	Al-mesh,20160510(2.8s)	Al-mesh,20160623(2.8s)

Al-poly,20150620(0.8s)	Al-poly,20160511(4.1s)

thin-Be,20150620(5.8s)	thin-Be,20160511(11s)

med-Be,20150508(32s)	med-Be,20160513(23s)

med-Al,20150509(23s)	med-Al,20160512(32s)