XRT Stray Light Study 4 -- Measurement and Correction.

Link to the 3rd test page.
Link to the 5th & 6th tests page.

(05 July, 2014 by Aki Takeda)

1. Stray light correction project -- the 4th test.

1.1 Purposes of the 4th test.

1.2 Test sequence.

The fourth test was performed on 03-July-2014, 18:30 -- 18:50UT.

2. Result of the test observation.

2.1 Solar condition


2.2 Sunset light curves

Light curve from the 1st to 3rd tests

2.3 Stray light images

Thin-Be stray light images obtained (movie).

No significant stray light detected.

Ti-poly stray light images obtained (movie).

2.4 Comparison of the Stray-light images (2nd and 4th tests).

If the stray light images (taken at the same pointing) do not(or only a little) vary with time, you can use a single stray image to correct images taken outside eclipse season. The Ti-poly stray-light images taken on 15-May-2014(2nd test) and 3-Jul-2014(4th test) were compared.

The left image is the difference image of the stray-light images taken at the 2nd and 4th tests:

dd1: stray light image from the test 2 (15-May-2014, 18:25:03, exp. 1440msec)
ii1: index(FITS header) structure of dd2
dd2: stray light image from the test 4 (03-Jul-2014, 18:36:59, exp. 1440msec)
ii2: index(FITS header) structure of dd2

[diff_img] = [dd2] - [dd1]

Their difference image is almost featueless, with stripes (as we see in dark frames) and subtle trace of solar disk. Their intensity level on the average is zero with noise roughly ± 5 DN.