Modification of Hinode/XRT temperature response functions through full-disk XRT irradiance study


Aki Takeda as a project prepared for REU 2020

Project description

MSU is home of Hinode/XRT Synoptic Composite Image Archive (SCIA, http://solar.physics.montana.edu/HINODE/XRT/SCIA/latest_month.html, which is the archive of soft X-ray full-Sun images obtained with the X-Ray Telescope aboard the Hinode satellite. Our images are posted daily to the SolarMonitor, a popular site for solar researchers to check the current solar condition.

We will process the XRT/SCIA images taken from 2007 to date to derive solar soft X-ray irradiance during this period. Just like all living creatures, XRT instruments are aging over more than 12 years of operation in space. We should carefully separate the variation of the solar signals from that caused by the characteristic change of the instrument. We will use other source of soft X-ray irradiance (GOES/XRS, TIMED/SEE) to calibrate XRT's temperature response functions and to obtain reliable values of XRT irradiance.

MSU's REU program for 2020 summer was cancelled due to the Covid-19 pandemic (announce made on 13 April), and this means we became unable to work on this project with our REU student (Kara Hokenstad from Whitworth University, WA). However, this project contains some hot topic whose study should not be postponed until the next REU opportunity in 2021 summer. Therefore, we decided to turn this project into the one between Suman Panda (co-mentor of my REU project) and myself to perform during this summer (June and July, 2020).

We redefine the goal of our summer project as follows: (1) Derive XRT soft X-ray irradiance from the XRT full-sun composite images from 2008 through the most recent. (2) By comparing them with other instruments (GOES/XRS, TIMED/SEE), calibrate XRT's effective area function taking proper account of the stray light contamination caused by the pre-filter failure.

XRT soft X-ray irradiance

IMPORTANT NOTE: Since 2012 May, XRT started to suffer the visible stray light contamination caused by a series of failures (appearance of small openings) on the XRT pre-filter. The XRT irradiance derived with this method is affected by the stray light in the following two ways:

(1) Subtraction of stray light image from each X-ray images.
(2) Modify XRT response functions (through effective area functions) so that they reflect the contamination of the stray light.

While the correction of (1) is included in the process (step 2) of irradiance calculation, (2) has not been considered in the previous studies because there was no direct way to estimate the amount of opening of the pre-filter. This project aims to provide the best possible estimate of the amount and modification of the XRT effective area functions and temperature response functions.

Important dates : pre-filter failure events 

IDL> check_sl_phase()
--- phase 0 : 23-Oct-2006 10:00
--- phase 1 :  9-May-2012 12:00   --- 1st failure event
--- phase 2 : 14-Jun-2015 12:30   --- 2nd
--- phase 3 : 27-May-2017 11:00   --- 3rd
--- phase 4 : 29-May-2018 00:00   --- 4th

Compare with GOES/XRT (work in 2015) (work in 2019)

Ongoing irradiance work (work in 2020)

GOES/XRS irradiances

GOES: The Geostationary Operational Environmental Satellite
XRS: X-Ray Sensor
Recent announcement from NCEI         Data access page 
[table 2.]
Chronology of primary and secondary satellites for XRS measurements since 1986
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Start Date  Time   Primary Secondary      Remarks
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2015-06-09  00:00  GOES-15  GOES-13  (AkT from SolarMonitor plots)     
2015-05-21  00:00  GOES-14  GOES-13  (AkT from SolarMonitor plots)     
2015-01-24  00:00  GOES-15  GOES-13  (AkT from SolarMonitor plots)     
2012-11-19  16:31  GOES-15  None
2012-10-23  16:00  GOES-14  GOES-15
2011-09-01   0:00  GOES-15  GOES-14
2010-10-28   0:00  GOES-15  None
2010-09-01   0:00  GOES-14  GOES-15
2009-12-01   0:00  GOES-14  None     GOES-10 decommissioned
2008-02-10  16:30  GOES-10  None     GOES-11 XRS failure
2007-12-18   0:00  GOES-11  None     GOES-10 not tracked due to antenna problems
2007-12-05   0:00  GOES-11  GOES-10
2007-11-21   0:00  GOES-11  None     GOES-10 not tracked due to antenna problems
2007-04-12   0:00  GOES-11  GOES-10
2007-01-01   0:00  GOES-10  GOES-11
2006-06-28   0:00  GOES-12  GOES-11
2006-06-22  14:00  GOES-12  None
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TIMED/SEE irradiances

TIMED: Thermosphere Ionosphere Mesosphere Energetics and Dynamics
SEE: Solar EUV Experiment
data access page





Weekly goals (2020)

Results

We calculated the XRT irradiance from full-Sun integrated filter-ratio temperatures and emission measures, and compared with the X-ray flux observed by GOES/XRS(1-8A) and TIMED/SEE(1-60A and 1-200A).

2015 XRT irradiance (3-10A) with stray light modification

Resources