3.3.3 HXTPRO (Sakao)

Following is a description on the HXT image synthesis using the FORTRAN programs with an IDL user interface. The programs, which make use of the Maximum Entropy Image restoration procedure, were originally developed on FACOM mainframe computers at ISAS. At present, the image synthesis is available on SUN machines. Neither MIPS nor DEC machines are supported yet.

1. After extracting HXT data using YODAT and obtaining the flare location, type in the following command:
   IDL> .run hxtpro
    

2. * Execute HXT MOVIE setup code: [Default: Y ] ?

   Choose `Y' for the above prompt. This step enables you to choose

   • HXT energy band in which images are synthesized (step (3)),
   • background data interval (step (4)), and
   • flare data interval (step (5))
   on your CRT display. If you choose `N', then steps (3), (4), and (5) are skipped.

3. * Enter HXT Channel to use in Image synthesis: [Default: 0 ] Enter either of 0,1,2, or 3 (0=L, 1=M1, 2=M2, 3=H bands, respectively).

4. There appears an HXT time profile in the energy band specified in the step (3). Choose background a data interval by clicking mouse buttons. See messages which appear in your IDL window for details. After choosing BGD interval, there is a message:

            Write Comments for this data structure >

   Simply press return if you do not have anything special to comment for the selected BGD data, which is stored in a variable named bkgd. The BGD data thus selected are also contained in a file named ``flare.bgd'' on the current directory. This file can be read using the following command even if you exit from IDL and re-enter:
   IDL> rd_hxtdat,bkgd,'flare.bgd'
    

5. There appears another HXT time profile. Choose flare data interval of which you want to make an image. The procedure is just the same as in step (4). The selected flare data are stored in a variable named flare. Background subtraction is conducted in this step. The BGD-subtracted data are stored in a variable hxt and is also stored in a file ``hxt_trn.dat'' on the current directory. This file can be read by the same command as above.

   IMPORTANT NOTICE: When choosing a flare data interval, it is recommended not to accumulate too many X-ray counts; usually accumulated hard X-ray counts of e.g. 100-500 cts/SC are enough for synthesizing an image (depending on profiles of hard X-ray sources etc.). Suppose you are analyzing flare data in flare-high mode. Each data point in the time profile corresponds to 2-s of data. As the unit of Y axis is cts/s/SC, if you choose one data point which has a Y value of 100, it means that you have accumulated 100 cts/s/SC 2 s = 200 cts/SC, which is already enough for making an image. Even if you accumulate larger counts than the above values, the image synthesis program can somehow make images, but with increased possibility that an iteration procedure in the program would not converge sufficiently. If the accumulated counts are high, there appears a warning message saying:

         % \$MAIN\$: ** Warning: Recommended count level is 100 < total , 200
         * Is this O.K.:  [Default: N ] ?

6. The Image Synthesis program uses a JCL-style control file

         * Create JCL file  [Default: Y ] ?

   Simply type-in `Y' if it is the first time for you to synthesize an image of the flare which you are now working on.

7. * Enter HXT Flare Coordinates, FOV Exp. Fact.: [Default: (None) ] Type-in HXT flare location (x0,y0) and the size of the HXT image synthesis field-of-view. The location (x0,y0) is given in section 3.3.1. The default size of the HXT FOV is 1.0, which provides us with a resultant image array of 6464 pixels with the same pixel size as SXT, thus making it easy to compare HXT images with SXT images. If you type 2.0 for the HXT FOV size, it means that you expand the HXT image synthesis FOV by a factor of 2.0; you will obtain an HXT image of 6464 pixels with its pixel size twice as large as the SXT one. For example, in the case of 15 November, 1991 flare, xy0 obtained in section 3.3.1 is xy0 = (,) and in the nominal case type

         -2.09, -4.84, 1.0

   for the above prompt.

8. * Enter Comment: Write comments (if any) for the current image synthesis. After this step, a control file (JCL file) for the FORTRAN image synthesis programs ``hxtmve.jcl'' is written on the current directory.

9. * Execute HXT MOVIE task: [Default: Y ] ? Type `Y' for starting image synthesis procedure. The procedure typically takes 30 s - 5 min to make an image. The synthesized HXT image as well as some other information such as start and end times of data accumulation are contained in a file named ``hxt_img.dat'' on the current directory. The image file can be read-in and the synthesized image is displayed by the following commands:
   IDL> rd_hxtimg,img,hdr,inf,'hxt_img.dat' ; (read-in image file)
   
   IDL> disp_hxtimg,img,hdr,inf ; (display)
   

10. * Convert output to HXI file: [Default: N ] ? An HXI file is produced after typing-in `Y' for the above prompt.  

11. * Read and Display Image: [Default: Y ] ? If you type-in `Y', the synthesized image is displayed using DISP_HXTIMG.