2.1.7  Direct Reading of the Observing Log

A sample standard calling sequence for reading the observing log data files for all instruments for a 12-hour period starting at 00:00 on 8-May-92 is:
 
IDL >  rd_obs, '8-may-92', '8-may-92 12:00', bcs, sxtf, sxtp, w_h, fid
An example for reading only SXT full frame entries is:
 
IDL >  rd_obs, '1-jan-92', '1-jan-93', bcs, sxtf, /nobcs
Be aware that these datasets can get quite large so the time spans should probably not exceed 10 days unless you are only accessing SXT full frame entries. See the Reference Guide and the documentation header for RD_OBS for more details.

2.2  Summary SXT Full-frame image data

2.2.1  The Monthly SXT FFI files (SFM)

XMOVIE_SFM, DISP_MONTH, GET_SFM

2.2.2  Browsing the Laser Movie (at ISAS, LPARL or MSU)

A laser disk movie exists at both ISAS and LPARL which contains SXT images for the whole Yohkoh mission. These full frame images are all of the SFD images which are available, which means 50-100 images a day for over two years so far. It is possible to browse through the video recordings using a remote control to look for events of a specific type or a specific time.

The routine VIDEO_MENU will allow a user to access the ``special laser movie'' disk which has individual movies of particular events. See the description in the Reference Guide for more details.

2.3  Accessing the Yohkoh Data

2.3.1   Interactive Access (YODAT)

1. Shows what data are on line
2. Lets you select specific files to read and display
3. Reads the ROADMAP for the selected files
4. If you select data sets to be read, it creates the variables data and index which you can then manipulate using IDL or other higher-level Yohkoh routines.

This procedure is run by typing (make sure that yodat is in lower case if you are running on a Unix or Ultrix machine):
 
IDL >  .run yodat
The prompt that you will receive will look something like this:

% Compiled module: $MAIN$.
               *******  YODAT V9.2 (7-Jul-93)  *******

It is possible to have YODAT extract every "n"th dataset by setting
the variable QYODAT_NSAMP to 1.  You will be asked one extra question

It is possible to read the Ground Based Observation (GBO) FITS files
by using a command like: MENU g*
          gb_ files are from Big Bear, gk_ are from Kitt Peak
RFITS will be called with /SCALE option if QYODAT_SCALE is set to 1

Enter MENU if you want to use the filenames menu option
Enter SAME if you want to access the same fileID for a different instrument
Enter MANY if you want to use menu option and extract many files
Enter TIME if you want to enter the start/end time to extract
Enter QUIT to abort out of YODAT

Enter file name (or wild cards)

• You can type the full file name, including the directory if the data file does not exist in the default directory. Wild cards are acceptable (e.g., spr9301*.*).
• You can use the MENU option to get a listing of all of the files that are on-line (this option uses the output of DATA_PATHS to get a list of the data directories). For example, if you type menu spr*, you will get a list of all SPR files that are on-line. Or if you type menu bda9207* you get a list of all BDA files for Jul-92 that are on-line. You can only extract one file with the MENU option so click on the one file you wish to read.
• You can use the MANY option to select several files. This option is also menu driven, and is similar to the MENU option but you can select multiple files. After you have selected all the files you want to read, click on QUIT/EXIT.
• If you have already read a file, and wish to get the data for the same time but from a different experiment, you can use the SAME option. For example, if you have just read spr911115.2141, and want to get the BDA file for that orbit, type same bda.
• Once you have selected a file, you can re-run YODAT and simply hit RETURN and the same file is selected again so you can select a different set of down-line options.
• If you type quit, then YODAT will be stopped.
• If you are running YODAT over the network, then it might not be practical to run options which create an X-window. You can specify the file and directory using wild cards. The list of selected files will then appear with a number next to each file. You can then enter the starting and ending file number to select a set of files. For example, you could type
  ``/yd*/*/spr930623*'' or ``/yd6/flares/spr91*''.

The ``MENU'' and ``MANY'' options search all data directories which are returned by the function DATA_PATHS. At ISAS and LPARL this routine automatically checks for new data directories that are on-line, in addition to some ``hardwired'' directories which it always checks. It is possible for a user to add directories to the list which DATA_PATHS returns by using the routine NEW_DPATH. In the following example, the user adds the directory ``/yd3/morrison/agu_paper'' to the list of directories which will be checked by YODAT.
 
IDL >  new_dpath, '/yd3/morrison/agu_paper'
The second step in accessing any data set is to perform a quick review of the data available, and select the data sets to be read. The options for selecting the data are listed below.

Enter the number of data sets to extract
   * If you enter 0, all datasets will be extracted
   * If you enter -99, then it uses the datasets specified in variable "SS"
   * If you enter -888, then the file is not read
   * For SXT, enter a negative # (from -1 to -13) to access only that seq#
   * For SXT, enter -777 for sequence menu option
              Enter -776 to use "show_obs3" and select
              Enter -775 to use "plot_fov" and select
              Enter -774 to list the sequence summary
              Enter -773 to use "show_obs4" and select
              Enter -772 to use SSWHERE to select
   * For HXT, enter -666 to plot and select on SUM_L light curve
              Enter -665 to plot and select on SUM_M1 light curve
              Enter -664 to plot and select on SUM_M2 light curve
              Enter -663 to plot and select on SUM_H light curve
   * For WBS, enter -555 to plot and select on SXS1 light curve
              Enter -554 to plot and select on SXS2 light curve
              Enter -553 to plot and select on HXS light curve
   * For BCS, enter -444 to plot and select on S XV light curve
              Enter -443 to plot and select on Ca XIX light curve
              Enter -442 to plot and select on Fe XXV light curve
              Enter -441 to plot and select on FE XXVI light curve
   * For any, enter -333 to extract only flare mode data

If you selected data to be read, then the results are saved in the following variables:

infil	the input file(s)
index	the index structure for datasets extracted
data	the data (array or structure) for datasets extracted
roadmap	the complete roadmap for all datasets in infil
dset_arr	the list of dataset numbers selected
info_array	for SXT only, a text array describing each image

For SXT options `SHOW_OBS3', `SHOW_OBS4', and `SSWHERE', see the description in the Reference Guide. The light curve options (all of the -400, -500, and -600 series) will show a light curve of the selected channel. YODAT will prompt you with the instructions at each step. It is possible to select the range in time you wish to look at by:

1. Click with the left button at the starting time
2. Click with the right button at the ending time
3. Click with the middle button to exit

An example of how one would use the -99 option is:

1. Run YODAT to select the file and to read the roadmap.
2. Exit out of YODAT with the -888 option.
3. Select the data to be extract using some high-level routine or simple IDL `where' commands. Put the results in the variable `ss'.
4. Run YODAT again selecting the same file by just hitting RETURN.
5. Selecting option -99.

2.3.2  Advanced YODAT Options

It is possible to use the -777 option to select SXT data by the sequence table entry (all images taken with the same filter, resolution and field of view). If you wish to abort from this option, click on the title (the heading of the table). The most common technique is to just select one sequence entry, but it is possible to select many entries. The procedure is to select option -777, and then:

1. Click on ``Enable option to select multiple sequences (reset)''
2. Click on all of the sequence entries you wish to extract
3. Click on ``If enabled selecting multiple options, now extract data''

Another option is to use the -772 option to call SSWHERE which allows the selection of SXT data based on filter, image resolution, DP mode and rate, exposure duration, and several other options. See the SSWHERE description in the Reference Guide for more details.

2.3.3  Lowlevel Access Routine (READ_XDA)

2.3.4  Most Common BCS Display Routines

The BCS can provide detailed light curves and spectra. After reading the BCS data with YODAT, you may wish to use the following commands:

 
IDL >  plott_bda, index       ;light curve of all 4 chan
IDL >  plott_bda, roadmap, psym=10       ;light curve of all 4 chan
IDL >  wbda, index, data       ;light curves and spectral plots
IDL >  plots_bda, index, data       ;spectral plot of all 4 chan

2.3.5  Most Common HXT Display Routines

Raw HXT data can provide light curves and spectra of the non-theraml emission in flares. After reading the HXT data with YODAT, you may wish to use the following commands:
 
IDL >  plott_hda, index       ;light curve of all 4 chan
IDL >  plott_hda, roadmap, psym=10       ;light curve of all 4 chan

2.3.6  Most Common SXT Display Routines

The SXT provides images of the thermal plasma in flare, active regions, and the quiet sun. After reading the SXT data with YODAT, you may wish to use the following commands:
 
IDL >  stepper, data       ;movie of data
IDL >  stepper, data, xsiz=512       ;movie of data enlarged to 512x512
IDL >  stepper, data, info=info_array       ;movie of data with times...
IDL >  xy_raster, index, data       ;raster display of data
IDL >  sxt_prep, index, data, index2, data2, /reg       ;calibrate data
IDL >  show_obs3, index       ;time line of data

2.3.7  Most Common WBS Display Routines

The WBS provides light curves and spectra from soft X-ray to gamma rays. After reading the WBS data with YODAT, you may wish to use the following commands:
 
IDL >  plott_wda, index       ;light curve of 7 sub-instruments
IDL >  plott_wda, roadmap, psym=10       ;light curve of 7 sub-instruments
IDL >  plots_wda, index, data       ;simple spectral plots

2.4  How to Perform Spectral Fitting

It is possible to perform spectral fitting on the HXT, WBS and SXT data by using several routines written by Jim McTiernan. You can fit three or more filters, and thermal and non-thermal spectra. There are programs called SXTHXT_FSP and SXTHXTBOX_FSP, which will fit combined spectra for the two instruments (SXT and HXT). See the reference manual for details on how to run the program.

2.5  Selection and Extraction of an Arbitrary Shaped Sub-Image (WDEFROI) [*]

The WDEFROI function allows the user to select and cut-out an arbitrary shaped region-of-interest (ROI) from a displayed image via point and click with the mouse. With WDEFROI one can isolate a small intricately shaped active region from a larger image for further analysis. This can be particularly useful for reducing the computation time for calculating temperatures and emission measures of large data cubes. WDEFROI is not SXT specific, so it can be used on ground-based data or other derived data such as temperatures and emission measure. One can obtain light curves of the selected ROIs by passing normalized data and the times of data.

Example call to WDEFROI to obtain a sub-image via the keyword image:
 
IDL >  sub_img = wdefroi(data, /image)
The program starts by bringing up the 1st image and running STEPPER to allow the user to pick a working image frame from the variable data for selecting ROIs (One can specify the working image frame by using the sub=image_number keyword and avoid running STEPPER). Once the working frame has been selected (say image 5), the user should exit STEPPER, and a widget window will appear entitled WDEFROI.

The top row of buttons of this widget is used to pick the mode of ROI selection and to change the color table (via XLOADCT). Below these buttons is the online instruction box which displays useful general information and specific information on how to make box, polygon, and contour selections with the mouse. This is followed by some contour controls, namely a slider widget which can be used to set the contour level at a specific value. Then there is a row of control buttons: a select button to blacken-out all but the selected area of the image; reset button to re-display the original image; light curve to display a light curve of the selected area; exit to quit the widget and to return to IDL command line. The final row has a display box for the total number of pixels selected by box, polygon, and contour.

Example call to also plot light curves from normalized data:
 
IDL >  sub_img = wdefroi(norm_data, /image, zoom=6, sub=5, /lc, time=index)
Where, norm_data is a data cube of small images say 64 by 64 pixels, zoom specifies a zoom factor of 6, lc keyword requests light curve plot, and the times for the light curve are passed via the time keyword.

Note: If the input data cube contains full frame images and the area of interest is very small it may be best to call WDEFROI twice: 1st to isolate the general area from the full context image and a second time with some zoom factor to make contouring and extracting the smaller features easier.