Click here to see the entire HESSI GUI Guide
|Selecting Time and Energy Intervals|
|Selecting Collimators, Harmonics, Time bins|
|Selecting Image Algorithm|
Cross Reference Tables for Widget Names and Object Parameters
|Snapshot of Image and Movie Widget|
The HESSI Image Widget is a graphical interface to the HESSI image object. The object and the interface are connected closely; the interface provides an easy way to set parameters in the object and call the process method of the object to generate an image.
This widget is activated when you click File / 'Retrieve/Process Data' / Image in the Main GUI Window.
Note: This widget interface changed significantly in March 2005 to work with the new image object that handles image cubes. The most significant new features are discussed below in the 'Selecting Input Source' and 'Viewing Images' sections.
When you enter the Image Widget, the current values of imaging parameters are reflected in the widget values.
The only parameter that will be set for you, and only if you've selected a new time interval or flare, is the default imaging time interval which will be set to 4 seconds at the peak of the flare.
When you change any of the imaging parameters, they are set in the image object, and are remembered the next time you enter the image widget. You can reset the parameters to default values by clicking the 'Reset to defaults' button.
This document describes how to use the widgets to set parameters, but will not attempt to explain how the image algorithms work or what the image object parameters mean. Refer to the Imaging section of the RHESSI Data and Software Center for a complete description of the image algorithms and the HESSI Data Object Parameter tables for a list of the control and info parameters that apply to imaging. Below are cross-reference tables showing the object control parameter names corresponding to the names in the widgets.
Changing most of the parameters is straightforward. The ones that aren't are described below.
Selecting Input Source
There are three input choices:
- Raw Data - In this mode, you can set any control parameters you want and click 'Make/Plot Images' (or Write FITS file) to generate the images specified. The data source is the raw Level-0 telemetry files. If you opted for sending the images to the GUI, a Chooser widget will appear after the images are generated to allow you to plot a subset (including all or none) of the images generated in the GUI. Until you change a control parameter, you can click Make/Plot Images to see the Chooser selection widget again, and choose different images to plot in the GUI without reprocessing. Similarly, once the images have been generated, you can click 'Write FITS file' to write an image FITS file, 'Panel Display' to see all images at once, or 'Movie' to generate a movie of the images without any reprocessing. However, as soon as you change a control parameter the next click of any of those buttons will require reprocessing the images. Note that you don't have to send the images to the GUI in order to see them in the 'Panel Display' or 'Movie' options.
- Image FITS file - After selecting this option, either enter your image FITS file name in the text widget, or browse to open a file. All of the image object parameters will be read from the FITS file, and the widget values will be updated to reflect the new values. All of the buttons that allow you to change control parameters are desensitized since you are not allowed to change parameters when reading from an image FITS file. By default, a Chooser widget appears to let you choose which images to show in the GUI. You don't have to select any at this point. You can click 'Plot Images' any time to see the Chooser widget again, or you can display all the images at once via 'Panel Display' or make a movie.
- Eventlist FITS file - This is similar to the 'Raw Data' option except that instead of using the raw Level-0 telemetry files as input, you use an eventlist FITS file (eventlist files can speed up data accumulation). You must be careful to use a time interval, energy range, and detector selection that are included in your eventlist file.
Selecting Time and Energy Intervals
To select time and/or energy intervals, click the 'Change...' button on the Image Widget. The 'Select Intervals' widget that appears shows the intervals that are currently defined. There are several ways to change the intervals:
- Below the area that shows the currently defined intervals, there are buttons that let you edit or delete a single interval (select which one by highlighting it in the droplist), or edit or delete the entire list. To edit, simply change the text in the XTEXTEDIT window, and click 'Finished editing'. Be careful not to change the format of the interval entries.
- If your current plot is of the right type (time or energy on x axis), you can choose to define intervals graphically.
- You can read intervals from a file you created in this widget previously using the 'Save Current Intervals to File' button.
- Or you can define an interval manually, and
- either add it to the current list or replace the current list
- create n intervals starting from that start time with that delta and either add them to the current list or replace the current list
- create n intervals by dividing that interval into n evenly spaced intervals and either add them to the current list or replace the current list
Note: in each case you must click either the 'Add to List' or the 'Replace List' button to move the intervals into the current list. Click Accept to transfer these intervals to the Image Widget. Note that in the Image Widget, the pull-down widget showing the current intervals is for display only; you can not select an interval using that pull-down widget. To change your selection, you must click the 'Change' button again.
Selecting Collimators, Harmonics, Time bins
To change collimator options, click the Change button in the collimator box.
Note: As of October, 2001, the following options are not available:
- rear segment - there are no rear segment events in the simulated data.
- harmonics other than the fundamental - the software can't handle the higher harmonics yet.
If the 'Calculate time bins automatically' box is enabled, then the Time Bin column for each collimator is insensitive. If it is disabled, then you can set the elements in the Time Bin column. These elements are the multipliers on Time_Bin_Minimum for each collimator. The units for the time bins are binary microseconds (bus). (There are 1024 binary microseconds in a millisecond.) Notice that the result of the multiplier on the Time Bin Minimum is shown in the column to the left of the editable fields.
Selecting Image Algorithm
Use the droplist to select the image algorithm. For all algorithms except Back Projection you can set options to control the reconstruction process by clicking the 'Set Parameters' button.
If the Clean algorithm is selected, one of the options available is 'Define/Modify clean boxes after BPROJ'. If this option is enabled, then after the Clean routine makes the Back Projection map (which is always its first step), it will pause and display the map with an accompanying widget that allows you to draw one or more regions on the image. When you have finished defining the 'clean boxes', the Clean routine will resume, but will limit its search for maxima to those regions. The next time you make an image with Clean, it remembers and uses the boxes that were defined previously. You have the option to delete them or redefine them. Another way to set the 'clean boxes' is by clicking the 'Mark Clean Boxes' button in the main Image widget. This button becomes active only if there is an image (any algorithm) displayed in the Main GUI Window, and the image algorithm selection is set to Clean.
After setting the parameters you want to change, clicking 'Make/Plot Images', 'Write FITS file', 'Panel Display', or 'Movie' will start generating the images. There are options to give you more information while generating the images including a progress bar with a Cancel button, verbose mode to print more text in the IDL output log, and an option to show each image in a little window while they're being generated (these images are not brought into the GUI, but are available just so you can see whether the images look all right).
Note that some of the reconstruction algorithms can take a very long time to make an image. Back Projection is usually the fastest, but produces the least reliable image. Clean, MEM Sato, and MEM Vis depend on the number of iterations or Lambda values you ask for. And Pixon can take hours, but does a very good job.
For all algorithms except Back Projection, a progress/cancel widget (this is in addition to the overall image cube progress bar) appears while the reconstruction is in progress (unless you disabled this option) that gives you an estimate of the percent completed, and has a 'Cancel' button to let you interrupt the reconstruction. If you click the cancel button, then the image that has been created so far will be displayed. If the reconstruction had not gotten far enough to even make the first attempt at an image, then nothing will be returned or displayed.
Note that all three of these options will cause reprocessing of the images if you have changed any control parameters or haven't generated the images yet.
Table 1. Image Widget Names Cross-Referenced to Object Parameter Names
|Widget Name||Object Parameter Name|
|Image Time Interval||im_time_interval, im_time_bin, obs_time_interval, time_range|
|Energy Band||im_energy_binning, energy_band|
|Time Bin Minimum||time_bin_min|
|Calculate time bins automatically||use_auto_time_bin|
|Force multipliers to powers of two||cbe_powers_of_two|
|Offset of Map Center from Sun Center||xyoffset|
|Simulated Aspect Solution||aspect_sim|
|Variable Flux Correction||use_flux_var|
|Flux Smoothing Time||smoothing time|
Table 2. Clean Algorithm Widget Names
Cross-Referenced to Object Parameter Names
|Widget Name||CLEAN Parameter Name|
|Max # iterations||clean_niter|
|No chi-square test||clean_no_chi2|
|Stop if negative max||clean_negative_max_test|
|Restart from last clean||clean_more_iter|
|Show Chisquare Test||clean_show_chi|
|Show progress/cancel bar||clean_progress_bar|
|Define/Modify clean boxes after BPROJ||clean_mark_box|
Table 3. MEM Sato MEMVIS Algorithm Widget Names
Cross-Referenced to Object Parameter Names
|Widget Name||Sato Parameter Name||VIS Parameter Name|
|Max # iterations||sato_iter_max||vis_iter_max|
|No chi-square test||sato_no_chi2||vis_no_chi2|
|Show progress/cancel bar||sato_progress_bar||vis_progress_bar|
Table 4. Pixon Algorithm Widget Names Cross-Referenced to Object Parameter Names
|Widget Name||Pixon Parameter Name|
|Show progress/cancel bar||pixon_progress_bar|
Table 5. Forward Fit Algorithm Widget Names Cross-Referenced to Object Parameter Names
|Widget Name||Forward Fit Parameter Name|
|# Parameters per Source||ff_n_par|
|Max # iterations||ff_nitmax|
|Show progress/cancel bar||ff_progress_bar|
Last updated 07 November, 2008 by Kim Tolbert , 301-286-3965