This HELP text describes the operation of this IDL viewing and analysis program which allows a user to: (1) view ISIS-1 or ISIS-2 topside ionogram files retrieved from the National Space Science Data Center (NSSDC), optimize the displayed frequency and/or apparent-range scales and apply amplitude thresholding if desired, and print the resulting ionogram image with world-map information, (2) perform precise scaling of frequency-mark onset times and produce new ionogram files with frequencies based on interpolations between these new onset times, (3) calculate frequencies of resonances and wave cutoffs based on one selected resonance or wave cutoff input value, (4) produce plots including topside electron-density (Ne) profiles from the ionogram reflection traces and (5) produce output files that will allow these profiles to be combined to produce topside Ne contours along the orbital path. Upon start up, there is a pull-down menu in the upper left corner entitled ISIS Properties with the following 8 options: Load CDF Load Binary (.os2bin) Load Binary (.bin) Traces Res/Cutoff Line Plot Color Output The first three allow a choice of input files, the second-to-last allows the user to select the desired color for the amplitude-modulated signal intensity and the last one is used to output the ionogram image. The other three are used to work with the data. Descriptions follow: Load CDF Row #1 (top): Exit to quit program. Help to read this help text. Amplitude thresholding: "min" and "max" sets the limits of the relative amplitude scale. The default value covers the complete relative amplitude range (linear scale) from 0 to 255. If the values are changed so as to view the ionogram with different amplitude limits, click the 'ENTER' button. (If the displayed amplitude range is acceptable, there is no need to click 'ENTER'.) Row #2: cursor gives the 5 coordinates of the cursor: 2 on x (sweep time in seconds & frequency in MHz), 2 on y (delay time in ms & apparent range in km) and the relative amplitude (linear scale from 0 to 255 which corresponds to 4.5V). Row #3: Select CDF to start over with the file selection process, i.e., select the directory containing the ISIS CDF files and then the ISIS CDF file for scaling. After selecting a file, click "OK" and the corresponding ionogram is displayed on the screen. Previous to go back one ionogram. Next to go forward one ionogram. Filter to clean up ionograms containing many vertical lines (caused by amplitude vs. delay-time scan lines at a given frequency that usually only contain a few data samples, called overflow scan lines, which are sometimes produced during the A/D operation). Row #4 : min & max time to select desired sweep times. min & max apparent range to select desired apparent ranges. Re-size after making previous selections (can also be used without making previous selections to re-size ionogram to fit screen display). Reset to return to full original display. Color Row #3: Color contains a pull-down menu with color options for the ionogram display. Row #4: Color X & Color Y contains pull-down menus with color options for the scaled trace points on the ionogram display. Output This option is used to output the ionogram image with a file name where the last two characters have been changed as desired (a-z, 0-9). Traces Here the user can interactively scale the ionospheric reflection traces on ISIS-1 or ISIS-2 topside ionograms and invert them to vertical Ne profiles from the satellite altitude down to (or slightly above) the altitude of the Ne peak. (Propagation conditions, due to antenna orientation and medium characteristics, determines how close the profile extends to the peak altitude.) This program is based on scaling two of the three ionospheric reflection traces that usually appear on topside ionograms, namely, the extraordinary (X)- and ordinary (O)-mode traces. The third trace, due to the slow branch of the X mode, is known as the Z-mode trace and is not scaled even though it is often more prominent than the O-mode trace (particularly at mid-to-high latitudes). The Z-mode trace has a wave cutoff frequency at the satellite (fZS) which is less than that of the O-mode trace (fOS) which, in turn, is less than the that of the X-mode trace (fXS). The Z-mode trace is often helpful in identifying the start of the O-mode trace since it often reaches its maximum delay time (or apparent range) near the electron plasma frequency resonance (particularly at mid-to-high latitudes) which corresponds to fOS. The calculation of the vertical topside Ne profile is based on the scaling of the X-mode trace. The scaling of the O-mode trace is performed in order to obtain confidence in trace identification, quality of scaling and validity of the assumptions used in the inversion program. This confidence, or lack thereof, is obtained by inspecting the plots that are available after executing the analysis program. This analysis program includes a FORTRAN true-height analysis program, based on the work of John E. Jackson [Proc. IEEE, 57, 960-976, 1969], and FORTRAN programs to calculate the geographic coordinates of the satellite and the corresponding magnetic parameters (WORLD-MAP, FIELDG programs; the latter uses an epoch date of 1965). The first two rows under Traces are the same as described for Load CDF above. Row #3 contains: Scale Trace contains two options in a pull-down menu: Scale X trace to be selected first and Scale O trace to be selected after the X-trace scaling is complete. Jackson contains four options in a pull-down menu: Variable Known assumes a variable satellite position and a known FXS value, Variable Unknown assumes a variable satellite position and an unknown FXS, Fixed Known assumes a fixed satellite position and a known FXS value, Fixed Unknown assumes a fixed satellite position and an unknown FXS. Save File contains a suggested file name for the output data file for the scaled X- and O-mode traces. It contains the directory name, satellite identification (i1 or i2 for ISIS 1 or 2), the 3-character station code, the last two digits of the year, the day number, the UT hour minute and second corresponding to the ionogram frame-sync time and two characters to designate the version number for the scaled ionogram trace (a-z, 0-9). Cleanup All Traces to remove "O" & "X" symbols on traces from previous scaling. Object Plot contains five options in a pull-down menu: Plot O displays the O-mode trace, calculated from the Ne profile deduced from the scaled X-mode trace, together with the scaled X-mode points and the scaled O-mode points for comparison with the calculated O-mode points. Good agreement provides a degree of confidence in the assumptions used by the Jackson true-height analysis program (vertical propagation in a horizontally-stratified ionosphere) and in the identification of the scaled ionogram traces. Plot Ne displays the Ne profile deduced from the scaled X-mode trace. Plot fN displays the electron plasma frequency profile deduced from the scaled X-mode trace. Note: [fN (kHz)]**2 Å 80.6 [Ne (cm-3)]. Plot 3-Ne allows three Ne profiles to be plotted on one figure (as selected from a list of three or more Ne files from previously-scaled ionograms). Plot multi-Ne allows similar plot as above except for more than three Ne profiles. Direct Plot same as above except based on a different IDL program option. Row #4 Re-Load Trace File contains 5 options in a pull-down menu that allows a previously-scaled X-mode trace (.tra) file to be loaded so that this same .tra file can be used for one of the other 3 Jackson-program options. (Note: the option used to produced the .tra file under investigation is given in the upper right hand corner of one of the plots described above.) Row #5 Output to Traces File allows the file name for a trace file, or the files for the Object or Direct plots, to be changed before selecting Save Traces as File. It is suggested that changes be made to the last two characters (a-z, 0-9) to designate new version numbers. Row #6 (below ionogram display) Output Information contains information concerning the status of the attempt to run the Jackson true-height analysis program. Scaling procedure to follow under Traces: After selecting Scale X trace under Scale Trace, use the mouse button to enter up to 50 points (with the frequencies monotonically increasing) along the X-mode trace. Next select Scale O trace and scale the O trace in the same manner. (This scaling is only used to compare with the calculated O-mode trace from the Jackson program.) After scaling the O-mode trace, select Variable Known under Jackson. If the program executes successfully, a message "Jackson program ran successfully" appear in Output Information below ionogram and graphs will result from initiating options under Object Plot. If it doesn't run the message "Jackson program failed, return to Load CDF to reload ionogram (Select CDF) and try again" will appear below the ionogram. The user can (a) re-scale the ionogram and try the same option under Jackson, (b) re-scale the ionogram and try a different option, or (c) re-load one of the previously scaled X-mode trace files for this ionogram, if available, and try one of the other option under Jackson. Res/Cutoff calculates resonances and cutoff values after a mouse click is made on a resonance or cutoff believed to have been correctly identified. The first two rows under Res/Cutoff are the same as described for Load CDF above. Row #3 contains 8 options, from Z cutoff through Qn Resonance; the last 4 contain pull-down menus. Click on the appropriate option after clicking on the corresponding resonance or cutoff feature. The results of calculating a large number of resonance and cutoff values from this input value (and the model value for fH - or an input value as entered on row #5 below) are given on a separate screen. Some of the principal values are given under Output Information below the ionogram display. Row #4 Output to Res/cutoff File allows a file name to be selected for the calculated resonance and cutoff values (the results from several input selections on one ionogram are all on the same file). New File saves the file name given at the left. Row #5 Input values displays scaled resonance or cutoff values and fH from model (or from input if input value is entered). Output Information (below the ionogram image) displays the input scaled resonance or cutoff value, the input fH value and calculated values of some of the principal resonances & cutoffs (more values are given on a separate screen). Line Plot allows detailed scaling of features from an amplitude vs. delay-time scan corresponding to the location of the cursor click on the ionogram below. If it is used to accurately scale frequency-mark onset times, then a new ionogram file can be produced based on interpolation between the new frequency-mark onset times. The first two rows under Line Plot are the same as described for Load CDF above. Below these two rows a line plot appears after clicking somewhere on the ionogram displayed below the line-plot window. The resulting line plot displays a receiver-amplitude vs. delay-time plot corresponding to the frequency line selected by the mouse click. To the right of the line-plot window are 4 control buttons that allow the selected frequency/delay-time position to be controlled either frequency-line by frequency-line (Left & Right) or range-bin by range-bin in delay-time (Up & Down). Freq Marks contains a pull-down menu with the sweep-times corresponding to each of the frequency marks as determined during the auto-detection routine during the A/D operation. These times (which correspond to the start of the first frequency line containing a frequency marker over all delay times) can be replaced by a more accurate scalings of the frequency-mark onset times based on the line plots. This replacement is performed by first positioning the line-plot indicator on the frequency-mark onset time. Next, select the appropriate frequency marker from the pull-down menu. Each time this process is performed, an asterisk is placed in the appropriate location in the pull-down menu. Use "Write Revised Ionogram File" to create a new ionogram based on interpolations between these new frequency-mark onset times. This capability allows the user to salvage an ionogram for scaling that originally had negative frequency values (indicating that the A/D auto-detection routine could not confidently identify the frequency markers). In order to scale this new ionogram, it is necessary to return to Load CDF under ISIS Properties and choose Select CDF to find the file just created. Use "Write Amplitude File" to produce an output A-scan file corresponding to the displayed amplitude line plot. The default is a file for a single scan line. If more lines are desired in the file, enter the number in the box below. The file name, displayed in the window below the ionogram, will include the time of the A-scan displayed and the number of lines (up to 9999) in the file. Note: a typical ionogram contains of the order of 1000 lines. The file will contain the sweep time, interpolated frequency of the line scan, the corresponding AGC voltage and the number of rows of data each containing delay time, apparent range, amplitude(0-255) and the calculated receiver input power PI in dBm. Note: the above coordinates and corresponding amplitude values are also recorded with each mouse click in the window display below the ionogram. Between the line-plot & ionogram displays, Displayed circle gives the 5 coordinates of the displayed circle on the ionogram display. This circle will persist into later windows selected under ISIS Properties. It can be removed by using Reset on the Load CDF display. The current version of the Jackson true-height analysis program produces one .tra and 10 .dat output files. The file resulting from the scaling of the X & O traces has the extension .tra. It has the ionogram information used as the input to the Jackson true-height analysis program plus additional information concerning the amplitude of each scaled point. The first two lines contain world-map information corresponding to the time of the start of the X-mode trace. The next line contains header information with the ionogram frame-sync time given to the millisecond. It is followed by the number of points scaled, and 7 columns of data for each of the scaled traces (X & O). The first two columns give the coordinates of the scaled point in terms of apparent range (km) and frequency (MHz) (the Jackson true-height analysis program use these data as input), the next two give the coordinates in terms of delay time (ms) and ionogram time (sec) (relative to the frame-sync time). The last three columns give (1) the video amplitude (Ampl) of the scaled point using a linear scale from 0 to 255 (where 0 corresponds to telemetry zero and 255 corresponds to a video output of 4.5 V), (2) the automatic gain control voltage in volts (VAGC) corresponding to the receiver listening scan line (vertical direction on the ionogram) containing the scaled point, and (3) the calculated receiver input power (pi) in dBm (decibels relative to 1 mW) based on equations that use Amp and VAGC [H. G. James, Communications Research Centre, Ottawa, personal communication, 1999]. The first line of the first three of the ten .dat files contains header information with the ionogram frame-sync time given to the millisecond. On the next seven files, the time corresponds to the first scaled point on the X-mode trace. The 10 .dat files are described below: 1. x_fhp_SSSYYDOYHHMMSSTn scaled X-mode trace (frequency (MHz) and apparent range (km) values) as used by the program (may be different than x_scal... file because some "offending" input points may have been removed because the frequency was not monotonically increasing from point-to-point). 2. x_scal_SSSYYDOYHHMMSSTn originally scaled X-mode points (apparent range (km), frequency (MHz), delay time (ms), ionogram time (sec) and amplitude (linear scale from 0 to 255) of each scaled point). 3. o_scal_SSSYYDOYHHMMSSTn scaled O-mode trace (if present) (apparent range (km), frequency (MHz), delay time (ms), ionogram time (sec) and amplitude (linear scale from 0 to 255) of each scaled point). 4. nhout_SSSYYDOYHHMMSSTn original output file from the Jackson true-height analysis program. Information from this file has been used to produce the files described below. It is retained here because it may contain additional useful information. For example, it contains some parameters for setting up and plotting contour plots (which the program no longer does - such plots are now made from information in the appropriate output file using other software packages). 5. ne_prof_SSSYYDOYHHMMSSTn calculated electron-density (Ne) profile (Ne (cm-3) and true height (km). 6. plas_freq_SSSYYDOYHHMMSSTn calculated plasma-frequency (fN) profile (fN (MHz) and true height (km)). 7. ne_sel_alt_SSSYYDOYHHMMSSTn Ne at selected altitudes (true height (km) and Ne (cm-3)). 8. alt_sel_ne_SSSYYDOYHHMMSSTn altitude at selected Ne (true height (km) and Ne (cm-3)). 9. o_tra_SSSYYDOYHHMMSSTn calculated O-mode trace (frequency (MHz) and apparent range (km)). 10. wmap_SSSYYDOYHHMMSSTn world map information corresponding to the first scaled X-modemode trace point) where SSSYYDOYHHMMSSTn is: SSS station id YY year DOY day of year HH hour MM minute SS second Tn version number (example: NE_PROF_QUI70108194608T1.DAT) -- Robert F. Benson Code 692, NASA/Goddard Space Flight Center Greenbelt, MD 20771 Phone: 301-286-4037 Fax:301-286-1433 email: robert.f.benson@nasa.gov