This HELP text describes the operation of this IDL viewing and analysis program which allows a user to interactively scale the ionospheric reflection traces on ISIS-II topside ionograms and invert them to vertical electron-density (Ne) profiles from the satellite altitude down to (or slightly above) the altitude of the peak of the Ne profile. (Propagation conditions existing at the time the ionogram was recorded, due to antenna orientation and medium characteristics, determines how close the profile extends all the way 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, which has the lowest-frequency wave cutoff at the satellite, is often helpful in identifying the start of the O-mode trace since it reaches its maximum delay time (or apparent range) near the electron plasma frequency resonance (particularly at mid-to-high latitudes) which corresponds to the start of the O-mode trace (which, in turn, is at a lower frequency than the start of the X-mode trace). The calculation of the vertical 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 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). Items 1-3 below provide information on how to get started and items 4 - 24 give descriptions of buttons below the top line of information on the screen. These descriptions are followed by a description of the 10 output files produced by this version of the Jackson true-height analysis program. 1: The first step is to 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. This ionogram is a display of apparent range from the satellite position vs. time after the frame sync (upper of the two scales below the ionogram) or frequency (lower of the two scales). The most common mode of operation combined 3.3 s of fixed-frequency soundings followed by swept-frequency sounding from 0.1 MHz to either 10 or 20 MHz. (Note: Large negative frequenecy values indicate that the frequency markers could not be confidently identified by the software used to produce the digital ionograms.) Below the frequency scale is a display of world-map information corresponding to the file (frame-sync) time. 2: 'filename(traces):' is a string that contains a suggested file name for the output data file for the scaled extraordinary (X)- and ordinary (O)-mode traces. It contains the directory name, satellite identification (i2 for ISIS 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. These last two characters can be changed as desired (a-z, 0-9). Next, click the "Scale X-Trace" button and use the mouse button to enter up to 50 points (with the frequencies monotonically increasing) along the X-mode trace. After each click of the mouse button, the corresponding values for apparent range (km), frequency (MHz), echo delay time (ms), ionogram sweep time from the frame-sync time (s), video signal amplitude (linear scale from 0 to 255 which corresponds to 4.5 V), the automatic gain control (AGC) voltage (V) and the calculated receiver input power (dBm) are displayed at the bottom of the ionogram (these values are described in more detail later in this paragraph). Next, click "Scale O Trace" and scale the O-mode trace in a similar manner. The file resulting from the scaling of these two 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]. 3: "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 any desired amplitude threshold, click the 'ENTER' button. (If the displayed amplitude range is acceptable, there is no need to click 'ENTER'.) 4: "Scale O Trace" to be clicked after scaling the X-mode trace. It is scaled using the mouse in the same manner as was used for the X-mode trace. The O-mode trace scaling is only used to compare with the calculated O-mode trace from the Jackson program. After scaling the O-mode trace, select one of the four following options available with the Jackson true-height inversion program. Option #5 is recommended. If the program executes successfully, the world-map information corresponding to the time of the start of the X-mode trace will appear below the ionogram image and graphs will result from initiating options (9), (10) and (11) below. If it doesn't run the message "Jackson program failed, try again after clicking "Re-plot Iono" button" will appear below the ionogram. The user can (a) re-scale the ionogram and try the same option, (b) re-scale the ionogram and try a different option, or (c) re-load one of the previously scaled X-mode trace files (see item #21) and try one of the other Jackson-program options. 5: 'Jackson-VK' assumes a variable satellite position and a known FXS value. (Same as (7) below except that the satellite motion during the time interval covered by the ionospheric reflection trace is not neglected.) 6: 'Jackson-VUK' assumes a variable satellite position and an unknown FXS value. (Same as (8) below except that the satellite motion during the time interval covered by the ionospheric reflection trace is not neglected.) 7: 'Jackson-FK' assumes a fixed satellite position and a known value for the start of the X-modetrace at the satellite (FXS). In this case, fXs is set equal to fH(1) + 0.001, where fH(1) is the calculated value of the electron gyrofrequency at the satellite location (fHs) corresponding to the time of the first input X-mode trace point. If the frequency of this point (f(1)) is greater than or equal to the calculated fXs, then the program uses the first trace point (f(1)) as entered. If the f(1) < fXs then f(1) is set equal to fXs. 8: 'Jackson-FUK' assumes a fixed satellite position and an unknown FXS value. As in (7) above, fXs is replaced by fH(1) + 0.001. In this case, however, f(1) (the first scaled input X-mode trace frequency value) is replaced by fXs. The delay time, iono time , etc. from the input trace file are not changed. 9: 'Plot O' displays the O-mode trace using "O" symbols, calculated from the Ne profile deduced from the scaled X-mode trace, together with the scaled X-mode points (as "X" symbols) and the scaled O-mode points (as solid dots) for comparison with the calculated O-mode points. Good agreement provides a degree of confidence in the assumption of vertical propagation in a horizontally-stratified ionosphere, as used by the Jackson true-height analysis program, and in the correct identification of the ionogram traces scaled. 10: 'Plot Ne' displays the Ne profile deduced from the scaled X-mode trace. 11: 'Plot Fn' displays the electron plasma frequency (fN) profile deduced from the scaled X-mode trace. The relationship between fN and Ne is approximatel given by the expression [fN (kHz)]**2 = 80.6 [Ne (cm-3)]. 12: 'Print Plot' creates a postscript file (.ps) of a displayed plot (from 9, 10 or 11 above). 13: 'Re-Plot Iono' re-plots an ionogram that has been processed through the Jackson program (using one of the options described in 5 - 8 above). 14: 'Print Iono' creates a postscript file (.ps) of the ionogram. 15: 'Iono GIF' creates a GIF file (.gif) of the ionogram. 16: ' Color' to change a B&W ionogram to a color ionogram. 17: ' B/W' to change a color ionogram to a B&W ionogram. 18: 'Select File' allows the user to select a specific ISIS CDF file. After selecting, the corresponding ionogram is displayed on the screen. 19: 'Next File' selects the next ISIS CDF file and displays the corresponding ionogram on the screen. 20: 'Previous File' selects the previous ISIS CDF file and displays the corresponding ionogram on the screen. 21: 'Re-Load Trace file' 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 obtained from items 9 or 10 above.) 22: 'Plot 3-Ne' allows three Ne profiles to be plotted on one figure. These profiles are selected from a list of three or more Ne files produced from previous ionogram scaling. 23: 'Help' produces the information on this page. 24: 'Exit' quits the analysis program. 25: 'Res/Cutoff' and 'n value'. Prior to scaling the X trace as described above, it may be desired to check the values of plasma resonances or other features of interest. Each click of the mouse will produce the 7 output values described in (2) above. If one of these values is believed to correspond to a particular resonance or wave cutoff value then, if that value is selected under the Res/Cutoff pull-down menu, selected resonances and cutoffs are calculated and displayed below the ionogram. If a Dn or Qn resonance is selected, then the appropriate n value must be selected from the pull-down 'n value' menu before the calculations are initiated. A more complete calculated output is available from the window behind the ionogram display. If it is desired to save these resonance and cutoff calculations, they can be saved under a file name specified on the last line above the ionogram. The r1 before the '.res' can be changed to any desired values between a-z and 1-9. The equations used to calculate Dn are (1),(2) and (3) of Benson and Osherovich [J. Geophys. Res., 97, 19, 413, 1992; the Qn resonances were calculated from the zero group velocity points of the Bernstein-mode dispersion curves as described by Warren and Hagg [Nature, 220, 466, 1968]. Note: as of October, 2000, not all of the options on these pull-down menus are operational. The current version of the Jackson true-height analysis program produces 10 output files. The first line of the first three 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 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)