PROCEDURE: plot_fa_crossing PURPOSE: Plots magnetic footprint of spacecraft across earth. (FLAT,FLNG) Shows the night/day terminator, auroral ovals, apogee and perigee footprints, etc. (See examples below.) Keywords are grouped into categories: TIMESPAN, VIEW, DISPLAY, AURORAL ZONE, MISCELLANEOUS. TIMESPAN KEYWORDS: ORBIT The orbit to plot. If unset, will plot over interval containing present time and show craft position right now (unless TMIN and TMAX are set). ORBIT cannot be greater than the last orbit listed in the predicted orbit almanac file. TMIN, TMAX Time points to be included on the chart. Use these if you want to display timespan in distant future. Should not be more than a couple hours apart. Format of TMIN and TMAX must be the type of string accepted by str_to_time() or a double float in seconds since 1970. ORBIT must not be set if these keywords are to be used. These times will be labeled on the map as t1 and t2. (Good for showing AOS and LOS taken from contact schedules.) XMARK Set this to a time (string or double float) to have that point labeled on the map as a big X. If none of ORBIT, TMIN, TMAX are set then this time will be used as the reference time for which to create the plot. (Good for showing conjunctions.) VIEW KEYWORDS: KIRUNA, POKER, WALLOPS, MCMURDO, CANBERRA, SANTIAGO, BERKELEY: Set any of these for an overhead view of the station. VIEWPOINT This allows arbitrary views of the Earth. Should be a 3-element array designating lattitude, longitude, and rotation in degrees. WHOLE If set, will not confine plot to polar regions. SOUTH Set to view earth from directly over South Pole. MAGPOLE View from above the magnetic pole with magnetic local noon at the top of the plot. Gridlines are still geographic. Poles are not symmetric because of the eccentric dipole. (When this keyword is not set the display defaults to above the geographic poles, with geographic local noon at the top.) ZOOM Enlarges the map. 1 is normal, 2 is twice as big. See WINSIZE keyword for zooming in postscript mode. DISPLAY KEYWORDS: WINSIZE The width of the plot window in pixels. Default width is 640. Height is scaled automatically so that lattitude lines will be circular when output on a Tek printer: H = W * 1.031. In PostScript mode (POST keyword set), WINSIZE acts like a magnification factor; WINSIZE=10 is normal. PC Set this to nonzero if you are using a windowing system that does not provide backing store to retain hidden windows. This keyword also sets the VECTOR_FONTS keyword. GREY Set this keyword to output the plot in greyscale. (Run @startup to restore colortable.) FILL Fills oceans and continents with solid color to make a pretty plot. Setting this keyword when printing to a color printer is discouraged. VECTOR_FONTS Disable switch to device (hardware) font from (default) Hershey vector-drawn fonts. Device fonts may be prettier, but vector fonts are device independent. POST Set this to a filename to direct the ouput to an 8-bit color postscript file instead of the graphics window. When viewing the postscript file, be sure your viewer is set to 8 bits, not 24, and that it is displaying "perfect colors". (Do not add ".ps" to the name.) GIF Captures the image on the output graphics window to a GIF file. (Add ".gif" to the name yourself.) AURORAL ZONE KEYWORDS: ACTIVITY Set the Activity Index of aurora. ( 0-6, default 3) SSCZONE Show the auroral zone used by the Satellite Situation Center instead of the one from Holzworth and Meng. (THIS IS NOT PERFECTED YET.) See auroral_zone_ssc.pro and notes below. MISCELLANEOUS KEYWORDS: POLAR Plots the magnetic footprint of the POLAR spacecraft and information about its closest approach to that of FAST. Good for finding conjunctions or displaying known ones. (For a description of how POLAR orbit data is obtained, see the documentation for get_po_orbit.pro.) DRAG_PROP If set, the orbit propagator will include the effects of atmospheric drag. The orbit track may be inaccurate by a few degrees for propagations as short as a few weeks. This keyword minimizes this error. ALMANAC_INFO Prints a line under the plot title telling the orbit file used, the last epoch in that orbit file, and whether or not drag was included in the orbit propagation. EXAMPLES: Show what FAST is doing now, and make it pretty: IDL> plot_fa_crossing, /fill Show what FAST is doing for Christmas, make output greyscale, and copy output to a GIF file: IDL> plot_fa_crossing, xmark='98-12-25/00:00:00', $ gif='~/images/northpole.gif', /grey Show the polar crossing of orbit 3000 from a bird's-eye view over Canberra, and send the output to an 8-bit color postscript file: IDL> plot_fa_crossing, /can, post='~/images/orb3000', $ orbit=3000 NOTES ON THE AURORAL ZONE: The auroral zone is drawn using a procedure by Jim Clemens (suggested by Holzworth & Meng, and corrected by Mike Temerin). The source for this procedure is "Mathematical Representation of the Auroral Oval", R.H. Holzworth and C.-I. Meng, Geophysical Research Letters, Vol.2, No.9, Sept 1975. The mathematical representation of the auroral ovals is found by fitting Feldstein statistical ovals in corrected geomagnetic coordinates to a 7-parameter Fourier series: theta = A1 + A2 cos(phi + A3) + A4 cos(2phi + 2A5) + A6 cos(3phi + 3A7) theta = corrected geomagnetic co-lattitude phi = 2(pi)(MLT)/(24hrs) The best fit constants are found for each value of Q=0..6, where Q is the activity index which describes how quiet (0) or active (6) the Feldstein auroral ovals are. The characteristic radius A1 of the ovals increases monotonically with Q. (Source: Holzworth and Meng.) The function azonloc.pro generates the southern auroral oval by reflection of the northern oval through the magnetic equator. The formula in Holzworth and Meng gives the ovals in corrected geomagnetic coordinates. The procedure transform_mag_geo.pro converts them to geograhic coordinates using the eccentric dipole model. CREATED BY: J.Rauchleiba 96-12-20