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TrackingThere are several ways to view a satellite in orbit. Not all methods are covered by this program, however, there are a few variations. The most common is discussed on this page. Other methods available are linked to the left. A simple way to view an orbit is to display it on a world map. Most "real" tracking programs include this option. Since I seem to have a hard time visualizing the orbits of satellites I've added this tracking screen to further depict the orbit. (See note 1 at the bottom of this page.)
This screen incorporates three forms, a Map display, a Satellite Rise Selector (lower right of map) and a Text display. As shown above, all three screens appear on the desktop. note: In normal operation, the Text display will match the satellite displayed on the map. In the above example, I've captured the "Tracking Data" screen at a different time to illustrate the improved rise time function. Don't be confused by this screen capture. When running the program, the values displayed under the satellite on the map will match the data displayed on the Text Display. I've added a status bar to the bottom of the display so the "text" screen may not be all that necessary unless you're after some details. The Text screen ALWAYS lays on top of the map screen. The Satellite Rise Selector is also always on top of the map. You can dismiss the Satellite Rise Selector, and bring it back by selecting that option on the Pass Schedule Menu. By pressing Previous and Next on the Rise Selector you can move backward or forward in time to the previous or next rise of the satellite on the map. In this way, you can fairly quickly see several passes over your home location. The small map included in this screen capture is only intended to show the scalability of the map display. Notice that the menu disappears when the screen is reduced to a width narrower than the width of the menu. The latitude/longitude labels are also removed once the display becomes too small to include them with out cluttering. Each instance of Element Manager will only display ONE tracking map at a time. Of course, you can run multiple instances of the program and get two maps on the screen. Your ability to do this will depend on the amount of RAM you have. Too little, and the background copy of Element Manager will "go to sleep" while it is stored to virtual memory (swap file) on your hard drive. Once again, if you need to display multiple satellites, try real tracking programs. When you first select Track, only the map screen is displayed. An additional Menu Selection is also displayed after "Elements At Epoch" at the end of the Menu Bar, "Show Text". If you click on this selection, the text window appears. A Hidden Feature!! Double Clicking on the map itself will open and close the text box display. Point your mouse anywhere on the tracking map and right click. A popup menu offers some tracking specific information and options. You can move forward to the next satellite rise, back to the previous rise and restore realtime (system) tracking. The popup menu also informs you of the latitude and longitude of the location where you right clicked on the map. In the above display, I have pointed to South America to illustrate this feature. You can click on the lat/long or on the "Set as Ground Station" option that appears on the popup menu to change the "Ground Station" to that latitude and longitude. You can also Restore Home Coords, which will reset the ground station to the latitude/longitude coordinates you entered on the Setup Screen as your home location. If you wish to make NO changes, just click on any part of the display OTHER than the popup menu and that menu will disappear leaving the display map unaffected. What's nice about this new layout? The map screen is fully sizable as shown above. You can grab a border and stretch the map both vertically and horizontally. Shrink the display down to postage stamp size, or maximize the window and fill the whole screen. The graphic overlays (ground track, satellite, observer and Sun) as well as the map resolution adjust in size and resolution when the screen is scaled up and down to ensure better display properties . FileOnce you have the display set up the way you like it, click on File, and select "Save Current Settings". Next time you run Element Manager, these values will be used. If you do NOT save the settings, they will continue in effect until the program is next run. Map Setup
The future orbits are plotted in yellow dots (or line), the previous orbit is in red dots. For example, on the above screen shot, the ISS is heading northeast over North America. Instead of waiting for the screen to update, you can quickly see that the red orbit (previous orbit) is behind and to the southwest of ISS while the future orbital track in Yellow is to the northeast. If you do not select previous orbit the program will display 3 or 4 red dots (or a short red line segment) to indicate where the satellite was during the previous few minutes. This should help determine direction of travel as discussed above. Range CirclesYou can toggle on and off two range circles, one around your home location, another under the satellite. These circles represent the area of the earth visible to the satellite and the range from your station at which the satellite, at its current orbital altitude, will become visible (rise above your local horizon) to you. Be advised, the range circle around the observer location may, probably, will be inaccurate if you are viewing the orbit of a satellite in an eccentric orbit. The range distance around your location is computed from the current altitude of the satellite, not the altitude of that satellite as it comes over your local horizon. Never the less, it works well for sats in nearly circular orbits. Even circular orbiting satellites will have a slightly inaccurate footprint as it is computed for a spherical earth not the oblate spheroid we live on. For satellites in eccentric orbits, the higher the degree of eccentricity, the more inaccurate the home range circle. The last option under Range Circles, is the Terminator. When this option is active a fairly accurate line showing the terminator is drawn on the screen as a line that alternates between black and white. The sun is also displayed at it's current position over the Earth thus indicating the day side of the line. GridThe grid on the map may be set to off, 15 degree increments, or as shown above, 30 degree increments. You can also toggle the labels for the grid on/off. Labels on MapYou can have Element Manager add data about a satellite right on the map. If the satellite is above your ground station's local horizon then this display shows azimuth and elevation (large map). If the satellite is below your local horizon then the labels show azimuth and range (small map) to the satellite. Distance is displayed in the currently active measurement system. The labels are normally displayed under the satellite. However, when a satellite approaches a screen border it moves above or to the right or left to ensure readability. I've set the switch from Range to Elevation at -1 (negative one) degrees elevation. This gives you a slight advance notice of an imminent rise. However, a grazing pass by your home station might cause the range to switch to elevation even thought the satellite will never actually rise above your local horizon. Restore Home CoordsIf you right clicked on a position on the map, and then set that postion as your new ground station location, clicking on this menu choice will restore the latitude and longitude of your home station as entered on the setup screen. This option is also available on the right click popup menu. Save Current Ground Station as Home StationThis is similar to "Save current settings" under the file menu with this one behavior exception. "Save Current Settings" always saves the "Home Ground Station" as the one currently specified on the Setup Screen. But, if you select this option, then the currently active Ground Station becomes the Home station and is saved, overwriting the old home station. Time ModeYou can select a "Time Mode". Either Real Time, default after every startup of the program, Static Time or you can set any time. Notice above that the Window Title bar reflects which mode the program is currently operating. In the screen shot above, I was using the "Pass Selector" to move the ISS's position forward in time until it was properly displayed to match the text of this text ("heading northeast over North America") and so, the title bar indicates "User Selected Rise". If you want to examine passes for some future date, use the "Set Time" mode from this menu, select the date and time and then run pass predictions or use the Rise Locator. The time mode can NOT be saved to default to static. You must set it each time you first run the program. However, it does remain in effect until you return to manually select Real Time mode or shut down the program. Real time uses your system clock, the UTC offset you entered on the setup screen and calculates the current real time location of the satellite. The position is updated every second. If you have room on your screen you can move the windows around so you can see both the main screen and the tracking screen. Try the shrink option on the menu of the main screen and resize the tracking screen by pulling on its borders. You can then cursor or mouse click your way through the satellites on the Main Screen and each newly selected satellite will be plotted in its current real time position on the map display. Static Time, when selected, opens a dialog box where you enter a specific date and time. When you press the set button in this dialog box, EM returns to the tracking display and shows the location of the selected satellite at that set time. As noted above, you can cursor or mouse click around the Main Screen Display to select different satellites to be shown on the Tracking Screen. However, with static time enabled, each satellite will be plotted at the set static time. User Selectable time plots "realtime" satellite progress on the maps, however the time used is set by the user. You MUST enter the offset between your computer's clock and UTC for satelllites to be accurately plotted. Do this on the Setup screen. Also, if you wish to see accurate range and bearings from your location to the satellite you need to enter your Latitude and Longitude in the program (also on the setup screen). Once you've entered this data, click on the Save button and these values will be loaded each time you start the program. Pass ScheduleA schedule of passes over your location is generated for the time set in the program. If you're in real time mode, the schedule will start at the current time. If you are in static time, the pass schedule will start at that time. If you have set a specific date and time, the pass schedule will be generated starting at that time. For details, see the Pass Schedule Page. You can also click on "Show Pass Toolbar" on the Pass Schedule menu and the "Satellite Rise Selector" will open in the upper left corner of the map display. You can use this tool to move forward to the next satellite rise, back to the previous satellite rise or restore realtime (system time) operations. If a satellite's current elevation above the horizon is less than 1 degree, the program goes back to next previous rise. If the satellite is more than 1 degree above the horizon then the program backs the satellite to the rise location for that pass. Elements At EpochAn element set is created and displayed for the time currently active in Element Manager. This element set should be regarded as suspect. For maximum accuracy, the SGP4/SDP4 models should be used for propagating element sets into the future or past. EM does not use the full models but a limited subset of SGP4. So, this screen should be used for general information. It's nice to know were these parameters are currently and although not as accurate as they might be, Element Manager still gives a very close answer. It's usually within a degree of sgp4 models at lat/long on LEO birds. Show Text/Hide TextSelect this option and the text data about the satellite's current position is displayed. This is shown above in the Tracking Data window. This window will ALWAYS stay on top of the Tracking Map screen, thus, you can full screen the map and it will still be visible. When closed the menu selection says "Show Text" but when you open the Tracking Data Screen then the menu choice changes to "Hide Text", as shown above. The "Next Rise" box now displays much more accurate information. As long as the satellite is not near geosynchronous orbit a computation is made for the next rise time no matter how far in the future that should be. Also, once the satellite rises above the local horizon, this box switches to indicate when the satellite "Will Set". These times are the interval between currently set tracking time and that event. Not a time of day. This should be obvious as the time counts down second by second to the event.
Note: The tracking process requires significant processor time and so slows down the program in other areas. For example, suppose you have this screen open and open the Orbital View screen. Each time you move to the next or previous satellite on that screen, Element Manager has to re-compute the orbital path for that new satellite. Normally you can click through the satellites on the Orbital View screen very rapidly, but with the Tracking screen open this slows down significantly. To solve this problem, close the Tracking View screen. The program will then cease computing orbital data and return to its previously sprightly self. If you find this screen too limited to plan satellite operations, don't expect me to add features. I have intentionally made this screen extremely limited. I have no desire to compete with competent programmers in the orbital tracking arena. This display is only provided to give another perspective on the orbital path of the satellite of interest. Should you need to plan for satellite operations, download a "real" tracking program that devotes itself to that task. A search of the internet should turn up plenty. I personally like: Satspy from Acappella
Publishing - a great tool for Visual Observing But, this is a very subjective world we live in, so, poke around and see what you find of interest. For visual observers you really should stop by the Visual Observers' home page: http://www2.satellite.eu.org/sat/vsohp/satintro.html This page has a wealth of information that will assist any satellite tracker, but it does cater to visual observations. You'll find links to lots of interesting sites including many tracking programs.
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