Orbital View

I've always had a hard time visualizing the orbits of satellites. If eccentricity starts to creep up I know generally what the orbit will look like, but not a real accurate vision. So ...

I've designed this screen to help me! If you like it so much the better. What you are seeing here is the relationship of the orbit of the selected satellite to the Earth.

Satellites with orbital periods greater than 225 minutes will suffer from inaccuracy since their positions should be propagated using SDP4 algorithms. Because these are not included in EM, a warning about accuracy now appears on this screen as well as the Tracking Screen when orbital periods exceed the 225 minute demarcation.

When you have all the options for this screen active the program plots

	the semi-major and semi-minor axes
	a line across the earth representing the satellite's inclination along with the actual inclination value
	a line from the center of the ellipse to the current position of the satellite
	the current position of the satellite on the orbit ellipse along with the mean anomaly value of that position.

The last two options will only display if you have the "Tracking Screen" active and the line will only plot if the satellite is also plotted. Satellites ALWAYS move in a counter clockwise motion. So, in the example above, Oscar 10 is descending towards its perigee and is currently 245.9° from the argument of perigee.

All of these options can be saved to the initialization file from the Options menu or the Setup Screen.

Clicking on the Previous or Next Satellite buttons will allow you to scroll up and down through the currently active elements. You can also use the cursor keys.

On the Menu

Click on "Options" and you can:

	Toggle on and off the inclination line
	Toggle on and off Semi-major and semi-minor axes lines.
	Toggle on and off whether or not to show the satellite's current position along the ellipse.
	Toggle on and off the line from the ellipse center to the satellite.
	Save these settings

Click on Shrink and the screen collapses to just the graphic portion of the display. I've added this Shrink option here and on the main screen so I can have them both displayed on the screen simultaneously. Double clicking on the graphic shrinks and expands the display too.

Click on the Track button and the Map Plot tracking screen will open displaying the current position of the satellite.

A little additional data is broken down on this screen.

The maximum elevation as seen from the observer's "home latitude" is shown for both the perigee and apogee altitudes

The International Launch Data is there

The orbital elements include the 2nd order of mean motion term and the bstar drag term.

In order to keep the program "universal" in scope, it is designed to work on a 640x480 and up display. With that limitation, room was lacking on the main screen for these additional breakdowns. Of course, they're present in the 2 line display.

last edit 27-Nov-2005
maintained by Rick von Glahn