Voyager Applets:
Controls Explained

Tour Home
Mission to Mars:

Along the top, you will find three text boxes, in which you enter the semimajor axis (a) and eccentricity (e) of the spacescraft orbit, and the orbital angle (theta) of Mars.

Type in a, e, and theta and hit the Enter key. You will see the positions of Earth and Mars at launch, as well as the position of the spacecraft shown in red. Hit "Launch" to launch the probe, "Stop" to stop the probe, and "Reset" to start back at the Earth again.

If you get the message "a,e invalid - probe must launch from Earth", this means that you entered a combination of a and e which has the probe at perihelion somewhere other than on the Earth. Remember that in a Hohmann transfer orbit, perihelion is the launch point.

Grand Tour:

Grand Tour is much like Mission to Mars. At the top of the applet, you will see text boxes to enter in the semimajor axis and eccentricity of each leg of the journey. You also will see a column of textboxes for you to enter the starting angle of each of the four outer planets to be visited.

So again, enter e and a for each part, along with the starting angles of each planet. Hit Enter. Hit "Launch" to launch the probe, "Stop" to stop the probe, and "Reset" to start back at the Earth again.

If you want to see the path Voyager 2 took, click the little "Voyager" checkbox at the bottom of the applet and hit "Launch".