Introduction

The tracking system JAVA applet was developed by Patrick Meyer and Tim Horvath. It is intended for entertainment and should not be used for detailed analysis.

Before writing us, be sure your question isn't answered by our FAQ.

How it works

The tracking system calculates an approximate location for a list of satellites (including spacecraft). Each satellite is assigned a color used for displaying the ground trace, captions, location, and countdown clock.

Upon start-up the applet loads its state vectors from the our web site. If you leave the applet running, the applet attempts to download new state vectors at least once per day.  It downloads every three hours for the Space Shuttle.

If a shuttle is awaiting launch, the launch time is shown in the satellites assigned color in the left corner of the earth map above the current time.

Time is shown in Greenwich Mean Time (Coordinated Universal Time) in the lower left hand corner. This time is dependent on the system time of your computer. If the system time on your computer is not correct, J-Track attempts to overcome this by comparing your System's time to our System's time.

The map is a Mercator Projection and the tracking circles around each satellite represent where the satellite is most likely visible from the earth given optimal viewing conditions.

It Doesn't Work!!!

We are sorry if J-Track doesn't work for you.  We did our best to test it under Windows 95/NT and Macintosh OS 7.5.x, though not always with good results.  JAVA is not as platform independent as it could be.  We have seen it function properly for -

• Internet Explorer 3.0.2, Windows 95/NT
• Internet Explorer 3.0.1, Macintosh
• Netscape 3.0, 4.0, Windows 95/NT
• Netscape 3.0, Macintosh

It does not work for -

• Netscape 4.0, Macintosh - it has a strange Date problem, thought the satellite locations appear to be correct.
• Internet Explorer 4.0P1, Macintosh - who knows!

Display Controls

Main Display

Configuration Controls

At startup, J-Track only loads the default satellites.  You can expand the list of satellites to choose from by clicking on the "Add More" button.

• Adding a Satellite - select a category of satellites, then select the satellites you wish to add to the tracking display.  When they are selected click the "Add" button.  You can only track 10 satellites.
• Removing a Satellite - select the satellite in the "Tracked satellites" list and click the "Remove" button.
• Synchronizing Clock - J-Track attempt to ensure that your clock and our clock match.  You can force a resynchronization using the "Sync. Clock" button.

On J-Track a caption is shown below the spacecraft. You can choose to display either

• None - No caption
• Name - the name of the spacecraft
• Vector Date - the time the state vector was calculated
• Vector Age - how long it has been since this state vector was calculated.

Other options include -

• Weather - The weather toggle activates the downloading of a weather image created by Intellicast. This will display a weather summary map generated within the last 12 hours.
• Grid - Shows latitude and longitude lines.
• Day/Night - Shows where on earth it is day and where it is night
• Sun - Shows a projection of the current location of the sun.
• Visibility - Current not available.