Information

Information on the use and origin of this website, including future planned upgrades, as well as definitions of orbital elements as used by NORAD when developing Two Line Element Sets (TLE's).


This project came about from a desire to provide satellite propagation data to interested users. TLE Data is readily available from sites such as Celestrak at http://www.celestrak.com but the ability to portray what this actually represents in 3D space is not usually readily available unless you are willing to purchase a stand-alone program designed for this purpose. These software suites are typically either expensive to purchase for the relative value that most users will get out of them or they offer limited options.

This website has been designed to fairly quickly pull up Orbital Element data from a database and, after choosing some options, generate a near real-time KML file that can be directly imported into the embedded Google Earth™ Plug-in on the site. Basic use of the site is detailed here.

  1. Pull-up the desired Celestrak "Constellation" (i.e. group of satellites) by using the pull-down for the respective group and then clicking the "Change Group" button. The default is the "Space Stations" group.
  2. If desired, choose a Satellite pull-down within the group or leave it blank. Leaving it blank will generate the entire group in the Google Earth™ Window. The size of the group is limited to 150 satellites because of the length of time it takes to create each file and the amount of time it takes to import into the window.
  3. If desired, choose one of approximately 1500 ground sites around the world that are currently available. Leaving it blank will default to Colorado Springs, CO.
  4. If desired, choose a Field of Regard (viewing angle straight down from the satellite to the side) that you would like to depict for the satellite. Leaving this value blank will not generate a conic model. The maximum value available for any particular satellite is the rim of the Earth (i.e. the model will not depict past the outside edge of the Earth).
  5. When complete simply click "Create KML" and then acknowledge the pop-up box. Depending on the size of the group of satellites being generated there may be a lag between creating the KML and then being able to import into the Google Earth™ Window. The group will generate every four seconds.
  6. If your data is not automatically brought into the Google Earth window or if not all of the satellites immediately show up, click on "Import KML" to view generated KML.
  7. Scroll around the Google Earth™ window with controls similar to when using the Desktop client.
  8. If desired, or if your browser doesn't support the Google Earth™ plug-in, you can also open the generated files into the actual Google Earth™ program by clicking the link.

Below is descriptions of information shown for each satellite on the Orbits tab. For additional information on the Orbital Elements click here. The Orbital Elements differ slightly from the data given in a TLE. The TLE uses Mean Motion to describe the size of the orbit (in orbits per day around the central body) whereas Semi-Major Axis describes the size of the orbit by specifying the radius of the major (long) axis of the orbit.

  • ID: The sequential number of the satellite in the current group.
  • Satellite: The satellite name.
  • Norad: The designated NORAD number assigned to each man-made object in orbit. No two numbers are the same and are assigned to all objects (ex. debris), not just satellites.
  • Epoch Time: The time at which the current TLE snapshot was taken. The first two digits are the last two digits of the current year. The next three digits before and the eight digits following the decimal point are the day and fraction of the day of the year.
  • UTC: The time of Epoch translated to Coordinated Universal Time (Greenwich Mean Time).
  • Inclination: Inclined plane of the satellite's orbit from the equator given in degrees from 0 to 180.
  • RAAN: Right Ascension of the Ascending Node. The Ascending Node is the point where the satellite's orbit crosses the equator moving from the Southern Hemisphere to the Northern. Right Ascension is the angle in degrees from the Celestial Equinox to the Ascending Node.
  • Eccentricity: A perfectly circular orbit (impossible to achieve) has an eccentricity of 0, whereas a parabolic orbit has an eccentricity of 1. All orbits available here are somewhere between 0 and 1, indicating some type of elliptical orbit.
  • Argument of Perigee: The angle in degrees based on the satellite's direction of travel from the Ascending Node to the point where the satellite is closest to the Earth. Remember that orbits here will never be perfectly circular so some point in the orbit will always be closer to the Earth than at any other time.
  • Mean Anomaly: Angle in degrees measured in the satellite's direction of travel from Argument of Perigee. The "Mean" implies that this is an average calculation of the satellite's location at the TLE snapshot.
  • Mean Motion: The number of revolutions around the Earth the satellite will orbit in one day.