Natural vs Man Made Satellites

Natural satellites orbit larger bodies, including planets and exoplanets. Moons are an example of natural satellites. Typically you will hear people refer to natural satellites as moons so as not to confuse them with man made satellites.

Man made satellites, commonly called artificial satellites, also orbit Earth. Among the most famous of these is the Hubble Space Telescope (HST). Launched in 1990, scientists consider HST to be the most important satellite in history. It has been responsible for pictures of black holes and gamma rays as well as the discovery of dark energy.

 

However, HST is quite old and many repairs are needed. Astrophysicists, astronomers, other scientists, politicians and space-loving civilians were appalled in 2004 when NASA correspondents announced they would not rescue Hubble due to safety issues.

Since the destruction of the shuttle Columbia, and the violent death of its crew in 2003, NASA has severely restricted its space flights. Genesis became the first recovery spacecraft after the Columbia incident to leave the Earth and return. Its mission was to collect solar wind samples for future study at NASA.

 

The European Space Agency launched its own man made satellite, Envisat, in 2002. The purpose of Envisat is to observe Earth's land, oceans, atmosphere and ice. As part of ESA's Polar Platform, Envisat orbits the North and South Poles.

Many artificial satellites can be seen at night if you are far enough away from the pollution of cities and densely populated suburbs. If the moon is full or very bright, chances are you'll miss any visible man made satellites.

 

The best times to view artificial satellites are the two hours after dusk and the two hours before dawn. Artificial satellites need to reflect the Sun in order to be seen on Earth. If it's in the Earth's shadow, it will not be visible. It is important to remember that the higher the altitude of the satellite, the longer you'll get to see it.

 

One example of a visible artificial satellite is the MIR space station, which is the largest man made object in orbit. You can see MIR from anywhere on Earth. Most visible artificial satellites, like Envisat, have a polar orbit. Therefore, you can witness them traveling in a north-south direction.

 

Satellites move very quickly. You may see one coming from the South before dawn. Later in the day, after dusk, you could see the same satellite coming from the North. Very few satellites that travel east to west or west to east can be seen by amateur sky-watchers.

NASA offers a state of the art satellite-tracking system at its Web site. Live 2D Satellite Tracking Maps indicate the locations of HST, Chandra X-Ray Observatory and most man made satellites, except Space Shuttle and International Space Station.

 

Visit NASA's Sighting Opportunities Page for more information.

 

 

Astronomical Institute/Utrecht University (2008). Astronomy Answerbook: Equipment. Retreived March 13, 2008, from the Astronomy Answers Web site.

 

David, Leonard (2006). The Genesis Payload: Just How Dangerous Are Its Contents? Retrieved March 12, 2008, from the Space.com Web site.

 

ESA Earthnet (2006). Missions: History? Retrieved March 12, 2008, from the Envisat Web site.

 

Hubble Site (2008). Hubble Site: Out of the Ordinary, Out of This World. Retrieved March 12, 2008, from the Hubble Web site.

 

Roberts, Greg. (1999). Artificial Satellite Tracking. Retrieved March 13, 2008, from the South African Astronomical Observatory Web site.

 

Science @ NASA (2006). Satellite Tracking. Retrieved March 13, 2008, from the NASA Web site.

 

Space Today Online (2006). Hubble Telescope. Retrieved March 12, 2008, from the Space Today Online Web site.