Tuesday, 5 July 2011

Has it gone over your head! (3)

Since 1957, and the launch of Sputnik one.  A whole junkyard of materials have been put into Low Earth Orbit. Many satellites have decayed in their orbit, fallen back to earth and burned up in the atmosphere. Orbital decay is the process of prolonged reduction in the altitude of a satellite's orbit. This can be due to drag produced by the atmosphere due to collisions between the satellite and surrounding air molecules. However, there are many satellites still in orbit which we can observe.

The Low Earth Orbit is becoming congested with a great deal of space debris which has caused a growing concern in recent years, since collisions at orbital velocities can be highly damaging or dangerous.  Collisions can produce even more space debris as bits break off. The process, is called the Kessler Syndrome. The Joint Space Operations Center, part of United States Strategic Command, currently tracks more than 8,500 objects larger than 10 cm in  Low Earth Orbit, however an Arecibo Observatory study suggested there could be about one million objects larger than 2 millimeters, which are too small to be seen from the ground.

So on those clear evenings away from the lights of towns and cities it is possible to see space craft circling around the Earth.  Some are weather satellites, others are used for communications and earth mapping. We have all had a look at Google maps it is the Earth orbiting satellites that the pictures come from. Another use of satellites is for global positioning with your in car satnav. Not forgetting that Television is also another use for satellite systems.

The first and most essential step in observing spacecraft is obviously to know when and where to look. There are now many satellite tracking programs, both online and offline, that can give you the sky coordinates for a given object at a given time and location.

Click to make bigger

The easiest way to get started perhaps is to use Heavens Above an online program to find the time and coordinates of satellites that are passing over your location. You can get a list of all the satellite passing over your location. See list on the left.

Click to make bigger
Remember to bookmark the prediction page that is returned after you submit your location information. The bookmark holds your location so that the next time that you click on this bookmark, you will get the satellite visibility page already setup for you. Clicking on a specific satellite will generate a star chart that you can use to identify where the satellite will be in the night sky.

Generally speaking if you choose a generic location like Birmingham, the predictions will be good enough for just about anywhere on the UK canal systems.


No comments:

Post a Comment

Please put your name to your comment. Comments without a name may automatically be treated as spam and might not be included.

If you do not wish your comment to be published say so in your comment. If you have a tip or sensitive information you’d prefer to share anonymously, you may do so. I will delete the comment after reading.