|Photo Credit: Thierry Legault used with permission|
One of the more exciting things to see in the night sky are the thousands of satellites that move across the sky throughout the day and night. When they are in the right position to reflect some of the Sun’s light we are able to see them in the night sky. The best time to view satellites is in an area without a lot of light pollution shortly after sunset or shortly before sunrise.
Satellites are any moon, planet or machine that orbits a star or a planet. So the Earth is a satellite because it orbits the Sun and the moon is a satellite because it orbits the Earth. The image at left, though not taken in the night sky shows two satellites, the Moon and in the upper left the International Space Station. We are going to talk mainly about man-made satellites, which for the most part orbit the Earth and are used for a variety of scientific and communications purposes.
Fun Facts:There are over 1000 operational satellites in orbit around the Earth, but there are more that 21,000 objects larger than 10cm orbiting earth.
The first man-made satellite was put in to orbit in 1957, when the Russians put Sputnik 1 into orbit around the earth.
|STS 119 Crew, NASA|
The largest man-made satellite is the International SpaceStation. Construction was started on the ISS in 1998 and it is a joint mission of the nations of the United States, Russia, Japan, Canada and the EuropeanUnion.
Collisions between satellites are rare because when a satellite is launched, it is placed into an orbit designed to avoid other satellites.
There are many locations for satellite orbits including Low Earth Orbit, where you can find satellites like the International Space Station, and geosynchronous orbit, where the Solar Dynamics Observatory can be found.
There are approximately 100 so-called Iridium satellites which occasionally and predictably reflect sunlight very brightly off of their antennae arrays in a phenomenon called an Iridium Flare
Spot the Station- looking for the International Space Station.