How many satellites are flying above us?

Mr. Nicholas Johnson, a former industry leader in the orbit of orbital debris of NASA, talks about artificial satellites flying in orbit.

1. How many satellites?

Currently, there are about 1100 artificial satellites working on Earth's orbit, including satellites from governments as well as private companies. There are also about 2600 satellites that are no longer working but are still flying above us. The first satellite in the world was Sputnik 1 , launched by the Soviet Union in 1957. The oldest ' satellite ' still orbiting Earth was launched in 1958, but it no longer works.

2. The size of the satellites

The satellites have different sizes. The Federal Communications Commission says the satellite can be as big as a small bus, weighing up to 6 tons. Most satellites weigh several tons or less. Some short-lived satellites are only more than 10 centimeters in size and weigh 0.99 kilograms (4 inches cubes, 2 pounds).

Depending on the effect, each satellite has a different position.

3. The use of satellites

Satellites have different uses. GPS satellites (Global Positioning System) help guide the way. Some satellites relay phone or television signals. Some are used to forecast the weather, serve national defense, scientific and agricultural research, for example monitoring crops and drought-stricken areas. The Union of Concerned Scientists (Union of Concerned Scientists) says 60% of satellites are used for communications.

4. Location of satellites

This depends on the effect of the satellite . Information satellites stand at a fixed position about 35,400km (22,000 miles) above the equatorial sky to relay the signal. GPS satellites are at least 20 thousand kilometers (12,400 miles) above the ground, at that height it is enough to cover a large area of ​​the Earth. For comparison, we know the International Space Station is about 400km (260 miles) from the ground. Very few satellites fly at lower altitudes than ISS. Some satellites are in a fixed position, but some satellites fly over the poles of the Earth, or as they need to fly from place to place.

5. The effect of satellites

A British communications satellite has picked up the signal of the mysterious missing MH370 flight, the signal analysis has helped authorities come to the conclusion that the plane crashed in a remote area of ​​the southern Indian Ocean. This week the Thai government said one of its satellites found 300 objects that could be debris from the plane. Some satellites have been moved to a position where they can be observed.

6. Whose satellites are there?

Governments and private companies. According to UCS, more than 50 countries have satellites or share satellites with other countries. The US currently has 502 satellites, Russia has 118, China has 116. Thailand has 4 satellites and shares one satellite with another country.

7. What if the satellites stop working?

Retired satellites can collide with active satellites, so there are rules and recommendations to avoid increasing space junk. For example, suggest that satellites flying below a certain height should be put into a guaranteed orbit within 25 years that they will fall to Earth and be burned. With satellites flying at higher altitudes, the proposal is to push them into higher orbit to make way for other satellites.