Is it possible to see ship routes from space? Why does the stock market depend on data from space? How can satellites help to make climate change visible and how can space travel become more ecofriendly?
Putting satellites into orbit involves the same kinds of actions and ideas. First of all the satellite is placed on top of a huge rocket to carry it away from the Earth and up through the atmosphere. Once it is at the required height, sideways rocket thrusts of just the right strength are applied to send the satellite into orbit at the correct speed.
If the satellite is thrown
out too slowly it will fall to Earth because the centripetal pull of gravity is too great. If the satellite is thrown out too fast it will escape from the Earth’s orbit because the gravitational pull is not sufficient to provide the required centripetal force. With the correct launch speed
the satellite continues in its falling orbit around the Earth.
It is just a matter of setting the horizontal speed of the satellite such that the gravitational pull of the Earth (at the given height) tugs it round on its orbital path.
As the satellite is launched from the carrier rocket, a rocket thrust acts to throw it out in the desired direction at the prescribed speed. The crucial point to understand here is that the satellite speeds up only for as long as the rocket thrust is acting. Once the rocket motor is switched off the satellite continues at the final speed achieved, neither speeding up nor slowing down, and the gravitational pull of the Earth continuously tugs the satellite in and along its orbital path. In this sense, the satellite just keeps going itself
.
If the satellite was moving through empty space it would stay in its orbit forever, there being no forces acting to speed it up or to slow it down. In reality low orbit Earth satellites are not travelling through empty space and so experience a resistive force or drag
due to the thin
atmosphere which they encounter. In such circumstances, occasional rocket thrusts are needed to maintain the motion of the satellite, otherwise it will fall to Earth.
Today, thousands of satellites are currently orbiting in soace, maintaining high speeds—often over 17,000 mph—to balance Earth’s gravity and stay in orbit rather than falling back to Earth. They operate above the atmosphere to provide communication, weather, and GPS data, with some orbiting at low altitudes and others in higher, geostationary, or polar orbits.
For example, many areas of our everyday lives depend on data from space – such as a functioning infrastructure, banking, logistics, telecommunications and navigation – but climate change can also be made tangible and visible with the help of measurements and images from space.
Prof. Förstner also provided insights into current missions and topics in space research, which is taking place worldwide and at RC SPACE. He also presented the dtec.bw-funded SeRANIS project at UniBw M, a dedicated satellite mission of the researchers. Among other things, he explained to the attendees on site and to the viewers who followed the livestream from home which different entities and disciplines are involved in a satellite mission and how complex their interaction is.
As of May the 4th, 2025, the satellite tracking website “Orbiting Now” lists 12,149 active satellites in various Earth orbits. A deeper dive into numbers of satellite that are in space reveals how small satellites have come to dominate low Earth orbit (LEO).
In the three main categories of Earth orbits, small satellites dominate LEO while large satellites dominate geostationary orbit (GEO) and medium Earth orbit (MEO).
- GEO 9%
- MEO 2%
- LEO 88%
Low orbits are easier to reach and have certain advantages for small satellites. Radio signals take much less time to reach LEO than GEO. As a result, low-orbiting communications satellites can deliver higher-quality internet service. Being closer to Earth also lets satellites communicate with Industrial Internet of Things (IoT) devices despite these devices’ low-power radios.
Right now, there are nearly 6,000 satellites circling our tiny planet. About 60% of those are defunct satellites—space junk—and roughly 40% are operational.
As highlighted in the chart above, The Union of Concerned Scientists (UCS), determined that 2,666 operational satellites circled the globe in April of 2020.
Over the coming decade, it’s estimated by Euroconsult that 990 satellites will be launched every year. This means that by 2028, there could be 15,000 satellites in orbit.