Satellites: Versatile orbital helpers
Thousands of satellites orbit around the earth to make people’s lives easier, with an astonishing range of potential applications backed by equally impressive technologies.
© Wolfram Schroll
When the Soviet Union launched Sputnik 1, the first ever satellite, into space on 4 October 1957 from its launch pad in Baikonur, the western world and the USA was left speechless. “Sputnik shock syndrome” was the watchword as this small metal ball, weighing less than 100 kilos, tirelessly made its way around the globe, transmitting a beeping signal as it did so. After around three months and 1,400 orbits later, the satellite burned up in the atmosphere, but its existence marked the beginning of an ambitious competition between the Soviet Union and the USA for supremacy in space – as well as the birth of modern satellite technologies.
Satellites are becoming increasingly compact, offering greater performance at a lighter weight, yet their complexity is increasing at the same time. They help people with many aspects of their daily lives, from navigation through to transmitting internet and TV signals. Most satellites derive their energy from solar cells, with phases spent in darkness being powered by backup batteries.
As at 2017, a total of 4,635 satellites were orbiting the globe at different heights, each in its own individual orbit. These orbits are based on precisely defined speeds so that they cannot fall back to earth. Geostationary orbits are unusual in this respect: satellites are positioned approximately 36,000 kilometres above a fixed point on the earth. These orbits are used in applications such as telecoms satellites: for instance, to aenable a satellite dish to be pointed in a particular direction.
Navigation: accuracy thanks to satellites
Navigation is one of the most important everyday applications for satellites. The best-known system is the Global Positioning System (officially known as Navstar GPS), which is operated by the US military. The first GPS satellite was launched in 1978, and the system has been fully operational since 1973, now allowing accuracy to within a few metres. The system is based on a total of 24 satellites, which are positioned in a number of orbits, 20,200 kilometres above the earth’s service and, in simple terms, allow a position on earth to be determined by measuring high-accuracy signals from at least three satellites. As well as the Americans, other nations have built their own navigational satellite systems or are in the process of doing so: Russia has GLONASS, the EU has Galileo and China has Beidou.
exact positioning by navigation satellite
The main beneficiary of GPS is the aviation sector: hardly any planes now take off without satellite navigations, whether that involves the high-end avionics of a jet or an iPad in an ultralight leisure aircraft. As a consequence, however, more and more ground-based navigational installations are being switched off in favour of GPS navigation. GPS-based approaches have long been possible under instrument flight rules, provided that the appropriate corrective technologies are in place. In the case of ADS-B (Automatic Dependent Surveillance - Broadcast), which must be installed in all aircraft in the USA by 2020, the transponder signal is complemented by position data with the aim of preventing collisions in densely-packed airspace. Meanwhile, GPS has become an essential tool for motorists, shipping lines, and many other aspects of life.
The internet comes from space
Telecommunications satellites are also ubiquitous in the worlds of aviation and shipping. While satellite connections are still relatively slow and expensive, they expand the reach of the internet into aircraft and ships that are far removed from civilisation. Anyone who goes online from an airliner to stay in touch with the world will do so using a satellite connection – even if it is supported by a ground station. One of the best known providers of satellite internet is the American company, Iridium Communications.
Data about storms, clouds and other meteorological phenomena can be accessed at any time using a smartphone or a home PC. This is possible thanks to the permanent presence of weather satellites such as Meteosat, which is operated by the European EUMETSAT organisation. These also make it possible to carry out long-term climate observations as well as to make local forecasts.
progress and networking through satellite communication
The list of applications for satellites is virtually endless. Some satellites perform spying duties and have taken on the role formerly performed by spy planes. Others are used for research purposes – ESA’s GOCE research satellite was able to provide a detailed elevation profile of the earth. Other satellites keep a watchful eye over the earth to protect against natural disasters, and the European Space Agency, ESA, is building the Copernicus system for this purpose. The Frankfurter Rundschau wrote: “Sentinel satellites are at the heart of the Copernicus programme. They work with a radar technology that provides much more accurate imagery than was possible with previous satellites.” The next satellite launch is not planned until June of next year.
One of the more unusual applications is the use of satellites to control energy supplies. Wind turbines and solar farms can be controlled globally from a central point, while water and gas pipelines can also be controller by their operators in the same way. This is all made possible via a solution provided by German companies.
A new generation of electrically powered satellites
The trend is for satellites to become smaller and lighter all the time, which is unsurprising in view of the high costs of transporting a payload into space. A research contest in 2017 showed exactly how small a satellite can become: then 18-year-old Rifath Shaarook from India used a 3D printer to develop a miniature satellite that weighed just 64g, which was launched into space by NASA.
One way to save weight in larger satellites is to use a built-in electric power unit. Satellites generally have a chemical power unit on board to allow them to correct course, but engineers are using electrical ion power for the latest generation of satellites. Europeans are at the forefront of this movement. By way of example, the Eutelsat 72B telecommunications satellite is able to reduce its weight to “only” 3.5 tonnes – which is still two tonnes less than it would have weighed with a traditional power unit. The energy that is required is provided by on-board solar cells.
The scientists are already working on new and more efficient processes in the initial phase. To minimize the enormous drag in the lower atmosphere, for example, a rocket is not launched from the very beginning. Bloostar is a concept in which the actual rocket with a balloon is brought to approx. 22,000m before the ignition takes place.
the new generation of space launches
The dark side: space debris
Aviation and space travel have long been responsible for extensive traffic levels around our planet. The German Space Centre (DLR) has taken up the cause of coordinating this traffic via its Space Traffic Management concept for integrated space and air traffic control.
However, another type of traffic cannot be controlled so easily. Over the course of several decades, people have left behind a large quantity of debris in space: the remains of spent rocket boosters, obsolete satellites and other trash speed through space like bullets and will continue their orbits for a long time to come. It is estimated that around 6,500 tonnes of cosmic waste are circling the earth – with constant collisions leaving behind new, smaller but no less destructive pieces of debris that not only endanger satellites, but also threaten manned space flight as well.