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Satellites

The first weather satellite

In 1958, NASA received the order to build a weather satellite. Tiros I was the end product of two years of development work. The pioneer had the shape of a cylinder and, with a diameter of approximately one meter and a height of 0.5 meters, was small and light compared to today's satellites.

No matter whether it's a bike tour, gardening or beer garden - many of us don't take a step outside without having the weather in sight first. This has only become possible thanks to weather satellites. Satellite meteorology has become an indispensable part of modern weather forecasting. Since its beginnings in the early 1960s, it has developed rapidly and today provides much more than just photos or the cloud films known from news broadcasts.

Next generation satellite networks

Global networking, digitalization and constantly growing data volumes - the importance of communication systems has increased rapidly. The expansion of satellite networks will form the basis for our communication systems of tomorrow. The traditional main areas of application for satellites are weather satellites and radio and television satellites. In the field of telecommunications, satellites are used as a means of communication to hard-to-reach areas, for global mobile communications and for location-based services such as traffic information and navigation. A satellite system consists of at least one satellite and one ground station. A satellite receives a weak ground signal, amplifies it and sends this signal back to earth.  

A distinction is made between systems with geostationary satellites and satellites that change position. A geostationary satellite is an artificial earth satellite that is located about 36,000 km above the earth's surface in a so-called geostationary orbit. The satellites move at a speed of one revolution of the earth per day and thus at the same angular velocity as the observer on earth. It therefore seems to stand still. The geostationary satellite is of technical relevance primarily for communications and television satellites. Once the domestic SAT antenna has been aligned, it thus delivers television pictures without continuous readjustment.

Already in the late 1970s, satellites were used for communication over long distances, but the transmitting and receiving equipment was stationary. In the late 1980s, Canada used satellite telephones for the first time to provide telecommunications to sparsely populated areas without having to provide the necessary infrastructure. The satellites used were located at geostationary positions (GEO).

Next Generation Platform (Neosat)

The Next Generation Platform (Neosat) programme of the European Space Agency ESA is developing next-generation satellite platforms. An elementary component in the use of state-of-the-art satellite technology is the parallel development of mechanisms suitable for space travel. Space travelers speak of basic functions such as:

  • Deployment (extending solar panels, for example),
  • Pointing (positioning of antennas)
  • Solar Arrays (tracking the solar panels to the sun)
  • Thruster Pointing (positioning of the thrusters of the satellite)

Within Neosat, Harmonic Drive® gears are used in these applications. What they all have in common is the customer-specific adaptation to the special environmental conditions and design requirements of the customer. Various design factors are decisive for our market position in the field of precision gear technology for ESA missions. Weight, hollow shaft diameter, stiffness and reverse torque are, among other factors, design features when selecting the appropriate gear unit. One of the greatest influences in the selection of gear and lubricant is the required service life. This varies greatly depending on the application and is determined by the specified lifetime of the satellite.

The service life of the satellite is largely determined by the internal fuel reserves for position control. After a service life of approx. 10-15 years, these reserves are usually used up. In addition, the technology of the satellite is already well advanced at this time. The Spanish company SENER Group has developed a complete family of rotary actuators for space applications in a co-financed program with ESA. For Neosat, SENER was commissioned with the series production of the DTA rotary actuator.

The DTA family is characterized by a high detent torque, hence the name "Detent torque actuators". All DTA products are based on a modular design, which enables the rapid development of new variants with a short time-to-market. The mechanisms are available with a range of electric motors, sensors and accessories. The Harmonic Drive® gear was originally developed for aerospace applications. The high single-stage reduction ratio, compact design and low weight are key advantages of the Harmonic Drive® gearhead for use in numerous satellite actuators. For the DTA rotary actuator, a Harmonic Drive® installation kit of the CPL-2A series with high reduction ratio is used.

The CPL-2A series mounting kits are available in five sizes with reduction ratios of 50, 80, 100, 120 and 160 with a repeatable peak torque between 18 and 372 Nm and a power density of 340 to 735 Nm/kg and offer lowest mass moments of inertia. The CPL-2A series is extremely light due to the restriction of components to the essentials, reduced cross sections and optimised hole patterns. The large hollow shaft allows the feed-through of supply lines, shafts and cables for further drive systems. Due to the positioning accuracy, stable machine characteristics with short cycle times are guaranteed.

The mounting kit used is integrated in a lightweight housing and is driven by a kit motor. The gearbox has a Solid Wave Generator; the Flexspline is connected to the output flange, which is supported by thin-section ball bearings. The Circular Spline has been modified to allow easy installation in the housing. The CPL-2A series mounting kit is made of stainless steel and uses grease lubrication suitable for use in space.