Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


New star tracker for satellites

Small satellites are an exciting option for space projects because their launch costs are relatively low. Before using them for Earth observation or other tasks, however, there are still some technical challenges to be met.

This is what scientists of the University of Würzburg are currently concerned with.

Satellites are launched into orbit by means of carrier rockets. The larger and heavier they are, the more expensive the endeavor: "In case of really bulky satellites weighing several tons, the launch costs range from 50 to 150 million euros, depending on the launch rocket," says Professor Hakan Kayal of the Department of Computer Engineering at the University of Würzburg.

In contrast, the launch of a miniaturized one-kilogram satellite costs only about 40,000 euros. The Würzburg computer scientists have already gained some experience in working with satellites of this scale. The first specimen of the UWE (University of Würzburg Experimental Satellite) was launched into orbit in 2005; UWE-2 is to follow suit early in September.

"A particularly promising strategy is to let several miniaturized satellites cooperate as sensor networks," explains Professor Kayal. This means: The satellites are able to perform simultaneous measurements at different positions in the orbit - gathering much more detailed information than would be possible with only one large satellite.

Position control of the satellites in space

Collecting data on planet Earth, localizing orbital space debris or observing remote galaxies: All this and more could be implemented with a fleet of miniaturized satellites. For most of the applications, e.g. for Earth observation, a precisely defined orientation of the satellites is of the highest significance. Without active position control, a satellite would spin in space uncontrollably, for which zero gravity is to blame.

Star trackers evaluate star images

How can the position of a satellite be controlled in space? For this task, the satellite needs high-precision sensors to determine its current position. According to Professor Kayal, the most suitable devices for his purpose are so-called star trackers: They evaluate star images that they have previously captured with a camera. After recognizing a certain star pattern, they can autonomously process this information and clearly identify the orientation of the satellite.

In the next step, the satellite has to be pointed to the desired direction, e.g. through the interaction of small internal wheels. If one of the wheels turns, the satellite moves to the opposite direction under zero gravity conditions. "If you have at least one wheel per axis, you can turn the satellite to any spatial direction," says Hakan Kayal.

Objective: star tracker for miniaturized satellites

Most of the larger satellites already have star trackers in operation. Now, a star tracker for miniaturized satellites to be named STELLA, scheduled to be ready for launch within two years, is planned to be developed and manufactured at the University of Würzburg. Hakan Kayal's project is funded by the German Aerospace Center (DLR) with just under half a million euros. Two scientific assistants and four student assistants are allocated to take part in the project. Furthermore, some additional students are to be involved within the scope of a master's or bachelor's thesis. A new bachelor degree program in aerospace engineering will start at the University of Würzburg in the winter 2009/10.

"The new star tracker will considerably expand the applicability of pico- and nanosatellites," predicts the Würzburg professor. The established classification system defines pico- and nanosatellites as satellites with a weight between 0.1 and 1 kg (pico) or between 1 and 10 kg (nano).

Localization of space debris in orbit

In future, the Würzburg team wants to use the star tracker for research projects requiring on-board processing of image data. Autonomous destination planning of satellites or the localization of orbital space debris are examples of such projects.

The latter issue is considered to be urgent: According to Hakan Kayal, the risk of damage to satellites in orbit through space debris has significantly increased in recent years. At the same time, the dependence of people on the infrastructure in orbit for such purposes as communication, navigation or Earth observation has risen.

So far, there is no European system in existence for monitoring space events. Therefore, the European Space Agency (ESA) has just recently started a new program: It is envisioned to provide Europe with an independent capability to find all objects in orbit and to assess and avoid possible risks to the operation of its satellites. Professor Kayal wants to make his contribution to the implementation of this task.


Prof. Dr. Hakan Kayal, T +49 (0)931 - 31-86649,

Appointed in April 2008, Hakan Kayal is Professor for Spacecraft Control and System Design at the Department of Computer Engineering (Robotics and Telematics) of the University of Würzburg.

Robert Emmerich | idw
Further information:

More articles from Information Technology:

nachricht Fraunhofer FIT joins Facebook's Telecom Infra Project
25.10.2016 | Fraunhofer-Institut für Angewandte Informationstechnik FIT

nachricht Stanford researchers create new special-purpose computer that may someday save us billions
21.10.2016 | Stanford University

All articles from Information Technology >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Ice shelf vibrations cause unusual waves in Antarctic atmosphere

25.10.2016 | Earth Sciences

Fluorescent holography: Upending the world of biological imaging

25.10.2016 | Power and Electrical Engineering

Etching Microstructures with Lasers

25.10.2016 | Process Engineering

More VideoLinks >>>