Ab dem 30. Januar 2012 fand am Institut für Raumfahrtsysteme (IRS) eine dreitägige Schulung in der Systems Engineering Software Engineering Base der Firma Aucotec statt.

Inhalt der Schulung waren vor allem die Grundstruktur und –funktionen der Software an Beispielprojekten. Der Fokus lag dabei auf dem Cable Modul, das am IRS vorrangig für die Auslegung und Visualisierung des Harness des Flying Laptop und für zukünftige Satellitenprojekte genutzt werden wird.

Die in der Industrie, unter anderem bei EADS Astrium, international verbreitete Softwarelösung rund um das Thema Systems Engineering Engineering Base steht ab sofort allen Mitarbeitern und Studenten des IRS im hauseigenen CIP Pool zur Verfügung.

Wir bedanken uns an dieser Stelle nochmals rechtherzlich für die sehr gute und kompetente Einführung und das Entgegenkommen der Hersteller-Firma Aucotec, die uns die Software zu Campuskonditionen zur Verfügung stellt.

For the manufacturing of the main structure CFRP (carbon-fiber-reinforced plastic) components of the Flying Laptop an own production laboratory has been established.

Wie in Satellitenprojekten üblich, so müssen die einzelnen Komponenten der Flying Laptop vor dem Start einige Tests über sich ergehen lassen. Diese sollen sicherstellen, dass sie während des Transports ins All an Bord der Trägerrakete keine Beschädigungen davontragen und nach dem Absetzen des Satelliten auf seiner Umlaufbahn voll funktionstüchtig sind.

The Small Satellite Team at the IRS wishes Merry Christmas and a Happy New Year!

We would like to thank all our partners, students and everyone else involved and interested in the project for the support. We are happy to continue the collaboration in the year 2012.

During the last weeks, the engineering model of the Power Control and Distribution Unit (PCDU) was connected to the satellite simulation environment in the MDVE-Lab (Model Based Development and Verfification Environment) in order to test it using the complete commanding path.

In the third Quarter of 2011, we received the engineering and flight models (EMs and FMs) of the sun sensors for the small satellite Flying Laptop. The team's gratitute goes to Azur Space for sponsoring the GaAs-cells; to Qioptiq for the donation of the cover glasses for the solar cells and to the people of Astrium Ottobrunn, who kindly assembled the sun sensors.

The incoming inspection, at which the delivered parts are checked for transportation damage and other defects, was also cunducted succesfully.

As mentioned above, the core element of the sun sensors of the Flying Laptop are GaAs solar cells. The cells produce a current which is directly correlated to the power of the beam of light. The point of operation of the cells is defined by using two, in parallel load resistors. By applying Ohm's law and measuring the voltage drop across the well-known resistors it is possible to calculate the current of the solar cells. This measurement is done by the satellite's power control and distribution unit (PCDU). Subsequently, the information is routed to the on-board computer (OBC), where it is correlated to determine the direction of the sun relative to the satellite.

However, the correlation between the obtained measurements and the sun direction is more complex. This is because solar cells do not distiguish between different light sources. Additionally, under certain conditions the Earth reflects up to one-third of the sun's light power. Therefore, it is difficult to assess wether the sun sensor measures the light from the sun at an acute angle, or "sees" the reflected light from the earth directly.

Due to this signal distoration and for defining the accuracy of the Sun Sensor system a characterization of the cells has to be done. First, this includes a set-up for measuring the behavior of the solar cells at different temperatures. Due to the large temperature differences in space the open-circuit voltage varies greatly. This effect is problematic if the point of operation defined by the load resistors slips behind the maximum power point (the last point on the right side of the graph, before the current drops rapidly; compare last figure). Then, the correlation is not only dependent on the angle of incident but also on the temperature and becomes ambiguous.

Second, an experiemental measurement of the angles of incident, using a calibrated light source, is necessary. This shall verify that the correlation is mainly subject to the cosine law and that unknown effects at small angles (e.g. refraction in the cover glass, scattered light, ...) are negligible. Our thanks goes to the people of the Institute of Photovoltaik of the University of Stuttgart, who allowed us to use their solar simulator for the characterization

Dr.-Ing. Jens Eickhoff was appointed Honorary Professor of the University of Stuttgart at October 26th 2011. Professor Eickhoff from Astrium Satellites Friedrichshafen has been holding lectures at the University of Stuttgart for almost a decade now. At the moment he is publishing his second book on spacecraft technology. The Flying Laptop team is very glad about this appointment because Professor Eickhoff has been supporting the team in a lot of issues for the last years. The team wants to thank Professor Eickhoff for this support and for the outstanding cooperation. Thanks are also given to Professor Benz (see below) who is consultant for the development of the satellite, too. The good cooperation with both professors is an excellent example for associating industry with university. The team is looking forward to continuing this cooperation in future.

Dieses Semester wird erneut mit Studenten der Vertiefung Raumfahrtsysteme ein Kleinsatellitenprojekt durchgeführt, in dem in Gruppenarbeit Phase A Studien von Kleinsatellitenmissionen ausgearbeitet werden. Das diesjährige Kleinsatellitenprojekt erfolgt in Kooperation mit der Universität der Azoren.

Nach den guten Erfahrungen des ersten Kleinsatellitenprojekts, in dem 12 Studenten in Gruppenarbeit vier Kleinsatellitenmissionen zur Beobachtung von Waldrodungen auf Sumatra entworfen haben, wird auch dieses Semester im Rahmen der Vorlesung Kleinsatellitenentwurf II das Kleinsatellitenprojekt durchgeführt. In diesem Jahr stellt die wissenschaftliche Beobachtung der Azoren das primäre Missionsziel dar. Um den realen Bezug der zu entwerfenden Missionen zu schärfen, werden die Studien in Kooperation mit der Universität der Azoren erarbeitet. Die Forschungsschwerpunkte der ansässige Universität befinden sich auf dem Gebiet der wissenschaftlichen Anwendungen.