Improved Attitude Control Sensors for a High Performance Navigation System of the Micro-Satellite Flying Laptop
- Paper number
IAC-06-E2.3.02
- Author
Mr. Dominik Saile, University of Stuttgart, Germany
- Coauthor
Mr. Georg Grillmayer, University of Stuttgart, Germany
- Coauthor
Mr. Christian Waidmann, University of Stuttgart, Germany
- Coauthor
Mr. Matthias Waidmann, University of Stuttgart, Germany
- Coauthor
Mrs. Viola Wolter, Steinbeis Transferzentrum Raumfahrt, Germany
- Year
2006
- Abstract
The Institute of Space Systems (IRS) at the University of Stuttgart is in the implementation phase of its first micro-satellite Flying Laptop. The Flying Laptop is developed and built by faculty, PhD/master students and in cooperation with the industry. This paper provides an outline of the used attitude control sensors and actuators. Several new developments have been initiated and will be flown for the first time.
The GENIUS GPS system is an experiment in cooperation with the DLR/GSOC for accurate determination of the spacecraft attitude from GPS measurements. Three separate antennas in an L-shape arrangement are used. By synchronizing the reference oscillators of the three Phoenix GPS receivers to a single ultra stable source the accuracy can be increased leading to real-time position, velocity and timing information with envisaged accuracies of 10 m, 0.1 m/s and 1 µs. For the measurement of the satellite’s rotational rates the upgraded more accurate COTS fiber optic rate sensor "C-FORS" is used. The developed unit consists of the electronics for power supply and communication and the mechanical structure for compact mounting and additional radiation shielding of the four rate sensors arranged in a tetrahedron configuration. The star tracker Micro Advanced Stellar Compass (µASC) from the Technical University of Denmark is a further miniaturized development of the previous version providing an increased accuracy down to a few arcseconds. The µASC is equipped with two optical heads that are oriented such that simultaneous blinding or occultation by the Earth and Sun is avoided. A newly developed, low-power, digital magnetometer using a magneto-resistive sensor is used.
The on-board computer consists of a Field Programmable Gate Array (FPGA) based on a Xilinx Vertex II-Pro. The communication with the sensors and actuators is currently being tested on a simpler Spartan IIE development board. By using the Celoxica Handel-C language fast and effective implementation of complex algorithms for the FPGA can be achieved through programming in a high level language. The advantage of the FPGA over a micro-processor is already noticeable during performance tests of the engineering models. The parallel structure of a FPGA allows to exploit the limits of the sensors and actuators in order to achieve a high precision navigation system so far not possible for university built micro-satellites.
The paper is to be presented orally and includes a hardware demonstration.
- Abstract document