Applied Geomagnetics for Attitude Determination Experiment (AGADE)

Paper number

IAC-09.E2.1.7

Author

Mr. Sebastian M. Ernst, Germany

Year

2009

Abstract

The Applied Geomagnetics for Attitude Determination Experiment (AGADE) aims
for analysing and comparing a set of different commercial of-the-shelf small 3-axis
magnetometer assemblies as well as data analysis methods. The COTS magnetometers
are launched together with a high precision magnetometer on-board a ballistic rocket.
After the the flight, the resulting data is being used for evaluating ideas of advanced onboard
magnetic field data analysis software, which could be used in pico satellites'
attitude determination systems as well as in an experimental orbit determination
system based on pattern recognition algorithms.
The experiment's proposal was submitted to the German Aerospace Center (DLR)
within the REXUS programme on January 6th 2008. In the end of April 2008 the
experiment was finally chosen to fly on-board REXUS 6, which was launched on
March 12th 2009. A detailed report is expected to be released by the end of June 2009.
Finally, the experiment's set-up was developed by about nine students from the
Freiberg University of Mining and Technology (TU Bergakademie Freiberg) and the
Dresden University of Technology (TU Dresden) studying Geophysics, Electronics
Engineering, Computer Science, Mechanical Engineering and Aerospace Engineering.

My field of interest

With the decreasing size of electrical devices and computers over the past years it has
become possible to decrease the size of satellites as well. The standard allowing the
smallest satellites is currently the cubesat standard with a limited mass of only one
kilogram. This development caused the need for smaller ADSs. One possibility to
determine a spacecraft's attitude is to use a known magnetic field such as the earth's one
together with a reference model of it and to compare the determined field's orientation
with the reference model's.
Magnetometers are a typical payload for scientific satellites. If research is conduct on a
celestial body its magnetic field is interesting almost every time. But in these cases the
magnetometers are the payload itself or part if it. Compared to an ADS, the major
difference is that a payload has an higher priority, its low mass is not as important as it
is for subsystems around just fulfilling their basic tasks. Here the very small
magnetometers become a topic of interest. If their results would be good enough it
would be possible to build simple, small and lightweight ADSs. In fact this idea is not
new and these days such small magnetometers are in use on a couple of small satellites,
some of them build according to the cubesat standard. To the best of my knowledge
the only reliable, freely available studies about these sensors' accuracy and behaviour in
space are results of computer based simulations. In most cases an accuracy of 5 to 10
degree for attitude determination was reported for such sensors.
Traditionally, the IGRF is simply used as a reference for this kind of measurements.
An analysis of influences disturbing the measurements is sometimes not even
considered. So, as a student of Geophysics, I found some kind of a vacant topic by
applying knowledge from traditional exploration Geophysics, when I joined STARD.
It is working on the SOMP cubesat. Later, my work on its ADS basically led me to the
formation of the AGAD experiment.
In case of AGADE I am working on data analysis, which means an detailed local
magnetic field model of the rocket's flight path as well as an detailed model of the field
disturbances caused by the rocket and its components. This analysis should lead to an
conclusion of how far it is possible to go with such types of ADSs if there would be a
much better reference.
A further idea is to use the magnetic field sensors already included in ADCs to
determine a satellite's orbit. This is possible due to the specific shape of the earth's
magnetic field. First simulations have shown, that this idea basically works – based on
data collected over one low earth orbit – using some kind of pattern recognition and
the IGRF as a reference. I am planing to conduct further research on this issue by using
the gained knowledge of the sensor's data's characteristics.

Abstract document

IAC-09.E2.1.7.pdf

Manuscript document

IAC-09.E2.1.7.pdf (🔒 authorized access only).

To get the manuscript, please contact IAF Secretariat.