Sparse Array Antenna Concepts for Spaceborne SAR Applications: An Assessment of Synthesis Methods for Very Large Active Electronically Scanned Antenna Arrays

Antenna design for Ka-band SAR systems used in earth observation missions is demanding for two reasons. A narrow beamshape results in a large aperture, and the frequency band dictates a short spacing between neighboring radiating elements. In our case, this leads to a requirement of more than a million radiating elements. In this thesis it is...

Impact of non-gravitational forces on GPS-based precise orbit determination of low Earth orbiters

The modelling of non-gravitational forces acting on a satellite (especially a GNSS satellite) started half a century ago. Their modelling to low Earth orbiters (LEOs), however, are more recent because of the dominating atmospheric drag, the modelling of which requires the precision of recent atmospheric models. However, this is not an issue for...