5. CONCLUSION 
The objectives of this short paper have been to show that a relatively simple 
version of a bistatic radar system comprising an airborne real aperture radar 
receiver operating with the unavoidable ground reflections of geostationary 
communications satellite downlinks is capable to achieve a satisfactory system 
performance. 
There are several system options under discussion comprising for example a 
mechanically steered or even fixed pointed antenna. The latter results in a 
simple 1 pixel system, where the swathwidth is provided by several parallel 
flights and the signal to noise ratio is improved by 16 dB due to a longer 
integration time per look. 
Another system option is the leasing of one of the satellite transponders 
during BIPAR operations and the transmission of a cooperatively modulated com- 
munications signal. This could reject the need for the reference signal chain 
within the BIPAR receiver because the structure of the received signal is well 
known. 
Last but not least, arrival time separation (range gating) and synthetic 
aperture principles (doppler gating) could be applied in order to improve the 
system performance once again. 
All these options are up to further investigations and their viabilities are 
primarily driven by user requirements and available financial budgets. 
Compared to classical monostatic and bistatic radars, it can be concluded that 
BIPAR systems have the following advantages: 
- Low power consumption 
- High operational flexibility 
- Quiet and secret systems 
-uLowicost. 
BIPAR systems are typically not optimized with respect to radar applications, 
but they could provide a good compromise between user requirements, their need 
for a high amount of data, and funds available. BIPARs cannot replace large 
operational airborne and spaceborne radar systems, but in many cases they can 
support the scientific research, if no operational system was available. 
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