detection and adaptive speckle filtering [Madsen,1986], [Madsen,1987].This study also 
resulted in the development of digital off-line processors for both the airborne SAR-580 
system and the SEASAT satellite SAR system. Since 1984 the Institute has also conducted a 
number of studies of the feasibility of using SAR for scientific and commercial sea ice 
mapping [Skriver et al.,1986]. 
The project that will be described in this paper was officially commenced in January 1986. 
Its title is Coherent Radar Techniques and Advanced Signai Processing ( KRAS). The for- 
mal goal of the project is to establish a Danish research group with a solid knowledge base 
within the field of advanced coherent radar technology and high speed digital electronics. 
The concrete goal is to fly an experimental high resolution airborne C-band SAR in 1989. 
However, the system holds so much flexibility, that it can accommodate more general ex- 
periments with coherent radars. Flexibility is given high priority in the design. It is expected, 
that the applications of the system will span from geophysical science, which require wide 
swath but only medium resolution, to mapping experiments that calls for the hi ghest 
achievable resolution. It is also considered important, that the radiometric fidelity of the 
images is the highest achievable. Hence, special attention has been given to build in 
calibration loops in the radar and to some extent radiometer design techniques has been used 
to obtain the best possible component stability. 
II THE KRAS SAR SYSTEM 
The radar is a single frequency system operating at 5.3 GHz. It is designed to obtain a 
resolution down to 2 m by 2 m. The maximum range of the system is 80 km and the swath 
width is between 10 and 50 km depending on the resolution. Both maximum range and 
swath width are prepared for later upgrading. It is expected that the initial experiments will 
involve an installation on a Gulfstream G-3 aircraft from the Royal Danish Air Force. 
The KRAS system parameters are listed in Table 1 and the system block diagram is shown in 
figure 1. 
  
  
Frequency: 5.3 GHz 
Transmitter peak power: 2kW 
Receiver noise figure: 2.5 dB 
Total system losses ( estimated): 3 dB 
Pulse length: from 0.64 to 20 jus 
Maximum bandwidth: 100 MHz 
Antenna gain: 27 dB 
azimuth beamwidth: 2.72 
elevation pattern: 20? section of cosec sqr. pattern 
polarization: VV 
Resolution range: Variable 2, 4, 8 m 
azimuth: Variable 2, 4, 8 m 
Slant range mapping width: Variable 9.3, 21.6, 46.2 km 
Range: 80 km 
  
Table 1: KRAS system parameters 
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