Wim van Rossum 
  
THE PHARUS SYSTEM; AN OVERVIEW AND RECENT DEVELOPMENTS 
Wim van ROSSUM, Matern OTTEN, Arthur SMITH, Jos GROOT 
TNO-Physics and Electronics Laboratory, The Netherlands 
Radar Concepts and Signal processing 
Rossum(@fel.tno.nl 
Otten@fel.tno.nl 
A.J.E.Smith@fel.tno.nl 
Groot@fel.tno.ni 
  
KEY WORDS: SAR, Interferometry, MTI, Spotlight 
ABSTRACT 
The PHARUS system is a fully polarimetric C-band SAR with an active phased array antenna. PHARUS is an 
experimental system. It is meant for remote sensing research in many application areas, both civil and military, 
maritime and on land. The system performed its first test flight in 1995. In the following years a large amount of data 
was acquired. In the standard mode the resolution in both range and azimuth is about 3 m. The capability of PHARUS 
to obtain fully polarimetric images with a high resolution is extensively used. 
More advanced SAR applications require both high resolution and the flexibility that is offered only by phased array 
SAR systems. The PHARUS system, since it has an active array, which is fully programmable in its operating modes, 
allows investigations of these applications. Advanced SAR modes that are being investigated are: (sliding) spotlight 
SAR and interferometric SAR, both along track (Moving Target Indication) and across track (Repeat Pass 
Interferometry). The flight experiments are carried out in co-operation with the National Aerospace Laboratory. 
In this paper the status of the different new processing techniques is reported. These new techniques include doubling of 
the range resolution, increasing the azimuth resolution through spotlight processing, Displaced Phase Center Antenna 
MTI and Repeat Pass Interferometry. Also the use of PHARUS as a test bed for the ASAR modes of the ENVISAT 
satellite is shown. 
I INTRODUCTION AND OVERVIEW 
The PHARUS (PHased ARray Universal SAR) system is a fully polarimetric C-band Synthetic Aperture Radar (SAR) 
with an active phased array antenna. The system has been developed by the TNO Physics and Electronics Laboratory 
(TNO-FEL) in co-operation with the National Aerospace Laboratory (NLR) and the Delft University of Technology 
(DUT). The project is carried out with financial contributions from the Ministry of Defense and the Netherlands 
Remote Sensing Board (BCRS). PHARUS is an experimental system. It is meant for remote sensing research in many 
application areas, both civil and military, maritime and on land. It is an airborne system, flown with a Cessna Citation II 
aircraft. The system performed its first test flight in 1995. 
In the following years a large amount of data was acquired. In the standard mode the resolution in both range and 
azimuth is about 3 m. In Figure | an example of a high resolution SAR image is shown. The colors represent the 
different polarimetric channels. PHARUS is a fully polarimetric system, it can alternately transmit horizontal (H) and 
vertical (V) polarized beams while receiving simultaneously horizontal and vertical polarized signals. The intensity of 
the four channels HH, HV, VH and VV (the first letter signifies the polarization of the received signals, the second the 
polarization of the transmitted beam) are then represented in the following way: HH by red, HV+VH by green and VV 
by blue. 
  
340 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part Bl. Amsterdam 2000. 
  
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