Nuri Al-Nakib 
  
  
Figure 1: AeS-1 flight segment Figure 2: Rockwell Turbine Commander with radar 
antenna construction 
The ground segment consists of a laptop computer for flight planning, the data transcription system, the SAR and 
interferometric SAR (InSAR) processing facility, the archiving management system, and a GPS ground station. The 
flight segment consists of the radar antennas, a transmitter/receiver, a clock generator, a control computer, a disk 
array unit for data recording, and a flight control system. 
Due to its compact design, the AeS-1 system can be installed on rather small aircrafts. During the projects 
mentioned, the system was installed in a Rockwell Aero Commander 685 and a Rockwell Turbine Commander. The 
AeS-1 is a fully automatic system. As the flight control unit offers a display where the real track and its deviation 
relative to the nominal one are indicated, the pilot simply has to follow the displayed tracks. No co-pilot or operator 
is necessary. More informations on the system AeS-1 are reported in (Schwábisch et al., 1999). 
In the following, an exemplary workflow during a mapping project is described: 
In the beginning of a project the area to be flown has to be determined and entered into the flight planning software. 
This typically is carried out by using conventional maps. Additionally, flight track coordinates and radar settings 
like resolution, flight altitude, and swath width are determined. This could be done either in the project area or in the 
office. Ground activities, which are mainly consisting of differential GPS survey, must also be planned before the 
data acquisition starts. Examples are the determination of positions of corner reflectors and DGPS-transmitting 
ground stations. Corner reflectors appear in radar images as bright spots and are used as ground control points. 
Aluminium made corner reflectors with their smooth surface and triangular form are strongly reflecting radar 
signals. 
The pilot is guided during the flight by the automatic flight guidance system, which consists of a display in the 
aircraft's front desk and an online kinematic DGPS receiver. The DGPS receiver is coupled with an inertial 
navigation system (INS). The real time correction signal is transmitted during the flight from a GPS ground station, 
which is normally positioned on a base point with known coordinates nearby the project area. Additionally, the GPS 
ground stations are used for differential GPS ground survey of corner reflector and transmitting point positions. 
During the flight, the SAR raw data is stored on board on hard disk arrays with a capacity of 432 Gbyte. It is 
possible and usual to change the hard disks during an acquisition flight. With a maximum recording data rate of 32 
Mbyte/s a total acquisition time of nearly 4 hours can be realized. After landing, the recorded data is transcribed to 
Digital Linear Tapes (DLT's) with 35 Gbytes storage capacity. Also, ground station and aircraft GPS data, as well 
as the INS data are offline processed to the motion compensation data. Later, this motion compensation data is 
synchronized with the radar raw data. 
In mapping projects in Indonesia, Brazil and Venezuela it was very common to perform two flights a day. This 
means, that the process of data acquisition, data transcription and GPS processing must be optimized in relation to 
the computing facilities in order to guarantee a high operational performance. 
After the SAR raw data and motion compensation data transcription, the data has to pass through a chain of 
processing procedures, which are namely SAR processing, interferometric processing, phase filtering, absolute 
phase estimation, geocoding and mosaicking. The processing chain is devided into the processing and 
postprocessing part: In the processing part, the raw data is processed to a visible SAR image with a defined 
geometric resolution. The interferometric processing provides the height information for the same area. The 
postprocessing includes the process of geocoding, which is done by using the interferometric height, the motion 
  
20 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part Bl. Amsterdam 2000. 
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