“Africa and remote sensing are not for sissies”

South African Synthetic Aperture Radar II


SASAR II description

The SASAR II system, although complex in design has been developed to reduce the amount of work for the end user. A “System Controller (SysCon)” (high end PC with 64 bit bus) forms the center of the entire system, giving the user control over the radar via a “Radar Controller Unit (RCU)”. The SysCon interfaces with the  RCU through UDP commands over an Ethernet connection. Communication is possible in both directions, with the user receiving diagnostic information about the status of each sub-system, as well as providing control signals to each sub-system.












Block diagram of SASAR II


The SASAR II system is broken down into 10 sub-systems, namely:

1. System Controller (SysCon): User controlled PC that interfaces with the RCU over an Ethernet connection to control the Radar Unit.

2. The Radar Frequency Unit (RFU): This comprises the Transmitter, Receiver and the Antenna unit.

3. The Radar Digital Unit (RDU): This unit is comprised of the Digital Pulse Generator (DPG), Sampling Unit (SU) and the Timing Unit (TU)

4. The Frequency Distribution Unit (FDU): This produces the clocks and local oscillators that drive the system.

5. The Radar Controller Unit (RCU): Forms the “nervous” system for the Unit, providing the control signals and system diagnostics.

6. Navigation Unit (NAV): Provides the system with time and position information.

7. Data Storage Unit (DSU): Sampled data and time information is written to large disk array.

8. Power Supply unit (PSU): Supplies power to all relevant sub-systems.

9. Ground segment: Post processing on raw data is done here.

10. Radar Platform: In this case a twin propeller Aero Commander A90.

The SAR image covers the Antarctic Peninsula, which extends for 1000 km south to north and is situated between the Bellingshausen Sea to the west and the Weddell Sea to the east.

This is a region that has experienced exceptional atmospheric warming since the 1950s and is therefore of key interest for global change research. Over the last 50 years an average temperature increase of 2.5°C has been observed at the climate stations on the Peninsula. This has triggered the retreat and break-up of several ice shelves, culminating in the collapse of the two northern parts of the Larsen Ice Shelf in January 1995 (Larsen A) and in March 2002 (Larsen B). The launch of Envisat on 1 March 2002 occurred just in time to capture the dramatic break-up of Larsen B.