Instrument: Radar

The radar instrument is made up of three major subsystems: the RF electronics subsystem (RFES), the digital electronics subsystem (DES) and the antenna subsystem. Figure 1 below is a simplified instrument block diagram of the L-band radar. The RFES performs the transmit chirp generation, frequency up-conversion, filtering, and amplification during signal transmission. The RFES also controls the routing of the radar signal and the calibration signal.

The DES performs overall control and timing for the radar, frequency down-converts and digitizes the received echo, and routes the data to on-board data storage. The dual-channel digital receiver employs two high-speed analog-to-digital converters (ADCs) capable of handling down converted Lband signals. Filtering is performed by a combination of analog and digital filters implemented on field-programmable gate arrays (FPGAs). Radar data is recorded onto a 1.2 TB raid array along with associated metrology and radar telemetry information. The system includes the flexibility to operate both in interferometric and multi-frequency configurations even if the timing and bandwidth between the two frequencies are asynchronous.

Figure 1. UAVSAR Radar Block Diagram

Figure 1 (above), including aircraft real-time differential GPS and ground system interfaces, is shown. Color is used to code the various signal and control paths for the radar as indicated at the boot left of the figure. The Iridium communication system can be used to communicate with the radar and GPS systems while in flight. In particular, GPS satellite corrections can be loaded when the aircraft is out of range of the inmarsat-based correction system.