SAR Instrument

The C-SAR instrument is designed and developed by EADS Astrium GmbH of Germany. The instrument provides an all-weather, day and night imaging capability to capture measurement data at high and medium resolutions for land, coastal zones and ice observations.



The C-SAR instrument is an active phased array antenna providing fast scanning in elevation (to cover the large range of incidence angle and to support ScanSAR operation) and in azimuth (to allow use of TOPS technique to meet the required image performance). To meet the polarisation requirements, it has dual channel transmit and receive modules and H/V-polarised pairs of slotted waveguides.

It has an internal calibration scheme, where transmit signals are routed into the receiver to allow monitoring of amplitude/phase to facilitate high radiometric stability.

SENTINEL-1's metallised carbon-fibre-reinforced-plastic radiating waveguides ensure good radiometric stability even though these elements are not covered by the internal calibration scheme. The digital chirp generator and selectable receive filter bandwidths allow efficient use of on-board storage considering the ground range resolution dependence on incidence angle.

The key parameters of the SENTINEL-1 C-SAR instrument include:
Centre frequency 5.405 GHz (corresponding to a wavelength of ~5.5465763cm cm)
Bandwidth 0-100 MHz (programmable)
Polarisation HH+HV, VV+VH, VV, HH
Incidence angle range 20°- 46°
Look direction right
Antenna type Slotted waveguide radiators
Antenna size 12.3 m x 0.821 m
Antenna mass 880 kg (representing 40% of the total launch mass)
Azimuth beam width 0.23°
Azimuth beam steering range -0.9° to +0.9°
Elevation beam width 3.43°
Elevation beam steering range -13.0° to +12.3°
RF Peak power - 4.368 kW, - 4.075 kW (IW, dual polarisations)
Pulse width 5-100 µs (programmable)
Transmit duty cycle Max 12%, SM 8.5%, IW 9%, EW 5%, WV 0.8%
Receiver noise figure at module input 3 dB
Maximum range bandwidth 100 MHz
PRF (Pulse Repetition Frequency) 1 000 - 3 000 Hz (programmable)
Data compression FDBAQ (Flexible Dynamic Block Adaptive Quantization)
ADC sampling frequency 300 MHz (real sampling)
Data quantisation 10 bit
Total instrument mass (including antenna) 945 kg
Attitude steering Zero-Doppler steering and roll steering



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