NASA SIR-C/X-SAR Mission

## NASA SIR-C/X-SAR Mission

SIR-C/X-SAR is a joint project of the National Aeronautics and Space Administration (NASA), the German Space Agency (DARA) and the Italian Space Agency (ASI). It was flown aboard the space shuttle from 9 to 20 April 1994 and 30 Spetember to 11 October 1994.

The multifrequency, multipolarization Synthetic Aperture Radar (SAR) system allows measurement of radar backscattering signature of the Earth's surface from space, at three different frequencies (L, C and X-bands) and at different polarizations.

The SIR-C instrument is a two-frequency radar including L-band (23 cm wavelength) and C-band (6 cm wavelength) with four polarizations (HH, HV, VH, VV). The X-SAR instrument is a single-frequency radar with X-band (3 cm wavelength) and vertical polarization (VV).

SIR-C/X-SAR System Characteristics

PARAMETER | L-BAND | C-BAND | X-BAND
--- | --- | --- | ---
Wavelength | 0.235 m | 0.058 m | 0.031 m
Swath Width | 15 to 90 km | 15 to 90 km | 15 to 40 km
Pulse Length | 33.8, 16.9, 8.5 us | 33.8, 16.9, 8.5 us | 40 us
Data Rate | 90 Mbits/s | 90 Mbits/s | 45 Mbits/s
Data Format | 8,4 bits/word | 8,4 bits/word | 8,4 bits/word
| (8,4) BFPQ | (8,4) BFPQ | (8,4) BFPQ

BFPQ = Block Floating Point Quantization, a form of data compression from 8 bits per sample to 4 bits per sample.

System Parameters

Orbital Altitude | 225 km
Resolution | typically 30 x 30 m on the surface
Look Angle Range | 17 to 63 degrees from nadir
Bandwidth | 10, 20 and 40 MHz
Pulse Repetition Rate | 1395 to 1736 pulses per second
Total Science Data | 50 hours/channel/mission
Total Instrument Mass | 11,000 kg
DC Power Consumption | 3000 to 9000 W

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