AltiKa, a dual-frequency radiometer

The radiometer onboard Saral is included in the AltiKa instrument since it shares the same antenna. It operates in dual-frequency (23.8 and 37 GHz) to correct altimetry measurements from wet troposphere crossing effects.

The AltiKa radiometer operates in dual-frequency channel microwave radiometer:

  • 23.8 GHz+/- 200 MHz: Brightness temperature measurements give information related to the water vapor content.
  • 37 GHz +/- 500 MHz: Brightness temperature measurements give information about cloud liquid water.

Both Brightness temperatures, in addition to the altimeter estimated backscatter coefficient σ0, are applied to calculate the troposphere correction range.

The radiometer must be swiffed- off during radar altimeter emission.

AltiKa radiometer architecture. Credits Cnes.

Characteristics

Radiometer band 23.8 GHz +/- 200 MHz - 37 GHz +/- 500 MHz
Radiometric sensitivity < 0.3 K
Radiometric Bias < 1 K
Radiometric averaging 200 ms