Gain nonlinearity calibration of the SMILES receiver

The Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) was launched in September 2009 and has successfully observed the stratosphere for half a year. Before launch we measured the receiver gain nonlinearity. The gain compression of the SMILES receiver is estimated to be 2.6 to 4.3% from the measurement. The nonlinearity correction is applied to the observed data in space. Data are satisfactory corrected in the stratosphere but not in the higher altitude. The reason of the unsuccessful correction is discussed and attributed to our overestimation of the broadband nonlinearity.