Ozone mapper profiler suite early orbit linearity performance evaluation

The linearity of the Ozone Mapping and Profiler Suite Nadir instruments´ radiometric response is characterized using two onboard LED calibrators with a series of lamp exposures of various times and therefore varying count levels. It is specified that the non-linearity of the nadir sensors shall be no more than 2% of full well, the linear degradation rate of the LED output shall be less than 1% per minute, and the high-frequency LED current variability shall be less than 0.1% RMS. During the on-orbit characterization, we monitor the lamp signal drifts, temperature dependency and nonlinearity sensitivity. The lamp signal variations are compensated prior to the calculation of the sensors´ linear calibration coefficients. The calibration coefficients are derived by interpolating between measured count levels and ideal linearized count levels. System nonlinearity is estimated by fitting normalized signal count rates to a second order polynomial function. Additionally, sensor on-orbit dynamic range is verified and thermal impact on nonlinearity sensitivity is analyzed. Our results demonstrate that sensor linearity performance meets the system requirement.