A space-based infrared camera was launched to collect atmospheric radiation data. In order to investigate its performance quantitatively both under pre-launch and post-launch conditions, a practical estimation model of radiometric calibration precision was proposed that only depended on the measured image data from ground and on-orbit blackbody-based calibration tests. The model treated the calibration error as a consequence of two independent factors. One was introduced by using the calibration equation to represent the relationship between the object apparent radiance and the camera digital response, and the other was the measurement uncertainty when imaging a target with known constant emission. Distribution maps of the errors for the focal plane array were constructed by means of estimating the calibration error pixel-wisely. Results show that the camera’s performance after launch is slightly worse than that before launch. The pixels with calibration errors more than 10% only account for about 5% for this camera, and they generally locate in the edge of the focal plane. The maps will be helpful in weighing the validity of sampled data at the pixel level.