The radiometric calibration procedure, applied on VNREDSat-1 raw data shall correct and minimize the radiometric non-uniform gain and offset, occurred by the nature of the optical payload. The procedure is based on the radiometric model, built to transform the incoming radiance into camera output signal. Within this radiometric model, the radiometric parameters such as dark noise and pixel response non-uniformity shall be separated. The output signal of dark noise shall be measured by capturing image scene of the ocean at night. The output signal of pixel response non-uniformity shall be measured by capturing image scene of uniform radiance image scene such as the dessert or grass field. All the radiometric calibration parameter after calculated shall be saved into a calibration file, which is kept on the control station and image processing station.

Optical instrument on Earth observation satellite performs the conversion from incoming radiance to digital image. Practically, there is always distortion or noise infringed on the output image. On the other hand, the instrument is suffering from degradation due to hard operating environment and aging. Therefore measurement and correction of optical image quality parameters must be done by ground station in order to maintain the reliable and accurate remote sensing products. This paper describes the methodology to evaluate the Modulation Transfer Function (MTF) and Signal to Noise Ratio (SNR) of received images to control the image quality of the optical satellite. MTF and SNR of VNREDSat-1 satellite are verified using on-ground calibration sites in Vietnam. The output provides important figures for next-step instrument calibration process.