As traditional joint transform correlators based on space light modulators can not adapt to the radioactive environment in space, a new correlator implemented by an electronic processor was introduced and testified. First, the traditional optical device was replaced by a digital processor to allow the new correlator to adapt to the radioactive environment. Then, a self-correlation calculation was added to the joint transform processing to eliminate the influence of zero-level diffraction, and the over-sampled discrete Fourier transform method was introduced to increase the measurement precision. Finally, the static measurement with a linear platform was performed to testify the improved joint transform correlator. Experimental results indicate that the measuring precision of the system on subpixel displacement is within 0.22 pixel(Root Mean Square, RMS). The improved joint transform correlator is good at both space environment adaptability and realization, its measurement precision can satisfy the system requirements of satellite cameras for the image motion compensation, and has a good application prospect.