This paper presents a solution for real-time satellite image processing. The focus is on the detection of changes in MODIS images. We present a distributed algorithm for change detection which is based on extracting relevant parameters from MODIS spectral bands. The algorithm detects the changes between two images of the same geographical area at different time moments. The algorithm, able to run in a Grid system, is scalable, fault-tolerant. We present the experimental results of this algorithm considering three spectral bands and different input images. We also propose a method to integrate applications based on this algorithm into the MedioGRID architecture.