In this paper, we analyze the accomplishment of a study for a low cost system, named PicoAgri, to monitor the status of agricultural fields. We here deal with the small detection system we are developing representing the first element to build the final PicoAgri concept: a system consisting of two elements, an array of small satellites coupled to drones. The array of CubeSat small satellites will provide data for an initial multispectral analysis with a resolution at ground of 30 m; when required a well localized area will be explored employing suitable drones capable of analyzing the territory with a resolution at least two orders of magnitude higher.