COSPEC (COrrelation SPECtrometer) remote sensors constitute a family of spectroscopic instruments that was developed in Canada in the 70's by Barringer Research Ltd. The last and also the best commercial model of this family was the COSPEC V (1981). When COSPEC V is utilized as a passive remote sensor, it uses a part of the UV-Vis spectral content of the zenith sky natural background to detect the presence of SO2 or NO2 traces in the atmosphere. COSPEC instruments became quite popular in the 70's and 80's and they were used especially in studies on air pollution coming from the industrial sector. Their most common application was the tracking from ground level of SO2 enriched industrial plumes. Step by step, the parallel growing of LIDAR's family, with more and more powerful instruments, together with the COSPEC's own technical limitations have driven this sensor to be unfairly forgotten. In the last few years and in spite of all these problems, COSPEC V has been widely used again by our research group in different projects related to transport and diffusion of air pollutants. In these occasions, this instrument has not been applied to study single industrial sources but urban atmospheres rich in NOR, where NO2 is the suitable target gas. The results of these studies have demonstrated the big potential of this remote sensor and possibly the necessity of its technical improvement and renewal. In this work, the most important instrumental problems of the original COSPEC V together with the optical and electronic solutions introduced are presented. As a result of the COSPEC's redesign, a new instrument has been developed: DICOSPEC (DIgital COrrelation SPECtrometer), whose performance is clearly better than COSPEC V's and whose handling by non-experts has been proven to be easier.