contemplates the future of DOAS in the context of current and past achievements. The future of passive DOASPassive DOAS may include improvements of MAX-DOASMulti-Axis DOAS (MAX-DOAS) and Satellite DOASSatellite DOAS (S-DOAS) techniques, the expanded use of imaging and tomography DOAS, and new applications for aerosol and cloud monitoring. Active DOASActive DOAS may see expansion into new wavelength regions, and thus new trace gases, more widespread use for industrial monitoring, and improvements in cavity enhanced (CE-)DOAS, broadband LIDARLIght Detection And Ranging (LIDAR), and tomography techniques. The final section of this chapter is dedicated to future developments of the technology underlying DOAS, such as new light sourcesLightsources, detectors, spectrometers and softwareSoftware.