The solar occultation measurement technique is a very simple method of measuring vertical profiles of atmospheric optical depth profiles from Earth orbit using the sun as a light source. As the spacecraft orbits the Earth, the SAGE instrument points toward the sun and measures its intensity. It observes sunsets when the spacecraft moves from the sunlit toward the dark side of the Earth. Before each sunset starts, the line-of-sight (LOS) between the spacecraft and the sun is unobstructed by the atmosphere so that the sun's intensity as measured by the SAGE instrument is unattenuated. But, when the spacecraft starts to dip below the horizon so that the LOS passes through a portion of the atmosphere, the sun's intensity will be attenuated due to aerosols and gases in the atmosphere that scatter and absorb sunlight. During sunrise events, when the spacecraft moves from the dark towards the sunlit side of Earth, the sun is first viewed through the atmosphere, and then along an unobstructed path when the spacecraft rises above the horizon. Thus, the measurement sequence during sunrise is just the reverse of that during sunset. In both instances the SAGE instrument acquires a measure of attenuation caused by aerosols and gases in the atmosphere, thereby making it possible to quantify these species as a function of altitude.

Typically the spacecraft orbits the Earth approximately once every 90 minutes or sixteen times per day, depending on orbital parameters. Each orbit provides two measurement opportunities, one for each sunset and one for each sunrise. Therefore SAGE can acquire 32 separate measurements during each 24-hour period, and measurement occurs at a different geographical locations over the Earth depending on the spacecraft orbit. The number of measurement opportunities and the geographical coverage can be increased when measurements are made during both lunar and solar occultation events.