Sky Sensing: Active Carbon Sensing

To passively sense carbon, we measure reflected sunlight. As sunlight shines down on Earth, some of it is reflected by the atmosphere, some of it is absorbed, and some shines right through. Once the sunlight hits the surface of the Earth, it is either reflected or absorbed. The sunlight reflecting off the Earth passes back through the atmosphere, which absorbs some, reflects some, or lets some pass right through. When we look at the absorption spectra of this reflected sunlight, we can determine which elements in the atmosphere the light passed through.

The disadvantage to passively sensing carbon is that if we are measuring carbon in a single location, we can only do it during the daytime—when that location is facing the Sun. At night time that location is not receiving sunlight; sunlight isn’t reflecting off of that location, and therefore we cannot look at the absorption spectra of the reflected sunlight.

Active carbon sensing would involve a laser. We would shine a laser light down to Earth, the light would reflect and we would be able to measure the absorption spectra of the reflected laser light. This would allow us to measure carbon in a single location throughout the day and night. Although scientists are currently using lasers in similar ways to measure other things, the technology for active carbon remote sensing is still being developed.

Next

Remote Sensing | Active Vs Passive | Active Carbon Sensing | Satellites | Geostationary Vs Polar Orbiting | Earth Now | Other Kinds of Remote Sensing