OCO-2 Instrument

OCO-2 does not measure CO₂ or SIF directly. The instrument measures the spectrally-resolved intensity of the reflected sunlight from which CO₂ and SIF are derived.

Three separate spectrometers simultaneously measure the intensity of reflected sunlight across three wavelength bands - CO₂ (at 1.61 um), CO₂ (at 2.06 um) and O₂ (at 0.76um). The absorption levels increase the more of each gas that the sunlight has passed through.

The OCO-2 spectra must be very accurate. To eliminate energy from other sources that would generate measurement errors, the light detectors [Focal Plane Arrays (FPAs)] for each spectrometer must remain very cold (-120° C or -184° F). A refrigeration device called a cryocooler is used to maintain and control the FPA temperatures.

To Learn More
Read a paper from the OCO-2 team describing the OCO-2 spectrometer and its performance shortly after launch. https://amt.copernicus.org/articles/10/59/2017/amt-10-59-2017.pdf