A new algorithm has been developed which permits, for the first time, real-time data reduction of nadir measurements taken with a gas-filter correlation radiometer to determine tropospheric carbon-monoxide concentrations. The algorithm significantly reduces the complexity of the equations to be solved while providing accuracy comparable to line-by-line calculations. The method is based on a regression analysis technique using a truncated power series representation of the primary instrument output signals to infer directly a weighted average of trace gas concentration. The results produced by a microcomputer-based implementation of this technique are compared with those produced by the more rigorous line-by-line methods. This algorithm has been used in the reduction of MAPS Shuttle and aircraft data.
H. Andrew Wallio, Joseph C. Casas, Barbara B. Gormsen, Henry G. Reichle, Jr., and Mary S. Saylor, "Carbon monoxide mixing ratio inference from gas filter radiometer data," Appl. Opt. 22, 749-754 (1983)