NOVELTY - A gas filter correlation radiometry method involves providing gas filter correlation radiometer (GFCR) instrument (100) capable of making measurement viewing through gas cell; including in gas cell gas having chemical composition is different than that of target gas in atmospheric region being examined by GFCR instrument, where gas possessing light absorption features with a portion being partially correlated with light absorption features of target gas; adjusting measurement viewing to generate positive correlation for the portion where GFCR instrument generates signal (300) indicative.    USE - As gas filter correlation radiometry method, used for measuring column density of water vapor from Mars orbit, where the gas comprises methane; measurement of ozone in proximity to the Earth's surface, where the gas comprises carbonic sulfide; measurement of wind velocity and atmospheric temperature from an Earth orbit using nitric oxide as the target gas, where the gas comprises carbonic sulfide; or measurement of atmospheric column density from an Earth orbit using oxygen as the target gas, where the gas comprises hydrogen fluoride (claimed).    ADVANTAGE - The gas filter correlation radiometer (GFCR) system has added advantage that the absorption features of the dissimilar gas included in the gas cell (of GFCR instrument) need only be partially correlated with the absorption features of the atmospheric target gas.    DETAILED DESCRIPTION - A gas filter correlation radiometry method involves providing gas filter correlation radiometer (GFCR) instrument (100) capable of making measurement viewing through gas cell; including in the gas cell gas having a chemical composition that is different than that of target gas in an atmospheric region being examined by the GFCR instrument, where gas possessing light absorption features with a portion being partially correlated with light absorption features of target gas; adjusting the measurement viewing to generate at least one positive correlation for the portion where the GFCR instrument generates a signal (300) indicative; and performing gas filter correlation radiometry application using the signal. An INDEPENDENT CLAIM is included for gas filter correlation radiometer (GFCR) system, comprising GFCR instrument that includes gas cell (106) and spectral filter, where a measurement viewing is made by GFCR instrument when light energy passes through the spectral filter and the gas cell, gas populating the gas cell, where the gas having a chemical composition that is different than that of a target gas in an atmospheric region being examined by the GFCR instrument; and the spectral filter defining a bandpass where positive correlations for the portion can be generated, where the GFCR instrument generates a signal indicative of the positive correlations.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of gas filter correlation radiometer.    Gas filter correlation radiometer instrument (100)    Processing train (102)    Processor (104)    Gas cell (106)    Spectral filter (108)    Light energy (200)    Signal (300)