The primary objective for the MOPITT algorithm test radiometer (MATR) is to support the pre-launch testing of data retrieval algorithms for the MOPITT satellite instrument. Particular areas of concern in the retrieval are the effects of variable ground reflectance, the operation of the PMR, the accuracy of the CH4 spectral data in the HITRAN data base, and the calculated interference from water vapor. The review panel for the MOPITT algorithm theoretical basis document strongly encouraged a ground-air field effort to obtain measurements of the real atmosphere with prototype instruments. The plans for MATR include three detection channels. Channel one will use a length modulator cell (LMC) followed by a detector system with a spectral bandpass near 2.3 micrometer. This LMC will be filled with CO (or alternatively with CH4) to make total column measurements that are strongly weighted near the surface. Channel two will use the same length modulator cell (LMC) as channel one, but it will use a detector system with a spectral bandpass near 4.6 micrometer. This channel will be sensitive to CO primarily in the free troposphere. Channel three will use a pressure modulator cell (PMC) followed by a detector system with a spectral bandpass also near 4.6 micrometer. This channel will be sensitive to CO primarily in the upper troposphere and lower stratosphere. A first round of laboratory, ground-based atmospheric, and airborne measurements have been completed to date using the 2.3 micrometer CH4 channel. The current status of MATR will be presented, along with results obtained to date.