The validation of MOPITT measurements of atmospheric carbon monoxide (CO) and methane (CH4) will require independent, simultaneous, co-located measurements from ground- and aeroplane-based instruments. Recently, a program of MOPITT validation measurements in Russia and Canada has been proposed. This program will use three (nearly) identical Russian-made medium-resolution grating spectrometers (known as Sarcophagus) capable of measuring the atmospheric column concentration of CO and CH4. Two of these instruments are located in Russia, and one in Canada. The similarity of these instruments provides the opportunity of acquiring a highly correlated validation dataset from diverse locations around the globe. As part of this program, we are proposing to inter- calibrate these instruments using a set of standard gas cells. These cells will be regularly shipped between the instruments for calibration and inter-comparison purposes. These measurements will be made relative to measurements from a very high-resolution Difference Frequency Laser Spectrometer (DFLS) located at the University of Toronto. In this paper we present the results of a test of this inter-calibration experiment using a single CO gas cell and involving Sarcophagus, a high resolution Fourier Transform Spectrometer (FTS) and the University of Toronto DFLS.