Abstract: The results obtained from test ground-based measurements with a new satellite instrument for mo-nitoring the Earth’s ozone layer are considered. The developed spectrometer, called ozonometer-TM, is to be installed aboard small near-Earth spacecraft (Ionosphere). The ozonometer-TM has been developed for monitoring the total ozone content based on the nadir satellite measurements of reflected and scattered light. This instrument operates within a spectral range of 300–500 nm with a spectral resolution of about 0.3–0.6 nm. Its qualification prototype has been manufactured and a number of test ground-based measurements have been performed at the Kislovodsk High-Mountain Station and in Orel. Estimates of the total ozone content have been obtained and compared with independent satellite data obtained during practically the same time period.