The Total Ozone Mapping Spectrometer (TOMS) instrument, is managed by The Goddard Space Flight Center (NASA). From satellites such as Nimbus-7 it makes measurements of the total ozone in a column of air (from ground to space). By making 14 polar orbits each day, this single instrument provides daily maps of ozone covering most of the globe. With just the one instrument circling around and around, the problems of calibration differences between sites are very much reduced. With the abundance of global data, one can calculate statistics on ozone changes that are reliable and robust. As of this writing, there are no TOMS instruments measuring ozone. Designed to last about two years, the first TOMS, which flew on board the Nimbus 7 spacecraft (at an altitude of about 950 km), began operations in November 1978 and lasted until May 1993. The second TOMS instrument was launched in August 1991 aboard the Russian Meteor-3 spacecraft (at about 1205 km altitude); it failed in December 1994.