The ESRO 4 gas analyzer

On 22 November 1972 a gas analyzer was launched into earth orbit on board the satellite ESRO 4. This mass spectrometer for the investigation of the upper atmosphere composition and density employs a spherical antechamber connected to an electron impact ion source, an analyzing field of the monopole type, and a threefold detector system including one multiplier operated in the analog mode. The instrument measures neutral constituent number densities within the mass range 1−44 amu. The sampling frequency is one mass scan per 9 sec using a total bit rate of 90 bps. The laboratory calibration of the instrument sensitivities was performed using a gas flow method.